A  TEXT-BOOK  OF 

HUMAN  PHYSIOLOGY, 


IN'CLUDING 


HISTOLOGY  AND   MICROSCOPICAL  ANATOMY 

WITH 
SPECIAL   REFERENCE   TO   THE    REQUIREMENTS   OF 

PRACTICAL  MEDICINE. 


DR.  L.  LANDOIS. 


SECOND    AMERICAN, 
TRANSLATED  FROM  THE  FIFTH  GERMAN  EDITION. 


WITH    ADDITIONS    BY 


WILLIAM  STIRLING,  M.D.,  Sc.D, 


ANU    HISTOLOGY    IN   OWES  S  COLLEGE   AND  VICH>KIA    UX 
HONOfKS   SCHOOL  OF  SCIENCE,    UNIVERSITY    OF    OXFOKD 


FIVE  HUNDRED  AND  EIGHTY-THREE   ILLUSTRATIONS. 


PHILADELPHIA: 
P.    BLAKISTON,    SON    &    CO. 

No.    10 1  2    Walnut    Street. 
1887. 


SIR   JOSEPH    LISTER,    Baronet, 

M.D.,  D.C.L.,  LL.D.,  F.R.SS.  (LOND.  AND  EDIN.), 

CLINICAL  SURGERY    IN    KlNO's   COLLEGE,    LONDON;    SURGEON    EXTRAORDINARY    TO    Tl 
lERLY    REGIUS    PROFESSOR    OF    CLINICAL  SURGERY    IN   THE   UNIVERSITY   OF    EDINEURGF 

IN    ADMIRATION    OF 

'CfiTic  ^lUnii  oP  Science, 

WHOSE   BRILLIANT    DISCOVERIES   HAVE   REVOLUTIONIZED 

MEDICAL   PRACTICE,   AND 

CONTRIBUTED    INCALCULABLY   TO   THE  WELL-BEING   OF   MANKIND; 

AND     IN     GRATITUDE    TO 

'Csfte  'Tlccicfier, 

WHOSE   NOBLE   EARNESTNESS   IN   INCULCATING 

THE  SACREDNESS   OF   HUMAN   LIFE 

STIRRED    THE    HEARTS    OF    ALL    WHO    HEARD    HIM: 

BY    HIS    FORMER    PUPIL, 

THE  TRANSLATOR. 


PREFATORY  NOTE  TO  SECOND  ENGLISH  EDITION. 


That  a  Second  Edition  of  this  "  Text-Book  of  Physiology  "  has  been  called 
for  within  little  more  than  six  months  after  the  publication  of  the  complete  work, 
indicates  that  the  work  has  met  a  felt  want. 

In  this  Edition,  the  distinctive  character  of  the  work  has  been  adhered  to  and 
extended,  matter  being  added  bringing  forward  more  clearly  the  relation  of  Physi- 
ology to  Practical  Medicine  AND  Surgery;  the  additions  have  chiefly  been 
derived  from  the  Fifth  German  Edition,  but  there  has  been  incorporated  a  large 
amount  of  new  matter. 

The  number  of  Woodcuts  has  been  increased  from  494  to  5S3,  to  most  of  the 
Chapters  I  have  added  a  paragraph  on  the  Action  of  Drugs,  and  the  Chapters 
on  the  Nervous  System  have  been  largely  recast,  partly  with  the  aid  of  the  Lec- 
tures on  the  Diseases  of  the  Brain,  by  Dr.  Gowers. 

I  would  wish  to  tender  my  thanks  to  Dr.  Lauder  Brunton  for  the  use  of  some 
illustrations,  and  for  information  derived  from  his  Text-Book  of  Pluirmacology, 
Therapeutics,  and  Materia  Medica.  For  some  suggestions  relating  to  the  Nervous 
System  I  am  indebted  to  my  friend  Professor  Schafer,  also  to  Dr.  Sidney  Martin, 
who  was  kind  enough  to  write  the  paragraph  on  "  Vegetable  Proteid  Bodies,"  arid 
to  Dr.  Berry  Hart  for  suggestions  on  the  Chapters  on  Reproduction. 

Some  of  the  new  illustrations  are  taken  from  Schenk's  Grundriss  der  normalen 
Histologic.  For  some  of  the  new  illustrations  I  am  indebted  to  Professors  Victor 
Horsley,  Rutherford  and  Charteris,  Drs.  Hart  and  Johnson,  and  Mr.  Martindale. 
The  others  are  acknowledged  elsewhere. 

Altogether,  the  work  has  been  carefully  revised,  and  I  trust  this  Edition  will 
prove  as  useful  to  Practitioners  and  Students  as  the  last  one. 

WILLIAM    STIRLING. 
The  Owens  College, 

Manchester,  ywwf,  18S6. 


Digitized  by  the  Internet  Archive 

in  2010  with  funding  from 
Columbia  University  Libraries 


http://www.archive.org/details/textbookofhumanpOOIand 


PREFACE  TO  FIRST  ENGLISH  EDITION. 


The  fact  that  Professor  Landois'  "Lehrluch  der  F/iysiologie  dcs  Mensc/n-n" 
has  already  passed  through  four  large  editions  since  its  first  appearance  in  iSSo, 
shows  that  in  some  special  way  it  has  met  the  wants  of  Students  and  Practitioners 
in  Germany.  The  characteristic  which  has  thus  commended  the  work  will  be 
found  mainly  to  lie  in  its  eminent  practicality ;  and  it  is  this  consideration  which 
has  induced  me  to  undertake  the  task  of  putting  it  into  an  English  dress  for 
English  readers. 

Landois'  work,  in  fact,  forms  a  Bridge  between  Physiology  and  the  Practice  of 
Medicine.  It  never  loses  sight  of  the  fact  that  the  Student  of  to-day  is  the  prac- 
ticing Physician  of  to-morrow.  Thus,  to  every  Section  is  appended — after  a  full 
description  of  the  normal  processes — a  short  resume  of  the  pathological  variations, 
the  object  of  this  being  to  direct  the  attention  of  the  Student,  from  the  outset,  to 
the  field  of  his  future  practice,  and  to  show  him  to  what  extent  pathological  pro- 
cesses are  a  disturbance  of  the  normal  activities. 

In  the  same  way,  the  work  offers  to  the  busy  physician  in  practice  a  ready  means 
of  refreshing  his  memory  on  the  theoretical  aspects  of  Medicine.  He  can  pass 
backioard  from  the  examination  of  pathological  phenomena  to  the  normal  pro- 
cesses, and,  in  the  study  of  these,  find  new  indications  and  new  lights  for  the 
appreciation  and  treatment  of  the  cases  under  consideration. 

With  this  object  in  view,  all  the  methods  of  investigation  which  may  wich 
advantage  be  used  by  the  Practitioner,  are  carefully  and  fully  described  ;  and 
Histology,  also,  occupies  a  larger  place  than  is  usually  assigned  to  it  in  Text-books 
of  Physiology. 

A  word  as  to  my  own  share  in  the  present  version  ; — 

(i.)  In  the  task  of  translating,  I  have  endeavored  throughout  to  convey  the 
author's  meaning  accurately,  without  a  too  rigid  adherence  to  the  original.  Those 
who  from  experience  know  something  of  the  difficulties  of  such  an  undertaking 
will  be  most  ready  to  pardon  any  shortcomings  they  may  detect. 

(2.)  Very  considerable  additions  have  been  made  to  the  Histological  and  also 
(where  it  has  seemed  necessary)  to  the  Physiological  sections.  All  such  additions 
are  enclosed  within  square  brackets  [].  I  have  to  acknowledge  my  indebtedness 
to  many  valuable  Papers  in  the  various  Medical  Journals — British  and  Foreign — 
and  also  to  the  Histological  Treatises  of  Cadiat,  Ranvier  and  Klein;  Quain's 
Anatiimy,  vol.  11,  ninth  edition;  Htxm.dinn'' s  JIandbuch  der  Fhysiologie ;  and  the 
Text-books  on  Physiology,  by  Rutherford,  Foster  and  Kirkes ;  Gamgee's  Physio- 
logical Chemistry  ;  Ewald's  Digestion  ;  and  Robert's  Digestive  Ferments. 

(3.)  The  Illustrations  have  been  increased  to  494  in  the  English  version.     These 


X  PREFACE   TO    FIRST   EDITION. 

additional  diagrams,  with  the  sources  whence  derived,  are  distinguished  in  the 
List  of  Woodcuts  by  an  asterisk. 

There  only  remains  for  me  now  to  express  my  thanks  to  all  who  have  kindly 
helped  in  the  progress  of  the  work,  either  by  furnishing  Illustrations  or  otherwise 

especially  to  Drs.   Byrom   Bram well.  Dudgeon,  Lauder  Brunton,  and   Knott; 

Mr.  Hawksley;  Professors  Hamilton  and  M'Kendrick;  to  my  esteemed  teacher 
and  friend,  Professor  Ludwig,  of  Leipzic ;  and,  finally,  to  my  friend,  Mr.  A.  W. 
Robertson,  M.  A.,  formerly  Assistant  Librarian  in  the  University,  and  now  Libra- 
rian of  the  Aberdeen  Public  Library,  for  much  valuable  assistance  while  the  work 
was  passing  through  the  press. 

The  Second  Part  will,  it  is  hoped,  be  issued  early  in  1885. 

In  conclusion — and  forgetting  for  the  moment  my  own  connection  with  it— I 
heartily  commend  the  work  fcr  sd  to  the  attention  of  Medical  Men,  and  can  wish 
for  it  no  better  fate  than  that  it  may  speedily  become  as  popular  in  this  country  as 
it  is  in  its  Fatherland. 

WILLL\M  STIRLING. 
Aberdeen  University, 
NoT^mber^  1SS4. 


GENERAL  CONTENTS. 


INTRODUCTION. 

The  Scope  of  Physiology,  and  its  Relation  to  the  other  Branches  of  Natural  Science    .    .    .  xxx 

Matter xxxi 

Forces xxxii 

Law  of  the  Conservation  of  Energy xxxvi 

Animals  and  Plants xxxvi 

Vital  Energy  and  Life xxxix 

I.  PHYSIOLOGY  OF  THE  BLOOD. 

1.  Physical  Properties  of  the  Blood 17 

2.  Microscopic  Examination  of  the  Blood iS 

3.  Histology  of  the  Human  Red  Blood  Corpuscles 21 

4.  Effects  of  Reagents  on  the  Blood  Corpuscles 21 

5.  Preparation  of  the  Stroma — Making  Blood  "  Lake-Colored  " 23 

6.  Form  and  Size  of  the  Blood  Corpuscles  of  Different  Animals 24 

7.  Origin  of  the  Red  Blood  Corpuscles 25 

8.  Decay  of  the  Red  Blood  Corpuscles 2S 

9.  The  Colorless  Corpuscles — Leucocytes — Blood  Plates — Granules 29 

10.  Abnormal  Changes  of  the  Blood  Corpuscles 34 

11.  Chemical  Constituents  of  the  Red  Blood  Corpuscles 35 

12.  Preparation  of  Haemoglobin  Crystals 36 

13.  Quantitative  Estimation  of  Haemoglobin 36 

14.  Use  of  Spectroscope 38 

15.  Compounds  of  Ha:moglobin — Methsemoglobin 39 

16.  Carbonic  Oxide- H.iemoglobin — Poisoning  with  Carbonic  Oxide 40 

17.  Other  Compounds  — Haemoglobin 42 

iS.  Decomposition  of  Haemoglobin 42 

19.  Ha-min  and  Blood  Tests 43 

20.  Haematoidin 44 

21.  The  Colorless  Proteid  of  Hoemoglobin ^^ 

22.  Proteids  of  the  Stroma 44 

23.  The  other  Constituents  of  Red  Blood  Corpuscles 45 

24.  Chemical  Composition  of  the  Colorless  Corpuscles 45 

25.  Blood  Plasma,  and  its  Relation  to  Serum 46 

26.  Preparation  of  Plasma 46 

27.  Fibrin — Coagulation  of  the  Blood 47 

28.  General  Phenomena  of  Coagulation 48 

29.  Cause  of  Coagulation  of  the  Blood 49 

30.  Source  of  the  Fibrin  Factors 53 

31.  Relation  of  the  Red  Blood  Corpuscles  to  the  Formation  of  Fibrin 54 

32.  Chemical  Composition  of  the  Plasma  and  Serum 54 

33.  The  Gases  of  the  Blood 56 

34.  Extraction  of  the  Blood  Gases 57 

35.  Quantitative  Estimation  of  the  Blood  (iases 59 

36.  The  Blood  Gases 59 

37.  Is  Ozone  (O3)  present  in  Blood? 60 

38.  Carbon  dioxide  and  Nitrogen  in  Blood 6t 

39.  .■\rterial  and  Venous  Blood 62 

40.  Quantity  of  Blood 63 

41.  Variations  from  the  Norma!  Conditions  of  the  Blood 63 

II.    PHYSIOLOGY  OF  THE  CIRCULATION. 

42.  General  View  of  the  Circulation 67 

43.  The  Heart 67 

44.  Arrangement  of  the  Cardiac  Muscular  Fibres 68 

45.  .\rrangenient  of  the  Ventricular  Fibres 70 


SECTION  PAGE 

46.  Pericardium,  Endocardium,  Valves      7' 

47.  Automatic  Regulation  of  tlie  Heart 73 

48.  The  Movements  of  the  Heart      75 

49.  Pathological  Disturbances  of  Cardiac  Action 77 

50.  The  Apex  Beat — The  Cardiogram 7^ 

51.  The  Time  occupied  by  the  Cardiac  Movemenis 83 

52.  Pathological  Disturbance  of  the  Cardiac  Impulse      85 

53.  The  Heart  Sounds 88 

54.  Variations  of  the  Heart  Sounds 92 

55.  The  Duration  of  the  Movements  of  the  Heart       92 

56.  Physical  Examination  of  the  Heart 9^ 

57.  Innervation  of  Heart — Cardiac  Nerves 92 

58.  The  Automatic  Motor  Centres  of  the  Heart 95 

59.  The  Cardio-Pneumatic  Movements 104 

60.  Influence  of  the  Respiratory  Pressure  of  the  Heart       105 

THE   CIRCULATION. 

61.  The  Flow  of  Fluids  through  Tubes 108 

62.  Propelling  Force,  Velocity  of  Current,  Lateral  Pressure 108 

63.  Currents  through  Capillary  Tubes 110 

64.  Movements  of  Fluids  and  Wave  Motion  in  Elastic  Tubes no 

65.  Structure  and  Properties  of  the  Blood  Vessels in 

66.  The  Pulse— Historical "6 

67.  Instruments  for  Investigating  the  Pulse n? 

68.  The  Pulse  Curve  or  Sphygmogram       122 

69.  Dicrotic  Pulse 126 

70.  Characters  of  the  Pulse 127 

71.  Variations  in  the  Strength,  Tension  and  Volume  of  the  Pulse      128 

72.  The  Pulse  Curves  of  various  Arteries 129 

73.  Anacrotism      '3° 

74.  Influence  of  the  Respiratory  Movements  on  the  Pulse  Curve 131 

75.  Influence  of  Pressure  upon  the  Form  of  the  Pulse  Curve 133 

76.  Rapidity  of  Transmission  of  Pulse  Waves 134 

77.  Propagation  of  the  Pulse  Wave  in  Elastic  Tubes 134 

78.  Velocity  of  the  Pulse  Wave  in  Man 136 

79.  Further  Pulsatile  Phenomena I37 

80.  Vibrations  Communicated  to  the  Body  by  the  Action  of  the  Heart 137 

81.  The  Blood  Current 139 

82.  Schemata  of  the  Circulation      140 

83.  Capacity  of  the  Ventricles 140 

84.  Estimation  of  the  Blood  Pressure I4' 

85.  Blood  Pressure  in  the  Arteries '45 

86.  Blood  Pressure  in  the  Capillaries >S' 

87.  Blood  Pressure  in  the  Veins '52 

88.  Blood  Pressure  in  the  Pulmonary  Artery IS3 

89.  Measurement  of  the  Velocity  of  the  Blood  Stream I55 

90.  Velocity  of  the  Blood  in  Arteries,  Capillaries,  and  Veins '57 

91.  Estimation  of  the  Capacity  of  the  Ventricles '59 

92.  The  Duration  of  the  Circulation '59 

93.  Work  of  the   Heart '59 

94.  Blood  Current  in  the  Smaller  Vessels 160 

95.  Passage  of  the  Blood  Corpuscles  out  of  the  Vessels— [Diapedesis] 162 

96.  Movement  of  the  Blood  in  the  Veins 163 

97.  Sounds  or  Bruits  within  Arteries I04 

98.  Venous  Murmurs '^4 

99.  The  Venous  Pulse — Phlebogram 165 

100.  Distribution  of  the  Blood 167 

101.  Plethysmography '67 

102.  Transfusion  of  Blood lo" 

THE  BLOOD  GLANDS. 

103.  The    Spleen — Thymus— Thyroid — Suprarenal    Capsules— Hypophysis    Cerebri—Coc- 

cygeal and  Carotid  Glands  172 

104.  Comparative '°' 

105.  Historical  Retrospect '82 


CONTENTS.  XIU 


III.    PHYSIOLOGY    OF    RESPIRATION. 


CTION 


106.  Structure  of  the  Air  Passages  and  Lungs 183 

107.  Mechanism  of  Respiration 19° 

108.  Quantity  of  Gases  Respired 191 

109.  Number  of  Respirations • '9- 

iio.  Time  occupied  by  the  Respiratory  Movements 192 

111.  Pathological  Variations  of  the  Respiratory  Movements 195 

112.  General  View  of  the  Respiratory  Muscles 196 

113.  Action  of  the  Individual  Respiratory  Muscles 197 

114.  Relative  Size  of  the  Chest 201 

115.  Pathological  Variations  of  the  Percussion  Sounds 203 

116.  The  Normal  Respiratory  Sounds 204 

117.  Pathological  Respiratory  Sounds 204 

ilS.  Pressure  in  the  Air  Passages  during  Respiration 205 

119.  Appendix  to  Respiration 207 

120.  Peculiarly  Modified  Respiratory  Sounds 207 

CHEMISTRY  OF  RESPIRATION. 

121.  Quantitative  Estimation  of  CO2,  O,  and  Watery  Vapor 209 

122.  Methods  of  Investigation 209 

123.  Composition  and  Properties  of  Atmospheric  Air 212 

124.  Composition  of  Expired  Air 212 

125.  Daily  Quantity  of  Gases  Exchanged 213 

126.  Review  of  the  Daily  Gaseous  Income  and  Expenditure 213 

127.  Conditions  Influencing  the  Gaseous  Exchanges 213 

1 2$.   Diffusion  of  Gases  within  the  Lungs 216 

129.  Exchange  of  Gases  between  the  Blood  and  Air 216 

130.  Dissociation  of  Gases 21S 

131.  Cutaneous  Respiration 219 

132.  Internal   Respiration 219 

133.  Respiration  in  a  Closed  Space 221 

134.  Dyspncea  and  Asphyxia 222 

135.  Respiration  of  Foreign  Gases 225 

136.  Accidental  Impurities  of  the  Air 225 

137.  Ventilation  of  Rooms 226 

138.  Formation  of  Mucus 227 

139.  Action  of  the  Atmospheric  Pressure 229 

140.  Comparative  and  Historical 230 

IV.     PHYSIOLOGY    OF    DIGESTION. 

141.  The  Mouth  and  its  Glands 232 

142.  The  Salivary  Glands 233 

1 1,.  Histc'l  igical  Changes  in  the  .Salivary  Glands 235 

144.  The  Nerves  of  the  Salivary  Glands 237 

145.  Action  of  Nerves  on  the  Salivary  Secretion 237 

146.  The  Saliva  of  the  Individual  Glands 242 

147.  The  Mixed  .Saliva  in  the  Mouth 243 

148.  Physiological  Action  of  Saliva 244 

149.  Tests  for  Sugar 246 

150.  (Quantitative  Estimation  of  Sugar 247 

151.  Mechanism  of  the  Digestive  Apparatus 248 

152.  Introduction  of  the  Food 248 

153.  The  Movements  of  Mastication 248 

154.  Structure  and  Development  of  the  Teeth 249 

155.  Movements  of  the  Tongue 253 

156.  Deglutition 254 

157.  Movements  of  the  Stcunach 256 

158.  Vomiting 257 

159.  Movements  of  the  Intestine 259 

160.  Excretion  of  Foecal  Matter 260 

161.  Influence  of  Nerves  on  the  Intestine 262 

162.  Structure  of  the  Stomach 266 

163.  The  Gastric   Juice 269 

164.  Secretion  of  Gastric  Juice 269 


SECTICN  PACE 

165.  Methods  of  obtaining  Gastric  Juice 273 

166.  Process  of  Gastric  Digestion 274 

167.  Gases  in  the  Stomach    . 27S 

168.  Structure  of  the  Pancreas 27S 

169.  The  Pancreatic  Juice 279 

170.  Digestive  Action  of  the  Pancreatic  Juice    . 280 

171.  The  Secretion  of  the  Pancreatic  Juice 2S3 

172.  Preparation  of  Peptonized  Food 284 

173.  Structure  of  the  Liver 284 

174.  Chemical  Composition  of  the  Liver  Cells 288 

175.  Diabetes  Mellitus,  or  Glycosuria 290 

176.  The  Functions  of  the  Liver 292 

177.  Constituents  of  the  Bile 293 

178.  Secretion  of  Bile 296 

179.  Excretion  of  Bile • 298 

180.  Reabsorption  of  Bile 299 

181.  Functions  of  the  Bile 3°' 

182.  Fate  of  the  Bile  in  the  Intestine 302 

183.  The  Intestinal  Juice 3°3 

184.  Fermentation  Processes  in  the  Intestine 307 

185.  Processes  in  the  Large  Intestine 3" 

186.  Pathological  Variations 3^4 

187.  Comparative  Physiology 3'*' 

iSS.  Historical  Retrospect 3' 7 

V.    PHYSIOLOGY    OF    ABSORPTION. 

189.  The  Organs  of  Absorption 319 

190.  Structure  of  the  Small  and  Large  Intestines 319 

191.  Absorption  of  the  Digested  Food 325 

192.  Absorptive  Activity  of  the  Wall  of  the  Intestine 327 

193.  Influence  of  the  Nervous  System 33' 

194.  Feeding  with  "Nutrient  Enemata" 33' 

195.  Chyle  Vessels  and  Lymphatics 33^ 

196.  Origin  of  the  Lymphatics 33^ 

197.  The  Lymph  Glands 335 

198.  Properties  of  Chyle  and  Lymph 337 

199.  Quantity  of  Lymph  and  Chyle 339 

200.  Origin  of  Lymph 34° 

201.  Movement  of  Chyle  and  Lymph 34' 

202.  Absorption  of  Parenchymatous  Effusions 344 

203.  Congestion  of  Lymph,  Serous  Effusions  and  Qidema 344 

204.  Comparative  Physiology 34^ 

205.  Historical  Retrospect 34^ 

VI.    PHYSIOLOGY    OF    ANIMAL    HEAT. 

206.  Sources  of  Heat 347 

207.  Homoiothermal  and  Poikilothermal  Animals 35° 

208.  Methods  of  Estimating  Temperature — Thermometry 351 

209.  Temjierature — Topography 353 

210.  Conditions  Influencing  the  Temperature  of  Organs 354 

211.  Estimation  of  the  Amount  of  Heat — Calorimetry 35^ 

212.  Thermal  Conductivity  of  Animal  Tissues 357 

213.  Variations  of  the  Mean  Temperature 35^ 

214.  Regulation  of  the  Temperature 3^' 

215.  Income  and  Expenditure  of  Heat 3^3 

2 1 6.  Variations  in  Heat  Production 3^5 

217.  Relation  of  Heat  Production  to  Bodily  Work 3^5 

218.  Accommodation  for  different  Temperatures 3^6 

219.  Storage  of  Heat  in  the  Body 3''7 

220.  Fever 3^7 

221.  Artificial  Increase  of  the  Temperature 3^9 

222.  Employment  of  Heat 3°9 

223.  Increase  of  Temperature  post-mortem 3^^^ 

224.  Action  of  Cold  on  the  Body 37° 


CONTENTS. 


FAGB 


SBCTION 

225.  Artificial  Lowering  of  Tempeialure 37° 

226.  Employment  of  Cold 37i 

227.  Heat  of  Inflamed  Parts 372 

228.  Historical  and  Comparative • 37^ 

VII.  PHYSIOLOGY  OF  THE  METABOLIC   PHENOMENA  OF  THE  BODY. 

229.  General  View  of  Food  Stuffs 373 

230.  Structure  and  Secretion  of  the  Mammary  Glands 375 

231.  Mdk  and  its  Preparations 377 

232.  Eggs 381 

233.  Flesh  and  its  Preparations 3°' 

234.  Vegetable  Foods 3^3 

235.  Condiments — Coffee,  Tea,  and  Alcohol 3^5 

PHENOMENA   AND    LAWS   OF   METABOLISM. 

236.  Eiiuilibrium  of  the  Metabolism 3^8 

237.  Metabolism  during  Hunger  and  Starvation 394 

238.  Metabolism  during  a  purely  Flesh  Diet 39^ 

239.  A  Diet  of  Fat  or  of  Carbohydrates 397 

240.  Mixture  of  Flesh  and  Fat 397 

241.  Origin  of  Fat  in  the  Body 39^ 

242.  Corpulence 399 

243.  The  Metabolism  of  the  Tissues    .    .        4°° 

244.  Regeneration  of  Organs  and  Tissues 4^2 

245.  Transplantation  of  the  Tissues 4°$ 

246.  Increase  in  Size  and  Weight  during  Growth 40S 

GENERAL  VIEW  OF   THE  CHEMICAL  CONSTITUENTS  OF  THE  ORGANISM. 

247.  Inorganic  Con'stituents 407 

248.  Organic  Compounds — Proteids 4°^ 

249.  The  Animal  and  Vegetable  Proteids  and  their  Properties 409 

250.  The  Albuminoids 4' I 

251.  The  Fats 4>2 

252.  The  Carbohydrates 415 

253.  Historical  Retrospect 4' 7 

VIII.  THE    SECRETION    OF   URINE. 

254.  Structure  of  the  Kidney 4'9 

255.  The  Urine 426 

256.  Urea 43° 

257.  Qualitative  and  Quantitative  Estimation  of   Urea 432 

258.  Uric  Acid 434 

259.  Qualitative  and  Quantitative  Estimation  of  Uric  Acid 435 

260.  Krealinin  and  other  Substances 43^ 

261.  Coloring  Matters  of  the  Urine 439 

262.  Indigo,  Phenol,  Kresol,  Pyrokatechin      44° 

263.  Spontaneous  Changes  in  Urine,  Fermentations 443 

264.  Albumin  in  Urine 445 

265.  Blood  in  Urine 447 

266.  Bile  in  Urine 45° 

267.  Sugar  in  Urine 45' 

268.  Cystin 454 

269.  I.eucin,  Tyrosin 454 

270.  Deposits  in  Urine 455 

271.  General  Scheme  for  Detecting  Urinary  Deposits 457 

272.  Urinary  Calculi 45^ 

273.  The  Secretion  of  Urine 459 

274.  The  Preparation  of  Urine 4^3 

275.  Passage  of  Various  Substances  into  the  Urine 465 

276.  Influence  of  Ntrves  on  the  Renal  Secretion 4^5 

277.  Urjemia,  .Vmmonii^niia 4''9 


XVI  CONTENTS. 

SECTION  PAr.E 

27S.  Structure  and  Functions  of  the  Ureter 470 

279.  Urinary  Bladder  and  Urethra 471 

280.  Accumulation  and  Retention  of  Urine 472 

281.  Retention  and  Incontinence  of  Urine 475 

282.  Comparative  and  Historical 475 

IX.   FUNCTIONS    OF    THE    SKIN. 

2S3.  Structure  of  the  Skin 477 

284.  Nails  and  Hair 479 

285.  The  Glands  of  the  Skm 482 

286.  The  Skin  as  a  Protective  Covering 483 

2S7.    Cutaneous  Respiration  and  Secretion — Sweat 4S4 

28S.  Conditions  Influencing  the  Secretion  of  Sweat 486 

289.  Pathological  Variations 488 

290.  Cutaneous  Absorption—  Galvanic  Conduction 489 

291.  Comparative — Historical 49° 

X.  PHYSIOLOGY  OF  THE  MOTOR  APPARATUS. 

292.  Ciliary  Motion,  Pigment  Cells 49' 

292A. Structure  and  Arrangement  of  the  Muscles 493 

293.  Physical  and  Chemical  Properties  of  Mu^cle 5°° 

294.  Metabolism  in  Muscle 5°^ 

295.  Rigor  mortis 5°4 

296.  Muscular  Excitability 5°^ 

297.  Changes  in  a  Muscle  during  Contraction 5^' 

298.  Muscular  Contraction 5 '3 

299.  Rapidity  of  IVansmission  of  a  Muscular  Contraction 5^3 

300.  Muscular  Work 524 

301.  The  Elasticity  of  Muscle 526 

302.  Formation  of  Heat  in  an  Active  Muscle 5^9 

303.  The  Muscle  Sound 53° 

304.  J'atigue  of  Muscle S3' 

305.  The  Mechanism  of  the  Joints 533 

306.  Arrangement  and  Uses  of  the  ^luscles  of  the  Body 53S 

307.  Gymnastics — Pathological  Motor  Variations 53^ 

30S.  Standing 539 

309.  Sitting 54° 

310.  Walking  and  Running 54' 

311.  Comparative 543 

VOICE   AND   SPEECH, 

312.  Voice  and  Speech 545 

313.  Arrangement  of  the  Larynx      545 

314.  Organs  of  Voice — Laryngoscopy      55' 

315.  Conditions  Modifying  the  Laryngeal  Sounds 553 

316.  Range  of  the  Voice 554 

317.  Speech — The  Vowels 555 

318.  The  Consonants 557 

319.  Pathological  Variations  of  Voice  and  Speech      55^ 

320.  Comparative — Historical 559 

XI.  GENERAL  PHYSIOLOGY  OF  THE  NERVES  AND  ELECTRO- 
PHYSIOLOGY. 

321.  Structure  and  Arrangement  of  the  Nerve  Elements 5^' 

322    Chemistry  of  the  Nerve  Substance 5^^ 

323.  Metabolism  of  Nerves 5^8 

324.  Excitability  of  Nerves — Stimuli 5''^ 

325.  Diminution  of  the  Excitability — Degene.ation  and  Regeneration  of  Nerves     ....  572 

326.  The  Galvanic  Current 577 

327.  Action  of  the  Galvanic  Current — Galvanometer 578 

328.  Electrolysis 579 

329.  Induction — Extra  Current — Magneto- Induction 584 


CONTENTS.  XVU 


SECTION 


PAGB 


330.  bu  EoisReymond's  Inductorium 5^^ 

331.  Electrical  Currents  in  Passive  Muscle  and  Nerve 5^8 

332.  Currents  of  Stimulated  Muscle  and  Nerve 59' 

333.  Currents  in  Nerve  and  Muscle  during  Electrotonus 594 

334.  Theories  of  Muscle  and  Nerve  Currents 595 

335.  Electrotonic  Alteration  of  the  Excitability 597 

336.  Electrotonus — Law  of  Contraction 600 

337.  Rapidity  of  Transmission  of  Nervous  Impulses 602 

338.  Double  Conduction  in  Nerves 605 

339.  Therapeutical  Uses  of  Electricity — Reaction  of  Degeneration 606 

340.  Electrical  Charging  of  the  Body 611 

341.  Comparative — Historical 611 

XII.  PHYSIOLOGY  OF  THE  PERIPHERAL  NERVES. 

342.  Classification  of  Nerve  Fibres 613 

343.  Nervus  Olfactorius 615 

344.  Nervus  Opticus 616 

345.  Nervus  Oculomotorius 618 

346.  Nervus  Trochlearis 621 

347.  Nervus  Trigeminus 621 

348.  Nervus  Abducens 630 

349.  Nervus  Facialis 631 

350.  Nervus  Acusticus ^34 

351.  Nervus  Glosso-pharyngeus 637 

352.  Nervus  Vagus      638 

353.  Nervus  Accessorius 644 

354.  Nervus  Hypoglossus 645 

355.  The  Spinal  Nerves 645 

356.  The  Sympathetic  Ner\-e 649 

357.  Comparative — Historical 652 

XIII.  PHYSIOLOGY    OF    THE    NERVE    CENTRES. 

358.  General 653 

359.  Structure  of  the  Spinal  Cord ■ ''54 

360.  Spinal  Reflexes 661 

361.  Inhibition  of  the  Reflexes 664 

362.  Centres  in  the  Spinal  Cord 668 

363.  Excitability  of  the  Spinal  Cord 67° 

364.  The  Conducting  Paths  in  the  Spinal  Cord 671 

365.  General  .Schema  of  the  Brain ' 675 

366.  The  Medulla  Oblongata 681 

367.  Reflex  Centres  of  the  Medulla  Oblongata 685 

36S.  The  Respiratory  Centre 686 

369.  The  Cardio- Inhibitory  Centre 691 

370.  The  Accelerans  Cordis  Centre 693 

371.  Vasomotor  Centre  and  Vasomotor  Nerves 695 

372.  Vaso-dilator  Centre  and  Vaso-dilator  Nerves 7°' 

373.  The  .Spasm  Centre — The  Sweat  Centre 7°2 

374.  Psychical  Functions  of  the  Cerebrum 703 

375.  Structure  of  the  Cerebrum — Motor  Cortical  Centres 709 

376.  The  Sensory  Cortical  Centres 7^1 

377.  The  Thermal  Cortical  Centres 7^4 

378.  Topography  of  the  Cortex  Cerebri 7^5 

379.  The  Basal  Ganglia— The  Midbrain 733 

380.  The  Structure  and  Functions  of  the  Cerebellum 739 

381.  The  Protective  Apparatus  of  the  Brain 742 

382.  Comparative — -Historical 746 

XIV.    PHYSIOLOGY    OF   THE    SENSE    ORGANS. 

I.  SIGHT. 

383.  Introductory  Observations 748 

384.  Histology  of  the  Eye 75° 

385.  Dioptric  Observations 759 


CONTENTS. 

rACB 

386.  Fonnation  of  a  Retinal  Image 764 

387.  Accommodation  of  the  Eye      766 

388.  Normal  and  Abnormal  Refraction 770 

389.  The  Power  of  Accommodation ^^2 

390.  Spectacles 773 

391.  Chromatic  Aberration  and  Astigmatism 774 

392.  The  Iris 775 

393.  Entoptical  Phenomena 779 

394.  Illumination  of  the  Eye — The  Ophthalmoscope 781 

395.  Activity  of  the  Retina  in  Vision 785 

396.  Perception  of  Colors 79° 

397.  Color  Blindness 794 

398.  Stimulation  of  the  Retina 796 

399.  Movements  of  the  Eyeballs 799 

4CK).  Binocular  Vision 803 

401.  Single  Vision — Identical  Points 803 

402.  Stereoscopic  Vision 805 

403.  Estimation  of  Size  and  Distance 808 

404.  Protective  Organs  of  the  Eye 810 

405.  Comparative — Historical 812 

2.  HEARING. 

406.  Structure  of  the  Organ  of  Hearing 814 

407.  Physical  Introduction 815 

408.  Ear  Muscles 816 

409.  Tympanic  Membrane 816 

410.  The  Auditory  Ossicles  and  their  Muscles 819 

411.  Eustachian  Tube — Tympanum 822 

412.  Conduction  of  Sound  in  the  Labyrinth 824 

413.  Structure  of  the  Labyrinth 825 

414.  Auditory  Perceptions  of  Pitch 828 

415.  Perception  of  Quality — Vowels 830 

416.  Action  of  the  Labyrinth 833 

417.  Harmony — Discords — Beats 835 

418.  Perception  of  Sound 836 

419.  Comparative — Historical 837 

3.  SMELL. 

420.  Structure  of  the  Organ  of  Smell 839 

421.  Olfactory  Sensations" 840 

4.  TASTE. 

422.  Position  and  Structure  of  the  Organs  of  Taste 841 

423.  Gustatory  Sensations 842 

5.  TOUCH. 

424.  Terminations  of  Sensory  Nerves 844 

425.  Sensory  and  Tactile  Sensations 846 

426.  The  Sense  of  Locality 847 

427.  The  Pressure  Sense 850 

428.  The  Temperature  Sense 852 

429.  Common  Sensation — Pain 853 

430.  The  Muscular  Sense 854 

XV.    PHYSIOLOGY    OF    REPRODUCTION    AND    DEVELOPMENT. 

431.  Forms  of  Reproduction 857 

432.  Testis — Seminal  Fluid 857 

433.  The  Ovary— Ovum— Uterus 862 

434.  Puberty 866 

435.  Menstruation 867 

436.  Penis — Erection      869 


SECTION  PAGE 

437.  Ejaculation — Reception  of  the  Semen 872 

438.  Fertilization  of  the  Ovum 872 

439.  Impregnation  and  Cleavage  of  the  Ovum 873 

440.  Structures  formed  from  the  Epiblast .    .    .  877 

441.  Structures  formed  from  the  Mesoblast  and  Hypoblast 877 

442.  Formation  of  the  Heart  and  Embrjo 878 

443.  Further  Formation  of  the  Body 880 

444.  Formation  of  the  Amnion  and  Allantois 881 

445.  Human  Fcetal  Membranes — Placenta      882 

446.  Chronology  of  Human  Development 886 

447.  Formation  of  the  Osseous  System 888 

448.  Development  of  the  Vascular  System 892 

449.  Formation  of  the  Intestinal  Canal 895 

450.  Development  of  the  Genito-urinary  Organs 897 

451.  Formation  of  the  Central  Nervous  System 900 

452.  Development  of  the  Sense  Organs 901 

453.  Birth 902 

454.  Comparative — Historical 903 


LIST  OF   ILLUSTRATIONS. 


PAGE 


FIGURE 

1.  Human  colored  blood  corpuscles >9 

2.  Apparatus  of  Abbe  and  Zeiss  for  estimating  the  blood  corpuscles 20 

3.  Mixer ^° 

*4.  Gower's  hEemacytometer  [HawAsley) 20 

5.  Red  blood  corpuscles  showing  various  changes  of  shape 21 

6.  Vasoformative  cells 26 

7.  White  blood  corpuscles 29 

*8.  White  blood  corpuscles  (A'lein) 3° 

g.  Amreboid  movements 3^ 

10.  Blood  plates  and  their  derivatives 33 

11.  Hsemoglobin  crystals 3S 

*I2.  Gower's  hcemoglobinometer  (//atiZ/fjAy) 37 

13.  Scheme  of  a  spectroscope      3° 

14.  Various  spectra  of  hfemoglobin 39 

15.  Hjeniin  crystals 43 

16.  Ha;min  crystals  prepared  from  traces  of  blood 43 

17.  Hsematoidin  crystals 44 

*l8.  Hewson's  experiment 5° 

19.  Scheme  of  Pfliiger's  gas  pump 5^ 

20.  Micrococcus,  bacterium,  vibrio 0° 

*2I.   Bacillus  anthracis °° 

*22.   Scheme  of  the  circulation 67 

23.  Muscular  fibres  from  the  heart 68 

24.  Muscular  fibres  in  the  left  auricle 69 

25.  Muscular  fibres  in  the  ventricles 7° 

*26.  Lymphatic  from  the  pericardium  (Crt<j'/fl/)      7' 

*27.  Section  of  the  endocardium  [Cadial) 7' 

*28.  Purkinje's  fibres  (Ranvier) T- 

29.  Cast  of  the  ventricles  of  the  human  heart 1^ 

30.  The  closed  semilunar  valves 77 

*3I,  Various  cardiographs  [Hermann) 79 

32.  Curves  of  the  apex  beat 79 

33.  Changes  of  the  heart  during  systole,  and  sections  of  thorax 80 

*34.  Dog's  heart,  posterior  surface  (LuJwig  ami  //esse) ^2 

*35.  Left  lateral  surface  [Ludwig  and  I/esse) °2 

*36.  Anterior  surface  [Ludwig  and  //esse)      "3 

*37.  Base  of  heart  [Ludwig  and  Hesse)      °3 

*38.  Base  of  heart  in  systole  and  diastole  (Z«</w4'' '""^  •'^''f^^) °^ 

39.  Curves  from  a  rabbit's  ventricle °4 

*40.  Marey's  registering  tambour  [Hermann) "S 

41.  Curves  obtained  with  a  cardiac  sound °" 

42.  Curves  from  the  cardiac  impulse *7 

*43.  Scheme  of  cardiac  cycle *9 

*44.  Position  of  the  heart  in  the  chest  {/.ttschka  and  Cairdiier) 9° 

*45.  Heart  of  frog  from  the  front  [E(ker) 94 

*46.   Heart  of  frog  from  behind  [Ecker)      94 

*47.  Auricular  septum  [Ecker)      95 

48.  Bipolar  nerve  cells  from  a  frog's  heart 95 

49.  Frog's  heart  (^I'/J'tv) 95 

*49a.  Scheme  of  frog's  heart  [Brunton)      95 

*50.  Stannius's  experiment  [Brunton) 97 

*5i.  Scheme  of  a  frog  manometer  {^Stirling) 9° 

*52.  Perfusion  cannula  [Kronecker  and  Stirling) 9" 

*53.  Roy's  tonometer  (Stirling) 99 

*54.  Luciani's  groups  of  cardiac  pulsations  (AVrwffHK) 1°° 

*55.  Curves  of  a  frog's  heart  at  different  temperatures  (//(■)•»;<;««) lOl 

xxi 


XXU  ILLUSTRATIONS. 

FIGURE  PAGE 

56.  Cardio-pneumograph  of  Landois 104 

57.  Apparatus  for  showing  the  effect  of  respiration 106 

58.  Cylindrical  vessel  filled  with  water 108 

59.  Cylindrical  vessel  with  manometers 109 

60.  Small  artery  with  its  various  coats Ill 

61.  Capillaries  injected  with  silver  nitrate 112 

*62.  Longitudinal  section  of  a  vein  at  a  valve  (Caa'iVi^) 114 

63.  Poiseuille's  pulse  measurer      117 

64.  Sphygmometer  of  Herisson 117 

65.  Scheme  of  Marey's  sphygmograph 118 

*66.  Marey's  improved  sphygmograph  [B.  Bramwell) 1 18 

*67.  Scheme  of  Marey's  sphygmograph  in  working  order  (B.  Bramwell) 118 

*68.   Scheme  of  Marey's  sphygmograph  (B.  Brannvell) 118 

*69.   Dudgeon's  sphygmograph  [Dud^^eoti) 1 19 

*70.   Mode  of  applying  Dudgeon's  sphygmograph  (Z)«i4'fC7;) 119 

*7i.  Sphygmogram  (Dudgeon) 120 

72.  Scheme  of  Brondgeest's  pansphygmograph      120 

73.  Scheme  of  Landois'  angiograph 121 

74.  Pulse  curves  of  the  carotid,  radial,  and  posterior  tibial  arteries      121 

75.  Landois's  gas  sphygmoscope 122 

76.  Hasmautographic  curve 122 

*77.  Sphygmogram  of  radial  artery  (Dudgeon) 123 

78.  Sphygmograms  of  various  arteries      123 

79.  Pulsus  dicrotus,  P.  caprizans,  P.  monocrotus 124 

*8o.  Aortic  regurgitation      126 

*8l.  Pulsus  dicrotus      126 

*S2.  Hyperdicrotic  pulse      127 

83.  Pulsus  alternans 128 

84.  Curves  of  the  posterior  tibial  and  pedal  arteries 130 

85.  Anacrotic  pulse  curves 130 

86.  Anacrotic  pulse  curves 13' 

87.  Influence  of  the  respiration  on  the  sphygmogram 131 

88.  Pulse  curves  during  Miiller's  and  Valsalva's  experiments       132 

89.  Pulsus  paradoxus 133 

90.  Various  radial  curves  altered  by  pressure       134 

91.  Apparatus  for  measuring  the  velocity  of  the  pulse  wave 135 

92.  Tracing  obtained  from  91 1 35 

93.  Pulse  tracings  of  the  radial  artery 136 

94.  Tracings  from  the  posterior  tibial  and  carotid  arteries 136 

95.  Apparatus  for  registering  the  molar  motions  of  the  body 138 

96.  Vibration  and  heart  curves      138 

97.  Ludwig  and  Kick's  kymographs 14I 

♦98.   Ludwig's  improved  revolving  cylinder  (Nermann) , 142 

*99.  Blood- pressure  tracing  of  the  carotid  of  a  dog  (Hermann) 143 

*IOO.  pick's  spring  manometer,  by  Hering  (Hermann) 144 

lOI.   Kick's  flat-spring  kymograph 144 

*I02.  Scheme  of  height  of  blood  pressure      145 

^103.  Depressor  curve  (S/irling) 147 

104.   Blood  pressure  and  respiration  tracings  taken  simultaneously 147 

*io5.  Blood  pressure  tracing  during  stimulation  of  the  vagus  (Stirling) 149 

^  °  ■    l  Apparatus  of  V.  Kries  for  capillary  pressure  (C.  Ludzvig) 151 

*lo8.  Scheme  of  the  blood  pressure 152 

109.  Volkmann's  hajmadromometer 156 

no.  Ludwig  and  Dogiel's  rheometer 156 

111.  Vierordt's  hcematachometer 156 

112.  Dromograph      IS7 

113.  Scheme  of  sectional  arei  (after  Yeo) IS7 

114.  Diapedesis 162 

115.  Various  forms  of  venous  pulse 166 

116.  Mosso's  plethysmograph 168 

*II7.  Trabecuke  of  the  spleen  (Cadiat) 172 

*Il8.  Adenoid  tissue  of  spleen  (Cadiat) I72 

*II9.   Malpighian  corpuscle  of  the  spleen  (Caaiat) 173 

*I20.  Tracing  of  a  splenic  cur\'e  (J^oy) 176 

*I2I.  Thymus  gland  (Cadiat) 1 78 


ILLUSTRATIONS. 


FIGURE 


122.  Elements  of  the  thymus  gland  [Cadial) 178 

♦123.  Thyroid  gland  (Gi,/;;?/) 179 

*I24.  Suprarenal  capsule  (Cadiat) j8o 

*I25.  Human  bronchus  [Hamilton') ^.    .    .    .  1S4 

*126.  Air  vesicles  injected  with  silver  nitrate  {Hamilton) 186 

127.  Scheme  of  the  air  vesicles  of  lung 187 

*I28.  Interlobular  septa  of  lung  (//ij»«'//<7«) 188 

1 29.  Scheme  of  Hutchinson's  spirometer I9I 

130.  Marey's  stethograph  (Af  A'enJrici) 193 

131.  Brondgeest's  tambour  and  curve 193 

132.  Pneumatogram  .  • 194 

133.  Section  through  diaphragm  {Hermann) 198 

134.  Action  of  intercostal  muscles 199 

135.  Cyrtometer  curve 201 

136.  Sibson's  thoracometer 202 

137.  Topography  of  the  lungs  and  heart 202 

138.  Andral  and  Gavarret's  respiration  apparatus 210 

139.  Scharling's  apparatus 210 

140.  Regnault  and  Reiset's  apparatus 211 

141.  V.  Pettenkofer's  apparatus 211 

142.  Valentin  and  Brunner's  apparatus 213 

143.  Ciliated  epithelium  {Sckenk) 225 

144.  Objects  found  in  sputum 22S 

♦145.  Squamous  epithelium  of  mouth 232 

146.  Mucous  follicle  {Scheni) 233 

147.  Rodded  epithelium  of  a  salivary  duct 233 

148.  Histology  of  the  salivary  glands 234 

*I49.  Human  submaxillary  gland  {Hddenhain) 235 

^150.    I  gecjions  of  a  serous  gland  (v^/aVw^aiK) 236 

*I52.  Diagram  of  a  salivary  gland  (Z.  .5/-««/ok) 240 

153.  Apparatus  for  estimation  of  sugar 247 

154.  Polarization  apparatus      247 

155.  Vertical  section  of  a  tooth 250 

156.  Dentine  25° 

157.  Interglobular  spaces 250 

158.  Dentine  and  enamel 251 

159.  Dentine  and  crusta  petrosa      251 

160.  \ 

161.  !■  Development  of  a  tooth 252 

162.  j 

163.  Section  of  oesophagus  (Schenk) 256 

164.  Perinjeum  and  its  muscles 260 

165.  Levator  ani  externus  and  internus 261 

*l66.  Auerbach's  plexus  (Caa'/i?/) 263 

*l67.   Meissner's  plexus  {Cadiat)      264 

168.  Goblet  cells 266 

169.  Surface  section  of  gastric  mucous  membrane 266 

170.  Fundus  gland  of  the  stomach 267 

171.  Pyloric  gland 267 

172.  Scheme  of  the  gastric  mucous  membrane      268 

*I73.  Pyloric  mucous  membrane  (Hermann)      270 

*I74.  Pyloric  glands  during  digestion  [Hermann) 270 

*I75.  Scheme  of  pyloric  fistula  ( .S/!>//«^) 271 

*I76.  Section  of  the  tubes  of  the  pancreas  {//<frw<«»») 278 

177.  Changes  of  the  pancreatic  cells  during  activity 279 

178.  Scheme  of  a  liver  lobule 285 

*I79.   Human  liver  cells  (Cadial) 286 

*l8o.   Liver  cells  during  fasting  (Hermann) 286 

181.  Bile  ducts 287 

182.  Various  appearances  of  the  liver  cells 287 

183.  Interlobular  bile  duct 287 

*l84.  Cholesterin  {Ailken) 296 

*l85.  Biliary  fistula:  (Stirling)       298 

186.  Longitudinal  section  of  the  small  intestine  {Schenk) 304 

187.  Transverse  section  of  Lieberkiihn's  follicles  {Schenk) 305 


xxiv  ILLUSTRATIONS. 

PIGURK  PAGB 

*l8S.  Schemata  of  intestinal  fistulae  {S/ir/iMg) 305 

*|89.  Moreau's  fistula  (after  Brunton) 306 

190.  Bacterium  aceti  and  B.  butyricus 308 

191.  Bacillus  subtilis 3°9 

192.  Bacteria  of  fieces      3'3 

*I93.  Scheme  of  intestinal  absorption  (Beaunis) 319 

*I94.  Villi  of  smalliniestine  injected  (Gi(?'ia/) 320 

195.  Scheme  of  an  intestinal  villus 320 

196.  Injected  villus  (S<hfnk) 32I 

*I97.   Villi  and  Lieberkiihn's  follicles  (CatZ/rt/) 322 

*I98.  Section  of  a  solitary  follicle  ( Cfl(//a/J '. 323 

*I99.   Section  of  a  Peyers  patch  (  Ca(/ja/) 323 

*200.  Section  of  Auerbach's  plexus  ( Cadiat) 324 

20I.  Section  of  large  intestine  {Schetik) 324. 

*202.  Lieberkiihn's  gland  (Hermann) 325 

203.  Endosmometer 3^^ 

204.  Origin  of  lymphatics  in  the  tendon  of  diaphragm 333 

*205.  Lymphatics  of  diaphragm  silvered  (Banvier) 334 

206.  Perivascular  lymphatics 334 

207.  Stomata  from  lymph  sack  of  frog 334 

208.  Section  of  two  lymph  follicles 335 

*209.  Scheme  of  a  lymphatic  gland  {Sharpey) 336 

210.   Part  of  a  lymphatic  gland 337 

*2II.  Section  of  the  central  tendon  of  diaphragm  (-ffr««/c«) 342 

*2I2.  Section  of  fascia  lata  of  a  dog  (5)-ttH/cH) 342 

*2I3.  Lymph  hearts  (Ecier) 343 

214.  Water  calorimeter  of  Favre  and  Silbermann 347 

215.  Walferdin's  metastatic  thermometer 351 

216.  Scheme  of  thermo-electric  arrangements 352 

217.  Kopp's  apparatus  for  specific  heat 356 

218.  Daily  variations  of  temperature 359 

*2I9.  Acini  of  the  mammary  gland  of  a  sheep  (G;a'/«/j 375 

220.  Milk  glands  during  inaction  and  secretion 376 

*22I.  Milk  and  colostrum  (Stirling) 377 

*222.  Section  of  a  grain  of  wheat  (Blyth) .' 384 

223.  Yeast  cells  growing 387 

224.  Composition  of  animal  and  vegetable  foods 391 

^225.  Starch  grains 4'^ 

*226.  Longitudinal  section  of  the  kidney  (I/c-nlf) 419 

*227.  Malpighian  pyramid  (  73'Ji'K  a/Ztv  Z«(/7wV)      420 

228.  Scheme  of  the  uriniferous  tubules  {Klein  and  XobU  Smith) 421 

229.  Scheme  of  the  structure  of  the  kidney 422 

230.  Glomerulus  and  renal  tubules 423 

*23I.  Convoluted  renal  tubule  (Heidenliain) 424 

*232.   Irregular  tubule  (  Tyson  after  A'/ein) 424 

♦233.  Transverse  section  of  the  apex  of  a  Malpighian  pyramid  (Caa'/rt/) 426 

*234.  Development  of  a  glomerulus  (Cadiat) 426 

235A. Graduated  urinary  flask 427 

235B.Urinometer 4^7 

236.  Graduated  burette 429 

237.  Urea  and  urea  nitrate 43" 

*238.  Oxalate  of  urea  (a//«- jSm/,?) 43' 

239.  Urameter  (Cliarteris) 433 

240.  Squibb's  method  for  urea  (Martindale) 433 

241.  Graduated  pipette 433 

♦242.  Uric  acid 434 

*243.  Uric  acid  (  »£•<//) 434 

244.  Kreatinin-zinc  chloride 437 

*245.  Oxalate  of  lime  ( Wedl) 437 

*246.  Oxalate  of  lime 437 

247.  Hippuric  acid 43^ 

248.  Spermatozoa  and  calcic  phosphate 442 

249.  Deposit  in  urine  during  the  '•  acid  fermentation  " 444 

250.  Deposit  in  ammoniacal  urine 444 

251.  Deposit  in  ammoniacal  urine 444 

*252.  Animonio-magnesic  phosphate  and  urates 444 


ILLUSTRATIONS. 


PICURB 


253.  Blood  corpuscles  in  urine 44^ 

254.  Peculiar  forms  of  blood  corpuscles 44^ 

255.  Colored  and  colorless  corpuscles  in  urine 449 

256.  Blood  corpuscles  and  triple  phosphate .    .    .  449 

257.  Spectroscopic  examination  of  urine 45° 

*257A.Picro-Saccharimeter  [G.  Johnson) 453 

♦258.   lno&\i  (Beale  ,ifter  Fxnke) 453 

259.  Cystin  and  oxalate  of  lime 454 

260.  Leucin,  tyrosin  and  ammonium  urate 454 

261.  Epithelium  from  the  genitourinary  apparatus 455 

262.  Micrococci  and  fungi  in  urine 45^ 

263.  Blood  and  granular  tube  casts 45^ 

264.  Hyaline  casts 457 

*2b$.  Oncamelex  (Stirling,  after  Jioy) 467 

*266.  Oncograph  (Stirling,  after  Hoy) 4^7 

*267.  Renal  oncograph  curve  (Stirling,  after  Koy) 468 

*268.  Transitional  epithelieum  (Beale) 47' 

269.  View  of  the  trigone  of  the  bladder 471 

*270.  Nervous  mechanism  of  micturition  (/'071'fr) 474 

*27I.  Section  of  epidermis  and  its  nerves 477 

272.  Scheme  of  the  structure  of  the  skin 47^ 

273.  Vertical  section  of  the  skin 479 

*274.  Papillae  of  the  skin  injected 479 

*275.  Margarin  crystals  in  fat  cells 479 

276.  Transverse  section  of  a  nail 480 

277.  Transverse  section  of  a  hair  follicle 481 

278.  Section  of  a  hair  follicle 48' 

279.  Sebaceous  gland 4^3 

280.  Ciliated  epithelium 49' 

281.  Histology  of  muscular  tissue 494 

*282.   Muscular  fibre  (  Quain) 495 

283.  Tendon  attached  to  a  muscle 49^ 

*284.  Injected  blood  vessels  of  muscle  (A'olliker) 496 

285.  Motorial  end  plates 497 

286.  Termination  of  a  nerve  in  muscle      498 

*287.  Nerve  ending  in  smooth  muscle  (Cadiat) 499 

*288.  Non-striped  muscle  cell  (Stirling)      499 

*289.  Frog  with  its  sciatic  artery  ligatured 508 

*290.  Scheme  of  the  curara  experiment  (a/?!"/- A'«//4^//o7a) 509 

*29I.  Platinum  electrodes  (£lliott  Brotliers) 509 

292.  Microscopic  appearances  in  contracting  muscle 512 

293.  Helmholtz's  myograph 5'3 

*294.  Pendulum  myograph 5^4 

*295.  Scheme  of  the  pendulum  myograph  (Stirling) 515 

*296.   Du  Bois-Reymond's  spring  myograph 516 

297.   Muscle  curve 5'^ 

*298.   Muscle  curve  (Rutherford) 5'7 

*299.  Method  of  studying  a  muscular  contraction  (after  Rutherford) 518 

300.  Muscle  curves S'9 

301.  Muscle  curves,  opening  and  closing  shocks 519 

302.  Muscle  curves,  tetanus 5^' 

♦303.  Curves  of  a  red  and  pale  muscle  (A>o«C£.*i?r  aK(/5/i>/;>jf) 522 

♦304.   Muscle  caT\es  (K'ronecker  and  Stirling) 522 

*305.  Tone  inductorium  (Kroneeker  and  Stirling) 522 

*3o6.   Muscle  curves  (Marey) 5^4 

♦307.   Height  of  the  lift  by  a  muscle 525 

*3o8.  Dynamometer 5^^ 

*309.  Curves  of  elasticity  (after  Marey) 527 

*3lo.  Curve  of  elasticity  of  a  muscle  (after  Marey)      527 

311.  Curve  of  elasticity  (Marey) 527 

*3I2.  Fatigue  curve  (Waller) 533 

*3I3.  Orders  of  levers 53^ 

*3I4.  Scheme  of  the  action  of  muscles  on  bones 537 

315.  Phases  of  walking 54' 

316.  Instantaneous  photograph  of  a  person  walking 542 

317.  Instantaneous  photograph  of  a  runner 543 


XXVI  ILLUSTRATIONS. 

FIGURE  PAGE 

31S.   Instantaneous  photograph  of  a  person  jumping 543 

319.  Larynx  from  the  front 546 

320.  Larynx  from  behind 546 

321.  Larynx  from  behind 547 

322.  Nerves  of  the  larynx 547 

323.  Action  of  the  posterior  crico-arytenoid  muscles 548 

324.  Action  of  the  arytenoid  muscles 548 

325.  Action  of  the  lateral  crico-arytenoid  muscles 549 

326.  Vertical  section  of  the  head  and  neck 550 

327.  Examination  of  the  larynx 551 

328.  Laryngoscopic  view  of  the  larynx 552 

329.  View  of  the  larynx  during  a  high  note 553 

330.  View  of  the  larynx  during  a  deep  inspiration 553 

331.  Rhinoscopy 553 

332.  View  of  the  posterior  nares 553 

333.  Parts  concerned  in  phonation 556 

334.  Tumors  on  the  vocal  cords  .    .    > 558 

335.  Histology  of  nervous  tissues 562 

*336.  Sympathetic  nerve  fibre  (Ranvier) 563 

*337.  Transverse  sections  of  nerve  fibres 563 

338.  Medullated  ner\e  fibre 563 

*339.  Ranvier's  crosses  {Kaiivier) 563 

340.  Transverse  section  of  a  nerve 5^5 

*34I.  Cell  from  the  Gasserian  ganglion  (Schwalbc-) 566 

342.  Degeneration  and  regeneration  of  nerve  fibres 573 

*343.  Waller's  experiments  (after Valton) 574 

344.  Rheocord  of  Du  Bois  Keymond 578 

345.  Scheme  of  a  galvanometer 580 

*346.  Large  Grove's  battery  [Gsiheidlen) 580 

*347.  Grennet's  battery  (Gscheidlen) 581 

*348.  Leclanche's  element  [Gscheidlen) 581 

*349.   Non-polarizable  electrodes  (Elliott  Brothers) 582 

*350.  Thomson's  galvanometer  (i^/Z/o// ^roMcA-i)      583 

*35I.   Lamp  and  scale  (Elliott  Brothers) 583 

*352.  Galvanometer  shunt  (Elliott  Brothers) 583 

*353*  Scheme  of  the  induced  currents  (Hermann) 585 

*354.  Helmholtz's  modification  (Hermann) 585 

355.  Scheme  of  an  induction  machine 586 

*356.   Inductorium  (Elliott  Brothers) 587 

357.  StShrer's  apparatus 587 

*358.   YnzlSonV^'j  (Elliott  Brothers) 587 

*359-  P'ug  key  (Elliott  Brothers) 588 

*36o.  Capillary  contact  (Kronceker  and  Stirling)      588 

361.  Scheme  of  the  muscle  current 589 

362.  Capillary  electrometer 589 

*363.  Secondary  contraction 592 

*364.  Nen-e-niuscie  preparation 592 

365.  Bernstein's  differential  rheotome 593 

366.  Nerve  current  in  electrotonus 595 

367.  Scheme  of  electrotonic  excitability 598 

368.  Method  of  testing  electrotonic  excitability 599 

369.  Distribution  of  an  electrical  current 599 

370.  Velocity  of  nerve  energy 603 

*37i.  Scheme  for  testing  velocity  of  a  nerve  impulse 604 

*372.  Curves  of  a  nerve  impulse  (Marey) 604 

*373-  Sponge  rheophores  (  Weiss) 607 

*374.  Disk  rheophore  (  Weiss) 607 

*375.  Metallic  brush  (  Weiss) 607 

376.  Motor  points  of  the  arm 608 

377.  Motor  points  of  the  arm 608 

378.  Motor  points  of  the  leg 609 

379.  Motor  points  of  the  leg 610 

*38o.  Scheme  of  a  reflex  act  (Stirling) 615 

381.  Optic  chiasma 617 

*382.  Decussation  of  the  optic  tracts  ( C4«/-fo/) 618 

*383.  Scheme  of  images  in  squinting  (Bristowe) 619 


ILLUSTRATIONS. 


FIGURE 


384.  Medulla  oblongata 620 

*385.  Under  surface  of  the  brain 622 

386.  Connections  of  the  cranial  nerves 625 

387.  Sensory  nerves  of  the  face 629 

388.  Motor  points  of  the  face  and  neck '  .    .    .    .  633 

*389.  Disposition  of  the  semicircular  canals  (  W.  Stirling) 636 

*390.  Cardiac  nerves  of  the  rabbit  ( IV.  Stirling) 640 

*39i.  Spinal  ganglion  (Cadiat) 646 

392.  Cutaneous  nerves  of  the  arm 647 

393.  Cutaneous  nerves  of  the  leg  [Henh]      647 

394.  Transverse  section  of  the  spinal  cord 654 

*395.  Transverse  section  of  the  white  matter  (Cndiai) 655 

*396.  Multipolar  nerve  cells  of  the  cord  ( Car//rt/) 655 

*397.  Relation  of  while  and  gray  matter  of  the  cord  (Sc/ui/er) 655 

*398.  Transverse  sections  of  the  spinal  cord 656 

*399.  Transverse  section  of  the  cord  (Cadiat) 657 

*400.   Longitudinal  section  of  i\i&  cori  {Cadiat) 658 

*40i.   Multipolar  nerve  cell 658 

*402.  Injected  blood  vessels  of  the  cord  [Kolliker) 658 

403.  Conducting  paths  in  the  cord 658 

*404.  Degeneration  paths  in  the  cord  (j5?-aOT7//(;//) 660 

*405.  Scheme  of  a  reflex  act  (  W.  S/irling) 661 

*406.  Section  of  a  spinal  segment  ( IV.  Stirling) 661 

*407.   Propagation  of  reflex  movements  (i9fa««M)      662 

*4o8.   Effect  of  section  on  half  of  the  cord  (Erb) 674 

*409.  Brain,  ventricles  and  basal  ganglia 675 

410.  Scheme  of  the  brain 676 

*4II.  Connections  of  the  cerebellum 677 

*4I2.  Diagram  of  a  spinal  segment  (5;rtOTTWf//) 680 

*4I3.  Section  across  the  pyramids  (Schwalhe) 681 

*4I4.  Section  of  the  medulla  oblongata  (5(-A7wa//'f) 683 

*4I5.  Section  of  the  olivary  body  (Sc/iwall'e) 683 

*4i6.  Scheme  of  the  respiratory  centres  [Rutherford) 687 

*4I7.  Scheme  of  the  accelerans  fibres  (  M<  5/«V/«i> ) 693 

*4i8.  Cardiac  plexus  of  a  cat  (5y7iw) 694 

*4I9.  Frog  without  its  cerebrum  (Stirling,  after  Goltz) 705 

*420.  Frog  without  its  cerebrum  [Stirling,  after  Goltz) 705 

*42I.  Pigeon  with  its  cerebrum  removed  (a/?^r  Z)a//o») 705 

*422.  Cerebral  convolution 709 

*423.  Cerebral  convolution  injected      7'° 

*424.   Left  side  of  the  human  brain  (jE'c/^^r) 71 1 

*425.  Inner  aspect  of  right  hemisphere  (^£<-/v;^)      712 

*426.  Left  frontal  lobe  and  island  of  Kei\  [Turner)      713 

*427.  Brain  from  above  [Ecker) 7'4 

428.  Cerebrum  of  dog,  carp,  frog,  pigeon,  and  rabbit 716 

429.  Relation  of  the  cerebral  convolutions  to  the  skull 717 

*430.   Molor  cenlKs  [after  Si/iafer  and  Horsley) 718 

*43I.  Motor  areas  (after  Cowers) 7'9 

432.  Psycho-optic  fibres  [Alunk] 722 

*433.  Section  of  a  cerebral  hemisphere  [Horsley)    ■ 726 

*434.  Secondary  degeneration  in  a  crus  ( Chareot)      728 

*435.  Transverse  section  of  the  crus  cerebri  ( C/;(r;ro^) 728 

*436.  Scheme  of  aphasia  (/^;V//M«>h) 73° 

*437.  Scheme  of  aphasia  (iiVA/Zic/OT) •     .  73° 

*438.  Relation  of  the  convolutions  to  the  skull  [R.  W.  Reid) 732 

*439.  Basal  ganglia  and  the  ventricles 734 

*440.  Transverse  section  of  the  right  hemisphere  [Gegenbaur] 736 

*44I.  Fibres  in  pons  [Erb) 73^ 

*442.  Section  of  the  cerebellum  [Saniey) 740 

*443.  Cortex  cerebri  and  its  membranes  [Seh-valbe) 740 

*444.   Pigeon  with  its  cerebellum  removed  [Dalton) 742 

*445.  Circle  of  Willis  ( C/;a?ro/) • 744 

*446.  Ganglionic  arteries  ( Charcot)      745 

*447.  Corneal  corpuscles  [Ranvier)      750 

*448.  Corneal  spaces  (Ranvier) 75° 

449.  Junction  of  the  cornea  and  sclerotic 751 


XXVIll  ILLUSTRATIONS. 

FIGURE  PAGE 

*45o.  Vertical  section  of  cornea  [Ranvier] • 752 

*45I.  Horizontal  section  of  cornea  (j?<7«i'/V>-) 75^ 

452.  Blood  vessels  of  the  eyeball 753 

*453.  Vertical  section  human  retina  (Cadial) 755 

454.  Layers  of  the  retina 755 

*455-  Vertical  section  of  the  fovea  centralis  [Cadial) 756 

*456.  Fibres  of  the  lens  (A'o//ikt-r) 757 

457.  Section  of  the  optic  nerve 758 

458.  Action  of  lenses  on  light "jito 

459.  Refraction  of  light 7^ 

460.  Construction  of  the  refracted  ray 760 

461.  Optical  cardinal  points 762 

462.  Construction  of  the  refracted  ray "jbz 

463.  Construction  of  the  image 763 

464.  Refracted  ray  in  several  media 763 

465.  Visual  angle  and  retinal  image 764 

466.  Scheme  of  the  ophthalmometer 7^5 

467.  Horizontal  section  of  the  eyeball 767 

468.  Scheme  of  accommodation 767 

469.  Sanson-Purkinje's  images 768 

*470.   Phakoscope  (AI' Kendrici) 7^8 

471.  Scheiner's  experiment 77° 

472.  Refraction  of  the  eye 771 

473.  Myopic  eye 77' 

474.  Hypermetrophic  eye 77^ 

475.  Power  of  accommodation 772 

*476.  Diagram  of  astigmatism  (Tv-w/) 775 

477.  Cylindrical  glasses 775 

*478.  Scheme  of  the  nerves  of  the  iris  {-Brb) 777 

*479.  Pupilonieter  ( Gotham') 778 

*4So.   Pupilometer  [Gorham) 778 

481.  Entoptical  shadows 779 

482.  Scheme  of  the  original  ophthalmoscope 781 

483.  Scheme  of  the  indirect  method 782 

484.  Action  of  a  divergent  lens 782 

485.  Action  of  a  divergent  lens 782 

486.  View  of  the  fundus  oculi 783 

*487.  Morton's  ophthalmoscope  (/"/V^a/'rf  OKt/ t«r/7) 783 

*488.  Frost's  artificial  eye  (Frost) 784 

489.  Action  of  the  orthoscope 784 

*490.  Mariotte's  experiment 785 

491.  Horizontal  section  of  the  right  eye 786 

*492.  M' Hardy's  perimeter  ( /'?V/'(7r^  <7«(/ O/rry)      - 787 

*493.  Priestley  Smith's  perimeter  [Pickard  and  Curry) 788 

494.  Perimetric  chart 789 

495.  Geometrical  color  cone 792 

496.  Action  of  light  rays  on  the  retina 793 

*497.   Cones  of  the  retina  (Stirling,  after  Engelmann) 797 

*498.  Irradiation 797 

499.  Scheme  of  the  action  of  the  ocular  muscles 802 

500.  Identical  points  of  the  retina 804 

501.  The  horopter 804 

502.  Two  stereoscopic  drawings 805 

503.  Brewster's  stereoscope 806 

504.  Wheatstone's  stereoscope 806 

505.  Telestereoscope 807 

506.  Wheatstone's  pseudoscope 807 

507.  Rollett's  apparatus 809 

*5o8.  ZoUner's  Imes 809 

509.  Section  of  an  eyelid 8tl 

510.  Scheme  of  the  organ  of  hearing 814 

511.  External  auditory  meatus 816 

512.  Left  tympanic  membrane  and  ossicles 817 

513.  Membrana  tympani  and  ossicles 817 

514.  Tympanic  membrane  from  within 817 


ILLUSTRATIONS.  XXIX 

PFGURE  PAGE 

*5I5.   "E&r  %p&c\i[3.  {Krohiie  and  Sesemann) 8l8 

*5i6.  Toynbee's  artificial  membrana  tj'mpani  (A'r«^«^  aW  Sfie-maww) 8l8 

517.  Right  auditory  ossicles 818 

518.  Tympanum  and  auditory  ossicles 819 

519.  Tensor  tympani  and  Eustachian  tube 821 

520.  Right  stapedius  muscle 822 

*52I.  Eustachian  catheter 823 

*522.   Politzer's  ear  bag  (JCro/me  and  Sesemann) 823 

523.  Right  labyrinth 824 

524.  Scheme  of  the  cochlea 825 

*525.  Interior  of  the  right  labyrinth 826 

*526.  Semicircular  canals 820 

527.  Scheme  of  the  canalis  cochlearis 827 

*S28.  Gallon's  whistle  [Krohite  and  Sesemann) 829 

529.  Curve  of  a  musical  note  and  its  overtones 831 

*530.  Kcenig's  manometric  capsule  {Kanig) 832 

*53i.  Flame  pictures  of  vowels  (A'(r«/i^) 833 

*532.  Kcenig's  analyzing  apparatus  [Ka:>iig) 835 

533.  Olfactory  cells 839 

534.  Nasal  and  pharyngo-nasal  cavities 839 

535.  Circumvallate  papilla  and  taste  bulbs 841 

*S36.  Wagner's  touch  corpuscle  (Jianvifi) 844 

537.  Vertical  section  of  skin 844 

538.  Pacini's  corpuscle 845 

*S39-   Bouchon  epidermique  (Hanvier) 846 

540.  ^^sthesiometer 847 

541.  ^sthesiometer  of  Sieveking 848 

*542.  Aristotle's  experiment 849 

543.  Landois'  pressure  mercurial  balance 850 

*S44.  Karyokinesis  (  Cegenbatir) 856 

*545.  Section  of  testis  (Scheni) 858 

*546.  Tubule  of  testis  {Scheiik) 859 

*547.  Section  of  epididymis  (.Si/ifB.^) 859 

548.  Spermatic  crystals 860 

549.  Spermatozoa      861 

550.  Spermatogenesis 861 

*55I.  h  csl'i  ovary  [Hart  and  Barbour,  aftir  Schron) 862 

*552.  Section  of  an  ovary  (Turner) 863 

553.  Ovary  and  polar  globules 864 

*554.   ^{\xcausmtmhr2MS  o{  ihsuiems  {ffart  and  Barbour,  after  Turner) 865 

*555.  Fallopian  tube  and  its  annexes  (Nenie) 866 

*556.  Section  of  Fallopian  tube  [Scheni) 867 

*S57-  Uterus  before  menstruation  (J.  Williams) 868 

*558.  Uterus  after  menstruation  {J.  IVilliams) 868 

*559.  Erectile  tissue  (Cadiat) 869 

560.  The  urethra  and  adjoining  muscles 871 

561.  Cleavage  of  the  yelk 874 

562.  The  blastoderm 875 

563.  Schemata  of  development 876 

*564.  Embryo  of  the  mole  ( IV.  K.  Parker) 881 

*565.  Uterine  mucous  membrane  (Cw/^) 883 

*566.  Placental  villi  {Cadiat) 884 

567.  Hare  lip 889 

*S68.  Meckel's  cartilage  (  W.  K.  Parker) 889 

569.  Centres  of  ossification  in  the  innominate  bone 890 

570.  Development  of  the  heart 893 

571.  The  aortic  arches 893 

572.  Veins  of  the  embryo 894 

573.  Development  of  the  veins  and  portal  system 895 

574.  Development  of  the  intestine 896 

575.  Development  of  the  lungs 896 

576.  Formation  of  the  omentum 896 

577.  Development  of  the  internal  generative  organs 897 


XXX  ILLUSTRATIONS. 

PIGtTRE  PAGE 

578.  Development  of  the  external  genitals 899 

*s79-  1  r  900 

*cS        I    Changes  in  the  external  organs  of  generation  in  the  female  (after  Schrccder)  .       -j  ^ 

*S82.    J  [  900 

583.  Development  of  the  eye 901 


[The  illustrations  indicated  by  the  word  Hermann  are  from  Hermann's  Handhuch  dcr  Physi- 
ologie;  by  Cadiat,  from  Cadiat's  Traiti  d'Anatomie  Gencrale;  by  Ranvier,  from  Ranvier's  Traite 
Technique  d' Histologie :  by  Brunton,  from  The  Practitioner ;  Brunton's  Text-Book  of  Pharma- 
cology, Therapeutics,  and  Materia  Afedica  ;  by  Schenk,  from  Schenk's  Grundriss  der  normalen 
Histologic  ;  by  Ecker,  from  Ecker's  Anatomie  des  Frosches.'\ 


INTRODUCTION. 


THE  SCOPE  OF  PHYSIOLOGY  AND  ITS  RELATIONS  TO  OTHER  BRANCHES 
OF  NATURAL  SCIENCE. 

Physiology  is  the  science  of  the  vital  phenomena  of  organisms,  or,  broadly, 
it  is  the  Doctrine  of  Life.  Correspondingly  to  the  divisions  of  organisms,  we 
distinguish — (i)  Animal  Physiology  ;  (2)  Vegetable  Physiology  ;  and  {t,)  the  Physi- 
ology of  the  Lowest  Living  Organisms,  which  stand  on  the  border  line  of  animals 
and  plants,  /.  e.,  the  so-called  Protista  oi  Haeckel,  micro-organisms,  and  those 
elementary  organisms  or  cells  which  exist  on  the  same  level. 

The  object  of  Physiology  is  to  establish  these  phenomena,  to  determine  their 
regularity  and  causes,  and  to  refer  them  to  the  general  fundamental  laws  of 
Natural  Science,  viz.,  the  Laws  of  Physics  and  of  Chemistry. 

The  following  Scheme  shows  the  relation  of  Physiology  to  the  allied  branches 
of  Natural  Science  : — 

BIOLOGY. 

The  science  of  organized  beings  or  organisms  (animals,  plants,  protistae,  and 
elementary  organisms). 


L  MORPHOLOGY. 

The  doctrine  of  the  form  of  organ- 
isms. 


IL  PHYSIOLOGY. 


General 
Morphology. 

The  doctrine  of  the 
formed  elementary 
constituents  of  or- 
ganisms. 

(Histology) — 

(a)  Histology     of 

Plants. 

[b)  Histology  of  Ani- 

mals. 


Special 
Morphology. 

The  doctrine  of  the 
parts  and  orgnns  of 
organisms. 


( Organology 
Anatomy) — 

(a)   Phytotomy. 

{/>)  Zootomy. 


The  doctrine  of  the  vital  phenom- 
ena of  organisms. 


General 
Physiology. 

The  doctrine  of  vital 
phenomena  in  gen- 
eral— 

(n)  Of  Plants. 

(l>)  Of  Animals. 


Special 
Physiology, 

The  doctrine  of  the 
activities  of  the  in- 
dividual organs — 

[a)  Of  Plants. 

\b)  Of  Animals. 


in.  EMBRYOLOGY. 

The  doctrine  of  the  generation  and  development  of  organisms. 

fi.  History  of  the  development 
of  single  beings,  of  the  indi- 
vidual (e.g.,  of  man)  from  the 
ovum  onward  (Ontogeny) — 

(a)   In  Plants. 

(/>)   In  Animals. 


Morphological  part  of  the  doc- 
trine of  development,  /.  f., 
the  doctrine  of  form  in  its 
stages  of  development — 

[a)  General. 

[b)  Special. 


2.  History  of  the  development 
of  a  whole  stock  of  organisms 
from  the  lowest  forms  of  the 
series  upward  (Phylogeny) — 

(a)  In  Plants. 

[b)  In  Animals. 

xxxi 


Physiological  part  of  the  doc- 
trine of  development,  /'.  e., 
the  doctrine  of  the  activity 
during  development — 

[a)  General, 

{b)  Special. 


XXXll  INTRODUCTION. 

Morphology  and  Physiology  are  of  equal  rank  in  biological  science,  and  a 
previous  acquaintance  with  Morphology  is  assumed  as  a  basis  for  the  comprehen- 
sion of  Physiology,  since  the  work  of  an  organ  can  only  be  properly  understood 
when  its  external  form  and  its  internal  arrangements  are  known.  Development 
occupies  a  middle  place  between  Morphology  and  Physiology  ;  it  is  a  morpho- 
logical discipline  in  so  far  as  it  is  concerned  with  the  description  of  the  parts  of 
the  developing  organism  ;  it  is  a  physiological  doctrine  in  so  far  as  it  studies  the 
activities  and  vital  phenomena  during  the  course  of  development. 

MATTER. 

The  entire  visible  world,  including  all  organisms,  consists  of  matter,  /.  e.,  of 
substance  which  occupies  space. 

We  distinguish  ponderable  matter  which  has  weight,  and  imponderable  matter 
which  cannot  be  weighed  in  a  balance.     The  latter  is  generally  termed  ether. 

In  ponderable  materials,  again,  we  distinguish  their  form,  i.  e.,  the  nature  of 
their  limiting  surfaces;  further,  their  volume,  i.  e.,  the  amount  of  space  which 
they  occupy ;  and  lastly,  their  aggregate  condition,  i.  e.,  whether  they  are  solid, 
fluid,  or  gaseous  bodies. 

Ether. — The  ether  fills  the  space  of  the  universe,  certainly  as  far  as  the  most 
distant  visible  stars.  This  ether,  notwithstanding  its  imponderability,  possesses 
distinct  mechanical  properties;  it  is  infinitely  more  attenuated  than  any  known 
kind  of  gas,  and  behaves  more  like  a  solid  body  than  a  gas,  resembling  a  gelatin- 
ous mass  rather  than  the  air.  It  participates  in  the  luminous  phenomena  due  to 
the  vibrations  of  the  atoms  of  the  fixed  stars,  and  hence  it  is  the  transmitter  of 
light,  which  is  conducted  by  means  of  its  vibrations,  with  inconceivable  rapidity 
(42,220  geographical  miles  per  second)  to  our  visual  organs  {Tyndall). 

Imponderable  matter  (ether)  and  ponderable  matter  are  not  separated  sharply 
from  each  other  ;  rather  does  the  ether  penetrate  into  all  the  spaces  existing 
between  the  smallest  particles  of  ponderable  matter. 

Particles. — Supposing  that  ponderable  matter  were  to  be  subdivided  continu- 
ously into  smaller  and  smaller  portions,  until  we  reached  the  last  stage  of  division 
in  which  it  is  possible  to  recognize  the  aggregate  condition  of  the  matter  operated 
upon,  we  should  call  the  finely-divided  portions  of  matter  in  this  state  particles. 
Particles  of  iron  would  still  be  recognized  as  solid,  particles  of  water  as  fluid, 
particles  of  oxygen  as  gaseous. 

Molecules. — Supposing,  however,  the  process  of  division  of  the  particles  to 
be  carried  further  still,  we  should  at  last  reach  a  limit  beyond  which,  neither 
by  mechanical  nor  by  physical  means,  could  any  further  division  be  effected. 
We  should  have  arrived  at  the  molecules.  A  molecule,  therefore,  is  the  smallest 
amount  of  matter  which  can  still  exist  in  a  free  condition,  and  which  as  a  unit 
no  longer  exhibits  the  aggregate  condition. 

Atoms. — But  even  molecules  are  not  the  final  units  of  matter,  since  every 
molecule  consists  of  a  group  of  smaller  units,  called  atoms.  An  atom  cannot 
exist  by  itself  in  a  free  condition,  but  the  atoms  unite  with  other  similar  or  dis- 
similar atoms  to  form  groups,  which  are  called  molecules.  Atoms  are  incapable 
of  furtlier  subdivision,  hence  their  name.  We  assume  that  the  atoms  are  invari- 
ably of  the  same  size,  and  that  they  are  solid.  From  a  chemical  point  of  view, 
the  atom  of  an  elementary  body  (element)  is  the  smallest  amount  of  the  element 
which  can  enter  into  a  chemical  combination.  Just  as  ponderable  matter  consists 
in  its  ultimate  parts  of  ponderable  atoms,  so  does  the  ether  consist  of  analogous 
small  ether  atoms. 

Ponderable  and  Imponderable  Atoms. — The  ponderable  atoms  within 
ponderable  matter  are  arranged  in  a  definite  relation  to  the  ether  atoms.  The 
ponderable  atoms  mutually  attract  each  other,  and  similarly  they  attract  the  im- 
ponderable ether  atoms  ;  but  the  ether  atoms  repel  each  other.     Hence,  in  pon- 


INTRODUCTION,  XXXIII 

derable  masses,  ether  atoms  surround  every  ponderable  atom.  These  masses,  in 
virtue  of  the  attraction  of  the  ponderable  atoms,  tend  to  come  together,  but  only 
to  the  extent  permitted  by  the  surrounding  ether  atoms.  Thus  the  ponderable 
atoms  can  never  come  so  close  as  not  to  leave  interspaces.  All  niatter  must, 
therefore,  be  regarded  as  more  or  less  loose  and  open  in  texture,  a  condition  due 
to  the  interpenetrating  ether  atoms,  which  resist  the  direct  contact  of  the  ponder- 
able atoms. 

Aggregate  Condition  of  Atoms. — The  relative  arrangement  of  the  mole- 
cules, /.  e.,  the  smallest  particles  of  matter  which  can  be  isolated  in  a  free  condi- 
tion, determines  the  aggregate  condition  of  the  body. 

Within  a  solid  body,  characterized  by  the  permanence  of  its  volume  as  well  as 
by  the  independence  of  its  form,  the  molecules  are  so  arranged  that  they  cannot 
readily  be  displaced  from  their  relative  position. 

Fluid  bodies,  although  their  volume  is  permanent,  readily  change  their  shape, 
and  their  molecules  are  in  a  condition  of  continual  movement. 

When  this  movement  of  the  molecules  takes  so  wide  a  range  that  the  individual 
molecules  fly  apart,  the  body  becomes  gaseous,  and  as  such  is  characterized  by 
the  instability  of  its  form  as  well  as  by  the  changeableness  of  its  volume. 

Physics  is  the  study  of  these  molecules  and  their  motions. 

FORCES. 

I.  Gravitation — ^Al^o^k  done. — All  phenomena  appertain  to  matter.  These 
phenomena  are  the  appreciable  expression  of  the  forces  inherent  in  matter.  The 
forces  themselves  are  not  appreciable,  they  are  the  causes  of  the  phenomena. 

Gravitation. — The  law  of  gravitation  postulates  that  every  particle  of  pon- 
derable matter  in  the  universe  attracts  every  other  particle  with  a  certain  force. 
This  force  is  inversely  as  the  square  of  the  distance.  Further,  the  attractive  force 
is  directly  proportional  to  the  amount  of  the  attracting  matter,  without  any  refer- 
ence to  the  quality  of  the  body.  We  may  estimate  the  intensity  of  gravitation 
by  the  extent  of  the  movement  which  it  communicates  to  a  body  allowed  to  fall, 
for  one  second,  through  a  given  distance,  in  a  space  free  from  air.  Such  a  body 
will  fall  in  vacuo  9.809  metres  per  second.  This  fact  has  been  arrived  at  experi- 
mentally. 

Let  us  represent  i;  =  9.809  metres,  the  final  velocity  of  the  freely  falling  body  at  the  end  of  one 
second.     The  velocity,  V,  of  the  freely  falling  body  is  proportional  to  the  time,  /,  so  that 

V=.?/ (I); 

i.e.,  at  the  end  of  the  1st  sec,  V  =^,  i  =^'-  =:  9.S09  M — the  distance  traversed — 

s  =S^  r- (2); 

2 

i.e.,  the  distances  are  as  the  square  of  the  times.  Hence,  from  (i)  and  (2)  it  follows  (by  eliminat- 
ing /)  that — 

V  =   y'2is (3). 

The  velocities  are  as  the  square  roots  of  the  distances  traversed — 

Therefore,  ^  .r (4). 

~S 
The  freely  falling  body,  and  in  fact  every  freely  moving  body,  possesses  kinetic 
energy,  and  is  in  a  certain  sense  a  magazine  of  energy.  The  kinetic  energy  of 
any  moving  body  is  always  equal  to  the  product  of  its  weight  (estimated  by  the 
balance),  and  the  height  to  which  it  would  rise  from  the  earth,  if  it  were  thrown 
from  the  earth  with  its  own  velocity. 

Let  \V  represent  the  kinetic  energy  of  the  moving  body,  and  P  its  weight,  then  W  =  V.s,  so  that 
from  (4)  it  follows  that — 

W=P''' (5). 

%' 

Hence,  the  kinetic  energy  of  a  body  is  proportional  to  the  square  of  its  velocity. 


XXXIV  INTRODUCTION. 

Work. — If  a  force  (pressure,  strain,  tension)  be  so  applied  to  a  body  as  to  move 
it,  a  certain  amount  of  work  is  performed.  The  amount  of  work  is  equal  to  the 
product  of  the  amount  of  the  pressure  or  strain  which  moves  the  body,  and  of  the 
distance  through  which  it  is  moved. 

Let  K  represent  the  force  acting  on  the  body,  and  S  the  distance,  then  the  worl<  W  =:  KS.  The 
attraction  between  the  earth  and  any  body  raised  above  it  is  a  source  of  worlc. 

It  is  usual  to  express  the  value  of  K  in  kilogrammes,  and  .S  in  metres,  so  that 
the  "unit  of  work"  is  the  kilogramme-metre,  i.e.,  the  force  which  is  re- 
quired to  raise  i  kilo,  to  the  height  of  i  metre. 

2.  Potential  Energy. —  The  iransfiirmation  of  Potenfial  into  Kiintic  energy 
anil  conversely:  Besides  kinetic  energy,  there  is  also  "potential  energy,"  or 
energy  of  position.  By  this  term  are  meant  various  forms  of  energy,  which  are 
suspended  in  their  action,  and  which,  although  they  may  cause  motion,  are  not 
in  themselves  motion.  A  coiled  watch-spring  kept  in  this  position,  a  stone  resting 
upon  a  tower,  are  instances  of  bodies  possessing  potential  energy,  or  the  energy  of 
position.  It  requires  merely  a  push  to  develop  kinetic  from  the  potential  energy, 
or  to  transform  potential  into  kinetic  energy. 

Work,  w,  was  performed  in  raising  the  stone  to  rest  upon  the  tower. 

w  --: /,  s,  where/  =  the  weight  and  s  =  the  height. 
p  =  m  .g,  is  ^  the  product  of  the  mass  (m),  and  the  force  of  gravity  ( g'),  so  that  to  =  m  g  s. 

This  is  at  the  same  time  the  expression  for  the  potential  energy  of  the  stone. 
This  potential  energy  may  readily  be  transformed  into  kinetic  energy  by  merely 
pushing  the  stone  so  that  it  falls  from  the  tower.  The  kinetic  energy  of  the  stone 
is  equal  to  the  final  velocity  with  which  it  impinges  upon  the  earth. 

V    =  -\/ig  s  (see  above  (3)  ). 
V2  =        2gS. 
mV-  =      2m  s  s. 


m  g  s  was  the  expression  tor  the  potential  energy  of  the  stone  while  it  was  still  rest- 
ing on  the  height ;  —  Vj  is  the  kinetic  energy  corresponding   to   this  potential 

energy  (^Briickc'). 

Potential  energy  may  be  transformed  into  mechanical  energy  under  the  most 
varied  conditions ;  it  may  also  be  transferred  from  one  body  to  another. 

The  movement  of  a  pendulum  is  a  striking  example  of  the  former.  When  the  pendulum  is  at 
the  highest  point  of  its  excursion,  it  must  be  regarded  as  absolutely  at  rest  for  an  instant,  and  as  en- 
dowed with  potential  energy,  thus  corresponding  with  the  raised  stone  in  the  previous  instance. 
During  the  swing  of  the  pendulum  this  potential  energy  is  changed  into  kinetic  energy,  which  is 
greatest  when  the  pendulum  is  moving  most  rapidly  toward  the  vertical.  As  it  rises  again  from  the 
vertical  po.sition,  it  moves  more  slowly,  and  the  kinetic  energy  is  changed  mto  potential  energy, 
which  once  more  reaches  its  maximum  when  the  pendulum  comes  to  rest  at  the  utmost  limit  of  its 
excursion.  Were  it  not  for  the  resistances  continually  opposed  to  its  movements,  such  as  the  resist- 
ance of  the  air  and  friction,  the  movement  of  the  pendulum,  due  to  the  alternating  change  of  kinetic 
into  potential  energy  and  viie  versa.,  would  continue  uninterruptedly,  as  with  a  mathematical  pendu- 
lum. Suppose  the  swinging  ball  of  the  pendulum,  when  exactly  in  a  vertical  position,  impinged 
upon  a  resting  but  moving  sphere,  the  potential  energy  of  the  ball  of  the  pendulum  would  be  trans- 
ferred directly  to  the  sphere,  provided  that  the  elasticity  of  the  ball  of  the  pendulum  and  the  sphere 
were  complete ;  the  pendulum  would  come  to  rest,  while  the  sphere  would  move  onward  with  an 
equal  amount  of  kinetic  energy,  provided  there  were  no  resistance  to  its  movement.  This  is  an  ex- 
ample of  the  transference  of  kinetic  energy  from  one  body  to  another.  Lastly,  suppose  that  a 
stretched  watch-spring  on  uncoiling  causes  another  spring  to  become  coiled  ;  and  we  have  another 
example  of  the  transference  of  kinetic  energy  from  one  body  to  another. 

The  following  general  statement  is  deducible  from  the  foregoing  examples  :  If, 
in  a  system,  the  individual  moving  masses  approach  the  final  position  of  equili- 
brium, then  in  this  system  the  sum  of  the  kinetic  energies  increases  ;  if,  on   the 


INTRODUCTION.  XXXV 

other  hand,  the  particles  move  away  from  the  final  jjosition  of  equilibrium,  then 
the  sum  of  the  potential  energies  is  increased  at  the  expense  of  the  kinetic  ener- 
gies, i.e.,  the  kinetic  energies  diminish  {^BriUke'). 

The  pendulum,  which,  after  swinging  from  the  highest  point  of  its  excursion,  approaches  the  ver- 
tical position,  i.e.,  the  position  of  equilibrium  of  a  passive  pendulum,  has  in  this  position  the  largest 
amount  of  potential  energy  ;  as  it  again  ascends  to  the  highest  point  of  its  excursion  on  the  other 
side,  it  again  gradually  receives  the  maximum  of  potential  energy  at  the  expense  of  the  gradually 
diminishing  movement,  and,  therefore,  of  the  kinetic  energy. 

3.  Heat. — Its  Relation  to  Potential  and  Kinetic  Energy. — If  a  lead  weight  be 
thrown  from  a  high  tower  to  the  earth,  and  if  it  strike  an  unyielding  substance,  the 
movement  of  the  mass  of  lead  is  not  only  arrested,  but  the  kinetic  energy  (which 
to  the  eye  appears  to  be  lost)  is  transformed  into  a  lively  vibratory  moveinent  of 
the  atoms.  When  the  lead  meets  the  earth,  heat  is  produced.  The  amount  of 
heat  produced  is  proportional  to  the  kinetic  energy,  which  is  transformed  through 
the  concussion.  At  the  moment  when  the  lead  weight  reaches  the  earth,  the  atoms 
are  thrown  into  vibrations  ;  they  impinge  upon  each  other ;  then  rebound  again  from 
each  other  in  consei]uence  of  their  elasticity,  which  opposes  their  direct  juxtapo- 
sition ;  they  fly  asunder  to  the  maximum  extent  permitted  by  the  attractive  force 
of  the  ponderable  atoms,  and  thus  oscillate  to  and  fro.  All  the  atoms  vibrate  like 
a  pendulum,  until  their  movement  is  commimicated  to  the  ethereal  atoms  surround- 
ing them  on  every  side,  i.e.,  until  the  heat  of  the  heated  mass  is  "  radiated. '^  Heat 
is  thus  a  vibratory  movement  of  the  atoms. 

As  the  amount  of  heat  produced  is  ]iroportional  to  the  kinetic  energy,  which  is 
transformed  through  the  concussion,  we  must  find  an  adequate  measure  for  both 
forces. 

Heat  Unit. — As  a  standard  of  measure  of  iieat,  we  have  the  "  heat  unit  "  or 
calorie.  The  '•  heat  unit  "  or  calorie  is  the  amount  of  energy  required  to  raise 
the  temijerature  of  i  gramme  of  water  1°  C.  The  "  heat  unit"  corresponds  to 
425.5  gramme-metres,  i.e.,  the  same  energy  required  to  heat  i  gramme  of  water 
1°  C.  would  raise  a  weight  of  425.5  grammes  to  the  height  of  i  metre  ;  or,  a  weight 
of  425.5  grammes,  if  allowed  to  fall  from  the  height  of  i  metre,  would  by  its  con- 
cussion produce  as  much  heat  as  would  raise  the  temperature  of  i  gramme  of  water 
1°  C.  The  "mechanical  equivalent"  of  the  heat  unit  is,  therefore,  425.5 
gramme-metres. 

It  is  evident  that  from  the  collision  of  moving  masses  an  immeasurable  amount  of  heat  can  be 
produced.  Let  us  ajjply  what  has  already  been  said  to  the  earth.  Suppose  the  earth  to  be  dis- 
turbed in  its  orbit,  and  suppose  further  that,  owing  to  the  attraction  of  the  sun,  it  were  to  impinge 
on  the  latter  (whereby,  according  to  J.  R.  Mayer,  its  final  velocity  would  be  85  geographical  miles 
per  second),  the  amount  of  heat  produced  by  the  collision  would  be  equal  to  that  produced  by  the 
combustion  of  a  mass  of  pure  charcoal  more  than  5000  times  as  heavy  {Julius  Robert  Mayer,  Helm- 
holtz). 

Thus,  the  heat  of  the  sun  itself  can  be  produced  by  the  collision  of  masses  of  cold  mitter.  If  the 
cold  matter  of  the  universe  were  thrown  into  space,  and  there  left  to  the  attraction  of  its  particles, 
the  collision  of  these  particles  would  ultimately  produce  the  light  of  the  stars.  At  the  present  time, 
numerous  cosmic  bodies  collide  in  space,  while  innumerable  small  meteors  (94,000  to  188,000  bil- 
lions of  kilos,  per  minute)  fall  hito  the  sun.  The  force  of  gravity  is,  perhaps,  in  fact,  the  only  source 
of  all  heat  (_/.  R.  Mayer,  Yyndatl  ). 

We  have  a  homely  examjile  of  the  transformation  of  kinetic  energy  into  heat  in  the  fact  that  a 
blacksmith  may  make  a  piece  of  iron  red  hot  by  hammering  it.  Of  the  conversion  of  heat  into  ki- 
netic energy,  we  have  an  example  in  the  hot  watery  vapor  (steam)  of  the  steam  engine  raising  the 
piston.  An  example  of  the  conversion  of  potential  energy  into  lieat  occurs  in  a  metallic  spring, 
when  it  uncoils  and  is  so  placed  as  to  rub  against  a  rough  surface,  producing  heat  by  friction. 

4.  Chemical  Affinity  :  Relation  to  Heat. — While  gravity  acts  upon  the 
particles  of  matter  without  reference  to  the  composition  of  the  body,  there  is  an- 
other atomic  force  which  acts  between  atoms  of  a  chemically  different  nature  ;  this 
is  chemical  affinity.  This  is  the  force  in  virtue  of  which  the  atoms  of  chemi- 
cally different  bodies  unite  to  form  a  chemical  compound.  The  force  itself 
varies  greatly  between  the  atoms  of  different   chemical   bodies  ;   thus  we  speak  of 


XXXVl  INTRODUCTION. 

strong  chemical  affinities  and  weak  affinities.  Just  as  we  were  able  to  estimate  the 
potential  energy  of  a  body  in  motion  from  the  amount  of  heat  which  was  produced 
when  it  collided  with  an  unyielding  body,  so  we  can  measure  the  amount  of  the 
chemical  affinity  by  the  amount  of  heat  which  is  formed  when  the  atoms  of  chem- 
ically different  bodies  unite  to  form  a  chemical  compound.  .\s  a  rule,  heat 
is  formed  when  separate  chemically  different  atoms  form  a  compound  body. 
When,  in  virtue  of  chemical  affinity,  the  atoms  of  i  kilo,  of  hydrogen  and  S  kilos, 
of  oxygen  unite  to  form  the  chemical  compound  wah-r,  an  amount  of  heat  is  there- 
by evolved  which  is  equal  to  that  produced  by  a  weight  of  47,000  kilos,  falling 
and  colliding  with  the  earth  from  a  height  of  1000  feet  above  the  surface  of  the 
earth.  If  i  gram,  of  H  be  burned  along  with  the  requisite  amount  of  O  to  form 
water,  it  yields  34,460  heat  units  or  calories ;  and  i  gram,  carbon  burned 
to  carbonic  acid  (carbon  dioxide)  yields  8080  heat  units.  Wherever,  in 
chemical  processes,  strong  chemical  affinities  are  satisfied,  heat  is  set  free,  i.e., 
chemical  affnity  is  changed  into  heat.  Chemical  affinity  is  a  form  of  potential 
energy  obtaining  between  the  most  different  atoms,  which  during  chemical  pro- 
cesses is  changed  into  heat.  Conversely,  in  those  chemical  processes  where  strong 
affinities  are  dissolved,  and  chemically-united  atoms  thereby  pulled  asunder,  there 
must  be  a  diminution  of  temperature,  or,  as  it  is  said,  heat  becomes  latent — that  is, 
the  energy  of  the  heat  which  has  become  latent  is  changed  into  chemical  energy, 
and  this,  after  decomposition  of  the  compound  chemical  body,  is  again  represented 
by  the  chemical  affinity  between  its  isolated  different  atoms. 

LAW  OF  THE  CONSERVATION  OF  ENERGY. 

Julius  Robert  Mayer  and  Helraholtz  have  established  the  important  law  that,  in 
a  system  which  does  not  receive  any  influence  and  impression  from  without,  the 
sum  of  all  the  forces  acting  within  it  is  always  the  same.  The  various  forms  of 
energy  can  be  transformed  one  into  the  other,  so  that  kinetic  energy  may  be  trans- 
formed into  potential  energy,  and  vice  versa,  but  there  is  never  any  part  of  the  energy 
lost.  The  transformation  takes  place  in  such  measure  that,  from  a  certain  definite 
amount  of  one  form  of  energy,  a  definite  amount  of  another  can  be  obtained. 

The  various  forms  of  energy  acting  in  organisms  occur  in  the  following 
modifications  :  — 

1.  Molar  motion  (ordinary  movements),  as  in  the  movements  of  the  whole 
body,  of  the  limbs,  or  of  the  intestines,  and  even  those  observable  microscopically 
in  connection  with  cells. 

2.  Movements  of  Atoms  as  Heat. — We  know,  in  connection  with  the 
vibration  of  atoms,  that  the  number  of  vibrations  in  the  unit  of  time  determines 
whether  the  oscillations  appear  as  heat,  light,  or  chemically-active  vibrations. 
Heat  vibrations  have  the  smallest  number,  while  chemically-active  vibrations  have 
the  largest  number,  light  vibrations  standing  between  the  two.  In  the  human 
body  we  only  observe  heat  vibrations,  but  some  of  the  lower  animals  are  capable 
of  exhibiting  the  phenomena  of  light. 

In  the  human  organism,  the  molar  movements  in  the  individual  organs  are 
constantly  being  transformed  into  heat,  e.  g.,  the  kinetic  energy  in  the  organs  of 
the  circulation  is  transformed  by  friction  into  heat.  The  measure  of  this  is  the 
"unit  of  work "  =  I  gramme-metre,  and  the  "unit  of  heat  "  =  425.5 
gramme-metres. 

3.  Potential  Energy. — The  organism  contains  many  chemical  compounds 
which  are  characterized  by  the  great  complexity  of  their  constitution,  by  the 
imperfect  saturation  of  their  affinities,  and  hence  by  their  great  tendency  to  split 
up  into  simpler  bodies. 

The  body  can  transform  the  potential  energy  into  heat  as  well  as  into  kinetic 
energy,  the  latter  always  in  conjunction  with  the  former,  but  the  former  always  by 
itself  alone.      The  simplest  measure  of  the  potential  energy  is  the  amount  of  heat. 


INTRODUCTION.  XXXVU 

which  can  be  obtained  b\-  complete  combustion  of  the  chemical  compounds 
representing  the  potential  energy.  The  number  of  work  units  can  then  be  calcu- 
lated from  the  amount  of  heat  produced. 

4.  The  phenomena  of  electricity,  magnetism  and  diamagnetism  may  be 
recognized  in  two  directions,  as  movements  of  the  smallest  particles,  which  are 
recognized  in  the  glowing  of  a  thin  wire  when  it  is  traversed  by  strong  electrical 
currents  (against  considerable  resistance),  and  also  as  molar  movement,  as  in  the 
attraction  or  repulsion  of  the  magnetic  needle.  Electrical  phenomena  are  mani- 
fested in  our  bodies  by  muscle,  nerve,  and  glands,  but  these  phenomena  are  rela- 
tively small  in  amount  when  compared  with  the  other  forms  of  energy.  It  is  not 
improbable  that  the  electrical  phenomena  of  our  bodies  become  almost  completely 
transformed  into  heat.  As  yet  experiment  has  not  determined  with  accuracy  a 
"unit  of  electricity"  directly  comparable  with  the  "heat  unit  "  and  the  "work 
unit." 

It  is  quite  certain  that  within  the  organism  one  form  of  energy  can  be  trans- 
formed into  another  form,  and  that  a  certain  amount  of  one  form  will  yield  a 
definite  amount  of  another  form;  further,  that  new  energy  never  arises  sponta- 
neously, nor  is  energy  already  present  ever  destroyed,  so  that  in  the  organism  the 
law  of  the  conservation  of  energy  is  continually  in  action. 

.\NIMALS  AND  PLANTS. 

The  animal  body  contains  a  quantity  of  chemically-potential  energy  stored  up 
in  its  constituents.  The  total  amount  of  the  energy  present  in  the  human  body 
might  be  measured  by  burning  completely  an  entire  human  body  in  a  calorimeter, 
and  thereby  determining  how  many  heat  units  are  produced  when  it  is  reduced  to 
ashes  (see  Animal  Heat). 

The  chemical  compounds  containing  the  potential  energy  are  characterized  by 
the  complicated  relative  position  of  their  atoms,  by  a  comparatively  imperfect 
saturation  of  the  affinities  of  their  atoms,  by  the  relatively  small  amount  of  oxy- 
gen which  they  contain,  by  their  great  tendency  to  decomposition,  and  the  facility 
with  which  they  undergo  decomposition. 

If  a  man  were  not  supplied  with  food  he  would  lose  50  grammes  of  his  body 
weight  every  hour  ;  the  material  part  of  his  body,  which  contains  the  potential 
energy,  is  used  up,  oxygen  is  absorbed,  and  a  continual  process  of  combustion 
takes  place  ;  by  the  process  of  combustion  simpler  substances  are  formed  from  the 
more  complex  compounds,  whereby  potential  is  converted  into  kinetic  energy. 
It  is  immaterial  whether  the  combustion  is  rapid  or  slow  ;  the  same  amount  of 
the  same  chemical  substances  always  produces  the  same  amount  of  kinetic  energy, 
/.  e.,  of  heat. 

A  person,  when  fasting,  experiences  after  a  certain  time  the  disagreeable  feeling 
of  exhaustion  of  his  reserve  of  potential  energy,  hunger  sets  in,  and  he  takes 
food.  All  food  for  the  animal  kingdom  is  obtained,  either  directly  or  indirectly, 
from  the  vegetable  kingdom.  Even  carnivora,  which  eat  the  flesh  of  other  animals, 
only  eat  organized  matter  which  has  been  formed  from  vegetable  food.  The 
existence  of  the  animal  kingdom  presupposes  the  existence  of  the  vegetable  king- 
dom. 

All  substances,  therefore,  necessary  for  the  food  of  animals  occur  in  vegetables. 
Besides  water  and  the  inorganic  constituents,  plants  contain,  among  other 
organic  compounds,  the  following  three  chief  representatives  of  food  stuffs — fats, 
carbohydrates  and  proteids. 

.\ll  these  contain  stores  of  potential  energy,  in  virtue  of  their  complex  chemical 
constitution. 

The  fats  contain  —  -^  C./H,„_,0(OH)  =  fatty  acids  \  .^        . 
1  lie  tats  contain  .        ^  4-C,H,(_OH),=  glycerine        J  '■^  2oiJ. 


XXXVIU  INTRODUCTION. 

The  carbohydrates  contain  : — Ci-.HkiO,         .         .        (*?  252). 

I  t:-  51-5-54-5  1 
I   H.      6.9-  7.3  I 

'1  he  proteids  contain  i)er  cent.  : — '  N.  15.  2-17.0  ;  (§§  24S  and  249). 

I  O.  20.9-23.5  I 
I  S.      0.3-  2.0  I 

A  man  who  takes  a  certain  amount  of  this  food  adds  thereto  oxygen  from  the 
air  in  the  process  of  respiration.  Combustion  or  o.xidation  then  takes  place, 
whereby  chemically  potential  energy  is  transformed  into  heat. 

It  is  evident  that  the  products  of  this  combustion  must  be  bodies  of  simpler 
constitution — bodies  with  less  complex  arrangement  of  their  atoms,  with  the 
greatest  possible  saturation  of  the  affinities  of  their  atoms,  of  greater  stability, 
partly  rich  in  O,  and  possessing  either  no  potential  energy,  or  only  very  little. 
These  bodies  are  carbon  dioxide,  C().^;  w/ater,  H.^O  ;  and  as  the  chief  repre- 
sentative of  the  nitrogenous  excreta,  urea  (CO(NH,).),  which  has  still  a  small 
amount  of  potential  energy,  but  which  outside  the  body  readily  splits  into  COj 
and  ammonia  (NH3). 

The  human  body  is  an  organism  in  which,  by  the  phenomena  of  oxidation,  the 
complex  nutritive  materials  of  the  vegetable  kingdom,  which  are  highly  charged 
with  potential  energy,  are  transformed  into  simple  chemical  bodies,  whereby  the 
potential  energy  is  transformed  mto  the  equivalent  amount  of  kinetic  energy  (heat, 
work,  electrical  phenomena). 

But  how  do  plants  form  these  complex '  food  stuffs  so  rich  in  potential  energy  ? 
It  is  plain  that  the  potential  energy  of  plants  must  be  obtained  from  some  other 
form  of  energy.  This  potential  energy  is  supplied  to  plants  by  the  rays  of  the 
sun,  whose  chemical  light  rays  are  absorbed  by  plants.  Without  the  rays  of  the 
sun  there  could  be  no  plants.  Plants  absorb  from  the  air  and  the  soil  CO2,  H.^O, 
NH3,  and  N,  of  which  carbon  dioxide,  water,  and  ammonia  (from  urea)  are  also 
]5roduced  by  the  excreta  of  animals.  Plants  absorb  the  kinetic  energy  of  light  from 
the  sun's  rays  and  transform  it  into  potential  energy,  which  is  accumulated  during 
the  growth  of  the  plant  in  its  tissues,  and  in  the  food  stuffs  produced  in  them 
during  their  growth.  This  formation  of  complex  chemical  compounds  is  accom- 
panied by  the  simultaneous  excretion  of  O. 

Occasionally,  kinetic  energy,  such  as  we  universally  meet  with  in  animals,  is  liberated  in  plants. 
Many  plants  develop  considerable  quantities  of  heat  in  their  flowers,  e.  g.,  the  arum  tribe.  We 
must  also  remember  that  during  the  formation  of  the  solid  parts  of  plants,  when  fluid  juices  are 
changed  into  solid  masses,  heat  is  set  free.  In  plants,  under  certain  circumstances,  O  is  absorbed, 
and  COj  is  excreted,  but  these  processes  are  so  trivial  as  compared  with  the  typical  condition  in  the 
vegetable  kingdom,  that  they  may  be  regarded  as  of  small  moment. 

Plants,  therefore,  are  organisms  which,  by  a  reduction  process,  transform 
simple  stable  combinations  into  complex  compounds,  whereby  potential  solar 
energy  is  transformed  into  the  chemically-potential  energy  of  vegetable  tissues. 
Animals  are  living  beings,  which  by  oxidation  decompose  or  break  up  the  com- 
plex grouping  of  atoms  manufactured  by  plants,  whereby  potential  is  transformed 
into  kinetic  energy.  Thus  there  is  a  constant  circulation  of  matter  and  a  con- 
stant exchange  of  energy  between  plants  and  animals.  All  the  energy  of  animals 
is  derived  from  plants.  All  the  energy  of  plants  arises  from  the  sun.  Thus  the 
sun  is  the  cause,  the  original  source  of  all  energy  in  the  organism, ;.  e.,  of  the  whole 
of  life. 

As  the  formation  of  solar  heat  and  solar  light  is  explicable  by  the  gravitation 
of  masses,  gravity  is,  perhaps,  the  original  form  of  energy  of  all  life. 

We  may  thus  represent  the  formation  of  kinetic  energy  in  the  animal  body  from 
the  potential  energy  of  plants.  Let  us  suppose  the  atoms  of  the  substances 
formed  in  organisms,  as  simple  small   Ijodies,  balls,  or  blocks.     .\s    long  as  these 


INTRODUCTION.  XXXIX 

lie  in  a  single  layer,  or  in  a  few  layers,  upon  the  surface,  there  is  a  stable  arrange- 
ment, and  they  continue  to  remain  at  rest.  If,  however,  an  artificial  tower  be 
built  of  these  blocks,  so  that  an  unstable  erection  is  produced,  and  the  same  tower 
be  afterwards  knocked  down,  then  for  this  purpose  we  require — (i)  the  motor 
power  of  the  workman  who  lifts  and  carries  the  blocks;  (2)  a  blow  or  other 
impulse  from  without  applied  to  the  unstable  structure — when  the  atoms  will  fall 
together,  and  as  they  fall  collide  with  each  other  and  produce  heat.  Thus  the 
energy  employed  by  the  workman  is  again  transformed  into  the  last-named  form 
of  energy. 

In  plants,  the  complex  unstable  building  of  the  groups  of  atoms  is  carried  on, 
the  constructor  being  the  sun.  In  animals,  which  eat  plants,  the  complex  groups 
of  the  atoms  are  tumbled  down,  with  the  liberation  of  kinetic  energy. 

VITAL  ENERGY  AND  LIFE. 

The  forces  which  act  in  organisms,  in  plants,  and  animals  are  exactly  the  same 
as  are  recognizable  as  acting  in  dead  matter.  A  so-called  '"  vital  force,"  as  a 
special  force  of  a  peculiar  kind,  causing  and  governing  the  vital  phenomena  of 
living  beings,  does  not  exist.  The  forces  of  all  matter,  of  organized  as  well  as 
unorganized,  exist  in  connection  with  their  smallest  particles  or  atoms.  As,  how- 
ever, the  smallest  particles  of  organized  matter  are,  for  the  most  part,  arranged  in 
a  very  complicated  way,  compared  with  the  much  simpler  composition  of  inor- 
ganic bodies,  so  the  forces  of  the  organism  connected  with  the  smallest  particles 
yield  more  complicated  phenomena  and  combinations,  whereby  it  is  excessively 
difficult  to  ascribe  the  vital  phenomena  in  organisms  to  the  simple  fundamental 
laws  of  physics  and  chemistry. 

The  Exchange  of  Material,  or  Metabolism  (  "  Stoffiveihsel "  )  as  a  Sign 
of  Life. — Nevertheless,  there  apjjears  to  be  a  special  exchange  of  matter  and 
energy  peculiar  to  living  beings.  This  consists  in  the  capacity  of  organisms  to  as- 
similate the  matter  of  their  surroundings,  and  to  work  it  up  into  their  own  consti- 
tution, so  that  it  forms  for  a  time  an  integral  part  of  the  living  being,  to  be  given 
off  again.  The  whole  series  of  phenomena  is  called  Metabolism  or  Stoffwech- 
sel,  which  consists  in  the  introduction,  assimilation,  integration,  and  excretion  of 
matter. 

We  have  already  shown  that  the  metabolism  of  plants  and  that  of  animals  are 
quite  different.  The  processes,  as  already  described,  actually  occur  in  the  typical 
higher  plants  and  animals. 

But  there  is  a  large  group  of  organisms  which,  throughout  their  entire  organiza- 
tion, exhibit  so  low  a  degree  of  development,  that  by  some  observers  they  are 
considered  as  undifferentiated  "  ground  forms."  They  are  regarded  as  neither 
plants  nor  animals,  and  are  the  most  simple  forms  of  animated  matter.  Hsckel 
has  called  these  organisms  Protistae,  as  being  the  original  and  primitive  forms. 

We  must  assume  that,  corresponding  with  their  simpler  vital  conditions,  their 
metabolism  is  also  simpler,  but  on  this  point  we  still  require  further  observations. 


ERRATA 


Page  42,  sixth  line  from  bottom,  "  Fig.  11.5"  should  be  "Fig.  14.5." 
Page  45,  sixteenth  line  from  top,  read  hiemoglobin. 
Page  79,  Fig.  32,  the  letters  D  E  are  omitted. 

Page  84,  twentieth  line  from  top,  "  Fig.  31,  E  "  should  be  "  Fig.  32,  E." 
Page  loi,  Fig.  55,  the, section  marked  b  is  reversed. 

Page  133,  Section  75,  the  references  to  Fig.  90  are  incorrect,  because  a  portion  of  the  cut  has  been 
omitted. 

Page  138,  second  line  from  bottom,  "  Fig.  96  "  should  be  "  Fig.  95." 

Page  734,  fourth  line  from  top,  "cordate"  should  be  "caudate." 

Page  757,  eleventh  line  from  bottom,  "meredional"  should  be  "meridional." 


PHYSIOLOGY  OF  THE  BLOOD. 


[The  blood  is  aptly  described  by  Claude  Bernard  as  an  internal  medium  which 
acts  as  a  "  go-between  "  or  medium  of  exchange  for  the  outer  world  and  the 
tissues.  Into  it  are  poured  those  substances  which  have  been  subjected  to  the 
action  of  the  digestive  fluids,  and  in  the  lungs  or  other  respiratory  organs  it 
receives  oxygen.  It  thus  contains  new  substances,  but  in  its  passage  through  the 
tissues  it  gives  up  some  of  these  new  substances,  and  receives  in  exchange  certain 
effete  or  waste  products  and  more  or  less  useless  substances  which  have  to  be 
got  rid  of.  Its  composition  is  thus  highly  complex,  containing,  as  it  does,  things 
both  new  and  old.  Besides  carrying  the  new  nutrient  fluids  to  the  tissues,  it  is 
also  the  great  oxygen  carrier,  as  well  as  the  medium  by  which  part  of  the  waste 
pre  ducts,  e.g.,  CO„  urea,  are  removed //'w«  the  tissues  and  brought  to  the  organs, 
e.  g.,  the  lungs,  kidneys,  skin,  which  eliminate  them  from  the  body.  It  is  at  once 
a  great  pabulum-supplying  medium  and  a  channel  for  getting  rid  of  useless  mate- 
rials. As  the  composition  of  the  organs  through  which  the  blood  flows  varies,  it 
is  evident  that  its  com])osition  must  vary  in  different  parts  of  the  circulatory 
system  ;  and  it  also  varies  in  the  same  individual  under  different  conditions. 
Still,  with  slight  variations,  there  are  certain  general  physical,  histological  and 
chemical  properties  which  characterize  blood  as  a  w/wie.'\ 

I.  PHYSICAL  PROPERTIES  OF  THE   BLOOD.— (i)   Color.— 

The  color  of  blood  varies  from  a  bright  scarlet  red  in  the  arteries  to  a  deep,  dark, 
bluish-red  in  the  veins.  Oxygen  (and,  therefore,  the  air)  makes  the  blood  bright 
red;  want  of  oxygen  makes  it  dark.  Blood  free  from  oxygen  (and  also  venous 
blood)  is  dicliroic — /.  c,  by  reflected  light  it  appears  dark  red,  while  by  transmitted 
light  it  is  green  [Briieke).     [Arterial  blood  is  monochroic] 

In  thin  layers  blood  is  opaque,  as  is  easily  shown  by  shaking  blood  so  as  to 
form  bubbles,  or  by  allowing  blood  to  fall  upon  a  plate  with  a  pattern  on  it,  and 
pouring  it  off  again.  Blood  behaves,  therefore,  like  an  "opaque  color"  (Rolleit), 
as  its  coloring  matter  is  suspended  in  the  form  of  fine  particles — the  blood  cor- 
puscles. 

Hence,  it  is  possible  to  separate  the  coloring  matter  from  the  fluid  part  of  the  blood  by  filtration. 
This  is  accomplished  by  mixing  the  blood  with  fluids  which  render  the  blood  corpuscles  sticky  or 
rough.  If  mammalian  blood  be  treated  with  one-seventh  of  its  volume  of  solution  of  sodic  sulphate 
[Figitier),  or  if  frogs'  blood  be  mixed  with  a  2  per  cent,  solution  of  sugar  [Joh.  A/iiller]  and 
filtered,  the  shriveled  corpuscles,  now  robbed  of  part  of  their  water,  remain  upon  the  filter. 

(2)  Reaction. — The  reaction  is  alkaline,  owing  to  the  presence  of  disodic 
phosphate,  Naj.H.PO,  (A/a/v)  [and  bicarbonate  of  soda].  After  blood  is  shed, 
its  alkalinity  rapidly  diminishes,  and  this  occurs  more  rapidly  the  greater  the 
alkalinity  of  the  blood.  This  is  due  to  the  formation  of  an  acid,  in  which,  perhaps, 
the  colored  corpuscles  take  part,  owing  to  the  decomposition  of  their  coloring 
matter.  A  high  temperature  and  the  addition  of  an  alkali  favor  the  formation  of 
the  acid  (TV;  Zuntz). 

The  alkaline  reaction  of  blood  is  diminished  :  [a)  by  great  muscular  exertion,  owing  to  the 
formation  of  a  large  amount  of  acid  in  the  muscles;  (b)  during  coagulation  ;  [c)  in  old  blood,  or 
blood  dissolved  by  water  from  old  blood  stains,  such  blood  being  usually  acid ;  fresh  cruor  has  a 
stronger  alkaline  reaction  than  serum;  (d\  after  the  prolonged  use  of  soda  the  alkalinity  is  in- 
creased [Duliilir),  after  the  use  of  acids  it  is  decreased. 
2  17 


18  MICROSCOPIC    EXAMINATION    OF   THE    BLOOD. 

Pathological. — The  alkalinity  is  less  in  persons  suffering  from  ana;mia,  cachectic  conditions, 
and  chronic  rheumatism  [Lepine),  and  also  in  cholera.  [Immediately  before  death  by  cholera  it 
may  be  acid  (Can/ani)/] 

Methods. — Owing  to  the  color  of  the  blood  we  cannot  employ  ordinary  litmus  paper  to  test  its 
reaction.  One  or  other  of  the  following  methods  may  be  used  :  ( I )  Moisten  a  strip  of  glazed  red 
litmus  paper  with  solution  of  common  salt,  and  dip  it  quickly  into  the  bit  od,  or  allow  a  drop  of 
blood  to  fall  on  tlie  paper,  and  rapidly  wipe  it  oft*  before  its  coloring  matter  has  time  to  penetrate 
and  tinge  the  paper  (Ziintz).  (2)  Kiihne  made  a  small  cup  of  parchment  paper,  which  was  placed 
in  water  in  a  watch  glass.  The  colorless  diftusate  was  afterward  tested  with  litmus  paper.  (3) 
Liebreich  used  thin  plates  of  plaster-of- Paris  of  a  perfectly  neutral  reaction.  These  are  dried,  and 
afterward  moistened  with  a  neutral  solution  of  litmus.  When  a  drop  of  blood  is  placed  upon  the 
porous  plate,  the  fluid  part  of  the  blood  passes  into  it,  while  the  corpuscles  remain  at  the  surface. 
The  corpuscles  are  washed  off"  with  water,  and  the  altered  color  of  the  litmus-stained  slab  is  ap- 
parent. [(4)  Schafer  uses  dry,  faintly-reddened,  glazed  litmus  paper,  and  on  it  is  placed  a  drop  of 
blood,  which  is  wiped  off  after  a  few  seconds.  The  place  where  the  blood  rested  is  indicated  by  a 
well-defined  blue  patch  upon  a  red  or  violet  ground.] 

(3)  Odor. — Blood  emits  a  peculiar  odor  {Halitus  sanguinis),  which  differs  in 
animals  and  man. 

It  depends  upon  the  presence  of  volatile  fatty  acids  [Mat/eucci).  If  concentrated  sulphuric  acid 
be  added  to  blood,  whereby  the  volatile  fatty  acids  are  set  free  from  their  combinations  with  alka- 
lies, the  characteristic  odor  becomes  much  more  perceptible  (Barruel).  [The  odor  is  somewhat 
similar  to  that  of  butyric  acid.] 

(4)  Taste. — Blood  has  a  saline  taste,  depending  upon  the  salts  dissolved  in  the 
fluid  of  the  blood. 

(5)  Specific  Gravity. — The  specific  gravity  is  1055  (extreme  limits  1045- 
1075) ;  in  women  and  young  persons  it  is  somewhat  less.  The  specific  gravity  of 
the  blood  corpuscles  is  1105,  that  of  the  plasma  1027.  Hence,  the  corpuscles 
tend  to  sink. 

The  specific  gravity  of  the  red  blood  corpuscles  is  estimated  by  allowing  the  corpuscles  to  subside 
to  the  bottom  (which  occurs  most  readily  in  the  blood  of  the  horse) ;  but  it  is  more  correctly  esti- 
mated by  placing  the  i)lood  in  a  tall  cylindrical  vessel,  and  setting  the  latter  in  the  radius  of  the 
revolving  disk  of  a  centrifugal  apparatus,  the  base  of  the  cylinder  being  directed  outward.  The 
drinking  of  water  and  hunger  diminish  the  specific  gravity  temporarily,  while  thirst  and  the  digestion 
of  dry  food  raise  it.  If  blood  be  passed  through  an  organ  artificially,  its  specific  gravity  rises  in 
consequence  of  the  absorption  of  dissolved  matters  and  the  giving  off  of  water.  It  falls  after  hem- 
orrhage, and  is  less  in  badly-nourished  individuals. 

(6)  [Temperature. — Blood  is  viscid,  and  its  temperature  varies  from  36.5°  C. 
(97.7°  F.)  to  37.8°  C.  (100°  F.).  The  warmest  blood  in  the  body  is  that  of  the 
hepatic  vein,  while  that  of  the  right  ventricle  is  warmer  than  that  of  the  left  side 
of  the  heart,  §  210.] 

2.  MICROSCOPIC  EXAMINATION  OF  THE  BLOOD.— [Blood, 

when  examined  by  the  microscope,  is  seen  to  consist  of  an  enormous  number  of 
corpuscles — colored  and  colorless — floating  in  a  transparent  fluid,  the  plasma, 
or  liquor  sanguinis.'\ 

The  RED  blood  corpuscles  were  discovered  in  frogs'  blood  by  Swammerdam  in 
1658,  ai'd  in  human  blood  by  Leeuwenhoek  in  1673. 

Characters  of  Human  Blood — ((7)  Form. — The  human  red  blood  cor- 
puscles are  circular,  coin-shaped,  homogeneous  disks,  with  saucer-like  depressions 
on  both  surfaces,  and  with  rounded  margins ;  in  other  words,  they  are  bi-concave, 
circular,  non-nucleated  disks. 

{b)  Size. — According  to  Welcker  the  diameter  {a />)  is  7.7  //,*  the  greatest 
thickness  {c d)  1.9  11  (Fig.  i,  C)  [/.  e.,  it  is  ^35^  to  ^^nr  ^^  ^"  '"•^'^  '"^  diameter, 
and  about  one-fourth  of  that  in  thickness]. 

The  corpuscles  are  slightly  diminished  in  size  by  septic  fever,  inanition,  after  the  .subcutaneous 
injection  of  morphia,  increased  bodily  temperature,  and  CO,,;  while  they  are  increased  h-j  O,  wa- 
tery condition  of  the  blood,  cold,  consumption  of  alcohol,  <|uinine,  hydrocyanic  acid  and  acute 
anaemia  [Manassein).     Compare  ?  113. 

:-thousandth  of  a  millimetre  (,'/-  =  o.cxji  mm.',  and  is  the  sign  of  a  micro-mitli- 


MICROSCOPIC    EXAMINATION    OF   THE    BLOOD. 


19 


If  the  total  amount  of  blood  in  a  man  be  taken  at  4400  cubic  centimetres,  the  corpuscles  therein 
contamed  have  a  surface  of  2816  square  metres,  which  is  equal  to  a  square  surface  with  a  side  of  So 
paces;  176  cubic  centimetres  of  blood  pass  through  the  lungs  in  a  second,  and  the  blood  corpuscles 
in  this  amount  of  blood  have  a  superficies  of  81  square  metres,  equal  to  a  square  surface  with  a  side 
of  13  paces  (  Welder). 

(c)  Weight. — The  weight  of  a  blood  corpuscle,  according  to  Welcker,  is 
0.00008  milligramtnes. 

{(i)  Number. — According  to  Vierordt,  the  number  exceeds  5,000,000  per 
cubic  millimetre  in  the  male,  and  4,500,000  in  the  female;  so  that  in  10  tbs.  of 
blood  there  are  25  billions  of  corpuscles.  As  a  general  rule,  the  number  is  in 
inverse  ratio  to  the  amount  of  plasma  ;  hence,  the  number  must  vary  with  the 
state  of  contraction  of  the  blood  vessels,  the  pressure-diffusion  currents  and  other 
conditions. 

The  number  of  red  corpuscles  is  increased ;  in  venous  blood  (especially  in  the  small  cutaneous 
veins),  after  the  use  of  solid  food.  After  much  sweating,  and  the  excretion  of  water  by  the  bowel 
and  kidney;  during  inanition,  because  the  blood  plasma  undergoes  decomposition  sooner  than  the 
blood  corpuscles  themselves  (Biinlzen);  in  the  blood  of  the  newly-born  child  (Paniim  and  So- 
reiisen),  especially  when  the  umbilical  cord  is  long  in  being  tied  (^  40) ;  [from  the  fourth  day  onward 
the  number  is  diminished  (Hayem)'\,  in  persons  of  robust  constitution,  and  in  those  who  live  in  the 

Fig.  I. 


A,  Human  colored  blood  corpuscles — i,  seen  on  the  flat ;  2,  on  edge  ;  3,  rouleau  of  colored  corpuscles  slightly  sepa- 
rated. B,  colored  amphibian  blood  corpuscles— i,  seen  on  the  flat,  and  2,  on  edge.  C,  ideal  transverse  section 
of  a  human  colored  blood  corpuscle  magnified  5000  times  linear — a  d,  diameter  ;  c  d,  thickness. 

country.  The  number  is  diminished,  during  pregnancy,  after  copious  draughts  of  water.  In  the 
earlier  perioil  of  fcetal  life  the  number  is  only  J-I  million  in  i  c.  c.  (Cohnheim,  Zuntz). 
(The  pathological  conditions  which  affect  the  number  of  corpuscles  are  given  at  \  10.) 
Methods  of  Estimating  the  Number  of  Blood  Corpuscles. — The  pointed  end  of  a  glass 
pipette  (Fig.  3),  the  mixer,  is  dipped  into  the  blood,  and  by  sucking  the  elastic  tube/",  blood  is 
drawn  into  the  tube  until  it  reaches  the  mark  \,  on  the  stem  of  the  pipette,  or  until  the  mark  I  is 
reached.  The  caremlly-cleaned  point  of  the  pipette  is  dipped  into  the  artificial  serum,  and  this  is 
sucked  inio  the  pipette  until  it  reaches  the  mark,  loi.  The  artificial  serum  consists  of  i  vol.  of 
solution  of  gum  arable  (sp.  gr.  1020)  and  3  vols,  of  a  solution  of  equal  parts  of  sodic  sulphate  and 
sodic  chloride  (sp.  gr.  1020).  The  process  of  mi.xing  the  two  fluids  is  aided  by  the  presence  of  a 
little  gla,ss  ball  [a)  in  the  bulb  of  the  pipette.  If  blood  is  sucked  up  to  the  mark  \,  the  strength  of 
the  mixture  is  I  :  200;  if  to  the  mark  i,  it  is  I  :  100.  A  small  drop  of  the  mixture  is  allowed  to 
run  into  the  counling  chamber  of  Abb6  and  Zeiss  (Fig.  2)  (the  first  portions  are  not  used,  in  order  to 
obtain  a  uniform  sample  from  the  bulb  of  the  pipette).  This  chamber  consists  of  a  gla^s  receptacle 
0.1  mm.  deep,  with  its  base  divided  into  squares,  and  cemented  to  a  microscopic  slide,  the  whole 
being  covered  with  a  microscopic  covering  glass.  The  space  over  each  square  =  j^^^jj  cubic  milli- 
metre. Count,  with  the  aid  of  a  microscope,  the  number  of  blood  corpuscles  in  each  square,  and 
the  number  found,  multiplied  by  4000,  will  give  the  number  of  blood  corpuscles  in  i  c.mm.  This 
number,  again,  must  be  multiplied  by  100  or  200,  according  as  the  blood  was  diluted  100  or  200 
times.  To  ensure  greater  accuracy,  it  is  well  to  count  the  number  in  several  squares,  and  to  take 
the  mean  of  these.     [The  method  of  Malassez  was  described  in  the  last  edition  of  this  work.] 


20 


MICROSCOPIC    EXAMINATION    OF   THE    BLOOD. 


Apparatus  of  Abbe  and  Zeiss  for  counting  the  number  of 
corpuscles.  A,  in  section;  C,  surface  view  wiihout 
cover  glass  ;  B,  microscopic  appearance  with  the 
blood  corpuscles. 

Fin.  4. 


1  he    Melangettr,   pipette 


Gowers"  apparatus,  made  by  Hawksley.  London.  A,  pipette  for  measuring  the  diluting  solution  ;  B,  capillary  tube 
for  measuring  the  blood;  C,  cell  with  divisions  on  the  floor,  mounted  on  a  slide,  to  which  springs  are  fixed  to 
secure  the  cover  glass  ;  D,  vessel  in  which  the  solution  is  made;  E,  spud  for  mixing  the  blood  and  solution; 
F,  guarded  spear-pointed  needle. 


EFFECTS    OF    REAGENTS    ON    BLOOD    CORPUSCLES.  21 

[The  following  is  a  description  of  Cowers'  instrument  (Fig.  4):  "The  Hsemacytometer 
consists  of — (l)  a  small  pipette,  which,  when  filled  to  the  mark  on  its  stem,  holds  e.\actly  995 
cubic  millimetres.  It  is  furnished  with  an  India-rubber  tube  and  mouthpiece  to  facilitate  filling 
and  emptying.  (2)  A  capillary  tube  marked  to  contain  exactly  5  cubic  millimetres,  with  India- 
rubber  tube  for  filling,  etc.  (3)  A  small  glass  jar  in  which  the  dilution  is  ma<le.  (4)  A  glass 
stirrer  for  mixing  the  blood  and  solution  in  the  glass  jar.  (5)  A  brass  stage  plate,  carrying  a  glass 
slip,  on  which  is  a  cell,  i  of  a  millimetre  deep.  The  bottom  of  this  is  aivided  into  j'j  millimetre 
squares.  Upon  the  top  of  the  cell  rests  the  cover  glass,  which  is  kept  in  its  place  by  the  pressure 
of  two  springs  proceeding  from  the  ends  of  the  stage  plate." 

The  diluting  solution  used  is  a  solution  of  sodic  sulphate  in  distilled  water,  sp.  gr.  1025,  or  the 
following — sodic  sulphate,  104  grains;  acetic  acid,  I  drachm;  distilled  water,  4  oz. 

"995  cubic  millimetres  of  the  solution  are  placed  in  the  mixing  jar;  5  cubic  millimetres  of 
blood  are  drawn  into  the  capillary  tube  from  a  puncture  in  the  finger,  and  then  blown  into  the 
solution.  The  two  fluids  are  well  mixed  by  rotating  the  stirrer  between  the  thumb  and  finger, 
and  a  small  drop  of  this  dilution  is  placed  in  the  centre  of  the  cell,  the  covering  glass  gently  put 
upon  the  cell,  and  secured  by  the  two  springs,  and  the  plate  placed  upon  the  stage  of  the 
microscope.  The  lens  is  then  focused  for  the  squares.  In  a  few  minutes  the  corpuscles  have 
sunk  to  the  bottom  of  the  cell,  and  are  seen  at  rest  on  the  squares.  The  number  in  ten  squares  is 
then  counted,  and  this,  multiplied  by  ro,ooo,  gives  the  number  in  a  cubic  millimetre  of  blood." 

To  estimate  the  colorless  corpuscles  only,  mix  the  blood  with  10  parts  of  0.5  per  cent,  solution 
of  acetic  acid,  which  destroys  all  the  red  corpuscles  (  '/7ioma).'\ 

(e)  Red  blood  corpuscles  are  characterized  by  their  great  elasticity,  flexi- 
bility and  softness.  [The  elastic  property  is  shown  by  the  great  extent  to 
which  red  corpuscles  still  within  the  circulation  may  be  distorted,  and  yet  resume 
their  original  form  as  soon  as  the  pressure  is  removed.] 

3.  HISTOLOGY  OF  THE  HUMAN  RED  BLOOD  CORPUS- 
CLES.— When  observed  singly,  blood  corpuscles  have  a  yellow  color  with  a 
slight  tinge  of  green  ;  they  seem  to  be  devoid  of  an  envelope,  are  certainly  non- 
nucleated,  and  appear  to  be  homogeneous  throughout.  Each  corpuscle  consists  (i) 
of  a  framc7iiork,  an  exceedingly  pale,  transparent,  soft  protoplasm — the  stroma 
{Rollett)  ;  and  (2)  of  the  red  pigment,  or  htemoglobin,  which  impregnates  the 
stroma,  much  as  fluid  passes  into  and  is  retained  in  the  interstices  of  a  bath-sponge. 
Some  observers  (.5(V/<V?(V-,  Ebcrhardt,  Strieker)  maintain  that  the  corpuscles  contain 
a  nucleus,  but  this  is  certainly  a  mistake. 

4.  EFFECTS  OF    REAGENTS.— (A)    On  the  Vital  Phenomena. 

Blood  corpuscles  contained  in  shed  blood — or  even  in  defibrinated  blood,  when  it 
is  reintroduced  into  the  circulation — retain  their  vitality  and  functions  undimin- 
ished. Heat  acts  powerfully  on  their  vitality,  for  if  blood  be  heated  to  52°  C, 
the  vitality  of  the  red  corpuscles  is  extinguished.  Mammalian  blood  may  be  kept 
for  four  or  five  days  in  a  vessel  under  iced  water,  and  still  retain  its  functions ;  but 
if  it  be  kept  longer,  and  reintroduced  into  the  circulation,  the  corpuscles  rapidly 
break  up — a  proof  that  they  have  lost  their  vitality  (^Landois).  Crenation. — 
Blood  freshly  shed  from  an  artery  frequently  shows  a  transformat  on  of  the  corpus- 
cles into  a  peculiar  mulberry  shape.  [This  is  the  so-called  crenation  of  the  colored 
corpuscles.  It  is  produced  by  poisoning  with  Calabar  bean  (  T.  R.  Fraser),  and 
also  by  the  addition  of  a  2  per  cent,  solution  of  common  salt.]  The  blood  of 
many  persons  crenates  spontaneously — a  condition  ascribed  to  an  active  contrac- 
tion ot  the  stroma  i^Kli'bs),  but  it  is  doubtful  if  this  is  the  cause.  Max  Schultze 
observed  that  the  red  corpuscles  of  the  embryo  chick  undergo  active  contraction. 

(B)  On  the  External  Characters. — Many  agents  affect  the  external  char- 
acters of  the  corpuscles. 

{a)  The  Color  is  changed  by  many  gases.  O  makes  blood  scarlet,  want  of  O 
renders  it  dark  bluish-red,  CO  makes  it  cherry-red,  NO  violet-red.  There  is  no 
difference  between  the  shape  of  corpuscles  in  arterial  and  venous  blood,  as  was 
supposed  by  Harless.  All  reagents  {e.  g.,  a  concentrated  solution  of  sodic  sul- 
phate) which  cause  great  shrinking  of  the  colored  corpuscles  produce  a  very 
bright  scarlet  or  brick-red  color  (^Bartho/inus,  1661).  The  red  color  so  produced 
is  quite  different  from  the  scarlet-red  of  arterial  blood.     Reagents  which  render 


22 


EFFECTS  OF  REAGENTS  ON  KLOOD  CORPUSCLES. 


blood  corpuscles  globular  darken  the  blood,  e.g.,  water.  [The  contrast  is  very- 
striking,  if  we  compare  blood  to  which  a  lo  per  cent,  solution  of  common  salt 
has  been  added  with  blood  to  which  water  has  been  added.  With  reflected  light 
the  one  is  bright  red,  and  the  other  a  very  dark,  deep  crimson,  almost  black.] 

{/y)  Change  of  Position  and  Form. — A  very  common  phenomenon  in 
shed  blood  is  the  tendency  of  the  corpuscles  to  run  into  rouleaux  (Fig.  i.  A,  3). 

Conditions  that  increa'ie  the  coagulability  of  the  blood  favor  this  phenomenon,  which  is  ascribed 
by  Dogiel  to  the  attraction  of  the  disks  and  the  formation  of  a  sticky  substance.  [The  cause  of  the 
arrangement  of  the  red  corpuscles  into  rouleaux  is  by  no  means  clear.  They  may  be  detached 
from  each  other  by  gently  touching  the  cover  glass,  but  the  rouleaux  may  reform.  Liiler  suggested 
that  the  surfaces  of  the  corpuscles  were  so  altered  that  tley  became  adhesive,  and  thus  coiiered. 
Norris  h.is  made  some  ingenious  experiments  with  corks  weighted  with  tacks  or  pins,  so  as  to  pro- 
duce partial  submersion  of  the  cork  disks.  These  disks  rapidly  cohere,  owing  to  capillarity,  and 
form  rouleaux.  If  the  disks  be  completely  submerged  they  remain  apart,  as  occurs  with  unaltered 
blood  corpuscles  within  the  blood  vessels.  If,  however,  the  corpuscles  be  dipped  in  petroleum,  and 
then  placed  in  water,  rouleaux  are  formed.]  If  reagen's  which  cause  the  corpuscles  to  swell  up  be 
added  to  the  blood,  the  corpuscles  become  globular  and  the  rouleaux  break.  According  to  E. 
Weber  and  Suchard,  the  uniting  medium  is  not  fibrin  (ahhough  it  may  sometimes  assume  a  fibrous 
form),  but  belongs  to  the  peripheral  layer  of  the  corpuscles. 

(^)  The  Changes  of  Form  which,  after  blood  is  shed,  the  red  corpuscles 
undergo  until  they  are  gradually  dissolved,  are  iinportant.  Some  reageants  rapidly 
produce  this  series  of  events,  eg.,  the  discharge  of  a   Leyden  jar  causes  the 


d  blood  corpuscles,  showing 
pression  more  or  less  in  focus 
/,  stroma ;  _/",  a  frog's  blood 


changes  of  sh.ipc.  a,  b. 
e,  mulberry  forms  ;  ^,/i, 
,  partly  shriveled,  owinj 


puscles,  with  the  central  de- 
les;  k,  pale  decolorized  corpuscles; 
a  strong  saline  solution. 


corpuscles  to  crenate,  so  that  their  surfaces  are  beset  with  large  or  small  projec- 
tions (Fig.  5,  c,  d,  e,  g,  h)  ;  it  also  causes  the  corpuscles  to  assume  a  spherical  form 
(/,  /),  when  they  are  smaller  than  normal.  The  corpuscles  so  altered  are  sticky, 
and  run  together  like  drops  of  oil,  forming  larger  spheres.  The  prolonged  action 
of  the  electrical  spark  causes  the  hemoglobin  to  separate  from  the  stroma  (k), 
whereby  the  fluid  part  of  the  blood  is  reddened,  while  the  stroina  is  recognizable 
only  as  a  faint  .shadow  (/).  Similar  forms  are  to  be  found  in  decomposing  blood, 
as  well  as  after  the  action  of  many  other  reagents. 

Action  of  Heat. — When  blood  is  heated,  on  a  warm  stage,  to  52°  C.  the 
corpuscles  begin  to  undergo  remarkable  changes.  Some  of  them  become  spherical, 
others  biscuit-shaped ;  some  are  perforated,  while  in  others  small  portions  become 
detached  and  swim  about  in  the  surrounding  fluid,  a  proof  that  heat  destroys  the 
histological  individuality  of  the  corpuscles  {Max  Schultze).  If  the  heat  be  con- 
tinued, the  corpuscles  are  ultimately  dissolved  (§  10,  3). 

Heat  acts  like  the  addition  of  a  concentrated  solution  of  urea  to  blood.  If  strong  pressure  be 
exerted  upon  a  microscopic  preparation,  the  blood  corpuscles  are  compressed,  and  may  break  in 
pieces.  This  latter  process  of  breaking  up  the  corpuscles  is  called  hsemocytotrypsis,  in  distinc- 
tion to  that  of  solution  of  the  corpuscles  or  haemocytolysis. 

Cytozoon  or  Wiirmchen — Gaale's  Experiment. —  The  following  remarkable  observation 
made  by  Gaule  deserves  mention   here  :    A  few  drops  of  freshly-shed   frog's  blood  are  mixed  with 


LAKE-COLORED    BLOOD.  23 

5  c.c.  of  0.6  per  cent,  solution  of  common  salt,  and  the  mixture  defibrinated  by  shaking  it  along 
with  a  few  c.c.  of  mercury.  A  drop  of  the  defibrinated  blood  is  examined  on  a  hot  stage  (30-32° 
C. )  under  a  microscope,  when  a  protoplasmic  mass,  the  so-called  "  'd'iirmcken,"  escapes,  with  a 
lively  movement,  from  many  corpuscles,  and  ultimately  dissolves.  .Similar  "cytozoa"  were  dis- 
covered by  Gaule  in  the  epithelium  of  the  cornea,  of  the  stomach  and  intestine,  in  connective  tissue, 
in  most  of  the  large  glands,  and  in  the  retina  (frog,  triton).  In  mammals  also  he  found  similar  but 
smaller  structures.  Most  probably  these  structures  are  parasitic  in  their  nature,  as  suggested  by 
Ray  Lankester,  who  called  the  parasite  Drepanuliutn  rnnarum. 

If  a  finger  moistened  with  blood  be  rapidly  drawn  across  a  warm  slip  of  glass, 
so  that  the  fluid  dries  rapidly,  very  remarkable  corpuscle  shapes,  showing  their 
great  ductility  and  softness,  are  observed  under  the  microscope. 

(For  the  effects  of  chemical  reagents  see  p.  24.) 

[Staining  Reagents. — Such  reagents  as  magenta,  picrocarmine,  carmine, 
and  many  ot  the  aniline  dyes,  stain  the  nucleus  deep  red  when  such  is  present,  and 
although  they  must  traverse  the  haemoglobin  to  reach  the  nucleus,  the  haemoglobin 
itself  is  not  stained.  When  no  nucleus  is  present,  therefore,  the  corpuscles  are 
not  stained.  Magenta  (as  pointed  out  by  Roberts)  causes  one  or  more  small  spots 
or  maculffi  to  appear  on  the  edge  of  the  corpuscles.  What  its  significance  is,  is 
entirely  unknown.  Normal  saUne  solution  (6  per  cent.  NaCl),  tinged  with  methyl- 
violet,  is  a  good  staining  and  preservative  agent  {Bizzozero).'\ 

[Effect  of  Agitation  with  Mercury. — Meltzer  and  Welch  find  that  if  ox  blood  be  shaken  up 
with  mercury  for  7  or  8  hour.s,  the  agitation  causes  the  corpuscles  completely  to  disappear,  no  trace 
of  stroma  or  particles  of  the  corpuscles  being  found  in  the  Huid.  On  the  other  hand,  the  addition  of 
pyrogallicacid  (20  per  cent  ),potassic  chlorate  (6  per  cent.),  and  silver  nitrate  (3  per  cent. ),  completely 
prevents  this  dissolution  of  the  corpuscles,  even  though  tiie  shaking  be  kept  up  for  fourteen  days.] 

If  blood  be  mixed  with  concentrated  gum,  and  if  concentrated  salt  solution  be  added  to  it  under 
the  microscope,  the  corpuscles  assume  elongated  forms  [Lind7i>u?-m).  Similar  iorms  are  obtained 
by  mixing  blood  with  an  equal  volume  of  gelatine  at  36°  C,  allowing  it  to  cool,  and  then  making 
seciiuns  of  the  coagulated  mass  [Rollett).  The  corpuscles  may  be  broken  up  by  pressing  firmly  on 
the  cover  glass,     in  all  these  experiments  no  trace  of  an  envelope  is  observed. 

Conservation  of  the  Red  Blood  Corpuscles. — The  blood  corpuscles  retain  their  characters 
in  the  following  fluids  : — 

Haycms  Fluid. 


Hydrarg.  bichlor., 0.5 

Sodic  sulphate, 5.0 

Sodic  chloride, i.o 

Distilled  water, 200.0 


Hydrarg.  bichlor., 2 

Sodic  chloride, 4 

Glycerine, 26 

Distilled  Water 226 

To  be  diluted  with  2  parts  of  distilled  water 
before  being  used. 

[An  excellent  reagent  for  ''  fixing  "  the  blood  corpuscles  is  either  a  dilute  solution  or  the  vapor 
of  osmic  acid.] 

In  investigating  blood  with  the  microscope  for  forensic  purposes,  it  is  necessary  to  have  a 
solvent  for  the  blood  when  it  occurs  as  stains  on  a  garment  or  instrument.  Dried  stains  are  dis- 
solved by  a  concentrated  (  Virchow),  or  a  30  per  cent.  (Malinin)  solution  of  caustic  potash,  or  with 
one  of  the  preserving  fluids,  care  being  taken  to  avoid  friction.  If  the  slain  be  softened  with  con- 
centrated tartaric  acid,  the  colorless  corpuscles  are  specially  distinct  (Stiuice).  Nevertheless,  cor- 
puscles are  often  not  found  in  such  stains.  If  the  corpuscles  have  become  very  pale,  their  color 
may  be  improved  by  adding  a  solution  of  iodine  in  iodide  of  potassium,  a  s..turated  solution  of 
picric  acid,  20  per  cent,  pyrugallic  acid,  or  3  per  cent,  solution  of  silver  nitrate  [AJe/tzer  and  Welch), 

5.  PREPARATION  OF  THE  STROMA— MAKING  BLOOD 
"  LAKE-COLORED." — There  are  many  reagents  which  separate  the  haemo- 
globin from  the  stroma.  The  haemoglobin  dissolves  in  the  serum  ;  the  blood  then 
becomes  transparent,  as  it  contains  its  coloring  matter  in  solution,  and  hence  is 
called  "Lake-colored"  by  Rollett.  Lake-colored  blood  is  dark  red.  The 
aggregate  condition  of  the  haemoglobin  is  not  altered  when  the  corpuscles  are 
dissolved  ;  it  only  changes  its  place,  leaving  the  stroma  and  passing  into  the 
serum.      Hence,  the  temperature  of  the  blood  is  not  lowered  thereby  \Landois). 

Methods. — To  obtain  a  large  quantity  of  the  stroma  for  chemical  purposes,  add  10  vols,  of  a 
solution  of  common  salt  (I  vol.  concentrated  solution,  and  15  to  20  vols,  of  water)  to  1  vol.  of 
defibrinated  blood,  when  the  stromata  are  thruwn  down  as  a  whitish  precipitate. 


24  FORM    AND    SIZE   OF    BLOOD    CORPUSCLES. 

For  microscopUal  purposes,  mix  blood  with  an  equal  volume  of  a  concentrated  solution  of  sodic 
sulphate,  and  cautiously  add  a  I  per  cent,  solution  of  tartaric  acid  ( Landois). 

The  following  reagents  cause  a  separation  of  the  stroma  from  the  hemoglobin  : — 
(a)  Physical  Agents.— i.  Heating  the  blood  to  60°  C.  \Schult:e)\  the  temperature,  however, 
varies  for  the  blood  of  diiTerent  animals.  2.  Repeated  freezing  and  thawing  of  the  blood 
(RoUell).  3.  Sparks  from  an  electrical  machine  (l-ui  not  after  the  addition  of  salts  to  the  blood) 
\Kollell)\  the  constant  and  induced  currents  [iWiiniann). 
{b\  Chemically  active  Substances  produced  within  the  Body. — 4.  Bile  (//iine/i'/i/),  orWe 
salts  [Planner,  v.  Dusch],  5.  Serum  of  other  species  of  animals  (Landois);  thus  dog's  serum 
and  frog's  serum  dissolve  the  blood  corpuscles  of  the  rabbit  in  a  few  minutes.  6.  The  addition 
of  lake-colored  blood  of  many  species  of  animals  (Landois). 
(<■)  Other  Chemical  Reagents. — 7.  Water.  8.  Conduction  of  vapor  of  chloroform  (5o.Yi-AtT) ; 
ether  {v.  IViUic/i) ;  amyis,  small  quanlitiei  of  alcohol  (Rollctt)  ;  thymol  [Marcliand)  ;  nitrolieiizol, 
ethylic  ether,  aceton,  petroleum  ether,  etc.  (L.  Lewin).  9.  Antimoniuretted  hydrogen,  arseniu- 
retted  hydrogen;  carbon  uisulphide  {Hiinefeld,  Hermann] ;  boracic  acid  (2  per  cent.),  added  to 
amphibian  blood,  causes  the  red  ma-s  (which  also  encloses  the  nucleus  when  such  is  present), 
the  so-called  zooid,  to  separate  from  the  acoiii.  The  zooid  may  shrink  from  ihe  periphery  of  the 
corpuscle,  or  it  may  even  pass  out  of  the  corpuscle  altogether  [Briie^e];  Briicke  regards  the 
stroma  in  a  certain  sense  as  a  house,  in  which  the  remainder  of  the  substance  of  the  corpuscle, 
the  chief  part  endowed  with  vital  phenomena,  lives.  11.  Strong  solutions  of  aeids  dissolve  the 
Corpuscles;  more  dilute  solutions  cause  precipitates  in  the  haemoglobin.  Thi>  is  easily  seen  with 
carbolic  acid  {J/ii/s  and  Lanaois ;  Stirling  and  A'nnnie).  12.  Alkalies  oi  moderate  strength 
cause  sudden  solution.  A  10  per  cent,  solution  of  potash,  placed  at  the  margin  of  a  cover  glass, 
shows  the  process  of  solution  going  on  under  the  microscope.  At  first  the  corpuscles  become 
globular,  and  so  appear  smaller,  but  afterward  they  burst  like  soap  bubbles.  [NH^Cl  injected 
into  the  blood  causts  vacuolation  of  the  red  cor(jUscles  [BobrilziY)-^ 
[Tannic  Acid. — A  freshly-prepared  solution  of  tannic  acid  has  a  remarkable  effect  on  the  colored 
blood  corpuscles  of  man  and  animals — causing  a  separation  of  the  haemoglobin  and  the  stroma. 
The  usual  eftect  is  to  produce  one  or  more  granular  buds  of  haemoglobin  on  the  side  of  the  cor- 
puscles; more  rarely  the  haemoglobin  collects  around  the  nucleus,  if  such  be  present  (IV. 
A'oberls).'] 
[Ammonium  or  Potassium  Sulphocyanide  removes  the  hsemoglobin,  and  reveals  a  reticular 
structure — inlra  nuclear  plexus  of  fibrils  (Stirling  and  Rannie)."] 

The  quantity  of  gases  contained  in  the  blood  corpuscles  exercises  an  important  influence  on  their 
solubility.  The  corpuscles  of  venous  blood,  which  contains  much  CO,,  are  more  easily  dissolved 
than  those  of  arterial  blood;  while  between  both  stands  blood  containing  CO  (Landois,  Lilterski, 
Lipine).     When  the  gases  are  completely  removed  from  the  blood,  it  becomes  lake-colored. 

Salts  increase  the  resistance  of  the  corpuscles  to  physical  means  of  solution, 
while  they  facilitate  the  action  of  chemical  solvents  (Bernstein  and  Becker). 

Resistance  to  Solvents. — The  red  blood  corpuscles  offer  a  certain  degree 
of  resistance  to  the  action  of  solvents. 

Method. — Mix  a  small  drop  of  blood  with  an  equal  volume  of  a  3  per  cent,  solution  of  sodic 
chloride,  and  then  add  distilled  water  until  all  the  colored  corpuscles  are  dissolved.  Fill  the  mixer 
(Fig.  3)  up  to  the  mark  I  with  blood  obtained  by  pricking  the  finger,  and  blow  this  blood  into  an 
equal  volume  of  a  3  per  cent,  solution  of  NaCl  previously  placed  in  a  hollow  in  a  micro.scopic  glass 
slide.  Mix  the  tluids,  and  the  corpuscles  will  remain  undissolved.  By  means  of  the  pipette  add 
distilled  water,  and  go  on  doing  so  until  all  the  corpuscles  are  dissjlved;  which  is  ascertained 
with  the  microscope.  In  normal  blood,  solution  of  the  corpuscles  occurs  after  30  volumes  of  dis- 
tilled water  have  been  added  to  the  blood  (Landois). 

There  are  some  individuals  whose  blood  is  more  soluble  than  that  of  others ;  their  corpuscles  are 
soft,  and  readily  undergo  changes.  Many  conditions  again,  such  as  choUemia,  poisoning  with  sub- 
stances which  dissjlve  the  corpuscles,  and  a  markedly  venous  condition  of  the  blood,  affect  the 
corpuscles.  Interesting  observations  are  to  be  made  on  the  blood  in  infectious  diseases,  h.iemoglo- 
binuria,  and  in  cases  of  burning.  In  anaemia  and  fever,  the  capacity  for  resistance  seems  to  be 
diminished  (Peiper).  [Sodic  salicylate,  benzoate  and  colchicin  dissolve  the  red  corpuscles  (A'. 
Paton).'\ 

6.  FORM  AND  SIZE  OF  THE  BLOOD  CORPUSCLES  OF 
DIFFERENT  ANIMALS.— .\11  mammals  (with  the  e.xception  of  the  camel, 
llama,  alpaca,  and  their  allies),  and  the  cyclostoniata  among  fishes,  e.g.,  Petromy- 
zon,  possess  circular,  bi-concave,  non- nucleated,  disk-shaped  corpuscles. 

Elliptical  corpuscles  without  a  nucleus  are  found  in  the  above-named  mammals, 
while  all  birds,  reptiles,  amphibians  (Fig.  r,  B,  i,  2),  and  fishes  (excejit  cyclosto- 
mata)  have  nucleated,  elliptical,  bi-convex  corpuscles. 


ORIGIN   OF   THE    RED    BLOOD   CORPUSCLES. 


25 


Size  {fx  =  o.ooi  Millimetre). 

Of  the  Disk-shaped 
Corpuscles. 

Of  the  Elliptical  Corpuscles. 

Short  Diameter. 

1 
Long  Diameter. 

Elephant,   ....      94.'-' 
Man,      .....      7.7  " 

Dog 7-3  " 

Rabbit 6.9  " 

Cat, 6.5  " 

Sheep 5.0  " 

Goat 4'   " 

Musk  deer,      ...       2.5  " 

Llama 4.0  /x 

Dove,      6.5  " 

f-'og.      '5-7  " 

Irilon, ig-S  " 

Proteus 35  0  " 

The  corpuscles  of   Amphiu 
than  those  of  Proteus  (Riddel). 

8.0  1). 
14.7   •' 
22.3   " 
293  •' 

58.0  " 

Tia  are  nearly  one  third  larger 

Among  vertebrates,  amphioxus  has  colorless  blood.  The  large  blood  corpuscles  of  many 
amphibia,  t-.i,'.,  amphiuma,  are  visible  to  the  naked  eye.  The  blood  corpuscles  of  the  frog  contain, 
in  addition  to  a  nucleus,  a  nucleolus  (Aiierbach,  Ranvim),  [and  the  same  is  true  of  the  colored  cor- 
puscles of  the  newt  [Stirling^.  The  nucleolus  is  revealed  by  acting  on  the  corpuscles  with  dilute 
alcohol  (I,  alcohol;  2,  water;  Ranvier's  '•  alcool  au  //«i").]  It  is  evident  that  the  larger  the 
blood  corpuscles  are,  the  smaller  must  be  the  number  and  total  superficies  of  corpuscles  in  a  given 
volume  of  blood,  in  birds,  however,  the  number  is  relatively  larger  than  in  other  classes  of  verte- 
brates, notwithstanding  the  larger  size  of  their  corpuscles;  this,  doubtless,  has  a  relation  to  the  very 
energetic  metabolism  that  lakes  place  in  birds  (Mulassez).  Among  mammals,  carnivora  have 
more  bliod  corpuscles  than  herbivora.  Welcker  has  ascertained  that  goat's  blood  contains  9,720,000 
corpuscles  per  cubic  millimetre;  the  llama's  13,000,000;  the  bullfinch's,  3,600,000;  the  lizard'.s, 
1,420,000;  the  frog's,  404,000;  the  proteus',  36,000.  In  hybernating  animals,  Vierordt  found 
that  the  number  of  corpuscles  diminished  from  7,000,000  to  2,000,000  per  cubic  millimetre  during 
hybernation. 

The  invertebrata  generally  have  colorless  blood,  with  colorless  corpuscles;  but  the  earthworm, 
and  the  larva  of  the  large  gnats,  etc.,  have  red  blood  whose  plasma  contains  haemoglobin,  while  the 
blood  corpuscles  themselves  are  colorless.  Many  invertebrates  possess  red,  violet,  brown,  or  green 
opalescent  blood  with  colorless  corpuscles  (amreboid  cells).  In  cephalopods,  and  some  crabs,  the 
blood  IS  blue,  owing  to  the  presence  of  a  coloring  matter  (Haemocyanin)  which  contains  copper, 
and  combines  with  O  [Bert,  Rabuteau  and  Papillon,  Fi-edirin],  and  Krukenberg). 

[Elaborate  measurements  of  the  blood  corpusc'es  have  been  made  in  this  country  by  Gulliver,  but 
the  relative  size  may  be  best  appreciated  by  comparing  the  corpuscles  from  various  vertebrates. 
There  is  no  relation  between  the  size  of  the  animal  and  the  size  of  its  blood  corpuscles.] 

7.  ORIGIN  OF  THE  RED  BLOOD  CORPUSCLES.— (A)  Origin 
of  the  Nucleated  Red  Corpuscles  during  Embryonic  Life. — Blood  cor- 
puscles are  developed  in  the  fowl  during  the  first  days  of  embryonic  life.  [They 
appear  in  groups  within  the  large  branched  cells  of  the  mesoblast,  in  the  vascular 
area  of  the  blastoderm  outside  the  developing  body  of  the  chick  or  embryo,  wliere 
they  form  the  '■'blood  islands''  of  Pander.  The  mother  cells  form  an  irregular 
network  by  the  union  of  the  processes  of  adjoining  cells,  and  meantime  the  central 
masses  split  up,  and  the  nuclei  multiply.  The  small  nucleated  masses  of  pro- 
toplasm, which  represent  the  blood  corpuscles,  acquire  a  reddish  hue,  while  the 
surrounding  protoplasm,  and  also  that  of  the  processes,  becomes  vacuolated  or 
hollowed  out,  constituting  a  branching  system  of  canals ;  the  outer  part  of  the 
cells  remaining  with  their  nuclei  to  form  the  walls  of  the  future  blood  vessels.  A 
fluid  appears  within  this  system  of  branched  canals  in  which  the  corpuscles  lie, 
and  gradually  a  communication  is  established  with  the  blood  vessels  developed  in 
connection  with  the  heart.] 

[According  to  Klein,  the  nuclei  of  the  protoplasmic  wall  may  also  proliferate, 
and  give  rise  to  new  corpuscles,  which  are  washed  away  to  form  blood  corpuscles.] 
At  first  the  corpuscles  are  devoid  of  pigment,  nucleated,  globular,  larger,  and 
more  irregular  than  the  permanent  corpuscles,  and  they  also  e.xhibit  amoeboid 
movements.  They  become  colored,  retain  their  nucleus,  and  are  capable  of  under- 
going multiplication  by  division  ;  and,  in  fact,  Remak  observed  all  the  stages  of 
the  process  oi  division.     The  process  of  division  is  best  seen  from  the  3d-5th  day 


26 


ORIGIN    OK   THE    RED    BLOOD   CORPUSCLES. 


of  incubation.  Increase  by  division  also  takes  place  in  the  larvae  of  the  salaman- 
der, triton  and  toad  (Flemming,  Percrneschko),  and  also  during  the  intra-uterine 
life  of  a  mammal,  in  the  spleen,  bone  marrow,  the  liver  and  the  circulating  blood 
{Biszozero,  E berth). 

After  the  liver  is  developed,  blood  corpuscles  seem  to  be  formed  in  it  {E.  H. 
Weber,  Kolliker).  Neumann  found  in  the  liver  of  the  embryo  protoplasmic  cells 
containing  red  blood  corpuscles.  Cells,  some  with,  others  without,  Hb,  but  with 
large  nuclei,  have  been  found.  These  cells  increase  by  division,  their  nucleus 
shrivels,  and  they  then  ultimately  form  blood  corpuscles  I^Lihait).  The  spleen 
is  also  regarded  as  a  centre  of  their  formation,  but  this  seems  to  be  the  case  only 
during  embryonic  life  (Net/mann).  Here  the  red  corpuscles  are  said  to  arise  from 
yellow,  round,  nucleated  cells,  which  represent  transition  forms.  Foa  and  Sal- 
violi  found  red  corpuscles  forming  endogenously  within  large  protoplasmic  cells 
in  lymphatic  glands.  In  the  later  ])eriod  of  embryonic  life,  the  characteristic 
non-nucleated  corpuscles  seem  to  be  developed  from  the  nucleated  corpuscles. 
The  nucleus  becomes  smaller  and  smaller,  breaks  up,  and  gradually  disappears. 
In  the  human  embryo  at  the  fourth  week  only  nucleated  corpuscles  are  found  ;  at 
the  third  month  their  number  is  still  \-\  of  the  total  corpuscles,  while  at  the  end 
of  foetal  life  nucleated  blood  corpuscles  are  very  rarely  found.     Of  course,  in 


.iiiijii  of  red  blood  corpuscles  withi] 
,  r,  the  formed  corpuscles ;  K,  K,  n 


:ntum  of  a  r.ibbit  seven  d.iys 
rocesses  which  ultimately  unit 


animals  with  nucleated  blood  corpuscles,  the  nucleus  of  the  embryonic  blood  cor- 
puscles remains. 

(B)  Development  of  Blood  Vessels,  Formation  of  Blood  Vessels 
and  Blood  Corpuscles  during  Post-embryonic  Life. — Kolliker  assumed 
that,  in  the  tail  of  the  tadpole,  capillaries  are  formed  by  the  anastomoses  of  the 
processes  of  branched  and  radiating  connective-tissue  corpuscles.  These  cor- 
puscles lose  their  nuclei  and  protoplasm,  become  hollowed  out,  join  with  neigh- 
boring capillaries,  and  thus  form  new  blood  channels.  J.  Arnold  and  von  Golu- 
bew,  on  the  other  hand,  oppose  this  view.  They  assert  that  the  blood  capillaries 
in  the  tail  of  the  tadpole  give  off  solid  buds  at  different  places,  which  grow  more 
and  more  into  the  surrounding  tissues,  and  anastomose  with  each  other;  their  pro- 
toplasm and  contents  disappearing,  they  become  hollow  and  a  branched  system  of 
capillaries  is  formed  in  the  tissues.  Ranvier,  be  it  remarked,  noticed  the  same 
mode  of  growth  in  the  omentum  of  newly-born  kittens. 

The  latter  observer  has  recently  studied  the  development  of  blood  vessels  and 
blood  corpuscles  in  the  omentum  of  young  rabbits.  These  animals,  when  a  week 
old,  have,  in  their  omentum,  little  white  or  milk  spots  {"  taches  /aiteuses,"  Ran- 
vier), in  which  lie  "  vaso-formative  cells,"  /.  e.,  highly  refractive  cells  of  vari- 
able shape,  with  long  cylindrical  protoplasmic  processes  (Fig.  6).     In  its  refractive 


ORIGIN    OF   THE    RED    BLOOD    CORPUSCLES.  27 

power  the  protoplasm  of  these  cells  resembles  that  of  lymph  corpuscles.  Long, 
rod-like  nuclei  lie  within  these  cells  (K,  K),  and  also  red  blood  corpuscles  {r,  r), 
and  both  are  surrounded  with  protoplasm.  These  vaso-formative  cells  give  off 
protoplasmic  points  and  processes  {a,  a),  some  of  which  end  free,  while  others 
form  a  network.  Here  and  there  elongated  connective  tissue  corpuscles  lie  on 
the  branches,  and  ultimately  form  the  adventitia  of  the  blood  vessel. 

The  vaso-formative  cells  have  many  forms :  they  may  be  elongated  cylinders 
ending  in  points,  or  more  round  and  oval,  resembling  lymph  cells,  or  they  may 
be  modified  connective-tissue  corpuscles,  as  observed  by  Schafer  in  the  sub- 
cutaneous tissue  of  young  rats.  These  cells  are  ahvavs  the  seat  of  origin  of 
non- nucleated  red  blood  corpuscles,  which  arise  in  the  protoplasm  of  vaso-formative 
cells,  as  chlorophyll  grains  or  starch  granules  arise  within  the  cells  of  plants. 
The  corpuscles  escape  and  are  washed  into  the  circulation,  when  the  cells  form 
connections  with  the  circulatory  system  by  means  of  their  processes.  It  is 
probable  that  the  vessels  so  formed  in  the  omentum  are  only  temporary.  May 
it  not  be  that  there  are  many  other  situations  in  the  body  where  blood  is 
regenerated  ? 

[The  observations  of  Schafer  also  prove  the  intra- cellular  origin  of  red  blood 
corpuscles,  and  although  this  mode  usually  cea.ses  before  birth,  still  it  is  found  in 
the  rat  at  birth.  The  protoplasm  of  the  subcutaneous  connective-tissue 
corpuscles,  which  are  derived  from  the  mesoblast,  has  in  it  small  colored 
globules  about  the  size  of  a  colored  corpuscle.  The  mother  cells  elongate, 
become  pointed  at  their  ends,  and  unite  with  processes  from  adjoining  cells. 
The  cells  become  vacuolated  ;  fluid  or  plasma,  in  which  the  liberated  corpuscles 
float,  appears  in  their  interior,  and  ultimately  a  communication  is  established 
with  the  general  circulation.] 

Similar  observations  have  been  made  by  Neumann  in  the  embryonic  liver;  by  Wissotzky  in  the 
rabbit's  amnion;  by  Klein  in  the  embryo  chicle  ;  and  by  Leboucq  and  Hayem  in  various  animals; 
all  of  which  go  to  show  that  at  a  certain  early  period  of  development  blooi  corpuscles  are  formed 
within  other  large  cells  of  the  mesoblast,  and  that  part  of  the  protoplasm  of  these  blood-forming  cells 
remains  to  form  the  wall  of  the  future  b^ood  vessel. 

[According  to  Bayerl  red  blood  corpuscles  are  formed  within  cartilage  capsules  at  the  line  of 
ossification  in  the  ribs  and  bones  of  the  extremities  of  mammalian  and  human  embryos.] 

(C )  Later  Formation  of  Red  Blood  Corpuscles. — There  is  much  diversity 
of  opinion  as  to  how  colored  blood  corijuscles  are  formed  in  mammals  at  a  later 
period.  [They  have  been  described  as  derived  from  colorless  corpuscles,  one  set 
of  observers  (including  KoUiker)  maintaining  that  the  nucleus  of  these  corpuscles 
disappears,  while  the  perinuclear  portion  remains,  becomes  flattened  and  colored, 
and  assumes  the  characters  of  the  mammalian  blood  corpuscles.  On  the  other 
hand,  other  observers  (including  Wharton  Jones,  Gulliver,  Busk,  Huxley  and 
Balfour)  are  of  opinion  that  the  nucleus  becomes  pigmented,  and  forms  the 
future  blood  corpuscle.  It  is  still  doubtful,  however,  whether  colored  corpuscles 
are  developed  in  either  of  these  ways.]  Neumann  and  Bizzozero  described 
peculiar  corpuscles  occurring  in  the  red  marrow  of  bone,  which  they  maintain 
become  developed  into  colored  blood  corpuscles,  undergoing  a  series  of  changes, 
and  forming  a  series  of  intermediate  forms,  which  may  be  detected  in  the  red 
marrow.  Bizzozero  holds  that  it  is  the  nucleus  of  the  marrow  cell  which  is 
colored,  while  Neumann  thinks  that  it  is  the  perinuclear  part  which  becomes 
colored,  and  forms  the  blood  corpuscle.  Schafer's  observations  on  the  red 
marrow  of  the  guinea  pig  rather  tend  to  confirm  Neumann's  view.  These 
transition  cells  are  said  by  Erb  to  be  more  numerous  after  severe  hemorrhage, 
the  number  of  them  occurring  in  the  blood  corresponding  with  the  energy  of  the 
formative  process.  In  dogs  and  guinea  pigs,  which  he  had  rendered  anjemic, 
Bizzozero  found  in  the  marrow  and  spleen  nucleated  red  blood  corpuscles,  which 
increased  by  division.  According  to  Neumann,  the  bone  marrow  of  adults 
contains  all  transition  forms,  from  nucleated  colored   corpuscles  to  true  red  blood 


28  DECAY  OF  THE  RED  BLOOD  CORPUSCLES. 

corpuscles.     After  copious  hemorrhage,  these  transition  forms  appear  in  numbers 
in  the  blood  stream. 

Red  or  blood-forming  marrow  occurs  in  the  bones  of  the  skull,  and  in  ^lo^t  of  the  bones  of  the 
trunk,  while  the  bones  of  the  extremities  either  contain  yellow  marrow  (which  is  essentially  fatly 
in  its  nature),  or,  at  most,  it  is  only  the  heads  of  the  long  bones  that  contain  red  marrow.  When 
the  blood  regeneration  process  is  very  active,  however,  the  jellow  marrow  may  be  changed  into  red, 
even  throughout  all  the  bones  of  the  extremities  (A'eumann). 

Rindfleisch  also  regards  the  connective  substance  of  the  red  marrow  and  the  spleen  as  the  mother- 
tissue  of  the  red  blood  corpuscles,  the  connective  substance  or  the  hreniatogenous  connective  tissue 
either  temporarily  or  permanently  forming  red  blood  corpuscles.  Once  the  red  corpuscles  are 
formed,  they  easily  enter  the  blood  stream,  as  the  capillaries  or  veins  of  the  red  marrow  have  either 
no  walls  [Hoyer,  KoHmann),  or  exceedingly  thin,  perforated  walls.  Similar  conditions  obtain  in 
the  spleen. 

Bizzozero  and  Torre  found  that,  after  severe  hemorrhage  in  birds,  the  marrow  of  the  bones 
contained  globular,  granular,  nucleated  cells,  whose  protoplasm  was  colored  with  h3;moglobin, 
while  between  these  and  the  oval,  biconvex,  nucleated  corpuscles  of  the  bird,  there  were  numerous 
transition  stages.  The  spleen  of  the  Ijird  seems  to  be  of  much  less  importance  in  the  formation  of 
blood  corpuscles  {A'orn).  AH  these  observations  prove  that  the  red  marrow  of  the  bones  is  a  great 
manufactory  lor  colored  blood  corpuscles. 

V.  Recklinghausen  observed  the  direct  Jransformation  of  these  intermediate  forms  into  blood 
corpuscles  in  Irogs'  blood  which  was  kept  for  several  days  in  a  moist  chamber.  A.  Schmidt  and- 
Semmer  found  in  the  blood  large  lymph  Ctlls,  filled  with  granules  of  hiemogoblin,  and  they  legard 
these  as  intermediate  forms  between  colorless  and  colored  corpuscles. 

[Malassez,  from  an  investigation  of  the  red  marrow  of  young  kids,  finds  that  the  cells  of  the  red 
marrow  and  certain  cells  in  the  spleen  form  rounded  colored  projections  or  buds  on  their  surface, 
'ihese  gel  detached  and  form  young  blood  corpuscles,  which  soon  become  disk-shaped;  while  the 
mother  cell  itself  continues  to  produce  other  colored  corpuscles.  Thus  gemmation  of  the  splenic 
and  medullary  cells  constitutes  one  great  process  in  the  manufacture  of  blood  corpuscles.  Hence 
it  is  apparent  why  diseases  of  the  bone  in  children  lead  to  ana;mia,  and  soon  bring  about  a  cachectic 
condition.] 

[In  mammals,  birds,  reptiles,  and  tailless  amphibians,  colored  blood  corpuscles  divide  in  bone 
marrow.  In  the  tailed  amphibians  (  Triton  crista'us)  the  bone  marrow  consists  of  fat,  and  shows 
none  of  the  characters  of  a  blood-forming  organ.  In  tailed  amphibians,  again,  Bizzozero  and  Torre 
find  the  first  example  of  animals  in  which,  in  atlults,  red  blood  corpuscles  are  formed  in  the  spleen, 
where  the  process  of  indirect  division  is  very  marked,  especially  if  the  corpuscles  be  stained  by 
methyl-violet  in  i^  per  cent.  NaCl  solution,  and  afterwaid  with  ^','  per  cent,  acetic  acid.] 

8.  DECAY  OF  THE  RED  BLOOD  CORPUSCLES.— The  blood 
corpuscles  must  positively  undergo  decay  within  a  limited  time,  and  the  liver  is 
regarded  as  one  of  the  chief  places  in  which  their  disintegration  occurs,  because 
bile  pigments  are  formed  from  haemoglobin,  and  the  blood  of  the  hepatic  vein 
contains  fewer  red  corpuscles  than  the  blood  of  the  portal  vein. 

The  splenic  pulp  contains  cells  which  seem  to  indicate  that  colored  corpuscles 
are  broken  up  within  it.  These  are  the  so-called  "  blood-corpuscle-containiiig 
cells."  Quincke's  observations  go  to  show  that  the  red  corpuscles — which  may 
live  from  three  to  four  weeks — when  about  to  disintegrate,  are  taken  up  by  white 
blood  corpuscles,  and  by  the  cells  of  the  spleen  and  the  bone  marrow,  and  are 
stored  up  chiefly  in  the  capillaries  of  the  liver,  in  the  spleen,  and  in  the  marrow 
of  bone.  They  are  transfortned,  partly  into  colored,  and  partly  into  colorless 
proteids  which  contain  iron,  and  are  either  deposited  in  a  granular  form,  or  are 
dissolved.  Part  of  the  products  of  decomposition  is  used  for  the  formation  of 
new  blood  corpuscles  in  the  marrow  and  in  the  spleen,  and  also  perhaps  in  the 
liver,  while  a  portion  of  the  iron  is  excreted  by  the  liver  in  the  bile. 

That  the  normal  red  blood  corpuscles  and  other  particles  suspended  in  the  blood  stream  are  not 
taken  up  in  this  way,  may  be  due  to  their  being  smooth  and  polished.  As  the  corpuscles  grow 
-  older  and  become  more  rigid,  they,  as  it  were,  are  caught  by  the  amceboid  cells.  As  cells  con- 
taining blood  corpuscles  are  very  rarely  found  in  the  general  circulation,  one  may  assume  that  the 
occurrence  of  these  cells  within  the  spleen,  liver  and  marrow  of  bone  is  favored  by  the  slowness  of 
the  circulation  in  these  organs  (Quincke). 

Pathological. — In  certain  pathological  conditions,  ferruginous  substances  derived  from  the  red 
blood  corpuscles  are  found  in  the  spleen,  in  the  marrow  of  bone,  and  in  the  capillaries  of  the 
liver:  (I)  When  the  disintegration  of  blood  corpuscles  is  increased,  as  in  3.nxni\a  (Sta/iel).  (2) 
When  the  formation  of  red  blood  corpuscles  from  the  old  material  is  diminished.     If  the  excretion 


THE   COLORLESS   BLOOD   CORPUSCLES. 


29 


from  the  liver  cells  be  prevented,  iron  accumulates  within  them;  it  is  also  more  abundant  in  the 
blood  serum,  and  it  may  even  accumulate  in  the  secretory  cells  of  the  cortex  of  the  kidney  and 
pancreas,  in  gland  cells,  and  in  the  tissue  elements  of  other  organs  [Qtiimke).  When  the  amount 
of  blood  is  greatly  increased  (in  dogs),  after  four  weeks  an  enormous  number  of  granules  containing 
iron  occur  in  the  leucocytes  of  the  liver  capillaries,  the  cells  of  the  spleen,  bone  marrow,  lymph 
glands,  the  liver  cells,  and  the  epithelium  of  the  cortex  of  the  kidney  ( Quincke).  The'iron  reaction 
in  the  two  last  situations  occurs  after  the  introduction  of  hasmoglobin,  or  of  salts  of  iron  into  the 
blood  (Glae-jcck  and  v.  Stark). 

When  we  reflect  how  rapidly  (relatively)  large  quantities  of  blood  are  replaced 
after  heniorrhage  and  after  menstruation,  it  is  evident  that  there  must  be  a  brisk 
manufactory  somewhere.  As  to  the  number  of  corpuscles  which  daily  decay,  we 
have  in  some  measure  an  index  in  the  amount  of  bile  pigment  and  urine  pigment 
resulting  from  the  transformation  of  the  liberated  haemoglobin  (§  20). 

9.  THE  COLORLESS  CORPUSCLES  (LEUCOCYTES). 
BLOOD  PLATES  AND  ELEMENTARY  GRANULES.— I.  White 
Blood  Corpuscles. — Blood,  like  many  other  tissues,  contains  a  number  of  cells 

Fig.  7. 


White  blood  corpuscles.  A,  human.,  without  the  addit 
visible  ;  C,  after  the  action  of  acetic  acid  ;  D,  frogs' 
ment;    E,  fibrils  of  fibrin  from  co,igulated  blood  ;   F, 


^ 

f 


ion  of  any  reagent :  B,  after  the  addition  of  water,  i 
:orpuscles  showing  changes  of  shape  due  to  amoeboid  r 
:lementaty  granules. 


or  corpuscles  which  reach  it  from  without ;  the  corpuscles  vary  somewhat  in  form, 
and  are  called  colorless  or  white  blood  corpuscles,  or  "leucocytes" 
{Hewson,  1770).  Similar  corpuscles  are  found  in  lymph,  adenoid  tissue,  marrow 
of  bone,  as  wandering  cells  or  leucocytes,  in  connective  tissue,  and  also  between 
glandular  and  epithelial  cells.  They  all  consist  of  more  or  less  spherical  masses 
of  protoplasm,  which  is  sticky,  highly  refractile,  soft,  capable  of  movement,  and 
devoid  of  an  envelope  (Fig.  7).  When  they  are  quite  fresh  (A)  it  is  difficult  to 
detect  the  nucleus,  but  after  they  have  been  shed  for  some  time,  or  after  the 
addition  of  water  (B),  or  acetic  acid,  the  nucleus  (which  is  usually  a  compound 
one)  appears  ;  acetic  acid  clears  up  the  perinuclear  protoplasm,  and  reveals  the 
presence  of  the  nuclei,  of  which  the  number  varies  from  one  to  four,  although 
generally  three  are  found.  The  subsequent  addition  of  magenta  solution  stains 
the  nuclei  deeply.  Water  makes  the  contents  more  turbid,  and  causes  the 
corpuscles  to  swell  up.  One  or  more  nucleoli  may  be  present  in  the  nucleus. 
The  corpuscles  contain  proteids,  but  they  also  contain  fats,  lecithin,  and  salts 


80  THE    COLORLESS    BLOOD   CORPUSCLES. 

(§  24).  The  size  of  the  corpuscles  varies  from  four  to  thirteen  ,«,  and  as  a  rule 
they  are  abotit  ^3'13-jj  of  an  inch  in  diameter,  and  in  the  smallest  the  layer  of  the 
protoplasm  is  extremely  thin.  They  all  have  the  property  of  exhibiting  amceboid 
movements,  which  are  very  apparent  in'  the  larger  corpuscles.  These  movements 
were  discovered  by  Wharton  Jones  in  the  skate,  and  by  Davine  in  the  corpuscles 
of  man.     Max  Schultze  describes  three  different  forms  in  human  blood  :  — 

(i)  The  smallest,  round  forms,  less  than  the  red  corpuscles,  with  one  or  two 
nuclei,  and  a  very  small  amount  of  protoplasm  ; 

(2)  Round  forms,  the  same  size  as  the  colored  blood  corpuscles; 

(3)  The  large  amoeboid  corpuscles,  with  much  protoplasm  and  distinctly  evi- 
dent movements. 

[When  a  drop  of  human  blood  is  examined  under  the  microscope,  more  especially  after  the 
colored  blood  corpuscles  have  run  into  rouleaux,  the  colorless  corpuscles  may  readily  be  detected, 
there  being  usually  three  or  four  of  them  visible  in  the  field  at  once.  They  adhere  to  the  glass 
slide,  for  if  the  cover  glass  be  moved,  the  col  red  corpuscles  readily  glide  over  each  other,  while  the 
colorless  can  be  seen  still  adhering  to  the  slide.] 

[White  Corpuscles  of  Newt's  Blood. — The  characters  of  the  colorless  corpuscles  are  best 
studied  in  a  drop  of  newt's  blood.  Cut  otf  the  tip  of  the  tail  and  express  a  drop  of  blood  on  to  a 
slide,  cover  it  with  a  thin  glass,  and  examine.  Neglecting  the  colored  corpuscles,  search  for  the 
colorless,  of  which  there  are  three  varieties: — 

( 1)  The  Large,  Finely  Granular  Corpuscle,  which  is  about  jj^  of  an  inch  in  diameter,  irregu- 
lar in  outline,  with  fine  processes  or  pseudopodia  projecting  from  its  surface.  It  rapidly  changes  its 
shape  at  the  ordinary  temperature,  and  in  its  interior  a  bi-  or  tripartite  nucleus  may  be  seen,  sur- 
rounded with  fine  granular  protoplasm,  whose  outline  is  continually  changing  Sometimes  vacuoles 
are  seen  in  the  protoplasm. 

(2)  The  Coarsely  Granular  Variety  is  less  common  than  the  first  mentioned,  but  when  de- 
tected its  characters  are  distinct.  The  protoplasm  contains,  besides  a  nucleus,  a  large  number  of 
highly  refractive  granules,  and  the  corpuscle  usually  exhibits  active  amoeboid  movements;  suddenly 
the  granules  may  be  seen  to  rush  from  one  .side  of  the  corpuscle  to  the  other.  The  processes  are 
usually  more  blunt  than  those  emitted  by  (i).  The  relation  between  these  two  kinds  of  corpuscles 
has  not  been  ascertained. 

{3)  The  Small,  Colorless  Corpuscles  are  more  like  the  ordinary  human  colorless  corpuscle, 
and  they,  too,  exhibit  amceboid  movements. 

Two  kinds  of  colorless  corpuscles  like  (i)  and  (2)  exist  in  frogs'  blood.  In  the  coarsely  granular 
corpuscles  the  glancing  granules  may  be  of  a  fatty  nature,  since  they  dissolve  in  alcohol  and  ether, 
but  other  granules  exist  which  are  in.soluble  in  these  fluids,  and  the  nature  of  which  is  unknown. 
Very  large  colorless  corpuscles  exi»t  in  the  axolotl's  blood  (/ianvier).'] 

[Action  of  Reagents. — {a)  Water,  when  added  slowly,  causes  the  colorless 
corpuscles  to  become  globular,  and  the  granules  within  them  to  exhibit  Brownian 
movements  (Richardso/i,  S/nWcrr).  (b)  Pigments,  such  as  magenta  or  carmine, 
stain  the  nuclei  very  deeply,  and  the  protoplasm  to  a  less  extent,  (r)  Dilute 
Acetic  Acid  clears  up  the  surrounding  protoplasm  and  brings  clearly  into  view  the 
composite  nucleus,  which  may  be  stained  thereafter  with  magenta.  (^/)  Iodine 
gives  a  faint  port-wine  color  (horse's  blood  indicating  the  presence  of  glycogen 
best).  ((')  Dilute  Alcohol  causes  the  formation  of  clear 
Fir..  8.  blebs  on   the  surface  of  the  corpuscles,   and   brings  the 

nuclei  clearly  into  view  {Ranvicr,  Stirling).'] 

[.\  delicate  plexus  of  fibrils — intra-nuclear  plexus — 
exists  within  the  nucleus,  just  as  in  other  cells.  It  is  very 
probable  that  the  ])rotoplasm  itself  is  pervaded  by  a  similar 
plexus  of  fibrils,  and  that  it  is  continuous  with  the  intra- 
nuclear plexus  (Fig.  8).] 

The  colorless  corpuscles  divide,  and  in  this  way  repro- 
duce themselves  (Klein). 

The  Number  of  Colorless  Blood  Corpuscles  is 

very  much  less  than  that  of  the  red  corpuscles,  and  is  sub- 

1  1        ject  to  considerable  variations.     It  is  certain  that  the  color- 

piexus  of  a  colorless  cor-     |ess  corpusclcs  are  Very  much  fewer  in  shed  blood  than  in 

(A7«>r).*"     '""  "'"^^'     blood  still  within  the  circulation.     Immediately  after  blood 


AMCEBOID    MOVEMENTS    OF   THE   COLORLESS   CORPUSCLES. 


31 


is  shed,  an  enormous  number  of  white  corpuscles  disappear  (see  Formation  of 
Fibrin,  §  31).  [The  extent  to  which  this  occurs  is  questioned  by  different 
observers.] 

Al.  Schmidt  estimates  the  number  that  remain  at  ^'j,  of  the  whole  originally  present  in  the  circu- 
lating blood.     The  proportion  is  greater  in  children  than  in  adults  {Botichut  and  Diitfrisay). 

The  following  table  gives  the  number  in  shed  blood  : — 


Number  ok  White  Corpuscles  in  Proportion  to  Red  Corpuscles— 

In  Normal  Conditions. 

In  Different  Places. 

In  Different  Conditions. 

X  :  m  {Wdcker). 
I  :  357  [Molescholt]. 

Splenic  Vein,     l  :  60 
Splenic  Artery,  i  :  2260 
Hepatic  Vein,    i  :  170 
Portal  Vein,        i  :  740 
Generally   more  numerous   in 
Veins  than  Aijeries. 

Increased  by 
Digestion,  Loss  of  Blood,  Pro- 
longed Suppuration,  Parturi- 
tion, Leuka;mia,  Quinine,  Bit- 
ters. 

Diminished  by 
Hunger,  Bad  Nourishment. 

The  number  also  varies  with  the  A^re  and  Sex :- 


Age.  Sex. 

White.  Red. 

General  Conditions. 

White.  Red. 

Girls, 

Boys, 

Adults 

Old  Age, 

I  :  405 
I  :  226 
'  :  334 
I  :  38.                j 

While  fasting,    .    . 
After  a  meal,    .    , 
During  pregnancy. 

I  :  716 

I  :  347 
I  :  281 

The  old  method  of  Wchker  for  estimating  the  number  of  colorless  corpuscles  is  unsatisfactory. 
The  blood  was  defibrlnated,  placed  in  a  tall  vessel,  and  allowed  to  subside,  when  a  layer  of  color- 
less corpuscles  was  obtained  immediately  under  a  layer  of  serum.  [It  is  better  to  use  the  hasma- 
cytometer  (p.  21 )  as  improved  by  Cowers.] 

The  AmcEboid  Movements  of  the  white  corpuscles  (so  called  because  they 
resemble  the  movements  of  amceba)  consist  in  an  alternate  contraction  and 
relaxation  of  the  protoplasm  surrounding  the  nucleus.  Processes  are  given  off 
from  the  surface,  and  are  retracted  again  (like  the  pseudopodia  of  amoeba). 
There  is  an  internal  current  in  the  protoplasm,  and  the  nucleus  has  also  been 
observed  to  change  its  form  [and  exhibit  contractions  without  the  corpuscle  divid- 
ing. The  karyokinetic  figures  or  aster,  and  convolution  of  the  intranuclear 
plexus  have  been  seen]  {Lawiiowsky).  Two  series  of  phenomena  result  from  these 
movements:  (i)  The  '■  loandering"  or  locomotion  of  the  corpuscles  due  to  the 
extension  and  retraction  of  their  processes ;  (2)  the  absorption  of  smait  particles 
into  their  interior  (fat,  pigment,  foreign  bodies).  The  particles  adhere  to  the 
sticky  external  surface,  are  carried  into  the  interior  by  the  internal  currents 
(Freyer),  and  may  eventually  be  excreted,  just  as  particles  are  taken  up  by  amoeba 
and  the  effete  particles  excreted.  [Max  Schultze  observed  that  colored  particles 
were  readily  taken  up  by  these  corpuscles.] 

[Conditions  for  Movement. — In  order  that  the  amoeboid  movements  of  the 
leucocytes  may  take  place,  it  is  necessary  that  there  be — (i)  a  certain  temperature 
and  normal  atmospheric  pressure;  (2)  the  surrounding  medium,  within  certain 
limits,  must  be  "indifferent,"  and  contain  a  sufficient  amount  of  water  and 
oxygen  ;   (3)  there  must  be  a  basis  or  support  to  move  on.] 

Metschnikofl"  emphasizes  the  activity  of  the  leucocytes  in  retrogressive  processes,  whereby  the 
parts  to  be  removed  are  taken  up  by  them  in  line  granules,  and,  as  it  were,  are  "  eaten."  Hence, 
he  calls  such  cells  "  phagocytes."  They  nny  be  found  in  the  atrophied  tails  of  batrachians,  the 
Cells  containing  in  their  interior  whole  pieces  of  nerve  fibre  and  primitive  muscular  bundles.    Schizo- 


32 


AiMtEBOID    MOVEMENTS    OF    THE    COLORLESS    CORPUSCLES. 


mycetes  which  have  found  their  way  into  the  blood  (^  183)  have  been  found  to  be  partly  taken  up 
by  the  colorless  corpuscles. 

Effects  of  Reagents. — On  a  hot  stage  (35-40°  C.)  the  colorless  corpuscles 
of  warm-blooded  animals  retain  their  movements  for  a  long  time ;  at  40°  C. 
for  two  to  three  hours;  at  50°  C.  the  proteids  are  coagulated  and  cause  ^^  heat 
rigor"  and  death  [when  their  movements  no  longer  recur  on  lowering  the  tem- 
perature]. In  cold-blooded  animals  (frogs),  colorless  corpuscles  may  be  seen 
to  crawl  out  of  small  coagula,  in  a  moist  chamber,  and  move  about  in  the  serum. 
[Draw  a  drop  of  newt's  blood  into  a  capillary  tube,  seal  up  the  ends  of  the  latter 
and  allow  the  blood  to  coagulate.  After  a  time,  examine  the  tube  in  clove  oil, 
when  some  of  the  colorless  corpuscles  will  be  found  to  have  made  their  way  out  of 
the  clot.]     Induction  shocks  cause  them  to  withdraw  their  processes  and  become 

Fig.  9. 


spherical,  and,  if  the  shocks  be  not  too  severe,  their  movements  recommence. 
-Strong  and  continued  shocks  kill  them,  causing  them  to  swell  up,  and  completely 
disintegrating  them.      Oxygen  is  necessary  for  their  movements. 

Diapedesis. — These  amosboid  movements  are  of  special  interest  on  account 
of  the  "  wandering  out  "  (diapedesis)  of  colorless  blood  corpuscles  through  the 
walls  ot  the  blood  vessels  (§  95). 

[Effect  of  Drugs. — Acids  and  nllialics,  if  very  dilute,  at  first  increase,  but  afterward  arrest  their 
mcjvcments.  Sodic  chloride  in  a  I  per  cent,  solution  at  fiist  accelerates  their  movements,  but  after- 
ward produces  a  tetanic  contraction,  and,  it  may  be,  expulsion  of  any  food  particles  they  contain. 
The  Cinchona  alialoids — quinine,  quinidine,  cinchonidine  (I  :  1500) — quickly  arrest  the  locomo- 
tive movements,  as  well  as  the  protrusion  of  pscudopodia,  although  the  leucocjtes  of  different 
animals  vary  somewhat  in  their  resistance  to  the  action  of  drugs.      Quinine  not  only  arrests  the 


THE    BLOOD    PLATES.  33 

movements  of  the  leucocytes  when  applied  to  them  directly,  but  when  injected  into  the  circulation 
of  a  frog  to  the  amount  of  jsJirtr  psf  of  the  animal's  weight,  the  leucocytes  no  longer  pass  through 
the  walls  of  the  capillaries  '(Btn:).'\ 

The  chyle  contains  leucocytes,  which  are  more  resistant  than  those  of  the  blood,  but  less  so  than 
those  of  the  coagulable  transudations  (Heyl).  The  leucocytes  of  the  lymphatic  glands  may  also 
be  dissolved  (Rauschenbach). 

Relation  to  Aniline  Pigments. — Ehrlich  has  observed  a  remarkable  relation  of  the  white 
corpuscles  to  acid  (eosin,  picric  acid,  aurantia),  baiic  (dahlia,  acetate  of  rosanilin),  or  neulral 
(picrate  of  rosanilin)  reactions.  The  smallest  jirotoplasmic  granules  of  the  cells  have  diffeient 
chemical  affinities  for  these  pigments.  Thus  Ehrlich  distinguishes  "  eosinophile,"  *'  basophile," 
and  "  neutrophile  "  granules  within  the  cells.  Eosinophile  granules  occur  in  the  leucocytes  which 
come  from  bone  m-Axxow  (^myelogenic  leucocytes).  The  small  leucocytes,  j'.t".,  those  about  the  size 
of  a  colored  blood  corpuscle  or  slightly  larger,  are  formed  in  the  lymphatic  glands  {lymphogenic 
L.).  The  large  amosboid  multi-nucleated  cells  which  are  found  outside  Ijie  vessels  in  inflam- 
mations exhibit  a  neutrophile  reaction.  Their  origin  is  unknown,  and  so  is  that  of  the  large 
uni-nucleated  cells  and  the  large  cells  with  constricted  nuclei  {Ehrlich  and  Einhorn).  The 
eosinophile  corpuscles  are  considerably  increased  in  leukaemia.  The  basophile  granules  occur  also 
in  connective-tissue  corpuscles,  especially  in  the  neighborhood  of  epithelium ;  they  are  always 
greatly  increased  where  chronic  inflammation  occurs.  As  such  conditions  are  always  accompanied 
by  an  increased  supply  of  the  nutritive  materials  necessary  for  cells,  Ehrhch  has  called  these  cells 
"  Mastzellen  "  ;  they  do  not  occur  normally  in  human  blood. 

Fig.  io. 


'  Blood  plates"  and  their  deriv.-itives,  partly  after  Bizzozero  and  Laker,     i.  red  blood  corpuscles  on  the  flat;  2,  from 
changed   hlood  plates;  4,  a  lymph  corpuscle,  surrounded  with  blood  plates;   5,   blood  plates 


variously  altered  ;  6,  a  lymph  corpuscle  with  two  heaps  of  fused  blood  plates  and  threads  of  fibrin  ;  7.  group  of 
blood  plates  fused  or  run  together;  8,  a  similar  small  heap  of  partially  dissolved  blood  plates  with  fibrils  of  fibrin. 

11.  Blood  Plates. — Special  attention  has  recently  been  directed  to  another 
element  of  the  blood,  the  "  blood  plates  "  or  "  Blutpliittchen  "  of  Bizzozero  ; 
pale,  colorless,  oval,  round,  or  lenticular  discs  of  variable  size  (mean,  3  11). 
According  to  Hayem  (who  called  these  structures  haematoblasts,  supposing 
that  they  were  an  early  stage  in  the  development  of  the  red  blood  corpuscles), 
they  are  forty  times  as  numerous  as  the  leucocytes.  These  blood  plates  may  be 
recognized  in  circulating  blood,  as  in  the  mesentery  of  a  chloralized  guinea  pig 
and  the  wing  of  a  bat.  They  are  precipitated  in  enormous  numbers  upon  threads 
suspended  in  fresh  shed  blood  {Bizzozero).  They  may  be  obtained  from  blood 
flowing  directly  from  a  blood  vessel,  on  mixing  it  with  i  per  cent,  solution  of 
osmic  acid  or  Hayem's  fluid  (p.  23),  (Laker).  They  undergo  a  rapid  change  in 
shed  blood  (Fig.  10,  5),  disintegrating,  forming  small  particles,  and  ultimately 
dissolving.  When  several  occur  together  they  rapidly  unite,  form  small  groups 
(7),  and  collect  into  finely  granular  masses  or  "  Kornchenhaufen."  These  masses 
may  be  associated  in  coagulated  blood  with  fibrils  of  fibrin  (Fig.  10). 

[These  blood  plates  are  seen  in  shed  blood,  best  in  the  guinea  pig,  especially  if  it  be  mixed  with 
a  solution  of  sodic  sulphate  {sp.  gr.  1022)  or  i{  per  cent.  NaCl  tinged  with  methyl-violet  (Bi:zoscro).'] 
3 


34  CHANGES   OF   THE    RED   AND    WHITE   BLOOD    CORPUSCLES. 

Bizzozero  believes  that  they  are  the  agents  which  immediately  induce  coagulation  and  take  part  in 
the  formation  of  fibrin  during  coagtilalion  of  the  blood ;  Eberth  and  Schimmelbusch  ascribe  the 
formation  of  ihrombi  to  them.  It  is  not  yet  determined  whether  they  are  derived  from  partially 
dismtegrated  leucocytes,  as  a  consequence  of  alteration  of  the  blood  [Lniuit),  or  whether  they  are 
independent  formations.  Along  with  the  leucocytes  they  are  concerned  in  the  formation  of  fibrin 
[//lava).  These  structures  were  known  to  early  observers  (Mux  Schultze,  Kicss,  and  others); 
but  their  significance  has  been  variously  interpreted.  Halla  found  that  they  are  increased  in 
pregnancy,  and  Afanassiew  in  conditions  of  regeneration  of  the  blood.  [Gibson's  view  is  that  these 
blood  plate-;,  which  he  calls  colorh'ss  mi(rocyles,  are  derived  from  the  nucleus  of  young  red  blood 
corpuscles,  or,  occasionally  from  the  nucleus  of  white  corpuscles.] 

[As  to  the  ht^iuatoblasts,  or,  as  they  have  also  been  called,  the  "globules  of  Donn6 "  by 
Pouchet,  there  seems  to  be  some  confusion,  for  both  colored  and  colorless  granules  are  described 
under  these  names.  As  Gibson  suggests,  the  former  are,  perhaps,  parts  of  disintegrated  colored 
corpuscles,  whilst  theJatter  are  the  blood  plates.] 

[The  "invisible  blood  corpuscles"  described  by  Norris  seem  to  be  simply  decolorized  red 
corpuscles  {//art,  Giison).'\ 

III.  Elementary  Granules. — Blood,  especially  after  a  microscopic  prepara- 
tion has  been  made  for  a  short  time,  is  seen  to  contain  elementary  granules 
(Fig.  7,  F),  [i.e.,  the  elementary  particles  of  Zimmermann  and  Beale.  They  are 
irregular  bodies,  much  smaller  than  the  ordinary  corpuscles,  and  appear  to  consist 
of  masses  of  protoplasm  detached  from  the  surface  of  leucocytes,  or  derived  from 
the  disintegration  of  these  corpuscles,  or  of  the  blood  plates.  Others,  again,  are 
completely  spherical  granules,  either  consisting  of  some  proteid  substance  or  fatty 
in  their  nature.  The  protoplasmic  and  the  proteid  granules  disappear  on  the 
addition  of  acetic  acid,  while  the  fatty  granules  (which  are  most  numerous  after  a 
diet  rich  in  fats)  dissolve  in  ether]. 

[Gibson  is  of  opinion  that  some  of  the  granules  are  fragments  of  broken-down  red  corpuscles. 
He  calls  ihem  colored  muroov/trs,  and  considers  them  as  representing  one  stage  of  Hayem's  hsemato- 
blasts.] 

[It  seems,  then,  that  in  addition  to  the  red  and  white  corpuscles,  there  are  two 
distinct  elements  in  shed  blood,  one  the  colored  microcyie  of  Gibson,  derived  from 
broken-down  red  corpuscles,  and  the  other  the  blood  plates  ox  colorless  7)uirocyte.'\ 

[When  the  blood-forming  process  is  particularly  active,  "  nucleated  colored 
corpuscles,"  or  the  "corpuscles  of  Neumann,"  are  sometimes  found  in  the 
blood.  They  are  identical  with  the  nucleated  colored  blood  corpuscles  of  the 
fcetus,  being  somewhat  larger  than  the  non-nucleated  colored  corpuscle  (§  7).] 

IV.  In  coagulated  blood,  delicate  fibrils  or  threads  of  fibrin  (Fig.  7,  E,  and 
10,  6,  7,  8)  are  seen,  more  especially  after  the  corpuscles  have  run  into  rouleaux. 
At  the  nodes  of  these  fibres  are  found  granules  which  closely  resemble  those 
described  under  II.  [These  granules  and  fibres  are  stained  by  magenta  and 
iodine,  but  not  by  carmine  or  picrocarmine  {^Ranvier).'\ 

10.  ABNORMAL  CHANGES  OF  THE  RED  AND  WHITE  BLOOD  COR- 
PUSCLES.— ^I)  All  hemorrhages  diminish  the  number  of  red  corpuscles  (at  most  one-half), 
and  so  does  incnstniation.  The  loss  is  partly  covered  by  the  absorption  of  fluid  from  the  tissues. 
Menstruation  shows  us  that  a  moderate  loss  of  red  corpuscles  is  replaced  within  twenty-eight  days. 
When  a  large  amount  of  blood  is  lost,  so  that  all  the  vital  processes  are  lowered,  the  time  may  be 
extended  to  five  weeks.  In  acute  fevers,  as  the  temperature  increases,  the  number  of  rc^?"  corpuscles 
diminishes,  while  the  white  corpuscles  increase  in  number  (Riegel and  Boehmann,  /-/alia). 

By  greatly  cooling  peripheral  parts  of  the  body,  as  by  keeping  the  hands  in  iced  water,  in  some 
individuals  possessing  red  blood  corpuscles  of  low  resisting  power,  these  corpuscles  are  dissolved, 
the  blood  plasma  is  reddened,  and  even  hemoglobinuria  (^  265)  may  occur  [Lichlheim,  Boas). 

Diminished  production  of  new  red  corpuscles  causes  a  decrease,  since  blood  corpuscles  are 
continually  being  used  up.  In  chlorotic  girls  there  seems  to  be  a  congenital  weakness  in  the  blood- 
forming  and  blood-propelling  apparatus,  the  cause  of  which  is  to  be  sought  for  in  some  faulty  con- 
dition of  the  mesoblast.  In  them  the  heart  and  the  blood  vessels  are  small,  and  the  absolute  number 
of  corpuscles  may  be  diminished  one  half,  although  the  relative  number  may  be  retained,  while  in 
the  corpuscles  themselves  the  ha:moglobin  is  aiminished  almost  one-third  (Duncan,  Quincke) ;  but 
it  rises  again  after  the  administration  of  iron  (Hayem).  The  administration  of  iron  increase^  the 
amount  of  hitmoglobin  in  the  blood  (Scherpf).  1  he  amount  of  iron  in  the  blood  may  be  diminished 
one-half.     [The  action  of  iron  in  anaemic  persons  has  been  known  since  the  lime  of  Sydenham. 


CHEMICAL   CONSTITUENTS    OF   THE    RED    BLOOD    CORPUSCLES. 


35 


Hayem  also  finds  that  in  certain  forms  of  anxmia  there  is  considerable  variation  in  the  size  of  the 
red  corpuscles,  and  that  in  chronic  anaemia  the  mean  diameter  of  the  corpuscles  is  always  less  than 
normal  (7  /i  to  6  /i).  There  is,  moreover,  a  persistent  alteration  in  the  volume,  coloring pmoer,  and 
consistence  of  the  corpuscles,  consequently  a  want  of  accord  between  the  number  of'  the  corpuscles 
and  their  coloring  power,  ;'.  e.,  the  amount  of  ha-moglobin  which  they  contain,  as  was  pointed  out 
by  Johann  Duncan.]  In  so-called /ith/V/ohj-  ancemia,  in  which  the  continued  decrease  in  the  red 
corpuscles  may  ultimately  produce  death,  there  is  undoubtedly  a  severe  affection  of  the  blood-form- 
ing apparatus.  The  corpuscles  assume  many  abnormal  HinA  bizarre  forms  (microcytes),  often  beinj^ 
oval  or  tailed,  irregularly  shaped,  and  sometimes  very  pale  ;  while  numerous  cells  containing  blood 
corpuscles  are  found  in  the  marrow  of  bone  (Riess).  Curiously  enough,  in  this  disease,  although 
the  red  blood  corpuscles  are  diminished  in  number,  some  may  he  larger  and  contain  more  haemo- 
globin than  do  normal  corpuscles  (Zani-Z/c).  The  number  of  colored  corpuscles  is  also  diminished 
in  chronic  poisoning  by  lead  or  miasmata,  and  also  by  the  poison  of  syphilis. 

(2)  Abnormal  forms  of  the  red  corpuscles  have  been  observed  after  severe  bums  (Lesser) ;  the 
corpuscles  are  much  smaller,  and  under  the  influence  of  the  heat  particles  seem  to  be  detached 
from  them,  just  as  can  be  seen  happening  under  the  microscope  as  the  effect  of  heat  (IVertAeim). 
Disinlegralion  of  the  corpuscles  into  fine  droplets  has  been  observed  in  various  diseases,  as  in  severe 
malarial  fevers.  The  dark  granules  of  a  pigment  closely  related  to  hoematin  are  derived  from  the 
granules  arising  from  the  disintegration  of  the  blood  corpuscles,  and  these  particles  float  in  the  blood 
(Melanaemiaj.  They  are  partly  absorbed  by  the  colorless  corpuscles,  but  they  are  also  deposited 
in  the  spleen,  liver,  brain  and  bone  marrow  (Arnstein).  Sometimes  the  rei  corpuscles  are  ab- 
normally soft,  and  readily  yield  to  pressure. 

The  white  corpuscles  are  enormously  increased  in  number  in  Leukaemia  (/.  H.  Bennet  and 
I'lrchow) ;  sometimes  even  to  the  extent  of  the  red  corpuscles.  In  some  cases  the  blood  looks  as 
if  it  were  mixed  with  milk.  The  colorless  corpuscles  seem  to  be  formed  chiefly  in  bone  marrow 
{£.  A^eiimann),  but  also  in  the  spleen  and  lymphatic  glands  (myelogenic,  splenic  and  lymphatic 
leuka-mia). 

II.  CHEMICAL  CONSTITUENTS  OF  THE  RED  BLOOD 
CORPUSCLES.—  ij  The  coloring  matter  or  haemoglobin  (Hlj; 
f  Haimatogiobulin,  Hasmatocrystaliin  1,  is  the  cause  of  the  red  color  of  blood;  it 
also  occurs  in  muscle,  and  in  traces  in  the  fluid  part  of  blood,  but  in  this  last  case 
only  as  the  result  of  the  solution  of  some  red  corpuscles.  Ix.?, percentage  composi- 
tion is  :  C  53.85,  H  7.32,  N  16.17,  Fe  0.42,  S  0.39,  O  21.84  (dog).  Its  rational 
formula  is  unknown,  but  Preyer  gives  the  empirical  formula  C^qq,  H^jj,  Njj^, 
Fe,  S3,  Ojjg.  Although  it  is  a  colloid  substance  it  crystallizes  \Hiincfeld,  1840, 
Heichert)  m  all  classes  of  vertebrates,  according  to  the  rhombic  system,  and 
chiefly  in  rhombic  plates  or  prisms ;  in  the  guinea  pig  in  rhombic  tetrahedra 
(v.  Lang)  ;  in  the  squirrel,  however,  it  yields  hexagonal  plates.  The  varying 
forms,  perhaps,  correspond  to  slight  differences 
in  the  chemical  composition  in  different  cases. 
Crystals  separate  from  the  blood  of  all  classes  of 
vertebrata  during  the  slow  evaporation  of  lake- 
colored  blood,  but  with  varying  facility  (Fig.  11). 

The  coloring  matter  crystallizes  very  readily  firom  the 
blood  of  man,  dog,  mouse,  guinea  pig,  rat,  cat,  hedgehog, 
horse,  rabbit,  birds,  fishes;  with  difficulty  from  that  of  the 
sheep,  ox  and  pig.  Colored  crystals  are  not  obtained  from 
the  blood  of  the  frog.  More  rarely  a  crystal  is  formed  from 
a  single  corpuscle  enclosing  the  stroma.  Crystals  have  been 
found  near  the  nucleus  of  the  large  corpuscles  of  fishes,  and 
in  this  class  of  vertebrates  colorless  crystals  have  been 
observed. 

Hnemoglobin  crystals  are  doubly  refractive  and 
pleo-chromatic ;  they  are  bluish  red  with  trans- 
mitted light,  scarlet-red  by  reflected  light.  They 
contain  from  3  to  9  per  cent,  water  of  crystalliza- 
tion, and  are  soluble  in  water,  but  more  so  in 
dilute  alkalies.  They  are  insoluble  in  alcohol, 
ether,   chloroform,  and  fats.     The   solutions  are    Hemoglobin  cr>-suis    a,  *,  from  human 

d,        .  ,     -  n  ,     1*    1  ,  ■  blood;   c,  irom    the    cat;    tf ,  from   the 

ichroic  ;    red    m    reflected    light,   and  green    in         guinea  pig  ;<,  hamster  ;/,squjrrei. 


Fig. 


36  QUANTITATIVE    ESTIMATION    OF    H.-EMOGLOBIN. 

transmitted  light.  [The  solutions  are  readily  decomposed  by  boiling,  while  they 
are  precipitated  by  mineral  acids,  alcohol,  and  acetic  acid.] 

In  the  act  of  crystallization  the  haemoglobin  seems  to  undergo  some  internal  change.  Before  it 
crystallizes  it  does  not  diffuse  like  a  true  colloid,  and  it  also  rapidly  decomposes  hydric  peroxide. 
If  it  be  redissolved  after  crystallization,  it  diffuses,  although  only  to  a  small  extent,  but  it  no  longer 
decomposes  hydric  peroxide,  and  is  decolorized  by  it.  A  body  like  an  acid  is  deposited  from 
haemoglobin  at  the  positive  pole  of  a  battery.     [The  presence  of  O  favors  crystallization.] 

[Haemoglobin  exists  in  two  states,  either  as  reduced  haemoglobin,  i.  e.,  free 
from  oxygen,  or  as  oxyhjemoglobin.  The  former  is  non-crystalline.  They  differ 
in  their  color  and  spectra  ;  §  15.] 

12.  PREPARATION    OF    HiEMGGLOBIN    CRYSTALS.- Method   of   Rollett.— 

Place  defibrinated  blood  in  a  platinum  capsule,  allow  the  capsule  and  the  blood  to  freeze  by  placing 
them  in  a  freezing  mixture,  and  then  gradually  to  thaw  ;  pour  the  lake-colored  blood  into  a  plate, 
until  it  forms  a  stratum  not  more  than  i}<  mm.  in  thickness,  and  allow  it  to  evaporate  slowly  in  a 
cool  place,  when  crystals  will  separate. 

Method  of  Hoppe-Seyler. — Mix  defibrinated  blood  with  10  volumes  of  a  20  per  cent,  salt 
solution,  and  allow  it  to  stand  for  two  days.  Remove  the  clear  upper  fluid  with  a  pipette,  wash  the 
thick  deposit  of  blood  corpuscles  with  water,  and  afterward  shake  it  for  a  long  time  with  an  equal 
volume  of  ether,  which  dissolves  the  blood  corpuscles.  Remove  the  ether,  filter  the  lake-colored 
blood,  add  to  it  |^  of  its  volume  of  cold  (0°)  alcohol,  and  allow  the  mixture  to  stand  in  the  cold 
for  several  days.  The  numerous  crystals  can  be  collected  on  a  filter  and  pressed  between  folds  of 
blotting  paper. 

Method  of  Gscheidlen. — Crystals  several  centimetres  in  length  were  obtained  by  taking  de- 
fibrinated blood  which  had  been  exposed  for  twenty-four  hours  to  the  air,  and  keeping  it  in  a  closed 
tube  of  narrow  calibre  for  several  days  at  37°  C.  When  the  blood  is  spread  on  glass,  the  crystals 
form  rapidly.     [Vaccine  tubes  answer  very  well.] 

[Method  of  Sterling  and  Brito — It  is  in  many  cases  sufficient  to  mix  a  drop  of  blood  with 
a  few  drops  of  water  on  a  microscopic  slide,  and  to  seal  up  the  preparation.  After  a  few  days 
beautiful  crystals  are  developed.  The  addition  of  water  to  the  blood  of  some  animals,  such  as  the 
rat  and  the  guinea  pig,  is  rapidly  followed  by  the  formation  of  crystals  of  ha-moglobin.  Very  large 
crystals  m.iy  be  obtained  from  the  stomach  of  the  leech  several  days  after  it  has  sucked  blood.] 

13.  QUANTITATIVE  ESTIMATION  OF  HAEMOGLOBIN.  — (<z)  From  the 
Amount  of  Iron. — As  dry  (160°  C.)  haemoglobin  contains  0.42  per  cent,  of  iron,  the  amount  of 
iron  may  be  calculated  from  the  amount  of  haemoglobin.  If  »i  represents  the  percentage  amount 
of  metallic  iron,  then  the  percentage  of  hjemoglobin  in  blood  is 

I  GO  m 

0.42 
The  procedure  is  the  following :     Calcine  a  weighed  quantity  of  blood,  and  exhaust  the  ash  with 
HCl   to  obtain  feme   chloride,  which  is  transformed  into  ferrous  chloride.     The  solution  is  then 
titrated  with  potassic  pennanganate. 

{b)  Colorimetric  Method. — Prepare  a  dilute  watery  solution  of  hremoglobin  crystals  of  a 
known  strength.  With  this  compare  an  aqueous  dilution  of  the  blood  to  be  investigated,  by  adding 
water  to  it  until  the  color  of  the  test  solution  is  obtained.  Of  course,  the  solutions  must  be  com- 
pared in  vessels  with  parallel  sides  and  of  exactly  the  same  width,  so  as  to  give  the  same  thickness 
of  fluid  {Hoppe-Sryler).  [In  the  vessel  with  parallel  sides,  or,  haematinometer,  the  sides  are 
exactly  one  cenlimttre  apart.  Instead  of  using  a  standard  solution  of  oxyhemoglobin,  a  solution 
of  picrocarminate  of  ammonia  may  be  used  {^Kaje^i'sky,  Malassez).^ 

[c)  By  the  Spectroscope. — Preyer  found  that  an  0.8  per  cent,  watery  solution  (l  cm.  thick), 
allowed  the  red,  the  yellow,  and  the  first  strip  of  green  to  be  seen  (Fig.  14,  l).  Take  the  blood  to 
be- investigated  (about  0.5  cm  ),  and  dilute  it  with  water  untd  it  shows  exactly  the  same  optical 
effects  in  the  spectroscope.  If  k  is  the  percentage  of  Hb,  which  allows  green  to  pass  through  (0.8 
per  cent.),  b,  the  volume  of  blood  investigated  (about  0.5  cm.),  -i',  the  necessary  amount  of  water 
added  to  dilute  it,  then  x  =  the  percentage  of  Hb  in  the  blood  to  be  investigated — 
^k  (K,  +  *) 

b 

II  is  very  convenient  to  add  a  drop  of  caustic  potash  to  blood  and  then  to  shake  it  up  with  CO. 

[(</)  The  Haemoglobinometer  of  Gowers  is  used  for  the  clinical  estimation  of  haemoglobin 
(Fig.  12).]  "The  tint  of  the  dilution  of  a  given  volume  of  blood  with  distilled  water  is  taken  as 
the  index  of  the  amount  of  haemoglobin.  The  distilled  water  rapidly  dissolves  out  all  the  hsemo- 
globin,  as  is  shown  by  the  fact  that  the  tint  of  the  dilution  undergoes  no  change  on  standing.  The 
color  of  a  dilution  of  average  normal  blood  one  hundred  times  is  taken  as  the  standard.  The 
quantity  of  haemoglobin  is  indicated  by  the  amount  of  distilled  w'ater  needed  to  obtain  the  tint  with 


QUANTITATIVE    ESTIMATION    OF    H/EMOGLOBIN. 


37 


the  same  volume  of  blood  under  examination  as  was  taken  of  the  standard.  On  account  of  the 
instability  of  a  standard  dilution  of  blood,  tinted  glycerine  jelly  is  employed  instead.  This  is  per- 
fectly stable,  and  by  means  of  carmine  and  picrocarmine  the  exact  tint  of  diluted  blood  can  be 
obtained.  The  apparatus  consists  of  two  glass  lubes  of  exactly  the  same  size.  One  contains  (D)  a 
standard  of  the  tint  of  a  dilution  of  20  cubic  mm.  of  blood,  in  two  cubic  centimetres  of  water  (I  in 
icx)).  The  second  tube  (C)  is  graduated,  100  degrees  =  2  centimetres  (too  times  20  cubic  milli- 
metres). The  20  cubic  millimetres  of  blood  are  measured  by  a  capillaiy  pipette  (B)  (simdar  to,  but 
larger  than,  that  used  for  the  haemacytometer. )  This  quantity  of  the  blood  to  be  tested  is  ejected  into 
the  bottom  of  the  tube,  a  few  drops  of  distilled  water  being  first  placed  in  the  latter.  The  mixture 
is  rapidly  agitated,  to  prevent  the  coagulation  of  the  blood.  The  distilled  water  is  then  added,  drop 
by  drop  (from  the  pipette  stopper  of  a  bottle  (A)  supplied  for  that  purpose)  until  the  tint  of  the  dilution 
is  the  same  as  that  of  the  standard,  and  the  amount  of  water  which  has  been  added  (i.  e.,  the  degree 
of  dilution)  indicates  the  amount  of  hrcmoglobin. 

"  Since  average  normal  blood  yields  the  tint  of  the  standard  at  100  degrees  of  dilution,  the 
number  of  degrees  of  dilution  necessary  to  obtain  the  same  tint  with  a  given  specimen  of  blood  is 
the  percentage  proportion  of  the  hsemoglobin  contained  in  it,  compared  to  the  normal.  For  instance, 
the  20  cubic  millimetres  of  blood  from  a  patient  with  antemia  gave  the  standard  tint  of  30  degrees 
of  dilution.  Hence  it  contained  only  30  per  cent,  of  the  normal  quantity  of  hemoglobin.  By 
ascertaining  with  the  hEemacytometer  the  corpuscular  richness  of  the  blood,  we  are  able  to  compare 
the  two.     A  fraction,  of  which  the  numerator  is  the  percentage  of  haemoglobin,  and  the  denomi- 


FlG.   12. 


A,  pipette  bottle  for  distilled 

lancet  for  pricking  the  finger. 


B,  capillary  pipette  ;  C,  gratiuated  tube  ;    D,  tube  1 


nator  the  percentage  of  corpuscles,  gives  at  once  the  average  value  per  corpuscle.  Thus  the  blood 
mentioned  above  containing  30  per  cent,  of  hemoglobin,  contained  60  per  cent,  of  corpuscles  ; 
hence  the  average  value  of  each  corpuscle  was  ^||  or  \  of  the  normal.  Variations  in  the  amount  of 
hemoglobin  may  be  recorded  on  the  same  chart  as  that  employed  for  the  corpuscles. 

"  In  using  the  instrument,  the  tint  may  be  estimated  by  holding  the  tubes  between  the  eye  and  the 
window,  or  by  placing  a  piece  of  white  paper  behind  the  tubes;  the  former  is  perhaps  the  best. 
Care  must  be  taken  that  the  tubes  are  always  held  in  the  line  of  light,  not  below  it.  In  the  latter 
case  some  light  is  reflected  from  the  suspended  corpuscles  from  which  the  haemoglobin  has  been  dis- 
solved. If  the  value  of  the  corpuscles  is  small,  then  a  perceptibly  paler  tint  is  seen  when  the  tubes 
are  held  below  the  line  of  illumination.  If  all  the  light  is  transmitted  directly  through  the  tubes, 
the  corpuscles  do  not  interfere  with  the  tint.  In  practice  it  will  be  found  that,  during  six  or  eight 
degrees  of  dilution,  it  is  difficult  to  distinguish  a  difference  between  the  tint  of  the  tubes.  It  is 
therefore  necessary  to  note  the  degree  at  which  the  color  of  the  dilution  ceases  to  be  deeper  than  the 
standard,  and  also  that  at  which  it  is  distinctly  paler.  The  degree  midway  between  these  two  will 
represent  the  ha;moglobin  percentage. 

"  The  instrument  is  only  expected  to  yield  approximate  results,  accurate  within  two  or  three  per 
cent.     It  has,  however,  been  found  of  much  utility  in  clinical  observation." 

The  amount  of  hajmoglobin  in  man  is  13.77  per  cent.,  in  the  woman  12.59  P^"" 
cent.  (_/.  G.  Ott),  during  pregnancy  9  to  12  per  cent.  {Preycr).     According  to 


38 


USE    OF   THE    SPECTROSCOPE. 


Leichtenstern,  Hb  is  in  greatest  amount  in  the  blood  of  a  newly-born  infant,  but 
after  ten  weeks  the  excess  disappears.  Between  six  months  and  five  years  it 
becomes  least  in  amount,  reaches  its  second  highest  maximum  between  twenty-one 
and  forty-five,  and  then  sinks  again.  From  the  tenth  year  onward  the  blood  of 
the  female  is  poorer  in  Hb.  The  taking  of  food  causes  a  temporary  decrease  of 
the  Hb,  owing  to  the  dilution  of  the  blood. 

Pathological. — A  decrease  is  observable  during  recovery  from  febrile  conditions,  and  also  during 
phthisis,  cancer,  ulcer  of  the  stomach,  cardiac  disease,  chronic  diseases,  chlorosis,  leuktemia,  perni- 
cious ana?mia,  and  during  the  rapid  mercurial  treatment  of  syphilitic  persons. 

14.  USE  OF  THE  SPECTROSCOPE.— As  the  spectroscope  is  frequently  used  in  the  in- 
vestigation of  blood  and  other  substances  of  the  body,  it  will  be  convenient  to  give  a  short  descrip- 
tion of  the  instrument  here  (Fig.  13).  It  consists  of  (i )  a  lube.  A,  which  has  at  its  peripheral  end 
a  slit.,  S  (that  can  be  narrowed  or  widened).  At  the  other  end  a  collecting  lens,  C  (called  a  colli- 
mator), is  placed,  so  that  its  focus  is  in  exact  line  with  the  slit.  Light  (from  the  sun  or  a  lamp) 
passes  through  the  slit,  and  thus  goes  parallel  through  C  to  (2)  the  prism,  P,  which  decomposes 
the  parallel  rays  into  a  colored  spectrum,  r,  v.  (3)  Kn  astronomical  telescope  is  directed  to  the 
spectrum,  r,  v,  and  the  observer,  B,  with  the  aid  of  the  telescope,  sees  the  spectrum  magnified  from 


Fig.   13. 


spectroscope  for  observing  the  spectrum  of  blood.      A,  tube  :    S,  slit  ;  m 
1  front  of  it ;  P,  prism  ;  M,  Scale  ;  B,  eye  of  observer  looking  through  a  telescope 


er  of  bloot 
spectrum. 


six  to  eight  times.  (4)  A  third  tube,  D,  contains  a  delicate  scale,  M,  on  glass,  whose  image,  when 
illuminated,  is  reflected  from  the  prism  to  the  eye  of  the  observer,  so  that  he  sees  the  spectrum,  and 
over  and  above  it  the  scale.  To  keep  out  other  rays  of  light  the  inner  ends  of  the  three  tubes  are 
covered  by  metal  or  by  a  dark  cloth  (see  also  \  265). 

[The  micro-spectroscope,  e.g.,  that  known  as  the  '■  Sorliy-Browning"  micro  spectroscope,  may  be 
used  when  small  quantities  of  a  solution  are  to  be  examined.  While  the  corresponding  instrument 
of  Zeiss  is  also  most  admirable.] 

[Every  spectroscope  ought  to  give  two  spectra,  so  that  the  position  of  any  absorption  band  may  be 
definitely  ascertained.  The  spectroscope  is  fitted  into  the  ocular  end  of  the  tube  of  a  microscope 
instead  of  the  eye  piece.  Small  cells  for  containing  the  fluid  to  be  examined  are  made  from  short 
pieces  of  barometer  tubes  cemented  to  a  piece  of  glass.] 

Absorption  Spectra. — If  a  colored  medium  (e.g.,  a  solution  of  blood)  be  placed  between  the 
slit  and  a  source  of  light,  all  the  rays  of  colored  light  do  not  pass  through  it — some  are  absorbed  ; 
many  yellow  rays  are  alisorhed  by  blood,  hence  that  part  of  the  spectrum  appears  dark  to  the 
observer.     On  account  of  this  abs  )rption,  such  a  spectrum  is  called  an  "  absorption  spectrum." 

Flame  Spectra. — If  mineral  substances  be  burned  on  a  platinum  wire  in  a  non-ltiminous  flame 
(Bunsen's  burner)  in  front  of  the  slip,  the  elements  present  in  the  mineral  or  ash  give  a  special  colored 
band  or  bands,  which  have  a  definite  position.  .Sodium  gives  a  yellow,  potassium  a  red  and  a  violet 
line.     These  substances  are  found  in  burning  the  ashes  of  almost  all  organs. 


COMPOUNDS   OF    H/EMOGLOBIN. 


39 


If  sunlight  be  allowed  to  fall  upon  the  slit,  the  spectrum  shows  a  large  number  of  lines  [Fraiiti- 
hnfer's  lines)  which  occupy  definite  positions  in  the  colored  spectrum.  'Ihese  lines  are  indicated  by 
th;  letters  A,  B,  C,  D,  etc.,  ,>,  b,  (,  etc.  (Fig.  14). 

15.  COMPOUNDS  OF  H-^EMOGLOBIN  WITH  O  ; .  OXYH/E 
MOGLOBIN     AND     METHiEMOGLOBIN.  —  i.    Oxyheemoglobin 

(C^Hb)  behaves  as  a  weak  acid,  and  occurs  to  the  extent  of  86.78  to  94.30  per 
cent,  in  dry  human  red  corpuscles  {/Udell).  It  is  formed  very  readily  whenever 
Hb  comes  into  contact  with  O  or  atmospheric  air.  i  gramme  Hb  unites  with 
1.202  cubic  centimetres  of  O  at  o°  and  i  metre  Hg  pressure  {Hufuer).     Oxyhiemo- 


FiG.  14. 


Red.    Orange.  Yelli 


tTTmTnjrrnT 

bo  70  80  qo 

D  E  F 

us  spectra  of  haemoglobin  and  its  compounds. 


globin  is  a  very  loose  chemical  compound,  and  is  slightly  less  soluble  than  Hb; 
its  spectrum  shows  in  Vne  yello^o  and  the  green  two  dark  absorption  fiands  {Hoppe- 
Seyler)  whose  length  and  breadth  in  an  0.18  percent,  solution  are  given  in  Fig.  14 
(2Y      [If  the  solution  be  very  weiik,  only  the  narrow  band  near  D  is  obtained.] 

[The  two  absorption  bands  lie  between  the  lines  D  and  E,  the  band  nearer  D 
being  more  sharply  defined  and  narrower  than  the  second  band,  which  is  wider 
and  less  clearly  marked  off,  and  lies  nearer  E.] 

It  occurs  in  the  blood  corpuscles  circulating  in   arteries  and  capillaries,  as  was 


40  METIL-EMOGLOBIN. 

shown  by  the  spectroscopic  examination  of  the  ear  of  a  rabbit,  of  the  prepuce, 
and  the  web  of  the  fingers  {Vieivrdt). 

Reduction  of  Oxyhaemoglobin. — It  gives  up  its  O  very  readily,  however, 
even  when  means  which  set  free  absorbed  gases  are  used.  It  is  reduced  by  the 
removal  of  the  gases  by  the  air  pump,  by  the  (onduction  through  its  solution  of 
other  gases  (CO  and  NO),  and  by  heating  to  the  boiling  point.  In  the  circulating 
blood  its  O  is  very  rapidly  given  up  to  the  tissues,  so  that  in  suffocated  animals 
only  reduced  hcemoglohiii  is  found  in  the  arteries.  Some  constituents  of  the  serum 
and  sugar  use  up  O.  By  adding  to  a  solution  of-oxyhaemoglobin  reducing  sub- 
stances— e.  g.,  ammonium  sulphide,  ammoniated  tartarate  of  zinc  oxide  solution, 
iron  filings,  or  Stokes's  fluid  [tartaric  acid,  iron  protosulphate  and  excess  of 
ammonia] — the  two  absorption  bands  of  the  spectrum  disappear,  and  reduced 
hemoglobin  (gas  free)  (Fig.  14,  4),  with  one  absorption  band,  is  formed  (Stokes, 
1864).  [The  single  band  which  is  obtained  from  reduced  hemoglobin  lies  between 
D  and  E,  and  its  most  deeply  shaded  portion  is  opposite  the  interval  between  the 
two  bands  of  oxyhemoglobin.  Its  edges  are  less  sharply  defined.  The  color  of 
the  blood  changes  from  a  bright  red  to  a  brownish  tint.  Hoppe-Seyler  applies 
the  term  Ha-moglobin  to  the  reduced  substance,  to  distinguish  it  from  oxyhaemo- 
globin.] The  two  bands  are  reproduced  by  shaking  the  reduced  hemoglobin  with 
air,  whereby  O.^Hb  is  again  formed.  Solutions  of  oxyhaemoglobin  are  readily 
distinguished,  by  their  scarlet  color,  from  the  purplish  tint  of  reduced  hemoglobin. 

If  a  string  be  tied  round  the  base  of  two  fingers  so  as  to  interrupt  the  circulation,  the  spectro- 
scopic examination  shows  that  the  o.Nyhremoglobin  rapidly  passes  into  reduced  Hb  {Vicrordt). 
Cold  delays  this  reduction  {FilcJnie),  it  is  accelerated  in  youth,  during  muscular  activity,  or 
by  suppressed  respiration,  and  usually  also  during  fever  (Denning). 

The  spectroscopic  examination  of  small  blood  stains  is  often  of  the  utmost  forensic  importance. 
A  minimal  drop  is  sufficient.  Dissolve  the  stain  in  a  few  drops  of  distilled  water,  and  place  in  a 
thin  glass  tube  in  front  of  the  slit  of  the  spectroscope. 

[Hemoglobin  has  certain  remarkable  characters  : — 

(i)  Although  it  is  a  crystalloid  body  it  diffuses  with  difficulty  through  an 
animal  membrane,  owing  to  the  large  size  of  its  molecule. 

(2)  It  readily  combines  with  O  to  form  an  unstable  and  loose  chemical  com- 
pound, oxyhemoglobin. 

(3)  This  O  it  gives  up  readily  to  the  tissues  or  other  deoxidizing  reagents. 

(4)  Its  composition  is  very  complex,  for  in  addition  to  the  ordinary  elements 
present  in  proteids,  it  contains  a  remarkable  amount  of  iron  (0.4  per 
cent).] 

2.  Methaemoglobin  (^Hoppe  Seyler')  is  a  more  stable,  crystalline  compound. 
It  contains  the  same  amount  of  O  as  OjHb,  but  in  a  different  chemical  union, 
while  the  O  is  also  more  firmly  united  with  it  (Kiilz,  Hiifner,/.  G.  Ott).  It  shows 
_/tf«r  absorption  bands  like  hematin  in  acid  solution  (Fig.  14,  5),  of  which  those 
between  C  and  D  are  distinct ;  the  second  is  very  indistinct,  while  the  third  and 
fourth  readily  fuse,  so  that  these  last  are  only  well  seen  with  good  apparatus. 

Methaemoglobin  is  only  formed  from  solutions  of  Hb,  and  not  within  the  blood  corpuscles 
[v  Mering).  It  is  produced  spontaneously  in  old  brown  blood  stains,  in  the  crusts  of  bloody 
wounds,  in  blood  cysts,  and  in  bloody  urine.  It  is  also  formed  by  the  addition  of  minu/e  traces  of 
acid  to  blood,  or  by  heating  blood  with  a  trace  of  alkali.  Chemically,  it  can  be  prepared  in  a  solu- 
tion of  Hb,  by  the  action  of  potassic  ferricyanide  [Jih/erhe/m)  or  potassic  chlorate  (Marcliand), 
[or  by  adding  to  a  solution  of  Hb  a  freshly-prepared  solution  of  potassic  permanganate]. 

If  a  trace  of  ammonia  be  added  to  a  solution  of  methaemoglobin,  it  gives  an  alkaline  solution  of 
methcemoglobin,  which  shows  two  bands  like  oxyhjemoglobin,  of  which  the  first  one  is  the  broailer, 
and  extends  more  into  the  red.  If  ammonium  sulphide  be  added  to  the  metha;moglobin  solution, 
reduced  Hb  is  formed. 

16.  CARBONIC  OXIDE  H-^MOGLOBIN  AND  POISONING 
\A^ITH  CO. — 3.  CO-Haemoglobin  is  a  more  stable  chemical  compound  than 
the  foregoing,  and  is  produced  at  once  when  carbonic  oxide  is  brought  into  con- 


POISONING    BY   CARBONIC    OXIDE.  41 

tact  with  pure  Hb  or  OjHb  {CI.  Bernard,  i8j/).  It  has  an  intensely  florid  or 
c'/wrrj-reJ  color,  and  gives  two  absorption  bands,  very  like  those  of  02Hb,  but 
they  are  slightly  closer  together  and  lie  more  toward  the  violet  (Fig.  14,  3). 
Reducing  substances  (which  act  upon  HbOj)  do  not  affect  these  bands,  /.  e., 
they  cannot  convert  the  CO  compound  into  reduced  Hb.  .Another  good  test  to 
distinguish  it  from  HbO,  is  the  soJa  Usf.  If  a  10  per  cent,  solution  of  caustic 
soda  be  added  to  a  solution  of  CO-Hb.  and  heated,  it  gives  a  cinnabar-red  color  ; 
while,  with  an  HbOj  solution,  it  gives  a  dark  brown,  greenish,  greasy  mass 
(^Hoppc-Seyler).  Oxidizing  substances  [solutions  of  potassic  permanganate  (0.025 
per  cent.),  potassic  chlorate  (5  per  cent.),  and  dilute  chlorine  solution]  make 
solutions  of  CO-Hb  cherry-red  in  color,  while  they  turn  solutions  of  OjHb  pale 
yellow.  After  this  treatment  both  solutions  show  the  absorption  bands  of 
methremoglobin,  but  those  of  the  CO-Hb  appear  considerably  later.  If  ammo- 
nium sulphide  be  added,  O.^Hb  and  CO-Hb  are  reformed  (77/.  Weyl  and  v. 
Anrcp). 

On  account  of  its  stability,  CO-Hb  resists  external  influences  and  even  putrefaction  for  a  long 
time  [IIoppc'  Styh-r),  and  the  two  bands  of  the  spectrum  may  be  visible  after  many  months.  Lan- 
dois  ol)tained  the  soda  test  and  spectroscopic  bands  in  the  blood  of  a  woman  poisoned  eighteen 
months  previously  by  CO,  and  after  great  putrefaction  of  the  body  had  taken  place.  [Stirling  has 
kept  CO-Hb  in  a  stoppered  bottle  for  four  years  without  its  undergoing  putrefaction.] 

If  CO  is  breathed  by  man,  or  if  air  containing  it  be  inspired,  it  gradually  dis- 
places the  O,  volume  for  volume,  out  of  the  Hb  (Z.  Meyer),  and  death  soon 
occurs;  1000  c.cm.  inspired  at  once  will  kill  a  man.  .\  very  small  quantity  in 
the  air  (ttu  "TTnnr)  suffices,  in  a  relatively  short  time,  to  form  a  large  quantity  of 
CO-Hb  (  Grehant).  As  continued  contact  with  other  gases  (such  as  the  passing 
of  O  through  it  for  a  very  long  time),  gradually  separates  the  CO  from  the  Hb 
(with  the  formation  of  OjHb  {Donders)),  it  happens  that,  in  very  partial  poison- 
ing with  CO,  the  blood  gradually  gets  rid  of  the  latter,  so  that  only  a  very  small 
part  of  the  CO  is  e.\creted  by  the  respiratory  organs ;  the  largest  amount  is  more 
highly  oxidized  in  the  body  into  CO2  and  thus  excreted  (A'ries).  [CO-Hagmo- 
globin,  being  a  comparatively  stable  compound  when  once  formed,  circulates  in 
the  blood  vessels  ;  but  it  neither  gives  up  oxygen  to  the  tissues,  nor  takes  up 
oxygen  in  the  lungs,  hence  its  very  poisonous  properties.  The  real  cause  of 
death  in  animals  poisoned  with  it  is  that  the  internal  respiration  is  arrested.] 

[Gamgee  and  Zuntz  also  find  that  although  the  CO-Hb  compound  is  very  stable,  yet  it  may 
be  reduced  by  passing  air  or  neutral  gases  through  it  for  a  lengthened  period;  it  is  also  reduced 
when  blood  is  boiled  in  the  mercurial  pump.] 

Poisoning  with  Carbonic  Oxide. — Carbonic  oxide  is  formed  during  incomplete  combustion  of 
coal  or  coke,  and  passes  into  the  air  of  the  room,  provided  there  is  not  a  free  outlet  for  the  products 
of  combustion.  It  occurs  to  the  extent  of  12-2S  per  cent,  in  ordinary  gas,  which  largely  owes  its 
poisonous  properties  to  the  presence  of  CO.  If  the  O  be  gradually  displaced  from  the  blood  by 
the  respiration  of  air  containing  CO,  life  can  only  be  maintained  as  long  as  sufficient  O  can  be 
obtained  fiom  the  blood  to  support  the  oxidations  necessary  for  life.  Death  occurs  before  all  the 
O  is  displaced  from  the  blood.  CO  has  no  effect  when  directly  applied  to  muscle  and  nerve.  When 
it  is  inhaled,  there  is  first  stimulation  and  afterward  paralysis  of  the  nervous  system,  as  shown  by 
the  symptoms  induced,  (•.  i,^,  violent  headache,  great  restlessne>s,  excitement,  increased  activity  of 
the  heart  and  respiration,  salivation,  tremors  and  spisms.  Later,  unconsciousness,  weakness  and 
paralysis  occur,  labored  respiration,  diminished  heart  beat,  and,  Lastly,  complete  loss  of  sensibilitv, 
cessation  of  the  respiration  and  heart  beat,  and  death.  .'Vt  first  the  temperature  rises  several  tenths 
of  a  degree,  but  it  soon  falls  1°  or  more.  The  pulse  is  also  increased  at  first,  but  afterward  it 
becomes  very  small  and  frequent. 

In  poisoning  with  />!irf  CO  there  is  no  dyspnoea,  but  sometimes  muscular  spasms  occur,  the  coma 
not  being  verj'  marked.  There  is  also  temporary  but  pronounced  paralysis  of  the  limbs,  followed 
by  violent  spasms.  After  death,  the  heart  and  brain  are  congested  witii  intensely  florid  blood.  In 
poisoning  with  the  vapor  of  charcoal,  where  CO  and  COj  both  occur,  there  is  a  varj'ing  degree 
of  coma ;  pronounced  dyspnoea,  muscular  spasms  which  may  last  several  minutes,  gradual  paralysis 
and  asphyxia,  moniliform  contractions  and  subsequent  dilatation  of  the  blood  vessels,  with  conges- 
tion of  various  organs,  occur,  accompanied  by  a  fall  of  the  blood  pressure  {A7eis),  indicating  initial 
stimulation  and  subsequent  paralysis  of  the  vaso-motor  centre.  This  also  explains  the  variations  in 
the  temperature  and  the  occasional  occurrence  of  sugar  in  the  urine  after  poisoning  with  CO.     After 


42  DECOMPOSITION    OF    H.EMOGLOBIN. 

death,  the  blood  vessels  are  found  (o  be  filled  with  fluid  blood  of  an  exquisitely  bright  cherry-red 
color,  while  all  the  muscles  and  viscera  and  exposed  parts  of  the  body  (such  as  the  lips)  have  the 
same  color.  The  brain  is  soft  and  friable,  there  are  catarrh  of  the  respiratory  organs  and  degenera- 
tion of  the  muscles,  and  great  congestion  and  degeneration  of  the  liver,  kidneys  and  spleen.  The 
.spots  of  Wv'tdhy,  fasf-mor^em,  ate  bright  red.  After  recovery  from  poisoning  with  CO  there  may 
be  paraplegia  and  (although  more  rarely)  disturbances  of  the  cerebral  activity.  The  poisonous 
action  of  the  vapois  of  combusiion  was  known  to  .\ristotle. 

17.  OTHER  COMPOUNDS  OF  HiEMOGLOBIN.  —  4.  Nitric 
Oxide  Haemoglobin  (NO-Hb)  is  formed  when  NO  is  brought  into  contact 
with  Hb  (Z.  Hcnnaim). 

As  NO  has  a  great  affinity  for  O,  red  fumes  of  nitrogen  peroxide  (NO,)  being  formed  whenever 
the  two  gases  meet,  it  is  clear  that,  in  order  to  prepare  NO-HB,  the  O  must  first  be  removed.  This 
may  be  done  by  passing  H  through  it  [or  ammonia  may  be  added  to  the  blood,  and  a  stream  of 
NO  passed  through  it;  the  ammonia  combines  with  all  the  acid  formed  by  the  union  of  the  NO  with 
the  O  of  the  blood].  NO  Hb  is  a  more  stable  chemical  compound  \\a.n  CO-Hb,  which,  as  we  have 
seen,  is,  again,  more  stable  than  O^Hb.  It  has  a  bluish-violet  tint,  and  also  gives  two  absorption 
bands  in  the  spectrum  similar  to  those  of  the  other  two  compounds,  but  not  so  intense.  These 
bands  are  not  abolished  by  the  action  of  reducing  agents. 

The  three  compounds  of  Hb,  with  O,  CO  and  NO,  are  crystalline,  like  Hb; 
they  are  isomorphous,  and  their  solutions  are  not  dichroic.  All  three  gases  unite 
in  equal  volumes  with  Hb  {Preyer,  L.  Hermann).  If  O  be  conducted  through 
a  concentrated  solution  of  Hb  devoid  of  gases,  a  crystalline  mass  of  O.Hb  is 
thereby  readily  formed. 

[Nitrites,  e.g.,  amyl,  added  to  fresh  blood,  give  it  a  chocolate  color,  and  its  spectrum  is  that  of 
meth.-emoglobin.  The  compound  so  formed,  however,  is  less  stable  than  tliat  with  CO,  for  the 
decomposition  products  formed  in  the  blood  during  asphyxia  can  reduce  the  former  but  not  the  latter 
compound.] 

5.  Cyanogen,  CNH  {Hoppe-Seyler),  and  acetylene,  CjH^  [Bistrow  and  Liehreich),  form 
easily  decomposable  compounds  with  Hb.  The  former  occurs  in  poisoning  with  hydrocyanic  acid, 
and  has  a  spectium  identical  with  that  of  O^Hb,  and,  like  0,Hb,  it  is  reduced  by  special  agents. 
[The  existence  of  these  compounds  is,  however,  highly  doubtful  {Gamgee).'\ 

18.  DECOMPOSITION  OF  H.^MOGLOBIN.— In  solution  and  in  the  dry  state,  Hb 
gradually  becomes  decomposed,  whereby  the  iron-containing  pigment  hajmatin,  along  with  certain 
by-products,  formic,  lactic  and  butyric  acids,  are  formed. 

Hsemoglobin,  however,  tnay  be  decomposed  at  once  into  (i)  a  body  contain- 
ing iron,  hiematin,  and  (2)  a  colorless  proteid  closely  related  to  globulin;  by  {a) 
the  addition  of  all  acids,  even  by  CO.  in  the  presence  of  plenty  of  water:  {h) 
strong  alkalies;  (<:)  all  reagents  which  coagulate  albumin,  and  by  heat  at  7o°-8o^ 
C.  ;   {d^  by  ozone. 

(A)  Haematin  (Ceg,  Hjo,  Ns,  Fe.j,  0,„)  is  a  bluish-black,  amorphous  body, 
which  forms  about  4  per  cent,  of  hemoglobin  (dog).  It  is  insoluble  in  water, 
alcohol  and  ether;  soluble  in  dilute  alkalies  and  acids  and  in  acidulated  ether  and 
alcohol. 

Haetnochromogen. — When  Hb  containing  O  is  decomposed,  haematin  is  formed  at  once ;  while 
Hb  free  from  O,  on  being  decomposed,  forms,  first,  a  purplish-red  body,  Hcemochromogen  (Cj^.H^, 
N4,Fe05),  which  contains  less  O,  and  is  a  precursor  of  hcematin.  In  the  presence  of  O  it  becomes 
oxidized  and  passes  into  ha;matin.  In  solution,  it  gives  the  spectrum  shown  in  Fig.  14,  7  {Hoppe- 
Seyler). 

Hsemato- Porphyrin. — Dilute  acids  in  an  alkaline  solution  deprive  haemochromogen  of  its  iron, 
and  hie/iiato-porphvrin,  a  substance  which  remains  stable  in  contact  with  air,  is  produced.  It  may 
also  be  produced  from  hasmatin  by  the  action  of  acids,  so  that  haimatin  is  an  oxidation  stage  of 
haemochromogen.     The  following  derivatives  are  know  n  :  — 

(a)  Haematin  in  Acid  Solution  — Lecanu  extracted  it  from  dry  blood  corpuscles  by  using 
alcohol  containing  sulphuric  and  tartaric  acids.  If  acetic  acid  be  added  to  a  solution  of  Hb,  a 
m  ihogany-brown  fluid  is  obtained,  containing  haematin  in  acid  solution,  which  gives  a  spectrum 
with  /our  absorption  bands  in  the  yellow  and  green  (Fig.  II,  5). 

(ii  Haematin  in  Alkaline  Solution. — If  this  solution  he  treated  with  excess  of  ammonia, 
hcematin  in  alkaline  solution  is  formed,  which  gives  one  absorption  band  on  the  boundary  line 
between  red  and  yellow  (Fig.  14,  6). 

{c)  Reduced  Haematin. — Reducing  agents  cause  this  band  to  disappear,  and  produce  in  the 
yellow  two  broad \i3.n&s,  which  are  due  to  the  presence  of  "  reduced lucmatin"  (Fig.  14,  7). 


H.-EMIN    AND    BLOOD   TESTS. 


43 


Action  of  CO 2. — If  CO,  be  passed  through  a  solution  of  oxyha;moglobin  for  a  considerable 
time,  reduced  Hb  is  first  formed ;  but  if  the  process  be  prolonged  the  Hb  is  decomposed,  a  precipi- 
tate of  globulin  is  thrown  down,  and  an  absorption  band,  similar  to  that  obtained  when  Hb  is 
decomposed  with  acids,  is  observed  (see  p.  42). 

According  to  Zinoffsky's  analysis  there  are  exactly  two  atoms  of  S  to  each  atom  of  Fe  in  Hb. 

When  hiemoglubin  is  extravasated  into  the  subcutaneous  tissue,  it  becomes  so  altered  that  ulti- 
mately hydrated  oxide  of  iron  appears  in  its  place. 

19.  H^MIN  AND  BLOOD  TESTS.— In  1853  Teichmann  prepared 
crystals  from  blood,  which  Hoppe-Seyler  showed  to  be  chloride  of  hiematin  or 
hydrochlorate  of  hcematin.  The  presence  of  these  crystals  is  used  as  a  test  for 
blood  stains  or  blood  in  solution.  These  crystals  of  heemin  (Fig.  15)  are  prepared 
by  adding  a  small  crystal  of  common  salt  to  dry  blood  on  a  glass  slide,  and  then 
an  excess  of  glacial  acetic  acid  ;  the  whole  is  gently  heated  until  bubbles  of  gas 
are  given  off.  On  allowing  the  preparation  to  cool,  the  characteristic  hsmin 
crystals  are  obtained  (Ha;matin  -(-  2HCI). 

Characters. — When  well  formed,  the  crystals  are  small,  microscopic,  rhombic 
plates,  or  rhombic  rods;  sometimes  they  are  single — at  other  times  they  are  aggre- 
gated in  groups,  often  crossing  each  other.  Some  kinds  of  blood  (ox  and  pig) 
yield  very  irregular,  scarcely  crystalline,  masses.  The  crystalline  forms  of  h^emin 
are  identical  in  all  the  different  kinds  of  blood  that  have  been  examined  (Jahnke, 
Hogyes).     They  are  ilotibly  refractive  and pleo-chromatic  ;  by  transmitted  light  they 


Fig.   15. 


'/*♦ 


Va 


Fig.  16. 


^ 


// 


/  ■  'X 


^-'^i, . 


Haemin  crystals  of  \ 


are  mahogany  brown,  and   by  reflected  light   bluish   black,  glancing  like  steel. 
They  give  a  brown  streak  on  |)orcelain. 

(i)  Preparation  from  Dry  Blood  Stains. — Place  a  few  particles  of  the 
blood  stain  on  a  glass  slide,  add  two  to  three  drops  of  glacial  acetic  acid  and  a 
small  crystal  of  common  salt ;  cover  with  a  cover  glass,  and  heat  gently  over  the 
flame  of  a  spirit  lamp  until  bubbles  of  gas  are  given  off.  On  cooling,  the  crystals 
appear  in  the  ]ireparation  (Fig.  16). 

(2)  From  Stains  on  Porous  Bodies.— The  stained  object  (cloth,  wood, 
blotting  paper,  earth)  is  extracted  with  a  small  quantity  of  dilute  caustic  potash, 
and  afterward  with  water  in  a  watch  glass.  Both  solutions  are  carefully  filtered, 
and  tannic  acid  and  glacial  acetic  acid  are  added  until  an  acid  reaction  is  obtained. 
The  dark  precipitate  which  is  formed  is  collected  on  a  filter  and  washed.  A  small 
l^art  of  it  is  placed  on  a  microscope  slide,  a  granule  of  common  salt  is  added,  and 
the  whole  dried  ;  the  dry  stain  is  treated  as  in  (i)  {Striiwe.) 

(3)  From  Fluid  Blood. — Dry  the  blood  slowly  at  a  low  temperature,  and 
proceed  as  in  ( i). 

(4)  From  very  Dilute  Solutions  of  Haemoglobin. — (a)  Strmve's 
Method. — Add  to  the  fluid,  ammonia,  tannic  acid,  and  afterward  glacial  acetic 
acid,  until  it  is  acid  ;    soon  a  black  precipitate  of  tannate  of  ha;matin  is  thrown 


44  H.EMATOIDIN. 

down.  This  is  isolated,  washed,  dried,  and  treated  as  in  (i),  but  instead  of  NaCl 
a  granule  of  ammonium  chloride  is  added. 

(d)  Gulling  and  van  Geuns  recommend  the  addition  of  zinc  acetate,  wliich  gives  a  reddish  pre- 
cipitate; this  precipitate  is  to  be  treated  as  in  (l). 

Hjemin  crystals  may  sometimes  be  prepared  from  putrefyinfj  or  lake-colored 
blood,  but  they  are  very  small,  and  here  the  test  often  fails.  When  mixed  with 
iron  rust,  as  on  iron  weapons,  the  blood  crystals  are  generally  not  formed.  In 
such  cases,  scrape  off  the  stains  and  boil  them  with  dilute  caustic  potash.  If  blood 
be  present,  the  dissolved  hfematin  forms  a  fluid,  which  in  a  thin  layer  is  green  ;  in 
a  thick  layer,  red  {H.  Rose). 

Htemin  crystals  have  been  prepared  from  all  classes  of  vertebrates  and  from  the  blood  of  the 
earthworm. 

Chemical  Characters. — They  are  insoluble  in  water,  alcohol,  ether,  chloroform ;  but  concen- 
trated HoSOj  dissolves  them,  expelling  the  HCl,  and  giving  a  violet  red  color.  Ammonia  also  dis- 
solves them,  and  if  the  resulting  solution  be  evaporated,  heated  to  130°  C,  and  treated  with  boiling 
water  (which  extracts  the  ammonium  chloride), /;<rc/;<c-/«<(//H  is  obtained  {IloppeScyler)  as  a  bluish- 
^lack  substance,  which  on  being  pounded  forms  a  brown  and  amorphous  powder.  Its  solutions  in 
caustic  alkalies  are  dichroic ;  in  reflected  light  brownish  red  ;  in  transmitted  light,  in  a  thick  stratum, 
red — in  a  thin  one,  olive  green.     The  acid  solutions  are  monochromatic  and  brown. 

It  is  important  to  note  that  an  alcoholic  solution  of  haematin,  when  reduced  by 
tin  and  hydrochloric  acid,  yields  urobilin  {Hoppe-Seyler,  Ncuclu,  and  Sieber) 
(compare  Bile). 

20.  H.ffiMATOIDIN. — Virchow  discovered  this  important  derivative  from 
haemoglobin.  It  occurs  in  the  body  wherever  blood  stagnates  outside  the 
circulation,    and    becomes   decomposed — as    when    blood    is    extravasated    into 

the  tissues — e.g.,  the  brain — in  solidified  blood  plugs 
(thrombus)  ;  invariably  in  the  Graafian  follicles.  It 
contains  no  iron  (C32,  H36,  N,,  Oe),  and  crystallizes  in 
clinorhombic  prisms  (Fig.  17)  of  a  yellowish  brown 
color.  It  is  soluble  in  water,  alkalies,  carbon  disul- 
phide,  benzol,  and  chloroform.  Very  probably  it  is 
identical  with  one  of  the  bile  pigments — bilirubin 
lyValenteiner).  [When  acted  upon  by  impure  nitric 
acid  (Gmelin's  reaction),  it  gives  the  same  play  of 
1  crystals.  colors  as  bile.] 

Pathological. — In  cases  where  a  large  amount  of  blood  has  undergone  solution  within  the  blood 
vessels  (as  by  injecting  foreign  blood),  hajmatoidin  crj'slals  have  been  found  in  the  urine  (y.  Keckling- 
hausen,  Landois).     For  their  occurrence  in  urine,  in  jaundice  (J  180),  and  in  the  sputum  (ij  138). 

21.  (B.)  THE    COLORLESS    PROTEID    OF    HEMOGLOBIN. 

— It  is  closely  related  to  globulin  ;  but,  while  the  latter  is  precipitated  by  all 
acids,  even  by  COj,  and  re-dissolved  on  passing  O  through  it,  the  proteid  of 
haemoglobin,  on  the  other  hand,  is  not  dissolved  after  precipitation  on  passing 
through  it  a  stream  of  O. 

As  crystals  of  haemoglobin  can  be  decolorized  under  special  circumstances,  it  is  probable  that 
these  owe  their  crystalline  form  to  the  proteid  which  they  contain.  Landois  placed  crystals  of 
hcemoglobin  along  with  alcohol  in  a  dialyser,  putting  ether  aciduUted  with  sulphuric  acid  outside, 
and  thereby  obtained  colorless  crystals.  [If  frogs'  blood  be  sealed  up  on  a  microscopic  slide,  along 
with  a  few  drops  of  water,  for  several  days,  lon^;,  colorless,  acicular  crystals  are  developed  in  it 
{^Stirling  and  Brito).'\ 

22.  II.  PROTEIDS  OF  THE  STROMA.— Dry,  red,  human  blood 
corpuscles  contain  from  5. 10-12.24  psr  cent,  of  these  proteids  ;  but  little  is  known 
about  them  {/Udell).  One  of  them  is  globulin,  which  is  combined  with  a  body 
resembling  nuclein  {IVooldridge),  and  traces  of  a  diastatic  ferment  {v.  IVitticJi). 
The  stroma  tends  to  form  masses  which  resemble  fibrin  (Landois). 

L.  Brunton  found  a  body  resembling  mucin  in  the  nuclei  of  red  blood  corpuscles,  and  Miescher 
detected  nuclein  (^  250,  2). 


CHEMICAL   COMPOSITION    OF   THE    COLORLESS   CORPUSCLES.  45 

23.  THE  OTHER  CONSTITUENTS  OF  RED  BLOOD  COR- 
PUSCLES.— III.  Lecithin  (0.35-0.72  per  cent.)  in  dry  blood  corpuscles 
(JihMl),  (§  250,  2). 

It  is  regarded  as  a  glycerophosphate  of  neurin,  in  which,  in  the  radical  of  glycero-phosphoric 
acid,  two  atoms  of  H  are  replaced  by  two  of  the  radical  of  stearic  acid.  By  gentle  heat  glycero- 
phosphoric  acid  is  split  up  into  glycerine  and  phosphoric  acid  (^  250). 

Cholesterin  (0.25  per  cent.)  (§  250,  III),  no  Fats. 

These  substances  are  obtained  by  extracting  old  stromata  or  isolated  blood  corpuscles  with  ether. 
When  the  ether  evaporates,  the  characteristic  globular  forms  ("  myelin-forms  ")  of  lecithin  and 
crj'stals  of  cholesterin  are  recognized.  The  amount  of  lecithin  may  be  determined  from  the 
amount  of  phosphorus  in  the  ethereal  extract. 

IV.  Water  (681.63  per  1000 — C.  Schmidt). 

V.  Salts  (7.28  per  1000 — C.  Schmidt),  chiefly  compounds  oi  potash  and  phos- 
phoric acid ;  the  phosphoric  acid  is  derived  only  from  the  burned  lecithin  ;  while 
the  greater  part  of  the  sulphuric  acid  in  the  analysis  is  derived  from  the  burning 
of  the  hffimoglohin. 

Analysis  of  Blood.— 1000  parts,  by  weight,  of  horse's  blood  contain  : — 
344.18  blood  corpuscles  (containing  about  128  per  cent,  of  solids). 
655.82  plasma  (containing  about  10  per  cent,  of  solids). 

1000  parts,  by  weight,  of  moist  blood  corpuscles  contain  :  — 

Solids 367.9  (pig) ;  400.1  (ox). 

Water 632.1      "  599.9     •' 

The  solids  are  : — 

Pig.  Ox. 

Haemoglobin 261  2S0.5 

Albumin 86.1  107 

Lecithin,  Cholesterin  and    other  Organic  1 

Bodies .    [  '^-^  7  5 

Inorganic  Salts 8.9  4.8 

f  Potash 5.543  0.747 

I    Magnesia 0.158  0.017 

Including  •]    Chlorine >.504  '-635 

I    Phosphoric   Acid 2.067  o  703 

y  Soda o  2.093  (B""g6). 

[An  approximate  estimate  of  the  composition  of  human  blood  is  given  in  the 
following  table  : — 

Composition  of  Human  Blood  as  a  Whole. 

Water 7S0 

Solids — of  these — 

Corpuscles 1 34      "| 

Serum  Albumin  1 

Serum  Globulin  ) '         I 

Fibrin  of  Clot  (?  Fibrinogen) 2.2    !■  220 

Inorganic  Salts  (of  serum) 6.0 

E.xtractives 6.4 

F.atty  matters 1.4 

Gases,  O,  COo,  N.] 

24.  CHEMICAL  COMPOSITION  OF  THE  COLORLESS  COR- 
PUSCLES.— Investigations  have  been  made  on  ptis  cells,  which  closely  resemble 
colorless  blood  corpuscles.  They  contain  several  proteids  ;  alkali  albuminate,  a 
proteid  which  coagulates  at  48°  C,  and  another  resembling  myosin,  para- 
globulin,  peptone,  and  a  coagulating  ferment  ;  nuclein  in  the  nuclei  {Miescher) 
{%.  250,  2);  perhaps  also  glycogen  (§  252)  {Salomon),  lecithin,  cerebrin,  cholesterin, 
and  fat. 

100  parts,  by  weight,  of  dry  pus  contain — 

Earthy  Phosphates, 0.416     I      Potash, O.201 

Sodic  Phosphate, 0.606     |      Sodic  Chloride, 0.143 


46 


PREPARATION   OF    PLASMA. 


25.  BLOOD- PLASMA   AND  ITS    RELATION   TO    SERUM.— 

The  unaltered  fluid  in  which  the  blood  corpuscles  float  is  called  plasma,  or 
liquor  sanguinis.  This  fluid,  however,  after  blood  is  withdrawn  from  the 
vessels  rapidly  undergoes  a  change,  owing  to  the  formation  of  a  solid  fibrous 
substance  —  fibrin.  After  this  occurs,  the  new  fluid  which  remains  no  longer 
coagulates  spontaneously  (it  is  plasma,  minus  the  fibrin  factors),  and  is  called 
serum.  Apart  from  the  presence  of  the  fibrin  factors,  the  chemical  composition 
of  plasma  and  serum  are  the  same. 

[When  blood  coagulates,  the  following  table,  I,  shows  what  takes  place,  while  the  second  table,  11, 
shows  what  occurs  when  it  is  beaten  : — 


Coagulation. 
Blood. 


Corpuscles. 


Fibrin -factors. 
I 


II. 

When  beaten. 

Blood. 

I 


Corpuscles. 


Defibrinated  Blood. 


The  serum,  however,  still  contains  a  portion  of  the  fibrin  ferment,  and  also  some 
of  the  fibrinoplastin  or  fibrinoplastic  substance.  Plasma  is  a  clear,  transparent, 
slightly  thickish  fluid,  which,  in  most  animals  (rabbit,  o.x,  cat,  dog),  is  almost 
colorless ;  in  man  it  is  yellow,  and  in  the  horse  citron-yellow.] 

26.  PREPARATION    OF   PLASMA.— (A)  Without  Admixture.— 

Taking  advantage  of  the  fact  that  plasma,  when  cooled  to  o^  outside  the  body, 
does  not  coagulate  for  a  considerable  time,  Briicke  prepares  the  plasma  thus : 
Selecting  the  blood  of  the  horse  (because  it  coagulates  slowly,  and  its  corpuscles 
sink  rapidly  to  the  bottom),  he  receives  it,  as  it  flows  from  an  artery,  in  a  tall, 
narrow  glass,  placed  in  a  freezing  mixture,  and  cooled  to  0°.  The  blood  remains 
fluid,  and  the  colored  corpuscles  subsiding  in  a  few  hours,  the  plasma  remains 
above  as  a  clear  layer,  which  can  be  removed  with  a  cooled  pipette.  If  this  plasma 
be  then  passed  through  a  cooled  filter,  it  is  robbed  of  all  its  colorless  corpuscles. 
[Burdon-Sanderson  uses  a  vessel  consisting  of  three  compartments — the  outer  and 
inner  contain  ice,  while  the  blood  of  the  horse  is  caught  in  the  central  compart- 
ment, which  does  not  exceed  half  an  inch  in  diameter.] 

The  quantity  of  plasma  may  be  roughly  (but  only  roughly)  estimated  by  using  a 
tall,  graduated  measuring  glass.  If  the  plasma  be  warmed,  it  soon  coagulates 
(owing  to  the  formation  of  the  fibrin),  and  passes  into  a  trembling  jelly.  If,  how- 
ever, it  be  beaten  with  a  glass  rod,  the  fibrin  is  obtained  as  a  white,  stringy 
ma.ss,  adhering  to  the  rod.  The  quantity  of  fibrin  in  a  given  volume  of  plasma, 
is  about  0.7-1  per  cent.,  although  it  varies  much  in  different  cases. 

(B)  With  Admixture. — Blood  flowing  from  an  artery  is  caught  in  a  tall, 
graduated  measure  containing  ^  of  its  volume  of  a  concentrated  solution  ofsodic 
sulphate  {Hnuson) — or  in  a  25  per  cent,  solution  of  magnesic  sulphate  (i  vol.  to 
4  vols,  blood — Scminer) — or  1  vol.  blood  with  2  vols,  of  a  4  per  cent,  solution  of 
monophosphate  of  potash  {Masia).  When  the  blood  is  mixed  with  these  fluids 
and  put  in  a  cool  place,  the  corpuscles  subside,  and  the  clear  stratum  of  plasma 
mixed  with  the  salts  may  be  removed  with  a  pipette.  If  the  .salts  be  removed  by 
dialysis,  coagulation  occurs ;  or  it  may  be  caused  by  the  addition  of  water  i/oh. 
Mailer").  Blood  which  is  mixed  with  a  4  per  cent,  solution  of  common  salt  does 
not  coagulate,  so  that  it  also  may  be  used  for  the  preparation  of  plasma.  [For 
frogs'  blood  Johannes  Miiller  used  a  ^^  per  cent,  solution  of  cane  sugar,  which 


FIBRIN COAGULATION    OF   THE    BLOOD.  47 

permits  the  corpuscles  to  be  separated  from  the  plasma  by  filtration.     The  plasma 
mixed  with  the  sugar  coagulates  in  a  short  time.] 

27.  FIBRIN  — COAGULATION     OF     THE    BLOOD.  —  General 

Characters. — Fibrin  is  that  substance  which,  becoming  solid  in  shed  blood,  in 
plasma  and  in  lymph  causes  coagulation.  In  these  fluids,  when  left  to  themselves, 
fibrin  is  formed,  consisting  of  innumerable,  excessively  delicate,  closely  packed, 
microscopic,  doubly  refractive  {Hermann)  fibrils  (Fig.  7,  E|.  These  fibrils  en- 
tangle the  blood  corpuscles  as  in  a  spider's  web,  and  form  with  them  a  jelly-like, 
solid  mass,  called  the  blood  clot  or  placenta  sanguinis.  At  first  the  clot  is 
very  soft,  and  after  the  first  2  to  15  minutes  a  few  fibres  may  be  found  on  its 
surface  ;  these  may  be  removed  with  a  needle,  while  the  interior  of  the  clot  is 
still  fluid.  The  fibres  ultimately  extend  throughout  the  entire  mass,  which,  in 
this  stage,  has  been  called  criior.  After  from  12  to  15  hours  the  fibrin  contracts, 
or,  at  least,  shrinks  more  and  more  closely  round  the  corpuscles,  and  a  fairly 
solid,  trembling,  jelly-like  clot,  which  can  be  cut  with  a  knife,  is  formed.  During 
this  time  the  clot  has  expressed  from  its  substance  a  fluid — the  blood  serum. 
The  clot  takes  the  shape  of  the  vessel  in  which  the  blood  coagulates.  Fibrin  may 
be  obtained  by  washing  away  the  corpuscles  from  the  clot  with  a  stream  of  water. 
Crusta  Phlogistica. — If  the  corpuscles  subside  very  rapidly,  and  if  the  blood 
coagulates  slowly,  the  upper  stratum  of  the  clot  is  not  red,  but  only  yellowish,  on 
account  of  the  absence  of  colored  corpuscles.  This  is  regularly  the  case  in  horse's 
blood,  and  in  human  blood  it  is  observed  especially  in  inflammations;  hence  this 
layer  has  been  called  crusta  phlogistica.  Such  blood  contains  more  fibrin, 
and  so  coagulates  more  slowly. 

The  crusta  is  formed  under  other  circumstances,  but  the  cause  of  its  formation  is  not  always 
clear,  e.g.,  with  increased  sp.  gr.  of  the  corpuscles,  or  diminished  sp.  gr.  of  the  plasma  (as  in  hydrcemia 
and  chlorosis),  whereby  the  corpuscles  sink  more  rapidly,  and  also  during  pregnancy.  The  taller 
and  narrower  the  glass,  the  thicker  is  the  crusta  (compare  ^41).  The  upper  end  of  the  clot,  where 
there  are  few  corpuscles,  shrinks  more,  and  is,  therefore,  smaller  than  the  rest  of  the  clot.  Ihis 
upper,  lighter-colured  layer  is  called  the  "  huffy"  coat ;  this,  however,  gradually  passes,  both  as  to 
size  and  color,  into  the  normal  dark-colored  clot.  [Sometiines  the  upper  surface  of  the  clot  is 
concave  or  "  cupped."  The  older  physicians  used  to  attribute  great  importance  to  this  condition, 
and  also  to  the  ojcurrence  of  the  crusta  phlogistica,  or  buffy  coat.] 

Defibrinated  Blood.- — -If  freshly-shed  blood  be  beaten  or  whipped  with  a 
glass  rod  or  with  a  bundle  of  twigs,  fibrin  is  deposited  on  the  rod  of  twigs  in  the 
form  of  a  solid,  fibrous,  yellowish-white,  elastic  mass,  and  the  blood  which  remains 
is  called  '■^  dffibrinated  blood'''  (p.  46).  [The  twigs  and  fibrin  must  be  washed  in 
a  stream  of  water,  to  remove  adhering  corpuscles.] 

Coagulation  of  Plasma. — Plasma  shows  phenomena  exactly  analogous,  save 
that  there  is  no  well-defined  clot,  owing  to  the  absence  of  the  resisting  corpuscles; 
there  is,  however,  always  a  soft,  trembling  jelly  formed  when  plasma  coagulates. 
[In  Hewson's  experiment  on  the  blood  of  a  horse  tied  in  a  vein,  he  found  that 
the  plasma  coagulated — fibrin  being  formed,  so  that  he  showed  coagulation  to  be 
due  to  changes  in  the  plasma  itself  (§  29).] 

Properties  of  Fibrin. — .\lthough  the  fibrin  appears  voluminous,  it  only  occurs 
to  the  extent  of  0.2  per  cent,  (o.i  to  0.3  per  cent.)  in  the  blood.  The  amount 
varies  considerably  in  two  samples  of  the  same  blood  {Sig-  Mayer).  It  is  insol- 
uble in  water  and  ether ;  alcohol  shrivels  it  by  extracting  water ;  dilute  hydro- 
chloric acid  (0.1  per  cent.)  causes  it  to  swell  up  and  become  clear,  and  changes 
it  into  syntonin  or  acid  albumin  (§  249,  III).  When  fresh,  it  has  a  grayish- 
yellow,  fibrous  appearance  and  is  elastic  ;  when  dried,  it  is  horny,  transparent, 
brittle  and  friable. 

When  fresh,  it  dissolves  in  6  to  8  per  cent,  solutions  of  sodium  nitrate  or  sulphate,  in  dilute  alka- 
lies and  in  ammonia,  thus  forming  alkali  albuminate.  Heat  does  not  coagulate  these  solutions. 
Hydric  peroxide  is  rapidly  decomposed  by  fibrin  into  water  and  O  (  Thenard).  Fibrin  which  has 
been  exposed  to  the  air  for  a  long  time  is  no  longer  soluble  in  solution  of  potassic  nitrate,  but  in 


48  GENERAL    PHENOMENA   OF   COAGULATION. 

neurin  [Maul/iner).    During  putrefaction,  it  passes  into  solution,  albumen  being  formed  {J.  v.  Ln-ii^). 
Fibrin  contains  iron,  calcic  and  magnesic  phosphates,  whose  origin  is  unknown. 

Time  for  Coagulation. — According  to  H.  Nasse,  the  first  appearance  of  a  coigulum  occurs  in 
man's  blood  after  3  minuter  45  seconds,  in  women's  blood  after  2  minutes  20  seconds.  Age  has  no 
effect;   withdrawal  of  food  accelerates  coagulation  (A.  VierorJt). 

28.  GENERAL  PHENOMENA  OF  COAGULATION.— I.  Blood 
which  is  in  direct  contact  with  the  living  and  unaltered  blood  vessels 
does  not  coagulate  (Thackrah,  1819). — [Hewson  (^1772)  found  that  when  he 
tied  the  jugular  vein  of  a  horse  in  two  places,  and  excised  it  (Fig.  18),  the  blood 
did  not  coagulate  for  a  long  time.]  This  important  fact  was  confirmed  by  Briicke 
(1857),  who  filled  the  heart  of  a  tortoise  with  blood  which  had  stood  fifteen 
minutes  exposed  to  the  air  at  0°,  and  kept  it  in  a  moist  chamber.  The  blood 
was  still  fluid  at  the  end  of  5  V2  hours,  while  the  heart  itself  still  continued  to 
beat.  He  observed  that  at  0°  the  blood  was  uncoagulated  in  the  contracting 
heart  of  a  tortoise  after  eight  days.  Blood  inside  a  contracting  frog's  heart 
preserved  under  mercury  does  not  coagulate.  If  the  wall  of  the  vessel  be  altered 
by  pathological  processes  {c-g-,  if  the  intima  becomes  rough  and  uneven,  or 
undergoes  inflammatory  change),  coagulation  is  apt  to  occur  at  these  places. 
Blood  rapidly  coagulates  in  a  deaii  heart,  or  in  blood  vessels  (but  not  in  capilla- 
ries) or  other  canals  (^.^.,  the  ureter)  (  F/>i-/i(?K').  If  blood  stagnates  in  a  living 
vessel,  coagulation  begins  in  the  central  axis,  because  here  there  is  no  contact 
with  the  wall  of  the  living  blood  vessel. 

II.  Conditions  which  Hinder  or  Delay  Coagulation. — (a)  The  addition 
of  small  quantities  of  alkalies  and  ammonia,  or  of  concentrated  solutions  of  neutral 
salts  of  the  alkalies  and  earths  (alkaline  chlorides,  sulphates,  phosphates,  nitrates, 
carbonates).  Magnesic  sulphate  acts  inost  favorably  in  delaying  coagulation  (i 
vol.  solution  of  28  per  cent,  to  3)4  vols,  blood  of  the  horse). 

{b)  The  precipitation  of  the  fibrinoplastin  by  adding  weak  acids,  or  by  CO2. 

By  the  addition  oi  acetic  acid  ^n\\\  the  reaction  is  acid,  the  coagulation  is  completely  arrested. 
A  large  amount  of  CO  2  delays  it,  and  hence  venous  blood  coagulates  more  slowly  than  arterial. 
Hence,  also,  the  blood  of  suffocated  persons  remains  fluid. 

(<:)  The  addition  of  egg  albumin,  syrup,  glycerine  and  much  water.  If  un- 
coagulated blood  be  brought  into  contact  with  a  layer  of  already-formed  fibrin, 
coagulation  occurs  later. 

{li)  By  cold  at  0°  coagulation  may  be  delayed  for  one  hour  (J.  Daiy).  If 
blood  is  frozen  at  once,  after  thawing,  it  is  still  fluid,  and  then  coagulates  (^Hew- 
son).    When  shed  blood  is  under  high  pressure  it  coagulates  slowly  (Landois). 

{e)  Blood  of  embryo  fowls  does  not  coagulate  before  the  twelfth  or  fourteenth 
day  of  incubation  {Boll) ;  that  of  the  hepatic  vein  very  slightly;  menstrual  blood 
shows  little  tendency  to  coagulate  when  alkaline  mucus  from  the  vagina  is  mixed 
with  it.     If  it  be  rapidly  discharged  it  coagulates  in  masses. 

(/)  Blood  rich  in  fibrin  from  inflamed  parts  coagulates  slowly,  but  the  clot 
so  formed  is  firm. 

Haeinophilia. — A  very  slight  scratch  in  some  persons  may  cause  very  free  bleeding.  These 
persons  are  called  colloquially  "  bleeders,"  and  are  said  to  have  haemophilia  or  the  hemorrhagic 
diathesis.  In  *'  bleeders  "  coagulation  seems  not  to  talvc  place,  owing  to  a  want  of  the  substances 
producing  fibrin  ;  hence,  in  these  cases,  wounds  of  vessels  are  not  plugged  with  fiijrin.  [.V  ten- 
dency to  hemorrhage  occurs  m  scurvy,  purpura,  in  some  infectious  diseases,  such  as  typhus,  plague, 
yellow  fever,  and  in  poisoning  with  phosphorus.] 

Injection  of  Peptones. — Albertoni  observed  that  if  tryptic  pancreas  ferment  (dissolved  in  gly- 
cerine) be  injected  into  the  blood  of  an  animal,  the  blood  does  not  coagulate.  Schmidt-Mulheim 
found  that  after  the  injection  oi pure peftonemio  the  blood  (0.3  to  0.6  grammes  per  kilo.)  of  a  dog, 
the  blood  lost  its  power  of  coagulating.  [This  occurs  in  tlie  dog,  but  not  in  the  rabbit,  moreover, 
although  gastric  peptone  prevents  coagulation,  try-plon  or  pancreas  ferment  does  not  do  so  (^Fano). 
Peptonized  blood,  etc.,  coagulates  when  it  is  treated  with  CO,  or  water.]  A  substance  is  formed 
in  the  plasma,  which  prevents  coagulation,  but  which  is  precipitated  by  C02.  Lymph  behaves 
similarly  (fano).  After  peptones  are  injected,  there  is  a  great  solution  of  leucocytes  in  the  blood 
(v.  Samson- Himmelstjerna).     The  secretion  of  the  mouth  of  the  medicinal  leech  [although  its 


GENERAL    PHENOMENA   OF    COAGULATION.  49 

action  is  not  due  to  a  ferment  [Haycrn/t)'],  z.nA  snake  poison  also  prevent  coagulation  (Wa/l). 
[Diastatic  ferment  also  prevents  coagulation  (Saivioli).'] 

[tJluod  coagulates  more  slowly  in  a  smooth  than  a  rough  vessel,  and  also  in  a  shallow  vessel  than 
in  a  deep  one.] 

III.  Coagulation  is  accelerated — {a)  By  contact  with  Foreign  Sub- 
stances of  all  kinds  ;  hence,  threads  or  needles  introduced  into  arteries  are 
rapidly  covered  with  fibrin.  Even  the  introduction  of  air  bubbles  into  the  circu- 
lation accelerates  it,  and  the  pathologically  altered  wall  of  a  vessel  acts  like  a 
foreign  body.  Blood  shed  from  an  artery  rapidly  coagulates  on  the  walls  of 
vessels,  on  the  surfaces  exposed  freely  to  air,  and  on  the  rods  or  twigs  by  which 
it  is  beat.  The  passage  through  it  of  indifferent  gases,  such  as  N  and  H,  and 
the  addition  of  HjO  have  the  same  effect. 

{b)  Heating  from  39°  to  55°  C.  rapidly  facilitates  coagulation  {Hewson). 

{/)  Agitation  of  the  blood,  as  shown  by  Hewson  and  Hunter. 

\{ji)  The  addition  of  a  small  quantity  of  water. 

(e)  A  watery  condition  of  the  blood,  but  in  this  case  the  clot  is  small  and  soft. 

(/)  Contact  with  oxygen.] 

IV.  Rapidity  of  Coagulation. — Among  vertebrates,  the  blood  of  birds 
(especially  of  the  pigeon),  coagulates  almost  momentarily;  in  cold-blooded 
animals  coagulation  occurs  much  more  slowly,  while  mammals  stand  midway 
between  the  two. 

[The  blood  of  a  fowl  begins  to  coagulate  in  jj  to  I  )^  minute  ;  that  of  a  pig,  sheep,  rabbit,  in 
^  to  i^  minute;  of  a  dog,  i  to  3  minutes;  of  a  horse  and  ox,  5  to  13  minutes;  of  man,  3  to  4 
minutes ;  solidification  is  completed  in  9  to  11  minutes,  but  rather  sooner  in  the  case  of  women 
f^Nasse).'\  The  blood  of  invertebrates,  which  is  usually  colorless  when  it  is  oxidized  (J  32),  forms 
a  sjft,  whitish  clot  of  fibrin.      Even  in  lympk  and  chyle,  a  small  soft  clot  is  formed. 

V.  When  coagulation  occurs,  the  aggregate  condition  of  the  fibrin  factors  is 
altered,  so  that  heat  must  be  set  free  (  Valentin,  1884,  Schiffer,  Lepine).  The  rise 
in  the  temperature  may  be  ascertained  with  a  very  delicate  thermometer. 

VI.  In  blood  shed  from  an  artery,  the  degree  of  alkalinity  diminishes  from  the 
time  of  its  being  shed  until  coagulation  is  completed  {Pfliigcr  and  Zuntz).  This 
is  probably  due  to  a  decomposition  in  the  blood,  whereby  an  acid  is  developed, 
which  diminishes  the  alkalinity  (p.  17). 

VIL  Whether  or  not  electricity  is  developed  is  not  positively  proved.  Hermann  supposes  that 
the  parts  already  coagulated  are  negative,  while  non  coagulated  parts  are  positive ;  but  this  has  not 
been  clearly  shown. 

VIII.  During  coagulation  there  is  a  diminution  of  the  O  in  the  blood,  although 
a  similar  decrease  also  occurs  in  non-coagulated  blood.  Traces  of  ammonia  are 
also  given  off,  which  Richardson  erroneously  supposed  to  be  the  cause  of  the 
coagulation  of  the  blood. 

[This  is  refuted — (t)  by  the  fact  that  blood,  when  collected  under  mercury  (whereby  no  escape 
of  ammonia  is  possible),  also  coagulates;  and  (2)  by  the  following  experiment  of  Lister:  He 
placed  two  ligatures  on  a  ve.n  containing  blood,  moistening  one  half  of  the  outer  surface  of  the 
vein  with  ammonia,  leaving  the  other  half  intact.  The  blood  coagulated  in  the  first  half,  and  not  in 
the  other,  owing  to  the  properties  of  the  wall  of  the  vein  of  the  former  being  altered.  Lister  also 
proved  that  blood  will  remain  fluid  for  hours  in  a  vein  after  it  has  been  fiecly  exposed  to  the  air, 
and  even  after  it  has  been  poured  in  a  thin  stream  from  one  vein  to  another.]  Neither  the  decrease 
of  O  nor  the  evolution  of  ammonia  seims  to  have  any  causal  connection  with  the  formation  of 
fibrin. 

Pathological. — When  the  blood  coagulates  within  the  vessels  during  life,  the  process  is  called 
thrombosis,  and  the  coagulum  or  plug  so  formed  is  tenned  a  thrombus.  When  a  clot  of  blood  or 
other  body  is  carried  by  the  blood  stream  to  another  part  of  the  vascular  system  where  it  blocks  up  a 
vessel,  the  plug  is  called  an  embolus,  and  the  result  embolism. 

29.  CAUSE  OF  THE  COAGULATION  OF  THE  BLOOD.— 

Perhaps  this  subject  is  best  treated  historically. 

[Hewson's  Experiments  (1772). — Hewson  tied  the  jugular  vein  of  a  horse  between  two  liga- 
tures, removed  it,  and  then  suspended  it  by  one  end  (Fig.  18).     He  found  that  the  blood  remained 
4 


50  CAUSE  OF  THE  COAGULATION  OF  THE  BLOOD. 

fluid  for  a  long  time  (48  hours),  while  the  red  corpuscles  sank  (R.C.)  and  left  a  clear  layer  of  plasma 
on  the  surface  (P).     When  he  drew  off  some  of  this  clear  plasma  it  coagu- 
FiG.   18.  lated,  thus  proving  coagulation  to  be  due  to  changes  in  the  plasma.     Lister 

repeated  this  experiment,  and  found  that  even  if  the  upper  end  of  the  tube 
he  opened  and  the  blood  freely  exposed  to  the  air,  coagulation  is  but  slightly 
hastened.  Moreover,  he  proved  that  the  blood  might  be  poured  from  one 
vein  into  another,  just  as  one  would  pour  fluid  from  one  test-tube  into 
another.  In  this  case  there  were  two  test-tubes,  i.e.,  the  veins — and 
although  the  blood,  on  being  poured  from  the  one  to  the  other,  came  into 
contact  with  the  air,  it  did  not  coagulate.  Hewson,  however,  found  that 
blood  poured  from  the  vein  into  a  glass  vessel  coagulated,  so  that,  in  his 
opinion,  the  blood  vessels  exerted  a  restraining  influence  on  the  coagulation. 
By  cooling  the  blood  and  preventing  it  from  coagulating,  he  proved  that 
coagulation  was  not  due  to  the  loss  of  heat.  Nor  could  it  be  a  vital  act,  as 
sodic  sulphate  or  other  neutral  salt  prevented  coagulation  indefinitely,  but 
coagulation  took  place  when  the  blood  was  diluted  with  water.] 

[Buchanan's  Researches. — The  serous  sacs  of  the  body  contain  a 
fluid  which  in  some  respects  closely  resembles  lymph.  The  pericardium 
contains  pericardial  fluid,  which  in  some  animals  coagulates  spontaneously 
vein  01  a  iior.^e  tied  be-  (t'.j,'.,  in  the  rabbit,  ox,  horse,  and  sheep),  if  the  fluid  be  removed  imnieJi- 
pTasma'"°W?r""^whit^'  "'''-''  "fi^''  '^''"''''-  ^f  '^is  be  not  done  till  several  hours  after  death,  the 
and  RC,  red  corpuscles',  fluid  does  not  Coagulate  spontaneously.  The  fluid  of  the  tunica  vaginalis 
of  the  testis,  again,  sometimes  accumulates  to  a  great  extent,  and  constitutes 
hydrocele,  but  this  fluid  shows  no  tendency  to  coagulate  spontaneously.  Andrew  Buchanan  found, 
however,  that  if  to  the  fluid  of  ascites,  to  pleuritic  fluid,  or  to  hydrocele  fluid,  there  be  added  clear 
blood  serum,  then  coagulation  takes  place,  i.e.,  two  fluids — neither  of  which  shows  any  tendency 
by  itself  to  coagulate — form  a  clot  when  they  are  mixed  (1831).  He  also  found  that  if  "  washed 
blood  clot  "  (which  consists  of  a  mixture  of  fibrin  and  colorless  corpuscles)  be  added  to  hydrocele 
fluid,  coagulation  occurred.  He  compared  the  action  of  washed  blood  clot  to  the  action  of  rennet 
in  coagulating  milk,  and  he  imagined  the  agents  which  determined  the  coagulation  to  be  the  colorless 
corpuscles.  Thus,  the  buffy  coat  of  horses'  blood  is  a  powerful  agent,  and  it  contains  very  numerous 
colorless  corpuscles.  He  finally  concluded  that  some  constituent  in  the  plasma,  to  which  he  gave  the 
name  of  a  "  soluble  fibrin,"  is  acted  upon  by  the  colorless  corpuscles  and  converted  into  fibrin.  The 
soluble  fibrin  of  Buchanan  is  comparable  to  the  fibrinogen  in  Hammarslen's  theory.  But  Buchanan 
did  not  separate  the  substance.] 

[Denis's  Plasmine. — Denis  mixed  uncoagulated  blood  with  a  saturated  solution  of  sodic  sul- 
phate, allowed  the  corpuscles  to  subside,  and  decanted  the  clear  fluid,  which  was  mixed  with  sodic 
chloride,  until  a  large  amount  of  precipitate  had  been  obtained.  The  precipitate,  when  washed  with 
a  saturated  solution  of  sodic  chloride,  he  called  plasmine  (1859).  If  plasmine  be  mixed  with 
water,  it  coagulates  spontaneously,  resulting  m  the  formation  of  fibrin,  while  another  proteid  remains 
in  solution.  According  to  the  view  of  Denis,  fibrin  is  produced  by  the  splitting  up  of  plasmine  into 
two  bodies — fibrin  and  an  insoluble  proteid.] 

[Researches  of  A.  Schmidt  (1861 ). — This  observer  rediscovered  the  chief  facts  already  known 
to  Buchanan,  viz.,  that  some  fluids  which  do  not  coagulate  spontaneously,  clot  when  mixed  with 
other  fluids,  which  also  show  no  tendency  to  coagulate  spontaneously,  e.g.,  hydrocele  fluid  and  blood 
serum.  He  proceeded  to  isolate  from  these  fluids  the  bodies  which  are  described  as  fibrinogen  and 
fibrinoplastin.  The  bodies  so  obtained  were  not  pure,  but  Schmidt  supposed  that  the  formation  of 
fibrin  was  due  to  the  interaction  of  these  two  proteids.  The  reason  why  hydrocele  fluid  did  not 
coagulate,  he  said,  was  that  it  contained  fibrinogen  and  no  fibrinoplastin,  while  blood  serum  con- 
tained the  latter, but  not  the  former.  Schmidt  afterward  discovered  that  these  two  substances  maybe 
present  in  a  fluid,  and  yet  that  coagulation  may  not  occur  (e.g.,  occasionally  in  hydrocele  fluid).  He 
supposed,  therefore,  that  blood  or  blood  serum  contained  some  other  constituent  necessary  for  coagu- 
lation.    This  he  afterward  isolated  in  an  impure  condition  and  caWeA  fibrin  ferment  [Gamgee).'\ 

Alexander  Schmidt's  theory  is  that  fibrin  is  formed  by  the  coming  together  of 
.two  proteid  substances  yi\\'\c\\  occmx  dissolved  in  the  plasma  or  liquor  sanguinis, 
viz.  :  (i)  Fibrinogen,  i.e.,  the  substance  which  yields  the  chief  mass  of  the  fibrin, 
and  (2)  Fibrinoplastic  substance  or  fibrinoplastin,  [  =  serum  globulin  (^Th.  Weyl 
and  Hoppe-Seyler)  or  paraglobulin  (^Kiihne)  §  32].  In  order  to  determine  the 
coagulation  a  ferment  seems  to  be  necessary,  and  this  is  supplied  by  (3)  the 
.Fibrin  ferment. 

I.  Properties  of  these  Substances. — Fibrinogen  and  fibrinoplastin  are 
not  distinguished  from  each  other  by  well-marked  chemical  characters.  Still 
they  differ,  as  follows  :  — 

(a)  Fibrinoplastin  is  more  easily  precipitated  from  its  solutions  than  fibrinogen. 


CAUSE  OF  THE  COAGULATION  OF  THE  BLOOD.  51 

(^b)  It  is  more  readily  redissolved  when  once  it  is  precipitated. 

(c)  It  forms  when  precipitated  a  very  light  granular  powder. 

{d)  Fibrinogen  adheres  as  a  sticky  deposit  to  the  side  of  the  vessel.  It  coagu- 
lates at  56°  C. 

Both  substances  closely  resemble  globulin  in  their  chemical  composition 
(Kuhne  called  fibrinoplastin  paraglobulin),  and  in  their  reactions  they  are  not 
unlike  myosin.  Like  all  globulins,  they  require  a  trace  of  common  salt  for  their 
solution  (§  249). 

On  account  of  their  great  similarity,  both  substances  are  not  usually  prepared 
from  blood  plasma.  Fibrinogen  is  prepared  from  scnnis  transudations  (pericardial, 
abdominal,  or  pleuritic  fluid,  or  the  fluid  of  hydrocele),  which  contain  no  fibrino- 
plastin. Fibrinoplastin  is  most  readily  prepared  from  serum,  in  which  there  is 
still  plenty  of  fibrinoplastin,  but  no  fibrinogen. 

2.  Preparation  of  Fibrinoplastin,  Serum  Globulin,  or  Paraglobu- 
lin.— ((7)  Dilute  blood  serum  with  twelve  times  its  volume  of  ice-cold  water,  and 
almost  neutralize  it  with  acetic  acid  [add  4  drops  of  a  25  per  cent,  solution  of 
acetic  acid  to  every  120  c.c.  of  diluted  serum]  ;  or  (/')  pass  a  stream  of  carbon 
dio.xide  through  the  diluted  serum,  which  soon  becomes  turbid  ;  and  after  a  time 
a  fine  white  powder,  copious  and  granular,  is  precipitated  {Schtnidt,  1862). 

[(<■)  The  serum  may  be  dialysed  for  a  day  ;  at  the  end  of  this  time  the  contents  of  the  dialyser 
have  become  turbid,  and  when  a  current  of  COj  is  passed  through  them,  a  precipitate  of  tibrino- 
plastin  is  obtained.] 

\_{d)  Method  of  Hammarsten. — All  the  fibrinoplastin  in  serum  is  not  pre- 
cipitated either  by  adding  acetic  acid  or  by  COj.  Hammarsten  found,  however, 
that  if  crystals  of  magnesium  sulphate  be  added  to  complete  saturation,  it  precipi- 
tates the  whole  of  the  serum  globulin,  but  does  not  precipitate  serum  albumin 
{Gamgee)  ;  it  seems  that  in  the  ox  and  horse  serum  globulin  is  more  abundant 
than  serum  albumin,  while  in  the  dog  and  rabbit  the  reverse  obtains ;  (com- 
pare §  32).] 

Schmidt  found  that  100  c.c.  of  the  serum  of  the  ox  blood  yielded  0.7  to  0.8  grms. ;  horse's 
serum,  0.3  to  0.56  grms.  of  dry  fibrinoplastin.  Fibrinoplastin  occurs  not  only  in  serum,  but 
also  in  red  blood  corpuscles,  in  the  fluids  of  connective  tissue,  and  in  the  juices  of  the  cornea. 

3.  Preparation  of  Fibrinogen.— This  is  best  prepared  from  hydrocele 
fluid,  although  it  may  also  be  obtained  from  the  fluids  of  serous  cavities,  e.g.,  the 
pleura,  pericardium,  or  peritoneum.  It  does  not  exist  in  blood  serum,  although 
it  does  exist  in  blood  plasma,  lymph,  and  chyle,  from  which  it  may  be  obtained 
by  a  stream  of  COj,  after  the  paraglobulin  is  precipitated,  {a)  Dilute  hydrocele 
fluid  with  ten  to  fifteen  times  its  volume  of  water,  and  pass  a  stream  of  COj 
through  it;  or  {b)  carefully  neutralize  it  by  adding  acetic  acid,  (c)  .'Vdd  powdered 
common  salt  to  saturation  to  a  serous  transudation,  when  a  sticky,  glutinous  (not 
very  abundant)  precipitate  of  fibrinogen  is  obtained. 

[Hammarsten  and  Eichwald  find  that,  although  paraglobulin  and  fibrinogen  are 
soluble  in  solutions  of  common  salt  (containing  5  to  8  per  cent,  of  the  salt),  a 
saline  solution  of  12  to  16  per  cent,  is  required  to  precipitate  the  fibrinogen, 
leaving  still  in  solution  paraglobulin,  which  is  not  precipitated  until  the  amount 
of  salt  exceeds  20  per  cent.  {Ganigee).'\ 

Hammarsten  found  that  it  may  be  prepared  from  blood  (of  the  horse)  by  first 
precipitating  all  the  serum  globulin  or  fibrinoplastin  with  crystals  of  magnesium 
sulphate,  and  subsequent  filtration,  which  removes  the  corpuscles;  a  clear,  salted 
plasma  is  thus  obtained.  If  to  the  filtrate  a  saturated  solution  of  common  salt  be 
added,  a  turbid,  flaky,  impure  precipitate  of  fibrinogen  is  obtained.  This  may  be 
dissolved  in  dilute  common  salt,  and  again  precipitated  bv  a  saturated  solution 
of  NaCl. 

Properties  of  the  Fibrin  Factors. — They  are  insoluble  in  pure  water,  but 
dissolve  in  water  containing  O  in  solution.     Both  are  soluble  in  very  dilute  alka- 


52  THE    FIBRIN    FACTORS. 

lies,  e.g.,  caustic  soda,  and  are  precipitated  from  this  solution  by  CO,.  They  are 
soluble  in  dilute  common  salt — like  all  globulins — but  if  a  certain  amount  of 
common  salt  be  added  in  excess  they  are  precipitated.  Very  dilute  hydrochloric 
acid  dissolves  them,  but  after  several  hours  they  become  changed  into  a  body 
resembling  syntonin  or  acid  albumin  (§  249,  III). 

Fibrinogen  dissolved  in  a  weak  solution  of  common  salt  (i  to  5  per  cent.)  is 
reprecipitated  on  adding  water,  so  that  it  resembles  fibrin.  Its  solution  in  com- 
mon salt  coagulates  at  52°  to  55°  C.  (Hammarsten,  Frediricq). 

[Frediricq  finds  that  fibrinogen  e.xists  as  such  in  the  plasma ;  it  coagulates  at 
56"  C,  and  the  plasma  thereafter  is  uncoagulable  (^Gamgee).'\ 

4.  Preparation  of  the  Fibrin  Ferment. — Mix  blood  serum  (ox)  with 
twenty  times  its  volume  of  strong  alcohol,  and  filter  off  the  deposit  thereby  pro- 
duced after  one  month.  The  deposit  on  the  filter  consists  of  albumin  and  the 
ferment  ;  dry  it  carefully  over  sulphuric  acid,  and  reduce  to  a  powder.  Triturate 
one  grainme  of  the  powder  with  65  c.c.  of  water  for  ten  minutes,  and  filter.  The 
ferment  is  dissolved  by  the  water,  and  passes  through  the  filter,  while  the  coagu- 
lated albumin  remains  behind  (Schmidt). 

In  the  preparation  of  fibrinoplastin,  the  ferment  is  carried  down  with  it  mechanically.  The 
ferment  seems  to  be  formed  first  in  fluids  outside  the  body,  very  probably  by  the  solution  of  the 
colorless  corpuscles.  More  ferment  is  formed  in  the  blood  the  longer  the  interval  between  its  being 
shed  and  its  coagulation.  It  is  destroyed  at  70°  C.  Blood  flowing  directly  from  an  artery  into 
alcohol  contains  no  ferment.  It  is  also  formed  in  other  protoplasmic  parts  (Rauschenbach),  eg.,  in 
dead  muscle,  brain,  suprarenal  capsule,  spermatozoa,  testicle  [Foa  and  Pellacani),  and  in  vegetable 
micro-organisms  {e.g.,  yeast  and  protozoa]  (Gro/imann)  [so  that  it  would  seem  to  be  a  general 
product  of  protoplasm].  [As  the  ferment  does  not  preexist  in  colorless  blood  corpuscles,  it  seems 
to  be  formed  from  some  mother  substance  in  them,  the  blood  plasma  itself  decomposing  this  sub- 
stance ( A\7iist/ien/>ai/i).~\ 

[Gamgee's  Method. — Buchanan's  "  washed  blood  clot"  (p.  50)  is  digested  in  an  8  per  cent, 
solution  of  common  salt.  The  solution  so  obtained  possesses  in  an  intense  degree  the  properties  of 
Schmidt's  fibrin  ferment.] 

Coagulation  Experiments. — According  to  A.  Schmidt,  if  the  pure  solutions 

of  ( I )  fibrinogen,  (2)  fibrinoplastin,  and  (3)  fibrin  ferment  be  mixed,  fibrin  is 
formed.  The  process  goes  on  best  at  the  temperature  of  the  body  ;  it  is  delayed 
at  0°  ;  and  the  ferment  is  destroyed  at  the  boiling  point.  The  presence  of  O  seems 
necessary  for  coagulation.  The  amount  of  ferment  appears  to  be  immaterial ; 
large  quantities  produce  more  rapid  coagulation,  but  the  amount  of  fibrin  formed 
is  not  greater. 

The  amount  of  salts  present  has  a  remarkable  relation  to  coagulation. 
Solutions  of  the  fibrin  factors  deprived  of  salts,  and  redissolved  in  very  dilute 
caustic  soda,  when  mixed,  do  not  coagulate  until  sufficient  NaCl  be  added  to 
make  a  i  per  cent,  solution  of  this  salt  (Schmid/). 

When  blood  or  blood  plasma  coagulates,  all  the  fibrinogen  is  used  up,  so  that 
the  serum  contains  only  fibrinoplastin  and  fibrin  ferment ;  hence,  the  addition 
of  hydrocele  fluid  (which  contains  fibrinogen)  to  serum  causes  coagulation. 

According  to  Hammarsten,  fibrin  is  formed  when  the  ferment  is  added  to  a 
solution  of  fibrinogen. 

[Foa  and  Pellacani  find  that  a  filtered  watery  extract  of  fresh  brain,  cap.-u!e  of  the  kidneys,  testes, 
and  some  other  tissues,  when  injected  into  the  blood  vessels  of  a  rabbit,  causes  coagulation  of  the 
blood  in  the  pulmonary  circulation  and  the  heart,  death  being  caused  by  the  action  of  a  substance 
identical  with  the  fibrin  ferment.] 

[Hammarsten's  Theory  of  Coagulation. — Ilammersten's  researches  led  him  to  believe  that 
fibrinoplastin  is  quite  unnecessary  for  coagulation.  According  to  him,  fibrin  is  formed  from  one 
body,  \\z.,  fibrinogen,  which  is  present  in  plasma  when  it  is  acted  upon  by  the  fibrin  ferment ;  the 
latter,  however,  has  not  been  obtained  in  a  pure  state.  Neither  he  nor  Schmidt  asserts  that  this 
body  is  of  the  nature  of  a  ferment,  although  they  use  the  term  for  convenience.  It  is  quite  certain 
that  fibrin  may  be  formed  when  no  fibrinoplastin  is  present,  coagulation  being  caused  i^y  the  addi- 
tion of  calcic  chloride  or  casein  prepared  in  a  special  way.  But,  whether  OHt' or /wo  proteids  be 
required,  in  all  cases  it  is  clear  that  a  certain  quantity  of  salts,  especially  of  NaCl,  is  necessary.] 


SOURCE    OF   THE    FIBRIN    FACTORS.  53 

[The  main  drift  of  the  foregoing  evidence  points  to  the  presence  of  one  proteid 
—fibrinogen — in  the  plasma,  which,  under  certain  circumstances,  yields  fibrin.  In 
shed  blood  this  act  seems  to  be  determined  by  a  ferment,  perhaps  .derived  from 
the  disintegration  of  colorless  corpuscles.] 

[Theory  of  ^A^ooldridge. — Wooldridge  attributes  great  importance  to  lecithin.  In  shed  blood 
the  coagulation  is  brought  about  by  the  interaction  of  the  plasma  and  the  colorless  corpuscles.  If 
lecithin  (which  is  present  in  considerable  amount  in  the  colorless  corpuscles)  diffuses  into  the  blood, 
coagulation  takes  place.  When  peptone  is  injected  into  the  blood  of  the  dog,  the  blood  does  not 
clot;  this  is  due,  according  to  Wooldridge,  to  the  peptone  "preventing  the  interaction  of  leucocytes 
and  plasma."  If,  however,  the  corpuscular  elements  are  removed  by  the  centrifugal  machine,  the 
peptone  plasma  can  be  made  to  clot.  He  also  believes  that  fibrin  ferment  does  not  preexist  in 
normal  plasma,  but  that  "  it  may  make  its  appearance  in  that  plasma  in  the  absence  of  all  cellular 
elements,  and  must,  therefore,  come  from  some  constituent  or  constituents  of  the  plasma  itself."] 

30.  SOURCE  OF  THE  FIBRIN  FACTORS.— Al.  Schmidt  maintains 
that  all  the  three  substances  out  of  which  fibrin  is  said  to  be  formed  arise  from 
the  breaking  up  of  colorless  blood  corpuscles.  In  the  blood  of  man  and  mam- 
mals fibrinogen  exists  dissolved  in  the  circulating  blood  as  a  dissolution  product 
of  the  retrogressive  changes  of  the  white  corpuscles.  Plasma  contains  dissolved 
fibrinogen  and  serum  albumin.  The  circulating  blood  is  very  rich  in  colorless 
blood  corpuscles — much  richer,  indeed,  than  was  formerly  supposed  {Schmidt, 
Landois).  As  soon  as  blood  is  shed  from  an  artery,  enormous  numbers  of  the 
colorless  corpuscles  are  dissolved  (Mantcgazza) — according  to  Ale.x.  Schmidt,  71.7 
per  cent,  (horse).  First  the  body  of  the  cell  disappears,  and  then  the  nucleus 
{Hlava).  The  products  of  their  dissolution  are  dissolved  in  the  plasma,  and  one 
of  these  products  is  fibrinoplastin.  At  the  same  time  the  fibrin  ferment  is  also 
produced,  so  that  it  would  seem  not  to  exist  in  the  intact  blood  corpuscles. 
Fibrinoplastin  and  fibrin  ferment  are  also  produced  by  the  "  transition  forms'" 
of  blood  corpuscles,  i.e.,  those  forms  which  are  intermediate  between  the  red  and 
the  white  corpuscles.  They  seem  to  break  up  immediately  after  blood  is  shed. 
The  blood  plates  (p.  33)  are  also,  probably,  sources  of  these  substances. 

In  amphibians  and  birds  the  red  nucleated  corpuscles  rapidly  break  up  after  blood  is  shed,  and 
yield  the  substance  or  substances  which  form  fibrin.  Al.  Schmidt  convinced  himself  that  in  these 
animals  fibrinogen  is  originally,  also,  a  constituent  of  the  blood  corpuscles. 

It  is  clear,  therefore,  according  to  Schmidt's  view,  that  as  soon  as  the  blood 
corpuscles,  white  or  red,  are  dissolved,  the  fibrin  factors  pass  into  solution,  and 
the  formation  of  fibrin  by  the  interaction  of  the  three  substances  will  ensue. 

If  a  large  number  of  leucocytes  be  introduced  into  the  circulation  of  an  animal, 
the  leucocytes  are  dissolved  in  great  numbers  in  the  blood,  so  that  death  takes 
place  by  diffuse  coagulation.  Should  the  animal  survive  the  immediate  danger  of 
death,  the  blood,  owing  to  the  want  of  leucocytes,  is  completely  incapable  of 
coagulating  {Grotli). 

[It  is  worthy  of  remark  to  recall  the  conclusion  arrived  at  by  And.  Buchanan,  viz.,  that  the 
potential  element  of  his  "  washed  blood  clot "  resided  in  the  colorless  corpuscles,  "  primary  cells  or 
vesicles."  He,  like  Schmidt,  found  that  the  buffy  coat  of  horses'  blood,  which  is  very  rich  in  white 
corpuscles,  produced  coagulation  rapidly.  Buchanan  compared  the  action  of  his  washed  clot  to 
that  of  rennet  in  coagulating  milk.] 

Pathological  — A  I.  Schmidt  and  his  pupils,  Jakowicki  and  Birk,  have  shown  that  some  ferment, 
probably  derived  from  the  dissolution  of  colorless  corpuscles,  is  found  in  circulating  blood,  and  that 
it  is  more  abundant  in  venous  than  in  arterial  blood,  while  it  is  most  abundant  in  shed  blood.  It 
is  specially  remarkable  that  in  se/'/ic  fever  the  amount  of  ferment  in  blood  may  increase  to  such  an 
extent  as  to  permit  the  occurrence  of  spontaneous  coagulation  (thrombosis),  which  may  even  pro 
duce  death  [Am.  A'ohler).  In  febrile  cases  generally,  the  amount  of  ferment  is  somewhat  more 
abundant  {EJelberg  anJ  Birk).  Af.er  the  injection  of  ichor  into  the  blood,  an  enormous  number 
of  colorless  corpuscles  are  dissolved  (F.  Hoffman).  The  injection  of  peptone  (Hb)  and,  to  a  less 
degree,  of  distilled  water,  is  followed  by  solution  of  numerous  leucocytes. 

There  are  changes  in  the  blood,  constituting  true  bload  diseases,  in  which  the  physiological  meta- 
bolism of  the  colorless  corpuscles  is  enormously  increased,  so  that  the  metabolic  products  accumu- 
late in  the  blood  \Alex.  Sc/imidt).  The  result  of  this  is  spontaneous  coagulation  within  the  circu- 
latory system,  and  death  even  may  occur;  at  the  least,  there  is  an  increase  of  temperature.  After 
such  a  condition,  the  coagulability  of  such  blood  is  diminished. 


54  CHEMICAL   COMPOSITION    OF   THE    PLASMA   AND    SERUM. 

31.  RELATION  OF  THE  RED  BLOOD  CORPUSCLES  TO  THE  FORMA- 
TION OF  FIBRIN. — After  the  investigations  of  several  observers  had  shown  that  the  red  blood 
corpuscles  [bird  [Hoppe-Siyler)^,  horse  (Beynsiiis),  frog  (A.  Schtmdt  and  Semnu-r]  participate  in 
the  production  of  fibrin,  Landois  observed,  in  1874,  under  the  microscope,  that  the  stromala  of  the 
red  blood  corpuscles  of  the  mammals  passed  into  fibrin.  If  a  drop  of  dcfibrinated  rabbit's  blood  be 
placed  in  serum  of  frog's  blood,  without  mixing  them,  the  red  corpuscles  can  be  seen  collecting 
together;  their  surfaces  are  sticky,  and  they  can  only  be  sep.irated  by  a  certain  pressure  on  the 
cover  glass,  whereby  some  of  the  new  spherical  corpuscles  are  drawn  out  into  threads.  The  cor- 
puscles soon  become  spherical,  and  those  at  the  margin  allow  the  hcemoglobin  to  escape,  when  the 
decolorization  progresses,  from  the  margin  inward,  until  at  last  there  remains  a  mass  of  stroma 
adhering  together.  The  stroma  substance  is  very  sticky,  but  soon  the  cell  contours  disappear,  and 
the  stromata  adhere  and  form  fine  fibres.  Thus  (according  to  Landois)  the  formation  of  fibrin  from 
reii  blood  corpuscles  can  be  traced  step  by  step.  The  red  blood  corpuscles  of  man  and  animals, 
when  dissolved  in  the  serum  of  other  animals,  show  much  the  same  phenomena. 

Stroma  Fibrin  and  Plasma  Fibrin. — Landois  calls  fibrin  formed  direct  from  strcma,  stroma 
fibrin.  Fibrin  which  is  formed  in  the  usual  way  by  the  fibrin  factors  he  ca\\% p!as?iia  fibrin.  The 
stroma  fibrin  is  closely  related  chemically  to  stroma  itself;  and  as  yet  the  two  kinds  of  fibrin  have 
not  been  sharply  distinguished  chemically.  Substances  which  rapidly  dissolve  red  corpuscles  cause 
extensive  coagulation,  e  g.,  injection  of  bile  or  bile  salts,  or  lake-colored  blood,  into  arteries 
(A'autiyn  and  Francken).  After  the  injection  of  foreign  blood  the  newly-injected  blood  often 
breaks  up  in  the  blood  vessels  of  the  recipient,  while  the  finer  vessels  are  frequently  found  plugged 
with  small  thrombi  (see  Transfusion,  \  102). 

Coagulable  Fluids. — With  regard  to  coagulability,  fluids  containing  proteids 
may  be  classified  thus: — 

(1)  Those  that  coagulate  spontaneously,  i.  e.,  blood,  lymph,  chyle. 

(2)  Those  capable  of  coagulating,  e.g.,  fluids  secreted  pathologically  in  serous  cavities;  for 
example,  hydrocele  fluid,  which,  as  usually  containing  fibrinogen  only,  does  not  coagulate  sponta- 
neously, cogaulates  on  the  addition  of  fibrinoplastin  and  ferment  (or  of  blood  serum  in  which  both 
occur). 

(3)  Those  which  do  not  coagulate,  e.  g.,  inWk  or  seminal  fluid,  which  do  not  seem  to  contain 
fibrinogen. 

32.  CHEMICAL  COMPOSITION  OF  THE  PLASMA  AND 
SERUM. — I.  Proteids  occur  to  the  amount  of  8  to  10  percent,  in  the  plasma. 
Only  0.2  per  cent,  of  these  go  to  form  fibrin.  When  coagulation  has  taken 
place,  and  after  the  separation  of  the  fibrin,  the  plasma  becomes  converted  into 
serum.  The  sp.  gr.  of  human  serum  is  102710  1029.  It  contains  several  proteids. 
[According  to  Hammarsten,  human  serum  contains  9.2075  per  cent,  of  solids — 
of  these,  3.103  =^  serum  globulin,  and  4.516  =  serum  albumin,  /.  e.,  in  the 
ratio  of  i  :  1.5 11.  The  total  amount  of  proteids  in  blood  seems  to  be  much 
more  constant  than  are  the  relative  proportions  of  serum  albumin  and  serum 
globulin  (Salvioli').'] 

[a)  Serum  Globulin  (77/.  Weyl^  or  Paraglobulin,  2  to  4  per  cent.,  was 
formerly  believed  to  occur  in  much  smaller  amount  than  it  actually  does.  Ham- 
marsten found  that  if  serum  be  diluted  with  two  volumes  of  water,  and  crystals  of 
magnesium  sulphate  be  added  to  saturation,  serum  globulin  is  precipitated,  but 
not  serum  albumin.  In  the  serum  of  the  horse  and  ox,  serum  globulin  is  more 
abundant  than  serum  albumin,  while  in  the  serum  of  the  rabbit  and  dog  the 
reverse  is  the  case.  It  is  soluble  in  10  per  cent,  solution  of  common  salt,  and 
coagulates  at  75°  C. 

[Serum  globulin  was  carefully  described  by  Panum  under  the  name  of  "  serum  casein  ;"  by  Al. 
Schmidt,  as  "  fibrinoplastic  substance  ;"   and  by  Kiihne,  as  "  paraglobulin."] 

As  already  mentioned,  it  may  also  be  precipitated,  in  part,  by  diluting  serum  with  lo  to  15  vols, 
of  water,  and  passing  a  stream  of  COj  through  it  (p.  51).  If  a  trace  oi  acetic  acid  be  added  to 
serum  afer  the  separation  of  the  serum  globulin,  Kiihne  finds  that  a  fine  precipitate  of  what  he  calls 
soda  albuminate  occurs.  [It  is,  however,  highly  doubtful  if  an  alkali  albuminate  does  occur  in  the 
blood.  Hammarsten  found  that  CO2  does  not  precipitate  all  the  serum  globulin,  so  that  it  is  impos- 
sible that  Kiihne's  soda  albuminate  exists  as  a  distinct  substance  in  serum.] 

According  to  A.  E.  P.urckhard,  magnesium  sulphate  not  only  precipitates  serum  globulin,  but  also 
another  proteid  substance  more  closely  resembling  albumin.  During  hunger  the  globulin  increases 
and  the  albumin  diminishes. 


PROTEIDS    OF   THE    SERUM.  55 

(&)  Serum  Albumin. — Its  solutions  begin  to  be  turbid  at  60°  C,  and  coagu- 
lation occurs  at  73°  C,  the  fluid  becoming  slightly  more  alkaline  at  the  same 
time.  The  amount  is  about  3  to  4  per  cent.  (^Fredericq).  If  sodium  chloride  be 
cautiously  added  to  serum,  the  coagulating  temperature  may  be  lowered  to  50° 
C.  It  has  a  rotatory  ]}ower  of  —  56°.  It  is  changed  into  syntonin  or  acid 
albumin  by  the  action  of  dilute  HCl,  and  by  dilute  alkalies  into  alkali  albuminate. 

[Serum  Albumin  v.  Egg  Albumin. — Although  serum  albumin  is  closely  related  to  egg  albu- 
min, they  differ — («)  a.s  regards  their  action  upon  polarized  light;  (b)  the  precipitate  produced  by 
adding  HCl  or  HNO3  is  readily  soluble  in  4  c.c.  of  the  reagent  in  the  case  of  serum  albumin, 
while  the  precipitate  in  egg  albumin  is  dissolved  with  very  great  difficulty  ;  (c)  egg  albumin,  injected 
into  the  veins,  is  excreted  in  the  urine  as  a  foreign  body,  while  serum  albumin  is  not  [Slockvis)  ; 
(d)  serum  albumin  is  not  coagulated  by  ether,  while  egg  albumin  is,  if  the  solution  is  not  alkaline 

(?  249)-] 

[Serum  albumin  has  never  been  obtained  from  free  salts,  even  when  it  is  dialysed  for  a  very  long 
time,  as  was  maintained  by  Aronstein,  whose  results  have  not  been  confirmed  by  Heynsius,  Haas, 
Huizinga,  Salkowski  and  others] 

After  all  the  paraglobulin  (serum  globulin)  in  serum  is  precipitated  by  magnesium  sulphate,  serum 
albumin  still  remains  in  soluiion.  If  this  solution  be  heated  to  40  or  50°  C.  a  copious  precipitate 
of  non-coagulated  serum  albumin  is  obtained,  which  is  soluble  in  water.  If  the  serum  albumin  be 
filtered  from  the  fluid,  and  if  the  clear  fluid  be  heated  to  over  60°  C,  P'redericq  found  that  it  becomes 
turbid  from  the  precipitation  of  other  proteids  ;  the  amount  of  these  other  bodies,  however,  is  small. 

[Proteids  of  the  Serum. — Halliburton  has  shown,  by  the  method  of  "frac- 
tional heat  coagulation  "  (i.  c,  ascertaining  the  temperature  at  which  a  proteid  is 
coagulated,  filtering  the  fluid  and  again  heating  the  filtrate  to  a  higher  tempera- 
ture), that  from  the  same  fluid  perhaps  two  or  more  proteids,  all  with  different 
temperatures  of  coagulation,  may  be  obtained.  Care  must  be  taken  to  keep  the 
reaction  constant.  He  finds  that  serum  globulin  coagulates  at  75°  C,  while  serum 
albumin  in  reality  consists  of  three  proteids,  which  coagulate  at  different  tempera- 
tures ;  ((?)  at  73°,  (/')  at  77°,  and  (/)  at  84°  C] 

[Precipitation  by  Salts. — Sulphate  of  magnesia  not  only  precipitates  serum 
globulin  but  also  fibrinogen  (Hallilnirton).  The  fluid  must  be  shaken  for  several 
hours,  to  get  complete  saturation.  Sodic  sulphate,  when  added  to  serum  deprived 
of  its  globulin  by  MgSOi,  precipitates  serum  albumin,  but  it  produces  no  precipi- 
tate with  pure  serum.  In  this  way  serum  albumin  may  be  obtained  in  a  pure,  un- 
coagulated  and  still  soluble  condition.  But  Halliburton  finds  that  serum  globulin 
is  thrown  down  by  sodic  nitrate,  acetate,  or  carbonate  ;  while  all  the  proteids  of 
the  serum  are  precipitated  by  potassic  acetate  or  phosphate,  and  the  same  result  is 
brought  about  by  adding  two  salts,  e.  g.,  MgSO,  and  Na^SOj  (in  this  case  sodio- 
magnesic  sulphate  is  formed)  ;  MgSO,  and  NaNOs  ;  MgSO,  and  KI ;  NaCl  and 
Na^SO,.  After  serum  globulin  is  thrown  down  by  MgSO,,  the  addition  of  MgSO, 
and  NajSO,  or  the  double  salt,  precipitates  the  serum  albumin,  which  is  still 
soluble  in  water.] 

[The  plasma  of  invertebrata  fdecapol  crustaceans,  some  gasteropods,  cephalopods,  etc.)  clots 
like  vertebrate  blood,  and  contains  fibrinogen,  but  it  is  noteworthy  that,  in  addition,  there  is  found  in 
it  a  substance  corresponding  to  haemoglobin,  and  called  by  Fredericq,  Haemocyanin.  It  exists  like 
Hb  in  two  conditions,  one  reduced  and  the  other  oxyhsemocyanin,  the  former  being  colorless,  the 
latter  blue.  In  its  general  characters  it  resembles  Hb,  although  it  contains  copper  instead  of  iron, 
and  gives  no  absorption  bands  {Halliburton).  In  the  blood  of  some  decapod  crustaceans  there  is  a 
reddish  pigment,  Tetronerythrin,  which  is  identical  with  that  in  the  exoskelcton  and  hypoderm. 
It  belongs  to  the  group  of  lipochromes,  like  some  of  the  pigments  of  the  retina.  The  hcemocyanin 
is  respiratory  in  function,  and  it  is  remarkable  that  it  is  contained  in  the  plasma,  and  not  in  the 
formed  elements,  like  the  Hb  of  vertebrates.  So  that,  stated  broadly,  in  these  Invertebrates  the 
plasma  is  both  nutritive  and  respiratory  in  its  functions,  while  in  Vertebrates  the  red  corpuscles 
chiefly  are  respiratory  and  the  plasma  nutritive  (Fredericq).'] 

II.  Fats  (o.  I  to  0.2  per  cent.). — Neutral  fats  (tristearin,  tripalmitin,  triolein) 
occur  in  the  blood  in  the  form  of  small  microscopic  granules  which,  after  a  meal 
rich  in  fat  (or  milk),  render  the  serum  quite  milky. 

[The  amount  of  fat  in  the  serum  of  fasting  animals  is  about  0.2  per  cent.  ; 
during  digestion  0.4  to  0.6  per  cent. ;  and  in  dogs  fed  on  a  diet  rich  in  fat  it  may 


56  GASES   OF   THE    BLOOD. 

be  1.25  per  cent.  There  are  also  minute  traces  of  fatty  acids  (succinic).  Rohrig 
showed  that  soluble  soaps,  t.  e.,  alkaline  salts  of  the  fatty  acids,  cannot  exist  in  the 
blood.  Cholesterin  may  be  considered  along  with  the  fats.  It  occurs  in 
considerable  amount  in  nerve  tissues,  and,  like  fats,  is  extracted  by  ether  from  the 
dry  residue  of  blood  serum.  Hoppe-Seyler  found  0.019  to  °-3i4  per  cent,  in  the 
serum  of  the  blood  of  fattened  geese.  There  is  no  fat  in  the  red  blood  corpuscles 
(^Hoppe-Seyler').  Lecithin  (its  decomposition  products,  glycerin-phosphoric  acid 
and  protagon)  occur  in  serum  and  also  in  the  blood  corpuscles.] 

III.  Traces  of  Grape  Sugar  [o.  i  to  o.  15  per  cent.  {Seegen)  more  in  the  hepatic 
vein  (0.23  per  cent.)],  derived  from  the  liver  and  muscles,  is  increased  after 
hemorrhage  (§  175)  (Bernard,  v.  Mering) ;  some  glycogen  (Faiy'),  and  another 
reducing  fermentative  substance  also  increased  by  hemorrhage  (_/.  G.  Off). 

The  amount  of  grape  sugar  in  the  blood  increases  with  the  absorjition  of  sugar  from  the  intestine, 
and  this  increase  is  most  obvious  in  the  blood  of  the  portal  and  hepatic  veins ;  there  is  also  a  slight 
increase  in  the  arterial  blood,  but  there  it  is  rapidly  changed.  The  presence  of  sugar  is  ascertained 
by  co.igulating  blood  by  boiling  it  with  sodium  sulphate,  pressing  out  the  fluid  and  testing  it  for 
sugar  with  Fehling's  solution  (CI.  Bernard).     Pavy  coagulates  the  blood  with  alcohol. 

IV.  Extractives. — Kreatin,  urea  (0.016  per  cent.,  increased  after  food), 
succinic  acid,  and  uric  acid  (more  abundant  in  gouty  conditions),  guanin  (?),  car- 
baminic  acid  ;  all  occur  in  very  small  amounts. 

V.  Sarcolactic  Acid  and  Indican,  also  in  small  amount. 

VI.  Salts  (.085  to  .09  per  cent.). — The  most  abundant  salt  is  sodium  chloride 
(0.5  per  cent.),  and  next  to  it  sodium  carbonate.  [It  is  most  important  to  note 
that  the  soda  salts  are  far  more  abundant  in  the  serum  than  the  potassium  salts. 
The  ratio  may  be  as  high  as  to  :  i.]  Animal  diet  increases  the  amount  of  salts, 
vegetable  food  diminishes  it  temporarily. 

Salts  in  human  blood  serum  (Hoppt-Scykr). 

Sodic    Chloride,   4.92    per    1000      |  Sodic  Phosph.ate,  .    .      015  per  1000 

"        Sulphate,     0.44  "  Calcic  Phosphate,      ■   lo7j        " 

"        Carbonate,  0.21  "  j  Magnesic, / 

VII.  Water  about  90  per  cent. 

VIII.  A  yellow  Pigment. 

Thudichum  regards  the  pigment  of  the  serum  as  lutein;  Maly,  as  hydrobilirubin ;  and  MacMunn 
as  choletelin. 

33.  THE  GASES  OF  THE  BLOOD.  -Absorption  of  Gases  by  Solid  Bodies  and  by 
Fluids. — Absorption  by  Solid  Bodies. — A  considerable  attraction  exists  between  the  particles  of 
solid  porous  bodies  and  gaseous  substances,  so  that  gases  are  attracted  and  condensed  within  the 
pores  of  solid  bodies,  i.  e.,  the  gases  are  absorbed.  Thus  I  volume  of  boxwood  charcoal  (at  12° 
C.  and  ordinary  barometric  pressure)  absorbs  35  volumes  CO^,  9.4  vol.  O,  7.5  vol.  N,  1.75  vol.  H. 
Heat  is  always  formed  when  gases  are  absorbed,  and  the  amount  of  heat  evolved  bears  a  relation  to 
the  energy  with  which  the  absorption  takes  place.  Non-porous  bodies  are  similarly  invested  by  a 
layer  of  condensed  gases  ou  their  surfaee. 

By  Fluids. — Fluids  can  also  absorb  gases.  .4  known  quantity  of  Jliiid  at  different  pressures 
always  absorbs  the  same  %'o!unie  of  gas.  Whether  the  pressure  be  great  or  small,  the  volume  of  the 
gas  absorbed  is  equally  great  (IF.  //enry).  But  according  to  Boyle  and  Mariotte's  law  (1679), 
when  the  pressure  within  the  same  volume  of  gas  is  increased,  the  volume  varies  inversely  as  the 
pressure. 

Hence  it  follows  that,  with  varying  pressure,  the  volume  of  gas  absorbed  remains  the  same,  but 
the  quantity  of  gas  [weight,  density)  is  directly  proportional  to  the  pressure.  If  the  pressure  =0, 
the  weight  of  the  gas  absorbed  must  also  =  o.  As  a  necessary  result  of  this,  we  see  that  (i) 
fluids  can  be  freed  of  their  absorbed  gases  in  a  vacuum  under  an  air  pump. 

Coefficient  of  Absorption  means  the  T'lj/aOTf  of  a  gas  (0°  C. )  which  is  absorbed  by  a  unit  of 
volume  of  a  liquid  (at  700  mm.  Hg)  at  a  given  temperature.  The  volume  of  a  gas  absorbed,  and 
therefo  e  the  coefficient  of  absorption,  is  quite  independent  of  the  pressure,  while  the  -weight  of  the 
gas  is  proportional  to  it.  Temperature  has  an  important  influence  on  the  coefficient  of  absorption. 
With  a  low  temperature  it  is  greatest;  it  diminishes  as  the  temperature  increases;  and  at  the  boiling 
point  A^^o.  Hence,  it  follows  that  (2)  absorbed  gases  may  be  expelled  from  fluids  simply  by 
causitig  the  fluids  to  boil.  The  coefficient  of  absorption  diminishes  for  different  fluids  and  gases, 
with  increasing  temperature,  in  a  special,  and  by  no  means  uniform,  manner,  which  must  be  deter- 


EXTRACTION   OF   THE   BLOOD    GASES.  57 

mined  empirically  for  each  liquid  and  gas.  Thus  the  coefficient  of  absorption  for  CO^  in  water 
diminishes  with  an  increasing  temperature,  while  that  for  H  in  water  remains  unchanged  between 
0°  and  20°  C. 

Diffusion  and  Absorption  of  Gases. — Diffusion  of  Gases. — Gases  which  do  not  enter  into 
chemical  combinations  with  each  other  mix  with  each  other  in  quite  a  regular  proportion.  If,  e.  g., 
the  necks  of  two  flasks  be  placed  in  communicaiion  by  means  of  a  glass  or  other  tube,  and  if  the 
lower  flask  contain  CO^,  and  the  upper  one  H,  the  gases  mix  quite  independently  of  their  different 
specific  gravities^  both  gases  forming  in  each  flask  a  perfectly  uniform  mixture.  The  phenomenon 
is  called  the  diffusion  of  gases.  If  a  porous  7nembrane  be  previously  inserted  between  the  gases, 
the  exchange  of  gases  still  goes  on  through  the  membrane.  But  (as  with  endosmosis  in  fluids) 
the  gases  pass  with  unequal  rapidity  through  the  pores,  so  that  at  the  beginning  of  the  experiment  a 
larger  amount  of  gas  is  found  on  one  side  of  the  membrane  than  on  the  other.  According  to  Gra- 
ham, the  rapidity  of  the  diffusion  of  the  gases  through  the  pores  is  inversely  proportional  to  the 
square  root  of  their  specific  gravities.     (According  to  Bunsen,  however,  this  is  not  quite  correct.) 

Different  Gases  Forming  a  Gaseous  Mixture  do  not  Exert  Pressure  upon  One  Another. 
— Gases,  therefore,  pass  into  a  space  filled  with  another  gas,  as  they  would  pass  into  a  vacuum.  If 
the  surface  of  a  fluid  containing  absorbed  gases  be  placed  in  contact  with  a  very  large  quantity  of 
another  gas,  the  absorbed  gases  difiuse  into  the  latter.  Hence,  absorbed  gases  can  be  removed  by 
(3)  passing  a  stream  of  another  gas  through  the  fluid,  or  by  merely  shaking  up  the  fluid  with  another 
gas. 

Partial  Pressure. — \f  two  or  more  gases  are  mixed  m  a  closed  space  over  a  fluid,  as  the  difierent 
gases  existing  in  a  gaseous  mixture  exert  no  pressure  upon  each  other,  the  several  gases  are 
absorbed.  The  weight  of  each  absorbed  is  proportional  to  the  pressure  under  which  each  gas 
would  be  were  it  the  only  gas  in  the  space.  This  pressure  is  called  the  partial  pressure  of  a 
gas  {  Bunsen).  The  absorption  of  gases  from  their  mixlures.  therefore,  is  proportional  to  the  par- 
tial pressure.  The  partial  pressure  of  a  gas  in  a  space  is  at  the  same  time  the  expression  for  the 
tension  of  the  gas  absorbed  by  a  fluid. 

The  air  contains  0.2096  volume  of  O,  and  0.7904  volume  N.  If  i  volume  of  the  air  be  placed 
under  a  pressure,  P,  over  water,  the  partial  pressure  under  which  O  is  absorbed  =  0.2096  P ;  that 
for  N  =0.7904  P.  At  0°  C,  and  760  mm.  pressure,  i  volume  of  water  absorbs  0.02477  volume  of 
air,  consisting  of  0.00S62  volume  O,  and  0.01615  volume  N.  It  contains,  therefore,  34  per  cent. 
O  and  66  per  cent.  N.  Therefore,  water  absorbs  from  the  air  a  mi.xture  of  gases  containing  a 
larger  percentage  of  O  than  the  air  itself. 

34.  EXTRACTION  OF  THE  BLOOD  GASES.— [The  blood  to  be  analyzed  must  be 
collected  over  mercury,  so  as  to  avoid  its  contact  with  air.  This  is  easily  done  by  means  of  a  special 
apparatus,  consisting  of  a  graduated  tube  filled  witli  mercury  and  communicating  with  a  glass  globe 
also  filled  with  mercury,  which  can  be  lowered  as  the  blood  flows  into  the  graduated  tube.] 

The  extraction  of  the  gases  from  the  blood,  and  their  collection  for  chemical  analysis,  are  carried 
out  by  means  of  the  mercurial  pump  (C.  Ludwig).  Fig.  19  shows  in  a  diagrammatic  form  the 
arrangement  of  Plluger's  gas  pump. 

It  consists  of  a  receptacle  for  the  blood  or  "  blood  bulb  "  (A),  a  glass  globe  capable  of 
containing  250  to  300  c.c,  connected  above  and  below  with  tubes,  each  of  which  is  provided  with 
a  stop-cock,  a  and  b  ;  b  is  an  ordinary  stop-cock,  while  a  has  through  its  long  axis  a  perforation 
which  opens  at  x,  and  is  so  arranged  that,  according  to  the  position  of  the  handle,  it  leads  up  into 
the  blood  bulb  (position  .r,  n),  or  downward  through  the  lower  tube  (position  .x' ,  a').  This  blood 
bulb  is  first  completely  emptied  of  air  (by  means  of  a  mercurial  air  pump),  and  then  carefully 
weighed.  One  end  [x')  of  it  is  tied  into  an  artery  or  a  vein  of  an  animal,  and  when  the  lower 
stop  cock  is  placed  in  the  position  (.v,  a)  blood  flows  into  the  receptacle.  When  the  necessar)' 
amount  of  blood  is  collected  the  lower  stop-cock  is  put  into  the  position  x',  a',  and  the  blood  bulb, 
after  being  cleaned  most  carefully,  is  weighed,  to  ascertain  the  weight  of  the  amount  of  blood  col- 
lected. The  second  pirt  of  the  apparatus  consists  of  the  froth  chamber,  B,  leading  upward  and 
downward  into  tubes,  each  of  which  is  provided  with  an  ordinary  stop-cock,  c  and  d.  The  froth 
chamber,  as  its  name  denotes,  is  to  catch  the  froth  which  is  formed  during  the  energetic  evolution  of 
the  gases  from  the  blood.  The  lower  aperture  of  the  froth  chamber  is  connected  by  means  of  a 
well-ground  tube  with  the  blood  bulb,  while  above  it  communicates  with  the  third  part  of  the 
apparatus,  the  drying  chamber,  G.  This  consists  of  a  |J-shaped  tube,  provided  below  with  a 
small  glass  bulb,  which  is  half  filled  with  sulphuric  acid,  while  in  its  limbs  are  placed  pieces  of 
pumice  stone  also  moistened  with  sulphuric  acid-  As  the  blood  gases  pass  through  this  apparatus 
(which  may  be  shut  off  by  the  stopcocks,  e  and/"),  they  are  freed  from  their  watery  vapor  by  the 
sulphuric  acid,  so  that  they  pass  quite  dry  through  the  stop-cock,  f.  The  short,  well-ground  tube, 
D,  is  fixed  toy,  and  to  the  former  is  attached  t\\e  smaW  barometric  tube  or  manometer, y,  wh\ch 
indicates  the  extent  of  the  vacuum.  From  D  we  pass  to  the  pump  proper.  This  consists  of  two 
lar^e  glass  bulbs,  which  are  continued  above  and  below  into  open  tubes ;  the  lower  tubes,  Z  and  -c, 
being  united  by  a  caoutchouc  tube,  G.  Both  the  bulbs  and  caoutchouc  tube  contain  mercun- — the 
bulbs  being  about  half  full,  and  F  being  larger  than  E.  The  bulb  E  is  fixed  ;  but  F  can  be  raised 
or  lowered  by  means  of  a  pulley  with  a  rack  and  pinion  motion.  If  F  be  raised,  E  is  filled  ;  if  F 
be  lowered,  E  is  emptied.     The  upper  end  of  E  divides  into  two  tubes,  ^^  and /i,  of  which  g  is 


58 


EXTRACTION    OF   THE    BLOOD    GASES. 


united  to  D.  The  ascending  tube,  h  (gas-delivery  tube),  is  very  narrow,  and  is  bent  so  that  its 
free  end  dips  into  a  vessel  containing  mercury,  v  (a  pneumatic  trough),  and  the  opening  is  placed 
exactly  under  the  tube  for  collecting  the  gases,  the  eudiometer,  J,  which  is  also  tilled  with  mercury. 
Where^and  H  unite,  there  is  a  two-way  stopcock,  which  in  one  position,  H,  places  E  in  commu- 
nication with  A,  B,  G,  D,  the  chambers  to  be  exhausted,  and  in  the  position  K,  shuts  off  A,  B,  G, 
D,  and  places  the  bulb,  E,  in  communication  with  the  gas-delivery  tube,  //,  and  the  eudiometer,  J. 

B,  G,  D  are  completely  emptied  of  air,  thus  ;     The  stop-cock  is  placed  in  the  position,  K;  raise 
F  until  drops  of  mercury  issue  from  the  fine  tube,  /  (not  yet  placed  under  J) ;  place  the  stop-cock 

Fig.  19. 


Scheme  of  Pfliiser's  Gas  Pump.  A,  blood  bulb;  a,  stop-cock,  with  a  longitudinal  perforation  opening  upward  ;  a', 
the  same  opening  downward  ;  b  and  c,  stop-cocks:  B,  froth  chamber;  d,e,/,  stop-cocks;  G,  drying  cham- 
bers, containing  sulphuric  acid  and  pumice  stone  :  D,  tube,  v  "  " 


in  the  position  H,  lower  F;  stop-cock  in  position,  K  and  so  on  until  the  barometer,  y,  indicates  a 
complete  vacuum.  J  is  now  placed  over  i.  Open  the  cocks  f  and  i,  so  that  the  blood  bulb.  A, 
communicates  with  the  rest  of  the  apparatus,  and  the  blood  gases  froth  up  in  B,  and  after  being 
dried  in  G  pass  toward  E.  Lower  F,  and  they  pass  into  E;  stop-cock  in  position  K,  raise  F,  and 
the  gases  are  collected  in  J,  under  mercury.  The  repeated  lowering  and  raising  of  F  with  the 
corresponding  position  of  the  stop-cocks  ultimately  drives  all  the  gases  into  J.  The  removal  of 
the  gases  is  greatly  facilitated  by  placing  the  blood  bulb,  A,  in  a  vessel  containing  water  at 
60°  C. 


THE    BLOOD    GASES.  59 

It  is  well  to  remove  the  gases  from  the  blood  immediately  after  it  is  collected  from  a  bloodvessel, 
because  the  O  undergoes  a  diminution  if  the  blood  be  kept.  Of  course,  in  making  several  analyses 
it  is  difficult  to  do  this,  and  the  best  plan  to  pursue  in  that  case  is  to  keep  the  receptacles  containing 
the  blood  on  ice. 

Mayow  (1670)  observed  that  gases  were  given  off  from  blood  in  vacuo.  MSgnus  (1837) 
investigated  the  percentage  composition  of  the  blood  gases.  The  more  important  recent  inves- 
tigations have  been  made  by  Loihar  Meyer  (1857),  and  by  the  pupils  of  C.  Ludwig  and  E.  Pfliiger. 

35.  QUANTITATIVE  ESTIMATION  OF  THE  BLOOD 
GASES. — The  gases  obtained  from  blood  consist  of  O,  COj,  and  N.  Pfliiger 
obtained  (at  0°  C.  and  i  metre  Hg  pressure),  47.3  volumes  per  cent,  consisting 
of— 

O  16.9  per  cent.  ;  COj  29  per  cent.  ;  N  1.4  per  cent. 
As  is  shown  in  Fig.  19,  the  gases  are  obtained  in  an  eudiometer,  i.  e.,  in  a  nar- 
row tube,  J,  closed  at  one  end,  and  with  a  very  exact  scale  marked  on  it,  and 
having  two  fine  platinum  wires  melted   into  its  upper  end,  with  their  free  ends 
projecting  into  the  tube  (/  and  «). 

(i)  Estimation  of  the  CO2. — A  small  ball  of  fused  caustic  po/as/i.  fi.\ed  on  a  platinum  wire,  is 
introduced  into  the  mixture  of  gases  through  the  lower  end  of  the  eudiometer,  under  cover  of  the 
mercury.  The  surface  of  the  potash  ball  is  moistened  before  it  is  introduced.  The  CO,  unites 
with  the  potash  to  form  potassium  carbonate.  After  it  has  been  in  for  a  considerable  time  (24  hours), 
it  is  withdrawn  in  a  similar  manner.  The  diminution  in  volume  indicates  the  amount  of  COj 
absorbed. 

(2)  Estimation  of  the  O. — [a]  Just  as  in  estimating  the  CO2,  a  ball  of  phosphorus  on  a 
platinum  wire  is  introduced  into  the  eudiometer  (Bertholef);  it  absorbs  the  O  and  forms  phosphoric 
acid.  Another  plan  is  to  employ  a  small  papier-mache  ball  saturated  with  pyroi^allic  acid  in  caustic 
potash,  which  rapidly  absorbs  O  {Liebig).  After  the  ball  is  removed,  the  diminution  in  volume 
indicates  the  quantity  of  O. 

(b)  The  O  is  most  easily  and  accurately  estimated  by  explodini;  it  in  the  eudiometer  (  Volta  and 
Bunsen).  Introduce  a  sufficient  quantitv  of  H  into  the  eudiometer,  and  accurately  ascertain  its 
volume;  an  electrical  spark  is  now  passed  between  the  wires,  /  and  «,  through  the  mixture  of  gases; 
the  O  and  H  unite  to  form  water,  which  causes  a  diminution  in  the  volume  of  the  gases  in  the 
eudiometer,  of  which  J-^  is  due  to  the  O  used  to  form  water  (HjO). 

(<■)  Estimation  of  the  N.— When  the  CO,  and  O  are  estimated  by  the  above  method,  the 
remainder  is  pure  N. 

36.  THE  BLOOD  GASES.— [In  hitman  blood  the  average  is  estimated  to 
be,  at  0°  C  and  i  metre  pressure, 

C  CO2  N 

Arterial  blood 16  30         i  to  2  per  cent. 

Venous  blood, 6  to  10  35  1  to  2       " 

or,  calculated  at  0°  C.  and  760  mrn.  pressure. 

Arterial  blood 20  39         1.4  per  cent. 

Venous  blood, 8  to  12  46         1.4        "       ] 

I.  Oxygen  exists  in  arterial  blood  (dog),  on  an  average,  to  the  extent  of  1 7 
volumes  per  cent,  (at  0°  C.  and  i  metre  Hg  pressure)  {Pfliiger).  According  to 
Pfliiger,  arterial  blood  (dog)  is  saturated  to  Jg-  with  O,  while,  according  to  Hiifner, 
it  is  saturated  to  the  extent  of  \^.  In  venous  blood  the  quantity  varies  very  greatly  ; 
in  the  blood  of  a  passive  muscle  6  volumes  per  cent,  have  been  found  ;  while  in 
the  blood  after  asphyxia  it  is  absent,  or  occurs  only  in  traces.  It  is  certainly  more 
abundant  in  the  comparatively  red  blood  of  active  glands  (salivary  glands,  kidney), 
than  in  ordinary  dark  venous  blood. 

[Modifying  Conditions. — The  amount  of  O  obtainable  from  the  blood  depends  upon  the  organ 
from  which  the  blood  comes,  or  whether  the  organ  be  active  or  at  rest.     Thus  the  O  present  in  the 

Carotid  artery  is 21  per  cent.     |     Renal  vein  (kidney  active),   17  per  cent. 

Renal  artery, 19       "  |     Renal  vein  (kidney  at  rest),       6         " 

Bert  finds  that  increase  of  the  atmospheric  pressure  from  I  to  to  atmospheres  increases  the  amount 
of  O  in  arterial  blood  from  20  to  over  24  per  cent.,  and  that  of  N  from  i.S  to  over  9  per  cent.,  while 
the  CO,  is  but  slightly  affected.] 

The  O  in  Blood  occurs — {a')  simply  absorbed  xn  the  plasma.  This  is  only 
a  minimal  amount,  and  does  not  exceed  what  distilled  water  at  the  temperature  of 


60  THE    BLOOD    GASES    AND   OZONE. 

the  body  would  take  up  at  the  partial  pressure  of  the  O  in  the  air  of  the  lungs 
{Lot/iar  Meyer).  According  to  Fernet,  serum  takes  up  slightly  more  O  than  cor- 
responds to  the  pressure,  and  this  is  perhaps  due  to  the  trace  of  hremoglobin  con- 
tained in  the  plasma  or  the  serum,  and  which  is  derived  from  the  solution  of  red 
corpuscles. 

(h)  Almost  the  total  O  of  the  blood  is  chemically  united,  and  therefore  not 
subject  to  the  law  of  absorption.  It  is  loosely  united  to  the  hasmoglobin  of  the 
red  corpuscles,  with  which  it  forms  oxyhcemoglobin  (§  15). 

The  absorption  of  this  quantity  of  O  is  completely  independent  of  pressure ;  hence,  animals  con- 
fined in  a  closed  space  until  they  are  nearly  asphyxiated,  can  use  up  almost  all  the  O  from  (he 
surrounding  atmosphere.  The  fact  of  the  union  being  independent  of  pressure  is  proved  by  the 
following  :  The  blood  only  gives  off  copiously  its  chemically  united  O,  when  the  atmospheric  pres- 
sure is  lowered  to  20  millimetres,  Hg.  (  Worm  Miiller) ;  and,  conversely,  blood  only  takes  up  a  little 
more  O  when  the  pressure  is  increased  to  6  atmospheres  (Bert). 

Physical  Methods  of  obtaining  O  from  Blood.^Notwithstanding  this 
chemical  union  between  the  Hb  and  O,  however,  the  total  O  of  the  blood  can  be 
expelled  from  its  state  of  combination  by  those  means  which  set  free  absorbed 
gases — {a)  by  introducing  blood  into  a  Torricellian  vacuum  ;  (/')  by  boiling  ;  {c) 
by  the  conduction  of  other  gases  [H,  N,  CO,  or  NO]  through  the  blood,  because 
the  chemical  union  of  the  oxyhemoglobin  is  so  loose  that  it  is  decomposed  even 
by  these  physical  means. 

Chemical  Reagents. — Among  chemical  reagents  the  following  reducing 
substances — ammonium  sulphide,  sulphuretted  hydrogen,  alkaline  solutions  of 
sub-salts,  iron  filings,  etc.,  rob  blood  of  its  O  (p.  40). 

With  regard  to  the  taking  up  of  O,  the  total  quantity  of  blood  behaves  exactly 
like  a  solution  of  haemoglobin  free  from  O  {Preyer).  The  absorption  of  O  is 
more  rapid  in  blood  than  in  a  solution  of  Hb. 

Relation  to  Fe. — The  amount  of  iron  in  the  blood  (0.55  in  1000  parts)  stands  in  direct  relation 
to  the  amount  of  Hb;  this  to  the  quantity  of  blood  corpuscles;  and  this,  in  turn,  to  the  specific 
gravity  of  the  blood.  The  amount  of  O  in  the  blood,  therefore,  is  nearly  proportional  to  the  specific 
gravity  of  the  blood,  and  it  is  also  in  proportion  to  the  amount  of  iron  in  the  blood.  Picard  affirms 
that  2.36  grammes  of  iron  in  the  blood  can  fix  chemically  i  grm.  O ;  while,  according  to  Hoppe- 
Seyler,  the  proportion  is  i  atom  iron  to  2  atoms  O. 

During  morphia  narcosis  the  amount  of  O  in  the  blood  is  diminished  (E-vald) ;  after  hemorrhage 
the  arterial  blood  is  saturated  with  O  (/.  G.  Ott). 

Disappearance  of  O. — Even  immediately  after  blood  is  shed,  there  is  a  slight  disapp 'arance  of 
O,  as  a  physiological  index  of  respiration  of  the  tissues  within  the  living  blood  itself  (\  132). 

When  blood  is  kept  long  outside  of  tile  blood  vessels,  the  quantity  of  O  gradually  diminislies,  and 
if  it  be  kept  for  a  length  of  tim?  at  a  high  temperature  it  may  disappear  altogether.  This  depends 
upon  decomposition  occurring  within  the  blood.  By  this  decomposition  in  the  blood  (cadaveric 
phenomenon),  reducing  substances  are  formed  which  consume  the  O.  All  kinds  of  blood,  however, 
do  not  act  with  equal  energy  in  consuming  O,  e.  g.,  venous  blood  from  active  muscles  acts  most 
energetically,  while  that  from  the  hepatic  vein  has  very  little  effect.  CO2  appears  in  the  blood  in 
place  of  the  O,  and  the  color  darkens.  The  amount  of  COj  produced  is  sometimes  greater  than 
that  of  the  O  consumed. 

If  blood  (or  a  solution  of  oxyhsemoglobin)  be  acte  1  upon  by  acids  (e. g.,  tartaric  acid)  until  it  is 
strongly  acid.  O  may  be  pumped  out  in  considerably  less  amount,  while  the  formation  of  CO2  is  not 
increased.  We  must,  therefore,  assume  that,  during  the  decomposition  of  the  Hb  caused  by  the 
acids  (5  18),  a  decomposition  product  becomes  more  highly  oxidized  by  the  intense  chemical  union 
of  the  O  at  the  moment  of  its  origin  [Lothar  Meyer ^  Zuntz,  Strasshurg).  The  same  phenomenon 
occurs  when  oxyhemoglobin  is  decomposed  by  boiling. 

37.  IS  OZONE  (O3)  PRESENT  IN  BLOOD?— On  accoimt  of  the 
numerous  and  energetic  oxidations  which  occur  in  connection  with  the  blood,  the 
question  has  often  been  raised  as  to  whether  the  O  of  the  blood  exists  in  the  form 
of  active  O  (O,),  or  ozone.  Ozone,  however,  is  contained  neither  in  the  blood 
itself  {Sclwiibein)  nor  in  the  blood  gases  obtained  from  it.  Nevertheless,  the  red 
corpuscles  (and  Hb)  have  a  distinct  relation  to  ozone. 

(i)  Tests  for  Ozone. — Hremoglobin  acts  as  a  conveyer  of  ozone,  i.e.,  it  is  able  to  remove  the 
active  O  of  other  bodies  and  to  convey  or  transfer  it  at  once  to   other  easily  oxidizable  substances. 


CARBON    DIOXIDE    AND    NITROGEN    IN    BLOOD.  61 

(a)  Turpentine  which  has  been  exposed  to  the  air  for  a  long  time  always  contains  ozone.  The  tests 
for  the  latter  are  starch  and  potassium  iodide,  the  ozone  decomposing  the  iodide,  when  the  iodine 
strikes  a  lAae  with  the  starch.  {6)  Freshly-prepared  tincture  of  guaiacum  is  also  rendered  blue  by 
ozone.  If  some  tincture  of  guaiacum  be  added  to  turpentine  there  is  no  reaction,  but  on  adding  a 
drop  of  blood  a  deep  blue  color  is  immediately  produced,  /.  f.,  blood  takes  the  ozone  ffom  the  tur- 
pentine and  conveys  it  at  once  to  the  dissolved  guaiacum,  which  becomes  blue  [Schonhein,  His).  It 
is  immaterial  whether  the  Hb  contains  O  or  not. 

(2)  It  has  been  asserted  also  that  haemoglobin  acts  as  an  ozone  producer,  i.e., 
that  it  can  convert  the  ordinary  O  of  the  air  into  ozone.  Hence  the  reason  why 
red  blood  corpuscles  alone  render  guaiacum  blue.  This  reaction  succeeds  best 
when  the  guaiacum  solution  is  allowed  to  dry  on  blotting  paper,  and  a  few  drops 
of  blood  (diluted  5  to  10  times)  are  poured  on  it.  That  the  Hb  forms  ozone  from 
the  surrounding  O,  is  shown  by  the  experiment  in  which  even  red  blood  cor- 
puscles containing  carbonic  oxide  were  found  to  cause  the  blue  color  {^Kilhne  and 
Schoh). 

According  to  Pfluger,  however,  these  reactions  only  occur  from  decomposition 
of  the  Hb,  and  as  a  result  of  this  view  the  blood  corpuscles  cannot  be  regarded 
as  producers  of  ozone. 

Sulphuretted  hydrogen  is  decomposed  by  blood  (as  by  ozone  itself)  into  sulphur  and  water. 
Hydiic  peroxide  is  decomposed  by  blood  into  O  and  water  [but  this  reaction  is  prevented  by  the 
addition  of  a  small  amount  of  hydrocyanic  acid  (Schonbein)].  Crystallized  Hb  does  not  do  this, 
and  HjOj  may  be  cautiously  injected  into  the  bloodvessels  of  animals.  This  would  show  that 
tindiange'd  Hb  does  not  produce  ozone. 

Various  Forms  of  Oxygen. — There  are  three  forms  of  oxygen:  (i)  The  ordinary  oxygen 
(O.2)  in  tlie  air.  (2)  Active  or  nascent  oxygen  (O),  which  never  can  occur  in  the  free  state,  but  the 
moment  it  is  formed  acts  as  a  powerful  oxidizing  agent  and  produces  chemical  compounds.  It 
converts  w.iter  into  hydric  peroxide — the  N  of  the  air  into  nitrous  and  nitric  acids,  and  even  CO 
into  CO2,  which  ozone  does  not.  It  certainly  plays  an  important  part  in  the  organism.  (3)  Ozone 
(O3 ),  which  is  formed  by  the  decomposition  of  several  molecules  of  ordinary  oxygen  (O2 )  into  two 
atoms  of  O,  and  the  appropriation  of  each  of  these  atoms  by  a  molecule  of  undecomposed  oxygen. 
It  is  oxygen  condensed  to  |  of  its  volume. 

38.  CARBON  DIOXIDE  AND  NITROGEN  IN  BLOOD.— H. 
Carbon  Dioxide. — In  arterial  blood  there  are  about  30  volumes  per  cent,  of 
COj  (at  0°  C.  and  i  metre  pressure — Setschenow);  but  in  venous  blood  the  amount 
is  very  variable,  e.g.,  in  the  venous  blood  of  passive  muscles  there  are  35  volumes 
per  cent.  {Sezei/ctnu),  while  in  the  blood  of  asphyxia  there  may  be  52.6  volumes 
per  cent.  The  amount  of  COj  in  the  lymph  of  asphyxia  is  less  than  that  in  the 
blood  (Buchner,  Gaiile). 

The  CO2  in  the  entire  mass  of  the  blood  may  be  extracted  froin  it  or  completely 
pumped  out,  but  during  the  process  of  evacuation,  or  removal  of  the  gas,  a  new 
projierty  of  the  red  blood  corpuscles  is  produced,  whereby  they  assume  the  func- 
tion of  an  acid,  and  thus  aid  in  the  c/ifw/Va/ expulsion  of  the  COj.  This  acid- 
like property  of  the  red  corpuscles  occurs  especially  in  the  presence  of  O  and 
heat. 

(A)  The  COo  in  the  Plasma.— 77;(;  largest  portion  of  the  CO^  belongs  to  the 
plasma  (or  serum)  and  it  appears  all  to  be  in  a  state  of  chemical  combination. 
Serum  takes  up  CO,  quite  independently  of  pressure,  hence  it  cannot  be  merely 
absorbed.  A  certain  part  of  the  CO.j  can  be  removed  from  the  serum  (plasma)  by 
the  Torricellian  vacuum,  while  another  part  is  obtained  only  after  the  addition  of 
an  acid.  [The  latter  is  called  the  "  fixed"  CO.^,  while  the  former  is  known  as  the 
"  loose  "  CO.j.] 

The  union  of  CO.^  in  the  serum  may  take  place  in  the  following  ways : — 

(i)  CO2  is  united  to  the  soda  of  the  plasma  in  the  form  of  "  sodic  carbonate." 
This  portion  of  the  COi  can  only  be  displaced  from  its  combination  by  the  addi- 
tion of  an  acid.  (In  depriving  blood  of  its  gases  the  red  corpuscles  play  the  role 
of  an  acid.) 

(2)  A  portion  of  the  CO2  is  loosely  united  to  sodic  carbonate  in  the  form  of 
sodic  bicarbonate ;  the  carbonate  takes  up  i  equivalent  of  CO2 ;   NajCOj -f- COj -f- 


62  ARTERIAL    AND    VENOUS    BLOOD. 

HjO  =  2NaHC03.     This  CO,  may  be  pumped  out,  as  in  the  process  the  bi- 
carbonate splits  up  again  into  the  neutral  carbonate  and  COj. 

Preyer  has  objected  to  this  view  on  the  ground  that  blood  is  alkaline  in  reaction,  while  all 
solutions  that  contain  COj  in  a  state  of  absorption,  or  loose  chemical  combination,  are  always  acid. 
PflUger  and  Zuntz  showed  that  blood,  after  being  completely  saturated  with  CO^  still  remains 
alkaline. 

As  the  bicarbonate  only  gives  up  its  COj  very  slowly  in  vacuo,  while  blood  gives  off  its  CO^  very 
energetically,  perhaps  the  soda,  united  with  an  albuminous  body,  combines  with  the  CO2  and  forms 
a  complex  compound,  from  which  the  COo  is  rapidly  given  otf  in  vaiuo. 

(3)  A  minimal  portion  of  the  COj  may  be  chemically  united  in  the  plasma  with 
neutral sodic phosphate  {Fernet).  One  equivalent  of  this  salt  can  fi.K  one  equiva- 
lent of  CO.,,  so  acid  sodium  phosphate  and  acid  sodium  carbonate  are  formed, 
Na^HPO,  +  CO,  +  H2O  =  NaH.PO,  +  NaH.CO,  {Hermann).  When  the  gases 
are  removed  the  COj  escapes,  and  neutral  sodic  phosphate  remains. 

It  is  probable,  however,  that  almost  all  the  sadic  phosphate  found  in  the  blood-ash  arises  from 
the  burning  uf  lecithin ;  we  have,  therefore,  to  consider  only  the  very  small  amount  of  this  salt 
which  occurs  in  the  plasma  (Hoppe-Seyler  and  Sertoli). 

(B)  The  COo  in  the  Blood  Corpuscles. — The  red  corpuscles  contain  COj 
in  a  loose  chemical  combination;  lor  (i)  a  volume  of  blooa  can  fix  nearly  as 
much  CO^  as  an  equal  volume  of  serum  lyLudwig,  Al.  Schmidt);  and  (2)  with 
increasing  pressure,  the  absorption  of  COj  by  blood  takes  place  in  a  different 
ratio  from  what  occurs  with  serum  (PflUger,  Zuntz).  The  red  corpuscles  may  fix 
more  COj  than  their  own  volume,  and  the  union  of  the  CO,  seems  to  depend 
upon  the  Hb;  for  Setschenow  found  that  when  Hb  was  acted  on  by  CO..,,  its  power 
of  fixing  the  latter  was  increased,  which  is,  perhaps,  due  to  the  formation  of  some 
substance  (paraglobuiin)  more  suited  for  fixing  CO..,.  The  colorless  corpuscles 
also  fix  CO.j  after  the  manner  of  the  serum  constituents,  and  to  the  extent  of  \  to 
jV  of  the  absorbing  power  of  serum  (Setschenow). 

III.  Nitrogen  exists  in  the  blood  to  the  extent  of  1.4  to  1.6  vol.  per  cent., 
and  it  appears  to  be  simply  absorbed. 

After  the  use  of  I,  Hg,  sodic  oxalate  and  nitrate,  there  is  a  diminution  of  CO2  in  arterial  blood 
(Feitctberg),  and  also  in  fever  [Geppert,  A/iniowski).  [In  the  last  case  it  is,  perhaps,  due  to  the 
diminished  alkalinity,  and  this  is,  in  part,  owing  to  the  acid  products  formed  by  the  decomposition 
of  the  tissues.] 

It  is  still  doubtful  whether  a  small  part  of  the  N  exists  chemically  united  in  the  red  corpuscles. 
Outside  the  body,  when  blood  is  heated,  and  when  there  is  a  free  supply  of  O  and  warmth,  it  gives 
off  very  minute  quantities  of  ammonia,  which  are,  perhaps,  derived  from  the  decomposition  of 
some  salt  of  ammonia  as  yet  unknown  (A'ii/ine  and  ^tratich). 

39.  ARTERIAL  AND  VENOUS  BLOOD.— Arterial  blood  contains 
in  solution  all  those  substances  which  are  necessary  lor  the  nutrition  of  the  tissues, 
those  which  are  employed  in  secretion,  and  it  also  contains  a  rich  supply  of  O. 
Venous  blood  must  contain  less  of  all  these,  but,  in  addition,  it  holds  the  used-up 
or  effete  substances  derived  from  the  tissues,  and  the  products  of  their  retrogressive 
metabolism  are  more  numerous  ;  there  is  in  venous  blood  a  larger  amount  of  CO,, 

It  is  evident,  also,  that  the  blood  of  certain  veins  must  have  special  characters. 
e.g.,  that  of  the  portal  and  hepatic  veins. 

[.According  to  C.  .Schmidt,  the  blood  of  the  portal  vein  contains  more  water,  plasma,  salts  and 
fats,  but  less  extractives  and  corpuscles,  than  the  blood  of  the  hepatic  vein;  while  ^when  an  animal 
is  not  digesting)  sugar  is  absent,  or,  at  least,  only  in  traces  in  the  portal  vein,  and  in  considerable 
amount  in  the  hepatic  vein  (^  175).] 

The  following  are  the  most  important  points  of  difference  between  arterial 
blood  and  venous  blood  : — 

Arterial  Blood  contains — 


more  O, 
less  COj, 
more  water, 
more  fibrin. 


more  extractives, 

more  salts, 

more  sugar, 

fewer  blood  corpuscles, 


less  urea. 

It  is  bright  red,  and  not 

dichroic. 
-As  a  rule,  it  is  1°  C.  warmer. 


ABNORMAL   CONDITIONS    OF   THE    BLOOD.  63 

The  bright-red  color  of  arterial  blood  depends  on  the  presence  of  oxyhaemo- 
globin,  while  the  dark  color  of  venous  blood  is  due  to  its  smaller  proportion  of 
oxyhemoglobin  and  the  quantity  of  reduced  hjemoglobin  which  it  contains.  The 
dark  change  of  color  is  not  to  be  attributed  to  the  larger  quantity  of  CCX  in  venous 
blood  {^M a  re  hand ) ;  for  if  equal  qualities  of  O  be  added  to  two  portions  of  blood, 
and  if  CO,  be  added  to  one  of  them,  the  color  is  not  changed  (^FJluger). 

40.  QUANTITY  OF  BLOOD. — In  the  adult,  the  quantity  of  blood  is 
equal  to  j^j  of  the  body  weight  (Bischoff)  ;  in  newly -born  children  -^  (  IVelcker). 

According  to  Schiicking,  the  amount  of  blood  in  a  newly-born  child  depends,  to  some  extent, 
upon  the  time  at  which  the  umbihcal  cord  is  ligatured.  The  amount  =  y'j  of  the  body  weight  when 
the  cord  is  tied  at  once,  while  if  it  is  tied  somewhat  later,  it  may  be  \.  Immediate  ligature  of  the 
cord  may,  therefore,  deprive  a  newly. born  child  of  a  hundred  grammes  of  blood.  Further,  the 
number  of  corpuscles  is  less  in  a  child  after  immediate  ligature  of  the  umbilical  cord  than  when  it 
is  tied  somewhat  later  (He/o/). 

Various  methods  are  adopted  to  ascertain  the  amount  of  blood,  but  perhaps 
that  of  Welcker  is  the  best. 

The  methods  of  Valentin  (1838)  and  Ed.  Weber  (1850)  are  not  now  used,  as  the  results  obtained 
are  not  sufficiently  accurate. 

Method  of  Welcker  (1854). — Begin  by  taking  the  weight  of  the  animal  to  be  experimented 
on;  place  a  cannula  in  the  carotid,  and  allow  the  blood  to  run  into  a  flask  previously  weighed,  and 
in  which  small  pebbles  (or  Hg)  have  been  placed,  in  order  to  defibrlnate  the  blood  by  shaking. 
Take  a  part  of  this  defiiirinated  blood,  and  make  it  cherry-red  in  color  by  passing  through  it  a 
stream  of  CO  (because  ordinary  blood  varies  in  color  according  to  the  amount  of  O  contained  in  it 
— Gscheidlen,  Heidenhain).  Tie  a  H" -shaped  canula  in  the  two  cut  ends  of  the  carotid,  and  allow 
a  0.6  per  cent,  solution  of  common  salt  to  flow  into  the  vessel  from  a  pressure  bottle;  collect  the 
colored  fluid  issuing  from  the  jugular  veins  and  inferior  vena  cava  until  the  fluid  is  quite  clear. 
The  entire  body  is  then  chopped  up  (with  the  exception  of  the  contents  of  the  stomach  and  intes- 
tines, which  are  weighed,  and  their  weight  deducted  from  the  body  w-eight),  and  extracted  with 
water,  and  after  twenty-four  hours  the  fluid  is  exp.essed.  This  water,  as  well  as  the  washings  with 
salt  solution,  are  collected  and  weighed,  and  part  of  the  mixture  is  saturated  with  CO.  A  sample 
of  this  dilute  blood  is  placed  in  a  vessel  with  parallel  sides  (i  cm.  apart),  opposite  the  light  (the 
so-called  hix'matinometer),  and  in  a  second  vessel  of  the  same  dimensions  a  sample  of  the  undi- 
luted CO  blood  is  diluted  with  water  from  a  burette  until  both  fluids  give  the  same  intensity  of 
color.  From  the  quantity  of  water  required  to  dilute  the  blood  to  the  lint  of  the  washings  of  the 
blood  vessels,  the  quantity  of  blood  in  the  washings  is  calculated.  (On  chopping  up  the  muscles 
alone,  we  obtain  the  amount  of  Hb  present  in  them,  which  is  not  taken  into  calculation —A7;/;«,?.) 

Quantity  of  Blood  in  Various  Animals. — The  quantity  of  blood  in  the 
mouse  =  yV  to  -^^  ;  guinea  pig  y^^  (J-  to  jL) ;  rabbit  =  ^iy  (-j^  to  ^V) ;  dog 
=  tV  (tV  to  tV  ;  '^at  ==  jf  5  ;  birds  =  ^V  to  yV  i  frog  =  tV  to  ^V  i  ^shes  =  J^ 
to  ^  of  the  body  weight  (^without  the  contents  of  the  stomach  and  intestines). 

Tne  specific  gravity  of  the  blood  ought  always  to  be  taken  when  estimating  the 
amount  of  blood.  The  amount  of  blood  is  diminished  during  inanition ;  fat 
persons  have  relatively  less  blood  ;  after  hemorrhage  the  loss  is  at  first  replaced  by 
a  watery  fluid,  while  the  blood  corpuscles  are  gradually  regenerated. 

Blood  in  Organs. — The  estimation  of  the  quantity  of  blood  in  different  organs 
is  done  by  suddenly  ligaturing  their  blood  vessels  intra  vttam.  A  watery  extract 
of  the  chopped-up  organ  is  prepared,  and  the  quantity  of  blood  estimated  as 
described  above.  [Roughly  it  may  be  said  that  the  lungs,  heart,  large  arteries, 
and  veins  contain  j^  ;  the  muscles  of  the  skeleton,  y^  ;  the  liver,  }(  ;  and  other 
organs,  }(  {/ian/<:e).~\ 

41.  VARIATIONS  FROM  THE  NORMAL  CONDITION  OF  THE  BLOOD.— 
(A)  Pojyaemia. — (I)  An  increase  m  the  entire  mass  of  the  h\ood,  itiiiform/v  in  all  organs,  caw- 
stitutes/o/i'tt-w^ij  (or //t'Mor«),  and  in  over-nourished  individuals  it  may  approach  a  pathological 
condition.  A  bluish-red  color  of  the  skin,  swollen  veins,  large  arteries,  hard,  full  pulse,  injection 
of  the  capillaries  and  smaller  vessels  of  the  visible  mucous  membranes  are  signs  of  this  state,  and 
when  accompanied  by  congestion  of  the  brain,  give  rise  to  vertigo  and  congestion  of  the  lungs,  as 
shown  by  breathlessness.  After  major  amputations  with  little  loss  of  blood  a  relative  increase  of 
blood  has  been  found  (?)  {plethora  apocoptica).     [In  this  case,  the  plethora  is  transient.] 

Transfusion. —  Polya;mia  may  be  produced  artificially  by  the  injection  of  blood  of  the  same 
species.     If  the  normal  quantity  of  blood  be  increased  83  per  cent,  no  abnormal  condition  occurs. 


64  ABNORMAL   CONDITIONS   OF   THE    BLOOD. 

because  the  blood  pressure  is  not  permanently  raised.  The  excess  of  blood  is  accommodated  in 
the  greatly  distended  capillaries,  which  may  be  stretched  beyond  their  normal  elasticity  ( IVorm 
Mailer).  If  it  be  increased  to  150  per  cent,  there  are  variations  in  the  blood  pressure,  life  is 
endangered,  and  there  may  be  sudden  rupture  of  blood  vessels  (  Worm  Miitler). 

Fate  of  Transfused  Blood. — After  the  transfusion  of  blood  the  formation  of  lymph  is  greatly 
increased  ;  but  in  one  or  two  days  the  serum  is  used  up,  the  water  is  excreted  chiefly  by  the  urine, 
and  the  albumin  is  partly  changed  into  urea  (Zhwi/ok).  Hence,  the  blood  at  this  time  appears  to 
be  relatively  richer  in  blood  corpuscles  [Pamim,  Lesser,  ll'orm  Afii/Zer).  The  red  corpuscles 
break  up  much  more  slowly,  and  the  products  thereof  are  partly  excreted  as  urea  and  partly  (but 
not  constantly)  as  bile  pigments.  Even  after  a  month  an  increase  of  colored  blood  corpuscles  has 
been  observed  ( Tschirjew).  That  the  blood  corpuscles  are  broken  up  slmoly  in  the  economy  is 
proved  by  the  fact  that  the  amount  of  urea  is  much  larger  when  the  same  quantity  of  blood  is 
swallowed  by  the  animal  than  when  an  equal  amount  is  transfused  (Tsehirjeiu,  LanJois).  In  the 
latter  case  there  is  a  moderate  increase  of  the  urea,  lasting  for  days,  a  proof  of  the  slow  decomposi- 
tion of  the  red  corpuscles.  Pronounced  over-filling  of  the  vessels  causes  loss  of  appetite  and  a  ten- 
dency to  hemorrhage  of  the  mucous  membranes. 

(2)  Polyaemia  serosa  is  that  condition  in  which  the  amount  of  serum,  i.  e.,  the  amount  of 
water  in  the  blood,  is  increased.  This  may  be  produced  artilicially  by  the  transfusion  of  blood 
serum  from  the  same  species.  The  water  is  soon  given  off  in  the  urine,  and  the  albumin  is  decom- 
po.sed  into  urea,  without,  however,  passing  into  the  urine.  An  animal  forms  more  urea  in  a  short 
time  from  a  quantity  of  transfused  serum  than  from  the  same  quantity  of  blood,  a  proof  that  the 
blood  corpuscles  remain  longer  undecomposed  than  the  serum  [/^orster,  Landois),  If  serum  from 
another  species  of  animal  be  used  {e.  g.,  dog's  serum  transfused  into  a  rabbit),  the  blood  corpuscles 
of  the  recipient  are  dissolved;  hajmoglobinuna  is  produced  {Fonjick);  and  if  there  be  general  disso- 
lution of  the  corpuscles,  death  may  occur  [Landois). 

Polyaemia  aquosa  is  a  simple  increase  of  the  water  of  the  blood,  and  occurs  temporarily  after 
copious  drinking,  but  increased  diuresis  soon  restores  the  normal  condition.  Diseases  of  the  kid- 
neys which  destroy  their  secreting  parenchyma  produce  this  condition,  and  often  general  dropsy, 
owing  to  the  passage  of  water  into  the  tissues.  Ligature  of  the  ureter  produces  a  watery  condition 
of  the  blood. 

(3)  Plethora  polycythaemica,  Hyperglobulie. — An  increase  of  the  red  corpuscles  has  been 
assumed  to  occur  when  customary  regular  hemorrnagesare  interrupted,  e.  g.,  menstruation,  bleeding 
from  the  nose,  etc. ;  but  the  increase  of  corpuscles  has  not  been  dehnitely  proved.  There  is  a  proved 
case  of  temporary  polycythemia,  viz.,  when  similar  blood  is  transfused,  a  part  of  the  fluid  being  used 
up,  while  the  corpuscles  remain  unchanged  for  a  considerable  time.  There  is  a  remarkable  increase 
in  the  number  ol  blood  corpuscles  (to  8  82  millions  per  cubic  millimeter,  p.  18)  in  certain  severe 
cardiac  affections  where  there  is  great  congestion,  and  much  water  transudes  through  the  vessels. 
In  cases  of  hemiplegia,  for  the  same  reason,  the  number  of  corpuscles  is  greater  on  the  paralyzed 
congested  .side  (/"fH;!;/;//).  After  diarrhcea,  which  diminishes  the  water  of  the  blood,  there  is  also 
an  increase  {Brouardel).  There  is  a  temporary  increase  in  the  h.'ematoblasts  as  a  reparative  process 
after  severe  hemorrhage  (J  7),  or  alter  acute  diseases.  In  cachectic  conditions  this  increase  con- 
tinues, owing  to  tne  diminisned  non-conversion  of  these  corpuscles  into  red  corpuscles.  In  the 
last  stages  ol  cachexia  the  number  diminishes  more  and  more  until  the  formation  of  hnematoblasts 
ceases  (Nciyeiu). 

(4)  Plethora  hyperalbuminosa  is  a  term  applied  to  the  increase  of  albumins  in  the  plasma, 
such  as  occurs  after  taking  a  large  amount  of  food.  A  similar  condition  is  produced  by  transfusing 
the  serum  of  the  same  species,  whereby,  at  the  same  time,  the  urea  is  increased.  Injection  of  egg 
albumin  produces  albuminuria  (Stoiz'is  Le/tmann). 

[The  subcutaneous  injection  of  human  blood  has  been  practiced  with  good 
results  in  anemia  (t^.  Ziemssen).  When  defibrinated  human  blood  is  injected  sub- 
cutaneously,  while  its  passage  into  the  circulation  is  aided  by  massage,  it  causes 
neither  pam  nor  inflammation,  but  the  blood  of  anima/s,  and  a  solution  of  hsemo- 
globin,  always  induce  abscess  {Bciiczur).  Blood  is  also  rapidly  absorbed  when 
injected  in  small  amount  into  the  respiratory  passages.] 

Mellitaemia  — The  sugar  in  the  blood  is  panly  given  off  by  the  urine,  and  in  "  diabetes 
mellitus  "  1  kilo.  (2.2  It))  may  be  given  off  daily,  when  the  ciuanlity  of  urine  may  rise  to  25 
kilos.  To  replace  this  loss  a  large  amount  of  food  and  drink  is  required,  whereby  the  urea  may  be 
increased  threefold.  The  increased  production  of  sugar  causes  an  increased  decomposition  of 
albuminous  tissues;  hence,  the  urea  is  always  increased,  even  though  the  supply  of  albumin  be 
insufficient.  The  patient  loses  flesh ;  all  the  glands,  and  even  the  testicles,  atrophy  or  degenerate 
(pulmonary  phthisis  is  common) ;  the  skin  and  bones  become  thinner  ;  the  nervous  system  holds  out 
longest.  The  teeth  become  carious  on  account  of  the  acid  saliva,  the  crystalline  lens  becomes 
turbid  from  the  amount  of  sugar  in  the  fluid  of  the  eye  which  extracts  water  from  the  lens  (A'unde, 
JLeitliel),  and  wounds  heal  badly  because  of  the  abnormal  condition  of  the  blood.  Absence  of  all 
carbohydrates   in  the   food  causes  a  diminution  of  the  sugar  in  the  blood,  but  does  not  cause  it  to 


ABNORMAL   CONDITION'S   OF   THE    BLOOD.  65 

disappear  entirely.  [The  sugar  in  the  blood  is  also  increased  after  the  inhalation  of  chloroform  or 
amyl  nitrite,  and  after  tlie  use  of  curara,  nitrobenzole  and  chloral  (^  175)-] 

An  excessive  amount  of  inosite  has  been  found  in  the  blood  and  urine  (^  267),  constituting  melli- 
turia  inosita  ( I'o/il).  . 

Lipsemia,  or  an  increase  of  the  Fat  in  the  Blood,  occurs  after  every  meal  rich  in  fat,  so  that 
the  serum  may  become  turbid  like  milk.  Pathologically,  this  occurs  in  a  high  degree  in  drunk- 
ards and  in  corpulent  individuals.  When  there  is  great  decomposition  of  albumin  in  the  body 
(and,  therefore,  in  very  severe  diseases),  the  fat  in  the  blood  increases,  and  this  also  takes  place 
after  a  liberal  supply  of  easily  decomposable  carbohydrates  and  much  fat. 

The  Salts  remain  very  persistently  in  the  blood.  The  withdrawal  of  common  salt  produces 
albuminuria,  and,  if  all  salts  be  withheld,  paralytic  phenomena  occur  (Forster).  Over  feeding  with 
salted  food,  such  as  salt  meat,  has  caused  death  through  fatty  degeneration  of  the  tissues,  especially 
of  the  glands.  Withdrawal  of  lime  and  phosphoric  acid  produces  atrophy  and  softening  of  the 
bones.  In  infectious  diseases  and  dropsies  the  salts  of  the  blood  are  often  increased,  and  dimin- 
ished in  inHammatiun  and  cholera.  [NaCl  is  absent  from  the  urine  in  certain  stages  of  pneumonia, 
and  it  is  a  good  sign  when  the  chlorides  begin  to  return  to  the  urine.]  [In  Scurvy  the  corpus, 
cular  elements  are  diminished  in  amount,  but  we  have  not  precise  information  as  to  the  salts, 
although  this  disease  is  prevented,  in  persons  forced  to  live  upon  preserved  and  salted  food,  by  a 
liberal  use  of  the  salts — especially  potash  salts — of  the  organic  acids,  as  contained  in  lime  juice. 
In  Gout,  the  blood,  during  an  acute  attack,  and  also  in  chronic  gout,  contains  an  e.\cess  of  uric 
acid  [Garrod  ).] 

The  amount  of  fibrin  is  increased  [hyperinosis]  in  inflammations  of  the  lung  and  pleura 
[croupous  pneumonia,  erysipelas],  hence,  such  blood  forms  a  criista  phlogistica  (§  27).  In  other 
diseases  where  decomposition  of  the  blood  corpuscles  occurs,  the  fibrin  is  increased,  perhaps  because 
the  dissolved  red  corpuscles  yield  material  for  the  formation  of  fibrin.  .After  repeated  hemorrhages, 
Sigm.  Mayer  found  an  increase  of  fibrin.  Blood  rich  in  fibrin  is  said  to  coagulate  more  s/o-u/v  than 
when  less  fibrin  is  present — still  there  are  many  exceptions. 

For  the  abnormal  changes  of  the  red  and  white  blood  corpuscles,  see  ^  10 ;  for  Haemophilia, 
i  28. 

(H)  Diminution  of  the  Quantity  of  Blood,  or  its  Individual  Constituents. — (i)  Oligse- 
mia  vera.  Anaemia,  or  diminution  of  the  quantity  of  blood,  occurs  whenever  there  is  hemor- 
rhage. Life  is  endangered  in  newly-born  children  when  they  lose  a  few  ounces  of  blood;  in 
children  a  year  old,  on  losing  half  a  pound ;  and  in  adults,  when  one-half  of  the  total  blood  is 
lost.  Women  bear  loss  of  blood  much  better  than  men.  The  periodical  formation  of  blood  after 
each  menstruation  seems  to  enable  blood  to  be  renewed  more  rapidly  in  their  case.  Stout  persons, 
old  people,  and  children  do  not  bear  the  loss  of  blood  well.  The  more  rapidly  blood  is  lost,  the 
more  dangerous  it  is.  [A  moderate  loss  of  blood  is  soon  made  up,  but  the  fluid  part  is  more 
quickly  restored  than  are  the  corpuscles.] 

Symptoms  of  Loss  of  Blood. — Great  loss  of  blood  is  accompanied  by  general  paleness  and 
coldness  of  the  cutaneous  surface,  increased  oppression,  twitching  of  the  eyeballs,  noises  in  the  ears 
and  vertigo,  loss  of  voice,  great  breathlessness,  stoppage  of  secretions,  coma ;  dilatation  of  ihe 
pupils,  involuntary  evacuations  of  urine  and  fceces,  and  lastly,  general  convulsions,  are  sure  signs  of 
i/ea^/i  by  hemorrhage.  In  the  gravest  cases  restitution  is  only  possible  by  means  of  transfusion. 
Animals  can  bear  the  loss  of  one-fourth  of  their  entire  blood  without  the  blood  pressure  in  the 
arteries  permanently  failing,  because  the  blood  vessels  contract  and  accommodate  themselves  to  the 
smaller  quantity  of  blood  (in  consequence  of  the  stimulation  of  the  vasomotor  centre  in  the  medulla). 
The  I0.SS  of  one-third  of  the  total  blood  diminishes  the  blood  pressure  considerably  (one-fourth  in 
the  carotid  of  the  dog).  If  the  hemorrhage  is  not  such  as  to  cause  death,  the  fluid  part  of  the 
blood  and  the  dissolved  salts  are  restored  by  absorption  from  the  tissues,  the  blood  pressure  gradu- 
ally rises,  and  then  the  albumin  is  restored,  though  a  longer  time  is  required  for  the  formation  of 
red  corpuscles.  At  first,  therefore,  the  blood  is  abnormally  rich  in  water  (Jtydrtrmia)  and  at  last 
abnormally  poor  in  corpuscles  lyoligocythizmip,  hypoglolnilie').  With  the  increased  lymph  stream 
which  pours  into  the  blood,  the  colorless  corpuscles  are  considerably  increased  above  normal,  and 
during  the  period  of  restitution  fewer  red  corpuscles  seem  to  be  used  up  (e.g.,  for  bile). 

After  moderate  bleeding  from  an  artery  in  animals,  Buntzen  observed  that  the  volume  of  the 
blood  was  restored  in  several  hours;  after  more  severe  hemorrhage  in  24  to  48  hours.  The  red 
blood  corpuscles,  after  a  lo^s  of  blood  equal  to  i.i  to  4.4  per  cent,  of  the  body  weight,  are  restored 
only  after  7  to  34  days.  The  regeneration  begins  after  24  hours.  During  the  period  of  regenera- 
tion the  number  of  the  smallest  blood  corpuscles  (heematoblasts)  is  increased.  Even  in  man  the 
duration  of  the  period  of  regeneration  depends  upon  the  amount  of  blood  lost  [Lyon)  The 
amount  of  hiiemoglobin  is  diminished  nearly  in  propoition  to  the  amount  of  the  hemorrhage  [Bizzo- 
zero  and  Sa/vio/i). 

Metabolism  in  Anaemia. — The  condition  of  the  metabolism  within  the  bodies  of  ana:mic  per- 
sons is  important.  The  decomposition  of  proteids  is  increased  (the  same  is  the  case  in  hunger), 
hence  the  excretion  of  urea  is  increased  [Bauer,  Jiirgensen).  The  decomposition  of  fats,  on  the 
contrary,  is  diminished,  which  stands  in  relation  with  the  diminution  of  COj  given  oft".     Ana;mic 

5 


66 


ORGANISMS    IN    THE    BLOOD. 


and  chlorotic  persons  put  on  fat  easily.     The  fattening  of  cattle  is  aided  by  occasional  bleedings 
and  by  intercurrent  periods  of  hunger  (Aristotle). 

(2)  An  excessive  thickening  of  the  blood  through  loss  of  water  is  called  Oligsemia  sicca. 
This  occurs  in  man  after  copious  watery  evacuations,  as  in  cholera,  so  that  the  thick,  tarry  blood 
stagnates  in  the  vessels.  Perhaps  a  similar  condition — though  to  a  less  degree — may  exist  after 
very  copious  perspiration. 

(3)  If  the  proteids  in  blood  be  abnormally  diminished,  the  condition  is  called  Oligaemia  hyp- 
albnminosa  ;  they  may  be  diminished  about  one-half.  They  are  usually  replaced  by  an  excess  of 
water  in  the  blood  [so  that  the  blood  is  watery,  constituting  Hydraemia].  Loss  of  albumin  from 
the  blood  is  caused  directly  by  albuminuria  (25  grammes  of  albumin  may  be  given  off  by  the 
urine  daily),  persistent  suppuration,  great  loss  of  milk,  extensive  cutaneous  ulceration,  albuminous 
diarrhoia  (dysentery).  Frequent  and  copious  hemorrhages,  however,  by  increasing  the  absorption 
of  water  into  the  vessels,  at  first  produce  oligemia  hypalbuminosa. 

[Organisms  in  the  Blood. — The  presence  of  animal  and  vegetable  parasites  in  the  blood  gives 
rise  to  certain  diseases.     Some  of  these,  and  especially  the  vegetable  organisms,  have  the  power  of 


Fig.  20. 


Fig.  21. 


-y      fr^^ 


///  y\\- 


A,  diagram   of 
rium;    C,   ■ 


sple 


B,  bade-  Bacillus   antl 

brios:    D,   bacilli;    E,  blood  (ox 

(Coliii). 

multiplying  in  the  blood.     The  vegetable  forms  belonging  to  the  Schizomycetes  are  frequently 
spoken  of  collecting  under  the  title  bacteria.     They  are  classified  by  Cohn  into 

L  Spha'robacteria 
IL   Microbacteria 
IlL  Desmobacteria 


exhibit  movements. 
IV.  Spirobacteria 

These  forms  are  shown  in  Fig.  20.  The  micrococci  (.\)  are  examples  of  I;  while  bacterium 
termo  (B)  is  an  example  of  II.  In  III  the  members  are  short  cylindrical  rods,  straight  (Bacillus, 
D)  or  wavy  (Vibrio,  C).  Splenic  fever  of  cattle  is  due  to  the  presence  of  Bacillus  anthracis  (  Fig. 
21).  These  rod-shaped  bodies  under  proper  conditions  divide  transversely  and  elongate,  but  they 
also  form  spores  in  their  interior,  which  in  turn,  under  appropriate  conditions,  may  germinate  (Fig. 
21).  Class  IV  is  represented  by  two  genera,  Spirochffita  and  Spirillum  (Fig.  20),  the  former  with 
close,  and  the  latter  with  open  spirals.  The  Spirochaeta  Obermeieri  (often  spoken  of  as  "Spirillum") 
is  present  in  the  blood  during  the  paroxysms  in  persons  suffering  from  relapsing  fever.  Among 
animal  parasites  are  Filaria  sanguinis;  Bilharzia  haematobia,  which  occurs  in  the  portal  vein  and  in 
the  veins  of  the  urinary  apparatus.] 


PHYSIOLOGY  OF  THE  CIRCULATION. 


42.  GENERAL    VIEW    OF    THE    CIRCULATION.— The   blood 
within  the  vessels  is  in  a  state  of  continual  motion,  ^^^ 
being  carried  from  the  ventricles  by  the  large  arteries 
(aorta  and  pulmonary)  and  their  branches  to  the  system 
of  capillary  vessels, //-c)w  which  again  it  passes  into  the 
veins  that  end  in  the  atria  of  the  auricles  (  W.  Harvey). 

The  Cause  of  the  Circulation  is  the  difference  of 
pressure  which  exists  between  the  blood  in  the  aorta 
and  pulmonary  artery  on  the  one  hand,  and  the  two 
vense  cavte  and  the  four  pulmonary  veins  on  the  other. 
The  blood,  of  course,  moves  continually,  in  its  closed 
tubular  system,  in  the  direction  of  least  resistance. 
The  greater  the  difference  of  pressure,  the  more  rapid 
the  movement  will  be.  The  cessation  of  the  difference 
of  pressure  (as  after  death)  naturally  brings  the  move- 
ment to  a  standstill  (§  81). 

The  circulation  is  usually  divided  into — 

(i)  The  greater,  or  systemic  circulation, 
which  includes  the  course  of  the  blood  from  the  left 
auricle  and  left  ventricle,  through  the  aorta  and  all 
its  branches,  the  capillaries  of  the  body  and  the  veins, 
until  the  two  vens  cavte  terminate  in  the  right  auricle. 

(2)  The  lesser,  or  pulmonic  circulation, 
which  includes  the  course  from  the  right  auricle  and 
right  ventricle,  the  pulmonary  artery,  the  pulmonary 
capillaries,  and  the  four  pulmonary  veins  springing 
.  from  them,  until  these  open  into  the  left  auricle. 

(3J  The  portal  circulation,  which  is  sometimes 
spoken  of  as  a  special  circulatory  system,  although  it 
represents  only  a  second  set  of  capillaries  (within  the  sch. 
liver)  introduced  into  the  course  of  a  venous  trunk. 
It  consists  of  the  vena  portarum — formed  by  the  union 
of  the  intestinal  or  mesenteric  and  splenic  veins,  and 
it  passes  into  the  liver,  where  it  divides  into  capillaries, 
from  which  the  hepatic  veins  arise.  These  last  veins 
join  the  inferior  vena  cava. 

Strictly  speaking,  however,  there  is  no  special  portal  circulation. 

.Similar  arrangements  occur  in  other  animals  in  different  places;  ''" 

€.g,y  snakes  have  such  a  system  in  their  suprarenal  capsules,  and  the  frog  in  its  kidneys. 

When  an  artery  splits  up  into  fine  branches  during  its  course,  and  these  branches  do  not  form 
capillaries,  but  reunite  into  an  arterial  trunk,  a  rete  mirabile  is  formed,  such  as  occurs  in  apes  and 
edemata.  Microscopic  retia  mirabilia  exist  in  the  human  mesentery  [Sc/wbl).  Similar  arrange- 
ments may  exist  on  veins,  giving  rise  to  venous  retia  mirabilia. 

43.  THE  HEART.— Muscular  Fibres  of  the  Heart.— The  musculature 
of  tue  mammalian  heart  consists  of  short  (50  to  70  /;,  man),  very  fine,  transversely 
striated  muscular  fibres  (C  Krause,  i8jj),  which  are  actual  unicellular  elements 
{Eberth,  1866),  devoid  of  a  sarcolemma  ( 15  to  25  ,«  broad),  and  usually  divided 

67 


of  the  circulation — . 
ride;  A,  right  ventricle;  b, 
left  auricle  ;  B,  left  ventricle  ;  i, 
pulmonary  artery  ;  2,  aorta  with 
semilunar  valves ;  /,  area  of 
pulmonary  circulation  :  K,  area 
of  systemic  circulation  in  region 
supplying  the  superior  vena 
cava.o;  G,  area  supplying  the 
inferior  vena  cava,  u:  d,  d,  in- 
testine,;  ;«,  mesenteric  artery ; 
g,  portal  vein;    L,  liver;  h,  he- 


68 


ARRANGEMENT   OF   THE    CARDIAC    MUSCULAR    FIBRES. 


at  their  blunt  ends,  by  which  means  they  anastomose  and  form  a  network  (Fig. 
23,  A,  B).  The  individual  muscle  cells  contain  in  their  centre  an  oval  nucleus, 
and  are  held  together  by  a  cement  which  is  blackened  by  silver  nitrate,  and  dis- 
solved by  a  T,^  per  cent,  solution  of  caustic  potash.  This  cement  is  also  dissolved 
by  a  40  per  cent,  solution  of  nitric  acid.  The  transverse  stria;  are  not  very 
distinct,  and  not  unfrequently  there  is  an  appearance  of  longitudinal  striation, 
produced  by  a  number  of  very  small  granules  arranged  in  rows  within  the  fibres. 
The  fibres  are  gathered  lengthwise  in  bundles,  or  fasciculi,  surrounded  and  sepa- 
rated from  each  other  by  delicate  processes  of  the  perimysium.  When  the 
connective  tissue  is  dissolved  by  prolonged  boiling,  these  bundles  can  be  isolated, 
and  constitute  the  so-called  "  fibres"  of  the  heart.  The  transverse  sections  of  the 
bundles  in  the  auricles  are  polygonal  or  rounded,  while  in  the  ventricles  they  are 
somewhat  flattened.  [The  muscular  mass  of  the  heart  is  called  the  myocardium, 
and  is  invested  by  fibrous  tissue.  It  is  important  to  notice  that  the  connective 
tissue  of  the  visceral  pericardium  (epicardium)  is  continuous  with  that  of  the 
endocarduim  by  means  of  the  perimysium  surrounding  the  bundles  of  muscular 
fibres.]  The  fine  spaces  which  exist  between  these  bundles  form  narrow  lacuna;, 
lined  with  epithelium,  and  constituting  part  of  the  lymphatic  system  of  the  heart. 

Fig.  23. 


A,  branched  muscular  fibres  from  the  heart  of  a  mammal;    B,  transverse  section  of   the 

nective-tissue  corpuscles:  c,  capillaries;    C,  muscular  fibres  from  the  heart  of  a  frog, 

[The  cardiac  muscular  fibres  occupy  an  intermediate  position  between  striped  and  plain  muscular 
fibres.  Although  they  are  striped  they  are  involuntary,  not  being  directly  under  the  influence  of  the- 
will,  while  they  contract  more  slowly  than  a  voluntary  muscle  of  the  skeleton.] 

[In  the  frog's  heart  the  muscular  fibres  are,  in  shape,  elongated  spindles,  or  fusiform,  in  this 
respect  reseral>ling  the  plain  muscle  cells,  but  they  are  transversely  striped  (Fig.  23,  C).  They 
are  easily  isolated  by  means  of  a  33  per  cent,  solution  of  potash  or  dilute  alcohol  ( IVeissmann, 
Kanvicr).'] 

44.  ARRANGEMENT  OF  THE  CARDIAC  MUSCULAR 
FIBRES,    AND    THEIR    PHYSIOLOGICAL    IMPORTANCE.— 

The  study  of  the  emliryonic  heart  is  the  key  to  a  proper  understanding  of  the 
complicated  arrangement  of  the  fibres  in  the  adult  heart.  Tlie  simple  tubular 
heart  of  the  embryo  has  an  outer  circular  and  an  inner  longitudinal  layer  of  fibres. 
The  septum  is  formed  later ;  hence,  it  is  clear  that  a  part,  at  least,  of  the  fibres 
must  be  common  to  the  two  auricles,  and  a  part  also  to  the  two  ventricles,  since 
there  is  originally,  but  one  chamber  in  the  heart.  The  muscular  fibres  of  the 
auricles,  are,  however,  complctclv  separated  from  those  of  the  ventricles  by  the 
fibro-cartilaginous  rings  (Lieutaud,  1782).  In  the  auricles  the  fundamental 
arrangement  of  the  embryonic  fibres  partly  remains,  while  in  the  ventricles  it 
becomes  obscured  as  the  cavities  undergo  a  sac-like  dilatation,  and  also  become 
twisted  in  a  spiral  manner. 

(i)  The  Muscular  Fibres  in  the  Auricles  are  completely  separated  from 
the|  fibres  of  the  ventricles  by  the_/f;5r«/j- rings  which  surround  the  auriculo-ventri- 


ARRANGEMENT   OF   THE    CARDIAC    MUSCULAR    FIBRES. 


69 


cular  orifices,  and  which  serve  as  an  attachment  for  the  auriculo-ventricular  valves 
(Fig.  24,  I).  The  auricles  are  much  thinner  than  the  ventricles,  and  their  fibres 
are  generally  arranged  in  two  layers ;  the  outer  transverse  layer  is  continuous  over 
both  auricles,  while  the  inner  one  is  directed  loiigittddinally.  The  outer  transverse 
fibres  may  be  traced  from  the  openings  of  the  venous  trunks  anteriorly  and  pos- 
teriorly over  the  auricular  walls.  The  longitudinal  fibres  are  specially  well  marked 
where  they  are  inserted  into  the  fibro-cartilaginous  rings,  while  in  some  parts  of 
the  anterior  auricular  wall  they  are  not  continuous.  In  the  auricular  septian,  some 
fibres,  circularly  disposed  around  the/(^W(7  crw/Zj  (formerly  the  embryonic  opening 
of  the  foramen  ovale)  are  well  marked.  Circular  bands  of  striped  muscle  exist 
around  the  veins  where  they  open  into  the  heart ;  these  are  least  marked  on  the 
inferior  vena  cava,  and  are  stronger  and  reach  higher  (2.5  cm.)  on  the  superior 
vena  cava  (Fig.  24,  II).  Similar  fibres  exist  around  the  pulmonary  veins,  where 
they  join  the  left  auricle,  and  these  fibres  (which  are  arranged  as  an  inner  circular 
and  an  outer  longitudinal  layer)  can  be  traced  to  the  hilus  of  the  lung  in  man  and 
some  mammals;  in  the  ape  and  rat  they  extend  on  the  pulmonary  veins  right  into 
the  lung.  In  the  mouse  and  bat,  again,  the  striped  muscular  fibres  pass  so  far 
into  the  lungs  that  the  walls  of  the  smaller  veins  are  largely  composed  of  striped 
muscle  {Stieda). 

FiG.  24. 


scular  fibres  on  the  left  auricle.     Observe  the  outer  transverse  and  inner  longitudinal  fibres,  the 
1  the  pulmonary  veins  (z/.  /.  i  ^   V,  the  left  ventricle  (John  Reld).     II.  Arrangement  ol  the  striped 
muscular  fibres  on  the  superior  vena  cava  {Elischer) — a,  opening  of  vena  azygos  ;  v,  auricle. 

Circular  muscular  fibres  are  found  where  the  vena  magna  cordis  enters  the  heart, 
and  in  the  Valvula  Thebesii  which  guards  it. 

From  a  physiological  point  of  view,  the  following  facts  are  to  be  noted  as  a 
result  of  the  anatomical  arrangement  :  — 

(i)  The  auricles  contj-act  independently  of  the  ventricles.  This  is  seen  when 
the  heart  is  about  to  die  ;  then  there  may  be  several  auricular  contractions  for  one 
ventricular,  and  at  last  only  the  auricles  pulsate.  The  auricular  portion  of  the 
right  auricle  beats  longest;  hence,  it  is  called  the  "  ultimum  moriens."  Inde- 
pendent rhythmical  contractions  of  the  vena;  cavse  and  pulmonary  veins  are  often 
noticed  after  the  heart  has  ceased  to  beat  {Haller,  Nysten).  [This  beating  can 
also  be  observed  in  those  veins  of  a  rabbit  after  the  heart  is  cut  out  of  the  body.] 

(2)  The  double  arrangement  of  the  fibres  (transverse  and  longitudinal)  pro- 
duces a  simultaneous  and  uniform  diminution  of  the  auricular  cavity  (such  as 
occurs  in  most  of  the  hollow  viscera). 

(3)  The  contraction  of  the  circular  muscular  fibres  around  the  venous  orifices, 
and  the  subsequent  contraction  of  the  auricle,  cause  these  veins  to  empty  them- 
selves into  the  auricle  ;  and  by  their  presence  and  action  they  prevent  any  large 
quantity  of  blood  from  passing  backward  into   the  veins  when   the  auricle  c/jn- 


70 


ARRANGEMENT   OF   THE   VENTRICULAR    FIBRES. 


tracts.  [No  valves  are  present  in  the  superior  and  inferior  vena  cava  in  the  adult 
heart,  or  in  the  pulmonary  veins,  hence  the  contraction  of  these  circular  muscular 
fibres  plays  an  important  part  in  preventing  any  reflux  of  blood  during  the  con- 
traction of  the  auricles.] 

45.  ARRANGEMENT    OF   THE   VENTRICULAR    FIBRES.— 

(2)  The  Muscular  Fibres  of  the  Ventricles. — The  fibres  in  the  thick  wall 
of  the  ventricles  are  arranged  in  several  layers  (Fig.  25,  A)  under  the  pericardium. 
First,  there  is  an  outer  lontyitiitlinal  layer  (.\),  which  is  in  the  form  of  single  bun- 
dles on  the  right  ventricle,  but  forms  a  complete  layer  on  the  left  ventricle,  where 
it  measures  about  one-eighth  of  the  thickness  of  the  ventricular  wall.  A  second 
loitgitudinal  layer  of  fibres  lies  on  the  inner  surface  of  the  ventricles,  distinctly 
visible  at  the  orifices,  and  within  the  vertically-placed  papillary  muscles,  while 
elsewhere  it  is  replaced  by  the  irregularly-arranged  trabecula;  carnea;.  Between 
these  two  layers  there  lies  the  thickest  layer,  consisting  of  more  or  less  transversely 

Fig.  25. 


^entricul; 
of  the 
(C.  Ludivig). 


view  of  the  apex  with  the  vortex  {Henfe)  : 
D,  fibres   passing   into  a  p.ipillary  muscle 


arranged  bundles,  which  may  be  broken  up  into  single  layers  more  or  less 
circularly  disposed.  The  deep  lymphatic  vessels  run  between  the  layers,  while  the 
blood  vessels  lie  within  the  substance  of  the  layers  and  are  surrounded  by  the 
primitive  bundles  of  muscular  fibres  {ffenle).  All  three  layers  are  not  completely 
independent  of  each  other ;  on  the  contrary,  the  fibres  which  run  obliquely  form 
a  gradual  transition  between  the  transverse  layers  and  the  inner  and  outer  longi- 
tudinal layers.  It  is  not,  however,  quite  correct  to  assume  that  the  outer  lon- 
gitudinal layer  gradually  passes  into  the  transverse,  and  this  again  into  the  inner 
longitudinal  layer  (as  is  shown  schematically  in  C)  ;  because,  as  Henle  pointed 
out,  the  transverse  fibres  are  relatively  far  greater  in  amount.  In  general,  the 
outer  longitudinal  fibres  are  so  arranged  as  to  cross  the  inner  longitudinal  layer  at 
an  acute  angle.  The  transverse  layers  lying  between  these  two  form  gradual 
transitions  between  these  directions.  At  the  apex  of  the  left  ventricle,  the  outer 
longitudinal  fibres  bend  or  curve  so  as  to  meet  at  the  so-called  vortex  ("Wirbel") 


PERICARDIUM,    ENDOCARDIUM,    VALVES. 


71 


B,  where  they  enter  the  muscular  substance,  and,  taking  an  upward  and  inward 
direction,  reach  the  papillary  muscles,  D  {Lower)  ;  although  it  is  a  mistake  to  say 
that  all  the  bundles  which  ascend  to  the  papillary  muscles  arise  from  the  vertical 
fibres  of  the^outer  surface;  many  seem  to  arise  independently  within  the  ven- 
tricular wall.  According  to  Henle,  all  the  external  longitudinal  fibres  do  not 
arise  from  the  fibrous  rings  or  the  roots  of  the  arteries. 

•  [The  assumption  that  the  muscles  of  the  ventricle  are  arranged  so  as  to  form  a  figure  of  8,  or  in 
loops,  seems  lo  be  incorrect ;  thus,  fibres  are  said  to  arise  at  the  base  of  the  ventricle,  to  pass  over 
it,  and  to  reach  the  vortex,  where  they  pass  into  the  interior  of  the  muscular  substance,  to  end 
either  in  the  papillary  muscles  or  high  up  on  the  inner  surface  of  the  heart  at  its  base.  Figs  C  and 
D  give  a  schematic  representation  of  this  view.] 

A  special  layer  of  circular  muscular  fibres,  which  acts  like  a  true  sphincter, 
surrounds  the  arterial  opening  of  the  left  ventricle,  and  seems  to  have  a  certain 
independence  of  action  {Henle'). 

Only  the  general  arrangement  of  the  ventricular  muscular  fibre=;  has  been  indicated  here  {Lower, 
Casp.  IVoljf,  lySo-gs).  C.  Ludwig  (1849),  ^"d  more  recently  Pettigrew  (1864),  have  made  the 
subject  a  special  study,  and  followed  out  its  complications.  .According  to  the  last  observer,  there 
are  seven  layers  in  the  ventricles,  viz.,  three  external,  a  fourth  or  central  layer,  and  three  internal. 
These  internal  layers  are  continuous  with  the  corresponding  external  layers  at  the  apex,  thus  —one 
and  seven,  two  and  six. 

46.  PERICARDIUM,  ENDOCARDIUM,  VALVES.— The  pericardium  encloses  within 

its  two  layers  [visceral  and  parietal]  a  lym])h  space — the  pericardial  space— which  contains  a  small 
quantity  of  lymph — the  pericardial  fluid.  It  has  the  structure  of  a  serous  membrane,  /.  e.,  it  con- 
sists of  connective  tissue  mixeul  with  fine  elastic  fibres  arranged  in  the  form  of  a  thin,  delicate  mem- 
brane, and  covered  on   its  free  surfaces  with 


a  single  layer  of  epithelium  or  endothelium, 
composed  of  irregular,  polygonal,  flat  cells. 

A  rich  lymphatic  network  lies  under  the 
pericardium  (Fig-  26)  and  endocardium ; 
and  also  in  the  deeper  layers  of  the  vis- 
ceral pericardium  next  the  heart,  but  sto- 
mata  have  not  been  found  leading  from 
the  pericardial  cavity  into  these  lymphat- 
ics, nor  do  these  openings  exist  on  the 
parietal  layer.  [Salvioli  has  shown  that 
lymphatic  spaces  also  lie  between  the  mus- 
cular bundles.]  Around  the  coronary  arter- 
ies of  the  heart  exist  lymph  vessels  and 
deposits  of  fat  (  IVedl),  which  lie  in  the 
furrows  and  grooves  in  the  subserosa  of  the 
epicardium  (visceral  layer). 

The  endocardium  (according to  Luschka) 
does  not  represent  the  intima  alone,  but  the 
wall  of  a  blood  vessel.  Next  the  cavity 
of  the  heart,  it  consists  of  a  sins^le  layer  of 
polygctnal,  fiat,  nucleated  endothelial  cells. 
[Under  this  there  is  a  nearly  homogeneous 
hyaline  layer  (Fig.  27,  «),  slightly  thicker  on 
the  left  side,  which  gives  tlie  endocardium 
its  polished  appearance.]  Then  follows,  as 
the  basis  of  the  membrane,  a  layer  of  fine 
elastic  fibres — stronger  in  the  auricles,  and 
in  some  places  thereof  assuming  the  char- 
acters of  a  fenestrated  membrane.  Between 
these  fibres  a  small  quantity  of  connective 
tissue  exists,  which  is  in  larger  amount  and 
more  areolar  in  its  characters  next  the 
myocardium.  Bundles  of  non-striped  mus- 
cular fibres  (few  in  the  auricles)  are 
scattered  and  arranged  for  the  most  part 
longitudinally   between    the    elastic    fibres. 

These    seem    evidently   meant   to    resist  the     Section  of  the  endocardi 
distention  which   is   apt  to  occur   when  the  rf"myoc»"dium"' 

heart    contracts    and    great    pressure    is    put  into  the  endocard 


FlG.  26. 


Fig.  27. 


im.     a,  hyaline  layer;  (^.network  ot 

,  network  of  stronger  elastic  fibres  ; 

,th   blood  vessels,  which   do   not  pass 


72 


STRUCTURE    OF   THE    VALVES. 


upon  the  endocardium.  In  all  cases  where  high  pressure  is  put  upon  walls  composed  of  soft  parts, 
we  always  find  muscular  fibres  present,  and  never  elastic  fibres  alone.  No  blood  vessels  occur  iu 
the  endocardium  [Lander,) 

The  valves  also  belong  to  the  endocardium — both  the  semilunar  valves  of  the 
aorta  and  pulmonary  artery,  which  prevent  the  blood  from  passing  feack  into  the 
ventricles,  and  the  tricuspid  (r/^/;^' auriculo-ventricular)  and  mitral  (/<// auriculo- 
ventricular),  which  protect  the  auricles  from  the  same  result.  The  lower  verte- 
brata  have  valves  in  the  orifices  of  the  vence  cavse  which  prevent  regurgitation  into 
them;  while  in  birds  and  some  mammals  these  valves  exist  in  a  rudimentary  con- 
dition. 

The  valves  are  fixed  by  means  of  their  base  to  xe.'ivsX'i.vA  fibrous  rings,  consist- 
ing of  elastic  and  fibrous  tissue.  They  are  formed  of  two  layers — (i)  the  fibrous, 
which  is  a  direct  continuation  of  the  fibrous  rings,  and  (2)  a  layer  of  elastic  ele- 
ments. The  elastic  layer  of  the  auriculo-ventricular  valves  is  an  immediate  pro- 
longation of  the  endocardium  of  the  auricles,  and  is  directed  toward  the  auricles. 
The  semilunar  valves  have  a  thin  elastic  layer  directed  toward  the  arteries,  which 
is  thickest  at  their  base.  The  connective-tissue  layer  directed  toward  the  ventricle 
is  about  half  the  thirkness  of  the  valve  itself. 

Muscular  Fibres  in  the  Valves. — The  auriculo-ventricularvalves  also  contain 
striped  iiiuseiilar  fibres  (Jieiil,  Gussenbauer).     Radiating  fibres  proceed  from  the 


Purkinje's  fibres  isolated 


leus.     X  3^* 


auricles  and  pass  into  the  valves,  which,  when  the  atria  contract,  retract  the 
valves  toward  their  base,  and  thus  make  a  larger  opening  for  the  passage  of  the 
blood  into  the  ventricles  ;  according  to  Paladino,  they  raise  the  valves  after  they 
have  been  pressed  down  by  the  blood  current.  This  observer  also  described  some 
longitudinal  fibres  which  proceed  from  the  ventricles  to  enter  these  valves.  There 
is  also  a  concentric  layer  of  fibres  arranged  near  their  point  of  attachment,  and 
directed  more  toward  their  ventricular  surface.  These  fibres  seem  to  contract, 
sphincter-like,  when  the  ventricle  contracts,  and  thus  approximate  the  base  of  the 
valves,  and  so  prevent  too  great  tension  being  put  upon  them.  The  larger  chordre 
tendine^  also  contain  striped  muscle  (Oehl),  while  a  delicate  muscular  network 
exists  in  the  valvula  Thebesii  and  valvula  Eustachii. 

Purkinje's  Fibres. — This  name  is  applied  to  an  anastomosing  system  of  grayish  fibres  which 
exist  in  the  subendocardial  tissue  of  the  ventricles,  especially  in  the  heart  of  the  .sheep  and  ox.  The 
filires  are  made  up  of  polyhedral,  clear  cells,  containing  some  granular  protoplasm,  and  usually  two 
nuclei  (Fig.  28).  The  margin  of  the  cells  are  striated.  Transition  forms  are  found  between  these 
cells  and  the  ordinary  cardiac  fibres;  in  fact,  these  cells  become  continuous  with  the  true  fully 
developed  cardiac  fibres.  They  represent  cells  which  have  been  arrested  in  their  development. 
They  are  absent  in  man  and  the  lower  vertebrates,  but  in  birds  and  some  mammals  they  are  well 
marked  (Sc/iwei^xer-Seidi'l,  /fancier). 

Blood  Vessels  occur  in  the  auriculo-ventricular  valves  only  where  muscular  fibres  are  present, 
while  the  semilunar  valves  are  usually  devoid  of  vessels  except  at  their  base.     The  best  figures  of 


AUTOMATIC  REGULATION  OF  THE  HEART.  73 

the  blood  vessels  of  the  valves  are  given  by  Langer.  The  network  of  lymphatics  in  the  endocar- 
dium reaches  toward  the  middle  of  the  valves  (Eberth  and  B,-lajeff). 

Weight  of  the  Heart. — According  to  W,  Miiller  the  proportion  between  the  weight  of  the 
body  and  the  heart  in  the  child,  and  until  the  body  reaches  40  kilos  ,  is  5  grms.  of  heart  substance 
to  I  kilo  of  body  weight;  when  the  body  weight  is  from  50  to  90  kilos  ,  the  ratio  is  I  kilo,  to  4 
grms.  of  heart  substance;  at  ico  kdos.  3.5  grms.  As  age  advances  the  auricles  become  stronger. 
The  right  ventricle  is  half  the  weight  of  the  left.  The  weight  of  the  heart  of  an  adult  man  is  about 
9  o«.  (I  oz.  =  29.2  grms.  I ;  female  =  8^  oz.  (Tlendinning,  as  a  mean  of  400  observations). 
[.'\ccording  to  Laennec  the  heart  is  about  the  size  of  the  closed  fist  of  the  individual.]  Blosfcld  and 
Dieberg  give  346  grms.  for  the  male,  and  310  to  340  grms.  for  the  female  heart.  The  specific  gravi/y 
of  the  heart  muscle  is  1.069  (^'"fff)-  The  thickness  of  the  left  ventricle  in  the  middle  in  man  is 
11.4  mm.,  and  in  woman  1 1.15  ;  that  of  the  right  is  4  i  and  3.6  mm.  respectively.  The  c  rcumfer- 
ence  of  the  tricuspid  orifice  in  man  is  i  iS  mm.,  and  in  woman  1 1 1.2  mm. ;  the  corresponding  num- 
bers for  the  mitral  being  106. 1  and  97.  The  circumference  of  the  pulmonary  artery  =  75.5  mm. 
(man),  and  74.7  mm.  (woman);  aorta  =  71. 1  mm.  (man),  and  68'0  mm.  (woman).  Sup.  vena 
cava  (circumference)  =  18  to  27  mm,  the  inferior  from  27  to  36  mm.  The  diameter  of  the  pul- 
monary veins  1513.53  to  15.79  mm.  [The  sizes  of  these  orifices  are  best  measured  by  means  of 
Cones  or  orifice  gauges  of  known  diameter.] 

47.  AUTOMATIC  REGULATION  OF  THE  HEART.— Coronary  Vessels.— Many 

observations  have  been  made  to  ascertain  whether  the  orifices  of  the  coronary  arteries  are  covered 
by  the  semilunar  valves  during  contraction  of  the  left  ventricle  (Thebesitis.  lyjg;  Briicie,  18 j4), 
or  whether  they  are  permanently  open  [Morgagni,  172 J ;  Hyrtl,  /8jj)  (Fig.  29). 

Anatomical  Investigations. — The  two  coronary  arteries  arise  from  the 
beginning  of  the  aorta  ///  //;<r  region  of  the  sinus  of  Valsalva.  [Hyrtl  asserts  that 
the  branches  of  the  coronary  arteries  do  not  anastomose,  but  this  is  certainly  not 
the  case  (Krause,  L.  Langer).  West  has  injected  the  one  artery  from  the  other.] 
The  position  of  origin  varies — (i)  either  the  origins  lie  within  the  sinus,  or  (2) 
their  openings  are  only  partially  reached  by  the  margins  of  the  semilunar  valves 
(which  is  usually  the  case  in  the  left  coronary  artery  of  man  and  the  ox),  or  (3) 
their  orifices  lie  clear  above  the  margins  of  the  valves.  Post-mortem  observations 
seem  to  show  that  during  contraction  of  the  ventricle  it  is  very  improbable  that 
the  semilunar  valves  constantly  cover  the  origin  of  the  coronary  arteries. 

The  Automatic  Regulation  of  the  Heart. — Briicke  attempted  to  show 
that  during  the  systole,  or  contraction  of  the  ventricle,  the  semilunar  valves 
covered  the  openings  of  the  coronary  arteries,  so  that  these  vessels  could  be  filled 
with  blood  only  during  the  diastole  or  relaxation  of  the  ventricle.  To  him  it 
seemed  that  ia)  the  diastolic  filling  of  the  coronary  arteries  would  help  to  dilate 
the  ventricles  ;  (i^)  on  the  contrary,  a  systolic  filling  of  these  arteries  would  oppose 
the  contraction,  because  the  systolic  filling  and  expulsion  of  the  blood  from  the 
coronary  arteries  would  diminish  the  force  of  the  ventricular  contraction.  [To 
this  supposed  arrangement  Briicke  gave  the  name  "  Selbststeuerung,"  which  may 
be  rendered  as  above,  or  as  "self-controlling"  action  of  the  heart  by  the  aortic 
valves.] 

Arguments  Against  Brucke's  View. — The  following  considerations  militate  against  this 
theory:  ( i )  Filling  the  coronary  vessels  under  a  high  pressure  in  a  dead  heart  causes  a  diminution 
of  the  ventricular  cavity  {v.  lVitlich\.  (2)  The  chief  trunks  of  the  coronary  arteries  lie  in  loose 
subpericardial  fatty  tissue  in  the  cardiac  sulci,  hence  a  dilatation  of  the  ventricle  through  this  agency 
is  most  unlikely  (Landois).  (3)  Experiments  on  animals  have  shown  that  a  coronarj'  artery  spouts, 
like  all  arteries,  during  the  systole  of  the  ventricle.  Von  Ziemssen  found  that  in  the  case  of  a 
woman  [Serafin),  who  had  a  large  part  of  the  anterior  ^all  of  the  thorax  removed  by  an  operation, 
the  heart  being  covered  only  by  a  thm  membrane,  the  pulse  in  the  coronary  arteries  was  synchronous 
with  the  pulse  in  the  pulmonary  artery.  H.  N.  Martin  and  Sedgwick  placed  a  manomettr  in 
connection  with  the  coronary  artery,  and  another  with  the  carotid,  in  a  large  dog,  and  they  found 
that  the  pulsations  occurred  simultaneously-  When  a  coronary  artery  is  divided,  the  blood  flows 
out  continuously,  but  undergoes  acceleration  during  the  systole  of  the  ventricles  [Endcmann,  Pcr/s). 
(4)  If  a  strong  intermittent  current  of  water  be  allowed  to  flow  through  a  sufficiently  wide  tube  into 
the  left  auricle  of  a  fresh  pig's  heart,  so  that  the  water  passes  into  the  aorta,  and  if  the  aorta  be 
provided  with  a  vertical  tube,  the  water  Hows  continuously  from  the  coronary  arteries,  and  is 
accelerated  during  the  systole.  (5)  It  is  exceedingly  improbable  that  the  coronary  arteries  should 
be  filled  during  the  diastole  while  all  the  other  arteries  are  filled  during  systole  of  the  ventricle. 
(6)  There  is  always  a  sufficient  quantity  of  blood  in  the  sinus  of  Valsalva  to  fill  the  arteries  during 


74  LIGATURE    OF   THE    CORONARY    ARTERIES. 

the  first  part  of  the  systole.  (7)  The  valves,  when  raised,  are  not  applied  directly  to  the  aortic  wall 
(Hamberger,  Riuiinger']  even  by  the  most  energetic  pressure  from  the  ventricle  (Sandborg  and 
Worm  liliiHeA.  (S)  Observations  on  voluntary  muscles  have  shown  that  the  small  arteries  dilate 
during  contraction  of  the  muscle,  and  the  blood  stream  is  accelerated.  (91  By  the  systolic  filling 
of  the  aorta  the  arterial  path  is  elongated — this  elastic  distention  is  compensated  before  the  diastole 
occurs.  Bv  the  recoil  of  the  aortic  walls  the  layer  of  blood  in  them  is  driven  backward  and  closes 
the  valves  (Ceradini).  According  to  Sandhorg  and  Worm  Miiller,  the  semilunar  valves  close  just 
after  the  ventricles  have  begun  to  relax,  which  agrees  with  the  curve  obtained  from  the  cardiac 
impulse  (Fig.  32,  A). 

During  the  systole,  the  small  arterial  trunks  lying  next  the  ventricular  cavities 
have  to  bear  a  higher  pressure  than  that  borne  by  the  aorta,  and  their  lumen  must 
be  compressed  during  the  systole  so  that  their  contents  are  propelled  toward  the 
veins. 

Peculiarities  of  the  Cardiac  Blood  Vessels  — The  capillary  vessels  of  the  myocardium  are 
very  numerous,  corresponding  to  the  energetic  activity  of  the  heart.  Where  they  pass  into  veins, 
several  unite  at  once  to  form  a  wide  venous  trunk  whereby  an  easy  passage  is  offered  to  the  blond. 
The  veins  are  provided  with  valves  so  that  (l)  durin;^  systole  of  the  right  auricle  the  venous  stream 
is  interrupted  ;  (2)  during  contraction  of  the  ventricles  the  blood  in  the  coronary  veins  is  similarly 
accelerated  as  in  the  veins  of  muscles. 

The  coronary  arteries  are  characterized  by  their  very  thick  connective  tissue  and  elastic  inlima, 
which  perhaps  accounts  for  the  frequent  occurrence  of  atheroma  of  these  vessels  [Henle).  Some 
observers  [Hyrtl  and  Henle)  maintain  that  the  coronary  arteries  do  not  anastomose,  but  this  is 
denied  by  Langer  and  Krause.  Many  of  the  small  lower  vertebrates  have  no  blood  vessels  in  their 
heart  muscle  e.g.,  frog  {Hyrtl). 

Coronary  Circulation. — The  phenomena  produced  ty  partial  obliteration  or 
ligature  of  the  coronary  arteries  are  most  important.  In  man  analogous  conditions 
occur,  as  in  atheroma  or  calcification  of  these  arteries. 

Ligature  of  the  Coronary  Arteries. — See  and  others  ligatured  the  coronary 
arteries  in  a  dog,  and  found  that  after  two  minutes  the  cardiac  contractions  gave 
place  to  twitchings  of  the  muscular  fibres,  and  ultimately  the  heart  ceased  to  beat. 
Ligature  of  the  anterior  coronary  artery  alone,  or  of  both  its  branches,  is  sufficient 
to  ])roduce  the  result.  If  the  ordinary  arteries  be  compressed  or  tied  in  a  rabbit, 
in  the  angle  between  the  bulbus  aorta;  and  the  ventricle,  the  heart's  action  is  soon 
weakened,  owing  to  the  sudden  ana;mia  and  to  the  retention  of  the  decomposition 
products  of  the  metabolism  in  the  heart  tnuscle  {v.  Bezold,  Erichseu).  Ligature 
of  one  artery  first  affects  the  corresponding  ventricle,  then  the  other  ventricle, 
and,  last  of  all,  the  auricles.  Hence,  compression  of  the  left  coronary  artery 
(with  simultaneous  artificial  respiration  in  a  curarized  animal)  causes  slowing  of 
the  contractions,  especially  of  the  left  ventricle,  while  the  right  one  at  first 
contracts  more  quickly,  and  then,  gradually,  its  rhythm  is  slowed.  The  contrac- 
tions of  the  left  ventricle  are  not  only  slowed  but  also  weakened,  while  the  right 
pulsates  with  undiminished  force.  Hence  it  follows  that,  as  the  left  half  of  the 
heart  cannot  expel  the  blood  in  sufficient  quantity,  the  left  auricle  becomes  filled, 
while  the  right  ventricle,  not  being  affected,  pumps  blood  into  the  lungs.  CEdema 
of  the  lungs  is  produced  by  the  high  pressure  in  the  pulmonary  circulation,  which 
is  propagated  from  the  right  heart  through  the  pulmonary  vessels  into  the  left 
auricle  {Samue/soii  and  Griinhagcn).  According  to  Sig.  Mayer,  protracted  dyspnoea 
causes  the  left  ventricle  to  beat  more  feebly  sooner  than  the  right,  so  that  the  left 
side  of  the  heart  becomes  congested.  Perhaps  this  may  explain  the  occurrence  of 
pulmonary  cedema  during  the  death  agony. 

Cohnheim  and  v.  Schulthess-Rechberg  found,  after  ligature  of  one  of  the  large  branches  of  a 
coronary  artery  in  a  large  dog,  that  at  the  end  of  a  minute  the  pulsations  became  discontinuous; 
several,  as  it  were,  do  not  occur.  This  intermittence  becomes  more  pronounced,  the  two  sides  of 
the  heart  do  not  contract  simultaneously  (arhythmia),  the  heart  beats  more  slowly,  and  the  blood 
pressure  falls.  Suddenly,  about  105  seconds  after  the  ligature  is  applied,  both  ventricles  cease  to 
beat,  and  there  is  the  greatest  fall  of  the  blood  pressure,  .'\fter  10  to  20  seconds,  twitching  move- 
ments occur  in  the  ventricles,  while  the  auricles  pulsate  regularly,  and  may  continue  to  do  so  for 
many  minutes,  but  the  ventricles  cease  to  beat  altogether  after  50  seconds.    Accordmg  to  Lukjanow, 


EVENTS  DURING  A  CARDIAC  CYCLE.  75 

there  is  a  peristaltic  condition  which  operates  upward  and  downward,  and  occurs  in  the  period 
bet'veen  the  regular  contraction  and  the  twitching  vibratory  movement. 

Pathological. — In  so-called  sclerosis  of  the  coronary  arteries,  in  old  age,  there  are  attacks  of 
diminished  cardiac  activity,  weakness  of  the  heart,  an  altered  rhythm  and  frequency,  with  con- 
sequent breathlessness ;  there  may  also  be  loss  of  consciousness,  congestions,  and  attacks  of  pul- 
monary redema. 

48.  MOVEMENTS  OF  THE  HEART.— Cardiac  Revolution.— The 

movement  of  the  heart  is  characterized  by  an  alternate  contraction  and  relaxation 
cif  the  cardiac  walls.  The  total  cardiac  movement  is  called  a  "  cardiac  revolu- 
tion," or  a  "  cardiac  cycle,"  and  consists  of  three  acts — the  contraction  or 
systole  of  the  auricles,  the  contraction  or  systole  of  the  ventricles,  and  the  pause 
(Fig.  43).  During  the  pause  the  auricles  and  ventricles  are  relaxed;  during  the 
contraction  of  the  auricles  the  ventricles  are  at  rest  ;  while  during  the  contraction 
of  the  ventricles  the  auricles  are  relaxed.  The  rest  during  the  phase  of  relaxation 
is  called  the  diastole.  The  following  is  the  sequence  of  events  in  the  heart  during 
a  cardiac  revolution  :  — 

EVENTS    DURING    A    CARDIAC    REVOLUTION. 

(A)  The  Blood  Flows  into  the  Auricles,  and  thus  distends  them  and 
the  auricular  appendices.     This  is  caused  by — 

(i )  'X\\<t pressure  of  the  blood  in  the  veuc-e  cavM  (right  side)  and  the  pulmonary 
veins  (left  side)  being  greater  than  the  pressure  in  the  auricles. 

(2)  The  elastic  traction  of  the  lungs  (§  68)  which,  after  complete  systole  of  the 
auricles,  pulls  asunder  the  now  relaxed  and  yielding  auricular  walls.  The  auricular 
appendages  are  also  filled  at  the  same  time,  and  they  act  to  a  certain  extent  as 
accessorv  reservoirs  for  the  large  supply  of  blood  streaming  into  the  auricles. 

(B)  The    Auricles  Contract,  and  we  observe  in   rapid  succession — 

(i)  The  contraction  and  emptying  of  the  auricular  appendix  toward  the  atrium. 
Simultaneously  the  mouths  of  the  veins  become  narrowed  {Haller,  Nysfen)  owing 
to  the  contraction  of  their  circular  muscular  fibres  (more  especially  the  superior 
vena  cava  and  the  pulmonary  veins). 

(2)  The  auricular  walls  contract  simultaneously  toward  the  auriculo-ventricular 
valves  and  the  venous  orifices,  whereby 

(3)  The  blood  is  driven  into  the  relaxed  ventricles,  which  are  considerably  dis- 
tended thereby. 

The  contraction  of  the  auricles  is  followed  by 

(a)  A  slight  stagnation  of  the  blood  in  the  large  venous  trunks,  as  can  be  easily 
observed  in  a  rabbit  after  division  of  the  pectoral  muscles  so  as  to  expose  the  junc- 
tion of  the  jugular  with  the  subclavian  vein.  There  is  no  proper  regurgitation  of 
the  blood,  but  only  a  partial  interruption  of  the  inflow  into  the  auricles,  because, 
as  already  mentioned,  the  mouths  of  the  veins  are  contracted,  and  because  the 
pressure  in  the  superior  vena  cava  and  in  the  pulmonary  veins  soon  holds  in  equili- 
brium any  reflux  of  blood  ;  and  lastly,  because  any  reflux  into  the  cardiac  veins  is 
prevented  by  valves.  The  movement  of  the  heart  causes  a  regular  pulsatile  phe- 
nomenon in  the  blood  of  the  veuce  cavae,  which  under  abnormal  circumstances 
may  produce  a  venous  pulse  (see  §  99). 

(b)  The  chief  motor  effect  of  the  contraction  of  the  auricles  is  the  dilatation  of 
the  relaxed  ventricle,  which  has  already  been  dilated  to  a  slight  extent  by  the 
elastic  traction  of  the  lungs. 

Aspiration  of  the  Ventricles. — The  dilatation  of  the  ventricles  has  been  ascribed  to  the  elas 
ticity  of  the  muscular  walls — the  strongly  contracted  ventricular  walls  (like  a  compressed  india- 
rubber  bag),  in  virtue  of  their  elasticity,  are  supposed,  in  returning  to  their  normal  resting  form,  to 
suck  in  or  aspirate  the  blood  under  a  negative  pressure;  this  power  on  the  part  of  the  ventricle  is 
not  great  (p.  77). 

(c')  when  the  ventricles  are  distended  by  the  inflowing  blood,  the  auriculo- 
ventricular  valves  are  floated  up,  partly  by  the  recoil  or  reflection  of  the  blood 


76 


EVENTS    DURING    A   CARDIAC    CYCLE. 


from  the  ventricular  wall,  and  partly  owing  to  their  lighter  specific  gravity, 
whereby  they  easily  float  into  a  more  or  less  horizontal  position.  The  valves  are 
also  raised  to  a  slight  extent  by  the  longitudinal  muscular  fibres,  which  pass  from 
the  auricles  into  the  cusps  of  the  valve  (^PahiJino). 

(C)  The  Ventricles  now  Contract,  and  simultaneously  the  auricles  relax, 
whereby 

(i)  The  muscular  walls  contract  forcibly  from  all  sides,  and  thus  diminish  the 
ventricular  cavity. 

(2)  The  blood  is  at  once  pressed  against  the  under  surface  of  the  auriculo- 
ventricular  valves,  whose  curved  margins  are  opposed  to  each  other  like  teeth, 


Fig.  29. 


Gypsum  cast  of  the  ventricles  of  the  human  heart — viewed  from  6  ■hind  ^ni  above  ;  the  walls  have  been  removed,  and 
only  the  fibrous  rings  and  the  auriculo-ventricular  valves  are  retained.  L,  left,  R,  right  ventricle  ;  S,  position  of 
septum  :  F,  left  fibrous  ring,  with  mitral  valve  closed  ;  D,  right  fibrous  ring,  with  tricuspid  closed  ;  A,  aorta,  with 
the  left  (C,)  and  right  (C)  coronary  arteries  ;  S,  sinus  of  Valsalva  ;  P,  pulmonary  artery. 

and  are  pressed  hermetiially  against  each  other  {Sandborg  and  Worm  Mi'iller) 
(Fig.  29).  It  is  impossil)le  for  the  blood  to  push  the  cusps  backward  into  the 
auricle,  as  the  chordae  tendineae  hold  fast  their  margins  and  surfaces  like  a  taut 
sail.  The  margins  of  the  neighboring  cusps  are  also  kept  in  apposition,  as  the 
chordae  tendineae  from  one  papillary  muscle  always  pass  to  the  adjoining  edges  of 
two  cusps  {John  Reid).  The  extent  to  which  the  ventricular  wall  is  shortened  is 
compensated  by  the  contraction  of  the  papillary  muscle,  and  also  of  the  large 
muscular  chord?e,  so  that  the  cusps  cannot  be  pushed  into  the  auricle  (p.  82). 
When  the  valves  are  closed  their  surfaces  are  horizontal,  so  that,  even  when  the 


PATHOLOGICAL   DISTURBANCES    OF   CARDIAC    ACTION.  77 

ventricles  are  contracted   to   their  greatest   extent,  there  remains   in  the  sufra- 
papillary  space  a  small  amount  of  blood  which   is  not  expelled  (Sandborg  and 
Worm  jWil/ler). 

(3)  Opening  of  the  Semilunar  Valves. — When  the  pressure  within  the  ventricle 
exceeds  that  in  the  arteries,  the  semilunar  valves  are  forced  open  and  stretched 
like  a  sail  across  the  pocket-like  sinus,  without,  however,  being  firmly  or  directly 
applied  to  the  wall  of  the  arteries  (pulmonary  and  aorta),  and  thus  the  blood 
enters  the  arteries. 

Negative  Pressure  in  the  Ventricle. — Goltz  and  Gaule  found  that  there  was  a  negative 
pressure  of  23.5  mm.  Hg  (dog)  in  the  interior  of  the  ventricle  during  a  certain  pha,se  of  the  heart's 
action.     This  they  determined  by  a  maximal  and  minimal  manometei'.     They  surmised  that  this 
phase    coincided    with    the    diastolic    dilatation,   for  which    they 
assumed  a  considerable  power  of  aspiration.     Marey  observed   a  Y\G.  50. 

similar  condition  and  ccilled  it  "vacuite  postsystolique,"  but  thought 
that  it  coincided  with  the  end  of  the  systole;  while  Moens  is  of 
opinion  that  this  negative  pressure  within  the  ventricle  obtains 
shortly  before  the  systole  has  reached  its  height,  i.  e.,  just  before  the 
inner  surface  of  the  ventricles  and  the  valves,  after  the  blood  is  ex- 
pelled, are  nearly  in  apposition.  He  explains  this  aspiration  as 
being  due  to  the  fonnation  of  an  empty  space  in  the  ventricle 
caused  by  the  energetic  expulsion  of  the  blood  through  the  aorta 
and  pulmonary  artery. 

(D)  Pause. — .^s  soon  as  the  ventricular  contraction 
ends,  and  the  ventricles  begin  to  relax,  the  semilunar 
valves  close  (Fig.  30).  The  diastole  of  the  ventricles  is 
followed  by  the  pause.  Under  normal  circumstances 
the  right  and  left  halves  of  the  heart  always  contract  or  Th 
relax  uniformly  and  simultaneously. 

49.     PATHOLOGICAL    DISTURBANCES    OF    CARDIAC    ACTION.— Cardiac 

Hypertrophy. — .All  resistances  to  the  movement  of  the  blood  through  the  various  chambers 
of  the  heart,  and  through  the  vessels  communicating  with  it,  cause  a  greater  amount  of  work 
to  be  thrown  upon  the  portion  of  the  heart  specially  related  to  this  part  of  the  circulatory 
system;  consequently,  there  is  produced  an  increase  in  the  thickness  of  the  muscular  walls  and 
dilatation  of  the  heart.  If  the  resistance  or  obstacle  does  not  act  upon  one  part  of  the  heart  alone, 
but  on  parts  lying  in  the  onward  direction  of  the  blood  stream,  the.se  parts  also  subsequently 
undergo  hypertrophy.  If  in  addition  to  the  muscular  thickening  of  a  part  of  the  heart  the  cavity 
is  simultaneously  dilated,  it  is  spoken  of  as  eccentric  hypertrophy  ox  hypertrophy  with  dilatation. 

The  obstacles  most  likely  to  occur  in  the  blood  vessels  are  narrowing  of  the  lumen  or  want  of 
elasticity  in  their  walls ;  in  the  heart,  narrowing  of  the  arterial  or  venous  orifices  or  insufficiency  or 
incompetency  of  the  valves.  Incompetency  of  the  valves  forms  an  obstruction  to  the  movement  of 
the  blood,  by  allowing  part  of  the  blood  to  flow  back  or  regurgitate,  thus  throwing  extra  work  upon 
the  heart. 

Thus  arise  (i)  Hypertrophy  of  the  left  ventricle,  owing  to  resistance  in  the  area  of  the  sys- 
temic circulation,  especially  in  the  arteries  and  capillaries —  not  in  the  veins.  Among  the  causes 
are,  constriction  of  tiie  oritice  or  other  parts  of  the  aorta,  calcification,  atheroma  and  want  of  elas- 
ticity of  the  large  arteries  and  irregular  dilatations  in  their  course  (Aneurisms)  ;  insufficiency  of  the 
aortic  valves,  in  which  case  the  same  pressure  always  obtains  withm  the  ventricle  and  in  the  aorta ; 
and  lastly,  contraction  of  the  kidneys,  so  that  the  excretion  of  water  by  these  organs  is  diminished. 
Even  in  mitral  insufficiency  compensatory  hypertrophy  of  the  left  ventricle  must  occur,  owing  to 
the  hypertrophy  of  the  left  atrium  in  consequence  of  the  increased  blood  pressure  in  the  pulmonary 
circuit. 

(2)  Hypertrophy  of  the  left  auricle  occurs  in  stenosis  of  the  left  auriculo- ventricular  orifice,  or 
in  insufticiency  of  the  mitral  valve,  and  it  occurs  also  as  a  result  of  aortic  insufficiency,  because  the 
auricle  has  to  overcome  the  continual  aortic  pressure  within  the  ventricle. 

(3)  Hypertrophy  of  the  right  ventricle  occurs  (a)  when  there  is  resistance  to  the  blood  stream 
through  the  pulmonary  circuit.  The  resistance  may  be  due  to  (r?)  obliteration  of  large  vascular 
areas,  in  consequence  of  destruction,  shrinking  or  compresMon  of  the  lungs,  and  the  disappearance 
of  numerous  capillaries  in  emphysematous  lungs;  (^)  overfilling  of  the  pulmonary  circuit  with 
blood,  in  consequence  of  stenosis  of  the  left  auriculo-ventricular  orifice,  or  mitral  insufficiency^ 
consequent  upon  hypertrophy  of  the  left  auricle  resulting  from  aortic  insufficiency,  (b)  Hyper- 
trophy of  the  right  ventricle  will  also  occur  when  the  valves  of  the  pulmonary  artery  are  insufficient, 
thus  permitting  the  blood  to  flow  back  into  the  ventricle,  so  that  the  pressure  within  the  pulmonary 
artery  prevails  within  the  right  ventricle  (very  rare). 


78  SYNCOPE,    CARDIAC    IMPULSE. 

(4)  Hypertrophy  of  the  right  auricle  occurs  in  consequence  of  the  last  named  condition,  and 
also  from  stenosis  of  the  tricuspid  orifice,  or  insufficiency  of  the  tricuspid  valve  (rare).  If  several 
lesions  occur  simuUaneously,  the  result  is  complex. 

Artificial  Injury  to  the  Valves. — O.  Rosenbach  has  made  experiments  on  the  action  of  the 
heart  when  its  valves  are  injured  artificially.  If  the  aortic  valves  are  perforated,  with  or  without 
simultaneous  injury  to  the  mitral  or  tricuspid  valves,  the  heart  does  more  work;  thus  the  physical 
defect  is  overcome  for  a  time,  so  that  the  blood  pressure  does  not  fall.  The  heart  seems  to  have  a 
store  of  reserve  energy,  which  is  called  into  play.  Soon,  however,  dilatation  takes  place,  on  account 
of  the  regurgitation  of  the  blood  into  the  heart.  Hypertrophy  then  occurs,  but  the  compensation, 
meanwhile,  must  be  obtained  through  the  reserve  energy  of  the  heart. 

Impeded  Diastole. — .^mong  causes  which  hinder  tne  diastole  of  the  heart  are — copious  effusions 
into  the  pericardium,  or  pressure  of  tumors  upon  the  heart.  The  systole  is  greatly  interfered  with 
when  the  heart  is  united  to  the  pericardium  and  to  the  connective  tissue  in  the  mediastinum.  As  a 
consequence,  the  connective  tissue,  and  even  the  thoracic  wall,  are  drawn  in  during  contraction  of 
the  heart,  so  that  there  is  a  retraction  of  the  region  of  the  apex  beat  during  systole,  and  a  protrusion 
of  this  part  during  the  diastole. 

[Palpitation  is  a  symptom  indicating,  generally,  very  rapid  and  quick  action  of  the  heart,  the 
pulsations  often  being  unequal  in  time  and  intensity,  while  the  person  is  generally  conscious  of  the 
irregularity  of  the  cardiac  action.  It  may  be  due  to  some  organic  condition  of  the  heart  itself, 
especially  where  the  cardiac  muscles  are  weak,  in  cases  of  dilatation  and  hypertrophy  of  the  left 
ventricle  where  the  heart  is  gradually  becoming  unable  to  overcome  the  resistances  offered  to  its 
work,  and  especially  during  exertion,  when  the  heart  is  taxed  above  its  strength.  It  may  also  occur 
where  the  blood  pressure  is  low,  as  in  an;emia,  so  that  the  heait  contracts  quickly,  there  being  little 
resistance  opposed  to  its  action.  The  excitability  of  the  cardiac  muscle  may  be  increased,  as  in 
fatty  heart,  when  very  slight  exertion  may  excite  it,  often  in  a  paroxysmal  way.  In  other  cases  it 
is  nervous  in  its  origin,  being  either  direct  or  reflex.  In  very  emotional  and  excitable  people 
(especially  in  women),  it  is  easily  set  up,  and  in  some  people  it  may  be  produced  reflexly  by  gastric 
or  intestinal  irritation  or  dyspepsia.  It  also  frequently  results  from  excesses  of  all  kinds  and  the 
over-use  of  tobacco.] 

[Action  of  Drugs. — The  remedies  to  be  used  obviously  depend  on  the  cause.  Where  the 
blood  pressure  is  low,  as  in  anaemia,  digitalis  and  iron  will  do  good;  the  former  by  increasing  the 
blood  pressure,  and  the  latter  by  improving  the  general  nutrition  of  the  body  and  the  blood  in 
particular.  In  neurotic  cases,  cardiac  sedatives  are  indicated,  while  in  cases  due  to  indigestion, 
hydrocyanic  acid  is  useful  (Srutihin).^ 

[Fainting  or  Syncope. — In  fainting,  the  person  loses  consciousness,  owing  to  a  sudden  arrest 
of  the  blood  supply  to  the  brain,  the  face  is  pallid,  the  respiration  is  feeble  or  ceases,  while  the 
heart  beats  but  feebly  or  not  at  all.  The  defective  supply  of  blood  to  the  brain  may  depend  upon 
sudden  arrest  of  the  heart's  action,  caused,  it  may  be,  by  a  fright,  or  the  heart's  action  may  be 
arrested  leHexly.  Any  cause  which  suddenly  diminishes  the  blood  pressure  may  produce  it,  or 
when  pressure  is  suddenly  removed  from  the  large  vessels,  as  in  tapping  the  abdomen  in  asci  es, 
without  at  the  same  time  giving  sulticient  support  to  the  abdominal  viscera.  When  a  person  has 
been  long  in  the  recumbent  position,  on  being  rapidly  set  up  in  bed,  he  may  faint.  In  some  forms 
of  heart  disease,  sudden  exertion  or  change  of  position  may  produce  it.]_ 

[Treatment. — The  object  is  to  restore  consciousness  and  the  action  of  the  heart.  Place  the 
person  m  the  horizontal  position,  with  the  head  low,  even  lower  tlian  the  body,  and  do  not  support 
it  with  piduws.  Dashing  cold  water  in  the  face,  so  as  to  stimulate  tne  fifth  nerve,  usually  succeeds 
in  causing  the  person  to  take  a  deep  inspiration.  In  other  cases,  a  sniff  of  smelling  salts  or  ammonia, 
acting  through  the  nasal  branch  01  the  fifth  nerve,  will  excite  the  cardiac  and  respiratory  functions 
{i  36S)-] 

50.  THE  APEX  BEAT,  THE  CARDIOGRAM,  CHANGES  IN 
THE  SHAPE  OF  THE  HEART.— Cardiac  Impulse.— By  the  term 
"  apex  beat,"  or  cardiac  impulse,  is  understood,  under  normal  circumstances, 
an  elevation  (perceptible  to  touch  and  sightj  in  a  circumscribed  area  of  the  Ji/fk 
left  intercostal  space,  caused  by  the  movement  of  the  heart.  [The  apex  beat  is 
felt  in  the  fifth  left  intercostal  space,  2  inches  below  the  nipple  and  i  inch  to  its 
sternal  side,  or  at  a  point  2  inches  to  the  left  of  the  sternum.]  The  impulse  is 
more  rarely  felt  in  the  fourth  intercostal  space,  and  it  is  much  less  distinct  when 
the  heart  beats  against  the  fifth  rib  itself.  The  position  and  force  of  the  cardiac 
impulse  vary  with  changes  in  the  position  of  the  body. 

[The  cardiac  impulse  is  synchronous  with  the  systole  of  the  heart,  but  although  this  name 
and  apex  beat  are  frequently  used  as  synonymous  terms,  it  is  to  be  remembered  that  the  impulse 
may  be  caused  by  different  parts  of  the  heart  being  in  contact  with  the  chest  wall.  The  cardiac 
impulse  is  usually  higher  than  normal  in  children,  while  it  is  lower  tluring  inspiration  than 
expiration.] 


THE    CARDIOGRAM. 
Fig.  31. 


79 


Various  cardiographs.     A,  original  form  as  used  by  ^^arey  ;    B,  improved  form  by  Marey :    C,  pansphygmograph 
ol  Brondgeest  ;    D,  cardiograph  of  Burdon-Sanderson  ;    E,  that  of  Grummach  and  v.  Knoll. 


.  lak 

1, 

from  the 

X  beat. 

A 

normal  c 

urve  from 

)  and 

E 

normal 

ves  from 

a  r 

nan,  reg 

stered  on 

cc.     I 

11  the  c 

rve 

,  a  b  means 

contraction  of  the 

,  closure  of  the  pulmonary  artery  valves ;  e/^  relaxation  of  diastole 


B,  from  a  dog  ;  C,  very  rapid  curve  from  a  dog  ; 
ating  glass  plaie  where  each  indentation  =  001613 
cics  ;  b  c-,  ventricular  systole  ;  d,  closure  of  the  aortic 


ar  syst( 
of  the 


80 


THE    CARDIOGRAM. 


[Methods. — To  obtain  a  curve  of  the  apex  beat  or  a  cardiogram,  we  may  use  one  or  other  of 
the  following  cardiographs  (Fig.  31).  Fig.  31,  A,  is  the  first  form  used  by  Marey,  and  it  consists  of 
an  oval  wooden  capsule  applied  in  an  air  tight  manner  over  the  apex  beat.  The  disk, /,  capable 
of  being  regulated  by  the  screw,  s,  presses  upon  the  region  of  the  apex  beat,  while  /  is  a  tube  which 
may  be  connected  with  a  recording  tambour  (Fig.  40).  B  is  an  improved  foiTn  of  the  instrument, 
consisting,  essentially,  of  a  tambour,  while  attached  to  the  membrane  is  a  button,  /,  to  be  applied 
over  the  apex  beat.  The  movements  of  the  air  within  the  capsule  are  communicated  by  the  tube, 
/,  to  a  recording  tambour.  Fig.  31,  C,  is  the  pansphygmograph  of  Brondgeest,  which  consists  of 
a  Marey's  tambour,  in  an  iron  horseshoe  frame,  and  adjustable  by  means  of  a  screw,  i.  Burdon- 
Sanderson's  cardiograph  is  shown  in  D.  The  button,  /,  carried  by  the  spring,  e,  does  not  rest 
upon  the  caoutchouc  membrane,  but  on  an  aluminium  plate  attached  to  it.  The  apparatus  is  adjusted 
to  the  chest  by  three  supports.  Fig.  31,  E,  shows  a  modified  instrument  on  the  same  principle,  by 
Grummach  and  v.  Knoll.  In  all  these  figures,  the  i  indicates  the  exit  tube,  communicating  with  a 
recording  tambour  (Fig.  40).  D  and  E  may  be  used  for  other  purposes,  e^.,  for  the  pulse,  so  that 
they  are  polygraphs.     See  also  Fig.  72  ] 

FiG.  33- 


I.  Schematic  horizontal  section  through  the  heart 
which  the  base  of  the  heart  undergoes  during  c 
triclc  during  diastole;  £■,  position  of  the  thorai 
during  systole,  with  e,  the  position  of  the 


apex  during  diastole  ;  /,  the 


nd  lungs,  and  the  thoracic  walls,  t 
intraction  of  the  ventricle — i,  2,  tra 
ic  wall  during  diastole  ;  rt,  i,  trans 
'  :  wall  during  systole.     II 


show  the  change  of  sh.ape 
sverse  diameter  of  the  ven- 
erse  diameter  of  the  heart 

Side  view  of  the  heart — i. 


'.  during  systole  ( C.  Lud-wig  and  Henfttt). 


Fig.  32,  A,  shows  the  cardiogram  or  the  impulse  curve  of  the  heart  of  a  healthy 
man  ;  B,  that  of  a  dog,  obtained  by  means  of  a  sphygmograph.  In  both  the 
following  points  are  lo  be  noticed  :  a  b,  corresponds  to  the  time  of  the  pause  and 
the  amtraction  of  the  auricles.  As  the  atria  contract  in  the  direction  of  the  a.\is 
of  the  heart  from  the  right  and  above  toward  the  left  and  below,  the  apex  of  the 
heart  moves  toward  the  intercostal  space.  The  two  or  three  smaller  elevations  are 
perhaps  caused  by  the  contractions  of  the  ends  of  the  veins,  the  auricular  appendi- 
ces, and  the  atria  themselves. 

Some  observers  ascribe  the  small  elevations  occurring  before  ^to  the  fiUingof  the  ventricle  during 
the  diastole,  whereby  it  is  pressed  against  the  intercostal  space  {Maiircr,  Griilzney). 

The  portion  be,  which  communicates  the  greatest  impulse  to  the  instrument  and 
also  to  one's  hand  when  it  is  placed  on  the  ape.x  beat,  is  caused  by  the  contraction 


CAUSE    OF   THE    CARDIAC    IMPULSE.  81 

of  the  ventricles,  and  during  it  the  first  sound  of  the  heart  occurs.  Frequently,  but 
erroneously,  the  cardiac  impulse  has  been  ascribed  to  the  contraction  of  the 
ventricles  alone.  It,  however,  is  due  to  all  those  conditions  which  cause  an  eleva- 
tion in  the  region  of  the  apex  beat. 

The  cause  of  the  ventricular  impulse  has  been  much  discussed.  It 
depends  upon  the  following  : — 

(•i)  The  base  of  the  heart  (auriculo-ventricular  groove)  represents  during 
diastole  a  transversely-placed  ellipse,  while  during  contraction  it  has  a  more  circular 
figure.  Thus,  the  long  diameter  of  the  ellipse  is  diminished  in  the  cat  from  28  to 
22.5  mm.  (C  Lutiwig);  the  small  diameter  is  increased  {^-^  to  \),  while  the  ba.se 
is  brought  nearer  to  the  chest  wall  (Arnold,  Ludwig),  (Fig.  33,  Ij.  This  alone 
does  not  cause  the  impulse,  but  the  basis  of  the  heart,  being  hardened  during  the 
systole  and  brought  nearer  to  the  chest  wall,  allows  the  apex  to  execute  the 
movement  which  causes  the  impulse  [compare  p.  82]. 

(2)  During  relaxation,  the  ventricle  lies  with  its  apex  obliquely  downward,  and 
with  its  long  axis  in  an  oblique  direction — -so  that  the  angles  formed  by  the  axis 
of  the  ventricles  with  the  diameter  of  the  base  are  unequal— represents  a  regular 
cone,  with  its  axis  at  right  angles  to  its  base.  Hence,  the  apex  must  be  erected 
from  below  and  behind,  forward  and  upward  {Harvey — "cor  sese  erigere"),  and 
when  hardened  during  systole  presses  itself  into  the  intercostal  space  {Ludwig), 

(3)  'rhe  ventricles  undergo  during  systole  a  slight  spiral  twisting  on  their  long 
axis  ( "  lateralem  inclinationem " — Harvey),  so  that  the  apex  is  brought  from 
behind  more  forward,  and  thus  a  greater  portion  of  the  left  ventricle  is  turned  to 
the  front.  This  rotation  is  caused  by  the  muscular  fibres  of  the  ventricles,  which 
proceed  from  that  part  of  the  fibrous  rings  between  the  auricles  and  ventricles 
which  lies  next  the  anterior  thoracic  wall.  The  fibres  pass  from  above  obliquely 
downward,  and  to  the  left,  and  also  run  in  part  upon  the  posterior  surface  of  the 
ventricles.  When  they  contract  in  the  axis  of  their  direction,  they  tend  to  raise 
the  apex,  and  also  to  bring  more  of  the  posterior  surface  of  the  heart  in  relation 
with  the  anterior  thoracic  wall  (^Hai-cey,  Kilrschner,  Wilckens).  This  rotation  is 
favored  by  the  slightly  spiral  arrangement  of  the  aorta  and  pulmonary  artery 
(^Kornitzer'). 

These  are  the  most  important  causes,  but  minor  causes  are  as  follows : — 

(4)  The  "reaction  impulse"  or  "recoil"  is  that  movement  which  the  ventricles 
are  said  to  undergo  (like  an  exploded  gun  or  rocket),  at  the  moment  when  the 
blaod  is  discharged  into  the  aorta  and  pulmonary  artery,  whereby  the  apex  goes 
in  the  opposite  direction,  /.  e.,  downward  and  slightly  outward  {Alderson  (182 j), 
Guthrod,  Skoda,  Hiffelsheim).  Landois,  however,  has  shown  that  the  mass  of 
blood  is  discharged  into  the  vessels  0.08  of  a  second  after  the  beginning  of  the 
systole,  while  the  cardiac  impulse  occurs  with  the  first  sound. 

(5)  When  the  blood  is  discharged  into  the  aorta  and  pulmonary  artery,  these 
vessels  are  slightly  elongated,  owing  to  the  increased  blood  pressure  (Senac).  As 
the  heart  is  suspended  from  above  by  these  vessels,  the  apex  is  pressed  slightly 
downward  and  forward  toward  the  intercostal  space  (?). 

Guttinann  and  Jahn  observed  that  the  cardiac  impulse  disappeared  after  suddenly  ligaturing  the 
aorta  and  pulmonary  artery,  while  Chauveau  and  Rosenstein  maintain  that  it  persists  after  this 
operation. 

As  the  cardiac  impulse  is  observed  in  the  empty  hearts  of  dead  animals,  (4)  and 
(5)  are  certainly  of  only  second-rate  importance.  Filehne  and  Pentzoldt  maintain 
that  the  apex  during  systole  does  not  move  to  the  left  and  downward,  as  must  be 
the  case  in  (4)  and  (5),  but  that  it  moves  upward  and  to  the  right — a  result 
corroborated  by  v.  Ziemssen. 

[Ban-  attributes  the  cause  of  the  impulse  to  the  rigidity  or  hardening  of  the  ventricle  during 
systole,  to  the  rotatory  movement  and  lengthening  downward  of  the  blood  column  in  the  aorta  and 
6 


82  CHANGE    IN    SHAPE   OF    HEART. 

pulmonary  arteiy,  while  toward  the  end  of  the  systole  the  maximum  of  recoil  takes  place  and  also 
contributes  to  cause  it.] 

It  is  to  be  remembered  that  as  the  apex  is  always  applied  to  the  chest  wall,  separated  from  it 
merely  by  the  thin  margin  of  the  lung,  it  only  presses  against  the  intercostal  space  during  systole 
(Kiwisc/i). 

After  the  apex  of  the  curve,  c,  has  been  reached  at  the  end  of  the  systole,  the 
curve  falls  rapidly,  as  the  ventricles  rapidly  become  relaxed.  In  the  descending 
part  of  the  curve,  at  d  and  e,  are  two  elevations,  which  occur  simultaneously  tci/h 
the  second  sound.  These  are  caused  by  the  sudden  closure  of  the  semilunar  valves, 
which,  occurring  suddenly,  is  propagated  through  the  axis  of  the  ventricle  to  its 
apex,  and  thus  causes  a  vibration  of  the  intercostal  space;  (/corresponds  to  the 
closure  of  the  aortic  valves,  and  e  to  the  closure  of  the  pulmonary  valves.  The 
closure  of  the  valves  in  these  two  vessels  is  not  simultaneous,  but  is  separated  by 
an  interval  of  0.05  to  0.09  sec.  The  aortic  valves  close  sooner  on  account  of  the 
greater  blood  pressure  there  {Landois  (i8~6),  Ott  and  Haas,  Malbranc,  Maurer, 
Griilzner,  Langendorff,  v.  Zicmssen,  and  Tcr  Gregonans). 

Complete  diastolic  relaxation  of  the  ventricle  occurs  froin  e  to/  in  the  curve. 
It  is  clear,  then,  that  the  cardiac  impulse  is  caused  chiefly  by  the  contraction  of  the 
ventricles,  while  the  auricular  systole  and  the  vibration  caused  by  the  closure  of 
the  semilunar  valves  are  also  concerned  in  its  production. 

[Change  in  Shape  of  Heart. — The  experiments  of  Ludwig  and  Hesse  on 
the  heart   of  the  dog  show   that  the  shape  of  the  ventricles  varies  remarkably 

Fig.  34.  Fig.  35. 


Left  lateral  surface. 

in  systole  and  diastole,  and  that  the   siiape  of  the  heart  as  found  post-mortem  is 
not  its  natural  shape.] 

[Method. —  Bleed  a  dog  rapidly  from  the  carotids,  defibnnate  the  blood,  expose  the  heart,  tie 
graduated  straight  tubes  into  the  pulmonary  artery  and  aorta,  and  ligature  the  auricular  vessels. 
Pour  the  blood  into  the  heart  until  it  is  dilated  under  a  pressure  equal  10  the  mean  arterial  pressure 
(150  mm.).  The  ventricles  are  in  Ihe  diastolic  phase,  the  auricles  still  pulsate.  A  plaster  cast  is 
now  rapidly  made  of  the  ventricles.  This  represents  the  diastolic  phase.  To  obtain  what  may  be 
regarded  as  the  systolic  phase,  a  heart,  similarly  prepared  but  emptied  of  blood,  is  suddenly 
plunged  into  a  hot  (50°  C),  saturated  solution  of  potasMC  bichromate,  when  the  heart  gives  one 
rapid  and  final  contraction  and  remains  permanently  contracted,  owing  to  the  heat  rigor,  its  proteids 
being  coagulated  (§  295)-  This  is  the  systolic  phase.  Little  pins  with  twisted  points  are  pre- 
viously inserted  in  the  organ,  to  mark  certain  parts  of  both  hearts,  for  comparison.] 

[In  diastole,  the  shape  of  the  ventricle  is  hemispheroidal,  the  apex  being 
rounded,  while  the  posterior  surface  is  flatter  than  the  anterior  (Fig.  34).  In  the 
plane  of  the  ventricular  base,  the  greatest  diameter  is  from  right  to  left,  and  the 
shortest  from  base  to  apex.  The  conus  arteriosus  is  above  the  plane  of  the  base. 
During  systo/e,  the  apex  is  more  pointed,  the  ventricle  more  conical,  while  all  the 
diameters  in  the  plane  of  the  base  are  equally  diminished,  hence  the  vertical 
measurement  from  base  to  apex  is  longer  now  than  either  of  the  diameters  at  the 
base  (Fig.  35).  The  conus  arteriosus  sinks  toward  the  plane  of  the  base,  while 
the  base  of   the  ventricle  becomes  more  circular,  so  that  the  difference  of  the 


TIME    OCCUPIED    BY   THE    CARDIAC    MOVEMENTS. 


83 


curvatures  of  the  anterior  and  posterior  surfaces  vanishes  (Fig.  36).  In  all  these 
figures  the  shaded  part  represents  diastole  and  the  clear  part  systole.  The  most 
remarkable  point  is  that  the  vertical  measurement  remains  unchanged.  This 
refers  to  the  left  ventricle,  which,  of  course,  forms  the  apex  ;  the  right  is  shortened. 
The  plane  of  the  ventricular  base  in  systole  is  about  one-half  of  what  it  is  in  dias- 
tole, and  as  shown  in  Fig.  38.  Thus  the  heart  is  diminished  in  all  its  diameters 
except  one,  the  arterial  orifices  are  scarcely  affected,  while  the  area  of  the  auriculo- 
ventricular  orifices  (M.T.)  is  diminished  about  one-half  (Fig.  37).  This  is  most 
important  in  connection  with  the  closure  of  the  auriculo-ventricular  valves  ;  as  it 
shows  that  the  muscular  fibres  of  the  heart,  by  diminishing  these  orifices  during 
systole,  greatly  aid  in  the  perfect  closure  of  these  valves.  Thus  we  explain  why 
defective  nutrition  of  the  cardiac  muscle  may  give  rise  to  incompetency  of  these 
valves,  without  the  valves  themselves  being  diseased  (Macalister).'\ 

[In  order  to  account  for  the  vertical  diameter  remaining  unchanged,  we  may 
represent  the  ventricular  fibres  as  consisting  of  three  layers,  viz.,  an  inner  and 
outer  set,  more  or  less  longitudinal,  and  a  middle  set,  circular.  Both  sets  will 
tend  when  they  contract  to  diminish  the  cavity,  but  the  shortening  of  the  longi- 
tudinal layers  is  compensated  for  by  the  contraction,  i.  e.,  the  elongation  pro- 
duced by  the  circular  set.] 

[In  order  to  obtain  the  shape  of  the  cavities,  dogs  were  taken  of  the  same  litter  and  as  nearly 
alike  as  possible.     One  heart  was  filled  with  blood,  as  already  described,  and  placed  in  a  cool  solu. 


Fin.  36. 


Fig.  37. 


Fig.  38. 


A,  aorta  ;   PA,  puln 

artery  ;  M.  mitral,  and 
T,  tricuspid  orifice. 


Projection  of  the  base  in  sys- 
tole and  diastole  RV, 
right,  and  LV,  left  v^n- 
\.nc\f:{Lud-wigand  Hesie). 


tion  of  potassic  bichromate,  whereby  it  w'as  slowly  hardened  in  the  diastolic  form,  while  the  othe 
was  plunged,  as  before,  in  a  hot  solution.     Casts  were  then  made  of  the  cavities.] 

51.  THE  TIME  OCCUPIED    BY    THE  CARDIAC  MOVEMENTS.— Methods.— 

The  time  occupied  by  the  szx\o\yi  phases  of  thi  movements  of  the  heart  may  be  determined  by  study- 
ing the  apex-beat  curve, 

(1)  If  we  know  at  what  rate  the  plate  on  which  the  curve  was  obtained  moved  during  the  experi- 
ment, of  course  all  that  is  necessary  is  to  measure  the  distance,  and  so  calculate  the  time  occupied 
by  any  event  (see  Pulse,  \  67). 

(2)  It  is  preferable,  however,  to  cause  a  tuning  fork,  whose  rate  of  vibration  is  known,  to  write 
its  vibrations  under  the  curve  of  the  apex  beat,  or  the  curve  may  be  written  upon  a  plate  attached  to 
a  vibrating  tuning  fork  (Fig.  32,  D,  E).  Such  a  curve  contains  fine  teeth,  caused  by  the  vibr.itions 
of  the  tuning  fork.  D  and  E  are  curves  obtained  from  the  cardiac  impulse  in  this  way  from  healthy 
students.  In  D  the  notch  a' is  not  indicated.  Each  complete  vibration  of  the  tuning  fork,  reckoned 
from  apex  to  apex  of  the  teeth  ^0.01613  second,  so  that  it  is  simply  necessary  to  count  the  number 
of  teeth  and  multiply,  to  obtain  the  time.  The  values  obtained  vary  within  certain  limits,  even  in 
health. 

Pause  and  Contraction  of  Auricles. — The  value  of  a  i  =  pause  +  con- 
traction of  the  auricles,  is  subject  to  the  greatest  variation,  and  depends  chiefly 
upon  the  number  of  heart  beats  per  minute.  The  more  quickly  the  heart  beats, 
the  smaller  is  the  pause,  and  conversely.  In  some  curves,  even  when  the  heart 
beats  slowly,  it  is  scarcely  possible  to  distinguish  the  auricular  contraction  (indi- 


84  DURATION    OF    CARDIAC    MOVEMENTS. 

cated  by  a  rise)  from  the  part  of  the  curve  corresponding  to  the  pause  (indicated 
by  a  horizontal  line).  In  one  case  (heart  beats  55  per  minute)  the  pause  =  0.4 
second,  the  auricular  contraction  =  0.177  second.  In  Fig.  32,  A,  the  time  occu- 
pied by  the  pause  +  the  auricular  contraction  (74  beats  per  minute)^  0.5  second. 
In  D,  a  b=  19  to  20  vibrations  =  0.32  second;  in  E  =  26  vibrations  =  0.42 
second. 

Ventricular  Systole. — The  ventricular  systole  is  calculated  from  the  begin- 
ning of  the  contraction  b,  to  e  when  the  semilunar  valves  are  closed  ;  it  lasts  from 
the  first  to  the  second  sound.  It  also  varies  somewhat,  but  is  more  constant.  When 
the  heart  beats  rapidly,  it  is  somewhat  less — during  slow  action,  greater.  In  E  = 
0.32  second  ;  in  D  =  0.29  second  ;  with  55  beats  per  minute  Landois  found  it  = 
0.34,  with  a  very  high  rate  of  beating  =  0.199  second. 

When  the  ventricles  beat  feebly,  they  contract  more  slowly,  as  can  be  shown  by  applying  the 
registering  apparatus  to  the  heart  of  an  animal  just  killed.  In  Fig.  39,  from  the  ventricle  of  a 
rabbit  just  killed,  the  slow  heart  heats,  B,  are  seen  to  last  longest. 

In  calculating  the  time  occupied  by  the  ventricular  systole  we  must  remember — (i)  The  time 
bel-u'een  the  two  sounds  of  the  heart,  /.  ^.,  from  the  beginning  of  the  first  to  the  end  of  the  second 
sound  (b  to  e). 

(2)  The  time  the  blood  flows  into  the  aorta,  \i\i\c\i  comes  to  an  end  at  the  depression  between  <r 
and  d  (in  Fig.  31,  E).  Its  commencement,  however,  does  not  coincide  with  b,  as  the  aortic  valves 
open  0.085  {Landois)  to  0.073  (A'/w)  second  after  the  beginning  of  the  ventricular  systole.  Hence 
the  aortic  current  lasts  0.08  to  0.09  second. 

This  is  calculated  in  the  following  way :  The  time  between  the  first  sound  of  the  heart  and  the 


Fig.  39. 


Curves  obtained  from  the  ventricle  of  a  rabbit,  and  written  upon  a  vibrating  plate  attached  to  a  tuning  fork  (vibration 
=  0.01613  second).    A,  tolerably  soon  after  death  ;  B,  from  the  dying  ventricle. 

pulse  in  the  axillary  artery  is  0.137  second,  and  of  this  time  0.052  second  is  occupied  in  the  propa- 
gation of  the  pulse  wave  along  the  30  cm.  of  artery  lying  between  the  root  of  the  aorta  and  the 
axilla.  Thus  the  pulse  wave  in  the  aorta  occurs  0.137  minus  0.052  =  0.085  second  after  the  begin- 
ning of  the  first  sound.  The  current  in  the  pulmonary  artery  is  interrupted  in  the  depression 
between  i/and  e. 

(3)  Lastly,  the  time  occupied  by  the  muscular  contraction  of  the  ventricle,  which  begins  at  /', 
reaches  its  greatest  extent  at  c,  and  is  completely  relaxed  aty;  The  apex  of  the  curve  c,  may  be 
higher  or  lower  according  to  the  flexibility  of  the  intercostal  space,  hence  the  position  of  c  varies. 
In  hypertrophy  with  dilatation  of  the  left  ventricle,  the  duration  of  the  ventricular  contraction  does 
not  greatly  exceed  the  normal. 

The  time  which  elapses  between  (/and  e,  i.  e.,  between  the  complete  closure  of 
the  aortic  and  pulmonary  valves,  is  greater  the  more  the  pressure  in  the  aorta 
exceeds  that  in  the  pulmonary  artery,  as  the  valves  are  closed  by  the  pressure  from 
above,  and  the  difference  in  time  may  be  0.05  second,  or  even  double  that  time, 
in  which  case  the  second  sound  appears  double  (compare  §  54).  If  the  aortic 
pressure  diminishes  while  that  in  the  pulmonary  artery  rises,  d  and  e  may  be  so  near 
each  other  that  they  are  no  longer  marked  as  distinct  elements  in  the  curve. 

The  time,  ef,  during  which  the  ventricles  relax  varies  somewliat  :  o.i  second 
may  be  taken  as  a  mean. 

Accelerated  Cardiac  Action.— When  the  action  of  the  heart  is  greatly  accelerated,  the  pause 
is  considerably  shortened  in  the  first  instance  [Dondei s),  and  to  a  less  extent  the  time  of  contraction 
of  the  auricles  and  ventricles.  When  the  pulse  rate  is  very  rapid,  the  systole  of  the  atria  coincides 
with  the  closure  of  the  arterial  valves  of  the  preceding  contraction, as  is  shown  in  Fig.  32,  C  (dog). 


ENDOCARDIAL    PRESSURE. 


85 


In  regisleiing  the  cardiac  impulse,  the  apparatus  is  separated  by  a  greater  or  less  extent  of  soft 
parts  from  the  heart  itself,  so  that  in  all  cases  the  intercostal  tissues  do  not  follow  exactly  the  move- 
ments of  the  heart,  and  thus  the  curve  obtained  may  not  coincide  mathematically  with  the  movements 
of  the  heart.  It  is  desirable  that  curves  be  obtained  from  persons  whose  hearts  are  exposed,  i.  e\,  in 
cases  of  Ectopia  cordis. 

Cleft  Sternum.  —Gibson  inscribed  cardiograms  from  the  heart  of  a  man  with  cleft  sternum.  The 
following  were  the  results  obtained  :  Auricular  contraction  ^0.115;  ventricular  contraction  ( i.  i/) 
=  0^8;  difference  between  closure  of  valves  (</,  ^■)  =  o.09;  ventricular  diastole  (e,  /)  =  o.il  ; 
pause  =  0.45  second. 

[Ventricular  Systole. — Chapman  has  calculated  the  duration  of  the  ventricular  systole  for 
varying  frequency  of  the  heart  beat,  as  follows,  in  sees : — 


Freqijency 
per  Min. 

Duration  of  Systole. 

Frequency 
per  Min. 

Duration  of  Systole. 

46-50 

.3600  (normal). 

{ 

86-  90 

3200  (exertion  and  normal). 

51-55 

.3425  (normal). 

86-  90 

2S00  (bath). 

f    56-60 

.3200  (bath). 

91-  95 

2690  (mixed  cases). 

\    56-60 

.3460  (normal). 

{ 

96-100 

2730  (normal). 

61-65 

.3200  (mixed  cases). 

96-100 

2540  (bath). 

66-75 

.3200  (mixed  casesj. 

101-105 

2543  (bath). 

7>-7S 

.3033  (bath). 

106-110 

2675  (exertion  only). 

r  76-80 
\   76-80 

.3300  (exertion  and  normal). 

111-115 

2475  (mixed  cases). 

.3032  (bath). 

1 16-120 

2350  (mixed  cases). 

f  81-S5 
t  81-S5 

.32^0  (exertion  and  normal). 

130 

2100  (exertion). 

.3030  (bath). 

Fig.  40. 


These  results  were  obtained  by  measurements  of  tracings  of  cardiograms  taken  after  a  Turkish 
bath,  or  after  exertion.] 

Endocardial  Pressure. — In  large  mammal.s,  such  as  the  horse,  Chauveau  and 
Marey  determined  the  duration  of  the  events 
that  occur  within  the  heart,  and  also  the 
endocardial  pressure,  by  means  of  a  cardiac 
sound.  Small  elastic  bags  attached  to  tubes 
were  introduced  through  the  jugular  vein 
into  the  right  auricle  and  ventricle.  Each 
of  these  tubes  was  connected  with  a  register- 
ing tambour  (Fig.  40),  and  simultaneous 
tracings  of  the  variations  of  pressure  within 
the  cavities  of  the  heart  were  obtained  by 
causing  the  writing  points  of  the  levers  of 
the  tambours  to  write  upon  a  revolving 
cylinder. 

Fig.  41,  A,  gives  the  result  obtained  when  the  elastic 
bag  was  placed  in  the  right  auricle,  introduced  through 
the  jugular  vein  and  superior  vena  cava  ;  B,  when  it 
was  pushed  through  the  tricuspid  valve  into  the  right 
ventricle ;  D,  in  the  root  of  the  aorta,  pushed  in  through 
the  carotid  ;  C,  pushed  past  the  semilunar  valves  into 
the  left  ventricle ;  while  at  E  a  similar  bag  has  been 
placed  externally  between  the  heart's  apex  and  the 
inner  wall  of  the  chest.  In  all  cases  71  =  auricular 
contraction  ;  V,  that  of  the  ventricle ;  s,  closure  of  semilunar  valves,  sooner  in  C  than  B;  P  ^  pause. 

Method. — The  cardiac  sound  consists  of  a  tube  containing  two  separate  air  passages,  and  in  con- 
nection with  each  of  these  there  is  a  small  elastic  bag  or  ampulla.  One  of  the  bags  is  fixed  to  the 
free  end  of  the  sound,  and  communicates  with  one  of  the  air  passages.  The  other  bag  is  placed  in 
connection  with  the  second  air  passage  in  the  sound,  and  at  such  a  distance  that,  when  the  former 
bag  lies  within  the  ventricle,  the  latter  is  in  the  auricle.  Each  bag  and  air  tube  communicating  with 
it  is  connected  with  a  Marey's  tambour  (Fig.  40),  provided  with  a  lever  which  inscribes  its  move- 
ments upon  a  revolving  cylinder.  Any  variation  of  pressure  within  the  auricle  or  ventricle  will 
atfect  the  elastic  ampulla;,  and  thus  raise  or  depress  the  lever.  Care  must  be  taken  that  the  writing 
points  of  the  levers  are  placed  exactly  above  each  other.  A  tracing  of  the  cardiac  impulse  is  taken 
siinultaneously  by  means  of  a  cardiograph  attached  to  a  separate  tambour. 


.rey's  registering  tambour, 
capsule,  T,  with  thin  ind 
it,  and  bearing  an  alun 
upon  the  writing  lever,  H 
walled  caoutchouc  tube, 
with  any  system  containing 
of  pressure. 


ngof  a  metallic 

er  stretched  over 

disk,  which  acts 

By  means  of  a  thick- 

t  may  be   connected 

5  to  record 


86 


PATHOLOGICAL    DLSTURBANCES   OF   THE    CARDIAC    IMPULSE. 


It  has  still  to  be  determined  whether  the  auricles  and  ventricles  act  alternately, 
so  that  at  the  moment  of  the  beginning  of  the  ventricular  contraction  the  auricles 
relax,  or  whether  the  ventricles  are  contracted  while  the  auricles  still  remain 
slightly  contracted,  so  that  the  whole  heart  is  contracted  for  a  short  time  at  least. 
The  latter  view  was  supported  by  Harvey,  Bonders,  Schiff,  and  others,  while 
Haller  and  many  of  the  more  recent  observers  support  the  view  that  the  action  of 
the  auricles  and  ventricles  alternates.  In  the  case  of  Frau  Serafin,  whose  heart 
was  exposed,  v.  Ziemssen  and  Ter  Gregorianz  obtained  curves  from  the  auricles, 
which  showed  that  the  contraction  of  the  auricles  continued  even  after  the  com- 
mencement of  the  ventricular  systole.  In  Marey's  curve  (Fig.  41)  the  contrac- 
tion of  the  ventricle  is  represented  as  following  that  of  the  auricle. 

Fig.  41. 


--  Right  Auricle. 


—  Left  Ventricle. 


btained  from  the  hcirt  by  the  cardiac  sound  i^Ckaia'eau  and  Murcy). 


52.  PATHOLOGICAL  DISTURBANCES  OF  THE  CARDIAC  IMPULSE.— 
Change  in  the  Position  of  the  Apex  Beat. — The  position  of  the  cardi.ic  impulse  is  changed — 
(l)liylhe  accumuUtion  of  fluids  (serum,  pus,  l)Iood)  or  g.TS  in  one  pleural  cavity.  A  copious 
effusion  into  the  left  pleural  cavity  compresses  the  lung,  and  may  displace  the  heart  toward  the 
right  side,  while  effusion  on  the  right  side  may  push  the  heart  more  to  the  left.  As  the  right 
heart  must  make  a  greater  eflbrt  to  propel  the  blood  through  the  compressed  lung,  the  cardiac 
impulse  is  usually  increased.  Advanced  emphysema  of  the  lung,  causing  the  diaphragm  to  be 
pressed  downward,  displaces  the  heart  downward  and  inward,  while  conversely  the  pushing  or 
pulling  up  of  the  diaphragm  (by  contraction  of  the  lung,  or  through  pressure  from  below)  causes 
the  apex  beat  to  be  displaced  upward  (even  to  the  third  intercostal  space),  and  also  slightly  to  the 
left.  Thickening  of  the  muscular  walls  and  dilatation  of  the  cavities  of  the  left  ventricle  (hyper- 
trophy with  dilatation)  make  that  ventricle  longer  and  broader,  while  the  increased  cardiac  impulse 


VARIATIONS   OF   THE    CARDIAC    IMPULSE. 


87 


may  be  felt  to  the  left  of  the  mammary  line,  and  in  the  axillary  line  in  the  sixth,  seven'h,  or  even 
eighth  intercostal  space.  Hypertrophy,  with  dilatation  of  the  right  side,  increases  the  breadth  of 
the  heart,  while  the  cardiac  impulse  is  felt  more  to  the  right,  even  to  the  right  of  the  sternum,  and 
at  the  same  time  it  may  be  slightly  beyond  the  left  mammary  line.  In  the  rare  cases  where  the 
heart  is  transposed,  the  apex  beat  is  felt  on  the  right  side.  When  the  cardiac  impulse  goes  to  the 
left  of  the  left  mammary  line,  or  to  the  right  of  the  parasternal  line,  the  heart  is  increased  in  breadth, 
and  there  is  hypertrophy  of  the  heart.  A  greatly  increased  cardiac  impulse  may  extend  to  several 
intercostal  spaces. 

The  cardiac  impulse  is  abnormally  weakened  during  atrophy  and  degeneration  of  the  cardiac 
muscle,  or  by  weakening  of  the  innervation  of  the  cardiac  ganglia.  It  is  also  weakened  when  the 
heart  is  separated  from  the  chest  wall  owing  to  the  collection  of  the  fluids  or  air  in  the  pericardium, 
or  by  a  greatly  distended  left  lung;  and,  indeed,  when  the  left  side  of  the  chest  is  filled  with  fluid, 
the  cardiac  impulse  may  be  extinguished.     The  same  occurs  when  the  left  ventricle  is  very  imper- 


nous  forms  of  curves  obtained  from  the  cardiac  impulse,  a,  b,  contraction  of  auricles  ;  ^,  c,  venincular  systole  ; 
d,  closure  of  aortic,  and  e  of  pulmonary  valves  ;  €,/,  diastole  of  ventricle  ;  P,  Q,  hypertrophy  and  dilatation  of 
the  left  ventricle;  E,  stenosis  of  the  aortic  orifice  ;  F,  mitral  insutBciency;  G,  mitral  stenosis  ;  L,  nervous  palpi- 
tation in  Basedow's  disease  ;  M,  case  of  so-called  hemisystole. 

fectly  filled  during  its  contraction  (in  consequence  of  marked  narrowing  of  the  mitral  orifice), 
or  when  it  can  only  empty  itself  very  slowly  and  gradually,  as  during  marked  narrowing  of  the 
aortic  orifice. 

An  increase  of  the  cardiac  impulse  occurs  during  hypertrophy  of  the  walls,  as  well  as  under  the 
influence  of  various  stimuli  (psychical,  inflammatory,  fel  rile,  toxic)  which  aflect  the  cardiac  ganglia. 
Great  hypertrophy  of  the  left  ventricle  causes  the  heart  to  heave,  so  that  a  part  of  the  left  chest  wall 
may  be  raised  and  also  vibrate  during  systole. 

A  pulling  in  of  the  anterior  wall  of  the  chest  during  cardiac  systole  occurs  in  the  third  and 
fourth  interspaces,  not  unfrequently  under  normal  circumstances,  sometimes  during  increa-sed  cardiac 
action,  and  in  eccentric  hypertrophy  of  the  ventricles.  As  the  heart's  apex  is  slightly  displaced,  and 
the  ventricle  becomes  slightly  smaller  during  its  systole,  the  empty  space  is  filled  by  the  yielding 
soft  parts  of  the  intercostal  space.  When  the  heart  is  united  with  the  pericardium  and  the  sur- 
rounding connective  tissue,  winch  renders  systolic  locomotion  of  the  heart  impossible,  retraction 


88  THE    HEART   SOUNDS. 

of  the  chest  wall  during  systole  takes  the  place  of  the  cardiac  impulse  {Skoda).  During  the 
diastole  a  diastolic  cardiac  impulse  of  the  corresponding  part  of  the  chest  wall  may  be  said  to 
occur. 

Changes  in  the  cardiac  impulse  are  best  ascertained  by  taking  graphic  representations  of  the 
cardiac  impulse,  and  studying  the  curves  so  obtained.  This  method  has  been  largely  followed  by 
many  clinicians. 

In  all  the  following  curves,  a,  *,  means  auricular  contraction;  /5,  ^,  ventricular  contraction;  d, 
closure  of  the  aortic  valves,  and  e  of  the  pulmonary;  e,f,  the  time  the  ventricle  is  relaxed 
(Fig-  42).      ■ 

In  curve  P  (much  reduced),  taken  from  a  case  of  marked  hypertrophy  with  dilatation,  the 
ventricular  contraction,  b,  c,  is  usually  very  great,  while  the  time  occupied  by  the  contraction  is  not 
much  increased.  P  and  Q  were  obtainpd  from  a  man  suffering  from  marked  eccentric  hypertrophy 
of  the  left  ventricle,  in  consequence  of  insufficiency  of  the  aortic  valves.  Curve  Q  was  taken 
intentionally  over  the  auriculo-ventricular  groove,  where  retraction  of  the  chest  wall  occurred  during 
systole ;  nevertheless,  the  individual  events  occurring  in  the  heart  are  indicated. 

Fig.  E  is  from  a  case  of  aortic  stenosis.  The  auricular  contr.iction  (17,  />)  lasts  only  a  short 
time  ;  the  ventricular  systole  is  obviously  lengthened,  and  after  a  short  elevation  (i,  c)  shows  a 
series  of  fine  indentations  (c,  e)  caused  by  tlie  blood  being  pressed  through  the  narrowed  and 
roughened  aorta. 

Fig  F,  from  a  case  of  insufficiency  of  the  mitral  valve,  shows  {a,  />)  well  marked  on  account 
of  the  increased  activity  of  the  left  auricle,  while  the  shock  (d)  from  the  closure  of  the  aortic  valves 
is  small,  on  account  of  the  diminished  tension  in  the  arterial  s\stcm.  On  the  other  hand,  the  shock 
from  the  accentuated  pulmonary  sound  (f)  is  ^ery  great,  and  is  in  the  apex  of  the  curve.  On 
account  of  the  great  tension  in  the  pulmonary  artery,  the  second  pulmonary  tone  may  be  so  strong, 
and  succeed  the  second  aortic  sound  (</)  so  rapidly,  that  both  almost  merge  completely  into  each 
other  (H  and  K). 

The  curve  of  stenosis  of  the  mitral  orifice  (G)  shows  a  long,  irregular-notched  auricular 
contraction  [a,  i)  caused  by  the  blood  being  forced  through  an  irregular  narrow  orifice.  The  ventricu- 
lar contraction  (d,  c)  is  feeble,  on  account  of  its  being  imperfectly  filled.  The  closures  of  the  two 
valves,  d  and  c,  are  relatively  far  apart,  and  one  can  hear  distinctly  a  reduplicated  second  sound. 
The  aortic  valves  close  rapidly,  because  the  aorta  is  imperfectly  supplied  with  blood,  while  the 
more  copious  inflow  of  blood  into  the  pulmonary  artery  causes  a  later  closure  of  its  valves 
{Geil'e/). 

If  the  heart  beats  rapidly  and  feebly — if  the  blood  pressure  in  the  aorta  and  pulmonary  artery 
be  low,  the  signs  of  closure  if  the  pulmonary  valves  may  be  absent — as  in  curve  L — taken  from  a 
girl  suffering  from  nervous  palpitation  and  morbus  Basedowii. 

In  very  rare  cases  of  insufficiency  of  the  mitral  valve,  it  has  been  observed  that  at  certain  times 
both  ventricles  contract  simultaneously,  as  in  a  normal  heart,  but  that  this  alternates  with  a  con- 
dition where  the  right  ventricle  alone  seems  to  contract.  Curve  M  is  such  a  curve,  obtained  by 
Malbranc,  who  called  this  condition  intermittent  hemisystole.  The  first  curve  (!)  is  like  a 
normal  curve,  during  which  the  whole  heart  acted  as  usual.  The  curve  II,  howe\er,  is  caused  by 
the  right  side  of  the  heart  alone  ;  it  wants  the  closure  of  the  aortic  valves,  d,  and  there  was  no 
pulse  in  the  arteries.  Owmg  to  insufficiency  of  the  triscupid  valve,  the  same  person  had  a  venous 
pulse  with  every  cardiac  impulse,  so  that  the  arterial  and  venous  pulses  first  occurred  together,  and 
then  the  venous  pulse  alone  occurred. 

In  these  cases  (Sioda,  v.  Bamberger,  Leydett)  the  mitral  insufficiency  leads  to  the  right  ventricle 
being  over-distended,  while  the  left  is  nearly  empty,  so  that  the  right  side  requires  to  coniract  more 
energetically  than  the  left.  It  does  not  seem  that  the  rii^ht  ventricle  alone  contracts  in  these  cases, 
but  rather  that  the  action  of  the  left  side  is  very  feeble. 

53.  THE  HEART  SOUNDS.— On  listening  over  the  region  of  tiie  heart 
in  a  healthy  man,  either  with  the  ear  applied  directly  to  the  chest  wall,  or  by  means 
of  a  stetho^cope  {Laennec,  i8ig),  we  hear  two  characteristic  sounds,  the  so-called 
"  heart  sounds."  Harvey  was  acquainted  with  these  sounds,  but  they  have 
been  more  careftilly  studied  by  clinicians  since  the  time  of  Laennec.  The  two 
sounds  are  called  first  and  second,  and  together  they  correspond  to  a  single  car- 
diac cycle.  These  sounds  are  separated  by  silences,  so  that  as  far  as  the  sounds 
are  concerned,  during  a  cardiac  cycle  we  have,  as  in  Fig.  43 — 

1.  The  first  sound. 

2.  The  first  or  short  silence. 

3.  The  second  sound. 

4.  The  second  or  long  silence. 

[This  diagram  shows  the  relation  of  the  events  occurring  in  the  heart  itself  to 
the  sounds  and  silences  (§  48).] 


THE    HEART   SOUNDS. 


89 


Relative  Duration. — There  is  no  absolute  duration  of  each  phase  of  a  cardiac 
cycle,  but  we  may  take  the  average  duration  calculated 
from  the  measurements  of  Gibson  in  a  case  of  fissure  of  ^"^  "^J- 

the  sternum  to  be  as  follows  : — 


Auricular  systole, 
Ventricular  systole, 
Ventricular  diastole. 


.112  sec. 
.368    " 
.578    " 


Cardiac  cycle,  1.058  sec. 

Suppose  we  divide  the  cycle  into  tenths  (  Walshe),  then 
the  first  sound  will  last  -f^,  the  first  silence  y^,  the  second 
sound  -f^,  and  the  long  silence  ^V  of  the  entire  period. 

The  first  sound  [long  or  systolic]  is  somewhat  duller, 
twice  as  long,  booming,  and  one-third  or  one-fourth 
deeper,  than  the  second  sound  ;  it  is  less  sharply  defined 
at  first,  and  is  synchronous  with  the  systole  of  the  ven- 
tricles {Turner).  The  second  sound  [short  or  dias- 
tolic]  is  clearer,  sharper,  shorter,   more  sudden,  and   is 

one-third  to  one-fourth   higher ;  it  is  sharply  defined  and   synchronous  with  the 
closure  of  the  semilunar  valves. 

The  sounds  emitted  during  each  cardiac  cycle  have  been  compared  to  the  pro- 
nunciation of  the  syllables  lubb,  diip.     Or  the  result  may  be  expressed  thus — 


erne  of  a  cardiac  cycle,  after 
Gairdner  and  Sharpey.  The 
inner  circle  shows  what 
events  occur  in  the  heart, 
and  the  outer,  the  relation  of 
the  sounds   and  silences    to 


i3- 

Bu 


^ 


m^--^ 


tup. 


Bu      ■      tup. 


[It  is  to  be  remembered  that  in  real ity/w^r  sounds  are  produced  in  the  heart, 
but  the  two  first  sounds  occur  together  and  the  two  second,  so  that  only  a  single 
first  and  a  single  second  sound  are  heard.] 

The  causes  of  the  first  sound  are  due  to  two  conditions.  As  the  sound  is 
heard  in  an  excised  heart  in  which  the  movements  of  the  valves  are  arrested,  and 
also  when  the  finger  is  introduced  into  the  auriculo-ventricular  orifices  so  as  to 
prevent  the  closure  of  the  valves  (  C.  Liidwig  and  Dogiel),  one  of  the  chief  factors 
lies  in  ihe  "  muscle  sound"  produced  by  the  contracting  muscular  fibres  of  the 
ventricles  {IVilliams,  iSjj).  This  sound  is  supported  and  increased  by  the  sound 
produced  by  the  tension  and  vibration  of  the  auriculo-ventricular  valves  and 
their  chords  tendineae  at  the  moment  of  the  ventricular  systole  {Rouanet,  Kiwisch, 
Bayer,  Giese).  Wintrich,  by  means  of  proper  resonators,  has  been  able  so  to 
analyze  the  first  sound  as  to  distinguish  the  clear,  short,  valvular  part  from  the . 
deep,  long,  muscular  sound. 

The  muscle  sound  produced  by  transversely-striped  muscle  does  not  occur  with  a  simple  contrac- 
tion, but  only  when  several  contractions  are  superposed  to  produce  tetanus  (J  303).  The  ventricular 
contraction  is  only  a  simple  co])traclion,  but  it  lasts  considerably  longer  than  the  contraction  of  other 
muscles,  and  herein  lies  the  cause  of  the  occurrence  of  the  muscle  sound  during  the  ventricular 
cc  ntraction. 

Defective  Heart  Sounds. — In  certain  conditions  (typhus,  fatty  degeneration  of  the  heart) 
where  the  muscular  substance  of  the  heart  is  much  weakened,  the  first  sound  may  be  completely 
inaudible.  Tn  aortic  insufficiency,  in  consequence  of  the  reflux  of  blood  from  the  aorta  into  the 
ventricle,  the  mitral  valve  is  gradually  stretched,  and  sometimes  even  before  the  beginning  of  the 
\  entricular  systole  the  tirst  sound  may  be  absent.  Both  pathological  cases  show  that  for  the  pro- 
duction of  the  first  sound,  muscle  sound  and  valve  sound  must  eventually  work  together,  and  that 
tl  e  tone  is  altered,  or  may  even  disappear,  when  one  of  these  causes  is  absent.  [Veo  and  Barrett 
stjie  that  the  sound  is  purely  muscular  (?)  ] 


90 


CAUSES    OF    THE    HEART    SOUNDS. 


The  cause  of  the  second  sound  is,  undoubtedly,  due  to  the  prompt  closure, 
and,  therefore,  sudden  stretching  or  tension,  of  the  semilunar  valves  of  the  aorta 
and  pulmonary  artery,  so  that  it  is  purely  a  valvular  sound  {Carsrce/I  and  Rouanety 
i8jo).  Perhaps  it  is  augmented  by  the  sudden  vibration  of  the  fluid  particles  in 
the  large  arterial  trunks.     As  already  pointed  out  (p.  82),  the  aortic  and  pulmo- 


FiG.  44. 


e  heart — its  several  parts  and  great  vessels  in  relation  to  the  front  of  the  thorax.  The  lungs  are  collapsed  to  their 
normal  extent,  as  after  death,  exposing  the  heart.  The  outlines  of  the  several  parts  of  the  heart  are  indicaied 
by  very  fine  dotted  lines.  The  area  of  propagation  of  valvular  murmurs  is  marked  out  by  more  visible  dotted 
lines.  A,  the  circle  of  mitral  murmur,  corresponds  to  the  left  apex  The  broad  and  somewhat  diffused  are  \^ 
rotighly  triangular,  is  the  region  of  tricuspid  murmurs,  and  corresponds  generally  with  the  right  ventricle,  where 
it  is  least  covered  by  lung.  The  letter  C  is  in  its  centre.  The  circumscribed  circjilir  area,  D.  is  the  part  over 
which  the  pulmonic  arterial  murmurs  are  commonly  heard  loudest.  In  many  c 
lower  down,  corresponding  to  the  conns  arteriosus  of  the  right  ventrir' 
The  internal  organs  and  parts  of  organs  are  indicated  by  letters  as  f 
dotting  ;  a  o,  arch  of  aorta,  seen  in  the  first  intercostal  space,  and  trac 
innominate  veins  ;  r  v,  right  ventricle  ;  l.  v,  left  ventricle. 


:  it  touches  the  wall  of  the  thora? 
>-.  att  right  auricle,  traced  in  fin 
;  dotting  on  the  sternum  ;  v.  i,  th 


nary  valves  do  not  close  simultaneously.  Usually,  however,  the  difference  in 
time  is  so  small  that  Iwih  valves  make  one  sound,  but  the  second  sound  may  be 
double  or  divided  when,  through  increase  of  the  difference  of  pressure  in  the 
aorta  and  pulmonary  artery,  the  interval  becomes  longer.     Even   in  health  this 


VARIATIONS    OF   THE    HEART   SOUNDS.  91 

may  be  the  case,  as  occurs  at  the  end  of  inspiration  or  the  beginning  of  expiration 
(v.  DuscJi). 

[The  second  sound  has  all  the  characters  of  a  valvular  sound.  That  the  aortic 
valves  are  concerned  in  its  production  is  proved  by  introducing  a  curved  wire 
through  the  left  carotid  artery  and  hooking  up  one  or  more  segments  of  the  valve, 
when  the  sound  is  modified,  and  it  may  disappear  or  be  replaced  by  an  abnormal 
sound  or  "murmur"  {Hope).  Again,  when  these  valves  are  diseased,  the  sound 
is  altered,  and  it  may  be  accompanied,  or  even  displaced,  by  murmurs.] 

Where  the  Sounds  are  Heard  Loudest. — The  sound  produced  by  the 
tricuspid  valve  is  heard  loudest  at  the  junction  of  the  lower  right  costal  cartilages 
with  the  sternum  ;  as  the  mitralvalve  lies  more  to  the  left  and  deeper  in  the  chest, 
and  is  covered  in  front  by  the  arterial  orifice,  the  mitral  sound  is  best  heard  at 
the  apex  beat,  or  immediately  above  it,  where  a  strip  of  the  left  ventricle  lies  next 
the  chest  wall.  [The  sound  is  conducted  to  the  part  nearest  the  ear  of  the  listener 
by  the  muscular  substance  of  the  heart.]  The  aortic  and  pulmonary  orifices  lie 
so  close  together  that  it  is  convenient  to  listen  for  the  second  {aortic^  sound  in 
the  direction  of  the  aorta,  where  it  comes  nearest  to  the  surface,  i.e.,  over  the 
second  right  costal  cartilage,  or  aortic  cartilage,  close  to  its  junction  with  the 
sternum.  The  sound,  although  produced  at  the  semilunar  valves,  is  carried 
upward  by  the  column  of  blood  and  by  the  walls  of  the  aorta.  The  sound  pro- 
duced by  the  pulmonary  artery  is  heard  most  distinctly  over  the  third  left  costal 
cartilage,  somewhat  to  the  left  and  external  to  the  margin  of  the  sternum  (Fig.  44). 

54.  VARIATIONS  OF  THE  HEART  SOUNDS.— .\n  increase  of  the  first  sound  of 
both  ventricles  indicates  a  more  energetic  contraction  of  the  ventricular  muscle  and  a  simultaneously 
gre.iter  and  more  sudden  tension  of  the  auriculo-ventricular  valves.  An  increase  of  the  secund 
sound  is  a  sign  of  increased  tension  in  the  interior  of  the  corresponding  large  arteries.  Hence, 
increase  of  the  second  (pulmonarj)  sound  indicates  overfilling  and  excessive  tension  in  the  pulmonarj' 
circuit. 

Feeble,  weak  action  of  the  heart,  as  well  as  abnormal  want  of  blood  in  the  heart,  causes  weak 
heart  sounds,  which  is  the  case  in  degenerations  of  the  heart  muscle. 

Irregularities  in  structure  of  the  individual  valves  may  cause  the  heart  sounds  to  become  "  impure.'" 
If  a  pathological  cavity,  filled  with  air,  be  so  placed,  and  of  such  a  form  as  to  act  as  a  resonator  to 
the  heart  sounds,  they  may  assume  a  "metallic"  character.  The  first  and  second  sounds  may  be 
"reduplicated"  or  [although  "duplication"  is  a  more  accurate  term  (£arr)'\  doubled.  The 
reduplication  of  the  first  sound  is  e.\plained  by  the  tension  of  the  tricuspid  and  that  of  the  mitral 
valves  not  occurring  simultaneously.  Sometimes  a  sound  is  produced  by  a  hypertrophied  auricle 
producing  an  audible  presystolic  sound,  i.e.,  a  sound  or  "murmur,"  preceding  the  first  sound. 
As  the  aortic  and  pulmonary  valves  do  not  close  quite  simultaneously,  a  reduplicated  second  sound 
is  only  an  increase  of  a  physiological  condition  [Landois).  All  conditions  which  cause  the  aortic 
valves  to  close  rapidly  (diminished  amount  of  blood  in  the  left  ventricle)  and  the  pulmonary  valves 
to  close  later  (congestion  of  the  right  ventricle — both  conditions  together  in  mitral  stenosis),  favor 
the  production  of  a  reduplicated  second  sound. 

Cardiac  Murmurs. — If  iriegularities  occur  in  the  valves,  either  in  cases  of  stenosis  or  in  in- 
sufficiency, so  that  the  blood  is  subjected  to  vibratory  oscillations  and  friction,  then,  instead  of  the 
heart  sounds,  other  sounds — murnnirs  or  bruits — arise  or  accompany  these.  A  combination  of  these 
sounds  is  always  accompanied  by  disturbances  of  the  circulation.  [These  murmurs  may  be  produced 
within  the  heart  when  they  are  termed  endocardial,  or  outside  it  when  they  are  called  exocardial 
murmurs.  But  other  murmurs  are  due  to  changes  in  the  quality  or  amount  of  the  blood,  when  they 
are  spoken  of  as  haemic  murmurs.  In  the  study  of  all  murmurs,  note  their  rhythm  or  exact  relation 
to  the  normal  sounds,  their  point  of  ma.ximum  intensity  and  the  direction  in  which  the  murmur  is 
propagated.'\  It  is  rare  that  tumors  or  other  deposits  projecting  into  the  ventricles  cause  murmur<, 
unless  there  be  present  at  the  same  time  lesions  of  the  valves  and  disturbances  of  the  circulation. 
The  cardiac  murmurs  or  bruits  are  always  related  to  the  systole  or  diastole,  and  usually  the  systolic 
are  more  accentuated  and  louder.  Sometimes  they  are  so  loud  that  the  thora.x  trembles  under  their 
irregular  oscillations  (fremitus,  fr^missement  cataire). 

In  cases  where  diastolic  murmurs  are  heard  there  are  alvvavs  anatomical  changes  in  the  cardiac 
mechanism.  These  are  insufficiency  of  the  arterial  valves,  or  stenosis  of  the  auriculo-ventricular 
orifices  (usually  the  left).  Systolic  murmurs  do  not  always  necessitate  a  disturbance  in  the  cardiac 
mechanism.  They  may  occur  on  the  left  side,  owing  to  insufficiency  of  the  mitral  valve,  stenosis  of 
the  aorta,  and  in  calcification  and  dilatation  of  the  ascending  part  of  the  aoita.  These  murmurs 
occur  very  much  less  frequently  on  the  right  side,  and  are  due  to  insufficiency  of  the  tricuspid  and 
stenosis  of  the  pulmonary  orifice. 


92  PHYSICAL   EXAMINATION    OF   THE    HEART. 

Functional  Murmurs. — Systolic  murmurs  of'en  occur  without  any  valvular  lesion,  although 
they  are  always  less  loud,  and  are  caused  by  abnormal  vibrations  of  the  valves  or  arterial  walls. 
They  occur  most  frequently  at  the  orifice  of  the  pulmonary  artery  [and  are  generally  heard  at  the 
base],  less  frequently  at  the  mitral,  and  still  le-^s  frequently  at  the  aortic  or  the  tricuspid  orifice. 
Amemia.  general  malnutrition,  acute  febrile  affections,  are  the  causes  of  these  murmurs.  [Some  of 
these  are  due  to  an  altered  condition  of  the  blood,  and  are  called  iiamic,  and  others  to  defective 
cardiac  muscular  nutrition  and  are  called  dynamic  (  ]Vtihhe)'\. 

Sounds  may  also  occur  during  a  certain  stage  of  inflammation  of  the  pericardium  (pericarditis) 
from  the  roughened  surfaces  of  this  membrane  rubbing  upon  each  other.  Audible  friction  sounds 
are  thus  produced,  and  the  vibration  may  even  be  perceptible  to  touch.  [These  are  "  friction 
sounds,"  and  quite  distinct  from  sounds  produced  within  the  heart  itself.] 

55.  DURATION  OF  THE  MOVEMENTS  OF  THE  HEART.— 

That  the  heart  continues  to  beat  for  some  time  after  it  is  cut  out  of  the  body,  was 
known  to  Cleanthes,  a  contemporary  of  Herophilus,  300  B.C.  The  movement 
lasts  longer  in  cold-blooded  animals  (frog,  turtle,  fish) — extending  even  to  days — 
than  in  mammals.  .\  rabbit's  heart  beats  from  3  minutes  up  to  36  minutes  after 
it  is  cut  out  of  the  body.  The  average  of  many  experiments  is  about  11  minutes. 
Panum  found  the  last  trace  of  contraction  to  occur  in  the  right  auricle  (rabbit) 
15  hours  after  death;  in  a  mouse's  heart,  46  hours;  in  a  dog's,  96  hours.  An 
excised  frog's  heart  beats,  at  the  longest,  234  days  (  Valentin).  In  a  human 
embryo  (third  month)  the  heart  was  found  beating  after  4  hours.  In  this  con- 
dition stimulation  causes  an  increase  and  acceleration  of  the  action.  .Afterward, 
the  ventricular  contraction  first  becomes  weaker,  and  soon  each  auricular  con- 
traction is  not  followed  by  a  ventricular  contraction,  two  or  more  of  the  former 
being  succeeded  by  only  one  of  the  latter.  .\t  the  same  time  the  ventricles 
contract  more  slowly  (Fig.  39),  and  soon  stop  altogether,  while  the  auricles  still 
continue  to  beat.  If  the  ventricles  be  stimulated  directly,  as  by  pricking  them 
with  a  pin,  they  may  execute  a  contraction.  The  left  auricle  soon  ceases  to  beat, 
while  the  right  auricle  still  continues  to  contract.  The  right  auricular  appendix 
continues  to  beat  longest,  as  was  observed  by  Galen  and  Cardanus  (1550).  The 
term  "ultimum  moriens  "  is  applied  to  it.  Similar  observations  have  been  made 
upon  the  hearts  of  persons  who  have  been  executed. 

If  the  heart  has  ceased  to  beat,  it  may  be  excited  to  contract  for  a  short  tirne 
by  direct  stimulation  {Hai-oey),  more  especially  by  heat ;  even  under  these  cir- 
cumstances the  auricles  and  their  appendices  are  the  last  parts  to  cease  contracting. 
As  a  general  rule,  direct  stimulation,  although  it  may  cause  the  heart  to  act  more 
vigorously  for  a  short  time,  brings  it  to  rest  sooner.  In  such  cases,  therefore,  the 
regular  sequence  of  events  ceases,  and  there  is  usually  a  twitching  movement  of 
the  muscular  fibres  of  the  heart.  C.  Ludwig  found  that,  even  after  the  excitability 
is  extinguished  in  the  mammalian  heart,  it  may  be  restored  by  injecting  arterial 
blood  into  the  coronary  arteries  :  lesion  of  these  vessels  is  followed  by  enfeebled 
action  of  the  heart  (§  47).  Hammer  found  that  in  a  man  whose  left  coronary 
artery  was  plugged,  the  pulse  fell  from  So  to  8  beats  per  minute. 

Action  of  Gases  on  the  Heart. — During  its  activity  the  heart  uses  O,  and  produces  CO,  so 
that  it  beats  longest  in  pure  O  (I2  hours)  (Castell),  and  not  so  long  in  N, — H  (l  hour)— COj  (lO 
minutes),  =C0  (42  minutes)— CI  (2  minutes),  or  in  a  vacuum  (20  to  30  minutes)  (Boyle,  ibyo: 
Fontana.  Tiedemann.  1847),  even  when  there  is  watery  vapor  present  to  prevent  evaporation.  If 
the  heart  be  reintroduced  into  O  it  begins  to  beat  again.  [A  frog's  heart  ceases  to  beat  in  compressed 
O  (10-12  atmo'-pheres)  in  about  one -third  of  the  time  it  would  do  were  it  simply  excised  and  left  to 
itself  (A'.  B.  Lehntann).  An  excised  heirt  suspended  in  ordinary  air  beats  three  to  four  times  as 
long  as  a  heart  which  is  placed  upon  a  glass  plate.]  A  heart  which  has  ceased  to  contract  sponta- 
neously may  contract  when  an  electrical  stimulus  is  applied  to  it,  but  it  does  not  do  so  for  a  longer 
time  than  other  muscles  (Budge). 

[56.  PHYSICAL  EXAMINATION  OF  THE  HEART.]— [The 
physical  methods  of  diagnosis  enable  us  to  obtain  precise  knowledge  regarding  the 
actual  state  of  the  heart.     The  methods  available  are  :  — 


THE    CARDIAC    NERVES.  93 

1.  Inspection.  I  3.   Percussion. 

2.  Palpation.  |  4.  Auscultation. 
To  arrive  at  a  correct  diagnosis  all  the  methods  must  be  employed.] 

[Inspection. — The  person  is  supposed  to  have  his  chest  e.\posed  and  to  be  in  the  recumbent  posi- 
lion.  It  is  important  to  remember  the  limits  of  the  heart.  The  base  corresponds  to  a  line  joining 
the  upper  margins  of  the  third  costal  cartilages,  the  apex  to  the  fifth  interspace,  while  transversely  it 
extends  from  a  little  to  the  right  of  the  sternum  to  within  a  little  of  the  left  nipple ;  this  area  occu- 
pied by  the  heart  being  called  the  deep  cardiac  region.  Hy  the  eye  we  can  dttect  any  alteration 
in  the  configuration  of  the  prjecordia,  bulging  or  retraction  of  the  region  as  a  whole  or  of  the  inter- 
costal spaces,  and  we  may  detect  variations  in  the  position,  character,  extent  of  the  cardiac  impulse, 
or  the  presence  of  other  visible  pulsations.] 

[Palpation. — By  placing  the  whole  hand  flat  upon  the  pra;cordia,  we  can  ascertain  the  presence 
or  absence,  the  situation  and  e.xlent,  and  any  alterations  in  the  characters  of  the  apex  beat  ;  or  we 
may  detect  the  existence  of  abnormal  pulsations,  vibrations,  thrills,  or  friction  in  this  region.  In 
feeling  for  the  apex  beat,  if  it  be  at  all  feeble,  it  is  well  to  make  the  patient  lean  forward.  Of 
course,  it  must  be  remembered  that  the  whole  heart  may  be  displaced  by  tumors  or  accumulations  of 
fluids  pressing  upon  it,  i.  e.,  conditions  external  to  itself,  or  the  apex  beat  may  be  displaced  from 
causes  within  the  heart  itself,  as  in  hypertrophy  of  the  left  ventricle.] 

[Percussion. — As  the  heart  is  a  solid  organ,  and  is  surrounded  hy  the  lungs,  which  contain  air, 
it  is  evident  that  the  sound  emitted  by  striking  the  chest  over  the  region  of  the  former  must  be  dif- 
ferent from  that  produced  over  the  latter.  Not  only  is  there  a  difference  in  the  sound  or  note  emitted, 
but  the  "  sensation  of  resistance  "  which  one  leels  on  percussing  the  two  organs  is  different.  We  may 
ascertain — 

1.  The  superficial  or  absolute  cardiac  dullne.ss. 

2.  The  deep  or  relative  dullness.] 

[Superficial  Cardiac  Dullness. — This,  theoretically,  is  the  part  of  the  heart  in  direct  contact 
with  the  chest  wall  and  uncovered  by  lung,  but  obviously  as  the  lungs  vary  in  size  duiing  respiration, 
it  must  be  smaller  during  inspiration  and  larger  during  expiration.  It  forms  a  roughly  triangular 
space,  whose  base  cannot  be  accurately  determined,  as  the  heart  dullness  merges  into  that  of  the 
liver,  situate  below  it,  but  it  corresponds  to  a  horizontal  line  2j4  inches  long,  extending  from  the 
apex  beat  to  the  middle  of  the  sternum.  The  internal  side  corresponding  to  the  left  edge  of  the 
sternum  is  2  inches  long,  and  reaches  from  the  junction  of  the  fourth  costal  cartilage  with  the  ster- 
num— apex  of  the  triangle — to  the  sternal  end  of  the  base  line.  'I  he  superior,  outer,  or  oblique  line, 
3  inches  in  length,  is  somewhat  curbed,  and  passes  downward  and  outward  from  the  apex  of  the 
triangle  to  the  apex  of  the  heart.] 

[Deep  Cardiac  Dullness. — By  this  method  theoretically  we  seek  to  define  the  exact  limits  of 
the  heart  as  a  whole,  and  thui  to  ascertain  its  absolute  size,  and  ol  course,  percussion  has  to  be  done 
through  a  certain  thickness  of  lung  tissue,  and  hence  one  must  strike  the  pleximeter  forcibly.  It 
extends  vertically  from  the  third  rib  and  ends  at  the  sixth,  but  owing  to  the  cardiac  merging  in  the 
hepatic  dullness,  this  lower  limit  cannot  be  accurately  ascertained  ;  while  transversely  at  the  fourth 
rib  it  extends  from  just  within  the  nipple  line  to  slightly  beyond  the  right  of  the  sternum.] 

[By  these  means  we  may  detect  increase  in  the  size  of  the  heart  or  alterations  in  the  relation  of  the 
lungs  to  the  heart,  fluid  in  pericardium,  etc.] 

[Auscultation. — This  is  one  of  the  most  valuable  methods,  for  by  it  we  can  detect  variations  and 
modifications  in  the  healthy  sounds  of  the  heart,  the  rhythm  and  frequency  of  the  heart  heat,  the 
existence  of  abnormal  sounds,  and  their  exact  relation  to  the  normal  sounds,  also  their  characteis 
and  relation  to  the  cardiac  cycle,  and  the  direction  in  which  these  sounds  are  propagated  [\  54).] 

57.  INNERVATION  OF  THE  HEART,  CARDIAC  NERVES. 

— [Intra-  and  Extra-Cardiac  Nervous  Mechanism. — When  the  heart  is 
removed  from  the  body,  or  when  all  the  nerves  which  pass  to  it  are  divided,  it 
still  beats  for  some  time,  so  that  its  movements  must  depend  upon  some  mechan- 
ism situated  within  itself.  The  ordinary  rhythmical  movements  of  the  heart  are 
undoubtedly  associated  loiih  the  presence  of  nerve  ganglia,  which  exist  in  the 
substance  of  the  heart — the  intra-cardiac  ganglia.  But  the  movements  of  the  heart 
are  influenced  by  nervous  impulses  which  reach  it  from  without,  so  that  there  falls 
to  be  studied  an  intra-cardiac  and  an  extra-cardiac  nervous  mechanism.] 

The  cardiac  plexus  is  composed  of  the  following  nerves  :  (i)  The  cardiac 
branches  of  the  vagus,  the  branch  of  the  same  name  from  the  external  branch  of 
the  superior  laryngeal,  a  branch  from  the  inferior  laryngeal,  and  sometimes 
branches  from  the  pulmonary  plexus  of  the  vagus  (more  numerous  on  the  right 
side)  ;  (2)  the  superior,  middle,  inferior,  and  lowest  cardiac  branches  of  the  three 
cervical  ganglia  and  the  first  thoracic  ganglia  of  the  sympathetic ;  (3)  the  incon- 


94 


THE    FROG  S    HEART. 


stant  twig  of  the  descending  branch  of  the  hypoglossal  nerve,  which,  according  to 
Luschka,  arises  from  the  upper  cervical  ganglia.  From  the  plexus  there  proceed 
— the  deep  and  the  supei-ficial  nerves  (the  latter  usually  at  the  division  of  the  pul- 
monary artery  under  the  arch  of  the  aorta,  and  containing  a  ganglion)  (§  370). 
The  following  nerves  may  be  separately  traced  from  the  plexus  : — 

((z)  The  plexus  coronarius  dexter  and  sinister  {Searpa),  which  contains 
the  vasomotor  iien<es  for  these  vessels  (physiological  proof  still  wanting)  as  well  as 
the  nerves  (sensory?)  proceeding  from  them  (to  the  pericardium?). 

(/')  Intra-Cardiac  Nerves  and  Ganglia. — The  nerves  lying  in  the  ^■•rwrrj 
of  the  heart  ix\A  in  its  substanee,  containing  numerous  ganglia  {^Remak),  which  are 
regarded  as  the  automatic  motor  centres  of  the  heart.  A  nervous  ring  containing 
numerous  ganglia  corresponds  to  the  margin  of  the  septum  atriorum ;  there  is 
another  in  the  auriculo-ventricular  groove.  Where  the  two  meet,  they  exchange 
fibres.  The  ganglia  usually  lie  near  the  pericardium.  In  mammals  the  two 
largest  ganglia  lie  near  the  orifice  of  the  superior  vena  cava — va.  birds  the  largest 
ganglion  (containing  thousands  of  ganglionic  cells)  lies  posteriorly  where  the  longi- 
tudinal and  transverse  sulci  cross  each  other.  Fine  branches,  also  provided  with 
small  ganglia,  proceed  from  these  ganglia,  and  penetrate  the  muscular  walls  of  the 
auricles  and  ventricles. 


Fig.  46. 


Heart  of  frog  from  the  front.     V,  single 
and  left  auricles  :  B,  bulbus  arterio«u 
and  3,  pulmo-cutaiieous  arteries  ;  C, 


,Ie ;  Ad,  As,  right  Heart  of  frog  from  behind,   s.i'. ,  si 

carotid,  z,  aorta,  opened;    ci,  inferior:    csd,  ess,  right  and 

Id  gland  {£cker).  left  superior  vens  cavse;  Z'/*.,  pulmonary 

vein  ;  Ad,  and  As,  right  and  left  auricles  ; 

Ap,  communication  between  the  right  and 

left  auricle  i,Ecier). 


[Frog's  Heart. — The  frog"s  heart  consists  of  the  sinus  venosiis,  into  whicli  open  the  single 
inferior  and  the  two  superior  vena;  cava-  (Fig.  46).  There  are  t~uv  nurir/c-s;  the  right  one  commu- 
nicates with  the  sinus  venosus,  and  opens  into  the  single  ventricle ;  the  left  auricle  also  opens  into  the 
single  venlricle  (Fig.  45,  f),  and  in  the  latter  are  mixed  the  venous  blood  returned  by  the  right 
auricle  and  the  arterial  blood  from  the  left  auricle.  The  aorta  with  its  biilhtts  arteiiostts  conducts 
the  blood  from  the  ventricle  (Figs.  46,  49<7).  The  various  orifices  are  guarded  by  projections  of 
tissue,  which  act  like  valves.  The  two  auricles  are  completely  separated  by  a  septum.  This  septum 
ends  posteriorly  in  a  free  concave  margin  (Fig.  49),  so  as  to  divide  the  auriculo-ventricular  orifice 
into  a  right  and  a  left  orifice.     Each  orifice  is  guarded  by  two  thick,  fleshy  valves,  which  close  it.] 

[Nerves. — The  two  cardiac  branches  of  the  vagi — the  nervi  cardiaci — proceed  to  the  poste- 
rior surface  of  the  sinus  venosus,  and  where  the  latter  joins  the  auricle  they  interlace,  and  are  mi.\ed 
with  a  number  of  ganglion  cells  (Figs.  47,  49«).  This  spot  is  called  Remak's  ganglion,  is  some- 
times single,  at  others  double,  and  it  can  be  seen  as  a  white  "  crescent  "  when  the  heart  is  lifted  up 
and  looked  at  from  behind  (Fig.  46).  The  cardiac  nerves  proceed  downward  on  the  auricular 
septum,  exchanging  fibres  in  their  course  to  join  two  ganglia  at  the  aunculo-ventricular  groove, 
and  known  as  Bidder's  Ganglia  (Figs.  47,  4912.  It  has  lieen  stated  by  one  observer  that  the 
bulbus  arteriosus  contains  ganglionic  cells,  but  this  is  denied  by  others.] 

According  to  Openchowsky,  every  part  of  the  heart  (frog,  trilon,  tortoise)  contains  nerve  fibres 
which  are  connected  with  every  muscular  fibre.  In  the  auricles,  at  the  end  of  the  non-medullated 
fibre,  a  tri-radiate  nucleus  exists  which  gives  off  fibrils  to  the  muscular  bundles. 

There  is  a  network  of  fine  nerve  fibres  distributed  immediately  under  the  endocardium ;  these 
fibres  act  partly  in  a  centripetal  direction  on  the  cardiac  ganglia,  and  are  partly  motor  for  the  endo- 
cardial muscles.     The  parietal  layer  of  the  pericardium  contains  (sensory)  nerve  fibres.     The  fol- 


MOTOR  CENTRES  OF  THE  HEART. 


95 


lowing  kinds  of  nerve  cells  are  found — unipolar  cells,  the  single  processes  of  which  afterward  divide ; 
bipolar  pyriform  cells  (Fig.  48),  which  in  the  frog  possess  a  straight  («)  and  usually,  also,  a  spiral 
process  (o). 

58.  THE  AUTOMATIC  MOTOR  CENTRES  OF  THE  HEART. 

— (i)  We  must  assume  that  the  nervous  centres  which  excite    tlie   cardiac   movc- 


Fic.  47. 


Fir,.  48. 


Auricular  septum  oi  a  frog's  heart,  a,  anterior,  and/,  poste- 
rior branch  of  the  cardiac  vagus  :  B,  Bidder's  ganglion 
(Ecker). 


Pyriform  ganglionic  bi-poiar  nerve-cell 
from  the  heart  of  afrog  m,  sheath; 
H,  straight  process;  o,  spiral  pro- 


ments,  and  maintain   the  rhythm  of  these  movements,  lie  within  the  heart,  and 
that  they  are,  probably,  represented  by  the  ganglia. 

(2)  There  are — not  one,  but  several  of  these  centres  in  the  heart,  which  are 
connected  with  each  other  by  conducting  paths.  As  long  as  the  heart  is  intact, 
all  its  parts  are  made  to  move  in  rhythmical  sequence  from  a  principal  central 
point,  an  impulse  being  conducted  from  this  centre  through  the  conducting  paths 


Fin.  49 
1''     u 


'm:,) 


Fig.  49(7. 


Longitudinal  section  o(  frog's  heart :  left  side  sho 


monary  vein,  with  a 
auricle;  v,  ventricle 
right  auricle  into  vei 
cardiac  nerves. 


sound,/',  projecting  into  Icf 
;  c,  c',  sound  projecting  fronr 
tricle;    «.  upper,  and  «     lowe 


Scheme  ot  nerves  of  frog's  heart.      ] 
and  B,  Bidder's  ganglia:  S.  V.,si 
A,  auricles:  V,  ventricle;   B.  A.,  bulbus  arte- 
riosus; va^.  vagi  (after  Brunton), 


(Donders),  What  the  ''discharging  forces"  of  these  regular  progressive  move- 
ments are  is  unknown.  If,  however,  the  heart  be  subjected  to  the  action  of  diffuse 
stimuli  {e.g. J  strong  electrical  currents),  all  the  centres  are  thrown  into  action, 
and  a  spasm-like  action  of  the  heart  occurs.  The  dominating  centre  lies  in  the 
auricles^  hence  the  regular  progressive  movement  usually  starts  from  them.      If  the 


96  EXPERIMENTS   ON    THE    HEART. 

excitability  is  diminished  (^-g-,  by  touching  the  septum  with  opium — Ludwig, 
Hoffd),  other  centres  seem  to  undertake  this  function,  in  which  case  the  move- 
ment may  extend  from  the  ventricles  to  the  auricles.  If  a  heart  be  cut  into 
pieces,  so  that  the  individual  pieces  still  remain  connected  with  each  other,  the 
regular  peristaltic  or  wave-like  movements  proceeding  from  the  auricles  to  the 
ventricle  may  continue  for  a  long  time  {Danders,  Engelmann).  If  the  heart, 
however,  be  completely  divided  into  two  distinct  pieces  (auricle  and  ventricle), 
the  movements  of  both  parts  continue,  but  not  in  the  same  sequence — they  beat 
at  different  rates.  According  to  Kronecker  and  Schniey,  in  the  dorj  s  heart  there 
is  a  spot  above  the  lower  limit  of  the  upper  third  of  the  ventricular  septum  which, 
when  it  is  injured,  brings  the  heart  to  a  standstill ;  this  has  been  called  a  coordi- 
nating centre. 

(3)  All  stimuli  of  moderate  strength  applied  directly  to  the  heart  cause  at  first 
an  ui crease  of  the  rhythmical  heart  beats;  stronger  stimuli  cause  a  diminution, 
and  it  may  be  paralysis,  which  is  often  preceded  by  a  convulsive  movement. 
Increased  activity  exhausts  the  energy  of  the  heart  sooner. 

(4)  The  auricular  centres  seem  to  be  more  excitable  than  those  of  the  ventricle  ; 
hence,  in  a  heart  left  to  itself  the  auricles  pulsate  longest. 

(5)  The  heart  may  be  excited  (reflexly)  from  its  inner  surface.  Weak  stimuli 
applied  to  the  inner  surface  of  the  heart  greatly  accelerate  the  heart's  action,  the 
stimulus  required  being  much  feebler  than  that  applied  to  the  external  surface  of 
the  heart.  Strong  stimuli,  which  bring  the  heart  to  rest,  also  act  more  easily 
when  applied  to  the  inner  surface  than  when  they  are  applied  to  its  outer  surface 
{Henry,  1832).     The  ventricle  is  always  the  part  first  to  be  paralyzed. 

(6)  In  order  that  the  heart  may  continue  to  contract,  it  is  necessary  that  it  be 
supplied  with  a  fluid  which,  in  addition  to  O  {Liuhvig,  Volkmann,  Goltz),  must 
contain  the  necessary  nutritive  materials.  The  most  perfect  fluid,  of  course,  is 
blood.  Hence,  the  heart,  after  a  time,  ceases  to  beat  in  an  indifferent  fluid  (0.6 
per  cent,  sodium  chloride),  but  its  activity  may  be  revived  by  supplying  it  with  a 
proper  nutritive  fluid. 

Cardiac  Nutritive  Fluids. — These  nutritive  fluids  are  such  as  contain  seium  albumin,  e.g.,  blood, 
serum  or  lymph.  Serum  retains  its  nutritive  properties  even  after  it  has  been  subjected  to  diffusion 
(Martins  and  Kronecker).  Milk  and  whey  (v.  Otl),  normal  saline  solution  (0.6  per  cent.  NaCl) 
mixed  with  blood,  albumin  or  peptone  and  0.3  per  cent,  sodium  carbonate  {Kroneelier,  Meruno- 
-uiicz  and  Stihioii)  a  trace  of  caustic  soda  (  Gaiiie),  or  a  solution  of  the  salts  of  serum,  are  suitable. 
Alkaline  solution  of  soda  revives  a  feebly  beating  heart  by  neutralizing  the  acid  formed  in  the 
cardiac  muscle  {S.  Ringer). 

(7)  The  independent  pulsations  of  parts  of  the  heart  which  are  devoid  of  ganglia 
show  that  the  presence  of  ganglia  is  not  absolutely  necessary  in  order  to  have 
rhythmical  pulsation.  Direct  stimulation  of  the  heart  may  cause  these  movements. 
But  the  ganglia  are  more  excitable  than  the  heart  muscle  itself,  and  they  conduct 
the  impulses  which  lead  to  the  regular  alternating  action  of  the  various  parts  of 
the  heart,  so  that  under  normal  circumstances  we  must  assume  that  the  action  of 
the  heart  is  governed  by  the  ganglia. 

The  chief  experiments  upon  which  the  above  statements  are  based  consist  of 
two  classes:    (i)  Where  the   heart   is   incised  or  divided;   and  (2)  where  it  is 

STIMULATED    DIRECTLY. 

(I)  Experiments  by  cutting  and  ligaturing  the  heart.  These  experiments 
have  been  made  chiefly  upon  the  heart  of  the  frog. 

The  Ligature  experiments  are  performed  by  tightening  and  then  relaxing  a 
ligature  placed  around  the  heart,  so  that  the  physiological  connection  is  destroyed, 
while  the  anatomical  or  mechanical  connections  (continuity  of  the  cardiac  wall, 
intact  condition  of  its  cavities)  still  exist.  The  most  important  of  these  experi- 
ments are — 

(I)  Stannius's  Experiment. — If  the  sinus  venosus  of  a  frog's  heart  be 
separated  from  the  auricles,  either  by  an  incision  or  by  a  ligature,  the  auricles  and 


SECTION    OF   THE    HEART.  97 

ventricle  stand  still  in  diastole,  while  the  veins  and  the  remainder  of  the  sinus 
continue  to  beat  (Fig.  50,  i).  If  a  second  incision  be  made  at  the  auriculo- 
ventricular  groove,  as  a  rule,  the  ventricle  begins  at  once  to  beat  again,  while  the 
auricles  remain  in  the  condition  of  diastolic  rest.  [Thus,  the  sinus  venosus  and 
ventricle  continue  to  beat,  while  the  auricle  stands  still,  but  the  two  former  no 
longer  beat  with  the  same  rhythm  ;  the  ventricle  usually  beats  more  slowly,  as  is 
shown  in  Fig.  50,  2,  by  the  large  zig-zags.]  According  to  the  position  of  the 
second  ligature  or  incision,  the  auricles  may  also  beat  along  with  the  ventricles, 
or  the  auricles  alone  may  beat,  while  the  ventricles  remain  at  rest  (1852). 

Theoretical. — Various  explanations  of  these  experiments  have  been  given:  (a)  Remak's  gan- 
glion in  the  sinus  venosus  is  distinguished  by  its  great  excitability,  while  Bidder's  ganglion  in  the 
auriculo-ventricular  groove  is  less  excitable  ;  in  the  normal  condition  of  the  heart  the  motor  impulse 
is  carried  from  the  former  to  the  latter.  If  the  sinus  venosus  be  separated  from  the  heart.  Remak's 
ganglion  has  no  action  on  the  heart.  The  heart  stops,  for  two  reasons — first,  because  Bidder's  gan- 
glion  alone  has  not  sufficient  energy  to  excite  it  to  action,  and  because  the  inhibitory  fibres  of  the 
vagus  going  to  the  heart  have  been  stimulated  by  being  divided  at  this  point  [Beiden/iain).  [That 
stimulation  of  the  inhibitory  fibres  of  the  vagus  is  not  the 
cause  of  the  standstill,  is  proved  by  the  fact  that  the  stand- 
still occurs  even  after  the  administration  of  atropine,  which 
paralyzes  the  cardiac  inhibitory  mechanism.]  The  passive 
heart,  however,  may  be  made  to  contract  by  mechanically 
stimulating  Bidder's  ganglion,  <?.  g.,  by  a  slight  prick  with  a 
needle  in  the  auriculo-ventricular  groove  (H.  Munk"),  or  by 
the  action  of  a  constant  current  of  moderate  strength  (Eck- 
/larj),  the  ventricular  pulsation  at  the  same  time  preceding 
the  auricular  (-/.  Bezold,  Bernstein).  If  the  auriculo-ven-  Stanmus's  experiment.  Scncme after  5r»>i- 
tricular  groove   be   divided,   the   ventricle   pulsates   again,  '<"<■     A,  ^"'■''=''=- .^'  ventr.,  SV    sinus 

because  Bidder's  ganglion  has  been  stimulated  by  the  act  of  whlch'parts  mnt!n^"t^  b'e°aT:  in  J^he 

dividing  it;  while,  at  the  same  time,  the  ventricle  is  with-  ventricle  beats  at  a  different  rate, 

drawn  from  the  inhibitory  influence  of  the  vagus  produced 

by  the  first  division  at  the  sinus  venosus.  If  the  line  of  separation  is  so  made  that  Bidder's  gan- 
glion remains  attached  to  the  auricles,  these  pulsate,  and  the  ventricle  rests;  if  it  be  divided  into 
halves,  the  auricles  and  ventricles  pulsate,  each  half  being  excited  by  the  portion  of  the  ganglion  in 
relation  with  it.  {b)  According  to  another  view,  both  Remak's  (a)  and  Bidder's  ganglia  [b]  are 
motor  centres,  but  in  the  auricles  there  is  m  addition  an  inhibitory  ganglionic  system  (c)  (Bezold, 
Traube).  Under  normal  circumstances  <;  +  (5  is  stronger  than  c,  while  c  is  stronger  than  a  ox  b 
separately.  If  the  sinus  venosus  be  separated  it  beats  in  virtue  of  a ;  on  the  other  hand,  the  heart 
rests  because  c  is  stronger  than  b.  If  the  section  be  made  at  the  level  of  the  auriculo  ventricular 
groove,  the  auricles  stand  still,  owing  to  c,  while  the  ventricle  beats,  owing  to  b. 

(2)  If  the  ventricle  of  a  frog's  heart  be  separated  from  the  rest  of  the  heart  by 
means  of  a  ligature,  or  by  an  incision  carried  through  it  at  the  level  of  the 
auriculo-ventricular  groove,  the  sinus  and  atria  pulsate  undisturbed  as  before 
lyDescartes,  1644),  but  the  ventricle  stands  still  in  diastole.  Local  stimulation  of 
the  ventricle  causes  a  single  contraction.  If  the  incision  be  so  made  that  the 
lower  margin  of  the  auricular  septum  reinains  attached  to  the  ventricle,  the  latter 
pulsates  {Roseiiberger,  i8jO).  Even  the  ventricles  of  a  rabbit's  heart,  when 
separated  with  a  part  of  the  auricles  in  connection  with  them,  pulsate  (^Tigerstedt). 

[Gaskell's  Clamp. — Gaskell  uses  a  clamp,  regulated  by  a  millimetre  screw,  to  compress  the  heart, 
and  thus  to  obstruct  the  passage  of  impulses  from  one  part  of  the  heart  to  the  other,  or  to  "  block  " 
the  way,  the  pulsations  of  the  auricles  and  ventricles  being  separately  registered,  as  described  at  p. 
loi.  By  compressing  the  heart  at  the  auriculo-ventricular  groove,  the  ratio  of  auricular  and  ven- 
tricular beats  alters,  and  instead  of  being  I  :  I,  there  may  be  2,  3,  or  more  auricular  beats  for  each 


beat  of  the  ventricle,  expressed  thus : —  -.  -.  — ,  — •  I 


{3)  Section  of  the  Heart. — Engelmann's  recent  experiments  show  that  if 
the  ventricle  of  a  frog's  heart  be  cut  up  into  two  or  more  strips  in  a  zig-zag  way, 
so  that  the  individual  parts  still  remain  connected  with  each  other  by  muscular 
tissue,  the  strips  still  beat  in  a  regularly  progressive,  rhythmical  manner,  provided 
one  strip  is  caused  to  contract.  The  rapidity  of  the  transmission  is  about  10  to 
30  mm.  per  sec.  {Enge/manii).  Hence,  it  appears  that  the  conducting  paths  for 
7 


98 


ACTION    OF    FLUIDS   ON    THE    HEART. 


the  impulse  causing  the  contraction  are  not  nervous,  but  must  be  the  contractile 
mass  itself.  It  has  not  been  proved  that  nerve  fibres  proceed  from  the  ganglia  to 
all  the  muscles. 

[According  to  Marchand's  experiments,  it  takes  a  very  long  time  for  the  excitement  to  pass  from 
the  auricles  to  the  ventricle — a  much  longer  time,  in  fact,  than  it  would  require  to  conduct  the 
excitement  through  muscle — so  that  it  is  probable  that  the  propagation  of  the  impulse  from  the 
auricles  to  the  ventricle  is  conducted  by  nervous  channels  to  the  auriculo-ventricular  nervous  appa- 
ratus. In  fact,  in  the  mammalian  heart  the  muscular  fibres  of  the  auricles  are  quite  distinct  from 
those  of  the  ventricle.] 

(4)  It  is  usually  stated  that  when  the  apex  of  a  frog's  heart  is  severed  from  the 
rest  of  the  heart,  it  no  longer  pulsates  {Ha'denhaui,  Goltz),  but  such  an  ape.x,  if 
stimulated  mechanically,  responds  with  a  single  contraction. 

Action  of  Fluids  on  the  Heart. — Haller  was  of  opinion  that  the  venous 
blood  was  the  natural  stimulus  which  caused  the  heart  to  contract.  That  this  is 
not  so,  is  proved  at  once  by  the  fact  that  the  heart  beats  rhythmically  when  it 
contains  no  blood. 


Fig.  51. 


Fir,.  52. 


Scheme  of  a  frog  manometer,  a,  h,  Mari- 
otte's  flasks  for  the  nutrient  fluids ;  s, 
stop-cock :  c,  cannula  :  m,  manometer ; 
h,  heart ;  d,  glass  cup  for  h :  e,  e',  elec- 
trodes; cyl,  revolving  cylinder. 


Double-way  or  perfusion  cannula  (nat.  size) 
for  a  frog's  heart,  c,  for  fixing  an  elec- 
trode ;  li,  the  heart  is  tied  over  the 
flanges ,  preventing  it  from  slipping  out ; 
e,  section  oft/. 


Blood  and  other  fluids  which  are  supplied  to  an  excised  heart  are  not  the  cause 
of  its  rhythmical  movements,  but  only  the  conditions  on  which  these  movements 
depend.  Thus,  a  heart  which  is  too  feeble  to  contract  may  be  made  to  do  so  by 
supplying  it  with  a  fluid  containing  proteids,  when  a  latent  intra-cardiac  mechan- 
ism is  brought  into  action,  the  albuminous  or  other  fluid  merely  supplying  the 
pabulum  for  the  excitable  elements. 

[Methods. — The  study  of  the  action  of  fluids  upon  the  excised  frog's  heart  has  been  rendered 
possible  by  the  invention  of  Ludwig's  "  frog  manometer."  The  apparatus  has  been  improved 
by  Ludwig's  pupils,  and  already  numerous  important  results  have  been  obtained.  The  apparatus 
(Fig.  51)  consists  of  ( i)  a  double-way  cannula,  <-,  which  is  tied  into  the  heart,  k  ;  (2)  a  manometer, 
m,  connected  with  c,  and  registering  the  movements  of  its  mercury  on  a  revolving  cylinder,  <■_>■/,■ 
(3)  two  Mariotte's  flasks,  a  and  i,  which  are  connected  with  the  other  limb  of  the  cannula.  Either 
a  oT  h  can  be  placed  in  communication  with  the  interior  of  the  heart  by  means  of  the  stop-cock,  s. 
The  fluid  in  one  graduated  tube  may  be  poisoned,  and  the  other  not ;  <^  is  a  glass  vessel  for  fluid,  in 
which  the  heart  pulsates,  e'  and  e  are  electrodes,  e  is  inserted  into  the  fluid  in  d,  e'  is  attached  to  the 
German  silver  cannula  which  is  shown  in  Fig.  52.] 

[In  the  tonometer  of  Roy  (Fig.  53)  the  ventricle,  h,  or  the  whole  heart,  is  placed  in  an  air-tight 


ACTION   OF    FLUIDS   ON   THE    HEART. 


99 


chamber,  o,  filled  with  oil,  or  with  oil  and  normal  saline  folution.  As  before,  a  "  perfusion  "  cannula 
is  tied  into  the  heart.  A  piston.  y>,  works  up  and  down  in  a  cylinder,  and  is  adjusted  by  means  of  a 
thin  flexible  animal  membrane,  such  as  is  used  by  perfumers.  Attached  to  the  piston  by  means  of  a 
thread  is  a  writing  lever,  /,  which  records  the  variations  of  pressure  within  the  chamber,  o.  When 
the  ventricle  contracts,  it  becomes  smaller,  diminishes  the  pressure  within  o^  and  hence  the  piston 
and  lever  rise;  conversely,  when  the  heart  dilates,  the  lever  and  piston  descend.  Variations  in  the 
volume  of  the  ventricle  may  be  registered,  without  in  any  way  interfering  with  the  flow  of  fluids 
through  it.] 

[Two  preparations  of  the  frog's  heart  have  been  used — (i)  The  "heart,"  in  which  case  the 
cannula  is  introduced  into  the  heart  through  the  sinus  venosus,  and  a  ligature  is  tied  over  it  aroitnd 
the  auricle.,  or  it  may  be  the  sinus  venosus.  Thus  the  auriculo-ventricular  ganglia  and  other  nervous 
structures  remain  in  the  preparation.  This  was  the  heart  preparation  employed  by  Luciani  and 
Rossbach.  (2)  In  the  "  heart  apex,"  or  apex  preparation,  the  cannula  is  introduced  as  before,  but 
the  ligature  is  lied  on  it  over  the  ventricle,  several  millimetres  below  the  auriculo-ventricular  groove, 
so  that  this  preparation  contains  none  of  the  auriculo-ventricular  ganglia,  and,  according  to  the  usual 
statement,  this  part  of  the  heart  is  devoid  of  nerve  ganglia.  This  is  the  preparation  which  was  used 
by  Bowditch,  Kronecker  and  Stirling,  Merunowicz,  and  others.  The  first  effect  of  the  application 
of  the  ligature  in  both  cases  is,  that  both  preparations  cease  to  beat,  but  the  '-heart"  usually  resumes 
its  ryhthmical  contractions  within  several  minutes,  while  the  "heart  apex"  does  not  contract  spon- 
taneously until  after  a  much  longer  time  ( 10  to  90  mins. )]. 

[If  the  "  heart  apex  "  be  filled  with  a  0.6  per  cent,  solution  of  common  salt,  the  contractions  are 


at  first  of  greater  extent,  but  they  afterward  cease,  and  the  preparation  passes  into  a  condition  of 
"apparent  death;"  while  if  the  action  of  the  fluid  be  prolonged,  the  heart  may  not  contract  at  all, 
even  when  it  is  stimulated  electrically  or  mechanically.  It  may  be  made,  however,  to  pulsate  again, 
if  it  be  supplied  with  saline  solution  containing  blood  (l  to  10  per  cent.).  The  "  Stille"  or  state  of 
quiescence  may  last  90  mins.  {Kronecker  and  Merunowicz).  If  the  ventricle  be  nipped  with  wire 
forceps  at  the  junction  of  the  upper  with  its  middle  third,  so  as  to  separate  the  lower  two-thirds  of 
the  ventricle  physiologically  but  not  anatomically  from  the  rest  of  the  heart,  then  the  apex  will  cease 
to  contract,  although  it  is  still  supplied  with  the  frog's  own  blood  (Bernstein,  Bowditch).  The 
physiologically  isolated  apex  may  be  made  to  beat  by  clamping  the  aortic  branches  so  as  to  prevent 
blood  passing  out  of  the  iieait,  and  thus  raising  the  intra-cardiac  pressure.  The  rate  of  the  beat  of 
the  apex  is  independent  of  and  slower  than  that  of  the  rest  of  the  heart.  This  experiment  proves 
that  the  amount  of  pressure  within  the  apex  cavity  is  an  important  factor  in  the  causation  of  the 
spontaneous  beats  of  the  ap^x  (  Gaskell).  If  blood  serum,  to  which  a  trace  of  delphinin  is  added, 
be  transfused  or  "  perfused  '  through  the  heart,  it  begins  to  beat  within  a  minute,  continues  to  beat 
for  several  seconds,  and  then  stands  still  in  diastole  {Bo7vditeh).  Quinine  [Schtschepotjew')  and  a 
mixture  of  atropine  and  muscarin  have  a  similar  action  (7'.  Basch).  These  experiments  show  that, 
prcroided  no  nervous  apparatus  e.xists  within  the  heart  apex,  the  cause  of  the  varying  contraction  is 
to  be  sought  for  in  the  musculature  of  the  heart  {Kronecker),  and  that  the  stimulus  necessary  for  the 
systole  of  the  heart's  apex  may  arise  within  itself  {.luhert).  If  there  is  no  nervous  apparatus  of  any 
kind  present,  then  we  must  assume  that  the  heart  muscle  may  execute  rhythmical  movements  inde- 
pendently of  the  presence  of  any  nervous  mechanism,  although  it  is  usually  assumed  that  the  ganglia 


100  ACTION    OF    HEAT   ON    THE    HEART. 

excite  (he  heart  muscle  to  pulsate  rhythmically.  It  is  by  no  means  definitely  proT'cd  that  the  heart 
apex  is  devoid  of  .all  nervous  structures,  which  may  act  as  originators  of  these  rhythmical  impulses.] 

[Action  of  Drugs. — If  the  heart  apex  contains  no  nervous  structures,  it  must  form  a  good  oliject 
for  the  study  of  the  action  of  drugs  on  the  cardiac  muscle.  Some  of  these  have  been  mentioned 
already.  Ringer  finds  that  a  calcium  salt  makes  the  contractions  higher  and  longer.  Dilute  acids 
added  to  saline  solution,  e.  g.,  lactic,  cause  complete  relaxation  of  the  cardiac  musculature,  while 
dilute  alkalies  produce  an  opposite  effect  or  tonic  contraction,  even  though  the  apex  be  not  pulsating. 
The  action  of  a  dilute  acid  may  be  set  aside  by  a  dilute  alkali  and  vice  versa.  Digitalin,  antiarin, 
barium,  and  veratria  act  like  alkalies,  while  saponin,  muscarin,  and  pilocarpin  have  the  eftect  of 
acids  (\  65).] 

[The  "  Heart  "  preparation  in  many  respects  behaves  like  the  foregoing,  /.  e.,  it  is  exhausted 
after  a  time  by  the  continued  application  of  normal  saline  solution  (0.6  per  cent.  NaCl),  while  its 
activity  may  be  restored  by  supplying  it  with  albuminous  and  other  fluids  (p.  98).] 

[C5)  Luciani  found  that  such  a  heart,  when  filled  with  pure  serum,  produced 
groups  of  pulsations  with  a  long  diastolic  pause  between  every  two  groups  (Fig.  54). 
The  successive  beats  in  each  group  assume  a  "  staircase  "  character  (p.  102).  These 
periodic  groups  undergo  many  changes  ;  they  occur  when  the  heart  is  filled  with 
pure  serum  free  from  blood  corpuscles,  and  they  disappear  and  give  place  to 
regular  pulsations  when  defibrinated  blood  or  serum  containing  hemoglobin  or 
normal  saline  solution  (^Rossbach)  is  used.  They  also  occur  when  the  blood  within 
the  heart  has  become  dark  colored,  /.  c,  when  it  has  been  deprived  of  certain  of 
its  constituents,  and  if  a  trace  of  veratrin  be  added  to  bright  red  blood  they 
occur.] 

(6)  The  same  apparatus  permits  of  the  application  of  electrical  stimuli  to  either 

Fig.  54. 


Four  groups  of  pulsations  with  intervening  pauses,  as  obtained  by  Luciani,  with  their  "  staircase  "  character.     The 
points  on  the  abscissa  were  marked  every  10  seconds. 

of  the  above-named  preparations.  An  apex  preparation,  when  stimulated  with 
even  a  weak  induction  shock,  always  gives  its  maximal  contraction,  and  when  a 
tetanizing  current  is  applied  tetanus  does  not  occur  {Kivneckcr  and  Stirling). 
When  the  opening  and  closing  shocks  of  a  sufficiently  strong  constant  current  are 
applied  to  the  heart  apex,  it  contracts  with  each  closing  or  opening  shock.  [When 
a  constant  current  is  applied  to  the  lower  two-thirds  of  the  ventricle  (heart  apex), 
under  certain  conditions  the  apex  contracts  rhytlimically.  This  is  an  important 
fact  in  connection  with  any  theory   of  the  cardiac  beat.] 

.  (7)  If  the  bulbus  aort^e  (frog)  be  ligatured,  it  still  pulsates,  provided  the 
internal  pressure  be  moderate.  Should  it  cease  to  beat,  a  single  stimulus  makes  it 
respond  by  a  series  of  contractions.  Increase  of  temperature  to  35°  C,  and 
raising  the  pressure  within  it,  increase  the  number  of  pulsations  {Engelmann'). 

(IIj  Direct  Stimulation  of  the  Heart. — All  direct  cardiac  stimuli  act 
more  energetically  on  the  inner  than  on  the  outer  surface  of  the  heart.  If  strong 
stimuli  are  applied  for  too  long  a  time,  the  ventricle  is  the  part  first  paralyzed. 

(a)  Thermal  Stimuli. — [Heat  affects  the  number  or  frequency  and  the  amplitude  of  the 
pulsations,  as  well  as  the  duration  of  the  systole  and  di.astole  and  the  excitability  of  the  heart.] 
Descartes  (1614)  observed  that  heat  increases  the  number  of  pulsations  of  an  eel's  heart.  A.  v. 
Humboldt  found  that  wlien  a  frog's  heart  was  placed  in  lukewarm  water,  the  number  of  beats 
increased  from  12  to  40  per  minute.  As  the  temperature  increases,  the  number  of  beats  is  at  first 
considerably  increased,  but  afterward  the  beats  again  become  fewer,  and  if  the  temperature  is 
raised  above  a  certain  limit  the  heart  stands  still,  the  myosin  of  which  its  fibres  consist  is  coagulated, 


ACTION    OF    MECHANICAL   AND    ELECTRICAL   STIMULI. 


101 


and  "  heat  rigor  "  occurs.  Even  before  this  stage  is  reached, 
however,  the  heart  may  stand  still,  the  muscular  fibres  appear- 
ing to  remain  contracted.  The  ventricles  u>ually  cease  to  beat 
before  the  auricles  (Sche/ske).  The  she  and  e.xleitt  of  the  con- 
tractions increase  up  to  about  20°  C,  but  above  this  point  they 
diminish  (Fig.  55).  The  time  occupied  by  any  single  con- 
traction at  20°  C  is  only  about  j'j  of  the  time  occupied  by  a 
contraction  occurring  at  5°  C. 

A  heart  which  has  been  warmed  is  capable  of  reacting  pretty 
rapidly  to  intermittent  stimuli,  while  a  heart  at  a  low  tempera- 
lure  reacts  only  to  stimuli  occurring  at  a  considerable  interval. 
If  a  frog  be  kept  in  a  cold  place  its  heart  beats  slowly  and 
does  little  work,  but  if  the  heart  be  supplied  with  the  extract 
of  a  frog  which  has  been  kept  warm,  it  is  rendered  more 
capable  of  doing  work  (Gaiile). 

Cold. — When  the  temperature  of  the  blood  is  diminished, 
the  heart  beats  slower  (Kielmeyer^  '793)-  A  frog's  heart 
placed  between  two  watch  glasses  and  laid  on  ice,  beats  very 
much  slower  {Lmlwig,  iSbi).  The  pulsations  of  a  frog's 
heart  stop  when  the  heart  is  exposed  to  a  temperature  of  4°  C. 
to  0°  {E.  Cyan).  If  a  frog's  heart  be  taken  out  of  warm  waier, 
and  suddenly  placed  upon  ice,  it  beats  more  rapidly,  and  con- 
versely, if  it  be  taken  from  ice  and  placed  over  warm  water,  it 
beats  more  slowly  at  first  and  more  ra|iKlly  afterw.ird  (Aristi<-i'\. 


Fig.  55. 


Fig. 


ot  a  frog's  heart  at  ig"^  C.  ;  ^,  at  34°  C.  :  ^,  at  3°  C. 


[Methods. — The  effect  of  heat  on  a  heart  may  be  studied  by  the  aid  of  the  frog  manometer,  the 
fluid  in  which  the  heart  is  placed  being  raised  to  any  temperature  required.  For  demonstration 
purposes,  the  heart  of  a  pithed  frog  is  excised  and  placed  on  a  glass  slide  under  a  light  lever,  such 
as  a  straw.  The  slide  is  warmed  by  means  of  a  spirit  lamp.  In  this  way  the  frequency  and  ampli- 
tude of  the  contractions  are  readily  made  visible  at  a  distince.] 

[Gaskell  fixes  the  heart  by  means  of  a  clamp  placed  round  the  auriculo-ventricular  groove, 
while  levers  are  placed  horizontally  above  and  below  the  heart.  These  levers  are  fixed  to  part  of 
the  auricles  and  to  the  apex  by  means  of  threads.  Each  part  of  the  heart  attached  to  a  lever,  as  it 
contracts,  pulls  upon  its  own  lever,  so  that  the  extent  and  duration  of  each  contraction  may  be 
registered.  This  method  is  applicable  for  studying  the  effect  of  the  vagus  and  other  nerves  upon 
the  heart.] 

(/')  Mechanical  Stimuli. — Pressure  applied  externally  to  the  heart  accelerates  its  action.  In 
the  case  of  Frau  Serafin,  v.  Ziemssen  found  that  slight  pressure  on  the  auriculo-ventricular  groove 
caused  a  second  short  contraction  of  both  ventricles  after  the  heart  beat.  Strong  pressure  causes  a 
very  irregular  action  of  the  cardiac  muscle.  This  may  readily  be  produced  by  compressing  the 
Ireshly-excised  heart  of  a  dog  between  the  fingers. 

The  intra-cardiac  pressure  also  affects  the  heart  beat  (p.  99).  If  the  pressure  within  the  heart 
be  increased,  the  heart  beats  are  gradually  increased;  if  it  be  diminished,  the  number  of  beats 
diminishes  (Lmhuig  and  Thiry).  If  the  intra-cardiac  pressure  be  very  greatly  increased,  the  heart's 
action  becomes  very  irregular  and  slower  (Heiden/iain).  A  heart  which  has  ceased  to  beat 
may,  under  certain  circumstances,  be  caused  to  execute  a  single  contraction,  if  it  be  stimulated 
mechanically. 

(c)  Electrical  Stimuli. — A  constant  electrical  current  of  moderate  strength  increases  the  number 
of  heart  beats,  v.  Ziemssen  found,  in  the  case  of  Frau  Serafin  (^47,  3),  that  the  number  of  beats 
was  doubled  when  a  constant  uninterrupted  strong  current  was  passed  through  the  ventricles.  If 
the  constant  current  be  very  strong,  or  if  tetanizing  induction  currents  be  used,  the  cardiac  muscle 
assumes  a  condition  resembling,  but  not  identical  with,  tetanus  (Lud-uiig and  Hoffa),  and,  of  course, 
this  results  in  a  fall  of  the  blood  pressure  (Sigm.  Mayer). 


102  ACTION    OF    ELECTRICAL   STIMULI    ON   THE    HEART. 

When  a  single  induction  shock  is  applied  to  the  ventricle  of  a  frog's  heart  during  systole,  it 
has  no  apparent  effect;  but  if  it  is  applied  during  diastole,  the  succeeding  contraction  takes  place 
sooner.  The  auricles  behave  in  a  similar  manner.  WTiile  they  are  contracted,  an  induction  shock 
has  no  effect;  if,  however,  the  stimulus  is  applied  during  diastole,  it  causes  a  contraction,  which  is 
followed  by  systole  of  the  ventricle  {^Hildebrand).  Even  when  strong  tetanizing  induction  shocks 
are  applied  to  the  heart,  they  do  not  produce  tetanus  of  the  entire  cardiac  musculature,  or,  as  it  is 
said,  "the  heart  knows  no  tetanus"  {Kronecker  and  Stirling).  Small,  white,  local,  wheallike  ele- 
vations— such  as  occur  when  the  intestinal  musculature  is  stimulated — appear  between  the  elec- 
trodes. They  may  last  several  minutes.  .\  frog's  heart,  which  yields  weak  and  irregular  contrac- 
tions, may  be  made  to  execute  regular  rhythmical  contractions  synchronous  with  the  stimuli,  if 
electrical  stimuli  are  used  (Bo-uiditc/i).  In  this  case  the  weakest  stimuli  (which  are  still  active) 
behave  like  the  stronger  stimuli — even  with  the  weak  stimulus,  the  heart  always  gives  the  strongest 
contraction  possible.  Hence,  this  minimal  electrical  stimulus  is  as  effective  as  a  "  ma.ximal  "  stimulus 
( Kronecker  and  Stirling). 

Human  Heart. — v.  Ziemssen  found  that  he  could  not  alter  the  heart  beats  of  the  human  heart 
(Frail  St'rayin,  ^47,  3),  even  with  strong  induction  currents.  The  ventricular  diastole  seemed  to 
be  less  complete,  and  there  were  irregularities  in  its  contraction.  By  0[:ening  and  closing,  or  by 
reversing  a  strong  constant  current  applied  to  the  heart,  the  number  of  beats  was  increased,  and  the 
increase  corresponded  with  the  number  of  electrical  stimuli;  thus,  when  the  electrical  stimuli  were 
120,  140,  180,  the  number  of  heart  beats  was  the  same,  the  pulse  beforehand  being  So.  When  180 
shocks  per  minute  were  applied,  the  action  of  the  heart  assumed  the  characters  of  the  pulsus 
alternaiis  (?  70,  4).  Minimal  .stimuli  were  also  found  to  act  like  maximal  stimuli.  The  normal 
pulse  rate  of  80  was  reduced  to  60  and  50,  when  the  number  of  shocks  was  reduced  in  the  same 
ratio.  The  rhythm  became,  at  the  same  time,  somewhat  irregular.  In  these  experiments  a  strong 
current  is  required,  and  v.  Basch  found  that  the  same  was  true  for  the  frog's  heart.  Even  in  healthy 
persons,  v.  Ziems  en  ascertained  that  the  energy  and  rhythm  of  the  heart  could  be  modified  by 
passing  an  electrical  current  through  the  uninjured  chest  wall.  [In  Frau  .Serafin's  case,  the  elec- 
trodes were  applied  to  the  heart,  sejiarated  from  it  merely  by  the  pericardium.  Ziemssen  found 
that  the  faradic  current  did  not  modify  the  heart's  action  when  the  thorax  was  intact,  but  that  the 
constant  current  did,  if  of  sufficient  strength.  Herbert  and  Dixon  Mann  obtained  negative  results 
with  both  kinds  of  electricity  in  the  normal  thorax.] 

[Method  — The  apparatus  (Fig.  52)  is  also  well  adapted  for  studying  the  effect  of  electrical 
currents  upon  the  heart.  Bowditch,  Kronecker  aud  Stirling,  and  other  observers,  used  the  '■  heart 
apex,"  as  it  does  not  contract  spontaneously  for  some  time  after  the  ligature  is  applied.  One  elec- 
trode is  attached  to  the  cannula,  and  the  other  is  placed  in  the  fluid  in  which  the  heart  is  bathed.] 

[Opening  induction  shocks,  if  of  sufficient  strength,  cause  the  heart  to  contract,  while  weak 
stimuli  have  no  effect;  on  the  other  hand,  moderate  stimuli,  when  they  do  cause  the  heart  to  con- 
tract, always  cause  a  maximal  contraction,  so  that  a  minimal  stimulus  acts  at  the  same  time  like  a 
maximal  stimulus.  The  heart  either  contracts  or  it  does  not  contract,  and  when  it  contracts,  the 
result  is  always  a  "maximal"  contraction.  Bowditch  found  that  the  excitability  of  the  heart 
was  increased  by  its  own  movements,  so  that  after  a  heart  had  once  contiacted,  the  strength 
of  the  stimulus  required  to  excite  the  next  contraction  may  be  greatly  diminished,  and  yet  the 
stimulus  be  effectual.  Usually,  the  amplitude  of  the  first  beat  so  produced  is  not  so  great  as 
the  second  beat,  and  the  second  is  less  than  the  third,  so  that  a  "  staircase  "  ("  Treppe  ")  of  beats 
of  successively  greater  extent  were  produced  (Fig.  54).  This  staircase  arrangement  occurs  even  when 
the  strength  of  the  stimulus  is  kept  constant,  so  that  the  production  of  one  contraction  facilitates 
the  occurrence  of  the  succeeding  one.  A  staircase  arrangement  of  the  pulsations  is  also  seen  in 
Luciani's  group;  (p.  100).  The  question,  whether  a  stimulus  will  cause  a  contraction,  depends 
upon  what  particular  phase  the  hean  is  in  when  the  shock  is  applied.  Even  comparatively  weak 
stimuli  will  cause  a  heart  to  contract,  provided  the  stimuli  are  applied  at  the  proper  moment  and  in 
the  proper  tempo,  ;'.  e.,  to  say,  they  become  what  are  called  "  infallible."  If  stimuli  are  applied  to 
the  heart  at  intervals  which  are  longer  than  the  time  the  heart  takes  to  execute  its  contraction,  they 
are  effectual  or  "  adequate ;  "  but  if  they  are  applied  before  the  period  of  pulsation  comes  to  an 
end.  then  they  are  ineffectual  (Kronecker).  It  is  quite  clear,  therefore,  that  the  relation  of  the 
strengtii  of  the  stimulus  to  the  extent  of  the  contraction  of  the  cardiac  muscle  is  quite  different  from 
what  occurs  in  a  muscle  of  the  skeleton,  where,  within  certain  limits,  the  amplitude  of  the  contrac- 
tion bears  a  relation  to  the  stimulus,  while  in  the  heart  the  contraction  is  always  maximal^ 

(d)  Chemical  Stimuli. — Many  chemical  substances,  when  applied  in  a  dilute  solution  to  the 
inner  surface  of  the  heart,  increase  the  heart  beats,  while  if  they  are  concentrated  or  allowed  to  act 
too  long,  they  diminish  the  heart  beats  and  paralyze  it.  Bile  (Budge),  bile  salts  (Kohrig)  diminish 
the  heart  beats  (also  when  they  are  absorbed  into  the  blood,  as  in  jaundice) ;  in  very  dilute  solu- 
tions, both  increase  the  heart  beats  (Landois).  A  similar  result  is  produced  by  acetic,  tartaric,  citric, 
(Bobrik)  and  phosphoric  acids  (Leyden).  Chloroform  and  ether,  applied  to  the  inner  surface, 
rapidly  diminish  the  heart  beats,  and  then  paralyze  it;  but  very  small  quantities  of  ether  (i  per 
cent.)  accelerate  the  heart  beat  of  the  frog  (Kronecker  and  M' Grcgor-Roberlson),  while  a  solution 
of  I  j^  to  2  per  cent,  passed  through  the  heart,  arrests  it  temporarily  or  completely.  Dilute  solu- 
tions of  opium,  strychnia  or   alcohol   applied  to  the   endocardium  increase  the   heart  beats  (C. 


NATURE    OF  A   CARDIAC    CONTRACTION.  103 

Luitvn'g) ;  if  concentrated,  they  rapidly  arrest  its  action.  Chloral-hydrate  paralyzes  the  heart  {P. 
V.  Rokitansk)'). 

Action  of  Gases. — When  blood  containing  different  gases  was  passed  through  a  frog's  heart, 
Klug  found  that  blood  containing  sulphurous  acid  rapidly  and  completely  killed  the  heart;  chlorine 
stimulated  the  heart  at  first,  and  ultimately  killed  it;  and  laughing  gas  rapidly  killed  it  also.  Blood 
containing  sulphuretted  hydrogen  paralyzed  the  heart  without  stimulating  it.  Carbonic  oxide  also 
paralyzed  it,  but  if  fresh  blood  was  transfused  the  heart  recovered.  [Blood  containing  O  excites  the 
heart  (Castell),  while  the  presence  of  much  CO.,  paralyzes  it,  and  the  presence  of  CO2  is  more 
injurious  than  the  want  of  O.     H  and  N  have  no  effect.] 

Rossbach  found  on  stimulating  the  ventricle  of  a  frog's  heart  at  a  circumscribed  area,  either 
mechanically,  chemically,  or  electrically,  during  systole,  that  the  part  so  stimulated  relaxes  in  partial 
diastole.  The  immedi.ite  direct  after  effect  of  this  stimulation  is,  that  the  muscular  fibres  in  the  part 
irritated  remain  somewhat  shriveled.  This  part  ceases  to  act,  and  has  lost  its  vital  functions.  If 
the  stimulus  is  applied  during  diastole,  the  part  irritated  always  relaxes  sooner,  and  its  diastole  lasts 
longer  than  does  that  of  the  parts  which  were  not  stimulated.  If  weak  stimuli  are  allowed  to  act 
for  a  long  time  U|X5n  any  part  of  the  ventricle  of  a  frog's  heart,  the  part  so  stimulated  always  relaxes 
sooner  than  the  non  stimulated  parts,  and  its  diastole  is  also  prolonged. 

Cardiac  Poisons  are  those  substances  whose  action  is  characterized  by  special  effects  upon  the 
movements  of  the  heart,  .\mong  these  s.x&  tteutral  salts  of  potash.  [Until  1863  it  was  believed 
that  these  salts  were  just  as  slightly  active  on  the  heart  as  the  soda  salts,  but  Bernard  and  Grandeau 
showed  that  very  small  doses  of  these  salts  produced  death,  the  heart  standing  still  in  diastole.  An 
excised  frog's  heart  ceases  to  beat  after  one-half  to  one  minute,  when  it  is  placed  in  a  2  per  cent, 
solution  of  polassic  chloride.]  Even  a  very  dilute  solution  of  yellow  prussiate  of  potash  injected 
into  the  heart  of  a  frog  causes  the'ventricle  to  stand  still  in  systole. 

As  early  as  i6gi,  Clayton  and  Moulin  .showed  the  poisonous  action  of  potassium  sulphate  and 
alum,  as  compared  with  the  non-poisonous  action  of  sodium  chloride,  which  was  demonstrated  l>y 
Courten,  in  1679.  Antiar  (Java  arrow  poison)  causes  the  ventricle  to  stand  still  in  systole  and  the 
auricles  in  diastole.  Some  heart  poisons,  in  small  doses,  diminish  the  heart's  action,  and  in  large 
doses  not  unfretjuently  accelerate  it,  e.  g.,  digitalis,  morphia,  nicotin.  Others,  when  given  in  small 
doses,  accelerate  its  action,  and  in  large  doses  slow  it — veratria,  aconitin,  camphor. 

Special  Actions  of  Cardiac  Poisons. — The  complicated  actions  of  various  poisons  upon  the 
heart  have  led  observers  to  sujipose  that  there  are  various  intra-cardiac  mechanisms  on  which  these 
substances  may  act.  Besides  the  rnusiular  fibres  of  the  heart  and  its  automatic  ganglia,  some  toxi- 
cologists  assume  that  there  are  inhibitory  ganglia  into  which  the  inhibitory  fibres  of  the  vagus  pass, 
and  accelerator  ganglia,  which  are  connected  with  the  accelerating  nerve  fibres  of  the  heart.  Both 
the  inhibitory  and  accelerator  ganglia  are  connected  Tvith  the  automatic  ganglia  by  conducting 
channels. 

Muscarin  stimulates  permanently  the  inhibitory  ganglia,  so  that  the  heart  stands  still  (Sckmiede- 
berg  and  A'oppe).  As  atropin  and  daturin  paralyze  these  ganglia,  the  stand-still  of  the  heart  brought 
about  by  muscarin  may  be  set  aside  by  atropin.  [If  a  frog's  heart  be  excised  and  placed  in  a  watch 
glass,  and  a  few  drops  of  a  very  dilute  solution  of  muscarin  be  placed  on  it  with  a  pipette,  it  ceases 
to  beat  within  a  few  minutes,  and  will  not  beat  again.  If,  however,  the  muscarin  be  removed,  and 
a  solution  of  atropine  applied  to  the  heart,  it  will  resume  its  contractions  after  a  short  time.]  Physos- 
tigmin  [Calabar  bean]  excites  the  energy  of  the  cardiac  muscle  to  such  an  extent,  that  stimulation 
of  the  vagus  no  longer  causes  the  heart  to  stand  still.  lodine-aldehyd,  chloroform,  and  chloral- 
hydrate  paralyze  the  .automatic  ganglia.  The  heart  stands  still,  and  it  cannot  be  made  to  contract 
again  by  atropine.  The  cardiac  muscle  itself  remains  excitable  after  the  action  of  muscarin  and 
iodine-aldchyd,  so  that  if  it  be  stimulated  it  contracts.  [According  to  Gaskell,  antiarin  and  digilalin 
solutions  produce  an  alteration  in  the  condition  of  the  muscular  tissue  of  the  apex  of  the  heart  of 
the  same  nature  as  that  produced  by  the  action  of  a  very  dilute  .alkali  solution,  while  the  action  of  a 
blood  solution  containing  muscarin  closely  resembles  that  of  a  dilute  acid  solution  (p.  100,  |  65).] 

[Nature  of  a  Cardiac  Contraction. — The  question  as  to  whether  this  is  a 
sini[)le  contraction  or  a  compound  tetanic  contraction  has  been  much  discussed. 
This  much  is  certain,  that  the  systolic  contraction  of  the  heart  is  of  very  much 
longer  duration  (8  to  10  times)  than  the  contraction  of  a  skeletal  muscle  produced 
by  stimulation  of  its  motor  nerve.  When  the  sciatic  nerve  of  a  nerve  muscle 
preparation  ("  rheoscopic  limb  ")  is  adjusted  upon  a  contracting  heart,  a  j-/m//^ 
secondary  twitch  of  the  limb,  and  not  a  tetanic  spasm,  is  produced  when  the 
heart  (auricle  or  ventricle)  contracts.  This  of  itself  is  not  sufficient  proof  that  the 
systole  is  a  simple  spasm,  for  tetanus  of  a  muscle  does  not  in  all  cases  give  rise  to 
secondary  tetanus  in  the  leg  of  a  rheoscopic  liinb.  Thus,  a  simple  "  initial  "  con- 
traction occurs  when  the  nerve  is  applied  to  a  muscle  tetanized  by  the  action  of 
strychnia,  and  the  contracted  diaphgram  gives  a  similar  result.  The  question 
whether  the  heart  can  be  tetanized,  has  been  answered  in  the  negative,  and  as  yet 


104 


THE   CARDIO-PNEUMATIC    MOVEMENT. 


it  has  not  been  shown  that  the  heart  can  be  tetanized  in  the  same  way  that  a  skel- 
etal muscle  is  tetanized.] 

The  peripheral  or  extra-cardiac  nerves  will  be  discussed  in  connection  with 
the  Nervous  System  (§  369  and  370). 

59.  THE    CARDIO  PNEUMATIC    MOVEMENT.— As    the    heart 

within  the  thorax  occupies  a  smaller  space  during  the  systole  than  during  the  dias- 
tole, it  follows  that  when  the  glottis  is  open,  air  must  be  drawn  into  the  chest  when 
the  heart  contracts  ;  whenever  the  heart  relaxes,  ;'.  e.,  during  diastole,  air  must  be 
expelled  through  the  open  glottis.  But  we  must  also  take  into  account  the  degree 
to  which  the  larger  intra-thoracic  vessels  are  filled  with  blood.  These  movements 
of  the  air  within  the  lungs,  although  slight,  seem  to  be  of  importance  in  hybernat- 
ing  animals.  In  animals  in  this  condition,  the  agitation  of  the  gases  in  the  lungs 
favors  the  exchange  of  CO^  and  O  in  the  lungs,  and  this  slow  current  of  air  is 
sufficient  to  aerate  the  blood  passing  through  the  lungs.  [Ceradini  called  the 
diminution  of  the  volume  of  the  entire  heart  which  occurs  during  systole  meio- 
cardia,  and  the  subsequent  increase  of  volume  when  the  heart  is  distended  to  its 
maxmium,  auxocardia.] 

Fig.  56. 


Landois'  cardio-pneumograph,  and  the  curves  obtained  therewith.     A  and  B,  from  man  :  i  and  2  correspond  to  the 
periods  of  the  first  and  second  heart  sounds  ;    C,  from  dog  :    D,  method  of  using  the  apparatus. 


Method. — The  cardio-pneumatic  movements,  i,  e.,  the  movement  of  the  respiratory  gases  de- 
pendent on  the  movements  of  the  heart  and  great  vessels,  may  be  demonstrated  in  animals  and  man. 
A  manomelric  flame  may  be  used.  Insert  one  limb  of  a  Y-tube  into  the  opened  trachea  of  an 
animal,  while  the  other  limb  passes  to  a  small  gas  jet,  and  connect  the  other  tube  with  a  gas  jet. 
It  is  clear  that  the  movements  of  the  heart  will  affect  the  column  of  gas,  and  thus  affect  the  flame. 
Large  animals  previously  curarized  are  best.  It  may  also  be  done  in  man  by  inserting  the  tube 
into  one  nostril,  while  the  other  nostril  and  the  mouth  are  closed.  [A  simpler  and  less  irritating 
plan  is  to  fill  a  wide  curved  glass  tube  with  tobacco  smoke,  and  insert  one  end  of  the  tube  into  one 
nostril  while  the  other  nostril  and  the  mouth  are  closed.  If  the  glottis  be  kept  open,  and  respiration 
be  stopped,  then  the  movements  of  the  column  of  smoke  within  the  tube  are  obvious.] 

Cardio-Pneumograph. — Ceradini  employed  a  special  instrument,  while  Landois  uses  his  cardio- 
pneumograph,  which  consists  of  a  tube  (D),  about  I  inch  in  diameter  and  6  to  8  inches  in  length; 
the  tube  is  bent  at  a  right  angle,  and  communicates  with  a  small  metal  capsule  about  the  size  of  a 
saucer  (T),  over  which  a  membrane  composed  of  collodion  and  castor  oil  is  loosely  stretched.  To 
this  memiirane  is  attached  a  glass  rod  (H)  used  as  a  writing  style,  which  records  its  movements  on 
a  glass  plate  (S)  moved  by  clock  work.  A  small  valve  (K)  is  placed  on  the  side  of  the  tube  (U), 
which  enables  the  experimenter  to  breathe  when  necessary.  The  tube  (D)  is  held  in  an  air-tight 
manner  between  the  lips,  the  nostrils  being  closed,  the  glottis  open,  and  respiration  stopped.  Fig. 
56,  A,  B,  C,  are  curves  obtained  in  this  way.     In  them  we  observe — 


INFLUENCE    OF   THE    RESPIRATION    ON    THE    HEART.  105 

(rt)  At  the  moment  of  the  first  sound  (i),  the  respiratory  gases  undergo  a  sharp  expiratory  move- 
ment, because  at  the  moment  of  the  first  part  of  the  ventricular  systole  the  blood  of  the  ventricle  has 
not  left  the  thorax,  while  venous  blood  is  streaming  into  the  right  auricle  through  the  venx  cavre, 
and  because  the  dilating  branches  of  the  pulmonary  artery  compress  the  accompanying  bronchi. 
The  blood  of  the  right  ventricle  has  not  yet  left  the  thora.x,  it  passes  merely  into  the  pulmonary- 
circuit.  The  expiratory  movement  is  diminished  somewhat  by  (a)  the  muscular  mass  of  the  ventricle 
occupying  slightly  less  bulk  during  the  contraction,  and  (b)  owing  to  the  thoracic  cavity  being  slightly 
increased  by  the  fifth  intercostal  space  being  pushed  forward  by  the  cardiac  impulse. 

(h)  Immediately  after  (i)  there  follows  a  strong  inspiratory  current  of  the  respiratory  gases.  As 
soon  as  the  blood  from  the  root  of  the  aorta  reaches  that  part  of  the  aorta  lying  outside  the  thorax, 
more  blood  leaves  the  chest  than  passes  into  it  simultaneously  through  the  venre  cavae. 

(c)  After  the  second  sound  (at  2),  indicated  sometimes  by  a  slight  depression  in  the  apex  of  the 
curve,  the  arterial  blood  accumulates,  and  hence  there  is  another  expiratory  movement  in  the  curv'e. 

(d)  The  peripheral  wave  movements  of  the  blood  from  the  thorax  cause  another  inspiratory 
movement  of  the  gases. 

(e)  More  blood  flows  into  the  chest  through  the  veins,  and  the  next  heart  beat  occurs. 

60.  INFLUENCE  OF  THE  RESPIRATORY  PRESSURE  ON 
THE   DILATATION  AND   CONTRACTION    OF  THE   HEART. 

— The  variation  in  pressure  to  which  all  the  intra-thoracic  organs  are  subjected, 
owing  to  the  increase  and  decrease  in  the  size  of  the  chest  caused  by  the  respi- 
ratory movements,  exerts  an  influence  on  the  movements  of  the  heart,  as  was 
proved  by  Carson  in  1S20,  and  by  Bonders  in  1854.  Examine  first  the  relations 
in  different  passive  conditions  of  the  thorax,  when  the  glottis  is  open. 

The  diastolic  dilatation  of  the  cavities  of  the  heart  (excluding  the  pressure  of 
the  venous  blood  and  the  elastic  stretching  of  the  relaxed  muscle  wall )  is  funda- 
mentally due  to  the  elastic  traction  of  tlie  lungs.  This  is  stronger  the  more  the 
lungs  are  distended  (inspiration),  and  is  less  active  the  more  the  lungs  are  con- 
tracted (expiration).      Hence  it  follows  : — 

(i)  When  the  greatest  possible  expiratory  effort  is  made  (of  course,  with  the 
glottis  open)  only  a  small  amount  of  blood  flows  into  the  cavities  of  the  heart ; 
the  heart  in  diastole  is  small  and  contains  a  small  amount  of  blood.  Hence  the 
systole  must  also  be  small,  which  further  gives  rise  to  a  small  pulse  beat. 

(2)  On  taking  the  greatest  possible  inspiration,  and  therefore  causing  the 
greatest  stretching  of  the  elastic  tissue  of  the  lungs,  the  elastic  traction  of  the 
lungs  is,  of  course,  greatest  (30  mm.  Hg — Donders^.  This  force  may  act  so 
energetically  as  to  interfere  with  the  contraction  of  the  thin-walled  atria  and 
appendices,  in  consequence  of  which  these  cavities  do  not  completely  empty 
themselves  into  the  ventricles.  The  heart  is  in  a  state  of  great  distention  in 
diastole,  and  is  filled  with  blood  ;  nevertheless,  in  consequence  of  the  limited 
action  of  the  auricles,  only  small  pulse  beats  are  observed.  In  several  individuals 
Bonders  found  the  pulse  to  be  smaller  and  slower ;  afterward  it  became  larger 
and  faster. 

(3)  When  the  chest  is  in  a  position  of  moderate  rest,  whereby  the  elastic 
traction  is  moderate  (7.5  mm.  Hg- — Bonders),  we  have  the  condition  most 
favorable  to  the  action  of  the  heart — sufficient  diastolic  dilatation  of  the  cavities 
of  the  heart,  as  well  as  unhindered  emptying  of  them  during  systole. 

A  very  important  factor  is  the  influence  exerted  upon  the  action  of  the  heart, 
by  the  volmitary  increase  or  diminution  of  the  intra-thoracic  pressure. 

(i)  Valsalva's  Experiment. — If  the  thorax  is  fixed  in  the  position  of 
deepest  inspiration,  and  the  glottis  be  then  closed,  and  if  a  powerful  expiratory 
effort  be  made  by  bringing  into  action  all  the  expiratory  muscles,  so  as  to  contract 
the  chest,  the  cavities  of  the  heart  are  so  compressed  that  the  circulation  of  the 
blood  is  temporarily  interrupted.  In  this  expiratory  phase  the  elastic  traction  is 
very  limited,  and  the  air  in  the  lungs  being  under  a  high  pressure  also  acts  upon 
the  heart  and  the  intra-thoracic  great  vessels.  No  blood  can  pass  into  the  thorax 
from  without ;  hence  the  visible  veins  swell  up  and  become  congested,  the  blood 
in  the  lungs  is  rapidly  forced  into  the  left  ventricle  by  the  compressed  air  in  the 
lungs,  and  the  blood  soon  passes  out  of  the  chest.     Hence  the  lungs  and  the 


106 


INFLUENCE   OF   THE    RESPIRATION    ON    THE    HEART. 


heart  contain  little  blood.  Hence,  also,  there  is  a  greater  supply  of  blood  in  the 
systemic  than  in  the  pulmonary  circulation  and  the  heart.  The  heart  sounds  dis- 
appear, and  the  pulse  is  absent  {E.  H.   Weber,  Donders). 

(2)  J.  Miiller's  Experiment. — Conversely,  if  after  the  deepest  possible 
expiration  the  glottis  be  closed,  and  the  chest  be  now  dilated  with  a  great  inspira- 
tory effort,  the  heart  is  powerfully  dilated,  the  elastric  traction  of  the  lungs,  and 
the  very  attenuated  air  in  these  organs  act  so  as  to  dilate  the  cavities  of  the  heart 
in  the  direction  of  the  lungs.  More  blood  flows  into  the  right  heart,  and  in  pro- 
portion as  the  right  auricle  and  ventricle  can  overcome  the  traction  outward,  the 
blood  vessels  of  the  lungs  become  filled  with  blood,  and  thus  partly  occupy  the 
lung  space.  Much  less  blood  is  driven  out  of  the  left  heart,  so  that  the  pulse  may 
disappear.     Hence,  the  heart  is  distended  with  blood  and  the  lungs  are  congested, 

Fig.  57. 


App:iratus  for  demonstrating  the  action  of  inspiration,  11,  and  expiration,  I,  on  the  heart  and  on  the  blood  streair 
P,/,  lungs  ;  H,  //,  heart  ;  L,  /,  closed  glottis  ;  M.  w/,  manometers  :  E,  e,  ingoing  blood  stream,  vein  ;  A,  a,  on 
going  blood  stream,  artery  ;   D,  diaphragm  during  expiration  ;  d,  during  inspiration. 


while  the  aortic  system  contains  a  small  amount  of  blood,  /.  e.,  the  systemic  cir- 
culation is  comparatively  empty,  while  the  heart  and  the  pulmonary  vessels  are 
engorged  with  blood. 

In  normal  respiration  the  air  in  the  lungs  during  inspiration  is  under  slight 
pressure,  while  during  ex[)iration  the  pressure  is  higher,  so  that  these  conditions 
favor  the  circulation  ;  inspiration  favors  the  supply  of  blood  (and  lymph)  through 
the  vena;  cavaj,  and  favors  the  occurrence  of  diastole.  In  operations  where  the 
axillary  or  jugular  vein  is  cut,  air  may  be  sucked  into  the  circulation  during  inspira- 
tion, and  cause  death.  Expiration  favors  the  flow  of  blood  in  the  aorta  and  its 
branches,  and  aids  the  systolic  emptying  of  the  heart.  The  arrangement  of  the 
valves  of  the  heart  causes  the  blood  to  move  in  a  definite  direction  through  it. 

The  elastic  traction  of  the  lungs  aids  the  lesser  circulation  through  the  lungs 


INFLUENCE   OF   THE    RESPIRATION    ON    THE    HEART.  107 

within  the  chest ;  the  blood  of  the  pulmonary  capillaries  is  exposed  to  the  pressure 
of  the  air  in  the  lungs,  while  the  blood  in  the  pulmonary  veins  is  exposed  to  a 
less  pressure,  as  the  elastic  traction  of  the  lungs,  by  dilating  the  left  auricle,  favors 
the  outflow  from  the  capillaries  into  the  left  auricle.  The  elastic  traction  of  the 
lungs  acts  slightly  as  a  disturbing  agent  on  the  right  ventricle,  and,  therefore,  on 
the  movement  of  blood  through  the  pulmonary  artery,  owing  to  the  overpowering 
force  of  the  blood  stream  through  the  pulmonary  artery,  as  against  the  elastic 
traction  of  the  lungs  (Donders). 

The  above  apparatus  (Fig.  57)  shows  the  effect  of  the  inspiratory  and  expiratory  movements  on 
the  dilatation  of  the  heart,  and  on  the  blood  stream  in  the  large  blood  vessels.  The  large  glass  vessel 
represents  the  thorax;  the  elastic  membrane.  D,  the  diaphragm;  P, /,  the  lungs;  L,  the  trachea 
supplied  with  a  stop-cock  to  represent  the  glottis;  H,  the  heart;  E,  the  vena;  cavae;  A,  the  aorta. 
If  the  glottis  be  closed,  and  the  expiratory  phase  imitated  by  pushing  up  D  as  in  I,  the  air  in  P.  P  is 
compressed,  the  heart,  H.  is  compressed,  the  venous  valve  closes,  the  arterial  is  opened,  and  the 
fluid  is  driven  out  through  A.  The  manometer,  M,  indicates  the  intrathoracic  pressure.  If  ihe 
glottis  be  closed,  and  tlie  inspiratory  phase  imitated,  as  in  \\,p,p  and  h  are  dilated,  the  venous 
valve  opens,  the  arterial  valve  closes;  hence,  venous  blood  flows  from  e*  into  the  heart.  Thus, 
inspiration  always  favors  the  venous  stream,  and  hinders  the  arterial ;  while  expiration  hinders  the 
venous,  and  favors  the  arterial  stream.  If  the  glottis  L  and  /  be  open,  the  air  in  P,  V,p,p  will  be 
changed  during  the  respiratory  movements  D  and  d,  so  that  the  action  on  the  heart  and  blood 
vessels  will  be  diminished,  but  it  will  still  persist,  although  to  a  much  less  extent. 


THE  CIRCULATION. 


6i.  THE  FLOW  OF  FLUIDS  THROUGH  TUBES.— Toricelli's  Theorem  (16431 


Fig,  5S. 


\u 


states  that  the  velocity  of  efflux  (v)  of  a  fluid — through  an  opening  at 
the  l)Otlom  of  a  cylindrical  vessel — is  exactly  the  same  as  the  velocity 
which  a  body  falling  fieely  would  act|uire,  were  it  to  fall  from  the 
surface  of  the  fluid  to  the  base  of  the  orifice  of  the  outflow.  If  A  be  the 
height  of  the  propelling  force,  the  velocity  of  efflux  is  given  by  the 
formula — 

V  ^  -y/  2  g  h  (where  g  =  9.8  metres). 

The  rapidity  of  outflow  increases  (as  shown  experimentally)  with  increase 
in  the  height  of  the  propelling  force,  h.     The  former  occurs  in  the  ratio, 
hj  1,2,  3,  when  h  increases  in  the  ratio,  i,  4,  9,  /.  e.,  the  velocity  of  efflux 

is  as  the  square  root  of  the  height  of  the  propelling  force.  Hence,  it  fol- 
lows that  the  velocity  of  efllux  depends  upon  the  height  of  the  liquid 
above  the  orifice  of  outflow,  and  not  upon  the  nature  of  the  fluid. 

Resistance. — Toricelli's  theorem,  however,  is  only  valid  when  all 
resistance  to  the  outflow  is  absent;  but,  in  fact,  in  every  physical  experi- 
ment such  resistance  exists.  Hence,  the  propelling  force,  //,  has  not  only 
Cylindrical  vessel  filled  with  to  cause  the  efflux  of  the  fluid,  but  has  also  to  overcome  resistance. 
w.iter.  /j,  height  of  the  These  two  forces  maybe  expressed  by  the  heights  of  two  columns  of 
hdaht"of  columntffluM  wter  placed  over  each  other,  viz.,  by  the  height  of  the  column  of  water 
required  to  overcome  the  Causing  the  outflow,  F,  and  the  height  of  the  column,  D,  which  over- 
resistance  ;  and  F. height  comes  the  resistance  opposed  to  the  outflow  of  the  fluid.  So  that 
of  column  of  fluid  caus-  ^^  r-     ,     r. 

ing  the  efflux.  A  =  F  +  D. 

62.  PROPELLING  FORCE— VELOCITY  OF  THE  CURRENT,  AND  LAT- 
ERAL PRESSURE.— In  the  case  of  a  fluid  flowing  through  a  tube,  which  it  fills  completely, 
we  have  to  consider  the  propelling  force,  h,  causing  the  fluid  to  flow  through  the  various  sections  of 
the  tube.     The  amount  of  the  propelling  force  depends  upon  two  factors: — 

( 1 )  On  the  velocity  of  the  cm  rent,  v  : 

(2)  On  the  pressure  (amount  of  resistance)  to  which  the  fluid  is  subjected  at  the  various  parts  of 
the  tube,  D. 

(i )  The  velocity  of  the  current,  v,  is  estimated — (a1  from  the  lumen,  /,  of  the  tube  ;  and  (B)  from 
the  quantity  of  fluid,  q,  which  flows  through  the  tube  in  the  unit  of  time.  So  that  i'  =  i/  :  /.  Both 
values,  q  as  well  as  I,  can  be  accurately  measured.     (The  circumference  of  a  round  tube  whose 

diameter  =</is  3.14.^.     The  sectional  area  (lumen  of  the  tube)  is  1^=— —  .d'^).      Having  in  this 

4 
way  determined  v,  from  it  we  may  calculate  the  height  of  the  column  of  fluid,  F,  which  will  give  this 
velocity,  2.  e.,  the  height  from  which  a  body  must  fall  in  vacuo,  in  order  to  attain  the  velocity,  v. 

In  this  case  F  ^  —  (where ^^  the  distance  traversed  by  a  falling  body  in  I  sec.  =  4.9  metres). 

(2)  The  pressure,  D  (amount  of  resistance),  is  measured  directly  by  placing  manometers  at 
different  parts  of  the  tube  (Fig.  59). 

'Xht  propelling  force  at  any  part  of  the  tube  is 

/i  =  F+  D; 


or. 


4,? 


D. 


(Donders.) 


This  is  proved  experimentally  by  taking  a  tall  cylindrical  vessel.  A,  of  sufficient  size,  which  is  kept 
filled  with  water  at  a  constant  level,  h.  The  outflow  rigid  tube,  a,  b,  has  in  connection  with  it  a 
number  of  tubes  placed  vertically,  i,  2,  3,  constituting  a  piezometer.  At  the  end  of  the  tube,  b,  there 
is  an  opening  with  a  short  tube  fixed  in  it,  from  which  the  water  issues  to  a  constant  height,  provided 
the  level  of  /;  is  kept  constant.  The  height  to  which  it  rises  depends  on  the  height  of  the  column 
of  fluid  causing  the  velocity,  F.  As  the  pressure  in  the  manometric  tubes,  D'  D^,  D^,  can  be  read 
off  directly,  the  propelling  force  of  the  water  at  the  sections  of  the  tubes,  I,  II,  III,  is— 
/5  =  F-f  Di;  F  +  D2;   F  +  D". 

108 


ESTIMATION    OF    RESISTANCE. 


109 


At  the  end  of  the  tube,/^  wl  ere  D*  =  O,  .4  =  F  +  O,  i.  e.,  h  ^¥.     In  the  cylinder  itself  it  is  the 
constant  pressure,  /;,  which  causes  the  movement  of  the  fluid. 

It  is  clear  that  the  propelling  force  of  the  water  gradually  diminishes  as  we  pass  from  the  part 
where  the  fluid  passes  out  of  the  cylinder  into  the  tube  toward  the  end  of  the  tube,  b.  The  water 
in  the  pressure  cylinder,  falling  from  the  height,/;,  only  rises  as  high  as  F  at  b.  This  diminution  of 
the  propelling  power  is  due  to  the  presence  of  resistances,  which  oppose  the  current  in  the  tube, 
i.  e.,  part  of  the  energy  is  transformed  into  heat.  As  the  propelling  power  at  b  is  represented  only  by 
F,  while  in  the  vessel  it  is  /;,  the  difference  must  be  due  to  the  sum  of  the  resistances,  D  ^  //  —  F; 
hence  it  follows  that  .4  =  F  +  D.  {Danders). 

ESTIMATION  OF  RESISTANCE.— Estimation  of  the  Resistance.— When  a  fluid 
flows  through  a  tube  of  uniform  calibre,  the  propelling  force,  h,  diminishes  from  point  to  point,  on 
account  of  the  uniformly  acting  resistance,  hence  the  sum  of  the  resistances  in  the  whole  tube  is 
directly  proportional  to  its  length.  In  a  uniformly  wide  tube,  fluid  flows  through  each  sectional 
area  with  equal  velocity,  hence  v  and  also  F  are  equal  in  all  parts  of  the  tube.  The  diminution 
which  h  (propelling  force)  undergoes  can  only  occur  from  a  diminution  of  pressure  D,  as  F  remains 
the  same  throughout  (and  /;  =  F  +  D)-  Experiment  with  the  pressure  cylinder  shows  that,  as  a 
matter  of  fact,  the  pressure  toward  the  outflow  end  of  the  tube  becomes  gradually  diminished. 

In  a  uniformiv  7oide  tube,  the  height  of  the  pressure  in  the  manometers  expresses  the  resistances 
opposed  to  the  current  of  fluid  which  it  has  to  overcome  in  its  course  frojn  the  point  investigated  to 
the  free  orifice  of  efflux. 

Nature  of  the  Resistance. — The  resistance  opposed  to  the  flow  of  a  fluid  depends  upon  the 
cohesion  of  the  particles  of  the  fluid  among  themselves.  During  the  current,  the  outer  layer  of 
fluid  which  is  next  the  wall  of  the  tube,  and  which  moistens  it,  is  at  rest   {Girard,  Poiseuille). 


Fig 


A  cylindiical  vessel  filled  with  water,     a,  tf,  outflow  tube,  along  which  are  placed  at  intervals  vertical  tubes,  1,2,3,  to 
estimate  the  pressure. 

All  the  other  layers  of  fluid,  which  may  be  represented  as  so  many  cylindrical  layers,  one  inside  the 
other,  move  more  rapidly  as  we  proceed  toward  the  axis  of  the  tube,  the  axial  thread  or  stream 
I  eing  the  most  rapidly  moving  part  of  the  liquid.  On  account  of  the  movement  of  the  cylindrical 
layers,  one  within  the  other,  a  part  of  the  propelling  energy  must  be  used  up.  The  amount  of  the 
resistance  greatly  depends  upon  the  amount  of  the  cohesive  force  which  the  particles  of  the  fluid 
have  for  each  other ;  the  more  firmly  the  particles  cohere  with  each  other,  the  greater  will  be  the 
resistance,  and  vice  versd.  Hence,  the  sticky  blood  current  experiences  greater  resistance  than  water 
or  ether. 

Heat  diminishes  the  cohesion  of  the  particles,  hence  it  also  diminishes  the  resistance  to  the  flow 
of  a  current.  These  resistances  are  first  developed  by,  and  result  from,  the  movement  of  the  particles 
of  the  fluid,  they  being,  as  it  were,  torn  from  each  other.  The  more  rapid  the  current,  therefore, 
I.  e.,  the  larger  the  number  of  particles  of  fluid  which  are  pulled  asunder  in  the  unit  of  time,  the 
greater  wilt  be  the  sum  of  the  resistance.  As  already  mentioned,  the  layer  of  fluid  lying  next  the 
tube,  and  moistening  it,  is  at  rest,  hence  the  material  which  composes  the  tube  exerts  no  influence 
on  the  resistance. 

EFFECT  OF    TUBES    OF    UNEQUAL    CALIBRE.— Unequal    Diameter.— When 

the  velocity  of  the  current  is  uniform,  the  resistance  depends  upon  the  diameter  of  the  tube — the 
smaller  the  diameter,  the  greater  the  resistance  ;  the  greater  the  diameter,  the  less  the  resistance. 
The  resistance  in  narrow  tubes,  however,  increases  more  rapidly  than  the  diameter  of  the  tube 
decreases,  as  has  been  proved  experimentally. 

In  tubes  of  unequal  calibre,  at  different  parts  of  their  course,  the  velocity  of  the  current  varies — 
it  is  slower  in  the  wide  part  of  the  tube  and  more  rapid  in  the  narrow  parts.     As  a  general  rule,  in 


110  MOVEMENT   OF    FLUIDS    IN    ELASTIC   TUBES. 

tubes  of  unequal  diameter  the  velocity  of  the  current  is  inversely  proportional  to  the  diameter  of  the 
corresponding  section  of  the  tube;  ;.  e.,  if  the  tube  be  cylindrical,  it  is  inversely  proportional  to  the 
square  of  the  diameter  of  the  circular  transverse  section.  In  tubes  of  unifonu  diameter,  the  pro- 
pelling force  of  the  moving  fluid  diminishes  uniformly  from  point  to  point,  but  in  tubes  of  unequal 
calibre  it  does  not  diminish  uniformly.  As  the  resistance  is  greater  in  narrow  tubes,  of  course  the 
propelling  force  must  diminish  more  rapidly  in  them  than  in  wide  tubes.  Hence,  within  the  wide 
parts  of  the  tube  the  pressure  is  greater  than  the  sum  of  the  resistances  still  to  be  overcome,  while 
in  the  narrow  portions  it  is  less  than  these. 

Tortuosities  and  Bending  of  the  Vessels  add  new  resistance,  and  the  fluid  presses  more 
strongly  on  the  convex  side  than  on  the  concave  side  of  the  bend,  and  there  the  resistance  to  the 
flow  is  greater  than  on  the  concave  side. 

Division  of  a  tube  into  two  or  more  branches  is  a  source  of  resistance,  and  diminishes  the  pro- 
pelling power.  When  a  tube  divides  into  two  smaller  tubes,  of  course  some  of  the  particles  of  the 
fluid  are  retarded,  while  others  are  accelerated,  on  account  of  the  unequal  velocities  of  the  different 
layers  of  the  fluid.  Many  particles  which  had  the  greatest  velocity  in  the  axial  layer  come  to  lie 
more  toward  the  side  of  the  tube,  where  they  move  more  slowly ;  and,  conversely,  many  of  those 
lying  in  the  outer  layers  reach  the  centre,  where  they  move  more  rapidly.  Hence,  some  of  the 
propelling  force  is  used  up  in  this  process,  and  the  pulling  asunder  of  the  particles  where  the  tube 
divides  acts  in  a  similar  manner.  If  two  tubes  join  to  form  one  tube,  new  resistance  is  thereby 
caused,  which  must  diminish  the  propelling  force.  The  sum  of  the  mean  velocities  in  both  branches 
is  independent  of  the  angle  at  which  division  takes  place  (Jacobion).  If  a  branch  be  opened  from 
a  tube,  the  principal  current  is  accelerated  to  a  considerable  extent,  no  matter  at  what  angle  the 
branch  may  be  given  off. 

63.  CURRENTS  THROUGH  CAPILLARY  TUBES.— Poiseuille  proved,  experiment- 

ally,  that  the  flow  in  the  capillaries  is  subject  to  special  conditions  : — 

( 1 )  The  quantity  of  fluid  which  flows  out  of  the  same  capillary  tube  is  proportional  to  the 
pressure. 

(2)  The  time  necessary  for  a  given  quantity  of  fluid  to  flow  out  (with  the  like  pressure,  diameter 
of  tube  and  temperature),  is  proportional  to  the  length  of  the  tubes. 

(3)  The  product  of  the  outflow  (other  things  being  equal)  is  as  the  fourth  power  of  the  diameter. 

(4)  The  velocity  of  the  current  is  proportional  to  the  pressure  and  to  the  square  of  the  diameter, 
and  inversely  proportional  to  the  length  of  the  tube. 

(5)  The  resistance  in  the  capillaries  is  proportional  to  the  velocity  of  the  current. 

64.  MOVEMENT  OF  FLUIDS  AND  WAVE  MOTION  IN  ELASTIC  TUBES.— 

(l)  When  an  uninterrupted  uniform  current  flows  through  an  elastic  tube,  it  follows  exactly  the 
same  laivs  as  if  the  tube  had  rigid  walls.  If  the  propelling  power  increases  or  diminishes,  the 
elastic  tubes  become  wider  or  narrower,  and  they  behave,  as  far  as  the  movement  of  the  fluid  is 
concerned,  as  wider  or  narrower  rigid  tubes. 

(2)  Wave  Motion. — If,  however,  more  fluid  be  forced  in  jerks  into  an  elastic  tube,  i.e.,  inter- 
ruptedly, the  first  part  of  the  tube  dilates  suddenly,  corresponding  to  the  quantity  of  fluid  propelled 
into  it.  The  jerk  communicates  an  oscillatory  movement  to  the  particles  of  the  fluid,  which  is 
communicated  to  all  the  fluid  particles  from  the  beginning  to  the  end  or  the  tube;  a  positive  wave  is 
thus  rapidly  propagated  throughout  the  whole  length  of  the  tube.  If  we  imagine  the  elastic  tube  to 
be  closed  at  its  peripheral  end,  the  positive  wave  will  be  reflected  from  the  point  of  occlusion,  and 
it  may  be  prop.agatea  to  and  Iro  through  the  tube  until  it  finally  disappears.  In  such  a  closed  tube 
a  sudden  jet  ot  fluid  produces  only  a  wave  movement,  i.e.,  only  a  vibratory  movement,  or  an  altera- 
tion in  the  shape  of  the  liquid,  there  being  no  actual  translation  of  the  particles  along  the  tube. 

(3)  If,  however,  fluid  be  pumped  interruptedly  or  by  jerks  into  an  elastic  tube  filled  with  fluid, 
in  which  there  is  already  a  continuous  current,  the  movement  of  the  current  is  combined  with  the 
wave  movement.  We  must  carefully  distinguish  the  movement  of  the  current  of  the  Jiuid,  i.e., 
the  translation  of  a  mass  of  fluid  through  the  tube,  from  the  wave  movement,  the  oscillatory  move- 
ment, or  movement  of  change  of  form  in  the  column  of  fluid.  In  the  former,  the  particles  are 
actually  translated,  while  in  the  latter  they  merely  vibrate.  The  current  in  elastic  tubes  is  slower 
than  the  wave  movement,  which  is  propagated  with  great  rapidity. 

This  last  case  obtains  in  the  aiterial  system.  Ihe  blood  in  the  arteries  is  already  in  a  state  of 
continual  movement,  directed  from  the  aorta  to  the  capillaries  (movement  of  the  current  of  blood) ; 
by  means  of  the  systole  of  the  left  ventricle,  a  quantity  of  fluid  is  suddenly  pumped  into  the  aorta, 
and  causes  3. positive  wave  [pulse  wave),  which  is  jjropagated  with  great  rapidity  to  the  terminations 
of  the  arteries,  while  the  current  of  the  blood  itself  moves  much  more  slowly. 

Rigid  and  Elastic  Tubes. — It  is  of  importance  to  contrast  the  movement  of  fluids  in  rigid  and 
in  elastic  tubes.  If  a  certain  quantity  of  fluid  be  forced  into  a  rigid  tube  under  a  certain  pressure, 
the  same  quantity  of  fluid  will  flow  out  at  once  at  the  other  end  of  the  tube,  provided  there  be  no 
special  resistance.  In  an  elastic  tube,  immediately  after  the  forcing  in  of  a  certain  quantity  of  fluid, 
at  first  only  a  small  quantity  flows  out,  and  the  remainder  flows  out  only  after  the  propelling  force 
has  ceased  to  act. 

If  an  equal  quantity  of  fluid  be  periodically  injected  into  a  rigid  tube,  with  each  jerk  an  equal 


STRUCTURE    OF   ARTERIES. 


Ill 


quantity  is  forced  out  at  the  other  end  of  the  tube,  and  the  outflow  lasts  exactly  as  long  as  the  jerk 
or  the  contraction,  and  the  pause  between  two  period,  of  outflow  is  exactly  the  same  as  between 
the  two  jerks  or  contractions.  In  an  elastic  tube  it  is  different,  as  the  outflow  continues  for  a  time 
after  the  jerk;  hence,  it  follows  that  a  continuous  outflow  current  will  be  produced  in  elastic  tubes 
when  the  time  between  two  jerks  is  made  shorter  than  the  duration  of  the  outflow  after  the  jerk  has 
been  completed.  When  fluid  is  pumped  periodically  into  rigid  tubes,  it  causes  a  sharp,  abrupt  out- 
flow synchronous  with  the  inflow,  and  the  outflow  becomes  continuous  only  when  the  inflow  is  con- 
tinuous and  uninterrupted.  In  elastic  tubes  an  intermittent  current,  under  the  above  conditions, 
causes  a  continuous  outflow,  which  is  increased  with  the  systole  or  contraction. 

65.  STRUCTURE  AND  PROPERTIES  OF  THE  BLOOD 
VESSELS.— In  the  body,  the  large  vessels  carry  the  blood  to  and  from  the 
various  tissues  and  organs,  while  the  thin-walled  capillaries  bring  the  blood  into 
intimate  relation  with  the  tissues.  Through  the  excessively  thin  walls  of  the 
capillaries  the  fluid  part  of  the  blood  transudes,  to  nourish  the  tissues  outside  the 
capillaries.  [At  the  same  time,  fluids  pass  from  the  tissues  into  the  blood.  Thus, 
there  is  an  exchange  between  the  blood  and  the  fluids  of  the  tissues.  The  fluid, 
after  it  passes  into  the  tissues,  constitutes  the  lymph,  and  acts  like  a  stream  irrigat- 
ing the  tissue  elements.] 

I.  The  Arteries  are  distinguished  from  veins  by  \.\\t\r  thicker  walls,  due  to  the 
greater  development  of  smooth,  muscular  and  elastic  tissues;  the  middle  coat 
(tunica  media)  of  the  arteries  is  specially  thick, 
while  the  outer  coat  (t.  adventitia)  is  relatively  thin. 
[The  absence  of  valves  is  by  no  means  a  character- 
istic feature.] 

The  arteries  consist  of  three  coats  (Fig.  60). 
(i)  The  Tunica  intima,  or  inner  coat,  consists 
of  a  layer  of  i^a)  irregular,  long,  fusiform,  nucle- 
ated, squamous  cells,  forming  the  excessively  thin, 
transparent  endothelium  {His,  1866),  immediately 
in  contact  with  the  blood  stream.  [Like  other 
endothelial  cells,  these  cells  are  held  together  by  a 
cement  substance  which  is  blackened  by  the  action 
of  silver  nitrate.] 

Outside  this  lies  a  very  thin,  more  or  less  fibrous, 
layer — sub-epithelial  layer — in  which  numerous 
spindle  or  branched  protoplasmic  cells  lie  em- 
bedded within  a  corresponding  system  of  plasma 
canals.  Outside  this  is  an  elastic  lamina  (fi), 
which,  in  the  smallest  arteries,  is  a  structureless  or 
fibrous  elastic  membrane — in  arteries  of  meilium 
size  it  is  a  fenestrated  membrane  {Henle^,  while  in 
the  largest  arteries  there  may  be  several  layers  of 
elastic  laminae  or  fenestrated  elastic  membrane 
mixed  with  connective  tissue.  [In  some  arteries 
the  elastic  membrane  is  distinctly  fibrous,  the  fibres 
being  chiefly  arranged  longitudinally.  It  may  be 
stripped  off,  when  it  forms  a  brittle  elastic  mem- 
brane, which  has  a  great  tendency  to  curl  up  at  its 

margins.  In  a  transverse  section  of  a  middle-  rf,  the  connective-tissue  outer  coat  (i. 
sized  artery  it  appears  as  a  bright,  wavy  line,  but 

the  curves  are  probably  produced  by  the  partial  collapse  of  the  vessel.  It  forms 
an  important  guide  to  the  pathologist  in  enabling  him  to  determine  which  coat  of 
the  artery  is  diseased.] 

In  middle-sized  and  large  arteries  a  few  non-striped  muscular  fibres  are  disposed 
lotigitu  din  ally  between  the  elastic  plates  or  laminae  {K.  Bardelehen).  Along  with 
the  circular  muscular  fibres  of  the  middle  coat,  they  may  act  so  as  to  narrow  the 
artery,  and  they  may  also  aid  in  keeping  the  lumen  of  the  vessel  open  and  of 


112 


STRUCTURE    OF    ARTERIES. 


uniform  calibre.  It  is  not  probable  that  when  they  act  by  themselves  they  dilate 
the  vessel. 

(  2  )  The  Tunica  media,  or  middle  coat,  contains  much  non-striped  muscle  (c), 
which  in  the  sma//fs/  arteries  consists  of  transversely  disposed  non-striped  muscu- 
lar fibres  lying  between  the  endothelium  and  the  T.  adventitia,  while  a  finely 
granular  tissue  with  few  elastic  fibres  forms  the  bond  of  union  between  them.  As 
we  proceed  from  the  very  smallest  to  the  small  arteries,  the  number  of  muscular 
fibres  become  so  great  as  to  form  a  well-marked  fibrous  ring  of  non-striped  muscle, 
in  which  there  is  comparatively  little  connective  tissue.  In  the  large  arteries  the 
amount  of  connective  tissue  is  considerably  increased,  and  between  the  layers  of 
fine  connective  tissue  numerous  (as  many  as  50)  thick,  elastic,  fibrous  or  fenes- 
trated laminje  are  concentrically  arranged. 

A  few  non-striped  fibres  lie  scattered  among  these,  and  some  of  them  are 
arranged  transversely,  while  a  few  have  an  oblique  or  longitudinal  direction. 

The  first  part  of  the  aorta  and  pulmonary  artery,  and  the  retinal  arteries  are  devoid  of  muscle. 
The  descending  aorta,  common  iliac,  and  popliteal  have  longitudinal  fibres  between  the  transverse 
ones.     Longitudinal   bundles  lying  inside  the  media  occur  in  the  renal,  splenic  and  internal  sper- 


t  which  is  blackened  by 


mitic  arteries.     Longitudinal  bundles  occur  both  on  the  outer  and  inner  surfaces  of  the  umbilical 
arteries,  which  are  very  muscular. 

(3)  The  Tunica  adventitia,  or  outer  coat,  in  the  smallest  axtmes  consists  of 
a  structureless  membrane  with  a  iew  connective-tissue  corpuscles  attached  to  it ;  in 
somewhat  larger  arteries  there  is  a  layer  of  fine,  fibrous,  elastic  tissue  mi.xed  with 
bundles  of  fibrillar  connective  tissue  (i/).  In  arteries  of  w/r/i^/Zif  «3c,  and  in  the 
largest  arteries  the  chief  mass  consists  of  bundles  of  fibrillar  connective  tissue  con- 
taining connective-tissue  corpuscles.  The  bundles  cross  each  other  in  a  variety 
of  directions,  and  fat  cells  often  lie  between  them.  Next  the  media  there  are 
numerous  fibrous  or  fenestrated  elastic  lamellae.  In  medium-sized  and  small 
arteries  the  elastic  tissue  next  the  media  takes  the  form  of  an  independent  elastic 
membrane  (Henle's  external  elastic  membrane).  Bundles  of  non-striped  muscle, 
arranged  longitudinally,  occur  in  the  adventitia  of  the  arteries  of  the  penis,  and 
in  the  renal,  splenic,  spermatic,  iliac,  hypogastric  and  superior  mesenteric  arteries. 

II.  The  capillaries,  while  retaining  their  diameter,  divide  and  reunite  so  as  to 
form  networks,  whose  shape  and  arrangement  differ  considerably  in  different  tis- 
sues.    The  diameter  of  the  capillaries  varies  considerably,  but  as  a  general  rule  it 


STRUCTURE    OF    VEINS.  113 

is  such  as  to  admit  freely  a  single  row  of  blood  corpuscles.  In  the  retina  and 
muscle  the  diameter  is  5-6  p.,  and  in  bone  marrow,  liver,  and  choroid  10-20  //. 
The  tubes  consist  of  a  single  layer  of  transparent,  excessively  thin,  nucleated, 
endothelial  cells  joined  to  each  other  by  their  margins  {Boyer,  Auerbach,  Eberth, 
Aeby,  1865). 

[The  nuclei  contain  a  well-marked  intranuclear  plexus  of  fibrils,  like  other  nuclei.]  The  cells 
are  more  fusiform  in  the  smaller  capillaries  and  more  polygonal  in  the  larger.  The  body  of  the 
cell  presents  the  characters  of  very  faintly  refractive  protoplasm,  but  it  is  doubtful  whether  the  body 
of  the  cell  is  endowed  with  the  property  of  contractility. 

Action  of  Silver  Nitrate.— If  a  dilute  solution  (/^^  per  cent.)  of  silver 
nitrate  be  injected  into  the  bloodvessels,  the  cement  substance  of  the  endothelium 
and  of  the  muscular  fibres  as  well,]  is  revealed  by  the  presence  of  the  black  "silver 
lines."  The  blackened  cement  substance  shows  little  specks  and  large  black  slits 
at  different  points.  It  is  not  certain  whether  these  are  actual  holes  (/.  Arnold) 
through  which  colorless  corpuscles  may  pass  out  of  the  vessels,  or  are  merely 
larger  accumulations  of  the  cement  substance. 

[.'\mold  called  these  small  areas  in  the  black  silver  lines  when  they  are  large  stomata,  and  when 
small  stigmata.  They  are  most  numerous  after  venous  congestion,  and  after  the  disturbances 
which  follow  inflammation  of  a  part  {Cchnheim,  Winiwarter).  They  are  not  always  present.  The 
existence  of  cement  substance  between  the  cells  may  also  be  inferred  from  the  fact  that  indigo- 
sulphate  of  soda  is  deposited  in  it  (  Thcma),  and  particles  of  cinnabar  and  China  ink  are  fixed  in  it, 
when  these  substances  are  injected  into  the  blood  (/oa).] 

Fine  anastomosing  fibrils  derived  from  non-medullated  nerves  terminate  in 
small  end  buds  in  relation  with  the  capillary  wall ;  ganglia  in  connection  with 
capillary  nerves  occur  only  in  the  region  of  the  sympathetic  (^Bremer  and  VVal- 
deyer). 

[If  a  capillarv  is  examined  in  a  perfectly  fresh  condition  (while  living)  and  with- 
out the  addition  of  any  reagent,  it  is  impossible  to  make  out  any  line  of  demarca- 
tion between  adjacent  cells,  owing  to  the  uniform  refractive  index  of  the  entire 
wall  of  the  tube.] 

The  small  vessels  next  in  size  to  the  capillaries  and  continuous  with  them  have 
a  completely  structureless  covering  in  addition  to  the  endothelium. 

III.  The  veins  are  generally  distinguished  from  the  arteries  by  their  lumen 
being  iviJer  than  the  lumen  of  the  corresponding  arteries ;  their  walls  are  thinner, 
on  account  of  the  smaller  amount  of  non-striped  muscle  and  elastic  tissue  (the 
non-striped  muscle  is  not  unfrequently  arranged  longitudinally  in  veins).  They 
are  aKo  more  extensile  (with  the  same  strain).  The  adventitia  is  usually  the 
thickest  coat. 

The  occurrence  of  valves  is  limited  to  the  veins  of  certain  areas,  (i)  The 
T.  intima  consists  of  a  layer  of  shorter  and  broader  endothelial  cells,  under 
which,  in  the  smallest  veins,  there  is  a  structureless  elastic  membrane,  sub- 
epithelial layer,  which  is  fibrous  in  veins  somewhat  larger  in  size,  but  in  all  cases 
is  thinner  than  in  the  arteries.  In  large  veins  it  may  assume  the  characters  of  a 
fenestrated  membrane,  which  is  double  in  some  parts  of  the  crural  and  iliac 
veins.  Isolated  muscular  fibres  exist  in  the  intima  of  the  femoral  and  popliteal 
veins. 

(2)  The  T.  media  of  the  larger  veins  consists  of  alternate  layers  of  elastic 
and  muscular  tissue  united  to  each  other  by  a  considerable  amount  of  connective 
tissue,  but  this  coat  is  always  thinner  than  in  the  corresponding  arteries.  This 
coat  diminishes  in  the  following  order  in  the  following  vessels  :  popliteal,  veins 
of  the  lower  extremity,  veins  of  the  upper  extremity,  superior  mesenteric,  other 
abdominal  veins,  hepatic,  pulmonary,  and  coronary  veins.  The  following  veins 
contain  no  muscle  :  veins  of  bone,  central  nervous  system  and  its  membranes, 
retina,  the  superior  cava,  with  the  large  trunks  that  open  into  it,  the  upper  part 
of  the  inferior  cava.     Of  course,  in  these  cases  the  media  is  very  thin.     In  the 


114 


PHYSICAL    PROPERTIES   OF   THE    BLOOD    VESSELS. 


smallest  veins  the  media  is  formed  of  fine  con- 
nective tissue,  with  very  few  muscular  fibres 
scattered  in  the  inner  part. 

(3)  The  T.  adventitia  is  thicker  than  that 
of  the  corresponding  arteries ;  it  contains  much 
connective  tissue,  usually  arranged  longitudin- 
ally, and  not  much  elastic  tissue.  Longitudinally 
arranged  muscular  fibres  occur  in  some  veins 
(renal,  portal,  inferior  cava  near  the  liver,  veins 
of  the  lower  extremities).  The  valves  consist 
of  fine  fibrillar  connective  tissue  with  branched 
cells.  An  elastic  network  e.xists  on  their  convex 
surface,  and  both  surfaces  are  covered  by  endo- 
thelium. The  valves  contain  many  muscular 
fibres  (Fig.  62).  [Ranvier  has  shown  that  the 
shape  of  the  epithelial  cells  covering  the  two 
surfaces  of  the  valves  differs.  On  the  side  over 
which  the  blood  passes,  they  are  more  elongated 
than  on  the  cardiac  side  of  the  valve,  where  the 
long  axes  of  the  cell  are  placed  transversely.] 

The  sinuses  of  the  dura  mater  are  spaces  covered  with 
endothelium.  The  spaces  are  either  duplicatures  of  the 
membrane,  or  channels  in  the  substance  of  the  tissue  itself. 

Cavernous  spaces  we  may  imagine  to  arise  by 
numerous  divisions  and  anastomoses  of  tolerably  large 
veins  of  unequal  calibre.  The  vascular  wall  appears  to 
be  much  perforated  and  like  a  sponge,  the  internal  space 
being  traversed  by  threads  and  strands  of  tissue,  which 
are  covered  with  endothelium  on  their  surfaces,  that  are 
in  contact  vi'ith  the  blood.  The  surrounding  wall  consists 
of  connective  tissue,  which  is  often  very  tough,  as  in  the 
corpus  cavernosum,  and  it  not  unfrequently  contains  non- 
striped  muscle. 

Cavernous  Formations  of  an  analogous 
nature  on  arteries  are  the  carotid  gland  oi  the 
frog  (Fig.  45),  and  a  similar  structure  on  the  pulmonary  arteries  and  aorta  of  the 
turtle,  and  the  coccvgeal  gland  of  man  (Luse/ika).  The  last  structure  is  richly 
supplied  with  sympathetic  nerve  fibres,  and  is  a  convoluted  mass  of  ampullated 
or  fusiform  dilatations  of  the  middle- sacral  artery  (Arnold),  surrounded  and 
permeated  by  non-striped  muscle  (Eberth). 

Vasa  Vasorum. —  [These  are  small  vessels  which  nourish  the  coats  of  the  arteries  and  veins. 
They  arise  from  one  part  of  a  vessel  and  enter  the  walls  of  the  same  or  another  vessel  at  a  lower 
level.  They  break  up  chiefly  in  the  outer  coat,  and  none  enter  the  inner  coat.]  In  structure  they 
resemble  otfier  small  blood  vessels.  The  blood  circulating  in  the  arterial  or  venous  wall  is  returned 
by  small  veins. 

[Lymphatics.— There  are  no  lymphatics  on  the  inner  surface  of  the  muscular  coat,  or  under 
the  intima  in  large  arteries.  They  are  numerous  in  a  gelatinous  layer  immediately  outside  the 
muscular  coat,  and  the  same  relation  obtains  in  large  muscular  veins  and  lymphatic  trunks  (Hoggan),'\ 

Intercellular  Blood  Channels. — Intercellular  blood  channels  of  narrow  calibre,  and  without 
walls,  occur  in  the  granulation  tissue  of  healing  wounds.  At  first  blood  plasma  alone  is  found 
between  the  formative  cells,  but  afterward  the  blood  current  forces  blood  corpuscles  through  the 
channels.  The  first  blood  vessels  in  the  developing  chick  are  formed  in  a  similar  way  from  the 
formative  cells  of  the  mesoblast. 

Properties  of  the  Blood  Vessels. — The  larger  blood  vessels  are  cylindrical 
tubes  composed  of  several  layers  of  various  tissues,  more  especially  elastic  tissue 
and  plain  muscular  fibres,  and  the  whole  is  lined  by  a  smooth  layer  of  endothelium. 
One  of  the  most  important  properties  is  the  contractility  of  the  vascular  wall,  in 
virtue  of  which  the  blood  vessel  becomes  contracted,  so  that  the  calibre  of  the 


ngitudinal  section  of  a  vein  at  the  level  of 
a  valve,  a,  hyaline  layer  of  the  internal 
coat ;  b,  elastic  lamina  ;  c,  groups  of 
smooth  muscular  fibres  divi  ' 
ly  :  t/y  longitudinal  muscular  fibres 


PHYSICAL    PROPERTIES   OF   THE    BLOOD    VESSELS.  llo 

vessel,  and  therefore  the  supply  of  blood  to  a  part,  are  altered.  The  contractility 
is  due  to  the  plain  muscular  fibres,  which  are,  for  the  most  part,  arranged  circu- 
larly. It  is  most  marked  in  the  small  arteries,  and  of  course  is  absent  where  no 
muscular  tissue  occurs.  The  amount  and  intensity  of  the  contraction  depend  upon 
the  development  of  the  muscular  tissue  ;  in  fact,  the  two  go  hand-in-hand.  [If 
an  artery  be  exposed  in  the  living  body  it  soon  contracts  under  the  stimulus  of 
the, atmosphere  (_/.  Hunter)  acting  upon  the  muscular  fibres.] 

[Action  of  Alkalies  and  Acids  on  the  Vascular  System. — Gaskell  finds  that  very  dilute 
alkalies  and  acids  have  a  remarkable  elfect  on  the  Ijlood  vessels  and  also  upon  the  heart.  A  very 
dilute  solution  of  lactic  acid  (I  part  to  10,000  parts  of  saline  solution),  passed  through  the  blood 
vessels  of  a  frog,  alway-;  enlarges  the  calibre  of  the  blood  vessels,  while  an  alkaline  solution  (i  part 
sodium  hydrate  to  10,000  or  20,000  parts  saline  solution)  always  diminishes  their  size,  usually  to 
absolute  closure,  and  indeed  the  artificial  constriction  of  the  blood  vessels  may  be  almost  complete. 
These  fluids  are  antagonistic  to  each  other  as  far  as  regards  their  action  on  the  calibre  of  the  arteries. 
Microscopic  observations  which  confirmed  these  results  were  also  made  on  the  blood  vessels  of  the 
mylo-liyoid  muscle  of  the  frog.  Dilute  alkaline  solutions  act  on  the  heart  in  the  same  way.  After 
a  series  of  beats,  the  ventricle  stops  beating,  the  stand  still  being  in  a  state  of  contraction.  Very 
dilute  lactic  acid  causes  the  ventricle  to  stand  still  in  the  position  of  complete  relaxation.  The 
action  of  the  acid  and  alkaline  solutions  are  antagonistic  in  their  action  on  the  ventricle.  Gaskell 
attaches  considerable  importance  to  the  "tonic"  and  "atonic"  conditions  of  the  whole  vascular 
system  produced  by  very  dilute  solutions  of  alkalies  and  acids  respectively.] 

[Other  Drugs. — Cash  and  Brunton  find  that  dilute  acids  have  a  tendency  to  increase  the 
transudation  through  the  vessels  and  produce  adema  of  the  surrounding  tissues.  They  also  ob- 
served that  barium,  calcium,  strontium,  copper,  iron,  and  tin  produce  contraction  of  the  blood  vessels 
when  solutions  of  their  salts  are  driven  through  them,  while  the  same  effect  is  produced  by  very 
dilute  solutions  of  potassium.  Nicotin,  atropin,  and  chloral  difier  in  their  action,  according  to  the 
dose.  In  these  experiments  the  effect  was  ascertained  by  the  amount  of  fluid  which  flowed  out  of 
the  vessels  in  a  given  time.] 

That  the  capillaries  undergo  dilatation  and  contraction,  owing  to  variations 
in  size  of  the  protoplasmic  elements  of  their  walls,  must  be  admitted. 

Strieker  has  described  capillaries  as  "  protoplasm  in  tubes,"  and  observed  that  they  exhibited 
movements  when  stimulated  in  living  animals.  Golubew  de.scribed  an  active  state  of  contraction  of 
the  capillary  wall,  but  he  regarded  the  nuclei  as  the  parts  which  underwent  change.  Tarchanoff 
found  that  mechanical  or  electrical  stimulation  caused  a  change  in  the  shape  and  size  of  the  nuclei, 
so  that  he  regards  these  as  the  actively  contractile  parts.  [Severini  also  attaches  great  importance 
to  the  contractility  of  the  capillaries  and  especially  uf  their  nuclei  as  influencing  the  blood  stream. 
Oxygen  acts  on  the  nuclei  of  the  capillary  wall  (membrana  nictitans  of  frog)  and  causes  them  to 
swell,  while  CO,  has  an  opposite  elfect.  The  circulation  through  a  lung  suddenly  filled  with  O 
or  atmospheric  air,  is  at  fiist  very  rapid,  but  soon  becomes  small,  while  with  COg  the  circulation 
remains  constant.]  Strieker's  observations  were  made  on  the  capillaries  of  tadpoles.  These  phe- 
nomena became  less  marked  as  the  animal  became  older.  Rouget  observed  the  same  result  in  the 
capillaries  of  new-born  mammals.  As  the  capillaries  are  excessively  thin  and  delicate,  and  as  they 
are  solt  structures,  it  is  obvious  that  the  form  of  the  individual  cells  must  depend  to  a  considerable 
extent  upon  the  degree  to  which  the  vessels  are  filled  with  blood.  In  vessels  which  are  distended 
with  blood  the  endothelial  cells  are  flattened,  but  when  the  capillaries  are  collapsed,  they  project 
more  or  less  into  the  lumen  of  the  vessel  [Renaiil). 

It  is  a  well-known  fact  that  the  capillaries  present  great  variations  in  their  diameter  at  different 
times.  As  these  variations  are  usually  accompanied  by  a  corresponding  contraction  or  dilatation  of 
the  arterioles,  it  is  usually  assumed  that  the  variations  in  the  diameter  of  the  capillaries  are  due  to 
differences  of  the  pressure  within  the  capillaries  thamselves,  viz,  to  the  elasticity  of  their  walls. 
Every  one  is  agreed  that  the  capillaries  are  very  elastic,  but  the  experiments  of  Roy  and  Graham 
lirown  show  that  they  are  contractile  as  well  as  elastic,  and  these  observers  conclude  that,  under 
normal  conditions,  it  is  by  the  contractility  of  the  capillary  wall  as  a  whole  that  the  diameter  of 
tnese  vessels  is  changed,  and  to  all  appearance  their  contractility  is  constantly  in  action.  "  The 
individual  capillaries  (in  all  probability)  contract  or  expand  in  accordance  with  the  requirements  of 
the  tissues  through  which  they  pass.  The  regulation  of  the  vascular  blood  How  is  thus  more  com- 
])Iete  than  is  usually  imagined"  [^Roy  and  Graham  Broiun), 

Physical  Properties. — Among  the  physical  properties  of  the  blood  vessels, 
elasticity  is  the  most  important;  their  eXasUc'xty  m  small  in  amoii/it,  i.  c,  ihcy 
offer  little  resistance  to  any  force  applied  to  them  so  as  to  distend  or  elongate 
them,  but  it  \i  perfect  in  quality,  i.  e.,  the  blood  vessels  rapidly  regain  their  original 
size  and  form  after  the  force  distending  them  is  removed. 


116  THE    PULSE. 

[Uses  of  Elasticity. — The  elasticity  of  the  arteries  is  of  the  utmost  importance  in  aiding  tlie 
conversion  of  the  unequal  movement  of  the  blood  in  the  large  arteries  into  a  uniform  How  in  the 
capillaries.  E.  H.  Weber  compared  the  elastic  wall  of  the  arteries  with  the  air  in  the  air  chamber 
of  a  tire-engine.  In  both  cases  an  elastic  medium  is  acted  upon— the  air  in  the  one  case  and  the 
elastic  tissue  in  the  other — which  in  turn  presses  upon  the  fluid,  propelling  it  onward  continually, 
while  the  action  of  the  pump  or  the  heart,  as  the  case  may  be,  is  intermittent.  The  ordinary  spray 
producer  acts  on  this  principle.  A  uniform  spray  or  jet  is  obtained  by  pumping  intermittently,  but 
only  when  the  resistance  is  such  as  to  bring  into  action  the  elasticity  of  the  bag  between  the  pump 
and  the  spray  orifice.] 

According  to  E.  H.  Weber,  Volkmann  and  Wertheim,  the  elongation  of  a  blood  vessel  (and 
most  moist  tissues)  is  not  proportional  to  the  weight  used  to  extend  it,  the  elongation  being  rela- 
tively less  with  a  large  weight  than  with  a  small  one,  so  that  the  curve  of  extension  is  nearly  [or, 
at  least,  bears  a  certain  relation  to]  a  hyperbola. 

According  to  Wundt,  we  have  not  only  to  consider  the  extension  produced  atyfr.r/by  the  weight, 
but  also  the  subsequent  "  elastic  after-effect,"  which  occurs  gradually.  The  elongation  which 
takes  place  during  the  last  few  moments  occurs  so  slowly  and  so  gradually  that  it  is  well  to  observe 
the  effect  by  means  of  a  magnifying  lens.  Variations  from  the  general  law  occur  to  this  extent, 
that  if  a  certain  weight  is  exceeded,  less  extension,  and,  it  may  be,  permanent  elongation  of  the 
artery  not  unfrequently  occur.  K.  Bardeleben  found,  especially  in  veins  elongated  to  40  or  50  per 
cent,  of  their  original  length,  that  when  the  weight  employed  increased  by  an  equal  amount  each 
time,  the  elongation  was  proportional  to  the  square  root  of  the  weight.  This  is  apart  from  any 
elastic  after- effect.  Veins  may  be  extended  to  at  least  50  per  cent,  of  their  length  without  passing 
the  limit  of  their  elasticity. 

[Roy  has  made  careful  experiments  upon  the  elastic  properties  of  the  arterial  wall.  A  portion 
of  an  artery,  so  that  it  could  be  distended  by  any  desired  internal  pressure,  was  enclosed  in  a  small 
vessel  containing  olive  oil.  The  small  vessel  with  oil  was  arranged  in  the  same  way  as  in  Fig.  53 
for  the  heart.  The  variations  of  the  contents  were  recorded  by  means  of  a  lever  writing  on  a  revolv- 
ing cylinder.  The  aorta  and  other  large  arteries  were  found  to  be  most  elastic  and  most  disten- 
sible at  pressures  corresponding  more  or  less  exactly  to  their  normal  blood  pressure,  while  in  veins 
the  relation  between  internal  pressure  and  the  cubic  capacity  is  very  different.  In  them  the  maxi- 
mum of  disiensibility  occurs  with  pressures  immediately  above  zero.  Speaking  generally,  the  cubic 
capacity  of  an  artery  is  greatly  increased  by  raising  the  intra-arterial  tension,  say  from  zero  to  about 
the  normal  internal  pressure  which  the  artery  sustains  during  life.  Thus  in  the  rabbit  the  capacity 
of  the  aorta  was  tjuadriiplcJ  by  raising  the  intra-arterial  pressure  from  zero  to  200  mm.  Hg,  while 
that  of  the  carotid  was  more  than  six  times  greater  at  that  pressure  than  it  was  in  ihe  undistended 
condition.  The  pulmonary  artery  is  distinguished  by  its  excessive  elastic  disiensibility.  Its  capa- 
city (rabbit)  was  increased  more  than  twelve  times  on  raising  the  internal  pressure  from  zero  to 
about  36  mm.  Hg.  Veins,  on  the  other  hand,  are  distinguished  by  the  relatively  small  increase  in 
their  cubic  capacity  produced  by  greatly  raising  the  internal  pressure,  so  that  the  enormous  changes 
in  the  capacity  of  the  veins  during  life  are  due  less  to  differences  in  the  pressure  than  to  the  great 
ditt'erences  in  the  quantity  of  blood  which  they  contain  (jVo)/).] 

Pathological. — Interference  with  the  nutrition  of  an  artery  alters  its  elasticity  [and  that  in  cases 
where  no  structural  changes  can  be  found.]  Marasmus  preceding  death  causes  the  arteries  to 
become  wider  than  normal  (A't'i').  Age  also  influences  their  elasticity — in  seme  old  people  they 
become  atheromatous  and  even  calcified.  [1  he  ratio  of  expansion  of  strips  of  the  aortic  wall  to 
the  weights  employed  to  strttch  them,  remains  much  the  same  from  childhood  up  to  a  certain  age 
{Koy).-\ 

Cohesion. — Blood  vessels  are  endowed  with  a  very  large  amount  of  cohesion, 
in  virtue  of  which  they  are  able  to  resist  even  considerable  internal  pressure  with- 
out giving  way.  The  carotid  of  a  sheep  is  ruptured  only  when  fourteen  times  the 
usual  pressure  it  is  called  upon  to  bear  is  put  upon  it  {Volkmann).  A  greater 
pressure  is  required  to  rupture  a  vein  than  an  artery  with  the  same  thickness  of  its 
wall.  The  carotid  of  a  dog  resi.sts  50  times  the  blood  pressure,  the  jugular  vein 
about  the  half  of  this  {Grehanl  and  Qiiinquand^. 

Pathological. — The  cohesion  of  the  arteries  is  diminished,  especially  in  old  age. 

66.  THE  PULSE— HISTORICAL.— Although  the  movement   of  the  pulse  in  the  super- 

ricially  placed  arteries  \\"as  known  to  the  ancients,  still  the  pulse,  as  it  was  affected  by  disease,  was 
more  studied  by  the  older  physicians  than  the  normal  pulse.  Hippocrates  (46010  337  B.  c.)  speaks 
of  the  former  as  (iifuyinJi,  while  Herophilus  (300  B.  c.)  contrasted  the  normal  pulse  {■KaXixi'xi') 
with  the  pulse  of  disease  (a<fu)-,'i.i/f).  He  lays  special  stress  upon  the  relative  time  occupied  by 
the  dilatation  and  contraction  of  the  arterial  tube,  and  compares  these  phenomena  with  the  notes  of 
music.  He  established  the  fact  that  the  rhythm  of  the  pulse  varies  in  the  newly-born,  in  the  adult, 
and  in  the  aged.  I'uither,  he  distinguished  the  size  ^fullness,  quiekness  ^i\A  frequency  of  the  pulse. 
Erasislratus  (f  2S0  B.  c),  a  contemporary  of  Herophilus,  made  correct  observations  on   the  ptilse 


INSTRUMENTS    FOR    INVESTIGATING    THE    PULSE. 


117 


wiKv.  He  points  out  that  the  pulse  occurs  sooner  in  arteries  near  the  heart  than  in  those  placed 
further  away  from  it,  because  the  pulse  proceeding  from  the  heart  passes  toward  the  periphery. 
Krasislratus  placed  a  cannula  in  the  course  of  an  artery,  and  he  found  that  the  pulse  could  still  be 
fell  on  the  distal  side  of  this  point.  Achigenes  gave  the  name  dicrotic  pulse  to  a  condition  which  he 
liad  observed  in  febrile  stales.  Galen  (131  to  202  A.  D.)  gave  more  exact  details  as  to  the  relations 
of  the  dilatation  and  contraction  of  the  arteries  during  the  movement  of  the  pulse,  and  supplied 
much  information  on  the  pulse  rhythm,  and  the  influence  of  temperament,  age,  sex,  period  of  the 
year,  climate,  sleep  and  waking,  cold  and  warm  baths,  on  its  rate  and  other  qualities.  Cusanus 
(1565)  was  the  first  person  to  count  t!ie  pulse  beats  with  tlie  aid  of  a  watch. 

67.  INSTRUMENTS  FOR  INVESTIGATING  THE  PULSE.— 

[The  characters  of  the  pulse  may  be  investigated  by:  — 

1.  The  eye  i ins/section.^ 

2.  The  finger  {palpation.') 

3.  Instruments.] 

[Two  or  three  fingers  are  placed  over  the  course  of  the  radial  artery,  and  the 
various  phenomena  in  connection  with  the  pulse  are  noted.      It  takes  much  prac- 


tice for  the  physician  to  acquire  the  tactiis  eruditus,  and,  notwithstanding  the 
value  of  instruments,  every  physician  should  make  a  careful  study  of  the  pulse 
beat  with  his  finger.] 

The  individual  phases  of  the  movement  of  the  pulse  could  oiily  be  accurately 
investigated  by  the  application  of  instruments  to  the  arteries. 

(1)  Poiseuille's  Box  Pulse  Measurer  (1829). — An  artery  (Fig.  63,  «.  «)  is  exposed  and 
placed  in  an  oblong  box  (K,  K|  filled  with  an  indifferent  fluid.  A  vertical  tube,  with  a  scale 
attached,  communicates  with  the  interior  of  the  box.  The  column  of  fluid  undergoes  a  variation 
with  every  jiulse  beat. 

(2)  Herisson's  Tubular  Sphygmometer  consists  of  a  glass  tube  whose  lower  end  is  covered 
with  an  elastic  membrane  ( Fig.  64).  The  tube  is  partly  filled  with  Hg.  The  membrane  is  placed 
over  the  position  of  a  pulsating  artery,  so  that  its  beat  causes  a  movement  in  the  Hg.  Chelius  used 
a  similar  instrument,  and  he  succeeded  with  this  instrument  in  showing  the  existence  of  the  double 
beat  (dicrotism)  in  the  normal  pulse  (1850). 

(3)  Vierordt's  Sphygmograph  (1855). — ^Tn  this,  one  of  the  earhest  sphvgmographs,  Vierordt 
departed  from  the  principle  of  a  fluctuating  fluid  column,  and  adopted  the  principle  of  the  lex'er. 


116 


MAREY  S    SPHVGMOGRAPH. 


I'pon  the  artery  rested  a  small  pad,  which  moved  a  complicated  system  of  levers.  At  first  he  used 
a  straw  6  inches  long,  which  rested  on  the  artery.  The  point  of  one  of  the  levers  inscribed  its 
movements  upon  a  revolving  cylinder.     This  instrument  was  soon  discarded. 

(4)  Marey's  Sphygmograph  consists  of  a  combination  of  a  lever  with  an  elastic  spring.  It 
consists  of  an  elastic  spring  (Fig.  65,  A)  fixed  at  one  end,  :,  free  at  the  other  end,  and  provided 
with  an  ivory  pad,  r,  which  is  pressed  by  the  spring  upon  the  radial  artery.     On  the  upper  surface 


Fig.  65. 


Scheme  of  M.irey's  sphygmugraph.  A,  spring  with  ivory  pad,  y,  which  rests  on  the  artery : 
i  into  ^:  z',  writing  lever;  P,  piece  of  smolced  glass  or  paper  moved  by  clockwork,  U  ; 
sion  of  A  ;  S,  arrangement  for  fixing  the  instrument  to  the  arm  of  the  patient. 


Marey's 
C,  i 
L,  s. 


ed  sphygmograph,  as  used  when  a  tracing  is  taken.    A,  steel  spring  ;  B,  first  le\  cr  ;  C,  writing  lever  ; 
f^ree  writing  end  ;   D,  screwfor  bringing  B  in  contact  with  C  ;  G,  slide  with  smoked  paper;  H, clockwork: 
;w  for  increasing  the  pressure  ;  M,  dial  indicating  the  amount  of  pressure  ;  K,  K,  straps  for  fixing  the  in- 
to the  arm,  and  the  arm  to  the  double-inclined  plane  or  support  {Byrom  Bramwell) 


Fig.  67. 


fFiG  67. — Scheme  showing  the  essential  part  of  the  instrument  ivken  in  working  order,  {.  e.,  the  turned  up  knife 
edge,  B",  of  the  short  lever  in  contact  with  the  writing  lever,  C.  Every  movement  of  the  steel  spring  at  A",  /.  e  , 
the  artery,  will  in  this  position  be  communicated  to  the  writing  lever.] 

[Fig  68.— Scheme  showing  the  essential  parts  of  the  \\Kiro,mi:n\.a/ter  incrense  o/lhf  pressure.  The  knife  edge,  B", 
is  no  longer  in  contact  with  the  writing  lever,  and  the  movements  of  the  steel  spring.  A",  /-  e.,  the  artery,  are  no 
longer  communicated  to  it  In  order  to  put  the  instrument  into  working  order,  the  knife  edge,  B",  must  be  raised 
to  the  position  indicated  by  the  dotted  lines.     This  is  effected  by  means  of  the  screw,  D  {Byrorn  Brafmtu-//).] 


of  the  pad  there  is  a  vertically-placed  fine-toothed  rod,  i,  which  is  pressed  upon  by  a  weak  spring, 
e,  so  that  its  teeth  dovetail  with  similar  teeth  in  the  small  wheel,  /,  from  whose  a.xis  there  projects 
a  long,  light,  wooden  lever,  t,  running  nearly  parallel  with  the  elastic  spring.  This  lever  has  a  fine 
style  at  its  free  end,  s,  which  writes  upon  a  smoked  plate,  P,  moved  by  clockwork.  U,  in  front  of 
the  style.  Marey's  instrument,  as  improved  by  Mahomed  and  others,  has  been  very  largely  used. 
[Its  more  complete  form,  as  in  Fig.  66,  where  it  is  shown  applied  to  the  arm,  consists  of — (i)  a 


dudgeon's  sphygmograph.  119 

steel  spring.  A,  which  is  provided  with  a  pad  resting  on  the  artery,  and  moves  with  each  movement 
of  the  artery ;  (2)  the  lever,  C.  which  records  the  movement  of  the  artery  and  spring  in  a  magnified 
form  on  the  smoked  paper,  G;  (3)  an  arrangement,  L,  whereby  the  esact  pressure  exerted  upon 
the  artery  is  indicated  on  the  dial,  M  (Ma/wmcd ) ;   (4)  the  clockwork,  H,  which  moves  the  smoked 


Fig.  69. 


Dudgeun's  sphygmograph. 

Fig.  70. 


Mode  of  applying  Dudgeon's  sphygmograph. 

paper.  G,  at  a  uniform  rate;  (5)  a  framework,  to  which  the  various  parts  of  the  instrument  are 
attached,  and  by  means  of  which  the  instrument  is  fastened  to  the  arm  by  straps,  K,  K  [Byrom 
Bram-.vell).'] 

[Application. — In  applying  the  sphygmograph,  cause  the  patient  to  seat  himself  beside  a  low 


120 


BRONDGEEST  S    PANSPHVGMOGRAPH. 


Flu.  71,  table,  and  place  his  arm  on  the   double-in- 

clined plane  (Fig.  66).  In  the  newer  foim 
of  in^trurnent,  the  lid  of  the  box  is  so  arranged 
as  to  unfold  to  make  this  support.  The  fingers 
might  to  he  semi-flexed.  Mark  the  position 
iif  the  radial  artery  with  ink.  See  that  the 
clockwork  is  wound  up,  and  apply  the  ivory 
pad  exactly  over  the  radial  artery  where  it 
lies  upon  the  radius,  fixing  it  to  the  arm  by 
the  non- elastic  straps  K,  K  (Fig.  66).  Fix 
the  slide  holding  the  smoked  paper  in  posi- 
tion. The  best  paper  to  use  is  that  with 
Sphygmogram— pressure  2  ounces.  a    very    smooth    surface     (albuminized    or 

enameled  card),  smoked  over  the  flame  of 
a  turpentine  lamp  or  over  a  piece  of  burning  camphor.  The  writing  style  is  so  arranged  as  to 
\A'rite  upon  the  smoked  paper  with  the  least  possible  friction.  The  most  important  part  of  the 
process  is  to  regulate  the  pressure  exerted  upon  the  artery  by  means  of  the  milled  head,  L.  This 
must   be  determined   for  each  ^ulse,  but  the  rule  is  to  graduate  the  pressure   until  the  greatest 


Fig.  72. 


me  of  Brondgeest's 
recording  (S,  S')  t; 
distant  artery.     1! 


sphygmograph,  on  the  principle  of  Upham  and  Marey's  tambours.  S,  S',  receiving  and 
mbours  with  writing  levers,  Zand  Z' ;  K.  K',  conducting  tubes;  /,  over  heart, /' over  a 
is  illustration  also  shows  the  principles  of  Marey's  cardiograph. 


amplitude  of  movement  of  the  lever  is  obtained.  Set  the  clockwork  going,  and  a  tracing  is 
obtained,  which  must  be  "  fixed"  by  dipping  it  in  a  rapidly-drying  varnish,  ?,?•.,  photographic.  In 
every  case,  scratch  on  the  tracing,  with  a  needle,  the  name,  date,  and  amount  of  pressure  employed.] 

[(5)  Dudgeon's  Sphygmograph. — This  is  a  most  convenient  form  of  sphygmograph.  Fig. 
69  shows  its  actual  size. 

The  instrument  after  being  carefully  adjusted  upon  the  radial  artery  is  kept  in  position  by  an 
inelastic  strap.  The  pres.sure  of  the  spring  is  regulated,  by  the  eccentric  wheel,  to  any  amount  from 
I  to  5  ounces.  As  in  other  instruments,  the  tracing  paper  is  moved  in  front  of  the  writing  needle 
by  means  of  clockwork.  The  writing  levers  are  so  adjusted  that  the  movements  of  the  artery  are 
magnified  fifty  times.] 

[Fig.  71  is  a  sphygmogram  taken  with  this  instrument  from  a  healthy  individual.  It  represents  a 
perfect  tracing;  a,  the  vertical  upward,  systolic  or  percussion  wave;  d,  apex;  r,  on  the  descent;  (/, 
first  tidal  or  predicrotic  wave  ;  e,  aortic  notch ;  /,  dicrotic  wave  {Di/Jgeon).'] 

(6)  Marey's  Tambours  are  also  employed  for  registering  the  movements  of  the  pulse.  They 
are  used  in  the  same  way  as  the  pansphygmograph  of  Brondgeest.  Fig.  72  shows  their  arrange- 
ment. Two  pairs  of  metallic  cups  (S,  S  and  .S',  S",  Upham's  capsules)  are  pierced  in  the  middle 
by  thin  metal  tubes,  whose  free  ends  are  connected  with  caoutchouc  tubes,  K  and  K'.  All  the 
four  metallic  vessels  are  covered  with  an  elastic  membrane.     On  S  and  S'  are  fixed  two  knob-like 


LANDOIS     ANGIOGRAPH. 


121 


pads,  /  and  /',  which  are  applied  to  the  pulsating  arteries,  and  the  metal  arcs,  B  and  B',  retain 
them  in  position.  On  the  other  tambours  are  arranged  the  writing  levers,  Z  and  Z'.  Pressure  on 
the  one  tambour  necessarily  compresses  the  air  and  makes  the  other,  with  which  it  is  connected, 
expand,  so  as  to  move  the  writing  lever.  This  arrangement  does  not  give  absolutely  exact  results; 
still,  it  is  very  easily  used  and  is  convenient.  In  Fig.  72  a  double  arrangement  is  shown,  whereby 
one  instrument,  B.  may  be  placed  over  the  heart,  and  the  other,  B',  on  a  distinct  artery. 

Landois'  Angiograph. — To  a  basal  plate,  G,  G,  are  fixed  two  upright  supports,/,  which  carry 
bet,ween  them  at  their  upper  part  the  movable  lever,  r/,  r,  carrying  a  rod  bearmg  a  pad,  e,  directed 
downward,  which  rests  on  the  pulse.  The  short  arm  carries  a  counterpoise,  </,  so  as  exactly  to  bal- 
ance the  long  arm.  The  long  arm  has  fixed  to  it  at  r  a  vertical  rod  provided  with  teetli,  /;,  which 
is  pressed  against  a  toothed  wheel  firmly  fixed  on  the  axis  of  the  very  light  writing  lever,  e/,  which 
is  supported  between  two  uprights,  y,  fixed  to  the  opposite  end  of  the  basal  plate,  G,  G.  The  writ- 
ing lever  is  equilibrated  by  means  of  a  light  weight.  The  writing  needle,  /■,  is  fixed  by  a  joint  to  e, 
and  it  writes  on  the  plate,  /.     The  first-mentioned  lever,  d,  r,  carries  a  shallow  cup,  Q,  just  above 


Fig.  73. 


Scheme  of  Landois"  angiograph. 


the  pad,  into  which  weights  mav  be  put  to  press  on  the  pulse.  In  this  instrument  the  weight  can 
be  measured  and  varied  ;  the  wilting  lever  moves  vertically  and  not  in  a  curve,  as  in  Marey's  appa- 
ratus, which  greatly  facilitates  the  measuring  of  the  curves  {Fig.  73). 

Other  sphygniographs  are  used,  both  in  this  country  and  abroad,  including  that  of  Sommerbrodt, 
which  is  a  complicated  form  of  Marey's  sphygmograph, 

and  those  of  Pond  and    Mach.     \n  choosing  a  sphyg-  Fig.  74. 

inograph,  that  instrument  is  to  be  preferred  whicli 
yields  a  curve  corresponding  most  closely  with  the 
variations  of  the  pressure  within  the  artery,  in  whicli 
the  resistance  of  the  instrument  is  small,  which  gives 
the  largest  curve,  and  in  which  the  part  in  contact 
with  the  artery  is  not  greatly  displaced  from  its  position 
of  equilibrium  (Mach). 

Characters   of    a    Pulse    Curve. — In 

every  ])ulse  curve — Sphvi:;mooram  or  Aui  e- 
KioGRAM — we  can  distinguish  the  asieinling 
part  (ascent)  of  the  curve,  t!ie  apex,  and  the 
descending  part  (descent).  Secondary  eleva- 
tions scarcely  ever  occur  in  the  ascent,  which  Pulse  curve  of  the  radial  artery  of  a  healthy  stu- 
,,  ^  ,      ,  .     ,         ,.  dent,  obtained  by  Landois   angiograph  writing 

IS     usually     represented      by     a     straight     line,  upon  a   plate   attached    to  a  vibrating  tuning 

while  they  occur  constantly   in    the  descent.  t^,(,,f^^^.  ''°"''''  "''""°"  corresponds  to 

Such  elevations  occurring  in  the  descent  are 

called  catacrotic,  and  those  in  the  ascent,  anacrotic  {Landois).  When  the 
recoil  elevation  or  dicrotic  wave  occurs  in  a  well-marked  form  in  the  descent,  the 
pulse  is  said  to  be  dicrotic,  and  when  it  occurs  twice  tricrotic. 

Measuring  Pulse  Curves. — If  the  smoked  surface  on  which  the  tracing  is  inscribed  is  moved 
at  a  uniform  rate  by  means  of  the  clockwork,  then  the  height  and  length  of  the  curve  are  measured 


122 


LANDOIS     GAS    SPHYGMOSCOPE. 


by  means  of  an  ordinary  rule.  If  we  know  the  rate  at  which  the  paper  was  moved,  then  it  is  easy 
to  calculate  the  duration  of  any  event  in  the  curve.  For  exact  observation  a  low-power  microscope 
with  a  micrometer  in  the  eye-piece  should  be  used. 


Fig-  75- 


L.indois'  gas  sphygmoscope 


tube  attaching  gla 


Fig.  76. 


For  the  method  of  smoking  the  paper  and  fixing  the  tracings  see  p.  120. 

It  is  very  convenient  to  write  the  curve  upon  a  plate  of  glass  fixed  to  a  tuning-fork  kept  in  vibra- 
tion.    Every  part  of  the  curve  shows  little  elevations  (whose  rate  of  vibration  is  known  beforehand). 
All  that  is   required   is  to  count   the   number   of    vibrations 
in  order  to  ascertain  the  duration  of  any  part  of  the   curve. 
(Fig-  74). 

Landois'  Gas  Sphygmoscope. — A  superficially  placed 
artery  communicates  its  movements  to  the  overlying  skin,  and 
also  to  any  freely  movable  body  in  contact  with  the  skin.  In 
this  instrument  (Fig.  75)  a  thin  layer  of  air  over  the  pulsating 
artery,  a,  is  enclosed  by  means  of  a  thin  piece  of  metal,  which 
is  so  adjusted  that  its  concave  side  forms  a  tunnel  of  air  over 
the  artery.  The  narrow  space  between  the  metallic  wall,  /', 
and  the  skin,  a,  is  filled  with  ordinary  gas,  one  end  of  the 
metal  shield  being  connected,  by  means  of  a  tube,  <,%  with  the 
gas  supply,  while  to  the  other  end  there  is  attached,  by  means 
of  a  short  piece  of  caoutchouc,  x,  q,  a  bent  glass  tube,  t,  with 
a  very  small  aperture,  which  acts  as  a  gas  burner.  The  gas  is 
allowed  to  flow  through  the  apparatus  at  a  low  pressure,  and 
is  so  regulated  that  the  flame,  7.',  is  only  a  few  millimetres  in 
height.  The  flame  rises  synchronously  with  every  pulse  beat, 
and  the  dicrotic  beat  in  the  normal  pulse  is  quite  observable. 

Czermak  phctographfd  a  beam  of  light  set  in  motion  by  the 
movements  of  the  pulse. 

Hsemautography. — Expose  a  large  artery  of  an  animal, 
and  divide  it  so  that  the  stream  of  blood  issuing  from  it  strikes 
against  a  piece  of  paper  drawn  in  front  of  the  blood  stream. 
A  curve  (Fig.  76)  is  obtained  which  corresponds  very  closely 
with  the  pulse  tracing  obtained  from  a  normal  artery.  In 
addition  to  the  primary  wave,  P,  there  is  a  distinct  "  recoil 
elevation,"  or  dicrotic  wave,  R.  and  Slight  vibrations,  e,e,  due 
to  the  variations  in  the  elasticity  of  the  arterial  wall.  The 
interest  which  attaches  to  a  curve  obtained  in  this  way  is,  that 
it  shows  the  movements  occur  in  the  blood  itself,  and  are 
communicated  as  waves  to  the  arterial  wall.  By  estimating 
the  amount  of  blood  in  the  various  parts  of  the  curve  we  obtain  a  knowledge  of  the  amount  of  blood 
discharged  by  the  divided  artery  during  the  systole  and  diastole  {i,  e.,  the  narrowing  and  dilatation ) 
of  the  artery — the  ratio  is  7  :  10.  Thus  in  the  utiit  of  time,  during  arterial  dilatation,  rather  more 
than  twice  as  much  blood  flows  out  as  happens  during  arterial  contraction. 

68.  THE  PULSE  TRACING  OR   SPHYGMOGRAM.— Analysis. 

— A  sphygmogram  or  pulse  tracing  consists  of  a  series  of  curves  (Fig.  77)  each 
one  of  which  corresponds  with  one  beat  of  the  heart.    Each  pulse  curve  consists  of — 

1.  The  line  of  ascent  {a  to  b  in  Fig.  77). 

2.  The  apex  (P  in  Fig.  79,  and  b  in  Fig.  77). 

3.  The  line  of  descent  (h  to  //). 

The  line  of  ascent,  up  stroke,  or  percussion  stroke  (Mahomed )  is  nearly  verti- 
cal, and  occurrs  during  the  dilatation  of  the  artery  produced  by  the  systole  of  the 


emautographic  curve  of  the  posterior 
tibial  artery  of  a  large  dog.  P,  pri- 
mary puLse  wave  ;  R,  dicrotic  or  recoil 
wave ;  *,  ^,  elevations  due  to  elasticity. 


THE    PULSE    CURVE. 


123 


left  ventricle,  and  occurs  when  the  aortic  valves  are  forced  open  and  the  ven- 
tricular contents  are  projected  into  the  arterial  system.  [The  ascent  is  nearly 
vertical,  but  in  some  cases,  where  the  ventricle  contracts  very  suddenly,  as  occa- 
sionally happens  in  aortic  regurgitation,  it  is  quite  vertical  (Fig.  80).] 

The  apex  or  percussion  wave  {Mahoiiu-d)  in  a  normal  pulse  is  pointed. 

The  line  of  descent  is  gradual,  and  corresponds  to  the  diminution  of  diameter 
or.  contraction  of  the  artery.  It  is  interrupted  by  tvio  completely  distinct  elevations 
or  secondary  waves.  The  more  distinct  of  the  two  occurs  as  a  well-marked  eleva- 
tion about  the  middle  of  the  descent  (R  in  Fig.  79  and/in  Fig.  77)  ;  it  is  called 
the  dicrotic  wave,  or,  with  reference  to  its  mode  of  origin,  the  "  recoil  wave.''' 

Fig.  77. 


Sphygmogram  of  ridial  artery  :  pressure  2  oz.  Each  part  of  the  curve  between  the  base  ot  o 
base  of  the  next  up  stroke  corresponds  to  a  beat  of  the  heart,  so  that  this  figure  shows  five 
of  a  sixth  ;  rt.  i  =  the  ascent,  b,  the  apex  of  the  up  stroke,  and  6  to  A  the  descent,  with  i 
the  first  tidal  or  predicrotic  wave,  e,  an  angle  or  notch,  the  aortic  notch,  _/",  a  second  elevati' 
WKve,  gt  a  slight  curve,  sometimes  called  tlie  second  tidal  wave.  The  descent  is  continued  1 
of  the  next  heart  beat  begins. 


le  up  stroke  and  the 
heart  beats  and  part 
n  elevation,  d,  called 
n,  called  the  dicrotic 
J  h,  where  the  ascent 


[.\s  the  descent  corresponds  to  the  time  when  blood  is  flowing  out  of  the  arte- 
ries at  the  periphery  into  the  capillaries,  its  direction  will  depend  on  the  rapidity 
of  this  outflow.  Thus,  it  will  be  more  rapid  in  paralysis  of  the  arterioles  and  very 
rapid  in  aortic  regurgitation,  where,  of  course,  much  of  the  blood  flows  backward 
into  the  left  ventricle  (Fig.  80).  In  this  case  the  artery  will  recoil  suddenly  from 
under  the  finger  or  pad  of  the  instrument,  and  this  constitutes  the  "  pulse  of  empty 
arteries."] 

The  dicrotic  wave,  recoil  wave  [or  aortic  systolic  wave  {Bramweliy\  (Fig. 
77),  corresponds  to  the  lime  following  the  closure  of  the  aortic  valves,  and  is  pre- 
ceded in  the  descent  by  a  slight  depression,  the  aortic  notch. 

Fig.  78. 


Irregular  pulse  of  mitral  regurgitation. 

[The  tidal  wave,  or  pre-dicrotic,  occurs  between  the  apex  and  the  dicrotic 
wave  (Fig.  77'/ |.  It  has  also  been  cdWtd  tht  second  ventricular  systolic  wave,  as 
it  occurs  after  the  first  systolic  wave  or  apex,  and  during  the  contraction  of  the 
ventricle  (BramweW).  The  tidal  wave  is  best  marked  in  a  hard  pulse,  /.  e.,  where 
the  blood  pressure  is  high,  so  that  it  is  usually  well  marked  in  cirrhotic  disease  of 
the  kidney,  accompanied  by  hypertrophy  of  the  left  ventricle.] 

[In  some  cases,  e.  g.,  mitral  res:uri^latton,  the  pre-dicrotic  wave  may  be  present  in  some  pulse 
heats  and  absent  in  others  (Fig.  78),  where  the  tidal  wave  is  present  in  the  largest  pulse  and  absent 
in  the  others,  while  the  base  line  is  uneven.  In  mitral  steno.si.s,  the  amount  of  blood  discharged 
into  the  left  ventricle  frequently  varies,  hence  the  variations  in  the  characters  of  the  arterial  pulse.] 


J24 


ORIGIN    AND    CHARACTERS    OF    THE    DICROTIC    WAVE. 


There  may  be  other  secondary  waves  in  the  lower  part  of  the  descent. 

[Respiratory  or  Base  Line. — If  a  line  be  drawn  so  as  to  touch  the  bases  of 
all  the  up  strokes,  we  obtain  a  straight  line,  hence  called  by  this  name.  The  base 
line  is  altered  m  disease  and  during  forced  respiration  (§  74).] 


Fig.  79. 


II,  III,  Spbygmograms  of  c 
cniml  ;  XIII,  posterior  tibi 
elevations  due  to  elasticity; 


;id  arterv:  IV,  axillarj' ;  V  to  IX,  radial;  X,  die 
XIV,  XV,  pedal.  In  all  the  curves  P  indicates  : 
elevation  caused  by  closure  of  the  semilunar  valve 


pex  ;    R,  dicrotic 
of  the  aorta. 


I.  Origin  and  Characters  of  the  Dicrotic  Wave. — The  dicrotic  or 
recoil  wave,  which  is  always  present  in  a  normal  pulse,  is  caused  thus:  During 
the  ventricular  systole,  a  mass  of  blood  is  propelled  into  the  already  full  aorta, 
whereby  a  positive  wave  is  rapidly  transmitted  from  the  aorta  throughout  the 
arterial  system,  even  to  the  smallest  arterioles,  in  which  this  primary  7vare  is 
extinguished.  As  soon  as  the  semilunar  valves  are  closed,  and  no  more  blood 
flows    into    the    arterial    system,  the  arteries,  which    were    previously    distended 


CHARACTERS   OF    THE    DICROTIC    WAVE.  125 

by  the  mass  of  blood  suddenly  thrown  into  them,  recoil  or  contract,  so  that, 
in  virtue  of  the  elasticity  (and  contractility)  of  their  walls,  they  exert  a  counter- 
Ijressure  upon  the  column  of  blood,  and  thus  the  blood  is  forced  onward. 
There  is  a  free  passage  for  it  toward  the  periphery,  but  toward  the  centre  (heart) 
it  impinges  upon  the  already  closed  semilunar  valves.  This  develops  a  new  posi- 
tive wave,  which  is  propagated  peripherally  through  the  arteries,  where  it  disap- 
pears in  their  finest  branches.  In  those  cases  where  there  is  sufficient  time  for  the 
complete  development  of  the  pulse  curve  (as  in  the  short  course  of  the  carotids, 
and  in  the  arteries  of  the  upper  arm,  but  not  in  those  of  the  lower  extremity,  on 
account  of  their  length),  a  second  reflected  wave  may  be  caused  in  exactly  the 
same  way  as  the  first. 

Just  as  the  pulse  occurs  later  in  the  more  peripherally  placed  arteries  than  in 
those  near  the  heart,  so  the  secondary  wave  reflected  from  the  closed  aortic  valves 
must  appear  later  in  the  peripheral  arteries.  Both  kinds  of  waves — the  primary 
pulse  wave,  the  secondary,  and,  eventually,  even  the  tertiary  reflected  wave— arise 
in  the  same  place,  and  take  the  same  course,  and  the  longer  the  course  they  have 
to  travel  to  any  part  of  the  arterial  system,  the  later  they  arrive  at  their  destination. 

The  following  points  regarding  the  dicrotic  wave  have  been  ascertained 
experimentally  :• — 

1.  The  dicrotic  wave  occurs  later  in  the  descending  part  of  the  curve  the  further 
the  artery  experimented  upon  is  distant  from  the  heart  {Landois,  i86j).  Compare 
the  curves.  Figs.  74,  84,  88. 

TTie  shortest  accessible  course  is  that  of  the  carotid,  where  the  dicrotic  wave  reaches  its  maximum 
0.35  to  0.37  sec.  after  the  beginning  of  the  pulse.  In  the  upper  extremity  the  apex  of  the  dicrotic 
wave  is  0.36  to  0.3S  to  0.40  sec.  after  the  beginning  of  the  pulse  beat.  The  longest  course  is  that 
of  the  arteries  of  the  lower  extremity.  The  apex  of  the  dicrotic  wave  occurs  0-45  to  0-52  to  059 
sec.  after  the  base  of  the  curve.     It  varies  with  the  height  of  the  individual, 

2.  The  dicrotic  elevation  in  the  descent  is  lower  {Naumanii),  and  is  less  dis- 
tinct {Landois),  the  further  the  artery  is  situated  from  the  heart.  This  is  just  what 
one  would  expect,  viz.,  the  longer  the  distance  which  the  wave  has  to  travel,  the 
less  distinct  it  must  become. 

3.  It  is  more  pronounced  in  a  pulse  where  the  primary  pulse  wave  is  short  and 
energetic  {Many,  Landois).  It  is  greatest  relatively  when  the  systole  of  the  heart 
is  short  and  energetic. 

4.  It  is  greater  the  lower  the  tension  or  pressure  of  the  blood  within  the  arte- 
ries {Marcy,  Landois),  [and  is  best  developed  in  a  soft  pulse].  In  Fig.  79,  IX 
and  X  were  obtained  when  the  tension  of  the  arterial  wall  was  low ;  V  and  VI, 
medium;  and  VII  with  /ligh  tension. 

Conditions  influencing  Arterial  Tension.— It  is  diminished  at  the  beginning  of  inspira- 
tion (9,  74),  by  hemorrhage,  stoppage  of  the  heart,  heat,  an  elevated  position  of  parts  of  the  body, 
amyl  nitrite  ;  it  is  increased  at  the  beginning  of  expiration  by  accelerated  action  of  the  heart,  stimu- 
lation of  vasomotor  nerves,  diminished  outflow  of  blood  at  the  periphery,  and  by  inflammatory  con- 
gestion (K'necJit) ;  further,  by  certain  poisons,  as  lead;  compression  of  other  large  arterial  trunks, 
action  of  cold  and  electricity  on  the  small  cutaneous  vessels,  and  by  impeded  outflow  of  venous 
lilood.    When  a  large  arterial  trunk  is  exposed  the  stimulation 

of  the  air  causes  it  to  contract,  resulting  in  an  increased  ten-  Y\G.  80. 

sion  within  ihe  vessel.  In  many  diseased  conditions  the  arterial 
tension  is  greatly  increased — \_e.  g.,  in  Blight's  disease,  where 
the  kidney  is  contracted  ("granular"),  and  where  the  left 
ventricle  is  hypertrophied]. 

In  all  these  conditions  increased  arterial  tension  is  indicated 
by  the  dicrotic  wave  being  less  high  and  less  distinct,  while 
with  rliminished  arterial  tension  it  is  a  larger  and  apparently 
more  independent  elevation.  Moens  has  shown  that  the  time 
between  the  primary  elevation  and  the  dicrotic  wave  increases 
with  increase  in  the  diameter  of  the  tube,  with  diminution  of 
its  thickne.ss,  and  when  its  coefficient  of  elasticity  diminishes. 

[The  dicrotic  wave  is  absent  or  but  slightly  marked  in  cases 
of  atheroma  and  in  aortic  regurgitation  (Fig.  80).  In  this 
figure  observe  also  the  vertical  character  of  the  up  stroke.] 


126  DICROTIC    PULSE. 

II.  Origin  and  Characteristics  of  the  Elastic  Elevations. — Besides 
the  dicrotic  wave,  a  number  of  small,  less-marked  elevations  occur  in  the  course 
of  the  descent  in  a  sphygmogram  (Fig.  79,  e,  e).  These  elevations  are  caused 
by  the  elastic  tube  being  thrown  into  vibrations  by  the  rapid  energetic  pulse 
wave,  just  as  an  elastic  membrane  vibrates  when  it  is  suddenly  stretched.  The 
artery  also  executes  vibratory  movements  when  it  passes  suddenly  from  the 
distended  to  the  relaxed  condition.  These  small  elevations  in  the  pulse  curve, 
caused  by  the  elastic  vibrations  of  the  arterial  wall,  are  called  "  elastic  eleva- 
tions "  by  Landois. 

(i)  The  elastic  vibrations  increase  in  number  in  one  and  the  same  artery  with 
the  degree  of  tension  of  the  elastic  arterial  wall.  A  very  high  tension  occurs  in 
the  cold  stage  of  intermittent  fever,  in  which  case  these  elevations  are  well  marked. 
^2)  If  the  tension  of  the  arterial  wall  be  greatly  diminished  these  elevations 
may  disappear,  so  that,  while  diminished  tension  favors  the  production  of  the 
dicrotic  wave,  it  acts  in  the  opposite  way  with  reference  to  the  "elastic  eleva- 
tions." (3)  In  diseases  of  the  arterial  walls  affecting  their  elasticity,  these  eleva- 
tions are  either  greatly  diminished  or  entirely  abolished.  (4)  The  further  the 
arteries  are  distant  from  the  heart,  the  higher  are  the  elastic  elevations.  (5) 
When  the  mean  pressure  within  the  arteries  is  increased  by  preventing  the  outflow 
of  blood  from  them,  the  elastic  vibrations  are  higher  and  nearer  the  apex  of  the 
curve.  (6)  They  vary  in  number  and  length  in  the  pulse  curves  obtained  from 
different  arteries  of  the  body. 

Fig.  Si. 


Development  of  the  Pulsus  dicrotus. — P.  caprizans  ;   P.  monocrotus. 

When  the  arm  is  held  in  an  upright  position,  after  five  minutes  the  blood  vessels  empty  themselves, 
and  collapse,  while  the  elasticity  of  the  arteries  is  diminished. 

6g.  DICROTIC  PULSE. — Sometimes  during  fever,  especially  when  the  temperature  is  high, 
a  dicrotic  pulse  may  lie  felt,  each  pulse  beat,  as  it  were,  being  composed  of  two  beats  (Fig.  79,  X), 
one  beat  bemg  large  and  the  other  small,  and  more  like  an  after  beat.  Both  beats  correspond  to  one 
beat  of  the  heart.  The  two  beats  are  quite  distinguishable  by  the  touch.  The  phenomenon  is  only 
an  exaggerated  condition  of  what  occurs  in  a  normal  pulse.  T/ie  sctisible  second  beat  is  tiolhing  more 
than  the  greatly  increased  dicrotic  elevation,  which,  under  ordinary  conditions,  is  not  felt  by  the  finger. 

Conditions. — The  occurrence  of  a  dicrotic  pulse  m  favored  ( i)  by  a  short  primary  pulse  wave,  as 
in  fevers,  where  the  heart  beats  rapidly. 

(2)  By  a'm/«M/;fa' tension  within  the  arterial  system.  A  short  systole  and  diminished  arterial 
blood  pressure  are  the  most  favorable  conditions  for  causing  a  dicrotic  pulse.  [So  that  dierotism  is 
best  marked  in  a  soft  pulse.]  The  double  beat  may  be  felt  only  at  certain  parts  of  the  arterial 
system,  while  at  other  parts  only  a  single  beat  is  felt.  A  favorite  site  is  the  radial  arteiy  of  one  or 
other  side,  where  conditions  favorable  to  its  occurrence  appear  to  exist.  'Ihis  seems  to  be  due  to  a 
local  diminution  of  the  blood  pressure  in  this  area,  owing  to  the  paralysis  of  its  vasomotor  nerves 
{^Landois).  If  the  tension  be  increased  by  compressing  other  large  arterial  trunks  or  the  veins  of  the 
part,  the  double  beat  becomes  a  simple  pulse  beat.  The  dicrotic  pulse  in  fever  seems  to  be  due  to 
the  increased  temperature  (39°  to  40°  C),  whereby  the  artery  is  more  distended,  and  the  heart  beat 
is  shorter  and  more  prompt  {Riegel). 

(3)  It  is  absolutely  necessary  that  the  elasticity  of  the  arterial  wall  be  normal.  The  dicrotic 
pulse  does  not  occur  in  old  persons  with  atheromatous  arteries  (Landois). 


CONDITIONS   AFFECTING   THE    PULSE    RATE.  127 

Monocrotic  Pulse. — In  F'ig.  8i,  A,  E,  C,  we  observe  the  gradual  passage  of  the  normal  radial 
curve.  A,  into  the  dicrotic  beat,  B  and  C,  where  the  dicrotic  wave,  ;•,  appears  as  an  independent 
elevation.  If  the  frequency  of  the  pulse  increases  more  and  more  in  fever,  the  next  following  pulse 
beat  may  occur  in  the  ascending  part  of  the  dicrotic  wave,  D,  E,  F,  and  it  may  even  occur  close  to 
the  apex,  G  (P.  caprizans).  If  the  next  following  beat  occurs  in  the  depression,  i,  between  the 
primary  elevation,  /,  and  the  dicrotic  elevation,  r,  the  latter  entirely  disappears,  and  the  curve,  H, 
assumes  what  Landois  calls  the  "  monocrotic  "  type. 

[Degrees  of  Dicrotism. — When  the  aortic  notch  reaches  the  respiratory  or  base  line,  the  tidal 
wave  having  disappeared,  the  pulse  is  said  to  be  fully  dicrotic. 

When  the  aortic  notch  falls  below  the  base  line,  i.  e.,  below  where  the  up  stroke  begins,  the  pulse 
is  said  to  be  hyperdicrotic  (Fig.  82).  This  form  occurs  during  high  fever  (104°  F.),  and  is  usually 
a  grave  sign,  indicating  exhaustion  and  the  need  for  stimulants.] 

70.  CHARACTERS  OF  THE  PULSE.— I.  Pulsus  Frequens  and  Rarus.— Frequency. 

— According  as  a  greater  or  less  number  of  heats  occur  in  a  given  time,  e.g.,  per  minute,  the  pulse 
is  said  to  be  frequent  or  rare.  The  normal  rate,  in  man  ^71  per  minute,  and  somewhat  more  in 
the  female  ;  in  fever  it  may  exceed  i2o  (250  have  been  counted  by  Bowles),  while  in  other  diseases 
it  may  fall  to  40,  and  even  10  to  15  {dc  Haen),  17  {Hartog),  and  14  (Cornil);  but  such  cases  are 
rare,  and  are  probably  due  to  an  aflection  of  the  cardiac  nerves  (g  41).  The  frequency  of  the  pulse 
is  usually  increased  when  the  respirations  are  deeper,  but  not  more  numerous,  i.  e.,  rapid  shallow 
respirations  do  not  affect  the  frequency  of  the  pulse,  but  deep  respirations  do  [A'noll). 

2.  Pulsus  Celer  and  Tardus. — Celerity  or  Rapidity. — If  the  pulse  wave  is  developed  so 
that  the  distention  of  the  artery  slowly  reaches  its  height,  and  the  relaxation  also  takes  phce  gradu- 
ally, we  have  the  p.  tardus  or  s/o7if  pulse,  the  opposite  condition  gives  rise  to  the  p.  celer  or  quick 
pulse.  The  rapidity  of  the  pulse  is  increased  by  quick  action  ot  the  heart,  power  of  expansion  of 
the  arterial  walls,  easy  efflux  of  blood  owing  to  the  dilatation  of  the  small  arteries,  and  l)y  nearness 
to  the  heart.  [The  quiekness  has  reference  to  a  single  pulse  beat,  the  frequency  to  a  number  of 
beats.]  In  a  quick  pulse,  the  curve  is  high  and  the  angle  at  the  apex  is  acute;  while  in  a  slow 
pulse  the  ascent  is  low  and  the  angle  at  the  apex  is  large. 

Fig.  82. 


WVWvV 


Hyperdicrotic  pulse. 

3.  Conditions  affecting  the  Pulse  Rate. — Frequency  in  Health. — In  man  the  normal  pulse 
rate  =:  71  to  72  beats  per  minute;  in  the  female  about  80.  In  some  individuals  the  pulse  rate  may 
be  higher  (90  to  100),  in  others  lower  (50),  and  such  a  fact  must  be  borne  in  mind.  The  following 
conditions  influence  it : — 

(fl)  Age. 

Ee.its  per 


Newly  born -130  to  140 

1  jear .    .    .  120  to  130 

2  years 105 

3  "  'oo 

4  "  97 

5  "  94  to  90 

10     "  about  90 


10  to  15  years 78 

15  to  20  '■  70 

20  to  25  "  70 

25  to  50  "  70 

60  '•  74 

80  "  79 

80  to  90  "  over  80 


{b)  The  length  of  the  body  has  a  certain  relation  to  the  frequency  of  the  pulse.  The  follow- 
ing results  have  been  obtained  by  Crarnecki  from  the  formulae  of  Volkmann  and  Rameaux  : — 

Length  of  Body  Pulse  i     Length  of  Body  Pulse 

in  10  cm.  Calculated.     Observed.  in  to  cm.  Calculi 

Soto     90.  . 90  103              140  to  150 69 

90  to  100 86  91              150  to  160 

100  to  no 81  87  j     160  to  170 

no  to  120 78  84  j     I70toi8o 

120  to  130 75  78              above  180 

130  to   140 72  76  I 

(c)  The  pulse  rate  is  increased  by  muscular  activity,  by  every  increase  of  the  arterial  blood 
pressure,  by  taking  of  food,  increased  temperature,  painful  sensations ,  by  psychical  disturbances, 
and  \in  extreme  debility^     Increased  heat,  fever,  or  pyrexia  increases  the  frequency,  and,  as  a  rule, 


lated. 

Observed 

69 

74 

67 

68 

6S 

65 

b3 

64 

60 

60 

128 


VARIATIONS    IN    THE    PULSE    RHYTHM. 


the  increase  varies  with  the  height  of  the  temperature.  [Dr.  Aitken  states  that  an  increase  of  the 
U-mperature  of  i°  F.  above  98°  K.  corresponds  with  an  increase  of  ten  pulse  beats  per  minute ; 
thus  : — 


leinp. 
98° 

99° 
100° 
101° 
102° 


e  Rate. 
60 

Temp.  F 
103° 

70 
80 
80 

104° 
105° 
106° 

100 

This  is  merely  an  approximate  estimate.]  It  is  more  frequent  when  a  person  is  slandiyig  than  when 
he  lies  down.  Music  accelerates  the  pulse  and  increases  the  blood  pressure  in  dogs  and  men 
[Doghl).     Exposure  to  increased  barometric  pressure  diminishes  the  frequency. 

The  variation  of  the  pulse  rate  during  the  day — 3  to  6  a.m.  =  61  beats;  8  to  11^  A.M.  = 
74.  It  then  falls  toward  2  p.m.;  toward  3  (at  dinner  time)  another  increase  takes  place  and  goes 
on  until  6  to  8  p.m.  =  70;  and  it  falls  until  midnight  =  54.  It  then  rises  again  toward  2  a.m., 
when  it  soon  falls  again,  and  afterward  rises,  as  before,  toward  3  to  6  a.m. 


[Pulse  Rate  in  Animals. 


Elephant . 
Camel  .  . 
Giraffe.  . 
Horse  .  . 
Ox  .  .  . 
Tapir  .  . 
Ass .  .  . 
Pig  .  .  . 
Lion.  .    . 


25-28 
2S-32 

66 
36-40 
45-50 

44 
46-50 
70-80 

40 


Per  Min. 
68 
74 
70-80 
70-So 
60 
96 

55 

90-100 

Cat 120-140 


Fir,.  83. 


Lioness .  .  .  . 
Tiger.  .  .  . 
Sheep   .    .    .    . 

Goat 

Leopard    .    .    . 
Wolf  (female), 
Hysena  . 
Dog 


Rabbit.  .  . 

Mouse.  .  . 

Goose  .  .  . 

Pigeon    .  . 

Hen    .    .  . 

Snake .   .  . 

Carp    .    .  . 

Frog    .    .  . 
Salamander. 


Per  Min. 

120-150 

150 

no 

136 
140 

24 
20 


(C<7//h).] 


4.  Variations  in  the  Pulse  Rhythm. — On  applying  the  fingers  to  the  normal  pulse,  we  feel  beat 
after  beat  occurring  at  apparently  equal  intervals.  Sometimes  in  a  normal  scries  a  beat  is  omitted 
=  pulsus  intermittens,  or  intermittent  pulse.  [In  feeling  an  intermittent  pulse,  we  imagine 
or  have  the  impression  that  a  beat  is  omitted.  This  inay  be  due  to  a  reflex  arrest  of  the  ventricular 
contraction,  caused  by  digestive  derangement,  in  which  case  it  has  no  great  significance  ;  but  if  it 
be  due  to  failure  of  the  ventricular  action,  intermittent  pulse  is  a  serious  symptom,  being  frequently 
present  when  the  muscular  walls  are  degenerated.]  At  other  times  the  beats  become  smaller  and 
smaller,  and  after  a  certain  time  begin  as  large  as  before  =  p.  myurus.  When  an  extra  beat  is 
intercalated  in  a  normal  series  =y  p.  intcrcurrens.  The  regular  alternation  of  a  high  and  a  low 
beat  =  p.  alternans  (  7)'a«fc).(Fig.  83).  In  the  p.  bigeminus  of  Traube  the  beats  occur  in 
pairs,  so  that  there  is  a  longer  pause  after  every  two  beats.  Traube  found  that  he  could  produce 
this  form  of  pulse  in  curarized  dogs  by  stopping  the  artificial  r.'spiration  for  a  long  time.  The  p. 
trigeminus  and  quadngeminus  occur  in  the  same  way.  but  the  irregularities  occur  after  every 
third  and  fourth  beat.  Knoll  found  that  in  animals  such  irregularities  of  the  pulse  were  apt 
to  occur,  as  well  as  great  irregularity  in  the  rhythm  generally,  when  there  is  great  resistance 
to  the  circulation,  and  consequently  the  heart  has  great  demands  upon  its  energy.  The  same 
occurs  in  man,  when  an  improper  relation  exists  between  the  force  of  the  cardiac  muscle 
and  the  work  it  has  to  do  {Rirgel).  Complete  irregularity  of  the  heart's  action  is  called 
arhythmia  cordis. 

71.  VARIATIONS  IN  THE  STRENGTH,  TENSION  AND  VOLUME  OF  THE 
PULSE.— Compressibility. —  The  relative  strength  or  compressibility  of  the  pulse  (p.  fortis 
and  debilis),  /.  e.,  whether  the  pulse  is  strong  or  -j'sak,  is  estimated  by  the  weight  which  the  pulse  is 


THE    PULSE    CURVES    OF   VARIOUS    ARTERIES.  129 

able  to  raise.  A  sphygmograph,  provided  with  an  index  indicating  the  amount  of  pressure  exerted 
upon  the  spring  pressing  upon  the  artery-,  may  be  used  (Fig.  66).  In  this  case,  as  soon  as  the 
pressure  exerted  upon  the  artery  overcomes  the  pulse  beat,  the  lever  ceases  to  move.  The  weight 
employed  indicates  the  strength  of  the  pulse.  [The  finger  may  be,  and  generally  is,  used.  The 
finger  is  pressed  upon  the  artery  until  the  pulse  beat  in  the  artery  beyond  the  point  of  pressure  is 
obliterated.  In  health  it  requires  a  pressure  of  several  ounces  to  do  this.  Handfield  Jones  uses  a 
sphygmometer  for  this  purpose.  It  is  constructed  like  a  cylindrical  letter  weight,  and  the  pressure 
is  exerted  by  means  of  a  spiral  spring  which  has  been  carefully  graduated.]  The  pulse  is  hard  or 
soft  when  the  artery,  according  to  the  mean  blood  pressure,  gives  a  feeling  of  greater  or  less  resist- 
ance to  the  finger,  and  this  quite  independent  of  the  energy  of  the  individual  pulse  beats  (p.  durus 
and  mollis). 

In  estimating  the  tension  of  the  artery  and  the  pulse,  /.  c,  whether  it  is  hard  or  soft,  it  is  import- 
ant to  observe  whether  the  artery  has  this  quality  only  during  the  pulse  wave,  i.  e.,  if  it  is  hard 
during  diastole,  or  whether  it  is  hard  or  soft  during  the  period  of  rest  of  the  arterial  wall.  All 
arteries  are  harder  and  less  compressible  during  the  pulse  beat  than  during  the  period  of  rest,  but 
an  artery  which  is  very  hard  during  the  pulse  beat  may  be  hard  also  during  the  pause  between  the 
pulse  beats,  or  it  may  t)e  very  soft,  as  in  insufficiency  of  the  aortic  valves.  In  this  case,  after  the  sys- 
tole of  the  left  ventricle,  owing  to  the  incompetency  of  the  aortic  semilunar  valves,  a  large  amount 
of  blood  flows  back  into  the  ventricle,  so  that  the  arteries  are  thereby  suddenly  rendered  partially 
empty.  [The  sudden  collapse  of  the  artery  gives  rise  to  the  characteristic  "  pulse  of  unfilled 
arteries."     Fig.  So.] 

Under  similar  conditions,  the  volume  of  the  pulse  is  obvious  from  the  size  of  the  sphygmogram, 
so  that  we  speak  of  a  large  and  a  small  pulse  (p.  magnus  and  parvus).  Sometimes  the  pulse  is  so 
thready  and  of  such  diminished  volume  that  it  can  scarcely  be  felt.  A  large  pulse  occurs  in  disease 
when,  owing  to  hypertrophy  of  the  left  ventricle,  a  large  amount  of  blood  is  forced  into  the  aorta. 
A  small  pulse  occurs  under  the  opposite  condition,  when  a  small  amount  of  blood  is  forced  into 
the  aorta,  either  from  a  diminution  of  the  total  amount  of  the  blood,  or  from  the  aortic  orifice  being 
narrowed  [aortic  stenosis],  or  from  disease  of  the  mitral  valve;  again,  where  the  ventricle  contracts 
feebly,  the  pulse  becomes  small  and  thready. 

Compare  the  two  Radials.  Sometimes  the  pulse  differs  on  the  two  sides,  or  it  may  be  absent  on 
one  side.  [The  pulse  wave  in  the  two  radials  is  often  different  when  an  aneurism  is  present  on  one 
side.] 

Angiometer.— Waldenburg  constructed  a  "  pulse  clock  "  to  register  the  tension,  the  diameter  of 
the  artery,  and  the  volume  of  the  pulse  upon  a  dial.  It  does  not  give  a  graphic  tracing,  the  results 
being  marked  by  the  position  of  an  indicator. 

72.  THE  PULSE  CURVES  OF  VARIOUS  ARTERIES.— i.  Carotid  (Fig.  79,  I,  II, 
III;  Fig.  88,  C  and  Cj). — The  ascending  part  is  very  steep— the  apex  of  the  curve  (Fig.  79,  P)  is 
sharp  and  high.  Below  the  apex  there  is  a  small  notch — the  "Aortic  Notch"  (Fig.  79,  K) — 
which  depends  on  a  positive  wave  formed  in  the  root  of  the  aorta,  owing  to  the  closure  of  the  aortic 
valves,  and  propagated  with  almost  wholly  undiminished  energy  into  the  carotid  artery.  Quite 
close  to  this  notch,  if  the  cur\'e  be  obtained  with  minimal  friction,  the  first  elastic  vibration  occurs 
(Fig.  79,  II,  e).  Above  the  middle  of  the  descending  part  of  the  curve  is  the  dicrotic  elevation,  R, 
produced  by  the  reflection  of  a  positive  wave  from  the  already  closed  semilunar  valves.  The  dicrotic 
wave  is  relatively  small,  on  account  of  the  high  tension  in  the  carotid  artery,  .-^fter  this  the  curve 
falls  rapidly,  but  in  its  lowest  third  two  small  elevations  may  be  seen.  Clf  these  the  former  is  due 
to  elastic  vibration.  The  latter  represents  a  second  dicrotic  wave  (Fig.  79,  III,  R)  (Landois, 
iMoens).  Here  there  is  a  true  tricrotism,  which  is  more  easily  obtained  from  the  carotid  on  account 
of  the  shortness  of  the  arterial  channel. 

2.  Axillary  Artery  (Fig.  79,  IV). — In  this  curve  the  ascent  is  very  steep,  while  in  the  descent 
near  the  apex  there  is  a  small  (aortic)  elevation,  K,  caused  by  a  positive  wave,  produced  by  the 
closure  of  the  aortic  valves.  Below  the  middle  there  is  a  tolerably  high  dicrotic  elevation,  R, 
higher  than  in  the  carotid  curve  ;  because  in  the  axillary  artery  the  arterial  tension  is  less,  and  per- 
mits a  greater  development  of  the  dicrotic  wave.  Further  on,  two  or  three  small  elastic  vibrations 
occur,  £•,  (•. 

3.  Radial  Artery  (Fig.  74;  Fig.  79,  V  to  X  ;  Fig,  88,  R  and  Rj).— The  line  of  ascent  (Fig. 
79)  is  tolerably  high  and  sudden —  somewhat  in  the  form  of  a  long/".  The  apex,  P,  is  well  marked. 
Below  this,  if  the  tension  be  high,  two  elastic  vibrations  may  occur  (V,  e,  e),  but  if  it  be  low  only 
one  (VI  to  IX,  e).     About  the  middle  of  the  cur\-e  is  the  well-marked  dicrotic  elevation,  R. 

This  wave  is  least  pronounced  in  a  small,  hard  pulse,  and  when  the  artery  is  much  distended 
(Fig.  79,  VII,  Rj) ;  it  is  larger  when  the  tension  is  low  (Fig.  79,  IX,  R),  and  is  greatest  of  all 
when  the  pulse  is  dicrotic  (X,  R).  Two  or  three  small  elastic  elevations  occur  in  the  lowest  part  of 
the  curve. 

4.  Femoral  Artery  (Fig.  79,  XI,  XII). — The  ascent  is  steep  and  high — the  apex  of  the  curve  is 
not  unfrequently  broad,  and  in  it  the  closure  of  the  aortic  valves  (K)  is  indicated.  The  curve  falls 
rapidly  toward  its  lowest  third.  The  dicrotic  elevation,  R,  occurs  late  after  the  beginning  of  the 
cur\'e,  and  there  are  also  small  elastic  elevations  {e,  e). 

9 


130 


ANACROTISM. 


Fig.  84.  5.  Pedal  Artery  (Fig.  79,  XIV,  XV),  and  Posterior  Tibial 

(Fig.  84  and  Fig.  79,  XIII). — In  pulse  curves  obtained  horn 
these  arteries,  tliere  are  \vell-marl<ed  indications  that  the  appa- 
ratus (heart)  producing  the  waves  is  placed  at  a  considerable 
distance.  The  ascent  is  oblique  and  low — the  dicrotic  elevation 
occurs  late.  Two  elastic  vibrations  (Fig.  79,  XIV,  ;■,<■)  occur  in 
the  descent,  but  they  are  very  close  to  the  apex,  while  the  elastic 
vibrations  at  the  lower  part  of  the  curve  are  feebly  marked. 
Fig.  84  is  from  the  posterior  tibial.  When  measured,  it  gives 
the  following  result : 

posterior  tibial.     Written  I     I  to  2 9.5    I 

by     the     angiograph     upon    a  1     I  to  3 20        [I  vibration  IS  = 

vibrating    plate    attached  to   a  1     I  to  4 3O.5     |        O.O1613  sec. 

tuning  fork.  [    I  to  6 61        J 

73.  ANACROTISM. — As  a  general  rule,  the  line  of  ascent  of  a  pulse  curve  has  the  form  of 
any,  and  is  nearly  vertical.  The  arterial  walls  are  thrown  into  elastic  vibration  by  the  pulse  beat, 
and  the  number  of  vibrations  depends  greatly  upon  the  tension  of  the  arterial  walls. 

The  distention  of  the  artery,  or  what  is  the  same  thing,  the  ascent  of  the  sphygmogram,  usually 
occurs  so  rapidly  that  it  is  equal  to  one  elastic  vibration.  The  elongated  /-shape  of  the  a.scent  is 
fundamentally  just  a  prolonged  elastic  vibration.  When  the  number  of  vibrations  causing  the 
elastic  vibration  is  small,  and  when  the  line  of  ascent  is  prolonged,  two  elevations  occasionally  occur 
in  the  line  of  ascent.  Such  a  condition  may  occur  normally  (Fig.  79,  VIII  at  i  and  2;  X  at  i  and 
2).  When  a  series  of  closely  placed  elastic  vibrations  occur  in  the  upper  part  of  the  line  of  ascent, 
so  that  the  ape.t  appears  dentate  and  forms  an  angle  with  the  line  of  ascent,  then  the  condition 
becomes  one  of  Anacrotism  (Fig.  85,  «,  11),  which,  when  it  becomes  so  marked,  may  be  charac- 
terized as  pathological  (Laiii/ois).  Anacrotism  of  the  pulse  occurs  when  the  time  of  the  influ.\  of 
the  blood  is  longer  than  the  time  occupied  by  an  elastic  vibration.     Hence  it  takes  place  : — 


Fig.  85. 


,1,  a,  the 


(i)  In  dilatation  and  hypertrophy  of  the  left  ventricle,  e.^.,  Fig.  85,  A,  a  tracing  from  the 
radial  artery  of  a  man  suffering  from  contracted  kidney.  The  large  volume  of  blood  expelled  with 
each  systole  requires  a  long  time  to  dilate  the  tense  arteries. 

(2)  When  the  extensibility  of  the  arterial  wall  is  diminished,  even  the  normal  amount  of 
blood  expelled  from  the  heart  at  every  systole  requires  a  long  time  to  dilate  the  artery.  This  occurs 
in  old  people,  where  the  arteries  tend  to  become  rigid,  e.g.,  in  atheroma.  Cold  also  stimulates  the 
arteries,  so  that  they  l:iecome  less  extensile.  Within  one  hour  after  a  tepid  bath,  the  pulse  assumes 
the  anacrotic  form  (Fig.  85,  D)  (C.  ;'.  LieHg). 

(3)  When  the  blood  stagnates  in  consequence  of  great  diminution  in  the  velocity  of  the  blood 
stream,  as  occurs  in  paralyzed  limbs,  the  volume  of  blood  propelled  into  the  artery  at  every  systole 
no  longer  produces  the  nonnal  distention  of  the  arterial  coats,  and  anacrotic  notches  occur  (Fig. 
85,  Bl. 

(4)  After  ligature  of  an  artery,  when  blood  slowly  reaches  the  peripheral  part  of  the  vessel 
through  a  relatively  small  collateral  circulation,  it  also  occurs.  If  the  brachial  artery  be  compressed 
so  that  blood  slowly  reaches  the  radial,  the  radial  pulse  may  become  anacrotic.  It  often  occurs  in 
stenosis  of  the  aorta,  as  the  blood  has  difficulty  in  getting  into  the  aorta  (Fig.  85,  C). 

Recurrent  Pulse. — If  the  radial  artery  be  compressed  at  the  wrist,  the  pulse 
beat  reappears  on  the  distal  side  of  the  point  of  pressure  through  the  arteries  of 
the  paltn  of  the  hand  {Janaiid,  Neidert).  The  curve  is  anacrotic,  and  the 
dicrotic  wave  is  diminished,  while  the  elastic  elevations  are  increased. 

(5)  A  special  form  of  anacrotism  occurs  in  cases  of  well-marked  insufficiency  of  the  aortic 
valves.  Practically,  in  these  cases,  the  aorta  remains  permanently  open.  The  contraction  of  the 
left  auricle  causes  in  the  blood  a  wave  motion,  which  is  at  once  propagated  through  the  open  mouth 
of  the  aorta  into  the  large  blood  vessels.     This  wave  is  followed  bv  the  wave  caused  by  the  con- 


INFLUENCE    OF    RESPIRATORY    MOVEMENTS    ON    PULSE    CURVE.     131 

traction  of  the  hypertrophied  left  ventricle ;  but,  of  course,  the  former  wave  is  not  so  large  as  the 
latter.  In  insutiiciency  of  the  aortic  valves,  the  auricular  wave  occurs  before  the  ventricular  wave 
in  the  ascending  part  of  the  curve.  The  auricular  is  well  marked  only  in  the  large  vessels,  for  it 
becomes  lost  in  the  peripheral  vessels.  Fig.  86,  I,  was  obtained  from  the  carotid  of  a  man  sulTering 
from  well-marked  insufficiency  of  the  aortic  valves,  with  considerable  hypertrophy  of  the  left  ventricle 
and  left  auricle.  The  ascent  is  steep,  caused  by  the  force  of  the  contracting  heart.  In  the  apex  of 
th^  curve  are  two  projections;  A  is  the  anacrotic  auricular  wave,  and  V  is  the  ventricular  wave. 
Fig.  86,  II,  is  a  curve  obtained  from  the  subclavian  artery  of  the  same  individual.  In  the  femoral 
artery,  the  auricular  projection  is  only  obtained  when  the  friction  of  the  writing  style  is  reduced  to 
the  minimum,  and  when  it  occurs,  it  immediately  precedes  the  beginning  of  the  ascent  (Fig.  86,  III, 
a).     The  pulse  curve,  in  cases  of  aortic  insufficiency,  is  also  characterized  by — (i)  its  considerable 


I,  II, III 


insufficiency  ot  tlie  i 


height ;  (2)  the  rapid  fall  of  the  lever  from  the  apex  of  the  curve,  because  a  large  part  of  the  blood 
which  is  forced  into  the  aorta  regurgitates  into  the  left  ventricle  when  the  ventricle  relaxes ;  (3)  not 
unfrequently,  a  projection  occurs  at  the  apex,  due  to  the  elastic  vibration  of  the  tense  arterial  wall ; 
(4)  the  dicrotic  wave  (K)  is  small  compared  with  the  size  of  the  curve  itself,  because  the  pulse 
wave,  owing  to  the  lesion  of  the  aortic  valves,  has  not  a  sufficiently  large  surface  to  be  reflected  from 
(Fig.  So).  The  great  height  of  the  curve  is  explained  by  the  large  amount  of  blood  projected  into 
the  aortic  system  by  the  greatly  hypertrophied  and  dilated  ventricle. 

74.  INFLUENCE  OF  THE  RESPIRATORY  MOVEMENTS 
ON  THE  PULSE  CURVE.— The  respiratory  movements  influence  the  pulse 
in  two  ways — (i)  in  a  purely  physical  way,  by  diminishing  the  arterial  pressure 
during  each  inspiration  and  increasing  it  during  expiration  ;  (2)  the  respiratory 

Fig.  87. 


spiration  upon  the  sphygmogram  (alter  Ricgel).     J,  du 


E,  during, 


movements  are  accompanied  by  stimulation  of  the  vasomotor  centre,  which 
produces  variations  of  the  blood  pressure. 

I.  Normal  Respiration. — During  inspiration,  owing  to  the  dilatation  of  the 
thorax,  more  arterial  blood  is  retained  within  the  chest,  while,  at  the  saine  time, 
venous  blood  is  sucked  into  the  right  auricle  by  the  aspiration  of  the  thorax  ;  as  a 
consequence  of  this,  the  tension  in  the  arteries  during  inspiration  must  be  less. 
The  diminution  of  the  chest  during  expiration  favors  the  flow  in  the  arteries, 
while  it  retards  the  flow  of  the  venous  blood  in  the  ven»  cav«,  two  factors  which 
raise  the  tension  in  the  arterial  system.     The  difference  of  pressure  explains  the 


132 


VALSALVA  S    AND    MULLER  S    EXPERIMENTS. 


difference  in  the  form  of  the  pulse  curve  obtained  during  inspiration  and  expira- 
tion, as  in  Fig.  87  and  Fig.  79,  I,  III,  IV,  in  which  J  indicates  the  part  of  the 
curve  which  occurred  during  inspiration,  and  E  the  expiratory  portion.  The  fol- 
lowing are  the  points  of  difference :  (i)  The  greater  distention  of  the  arteries 
during  expiration  causes  all  the  parts  of  the  curve  occurring  during  this  phase  to 
be  higher;  (z)  the  line  of  ascent  is  lengthened  during  expiration,  because  the 
expiratory  thoracic  movement  helps  to  increase  the  force  of  the  expiratory  wave  ; 
(3)  owing  to  the  increase  of  the  pressure,  the  dicrotic  wave  must  be  less  during 
expiration;  (4)  for  the  same  reason,  the  elastic  elevations  are  more  distinct  and 
occur  higher  in  the  curve  near  its  apex.  The  frequency  of  the  pulse  is  slightly 
greater  during  expiration  than  during  inspiration. 

2.  This  purely  mechanical  effect  of  the  respiratory  movements  is  modified  by 
the  simultaneous  stimulation  of  the  vasomotor  centre  which  accompanies  these 
movements.  At  the  beginning  of  insjjiration  the  blood  pressure  in  the  arteries  is 
lowest,  but  it  begins  to  rise  during  inspiration,  and  increases  until  the  end  of  the 
inspiratory  act,  reaching  its  maximum  at  the  beginning  of  expiration.  During 
the  remainder  of  the  expiration  the  blood  pressure  falls  until  it  reaches  its  lowest 
level  again  at  the  beginning  of  inspiration  (compare  S85,/),  the  pulse  curves  are 


nd  R,  radial,  during  MHllcr's  experiment ;  Q,  and  Rj,  from  the  < 
s.ilva's  experiment.     Curves  written  on  a  vibrating  surface. 


:  vessels  during  Val- 


similarly  modified,  and  exhibit  the  signs  of  greater  or  less  tension  of  the  arteries 
corresponding  to  the  phases  of  the  respiratory  movements  (Kkmeiisiewuz,  Knoll, 
Schrdl'cr,  Lowit).  ['I'here  is,  as  it  were,  a  displacement  of  the  blood-pressure 
curve  relative  to  the  respiratory  curve.] 

Forced  Respiration. — With  regard  to  the  effect  produced  on  the  pulse  curve 
by  a  powerful  expiration  and  a  forced  inspiration,  observers  are  by  no  means 
agreed. 

Valsalva's  Experiment. — Strong  expiratory  pressure  is  best  produced  by 
closing  tht;  mouth  and  nose,  and  then  making  a  great  expiratory  effort  (§  60)  ;  at 
first  there  is  increase  of  the  blood  pressure,  while  the  form  of  the  pulse  waves  re- 
sembles that  which  occurs  in  ordinary  expiration,  the  dicrotic  wave  being  less 
developed  ;  but,  when  the  forced  pressure  is  long  continued,  the  pulse  curves  have 
all  the  signs  of  diminished  tension  (Ric^^el,  Frank,  and  Sommerbrodt).  This  effect 
is  due  to  the  action  of  the  vasomotor  centre,  which  is  affected  rellexly  from  the 
pulmonary  nerves.  We  must  assume  that  forced  expiration,  such  as  occurs  in 
Valsalva's  experiment,  acts  by  depressing  the  activity  of  the  vasomotor  centre 
(§  37I'  II)-     Coughing   singing,  and  declaiming,  act  like  Valsalva's  experiment. 


INFLUEN'CE    OF    PRESSURE    OX    FORM    OF    PULSE    CURVE.  133 

while  the  frequency  of  the  pulse  is  increased  at  the  same  time  {Sommetbrodt). 
After  the  cessation  of  Valsalva's  experiment,  the  blood  pressure  rises  above  the 
normal  state  {Sommerbrodt),  almost  as  much  as  it  fell  below  it ;  the  normal  condi- 
tion being  restored  within  a  few  minutes  (Lenzmann). 

M tiller's  Experiment. — When  the  thorax  is  in  the  expiratory  phase,  close 
the  mouth  and  nose,  and  take  a  deep  inspiration  so  as  forcibly  to  expand  the 
chest  (S  60).  At  first  the  pulse  curves  have  the  characteristic  signs  of  diminished 
tension,  viz.,  a  higher  and  more  distinct  dicrotic  wave  ;  then  the  tension  can,  by 
nervous  influences,  be  increased,  just  as  in  Fig.  88,  where  C  and  R  are  tracings 
taken  from  the  carotid  and  radial  arteries  respectively,  during  Miiller's  experi- 
ment, in  which  the  dicrotic  waves,  ;-,  r.  indicate  the  diminished  tension  in  the 
vessels.  In  Ci  and  Ri,  taken  from  the  same  person  during  Valsalva's  experiment, 
the  opposite  condition  occurs. 

Compressed  Air. — On  expiritig  into  a  vessel  resembling  a  spirometer  (see  Respiration),  (Walden- 
berg's  respiration  apparatus),  and  tilled  with  compressed  air,  the  same  result  is  obtained  as  in  Val- 
salva's experiment — the  blood  pressure  falls  and  the  pulse  beats  increase  ;  conversely  the  inspira- 
tion from  this  apparatus,  of  air  under  less  pressure,  acts  like  Miiller's  experiment,  i.  i.,  it  increases 
the  effect  of  the  inspiration,  and  afterward  increases  the  blood  pressure,  which  may  either  remain 
increased  on  continuing  the  experiment,  or  may  fall  (Lenzmann). 

The  inspiration  of  compressed  air  diminishes  the  mean  blood  pressure  (Zunis)  and  the  after 
effect  continues  for  some  time.  The  pulse  is  more  frequent  both  during  and  alter  the  experiment. 
Expiration  in  rarefied  air  increases  the  blood  pressure  (Ziintz,  Lenzmann).  The  efiects  which 
depend  upon  the  action  of  the  nervous  system  do  not  occur  to  the  same  extent  in  all  cases.  Ex- 
posure to  compressed  air  in  a  pneumatic   cabinet  lowers  the  pulse  curve,  the  elastic  vibrations 

Fig.  S9. 


Pulsus  paradoxus  (after  Kussmaiil).     E,  expiration  ;  J,  inspiration. 


Ijecome  indistinct,  and  the  dicrotic  wave  diminishes  and  may  disappear  (v.  Vivenot).  The  heart's 
beat  is  slowed  and  the  blood  pressure  raised  [Bert,  Jacobsohn,  Lazarus').  Exposure  to  rarefied  air 
causes  the  opposite  result,  which  is  a  sign  of  diminished  arterial  tension. 

Pulsus  Paradoxus. — Under  pathological  conditions,  especially  when  there  is  union  of  the  heart 
or  its  large  vessels  with  the  surrounding  parts,  the  pulse  during  inspiration  may  be  extremely  small 
and  changed,  or  may  even  be  absent  (Fig.  89).  This  condition  has  been  called  pulsus  paradoxus 
( Griesingi-r,  A'lissmaiil). 

It  depends  upon  a  diminution  of  the  arterial  lumen  during  the  inspiratory  movement.  Even  in 
health,  it  is  possible,  by  a  change  of  the  inspiratory  movement,  to  produce  the  p.  paradoxus  [Ricge/, 
Sotnmi'rbrodt). 

75.  INFLUENCE  OF  PRESSURE  UPON  THE  FORM  OF  THE  PULSE 
CURVE. — ^It  is  most  important  to  know  tlie  actual  pressure  which  is  applied  to  an  artery 
while  a  sphygniogram  is  being  tiiken.  The  changes  affect  tlie  form  of  the  curve  as  well  as  the 
relation  of  the  individual  parts  thereof  In  Fig.  90,  <?,  b,  f",  d.  e  are  radial  curves ;  a  was  taken 
with  minimal  pressure,  b  with  100,  c,  200,  d  250,  and  e  450  grammes  pressure,  while  A,  B,  C,  D 
show  the  relations  as  to  the  time  of  occurrence  of  the  individual  phenomena  where  the  weight  was 
successively  increased.  The  study  of  these  curves  yields  the  following  results:  (i)  When  the  weight 
is  small,  the  dicrotic  wave  is  relatively  less;  the  whole  curve  is  high;  (2)  with  a  moderate  weight 
( 100  to  200  grammes)  the  dicrotic  wave  is  best  marked,  the  whole  curve  is  somewhat  lower;  (3)  on 
increasing  the  weight  the  size  of  the  dicrotic  wave  again  diminishes;  (4)  the  fine  elastic  vibrations 
preceding  the  dicrotic  wave  appear  first  when  a  weight  of  220  to  300  grammes  is  used;  (5)  the 
rapidity  of  the  pulse  changes  with  increasing  weight,  the  time  occupied  by  the  ascent  becoming 
shorter,  the  descent  becoming  longer ;  (6)  the  height  of  the  entire  curve  decreases  as  the  weight 
increases.  In  every  sphygmogram  the  pressure  under  which  it  was  obtained  ought  always  to  be 
stated. 

In  Fig.  90,  A,  B  are  curves  obtained  from  the  radial  artery  of  a  healthy  student.  The  pressure 
exerted  upon  the  artery  for  A  was  100;  B,  220  grms.     (i  vibration  =0.01613  sec). 


134 


I'ROPAGATION    OF    PULSE   WAVES    IN    ELASTIC   TUBES. 


If  pressure  be  exerted  upon  an  artery  for  a  long  time  the  strength  of  the  pulse  is  gradually  in- 
creased. If,  after  subjecting  an  artery  to  considerable  pressure,  a  lighter  weight  be  used,  not  unfre- 
quently  the  pulse  curve  assumes  the  form  of  a  dicrotic  pulse,  owing  to  the  greater  development  of 
the  dicrotic  elevation.  When  strong  pressure  is  applied,  the  blood  is  forced  to  find  its  way  through 
collateral  channels.  When  the  chief  artery  ceases  to  be  compressed,  the  total  area  is,  of  course, 
considerably  and  suddenly  enlarged,  which  results  in  the  production  of  a  dicrotic  elevation.  Fig. 
79,  X,  is  such  a  dicrotic  cun'e  obtained  after  considerable  pressure  had  lieen  applied  to  the  artery. 

76.  RAPIDITY  OF    TRANSMISSION  OF    PULSE  WAVES.— 

The  pulse  wave  ]3roceeds  throughout  the  arterial  system  from  the  root  of  the  aorta, 
so  that  the  pulse  is  felt  sooner  in  parts  lying  near  the  heart  than  in  the  peripheral 
arteries.  E.  H.  Weber  calculated  the  velocity  of  the  pulse  wave  as 
9.240  metres  [28^  feet]  per  second,  from  the  difference  in  time  between 
the  pulse  in  the  e.xternal  maxillary  artery  and  the  dorsal  artery  of  the  foot. 
Czermak  showed  that  the  elasticity  was  not  equal  in  all  the  arteries,  so  that  the 
velocity  of  the  pulse  wave  cannot  be  the  same  in  all.  The  pulse  wave  is  propa- 
gated more  slowly  in  the  arteries  with  soft  extensile  walls  than  in  arteries  with 
resistant  and  thick  walls,  so  that  it  is  transmitted  more  rapidly  in  the  arteries  of 
the  lower  extremities  than  in  those  of  the  upper.     It  is  still  slower  in  children. 

Fig.  90. 


Various  forms  ot  ' 


(radial)  obtained  by  gradually  increasing  the  pressure. 


77.  PROPAGATION  OF  THE    PULSE  WAVE    IN   ELASTIC    TUBES.— Waves 

similar  to  the  pulse  may  be  produced  in  elastic  tubes,  (i)  According  to  E.  H,  Weber,  the  velocity 
of  propagation  of  the  waves  is  11.205  metres  per  sec;  according  to  Donders,  11-13  metres 
(34-44  feet).  (2)  According  to  E.  H.  Weber  increased  internal  tension  causes  only  an  inconsid- 
erable decrease ;  Rive  found  a  great  decrease ;  Donders  found  no  obvious  difference ;  while  Marey 
found  an  increased  velocity.  (3)  Donders  found  the  velocity  to  be  the  saine  in  tubes  2  mm.  in  dia- 
meter, as  in  wider  tubes,  but  Marey  believes  that  the  velocity  varies  when  the  diameter  of  the  tube 
changes.  (4)  The  velocity  is  less,  the  smaller  the  elastic  coefficient.  (5)  The  velocity  increases 
with  increased  thickness  of  the  wall,  while  it  diminishes  when  the  specific  gravity  of  the  fluid 
increases. 

Moens  has  recently  formulated  the  following  laws  as  to  the  velocity  of  propagation  of  waves  in 
elastic  tubes:  (i)  It  is  inversely  proportional  to  the  square  root  of  the  specific  gravity  of  the 
fluid ;  (2)  it  is  as  the  square  root  of  the  thickness  of  the  wall,  the  lateral  pressure  being  the  same; 
(3)  it  is  inversely  as  the  square  root  of  the  diameter  of  the  tube,  the  lateral  pressure  being  the 
same  ;  (4)  it  is  as  the  square  root  of  the  elastic  coefficient  of  the  wall  of  the  tube,  the  lateral 
pressure  being  the  same  (  I'aleiitiii.) 

Experiments  with  Caoutchouc  Tubes. — For  this  purpose  Landois  employs  the  following 
apparatus  (Fig.  91)  :  A  large  tuning  fork,  A  (35  cm.  long),  carries  on  one  of  its  arms  a  glass  plate, 
P  (25  cm.  long  and  5  cm.  broad),  while  the  other  arm  is  weighted,  G.  The  tuning  fork  is  fixed  by 
an  iron  holder,  T,  to  a  movable  piece  of  wood,  which  can  be  pushed  along  with  the  hand  in  a 
groove  on  a  support,  H,  H.  When  the  glass  plate  is  smoked,  the  curved  needle  of  the  angiograph 
writes  its  movements  upon  it.     The  fork,  when  it  vibrates,  makes  little  teeth  in  the  curve,  and  the 


PROPAGATION    OF    PULSE    WAVES    IN    ELASTIC    TUBES. 


135 


value  of  each  vibration  is  estimated  beforehand.     Every  complete   vibration   in  this  instrument  is 
equal  to  0.01613  second. 

Velocity  of  the  Waves  in  Elastic  Tubes  filled  with  Water  or  Mercury.— Take  a  soft, 
extensible,  elastic  tube.  A,  S.So  metres  long,  i  mm.  thick,  and  7  mm.  diameter.  If  i  metre  of  the 
tube  is  weighted  with  i  kilo., it  elongates  68  cm.  An  ampulla,  B,  capable  of  containing  50  c.c,  is 
fixed  to  one  end  of  the  tube,  while  to  the  other  end  of  the  ampulla  is  fixed  a  mercurial  mano- 
ifteler,  Q. 

Fig.  91. 


Instrument  for  measuring  the  velocity  01  the  pulse  wave  in  an  elastic  tube  containing  water  01  mercury.  A,  tuning- 
fork  ;  B,  ampulla:  A,  elastic  tube;  P,  gl.iss  plate  smoked ;  Q,  manometer:  X,  pad  of  lever  of  angiograph  ; 
writing  style,  D. 

The  tube.  A,  is  shut  close  to  the  ampulla  ever)'  time  the  pressure  is  measured,  in  order  to  obviate 
the  occurrence  of  oscilkation  in  the  mercurj-.  A  certain  portion  of  the  tube,  say  8  metres,  is 
measured.  The  beginning,  a.  and  end,  b,  of  this  stretch  of  tubing  are  placed  under  the  pad,  X,  of 
the  angiograph.  When  a  positive  wave  is  produced  by  compressing  the  ampulla,  the  writing  lever 
is  raised  twice,  the  first  time  when  the  wave  passes  the  first  part  of  the  tube,  a,  under  the  pad,  and  the 
second  time  when  the  end  part  of  the  tube,  b,  is  distended  by  the  wave.  The  curve  obtained  is 
shown  in  Fig.  92,  in  which  the  two  elevations,  I    and  2,  are  obvious.     The  time  between  the  two 

Fig.  92. 


Pulse  curve   rem  an  elastic  tube  registered  upon  a  plate  attached  to  a  vibrating  tuning  fork. 

may  be  ascertained   by  counting  the  number  of  vibrations  of  the  tuning  fork.     The  experiments 
gave  the  following  results ; — 

(A)  The  velocity  of  the  wave  is  n.809  metres  per  second. 

(B)  "Dx^  intravascular  pressure  has  a  decided  influence  on  the  velocity:  thus,  in  the  tube,  A, 
with  18  cm.  (Hg)  pressure,  the  velocity  per  metre  =  0.093  second,  while  "'■'l'  ^i  cm.  pressure 
(Hg)  ^  0.095  second  per  metre. 

(C)  The  specific  gravity  of  the  liquid  influences  the  velocity  of  the  pulse  wave.  In  mercury  the 
wave  is  propagated  four  times  more  slowly  than  in  water  {^Marey  and  Landois). 


136 


VELOCITY    OF    THE    PULSE    WAVE    IN    MAN. 


(D)  The  velocity  in  a  tube  which  is  more  rigid  and  not  so  extensile  is  greater  than  in  a  tube 
which  is  easily  distended. 

78.  VELOCITY  OF  THE  PULSE  WAVE  IN  MAN.— Landois  obtained  the  follow- 
ing results  in  a  student  whose  height  was  174  centimetres  :  Difference  between  carotid  and  radial 
=  0.074  second  (the  distance  being  taken  as  62  centimetres) ;  carotid  and  femoral  =  o  06S  second; 
femoral  (^inguinal  region)  and  posterior  tibial  =  0.097  second  (distance  estimated  at  91  centimetres). 

[Waller  obtained  between  the  heart  and  carotid  o.  10  second;  heart  and  femoral,  0.18  second; 
heart  and  dorsalis  pedis,  0.22.] 

The  velocity  of  the  pulse  wave  in  the  arteries  of  the  upper  extremities  = 
9.43   metres   per  second,   and   in   those  of  the  lower  extremity  9.40  metres  per 


Fig.  93 


P                        \^      R 

HP 

second  [/.  e.,  about  30  feet  per  second].  The  velocity  is  greater  in  the  less 
extensile  arteries  of  the  lower  extremities  than  in  those  of  the  upper  limb.  For 
the  same  reason  it  is  less  in  the  peripheral  arteries  and  in  the  yielding  arteries  of 
children  {Czt-nnaf:). 

E.  H.  Weber  estimated  the  velocity  at  9.24  metres  per  second;  Garrod,  9-10.8  metres;  Grashey, 
8.5  metres;  Moens,  8.3  metres,  and  with  diminished  pressure  during  Valsalva's  experiment,  7.3 
metres  (§  60,  74). 

Influencing  Conditions. — In  animals,  hemorrhage  (Haller),  slowing  of  the  heart  produced  by 
stimulation  of  the  vagus  {AUens),  section  of  the  spinal  cord,  deep  morphia  narcosis,  and  dilatation 

Fig.  94. 


i  of  the  carotid  and  pc 
vibrating  plate  attached 


ograph, 


of  the  blood  vessels  by  heat,  produce  shwin:;  ot  the  velocity,  while  stimulation  of  the  spinal  cord 
accelerates  it  {Grttnffiiich). 

The  wave  length  of  the  pulse  wave  is  obtained  by  multiplying  the  dura- 
tion of  inflow  of  blood  into  the  aorta,  =  0.08  to  0.09  second  (§  51),  by  the  velo- 
city of  the  pulse  wave. 

Method. — Place  the  knobs  of  two  tambours  (Fig.  72)  upon  the  two  arteries  to  be  investigated, 
or  place  one  over  the  apex  beat  and  the  other  upon  an  artery.  These  receiving  tambours  are  con- 
nected  with  two  registering  tambours,  as  in  Brondgeest's  pansphygmograph  (J  67,  Fig.  72),  so  that 
their  writing  levers  are  directly  over  each  other,  and  so  arranged  as  to  write  simultaneously  on  one 


VIBRATIONS   COMMUNICATED   TO    THE    BODY    BY   THE    HEART.     137 

vibrating  plate  attached  to  a  tuning  fork.  [Or  they  may  be  made  to  write  upon  a  revolving  cylinder, 
whose  rate  of  movement  is  ascertained  by  causing  a  tuning  fork  of  a  known  rate  of  Wbration  to 
write  under  them.]  The  apparatus  is  improved  by  using  rigid  tubes  and  filling  them  with  water, in 
which  all  impulses  are  rapidly  communicated.  In  arteries  which  are  distant  from  each  otlier,  or  in 
the  case  of  the  heart  and  an  artery,  the  two  knobs  of  the  receiving  tambours  may  be  connected,  by 
means  of  a  Y-tube,  with  one  writing  lever.  In  Fig.  93.  B  is  a  cur\e  from  the  radial  artery  taken  in 
this  way.  In  it  v  H  P  indicates  contraction  of  the  ventricle ;  H,  the  apex  of  the  ventricular  contrac- 
tion; P,  the  primary  apex  of  the  radial  curve;  z;  the  beginning  of  the  ventricular  contraction;  p, 
of  the  radial  pulse.  A  is  the  cur\e  of  the  radial  artery  alone.  From  these  curves  it  is  evident 
that  in  this  instance  nine  vibrations  occur  between  the  beginning  of  the  ventricular  contraction  until 
the  beginning  of  the  pulse  in  the  radial  artery  =  0.15  second. 

In  Fig.  94  the  difference  between  the  carotid  and  the  posterior  tibial  pulse  ^  0.137  sec. 

Pathological. —  In  cases  of  dimiitished  extensibility  of  the  arteries,  e.g.^  in  atheroma  {§  77,  d), 
the  pulse  wave  is  propagated  more  rapidly.  Local  dilatations  of  the  arteries,  as  in  aneurisms, 
cause  a  retardation  of  the  wave,  and  a  similar  result  arises  from  local  constrictions.  Relaxation  of 
the  walls  of  the  vessels  in  high  fever  retards  the  movement  (Hamernjk). 

79.  OTHER  PULSATILE  PHENOMENA.— i.  In  the  mouth  and  nose,  when  they 
are  filled  with  air,  and  the  glottis  closed,  pulsatile  phenomena  (due  to  the  arteries  in  their  soft  parts), 
may  be  found  communicating  a  movement  to  the  contained  air.  The  cur\es  obtained  are  relatively 
small,  and  closely  resemble  the  curve  of  the  carotid.  A  similar  pulse  is  obtained  in  the  tympanum 
with  intact  membrana  tvmpani,  and  when  the  soft  parts  of  the  tympanum  are  congested  [S<:/i-cartze, 
Troltsch). 

2.  Entoptical  Pulse. — After  violent  exercise,  an  illumination,  corresponding  to  each  pulse  beat, 
occurs  on  a  dark  ojitical  field.  When  the  optical  field  is  bright,  an  analogous  darkening  occurs 
(Landois).  The  ophthalmoscope  occasionally  reveals  pulsation  of  the  retinal  arteries  [Jagerj,  which 
becomes  marked  in  insufficiency  of  the  aortic  valves  {Quincke^  O.  Becker^  Helfreieh). 

3.  Pulsatile  Muscular  Contraction. — The  orbicularis  palpebrarum  muscle  contracts  under 
similar  conditions  synchronously  with  the  pulse;  and  it  is,  perhaps,  due  to  the  pulse  beat  exciting 
the  sensory  nerves  reflexly.  The  brothers  ^Veber  found  that  not  unfrequently,  while  walking,  the 
step  and  pulse  gradually  and  involuntarily  coincide. 

4.  When  the  legs  are  crossed  as  one  sits  in  a  chair,  the  leg  which  is  supported  is  raised  with  each 
pulse  beat,  and  it  gives  also  a  second  or  dicrotic  elevation. 

5.  If,  while  a  person  is  quite  quiet,  the  incisor  teeth  of  the  lower  jaw  be  made  just  to  touch  the 
upper  incisors  very  lightly,  we  detect  a  double  beat  of  the  lower  against  the  upper  teeth,  owing  to 
the  pulse  beat  in  the  external  maxillary  artery  raising  the  lower  jaw.  The  second  elevation  is  due 
to  the  closure  of  the  semilunar  valves,  and  not  to  a  dicrotic  wave. 

6.  Brain  and  Fontanelles. — The  large  arteries  at  the  base  of  the  brain  communicate  a  move- 
ment to  it,  while  similar  movements  occur  with  respiration — rising  during  expiration  and  falling 
during  inspiration.  These  movements  are  visible  in  \\\t  fontanelles  of  infants.  The  respiratory 
movements  depend  upon  variations  in  the  amount  of  blood  in  the  veins  of  the  cranial  cavity,  and 
also  upon  the  respiratory  variations  of  the  blood  pressure. 

7.  .\mong  pathological  phenomena  are  the  beating  in  the  epigastrium,  e.g.,  in  hj-pertrophy  of 
the  right  or  left  ventricle,  caused,  it  may  be,  by  deep  insertion  of  the  diaphragm,  and  it  may  be 
partly  by  the  beating  of  a  dilated  abdominal  aorta  or  cceliac  axis. 

Abnormal  dilatations  (aneurisms)  of  the  arteries  cause  an  abnormal  pulsation,  while  they  pro- 
duce a  sloxoing  in  the  velocity  of  the  pulse  'wave  in  the  corresponding  artery.  Hence  the  pulse 
appears  later  in  such  an  artery  than  in  the  artery  on  the  healthy  side.  Hypertrophy  and  dilatation 
of  the  left  ventricle  cause  the  arteries  near  the  heart  to  pulsate  strongly.  In  the  analogous  condition 
of  the  right  ventricle,  the  beat  of  the  pulmonary  artery  may  be  seen  and  felt  in  the  second  left  inter- 
costal space. 

80.  VIBRATIONS  COMMUNICATED  TO  THE  BODY  BY  THE  ACTION 
OF  THE  HEART. — The  beating  of  the  heart  and  large  arteries  communicates  vibrations  to  the 
body  as  a  whole ;  the  vibration  lieing  not  simple  but  compound. 

Gordon  was  the  first  to  represent  this  pulsatory  vibration  graphically.  If  a  person  be  placed  in  an 
erect  altitude  in  the  scale  pan  of  a  large  balance,  the  index  oscillates,  and  its  movements  coincide 
with  the  heart's  movements  (  Gordon). 

Method. — Landois  employed  the  following  arrangement  (Fig.  95,  I):  Take  a  long,  four-sided 
box,  K,  open  at  the  top,  and  arrange  several  coils,  a,  b,  of  stout  caoutchouc  tubing  round  one  end. 
A  wooden  board,  B,  smaller  than  the  opening  in  the  box,  is  so  placed  that  it  rests  with  one  end  on 
the  caoutchouc  tubing,  and  with  the  other  on  the  narrow  end  of  the  box.  The  person  to  be  experi- 
mented upon,  A,  stands  vertically  and  firmly  on  this  board.  A  receiving  tambour,  /,  is  placed 
against  the  surface  of  the  board  next  the  elastic  tube,  which  registers  the  vibrations  of  the  foot 
support.  Fig.  Ill  is  a  curve  showing  such  vibrations,  each  heart  beat  being  followed  in  this  case  by 
four  oscillations.  To  ascertain  the  relations  and  causes  of  these  vibrations,  it  is  necessary  to  obtain, 
simultaneously,  a  tracing  of  the  heart  and  the  vibratory  cur\-e.  For  this  purpose  u'e  the  two  tam- 
bours of  Brondgeest's  pan.sphygmograph  (^  67,  6),  placing  one  knob  or  pad  over  the  heart  and  the 


138     VIBRATIONS    COMMUNICATED    TO    THE    BODY    BY    THE    HEART. 

other  on  the  foot  support,  and  allow  the  writing  tambours  to  inscribe  their  vibrations  on  a  glass  plate 
attached  to  a  tuning  fork. 

In  the  hmif?-  or  cnniiac  iiiipiihe  curve  (Fig.  96),  the  rapidly-rising  part  is  due  to  the  ventricular 
systole.  It  contains  eight  vibrations  (i  vib.  =  0.01613  s^c).  The  beginning  of  the  ventricular 
systole  is  indicated  in  the  figure  by  -36,  -3,  -17. 

If  the  corresponding  numbers  in  the  upper  or  vibratory  (iii-ve  are  studied,  it  is  obvious  that  at  the 

Fig.  95. 


upport  for   registering  the  mo 
graph;  a,  (^,  elastic   tubing.     II.  Vibration 
patient  suffering  from  insufficiency  of  the  ac 


of  the  body — K,  a  wooden  box 
rves  of  a  healthy  person.     III.  Similar  cui 
;  valves  and  great  hypertrophy  of  the  heart. 


moment  of  ventricular  systole  the  body  makes  a  downward  vibration,  i.e.,  it  exercises  greater  pressure 
upon  the  foot  support.  Gordon  interprets  his  curve  as  giving  exactly  the  opposite  result.  This  down- 
ward motion,  however,  lasted  only  during  five  vibrations  of  the  tuning  fork ;  during  the  last  three 
vibrations,  corresponding  to  the  systole,  there  is  an  ascent  of  the  body  corresponding  to  a  less  pressure 
upon  the  foot  plate.  When  the  ventricle  empties  itself,  it  undergoes  a  movement  in  a  downward 
and  outward  direction — Gutbrodt's  "  reaction  impulse." 

In  the  uffer  curve,  analogous  numbers  are  employed  to  indicate  the  vibrations  occurring  simulta- 


■ 

^^ 

■ 

Fk;.  q6 

■ 

^m 

^Vv/^ 

28 

Nl/ 

"•v. 

\}r\ 

30     A- 

-wvv^ 

n     10 

A 

\         1 

3b    / 

\l 

y  \ 

11  / 

\i. 

AAAAA/1 

Lft/i//;-' 

J   \ 

30 

^AAAA/■ 

\j 

The  upper  t 


:  of  a  healthy  person,  and  the  low 


the  apex  beat. 


neously,  viz.,  -28,  -11,  -10.  The  closure  ot  the  semilunar  valves  is  well  marked  in  the  three  heart 
beats  at  20,  -20.  This  closure  is  indicated  in  analogous  points  in  both  curves,  after  which  there  is 
a  descent  of  the  foot  support,  and  this  corresponds  to  the  downward  propagation  of  the  pulse  wave 
through  the  aorta  to  the  vessels  of  the  feet. 

Pathological. — In  insufficiency  of  the  aortic  valves,  as  shown   in   Fig.  96,  III,  the  vibration 
communicated  to  the  body  is  very  considerable. 


THE    BLOOD    CURRENT.  139 

8i.  THE  BLOOD  CURRENT. —  Cause.— The  closed  and  much 
branched  vascular  system,  whose  walls  are  endowed  with  elasticity  and  contrac- 
tility, is  not  only  completely  filled  with  blood,  but  it  is  over-filled.  The  total 
volume  of  the  blood  is  somewhat  greater  than  the  capacity  of  the  entire  vascular 
system.  Hence,  it  follows  that  the  mass  of  blood  must  exert  pressure  on  the 
walls  of  the  entire  system,  thus  causing  a  corresponding  dilatation  of  the  elastic 
vascular  walls  (^r/i'//;/(v-).  This  occurs  only  during  life;  after  death  the  muscles 
of  the  vessels  relax,  and  fluid  passes  into  the  tissues,  so  that  the  blood  vessels 
come  to  contain  less  fluid,  and  some  of  the  vessels  may  be  emptied. 

If  the  blood  were  uniformly  distributed  throughout  the  vascular  system,  and 
under  the  same  pressure,  it  would  remain  in  a  position  of  equilibrium  (as  after 
death).  If,  however,  the  pressure  be  raised  in  one  section  of  the  tube,  the  blood 
will  move  from  the  part  where  the  pressure  is  higher  to  where  it  is  lower  ;  so  that 
the  blood  current  is  a  result  of  the  difference  of  pressure  within  the  vas- 
cular system.  If  either  the  aorta  or  the  ven^e  cavK  be  suddenly  ligatured  in  a 
living  animal,  the  blood  continues  to  flow,  but  gradually  more  slowly,  until  the 
difference  of  pressure  is  equalized  throughout  the  entire  vascular  system. 

The  velocity  of  the  current  will  be  greater  the  greater  the  difference  of  pressure, 
and  the  less  the  resistance  opposed  to  the  blood  stream. 

The  difference  of  pressure  7vhich  causes  the  current  is  prmtuccd  by  the  heart 
(E.  H.  Weber).  Both  in  the  systemic  and  pulmonary  circulations,  the  point  of 
highest  pressure  is  in  the  root  or  beginning  of  the  arterial  system,  while  the  point 
of  lowest  pressure  is  in  the  terminal  portion  of  the  venous  orifices  at  the  heart. 
Hence,  the  blood  flows  continually  from  the  arteries  through  the  capillaries  into 
the  venous  trunks. 

The  heart  keeps  up  the  difference  of  pressure  required  to  produce  this  result ; 
with  each  systole  of  the  ventricles,  a  certain  quantity  of  blood  is  forced  into  the 
beginning  of  the  arteries,  while,  at  the  same  time,  an  equal  amount  flows  from  the 
venous  orifices  into  the  auricles  during  their  diastole  {E.  H.  Weber). 

Donders  added  another  important  fact,  viz.,  that  the  action  of  the  heart  not 
only  causes  the  difference  of  pressure  necessary  to  establish  a  blood  current,  but 
it  also  raises  the  mean  pressure  within  the  vascular  system.  The  termina- 
tions of  the  veins  at  the  heart  are  wider  and  more  extensible  than  the  arteries  where 
they  arise  from  the  heart  (Fig.  133).  .\s  the  heart  propels  a  volume  of  blood 
into  the  arteries  equal  to  that  which  it  receives  from  the  veins,  it  follows  that  the 
arterial  pressure  must  rise  more  rapidly  than  the  venous  pressure  diminishes,  since 
the  arteries  are  not  so  wide  nor  so  extensible  as  the  veins.  Thus  the  total  pressure 
must  also  increase. 

Cause  of  Continuous  Flow. — The  volume  of  blood  expelled  from  the  ven- 
tricles at  every  systole  would  give  rise  to  a  Jer/cy  or  intermittent  movement  of  the 
blood  stream — (  i)  if  the  tubes  had  rigid  walls,  as  in  such  tubes  any  pressure 
exerted  upon  their  contents  is  propagated  momentarily  throughout  the  length  of 
the  tube,  and  the  motion  of  the  fluid  ceases  when  the  propelling  force  ceases ; 
(2)  the  flow  would  also  be  intermittent  in  character  in  elastic  tubes  if  the  time 
between  two  successive  systoles  were  longer  than  the  duration  of  the  current 
necessary  for  the  compensation  of  the  difference  of  pressure  caused  by  the  systole. 
If  the  time  between  two  successive  systoles  be  shorter  than  the  time  necessary  to 
equilibrate  the  pressure,  the  current  will  become  continuous,  provided  the 
resistance  at  the  periphery  of  the  tube  be  sufficiently  great  to  bring  the  elasticity 
of  the  tube  into  action.  The  more  rapidly  systole  follows  systole,  the  greater 
becomes  the  difference  of  pressure,  and  the  more  distended  the  elastic  walls. 
Although  the  current  thus  produced  is  continuous,  a  sudden  rise  of  pressure  is 
caused  by  the  forcing  in  of  a  mass  of  blood  at  every  systole,  so  that  with  every 
systole  there  is  a  sudden  jerk  and  acceleration  0/  the  blood  stream  corresponding  to 
the  pulse  (compare  §  64). 


140  CURRENT   IN    THE    CAPILLARIES. 

This  sudden  jerk-like  acceleration  of  the  blood  current  is  propagated  through- 
out the  arterial  system  with  the  velocity  of  the  pulse  wave ;  both  phenomena  are 
due  to  the  same  fundamental  cause.  Every  pulse  beat  causes  a  temporary  rapid 
progressive  acceleration  of  the  particles  of  the  fluid.  But  just  as  the  form  move- 
ment of  the  pulse  is  not  a  simple  movement,  neither  is  the  pulsatile  acceleration 
a  simple  acceleration.  It  follows  the  course  of  the  development  of  the  pulse  wave. 
The  pulse  curve  is  the  graphic  representation  of  the  pulsatory  acceleration  of  the 
blood  stream.  Every  rise  in  the  curve  corresponds  to  an  acceleration,  every 
depression  to  a  retardation  of  the  current. 

[Method:  Rigid  and  Klastic  Tubes. — These  facts  are  capable  of  demonslration  by  means 
of  veiy  simple  ])h)sical  experiments.  Tie  a  Higginson's  syringe  to  a  piece  of  an  ordinary  gas  pipe. 
On  forcing  water  tiirough  tlie  tube,  by  compressing  the  elastic  pump,  the  water  will  flow  out  at  the 
other  end  of  the  tube  in  jets,  while  during  the  intervals  of  pulsation  no  water  will  flow  out.  As  the 
walls  of  the  tube  are  rigid,  just  as  much  fluid  flows  out  as  is  forced  into  the  tube.  If  a  similar 
arrangement  be  made,  and  a  long  elastic  tube  be  used,  a  continuous  outflow  is  obtained,  provided 
the  pulsations  occur  with  sufficient  raj^idity  and  the  length  of  the  tube,  or  the  resistance  at  its 
peripher}',  be  sufiicient  to  bring  the  elasticity  of  the  tube  in  action.  This  can  be  done  by  putting  a 
narrow  cannula  in  the  outflow  end  of  the  tube,  or  by  placing  a  clamp  on  it  so  as  to  diminish  the 
exit  aperture.  This  apparatus  converts  the  intermittent  flow  into  a  continuous  current.]  The  fire 
engine  is  a  good  example  of  the  conversion  of  an  intermittent  inflow  into  a  uniform  outflow.  The 
air  in  the  reservoir  is  in  a  state  of  elastic  tension,  and  it  represents  the  elasticity  of  the  vascular  walls. 
When  the  pump  is  worked  slowly,  the  outflow  of  the  w.ater  occurs  in  jets,  and  is  interrupted.  If  the 
pumping  movement  be  sufficiently  rapid,  the  compressed  air  in  the  reservoir  causes  a  continuous  out- 
flow, which  is  distinctly  accelerated  at  every  movement  of  the  pump.  [The  ordinary  spray-producer 
is  another  good  example.] 

[Thus,  there  are  two  factors — a  central  one,  the  heart,  and  a  peripheral  one, 
the  amount  of  resistance  in  the  arterioles.  Either  or  both  may  be  varied,  and  as 
this  is  done  so  will  the  pressure  and  velocity  vary.] 

Current  in  the  Capillaries. — In  the  capillary  7<essils  the  pulsatile  accelera- 
tion of  the  current  ceases  with  the  extinction  of  the  pulse  wave.  The  great  re- 
sistance which  is  offered  to  the  current  toward  the  capillary  area  causes  both  to 
disappear.  It  is  only  when  the  capillaries  are  greatly  dilated,  and  when  the  arterial 
blood  pressure  is  high,  that  the  pulse  is  prppagated  through  the  capillaries  into  the 
beginning  of  the  veins.  A  pulse  is  observed  in  the  veins  of  the  sub-maxillary 
gland  after  stimulation  of  the  chorda  tympani  nerve,  which  contains  the  vascular 
or  vaso-dilator  nerves  for  the  blood  vessels  of  this  gland.  If  the  finger  be  con- 
stricted with  an  elastic  band,  so  as  to  hinder  the  return  of  the  venous  blood,  and 
to  increase  the  arterial  blood  pressure,  while  at  the  same  time  dilating  the  capil- 
laries, an  intermittent  increased  redness  occurs,  which  corresponds  with  the  well- 
known  throbbing  sensation  in  the  swollen  finger.  This  is  due  to  the  capillary 
pulse.  [Roy  and  Graham  Brown  found  that  pulsatile  phenomena  were  produced 
in  the  capillaries  by  increasing  the  extra-vascular  pressure  (§86).  Quincke  called 
attention  to  the  capillary  pulse,  which  can  often  be  seen  under  the  finger  nails. 
Extend  the  fingers  completely,  when  a  whitish  area  appears  under  the  nails.  A 
red  area  near  the  free  margin  of  the  nail  advances  and  retires  with  each  pulse  beat. 
It  is  well  marked  in  some  diseased  conditions  of  the  heart,  especially  in  incom- 
petence of  the  aortic  valves,  and  is  probably  produced  by  increased  extra-vascular 
pressure.] 

82.  SCHEMATA  OF  THE  CIRCULATION.— E.  H.  Weber  constructed  a  scheme  of  the 
circulation.  It  consisted  of  a  force-pump  with  properly  arranged  valves  to  represent  the  heart,  por- 
tions of  gut  for  the  arteries  and  veins,  and  a  piece  of  glass  tubing,  containing  a  piece  of  sponge,  to 
represent  the  capillaries.  Various  schemes  have  been  invented,  including  the  very  complicated  one 
of  Marey  [the  extremely  ingenious  one  of  v.  Thanhoffer,  and  the  thoroughly  practical  one  of 
Rutherford.] 

83.  CAPACITY  OF  THE  VENTRICLES.— Since  the  right  and  left 
ventricles  contract  simultaneously,  and  just  the  same  volume  of  blood  passes 
through   the  pulmonary  as  through   the  systemic   circulation,  it   follows  that  the 


ESTIMATION    OF   THE    BLOOD    PRESSURE. 


141 


right  ventricle  must  be  just  as  capacious  as  the  left.     The  capacity  of  the  ven- 
tricles has  been  estimated  in  the  following  ways : — 

(i)  Directly,  by  filling  the  </i?<7</ ventricle  with  blood  (Santorhtt,  1724;  Legallois  and  Collin). 
This  method  is  unsatisfactory  and  inaccurate.  (2)  All  the  vessels  of  the  relaxed  heart  are  ligatured, 
the  heart  excised,  and  the  contents  of  the  cavities  estimated  (Ahegg,  1848).  (3)  Volkmann  estimated 
the  capacity  to  be  155  of  the  body  weight,  /.  c,  for  a  man  of  75  kilos. =  187.5  gfms.  [^  50  (Lud- 
wig  and  Hesse).] 

84.  ESTIMATION  OF  THE  BLOOD  PRESSURE.  —  (A)  In  Animals:  (i) 
Method  of  Hales. — The  Rev.  Stephen  Hales  (1727)  was  the  first  to  introduce  a  long  glass  tube 
into  a  blood  vessel  in  order  to  estimate  the  blood  pressure  by  measuring  the  height  of  the  column  of 
blood,  /.  £*.,  how  high  the  blood  rose  in  the  tube.  The  tube  was  provided  at  its  lower  end  with  a 
copper  tube  bent  at  a  right  angle  (Pitot's  tube).  [The  tube  he  used  was  one-sixth  of  an  inch  bore 
and  about  nine  feet  long,  and  was  inserted  into  the  femoral  artery  of  a  horse.  The  height  to  which 
the  blood  rose  in  the  tube  was  noted,  as  well  as  the  oscillations  that  occurred  with  every  pulsation. 
From  the  height  of  the  column  of  fluid  he  calculated  the  force  of  the  heart.] 

(2)  The  Haemadynamometer  of  Poiseuille. — This  observer  (1828)  used  a  U-shaped  tube  par- 
tially filled  with  mercury —  a  manometer — which  was  brought  into  connection  with  a  blood  vessel 
by  means  of  a  tigid  tube.     [The  mercury  oscillated  with  every  pulsation,  and  the  extent  of  the 


Fig.  97. 


I.  Scheme  of  C.  Ludwig's  kymograph.     II.  Fick's  spring  kymograph. 

o.scillations  was  read  off  by  means  of  a  scale  attached  to  the  bent  tube.     He  called  the  instrument  a 
hizmadynamometer.  ] 

[(3)  Vierordt  used  a  tube  5  or  6  feet  long,  and  filled  it  with  a  solution  of  sodium  carbonate,  thus 
preventing  much  blood  from  entering  the  tube,  while  at  the  same  time  the  soda  solution  prevented 
the  coagulation  of  the  blood.] 

(4)  C.  Ludwig's  Kymograph. — C.  Ludwig  employed  a  U-shaped  mano- 
meter of  the  same  kind,  but  he  placed  a  light  float  (Fig.  97,  d,  s)  upon  the  sur- 
face of  the  mercury  in  the  open  limb  of  the  tube.  A  writing  style,  f,  placed 
transversely  on  the  free  end  of  the  float,  inscribed  the  movements  of  the  float — 
and,  therefore,  of  the  mercury — upon  a  cylinder,  C,  caused  to  revolve  at  a  uniform 
rate.  This  apparatus  registered  the  height  of  the  blood  pressure,  as  well  as  the 
pulsatile  and  other  oscillations  occurring  in  the  mercury.  Volkmann  called  this 
instrument  a  kymograph  or  "  wave  writer."  The  difference  of  the  height  of 
the  column  of  mercury,  e,  d,  in  both  limbs  of  the  tube  indicates  the  pressure 
within  the  vessel.  If  the  height  of  the  column  of  mercury  be  multiplied  by  13.5, 
this  gives  the  height  of  the  corresponding  column  of  blood.     Setschenow  placed 


142 


LUDWIG  S    KYMOGRAPH, 


a  stop-cock  in  the  lower  bend,  /;,  of  the  tube.  If  this  be  closed  so  as  just  to  per- 
mit a  small  aperture  of  communication  to  remain,  the  pulsatile  vibrations  no 
longer  appear,  and  the  apparatus  indicates  the  mean  pressure.  By  the  term  mean 
pressure  is  meant  tlie  limit  of  pressure,  above  and  below  which  the  oscillations 
occurring  in  an  ordinary  blood  pressure  tracing  range.  [Briefly,  it  is  the  average 
elevation  of  the  mercurial  column.] 

In  a  blood-pressure  tracing,  such  as  Fig.  99,  eacli  of  the  smaller  waves  corresponds  to  a 

heart  beat,  the  ascent  corresponds  to  the  systole 
and  the  descent  to  the  diastole.  The  large  un- 
dulations are  due  to  the  respiratory  move- 
ments. It  is  clear  that  the  heart  beat  is  ex- 
pressed as  a  simple  rise  and  fall  (Fig.  99),  so 
that  the  curve  of  the  heart  beat  obtained  with 
a  mercurial  kymograph  dift'ers  from  a  sphygmo- 
graphic  curve.  A  perfect  recording  instrument 
ought  to  indicate  the  height  of  the  blood  pres- 
sure, and  also  the  size,  form,  and  duration  of 
any  wave  motion  communicated  to  it.  The 
mercurial  manometer  does  not  give  the  true 
form  of  the  pulse  wave,  as  the  mercury,  when 
once  set  in  motion,  executes  vibrations  of  its 
own,  owing  to  its  great  inertia,  and  thus  the 
finer  movements  of  the  pulse  wave  are  lost. 
Hence  a  mercurial  kymograph  is  used  for  regis- 
tering the  blood  pressure,  and  not  for  obtaining 
the  exact  form  of  the  pulse  wave.  Instruments 
with  less  inertia,  and  with  no  vibrations  pecu- 
liar to  themselves,  are  required  for  this  purpose. 
[The  theory  of  the  mercurial  manometer  has 
been  carefully  worked  out  by  Mach  and  also  by 
V.  Kries.] 

[Method. — Expose  the  carotid  of  a  chloral- 
ized  rabbit,  and  isolate  a  portion  of  the  vessel 
between  two  ligatures,  or  two  spring   clamps. 

,.    ,       „      ,  .  ,  With  a  pair  of  scissors  make  an  oblique  slit  into 

Ludwie's  improved  lorm  01  revolving  cylinder,  A^,  which  is  ^i  .  j     •    -      -^    -  ■    ,.-      i 

moved  by  the  clockwork  in  the  box, ..).  and  regulated  ^e    artery,  and    mto  It  msert   a  straight  glass 

by  a  Foucault's  regulator  placed  on  the  top  of  the  box.  Cannula,  directing  the  open  end  of  the  cannula 

The  disk,  D,  moved  by  the  clockwork,  presses  upon  the  toward  the  heart.  Fill  the  Cannula  with  a 
two  wheels.  «.  which  can  be  raised  or  lowered  bv  the  .-j,.-  rj-  t_  ..,■ 
screw  I  thus  altering  the  position  of  7/  on  A  so  as  to  saturated  solution  of  sodium  carbonate,  taking 
cause  the  cylinder  to  rotate  at  different  rates.  The  Care  that  no  air  bubbles  enter,  and  connect  it 
cylinder  itself  can  be  raised  by  the  handle,  v.  On  the  ^ith  the  lead  tube  which  goes  to  the  descend- 
left  side  of  the  figure  is  a  mercurial  manometer.    When    -         r     u     c  -1       .           i-u      *    u  l-   u 

the  cylinder  is  used,  it  is  covered  with  smoked  smooth  >ng  l">ib  of  ""^  manometer.     The   tube  which 
papei.  connects  the  artery  with   the  manometer  must 

be  flexible  and  yet  inelastic,  and  a  lead  tube  is 
best.  It  is  usual  to  connect  a  pressure  bottle,  containing  a  saturated  solution  of  sodium  carbon- 
ate, by  means  of  an  elastic  tube,  with  the  tube  attached  to  the  manometer.  This  bottle  can  be 
raised  or  lowered.  Before  beginning  the  experiment,  raise  the  pressure  bottle  until  there  is  a  posi- 
tive pressure  of  several  inches  of  mercury  in  the  manometer,  or  until  the  pressure  is  about  equal  to 
the  estimated  blood  pressure,  and  then  clamp  the  tube  of  the  pressure  bottle  where  it  joins  the  lead 
tube.  By  having  this  positive  pressure,  the  escape  of  blood  from  the  artery  into  the  solution  of 
sodium  carbonate  is  to  a  large  extent  avoided.  When  all  is  ready,  the  ligature  on  the  cardiac  side 
of  the  cannula  is  removed,  and  immediately  the  float  begins  to  oscillate  and  inscribe  its  movements 
upon  the  recording  surface.  The  fluid  within  the  artery  exerts  pressure  latterly  upon  the  sodium 
carbonate  solution,  and  this  in  turn  transmits  it  to  the  mercury.] 

[Precautions. — In  taking  a  blood-pressure  tracing,  after  seeing  that  the  apparatus  is  perfect, 
care  must  be  taken  that  the  animal  is  perfectly  quiescent,  as  every  movement  causes  a  rise  of  the 
blood  pressure.  This  may  be  secured  by  giving  curara  and  keejjing  up  artiflcial  respiration,  or  by 
carefully  regulated  inhalation  of  ether.  When  a  drug  is  to  be  injected  to  test  its  action,  if  it  be  in- 
troduced into  the  jugular  vein,  it  is  apt  to  affect  the  heart  directly.  This  may  be  avoided  by  inject- 
ing it  into  a  vein  of  the  leg,  the  peritoneum,  or  under  the  skin.  The  solution  of  the  drug  must  not 
contain  particles  which  will  block  up  the  capillaries.  Care  should  also  be  taken  that  the  carbonate 
of  soda  does  not  flow  back  into  the  arter)'.] 

[Continuous  Tracing. — When  we  have  occasion  to  take  a  tracing  for  any  length  of  time,  it 
must  be  written  upon  a  strij)  of  ]5aper  which  is  moved  at  a  uniform  rate  in  front  of  the  writing  style 
on  the  float  (Fig.  9S).     Various  arrangements  are  employed  for  this  purpose,  but  it  is  usual  to  cause 


SPRING    KYMOGRAPH. 


143 


a  cylinder  to  revolve  so  as  to  unfold  a  roll  or  riband  of  paper  placed  on  a  movable  bobbin.  As  the 
cylinder  revolves,  it  gradually  winds  oft"  the  strip  of  paper,  which  is  kept  applied  to  the  revolving 
surface  by  ivory  friction  wheels.  In  Kick's  complicated  kymograph  a  long  strip  of  smoked  paper 
is  used.  The  writing  style  may  consist  of  a  sable  brush,  or  a  fine  glass  pen  filled  with  aniline  blue 
dissolved  in  water,  to  which  a  little  alcohol  and  glycerine  are  added.] 

[In  order  to  measure  the  height  of  the  pressure,  we  must  know  the  position  of  the  abscissa 
or  line  of  no  pressure,  and  it  may  be  recorded  at  the  same  time  as  the  blood  pressure  or 
aQerward.] 

[In  Fig.  99,  O — x  is  the  zero  line  or  abscissa,  and  the  height  of  the  vertical  lines  or  ordinates 
may  be  measured  by  the  millimetre  scale  on  the  left  of  the  figure.  The  height  of  the  blood  pres- 
sure is  obtained  by  drawing  ordinates  from  the  curve  to  the  abscissa,  measuring  their  length,  and 
multiplying  by  two.] 

(5)  Spring  Kymograph.— A.  Fick  (1864)  constructed  a  "hollow  spring 
kymograph,"   on  the  principle  of  Bourdon's  manometer  (Fig.  97,  II). 

Fig.  99. 


BlooU  pressure 

ui-v 

■of  thee 

jrotid  ol  a  d. 

line,  or  abst 

issa 

:  y-y  i^ 

the  blood  p 

large  wave 

du 

e  to  the 

respiration. 

mercury. 

obtained  with  ; 


Iter.  O— .!-_lineol  1 
:h  one  caused  by  a  he 
ght  of  the 


A  hollow  C-shaped  metallic  spring,  F,  is  filled  with  alcohol.  One  end  of  the  hollow  spring  is 
closed,  and  the  other  end,  covered  by  a  membrane,  is  brought  into  connection  with  a  blood  vessel 
by  a  junction  piece  filled  with  a  solution  of  sodium  carbonate.  .\s  soon  as  the  communication 
with  the  artery  is  opened,  the  pressure  rises,  and  the  spring,  of  course,  tends  to  straighten  itself.  To 
the  closed  end,  b,  there  is  fixed  a  vertical  rod  attached  to  a  series  of  levers,  //,  /,  k,  e,  one  of  which 
writes  its  movements  upon  a  surface  moving  at  a  uniform  rate.  The  blood  pressure  and  the 
periodic  variations  of  the  pulse  are  both  recorded,  although  the  latter  is  not  done  with  absolute 
accuracy. 

[Hering  improved  Fick's  instrument  (Fig.  100).  a,  b,  c,  is  the  hollow  spring  filled  with  alcohol, 
and  communicating  at  a  with  the  lead  tube,  a",  passing  to  the  cannula  in  the  artery.  To  c  is  attached 
a  series  of  light  wooden  levers  with  a  writing  style  s.  The  lower  part  of  4  dips  into  a  vessel,  c, 
filled  with  oil  or  glycerine,  which  serves  to  damp  the  vibrations  of  the  levers.  At_/  is  a  syringe 
communicating  with  the  tube,  d,  filled  with  solution  of  sodic  carbonate,  and  used  for  regulating  the 
amount  of  fluid  in  the  tube  connecting  the  manometer  with  the  blood  vessel.  The  whole  apparatus 
can  be  raised  or  lowered  on  the  toothed  rod,  fi,  by  means  of  the  millhead  opposite  g,  to  which  all 
the  parts  of  the  apparatus  are  attached.] 


144 


FICK  S    FLAT   SPRING    KYMOGRAPH. 


(6)  Pick's  Flat  Spring  Kymograph. — Fig.  loi  shows  Fick's  latest  arrangement.  The  narrow 
tube,  i7,  a  (i  mm.  diam.)  is  placed  in  connection  with  a  blood  vessel  by  means  of  the  cannula,  ^, 
and  over  its  vertical  expanded  end,  .\,  is  fixed  a  caoutchouc  membrane,  with  a  projecting  point,  j, 
which  presses  against  a  horizontal  spring,  F,  joined  to  a  writing  lever,  H,  by  an  intermediate  piece, 
b.     The  whole  is  held  in  the  metallic  frame,  R  K. 

In  order  to  estimate  the  absolute  pressure,  the  instrument  must  be  compared  previously  with  a 
mercurial  manometer. 

Fig.  ioo. 


Fick's  spring  manometer, 


:d  by  Hering. 


fB)  In  man  the  blood  pressure  may  be  estimated  by  means  of  (i)  .\  properly 
graduated  sphygmograph  (§  67).  The  pressure  required  to  abolish  the  move- 
ment of  the  lever  indicates  approximately  the  vascular  tension.  Schobel  investi- 
gated the  radial  pulse  in  a  healthy  student,  and  obtained  a  mean  blood  pressure 
equal  to  550  grammes. 

(2)  By  a  manometric  method  v.  Basch  estimated  the  blood  pressure.     He 


Fick's  flat  spring  kymograph. 


placed  a  capsule  containing  fluid  upon  a  pulsating  artery,  while  the  capsule  itself 
communicated  with  a  mercurial  manometer.  .\s  soon  as  the  pressure  within  the 
manometer  sliglitly  exceeded  that  within  the  artery,  the  artery  was  compressed  so 
that  a  sphygmograph  placed  on  a  peripheral  portion  of  the  vessel  ceased  to  beat. 
[This  instrument  v.  Basch  called  a  Sphygmomanometer.]  Both  arrange- 
ments, however,  do  not  give  the  exact  pressure  within  the  artery  ;  they  only  indi- 


BLOOD    PRESSURE    IN    THE   ARTERIES.  145 

cate  the  pressure  which  is  required  to  compress  the  artery  and  the  overlying  soft 
parts.  The  pressure  required  to  compress  the  arterial  walls,  however,  is  very  small 
compared  with  the  blood  pressure.  It  is  only  4  mm.  Hg.  v.  Basch  estimated 
the  pressure  in  the  radial  artery  of  a  healthy  man  to  be  135  to  165  millimetres  of 
mercury. 

•Variations. — In  children  the  blood  pressure  increases  with  age,  height,  and  weight.  In  the 
superficial  temporal  artery,  from  2  to  3  years,  it  is  =  97  mm.  ;  from  I2  to  13  years,  113  mm.  Hg. 
{.4.  Eckerl,  c.  ^  100).  The  blood  pressure  is  raised  immediately  after  bodily  movements  ;  it  is 
higher  when  a  person  is  in  the  horizontal  position  than  when  sitting,  and  in  sitting  than  in  standing 
[Fn€timann\.  After  a  cold  as  well  as  after  a  warm  bath  (L.  Lek»U7nn],Xhe  first  effect  is  an 
increase  of  blood  pressure  and  of  the  iiuantily  of  urine  {Greflierg). 

85.  BLOOD  PRESSURE  IN  THE  ARTERIES.— The  following 
results  have  been  obtained  by  experiment  on  systemic  arteries  : — 

{a)  Mean  Blood  Pressure. — The  blood  pressure  is  very  considerable,  vary- 
ing within  pretty  wide  limits  :  in  the  large  arteries  of  large  mammals,  and  per- 
haps in  man,  it  is  ^140  to  160  millimetres  [5.4  to  6.4  inches]  of  a  mercurial 
column. 

The  following  results  have  been  obtained,  those  marked  thus  *  by  Poiseuille,  and  those  -|-  by 
Volkmann  :  — 


*  Carotid,  Horse,  161  mm. 

-f         "  "       122  to  214  mm. 

*  "  Dog,  151   mm. 

"  "     iTja\.Q\<)omxa.{Litdw>g). 

-f         "  Goat,  118  to  135  mm. 

-|-         "  Rabbit,  90  mm. 

4-         "  Fowl,  88  to  171  mm. 


-|-  Aorta  of  frog,  22  to  29  mm. 

-)-   Gill  artery  of  Pike,  35  to  84  mm. 
Brachial  artery  of  man  during  an  ope- 
ration, 1 10  to    120  mm.      [luiivre). 
Perhaps  too  low,  owing  to  the  in- 
jury. 


E.  Albert  estimated  the  blood  pressure  by  means  of  a  manometer,  placed  in  connection  with  the 
anterior  tibial  artery  of  a  boy  whose  leg  was  to  be  amputated,  to  be  100  to  160  mm.  Hg.  The  ele- 
vation with  each  pulse   beat   was  17  to 

20  mm. ;  coughing  raised  it  to  20  to  30  Fig.  102 

mm. ;  tight  bandaging  of   the  healthy 
leg,  15   mm.;  while   passive   elevation       ^■^■ 
of  the  body,  whereby  the  hydrostatic 
action    of    the   column  of   blood    was 
brought  into  play,  raised  it  40  mm. 

The  pressure  in  the  aorta  of  mam- 
m.als  varies  from  200  to  250  mm.  Hg. 
.\i  a  general  rule,  the  blood  pressure  in 
large  animals  is  higher  than  in  small  ° 

animals,  because  in  the  former  the  blood  ^^^  A  c  V  ""LT'a 

channel   is    considerably    longer,    and 

there   is  greater  resistance  to  be  over-    Scheme  of  ihe  height  ot  the  blood  pressure,  in  A,  the  arteries:  C, 
-.^  ,    .  ,,  capillaries,  and  V,  veins;    0-0,  is  the  abscissa  or  line  of  no 

come.     In  very  young  and  in  very  old  pressure  ;  L.  v.,  left  ventricle,  and  R.  A.,  right  auricle  ;  B.  P., 

animals  the  pressure  is  lower  than  in  the  height  of  the  blood  pressure, 

individuals  in  the  prime  of  life. 

The  arterial  pressure  in  the  fcetus  is  scarcely  the  half  of  that  of  the  newly-born,  while  the  venous 
pressure  is  higher,  the  difference  of  pressure  between  arterial  and  venous  blood  being  scarcely  half 
sc^great  as  in  adult  animals  [Co/instein  and  Ztin/z). 

The  Arterial  blood  pressure  is  highest  in  the  aorta,  and  falls  as  we  pass 
toward  the  smaller  vessels,  but  the  fall  is  very  gradual,  as  shown  in  Fig.  102. 

A  great  fall  takes  place  as  we  pass  from  the  area  of  the  arterioles  into  the  capil- 
lary area  (C),  while  it  is  less  in  the  venous  area,  and  negative  near  the  heart,  as 
indicated  in  the  dotted  line  passing  below  the  abscissa,  so  that  the  pressure  is 
lowest  in  the  cardiac  ends  of  the  venre  cava;  (compare  Fig.  108). 

(/')  Branching  of  the  Blood  Vessels. — ^Vithin  the  large  arteries  the  blood 
pressure  diminishes  relatively  little  as  we  pass  toward  the  periphery,  because  the 
difference  of  the  resistance  in  the  difterent  sections  of  large  tubes  is  very  small. 
.\s  soon,  however,  as  the  arteries  begin  to  divide  fretiuently,  and  undergo  a  coii- 
siderable  diminution  in  their  lumen,  the  blood  pressure  in  them  rapidl)'  diminishes, 


146    RESPIRATORY   UNDULATIONS    IN    THE    BLOOD-PRESSURE '  CURVE. 


because  the  propelling  energy  of  the  blood  is  much  weakened,  owing  to  the  resist- 
ance which  it  has  to  overcome  (§  99). 

((■)  Amount  of  Blood. — The  blood  pressure  is  increased  \\\\.\\  greatc-r  Ji/Hng 
of  the  arteries,  and  vice  versa  :  hence  it 


1.  With  increased  and  accelerated  action 

of  the  heart ; 

2.  In  plethoric  persons; 

3.  After  considerable  increase  of  the  quan- 

tity of   Islood    by  direct  transfusion, 
or  after  a  copious  meal. 


Decrrases 

1.  During  diminished  and  enfeebled  action 

of  the  heart ; 

2.  In  anaemic  persons; 

3.  After  hemorrhage  or  considerable  ex- 

cretions from  the  blond  l)y  sweating, 
the  urine,  severe  diarrhoea. 


The  blood  pressure  does  not  vary  in  the  same  proportion  as  the  variations  in  the  amount  of  blood. 
The  vascular  system,  in  virtue  of  its  muscular  tissue,  has  the  property,  within  liberally  wide  limits, 
of  accommodating  itself  to  larger  or  smaller  quantities  of  blood  (C  LuJwig  ami  IVorm  Mii/lfr,  \ 
102,  d).  [  In  fact,  a  large  amount  of  blood  may  be  transfused  without  materially  raising  the  blood 
pressure.]  Small  and  moderate  hemorrhages  (in  the  dog  to  2.8  per  cent,  of  the  body  weight)  have 
no  obvious  effect  on  the  blood  pressure.  After  a  slight  loss  of  blood  the  pressure  may  even  rise 
(■Worm  Midler).  If  a  large  amount  of  blood  be  withdrawn,  it  causes  a  great  fall  of  the  blood 
pressure  [Nn/es,  Magendif),  and  when  hemorrhage  occurs  to  4-6  per  cent,  of  the  body  weight,  the 
blood  pressure  =  o.  The  transfusion  of  a  moderate  amount  of  blood  does  not  raise  the  mean  arte- 
rial blood  pressure.  [There  are  important  practical  deductions  from  these  experiments,  viz.,  that 
the  blood  pressure  cannot  be  diminished  directly  by  moderate  bloodletting,  and  that  the  blood 
pressure  is  not  necessarily  high  in  plethoric  persons.] 

(r/)  Capacity  of  the  Vessels. — The  arterial  pressure  rises  when  the  capacity 
of  the  arterial  system  is  diminished,  and  conversely.  The  plain,  circularly- 
disposed  muscular  fibres  of  the  arteries  are  the  chief  agents  concerned  in  this  pro- 
cess. When  they  relax,  the  arterial  blood  pressure  falls,  and  when  they  contract, 
it  rises.  These  actions  of  muscular  fibres  are  controlled  and  regulated  by  the 
action  of  the  vasomotor  nerves  (§  371 ). 

{e)  Collateral  Vessels. — The  arterial  pressure  within  a  given  area  of  the 
vascular  system  must  rise  or  fall  according  as  the  neighboring  areas  are  diminished, 
whether  by  the  application  of  pressure,  or  a  ligattire,  or  are  rendered  impervious, 
or  as  these  areas  dilate.  The  application  of  cold  or  warmth  to  limited  areas  of 
the  body — increasing  or  diminishing  the  atmospheric  pressure  on  a  part — the 
paralysis  or  stimulation  of  certain  vasomotor  areas  (§  371),  all  produce  remark- 
able variations  in  the  blood  pressure.  [The  effect  of  dilatation  of  a  large  vascu- 
lar area  on  the  arterial  pressure  is  well  shown  by  what  happens  when  the  blood 
vessels  of  the  abdomen  are  dilated.  If  the  central  end  of  the  superior  car- 
diac nerve  of  a  rabbit  be  stimulated,  after  a  few  seconds  the  blood  vessels  of  the 
abdomen  dilate,  and  gradually  there  is  a  steady  fall  of  the  blood  pressure  in  the 
systemic  arteries.  Fig.  103  is  a  blood-pressure  tracing  showing  the  height  of  the 
blood  pressure  before  stimulation,  a.  The  stimulation  was  continued  from  a  to  /', 
and  after  a  certain  latent  period  there  is  a  steady  fall  of  the  blo(xl  pressure.  The 
nerve  which  causes  this  reflex  dihitation  of  the  abdominal  blood  vessels,  and  con- 
sequent lowering  of  the  blood  pressure,  is  also  called  the  depressor  nerve.] 

(/)  Respiratory  Undulations. — The  arterial  pressure  also  undergoes  regu- 
lar variations  or  undulations  owing  to  the  respiratory  movements.  These  undula- 
tions are  called  respiratory  undulations  (Figs.  99  and  104).  Stated  broadly, 
during  every  strong  inspiration  the  blood  pressure  falls,  and  during  expiration  it 
rises  (§  74).  This  is  not  quite  correct  (see  below).  These  undulations  may  be 
explained  by  the  fact  that,  with  every  expiration,  the  blood  in  the  aorta  is  sub- 
jected to  an  increase  of  pressure  through  the  compressed  air  in  the  chest ;  with 
every  inspiration,  on  the  other  hand,  it  is  ditninished,  owing  to  the  rarefaction  of 
the  air  in  the  lungs  acting  upon  the  aorta.  Besides,  the  inspiratory  movements  of 
the  chest  aspirate  blood  from  the  venae  cavae  toward  the  heart,  while  expiration 
retards  it,  and  thus  influences  the  blood  pressure.  The  undulations  are  most 
marked  in  the  arteries  lying  nearest  to  the  heart.     The  respiratory  inidulations  are 


RESPIRATORY    UNDULATIONS   IN   THE   BLOOD-PRESSURE  CURVE.    147 

due  in  part  to  a  stimulation  or  condition  of  excitement  of  the  vasomotor  centre, 
which  runs  ])arallel  with  the  respiratory  movements.  This  stimulation  of  the 
vasomotor  centre  causes  the  arteries  to  contract,  and  thus  the  blood  pressure  is 
raised.  The  variations  in  the  pressure  which  depend  upon  a  varying  activity  of 
the  vasomotor  centre  are  known  as  the  "curves  of  Traube  and  Hering"   (p. 

Fig.  I  or 


148).  In  Fig.  104  are  represented  a  blood  pressure  tracing  and  a  curve  of  the 
movements  of  respiration  (thick  line)  taken  simultaneously  in  a  dog  by  C.  Ludwig 
and  Embrodt.  The  blood-pressure  tracing  was  obtained  from  the  carotid  artery, 
while  the  pressure  within  the  thorax  was  measured  by  means  of  a  manometer 
placed   in  connection   with  one  pleural  cavity.     In   this  curve,  when  expiration 

Fir,.  104. 


Kymogr.'ipliic  blood-pressure  tracing  (upper,  thin  line),  and  i 
e.r,  expiration  :  tn,  inspiration  ;  c,  c,  heart  beats.  The 
respirations  [Ludwt'g  attd  Einbrodt.') 


e  (lower,  thick  line),  taken  simultaneously. 
in  the  blood-pressure  tracing  are  due  to 


begins  (at  c.v),  and  as  the  expiratory  pressure  rises,  the  blood  pressure  rises,  while 
when  inspiration  begins  (at  in)  both  fall.  The  blood  curve,  however,  begins  to 
rise  (at  c)  before  expiration  commences,  /.  e.,  during  the  last  part  of  the  act  of 
inspiration.  This  is  due  to  the  contraction  of  the  arteries,  caused  by  impulses 
sent  from  the  vasomotor  centre.     It  is  also  aided  bv  the  circumstance  that  durinir 


148  TRAUBE-HERING   CURVES. 

inspiration  there  is  an  increased  inflow  of  venous  blood  to  the  heart,  so  that  when 
it  contracts  more  blood  is  forced  into  the  arteries.  [The  maxima  and  minima  of 
the  two  curves  do  not  coincide  exactly,  but  in  addition  the  number  of  pulse  beats 
is  greater  in  the  ascent  than  in  the  descent.  This  is  well  marked  in  a  blood- 
jjressure  tracing  from  a  dog's  carotid,  while  in  a  rabbit  this  difference  of  the  pulse 
rate  is  but  slightly  marked.  The  smaller  number  of  pulse  beats  during  the  descent, 
— /.  e.,  during  the  greater  part  of  expiration — is  due  to  the  activity  of  the  cardio- 
inhibitory  centre  in  the  medulla  oblongata.  This  is  proved  by  the  fact,  that  sec- 
tion of  both  vagi  in  the  dog  causes  the  difference  of  pulse  rate  to  disappear,  while 
other  conditions  remain  the  same  as  before,  except  that  the  heart  beats  more 
rapidly.  It  would  seem  that  during  the  ascent,  the  cardio-inhibitorv  centre  is 
comparatively  inactive.  It  is  clear,  therefore,  that  the  respiratory  and  cardio- 
inhibitory  centres  in  the  medulla  oblongata  act,  to  a  certain  extent,  in  unison, 
so  that  it  is  reasonable  to  suppose  that  other  centres  situated  in  close  proximity  to 
these  may  also  act  in  unison  with  them,  or,  as  it  were,  "in  sympathy."  As 
already  stated,  the  vaso-motor  centre  is  also  in  action  during  a  particular  part 
of  the  time.] 

[If  a  dog  be  curarized  and  artificial  respiration  established,  the  respiratory 
undulations  still  occur,  although  in  a  modified  form.  In  artificial  respiration,  the 
mechanical  conditions,  as  regards  the  intra-thoracic  pressure,  are  exactly  the  reverse 
of  those  which  obtain  during  ordinary  respiration.  Air  is  forced  into  the  chest 
during  artificial  respiration,  so  that  the  pressure  within  the  chest  is  increased  during 
inspiration,  while  in  ordinary  inspiration  the  pressure  is  diminished.  Thus,  the 
same  mechanical  explanation  will  not  suffice  for  both  cases.] 

If  the  artificial  respiration  be  suddenly  interrupted  in  a  curarized  animal,  the 
blood  pressure  rises  steadily  and  rapidly.  This  rise  is  due  to  the  stimulation  of 
the  vasomotor  centre  in  the  medulla  oblongata  by  the  impure  blood.  This  causes 
contraction  of  the  small  arteries  throughout  the  body,  which  retards  the  outflow 
from  the  large  arteries,  and  thus  the  pressure  within  them  is  raised.  [Stated 
broadly,  the  arterial  pressure  depends  on  the  central  organ — the  heart,  and  on 
the  condition  of  the  peripheral  organs — the  small  arteries.  Both  are  influenced 
by  the  nervous  system.  If  the  action  of  the  vasomotor  centre  be  eliminated  by 
dividing  the  spinal  cord  in  the  cervical  region,  arrest  of  the  respiration  causes  a 
very  slight  rise  of  the  blood  pressure  ;  hence,  it  is  evident  that  venous  blood  acts 
but  slightlv  on  the  heart,  or  on  any  local  peripheral  nervous  mechanism,  or  on  the 
muscular  fibres  of  the  arteries.  This  experiment  shows  that  it  is  the  vasomotor 
centre  which  is  specially  acted  upon  by  the  venous  blood.] 

[Traube-Hering  Curves. — The  following  experiment  proves  that  the  varying 
activity  of  the  vasomotor  centres  suffices  to  produce  undulations  in  the  blood- 
pressure  tracing.  Take  a  dog,  curarize  it,  expose  both  vagi  and  establish  artificial 
respiration  ;  then  estimate  the  blood  pressure  in  the  carotid,  .\fter  section  of  the 
vagi,  the  heart  will  continue  to  beat  more  rapidly,  but  it  will  be  undisturbed  by 
the  cardio-inhibitory  centre.  Thus  the  central  factor  in  the  causation  of  the  blood 
pressure  remains  constant.  .Suddenly  interrupt  the  respiration,  and,  as  already 
stated,  the  blood  pressure  will  rise  steadily  and  uniformly,  owing  to  the  stimula- 
tion of  the  vasomotor  centre  by  the  venous  blood.  In  this  case  the  peripheral 
factor  or  state  of  tension  of  the  small  arteries  throughout  the  body  is  influenced 
by  the  condition  of  the  nerve  centre  which  controls  their  action.  After  a  time, 
the  blood  pressure  tracing  shows  a  series  of  bold  curves  higher  than  the  original 
tracing.  These  can  only  be  due  to  an  alteration  in  the  state  of  the  small  arteries, 
brought  about  by  a  condition  of  rhythmical  activity  of  the  vasomotor  centre. 
These  curves  were  described  and  figured  by  Traube,  and  are  called  the  Traube  or 
Traube-Hering  curves.  As  in  other  conditions,  stimulation  gives  place  to  exhaus- 
tion, and  soon  the  venous  blood  paralyzes  the  vasomotor  centre  and  the  small 
arteries  relax,  blood  flows  freely  out  of  the  larger  arteries,  and  the  blood  pressure 
rapidly  sinks.     Variations   in    the    blood    pressure   have   been  observed    after   a 


VARIATIONS  OF  THE  BLOOD  PRESSURE.  149 

mechanical  pump  has  Ijeen  substituted  for  the  heart,  i.e.,  after  all  respiratory 
movements  have  been  set  aside,  so  that  the  only  factor  which  would  account  for 
the  ])henomena  of  the  Traube-Hering  curves  is  the  variation  in  the  peripheral 
resistance  in  the  small  arteries,  determined  by  the  condition  of  the  vasomotor 
centre.] 

Variations. — The  respirator)'  undulations  of  tlie  blood  pressure  become  more  pronounced  the 
greater  the  force  of  the  respirations,  which  jjroduce  greater  variations  of  the  intra-thoracic  pressure. 
In  man,  the  diminution  of  the  pressure  within  the  trachea  is  I  mm.  Hg,  during  tranquil  inspiration, 
while  during  forced  respiration,  when  the  respiratory  passage  is  closed,  it  may  be  57  mm.  Con- 
versely, during  ordinary  expiration,  the  pressure  is  increased  within  the  trachea  2-3  mm.  Hg,  while 
during  forced  expiration,  owing  to  the  compression  of  the  abdominal  muscles,  it  may  reach  87 
mm.  Hg. 

Other  Factors. — The  increase  of  the  blood  pressure  during  inspiration,  as  well  as  the  fall  during 
expiration,  must,  in  part,  depend  upon  the  pressure  within  the  abdomen.  As  the  diaphragm  descends 
during  inspiration,  it  presses  upon  the  abdominal  contents,  including  the  abdominal  vessels,  whereby 

Fig.  105. 


lilood  pressure  tr.icing  t.-\ken  with  a 

the  blood  pressure  must  be  increased.  The  rever.se  effect  occurs  during  expiration  [Sc/iweitiburg). 
[Section  of  both  phrenic  nerves  and  opening  of  the  abdominal  cavity  cause  the  respiratory  undula- 
tions almost  entirely  to  disappear.  The  respiratory  undulations,  therefore,  depend  in  great  part 
upon  the  changes  of  the  abdominal  pressure  and  the  effect  of  these  changes  on  the  amount  of  blood 
in  the  abdominal  vessels.  When  making  a  blood-pressure  ex])erimenl,  pressure  upon  the  abdomen 
of  the  animal  with  the  liand  causes  the  blood  pressure  to  rise  rapidly.] 

( i,')  Variations  with  each  Pulse  Beat. — The  mean  arterial  pressure  under- 
goes a  variation  with  each  heart  beat  ox  pulse  hfat,  causing  the  so-called  pulsatory 
undulations  \  l-'ig.  104,  c).  The  mass  of  blood  forced  into  the  arteries  with 
each  ventricular  systole  causes  a  positive  wave  and  an  increase  of  the  jjressiire  cor- 
responding with  it,  which,  of  course,  corresponds,  in  its  development  and  in  its 
form,  with  the  pulse  curve. 

In  the  large  arteries,  Volkmann  found  the  increase  during  the  heart  beat  to  be  =  ^'^  (horse)  and 
y',-  (dog)  of  the  total  pressure. 


150  RELATION    OF    BLOOD    PRESSURE    TO    PULSE    RATE. 

None  of  tlie  apparatus  described  in  ^  84  gives  an  exact  representation  of  the  pulse  curve.  They 
all  show  simplv  a  rise  and  fall — a  simple  curve.  The  sphygmograph  alone  gives  a  true  expression 
of  the  undulations  in  the  hlood  pressure  which  are  due  to  the  heart  beat. 

(/?)  Arrest  of  the  Heart's  Action. — If  the  heart's  action  be  arrested  or 
interrupted  by  continued  Stimulation  of  the  vagus  {Bruiiinr.  /Sjj),  or  by  a 
high  positive  respiratory  piressure  {Einhrodt).  the  arterial  blood  pressure  falls 
enormously,  while  it  rises  in  the  veins  as  the  blood  flows  into  them  from  the 
arteries  to  equilibrate  the  difference  of  pressure  in  the  two  sets  of  vessels.  This 
experiment  shows  that,  even  when  the  difference  of  pressure  is  almost  entirely  set 
aside,  the  passive  blood  presses  upon  the  arterial  walls,  i.e.,  on  account  of  the 
overfilling  of  the  blood  vessels,  a  slight  pressure  is  exerted  upon  the  walls,  even 
when  there  is  no  circulation  ( Bncnncr).  [As  already  stated,  the  arterial  pressure 
depends  on  the  condition  of  the  central  organ — the  heart — and  on  the  peripheral 
organs — the  small  arteries.  If  the  action  of  the  heart  be  arrested,  then  the  blood 
pressure  rapidly  falls.  Fig.  105  shows  the  effect  on  the  blood  pressure,  of  arrest- 
ing the  action  of  the  heart,  by  stimulation  of  the  peripheral  end  of  the  vagus. 
There  is  a  sudden  tall  of  the  arterial  pressure,  as  shown  by  the  ra[)id  fall  of  the 
curve  from  a.'\ 

[Variations  in  Animals. — The  pressure  in  the  arterial  system  depends  upon  the  balance  between 
the  inflow  and  the  outflow,  /.  e.,  upon  the  heart  and  the  state  of  the  arterioles.  But  it  is  to  be 
noted  that  the  central  factor,  the  heart,  varies  in  diflerent  animals.  In  the  rabbit  the  heart  normally 
beats  rapidly,  so  that  section  of  the  vagi  does  not  cause  any  great  increase  in  the  number  of  beats, 
nor  is  the  lilood  pressure  much  raised  thereby.  In  the  dog,  on  the  other  hand,  the  beats  are 
considerably  increased  by  section  of  the  vagi,  while  the  blood  pressure  rises  considerably. 
Atropin  paralyzes  the  cardiac  terminations  of  the  vagus,  and  thereby  trebles  the  number  of  heart 
beats  in  the  dog,  while  it  only  raises  it  25  per  cent,  in  the  rabbit ;  in  man,  again,  the  number  may 
be  doubled.  As  Burton  has  shown,  this  difference  of  the  initial  number  of  heart  beats  and  the 
action  of  the  vagus  have  important  relations  to  the  action  of  drugs  on  the  blood  pressure.  For 
example,  if  an  intact  rabbit  be  caused  to  inhale  amyl  nitrite,  the  blood  pressure  falls  at  once 
and  rapidly,  while  in  the  dog  the  fall  may  be  slight.  The  pulse  of  the  dog,  however,  is  greatly 
accelerated,  so  much  so  as  to  be  nearly  as  rapid  as  that  of  the  rabbit.  In  both,  the  vessels  are 
dilated,  but  in  the  dog,  notwithstanding  this  dilatation,  which  per  se  would  cause  the  pressure  to 
fall,  the  heart  of  the  dog  beats  now  so  rapidly  as  to  compensate  for  this,  and  thus  keep  the 
blood  pressure  nearly  normal ;  while  the  increased  rate  of  beating  in  the  rabbit  is  not  sufticient 
for  this  puqiose.  If  the  vagi  in  the  dog  be  divided,  the  subsequent  inhalation  of  amyl  nitrite 
causes  a  fall  of  blood  pressure  like  that  in  the  rabbit  (Byttnton)^ 

[Relation  of  Blood  Pressure  to  Pulse  Rate. — When  the  blood  pressure 
rises  in  an  intact  animal,  as  a  rule  the  pulse  rate  falls,  owing  to  stimulation  of  the 
vagus  centre  increasing  the  cardio-inhibitory  action,  while  a  fall  of  blood  pressure 
is  accompanied  by  an  increase  of  the  number  of  pulse  beats,  for  the  opposite  rea- 
son, the  action  of  the  medullary  cardio-inhibitory  centre  being  increased.  But 
the  blood  pressure  may  be  increased  either  by  the  action  of  the  heart  or  the  arte- 
rioles. If  we  divide  the  vagi,  the  pulse  beats  more  quickly,  and  in  some  animals 
the  blood  pressure  rises  ;  in  this  case,  the  rise  in  the  two  curves  occurs  together, 
and  if  the  vagi  be  stimulated  there  is  a  sudden  fall  of  the  blood  pressure,  due  to 
arrest  of  the  heart's  action,  so  that  again  the  two  curves  are  parallel.  If  the  arte- 
rioles contract,  the  blood  pressure  rises,  but  by  and  by  the  pulse  rate  falls,  owing 
to  the  cardio-inhibitory  action  of  the  vagus  ;  while,  on  the  other  hand,  if  the  arte- 
rioles are  dilated,  the  blood  pressure  falls,  and  the  heart  beats  faster.  Thus,  in 
both  of  these  cases  the  jiulse  curve  and  blood-pressure  curve  run  in  opposite  direc- 
tions.    These  results  only  obtain  when  the  vagi  are  intact  (^Bninton).'\ 

For  the  effects  of  the  nervous  system  upon  the  blood  pressure,  see  "  Vasomotor  Centre"  (\ 

37')- 

Pathological. — In  persons  suflfering  from  granular  or  contracted  kidney  and  sclerosis  of  the 
arteries,  in  lead  poisoning,  and  after  the  injection  of  ergotin,  which  causes  contraction  of  the 
small  arteries,  it  is  found,  on  employing  the  method  of  v.  Basch,  that  the  blood  pressure  is  raised. 
It  is  also  increased  in  cases  of  cardiac  hypertrophy  with  dilatation,  and  by  digitalis  in  cardiac 
affections,  while  it  falls  after  the  injection  of  morphia  {Kristcller).  The  blood  pressure  falls  in  fever 
i^VVclzel),  a  fact  also  indicated  in  the  sphygmograni  \\  69).  In  chlorosis  and  phthisis  the  blood 
pressure  is  low  ( IValdenhiirg). 


BLOOD    PRESSURE    IN    THE    CAPILLARIES.  151 

86.  BLOOD  PRESSURE  IN  THE  CAPILLARIES.— Methods.— Direct  estimation  of 

the  capillary  pressure  is  not  possible,  on  account  of  the  smallness  of  the  capillary  tubes.  If  a  glass 
plate  of  known  dimensions  be  placed  on  a  portion  of  the  skin  rich  in  blood  vessels,  and  if  it  be 
weighted  until  the  capillaries  become  pale,  we  obtain  approximately  the  pressure  necessary  to  over- 
come the  capillary  pressure.  N.  v.  Kries  placed  a  small  glass  plate  (Figs.  io6,  107)  2.5-5  ^1-  mm., 
on  a  suitable  part  of  the  skin,  eg.,  the  skin  at  the  root  of  the  nail  on  the  terminal  phalanx,  or  on  the 
eaf  in  man,  and  on  the  gum  in  rabbits.  Into  a  scale  pan  attached  to  this,  weights  were  placed  until 
the  skin  became  pale.  The  pressure  in  the  capillaries  of  the  hand,  when  the  hand  is  raised,  Kries 
found  to  be  24  mm.  Hg. ;  when  the  hand  hangs  down,  54  mm.  Hg. ;  in  the  ear,  20  mm.;  and  in 
the  gum  of  a  rabbit,  32  mm. 

[Roy  and  Graham  Brown  ascertained  the  hydrostatic  pressure  necessary  to  occlude  the  vessels  in 
transparent  parts  placed  under  the  microscope,  e.g-.,  the  web  of  a  frog's  foot,  tongue  or  mesentery  of 
a  frog,  the  tails  of  newts  and  small  fishes.  The  upper  surface  of  the  part  to  be  investigated,  t.g.,  the 
web  of  a  frog's  foot,  is  made  just  to  touch  a  ihin  glass  plate.  The  under  surface  is  in  contact  with 
a  delicate  transparent  membrane  covering  the  upper  end  of  a  small  brass  cylinder,  whose  lower  end 
contains  a  piece  of  glass  fitted  air-tight  into  it.  The  interior  of  the  brass  cylinder  communicates  by 
means  of  a  tube  with  an  arrangement  for  obtaining  any  desired  pressure,  and  the  amount  of  the 
pressure  is  indicated  by  a  manometer.  Air  pressure  is  used,  and  this  is  obtained  by  compressing  a 
caoutchouc  bag  between  two  brass  plates.  The  membrane  to  be  investigated  lies  between  two  trans- 
parent media,  an  upper  one  of  glass  and  a  lower  one  of  transparent  membrane,  on  which  the  pres- 
sure acts.     .\ny  change  in  the  vessels  is  observable  by  means  of  the  microscope.     These  observers 

Fig.  106. 


Fig.  107. 


Apparatus  used  by  v.  Kries  for  estimating  the  capillary  pressure — rt,  the  small  square  of  glass.     In  Fig.  106  the  scale 
pan  for  the  weights  is  below,  and  in  Fig.  107  above. 

conclude  from  their  experiments  that  the  capillaries  are  contractile,  and  that  their  contractility  is,  to  all 
appearance,  in  constant  action.  The  regulation  of  the  peripheral  blood  stream  is  due  not  only  to 
the  cerebro-spinal  vasomotor  centres,  but  also  to  independent  peripheral  vasomotor  mechanisms, 
which  may  be  nervous  in  their  nature,  or  are  due  to  some  direct  action  on  the  walls  of  the  vessels 
(p.  .15).] 

Conditions  Influencing  Capillary  Pressure. — The  intra-capillary  blood 
pressure  in  a  given  area  increases — (  i)  When  the  afferent  small  arteries  dilate. 
When  they  are  dilated,  the  blood  pressure  within  the  large  arteries  is  propagated 
more  easily  into  them.  (2)  By  increasing  the  pressure  in  the  small  afferent  arte- 
ries. (3)  By  narrowing  the  diameter  of  the  veins  leading  from  the  capillary  area. 
Closure  of  the  veins  may  quadruple  the  pressure  (f.  Kries).  (4)  By  increasing 
the  pressure  in  the  veins,  e.g.,  by  altering  the  position  of  a  limb).  A  diminution 
of  the  capillary  pressure  is  caused  by  the  opposite  conditions. 

Changes  in  the  diameter  of  the  capillaries  influence  the  internal  pressure.  We  have  to  con- 
sider the  movements  of  the  capillary  wall  itself  (protoplasm  moveinents,  Strieker — p.  115),  as  well 
as  the  pressure,  swelling  and  consistence  of  the  surrounding  tissues.  The  resistance  to  the  blood 
stream  is  greatest  in  the  capillary  area,  and  it  is  evident  that  the  blood  in  a  long  capillary  must  exert 
more  pressure  at  the  commenceinent  than  at  the  end  of  the  capillary ;  in  the  middle  of  the  capillary 
area  the  blood  pressure  is  just  about  one-half  of  the  pressure  within  the  large  arteries  (Danders). 


152 


BLOOD    PRESSURE    IN    THE    VEINS. 


The  capillar}'  pressure  must  also  vary  in  difl'erent  parts  of  the  body.  Thus,  the  pressure  within  the 
intestinal  capillaries,  in  those  constituting  the  glomeruli  of  the  kidney,  and  in  those  of  lower  limbs 
when  the  person  is  in  the  erect  posture,  must  be  greater  than  in  other  regions,  depending,  in  the 
former  cases,  partly  upon  the  double  resistance  caused  by  two  sets  of  capillaries,  and  in  the  latter 
case  partly  on  purely  hydrostatic  causes. 

87.  BLOOD   PRESSURE   IN   THE  VEINS.— In  the  large  venous 

trunks  near  the  heart  ( innominate,  subclavian,  jugular )  a  mean  negative  pressure 
of  about  —  o.  I  mm.  Hg.  prevails  {H.  Jacohson).  Hence,  the  lymph  stream  can  flow 
unhindered.  As  the  distance  of  the  veins  from  the  heart  increases,  there  xs,  2. gradual 
increase  of  the  lateral  pressure  ;  in  the  external  facial  vein  (sheep)  =  -|-  3  mm.; 
brachial,  4.1  mm.,  and  in  its  branches  9  mm.;  crural,  11. 4  mm.  { Jac»6son). 
[The  pressure  is  said  to  be  negative  when  it  is  less  than  that  of  the  atmosphere.] 

[The  gradual  fall  of  the  blood  pressure  from  the  capillary  area  (C)  to  the  venous 
area  (V)  is  shown  in  Fig.  108,  while  within  the  thora.x,  where  the  veins  terminate 
in  the  right  auricle,  the  pressure  is  negative.] 

Conditions  Influencing  the  Venous  Pressure. — (i)  All  conditions  which 
diminish  the  difference  of  pressure  between  the  arterial  and  venous  systems  increase 
the  venous  pressure,  and  vice  versa. 

(2)  General  plethora  of  blood  increases  it ;  anaemia  diminishes  it. 

(3)  Respiration,  or  the  aspiration  of  the  thorax,  affects  specially  the  pressure  in 
the  veins  near  the  heart  ;  during  inspiration,  owing  to  the  diminished  tension, 
blood  flows  toward  the  chest,  while  during  expiration  it  is  retarded.  The  effects 
are  greater  the  deeper  the  respiratory  movement,  and  these  may  be  very  great 
when  the  respiratory  passages  are  closed  (§  60). 

[When  a  vein  is  exposed  at  the  root  of  the  neck,  it  collapses  during  inspiration,  and  fill"  during 
expiration — a  fact  which  was  known  to  Valsalva.  The  respiratory  movements  do  not  affect  the 
venous  stream  in  peripheral  veins.  The  veins  of  the  neck  and  face  become  distended  with  blood 
during  crying,  and  on  making  violent  expiratory  efibrts,  as  in  blowing  upon  a  wind  instrument, 
while  every  surgeon  is  w  ell  acquainted  with  the  fact  that  air  is  particularly  apt  to  be  sucked  into  the 
veins,  especially  in  operations  near  the  root  of  the  neck.  This  is  due  to  the  negative  intra-thoracic 
pressure  occurring  during  inspiration.] 

(4)  Aspiration  of  the  Heart. — Blood  is  sucked  or  aspirated   into  the  auricles 

when  they  dilate  (p.  77),  so  that  there  is  a  double 
Fig.  ioS.  aspiration — one  synchronous  with  inspiration,  and 

the  other,  which  is  but  slight,  synclironous  with 
the  heart  beat.  There  is  a  corresponding  retarda- 
tion of  the  blood  stream  in  the  venae  cavte,  caused 
by  the  contraction  of  the  auricle  (see  p.  75,  a). 
The  respiratory  and  cardiac  undulations  are  occa- 
sionally observable  in  the  jugular  vein  of  a  healthy 
',     person  (§  99). 


[Braune  showed  that  the  femoral  vein  under  Poupart's 
ligament   collapsed  when  the  lower  limb  was  rotated  out- 
ward  and   backward,  but  filled  again  when  the  limb  was 
restored  to  its  former  position.     All  the  veins  which  open 
,-''  into  the  femoral  vein  have  valves,  which  permit  blood  to 

pass  into  the  femoral  vein,  but  prevent  its  reflux.  This 
mechanism  acts,  to  a  slight  degree,  as  a  kind  of  suction  and 
pressure  apparatus  when  a  ))erson  walks,  and  thus  favors  the 
onward  movement  of  the  blood.] 

^'''a'ridef  ^''velSri,  "neriaiV  c\        (s)  Changes  in  the  position  of  the  limbs  or  of 
capillary:  and  v,  venous  areas    The    the  bodv,  for  hydrostatic   reasons,  greatlv  alter 

circle  indicates  the  parts  within  the  tho-        ,  '  ^  r,^,  .  r   ,  i        i      ' 

rax:  B.  P.,  pressure  in  the  aorta.  the  venous  pressure.      1  he  veuis  oi  the  lower  ex- 

tremity bear  the  greatest  pressure,  while,  at  the 
same  time,  they  contain  most  muscle  {K.  Bardelehen,  §65).  Hence,  when  these 
muscles,  from  any  cause,  become  insufficient,  dilatations  occur  in  the  veins,  giving 
rise  to  the  iiroduction  of  varicose  veins. 


BLOOD    PRESSURE    IX    THE    PULMONARY    ARTERY.  153 

[(6)  Movements  of  the  Voluntary  Muscles. — Veins  which  lie  between  muscles 
are  compressed  when  these  muscles  contract,  and  as  valves  exist  in  the  veins,  the 
flow  of  the  blood  is  accelerated  toward  the  heart ;  if  the  outflow  of  blood  be 
obstructed  in  any  way,  then  the  venous  pressure  on  the  distal  side  of  the  obstruc- 
tion may  be  greatly  increased.  When  a  fillet  is  tied  on  the  upper  arm,  and  the 
person  moves  the  muscles  of  tlie  forearm,  the  superficial  veins  become  turgid,  and 
can  be  distinctly  traced  on  the  surface  of  the  limb.] 

[(7)  G^/v/r/Vrexercises  a  greater  effect  upon  the  blood  stream  in  the  extensile 
veins  than  upon  the  stream  in  the  arteries.  It  acts  on  the  distribution  of  the 
blood,  and  thus  indirectly  on  the  motion  of  the  blood  stream.  It  favors  the 
emptying  of  descending  veins,  and  retards  the  emptying  of  ascending  veins,  so 
that  the  pressure  becomes  less  in  the  former  and  greater  in  the  latter.  If  the  posi- 
tion of  the  limb  be  changed,  the  conditions  of  pressure  are  also  altered  {Pas- 
chutiii).  If  a  person  be  suspended  with  the  head  hanging  downward,  the  face 
soon  becomes  turgid,  the  position  of  the  body  favoring  the  inflow  of  blood 
through  the  arteries,  and  retarding  the  outflow  through  the  veins.  If  the  hand 
hangs  down  it  contains  more  blood  in  the  veins  than  if  it  is  held  for  a  short  time 
over  the  head,  when  it  becomes  pale  and  bloodless.  As  Lister  has  shown,  the 
condition  of  the  vessels  in  the  limb  are  influenced  not  only  by  the  position  of  the 
limb,  but  also  by  the  fact  that  a  nervous  mechanism  is  called  into  play.] 

[Ligature  of  the  Portal  Yein. — The  pressure  and  other  conditions  vary  in  particular  veins. 
Thus,  if  the  portal  vein  be  ligatured,  there  is  congestion  of  the  capillaries  and  rootlets  of  the  portal 
vein,  and  dilatation  of  all  the  blood  vessels  in  the  abdomen,  and  gradually  nearly  all  the  blood  of 
the  animal  accumulates  within  its  belly,  so  that,  paradoxical  as  it  may  seem,  an  animal  may  be  bled 
into  its  own  belly,  .-^s  a  consequence  of  sudden  and  complete  ligature  of  this  vein,  the  arterial  blnod 
pressure  gradually  and  rapidly  falls,  and  the  animal  dies  very  quickly.  If  the  ligature  be  removed 
before  the  blood  pressure  falls  too  much,  the  animal  may  recover.  [Schifif  and  Laulenbach  regard 
the  symptoms  as  due  chiefly  to  the  action  of  a  poison,  for  when  the  blood  of  the  portal  vein  in  an 
animal  treated  in  this  way  is  injected  into  a  frog,  it  causes  death  within  a  few  hours,  while  the  ordi- 
nary blood  of  the  portal  vein  has  no  such  effect.] 

Ligature  of  the  Veins  of  a  Limb. — The  effect  of  ligaturing  or  compressing  all  the  veins  of  a 
limb  is  well  seen  in  cases  where  a  bandage  has  been  applied  too  tightly.  It  leads  to  congestion  and 
increase  of  pressure  within  the  veins  and  capillaries,  increased  transudation  of  fluid  through  the  capil- 
laries, and  consequent  adema  of  the  parts  beyond  the  obstruction.  Ligature  of  one  vein  does  not 
always  produce  cedema,  but  if  several  veins  of  a  limb  be  ligatured,  and  the  vasomotor  nerves  be 
divided  at  the  same  time,  the  rapid  production  of  cedema  is  ensured.  In  pathological  cases  the 
pressure  of  a  tumor  upon  a  large  vein  may  produce  similar  results  (  ^  203).] 

88.  BLOOD  PRESSURE  IN  THE  PULMONARY  ARTERY.  —  Methods.  —  (i) 
Direct  estimation  of  the  blood  pressure  in  the  pulmonary  artery  by  opening  the  chest  was  made 
by  C.  Ludwig  and  Beutner  ( 1850).  Artificial  respiration  was  kept  up,  and  the  manometer  was 
placed  in  connection  with  the  left  branch  of  the  pulmonary  artery.  The  circulation  through  the 
left  lung  of  cats  and  rabbits  was  thereby  completely  cut  oft^,  and  in  dogs  to  a  great  extent  inter- 
rupted. There  was  an  additional  disturbing  element,  viz.,  the  removal  of  the  elastic  force  of  the 
lungs  owing  to  the  opening  of  the  chest,  whereby  the  venous  blood  no  longer  flows  normally  into 
the  right  heart,  while  the  right  heart  itself  is  under  the  full  pressure  of  the  atmosphere. 

The  estimated  pressure  in  the  dog  =  29.6;  in  the  cat  ^=  17.6;  in  the  rabbit,  12  mm.  Hg.,  /.  e., 
in  the  dog  3  times,  the  rabbit  4  times,  and  the  cat  5  times  less  than  the  carotid  pressure. 

(2)  Hering  (1850)  experimented  upon  a  calf  with  ectopia  cordis.  He  introduced  glass  tubes 
directly  into  the  heart,  by  pushing  them  through  the  muscular  walls  of  the  ventricles.  The  blood 
ro.se  to  the  height  of  21  inches  in  the  right  tube,  and  33.4  inches  in  the  left 

(3)  Chauveau  and  Faivre  (1856)  introduced  a  catheter  through  the  jugular  vein  into  the  right 
ventricle,  and  placed  it  in  connection  with  a  recording  tambour  (p.  85). 

Indirect  measurements  have  been  made  by  comparing  the  relative  thickness  of  the  walls  of 
the  right  and  left  ventricles,  or  the  walls  of  the  pulmonary  artery  and  aorta,  for  there  must  be  a  re- 
lation between  the  pressure  and  the  thickness  of  the  muscle  in  the  two  cases. 

Ikutner  and  Marey  estimated  the  relation  of  the  pulmonary  artery  to  the  aortic 
pressure  as  i  to  3  ;  Goltz  and  Gaule  as  2  to  5  ;  Fick  and  Badoud  found  a  pres- 
sure of  60  mm.  in  the  pultnonary  artery  of  the  dog,  and  in  the  carotid  11 1  mm. 
Hg.  The  blood  pressure  within  the  pulmonary  artery  of  a  child  is  relatively 
iiigher  than  in  the  adult  (Beneke). 


154  IJLOOD    PRESSURE    IN    THE    rULMONARV    ARTERY. 

Elastic  Tension  of  Lungs. — The  lungs  within  the  chest  are  kept  in  a  state 
of  distention,  owing  to  the  fact  that  a  negative  pressure  exists  on  their  outer  pleural 
surface.  When  the  glottis  is  open,  the  inner  surface  of  the  lung  and  the  walls  of 
the  capillaries  in  the  pulmonary  air  vesicles  are  exposed  to  the  full  pressure  of  the 
air.  The  heart  and  the  large  blood  vessels  within  the  chest  are  not  exposed  to  the 
full  pressure  of  the  atmosphere,  but  only  to  the  pressure  which  corresponds  to  the 
atmospheric  pressure  minus  the  pressure  exerted  by  the  elastic  traction  of  the 
lungs  (§  60').  The  trunks  of  the  pulmonary  artery  and  veins  are  subjected  to  the 
same  conditions  of  pressure.  The  elastic  traction  of  the  lungs  is  greater  the  more 
they  are  distended.  The  blood  of  the  pulmonary  capillaries  will,  therefore,  tend 
to  flow  toward  the  large  blood  vessels.  As  the  elastic  traction  of  the  lungs  acts 
chiefly  on  the  thin-walled  pulmonary  veins,  while  the  semilunar  valves  of  the 
pulmonary  artery,  as  well  as  the  systole  of  the  right  ventricle,  prevent  the  blood 
from  flowing  backward,  it  follows  that  the  blood  in  the  capillaries  of  the  lesser 
circulation  must  flow  toward  the  pulmonary  veins. 

If  tubes  with  thin  walls  be  placed  in  the  walls  of  an  elastic  distensible  bag,  the 
lumen  of  these  tubes  changes  according  to  the  manner  in  which  the  bag  enclosing 
them  is  distended.  If  the  bag  be  directly  inflated  so  as  to  increase  the  pressure 
within  it,  the  lumen  of  the  tubes  is  diminished  (Funke  and  Latsihenberger).  If 
the  bag  be  placed  within  a  closed  space,  and  the  tension  within  this  space  be 
diminished  so  that  the  bag  thereby  becomes  distended,  the  tubes  in  its  wall  dilate. 
In  the  latter  case — viz.,  by  negative  aspiration — the  lungs  are  kept  distended 
within  the  thorax,  hence  the  blood  vessels  of  the  lungs  containing  air  are  wider 
than  those  of  collapsed  lungs  (^Quincke  am/  Pfa'ffer,  BonhUtcli  ami  Garland,  De 
Jdger).  Hence  also,  more  blood  flows  through  the  lungs  distended  within  the 
thorax  than  through  collapsed  lungs.  The  dilatation  which  takes  place  during  /«- 
spiration  acts  in  a  similar  manner.  The  negative  pressure  that  obtains  within  the 
lungs  during  inspiration  causes  a  considerable  dilatation  of  the  pulmonary  veins 
into  which  the  blood  of  the  lungs  flows  readily,  while  the  blood  under  high  pres- 
sure in  the  thick-walled  pulmonary  artery  scarcely  undergoes  any  alteration.  The 
velocity  of  the  blood  stream  m  the  pulmonary  vessels  is  accelerated  during  inspi- 
ration (  De  Jliger,  Lalcsqiie. ) 

The  blood  pressure  in  the  pulmonary  circuit  is  raised  when  the  lungs  are  inflated. 
Contraction  of  small  arteries,  which  causes  an  increase  of  the  blood  pressure  in 
the  systemic  circulation,  also  raises  the  pressure  in  the  pulmonary  circuit,  because 
more  blood  flows  to  the  right  side  of  the  heart  (i\  Opcnclunuski). 

The  vessels  of  the  pulmonary  circulation  are  very  distensible  and  their  tonus 
is  slight.  [Occlusion  of  one  branch  of  the  pulmonary  artery  does  not  raise  the 
pressure  within  the  aorta  (.Beiitner).  Even  when  one  pulmonary  artery  is  plugged 
with  an  embolon  of  paraffin,  the  pressure  within  the  aortic  system  is  not  raised 
{Lichthcim).  Thus,  when  a  large  branch  of  the  pulmonary  artery  becomes  im- 
pervious, the  obstruction  is  rapidly  compensated,  and  this  is  not  due  to  the  action 
of  the  nervous  system.  The  vasomotor  system  has  much  less  effect  upon  the 
pulmonary  blood  vessels  than  upon  those  of  the  systemic  circulation  (Badoiid, 
Hofmokl,  Lichihelm).  The  compensation  seems  to  be  due  chiefly  to  the  great  dis- 
tensibility  and  dilatation  of  the  pulmonary  vessels  {Lichtheii?l).~\ 

We  know  little  of  the  effect  of  physiological  conditions  upon  the  pulmonary 
artery.  According  to  Lichtheim  siispensian  of  the  respiration  causes  an  increase  of 
the  pressure.  [In  one  experiment  he  found  that  pressure  within  the  pulmonary 
artery  was  increased,  while  it  was  not  increased  in  the  carotid,  and  he  regards  this 
experiment  as  proving  the  existence  of  vasomotor  nerves  in  the  lung.]  Morel 
found  that  electrical  and  mechanical  stimulation  of  the  abdominal  organs  caused  a 
considerable  rise  of  pressure  in  the  pulmonary  artery  (dog). 

During  the  act  of  great  straining,  the  blood  at  first  flows  rapidly  out  of  the  pulmonary  veins  and 
afterward  ceases  to  flow,  because  the  inflow  of  blood  in  the  pulmonary  vessels  is  interfered  with. 
As  soon  as  the  straining  ceases,  blood  flows  rapidly  into  the  pulmonary  vessels  [Lii/i-sqiie). 


MEASUREMENT   OF   THE    VELOCITY    OF   THE    BLOOD    STREAM.       155 

Severini  found  that  the  blood  stream  through  the  kings  is  greater  and  more  rapid  when  the 
lungs  are  filled  with  air  rich  in  CO,  than  when  the  air  within  them  is  rich  in  O.  He  supposes 
that  these  gases  act  upon  the  vascular  ganglia  within  the  lung,  and  thus  affect  the  diameter  of 
the  vessels. 

Pathological. — Increase  of  the  pressure  within  the  area  of  the  pulmonary  artery  occurs  frequently 
in  man,  in  certain  cases  of  heart  disease.  In  these  cases  the  second  pulmonary  sound  is  always 
accentuated,  while  the  elevation  caused  thereby  in  the  cardiogram  is  always  more  marked  and 
occurs  earlier  (?  52). 

[Action  of  Drugs. — The  action  of  drugs  on  the  pulmonary  circulation  may  be  tested  by  Holm- 
gren's apparatus,  which  permits  of  distention  of  the  lung  and  retention  of  the  normal  circulation  in 
the  frog.  Cold  contracts  the  pulmonary  capillaries  to  one-third  of  their  diameter  (Bninton),  and 
anesthetics  arrest  the  pulmonary  circulation,  chloroform  being  most  and  ether  least  active,  while 
ethidene  is  intermediate  in  its  effect  [.^f  Kendric/;^  Coats,  A^eiiiffian).^ 

[Influence  of  the  Nervous  System. — The  pulmonary  circulation  is  much 
less  dependent  on  the  nervous  system  than  the  systemic  circulation.  Very  con- 
siderable variations  of  the  blood  pressure  within  the  other  parts  of  the  body  may 
occur,  while  the  pressure  within  the  right  heart  and  pulmonary  artery  is  but  slightly 
affected  thereby.  The  pressure  is  increased  by  electrical  stimulation  of  the  me- 
dulla oblongata,  and  it  falls  when  the  medulla  is  destroyed.  Section  and  stimula 
tion  of  the  central  or  peripheral  ends  of  the  vagi,  stimulation  of  the  splanchnics, 
and  of  the  central  end  of  the  sciatic,  have  but  a  minimal  influence  on  the  pressure 
of  the  pulmonary  artery  (Au/>ert).~\ 

8g.  MEASUREMENT  OF  THE  VELOCITY  OF  THE  BLOOD  STREAM.— 
Methods:  (i)  A.V/  Volkmann's  Hasmadromometer. — A  glass  tube  of  the  .shape  of  a  hair- 
pin, 60-130  cm.  long  and  2  or  3  mm.  broad,  with  a  scale  etched  on  it,  or  attached  to  it,  is  fixed  to  a 
metallic  basal  plate,  B,  so  that  each  limb  passes  to  a  stop-cock  with  three  channels.  The  basal  plate 
is  perforated  along  its  length,  and  carries  at  each  end  short  cannula;,  c,  e,  which  are  tied  into  the 
ends  of  a  divided  artery.  The  whole  apparatus  is  first  filled  with  water  [or,  better,  with  salt  solu- 
tion]. The  stop-cocks  are  moved  simultaneously,  as  they  are  attached  to  a  toothed  wheel,  and  have 
at  first  the  position  given  in  Fig.  109, 1,  so  that  the  blood  simply  flows  through  the  hole  in  the  basal 
piece.  I.e.,  directly  from  one  end  of  the  artery  to  the  other.  If  at  a  given  moment  the  stop-cock  is 
turned  in  the  direction  indicated  in  Fig.  109,  II,  the  blood  has  to  pass  through  the  glass  tube,  and 
the  time  it  takes  to  make  the  circuit  is  noted,  and  as  the  length  of  the  tube  is  known,  we  can  easily 
calculate  the  velocity  of  the  blood. 

Volkmann  found  the  velocity  to  be  in  the  carotid  (dog)  =  205  to  357  mm.  ; 
carotid  (horse)  =  306  ;  maxillary  (horse)  =  232  ;  metatarsal  =;  56  mm.  per  second. 
The  method  has  very  obvious  defects  arising  from  the  narrowness  of  the  tulie  ;  the 
introduction  of  such  a  tube  offers  new  resistance,  while  there  are  no  respiratory  or 
pulse  variations  observable  in  the  stream  in  the  glass  tube. 

(2)  C.  Ludwig  and  Dogiel  (1867)  devised  a  stromuhr  or  rheometer  for 
measuring  the  amount  of  blood  which  passed  through  an  artery  in  a  given  time 
(Fig.  no).  It  consists  of  two  glass  bulbs,  A  and  B,  of  exactly  the  same  capacity. 
These  bulbs  communicate  with  each  other  above,  their  lower  ends  being  fixed,  by 
means  of  the  tubes,  t-  and  d,  to  the  metal  disk,  f  e^.  This  disk  rotates  round  the 
axis,  X  Y,  so  that,  after  a  complete  revolution,  the  tube  <"  communicates  with  /, 
and  ^/ with  ^;  y  and  ^'- are  provided  with  horizontally  placed  cannula;,  /i  and/', 
which  are  tied  into  the  ends  of  the  divided  artery.  The  cannula  //  is  fixed  in 
the  central  end,  and />  in  the  peripheral  end  of  the  artery  (^-.^if.,  carotid)  ;  the 
bulb.  A,  is  filled  with  oil  and  B  w'th  defibrinated  blood  ;  at  a  certain  moment  the 
communication  through  /;  is  opened,  the  blood  flows  in,  driving  the  oil  before  it, 
and  passes  into  B,  while  the  defibrinated  blood  flows  through  I'  into  the  peripheral 
part  of  the  artery.  As  soon  as  the  oil  reaches  m — a  moment  which  is  instantly 
noted,  or,  what  is  better,  inscribed  upon  a  revolving  cylinder — the  bulbs.  A,  B, 
are  rotated  upon  the  axis,  X,  Y,  so  that  B  comes  to  occupy  the  position  of  A. 
The  same  experiment  is  repeated,  and  can  be  continued  for  a  long  time.  The 
quantity  of  blood  which  passes  in  the  unit  of  time  (i  sec.)  is  calculated  from 
the  time  necessary  to  fill  the  bulb  with  blood.  Important  results  are  obtained  by 
means  of  this  instrument. 


156       MEASUREMENT    OF    THE    VELOCITY   OF    THE    BLOOD    STREAM. 

[As  peptone  injected  into  the  blood  prevents  it  from  coagulating  (dog),  this  fact  has  been  turned 
to  account  in  using  the  rheometer.] 

Fig.  no. 


Fig.  109. 


Volkmann's  haemadromometer  (B).  I,  blond  flows  from 
artery  to  artery;  H,  blood  must  pass  through  the 
glass   tube  of    B  ;    c,  c,  cannulte   for   the  divided 


Ludwig  &  Dogiel's  stromuhr  or  rheometer- 
X,  Y,  axis  of  rotation;  A,  B,  glass 
bulbs  ;  h,  k,  cannulx  inserted  in  the  di- 
vided artery  ;  e,  e^,  rotates  on  g,/:  c. 


f 

iriia 

J 

iifJ! 

(3)  Vierordt's  Haematachometer  (1858)  consists  of 
a  small  meta!  l)ox  ( Fig.  in)  vvitli  parallel  glass  sides.  To 
the  narrow  sides  of  the  box  are  fitted  an  entrance,  e,  and  an 
exit  cannula,  11.  In  its  interior  is  suspended,  against  the 
entrance  opening,  a  pendulum,/,  whose  vibrations  may 
be  read  off  on  a  curved  scale.  [This  instrument,  as  well 
as  Volkmann's  apparatus,  have  only  an  historical  interest.] 

(4)  Chauveau  and  Lortet's  (Dromograph)  (i860) 
is  constructed  on  the  same  principle.  A  tube.  A,  B  (Fig. 
112)  of  sufficient  diameter,  with  a  side  tube  fixed  to  it, 
C,  which  can  be  placed  in  connection  with  a  manometer, 
is  introduced  into  the  carotid  arteiT  of  a  horse.  At  «  a 
small  piece  is  cut  out  and  provided  with   a  covering  of 


VELOCITY    OF   THE    BLOOD    IN    THE    BLOOD    VESSELS. 


157 


gutta-percha  which  has  a  small  hole  in  it;  through  this  a  light  pendulum,  a,  h,  with  a  long  index,  //, 
projects  into  the  tube,  ;.  e.,  into  the  blood  current,  which  causes  the  pendulum  to  vibrate,  and  the 
extent  of  the  vibrations  can  be  read  off  on  a  scale,  S,  S.  G  is  an  arrangement  to  permit  the  instru- 
ment to  be  held.  Both  this  and  the  former  instrument  are  tested  beforehand  with  a  stream  of  water 
sent  through  them  with  varying  velocities. 


Fig, 


Dromograph.     .-V,  B, 


b,  index  moving  i 


The  curve  of  the  velocity  may  be  written  off  on  a  smoked  glass,  moving  paral- 
lel with  the  index,  b.  The  dromograph  curve,  III,  shows  the  primary  elevation, 
P,  and  the  dicrotic  elevation,  R. 

90.  VELOCITY  OF  THE  BLOOD  IN  ARTERIES,  CAPIL- 
LARIES AND  VEINS.^(i)  Division  of  Vessels.— In  estimating  the 
velocity  of  the  blood,  it  is  imjiortant  to  remember  that  the  sectional  area  of  all 
the  branches  of  the  aorta  becomes  greater  as 
we  proceed  from  the  aorta  toward  the  capil- 
laries, so  that  the  capillary  area  is  700  times 
greater  than  the  sectional  area  of  the  aorta 
{Vierordt).  As  the  veins  join  and  form 
larger  trunks,  the  venous  area  gradually  be- 
comes smaller,  but  the  sectional  area  of  the 
venous  orifices  at  the  heart  is  greater  than 
that  of  the  corresponding  arterial  orifices. 
[This  is  shown  in  Fig.  113.  We  may  repre- 
sent the  result  as  two  cones  placed  base  to 
base,  the  bases  meeting  in  the  capillary  area 
i^Kiiss).  The  sectional  area  of  the  venous 
orifice  (V)  is  represented  larger  than  that  of 
the  arterial  (A).  The  increased  sectional  area  influences  the  velocity  of 
the  blood  current,  while  the  resistance  affects  the  pressure.] 

The  common  iliacs  are  an  exception ;  the  sum  of  their  sectional  areas  is  less  than  that  of  the 
aorta;  the  sections  of  the  four  pulmonary  veins  are  together  less  than  that  of  the  pulmonary  artery. 

(2)  Sectional  Area. — An  equal  (juantity  of  blood  must  pass  through  every 
section  of  the  circulatory  system,  through  the   pulmonic  as  well  as   through  the 


158  VELOCITY    OF   THE    BLOOD    IN    THE    BLOOD    VESSELS. 

systemic  circulation,  so  that  the  same  amount  of  blood  must  pass  through  the 
pulmonary  artery  and  aorta,  notwithstanding  the  very  unequal  blood  pressure  in 
these  two  vessels. 

(3)  Lumen. — The  velocity  of  the  current,  therefore,  in  various  sections  of 
the  vessels  must  be  inversely  as  their  lumen. 

(4)  Capillaries. — Hence,  the  velocity  must  diminish  very  considerably  as  we 
pass  from  the  root  of  the  aorta  and  the  pulmonary  artery  toward  the  capillaries, 
so  that  the  velocity  in  the  capillaries  of  mammals  =  0.8  millimetre  per  sec.  ; 
frog  =  0.53  mm.  (E.  H.  Wi-bt-r)  ;  man  =  0.6  to  0.9  (C.  //V/wvtV).  According 
to  A.  W.  Volkmann,  the  blood  in  mammalian  capillaries  flows  500  times  slower 
than  the  blood  in  the  aorta.  Hence,  on  this  view,  the  total  sectional  area  of  all 
the  capillaries  must  be  500  times  greater  than  that  of  the  aorta.  Bonders  found 
the  velocity  of  the  stream  in  the  small  afferent  arteries  to  be  10  times  faster  than 
in  the  capillaries. 

Veins. — The  current  becomes  accelerated  in  the  veins,  but  in  the  larger 
trunks  it  is  0.5  to  0.75  times  less  than  in  the  corresponding  arteries. 

(5)  Mean  Blood  Pressure. — The  velocity  of  the  blood  does  not  depend 
upon  the  wean  blood  pressure,  so  that  it  may  be  the  same  in  congested  and  in 
anaemic  parts  {Volkmann,  Hering). 

(6)  Difference  of  Pressure. — On  the  other  hand,  the  velocity  in  any  sec- 
tion of  a  vessel  is  dependent  on  the  difference  of  the  pressure  which  exists  at  the 
commencement  and  at  the  end  of  that  particular  section  of  a  blood  vessel ;  it 
depends,  therefore,  on  (i)  the  vis  a  tcrgo  (/.  c,  the  action  of  the  heart),  and  (2) 
on  the  amount  of  the  resistance  at  the  periphery  (dilatation  or  contraction  of  the 
small  vessels)  (C.  Ltuhvig  and  DogUl). 

Corresponding  to  the  smaller  difference  in  the  arterial  and  venous  pressure  in  the  foetus  (^  85), 
the  velocity  of  blood  is  less  in  this  case  [Cohnstein  and Zuntz). 

(7)  Pulsatory  Acceleration. — -With  t-wrj/wAc/^^fcz/a  corresponding  accelera- 
tion of  the  blood  current  (as  well  as  of  the  blood  pressure)  takes  place  in  the 
arteries  (pp.  149,  156).  In  large  vessels,  Vierordt  found  the  increase  of  the 
velocity  during  the  systole  to  be  greater  by  Y^  to  Yz  than  the  velocity  during  the 
diastole.  The  variations  in  the  velocity  caused  by  the  heart  beat  are  recorded  in 
Fig.  112,  obtained  by  Chauveau's  dromograph  from  the  carotid  of  a  horse.  The 
velocity  curve  corresponds  with  a  sphygmogram — P  represents  the  primary  eleva- 
tion and  R  the  dicrotic  wave.  This  acceleration,  as  well  as  the  pulse,  disappears 
in  the  capillaries.  A  pulsatory  acceleration,  more  rapid  during  its  first  phase,  is 
observable  in  the  small  arteries,  although  these  are  not  themselves  distended 
thereby. 

(8)  Respiratory  Effect. — Every  inspiration  7-etards  the  velocity  in  the  arter- 
ies, every  expiration  aids  it  somewhat ;  but  the  value  of  these  agencies  is  very 
small. 

If  we  comp.ire  wh.it  has  already  been  said  regarding  the  effect  of  the  respiration  on  the  contrac- 
tion and  dilatation  of  the  heart  and  on  the  blood  stream  (|  60),  it  is  clear  that  respiration  favors 
the  blood  stream,  so  does  artiticial  respiration.  When  artificial  respiration  is  interrupted,  the 
blood  stream  becomes  slower  [Dogit'l).  If  the  suspension  of  lespiration  lasts  somewhat  longer,  the 
current  is  again  accelerated  on  account  of  the  dyspnceic  stimulation  of  the  vasomotor  centre 
(Heidenhain)  (see  Vasomotor  Centre,  \  371,  I). 

(9)  Conditions  Affecting  Velocity  in  the  Veins. — Many  circumstances 
affect  the  velocity  of  the  blood  in  the  veins,  (i)  There  are  ;-(?s,7^ /a;- variations  in  the 
large  veins  near  the  heart  (  Valsalini)  due  to  the  respiration  and  t)ie  movements  of 
the  lieart  (§  50  and  60).  (2)  Ii-regular  variations  due  to  pressure,  e.  g.,  from 
contracting  muscles  (§  &■]),  friction  on  the  skin  in  the  direction  or  against  the 
direction  of  the  venous  current ;  the  position  of  a  limb  or  of  the  body.  The 
pump-like  action  of  the  veins  of  the  groin  on  moving  the  leg  has  been  referred  to 
(§  87).     When  the    lower   limb  is  e.xtended  and  rotated  outward,   the  femoral 


WORK    OF   THE    HEART.  159 

vein  in  the  iliac  fossa  collapses,  owing  to  an  internal  negative  pressure  ;  when  the 
thigh  is  flexed  and  raised  it  fills,  under  a  positive  pressure  {Braune).  A  similar 
condition  obtains  in  walking. 

gi.  ESTIMATION  OF  THE  CAPACITY  OF  THE  VENTRICLES.— Vierordt  cal- 
culated the  capacity  of  the  left  ventricle  from  the  velocity  of  the  blood  stream,  and  the  amount  of 
b[ood  discharged  per  second  by  the  right  carotid,  right  subclavian,  the  two  coronary  arteries,  and 
the  aorta  below  the  origin  of  the  innominate  artery.  He  estimated  that  with  every  systole  of  the 
heart,  172  cubic  centimetres  (equal  to  1S2  grammes  or  6  oz- )  of  blood  was  discharged  into  the 
aorta;  this,  therefore,  must  lie  the  capacity  of  the  left  ventricle  (compare  J  83). 

92.  THE  DURATION  OF  THE  CIRCULATION.— The  question 
as  to  how  long  the  blood  takes  to  make  a  complete  circuit  through  the  course 
of  the  circulation  was  first  answered  by  Hering  ( 1S29)  in  the  case  of  the  horse. 
He  injected  a  2  percent,  solution  of  potassium  ferrocyanide  into  a  special  vein, 
and  ascertained  (by  means  of  ferric  chloride)  when  this  substance  appeared  in  the 
blood  taken  frotn  the  corresponding  vein  on  the  opposite  side  of  the  body.  The 
ferrocyanide  may  also  be  injected  into  the  central  or  cardiac  end  of  the  jugular 
vein,  and  the  time  noted  at  which  its  presence  is  detected  in  the  blood  of  the 
peripheral  end  of  the  same  vein.  \'ierordt  (1S58)  improved  this  method  by 
placing  under  the  corresponding  vein  of  the  opposite  side  a  rotating  disk,  on  which 
was  fixed  a  nutnber  of  cups  at  regular  intervals.  The  first  appearance  of  the  potas- 
sium ferrocyanide  is  detected  by  adding  ferric  chloride  to  the  serum,  which  separ- 
ates from  the  satnples  of  blood  after  they  have  stood  for  a  time.  The  duration  of 
the  circulation  is  as  follows  :  — 

Horse 31.5    seconds.  I  Hedgehog,  7,61    .    .    .    seconds.  I  Duck 10.64  seconds. 

Dog 16.7  "  Cat,  6.69  "  Buzzard,  .    .    .     6.73 

Rabbit,     .    .    .      7.79       "  I  Goose,         10.S6  "       |  Fowl,   ....     5.17         " 

Results. — When  these  numbers  are  compared  with  the  frequency  of  the  normal 
pulse  beat  in  the  corresponding  animals,  the  following  deductions  are  obtained  : 

(i)  The  mean  time  required  for  the  circulation  is  accomplished  during  27  heart 
beats,  /.  e.,  for  man  :=  32.2  seconds,  supposing  the  heart  to  beat  72  times  per 
minute. 

(2)  Generally,  the  mean  time  for  the  circulation  in  two  warm-blooded  animals 
is  inversely  as  the  frequency  of  the  pulse  beats. 

Conditions  Influencing  the  Time. — The  time  is  influenced  by  the  follow- 
ing factors  : 

1.  Long  vascular  channels  {e.g.,  from  the  metarlarsal  vein  of  one  foot  to  the  other  foot)  re- 
quire a  longer  time  than  short  channels  (as  between  the  jugulars).  The  difference  may  be  equal  to 
10  per  cent,  of  the  time  required  to  complete  the  entire  circuit. 

2.  In  young  animals  (with  shorter  vascular  channels  and  higher  pulse  rate)  the  time  is  shorter 
than  in  old  animals. 

3.  Rapid  and  Energetic  cardiac  contractions  (as  during  muscular  exercise)  diminish  the  time. 
Hence  rapid  and  at  the  same  time  less  energetic  contractions  (as  after  section  of  both  vagi),  and 
slow  but  vigorous  systoles  (c.  g..,  after  slight  stimulation  of  the  vagus)  have  no  eftcct. 

C.  Vierordt  estimated  the  quantity  of  blood  in  a  man,  in  the  following  manner.  In  all  warm- 
blooded animals,  27  systoles  correspond  to  the  lime  for  completing  the  circulation.  Hence,  the 
total  mass  of  the  blood  must  be  equal  to  27  times  the  capacity  of  the  ventricle,  /.  e.,  in  man,  187.5 
grms.  y  27  =  5062.5  grms.  This  is  equal  to  yVy  of  the  body  weight  in  a  person  weighing  65. 8 
kilos,  (compare  (i  49). 

It  is  not  to  be  forgotten  that  the  salt  used  is  to  some  extent  poisonous  (p.  103),  but  Hermann  uses 
the  corresponding  innocuous  soda  salt  (25  per  cent.). 

Pathological. — The  duration  of  the  circulation  seems  to  be  increased  during  septic  fever  (E. 
Wolff). 

93.  WORK  OF  THE  HEART.— Johann  .\lfons  Borelli  (1679)  and  JuHus  Robert  Mayer 
estimated  the  work  done  by  the  heart.  The  work  of  a  motor  is  expressed  in  kilogramme  metres, 
;.  e.,  the  number  of  kilos,  which  the  motor  can  raise  in  the  unit  of  time  to  the  height  of  i  metre. 

The  left  ventricle  expels  0.188  kilo,  of  blood  {Volkmami)  with  each  systole, 
and  in  doing  so  it  overcomes  the  pressure  in  the  aorta,  which  is  equal  to  a  column 
of  blood  3.21  metres  in  height  (Dojuirrs).     [The  amount  of  blood  expelled  from 


160  BLOOD    CURRENT    IN    THE    SMALLEST   VESSELS. 

each  ventricle  during  the  systole  is  about  i8o  grms.  (6  oz. ).  It  is  forced  out 
against  a  pressure  of  250  mm.  Hg.  =  3.21  metres  of  blood.]  The  work  of  the 
heart  at  each  systole  is  0.188  X  3-21  =  0.604  kilogramme  metres.  If  the  number 
of  beats  =  75  per  minute,  then  the  work  of  the  left  ventricle  in  24  hours  = 
(0.604  X  75  X  60  X  24)  =  55>23o  kilogramme  metres.  While  the  "  work  "  done 
by  the  r^V//  ventricle  is  about  one-third  that  of  the  left,  and  therefore  =  21,740 
kilogramme  metres.  Both  ventricles  do  work  equal  to  86,970  kilogramme  metres. 
A  workman  during  eight  hours  produces  300,000  kilogramme  metres,  /.  e,  about 
four  times  as  much  as  the  heart.  As  the  whole  of  the  work  of  the  heart  is  con- 
sumed in  overcoming  the  resistance  within  the  circulation,  or  rather  is  converted 
into  heat,  the  body  must  be  partly  warmed  thereby  (425.5  gramme  metres  are 
equal  to  i  heat  unit,  /.  e.,  the  force  required  to  raise  425.5  grammes  to  the  height 
of  I  metre  may  be  made  to  raise  the  temperature  of  i  cubic  centimetre  of  water 
1°  C.)  So  that  204,000  "heat  units"  are  obtained  from  the  transformation  of 
the  kinetic  energy  of  the  heart. 

One  gramme  of  coal  when  burned  yields  8080  heat  units,  so  that  the  heart  yields 
as  much  energy  for  heating  the  body  as  if  about  25  grammes  of  coal  were  burned 
within  it  to  produce  heat. 

94.  BLOOD  CURRENT  IN  THE  SMALLER  VESSELS.— 
Methods. — The  most  important  observations  for  this  purpose  are  made  by  means 
of  the  microscope  on  transparent  parts  of  living  animals.  Malpighi  was  the 
first  to  observe  the  circulation  in  this  way  in  the  lung  of  a  frog  (1661). 

The  following  parts  have  been  employed  :  The  tails  of  tadpoles  and  small  fishes  ;  the  web, 
tongue,  mesentery,  and  lungs  of  curarized  (rogs{Co-u'/>e'r,  /■/04];  the  wing  of  the  bat,  the  third  eye- 
lid of  the  pigeon  or  fowl  ;  the  mesentery- ;  the  vessels  of  the  liver  of  frogs  and  newts  (  Gniithiiiscn), 
of  the  pia  mater  of  rabbits,  of  the  skin  on  the  belly  of  the  frog,  of  the  mucous  membrane  of  the 
inner  surface  of  the  human  lip  (Hiilei-'s  Cheilangioscope,  1S79) ;  of  the  conjunctiva  of  the  eyeball 
and  eyelids.      .Ml  these  may  be  examined  by  rrjlecli'ii  Wghl. 

[Holmgren's  Method. — In  studying  the  circulation  in  the  frog's  lung,  it  must  be  inflated.  A 
cannula  with  a  bulge  on  its  free  end  is  placed  in  the  larynx,  while  to  the  other  end  is  fixed  a  piece 
of  caoutchouc  tubing.  The  lung  is  inflated  and  then  the  caoutchouc  tube  is  closed,  after  which  the 
lung  is  placed  in  a  chamber  with  glass  above  and  below,  and  examined  microscopically.] 

[Entoptical  appearances  of  the  circulation  (Purkinje,  iS/j).  Under  certain  conditions  a 
person  may  detect  the  movement  of  the  blood  corpuscles  w'ithin  the  blood  vessels  of  his  own  eye. 
The  best  methori  is  that  of  Rood,  viz.,  to  look  at  the  sky  through  a  dark -blue  glass,  or  through  sev- 
eral pieces  of  cobalt  glass  placed  over  each  other  {^HeImholiz).'\ 

Form  and  Arrangement  of  Capillaries. — Regarding  the  form  and  arrangement  of  the 
capillaries,  we  find  that  :  — 

1.  The  diameter,  which  in  the  finest  permits  only  the  passage  of  single  corpuscles  in  a  row — 
one  behind  the  other — may  vary  from  5  /i  to  2  11.,  so  that  two  or  more  corpuscles  may  move 
abreast  when  the  capillary  is  at  its  widest. 

2.  The  length  is  about  0.5  mm.     They  terminate  in  small  veins. 

3.  The  number  is  very  variable,  and  the  capillaries  are  most  numerous  in  those  tissues  where 
the  metabolism  is  most  active,  as  in  lungs,  liver,  muscles— less  numerous  in  the  sclerotic  and  in 
the  nerve  trunks. 

4.  They  form  numerous  anastomoses,  and  give  rise  to  networks,  whose  form  and  arrangement  are 
largely  determined  by  the  arrangement  of  the  tissue  elements  themselves.  Tliey  form  simple  loops  in 
the  skin,  and  polygonal  networks  in  the  serous  membranes,  and  on  the  surface  of  many  gland  tubes; 
they  occur  in  the  form  of  elongated  networks,  with  short  connecting  branches  in  muscle  and  nerve,  as 
well  as  between  the  straight  tubules  of  the  kidney  ;  they  converge  radially  toward  a  central  point  in 
the  lobules  of  the  liver,  and  form  arches  in  the  free  margins  of  the  iris,  and  on  the  limit  of  the 
sclerotic  and  cornea. 

[A  great  contrast  as  to  the  vascularity  of  two  adjacent  parts  is  seen  in  the  gray  and  white 
matter  of  the  brain,  the  former  being  very  vascular,  the  latter  but  slightly  so.] 

[Direct  termination  of  Arteries  in  Veins. — .Arteries  sometimes  terminate  directly  in  veins, 
without  the  intervention  of  capillaries,  i'.<,'.,  in  the  ear  of  the  rabbit,  in  the  terminal  phalanges 
(jf  the  fingers  and  toes  in  man  and  some  animals,  in  the  cavernous  tissue  of  the  penis  {^Hoyer). 
They  may  be  regarded  as  secondary  channels  which  protect  the  circulation  of  adjacent  parts, 
and  they  m.ay  also  be  related  to  the  heat-regulating  mechanisms  of  peripheral  parts  (//.yw).] 

End  Arteries. — In  connection  with  the  termination  of  arteries  in  capillaries,  it  is  important 
to  ascertain  if  the  arterioles  are  "  end  or  terminal  arteries,''  i.  e.,  if  they  do  not  form  any  fur- 


CAPILLARY    CIRCULATION.  161 

ther  anastomoses  with  other  similar  arterioles,  but  terminate  directly  in  capillaries,  and  thus 
only  communicate  by  capillaries  with  neighboring  arterioles — or  the  arteries  may  anastomose  with 
other  arteries  just  before  they  break  up  into  capillaries.  This  distinction  is  important  in  connection 
with  the  nutrition  of  parts  supplied  by  such  arteries  (Co/inkeim). 

Capillary  Circulation. — On  observing  the  capillary  circulation,  we  notice 
th^t  the  red  corpuscles  move  only  in  the  axis  of  the  current  (axial  current),  while 
the  lateral  transparent  plasma  current  flowing  on  each  side  of  this  central  thread 
is  free  from  these  corpuscles.  [The  axial  current  is  the  more  rapid.]  This  plasma 
layer  or  "  Poiseuille's  space  "  is  seen  in  the  smallest  arteries  and  veins,  where 
I  is  taken  up  with  the  axial  current,  and  the  plasma  layer  occupies  ^  on  each  side 
of  it  (Fig.  114).  A  great  many,  but  not  all,  of  the  colorless  corpuscles  run  in 
this  layer.  It  is  much  less  distinct  in  the  capillaries.  Rud.  Wagner  stated  that  it 
is  absent  in  the  finest  vessels  of  the  lung  and  gills  [although  Gunning  was  unable 
to  confirm  this  statement.]  The  colored  corpuscles  move  in  the  smallest  capillaries 
in  single  Jilc,  one  after  the  other  ;  in  the  larger  vessels  several  corpuscles  may  move 
abreast,  with  a  _f/;V//«^'- motion,  and  in  their  course  they  may  turn  over  and  even 
be  twisted  if  any  obstruction  is  offered  to  the  blood  stream.  As  a  general  rule, 
in  these  vessels  the  movement  is  uniform,  but  at  a  sharp  bend  of  the  vessel  it  may 
partly  be  retarded  and  partly  accelerated.  Where  a  vessel  divides,  not  unfre- 
quently  a  corpuscle  remains  upon  the  projecting  angle  of  the  division,  and  is 
doubled  over  it  so  that  its  ends  project  into  the  two  branches  of  the  tube.  There 
it  may  remain  for  a  time,  until  it  is  dislodged,  when  it  soon  regains  its  original 
form,  on  account  of  its  elasticity.  Not  unfrequently  we  see  a  red  corpuscle  becom- 
ing bent  where  two  vessels  meet,  but  on  all  occasions  it  rapidly  regains  its  original 
form.     This  is  a  good  proof  of  the  elasticity  of  the  colored  corpuscles. 

Colorless  Corpuscles. — The  motion  of  the  colorless  corpuscles  is  quite  dif- 
ferent in  character  ;  they /-('// directly  on  the  vascular  juall,  moistened  on  their 
peripheral  zone  by  the  plasma  in  Poiseuille's  space,  their  other  surface  being  in 
contact  with  the  thread  of  colored  corpuscles  in  the  centre  of  the  stream. 
Schklarewsky  has  shown  by  physical  experiments,  that  the  particles  of  least  spe- 
cific gravity  in  all  capillaries  {e.g.,  of  glass)  are  pressed  toward  the  wall,  while 
those  of  greater  specific  gravity  remain  in  the  middle  of  the  stream.  [Graphite 
and  particles  of  carmine  were  suspended  in  water,  and  caused  to  circulate  through 
capillary  tubes  placed  under  a  microscope,  when  the  graphite  kept  the  centre  of 
the  stream,  and  the  carmine  moved  in  the  layer  next  the  wall  of  the  tube.] 

When  the  colorless  corpuscles  reach  the  wall  of  the  vessel,  they  must  roll  along, 
partly  on  account  of  their  surface  being  sticky,  whereby  they  readily  adhere  to  the 
vessel,  and  partly  because  one  surface  is  directed  toward  the  axis  of  the  vessel 
where  the  movement  is  most  rapid,  and  where  they  receive  impulses  directly  from 
the  rapidly  moving  colored  blood  corpuscles  {Doiulers).  The  rolling  motion  is 
not  always  uniform;  not  unfrequently  it  is  retrograde  in  direction,  which  seems  to 
be  due  to  an  irregular  adhesion  to  the  vascular  wall.  Their  slower  movement  (10 
to  12  times  slower  than  the  red  corpuscles)  is  partly  due  to  their  stickiness,  and 
partly  to  the  fact  that  as  they  are  placed  near  the  wall,  a  large  part  of  their  surface 
lies  in  the  peripheral  threads  of  the  fluid,  which,  of  course,  move  more  slowly  (in 
fact  the  layer  of  fluid  next  the  wall  is  passive — p.  109). 

[D.  J.  Hamilton  finds  that,  when  a  frog's  web  is  examined  in  a  vertical  posi- 
tion, by  far  the  greater  proportion  of  leucocytes  float  on  the  upper  surface,  and 
only  a  few  on  the  lower  surface,  of  a  small  blood  vessel.  In  experiments  to  deter- 
mine why  the  colored  corpuscles  float  or  glide  exclusively  in  the  axial  stream, 
while  a  great  many,  but  not  all,  of  the  leucocytes  roll  in  the  peripheral  layers, 
Hamilton  ascertained  that  the  nearer  the  suspended  body  approaches  to  the  spe- 
cific gravity  of  the  liquid  in  which  it  is  immersed,  the  more  it  tends  to  occupy 
the  centre  of  the  stream.  He  is  of  opinion  that  the  phenomenon  of  the  separa- 
tion of  the  blood  corpuscles  in  the  circulating  fluid  is  due  to  the  colorless  cor- 
puscles  being  specifically  lighter,   and    the   colored    either   of  the   same  or   of 


162 


DIAPEDESIS. 


very  slightly  greater  specific  gravity  than  the  blood  plasma.  Hamilton  contro- 
verts the  statement  of  Schklarewsky,  and  he  finds  that  it  is  the  relative  specific 
gravity  of  a  bod\»  which  ultimately  determines  its  position  in  a  tube.  These 
experiments  point  to  the  immense  importance  of  a  due  relation  subsisting  between 
the  specific  gravity  of  the  blood  plasma  and  that  of  the  corpuscles.] 

In  the  vessels  first  formed  in  the  incubated  egg,  as  well  as  in  those  of  young  tadpoles,  the  move- 
ment of  the  blood  from  the  heart  occurs  in  jerks  (Spa//amani,  jy6S). 

The  velocity  of  the  blood  stream  is  influenced  by  the  diameter  of  the  vessels, 
which  undergo  periodic  changes  of  calibre.  This  change  occurs  not  only  in 
vessels  provided  with  muscular  fibres,  but  also  in  the  capillaries,  which  vary  in 
diameter,  owing  to  the  contraction  of  the  cells  composing  their  walls  (p.  115). 

The  amount  of  water  in  the  blood  is  of  importance,  as  when  it  is  mcreased  the 
circulation  is  facilitated  and  accelerated  (  C.  A.  En'ald  ]  (%  62). 

The  velocity  of  the  blood  is  greater  in  the  pulmonary  than  in  the  systemic 
capillaries  {Hales,  172J)  ;  hence,  we  must  conclude  that  the  total  sectional  area 
of  the  pulmonary  capillaries  is  less  than  that  of  all  the  systemic  capillaries. 

95.  PASSAGE  OF  THE  BLOOD  CORPUSCLES  OUT  OF  THE  VESSELS— 
DIAPEDESIS. — Diapedesis. — If  the  circulation  be  studied  in  the  vessels  of  the  mesentery,  we 
may  observe  colorless  corpuscles  passing  out  of  the  vessels  in  greater  or  less  numbers  (Fig.  114). 
The  mere  contact  with  the  air  suffices  to  excite  slight  inflammation.  At  first,  the  colorless  cor- 
puscles in  the  plasma  space  move  more  slowly  ;  several  accumulate  near  each  other,  and  adhere  to 
the  walls — soon  they  bore  into  the  wall ;  ultimately  they  pass  quite  through  it,  and  may  wander  for  a 
distance  into  the  perivascular  tissues.  It  is  doubtful  whether  they  pass  through  the  so-called 
"  stomata  "  which  exist  between  the  endothelial  cells,  or  whether  they  simply  pass  through  the 
cement  substance  between  the  endothelial  cells  (p.  113).  This  process  is  called  Diapedesis,  and 
consists  of  several  acts  :  ( <7)  The  adhesion  of  lymph  cells  or  colorless  corpuscles  to  the  inner  surface 
of  the  vessel  (after  moving  more  slowly  along  the  wall  up  to  this  point).     (/>)  They  send  processes 

into  and  through  the  vascular  wall.     1  c)  The  body 
of  the  cell  is  drawn  after  or  follows  the  processes, 
whereby  the  corpuscle  appears  constricted  in  the 
centre   (Fig.  114,  c).     (d)  The  complete  passage 
of  the  corpuscle  through  the  wall,  and  its  further 
motion  in  virtue  of  its  own  amceboid  movements. 
1     Hering  observed   that  in  large  vessels  with  peri- 
vascular lymph  spaces,  the  corpuscles  passed  into 
these    latter,    hence,  cells    are     found     in    lymph 
before  it  has  passed  through  lymphatic  glands.  The 
cause  of  the  diapedesis  is  partly  due  to  the  inde- 
pendent locomotion  of  the   corpuscles,   and  it   is 
partly  a  physical  act,  viz.,  a  filtration  of  the  colloid 
mass  of  the  cell  under  the   force   of   the  blood 
pressure  {Hering) — in  the  latter  respect  depending 
upon   the  intravascular  pressure  and  the  velocity 
of  the  blood  stream.      Hering  regards  this  process, 
and  even  the  passage  of   the  colored  corpuscles 
diapedesis  of  the  colorlesi  corpuscles.    ».,  -u.T  vas-  through   the   vascular   wall,  as   a   normal    process, 
cular  walls  ;  a,  a,  Poiseuille's  space  ;  r,  r,  red  cor-  The  red  corpuscles  pass  out  of  the  vessels  when 
puscles;  /,  /,    colorless  corpuscles  adhering  to  the  the  venous  outtlow  is  obstructed,  which  also  causes 
g  .  j'jt  ^]^g   transudation  of  plasma  through   the  vascular 

wall.  Tlie  plasma  carries  the  colored  corpuscles 
along  with  it,  and  at  the  moment  of  their  passage  through  the  wall  they  assume  extraordinary 
shapes,  owing  to  the  tension  put  upon  them,  regaining  their  shape  as  soon  as  they  pass  out  (Coiin- 
heim'). 

This  remarkable  phenomenon  was  described  by  Waller  in  1846.  It  was  recently  redescribed  by 
Cohnheim,  and  according  to  him  the  oiit- wandering  is  a  sign  of  inflammation,  and  the  colorless  cor- 
puscles which  accumulate  in  the  tissues  are  to  be  regarded  as  pus  corpuscles,  which  may  undergo 
further  increase  by  division. 

Stasis. — When  a  strong  stimulus  acts  on  a  vascular  part,  hyjiera^mic  redness  and  swelting  occur. 
Microscopic  observation  shows  that  the  capillaries  and  the  small  vessels  are  dilated  and  overfilled 
with  blood  corpuscles;  in  some  cases  a  temporary  naiTowing  precedes  the  dilatation;  simultaneously 
the  velocity  of  the  stream  changes;  rarely  there  is  a  temporary  acceleration,  more  frequently  it  he- 
eotnes  slo7i'er.      If  the  action  of  the  stimulus  or  irritant  be  continued,  the  retardation  becomes  con- 


FlG.  114. 


Small  vessel  of  the 


enterj'  of  a  frog,  showing   the 


tided  corpuscles. 


MOVEMENT   OF   THE    BLOOD    IN    THE    VEINS.  163 

siderable,  the  stream  moves  in  jerks,  then  follows  a  to  and  fro  movement  of  the  blood  column — 
a  sign  that  stagnation  has  taken  place  in  other  vascular  areas.  At  last,  the  blood  stream  comes 
completely  to  a  standstill — stasis — and  the  blood  vessels  are  plugged  with  blood  corpuscles. 
Numerous  colorless  blood  corpuscles  are  found  in  the  stationary  blood.  While  these  various 
processes  are  taking  place,  the  colorless  coq:iuscles — more  rarely  the  red — pass  out  of  the  vessels. 
Under  favorable  circumstances  the  stasis  may  disappear.  The  swelling  which  occurs  in  the  neigh- 
l*rhood  of  inllamed  parts  is  chiefly  due  to  the  exudation  of  plasma  into  the  surrounding  tissues. 
[The  vapor  of  chloroform  causes  hyperajmia  of  the  web  {L:s/c-r).] 

96.  MOVEMENT  OF  THE  BLOOD  IN  THE  VEINS.— As  already 
mentioned,  in  the  smallest  veins  coming  from  tlie  capillaries  the  blood  stream  is 
more  rapid  than  in  the  capillaries  themselves,  but  less  so  than  in  the  correspond- 
ing arteries.  The  stream  is  uniform,  and  if  no  other  conditions  interfered  with 
it,  the  venous  stream  toward  the  heart  ought  to  be  uniform,  but  many  circum- 
stances affect  the  stream  in  different  parts  of  its  course.  Among  these  are:  (i) 
The  relative  /axncss,  great  distensihility  and  the  ready  compressibility  of  the  walls, 
even  of  the  thickest  veins.  (2)  The  incompleti'  filling  oi  the  veins,  which  does  not 
amount  to  any  considerable  distention  of  their  walls.  (3)  The  numerous  and  free 
anastomoses  between  adjoining  veins,  not  only  between  veins  lying  in  the  same 
plane,  but  also  between  superficial  and  deep  veins.  Hence,  if  the  course  of  the 
blood  be  obstructed  in  one  direction,  it  readily  finds  another  outlet.  (4)  The 
presence  of  numerous  valves,  which  permit  the  blood  stream  to  move  only  in  a 
centripetal  direction  (Fabricius  ah  Ai/iiapenile>ile).  They  are  absent  from  the 
smallest  veins,  and  are  most  numerous  in  those  of  middle  size. 

Law  of  the  Position  of  Valves. — The  venous  valves  always  have  two  pouches,  and  are  placed 
at  definite  intervals,  which  correspond  to  the  i,  2,  3,  or  n""  power  of  a  certain  "  fundamental  dis- 
tance," which  is  =  7  mm.  for  the  lower  extremity  and  5.5  mm.  for  the  upper.  Many  of  the  origi- 
nal valves  disappear.  On  the  proximal  side  of  every  valve  a  lateral  branch  opens  into  the  vein, 
while  on  the  distal  side  of  each  branch  lies  a  valve.  The  same  is  true  for  the  lymphatics  (A". 
Banlc-Mn-,i). 

Effect  of  Pressure. — As  soon  as  pressure  is  applied  to  the  veins,  the  ne.\t 
lowest  valves  close,  and  those  immediately  above  the  seat  of  pressure  open  and 
allow  the  blood  to  move  freely  toward  the  heart.  The  pressure  may  be  exerted 
from  without,  as  by  anything  placed  against  the  body  ;  the  thickened  contracted 
muscles,  especially  the  muscles  of  the  limbs,  compress  the  veins.  That  the  blood 
flows  out  of  a  divided  vein  more  rapidly  when  the  muscles  contract,  is  shown 
during  venesection.  If  the  muscles  are  kept  contracted,  the  venous  blood 
passing  out  of  the  muscles  collects  in  the  passive  parts,  e.  g.,  in  the  cutaneous 
veins.  The  pulsatile  pressure  of  the  arteries  accompanying  the  veins  favors  the 
venous  current  iOzanam).  From  a  hydrostatic  point  of  view,  the  valves  are 
of  considerable  importance,  as  they  serve  to  divide  the  column  of  blood  into 
•segments  {e.  g.,  in  the  crural  vein  in  the  erect  attitude),  so  that  the  fine  blood 
vessels  in  the  foot  are  not  subjected  to  the  whole  amount  of  the  hydrostatic 
pressure  in  the  veins. 


The  velocity  of  the  venous  blood  has  been  measured  directly  (with  the  hsemadromometer  and 
the  stromuhr — ^Sg).  Volkmann  found  it  to  be  225  ram.  per  sec.  in  the  jugular  vein.  Reil  ob- 
served that  2 '.<  times  more  blood  flowed  from  an  arterial  orifice  than  from  a  venous  orifice  of  the 
same  size.  The  velocity  of  the  venous  current  obviously  depends  upon  the  sectional  area  of  the 
vessel.  liorelli  estimated  the  capacity  of  the  venous  system  to  be  4  times  greater  than  that  of 
the  arterial;  while,  according  to  Haller,  the  ratio  is  9  to  4. 

Large  Veins. — As  we  proceed  from  the  small  veins  toward  the  venK  cavre,  the 
sectional  area  of  the  veins,  taken  as  a  whole,  becomes  less,  so  that  the  velocity  of 
the  current  increases  in  the  same  ratio.  The  velocity  of  the  current  in  the  venae 
cavK  may  lie  about  half  of  that  in  the  aorta  {Nailer'). 

As  the  pulmonary  veins  are  narrower  than  the  pulmonary  artery,  the  blood 
moves  more  rapidly  in  the  former. 

[Active  pulsation  occurs  in  the  veins  of  the  wing  of  the  bat  {Sc/iiff).~\ 


164  VENOUS    MURMURS. 

97.  SOUNDS  OF  BRUITS  WITHIN  ARTERIES.— These  murmurs,  sounds  or  bruits 
occur  either  .t/iiH/aHew«,r/i',  or  are  produced  by  the  a/'p/ica/ion  of  external  pressuye,v/hexthy  \hs 
lumen  of  the  vessel  is  diminished.  In  four-tirths  of  all  healthy  men,  two  sounds — corresponding 
in  duration  and  other  characters  to  the  two  heart  sounds — are  heard  in  the  carotid  (Conrad,  IFei/). 
Sometimes  only  the  second  heart  sound  is  distinguishable,  as  its  place  of  origin  is  near  to  the  carotid. 
They  are  not  true  arterial  sounds,  but  are  simply  "propagated  heart  sounds." 

Arterial  Sounds  or  murmurs  are  readily  produced  by  pressing  upon  a  strong 
artery,  r.g.,  the  crural  in  the  inguinal  region,  so  as  to  leave  only  a  narrow  passage 
for  the  blood  ("stenosal  murmur").  A  fine  blood  stream  passes  with  great 
rapidity  and  force  through  this  narrow  part  into  a  wider  portion  of  the  artery 
lying  behind  the  point  of  compression.  Thus  arises  the  "  pressure  stream  "  (/". 
JVta/ii'yer),  or  the  "  fluid  vein  "  ('•  Veine  fluide  "  of  Chauveau).  The  particles 
of  the  fluid  are  thrown  into  rapid  pscillation,  and  undergo  vibratorv  movements, 
and  by  their  movements  produce  the  sound  within  the  peripheral  dilated  portion 
of  the  tube.  A  sound  is  produced  in  the  fluid  by  pressure  \Corrigan,  Heynsius). 
The  sounds  are  not  caused  by  vibrations  of  the  vascular  wall,  as  supposed  by 
Bouillaud. 

A  murmur  of  this  sort  is  the  "sub-clavicular  murmur "  (j?m«),  occasionally  heard  during 
systole  in  the  subclavian  artery ;  it  occurs  when  the  two  layers  of  the  pleura  adhere  to  the  apex  of 
the  lung  (especially  in  tubercular  diseases  of  the  lungs),  whereby  the  subclavian  artery  undergoes  a 
local  constriction  due  to  its  being  made  tense  and  slightly  curved  (Friedreich).  This  result  is  indi- 
cated in  a  diminution  or  absence  of  the  pulse  wave  in  the  radial  artery  (  Weil). 

Arterial  murmurs  are  favored  by — (i)  Sufficient  delicacy  and  elasticity  of  the 
arterial  walls  (Th.  Weber).  (2)  Diminished  peripheral  resistance,  e.g.,  an  easy 
outflow  of  the  fluid  at  the  end  of  the  stream  {KhviscJi).  (3)  Accelerated  current 
in  the  vascular  system  generally.  (4)  \  considerable  difference  of  the  pressure 
in  the  narrow  and  wide  portions  of  the  tube  i^Marey).  (5)  Large  calibre  of  the 
arteries. 

It  is  obvious  that  arterial  murmurs  will  occur  in  the  human  body — (a)  When,  owing  to  patho- 
logical conditions,  the  arterial  tube  is  dilated  at  one  part,  into  which  the  blood  current  is  forcibly 
poured  from  the  normal  narrow  tube.  Dilatations  of  this  sort  are  called  aneurisms,  within  which 
murmurs  are  generally  audible.  (b\  When  pressure  is  exerted  tipon  an  artery,  c'.  ^j,"".,  by  the  pressure 
of  the  greatly  enlarged  arteries  during  pregnancy,  or  by  a  large  tumor  pressing  upon  a  large  artery. 
(<■)  A  murmur  corresponding  to  each  pulse  beat  is  heard,  especially  where  two  or  more  large  arteries 
lie  together;  hence,  during  pregnancy,  we  hear  the  uterine  murmur,  or  placental  bruit,  or  souffle 
in  the  greatly  dilated  utenne  arteries.  It  is  much  less  distinct  in  the  umbilical  arteries  of  the  cord 
(umbilical  murmurs).  Similar  sounds  are  heard  through  the  thin  walls  of  the  head  of  infants 
(Fisher,  jSjj).  -A.  murmur  due  to  the  systole  of  the  heart  is  often  he;ird  in  the  carotid  (Jurasz). 
In  such  cases  where  no  source  of  external  pressure  is  discoverable,  and  when  no  aneurism  is  present, 
the  spontaneously  occurring  sounds  are  favored,  when  at  the  moment  of  arterial  rest  (cardiac  systole) 
the  arterial  walls  are  distended  to  the  slightest  extent,  and  when  during  the  movement  of  the  pulse 
(cardiac  diastole)  the  tension  is  most  rapid  (  Traube,  U'eil),  i.  e.,  when  the  low  systolic  minimum^ 
tension  of  the  arterial  wall  passes  rapidly  into  the  high  maximum  tension.  This  is  especially  the 
case  in  insufficiency  of  the  aortic  valves,  in  which  case  the  sounds  in  the  arteries  are  audible  over  a 
wide  area.  If  the  minimum  tension  of  the  arterial  wall  is  relatively  great,  even  during  diastole,  the 
sounds  in  the  arteries  are  greatly  diminished. 

In  insufficiency  of  the  aortic  valves,  characteristic  sounds  may  be  heard  in  the  crural  artery. 
If  pressure  be  exerted  upon  the  artery,  a  double  blowing  murmur  is  heard ;  the  first  one  is  due  to  a 
large  mass  of  blood  being  propelled  into  the  artery  synchronously  with  the  heart  heat,  the  second  to 
the  fact  that  a  large  quantity  of  blood  flows  back  into  the  heart  during  di.astole  (Duroziez,  iSb/). 
If  no  pressure  be  exercised  two  sounds  are  heard,  and  these  seem  to  be  due  to  a  wave  propagated 
into  the  arteries  by  the  auricles  and  ventricles  respectively  (Landois) — compare  §  73,  Fig.  86,  III. 
In  atheroma  a  double  sound  may  sometimes  be  heard  (ii  73,  2). 

98.  VENOUS    MURMURS.— I.    Bruit   de    Diable.— This   sound   is 

heard  above  the  clavicles,  in  the  furrow  between  the  two  heads  of  the  sterno- 
mastoid,  most  frequently  on  the  right  side,  and  in  40  per  cent,  of  all  persons 
examined.  It  is  either  a  continuous  or  a  rhythmical  murmur,  occurring  during  the 
diastole  of  the  heart  or  during  inspiration  ;  it  has  a  whistling  or  rushing  character, 
or  even  a  musical  quality,  and  arises  within  the  bulb  of  the  common  jugular  vein. 


THE    VENOUS    PULSE.  165 

When  this  sound  is  heard  without  pressure  being  exerted  by  the  stethoscope,  it 
is  a  pathological  phenomenon.  If,  however,  pressure  be  exerted,  and  if,  at  the 
same  time,  the  person  examined  turns  his  head  to  the  opposite  side,  a  similar  sound 
is  heard  in  nearly  all  cases  (JFt-//).  The  pathological  dn/Zf  de  dia/>le  occuk 
especially  in  anajmic  persons,  in  lead  poisoning,  syphilitic  and  scrofulous  persons, 
^metimes  in  young  persons,  and  less  frequently  in  elderly  people.  Sometimes  a 
thrill  oi  the  vascular  wall  may  be  felt. 

Causes. — It  is  due  to  the  vibration  of  the  blood  flowing  in  from  the  relatively 
narrow  part  of  the  common  jugular  vein  into  the  wide  bulbous  portion  of  the 
vessel,  and  seems  to  occur  chiefly  when  the  walls  of  a  thin  part  of  the  vein  lie 
close  to  each  other,  so  that  the  current  must  purl  through  it.  It  is  clear  that  pres- 
sure from  without,  or  lateral  pressure,  as  by  turning  the  head  to  the  opposite  side, 
must  favor  its  occurrence.  Its  intensity  will  be  increased  when  the  velocity  of  the 
stream  is  increased,  hence  inspiration  and  the  diastolic  action  of  the  heart  <  both 
of  which  assist  the  venous  current)  increase  it.  The  erect  attitude  acts  in  a  similar 
manner.  A  similar  bruit  is  sometimes,  though  rarely,  heard  in  the  subclavian, 
axillary,  thyroid  (scrofula),  facial,  innominate  and  crural  veins  and  superior  cava. 

II.  Regurgitant  Murmurs. — On  making  a  sudden  effort,  a  murmur  maybe  heard  in  the  crural 
vem  during  expiration,  which  is  caused  by  a  centrifugal  current  of  blood,  owing  to  the  incompetence 
or  absence  of  the  valves  in  this  region.  If  the  valves  at  the  jugular  bulb  are  not  tight,  there  may 
be  a  bruit  with  expiration  [expiratory  jugular  vein  bruit — ffamernjk),  or  during  the  cardiac  systole 
(jtrj/fl/;V  jugular  vein  bruit — v.  Bamberger). 

III.  Valvular  Sounds  in  Veins. — When  the  tricuspid  valve  is  incompetent,  during  the  ventri- 
cular systole  a  large  volume  of  blood  is  propelled  backward  into  the  venn;  cava;.  The  venous  valves 
are  closed  suddenly  thereby  and  a  sound  produced.  This  occurs  at  the  bulb  or  dilatation  on  the 
jugular  vein  (:■.  Bamberger),  and  in  the  crural  vein  at  the  groin  [jV.  Freidreich),  i.  e.,  only  as  long 
as  the  valves  are  competent.  Forced  expiration  may  cause  a  valvular  sound  in  the  crural  vein.  IS'o 
sound  is  heard  in  the  veins  under  perfectly  normal  circumstances. 

99.  THE  VENOUS  PULSE— PHLEBOGRAM. -Methods.— A  tracing  of  the  move- 
ments of  a  vein,  taken  with  a  lightly-weighted  sphygmograph,  has  a  characteristic  form,  and  is 
called  a  phlebogram  (Fig.  1 15  1.  In  order  to  interpret  the  various  events  of  the  phlebogiam  it  is 
most  important  to  record  simultaneously  the  event  that  takes  place  in  the  heart.  The  auricular 
contraction  (compare  Fig.  41 )  is  synchronous  with  a  b  ;  b  e,  with  the  ventricular  systole,  during  which 
time  the  first  sound  occurs,  while  (7 1^  is  a  presystolic  movement.  The  carotid  pulse  coincides  nearly 
with  the  apex  of  the  cardiogram,  /.  e.,  almost  simultaneously  with  the  descending  limb  of  the  phle- 
bogram (Hiegel). 

Occasionally  in  healthy  individuals  a  ptilsatile  movement,  synchronous  with  the 
action  of  the  heart,  may  be  observed  in  the  common  jugular  vein.  It  is  either 
confined  to  the  lower  part  of  the  vein,  the  so-called  bulb,  or  extends  further  up 
along  the  trunk  of  the  vein.  In  the  latter  case,  the  valves  above  the  bulb  are 
insufficient,  which  is  by  no  means  rare,  even  in  health.  The  wave  motion  passes 
from  below  upward,  and  is  most  obvious  when  the  person  is  in  the  passive  hori- 
zontal position,  and  it  is  more  frequent  on  the  right  side,  because  the  right  vein 
lies  nearer  the  heart  than  the  left. 

The  venous  pulse  resembles  very  closely  the  tracing  of  the  cardiac  impulse 
{Landois).     Compare  Fig.  115,  i,  with  Fig.  32. 

It  is  obvious  that,  as  the  jugular  vein  is  in  direct  communication  with  the  right 
auricle,  and  as  the  pressure  within  it  is  low,  the  systole  of  the  right  auricle  must 
cause  a  positive  wave  to  be  propagated  toward  the  peripheral  end  of  the  jugular 
vein.  Fig.  115,  9  and  10,  are  venous  pulse  tracings  of  a  healthy  person  with 
insufficiency  of  the  valves  of  the  jugular  vein.  In  these  curves,  the  part  a,  l> 
corresponds  to  the  contraction  of  the  auricle.  Occasionally  this  part  consists  of 
two  elevations,  corresponding  to  the  contraction  of  the  atrium  and  auricle 
respectively.  As  the  blood  in  the  right  auricle  receives  an  impulse  from  the 
sudden  tension  of  the  triscupid  valve  synclironoits  -with  the  systole  of  the  right 
ventricle,  there  is  a  positive  wave  in  the  jugular  vein  in  Fig.  115,  9  and  10,  indi- 
cated by  /'.  e.     Lastly,  the  sudden  closure  of  the  pulmonary  valves  may  even  be 


166 


THE    VENOUS    PULSE. 


indicated  (c).  As  the  aorta  lies  in  direct  relation  with  the  pulmonary  artery,  the 
sudden  closure  of  its  valves  may  also  be  indicated  (Fig.  115,  9,  at  if).  During 
the  diastole  of  the  auricle  and  ventricle,  blood  flows  into  the  heart,  so  that  the 
vein  partly  collapses  and  the  lever  of  the  recording  instrument  descends  {Rifgel, 
Francois- Franck ) . 

Sinus  and  Retinal  Pulse. — The  blood  in  the  sinuses  of  the  drain  also  undergoes  a  pulsatile 
movement,  owing  to  the  fact  that  during  cardiac  diastole  much  blood  flows  into  the  veins  (Mosso). 
I'nder  favorable  circumstances,  this  movement  may  be  propagated  into  the  veins  of  the  retina,  con- 
stituting the  vaiotis  retinal  pulse  of  the  older  observers  [Helfreich). 

Jugular  Vein  Pulse. — The  venous  pulse  in  the  jugular  vein  is  far  better  marked  in  insufficiency 
of  the  tricuspid  valve,  and  the  vein  may  pulsate  violently,  but  if  its  valves  be  perfect  the  pulse  is  not 
propagated  along  the  vein,  so  that  <;  pulse  in  the  jugular  vein  is  not  necessarily  a  sign  of  insuffi- 
ciency of  the  tricuspid  valve,  but  only  of  insulificiency  of  the  valve  of  the  jugular  vein  (Friedreich). 

Liver  Pulse. — The  ventricular  systole  is  propagated  into  the  valveless  inferior  vena  cava,  and 


Fig.  115. 


rious  forms  of  venous  pulses,  chiefly  after  Friedreich — i-S  from  insufficiency  of  the  tricuspid  ;  9  and  ic,  pulse  ot 
the  jugular  vein  of  a  healthy  person.  In  all  the  curves,  a,  b  ^  contraction  of  the  right  auricle  ;  b,  c,  of  the  right 
ventricle  ;  d,  closure  of  the  aortic  valves ;  e,  closure  of  the  pulmonary  valves  :  e,_f,  diastole  of  the  right  ventricle. 


causes  the  liver  pulse.  With  each  systole  blood  passes  into  the  hepatic  veins,  so  that  the  liver 
undergoes  a  systolic  swelling  and  injection. 

Fig.  115,  2-8,  are  curves  of  the  pulse  in  the  common  jugular  vein  (after  Friedreich).  Although 
at  first  sight  the  curves  appear  to  be  very  different,  they  all  agree  in  this,  that  the  various  events 
occurring  in  the  heart  during  a  cardiac  revolution  are  indicated  more  or  less  completely.  In  all 
the  curves,  a,  b  =  auricular  contraction.  The  auricle,  when  it  contracts,  excites  a  positive  wave  in 
the  veins  [Gendrin  (/S4J),  Marey,  Friedreich).  The  elevation,  l\  c,  is  caused  by  the  large  blood 
wave  produced  in  the  veins,  owing  to  the  emptying  of  the  ventricle.  It  is  always  greater,  of 
course,  in  insufficiency  of  the  tricuspid  valves  than  under  noniial  circumstances  (Fig.  115,  9  and 
10).  In  the  latter  case,  the  closure  of  the  tricuspid  valve  causes  only  a  slight  wave  motion  in  the 
auricle.  The  apex,  c,  of  this  wave  may  be  higher  or  lower,  according  to  the  tension  in  the  vein 
and  the  pressure  exerted  by  the  sphygmograph.  As  a  general  rule,  at  least  one  notcli  (4,  5,  6,  e) 
follows  the  apex,  due  to  the  prompt  closure  of  the  valves  of  the  pulmonary  artery.  The  closure  of 
the  closely  adjacent  aortic  valves  may  cause  a  small  secondary  wave  near  to  e  (as  in  i  and  2,  d). 
The  curve  fails  towardy,  corresponding  to  the  diastole  of  the  heart. 

A  well-marked  venous  pulse  occurs  when  the  right  auricle  is  greatly  congested,  as  in  cases  of 
insufiiciency  of  the  mitral  valve  or  stenosis  of  the  same  orifice.     In  rare  cases,  in  addition  to  the 


PLETHYSMOGRAPHY.  167 

pulse  in  the  common  jugular  vein,  the  external  jugular,  the  facial,  thyroid,  external  thoracic  veins, 
or  even  the  veins  of  the  upper  and  lower  extremities  may  pulsate. 

A  similar  pulsation  must  occur  in  the  pulmonary  veins  in  mitral  insufficiency,  but,  of  course,  the 
result  is  not  visible. 

On  rare  occasions,  a  pulse  occurs  in  the  veins  on  the  back  of  the  hand  and  foot,  owing  to  the 
arterial  pulse  being  propagated  through  the  capillaries  into  the  veins.  This  may  occur  under 
normal  circumstances,  when  the  peripheral  ends  of  the  arteries  become  dilated  and  relaxed 
(Quinike),  or  when  the  blood  pressure  within  these  vessels  rises  rapidly  and  falls  as  suddenly, as  in 
insufficiency  of  the  aortic  valves. 

\n\>xog!ess\ve  effusion  iiilo  t/w  pi-ricardiiim,  At  first  the  carotid  pulse  becomes  smaller  and  the 
venous  pulse  larger;  beyond  a  certain  pressure,  the  latter  ceases  (I^iegel). 

IOC.  DISTRIBUTION  OF  THE  BLOOD.— Methods.— The  methods  adopted  do  not 
give  exact  results.  J.  Ranke  ligatured  the  parts  during  life,  removed  them,  and  investigated  the 
amount  of  blood  while  the  tissues  were  still  warm. 

In  the  rabbit,  one-fourth  of  the  total  amount  of  the  blood  is  found  in  each  of 
the  following :  (7,  in  the  passive  muscles  ;  />,  in  the  liver  ;  c,  in  the  organs  of  the 
circulation  (heart  and  great  vessels)  ;  </,  in  all  other  parts  together  (_/.  Hankc). 

Influencing  Conditions. — The  amount  of  blood  is  influenced  by — (i)  the  anatomical  distribution 
(vascularity  or  the  reverse)  of  the  vessels  as  a  whole  ;  (2)  the  diameter  of  the  vessels,  which  depends 
upon  physiological  causes — {(7)  on  the  blood  pressure  within  the  vessels;  (h)  on  the  condition  of 
the  vasomotor  or  vaso-dilator  nerves ;  [c]  on  the  condition  of  the  tissues  themselves,  e.g.,  the  vessels 
of  the  intestine  during  absorption ;  by  the  vessels  of  muscle  during  muscular  contraction  ;  of 
vessels  in  inflamed  parts. 

Activity  of  an  Organ. — The  most  important  factor,  however,  is  the  s/afe  of 
acfirify  of  t/ie  organ '\t.?,t\[ ;  hence,  the  saying,  "  ubi  irritatio,  ibi  afflu.xus."  We 
may  instance  the  congestion  of  the  salivary  glands  and  the  gastric  mucous  mem- 
brane during  digestion,  and  the  increased  vascularity  of  muscles  during  contrac- 
tion. As  the  activity  of  organs  varies  at  different  tmts,  ihe  amount  of  b/ood  in 
fhe  part  or  organ  goes  hand  in  hand  with  the  variations  in  its  state  of  activity  (^J. 
Ranke).  When  some  organs  are  congested  others  are  at  rest  ;  during  digestion, 
there  is  muscular  relaxation  and  less  mental  activity ;  violent  muscular  exertion 
retards  digestion — during  great  congestion  of  the  cutaneous  vessels  the  activity  of 
the  kidneys  diminishes.  Many  organs  (heart,  muscles  of  respiration,  certain 
nerve  centres)  seem  always  to  be  in  a  nearly  uniform  state  of  activity  and  vascu- 
larity. 

During  the  activity  of  an  organ,  the  amount  of  blood  in  it  may  be  increased  30 
])er  cent.,  nay  even  47  per  cent.  The  motor  organs  of  young  muscular  persons 
are  relatively  more  vascular  than  those  of  old  and  feeble  persons  (_/.  J?anie). 

During  a  condition  of  mental  activity,  the  carotid  is  dilated,  the  dicrotic  wave  in  the  carotid  curve  is 
increased  (the  radial  shows  the  opposite  condition),  and  the  pulse  is  increased  in  frequency  (Gley). 

In  the  condition  of  increased  activity,  a  more  rapid  reneical  oi  tht  blood  seems 
to  occur  ;  after  muscular  e.xertion  the  duration  of  the  circulation  diminishes 
{Vierordt). 

Age. — The  tlcvelopmeiit  of  the  heart  anJ  large  vessels  determines  a  ditl'erent  distribution  of  the 
blood  in  the  child  from  that  which  obtains  in  the  adult.  The  heart  is  relatively  small  from  infancy 
up  to  puberty,  the  vessels  are  relatively  large  ;  while  after  puberty  the  heart  is  large,  and  the  vessels 
are  relatively  smaller.  Hence,  it  follows  that  the  blood  pressure  in  the  arteries  of  the  systemic  cir- 
culation must  be  lower  in  the  child  than  in  the  adult.  The  pulmonary  artery  is  relatively  wide  in 
the  child,  while  the  aorta  is  relatively  small ;  after  puberty  both  vessels  have  nearly  the  same  size. 
Hence,  it  follows  that  the  blood  pressure  in  the  pulmonary  vessels  of  the  child  is  relatively  higher 
than  that  in  the  adult  {Beneke). 

loi.  PLETHYSMOGRAPHY.— Plethysmograph.— In  order  to  esti- 
mate and  register  the  amount  of  blood  in  a  limb,  Mosso  devised  an  instrument 
(Fig.  116),  which  he  termed  a  Plethysmograjih.  It  is  constructed  on  the  same 
principle  as  the  less  perfect  apparatus  of  Chelius  and  Fick. 

It  consists  of  a  long  cylindrical  glass  vessel,  G,   suited  to   accommodate   a   limb.     The  opening 
'  through  which  the  limb  is  introduced  is  closed  with  caoutchouc,  and  the  vessel    is  filled  with  water. 


168 


TRANSFUSION    OF    BLOOD. 


There  is  an  opening  in  the  side  of  tlie  vessel  in  which  a  manometer  tube,  filled  to  a  certain  height 
with  water,  is  fixed.  As  the  arm  is  enlarged  owing  to  the  increased  supply  of  arterial  blood  passing 
into  it  at  each  pulse  beat,  of  course,  the  water  column  in  the  manometer  is  raised.  Fick  placed  a 
float  upon  the  surface  of  the  water,  and  thus  enabled  the  variations  in  the  volume  of  the  fluid  to  be 
inscribed  on  a  revolving  cylinder.  The  curve  obtained  resembled  the  pulse  curve ;  it  was  even 
dicrotic.  In  Fig.  Ii6  the  movement  of  the  fluid  is  represented  as  conveyed  to  a  Marey's  tambour, 
T,  similar  to  the  recording  apparatus  employed  in  Brondgeest's  Pansphygmograph  (Figs.  40,  72). 

Results. — From  the  curve  obtained  we  learn  that — (i)  the  ftilsatik  variations 
in  the  volume  are  similar  to  the  pulse  curve.  As  the  venous  current  is  regarded  as 
uniform  in  the  passive  limb,  every  increase  of  the  volume  curve  indicates  a  greater 
velocity  of  the  arterial  current  toward  the  periphery,  and  I'ice  versa  {Ficli).  (2) 
The  respiratory  iinJulations  correspond  to  similar  variations  in  the  blood  pressure 
tracing  (S  85,/).  Vigorous  respiration  and  cessation  of  the  respiration  cause  a 
diminution  of  the  volume.  The  limb  swells  during  straining  {i\  Bascli)  and 
coughing,  but  diminishes  during  sighing.  (3)  Certain  periodic  undulations  occur, 
due  to  the  regular  periodic  contractions  of  the  small  arteries.  (4)  Other  undula- 
tions, due  to  various  accidental  causes,  affect  the  blood  pressure  :  changes  of  the 
position  of  a  limb  acting  hydrostatically,  and  dilatation  or  contraction  of  the 
vessels  in  other  vascular  regions.  (5)  Movement  of  the  muscles  of  the  limb  under 
observation  causes  diminution  of  volume  (e.xperiment  of  Fr.  Glisson.  1677)  ;  as 
the  venous  current  is  accelerated,  the  musculature  is  also  verv  slightlv  diminished  in 


J*^ 


Mosso's  Plethysmogniph.     G 


issel  for  holding  a  limb  ;  F,  flask  for  varyii 
T,  recording  app.iratus. 


volume,  even  when  the  intra-muscular  vessels  are  dilated.  (6)  Mental  exercise 
causes  a  diminution  in  the  volume  of  the  limb,  and  so  does  sleep  {AIosso).  Music 
influences  the  blood  pressure  in  dogs,  the  pressure  rising  or  falling  under  different 
conditions.  The  stimulation  of  the  auditory  nerve  is  transmitted  to  the  medulla 
oblongata,  where  it  acts  so  as  to  cause  acceleration  of  the  action  of  the  heart 
(^Dogiel).  Compression  of  the  afferent  artery  causes  a  decrease,  and  compression 
of  the  vein  an  increase  in  the  volume  of  the  limb  {Mosso). 

102.  TRANSFUSION  OF  BLOOD.— Transfusion  is  the  introduction  of 
blood  from  one  animal  into  the  vascular  system  of  another  animal. 

Historical. — The  first  indication  of  direct  transfusion  from  blood  vessel  to  blood  vessel  dates 
from  the  time  of  Cardanus,  in  1556.  After  the  discovery  of  the  circulation  in  England,  J.  Potter 
(1638)  evolved  the  idea  of  the  transfusion  of  blood.  Numerous  experiments  were  made  on  ani- 
mals. New  blood  was  transfused,  in  order  to  restore  life  in  animals  that  had  been  bled.  Boyle 
and  Lower  conducted  these  and  other  experiments.  The  blood  of  the  same  species,  as  well  as  the 
blood  of  other  species,  was  employed.  The  first  case  of  transfusion  on  man  was  performed  by 
Jean  Denis,  in  Paris  ( 1667),  lamb's  blood  being  used.  At  the  present  time,  when  transfusion  is 
practiced  on  man,  only  human  blood  is  used. 

(a)  The  red  corpuscles  are  the  most  important  elements  in  connection  with 
the  restorative  powers  of  the  blood.     They  seem  to  preserve  their  functions  even 


TRANSFUSION    OF    BLOOD.  169 

in  blood  which  has  been  defibrinated  outside  the  body  [Prevost  and  Dumas,  1821'). 
The  effect  of  various  reagents  upon  them  has  already  been  noticed  (§  4,  A). 

{F)  With  regard  to  the  gases  of  the  blood  corpuscles,  oxygenated  (arterial) 
blood  never  acts  injuriously ;  but  venous  blood  overcharged  with  carbonic  acid 
ought  only  to  be  transfused  when  the  respiration  is  sufficient  to  oxygenate  the 
blood  as  it  passes  through  the  pulmonary  capillaries,  whereby  venous  is  transformed 
into  arterial  blood.  If  the  respiratory  movements  have  ceased,  or  are  imperfectly 
performed,  the  blood  becomes  rapidly  richer  in  carbonic  acid,  and  in  this  condi- 
tion reaches  the  heart ;  thence  it  is  propelled  into  the  blood  vessels  of  the  medulla 
oblongata,  where  it  acts  as  a  powerful  stimulus  of  the  respiratory  centre,  causing 
dyspnoea,  convulsions  and  death. 

{c)  The  fibrin,  or  the  substances  from  which  it  is  formed  {%  29),  do  not  seem 
to  play  any  part  in  connection  with  the  restorative  powers  of  the  blood  ;  hence, 
defibrinated  blood  performs  all  the  functions  of  non-defibrinated  blood  within  the 
body  (Faniiin,  Landois). 

(</)  The  investigations  of  Worm  Miiller  showed  that  an  excess  of  ^2>  P^""  cent. 
of  blood  might  be  transfused  into  the  vascular  system  of  an  animal  without  pro- 
ducing any  injurious  effects.  Hence  it  follows  that  the  vascular  system  has  the 
power  of  accommodating  large  quantities  of  blood  within  it.  That  the  vascular 
system  can  accommodate  itself  to  a  diminished  amount  of  blood  has  been  known 
for  a  long  time  (§  85,  c).  [It  is  very  important  to  observe  that  the  transfusion 
of  a  large  quantity  of  blood  does  not  materially  or  permanently  raise  the  blood 
pressure.] 

■When  Employed. — The  transfusion  of  blood  is  used — (i)  in  acute  anaemia 
(§41.  I),  e.g.,  after  copious  hemorrhage.  New  blood  from  the  same  species  ot 
animal  is  introduced  directly  into  the  vessels,  to  supply  the  place  of  the  blood 
lost  by  the  hemorrhage. 

(2)  In  cases  of  poisoning,  where  the  blood  has  been  rendered  useless  by  being 
mixed  with  a  poisonous  substance,  and  hence  is  unable  to  support  life.  In  such 
cases,  remove  a  considerable  quantity  of  the  blood,  and  replace  it  by  fresh  blood. 
Carbonic  oxide  is  a  poison  of  this  kind  (Kiihne),  and  its  effects  on  the  body  have 
already  been  described  (§  16).  A  similar  practice  is  indicated  on  poisoning  with 
ether,  chloral,  chloroform,  opium,  morphia,  strychnine,  cobra  poison  and  such 
substances  as  dissolve  the  blood  corpuscles,  e.g.,  potassic  chlorate. 

(3)  Under  certain  pathological  conditions,  the  blood  may  become  so  altered 
in  quality  as  to  be  unable  to  support  life.  The  morphological  elements  of  the 
blood  may  be  altered,  and  so  may  the  relative  proportion  of  its  other  constituents. 
Among  these  conditions  may  be  cited  the  pathological  condition  of  uraemia,  due, 
it  may  be,  to  the  accumulation  of  urea  or  the  products  of  its  decomposition  within 
the  blood  [or  to  the  retention  of  the  potash  and  other  urinary  salts  (Feliz  and 
Ritter)'\  ;  accumulation  of  the  biliary  constituents  in  the  blood  (Cholsemia),  and 
great  increase  of  the  carbonic  acid.  All  these  three  conditions,  when  very  pro- 
nounced, may  cause  death.  In  these  cases,  part  of  the  impure  blood  may  be 
replaced  by  normal  human  blood  (Landois). 

Among  conditions  where  the  morplwlogical  constituents  of  the  blood  are  altered 
qualitatively  or  quantitatively  are  :  hydrsemia  (excessive  amount  of  water  in  the 
blood,  §  41,  i)  ;  oligocythasmia  (abnormal  diminution  of  red  corpuscles).  When 
these  conditions  are  highly  developed,  more  especially  in  pernicious  anaemia  (§  10, 
2),  healthy  blood  may  be  substituted.  Transfusion  is  not  suited  for  persons 
suffering  from  leukaemia  (compare  p.  33). 

After  Effects. — A  quarter  or  half  an  hour  after  normal  blood  has  been  injected 
into  the  blood  vessels  of  a  man,  there  is  a  greater  or  \ti%  febrile  reaction,  according 
to  the  amount  of  blood  transfused  (Fever,  §  220). 

Operation. — The  operative  procedure  to  -be  adopted  in  the  process  of  transfusion  varies  according 
as  defibrinated  or  non-de6brinated  blood  is  used.  In  order  to  defibrinate  blood,  some  blood  is 
withdrawn  from   the  vein  of  a  healthy  man  in  tlie  ordinary  way ;  it  is  collected  in  an  open  vessel 


170  TRANSFUSION    OF   BLOOD. 

and  whipped  or  beaten  with  a  glass  rod  until  all  the  fibrin  is  completely  removed  from  it.  It  is  then 
filtered  through  an  atlas  filter,  Seated  to  the  temperature  of  the  body  (by  placing  it  in  warm  water), 
and  injected,  by  means  of  a  syringe,  into  an  artery  opened  for  the  purpose.  .\  vein  (t'.  ^j,'.,  basilic 
or  great  saphenous)  may  be  selected  for  the  transfusion,  in  which  case  the  blood  is  driven  in  in  the 
direction  of  the  heart;  if  an  artery  is  selected  (radial  or  posterior  tibial),  the  blood  is  injected 
toward  the  periphery  [Hii/er)  or  toward  the  heart  [Landois,  ScAafir). 

Dangers. — It  is  most  important  not  to  permit  the  entrance  of  air  into  the  circulation,  for  if  it  be 
introduced  in  sufficient  quantity,  it  may  cause  death.  When  air  enters  the  circulation  it  reaches  the 
right  side  of  the  heart,  where,  ow'ing  to  the  movement  of  the  blood,  it  forms  air  bubbles  and  makes 
a  froth.  The  air  bubbles  are  pumped  into  the  branches  of  the  pulmonary  artery,  in  which  they  be- 
come impacted,  arrest  the  pulmonary  circulation,  and  rapidly  cause  death. 

If  non-defibrinated  human  blood  is  used,  the  blood  maybe  passed  diredly  from  the  arm  of  the 
giver  to  the  arm  of  the  receiver  by  means  of  a  flexible  tube.  The  tube  used  must  be  filled  with 
normal  saline  solution  to  prevent  the  entrance  of  air.  [J.  Duncan  collects  the  blood  shed  during 
an  operation  in  a  5  per  cent.  soKuion  of  sodic  phosphate  (/'(?-^i'),and  injects  the  mixture,  especially 
where  much  blood  has  been  lost  previously.] 

Peritoneal  Transfusion. — Recently,  the  injection  of  defibrinated  blood  into  the  peritoneal 
cavity  has  been  recommended.  The  blood  so  injected  is  absorbed  (Ponfick).  Even  after  twenty 
minutes  the  inmiber  of  blood  corpuscles  in  the  blood  of  the  recipient  (rabbit)  is  increased,  and  the 
number  is  greatest  on  the  first  or  second  day  (Bizzozero  and  Goigi).  The  operation,  however,  may 
cause  death,  and  one  fatal  case,  owing  to  peritonitis,  is  recorded  (Mosier).  It  is  evident  that  this 
method  of  transfusion  is  not  applicable  in  cases  where  blood  must  be  introduced  into  the  circulation 
as  rapidly  as  possible  (e.  g.,  after  severe  hemorrhage  or  in  certain  cases  of  poisoning).  [Blood  has 
been  injected  into  the  subcutaneous  cellular  tissue  of  the  abdomen  in  ca.ses  of  great  debility]. 

Heterogeneous  Blood. —  Tin-  Hood  of  animals  ought  never  to  be  transfused  into  the  blood  ves- 
sels of  man.  Some  surgeons  have  transfused  blood  directly  from  the  carotid  of  a  lamb  into  the 
human  subject.  It  is  to  be  remembtred,  however,  that  the  blood  corpuscles  of  the  sheep  are  rapidly 
dissolved  by  human  blood,  so  that  the  active  constituents  of  the  blood  are  rendered  useless  (Lan- 
dois). As  a  general  rule,  the  blood  serum  of  some  mammals  dissolves  the  blood  corpuscles  of  other 
mammals  (^  5'  5)- 

Solution  of  the  Blood  Corpuscles. — The  serum  of  dog's  blood  is  a  powerful  solvent,  while 
that  of  the  l>lood  of  the  horse  and  rabbit  dissolves  corpuscles  rel.atively  slowdy.  The  blood  corpus- 
cles of  mammals  vary  very  greatly  with  reference  to  their  power  to  resist  the  solvent  action  of  the 
serum  of  other  animals.  The  red  blood  corpuscles  of  rabbit's  blood  are  rapidly  dissolved  by  the 
blood  serum  of  other  aniiuals,  whilst  those  of  the  cat  and  dog  resist  the  solvent  action  much  longer. 
Solution  of  the  corpuscles  occurs  in  defibrinated  as  w-ell  as  in  ordinary  blood.  When  the  blood  of 
a  rabbit  or  lamb  is  injected  into  the  blood  vessels  of  a  dog,  they  are  dissolved  in  a  few  minutes.  If 
blood  be  withdrawn  by  pricking  the  skin  with  a  needle,  the  partially  dissolved  corpuscles  may  be 
detected. 

Liberation  of  Haemoglobin  and  Haemoglobinuria. — As  a  result  of  the  solution  of  the  col- 
ored corpuscles,  the  blood  plasma  is  reddened  by  the  liberated  h.T;moglobin.  Part  of  the  dissolved 
material  may  be  used  up  in  the  body  of  the  recipient,  some  of  it  for  the  formation  of  bile,  but  if 
the  solution  of  the  corpuscles  has  been  extensive,  the  hii^moglobin  is  e.xcreted  in  the  urine  (haemo- 
globinuria) in  less  amount  in  the  intestine,  the  bronchi,  and  the  serous  cavities  [Panum).  Bloody 
urine  has  been  observed  in  man  after  the  injection  of  100  grammes  of  lamb's  blood.  Even  some 
of  the  recipient's  blood  corpuscles  are  dissolved  by  the  serum  of  the  transfused  blood,  f.  ,^,^,  on 
transfusing  dog's  blood  into  man.  In  the  rabbit,  whose  corpuscles  are  readily  dissolved,  the  trans- 
fusion of  the  blood  serum  of  the  dog,  man,  pig,  sheep,  or  cat  produces  serious  symptoms,  and  even 
death.  The  dog,  whose  corpuscles  are  more  resistant,  bears  transfusion  of  other  kinds  of  blood 
well. 

Dangers — When  foreign  or  heterogeneous  blood  (/.  e.,  blood  from  a  different  species)  is  trans- 
fused, two  phenomena,  which  may  be  dangerous  to  life,  occur  : — 

(1)  Before  the  ccrpuscles  are  dissolved  they  usually  run  together  and  form  sticky  masses,  consist- 
ing of  10  or  12  corpuscles,  which  are  apt  to  occlude  capillaries.  After  a  time  they  give  up  their 
hfemoglobin,  leaving  the  stroma,  which  yields  a  sticky,  fibrin-like  mass  that  may  occlude  fine  vessels 

a  30-  .         ,  . 

(2)  The  presence  of  a  large  quantity  of  dissolved  haemoglobin  may  cause  extensive  coagulation 
within  the  blood  vessels.  The  injection  of  dissolved  hemoglobin  causes  extensive  coagulations 
[jVaunyn  and  Francken). 

The  coagulation  occurs  usually  in  the  venous  system  and  in  the  larger  vessels,  and  may  cause 
death  either  suddenly  or  after  a  considerable  time. 

Dissolved  hamoglobin  seems  greatly  to  increase  the  activity  of  the  fibrin  femient  (J  30),  perhaps 
by  accelerating  the  decomposition  of  the  colorless  corpuscles.  Haemoglobin  exposed  to  the  air 
gradually  loses  this  properly  ;  and  the  fibrin  ferment,  w-hen  in  contact  with  haemoglobin,  is  either 
destroyed  or  rendered  less  active  (Saehssendahl). 

Vascular  Symptoms. — .As  a  result  of  the  above-named  causes  of  occlusion  of  the  vessels,  there 
are  often   signs  of  the  circulation  being  impeded  in  various  organs.     In  man,  after  transfusion  of 


TRANSFUSION    OF   BLOOD.  171 

lamb's  blood,  the  skin  is  bluish  red,  in  consequence  of  the  stagnation  of  blood  in  the  cutaneous 
vessels.  Difficulty  of  breathing  occurs  from  obstruction  in  the  capillaries  of  the  lung  ;  while  there 
may  be  rupture  of  small  bronchial  vessels,  causing  sanguineous  expectoration.  The  dyspnrea  may 
increase,  especially  when  the  circulation  through  the  medulla  oblongata — the  seat  of  the  respiratory 
centre — is  interfered  with.  In  the  digestive  tract,  for  the  same  reason,  increased  peristalsis,  evacua- 
tion of  the  contents  of  the  rectum,  vomiting,  and  abdominal  pain  may  occur.  These  phenomena 
are  explained  by  the  fact  that  disturbances  of  the  circulation  in  the  intestinal  vessels  cause  increased 
ptristaltic  movements.  Degeneration  of  the  parenchyma  of  the  kidney  occurs  as  a  result  of  the 
occlusion  of  some  of  the  renal  vessels.  The  uriniferous  tubules  become  plugged  with  cylinders  of 
coagulated  albumin  (Ponfick).  Owing  to  the  occlusion  of  numerous  small  muscular  branches  the 
muscles  may  become  stiff,  or  coagulation  of  their  myosin  may  occur.  Other  symptoms,  referable  to 
the  nervous  system,  the  sense  organs  and  heart,  are  all  due  to  the  interference  with  the  circulation 
through  them.  An  important  symptom  is  the  occurrence  of  a  considerable  amount  of  fci'er  half  an 
hour  or  so  after  the  transfusion  of  heterogeneous  blood.  When  many  vessels  are  occluded,  rupture 
of  some  small  blood  vessels  may  take  place.  This  explains  the  occurrence  of  slight  yet  persistent 
hemorrhages,  which  occur  on  the  free  surfaces  of  the  mucous  and  serous  membranes,  and  in  the 
parenchyma  of  organs,  as  well  as  in  wounds.  The  blood  coagulates  with  difficulty,  and  imper- 
fectly. 

Transfusion  of  other  Fluids. — Other  substances  have  been  transfused.  Normal  Saline  So- 
lution (0.6  per  cent.  NaCl)  aids  the  circulation  in  a  purely  mechanical  way  (Goltz),  and  it  even 
excites  the  circulation  (Kronecker,  Sander,  Olt).  In  severe  a:tmia  this  fluid  cannot  maintain  life 
{Euienburg  and  Landois).  The  injection  of  Peptone,  even  in  moderate  amount,  is  dangerous  to 
life,  as  it  causes  paralysis  of  the  vessels.  The  injection  of  Milk  is  accompanied  with  danger;  fever 
occurs  after  the  injection,  and  the  milk  globules  cause  the  occlusion  of  many  vessels,  producing  sub- 
sequent degenerations.  Fat  may  appear  in  the  urine,  and  there  may  be  fatty  infiltration  of  the 
urinary  tubules.  The  urine  contains  sugar  and  albumin,  the  liver  cells  often  contain  fatty  granules, 
and  the  weight  of  the  body  diminishes.  If  too  large  a  quantity  of  milk  be  transfused,  death  occurs. 
When  unboiled  milk  is  injected,  numerous  bacteria  are  developed  in  the  blood  (Sclia/er). 


THE  BLOOD  GLANDS 


103. — I.  THE  SPLEEN. — Structure. — The  spleen  is  covered  by  the  peritoneum,  except  at 
the  hilus.  Under  this  serous  covering  there  is  a  tough,  thick,  elastic,  fibrous  capsule,  which 
closely  invests  the  organ  and  gives  a  covering  to  the  vessels  which  enter  or  leave  it  at  the  hilus,  so 
that  fibrous  tissue  is  carried  into  the  organ  along  the  course  of  the  vessels.  [The  capsule  cannot 
be  separated  without  tearing  the  splenic  pulp.]  Numerous  trabeculae  pass  into  the  spleen  from 
the  deep  surface  of  the  capsule.  These  trabecul;i;  branch  and  ana.stomose  so  as  to  produce  a  net- 
work of  sustentacular  tissue,  which  is  continuous  with  the  connective  tissue,  prolonged  inward  and 
surrounding  the  blood  vessels  (Fig.  117).  Thus,  the  connective  tissue  in  the  spleen,  as  in  other 
viscera,  is  continuous  throughout  the  organ.  In  this  way  an  irregular  dense  network  is  formed, 
comparable  to  the  meshes  of  a  bath  sponge.  [This  network  is  easily  demonstrated  by  washing  out 
the  pulp  lying  in  its  meshes  by  means  of  a  stream  of  water,  when  a  beautiful,  soft,  semi-elastic  net- 
work or  framework  of  rounded  and  flattened  threads  is  obtained.! 


Fig.  117. 


Spleen  of  a  cat  injected 
with  gelatine,  showing 
the  adenoid  reticulum. 


The  Capsule  is  composed  of  interlacing  bundles  of  connective  tissue  mixed  with  numerous  fine 
fibres  of  elastic  tissue  and  some  non-striped  muscular  fibres. 

Reticulum. — Within  the  meshes  of  the  trabecular  framework  there  is  disposed  a  very  delicate 
network  or  reticulum  of  adenoid  tissue  (Billroth),  which,  with  the  other  colored  elements  that  fill 
up  the  meshes,  constitute  the  splenic  pulp  (Fig.  118).  The  reticulum  is  continuous  with  the  fibres 
of  the  trabeculii;.  [If  a  fine  section  of  the  spleen  be  "  pencilled  "  in  water,  so  as  to  remove  the 
cellular  elements,  the  preparation  presents  much  the  same  characters  as  a  section  of  a  lymph  gland 
similarly  treated,  viz.,  a  very  fine  network  of  adenoid  tissue,  continuous  with,  and  surrounding  the 
walls  of,  the  blood  vessels.  The  spaces  of  this  tissue  are  filled  with  lymph  and  blood  corpuscles 
(//»).] 

The  Pulp  is  a  dark,  reddish-colored  semi-fluid  material,  which  may  be  squeezed  or  washed  out 
of  the  meshes  in  which  it  lies.  It  contains  a  large  number  of  colored  blood  corpuscles,  and  becomes 
brighter  when  it  is  exposed  to  the  action  of  the  oxygen  of  the  air. 

Blood  Vessels  and  Malpighian  Corpuscles. — The  large  splenic  artery  splits  up  into  several 
branches  before  it  enters  the  spleen,  and  it  is  accompanied  in  its  course  by  the  vein.  Both  vessels 
and  their  branches  are  enclosed  in  a  fibrous  sheath,  which  becomes  continuous  with  the  trabecul.t. 
The  smaller  branches  of  the  artery  gradually  lose  this  fibrous  investment,  and  each  one  ultimately 
divides  into  a  group  or  pencil  of  arterioles  (penicilli)  which  do  not  anastomose  with  each  other. 
[Thus  each  branch  is  terminal — a  condition  which  is  of  great  importance  in  connection  with  the 
pathology  of  embolism  or  infarction  of  the  vessels  of  the  spleen.]  At  the  points  of  division  of  the 
branches  of  the  artery,  or  scattered  along  their  course,  are  small  oval  or  globular  masses  of  adenoid 
tissue,  about  the  size  of  a  small  millet  seed  (j'j  to  ^^  inch  in  diameter} — the  Malpighian 
corpuscles.  [These  bodies  are  visible  to  the  naked  eye  as  small,  round  or  oval  white  structures, 
about  the  size  of  a  millet  seed,  in  a  section  of  a  fresh  spleen.]     Thev  are  very  numerous — [7000 

172 


BLOOD    VESSELS    OF   THE    SPLEEN. 


173 


m  man  (Safpev)'] — and  are  readily  detected  in  the  dark  reddish  pulp.  We  must  be  careful  not  to 
mistake  sections  of  the  trabecule  for  them.  These  corpuscles  consist  of  adenoid  tissue,  whose 
meshes  are  loaded  with  lymph  corpuscles,  and  they  present  exactly  the  same  structure  as  the 
solitary  follicles  of  the  intestine  (compare  Lymphatic  Glands,  \  197). 

[They  are  just  small  lymphatic  accumulations  around  the  arteries — peri-arterial  masses  of 
adenoid  tissue  similar  to  those  masses  that  occur  in  a  slightly  different  form  in  other  organs,  e.  g., 
thf  lungs.  In  a  section  of  the  spleen  the  artery  may  pass  through  the  centre  of  the  mass  or 
through  one  side  of  it,  and  in  some  cases  the  tissue  is  collected  unequally  on  opposite  sides  of  the 
vessel,  so  that  it  is  lob-sided.  They  are  not  surrounded  by  any  special  envelope.  In  some  animals 
the  lymphatic  tissue  is  continued  for  some  distance  along  the  small  arteries,  so  that  to  some  extent  it 
resembles  a  perivascular  sheath  of  adenoid  tissue  (IV.  jMiiller,  Sch-weiggir-Seidel).  In  a  well- 
injected  spleen,  a  few  fine  capillaries  are  to  be  found  within  these  corpuscles  (Sanders).  The  capil- 
laries distributed  in  the  substance  of  the  .Malpighian  corpuscle  (Fig.  119)  form  a  network,  and 
ultimately  pour  their  blood  into  the  spaces  in  the  pulp.  According  to  Robin  and  Legros,  these 
vessels  are  comparable  to  the  vasa.vasorum  of  other  blood  vessels.  According  to  Cadiat,  the  cor- 
puscles are  separated  from  the  splenic  pulp  by  a  lymphatic  sinus,  which  is  traversed  by  efferent 
capillaries  passing  to  the  pulp  (Fig.  119I.] 

Connection  of  Arteries  and  Veins. — It  is  very  dittlcult  to  determine  what  is  the  exact  mode 
of  termination  of  the  arteries  within  the  spleen,  more  especially  as  it  is  extremely  difficult  to  inject 
the  blood  vessels  of  the  spleen.     According  to  Stieda,  W.  Miiller,  Peremeschko  and  Klein,  the 

Fig.  119. 


Malpighian   corpuscle  ot  the  spleen  of  a  cat  injected,     a,  artery 
of  the  pulp  injected  ;  c,  the  artery  of  the  corpuscl 
space  around  the  corpuscle  is  the  lymphatic  sinus. 


Lciy  .iiuuiid  which  the  corpuscle  is  placed;  ^.  m 
ifying  in  the  lymphatic  tissue  composing  it.     The 


fine  "  capillary  arteries  "  formed  by  the  division  of  the  small  arteries  do  not  open  directly  into  the 
capillary  veins,  but  the  connection  between  the  arteries  and  veins  is  by  means  of  the  "  intermediary 
intercellular  spaces"  of  the  reticulum  of  the  spleen;  so  that,  according  to  this  view,  there  is  no 
continuous  channel  lined  throughout  by  epithelium  connecting  these  vessels  one  with  another. 
Thus,  the  blood  of  the  spleen  flows  into  the  spaces  of  the  adenoid  reticulum,  just  as  the  lymph 
stream  flows  through  the  spaces  in  a  lymph  gland.  According  to  Billroth  and  Kolliker,  a  closed 
blood  channel  actually  does  exist  between  the  capillary  arteries  and  the  veins,  consisting  of  dilated 
spaces  (similar  to  those  of  erectile  tissue).  These  intermediary  spaces  are  said  to  be  completely 
lined  by  spindle-shaped  epithelium,  which  abuts  externally  on  the  reticulum  of  the  pulp.  [.Accord- 
ing to  Frey,  owing  to  the  walls  of  the  terminal  vessels  being  incomplete — there  being  clefts  or  spaces 
between  the  cells  comj)osing  them — the  blood  passes  freely  into  spaces  of  the  adenoid  tissue  of  the 
pulp  "  in  the  same  way  as  the  water  of  a  river  finds  its  way  among  the  pebbles  of  its  bed,"  these 
"  intermediary  passages  "  being  bounded  directly  by  the  cells  and  fibres  of  the  network  of  the 
pulp.  From  these  passages  the  venous  radicles  arise.  A\  first,  their  walls  are  imperfect  and  crib- 
riform, and  they  often  present  peculiar  transverse  markings,  due  to  the  circular  disposition  of  the 
elastic  fibres  of  the  reticulum.  The  small  veins  have  at  first  a  different  course  from  the  arteries. 
They  anastomose  freely,  but  they  soon  become  ensheathed,  and  accompany  the  arteries  in  their 
course.] 

Elements  of  the  Pulp. — The  morphological  elements  are  very  various — (i)   Lymph  corpuscles 
of  various  sizes,  sometimes  partly  swollen,  and  at   other  times  with  granular  contents.     (2)  Red 


174  FUNCTIONS    OF   THE    SPLEEN. 

blood  corpuscles.  (3)  Transition  forms  between  I  and  2  [although  this  is  denied  by  some  observers 
{^7,  C)].  (4)  Cells  containing  red  blood  corpuscles  and  pigment  granules.  [These  cells  exhibit 
amceboid  movements.]     (Compare  ^8.) 

[The  Lymphatics  undoubtedly  arise  within  the  spleen.  The  lymphatics  which  leave  the  spleen 
are  not  numerous  (A'Sl/iker).  There  are  two  systems— a  superficial,  capsular  and  trabecular  system, 
and  a  perivascular  set.  The  superficial  lymphatics  in  the  capsule  are  rather  more  numerous. 
.Some  of  them  seem  to  communicate  with  the  lymphatics  within  the  organ  ( Tomsa,  Kolliker).  In 
the  horse's  spleen  they  communicate  with  the  lymphatics  in  the  trabecular  and  with  the  perivascular 
lymphatics.  The  exact  mode  of  origin  of  the  perivascular  system  is  unknown,  but  in  part,  at 
least,  it  begins  in  the  spaces  of  the  adenoid  tissue  of  the  Malpighian  corpuscles  and  perivascular 
adenoid  tissue,  and  runs  along  the  arteries  toward  the  hilus.  There  seem  to  be  no  afferent  lym- 
phatics in  the  spleen,  such  as  e.^ist  in  a  lymphatic  gland.] 

The  Nerves  of  the  spleen  are  composed,  for  the  most  part,  of  non-medullated  nerve  fibres,  and 
run  along  with  the  artery.  Their  e.xact  mode  of  termination  is  unknown,  but  they  probably  go  to 
the  blood  vessels  and  to  the  muscular  tissue  in  the  capsule  and  trabecula;.  [They  are  well  seen  in 
the  spleen  of  the  ox,  and  in  their  course  very  small  ganglia,  placed  wide  apart,  have  been  found  by 
Remak  and  W.  .Stirling.] 

Chemical  Composition. — Several  of  the  more  highly  oxidized  stages  of  albuminous  bodies 
exist  in  the  spleen.  Besides  the  ordinary  constituents  of  the  blood,  there  exist  leucin,  tyrosin, 
xanthin,  hypoxanthin,  also  lactic,  butyric,  acetic,  formic,  succinic  and  uric  acids,  and,  perhaps, 
glycero-phosphoric  acid  (Sa/kowsH) ;  cholesterin,  a  glutin-like  body,  inosite,  a  pigment  containing 
iron,  and  even  free  iron  oxide  (A'asse).  The  ash  is  rich  in  phosphoric  acid  and  iron — poor  irt 
chlorine  compounds.  The  splenic  juice  is  alkaline  in  reaction;  the  specific  gravity  of  the  spleen  = 
1059-1066.     [The  watery  extract  of  the  spleen  contains  a  proteid  combined  with  iron.] 

The  Functions  of  the  spleen  are  obscure,  but  we  know  some  facts  on  which 
to  form  a  theory.  [The  spleen  differs  from  other  organs  in  that  no  very  apparent 
effect  is  produced  by  it,  so  that  we  must  determine  its  uses  in  the  economy  from 
a  consideration  of  such  facts  as  the  following:  (i)  The  effects  of  its  removal  or 
extirpation.  (2)  The  changes  which  the  blood  undergoes  as  it  passes  through  it. 
(3)  Its  chemical  composition.  (4)  The  results  of  experiments  upon  it.  (5)  The 
effects  of  diseases.] 

(i )  Extirpation. — The  spleen  may  be  removed  from  an  animal — old  or  young 
— without  the  organism  suffering  any  very  obvious  change  (Galen').  The  human 
spleen  has  been  successfully  removed  by  Kol'trlc,  Fia/i,  Zacaralla  (iS^ip),  CreJe 
and  others.  As  a  result  (compensatory?),  the  lymphatic  glands  enlarge,  but  not 
constantly,  while  the  blood-forming  activity  of  the  red  marrow  of  bone  is  in- 
creased. Small  brownish-red  patches  were  observed  in  the  intestines  of  frogs 
after  extirpation  of  the  spleen.  These  new  formations  are  regarded  by  some 
observers  as  compensatory  organs.  Tizzoni  asserts  that  new  splenic  structures  are 
formed  in  the  omentum  (horse,  dog)  after  the  destruction  of  the  parenchyma  and 
blood  vessels  of  the  spleen.  The  spleen  is  absent  extremely  seldom  (Meinhard, 
Koch  and  IVachsmuth). 

[The  weight  of  the  animal  (dog)  diminishes  after  the  operation,  but  afterward  increases.  The 
number  of  red  blood  corpuscles  is  lessened,  reaching  its  minimum  about  the  150th  to  the  200th 
day,  while  that  of  the  colorless  corpuscles  is  greater.  The  lymphatic  glands  (especially  the  internal, 
and  those  in  the  neck,  mesentery  and  groin)  enlarge,  while,  on  section,  the  cortical  substance  of 
these  structures  is  redder,  owing  to  the  great  number  of  red  corpuscles,  many  nucleated  (Gibson), 
in  the  lymph  spaces.  The  marrow  of  all  the  long  bones  (those  of  the  foot  excepted)  becomes  very 
red  and  soft,  with  the  characters  of  embryonic  bone  marrow.  .Such  animals  withstand  hemorrhage 
(to  j/j  of  the  total  amount  of  blood)  without  any  specially  bad  resuhs  (TizMiii,  Il'mograi/ow), 
•Schindeler  observed  that  animals,  after  extirpation  of  the  spleen,  became  very  ravenous.] 

Schiff  stated,  that  after  extirpation  of  the  spleen,  the  pancreatic  juice  failed  to  digest  proteids. 
The  evidence  in  support  of  this  statement  is  unsatisfactory,  and  Mosler  affirms  that  this  operation 
has  no  effect  either  on  gastric  or  pancre.atic  digestion.  Heidenhain  also  found  a  similar  negative 
result.     The  operation  ought  to  be  performed  on  young  animals,  as  old  animals  often  succumb  to  it. 

[Regeneration. — Aher  entire  removal  of  the  spleen,  nodules  of  splenic  tissue  are  reproduced 
I  fox),  while  new  adenoid  tissue  is  formed  in  the  lymphatic  glands  and  in  Peyer's  patches,  the  paren- 
chyma of  the  former  coming  to  resemble  splenic  tissue  (  Tizzoni,  Jifcrnod).'] 

(2)  According  to  Gerlach  and  Funke,  the  spleen  is  a  blood-forming  gland. 
As  already  mentioned,  the  blood  of  the  splenic  vein  contains  far  more  colorless 
corpuscles  than   the  blood  of  the  splenic  artery  (p.  31).     Many  of  these  corpus- 


CONTRACTION   OF   THE    SPLEEN.  175 

cles  undergo  fatty  degeneration,  and  disappear  in  the  blood  stream  iVircliow). 
That  colorless  blood  corpuscles  are  formed  within  the  spleen  seems  to  be  proved 
by  the  enormous  number  of  these  corpuscles  which  are  found  in  the  blood 
in  cases  of  hyperplasia  of  the  spleen  or  leuksmia  (^Bennett  {/Sj2),  J'irchtno). 
Bizzozero  and  Salvioli  found  that  several  days  after  severe  hemorrhage,  the 
spleen  became  enlarged,  and  its  parenchyma  contained  numerous  red  nucleated 
hrematoblasts. 

According  to  Schiff,  extirpation  of  the  spleen  has  no  effect,  either  u\)o\\  the  absolute  or  relative 
number  of  colored  or  colorless  corpuscles.  [According  to  Picard  and  Malassez.  there  is  a  tempor- 
ary decrease  in  the  number  of  the  red  corpuscles  and  their  haemoglobin,  and  Gibson  also  finds  a 
primary  decrease  in  the  red  and  an  increase  in  the  number  of  the  white  corpuscles.] 

(3)  Other  observers  {KoHiker  and  Ecker')  regard  the  spleen  as  an  organ  in 
which  colored  blood  corpuscles  are  destroyed,  and  they  consider  the  large 
protoplasmic  cells  containing  pigment  granules  as  a  proof  ot^  this  (p.  28J.  Ac- 
cording to  the  observations  of  von  Kusnetzow,  these  structures  are  merely  lymph 
corpuscles,  which,  in  virtue  of  their  amceboid  movements,  have  entangled  colored 
blood  corpuscles.  [Such  corpuscles  exhibit  similar  properties  when  placed  upon 
a  warm  stage.]  Similar  cells  occur  in  e.xtravasations  of  blood  ( I'irc/nno].  The 
colored  blood  corpuscles  within  the  lymph  cells  gradually  become  disintegrated, 
and  give  rise  to  the  production  of  granules  of  hsmatin  and  other  derivatives  of 
hajmoglobin.  Hence,  the  spleen  contains  more  iron  than  corresponds  to  the 
atnount  of  blood  present  in  it.  When  we  consider  that  the  spleen  contains  a 
large  number  of  extractives  derived  from  the  decomposition  of  proteids,  it  is  very 
probable  that  colored  blood  corpuscles  are  destroyed  in  the  spleen.  Further,  the 
juice  of  the  spleen  contains  salts  similar  to  those  that  occur  in  the  red  blood  cor- 
puscles. 

The  blood  from  the  spleen  is  said  to  have  undergone  other  changes,  but  the  following  statement 
must  be  accepted  with  caution  :  The  blood  of  the  splenic  vein  contains  more  water  and  fibrin ;  its 
red  blood  corpuscles  are  smaller,  brighter,  less  flattened,  more  resistant,  and  do  not  form  rouleaux; 
its  haemoglobin  crystallizes  more  easily,  and  there  is  a  large  proportion  of  O  during  digestion. 

[The  spleen  has  very  direct  relations  to  the  blood  ;  in  it  colored  blood  cor- 
jiuscles  undergo  disintegration,  it  produces  colorless  corpuscles,  and  it  is  said  to 
transform  white  corpuscles  into  red  i^Credc  Gibson).'] 

(4)  Contraction. — In  virtue  of  the  plain  muscular  fibres  in  its  capsule  and 
trabecule,  the  spleen  undergoes  variations  in  its  volume  (A"<V//X'tv).  Stimulation 
of  the  spleen  (J?ud.  IVa^ner,  1S49)  or  its  nerves,  by  cold,  electricity,  quinine, 
eucalyptus,  ergot  of  rye,  and  other  "  splenic  reagents  "  {Mosifr),  causes  it  to 
contract,  whereby  it  becomes  paler,  and  its  surface  may  even  appear  granular. 
After  a  meal,  the  spleen  increases  in  size,  and  it  is  usually  largest  about  five  hours 
after  digestion  has  begun,  /.  e.,  at  a  time  when  the  digestive  organs  have  almost 
finished  their  work,  and  have  again  become  less  vascular.  After  a  time  it  regains 
its  original  volume.  For  this  reason  the  spleen  was  formerly  regarded  as  an  ap- 
paratus for  regulating  the  arnount  of  blood  in  the  digestive  organs.  [The  conges- 
tion of  the  spleen  after  a  meal  is  more  probably  related  to  the  formation  of  new 
colorless  corpuscles  than  to  the  destruction  of  red  corpuscles.  It  maybe,  however, 
that  some  of  the  ])roducts  of  digestion  are  partially  acted  upon  in  the  spleen,  and 
undergo  further  change  in  the  liver.]  There  is  a  relation  between  the  size  of  the 
spleen  and  that  of  the  liver,  for  it  is  found  that  when  the  .spleen  contracts — e.  g., 
by  stimulation  of  its  nerves — the  liver  becomes  enlarged,  as  if  it  were  injected 
with  more  lilood  than  usual  (Drosdow  and  Botschetschkarow). 

[Oncograph. — Botkin.  and  more  recently  Roy,  have  studied  various  condi- 
tions which  affect  the  size  of  the  spleen.  Roy's  observations  are  most  important. 
He  enclosed  the  spleen  of  a  living  animal  (dog)  in  a  box  with  rigid  walls,  and 
filled  with  oil,  after  the  manner  of  the  plethysmograph  (§  loi,  276).  Any  varia- 
tions in  the  size  of  tlie  oriran  caused  a  variation  in  the  amount  of  oil  within  the 


176  INFLUENCE    OF    NERVES   ON   THE    SPLEEN. 

box,  and  these  variations  were  recorded.  This  instrument  Roy  termed  an  "  onco- 
graph "   {ir^xiii,  volume).     The  blood  pressure  was  recorded  at  the  same  time. 

Roy  finds  that  the  circulation  through  the  spleen  is  peculiar,  and  that  it  is  not 
due  to  the  blood  pressure  within  the  arteries,  but  is  carried  on  chiefly  by  a  rhyth- 
mical contraction  of  the  muscular  fibres  of  the  capsule  and  trabecule.  The  spleen 
undergoes  very  regular  rhythmical  contractions  (systole)  and  dilatations  (dias- 
tole). This  alternation  of  systole  and  diastole  may  last  for  hours,  and  the  two 
events  together  occupy  about  one  minute  (Fig.  120).  Changes  in  the  arterial 
blood  pressure  have  comparatively  little  influence  on  the  volume  of  the  spleen. 
The  rhythmical  contractions,  although  modified,  still  go  on  after  section  of  the 
splenic  nerves.  This  would  seem  to  indicate  that  the  spleen  has  an  independent 
(nervous)  mechanism  within  itself,  causing  its  movements.] 

Influence  of  Nerves. — Section  of  the  splenic  nerves  causes  an  increase  in 
the  size  of  the  spleen ;  and  when  the  nerves  at  the  hilum  are  extirpated  it  swells 
and  assumes  a  deep  purple  color.     The  nerves  have  their  centre  in  the  medulla 


Tracing  ol  a  splenic  curve,  reduced  one-halt,  taken  with  the  oncograph.  The  upper  line  with  large  waves  is  the 
splenic  curve,  each  ascent  corresponds  to  .an  increase,  and  each  descent  to  a  diminution  in  the  volume  of  the 
spleen.  I'he  curve  beneath  is  a  blood-pressure  tracing  from  the  carotid  artery.  The  lowest  line  indicates  the 
time,  the  interruptions  of  the  marker  occurring  every  two  seconds.  The  vertical  lines,  a  and  6,  give  the  relative 
positions  of  the  lever  point  of  the  oncograph,  and  of*^  the  point  of  the  recording  style  of  the  kymograph  respect- 
ively {J^oy). 

oblongata,  and  so  far  they  are  comparable  to  vasomotor  nerves.  Stimulation  of 
the  medulla  oblongata,  either  directly  or  by  means  of  asphyxiated  blood,  causes 
contraction  of  the  spleen  [hence,  the  spleen  is  "  small  and  contracted  "  in  death 
from  asphyxia].  The  fibres  proceed  down  the  cord,  and  are  probably  joined  by 
other  fibres  derived  from  ganglion  cells  lying  opposite  the  first  to  the  fourth  cer- 
vical vertebra;,  which  cells  also  act  on  the  spleen.  The  fibres  leave  the  cord  in 
the  dorsal  region,  enter  the  left  splanchnic,  pass  through  the  semilunar  ganglion, 
and  thus  reach  the  splenic  plexus  (Jaschkoiintz).  Stimulation  of  the  peripheral 
ends  of  these  nerves  causes  contraction  of  the  spleen,  and  so  does  cold  applied 
to  the  spleen  directly  or  over  the  region  of  the  organ.  In  this  last  case  the  result 
is  brought  about  reflexly.  Section  or  paralysis  of  these  nerves  causes  dilatation, 
and  so  does  curara  or  continued  narcosis  {Belgak).  [Botkin  found  that  the  appli- 
cation of  the  induced  current  to  the  skin  over  the  spleen,  in  a  case  of  leukremia, 
caused  well-marked  contraction  of  the  spleen  in  all  its  dimensions  ;  the  spleen 
becoming  firmer,  and  its  surface  more  irregular.     The  result  lasted  much  longer 


THE   THYMUS.  177 

than  the  duration  of  the  stimulus.  The  same  occurred  in  a  case  of  enlarged 
lymphatic  glands.  After  a  time  the  organ  began  to  enlarge.  After  every  stimu- 
lation the  number  of  colorless  corpuscles  in  the  blood  increased,  and  the  condi- 
tion of  the  patient  improved.] 

[There  is  a  popular  notion  that  the  spleen  is  influenced  by  the  condition  of  the 
nervous  system.  Botkin  found  that  depressing  emotions  increased  its  size,  while 
exhilarating  ideas  diminished  it.  The  causes  of  these  changes  are  referable  not 
only  to  changes  in  the  amount  of  blood  in  the  spleen,  but  also  to  the  greater  or 
less  degree  of  contraction  of  its  muscular  tissue.  And  it  would  appear  that,  like 
the  small  arteries,  the  muscular  tissue  of  the  spleen  is  in  a  state  of  tonic  con- 
traction. The  size  of  the  spleen  may  be  influenced  reflexly.  Thus,  Tarchan- 
off"  found  that  stimulation  of  the  central  ttwA  of  the  vagus,  when  the  splanchnics 
were  intact,  caused  contraction  of  the  spleen,  while  stimulation  of  the  central 
end  of  the  sciatic  also  caused  contraction,  but  to  a  less  degree.  It  is  quite  cer- 
tain that  all  the  phenomena  are  not  due  to  the  action  of  vasomotor  nerves  on  the 
splenic  blood  vessels.  There  is  a  certain  amount  of  independent  action  of  the 
muscular  fibres  of  the  organ,  and  it  is  not  improbable  that  the  innervation  of  the 
spleen  is  similar  to  the  innervation  of  arteries,  and  that  it  has  a  motor  centre  in 
the  cord  capable  of  being  influenced  reflexly  by  afferent  nerves,  while  it  also  sends 
out  efferent  impulses.] 

[Roy  confirmed  most  of  these  results,  and  found  that  stimulation  of  (i)  the  cen- 
tral end  of  a  sensory  nerve  ;  (2)  of  the  peripheral  ends  of  both  splanchnics  ; 
(3)  of  the  peripheral  ends  of  both  vagi,  caused  contraction  of  the  spleen.  But 
even  after  section  of  the  splanchnics  and  vagi,  stimulation  of  a  sensory  nerve 
still  caused  contraction,  so  that  there  must  be  some  other  channel  as  yet  unknown. 
Bochefontaine  found  that  electrical  stimulation  of  certain  parts  of  the  cortex 
cerebri  produced  contraction  of  the  spleen.]  Sensory  nerves  seem  to  occur  only 
in  the  peritoneum  covering  the  spleen. 

Pressure  on  the  splenic  vein  causes  enlargement  of  the  spleen  (Mosler) ;  hence,  increased 
pressure  in  this  vein  (congestion  of  the  portal  vein,  cessation  of  hemorrhoidal  and  menstrual  dis- 
charges) also  cause  its  enlargement.  \Vith  regard  to  the  action  of  "  splenic  reagents,"  such  as 
quinine,  on  the  contraction  of  the  spleen,  Binz  is  of  opinion  that  this  drug  retards  the  formation 
of  the  colorless  blood  corpuscles,  so  that  its  chief  function  is  interfered  with  and  the  organ  becomes 
less  vascular.  It  is  not  definitely  decided,  however,  whether  it  is  contraction  or  dilatation  of  the 
spleen  that  alters  the  proportion  of  red  and  white  corpuscles  in  the  blood. 

Splenic  Tumors. — The  increase  in  size  of  the  spleen  in  various  diseases  early  attracted  the 
attention  of  physicians.  The  healthy  spleen  undergoes  several  variations  in  volume  during  the 
course  of  a  day,  corresponding  to  the  varying  activity  of  the  digestive  organs.  In  this  respect  the 
spleen  resembles  the  arteries.  In  many  fevers  ihe  spleen  becomes  greatly  enlarged,  probably  due 
to  paralysis  of  its  nerves.  It  is  greatly  increased  in  intermittent  fever  or  ague,  and  often  during  the 
course  of  typhus.  When  it  becomes  abnormally  enlarged,  and  remains  so  after  repeated  attacks  of 
the  ague,  it  is  greatly  hypertrophied  and  constitutes  "  ague  cake."  In  cases  of  splenic  leuksmia 
it  is  greatly  enlarged,  and  at  the  same  time  there  is  a  great  increase  in  the  number  of  colorless  cor- 
puscles in  the  blood  and  also  a  decrease  of  the  colored  ones  [\  10). 

II.  THE  THYMUS. — During  fo?tal  life  this  gland  is  largely  developed,  and  it  increases  during 
the  first  two  or  three  years  of  life,  remaining  stationary  until  the  tenth  or  fourteenth  year,  when  it 
begins  to  atrophy  and  undergo  fatty  degeneration.  [The  degeneration  begins  at  the  outer  part  of 
each  lobule  and  progress  inward  (//«).] 

Structure.  —  ["  It  consists  of  an  aggregation  of  lymph  follicles  (resembling  the  glands  of  Peyer) 
or  masses  of  adenoid  tissue  held  together  by  a  framework  of  connective  tissue  which  contains  blood 
vessels,  lymphatics,  and  a  few  nerves  (Fig.  I2l).  The  framework  of  connective  tissue  gives  off 
septa  which  divide  the  gland  into  lobes,  these  being  further  subdivided  by  finer  septa  into  lobules, 
the  lobules  being  separated  by  fine  intralobular  lamella-  of  connective  tissue  into  follicles  (0.5-1.5 
mm.).  These  follicles  make  up  the  gland  substance,  and  they  are  usually  polygonal  when  seen  in 
a  .section.  Each  foUicle  consists  of  a  cortical  and  a  medullary  part,  and  the  matrix  or  frame- 
work of  both  consists  of  a  fine  adenoid  reticulum  whose  meshes  are  filled  with  lymph  corpuscles  " 
(Kig.  122,  n).]  .Many  of  these  corpuscles  exhibit  various  stages  of  disintegration.  In  the  medulla 
are  found  the  concentric  corpuscles  of  Hassall.  ["  They  consist  of  a  central  granular  part, 
around  which  is  disposed  layers  of  flattened,  nucleated,  endothelial  cells  arranged  concentrically. 
When   seen  in  a  section  they  resemble  the  'cell  nests'  of  epithelioma  (Fig.  122,  h).     They  have 


178 


THE   THYROID. 


also  been  compared  to  similar  bodies  which  occur  in  the  prostate.  They  are  most  numerous  when 
the  gland  undergoes  its  retrograde  metamorphosis."] 

Simon,  His,  and  others  described  a  convoluted  blind  canal,  the  "central  canal,"  as  occurring 
within  the  gland,  and  on  it  the  follicles  were  said  to  be  placed.  Other  observers,  Jendrassik  and 
Klein,  either  deny  its  existence  or  regard  it  merely  as  a  lymphatic  or  an  artificial  product.  Numer- 
ous fine  lymphatics  penetrate  into  the  interior  of  the  organ,  and  many  are  distributed  over  its  sur- 
face, but  their  mode  of  origin  is  unknown.  [They  seem  to  be  channels  through  which  the  lymph 
corpuscles  are  conveyed  away  from  the  gland.]  Numerous  blood  vessels  are  also  distributed  to 
the  septa  and  follicles  (Fig.  121,  c). 

Chemical  Composition. — Besides  gelatin,  albumin,  soda  albumin,  there  are  sugar  and  fat, 
leuchin,  xanthin,  hypoxanthin,  formic,  acetic,  butyric,  and  succinic  acids.  Potash  and  phosphoric 
acid  are  more  abundant  in  the  as/i  than  soda,  calcium,  magnesium  (?  ammonium),  chlorine,  and 
sulphuric  acid  (7'.  Gorup-Besanez). 

Function. — As  long  as  it  exists,  it  seems  to  perform  the  functions  of  a  true  lymph  gland.  This 
view  is  supported  by  the  fact  that  in  reptiles  and  amphibians,  which  do  not  possess  lymph  glands, 
the  thymus  remains  as  a  permanently  active  organ.  That  the  thymus  forms  colorless  corpuscles  was 
hrst  maintained  by  Hewson,  and  confirmed  by  His  and  Jendrassik.  [Extirpation  (Frieiile/ien) 
gave  few  positive  resuUs,  but  chemical  investigation  shows  that  the  parenchyma  contains  a  large 
number  of  products  indicating  considerable  metabolic  activity.  The  volume  of  the  gland  undergoes 
variations  both  in  health  and  disease.]  • 


:tion  of  the  thymus  gland  of  a  cat,  showing  on 
complete  lobule  with  an  outer  cortical  part, 
centre,  <5,  and  parts  of  adjoining  lobules,  a 
lymphoid  tissue  ;  c,  blood  vessels  injected  ;  i 
connective  tissue. 


Elements  of  the  thymus  (  X  300).  a, 
lymph  corpuscles  ;  ^,  concentric 
corpuscle  of  Hassall. 


III.  THE  THYROID. — Structure. — In  a  connective-tissue  network  rich  in  cells  there  lie 
numerous  completely  closed  sacs  (0.0410  o.  i  mm.  in  diameter),  which  in  the  embryo  and  the 
newly-born  aniinal  are  composed  of  a  membrana  propria  lined  by  a  single  layer  of  nucleated  cubi- 
cal cells  (Fig.  123).  The  sacs  contain  a  transparent,  viscid,  albuminous  fluid.  [Not  unfrequently 
the  sacs  contain  many  colored  blood  corpuscles  (£a/>ei).  As  in  other  glands  there  are  lobes  and 
lobules.]  Each  sac  is  surrounded  by  a  plexus  of  capillaries  which  do  not  penetrate  the  membrana 
propria.  There  are  also  numerous  lymphatics.  -At  an  early  period  the  sacs  dilate,  their  cellular 
lining  atrophies,  and  their  contents  undergo  colloid  degeneration.  When  the  gland  vesicles  are 
greatly  enlarged  "  goitre  "  is  produced. 

The  Chemical  Composition  of  this  gland  has  not  been  much  investigated.  In  addition  to  the 
ordinary  constituents,  leucin,  xanthin,  sarkin,  lactic,  succinic,  and  volatile  fatty  acids  have  been 
found. 

[Excision. — The  effects  differ,  according  to  the  animal  operated  on.  Thisgland  has  been  excised 
in  the  human  subject  in  cases  of  goitre.  Reverdin  pointed  out  that  a  peculiar  condition  resulted, 
called  Cachexia  stumipriva,  and  practically  the  human  being  becomes  a  cretin.  This  operation, 
therefore,  is  highly  questionable  when  performed  on  man  (A'ochc-r).  Rabbits  endure  the  operation 
well.  Of  dogs,  only  a  very  small  number  survive,  nearly  all  die.  The  immediate  effects  are  fibril- 
lar contractions,  which  ultimately  influence  the  gait  of  the  animals,  convulsions,  aniesthesia,  great 
diminution  of  sensibility,  loss  of  flesh,  redness  of  the  ears  and  intense  heat  of  the  skin  (which  dis- 
appear after  several  days),  difficulty  in  seizing  and  eating  food,  kerato-conjunctivitis,  and  frequently 
disturbance  of  the  rhythm  of  respiration  with  dyspncea  and  spasms  of  the  abdominal  muscles  [^Scliiff^ 


THE    THYROID. 


179 


Zesas,J.  IViigner).  The  arterial  blood  contains  about  the  same  amount  of  O  as  venous  blood. 
Certain  parts  of  the  peripheral  nerves  undergo  a  kind  of  degeneration  similar  to  that  found  after 
nerve  stretching.  There  is  albuminuria  and  fall  of  the  blood  pressure  (Albertotii  and  Tizzoni). 
There  is  a  great  tendency  for  the  animal  to  run  backward.  Death  usually  occurs  between  the 
third  and  fourth  day,  the  animals  being  comatose  (  Wagner).  Schiff  found  that  if  one-half  of 
the  gland  was  excised  at  once,  and  the  other  half  a  month  afterward,  death  did  not  occur ;  but 
Wagner  denies  this,  for  he  asserts  that  the  remaining  half  hypertrophies,  and  if  it  be  excised 
d'eaih  occurs,  with  the  usual  symptoms.  In  monkeys,  five  days  after  the  operation,  there  are 
symptoms  of  nervous  disturbance.  The  animals  have  lost  their  appetite,  there  are  fibrillar  con- 
tractions of  the  muscles  of  the  face,  hands,  and  feet,  but  the  tremors  disappear  on  voluntary  efibrt. 
The  appetite  returns  and  is  increased,  but  notwithstanding,  the  animal  grows  thin  and  pale;  while 
the  tremors  increase  and  affect  all  the  muscles  of  the  body.  These  tremors  are  of  central  origin, 
because  they  disappear  on  dividing  the  nerve.  Thus  there  is  profound  alteration  of  the  motor 
powers.  Among  the  outward  symptoms  are  puffiness  of  the  eyelids,  swelling  of  the  abdomen, 
increased  hebetude,  and  dyspncea,  while  afterward  there  is  a  fall  of  the  temperature  and  imbecility; 
the  tremors  disappear,  there  is  a  pallor  of  the  skin,  and  ultimately,  after  five  to  seven  weeks,  the 
animals  die  in  a  comatose  state.  Thus  there  is  a  slow  onset  of  hebetude,  terminating  in  imbecility. 
Very   remarkable    changes   occur   in   the   blood.     There   is  a  steady  fall  of  the  blood  pressure, 

Fig.  123. 


■7:^^r-'e^i&/  .'i^W 


oligemia  (diminution  of  the  red  blood  corpuscles)  or  rather  profound  ansmia,  leucocythsmia 
or  leucocylosis,  the  colorless  corpuscles  being  increased  to  the  ratio  of  four  to  fourteen,  and 
lastly  mucin  is  present  in  the  blood,  although  normally  it  is  not  so.  The  salivary  glands 
are  hypertrophied,  owing  to  the  presence  of  mucin,  which  is  found  even  in  the  parotid, 
although  this  is  normally  a  serous  gland  (J  141  )•  The  swelling  of  the  abdomen  is  due  to 
hypertrophy  of  the  great  omentum.  Mucin  is  found  in  the  peritoneal  fluid,  and  the  spleen 
is  also  enlarged.  Thus  these  symptoms  present  many  features  in  common  with  those  of 
Myxoedena  described  by  Ord  {v.  Norsley).'] 

[Stages. — Horsley  distinguishes  three  stages.  The  first  or  neurotic  exhibits  constant  tremors, 
S  per  second,  and  young  animals  do  not  appear  to  survive  this  stage.  In  the  second  or  mucinoid 
stage,  mucin  is  deposited  in  the  tissues  and  blood;  this  change,  however,  is  only  seen  to  perfection 
in  monkeys.  If  these  animals  be  kept  at  a  high  artificial  temperature,  their  life  is  considerably 
prolonged.  In  the  third  atrophic  or  marasmic  period,  the  animals  die  of  marasmus,  while  they 
lose  their  excess  of  mucin.  Age  seems  to  exert  an  important  influence  in  thyroidectomy ;  young 
dogs  survive  but  a  short  time,  while  old  dogs  merely  exhibit  symptoms  of  indolence  and  incapacity  ; 
and  as  a  matter  of  fact,  the  activity  of  the  gland  seems  to  be  most  active  when  tissue  metabolism  is 
most  active.] 

[The  following  table,  after  Horsley,  indicates  the  symptoms  that  follow  : — 


180 


THE    SUPRARENAL   CAPSULES. 
Loss  of  the  Function  of  the  Thyroid  Gland. 


Stages. 

Duration. 

Symptoms. 

Remarks. 

L  Neurotic. 

I  to  2  weeks  in 
dogs;     I    t  0  3 
weeks   in    mon- 
keys. 

A   to  I    w  e  e  k  i  n 
dogs;    3   to   7 
weeks    in    mon- 
keys. 

Tremo  rs,  rigid  ity , 
dyspnoea. 

Young  dogs  and  monkeys 
alike  die  in  this  stage. 

IL  Mucinoid. 

Commencing  hebetude 
and  mucinoid  degen- 
eration of  the  connec- 
tive tissues. 

Dogs  survive  only  to  the 
beginning  of  this  stage ; 
monkeys  die  at  the  end, 
if  not  treated. 

in.  Atrophic. 

5  1 0  8  w  e  e  k  s  in 
monkeys. 

Complete  imbecility  and 
atrophy  of  all  tissues, 
especially  muscles. 

Monkeys  survive  accord- 
ing to  the  temperature 
of  the  air-bath. 

Fin    ,,_i. 


Functions The  functions  of  the  thyroid  gland  are  very  obscure.      Perhaps  it  may  be  an 

apparatus  for  regulating  the  blood  supply  to  the  head  (?).  It  becomes  enlarged  in  Basedow's 
disease,  in  which  there  is  great  palpitation  as  well  as  protrusion  of  the  eyeball  [Exophthalmos], 
which  seem  to  depend  upon  a  simultaneous  stimulation  of  the  accelerating  nerve  of  the  heart,  and 
the  sympathetic  fibres  for  the  smooth  muscles  in  the  orbital  cavity  and  the  eyelids,  as  well  as  of  the 
inhibitory  fibres  of  the  vessels  of  the  thyroid.  In  many  localities  it  is  common  to  find  swelling  of 
the  thyroid  constituting  goitre,  which  is  sometimes,  but  far  from  invariably,  associated  with  idiocy 
and  cretinism.  [Horsley  finds  that  its  removal  is  the  essential  cause  of  myxredena  and  cretinism. 
He  regards  it  (i)  as  a  blood-forming  gland,  so  that  it  has  a  ha^mapoietic  function,  but  Gibson 
finds  no  grounds  for  supporting  this  view.  During  the  anremia  resulting  from  its  removal,  the  blood 
of  the  thyroid  vein  contains  7  per  cent,  more  red  blood  corpuscles  than  the  corresponding  artery 
{Horsley).  (2)  It  seems  to  regulate  the  formation  of  mucin  in  the  body.  After  its  removal  the 
norma]  metabolism  is  no  longer  maintained, and  there  is  a 
corresponding  increasingly  defective  condition  of  nutrition.] 
Ill  the  Tunicata,  this  gland,  represented  by  a  groove, 
seireles  a  digestive  fluid.  In  vertebrates,  it  is  an  organ 
which  has  undergone  a  retrograde  change  (Gegenhaur). 

IV.  THE  SUPRARENAL  CAPSULES.— 
Structure. — These  organs  are  invested  by  a  thin  cap- 
sule which  sends  processes  into  the  interior  of  the  organ. 
They  consist  of  an  outer  (broad)  or  cortical  layer  and  an 
inner  (narrow)  or  medullary  layer.  The  former  is  yellow- 
ish in  color,  firm  and  striated,  while  the  latter  is  softer 
and  deeper  in  tint.  In  the  outermost  zone  of  the  cortex 
(Fig.  124,  b),  the  tiabeculx-  form  polygonal  meshes, 
whicli  contain  (he  cells  of  the  gland  substance ;  in  the 
broader  middle  zone  the  meshes  are  elongated,  and  the 
cells  filling  them  are  arranged  in  columns  radiating  out- 
ward. Here  the  cells  are  transparent  and  nucleated,  often 
containing  oil  globules;  in  the  innermost  narrow  zone  the 
polygonal  arrangement  prevails,  antl  the  cells  often  contain 
yellowish-brown  pigment.  In  the  medulla  [c)  the  stroma 
forms  a  reticulum  containing  groups  of  cells  of  very  irreg- 
ular shape.  Numerous  blood  vessels  occur  in  the  gland, 
especially  in  the  cortex.  [The  nerves  are  extremely 
numerous,  and  are  derived  from  the  renal  and  solar 
plexuses.  Many  of  the  fibres  are  medullated.  After 
they  enter  the  gland,  numerous  ganglionic  cells  occur  in 
the  plexuses  which  they  form.  Indeed,  some  observers 
regard  the  cells  of  the  medulla  as  nervous.  Undoubtedly, 
numerous  7nifltipolar  }ierve  cells  exist  within  the  gland.] — • 
{Eberth,  Creiq/itoit.  v.  Bninn). 

Chemical    Composition. — The   suprarenals   contain 
the  constituents  of  connective  tissue  and    nerve  tissue  ; 
also  leucin,  hypoxanthin,  benzoic,  hippuric,  and   tauro- 
lion  of  a  human  suprarenal  capsule.  «,  cap-  cliolic  acids,  taurin,  inosit,  fats,  and  a  body  which  becomes 
sule;/.,  gland  cells  of  the  cortex  arranged  in  pigmented    bv  oxidation.      Among  inorganic  substances 
columns;  c,  glandular  network  of  the  me-    ^  ^     ,  ,     ,'        ,       ■  ■  1  ,         , 

dulla  :  d,  blood  vessels.  potash  and  phosphoric  acid  are  most  abundant. 


HYPOPHYSIS   CEREBRI.  181 

The  function  of  the  suprarenal  body  is  very  obscure.  It  is  noticeable,  however,  that  in  Addi- 
son's disease  ("bronzed  skin"),  which  is  perhaps  primarily  a  nervous  affection,  these  glands 
have  frequenlly,  but  not  invariably,  been  found  to  be  diseased.  Owing  to  the  injury  to  adjacent 
abdominal  organs  extirpation  of  these  organs  is  often,  although  not  always,  fatal;  in  dogs  pig- 
mented patches  have  been  found  in  the  skin  near  the  mouth.  Brown  Sequard  thinks  they  may  be 
concerned  in  preventing  the  over-production  of  pigment  in  the  blood. 

.[Spectrum. — MacMunn  finds  that  the  medulla  of  the  suprarenal  bodies  (in  man,  cat,  dog, 
guinea  pig,  rat,  etc.)  gives  the  spectrum  of  htemochromogen  (?  iS),  while  the  co'^tex  shows  that  of 
what  he  calls  histohaematin,  the  latter  being  a  group  of  respiratory  pigments.  He  finds  that  hre- 
mochromogen  is  only  found  in  excretory  organs  (the  bile,  the  liver) ;  hence,  he  regards  the  medulla 
as  excretory,  so  that  part  of  the  function  of  the  adrenals  may  be  "to  metamorphose  effete  hoemo- 
globin  or  ha^matin  into  hsemachromogen,"  and  when  they  are  diseased,  the  effete  pigment  is  not 
removed ;  hence,  the  pigmentation  of  the  skin  and  mucous  membranes.  Taurocholic  acid  has  been 
found  in  the  medulla  (  Vulpinn).  MacMunn  believes  that  "  they  have  a  large  share  in  the  down- 
ward metamorphosis  of  coloring  matter."  Krukenberg  regards  the  pigment  as  a  pyrocatechin 
compound.] 

V.    HYPOPHYSIS  CEREBRI— COCCYGEAL  AND    CAROTID   GLANDS.— The 

hypophysis  cerebri,  or  pituitary  body,  consists  of  an  anterior  lower  or  larger  lobe,  partly  em- 
bracing the  posterior  lower  or  smaller  lobe.  These  two  lobes  are  distinct  in  their  structure  and 
development.  The  posterior  lobe  is  a  part  of  the  brain,  and  belongs  to  the  infundibulum.  The 
nervous  elements  are  displaced  by  the  ingrowth  of  connective  tissue  ann  blood  vessels.  The 
anterior  portion  represents  an  inflected  and  much  altered  portion  of  ectoderm,  from  which  it  is 
developed.  It  contains  gland-like  structures,  with  connective  tissue,  lymphatics  and  blood  vessels, 
the  whole  being  surrounded  by  a  capsule.  According  to  Ecker  and  Mihalkowicz,  it  resembles  the 
suprarenal  capsule  in  its  structure,  while,  according  to  other  observers,  in  some  animals  it  is  more 
like  the  thyroid.     Its  functions  are  entirely  unknown. 

[Excision. — Ilorsley  has  removed  this  gland  twice  successfully  in  dogs,  which  lived  from  five  to 
six  months.  No  nervous  or  other  symptoms  were  noticed,  but  when  the  cortex  of  the  brain  was 
exposed  and  stimulated,  a  great  increase  in  the  excitability  of  the  motor  regions  was  induced,  even 
slight  stimulation  being  followed  liy  violent  tetanus  and  prolonged  epilepsy.] 

Coccygeal  and  Carotid  Glands. — The  fonner,  which  lies  on  the  tip  of  the  coccyx,  is  composed, 
to  a  large  extent,  of  plexuses  of  small,  more  or  less  cavernous  arteries,  supported  and  enclosed  by 
septa  and  a  capsule  of  connective  tissue  (Z«i(7(/f«).  Between  these  lie  polyhedral  granular  cells, 
arranged  in  networks.  The  carotid  gland  (Fig.  45)  has  a  similar  structure  (p.  114).  Their  func- 
tions are  quite  unknown.  Perhaps  both  organs  may  be  regarded  as  the  remains  of  embryonal  blood 
vessels  (AriiolJ). 

104.  COMPARATIVE. — The  heart  in  fishes,  as  well  as  in  the  larva;  of  amphibians  with 
gills,  is  a  simple  venous  heart,  consisting  of  an  auricle  and  a  ventricle.  The  ventricle  propels  the 
blood  to  the  gills,  where  it  is  oxygenated  (arterialized) ;  thence  it  passes  into  the  aorta,  to  be  dis- 
tributed to  all  parts  of  the  body,  and  returns,  through  the  capillaries  of  the  body  and  the  veins,  to 
the  heart.  The  amphibians  (frogs)  have  two  auricles  and  one  ventricle.  From  the  latter  there 
proceeds  one  vessel  which  gives  off  the  pulmonary  arteries,  and  as  the  aorta  supphes  the  rest  of  the 
body  with  blood,  the  veins  of  the  systemic  circulation  carry  their  blood  to  the  right  auricle ;  those  of 
the  lung  into  the  left  auricle.  In  fishes  and  amphibians  there  is  a  dilatation  at  the  commencement 
of  the  aorta,  the  bulbus  arteriosus,  which  is  partly  provided  with  strong  muscles.  The  reptiles 
possess  two  separate  auricles  and  two  imperfectly-separated  ventricles.  The  aorta  and  pulmonary 
artery  arise  separately  from  the  two  latter  chambers.  The  venous  blooil  of  the  systemic  and  pulmo- 
nary circulations  flows  separately  into  tile  right  and  left  auricles,  and  the  two  streams  are  mixed  in 
the  ventricle.  In  some  reptiles,  the  opening  in  the  ventricular  septum  seems  capable  of  being  closed. 
The  crocodile  has  two  quite  separate  ventricles.  The  lower  vertebrates  have  valves  at  the  orifices 
of  the  vena;  cavK,  which  are  rudimentary  in  birds  and  some  mammals.  All  birds  and  mammals 
have  two  completely  separate  auricles  and  two  separate  ventricles.  In  the  halicore,  the  apex  of  the 
ventricles  is  deeply  cleft.  Some  animals  have  accessory  hearts, if .^., the  eel,  in  its  caudal  vein.  They 
are.  very  probably,  lymph  hearts  (A'oiin).  The  veins  of  the  wing  of  the  bat  pulsate  (Se/iiff).  The 
lowest  vertebrate,  amphioxus,  has  no  heart,  but  only  a  rhythmically-contracting  vessel. 

Among  blood  glands,  the  thymus  and  spleen  occur  throughout  the  vertebrata,  the  latter  being 
absent  only  in  amphioxus  and  a  few  fishes. 

Among  invertebrata  a  closed  vascular  system,  with  pulsatile  movement,  occurs  here  and  there, 
e,g.,  among  cchinodermata  (star  fishes,  sea  urchins,  holothurians)  and  the  higher  worms.  The 
insects  have  a  pulsating  "-dorsal  vessel"  as  the  central  organ  of  the  circulation,  which  is  a  con- 
tractile tube  provided  with  valves  and  dilated  by  muscular  action,  the  blood  being  propelled  rhythmi- 
cally in  one  direction  into  the  spaces  which  lie  among  the  tissues  and  organs,  so  that  these  animals 
do  not  possess  a  closed  vascular  system.  The  moUusca  have  a  heart,  with  a  lacunar  vascular 
system.  The  cephalopods  (cuttle  fish)  have  three  hearts — a  simple  arterial  heart  and  two  venous 
simple  gill  hearts,  each  placed  at  the  base  of  the  gills.     The  vessels  form  a  completely  closed  circuit. 


182  HISTORICAL    RETROSPECT   OF   THE    CIRCULATION. 

The  Imvest  animals  have  either  a  pulsatile  vesicle,  which  propels  the  colorless  juice  into  the  tissues 
(infusoria),  or  the  vascular  apparatus  may  be  entirely  absent. 

105.  HISTORICAL  RETROSPECT.— The  ancients  held  various  theories  regarding  the 
movement  of  the  blood,  but  they  knew  nothing  of  its  circulation.  According  to  Aristotle  (384  I!,  c), 
the  heart,  the  acropolis  of  the  boily,  prepared  in  its  cavities  the  blood,  which  streamed  through  the 
arteries  as  a  nutrient  fluid  to  all  parts  of  the  body,  but  never  returned  to  the  heart. 

With  Herophilus  and  Erasistratus  (300  B.c),lhe  celebrated  physicians  of  the  Alexandrian  school, 
originated  the  erroneous  view  that  the  arteries  contain  air,  which  was  supplied  to  them  by  the  respi- 
ration (hence  the  name  artery').  They  were  led  to  adopt  this  view  from  the  empty  condition  of  the 
arteries  after  death.  By  experiments  upon  animals,  Galen  disproved  this  view  (131-201  a.d.) — 
"  Whenever  I  injured  an  arterj-,"  he  says,  •'  blood  always  flowed  from  the  wounded  vessel.  On  tying 
part  of  an  artery  between  two  ligatures,  the  part  of  the  artery  so  included  is  always  filled  with 
blood." 

Still,  the  idea  of  a  single  centrifugal  movement  of  the  blood  was  retained,  and  it  was  assumed 
that  the  right  and  left  sides  of  the  heart  communicated  directly,  by  means  of  openings  in  the  septum 
of  the  heart,  until  Vesalius  showed  that  there  are  no  openings  in  the  septum.  Michael  Servetus 
(the  Spanish  monk,  burned  at  Geneva,  at  Calvin's  instigation,  in  1553)  discovered  the  pulmonary 
circulation.  Cesalpinus  confirmed  this  observation,  and  named  it  "  Circulatio."  Fabricius  ab  Aqua- 
pendente  (Padua,  1574)  investigated  the  valves  in  the  veins  more  carefully  (although  they  were 
known  in  the  fifth  century  to  Theodoretus,  Bishop  in  .Syria),  and  he  was  acquainted  with  the  cen- 
tripetal movement  of  the  blood  in  the  veins.  Up  to  this  time,  it  was  imagined  that  the  veins  carried 
blood  from  the  centre  to  the  peripherv-,  although  Vesalius  was  acquainted  with  the  centripetal  direc- 
tion of  the  blood  stream  in  the  large  venous  trunks.  At  length,  William  Harvey,  who  was  a 
pupil  of  Fabricius  (1604),  demonstrated  the  complete  circulation  (1616-1619),  and  published  his 
great  discovery  in  162S.  [For  the  history  of  the  discovery  of  the  circulation  of  the  blood,  see  the 
works  of  Willis  on  "  W.  Harvey,"  ''Servetus  and  Calvin,"  those  of  Kirchner,  and  the  v.irious 
Harveian  orations  ] 

According  to  Hippocrates,  the  heart  is  the  origin  of  all  the  vessels;  he  was  acquainted  with  the 
large  vessels  arising  from  the  heart,  the  valves,  the  chordce  tendinea?,  the  auricles,  and  the  closure 
of  the  semilunar  valves.  Aristotle  was  the  first  to  apply  the  terms  aorta  and  venje  cava" ;  the  school 
of  Erasistratus  used  the  term  carotid,  and  indicated  the  functions  of  the  venous  valves.  In  Cicero  a 
distinction  is  drawn  between  arteries  and  veins.  Celsus  mentions  that  if  a  vein  be  struck  below  the 
spot  where  a  ligature  has  been  applied  to  a  limb,  it  bleeds,  while  Aretaeus  (50  A.  D. )  knew  that 
arterial  blood  was  bright  and  venous  dark.  Pliny  (f  79  A.  D.)  described  the  pulsating  fontanelle  in 
the  child.  Galen  (131-203  A.  D.)  was  acquainted  with  the  existence  of  a  bone  in  the  septum  of 
the  heart  of  large  animals  (ox,  deer,  elephant).  He  also  surmised  that  the  veins  communicated 
with  the  arteries  by  fine  tubes.  The  demonstration  of  the  capillaries,  however,  was  only  possible 
by  the  use  of  the  microscope,  and  employing  this  instrument,  Malpighi  (1661)  was  the  first  to 
demonstrate  the  cajiillary  circulation.  Leuwenhoek  (1674)  described  the  capillary  circulation  more 
carefully,  as  it  may  be  seen  in  the  web  of  the  frog's  foot  and  other  transparent  membranes.  Blan- 
card  (1676)  proved  the  existence  of  capillary  passages  by  means  of  injections.  William  Cooper 
(1697)  proved  that  the  same  condition  exists  in  warm-blooded  animals,  and  Ruysch  made  similar 
injections.  Stenson  (born  163S)  established  the  muscular  nature  of  the  heart,  although  the  Hippo- 
cratic  and  Alexandrian  schools  had  already  surmised  the  fact.  Cole  proved  that  the  sectional  area 
of  the  blood  stream  became  wider  toward  the  capillaries  (16S1).  Joh.  Alfons  Borelli  (160S-1679) 
was  the  first  to  estimate  the  amount  of  work  done  by  the  heart. 


Physiology  of  Respiration. 


The  object  of  respiration  is  to  supply  the  oxygen  necessary  for  the  oxidation 
processes  that  go  on  in  the  body,  as  well  as  to  remove  the  carbonic  acid  formed 
within  the  body.  The  most  important  organs  for.  this  purpose  are  the  lungs. 
There  is  an  outer  and  an  inner  respiration — the  former  embraces  the  exchange 
of  gases  between  the  external  air  and  the  blood  gases  of  the  respiratory  organs 
(lungs  and  skin) — the  latter,  the  exchange  of  gases  between  the  blood  in  the  ca- 
pillaries of  the  systemic  circulation  and  the  tissues  of  the  body. 

[The  pulmonary  apparatus  consists  of  (i)  an  immense  number  of  small  sacs — 
the  air  vesicles  filled  with  air,  and  covered  externally  by  a  very  dense  plexus  of 
capillaries;  (2)  air  passages — the  nose,  pharynx,  larynx,  trachea,  and  bronchi 
communicating  with  (i)  ;  (3)  the  thorax  with  its  muscles,  acting  like  a  pair  of 
bellows,  and  moving  the  air  within  the  lungs.] 

106.  STRUCTURE  OF  THE  AIR  PASSAGES  AND  LUNGS.— The  lungs  are  com- 
pound tubular  (racemose  ?)  glauds,  which  separate  CO2  from  the  blood.  Each  lung  is  provided 
with  an  excretory  duct  (bronchus)  which  joins  the  common  respiratory  passage  of  both  lungs — the 
trachea. 

Trachea. — The  trachea  and  extra-pulmonary  bronchi  are  similar  in  structure.  The  basis  of  the 
trachea  consists  of  a  number  (16-20)  of  Q -shaped,  incomplete  cartilaginous  hoops  placed  over  each 
other.  These  rings  consist  of  hyaline  cartilage,  and  are  united  to  each  other  by  means  of  tough, 
fibrous  tissue  containing  much  elastic  tissue,  the  latter  being  arranged  chiefly  in  a  longitudinal  direc- 
tion. The  function  of  the  cartilages  is  to  keep  the  tube  open  under  varying  conditions  of  pres- 
sure. Pieces  of  cartilage  having  a  similar  function  occur  in  the  bronchi  and  their  branches,  but 
they  are  absent  from  the  bronchioles,  which  are  less  than  i  mm.  in  diameter.  In  the  smaller  bronchi 
the  cartdages  are  fewer  and  scattered  more  irregularly.  [In  a  transverse  section  of  a  large  intra- 
pulmonary  bronchus,  two,  three,  or  more  pieces  of  cartilage,  each  invested  by  its  perichondrium, 
may  be  found.]  At  the  points  where  the  bronchi  subdivide,  the  cartilages  assume  the  form  of  ir- 
regular plates  embedded  in  the  bronchial  wall. 

An  external  fibrous  layer  of  connective  tissue  and  elastic  fibres  covers  the  trachea  and  the  extra- 
pulmonary bronchi  externally.  Toward  the  oesophagus,  the  elastic  elements  are  more  numerous, 
and  there  are  also  a  few  bundles  of  plain  muscular  fibres  arranged  longitudinally.  Within  this  layer 
there  are  bundles  of  non-striped  miistiilar  fibres  which  pass  transversely  between  the  cartilages 
behind,  and  also  in  the  intervals  between  the  cartilages.  [These  pale  reddish  fibres  constitute  the 
trachealis  muscle,  and  are  attached  to  the  inner  surfaces  of  the  cartilages  by  means  of  elastic 
tendons  at  a  little  distance  from  their  free  ends  [Aliinniks,  1697).  The  arrangement  varies  in  dif- 
ferent animals— thus,  in  the  cat,  dog,  rabbit,  and  rat  the  muscular  fibres  are  attached  to  the  external 
surfaces  of  the  cartilages,  while  in  the  pig,  sheep,  and  ox  they  are  attached  to  their  internal  sur- 
faces (Stirling).}  .Some  muscular  fibres  are  arranged  longitudinally  external  to  the  transverse  fibres 
{Kramer).  The  function  of  these  muscular  fibres  is  to  prevent  too  great  distention  when  there  is 
great  pressure  within  the  air  passages. 

The  mucous  membrane  consists  of  a  basis  of  very  fine  connective  tissue,  containing  mvtch 
adenoid  tissue  with  numerous  lymph  corpuscles.  It  also  contains  numerous  elastic  fibres,  arranged 
chiefly  in  a  longitudinal  direction  under  the  basement  membrane.  They  are  also  abundant  in  the 
deep  layers  of  the  posterior  part  of  the  membrane  oppo-ite  the  intervals  between  the  cartilage^.  .\ 
small  quantity  of  loose  subtrucous  connective  tissue  containing  the  large  blood  vessels,  glands  and 
lymphatics  unites  the  mucous  membrane  to  the  perichondrium  of  the  cartilages.  The  epithelium 
consists  of  a  layer  of  columnar  ciliated  cells  with  several  layers  of  immature  cells  under  them. 
[The  superficial  layer  of  cells  is  columnar  and  ciliated  (Fig.  125,  li),  while  those  lying  under  them 
present  a  variety  of  forms,  and  below  all  is  a  layer  of  somewhat  flattened  squames,  ^,  resting  on  the 
basement  membrane,  d.  These  squames  constitute  a  layer  quite  distinct  from  the  basement  mem- 
brane, and  they  form  the  layer  described  as  Debove's  membrane.  They  are  active  germinating 
cells,  and  play  a  most  important  part  in  connection  with  the  regeneration  of  the  epithelium,  after 
the  superficial  layers  have  been  shed,  in  such  conditions  as  bronchitis  (y.  Drasch,  Hamilton).    Not 

183 


184 


STRUCTURE    OF   THE    TRACHEA. 


unfrequemly  a  little  viscid  mucus  {a)  lies  on  the  free  ends  of  the  cilia.  In  the  intermediate  layer, 
the  cells  are  more  or  less  pyriform  or  battledore-shaped  \Haniilto7i),  with  their  long,  tapering  pro- 
cess inserted  among  the  deepest  layer  of  squames.  According  to  Drasch,  this  long  process  is 
attached  to  one  of  these  cells  and  is  an  outgrowth  from  it,  the  whole  constituting  a  "  foot  cell."] 

Underneath  the  epithelial  is  the  homogeneous  basement  membrane,  through  which  fine  canals 
pass,  connecting  the  cement  of  the  epithelium  with  spaces  in  the  mucosa.  [This  membrane  is  well 
marked  in  the  human  trachea,  where  it  plays  an  important  part  in  many  pathological  conditions, 
('.  g.,  bronchitis.  It  is  stained  bright  red  with  picrocarmine.]  The  cilia  act  so  as  to  carry  any  secre- 
tion toward  the  larynx.  Goblet  cells  exist  between  the  ciliated  columnar  cells.  Numerous  small 
compound  tubular  mucous  glands  occur  in  the  mucous  membrane,  chiefly  betw'een  the  cartilages. 
Their  ducts  open  on  the  surface  by  means  of  a  slightly  funnel-shaped  aperture  into  which  the 
ciliated  epithelium  is  prolonged  for  a  short  distance.  [The  acini  of  some  of  these  glands  lie  out- 
side the  trachealis  muscle.  The  acini  are  lined  by  cubical  or  columnar  secretory  epithelium.  In 
some  animals  (dog)  these   cells  are  clear,  and  present   the  usual  characters  of  a  mucus-secreting 

Fig.  125. 


-^ 


i^^-V 


ansverse  section  of  part  of  a  normal  human  bronchus  (X  450).  a,  precipitated  mucus  on  the  surface  of  the  ciliated 
epithelium,  iJ;  i,  ciliated  columnar  epithelium  ;  f:,  deep  germinal  layer  of  cells  (Debove's  membrane) :  </,  elastic 
basement  membrane  :  e,  elastic  fibres  divided  transversely  (inner  fibrous  layer) ;  /,  bronchial  muscle  (non-striped) : 
g,  outer  fibrous  layer  with  leucocytes  and  pigment- granules  (black)  deposited  in  it.  The  lower  part  of  the  figure 
shows  a  mass  of  adenoid  tissue. 


gland  ;  in  man,  some  of  the  cells  may  be  clear,  and  others  "  granular,"  but  the  appearance  of  the 
cells  depends  upon  the  physiological  state  of  activity.]  These  glands  secrete  the  mucus,  which 
entangles  particles  inspired  with  the  air,  and  is  carried  toward  the  larynx  by  ciliary  action. 
[Numerous  lymphatics  exist  in  the  mucous  and  submucous  coat,  and  not  unfrequently  small  aggre- 
gations of  adenoid  tissue  occur  (especially  in  the  cat)  in  the  mucous  coat,  usually  around  the  ducts 
of  the  glands.  They  are  comparable  to  the  solitary  follicles  of  the  alimentan,-  tract.]  The  blood 
vessels  are  not  so  numerous  as  in  some  other  mucous  membranes.  [A  plexus  of  nerves  contain- 
taining  numerous  ganglionic  cells  at  the  nodes  exist  on  the  posterior  surface  of  the  trachealis  muscle. 
The  fibres  are  derived  from  the  vagus,  recurrent  laryngeal  aud  sympathetic  [C.  Frankciiluuiscr,  If. 
Slirlin:;,  A'aii da razi].'] 

[The  mucous  membrane  of  the  trachea  and  extra-pulmonary  bronchi,  tlierefore,  consists 
of  the  following  layers  from  within  outward  : — 
(I)  Stratified  columnar  ciliated  epithelium. 


STRUCTURE    OF   THE    BRO^•CHI    AND    BRONCHIOLES.  185 

(2)  A  layer  of  flattened  cells  (Debove's  membrane). 

(3)  A  clear  homogeneous  basement  membrane. 

(4)  A   basis  of  areolar  tissue,  with  adenoid  tissue  and  blood  vessels,  and  outside  this  a  layer 

of  longitudinal  elastic  fibres. 

Outside  this,  again,  is  the  submucous  coat,  consisting  of  loose  areolar  ti.ssue,  with  the  larger 
vessels,  lymphatics,  nerves  and  mucous  glands.] 

.  [The  Bronchi. — In  structure  the  extra-pulmonary  bronchi  resemble  the  trachea.  As  they 
pass  into  the  lung  they  divide  very  iVequently,  and  the  branches  do  not  anastomose.  In  the  intra- 
pulmonary  bronchi  the  subdivisions  become  finer  and  finer,  the  finest  branches  being  called 
terminal  bronchi,  or  bronchioles,  which  open  separately  into  clusters  of  air  vesicles.] 

[Eparterial  and  Hyparterial  Bronchi. — As  the  bronchi  proceed,  one  main  trunk  passes  into 
the  lung,  running  toward  its  base,  and  from  it  are  given  off  branches  dorsally  and  ventrally,  and 
these  branches  again  subdivide.  Aeby  has  shown  that  the  relation  of  the  branches  to  the  pul- 
monary artery  is  most  important.  In  man  one  main  branch  comes  off  from  the  right  bronchus  and 
proceeds  to  the  upper  right  lobe,  abo-c<i  the  place  where  the  pulmonary  artery  crosses  the  bronchus. 
Such  branches  are  called  eparttrial,  and  they  are  more  numerous  in  birds.  In  man,  all  the  branches, 
both  on  the  right  and  left  side,  come  off  below  the  point  where  the  pulmonary  artery  crosses  the 
bronchus,  and  are  called  hyparterial  bronchi  (C  Ahey^.'\ 

[In  the  middle-sized  intra-pulmonary  bronchi,  the  usual  characters  of  the  mucous  membrane 
are  retained,  only  it  is  thinner:  the  cartilages  assume  the  form  of  irregular  plates  .situated  in  the 
outer  wall  of  the  bronchus ;  while  the  muscular  fibres  are  disposed  in  a  complete  circle,  constituting 
the  bronchial  muscle  (Fig.  125,  f).  When  this  muscle  is  contracted,  or  when  the  bronchus  as  a 
whole  is  contracted,  the  mucous  membrane  is  thrown  into  longitudinal  folds,  and  opposite  these 
folds  the  elastic  fibres  form  large  elevations.  This  muscle  is  particularly  well  developed  in  the 
smaller  microscopic  bronchi.  Numerous  elastic  fibres,  e,  disposed  longitudinally,  exist  under  the 
basement  membrane,  d.  They  are  continuous  with  those  of  the  trachea,  and  are  prolonged 
onward  into  the  lung.  The  mucous  membrane  of  the  larger  intra-pulmonary  bronchi  consists 
of  the  following  layers  from  within  outward : — 

(1)  Stratified  columnar  ciliated  epithelium  (Fig.  125,  b). 

(2)  Debove's  membrane  (Fig.  125,  c). 

(3)  Transparent  homogeneous  basement  membrane  (Fig.  125,  d). 

(4)  Areolar  tissue  with  longitudinal  elastic  fibres  (Fig.  125,  e'). 

(5)  A   continuous  layer  of  non-striped  muscular  fibres  disposed   atoxXsAy  {bronchial  muscle — 

Fig.  125,/). 
Outside  this  is  the  submucous  coat,  consisting  of  areolar  tissue  mixed  with  much  adenoid  tissue 
(Fig.  125,^),  sometimes  arranged  in  the  form  of  cords,  the  lymph-follicular  cords  of  Klein.  It 
also  contains  the  acini  of  the  numerous  mucous  glands,  blood  vessels  and  lymphatics.  The  ducts 
of  the  glands  perforate  the  muscular  layer,  and  ojjen  on  the  free  surface  of  the  mucous  membtane. 
The  submucous  coat  is  connected  by  areolar  tissue  with  the  perichondrium  of  the  cartilages.  Out- 
side the  cartilages  are  the  nerves  and  nerve  ganglia  accompanying  the  bronchial  vessels.  The 
branches  of  the  pulmonary  artery  and  of  the  pulmonary  vein  usually  lie  on  opposite  sides  of  the 
bronchus,  while  there  are  several  branches  of  the  bronchial  arteries  and  veins.  Fat  cells  also 
occur  in  the  peri -bronchial  tissue.] 

In  the  small  bronchi  the  cartilages  and  glands  disappear,  but  the  circular  muscular  fibres  are 
well  developed.     They  are  lined  by  lower  columnar  ciliated  epithelium,  containing  goblet  cells. 

Bronchioles. — After  repeated  subdivision,  the  bronchi  form  the  "  smallest  bronchi'"  (about  0.5 
to  I  mm.)  or  lobular  bronchial  tubes.  Each  tube  is  lined  by  a  layer  of  cilated  epithelium,  but  the 
glands  and  cartilages  have  disappeared.  These  tubes  have  a  few  lateral  alveoli  or  air  cells  com- 
municating with  them.  Each  smallest  bronchus  ends  in  a  "respiratory  bronchiole"  {Kblliker), 
which  gradually  becomes  beset  with  more  air  cells,  and  in  which  squamous  epithelium  begins  to 
appear  between  the  ciliated  epithelial  cells.  [Each  bronchiole  opens  into  several  wider  alveolar 
or  lobular  passages.  Each  passage  is  completely  surrounded  with  air  cells,  and  from  it  are  given 
oflf  several  similar  but  wider  blind  branches,  the  infundibula,  which,  in  their  turn,  are  beset  on  all 
sides  with  alveoli  or  air  cells.  Several  infundibula  are  connected  with  each  bronchiole,  and  the 
former  are  wider  than  the  latter.  Each  bronchiole,  with  its  alveolar  passages,  infundibula,  and  air 
vesicles,  is  termed  a  lobule,  whose  base  is  directed  outward,  and  whose  apex  may  be  regarded  as  a 
terminal  bronchus.  The  lung  is  made  up  of  an  immense  number  of  these  lobules,  separated  from 
each  other  by  septa  of  connective  tissue,  the  interlobular  septa  (Fig.  128,  e)  which  are  continuous 
on  the  one  hand  with  the  sub-pleural  connective  tissue,  and  on  the  other  with  the  peri-bronchial  con- 
nective tissue.] 

[It  is  evident  that  there  is  an  alteration  in  the  structure  of  the  bronchi,  as  we  proceed  from  the 
larger  to  the  smaller  tubes.  The  cartilages  and  glands  are  the  first  structures  to  disappear.  The 
circular  bronchial  muscle  is  well  developed  in  the  smaller  bronchi  and  bronchioles,  and  exists  as  a 
continuous  thin  layer  over  the  alveolar  passages,  but  it  is  not  continued  over  and  between  the  air 
cells.  Elastic  fibres,  continuous,  on  the  one  hand,  with  those  in  the  smaller  bronchi,  and  on  the 
other  with  those  in  the  walls  of  the  air  cells,  lie  outside  the  muscular  fibres  in  the  bronchioles  and 
infundibula.    In  the  respiratory  bronchioles,  the  ciliated  epithelium  is  reduced  to  a  single  layer,  and 


186 


THE    BLOOD    VESSELS    OF   THE    LUNG. 


is  mixed  with  the  stratified  form  of  epithelium,  while  where  the  alveolar  passages  open  into  the  air 
cells  or  alveoli,  the  epithelium  is  non-ciliated,  low,  and  polyhedral.] 

Alveoli  or  Air  Cells. — The  form  of  the  air  cells,  which  are  250  IJ.  (yj^  inch)  in  diameter,  may 
be  more  or  less  spherical,  polygonal,  or  cup-shaped.  They  are  disposed  around  and  in  communica- 
tion with  the  alveolar  passages.  Their  form  is  determined  by  the  existence  of  a  nearly  structure- 
less membrane,  composed  of  slightly  fibrillated  connective  tissue  containing  a  few  corpuscles.  This 
is  surrounded  by  numerous  fine  elastic  fibres,  which  give  to  the  pulmonary  parenchyma  its  well- 
marked  elastic  characters  (Fig.  127,  c,  e).  These  fibres  often  bifurcate,  and  are  arranged  with  ref- 
erence to  the  alveolar  wall.  They  are  very  resistant,  and  in  some  cases  of  lung  disease  may  be 
recognized  in  the  sputum.  A  few  non-striped  muscular  fibres  exist  in  the  delicate  connective  tissue 
between  adjoining  air  vesicles  (Moleschott^.  These  muscular  fibres  sometimes  become  greatly 
developed  in  certain  diseases  (Arnold,  IK  Stirling).  The  air  cells  are  lined  by  two  kinds  of  cells — 
(l)  large,  transparent,  clear  polygonal  (nucleated?)  squames  or  placoids  (22-45 /i)  lying  over 
and  between  the  capillaries  in  the  alveolar  wall  (Fig.  126,  a) ;  (2)  small,  irregular,  "  granular," 
nucleated  cells  (7-15  !'■)  arranged  singly  or  in  groups  (two  or  threel  in  the  interstices  between  the 
capillaries.  They  are  well  seen  in  a  cat's  lung  (Fig.  126,1/).  [When  acted  on  with  nitrate  of 
silver  the  cement  substance  bounding  the  clear  cells  is  stained,  but  the  small  cells  become  of  a  uni- 
form brown,  granular  appearance,  so  that  they  are  readily  recognized.  Small  holes  or  "  pseudo- 
Fir;.  126. 


Air  vesicles  from  a  kitten  whose  lungs  were  injected  with  silver  nitrate  (  X  45°).  <*,  outlines  of  fully  developed 
squamous  epithelium  ;  6,  alveolar  wall ;  c,  young  epithelial  cell  losing  its  granular  appearance ;  d,  aggregation 
of  young  epithelial  cells  germinating. 

stomata "  seem  to  exist  in  the  cement  substance,  and  are  most  obvious  in  distended  alveoli 
[JOein).  They  open  into  the  lymph-canalicular  system  of  the  alveolar  wall  (A'lein),  and  through 
them  the  lymph  corpuscles,  which  are  always  to  be  found  on  the  surface  of  the  air  vesicles,  migrate, 
and  carry  with  them  into  the  lymphatics  particles  of  carbon  derived  from  the  air.]  In  the  alveolar 
walls  is  a  very  dense  plexus  of  fine  capillaries  (Fig.  127,  r),  which  lie  more  toward  the  cavity  of 
the  air  vesicle  {I\aimy),  being  covered  only  by  the  epithelial  lining  of  the  air  cells.  Between  two 
adjacent  alveoli  there  is  only  a  single  layer  of  capillaries  (man),  and  on  the  boundary  line  between 
two  air  cells  the  course  of  the  capillaries  is  twisted,  thus  projecting  sometimes  into  the  one  alveolus, 
sometimes  into  the  other. 

[The  number  of  Alveoli  is  stated  to  be  about  725  millions,  a  result  obtained  by  measuring  the 
size  of  the  air  vesicles  and  ascertaining  the  amount  of  air  in  the  lung  after  an  ordinary  inspiration, 
and  determining  how  much  of  this  air  is  in  the  air  vesicles  and  bronchi  respectively.  The  superficial 
area  of  the  air  vesic'es  is  about  90  square  metres,  or  100  times  greater  than  the  surface  of  the  body 
(.8  to  .9  sq.  metre)  [Fosi-nthal).'] 

The  Blood  vessels  of  the  lung  belong  to  two  different  systems  :  (A)  Pulmonary  vessels 
(lesser  circulation).  The  branches  of  the  pulmonary  artery  accompany  tile  bronchi  and  are  closely 
applied  to  them.  [As  they  proceed  they  branch,  but  the  branches  do  not  anastomose,  and  ultimately 
they  terminate  in  small  arterioles  which  supply  several  adjacent  alveoli,  each  arteriole  splitting  up 


THE    PLEURA    OF   THE    LUNG. 


187 


into  capillaries  for  se^'eral  z'n  cells  (Fig.  127,  ;■,  c).  An  efferent  vein  usually  arises  at  the  opposite 
side  of  the  air  cells  and  carries  away  the  purified  blood  from  the  capillaries.  In  their  course  these 
veins  unite  to  form  the  pulmonary  veins,  which  are  joined  in  their  course  by  a  few  small  bronchial 
veins  iZuckerkaniil).  The  veins  usually  anastomose  in  the  earlier  part  of  their  course,  while  the 
corresponding  arteries  do  not.]  Although  the  capillary  plexus  is  very  fine  and  dense,  its  sectional 
area  is  less  than  the  sectional  area  of  the  systemic  capillaries,  so  that  the  blood  stream  in  the  pulmo- 
nary capillaries  must  be  more  rapid  than  that  in  the  capillaries  of  the  body  generally.  The  pulmo- 
nary veins,  unlike  veins  generally,  are  collectively  narrower  than  the  pulmonary  artery  (water  is 
given  off  in  the  lung),  and  they  have  no  valves.  [The  pulmonary  artery  contains  venous  blood, 
and  the  pulmonary  veins  pure  or  arterial  blood.] 

(B)  The  bronchial  vessels  represent  the  nutrient  system  of  the  lungs.  They  (1-3)  arise  from 
the  aorta  (or  intercostal  arteries)  and  accompany  the  bronchi  without  anastomosing  with  the  branches 
of  the  pulmonary  artery.  In  their  course  they  give  branches  to  the  lymphatic  glands  at  the  hilum 
of  the  lung,  to  the  walls  of  the  large  blood  vessels  (vasa  vasorum),  the  pulmonar)'  pleura,  the 
bronchial  walls,  and  the  interlobular  septa.  The  blood  which  issues  from  their  capillaries  is  returned 

Fig.  127. 


epresentation  of  the  air  vesicles  of  the  lung,  v,  v,  blood  vessels  at  the  margins  of  an  alveolus  ; 
<:,  £■,  its  blood  capillaries  :  E,  relation  of  the  squamous  epithelium  of  an  alveolus  to  the  capillaries  in  its  wall  ;  y", 
alveolar  epithelium  shown  alone;  e,  c,  elastic  tissue  of  the  lung. 

— partly  by  the  pulmonary  veins — hence,  any  considerable  interference  with  the  pulmonar)'  circula- 
tion causes  congestion  of  the  bronchial  mucous  membrane,  resulting  in  a  catarrhal  condition  of  that 
membrane.  The  greater  part  of  the  blood  is  returned  by  the  bronchial  veins  which  open  into  the 
vena  azygos,  intercostal  vein,  or  superior  vena  cava.  The  veins  of  the  smaller  bronchi  (fourth  order 
onward)  open  into  the  pulmonary  veins,  and  the  anterior  bronchial  also  communicate  with  the  pul- 
monarj'  veins  (Zuckerkandl). 

[The  Pleura. — Each  pleural  cavity  is  distinct,  and  is  a  large  serous  sac,  which  really  belongs  to 
the  lymphatic  system  of  the  lung.  The  pleura  consists  of  two  layers,  visceral  and  parietal.  The 
visceral  pleura  covers  the  lung ;  the  parietal  portion  lines  the  wall  of  the  chest,  and  the  two  layers 
of  the  corresponding  pleura  are  continuous  witli  one  another  at  the  root  of  the  lung.  The  visceral 
pleura  is  the  thicker,  and  may  readily  be  separated  from  the  inner  surface  of  the  chest.  Structurally, 
the  pleura  resembles  a  serous  membrane,  and  consists  of  a  thin  layer  of  fibrous  tissue  covered  by  a 
layer  of  endothelium.  Under  this  layer,  or  the  pleura  proper,  is  a  deep  or  sub-serous  layer  of  looser 
areolar  tissue,  containing  many  elastic  fibres.  The  layer  of  the  pleura  pulmonalis  of  some  animals, 
as  the  guinea  pig,  contains  a  network  of  non-striped  muscular  fibres  (A7««).     Over  the  lung  it  is 


188 


THE    LYMPHATICS   OF   THE    LUNG. 


also  continuous  with  the  interlobular  septa.  The  interlobular  septa  (Fig.  12S,  f)  consist  of  bands 
of  fibrous  tissue  separating  adjoining  lobules,  and  they  become  continuous  with  the  peri-bronchial 
connective  tissue  entering  the  lung  at  its  hilum.  Thus  the  fibrous  framework  of  the  lung  is  continu- 
ous throughout  the  lung,  just  as  in  other  organs.  The  connection  of  the  sub-pleural  fibrous  tissue 
with  the  connective  tissue  within  the  substance  of  the  lung,  has  most  important  pathological  bearings. 
The  interlobular  septa  contain  lymphatics  and  blood  vessels.  The  endothelium  covering  the  parietal 
layer  is  of  the  ordinary  squamous  type,  but  on  the  pleura  pulmonalis  the  cells  are  less  flattened, 
more  polyhedral,  and  granular.  They  must  necessarily  vary  in  shape  with  changes  in  the  volume 
of  the  lung,  so  that  they  are  more  flattened  wdien  the  lung  is  distended,  as  during  inspiration  {Klein). 
The  pleura  contains  many  lymphatics,  which  communicate  by  means  of  stomata  with  the  pleural 
cavity.] 

[The  Lymphatics  of  the  lung  are  numerous  and  are  arranged  in  several  systems.  The  various 
air  cells  are  connected  with  each  other  by  very  delicate  connective  tissue,  and  according  to  J.  Ar- 
nold in  some  parts  this  interstitial  tissue  presents  characters  like  those  of  adenoid  tissue ;  so  that  the 
lung  is  traversed  by  a   system  of  juice  canals  or  "  Saft-canalchen."]      [In  the  deep  layer  of  the 

Fig.   128. 


pleura,  there  is  (a)  subpleural  plexus  of  lymphatics  partly  derived  from  the  pleura,  but  chiefly 
from  the  lymph-canalicular  system  of  the  pleural  alveoli.  Some  of  these  branches  proceed  to  the 
bronchial  glands,  but  others  pass  into  thei  nterlobular  septa,  where  they  join  [b)  the  perivascular 
lymphatics  which  arise  in  the  lymph-canalicular  system  of  the  alveoli.  These  trunks,  provided 
with  valves,  run  alongside  the  pulmonary  artery  and  vein,  and  in  their  course  they  form  frequent 
anastomoses.  Special  vessels  arise  within  the  walls  of  the  bronchi  and  occur  chiefly  in  the  outer 
coat  of  the  latter,  constituting  (<)  the  peri-bronchial  lymphatics,  which  anastomose  with  b.  The 
branches  of  these  two  sets  run  toward  the  bronchial  glands.  Not  unfrequently  (cat)  masses  of 
adenoid  tissue  are  found  in  the  course  of  these  lymphatics  (A'/t'/n).]  The  lymph-canalicular  system 
and  the  lymphatics  become  injected  when  fine  colored  particles  are  inspired,  or  are  introduced  into 
the  air  cells  artificially.  The  pigment  particles  pass  through  the  semi-fluid  cement  substance  into 
the  lymph-canalicular  system  and  thence  into  the  lymphatics  {v.  IVittich);  or,  according  io  Klein, 
they  pass  through  actual  holes  or  pores  in  the  cement  (p.  186).]  [This  pigmentation  is  well  seen 
in  coal  miner's  lung  or  anthracosis,  where  the  particles  of  carbon  pass  into  and  are  found  in  the 


PHYSICAL    PROPERTIES    0¥   THE    LUNGS.  189 

lymphatics.  Sikorski  and  Kiittner  showed  that  pigment  reached  the  lymphatics  this  way  during 
life.  If  pigment,  China  ink,  or  indigo  carmine  be  introduced  into  a  frog's  lung,  it  is  found  in  the 
Ivmphalic  system  of  the  lung.  Ruppert,  and  also  Schotielius,  showed  that  the  same  result  occuried 
in  dogs  after  the  inhalation  of  charcoal,  cinnabar,  or  precipitated  Berlin  blue,  and  von  Ins  after  the 
inhalation  of  silica.  A.  Schestopal  used  China  ink  and  cinnabar  suspended  in  3^  per  cent,  .salt 
solution.]  Excessively  fine  lymph  canals  lie  in  the  wall  of  the  alveoli  in  the  interspaces  of  the 
capillaries,  and  there  are  slight  dilatations  at  the  points  of  crossing  {IVydwozoff).  According  to 
Pferret  and  Renaut  every  air  cell  of  the  lung  of  the  ox  is  surrounded  by  a  large  lymph  space,  such 
as  occurs  in  the  salivary  glands.  When  a  large  quantity  of  fluid  is  injected  into  the  lung  it  is 
absorbed  with  great  rapidity ;  even  blood  corpuscles  rapidly  pass  into  the  lymphatics.  [Nothnagel 
found  that,  if  blood  was  sucked  in  the  lung  of  a  rabbit,  the  blood  corpuscles  were  found  within  the 
interstitial  connective  tissue  of  the  lung  after  2%  'o  5  minutes,  from  which  he  concludes  that  the 
communications  between  the  cavity  of  the  air  cells  and  the  lymphatics  must  be  very  numerous] 

The  superficial  lymphatics  of  the  pulmonary  pleura  communicate  with  the  pleural  cavity  by 
means  of  tree  openings  or  stotnata  (A/ein),  and  the  same  is  true  of  the  lymphatics  of  the  parietal 
pleura,  but  these  stomata  are  confined  to  limited  areas  over  the  diaphragmatic  pleura.  [The  lymph- 
.atics  in  the  costal  pleura  occur  over  the  intercostal  spaces  and  not  over  the  ribs  [Dybko-,.'ski).\  The 
large  arteries  of  the  lung  are  provided  with  lymphatics  which  lie  between  the  middle  and  outer 
coats  [Grant her).  [The  movements  of  the  lung  during  respiration  are  most  important  factors  in 
moving  the  lymph  onward  in  the  pulmonary  lymphatics.  The  return  of  the  lymph  is  prevented  by 
the  presence  of  valves.] 

[The  Nerves  of  the  lung  are  derived  from  the  anterior  and  posterior  pulmonary  plexuses,  and 
consist  of  branches  from  the  vagus  and  sympathetic.  They  enter  the  lungs  and  follow  the  distribu- 
tion of  the  bronchi,  several  sections  of  nerve  trunks  being  usually  found  in  a  transverse  section  of  a 
large  bronchial  tube.  These  nerves  lie  outside  the  cartilages,  and  are  in  close  relation  with  the 
branches  of  the  bronchial  arteries.  MeduUated  and  nonmeduUated  nerve  fibres  occur  in  the  nerves, 
which  also  contain  numerous  small  ganglia  (JiemaA,  Klein,  Stirling).  In  the  lung  of  the  calf 
tliese  ganglia  are  so  large  as  to  be  microscopic.  The  exact  mode  of  termination  of  the  nerve  fibres 
within  the  lung  has  yet  to  be  ascertained  in  mammals,  but  some  fibres  pass  to  the  bronchial  muscle, 
others  to  the  large  blood  vessels  of  the  lung,  and  it  is  highly  probable  that  the  mucous  glands  are 
also  supplied  with  nerve  filaments.  In  the  comparatively  simple  lungs  of  the  frog,  nen'es  with 
numerous  nerve  cells  in  their  course  are  found  [Arnold,  Stirling),  and  in  the  very  simple  lung  of 
the  newt,  there  are  also  numerous  ner\-e  cells  disposed  along  the  course  of  the  intra-pulmonary 
nerves.  Some  of  these  fibres  terminate  in  the  uniform  layer  of  non-striped  muscle  which  forms 
part  of  the  pulmonary  wall  in  the  frog  and  newt,  and  others  end  in  the  muscular  coat  of  the  pul- 
monary' blood  vessels  (Stirling).  The  functions  of  these  ganglia  are  unknown,  but  they  may  be 
compared  to  the  nerve  plexuses  existing  in  the  walls  of  the  digestive  tract.] 

The  Function  of  the  Non-striped  Muscle  of  the  entire  bronchial  system 
seems  to  be  to  offer  a  sufficient  amount  of  resistance  to  increased  pressure  within  the 
air  passages  ;  as  in  forced  expiration,  speaking,  singing,  blowing,  etc.  The  vagus 
IS  the  motor  nerve  for  these  fibres,  and  according  to  Longet  (1842),  the  "  lung- 
tonus  "  during  increased  tension  depends  upon  these  muscles.  It  is  not  proved 
to  what  extent  bronchial  (spasniodicj  asthma  depends  upon  contraction  of  these 
muscular  fibres  due  to  stimulation  of  the  vagus. 

[Effect  of  Nerves.^By  connecting  the  interior  of  a  small  bronchus  with  an  oncograph  (|  103) 
ill  the  case  of  curarized  dogs  (the  thorax  being  opened),  Graham  Brown  and  Roy  found  that  sec- 
tion of  one  vagus  causes  a  marked  expansion  of  the  bronchi  of  the  corresponding  lung,  while 
stimulation  of  the  peripheral  end  of  a  divided  vagus  causes  a  powerful  contraction  of  the  bronchi 
of  both  lungs.  .Stimulation  of  the  central  end  of  one  vagus,  the  other  being  intact,  also  causes  a 
contraction  (feebler)  under  the  same  circumstances.  Especially  in  etherized  dogs,  expansion  and 
not  contraction  results.  If  both  vagi  be  divided,  no  effect  is  produced  by  stimulation  of  the  central 
end  of  either  vagus.  It  seems  plain  that  the  vagi  contain  centripetal  or  aflTerent  fibres,  which  can 
cause  both  expansion  and  contraction  of  the  Ijronchi.  Asphyxia  causes  contraction  provided  the 
vagi  are  intact,  but  none  if  they  are  divided,  although  in  etherized  dogs  expansion  frequently  occurs, 
while  stimulation  of  the  central  end  of  other  sensory  nerves  has  very  rarely  any,  or  if  any,  but  a 
slight  effect  on  the  calibre  of  the  bronchi,  so  that  in  the  dog,  the  only  connection  between  the  cere- 
bro-spinal  centres  and, the  bronchi  is  through  the  vagi]. 

Chemistry. — In  addition  to  connective,  elastic,  and  muscular  tissue,  the  lungs  contain  lecithin, 
inosit,  uric  acid  (taurin  and  leucin  in  the  ox),  guanin,  xanthin  (?),  hypoxanthin  (dog)  —soda,  pot- 
ash, magnesium,  oxide  of  iron,  much  phosphoric  acid,  also  chlorine,  sulphuric  and  silicic  acids — in 
diabetes  sugar  occurs — in  purulent  infiltration  glycogen  and  sugar — in  renal  degeneration  urea,  oxalic 
acid,  and  ammonia  salts ;  and  in  diseases  where  decomposition  takes  place,  leucin  and  tryosin. 

[Physical  Properties  of  the  Lungs. — The  lungs,  in  virtue  of  the  large 
atnount  of  elastic  tissue  which  they  contain,  are  endowed  with  great  elasticity, 


190  MECHANISM    OF    RESPIRATION. 

SO  that  when  the  chest  is  opened  they  collapse.  If  a  cannula  with  a  small  lateral 
opening  be  tied  into  the  trachea  of  a  rabbit's  or  sheep's  lungs,  the  lungs  may  be 
inflated  with  a  pair  of  bellows  or  elastic  pump.  After  the  artificial  inflation,  the 
lungs,  owing  to  their  elasticity,  collapse  and  expel  the  greater  part  of  the  air.  As 
much  air  remains  within  the  light  spongy  tissue  of  the  lungs,  even  after  they  are 
removed  from  the  body,  a  healthy  lung  floats  in  water.  If  the  air  cells  are  filled 
with  pathological  fluids  or  blood,  as  in  certain  diseased  conditions  of  the  lung 
(pneumonia),  then  the  lungs,  or  parts  thereof,  may  sink  in  water.  The  lungs  of 
the  foetus,  before  respiration  has  taken  place,  sink  in  water,  but  after  respiration 
has  been  thoroughly  established  in  the  child,  the  lungs  float.  Hence,  this  hy- 
drostatic test  is  largely  used,  in  medico-legal  cases,  as  a  test  of  the  child  having 
breathed.  If  a  healthy  lung  be  squeezed  between  the  fingers,  it  emits  a  peculiar 
and  characteristic  fine,  crackling  sound,  owing  to  the  air  within  the  air  cells.  A 
similar  sound  is  heard  on  cutting  the  vesicular  tissue  of  the  lung.  The  color  of 
the  lungs  varies  much  ;  in  a  young  child  it  is  rose-pink,  but  afterward  it  becomes 
darker,  especially  in  persons  living  in  towns  or  a  smoky  atmosphere,  owing  to  the 
deposition  of  granules  of  carbon.  In  coal  miners  the  lungs  may  become  quite 
black.] 

[Excision  of  the  Lung. — Dogs  recover  after  the  excision  of  one  entire  lung,  and  they  even 
survive  the  removal  of  portions  of  lung  infected  with  tubercle  [Biondi).'] 

107.  MECHANISM  OF  RESPIRATION.— The  mechanism  of  respi- 
ration consists  in  an  alternate  dilatation  and  contraction  of  the  chest.  The  dila- 
tation is  called  inspiration,  the  contraction,  expiration.  .\s  the  whole  external 
surface  of  both  elastic  lungs  are  applied  directly  and  in  an  air-tight  manner,  by 
their  smooth,  moist,  pleural  investment,  to  the  inner  wall  of  the  chest,  which  is 
covered  by  the  parietal  pleura,  it  is  clear  that  the  lungs  must  be  distended  with 
every  dilatation  of  the  chest,  and  diminished  by  every  contraction  thereof.  These 
movements  of  the  lungs,  therefore,  are  entirely  passive,  and  are  dependent  on 
the  thoracic  movements  {Galen.) 

On  account  of  their  complete  elasticity  and  their  great  extensibility,  the  lungs 
are  able  to  accommodate  themselves  to  any  variation  in  the  size  of  the  thoracic 
cavity,  without  the  two  layers  of  the  pleura  becoming  separated  from  each  other. 
.\s  the  capacity  of  the  non-distended  chest  is  greater  than  the  volume  of  the  col- 
lapsed lungs  after  their  removal  from  the  body,  it  is  clear  that  the  lungs,  even  in 
their  natural  position  within  the  chest,  are  distended,  i.e.,  they  are  in  a  certain 
state  of  elastic  tension  (§  60).  The  tension  is  greater,  the  more  distended  the 
thoracic  cavity,  and  vice  versa.  As  soon  as  the  pleural  cavity  is  opened  by  per- 
foration from  without,  the  lungs,  in  virtue  of  their  elasticity,  collapse,  and  a  space 
filled  with  air  is  formed  between  the  surface  of  the  lungs  and  the  inner  surface  of 
the  thoracic  wall  (pneumothorax).  The  lungs  so  affected  are  rendered  useless 
for  respiration  ;  hence,  a  double  pneumothorax  causes  death. 

Pneumothorax. — It  is,  also  clear  that,  if  the  pulmonary  pleura  be  perforated  from  within  the 
lung,  air  will  pass  from  the  respiratory  passages  into  the  pleural  sac,  and  also  give  rise  to  pneumo- 
thorax. 

[Not  unfrequently  the  surgeon  is  called  on  to  open  the  chest,  say,  by  removing  a  portion  of  a  rib, 
to  allow  of  the  free  exit  of  pus  from  the  pleural  cavity.  If  this  be  done  with  proper  precautions, 
and  if  the  external  wound  be  allowed  to  heal,  after  a  time  the  air  in  the  pleural  cavity  becomes 
absorbed,  the  collapsed  lung  tends  to  regain  its  original  form,  and  again  becomes  functionally  active.] 

Estimation  of  Elastic  Tension. — If  a  manometer  be  introduced  through  an  intercostal  space 
into  the  pleural  cavity,  in  a  dead  subject,  we  can  measure,  by  means  of  a  column  of  mercury,  the 
amoutit  of  the  elastic  tension  required  to  keep  the  lung  in  its  position.  This  is  equal  to  6  mm.  in 
the  dead  subject,  as  well  as  in  the  condition  of  expiration.  If,  however,  the  thorax  be  brought  into 
the  position  of  inspiration,  by  the  application  of  traction  from  without,  the  elastic  tension  may  be 
increased  to  30  mm.  Hg.  [Doniiers). 

If  the  glottis  be  closed  and  a  deep  inspiration  taken,  the  air  within  the  lungs 
must  become  rarified,  because  it  has  to  fill  a  greater  space.  If  the  glottis  be  sud- 
denly opened,  the  atmospheric  air  passes  into  the  lungs  until  the  air  within  the 


SPIROMETRY   AND   VITAL   CAPACITY. 


191 


COMPLEMENTAL 


RESERVE   AIR 


I 


RESIDUAL   AIR 


lungs  has  the  same  density  as  the  atmosphere.  Conversely,  if  the  glottis  be  closed, 
and  if  an  expiratory  effort  be  made,  the  air  within  the  chest  must  be  compressed.  If 
the  glottis  be  suddenly  opened,  air  passes  out  of  the  lungs  until  the  pressure  outside 
and  inside  the  lung  is  equal.  As  the  glottis  remains  open  during  ordinary  respira- 
tion, the  equilibration  of  the  pressure  within  and  without  the  lungs  will  take  place 
gradually.  During  tranquil  inspiration  there  is  a  slight  negative  pressure  ;  during 
expiration,  a  slight  positive  pressure  in  the  lungs;  the  former^  i  mm.,  the  latter 
2-3  mm.  Hg.  in  the  human  trachea  (measured  in  cases  of  wounds  of  the  trachea). 

108.  QUANTITY  OF  GASES  RESPIRED.— As  the  lungs  within  the 
chest  never  give  out  all  the  air  they  contain,  it  is  clear  that  only  a  part  of  the  air 
of  the  lungs  is  changed  during  inspiration  and  expiration.  The  volume  of  this 
air  will  depend  upon  the  depth  of  the  respirations. 

Hutchinson  (1846)  distinguishes    the    following  points: — 

(1)  Residual  Air  is  the  volume  of  air  which  remains  in  the 
chest  after  the  most  complete  expiration.  It  is  equal  to  1230-1640 
c.  c.  [100-130  cubic  inches]. 

(2)  Reserve  or  Supplemental  Air  is  the  volume  of  air  which 
can  be  expelled  from  the  chest  after  a  normal  quiet  expiration.  It  is 
equal  to  1240-1S00  c.  c.  [100  cubic  inches]. 

(3)  Tidal  Air  is  the  volume  of  air  which  is  taken  in  and  given 
out  at  each  respiration.  It  is  equal  to  500  cubic  centimetres  [20 
cubic  inches]. 

(4)  Complemental  Air  is  the  volume  of  air  that  can  be  forcibly 
inspired  over  and  above  what  is  taken  in  at  a  normal  respiration.  It 
amounts  to  about  1500  c.  c.   [100-130  cubic  inches]. 

(5)  Vital  Capacity  is  the  term  applied  to  the 
volume  of  air  which  can  be  forcibly  expelled  from  the 
chest  after  the  deepest  possible  inspiration.  It  is  equal 
t0  3772c.c.  (or  230  cubic  inches)  for  an  Englishman 
(^Hutchinson),  and  3222  for  a  German  (^Haser). 

Hence,  after  every  quiet  inspiration,  both  lungs  con- 
tain (i  -f-  2  +  3)  =  3000  to  3900  c.cm.    [220  cubic 
inches];   after  a  quiet  expiration  (i   -f  2)  =  2500  to  3400  c.cm 
inches].     So  that  about  |-  to  |  of  the  air  in  the 
lungs  is  subject  to  renewal  at  each  respiration. 

Estimation  of  Vital  Capacity. — The  esti- 
mation of  the  vital  capacity  was  formerly  thought 
to  be  of  great  consequence,  but  at  the  present  time 
not  much  importance  is  attached  to  it,  nor  is  it  fre- 
quently measured  in  cases  of  disease.  It  is  esti- 
mated by  means  of  the  spirometer  of  Hutchinson. 
This  instrument  (Fig.  129),  consists  of  a  graduated 
cylinder  filled  with  water  and  inverted  like  a 
gasometer  over  water,  and  balanced  by  means 
of  a  counterpoise.  Into  this  cylinder  a  tube 
projects,  and  this  tube  is  connected  with  a 
mouth  piece.  The  person  to  be  experimented 
upon  takes  the  deepest  possible  inspiration, 
closes  his  nostrils,  and  breathes  forcibly  into 
the  mouth  piece  of  the  tube.  After  doing  so  the 
tube  is  closed.  The  cylinder  is  raised  by  the 
air  forced  into  it,  and  after  the  water  inside 
and  outside  the  cylinder  is  equalized,  the  height 
to  which  the  cylinder  is  raised  indicates  the 
amount  of  air  expired,  or  the  vital  or  respiratory 
capacity.  In  a  man  of  average  height,  5  feet  8 
inches,  it  is  equal  to  230  cubic  inches. 


[200  cubic 


Fig.  129. 


Scheme  of  Hutch 


192 


TIME    OCCUPIED    BY   THE    RESPIRATORY    MOVEMENTS. 


The  following  circumstances  alTecl  the  vital  capacity  : — 

(i)  The  Height. — Every  inch  added  to  the  height  of  persons  between  5  and  6  feet,  gives  an 
increase  of  the  vital  capacity  =  130  c.c.     [8  cubic  inches.] 

(2)  The  Body  weight. — When  the  body  weight  exceeds  the  normal  by  7  per  cent.,  there  is  a 
diminution  of  37  c.c.  of  the  vital  capacity  for  every  kilo,  of  increase. 

(3)  Age. — The  vital  capacity  is  at  its  maximum  at  35;  there  is  an  annual  decrease  of  23.4  c.c. 
from  this  age  onward  to  65,  and  backward  to  15  years  of  age. 

(4)  Sex. — It  is  less  in  women  than  men,  and  even  where  there  is  the  same  circumference  of 
chest,  and  the  same  height  in  a  man  and  a  woman,  the  ratio  is  10  :  7. 

(5)  Position. — More  air  is  respired  in  the  erect  than  in  the  recumbent  position. 

(6)  Disease. — .\bdominal  and  thoracic  diseases  diminish  it. 

109.  NUMBER  OF  RESPIRATIONS.— In  the  adult,  the  number  of 
respirations  varies  from  16  to  24  per  minute,  so  that  about  4  pulse  beats  occur 
during  each  respiration.  The  number  of  respirations  is  influenced  by  many 
conditions  :  — 

(1)  The  Position  of  the  Body. — In  the  adult,  iri  the  horizontal  position,  Guy  counted  13, 
while  sitting  19,  whde  standing  22,  respirations  per  minute. 

(2)  The  Age. — Quetelet  found  the  mean  number  of  respirations  in  300  individuals  to  be  : — 
Year.  Respirations.  [  Year.  Respirations. 

o  to    1 44      I        Average  201025, 1S.7      |      Average 

5, 26      [■    Number  per         2$  to  30 t6         !•    Number  per 

15    to  20 20      J         Minute.       )     301050, 18.1      J        Minute. 

(3)  The  State  of  Activity. — Gorham  counted  in  children  of  2  to  4  years  of  age,  during  stand- 
ing 32,  in  sleep  24,  respirations  per  minute.  During  bodily  exertion  the  number  of  respirations 
increases  before  the  heart  beats.  [Very  slight  muscular  exertion  suffices  to  increase  the  frequency 
of  the  respirations.] 

[(4)  The  Temperature  of  the  surrounding  medium. — The  respirations  become  more  numerous 
the  higher  the  surrounding  temperature,  but  this  result  only  occurs  when  the  actual  temperature  of 
the  blood  is  increased,  as  in  fever. 

(5)  Digestion. — There  is  a  slight  variation  during  the  course  of  the  day,  the  increase  being  most 
marked  after  mid-day  dinner  ( I'ierordt). 

(6)  The  Will  can  to  a  certain  extent  modify  the  number  and  also  the  depth  of  the  respirations, 
but  after  a  short  time  the  impulse  to  respire  overcomes  the  voluntary  impulse. 

(7)  The  Gases  of  the  Blood  have  a  marked  effect,  and  so  has  the  heat  of  the  blood  in  fever.] 
[{S)   In  Animals — 

Mammals. 

Per  Min. 
Hippopotamus,     ....  i 

Horse, 10-12 


Mammals 


Per  Mil 


Tiger 6 

Lion, 10 

Jaguar 11 

Panther, 18 

Cat, 24 

Dog,      IS 

Dromedary,      II 

Giraffe 8-10 

Ox 15-18 

Squirrel, 70 

Rabbit,      55 

Rat  (waking) 2IQ 

Rat  (asleep), 100 

Rhinoceros, 6-lo 


Fish. 


Ass, 


Condor  . 
Sparrow 
Pigeon 
Siskin    . 
Canary  . 


Kaja  .... 
Torpedo  .  . 
Perch  ... 
Mullet  .  .  . 
Eel  ...  . 
Hippocampus 


Min. 

5° 
S' 
30 
60 
50 
33 


Invertebrata. 

Crab 12 

Mollusca 14-65 

[P.  Berl).'] 


Reptiles. 

Snake 5 

Tortoise 12 

[(9)  In  Disease. — The  number  may  be  greatly  increased  from  many  causes,  e.g.,  in  fever, 
pleurisy  and  pneumonia,  some  heart  diseases,  or  in  certain  cases  of  alteration  of  the  blood,  as  in 
anjemia ;  anil  diminished  where  there  is  pressure  on  the  respiratory  centre  in  the  medulla,  in 
coma.     It  is  important  to  note  the  ratio  of  pulse  beats  to  respirations.] 

iio.  TIME  OCCUPIED  BY  THE  RESPIRATORY  MOVE- 
MENTS.— The  time  occupied  in  the  various  phases  of  a  respiration  can  only  be 
accurately  ascertained  by  obtaining  a  curve  or  pneumatogram  of  the  respiratory 
movements. 

Methods. — fl)  Vierordt  and  C.  Ludwig  transferred  the  movements  of  a  part  of  the  chest  wall 
to  a  lever  which  inscribed  its  movements  upon  a  revolving  cylinder.  Riegel  (1S73)  constructed  a 
"  double  stethograph  "  on  the  same  principle.     This  instrument  is  so  arranged  that  one  arm  of  the 


VARIOUS    FORMS   OF    STETHOGRAPHS. 


193 


lever  may  be  applied  in  connection  with  the  healthy  side  of  a  person's  chest,  and  the  other  on  the 
diseased  side. 

(2)  An  air  tambour,  such  as  is  used  in  Brondgeest's  pansphygmograph  (Fig.  131,  A)  may  be  used. 
It  consists  of  a  Ijrass  vessel,  a,  shaped  like  a  small  saucer.  The  mouth  of  the  brass  vessel  is  covered 


Fig 


Marey's  stethograph. 

with  a  double  layer  ot  caoutchouc  membrane,  i,  <-,  and  air  is  forced  in  between  the  two  layers  until 
the  external  membrane  bulges  outward.  This  is  placed  on  the  chest,  and  the  apparatus  is  fixed  in 
position  by  means  of  the  bands,  t/,  d.  The  cavity  of  the  tambour  communicates  by  means  of  a 
caoutchouc  tube,  .r,  with  a  recording  tambour,  which  inscribes  its  movements  upon  a  revolving  cyl- 

FlG.  131. 


.A,  Brondgeest's  tambo: 
the  capsule  ;  d,  c 
mal  respiratory  1 


fibrating  pla 


ovements,  b,  f,  inner  .ind  outer  caoutciiouc  membranes ; 
lit  to  the  chest ;  S,  tube  to  the  recording  tambour  ;  B,  n 
:  (each  vibration  =  0.01613  sec). 


inder.  Every  dilatation  of  the  chest  compresses  the  membrane,  and  thus  the  air  within  the  tambour 
is  also  compressed.  [A  somewhat  similar  apparatus  is  used  by  Burdon-Sanderson,  and  called  a 
"  recording  stethograph."  By  it  movements  of  the  corresponding  points  on  opposite  sides  of 
the  chest  can  be  investigated.] 

13 


194 


TIME   OCCUPIED    BY   THE    RESPIRATORY    MOVEMENTS. 


(3)  A  cannula  or  oesophageal  sound  may  be  introduced  into  J'^^'' P""'""  °^ 'J>^ '^^fj"^  TJj^^jf, 
lies  in  the  chest,  and  a  connection  established  with  Marey's  tambour,  p.  85  {Rosenthal).  [This 
mpfhnd  ilso  enables  one  to  measure  the  ;«//■«■//(<"•«'';''/'■"■''"■«'•  J  ,    ,.     .  .  j- 

Marev4  s"etWraph  or  Pneumograph.-[There  are  two  fonns  of  this  instrument,  one  modi- 
fie^by  P  Per  and&ore  modern  form  (Fig.  .30).  A  tambour  (/,)  is  fixed  at  right  angles  to  a 
thi;  elastic  plate  of  steel  (  /).  The  aluminium  disk  on  the  caoutchouc  of  the  Umbour  is  attached 
toLupigMI  I)  who.se  end  lies  in  contact  with  a  horizontal  screwy.)  Two  arms  (./,.)  are 
Ittachedo  opposite  sides  of  the  steel  plate,  and  to  them  the  belt  (.)  which  fastens  the  nistrument 
to  the  chest  °s  attached  When  the  chest  expands  these  two  arms  are  pulled  asunder,  the  steel  plate 
L  bent   and  the  tambour  is  aftected,  and  any  movement  of  the  tambour  is  transmitted  to  a  registering 

''Tn  th^  cL'e':fTnima 'sVlace'il'lheir  backs,  Snellen  introduced  a  long  needle  vertically  through 
the  abdommal  walls  into  ?he  liver.  Rosenthal  opened  the  abdomen  and  apphed  a  lever  to  the 
under  surface  of  the  diaphragm,  and  thus  registered  its  movements  (Phrenograph). 

The  curve  (Fig.  131,  B)  was  obtained  by  placing  the  tambour  of  a  Brondgeest's 


pansphygmograph  upon  the  xiphoid  process,  and  recording  the  ipovement  upon  a 
plate  attached  to  a  vibrating  tuning  fork.  The  /;»//;-^/.W  (ascending  hmb)  begins 
Sh  moderate  rapidity,  is  accelerated  in  the  middle  and  toward  the  end  again 
becomes  slower.  The  expiration  also  begins  with  moderate  rapidity,  is  'hen  accel- 
erated, and  becomes  much  slower  at  the  latter  part,  so  that  the  curve  falls  very 

^'^f^^^Jaiion  is  slightlv  shorter  tl>an  ^.v//r.//.«.-According  to  Sibson,  the  ratio 
for  an  adult  is  as  6  to  7  5  >"  women,  children  and  old  people  6  to  8  or  6  to  9^ 
Vierordt  found  the  ratio  to  be  10  to  1 4.1  (to  24.1 )  ;  J-  R^  t^vvald  1 1  to  12  It 
is  only  occasionally  that  cases  occur  where  inspiration  and  expiration  are  equally 
long,  or  where  expiration  is  shorter  than  inspiration.  When  respiration  proceeds 
quie  ly  and  ret;ukrly,  there  is  usually  no  pause  (complete  rest  of  the  chest  wal  ) 
ttuJn  the  in^iratiln  and  expiration  {Riegei).     The  very  flat  part  of  the  expira- 


PATHOLOGICAL   VARIATIONS    OF    RESPIRATORY    MOVEMENTS.        195 

tory  curve  has  been  wrongly  regarded  as  due  to  a  pause.     Of  course,  we  may  make 
a  voluntary  pause  between  two  respirations,  or  at  any  part  of  a  respiratory  act. 

Some  observers,  however,  have  described  a  pause  as  occurring  between  the  end  of  expiration  and 
the  beginning  of  the  next  inspiration  (expiration  pause),  and  also  another  pause  at  the  end  of  inspi- 
ration (inspiration  pause).  The  latter  is  always  of  very  short  duration,  and  considerably  shorter 
than  the  former. 

During  very  deep  and  slow  respiration,  there  is  usually  an  expiration  pause,  while  it  is  almost 
invariably  absent  during  rapid  breathing.  An  inspiration  pause  is  always  absent  under  normal  cir- 
cumstances, but  it  may  occur  under  pathological  conditions. 

In  certain  parts  of  the  respiratory  curve  slight  irregularities  may  appear,  which  are  sometimes 
due  to  vibrations  communicated  to  the  thoracic  walls  by  vigorous  heart  beats  (Fig.  132). 

The  "type"  of  respiration  may  be  ascertained  by  taking  curves  from  various 
parts  during  the  respiratory  movements.  Hutchinson  showed  that  in  the  female 
the  thorax  is  dilated  chiefly  by  raising  the  sternum  and  the  ribs  (Respiratio  cos- 
talis),  while  in  man,  it  is  caused  chiefly  by  a  descent  of  the  diaphragm  (Respi- 
ratio diaphragmatica  or  abdominalis).  In  the  former  there  is  the  so-called 
"costal  type,"  in  the  latter  the  "abdominal  or  diaphragmatic  type." 

Forced  Respiration. — This  difference  in  the  type  of  respiration  in  the  sexes  occurs  only  during 
normal  <|uiet  respiration.  During  deep  and  forced  respiration,  in  both  sexes,  the  dilatation  of  the 
chest  is  caused  chiefly  by  raising  the  chest  and  the  ribs.  In  man,  the  epigastrium  may  be  pulled  in 
sooner  than  it  is  protruded.  During  sleep,  the  type  of  respiration  in  both  sexes  is  thoracic,  while, 
at  the  same  time,  the  inspiratory  dilatation  of  the  chest  precedes  the  elevation  of  the  abdominal 
wall  iyMosso'). 

It  is  not  determined  whether  the  costal  type  of  respiration  in  the  female  depends  upon  the  con- 
striction of  the  chest  by  corsets  or  other  causes  [Siison),  or  whether  it  is  a  natural  adaptation  to  the 
child-bearing  function  in  women  ( Hiitiliiiiion).  Some  observers  maintain  that  the  difference  of  type 
is  quite  distinct,  even  in  sleep,  when  all  constrictions  are  removed,  and  that  similar  differences  are 
noticeable  in  young  children.  This  is  denied  by  others,  while  a  third  class  of  observers  hold  that 
the  costal  type  occurs  in  children  of  both  sexes,  and  they  ascribe  as  a  cause  the  greater  flexibility 
of  the  ribs  of  children  and  women,  which  permits  the  muscles  of  the  chest-  to  act  more  eflSciently 
upon  the  ribs.  [When  a  child  sucks,  it  breathes  exclusively  through  the  nose ;  hence,  catarrhal 
conditions  of  the  nasal  mucous  membrane  are  fraught  with  danger  to  the  child.] 

III.  PATHOLOGICAL  VARIATIONS  OF  THE  RESPIRATORY  MOVE- 
MENTS.— [Examination  of  the  Lungs. — The  same  methods  that  are  applicable  to  the  heart 
— viz.,  I,  Inspection  ;   II,  Palpation ;   III,  Percussion ;  and  IV,  . 'Auscultation — apply  here  also.] 

[By  Inspection  we  may  determine  the  presence  of  symmetrical  or  unilateral  alterations  in  the 
shape  of  the  chest,  the  presence  of  bulging  or  flattening  at  one  part,  and  variations  in  the  movement 
of  the  chest  walls,  liy  Palpation,  the  presence  or  absence,  character,  seat  and  extent  of  any  move- 
ments are  more  carefully  examined.  But  we  may  also  study  what  is  called  Vocal  fremitus  (J  I  '7)- 
For  Percussion  (jJ  114);  Auscultation  (J  "6).] 

[In  investigating  the  respiratory  movements,  we  should  observe  (l)  the  frequency  (^  109);  (2) 
the  type  (((  1 10) ;  (3)  the  nature,  character  and  extent  of  the  movements,  noting,  also,  whether  they 
are  accompanied  by  pain  or  not  (J  1 10) ;   (4)  the  rhythm.] 

I.  Changes  in  the  Mode  of  Movement  — In  persons  suffering  from  disease  of  the  respiratory 
organs,  the  dilatation  of  the  chest  may  be  diminished  (to  the  extent  of  5  or  6  cm.)  on  both  sides  or 
only  on  one  side.  In  affections  of  the  apex  of  the  lung  (in  phthisis),  the  subnormal  expansion  of 
the  upper  part  of  the  wall  of  the  chest  may  be  considerable.  Retraction  of  the  soft  parts  of  the 
thoracic  wall,  the  xiphoid  process,  and  the  parts  where  the  lower  ribs  are  inserted,  occurs  in  cases 
where  air  cannot  freely  enter  the  chest  during  inspiration,  e.  g.,  in  narrowing  of  the  larynx  ;  when 
this  retraction  is  confined  to  the  upper  part  of  the  thoracic  wall,  it  indicates  that  the  portion  of  the 
lung  lying  under  the  part  so  affected  is  le^s  extensile  and  diseased. 

Harrison's  Groove. — In  persons  suffering  from  chronic  difficulty  of  breathing,  and  in  whom, 
at  the  same  time,  the  diaphragm  acts  energetically,  there  is  a  slight  groove,  which  passes  horizon- 
tally outward  from  the  xiphoid  cartilage,  caused  by  the  pulling  in  of  the  soft  parts  and  correspond- 
ing to  the  insertion  of  the  diaphragm. 

The  duration  of  inspiration  is  lengthened  in  persons  suffering  from  narrowing  of  the  trachea 
or  larynx;  expiration  is  lengthened  In  cases  of  dilatation  of  the  lung,  as  in  emphysema,  where  all 
the  expir.xtory  muscles  must  be  brought  into  action  (Fig.  132,  II). 

II.  Variations  in  the  Rhythm. — When  the  respiratory  apparatus  is  much  affected,  there  is  either 
an  increa-.e  or  a  deepening  of  the  respirations,  or  both.  When  there  is  great  difficulty  of  breathing, 
this  is  called  Dyspnoea. 

Causes  of  Dyspnoea. — (l)  Limitation  of  the  exchange  of  the  respiratory  gases  in  the  blood 
due  to  — (a)  diminution  of  the  respiratory  surface  (as  in  some  diseases  of  the  lungs) ;   {b)  narrow- 


196  THE    MUSCLES   OF    FORCED    RESPIRATION. 

ing  of  the  respiratory  passages;  (c)  diminution  of  the  red  blood  corpuscles;  (i/)  disturbances  of  the 
respirator}'  mechanism  {e.  g.^  due  to  affections  of  the  respiratory  muscles  or  nerves,  or  painful  affec- 
tions of  tire  chest  wall)  ;  (<■)  impeded  circulation  through  the  lungs  due  to  various  forms  of  heart 
disease.  (2)  Heat  dyspncea. — The  frequency  of  the  respirations  is  increased  \n  febfi/e  conditions. 
The  warm  blood  acts  as  a  direct  irritant  of  the  respiratory  centre  in  the  medulla  oblongata,  and 
raises  the  number  of  respirations  to  30-60  per  minute  ("  Heat  dyspncea").  If  the  carotids  be 
placed  in  warm  tubes,  so  as  to  heat  the  blood  going  to  the  medulla  oblongata,  the  same  phenomena 
are  produced  {A.  Fick),     See  also  "  Respiyatoiy  centre"  {\  368). 

[Orthopnoea. — Sometimes  the  difficulty  of  breathing  is  so  great  that  the  person  can  only  respire  in 
the  erect  position,  /.  (-.,  when  he  sits  or  is  propped  up  in  bed.  This  occurs  frequently  toward  the 
close  of  some  Iieart  affections,  notably  in  mitral  lesions ;  dropsical  conditions,  especially  of  the 
cavities,  may  be  present.] 

CheyneStokes'  Phenomenon. — This  remarkable  phenomenon  occurs  in  certain  diseases, 
where  the  normal  supply  of  blood  to  the  brain  is  altered,  or  where  the  quality  of  the  blood  itself  is 
altered,  e.  g.,  in  certain  affections  of  the  brain  and  heart,  and  in  ur;vmic  poisoning.  Respiratory 
pauses  of  one-half  to  three-quarters  of  a  minute  alternate  with  a  short  period  {^2-%  min.)  of  in- 
creased respiratory  activity,  and  during  this  time  20-30  respirations  occur.  The  respirations  consti- 
tuting this  "  series  "  are  shallow  at  first;  gradually  they  become  deeper  and  more  dyspnceic  ;  and 
finally  become  shallow  or  superficial  again.  Then  follows  the  pause,  and  thus  there  is  an  alterna- 
tion of  pauses  and  series  (or  groups)  of  modified  respirations.  During  the  pause,  the  pupils  are 
contracted  and  inactive;  and  when  the  respirations  begin,  they  dilate  and  become  sensible  to  light ; 
the  eyeball  is  moved  as  a  whole  at  the  same  time  {Letibe).  Hein  observed  that  consciousness  was 
abolished  during  the  pause,  and  that  it  returned  when  respiration  commenced.  A  few  muscular  con- 
tractions may  occur  toward  the  end  of  the  pause  (rare). 

With  regard  to  the  causes  of  this  phenomenon  there  is  some  doubt.  According  to  Rosenbach, 
the  anomalous  nutrition  of  the  brain  causes,  certain  intracranial  centres,  especially  the  respiratory 
centre,  to  be  less  excitable  and  to  be  sooner  exhausted,  and  this  condition  reaches  its  maximum 
during  the  respiratory  pause.  During  the  pause  these  centres  recover,  and  they  again  become  more 
active.  As  soon  as  they  are  again  exhausted,  their  activity  ceases.  Luciani  also  regards  variations 
in  the  excitability  of  the  respiratory  centre  as  the  cause  of  the  phenomenon,  which  he  compares 
with  the  periodic  contraction  of  the  heart  (J  58).  He  observed  this  phenomenon  after  injury  to  the 
metiulla  oblongata  above  the  respiratory  centre,  and  after  apncea  produced  in  animals  deeply  narco- 
tized with  opium.  It  also  occurs  in  the  last  stages  of  asphyxia,  during  respiration  in  a  closed  space. 
Mosso  found  a  similar  phenomenon  normally  in  the  hybernating  dormouse  ( Myoxus)  [and  traces 
of  it  even  in  normal  sleep,  while  it  is  sometimes  observed  in  poisoning  by  morphia  or  chloral]. 

Periodic  Respiration  of  Frogs. —  If  frogs  be  kept  under  water,  or  if  the  aorta  be  clamped, 
after  several  hours,  they  become  passive.  If  they  be  taken  out  of  the  water,  or  if  the  clamp  be  re- 
moved from  tlie  aorta,  they  gradually  recover  and  always  exhibit  the  Cheyne-Stokes'  phenomena. 
In  such  frogs  the  blood  current  may  be  arrested  temporarily,  while  the  phenomenon  itself  remains 
(Sokolow  and  Liichsinger).  If  the  blood  current  be  arrested  by  ligature  of  the  aorta,  or  if  the 
frogs  be  bled,  the  respirations  occur  in  groups.  This  is  followed  by  a  few  single  respirations,  and 
then  the  respiration  ceases  completely.  During  the  pause  between  the  periods,  mechanical  stimu- 
lation of  the  skin  causes  the  discharge  of  a  group  of  respirations  [Siebert  and  Langendorff).  Mus- 
carin  and  digitalin  cause  periodic  respiration  in  frogs  [which  is  not  due  to  the  action  of  these  drugs 
on  the  heart]. 

112.  GENERAL   VIEW    OF   THE    RESPIRATORY   MUSCLES. 

(A)    Inspiration. 

I.  During  Ordinary  Inspir.^tion  are  Active. 

1.  The  diaphragm  (Nerviis  phrenic  us.') 

2.  The  Mm.  levatores  costarum  longi  et  breves  (Rami  posteriores  Abt.  dor- 
saiiuiri). 

3.  The  Mm.  intercostales  externi  et  intercartilaginei  {Nn.  interccntalcs). 

II.  During  Forced  Respiration  are  Active. 

((z)    Muscles  of  the  Trunk. 
I.   The  three  Mm.  scaleni  {^Rami  musculares  of  the  plexus  ccrvicalis  et  brachi- 
alls). 

sternocleidomastoideus  (Ram.  e.xternus  N.  accessorii). 

trapezius  (R.   externus  N.  accessorii  et  Ram.    musculares   plexus   cer- 


2. 

M. 

3- 

M. 

vicahs). 

4- 

M, 

pectoralis  minor  (Xn.  ihoracici  anteriores). 
5.   M.  serratus  posticus  superior  {N.  dorsalis  scapula). 


THE    ACTION    OF   THE    DIAPHRAGM.  197 

6.  Mm.   rhomboidei  (jV.  dorsalis  scapiihe). 

7.  Mm.  extensores  column;t'  vertebralis  {Ram.  posteriores  ncrvoriiin  dorsaliiiin. ) 
[8.   Mm.  serratus  anticus  major  {_N.  thoracicus  /ongus).  ?  ?] 

{b)   Muscles  of  the  Larynx. 

1.  M.  sX^mohyoxd^M's,  {Rant.  Jesceniie/is  hgpog/ossi). 

2.  M.  sternothyreoideus  (Ram.  descendens  hypag/oss:). 

3.  M.  crico-arytEenoideus  posticus  (N.  laryngeus  inferior  vagi). 

4.  M.  thyreo-arytaenoideus  ( 7V^.  laryn(jeus  inferior  vagi). 

{c)   Muscles  of  tJie  Face. 

1.  M.   dilatator  narium  anterior  et  posterior  (7V./(7c/(z/w). 

2.  M.  levator  alae  nasi  {N.  facialis). 

3.  The  dilators  of  the  mouth  and  nares,  during  forced  respiration  [''gasping 
for  breath  "],  {N.  facialis). 

{d)  Muscles  of  the  Pharynx. 

1.  M.  levator  veli  palatina  {N.  facialis). 

2.  M.  azygos  uvula;  {N.  facialis). 

3.  According  to  Garland,  the  pharynx  is  always  narrowed. 

(B)  Expiration. 

I.   During  Ordinary  Respiration. 

The  thoracic  cavity  is  diminished  by  the  weight  of  the  chest,  the  elasticity  of 
the  lungs,  costal  cartilages  and  abdominal  muscles. 

II.   During  Forced  Expiration. 
The  Abdominal  Muscles. 

1.  The  abdominal  muscles  [including  the  obliquus  externus  and  internus,  and 
transversalis  abdominis]  {Nn.  abdominis  internus  anteriores  e  nervis  intercostalibus, 
8-12). 

2.  Mm.  intercostales  interni,  so  far  as  they  lie  between  the  osseous  ribs,  and  the 
Mm.  infracostales  {Nn.  intercostales). 

3.  M.  triangularis  sterni  {Nn.  intercostales). 

4.  M.  serratus  posticus  inferior  {Ram  externi  ne/T.  dorsalium). 

5.  M.  quadratus  lumboruni  {Ram  muscular  e plexu  luinhali). 

113.  ACTION  OF  THE  INDIVIDUAL  RESPIRATORY  MUSCLES.— (A)  In- 
spiration.— (i)  The  Diaphragm  arises  from  the  cartilages  and  the  adjoining  osseous  parts  of  the 
lower  six  ribs  (costal  portion),  by  two  thick  processes  or  crura  from  the  upper  three  or  four  lumbar 
vertebra?,  and  a  sternal  portion  from  the  back  of  the  ensiform  process. 

It  represents  an  arched  double  cupola  or  dome-shaped  partition,  directed  toward  the  chest ;  in  the 
larger  concavity  on  the  right  side  lies  the  liver,  while  the  smaller  arch  on  the  left  side  is  occupied 
by  the  spleen  and  stomach.  During  the  passive  condition,  these  viscera  are  pressed  against  the 
under  surface  of  the  diaphragm,  by  the  elasticity  of  the  abdominal  walls  and  by  the  intra-abdominal 
pressure,  so  that  the  arcli  of  the  diaphragm  is  pressed  upward  into  the  chest.  The  elastic  traction 
of  the  lungs  also  aids  in  producing  this  result.  The  greater  part  of  the  upper  surface  of  the  central 
tendon  of  the  diaphragm  is  united  to  the  pericardium.  The  part  on  which  the  heart  rests,  and 
which  is  perforated  by  the  inferior  vena  cava  (foramen  quadrilaterum)  is  the  deepest  part  of  the 
middle  portion  of  the  diaphragm  during  the  ])assive  condition. 

Action  of  the  Diaphragm. — When  the  diaphragm  contracts,  both  arched 
portions  become  flatter,  and  the  chest  is  thereby  elongated  from  above  down- 
ward. In  this  act,  the  lateral  muscular  parts  of  the  diaphragm  pass  from  an 
arched  condition  into  a  flatter  form  (Fig.  133),  and  during  a  forced  inspiration, 
the  lowest  lateral  portions,  which,  during  rest,  are  in  contact  with  the  chest  wall, 


198 


CHANGES    IN    THE    CHEST. 


Fig.  133.  become  separated  from  it.     The  middle  of  the 

central  tendon  where  the  heart  rests  ( fixed  by 
means  of  the  pericardium  and  inferior  vena 
cava)  takes  no  share  in  this  movement,  espe- 
cially in  ordinary  quiet  breathing,  but  during 
the  deepest  inspiration  it  sinks  somewhat 
(JIc7sse). 

Undoubtedly,  the  diaphragm  is  the  most  powerful 
agent  in  increasing  the  cavity  of  the  chest.  Briicke, 
in  fact,  believes  that  in  addition  to  increasing  the 
length  of  the  thoracic  cavity  from  above  downward,  it 
also  increases  the  transverse  diameter  of  the  lower  part 
of  the  chest.  It  presses  upon  the  abdominal  viscera 
from  above,  and  strives  to  press  these  outward,  thus 
tending  to  push  out  the  adjoining  thoracic  wall.  If  the 
contents  of  the  abdomen  are  removed  from  a  living 
animal,  every  time  the  diaphragm  contracts  the  ribs  are 
drawn  inward  (Hallei-y  This,  of  course,  hinders  the 
chest  from  becoming  wider  below,  hence  the  presence 
of  the  abdominal  viscera  seems  to  be  necessary  for  the 
normal  activity  of  the  diaphragm. 

Every  contraction  of  the  diaphragm,  by  increasing 
the  intra-abdominal  pressure,  favors  the  venous  blood 
current  in  the  abdomen  toward  the  vena  cava  inferior 

,.  Phrenic  Nerve. — The  immense  importance  of  the 

>   on  trie      ,.      1  ,  .         .  '^ ,    .  ,    , 

»'hen  the    diaphragm  as  the  great  inspiratory  muscle  is  pro\ed  by 
scular  part  of  the  diaphragm  con-    the  fact  that,  after  both  phrenic  nerves  (third  and  fourth 
vedge-shaped  space,  with  its  apex    cervical   nenes)    are    divided,    death    occurs    (Budge, 
downward,  is   formed  around  the  circumfer-      r-    ,      ,         ^,       V,  ,         .  »  a    > 

ence  of  the  lower  part  of  the  chest,  so  that    Eiilenkamp).     The   phrenic  nerve   contains  some  sen- 
the  chest  is  enlarged  from  above  downward.    •  sory  fibres  for  the  pleura,  pericardium  and  a  portion  of 
the  diaphragm  [Sc/ireiber,  Henh\  Sitncalhe). 
The  contraction  of  the   diaphragm   is  not  to  be  regarded  as  a  "  simple  muscular  contraction," 
since  it  lasts  4  to  8  times  longer  than  a  simple  contraction ;  it  is  rather  a  short  tetanic  contraction, 
which  we   may  arrest  in  any  stage  of  its  activity,  without  bringing  into  action  any  antagonistic 
muscles  (Kroiiecier  aud  Marckwald). 

(2)  The  Elevators  of  the  Rib. — The  ribs  at  their  vertebral  ends  (which  lie  much  higher  than 
their  sternal  ends)  are  united  by  means  of  joints,  by  their  heads  and  tubercles,  to  the  bodies  and 
transverse  processes  of  the  vertebrae.  .\  horizontal  axis  can  be  drawn  through  both  joints,  around 
which  the  ribs  can  rotate  upward  and  downward.  If  the  axes  of  rotation  of  each  pair  of  ribs  be 
prolonged  on  both  sides  until  they  meet  in  the  middle  line,  the  angles  so  formed  are  greatest  above 
(125°),  and  smaller  below  (88°)  [A.  fV.  Volkmann).  Owing  to  the  ribs  being  curved,  we  can 
imagine  a  plane  which,  in  the  passive  (expiratory)  condition  of  the  chest,  has  a  slope  from  behind 
and  inward  to  the  front  and  outward.  If  the  ribs  move  on  their  axis  of  rotation  this  plane  be- 
comes more  horizontal,  and  the  thoracic  cavity  is  increased  in  its  transverse  diameter.  As  the  axis 
of  rotation  of  the  upper  ribs  runs  in  a  more  frontal,  and  that  of  the  lower  ribs  in  a  more  sagittal, 
direction,  the  elevation  of  the  upper  ribs  causes  a  greater  increase  from  before  backward,  and  the 
lower  ribs  from  within  outward  (as  the  movements  of  ribs  which  are  directed  downward  are  verti- 
cal to  the  axis).  The  costal  cartilages  undergo  a  slight  tension  at  the  same  time,  which  brings  their 
elasticity  into  play. 

Changes  in  the  Chest. — AH  "  iiis/tira/on'  niuscks"  7vhich  act  directly  upon 
the  chest  icall,  do  Sit  by  raising  the  ribs :  (a)  When  the  ribs  are  raised,  the  inter- 
costal spaces  are  widened,  {h)  When  the  upper  ribs  are  raised,  all  the  lower  ribs 
and  the  sternum  must  be  elevated  at  the  same  time,  because  all  the  ribs  are  con- 
nected with  each  other  by  means  of  the  soft  parts  of  the  intercostal  spaces,  {c) 
During  inspiration,  there  is  an  elevation  of  the  ribs  and  a  dilatation  of  the  inter- 
costal spaces.  (The  lowest  rib  is  an  exception;  during  forced  respiration,  at  least, 
it  is  drawn  downward.)  {d )  If,  on  a  preparation  of  the  chest,  the  ribs  be  raised  as 
in  inspiration,  we  may  regard  all  those  muscles  as  elevators  of  the  ribs  whose  origin 
and  insertion  become  approximated.  Every  one  is  agreed  that  the  sca/eni Bind  leva- 
tores  costarum  longi  et  brei-cs,  the  serratus  posticus  superior,  are  inspiratory  muscles. 
These  are  the  most  important  inspiratory  muscles  which  act  upon  the  ribs. 


INTERCOSTAL    MUSCLES. 


199 


Intercostal  Muscles. — With  regard  to  the  action  of  the  intercostal  muscles, 
there  is  a  great  difference  of  opinion.  According  to  the  above  experiment,  the 
external  intercostals  and  the  intercartilaginous  parts  of  the  internal  intercostals  act 
as  inspiratory  muscles,  while  the  remaining  portions  of  the  internal  intercostals  (as 
far  as  they  are  covered  by  the  external)  are  elongated  when  the  ribs  are  raised, 
while  they  shorten  when  the  chest  wall  descends.  A  muscle  shortens  only  during 
Its  activity.  The  internal  intercostals  were  regarded  by  Hamberger  as  depressors 
of  the  ribs  or  expiratory  muscles. 

In  Fig.  134, 1,  when  the  rods,  a  and  b  (which  represent  the  ribs),  are  raised,  the  intercostal  space 
must  be  widened  (ef^c  d).  On  the  opposite  side  of  the  figure,  it  is  evident  that  when  the  rods 
are  raised,  the  line,  g  h,  is  shortened  li  i<^  g  h,  direction  of  the  external  intercostals),  /  /«  is  length- 
ened {I  m<^  0  It,  direction  of  internal  intercostals).  Fig.  13^.  H,  shows,  that  when  the  ribs  are 
raised,  the  intercartilaginei,  indicated  by  j^' /;,  and  the  external  intercostals,  indicated  by  / /■,  are 
shortened.  When  the  ribs  are  raised,  the  position  of  the  muscular  fibres  is  indicated  liy  the  diagonal 
of  the  rhomb  becoming  shorter. 

Fig.  134. 


0 

y 

i/^ 

The  mode  of  action  of  the  intercostal  muscles  is  an  old  story,  Galen  (131-203  A.D.)  regarding 
the  externals  as  inspiratorj',  the  internals  as  expiratory.  Hamberger  (1727)  accepted  this  proposition, 
and  considered  the  intercartilaginei  also  as  inspiratory'.  Haller  looked  upon  both  the  external  and 
internal  intercostals  as  inspiratory,  while  Vesalius  (1540)  regarded  both  as  expiratory.  Landerer, 
observing  that  the  upper  two  or  three  intercostal  spaces  became  narrower  during  inspiration,  regarded 
both  as  active  during  inspiration  and  exp'ration.  They  keep  one  rib  attached  to  the  other,  so  that 
their  action  is  to  transmit  any  strain  put  upon  them  to  the  wall  of  the  chest.  On  this  view  they  will 
be  in  action,  even  when  the  distance  between  their  points  of  attachment  becomes  greater.  Landois 
regards  the  external  intercostals  and  intercartilaginei  as  active  o)i/r  during  inspiration,  the  internal 
intercostals  on/v  during  expiration.  [Martin  and  Hartwell  exposed  the  internal  intercostals  and 
observed  whether  they  contracted  along  with  the  diaphragm,  or  whether  the  contractions  of  these 
two  muscles  alternate.  As  the  result  of  their  experiments,  they  conclude  that  "  the  internal  inter- 
costal muscles  are  expiratory  throughout  the  whole  extent,  at  lea.st  in  the  dog  and  cat ;  and  that  in 
the  former  animal  they  are  almost  '  ordinary  '  muscles  of  respiration,  while  in  the  latter  they  are 
*  extraordinary  '  respiratory  mucles."]  Landois  is  of  the  opinion  that  the  d"///*'/"  action  of  these  mus- 
cles is  not  to  raise  or  depress  the  ribs,  but  rather  that  the  external  intercostals  and  the  intercartilaginei 


2(K)  MUSCLES   OF    FORCED    EXPIRATION. 

offer  resistance  to  the  inspiratory  dilatation  of  the  intercostal  spaces,  and  to  the  simultaneously 
increased  elastic  tension  of  the  lungs.  The  internal  intercostals  act  during  powerful  expiratory 
efforts  (e'.^'-.,  coughing),  and  oppose  the  distention  of  the  lungs  and  chest  caused  by  this  act.  Unless 
muscles  were  present  to  resist  the  uninterrupted  tension  and  pressure,  the  intercostal  substance 
would  become  so  distended  that  respiration  would  be  impossible.  [According  to  Rutherford,  the  inter- 
nal intercostals  are  probably  muscles  of  inspiration.] 

The  Pectoralis  Minor  and  (?  Serratus  Anticus  Major)  can  only  act  as 
elevators  of  the  ribs  when  the  shoulders  are  fixed,  partly  by  the  rhomboidei,  and 
partly  by  fi.xing  the  slToulder  joint  and  stipporting  the  arms,  as  is  done  instinctively 
by  persons  suffering  from  breathlessness. 

(3)  Muscles  acting  upon  the  Sternum,  Clavicle  and  Vertebral 
Column. — When  the  head  is  fixed  by  the  muscles  of  the  neck,  the  sternocleido- 
mastoid can  raise  the  manubrium  sterni,  and  the  sternal  end  of  the  clavicle  so 
that  the  thorax  is  raised  and  thereby  dilated.  The  scaleni  also  aid  in  this  act.  The 
clavicular  portion  of  the  trapezius  may  act  in  a  similar  although  less  energetic 
manner.  ^Vhen  the  vertebral  column  is  straig)itened,  it  causes  an  elevation  of  the 
upper  ribs,  and  a  dilatation  of  the  intercostal  spaces  which  aid  inspiration.  Dur- 
ing deep  respiration,  this  straightening  of  the  vertebral  column  takes  place  invol- 
untarily. 

(4)  Laryngeal  Movements. — During  labored  respiration,  with  every 
inspiration  the  larynx  descends  and  the  glottis  is  opened.  At  the  same  time 
the  palate  is  raised,  so  as  to  permit  a  free  passage  to  the  air  entering  through 
the  mouth. 

{5)  Facial  Movements. — During  labored  respiration,  the  facial  muscles  are 
involved  ;  there  is  an  inspiratory  dilatation  of  the  nostrils  (well  marked  in  the  horse 
and  rabbit).  When  the  need  for  respiration  is  very  great,  the  mouth  is  gradually 
widened,  and  the  person,  as  it  were,  gasps  for  breath.  During  expiration,  the 
muscles  that  are  active  during  (4)  and  (5)  relax,  so  that  a  position  of  equilibrium 
is  established  without  there  being  any  active  expiratory  movement  to  counteract 
the  inspiratory  movement.  Durmg  inspiration  the  pharynx  becomes  narrower 
(^Garland). 

(B)  Expiration. — Ordinary  expiration  occurs  without  the  aid  of  muscles, 
owing  to  the  weight  of  the  chest,  which  tends  to  fall  into  its  normal  position 
from  the  position  to  wliich  it  was  raised  during  inspiration.  This  is  aided  by  the 
elasticity  of  the  various  parts  of  the  chest.  When  the  costal  cartilages  are 
raised,  which  is  accompanied  by  a  slight  rotation  of  their  lower  margins  from 
below  forward  and  upward,  their  elasticity  is  called  into  play.  As  soon,  therefore, 
as  the  inspiratory  forces  cease,  the  costal  cartilages  return  to  theirnormal  position, 
— i.e.,  the  position  of  expiration — and  tend  to  imtwist  themselves;  at  the  same 
time,  the  elasticity  of  the  distended  lungs  draws  upon  the  thoracic  walls  and 
the  diaphragm.  Lastly,  the  tense  and  elastic  abdominal  walls,  which,  in 
man  chiefly,  are  stretched  and  pushed  forward,  tend  to  return  to  their  non-dis- 
tended, passive  condition  when  the  abdominal  viscera  are  relieved  from  the 
pressure  of  the  contracted  diaphragm.  (When  the  position  of  the  body  is  re- 
versed, the  action  of  the  weight  of  the  chest  is  removed  ;  but  in  place  of  it,  there 
is  the  weight  of  the  viscera  which  press  upon  the  diaphragm.) 

The  abdominal  muscles  [obliquus  internus  and  externus,  transversalis  abdo- 
minis and  levator  ani]  are  always  active  during  labored  respiration.  They  act  by 
diminishing  the  abdominal  cavity,  and  they  press  the  abdominal  contents  upward 
against  the  diaphragm.  When  they  act  simultaneously,  the  abdominal  cavity  is 
diminished  throughout  its  whole  extent.  The  Triangularis  sterni  depresses 
the  sternal  ends  of  the  united  cartilages  and  bones,  from  the  third  to  sixth  rib 
downward ;  and  the  Serratus  posticus  inferior  depresses  the  four  lowest  ribs, 
causing  the  others  to  follow.  It  is  aided  by  the  Quadratus  lumborum,  which 
depresses  the  last  rib.  According  to  Henle,  the  serratus  posticus  inferior  fixes 
the  lower  ribs  for  the  action  of  the  slips  of  the  diaphragm  inserted  into  them,  so 


RELATIVE    DIMENSIONS    OF   THE    CHEST. 


201 


that  it  acts  during  inspiration.     According  to  Landerer,  the  downward  movement 
of  the  ribs  in  the  lower  part  of  the  thorax  dilates  the  chest. 

In  the  erect  position,  when  the  vertebr.il  column  is  fixed,  deep  inspiration  and  expiration  naturally 
alter  the  position  of  the  centre  of  gravity,  so  that  during  inspiration,  owing  to  the  protrusion  of 
the  thoracic  and  abdominal  walls,  the  centre  of  gravity  lies  somewhat  more  to  the  front.  Hence, 
with  each  respiration  there  is  an  involuntary  balancing  of  the  body.  During  very  deep  inspiration, 
'  the  accompanying  straightening  of  the  vertebral  column  and  the  throwing  backward  of  the  head 
compensate  for  the  protrusion  of  the  anterior  walls  of  the  trunk. 

114.  RELATIVE  DIMENSIONS  OF  THE  CHEST.— It  is  important,  from  a  physi- 
cian's point  of  view,  to  know  the  dimensions  of  the  thorax,  and  also  the  variations  it  undergoes  at 
different  parts.  The  diameter  of  the  chest  is  ascertained  by  means  of  callipers ;  the  circumference, 
with  a  flexible  centimetre  or  other  measure. 

In  strong  men,  the  circumference  of  the  upper  part  of  the  chest  (immediately 
under  the  arms)  is  88  centimetres  (34.3  inches),  in  females,  82  centimetres  (32 
inchesj  ;    on  the  level  of  the  ensiform 


35- 


rve  t-iken  with  the  cyrtometer.     Left  side  of  the  chesl 
retracted  in  a  girl  twelve  years  of  age  {Eichhorsi). 


process,  82  centimetres  (32  inches)  and 
78  centimetres  (30.4  inches),  respect- 
ively. When  the  arms  are  placed  hori- 
zontally, during  the  phase  of  moderate 
expiration,  the  circumference  immedi- 
ately under  the  nipple  and  the  angles  of 
the  scapulae  is  equal  to  half  the  length  of 
the  body  ;  in  man,  82,  and  during  deep 
inspiration  89  centimetres.  The  cir- 
cumference at  the  level  of  the  ensiform 
cartilage  is  6  centimetres  less.  In  old 
people,  the  circumference  of  the  upper 
part  of  the  chest  is  diminished,  so  that 
the  lower  part  becomes  the  wider  of  the 
two.  The  right  half  of  the  chest  is 
usually  slightly  larger  than  the  left  half, 
owing  to  the  greater  development  of  the 
muscles  on  that  side.  The  long  diam- 
eter of  the  chest — from  the  clavicle  to 
the  margin  of  the  lowest  rib — varies  very  much. 

The  transverse  diameter  in  man,  above  and  below,  is  25  to  26  centimetres 
(9.7  to  10. 1  inches),  in  females  23  to  24  centimetres  (8.9  to  9.2  inches)  ;  above 
the  nipple  it  is  one  centimetre  more.  The  antero-posterior  diameter  (dis- 
tance of  anterior  chest  wall  from  the  tip  of  a  spinous  process)  in  the  upper 
part  of  the  chest  is  ^  17  (6.6  inches),  in  the  lower  19  centimetres  (7.4  inches). 
Valentin  found  that  in  man,  during  the  deepest  inspiration,  the  chest  on  a  level 
with  the  groove  in  the  heart  was  increased  about  ^V  to  \,  while  Sibson  estimates 
the  increase  at  the  level  of  the  nipple  to  be  -^^. 

Thoracometer. — In  order  to  obtain  a  knowledge  of  the  degree  of  movement — rising  or  falling 
— of  the  chest  wall  during  respiration,  various  instruments  have  been  invented.  The  thoracometer 
of  Sibson  (Fig.  136)  measures  the  elevation  in  different  parts  of  the  sternum.  It  consists  of  two 
metallic  bars  placed  at  right  angles  to  each  other;  one  of  them.  A,  is  placed  on  the  vertebral 
column.  On  B  there  is  placed  a  movable  transverse  bar,  C,  which  carries  on  its  free  end  a  toothed 
rod,  Z,  directed  downward.  The  lower  end  of  this  rod  is  provided  with  a  pad  which  rests  on  the 
sternum,  while  its  toothed  edge  drives  a  small  wheel  which  moves  an  index,  whose  excursions  are 
indicated  on  a  circle  with  a  scale  attached  to  it. 

The  Cyrtometer  of  Woillez  is  ver\'  useful.  A  brass  chain,  composed  of  movable  links,  is 
applied  in  a  definite  direction  to  part  of  the  chest  wall,  e.  g.,  transversely  on  a  level  with  the  nipple, 
or  vertically  upon  the  mammillary  or  axillary  lines  anteriorly.  There  are  freely  movable  links  at 
two  parts,  which  permit  the  chain  to  be  easily  removed,  so  that  as  a  whole  it  still  retains  its  form. 
The  chain  is  laid  upon  a  sheet  of  paper,  and  a  line  drawn  with  a  pencil  around  its  inner  margin 
gives  the  form  of  the  thorax  (Fig.  135).     [A  lead  wire  answers  the  same  purpose.] 


202 


LIMITS   OF   THE    LUNGS. 


Limits  of  the  Lungs. — The  extent  and  boundaries  of  the  kings  are  ascer- 
tained in  the  living  subject  by  means  of  percussion,  which  consists  in  lightly 
tapping  the  chest  wall  by  means  of  a  hammer  (percussion  hammer).     A  small 


Sibson's  ihoracometer. 

Fig.  137. 


^■^"-^^l 


Topography  ol  the  lungs  and  h'-art  dunnc  in-^ 
lung  during  deepest  expiratirn  m  n,  low  f 
heart  is  uncovered  by  lung,  dull  percu'^vion 
left  lung  re-iches  thib  line  during  deep  inspir 


ir.itiiMi  .Mill  I  \i.;i  .III'  'M  ir'    .''■'■■  '/.  /.  upward  limit  ot  margii 

linni  dnnii^  il.Tpi-^t  iiispir.uii  >ii :  .',.'',  t" ,  triangular  area  where 
ound  ;  (/,  tf ,  d" ,  mutned  percussion  sound  ;  /,  /',  anterior  margir 
tion,  and  during  deep  expiration  it  recedes  as  far  as  e^  e' . 


ivory  or  bony  plate  (pleximeter),  held  in  the  left  hand,  is  laid  on  the  chest,  and 
the  hammer  is  made  to  strike  this  plate,  whereby  a  sound  is  emitted,  which  sound 
varies  with  the  condition  of  the  subjacent  lung  tissue.     Whenever  the  lung  sub- 


PATHOLOGICAL   VARIATIONS    OF   THE    PERCUSSION    SOUNDS.        203 

Stance  in  contact  with  the  chest  wall  contains  air,  a  clear  resonant  tone  or  sound 
— such  as  is  obtained  by  striking  a  vessel  containing  air,  a  clear  percussion  sound 
— is  obtained.  Where  the  lung  does  not  contain  air,  a  dull  sound — like  striking 
a  limb — is  obtained.  If  the  parts  containing  air  be  very  thin,  or  are  only  partially 
filled  with  air,  the  sound  is  "muffled." 

Fig.  137  indicates  the  relations  of  the  lungs  to  the  anterior  surface  of  the  chest. 
The  apices  of  the  /u/i^s  reach  3  to  7  centimetres  (i.  i  to  2.7  inches)  above  the 
clavicles  anteriorly,  while  posteriorly  they  extend  from  the  spines  of  the  scapulae 
as  high  as  the  seventh  spinous  process.  The  loiver  margin  of  the  right  lung  in  the 
passive  position  (moderate  expiration)  of  the  chest,  commences  at  the  right  margin 
of  the  sternum  at  the  insertion  of  the  sixth  rib,  runs  under  the  right  nipple,  nearly 
parallel  to  the  upper  border  of  the  sixth  rib,  and  descends  a  little  in  the  axillary 
line,  to  the  upper  margin  of  the  seventh  rib.  On  the  left  side  (apart  from  the 
position  of  the  heart),  the  lower  limit  reaches  as  far  down  anteriorly  as  the  right. 
In  Fig.  137  the  line  a,  t,  b,  shows  the  lowest  limit  of  the  passive  lungs.  Posteri- 
orly, both  lungs  reach  as  far  down  as  the  tenth  rib.  During  the  deepest  inspiration, 
the  lungs  descend  anteriorly  as  far  as  between  the  sixth  and  seventh  ribs,  and 
posteriorly  to  the  eleventh  rib — whereby  the  diaphragm  is  separated  from  the 
thoracic  wall  (Fig.  133).  During  the  deepest  expiration,  the  lower  margins  of  the 
lungs  are  elevated  almost  as  much  as  they  descend  during  inspiration.  In  Fig. 
137,  /;;,  ;/,  indicates  the  margin  of  the  right  lung  during  deep  inspiration  ;  //,  /, 
during  deep  expiration. 

It  is  important  to  observe  the  relation  of  the  margin  of  the  left  lung  to  the  heart. 
In  Fig.  137  a  somewhat  triangular  space,  reaching  from  the  middle  of  the  point 
of  insertion  of  the  fourth  rib  to  the  sixth  rib  on  the  left  side  of  the  sternum,  is 
indicated.  In  the  passive  chest,  the  heart  lies  in  contact  with  the  thoracic  wall 
in  this  triangular  area  (§  56).  This  area  is  represented  by  the  triangle  /.  /',  /", 
and  percussion  over  it  gives  a  dull  sound  (superficial  dullness). 

In  the  area  of  the  larger  triangle  d,  d ,  d' ,  where  the  heart  is  separated  from  the 
chest  wall  by  the  thin  anterior  margins  of  the  lung,  percussion  gives  a  muffled 
sound,  while  further  outward  a  clear  lung  percussion  sound  is  obtained.  During 
deep  inspiration,  the  inner  margin  of  the  left  lung  reaches  over  the  heart  as  far  as 
the  insertion  of  the  mediastinum,  whereby  the  dull  sound  is  limited  to  the  smallest 
triangle,  /,  /,  /'.  Conversely,  during  very  complete  expiration,  the  margin  of  the 
lung  recedes  so  far  that  the  cardiac  dullness  embraces  the  space,  /,  e,  e . 

115.  PATHOLOGICAL  VARIATIONS  OF  THE  PERCUSSION  SOUNDS.— 
Abnormal  Dullness. — The  normal  clear  resonant  percussion  sound  of  the  lungs  becomes  muffled 
when  infiltration  takes  place  into  the  lungs,  so  as  to  diminish  the  normal  amount  of  air  within  them, 
or  when  the  lungs  are  compressed  from  without,  e.  g.,  by  effusion  of  blood  into  the  pleura.  The 
percussion  sound  becomes  clearer  when  the  chest  wall  is  verj'  thin,  as  in  spare  individuals,  during 
very  deep  inspiration,  and  especially  in  emphysema,  where  the  air  vesicles  of  certain  parts  of  the 
lung  (apices  and  margins)  become  greatly  dilated. 

The  pitch  of  the  percussion  sound  ought  also  to  be  noted.  It  depends  upon  the  greater  or  less 
tension  of  the  elastic  pulmonary  tissue,  and  on  the  elasticity  of  the  thoracic  wall.  The  tension  of 
the  elastic  tissue  is  increased  during  inspiration  and  diminished  during  expiration,  so  that  even  under 
physiological  conditions  the  pitch  of  the  sound  varies. 

The  sound  is  said  to  be  tympanitic  (Skoda)  when  it  has  a  musical  quality  resembling  in  its 
timbre  the  sound  produced  on  a  drum,  and  when  it  has  a  slight  variation  in  pitch.  If  a  caoutchouc 
ball  be  placed  near  the  ear,  on  tapping  it  gently,  a  well-marked  tympanitic  sound  is  heard,  and  the 
sound  is  of  higher  pitch  the  smaller  the  diameter  of  the  ball.  A  tympanitic  sound  is  always  pro 
duced  on  tapping  the  trachea  in  the  neck.  A  tympanitic  sound  produced  over  the  chest  is  always 
indicative  of  a  diseased  condition.  It  occurs  in  cases  of  cavities  or  vomicae  within  the  substance  of 
the  lung  (the  sound  becomes-deeper  when  the  mouth,  or  better,  the  mouth  and  nose,  are  closed), 
when  air  is  present  in  one  pleural  cavity,  as  well  as  in  conditions  where  the  tension  of  the  pulmon- 
ary tissues  is  diminished.  The  tympanitic  sound  resembles  the  metallic  tinkling  which  is  heard  in 
large  pathological  cavities  in  the  lungs,  or  which  occurs  when  the  pleural  cavity  contains  air,  and 
when  the  conditions  which  permit  a  more  uniform  reflection  of  the  sound  waves  within  the  cavity 
are  present. 

[When  a  cavity,  freely  communicating  with  a  large  bronchus,  exists  in  the  upper  and  anterior 


204  PATHOLOGICAL    RESPIRATORY   SOUNDS. 

part  of  Ihe  lung,  a  peculiar  "  cracked-pot  "  sound  is  heard  on  percussing  over  the  part.  Some 
notion  of  this  sound  may  be  obtained  by  clasping  the  two  hands  so  as  to  bring  the  palms  nearly 
together,  leaving  an  air  space  between,  and  then  striking  them  on  the  knee.  When  percussion  is 
made  over  a  large  cavity  communicating  with  a  bronchus,  some  of  the  air  is  expelled,  and  the  sound 
thereby  emitted  is  blended  with  the  fundamental  note  of  the  air  in  the  cavity  itself,  the  combination 
of  these  two  sounds  thus  producing  the  "  cracked-pot  "  sound.] 

Resistance. — When  percussing  a  chest,  we  may  determine  whether  the  substance  lying  under 
the  portion  of  the  chest  under  examination  presents  great  or  small  resistance  to  the  blow,  either  of 
the  percussion  hammer  or  of  the  tips  of  the  fingers,  as  the  case  may  be,  [(•.  ^■-.,  in  great  pleuritic 
effusion  exerting  much  pressure  on,  and  so  distending  the  thorax  walls]. 

Phonotnetry. — If  the  stem  of  a  vibrating  tuning-fork  be  placed  on  the  chest  wall  over  a  part 
containing  air,  its  sound  is  intensified  ;  but  if  it  be  placed  over  a  portion  of  the  lung  which  contains 
little  or  no  air  its  sound  is  enfeebled  [von  Baas). 

Historical. — The  actual  discoverer  of  the  art  of  percussion  was  Auenbrugger  (f  1809).  Piorry 
and  Skoda  developed  the  art  and  theory  of  percussion,  while  Skoda  originated  and  developed  the 
physical  theory  (1839). 

116.  THE  NORMAL  RESPIRATORY  SOUNDS.— Normal  Ves- 
icular Sound. — If  the  ear  directly,  or  through  the  medium  of  a  stethoscope,  be 
placed  in  connection  with  the  chest-wall,  we  hear  over  the  entire  area,  where  the 
lung  is  in  contact  with  the  chest,  the  so-called  "  vesicular  "  sound,  which  is  audi- 
ble during  inspiration,  and  its  typical  characters  may  be  studied  by  listening  in  the 
infrascapular  region  in  an  adult.  It  is  a  fine  sighing  or  breezy  sound  [which 
gradually  increases  in  intensity  until  it  reaches  a  maximum,  and  falls  away  before 
expiration  begins].  It  is  said  to  be  caused  by  the  sudden  dilatation  of  the  air 
vesicles  (hence  "vesicular")  during  inspiration,  and  it  is  also  ascribed  to  the 
friction  of  the  current  of  air  entering  the  alveoli.  The  sound  has,  at  one  time, 
a  soft,  at  another,  a  sharper  character  ;  the  latter  occurs  constantly  in  children  up 
to  12  years  of  age.  In  their  case,  the  sound  is  sharper,  because  the  air,  in  enter- 
ing vesicles  one-third  narrower,  is  subjected  to  greater  friction.  [This  is  followed 
by  an  expiratory  sound,  which  may  be  absent  during  quiet  breathing.  It  is  a  feeble, 
sighing  sound,  of  an  indistinct,  soft  character,  caused  by  the  air  passing  out  of  the 
air  vesicles,  is  three  or  four  times  shorter  than  the  inspiratory,  is  loudest  at  first, 
and  soon  disappears,  the  latter  part  of  the  expiratory  act  giving  rise  to  no  audible 
sound.  Its  absence  is  not  a  sign  of  disease,  but  when  it  is  prolonged  and  loud, 
suspicion  is  aroused.] 

Bronchial  Respiration. — Within  the  larger  air  passages — larynx,  trachea, 
bronchi — during  inspiration  and  expiration,  there  are  loud,  rough,  harsh  sounds 
like  a  sharp  h  or  ch — the  '^  broncliial" — the  laryngeal,  tracheal,  or  "tubular" 
sound,  or  breathing.  [In  normal  bronchial  breathing,  as  heard  over  the  trachea, 
there  is  a  pause  between  the  inspiratory  and  expiratory  sounds,  which  are  of  nearly 
equal  duration  and  of  about  the  same  intensity  throughout.]  These  sounds  are  also 
heard  between  the  scapula;,  at  the  level  of  the  fourth  dorsal  vertebra  (bifurcation 
of  trachea),  and  they  occur  also  during  expiration,  being  slightly  louder  on  the 
right  side,  owing  to  the  slightly  greater  calibre  of  the  right  bronchus. 

At  all  other  parts  of  the  chest,  the  vesicular  sound  obscures  the  tubular  or  bron- 
chial sound.  If  the  air  vesicles  are  deprived  of  their  air,  the  tubular  breathing 
becomes  distinct. 

It  is  asserted  that,  when  lungs  containing  air  are  placed  over  the  trachea,  the  tubular  sound  there 
produced  becomes  vesicular.  In  this  case,  we  must  suppose  that  the  vesicular  sound  arises  from 
the  tubular  breathing  becoming  weakened,  and  being  acoustically  aUered,  by  being  conducted 
through  the  lung  alveoli  [Baas,  Pcnzolilt).  A  sighing  sound  is  often  produced  at  the  apertures  of 
the  nose  and  mouth  during  forced  respiration. 

117.  PATHOLOGICAL  RESPIRATORY  SOUNDS.— Historical.— Although  several 
abnormal  sounds  in  connection  with  diseases  of  the  respiratory  organs  were  known  to  Hippocrates 
(succussion  sound,  friction  and  several  catarrhal  sounds)  still,  Laennec  was  the  discoverer  of  the 
method  of  auscultation  (1S16),  while  Skoda  greatly  extended  our  knowledge  of  its  facts. 

[The  breath  sounds  heard  in  disease  may  be  merely  modifications  of  the  normal  vesicular  or 
bronchial  sounds,  or  new  sounds,  such  as  friction  sounds,  rales  or  rhonchi.] 

[Puerile  Breathing  is  merely  an  exaggerated  vesicular  sound,  so  called  because  it  resembles 


PRESSURE    IN    THE    AIR    PASSAGES    DURING    RESPIRATION.  205 

the  louder  vesicular  sound  heard  in  children.  It  occurs  when  some  part  of  the  lung  is  unable  to 
act,  and  there  is,  as  it  were,  extra  work  of  the  other  parts  to  compensate,  and  thus  the  sound  is 
exaggerated.] 

(1 )  Bronchial  or  Tubular  Breathing  occurs  over  the  entire  area  of  the  lung,  either  when  the 
air  vesicles  are  Ji-i'oid  of  air,  which  may  be  caused  by  the  exudation  of  fluid  or  solid  constituents, 
or  when  the  lungs  are  compressed  from  without.  In  both  cases  vesicular  sounds  disappear,  and  the 
condensed  or  solidified  lung  tissue  conducts  the  tubular  sound  of  the  large  bronchi  (o  the  surface  ol 
the  chest.  [The  sound  heard  over  a  hepatized  lobe  of  the  lung  in  pneumonia  is  a  typical  example.] 
It  also  occurs  in  large  cavities,  with  resistant  walls  near  the  surface  of  the  lung,  provided  these 
cavities  communicate  with  a  large  bronchus.     [In  this  case  it  is  termed  Cavernous  Breathing]. 

(2)  The  amphoric  sound  is  compared  to  that  produced  by  blowing  over  the  mouth  of  an  empty 
bottle.  It  occurs  either  when  a  cavity — at  least  the  size  of  the  fist — exists  in  the  lung,  which  is  so 
blown  into  during  respiration  that  a  peculiar  amphoric-liUe  sound,  with  a  metallic  timbre  called 
metallic  tinkling,  is  produced;  or  when  the  lung  still  contains  air,  and  is  capable  of  expansion; 
as  there  is  still  air  in  the  pleural  cavity,  it  acts  as  a  resonator,  and  causes  an  amphoric  sound, 
simultaneous  with  the  change  of  air  in  the  lungs.  [The  amphoric  sound  or  echo  and  metallic  tink- 
ling are  the  only  certain  signs  of  the  existence  of  a  cavity  in  the  lung.] 

(3)  If  obstruction  occurs  in  the  course  of  the  air  passages  of  the  lungs,  various  results  may 
accrue,  according  to  the  nature  of  the  resistance  :  (<?)  owing  to  various  causes,  c.  g.,  in  the  apices 
of  the  lungs  there  may  be  partial  swelling  of  the  walls  of  the  air  tubes  or  infiltration  into  the  air 
cells  which  hinders  the  regular  supply  of  air.  In  these  cases,  parts  of  the  lung  are  not  supplied 
with  air  continuously;  it  only  reaches  them  periodically.  In  these  cases  a  cog-wheel  sound 
occurs.  A  similar  sound  may  be  heard  occasionally  in  a  normal  lung,  when  the  muscles  of  the 
chest  contract  in  a  periodic  spasmodic  manner,  (b)  When  the  air  entering  large  bronchi  causes  the 
formation  of  bubble-i  in  the  mucus  which  may  have  accumulated  there, "  mucous  rales  "  are  pro- 
duced. They  also  occur  in  small  spaces  when  the  walls  are  separated  from  their  fluid  contents  by 
the  air  entering  during  inspiration,  or  when  the  walls,  being  adherent  to  each  other,  are  suddenly 
pulled  asunder.  The  rales  are  distinguished  as  ;«(j/j/(when  the  contents  are  fluid),  or  as  dry  (when 
the  contents  are  sticky) ;  they  may  be  inspiratory,  expiratory  or  continuous,  or  they  may  be  coarse 
or  fine;  further,  there  is  the  very  fine  crepitation  or  crackling  sound,  and  lastly,  the  metallic  tink- 
ling caused  in  large  cavities  through  resonance.  [Crepitation  or  Vesicular  Rales  are  fine  crepi- 
tating sounds  like  those  produced  by  rubbing  a  lock  of  hair  between  the  fingers  near  one's  ear;  they 
occur  only  during  inspiration,  and  are  a  proof  that  some  air  is  entering  the  air  vesicles.  It  is  heard 
in  its  typical  form  during  the  first  stage  of  pneumonia,  and  seems  to  be  produced  by  the  bursting  of 
minute  bubbles  of  air  in  a  fluid.]  (c)  When  the  mucous  membrane  of  the  bronchi  is  greatly 
swollen,  or  is  so  covered  with  viscid  mucus  that  the  air  must  force  its  way  through,  deep,  sonorous 
rhonchi  (rhonchi  sonori)  may  occur  in  the  large  air  passages,  and  clear,  shrill,  sibilant  sounds 
(rhonchi  sibilantes)  in  the  smaller  ones.  [Rhonchi  are  usually  due  to  catarrh  or  to  affections  of  the 
bronchial  mucous  membrane  or  bronchitis.]  When  there  is  extensive  bronchial  catarrh,  not  unfre- 
quently  we  feel  the  chest- wall  vibrating  with  the  rale  sounds  (Bronchial  fremitus). 

(4)  If  fluid  and  air  occur  together  in  one  pleural  cavity  in  which  the  lung  is  collapsed,  on  shak- 
ing the  person's  thorax  vigorously,  we  hear  a  sound  such  as  is  produced  when  air  and  water  are 
shaken  together  in  a  bottle.  This  is  the  succussion  sound  of  Hippocrates.  Much  more  rarely, 
this  sound  is  heard  under  similar  conditions  in  large  pulmonary  cavities. 

(5)  Pleural  Friction. — When  the  two  opposed  surfaces  of  the  pleura  are  inflamed,  have 
become  soft,  and  are  covered  with  exudation,  they  move  over  each  other  during  respiration,  and  in 
doing  so  give  rise  to  friction  sounds,  which  can  be  felt  (often  by  the  patient  himself),  and  can  also 
be  heard.     The  sound  is  comparable  to  the  sound  produced  by  bending  new  leather. 

(6)  Pectoral  Fremitus. — When  we  speak  or  sing  in  a  loud  tone,  the  walls  of  the  chest  vibrate, 
because  the  vibration  of  the  vocal  cords  is  propagated  throughout  the  entire  bronchial  ramifications. 
The  vibration  is,  of  course,  greatest  near  the  trachea  and  large  bronchi.  The  ear  cannot  detect  the 
sounds  distinctly.  If  there  be  much  exudation  or  air  in  the  pleura,  or  great  accumulation  of  mucus 
in  the  bronchi,  the  pectoral  fremitus  is  diminished  or  altogether  absent.  [In  health,  when  a  person 
speaks,  the  vocal  resonance  over  the  trachea,  although  loud,  may  be  inarticulate,  and  on  listening 
over  the  sternum  the  sound  is  diminished  and  quite  inarticulate ;  while  over  the  chest-wall  gener- 
ally, the  sound,  though  distinct,  is  feeble.] 

All  conditions  which  cause  bronchial  breathing  increase  the  pectoral  fremitus.  Under  normal 
circumstances,  therefore,  it  is  louder  where  bronchial  breathing  is  heard  normally.  The  ear  hears 
an  intensified  sound,  which  is  called  bronchophony  [which  is  a  sound  like  that  heard  normally 
over  the  trachea  or  bronchi,  but  audible  over  the  vesicular  lung  tissue.  The  conditions  that  cause  it 
are  the  same  as  those  on  which  bronchial  breathing  depends,  so  that  it  is  heard  in  pneumonia  and 
phthisis.  If,  through  effusion  into  the  pleura  or  inflammatory  processes  in  the  lung  tissue,  the 
bronchi  are  pressed  flat,  a  peculiar  bleating  sound  (aegophonyi  may  be  heard.] 

118.  PRESSURE  IN  THE  AIR  PASSAGES  AND  THORAX 
DURING  RESPIRATION.— Respiratory  Pressure.— If  a  manometer 
be  tied  into  ttie  trachea  of  an  animal,  so  that  the  respiration  goes  on  completely 


206  PRESSURE    IN    THE    AIR    PASSAGES    DURING    RESPIRATION. 

undisturbed,  /.  c. ,  normal  respiration,  during  every  inspiration  there  is  a  nega- 
tive pressure  (  —  3  mm.  Hg)  and  during  expiration  a  positive  pressure  ( Domiers). 
Donders  placed  the  U-shaped  manometer  tube  in  one  nostril,  closed  his  mouth, 
leaving  the  other  nostril  open,  and  respired  quietly.  During  every  quiet  inspira- 
tion the  mercury  showed  a  negative  pressure  of  —  i  mm.,  and  during  expiration, 
a  positive  j^ressure  of  2-3  mm.  (Hg). 

Forced  Respiration. — As  soon  as  the  air  was  inspired  or  expired  with  greater 
force,  the  variations  in  pressure  became  very  much  greater,  e.g.,  during  speaking, 
singing  and  coughing.  The  inspiratory  pressure  was  =  —  57  mm.  (36-74),  the 
greatest  expiratory  pressure  -f  87  (82-100)  mm.  Hg  {Danders).  The  pressure  of 
forced  expiration  therefore,  is  30  mm.  greater  than  the  inspiratory  pressure. 

Resistance  to  Inspiration. — Notwithstanding  this,  we  must  not  conclude 
that  the  expiratory  muscles  act  more  powerfully  than  the  inspiratory ;  for  during 
inspiration,  a  variety  of  resistances  have  to  be  overcome,  so  that  after  these  have 
been  met,  there  is  only  a  residue  of  the  force  for  the  aspiration  of  the  mercury. 
The  resistances  to  be  overcome  by  the  inspiratory  muscles  are — (i)  The  elastic 
tension  of  the  lungs,  which  during  the  deepest  expirations  =  6  mm.  ;  during  the 
deepest  inspirations  =  30  mm.  Hg  (§  107).  (2)  The  raising  of  the  weight  of 
the  chest.  (3)  The  elastic  torsion  of  the  costal  cartilages.  (4)  The  depression 
of  the  abdominal  contents,  and  the  elastic  distention  of  the  abdominal  walls.  All 
these  not  inconsiderable  resistances,  which  the  inspiratory  muscles  have  to  over- 
come, act  during  expiration,  and  aid  the  expiratory  muscles.  The  forces  con- 
cerned in  ins]iiration  are  decidedly  much  greater  than  those  of  expiration. 

Intra-thoracic  Pressure. — .\s  the  lungs  withm  the  chest,  in  virtue  of  their 
elasticity,  continually  strive  to  collapse,  necessarily  they  must  cause  a  negative 
pressure  luithin  tlie  chest.  This  amounts  in  dogs  during  inspiration,  to —  7.1  to 
— 7.5  mm.  Hg,  and  during  expiration  to  —  4  mm.  Hg  (Heynsiiis').  The  cor- 
responding values  for  man  have  been  estimated  at  —  4.5  mm.  Hg,  and  —  3  mm. 
Hg,  by  Hutchinson. 

[We  must  distinguish  between  respiratory  pressure  of  the  air  -wil/iin  the  respiratory  passages, 
and  the  intra-thoracic  pres-ure.  The  former  is  the  same  as  the  atmospheric  pressure  when  the  chest 
is  passive,  but  less  than  it  as  the  chest  is  lieing  enlarged,  and  greater  than  it  when  it  is  being  dimin- 
ished in  size.  The  intra-thoracic  pressure  is  the  pressure  within  the  chest,  but  outside  tlie  lutigs, 
;.^.,  in  the  pleura,  mediastinum,  etc.  It  is  negative,  !.  d.,  less  than  the  atmospheric  pressure,  and 
must  vary  with  the  degree  of  distention  of  the  lungs.] 

[Methods. — A  direct  estimation  was  made  by  Adamkiewicz  and  Jacobson.  A  trocar  with  its 
stylette  was  forced  into  the  fourth  left  intercostal  space  near  the  sternum  and  pushed  into  the  peri- 
cardium (sheep).  The  stylette  was  then  withdrawn,  and  the  trocar  connected  with  a  manometer, 
and  the  negative  pressure  of  —  3  to  —  5  mm.  Hg  was  obtained.  During  violent  dyspncea  it  was 
—  9  mm.  Hg.  Rosenthal  introduced  an  lesophageal  sound  with  an  elastic  ampulla  on  its  lower  end 
into  the  oesophagus,  so  that  the  ampulla  came  to  lie  opposite  the  posterior  mediastinum.  The  sound 
was  connected  with  a  registering  tambour  or  manometer.  During  inspiration  the  manometer  fell, 
and  during  CNpiration  it  rose.] 

Even  the  greatest  inspiratory  or  expiratory  pressure  is  always  much  less  than  the  blood  pressure 
in  the  large  arteries ;  but  if  the  pressure  be  calculated  upon  the  entire  respiratory  surface  of  the 
thorax,  very  considerable  results  are  obtained. 

Pneumatometer. — This  instrument  of  Waldenburg  is  merely  a  mercurial  manometer  fixed  to  a 
stand,  and  connected  to  an  elastic  tube  with  a  suitable  mouth  piece,  which  is  fitted  over  the  mouth 
and  nose,  while  the  variations  of  the  Hg  can  be  read  off  on  a  scale.  [In  the  male,  the  expiratory 
pressure  is  90-120  mm.  Hg,  and  the  respiratory  70-100.  The  relations  of  the  pressure  during  expi- 
ration and  inspiration  are  more  important  than  the  absolute  pressure.]  The  inspiratory  pressure  is 
diminished  in  nearly  all  diseases  where  the  expansion  of  the  lung  is  impaired  [phthisis],  or  the 
expiratory  pressure  is  diminished,  as  in  emphysema  and  asthma. 

Effects  of  the  first  Respiration  on  the  Thorax. — Until  birth,  the  airless  lungs  are  completely 
collapsed  (atelectic)  within  the  chest,  and  fill  it,  so  that  on  opening  the  chest  in  a  dead  foetus,  pneumo- 
thorax does  not  occur  (Bernstein).  Supposing,  however,  respiration  to  have  been  fully  established 
after  birth,  and  air  to  have  freely  entered  the  lungs,  if  a  manometer  be  placed  in  connection  with 
the  trachea  and  the  chest  be  opened,  the  manometer  will  register  a  pressure  of  6  mm.  Hg,  due  to 
the  collapse  of  the  elastic  lungs.  Bernstein  supposes  that  the  thorax  assumes  a  new  permanent  form, 
due  to  the  first  respiratory  distention;  it  is  as  if,  owing  to  the  respiratory  elevation  of  the  ribs,  the 
thorax  had  become   permanently  too  large  for  the  lungs,  which  are,  therefore,  kept  permanently  dis- 


PECULIARLY    MODIFIED    RESPIRATORY    MOVEMENTS.  207 

tended,  but  collapse  as  soon  as  air  passes  into  the  pleura.  When  a  lung  has  once  been  filled  with 
air,  it  cannot  be  emptied  by  pressure  from  without,  as  the  small  bronchi  are  compressed  before  the  air 
can  pass  out  of  the  alveoli.  The  expiratory  muscles  cannot  possibly  expel  all  the  air  from  the  lungs, 
while  the  inspiratory  muscular  force  is  sufficient  to  distend  the  lungs  beyond  their  elastic  equilibrium. 
Inspiration  distends  the  lungs,  increasing  their  elastic  tension,  while  expiration  diminishes  the  tension 
without  abolishing  it. 

119.  APPENDIX  TO  RESPIRATION.— Nasal  Breathing.— During 

quiet  respiration,  we  usually  breathe — or  ought  to  breathe — through  the  nostrils, 
the  mouth  being  closed.  The  current  of  air  passes  through  the  pharyngo-nasal 
cavity — so  that  in  its  course  during  inspiration,  it  is  (i)  loarmed  and  rendered 
moist,  and  thus  irritation  of  the  mucous  membrane  of  the  air  passages  by  the  cold 
air  is  prevented  ;  (2)  sxw^W  particles  of  soot,  or  other  foreign  substances  in  the  air, 
adhere  to,  and  become  embedded  in  the  mucus  covering  the  somewhat  tortuous 
walls  of  the  respiratory  passages,  and  are  carried  outward  by  the  agency  of  the 
ciliated  epithelium  of  the  respiratory  passages  ;  (3)  disagreeable  odors  and  certain 
impurities  are  detected  by  the  sense  of  smell. 

If  a  lung  be  inflated,  air  constantly  passes  through  the  walls  of  the  alveoli  and  trachea.  This 
also  occurs  during  violent  expiratory  efforts  (cutaneous  emphysema  in  whooping  cough),  so  that 
pneumothorax  may  occur  (_/.  A'.  EwalJ  and  Koberls). 

Pulmonary  CEdema,  or  the  exudation  of  lymph  or  serum  into  the  pulmonary  alveoli,  occurs — 
(i)  When  there  is  very  great  resistance  to  the  blood  stream  in  the  aorta  or  its  branches,  e.g.,  by 
ligaturing  all  the  arteries  going  to  the  head  {Sig.  Mayer),  or  the  arch  of  the  aorta,  so  that  only  one 
carotid  remains  pervious  [Welch).  (2)  When  the  pulmonary  veins  are  occluded.  (3)  When  the 
left  ventricle,  owing  to  mechanical  injury,  ceases  to  beat,  while  the  right  ventricle  goes  on  contract- 
ing (?  47)'  These  conditions  produce  at  the  same  time  ansmia  of  the  vasomotor  centre  which 
results  in  stimulation  of  that  centre,  and  consequent  contraction  of  all  the  small  arteries.  Thus  the 
blood  stream  through  the  veins  to  the  right  heart  is  favored,  and  this  in  its  turn  favors  the  produc- 
tion of  oedema  of  the  lungs. 

120.  PECULIARLY  MODIFIED  RESPIRATORY  MOVEMENTS.— (i)  Cough- 
ing.— Consists  in  a  sudden  violent  expiratory  explosion  after  a  previous  deep  inspiration  and  closure 
of  the  glottis,  whereby  the  glottis  is  forced  open,  and  any  substance,  fluid,  gaseous,  or  solid,  in 
contact  with  the  respiratory  mucous  membrane  is  violently  ejected  through  the  open  mouth.  It  is 
produced  voluntarily  or  reflexly;  in  the  latter  case,  it  can  be  controlled  by  the  will  only  to  a  limited 
extent. 

[Causes. — A  cough  may  be  discharged  reflexly  from  a  large  number  of  surfaces  :  ( l)  A  draught 
of  cold  air  striking  the  skin,  especially  of  the  upper  part  of  the  body.  This  may  cause  congestion 
of  blood  in  the  air  passages,  this  in  turn  exciting  the  cough.  (2)  More  frequently  it  is  discharged 
from  the  respiratory  mucous  membrane,  especially  of  the  larynx,  the  sensory  branches  of  the  vagus 
and  the  superior  laryngeal  nerve  being  the  afferent  nerves.  A  cough  cannot  be  discharged  from 
every  part  of  the  larynx,  thus  there  is  none  from  the  true  vocal  cords,  but  only  from  the  glottis 
respiratoria.  All  other  parts  of  the  larynx  are  inactive,  and  so  is  the  trachea  as  far  as  the  bifurca- 
tion, where  stimulation  excites  cough  \Kohts,  I'ulpian).  (3)  Sometimes  an  offending  body,  such 
as  a  pea  or  inspissated  cerumen  in  the  external  auditory  meatus,  gives  rise  to  coughing,  the  afferent 
nerve  being  the  auricular  branch  of  the  vagus.  (4)  There  seems  to  be  no  doubt  that  there  may  be 
a  "gastric  or  stomach  cough,"  produced  by  stimulation  of  the  gastric  branches  of  the  vagus,  espe- 
cially in  cases  of  indigestion,  accompanied  by  irritation  of  the  larynx  and  trachea.  ( 5)  Irritation  of 
the  costal  pleura  and  even  of  the  oesophagus  (A'ohts).  (6)  Irritation  of  some  parts  of  the  nose. 
(7)  Sometimes  also  from  irritation  of  the  pharynx,  as  by  an  elongated  uvula.  (8)  In  some  diseases 
of  the  liver,  spleen,  and  generative  organs,  when  pressure  is  exerted  on  these  parts.] 

(2)  Hawking,  or  clearing  the  throat. — An  expiratory  current  is  forced  in  a  continuous  stream 
through  the  narrow  space  between  the  root  of  the  tongue  and  the  depressed  soft  palate,  in  order  to 
assist  in  the  removal  of  foreign  bodies.  When  the  act  is  carried  out  periodically  the  closed  glottis 
is  suddenly  forced  open,  and  it  is  comparable  to  a  voluntary  gentle  cough.  This  act  can  only  be 
produced  voluntarily. 

(3)  Sneezing  consists  in  a  sudden  violent  expiratory  blast  through  the  nose,  for  the  removal  of 
mucus  or  foreign  bodies  (the  mouth  being  rarely  open)  after  a  simple  or  repeated  spasm-like  inspi- 
ration— the  glottis  remaining  open.  It  is  usually  caused  reflexly  by  stimulation  of  sensory  nerve 
fibres  of  the  nose  [nasal  branch  of  the  fifth  nerve],  or  by  sudden  exposure  to  a  bright  light  (Cassias 
Felix,  A.D.  97)  [the  afferent  nerve  is  the  optic].  This  reflex  act  may  be  interfered  with  to  a  certain 
extent,  or  even  prevented,  by  stimulation  of  sensory  nerves,  or  firmly  compressing  the  nose  where 
the  nasal  nerve  issues.  The  continued  use  of  sternutatories,  as  in  persons  who  take  snuff,  dulls  the 
sensory  nerves,  so  that  they  no  longer  act  when  stimulated  reflexly. 

[Sternutatories   or    Errhines,  such   as  powdered   ipecacuanha,  snuff,  and   euphorbium,  also 


208  PECULIARLY    MODIFIED    RESPIRATORY    MOVEMENTS. 

increase  the  secretion  from  the  nasal  glands.  The  afferent  impulse  sent  to  the  respiratory  centre 
also  affects  the  vasomotor  centre,  so  that  even  when  sneezing  does  not  occur  the  blood  pressure 
throughout  the  body  is  raised.] 

(4)  Snoring  occurs  during  respiration  through  the  open  mouth,  whereby  the  inspiratory  and 
expiratory  stream  of  air  throws  the  uvula  and  soft  palate  into  vibration.  It  is  involuntary,  and 
usually  occurs  during  sleep,  but  it  may  be  produced  voluntarily. 

(5)  Gargling  consists  in  the  slow  passage  of  the  expiratory  air  current  in  the  form  of  bubbles 
through  a  fluid  lying  between  the  tongue  and  the  soft  palate,  when  the  head  is  held  backward.  It 
is  a  voluntary  act. 

(6)  Crying,  caused  by  emotional  conditions,  consists  in  short,  deep  inspirations,  long  expirations 
with  the  glottis  narrowed,  relaxed  facial  and  jaw  muscles,  secretion  of  tears,  often  combined  with 
plaintive  inarticulate  expressions.  When  crying  is  long  continued,  sudden  and  spasmodic  involun- 
tary contractions  of  the  diaphragm  occur,  which  cause  the  inspiratory  sounds  in  the  pharynx  and 
larynx  known  as  solilung.     This  is  an  involuntary  act. 

(7)  Sighing  is  a  prolonged  inspiration,  usually  combined  with  a  plaintive  sound,  often  caused 
involuntarily,  owing  to  painful  or  unpleasant  recollections. 

(S I  Laughing  is  due  to  short,  rapid  expiratory  blasts  through  the  tense  vocal  cords,  which  cause 
a  cle.ir  tone,  and  there  are  characteristic  inarticulate  sounds  in  the  larynx,  with  vibrations  of  the  soft 
palate.  The  mouth  is  usually  open,  and  the  countenance  has  a  characteristic  expression,  owing  to 
the  action  of  the  M.  zygomaticus  major.  It  is  usually  involuntary,  and  can  only  be  suppressed,  to 
a  certain  degree,  by  the  will  (by  forcibly  closing  the  mouth  and  stopping  respiration). 

(9)  Yawning  is  a  prolonged  deep  in.spiration  occurring  after  successive  attempts  at  numerous 
inspirations — the  mouth,  fauces  and  glottis  being  wide  open;  expiration  shorter — both  acts  often 
accompanied  by  prolonged  characteristic  sounds.  It  is  quite  involuntary,  and  is  usually  excited  by 
drowsiness  or  ennui. 

[(10)  Hiccough  is  due  to  a  spasmodic  involuntary  contraction  of  the  diaphragm,  causing  an 
inspiration,  which  is  arrested  by  the  sudden  closure  of  the  glottis,  so  that  a  characteristic  sound  is 
emitted.  Not  unfrequently  it  is  due  to  irritation  of  the  gastric  mucous  membrane,  and  sometimes  it 
is  a  very  troublesome  symptom  in  ur.tmic  poisoning.] 


CHEMISTRY  OF  RESPIRATION. 


121.  QUANTITATIVE  ESTIMATION  OF  CARBONIC  ACID,  OXYGEN,  AND 
AVATERY  VAPOR.— I.  Estimation  of  CO,..— i.  The  volume  of  CO,  is  estimated  by  means 
of  the  anthracometer  (Fig.  138,  II)  of  Vieionlt.  The  volume  of  gas  is  collected  in  a  graduated 
tube,  r  r,  provided  with  a  bulb  at  one  end  (previously  filled  with  water  and  carefully  calibrated, 
i.  e.,  the  exact  amount  which  each  part  of  the  tube  contains  is  accurately  measured),  and  the  tube  is 
closed.  The  lower  end  has  a  stop-cock,  /;,  and  to  this  is  screwed  a  flask,  k,  completely  filled  with 
a  solution  of  caustic  potash ;  the  stopcock  is  then  opened,  the  potash  solution  is  allowed  to  ascend 
into  the  tube,  which  is  moved  about  until  all  the  CO,  unites  with  the  potash  to  form  potassium 
carbonate.  Hold  the  tube  vertically  and  allow  the  potash  to  run  back  into  the  flask,  close  the  stop- 
cock, and  remove  the  bottle  with  the  potash.  Place  the  stop-cock  under  water,  open  it  and  allow 
the  water  to  ascend  in  the  tube,  when  the  space  in  the  tube  occupied  by  the  fluid  indicates  the  volume 
of  CO,  which  is  combined  with  the  potash. 

2.  By  Weight. — A  large  quantity  of  the  mi.\ture  of  gases  which  has  to  be  investigated  is  made  to 
pass  through  a  Liebig's  bulb  filled  with  caustic  potash.  The  potash  apparatus  having  been  carefully 
weighed  beforehand,  the  increase  of  weight  indicates  the  amount  of  CO2  which  has  been  taken  up 
by  the  potash  from  the  air  passed  through  it. 

3.  By  Titration. — A  large  volume  of  the  air  to  be  investigated  is  conducted  through  a  known 
volume  of  a  solution  of  barium  hydrate.  The  COj  unites  with  the  barium  and  forms  barium  car- 
bonate. The  fluid  is  neutralized  with  a  standard  solution  of  o.xalic  acid,  and  the  more  barium  that 
has  united  with  the  CO,  the  smaller  will  be  the  amount  of  oxalic  acid  used,  and  vice  versa. 

II.  Estimation  of  Oxygen. — According  to  volume — [a)  By  the  union  of  the  O  with  potassium 
pyrogallate.  The  same  procedure  is  adopted  as  for  the  estimation  of  COj,  only  the  flask,  «,  is 
filled  with  the  pyrogallate  solution  instead  of  potash,  (b)  By  explosion  in  an  eudiometer  (see  Blood 
gases,  §  35). 

III.  Estimation  of  Watery  Vapor, — The  air  to  be  investigated  is  passed  through  a  bulb  con- 
taining  concentrated  sulphuric  acid,  or  through  a  tube  filled  with  pieces  of  calcium  chloride.  The 
amount  of  water  is  directly  indicated  by  the  increase  of  weight. 

122.  METHODS  OF  INVESTIGATION.— I.  Collecting  the  Expired  Air.— (i^  The 
air  expired  may  be  collected  in  the  cylinder  of  the  spirometer  (§  loS),  which  is  suspended  in  con- 
centrated salt  solution,  to  avoid  the  absorption  of  CO,. 

The  apparatus  of  Andral  and  Gavarret  is  thus  used  :  The  operator  breathed  several  times  into 
a  capacious  cylinder  (Fig.  13S).  A  mouth  piece  (M)  was  placed  air  tight  over  the  mouth.Vhile  the 
nostrils  were  closed.  The  direction  of  the  respiratory  current  was  regulated  by  two  sO' called 
"  Miiller's  Valves  "  (mercurial),  («  and  ^).  With  every  inspiration,  the  bottle  or  valve,  a  (filled 
below  with  Hg  and  hermetically  closed  above),  permits  the  air  inspired  to  pass  to  the  lungs — during 
every  expiration,  the  expired  air  can  pass  only  through  li  to  the  collecting  cylinder.  C. 

(2)  If  the  gases  given  oft"  by  the  skin  are  to  be  collected,  a  limb,  or  whatever  part  is  to  be  inves- 
tigated, is  secured  in  a  closed  vessel,  and  the  gases  so  obtained  are  analyzed. 

II.  The  most  important  apparatus  for  this  purpose  are  those  of— (a)  Scharling  (Fig.  139),  which 
consists  of  a  closed  box.  A,  of  sufficient  size  to  contain  a  man.  It  has  tw-o  openings — an  entrance 
opening,  z,  and  an  exit,  b.  The  latter  is  connected  with  an  aspirator,  C,  a  large  barrel  filled  with 
water.  When  the  stop-cock,  //,  is  opened,  and  the  water  flows  out  of  the  barrel,  fresh  air  will  rush 
in  continuously  into  the  box.  A,  and  the  air  mixed  with  the  expired  gases  will  be  drawn  toward  C. 
A  Liebig's  bulb,  d,  filled  with  caustic  potash,  is  connected  with  the  entrance  tube,  3,  through  which 
the  in-going  air  must  pass,  whereby  it  is  completely  deprived  of  CO,,  so  that  the  person  experimented 
on  is  supplied  with  air  free  from  COj.  The  air  passing  out  by  the  exit  tube,  b,  has  to  pass  first 
through  e,  where  it  gives  up  its  watery  vapor  to  sulphuric  acid,  whereby  the  amount  of  watery  vapor 
is  estimated  by  the  increase  of  the  weight  of  the  apparatus,  e.  Afterward,  the  air  passes  through  a 
bulb,  f,  containing  caustic  potash,  which  absorbs  all  the  CO^,  while  the  tube, ^,  filled  with  sulphuric 
acid,  absorbs  any  watery  vapor  that  may  have  come  from  f.  The  increase  of  weight  of  /and  g 
indicate  the  amount  of  CO,.     The  total  volume  of  air  used  is  known  from  the  capacity  of  C. 

(b)  Regnault  and  Reiset's  Apparatus  is  more  complicated,  and  is  used  when  it  is  necessary  to 

keep  animals  for  some  time  under  observation  in  a  bell  jar.     It  consists   (Fig.  140)   of  a  globe,  R, 

in  which  is  placed  the  dog  to  be  experimented  on.     Around  this  is  placed  a  cylinder,  o-o'  (provided 

with  a  thermometer,  /),  which  may  be  used  for  calorimetric  experiments.     A  tube,  c,  leads  into  the 

14  209 


210 


APPARATUS    FOR    EXAMINING    RESPIRED    AIR. 


globe,  R;  through  this  tube  passes  a  known  quantity  of  pure  oxygen  (Fig.  140,  O).  To  absorb 
anv  trace  of  COj,  a  vessel  cont.iinihg  potash  '.Fig.  140,  CO,)  is  placed  in  the  course  of  the  tube. 
The  vessel  for  measuring  the  O  is  emptied  toward  R,  through  a  solution  of  calcium  chloride  from  a 
large  pan  (CaClj)  provided  with  large  flasks.  Two  tubes,  </  and  e,  lead  from  R,  and  are  united  by 
caoutchouc  tubes  with  the  potash  bulbs  (KOH,  Ko/;),  which  can  be  raised  or  depressed  ahernately 
by  means  of  the  beam,  W.     In  this  way  they  aspirate  alternately  the   air   from  R,  and  the  caustic 


FlG.   138. 


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•^ 


n 

I.  Apparatus  of  Andral  and  Gavarret  for  collecting  the  expired  air.    C,  large  cylinder,  to  collect  the  air  expired  ;   P, 
weight,  to  balance  cylinder ;  a,  3,  two  Miiller's  valves  ;  M,  mouth  piece.     11.  Anthracometer  of  Vierordt. 

potash  absorbs  the  COj.  The  increase  of  weight  of  these  flasks  after  the  experiment  indicates  the 
amount  of  CO 2  expired.  The  manometer,/",  shows  whether  there  is  a  difference  of  the  pressure 
outside  and  inside  the  globe,  R. 

[c)  V.  Pettenkofer  has  invented  the  most  complete  apparatus  (Fig.  141).     It  consists  of  a  cham- 
ber, Z,  with  metallic  walls,  and  provided  with  a  door  and  a  window.     At  a  is  an  opening  for  the 

Fig.  139. 


nrs 


Respiratory  Apparatus  of  Scharling.  d,  bulb  containing  caustic  potash ,  to  absorb  CO,  from  in-going  air ;  A,  box  for 
m.in  or  animal  experimented  on ;  e  and  g,  lubes  cont,iining  sulphuric  acid,  to  aosorb  watery  vapor :  y",  potash 
bulb,  to  absorb  CO^  given  off;  C,  vessel  filled  with  water,  to  aspirate  air  through  the  foregoing  system;  h, 
stop-cock. 

admission  of  air,  while  a  large  double  suction  pump,  P  Pj  (driven  by  means  of  a  steam  engine) 
continually  renews  the  air  within  the  chamber.  The  air  passes  into  a  vessel,  b,  filled  with  pumice 
stone  saturated  with  sulphuric  acid,  in  which  it  is  dried ;  it  then  passes  through  a  large  gas  meter,  c, 
which  measures  the  total  amount  of  air  passing  through  it. 

After  the  air  is  measured,  it  is  emptied  outward  by  means  of  the  pump,  P  P,.     From  the  chief 
exit  tube,  x,  of  the  chamber,  provided  with  a  small  manometer,  i/,  a  narrow  laterally  placed  tube. 


APPARATUS    FOR    EXAMINING    RESPIRED    AIR. 


211 


«,  passes,  conducting  a  small  secondary  stream,  which  is  chemically  investigated.  This  current 
passes  through  the  suction  apparatus,  Vi.  Mj  (constructed  on  the  principle  of  Muller's  mercurial 
valve,  and  driven  by  a  steam  engine).     Before  reaching  this  apparatus,  the  air  passes  through  the 


Fig.  140. 


leme  of  the  Respiration  Apparatus  of  Regnault  and  Rciset.  /f,  globe  for  animal  :  g  g,  outer  casing  for  R,  pro- 
vided with  a  thermometer,  t ;  d  and  e,  exit  tubes  to  movable  potash  bulbs,  KOH  and  Ko/< :  O,  in-gouig  oxygen  ; 
COj,  vessel,  to  absorb  any  carbonic  acid;  CaCI,,  apparatus  for  estimating  the  amount  of  O  supplied;  /, 
manometer. 

Fig.   141. 


Respiration  Apparatus  of  v.  Pettenkofer.  Z,  chamber  for  person  experimented  on  ;  jr,  exit  tube  with  manometer,  y  ; 
b,  vessel  with  sulphuric  acid  ;  C,  gas  meter  ;  P  Pj,  pump ;  «,  secondary  current,  with,  k,  bulb ;  MM,,  suc- 
tion apparatus  ;  «,  gas  meter;  N,  stream  for  investigating  air  before  it  enters  Z. 


212  COMPOSITION    OF    EXTIRED    AIR. 

bulb,  K,  filled  with  sulphuric  acid,  whose  increase  in  weight  indicates  the  amount  oi  watery  vapor. 
After  passing  through  M  M,,  it  goes  through  the  tube,  R,  filled  with  baryta  solution,  which  takes 
up  the  CO,.  The  quantity  of  air  which  passes  through  the  accessory  current,  «,  is  measured  by  the 
smalt  gas  meter,  «,  from  which  it  passes  outward.  The  second  accessory  stream,  N,  enables  us  to 
investigate  the  air  before  it  enters  the  chamber,  and  it  is  arranged  in  exactly  the  same  way  as  h  . 

The  increase  of  CO.,  and  H,,0  in  the  accessory  stream,  n  (i.e.,  more  than  in  N),  indicates  the 
amount  of  C( ).,  given  off  by  the  person  in  the  chamber,  Z. 

123.  COMPOSITION  AND  PROPERTIES  OF  ATMOSPHERIC 
AIR. — I.   Dry  Air  contains  :  — 

G.is.  By  Weight.  By  Volume. 

O,        23.015  20.96 

N 76.985  79.02 

CO2 0.03-0.034 

2.  Aqueous  Vapor  is  always  present  in  the  air,  but  it  varies  greatly  in  amount, 
and  generally  increases  with  the  increase  of  the  temperature  of  the  air.  In  con- 
nection with  the  moisture  of  the  air  we  distinguish  {a)  the  absolute  moistun',  i.e., 
the  quantity  of  watery  vapor  which  a  volume  of  air  contains  in  the  form  of  vapor  ; 
and  \b'),  the  relative  moisture,  i.  e.,  the  amount  of  watery  vapor  which  a  volume  of 
air  contains  with  respect  to  its  temperature. 

Experience  shows  that  people  generally  can  breathe  most  comfortably  in  an  atmosphere  which  is  not 
completely  saturated  with  aqueous  vapor  according  to  its  temperature,  but  is  only  saturated  to  the 
extent  of  70  per  cent.  If  the  air  be  too  dry  it  irritates  the  respiratory  mucous  membrane  ;  if  too 
moist,  there  is  a  disagreeable  sensation,  and  if  it  be  too  warm,  a  feeling  of  closeness.  Hence,  it  is 
important  to  see  that  the  proper  amount  of  watery  vapor  is  present  in  the  air  of  our  sitting  rooms, 
bedrooms,  and  hospital  wards. 

The  absolute  amount  of  moisture  varies  :  In  towns  during  the  day  it  increases  with  increase  of 
temperature,  and  diminishes  when  the  temperature  falls ;  it  also  varies  with  the  direction  of  the 
wind,  season  of  the  year,  height  above  sea  level. 

The  relative  amount  of  moisture  is  greatest  at  sunrise,  least  at  midday ;  small  on  high  mountains  ; 
greater  in  winter  than  in  summer  ;  larger  with  a  south  or  west  wind  than  w-ith  a  north  or  east  wind. 

The  air  in  midsummer  contains  absolutely  three  times  as  much  watery  vapor  as  in  midwinter, 
nevertheless  the  air  in  summer  is  relatively  drier  than  the  air  in  winter. 

3.  The  air  Expands  by  Heat.  Rudberg  found  that  1000  volumes  of  air,  at 
0°,  expanded  to  1365  when  heated  to  100°  C. 

4.  The  Density  of  the  air  diminishes  with  increase  of  the  height  above  the 
sea-level. 

124.  COMPOSITION  OF  EXPIRED  AIR.— I.  The  expired  air  contains 
more  CO2 — in  normal  respiration  =  4.38  vols,  per  cent.  (3.3  to  5.5  per  cent.), 
so  that  it  contains  nearly  100  times  more  COj  than  the  atmospheric  air. 

2.  It  contains  less  O  (4.782  vols,  per  cent,  less)  than  the  atmospheric  air,  /.  e., 
it  contains  only  16.033  vols,  per  cent  of  O. 

3.  Respiratory  Quotient. — Hence,  during  respiration,  more  O  is  taken  into 
the  body  from  the  air  than  CO 2  is  given  off  (^Lavoisier) ;  so  that  the  volume  of 
the  expired  air  is  (4V— sV)  smaller  than  the  volume  of  the  air  inspired,  both  being 
calculated  as  dry,  at  the  same  temperature,  and  at  the  same  barometric  pressure. 
The  relation  of  the  O  absorbed  to  the  COj  given  off  is  4.38  :  4.782.  This  is 
expressed  by  the  "  respiratory  quotient  "  — 

CO2/      4-38  \  . 

-0-(,=  4:78-2;  =  °-9°6- 

4.  An  excessively  small  quantity  of  N  is  added  to  the  expired  air  {Rcgnault 
and  Reiset).  Segen  found  that  all  the  N  taken  in  with  the  food  did  not  reappear 
in  the  excreta  (urine  and  faeces),  and  he  assumed  that  a  small  part  of  it  was  given 
off  by  the  lungs. 

5.  During  ordinary  respiration,  the  expired  air  is  saturated  with  watery 
vapor.  It  is  evident,  therefore,  that  when  the  watery  vapor  in  the  air  varies, 
the  lungs  give  off  different  quantities  of  water  from  the  body.  The  percentage 
of  watery  vapor  falls  during  rapid  respiration  {Alolcschott). 


CONDITIONS    INFLUENCING    THE    EXCRETION    OF    CO.,. 


213 


6.  The  expired  air  is  -warmer  (36.3°  C).  It  is  very  near  the 
temperature  of  the  body,  and  even  although  the  temperature  of 
the  surrounding  atmosphere  be  very  variable,  the  temperature  of 
the  expired  air  still  remains  nearly  the  same. 

The  instrument  (Fig.  142)  was  used  by  Valentin  and  Brunner  to  determine  the 
.temperature  of  the  expired  air.  It  consists  of  a  glass  tube,  A,  A,  with  a  mouth 
piece,  B,  and  in  it  is  a  fine  thermometer,  C.  The  operator  breathes  through  the 
nose  and  expires  slowly  through  the  mouth  piece  into  the  tube. 


of 


°C. 


Tempera 
Expii 


°C. 


—  6.3       +  29-S 

+  «7-l9 +  36.2-37 

+  41 +  38-1 

+  34 +  3«-5 

7.  The  diminution  of  the  volume  of  the  expired  air  mentioned 
under  (3)  is  far  more  than  compensated  by  the  warming  which  the 
inspired  air  undergoes  in  the  resjiiratory  passages,  so  that  the 
volume  of  the  expired  air  is  one-ninth  greater  than  the  air  inspired. 

8.  A  very  small  quantity  of  ammonia  is  found  in  the  expired 
air  (^Regnault  and  Reisef)  =  0.0204  gramme  in  24  hours  {Lossen)  ; 
it  is  probably  derived  from  the  blood,  for  blood  exposed  to  the 
air  evolves  ammonia  {^Briicke). 

9.  Small  quantities  of  H  and  CH^  are  expired,  both  being  ab- 
sorbed from  the  intestine.  In  herbivora,  Reiset  found  that  30 
litres  of  CH^  were  expired  in  24  hours. 

125.  DAILY  QUANTITY  OF  GASES  EX- 
CHANGED.— As  under  normal  circumstances,  more  O  is  ab- 
sorbed than  there  is  COj  given  off  (equal  volumes  of  O  and  CO, 
contain  equal  quantities  of  O),  a  part  of  the  O  must  be  used  for 
other  oxidation  processes  in  the  body.  According  to  the  extent 
of  these  latter  processes,  the  ratio  of  the  O  taken  in  to  the  CO2 
given  out — 

/CO, 


^  0.906    norm 


ally) 


must  vary. 


The  amount  of  COj  given  ofT  may  be  less  than  the  "mean  "  above  stated. 
The  quantity  of  COj  alone  is  not  a  reliable  indication  of  the  entire  exchange  of 
gases  during  respiration ;  we  must  estimate  simultaneously  the  amount  of  O 
absorbed,  and  the  CO 2  given  off. 

126.  REVIEW  OF  DAILY  GASEOUS  INCOME  AND    EXPEN- 
DITURE. 

Income  in  24  hours.  Expenditure  in  24  hours. 


Oxygen — 

744  grms. 


:  5:6.500  c.cmtr.  ( I'l 


,-dt). 


(.At  0°  C.  and  mean  barometric  pressure.) 


(  Vierordt). 

(Sc/iarling), 

( Lic'liernieister). 

(Panum). 

(/fatiie). 

(  Valentin). 

(  Vierordt). 

127.  CONDITIONS  INFLUENCING  THE  GASEOUS  EX- 
CHANGES.— The  formation  of  CO,.,  in  all  probability,  consists  of  two  dis- 
tinct processes.  First,  compounds  containing  CO,  seem  to  be  formed  in  the 
tissues,  which  are  oxidation  products  of  substances  containing  carbon.  The  second 
process  consists  in  the  separation  of  this  CO,,  which,  however,  takes  place  without 


Carbonic  Acid — 

900  grms.  ^  455500  c.cmtr, 
36  grms.  per  hour. 

32.8  to  33.4  grms     " 
34  grms.  " 

31-5  to  33  grms. 
Water — 640  grms. 
330  grms. 


214 


CONDITIONS    INFLUENCING   THE    EXCRETION    OF   COj. 


the  absorption  of  O.     Both  processes  do  not  always  occur  simultaneously,  and  the 
one  process  may  exceed  the  other  in  extent  (Z.  Hermann,  Pfliiger). 

According  to  Schmiedeberg,  the  oxidation  in  the  tissues  depends  upon  a  synthesis  with  the  libera- 
tion of  HjO,  the  blood  supplying  the  necessary  O. 

The  following  circumstances  affect  these  processes  : — 

I.  Age. — Until  the  body  is  fully  developed,  the  COj  given  off  increases,  but 
it  diminishes  as  the  bodily  energies  decay.  Hence,  in  young  persons  the  O 
absorbed  is  relatively  greater  than  the  COj  given  off;  at  other  periods,  both  values 
are  pretty  constant.     Example  :  — 


Age — Years. 

In  34  hours. 

1 

CO,  Gram,  ex 

cretcd,     =     Carbon. 

0  Absorbed  Gram. 

8 

IS 

i6 

18-20 

443  gram. 
766      '• 
950      " 
1003      " 

=  121  Carbon. 
=  209        " 
=  259 
=  274 

375  grammes. 

652         " 

809 

854         " 

20-24 
40-60 
60-80 

1074      " 
889      " 
810      " 

=  293 
=  242 
=  221         " 

914 

757 
689 

The  absolute  amount  of  CO.,  given  off  is  less  in  children  than  in  adults  ;  but  if 
the  CO2  given  off  be  calculated  with  reference  to  body  weight,  then,  weight  for 
weight,  a  child  gives  off  twice  as  much  CO^  as  an  adult. 

2.  Sex. — Males,  from  the  eighth  year  onward  to  old  age,  give  off  about  one- 
third  more  CO.,  than  females  {A?idral  and  Gavarret).  This  difference  is  more 
marked  at  puberty,  when  the  difference  may  rise  to  one-half.  After  cessation  of 
the  menses,  there  is  an  increase,  and  in  old  age  the  amount  of  CO^  given  off 
diminishes.  Pregnancy  increases  the  amount,  owing  to  causes  which  are  easily 
understood. 

3.  The  Constitution. — As  a  general  rule,  muscular,  energetic  persons  use 
more  O  and  excrete  more  CO.;  than  less  active  persons  of  the  same  weight. 

4.  Alternation  of  Day  and  Night. — The  CO.,  given  off  is  diminished  about 
one-fourth  during  sleep  (Scharling).  This  diminution  is  caused  by  the  constant 
heat  of  the  surroundings  (bed),  darkness,  absence  of  muscular  activity,  and  the 
non-taking  of  food  (see  5,  6,  7,  9).  It  does  not  seem  that  any  O  is  stored  up 
during  sleep  {S.  Lewin).  After  awaking  in  the  morning,  the  respirations  are 
more  rapid  and  deeper,  and  thus  the  amount  of  CO.;  given  off  is  increased.  It 
decreases  during  the  forenoon,  until  dinner,  at  midday,  causes  another  increase. 
It  falls  during  the  afternoon,  and  increases  again  after  supper. 

During  hybernation,  when  no  food  is  taken,  and  when  the  respirations  cease,  or  are  enormously 
diminished,  the  respiratory  exchange  of  gases  is  carried  out  by  diffusion  and  by  the  cardio-pneumatic 
movements  (<!59).  The  CO,  given  off  falls  to  ,'j,  the  O  taken  in  to  ^j  of  what  they  are  in  the 
waking  condition  (  Valentin).  Much  less  CO^  is  given  off  than  O  taken  in,  so  that  the  body  weight 
may  increase  tlirough  the  excess  of  O. 

5.  Temperature  of  the  Surroundings. — Cold-blooded  Animals  become 
warmer  when  the  temperature  of  their  environment  is  raised,  and  they  give  off 
more  CO,  in  this  condition  than  when  they  are  cooler  (Spa//anzani),  e.g.,  a  frog, 
with  the  temperature  of  the  surroundings  at  39°  C,  excreted  three  times  as  much 
CO.;  as  when  the  temperature  was  6°  C.  {Moleschott). 

Warm-blooded  Animals  behave  somewhat  differently  when  the  temperature 
of  the  surrounding  medium  is  changed.  When  the  temperature  of  the  animal  is 
lowered  thereby,  there  is  a  considerable  decrease  in  the  amount  of  COj  given  off, 
as  in  cold-blooded  animals ;  but  if  the  temperature  of  the  animal   be  increased 


CONDITIONS    INFLUENCING   THE    EXCRETION    OF    CO.,. 


215 


(also  in  fever),  the  COj  is  increased  (C.  Ludwig  and  Sanders-Ezii).  Exactly  the 
reverse  obtains  when  the  temperature  of  the  surroundings  varies,  and  the  bodily 
temperature  remains  constant.  As  the  cold  of  the  surrounding  medium  increases, 
the  processes  of  oxidation  within  the  body  are  increased  through  some  as  yet  un- 
known reflex  mechanism  ;  the  number  and  depth  of  the  respirations  increase, 
whereby  more  O  is  taken  in  and  more  CO^  is  given  out  {Lavoisier).  A  man  in 
January  uses  32.2  grammes  O  per  hour;  in  July,  only  31.7  grammes.  In  animals, 
with  the  temperature  of  the  surroundings  at  8^  C,  the  CO2  given  off  was  one-third 
greater  than  with  a  temperature  of  38°  C.  When  the  temperature  of  the  air 
increases — the  body  temperature  remaming  the  same — the  respiratory  activity  and 
the  CO,  given  off  diminish,  while  the  pulse  remains  nearly  constant  {Vierordt). 
On  passing  suddenly  from  a  cold  to  a  warm  medium,  the  amount  of  COj  is  con- 
siderably diminished  ;  and,  conversely,  on  passing  from  a  warm  to  a  cold  medium, 
the  amount  is  considerably  increased  (§  214). 

6.  Muscular  Exercise  causes  a  considerable  increase  in  the  CO2  given  out 
{Schar/ing),  which  may  be  three  times  greater  during  walking  than  during  rest 
{Ed.  Smith).  Ludwig  and  Sczelkow  estimated  the  O  taken  in  and  the  CO.,  given 
off  by  a  rabbit  during  rest,  and  when  the  muscles  of  the  hind  limbs  were  tetanized. 
During  tetanus,  the  O  and  CO2  were  increased  considerably,  but  in  tetanized 
animals  more  O  was  given  off  in  the  CO.j  expired  than  was  taken  up  simultaneously 
during  respiration.  The  passive  animal  absorbed  nearly  twice  as  much  O  as  the 
amount  of  CO..  given  off  (§  294). 

7.  Taking  of  food  causes  constantly  a  not  inconsiderable  increase  in  the  COj 
given  off,  which  depends  upon  the  quantity  taken,  and  the  increase  generally 
occurs  about  an  hour  after  the  chief  meal — dmner  (  Vierordt).  During  inanition, 
the  exchange  of  gases  diminishes  considerably  until  death  occurs  {Letellier).  At 
first  the  COj  given  off  diminishes  more  quickly  than  the  O  is  taken  up.  The 
quality  of  the  food  influences  the  CO^  given  off  to  this  extent,  that  substances  rich 
in  carbon  (carbohydrates  and  fats)  cause  a  greater  excretion  of  CO,  than  substan- 
ces which  contain  less  C  (albumins).  Regnault  and  Reiset  found  that  a  dog  gave 
off  79  per  cent,  of  the  O  mspired  after  a  flesh  diet,  and  91  per  cent,  after  a  diet 
of  starch.  If  easily  oxidizable  substances  (glycerine  or  lactate  of  soda)  are  injected 
into  the  blood,  the  O  taken  in  and  the  CO,  given  off  undergo  a  considerable  in- 
crease {Ludwig  and  Scheremetjewsky).  Alcohols,  tea,  and  ethereal  oils  diminish 
the  CO.,  {Front,  Vierordt).  [Ed.  Smith  found  that  the  effects  produced  by  alco- 
holic drinks  varied  with  the  nature  of  the  spirituous  liquor.  Thus  brandy,  whisky, 
and  gin  diminish  the  amount ;  while  pure  alcohol,  rum,  ale,  and  porter  tend  to 
increase  it.] 

8.  The  Number  and  Depth  of  Respirations  have  practically  no  influence 
on  the  formation  of  CO,,  or  the  oxidation  processes  within  the  body,  these  being 
regulated  by  the  tissues  themselves,  by  some  mechanism  as  yet  unknown  {Pfliiger). 
They  have  a  marked  effect,  however,  upon  the  removal  of  the  already  formed  CO, 
from  the  body.  An  increase  in  the  ««/«/^fr  of  respirations  (their  depth  remaining 
the  same),  as  well  as  an  increase  of  their  depth,  the  number  remaining  the  same, 
cause  an  absolute  increase  in  the  amount  of  CO,  given  off,  which,  with  reference  to 
the  total  amount  of  gases  exchanged,  is  relatively  diminished.  The  following 
example  from  Vierordt  illustrates  this  : — 


No.  of  Rcsps. 
per  min. 

Vol  of  Air, 

Amount  of 

''zoT 

Depth  of  Resp, 

Amount  of 
COj. 

per  cent. 
CO,. 

12 

6000 

258  c.  cmtr. 

=  4-3% 

1          Soo 

21  c.  cmtr. 

=  4-3% 

24 

12000 

420         " 

=^  3-5  " 

1000 

36        " 

=  3-6" 

48 

24000 

744 

=  3.1" 

1        '500 

SI 

=  3-4" 

96 

48000 

1392       .  " 

=  2.9" 

2000 

64        •■ 

=  3-2  " 

3000 

72 

=  1.4" 

216    EXCHANGES   OF    GASES    BETWEEN    THE    AIR    AND   THE   BLOOD. 

9.  Exposure  to  a  bright  light  causes  an  increase  in  the  CO^  given  ofT  in  frogs  {^MoUschotty 
i8s^)\  in  mammals  and  birds  {S^bni  and  Piacentiiii)  ;  even  in  frogs  deprived  of  tlieir  lungs  (/«- 
itini)\  or  in  those  whose  spinal  cord  has  been  divided  high  up  [C/iasatunvitz),  The  consumption 
of  O  is  increased  at  the  same  time  (Pflitger  and  v.  Platen),  The  same  results  occur  in  blind  per- 
sons, although  to  a  less  degree.  Bluish  violet  light  is  almost  as  active  as  white  light,  while  red  light 
is  less  active  (MolesckotI  and  Fu/nni). 

10.  The  experiments  of  Urehant  on  dogs,  seem  to  show  that  intense  inflammation  of  the  bron- 
chial mucous  membrane  influences  the  CO,  given  ofli'.  » 

11.  Among  poisons,  thebaia  increases  the  CO,  given  off,  while  morphia,  codeia,  narcein,  nar- 
cotin,  papaverin,  diminish  it  (FiiUni). 

128.  DIFFUSION    OF    GASES   WITHIN    THE    LUNGS.— The 

air  within  the  air  vesicles  contains  most  CO,  and  least  O,  and  as  we  pass  from  the 
small  to  the  large  bronchi  and  onward  to  the  trachea,  the  composition  of  the  air 
gradually  approaches  more  closely  to  that  of  the  atmosphere  i^Allan  and  Pepys). 
Hence,  if  the  air  expired  be  collected  in  two  portions,  the  first  half  {i.e., 
the  air  from  the  larger  air  passages),  contains  less  CO,  (3.7  vols,  per  cent.)  than 
the  second  half  (5.4  vols,  per  cent.).  This  difference  in  the  percentage  of  gases 
gives  rise  to  a  diffusion  of  the  gases  within  the  air  passages ;  the  CO,  must  diffuse 
from  the  air  vesicles  outward,  and  the  O  from  the  atmosphere  and  nostrils  inward 
(§  33)-  This  inovement  is  aided  by  the  cardio-pneumatic  movement  {Landois 
§  59).  In  hybernating  animals  and  in  persons  apparently  but  not  actually  dead,  the 
exchange  of  gases  within  the  lungs  can  only  occur  in  the  above-mentioned  ways. 
For  ordinary  purposes  this  mechanism  is  insufficient,  and  there  are  added  the 
respiratory  movements  whereby  atmospheric  air  is  introduced  into  the  larger  air 
passages,  froin  which  and  into  which  the  diffusion  currents  of  O  and  COj  pass, 
on  account  of  the  difference  of  tension  of  the  gases. 

129.  EXCHANGE  OF  GASES  BETWEEN  THE  BLOOD  OF 
THE  PULMONARY  CAPILLARIES  AND  THE  AIR  IN  THE 
AIR  VESICLES. — This  exchange  of  gases  occurs  almost  exclusively  through 
the  agency  of  chemical  processes,  and  therefore  independently  of  the  diffusion  of 
gases. 

Method. — It  is  important  to  ascertain  the  tension  of  the  O  and  CO,  in  the  venous  blood  of  the 
pulmonary  capillaries.  Pfliiger  and  Woltberg  estimated  the  tension  by  "  catheterizing  the  lungs." 
An  elastic  catheter  was  introduced  through  an  opening  in  the  trachea  of  a  dog  into  the  bronchus 
leading  to  the  lowest  lobe  of  the  left  lung.  An  elastic  sac  was  placed  round  the  catheter,  and  when 
the  latter  was  introduced  into  the  bronchus,  the  sac  around  the  catheter  was  distended  so  as  to  plug 
the  bronchus.  No  air  could  escape  between  the  catheter  and  the  wall  of  the  bronchus.  The  outer 
end  of  the  catheter  was  closed  at  first,  and  the  dog  was  allowed  to  respire  quietly.  After  four 
minutes  the  air  in  the  air  vesicles  was  completely  in  equilibrium  with  the  blood  gases.  The  air  of 
the  lung  was  sucked  out  of  the  catheter  by  means  of  an  air  pump,  and  afterward  analyzed. 

Thus  we  may  measure  indirectly  the  tension  of  the  O  and  CO2  in  the  venous 
blood  of  the  pulmonary  capillaries.  The  direct  estimation  of  the  gases  in  differ- 
ent kinds  of  blood  is  made  by  shaking  up  the  blood  wnth  another  gas.  The  gases 
so  removed  indicate  directly  the  proportion  of  blood  gases. 

The  following  tabular  arrangement  indicates  the  tension  and  percentage  of  O 
and  CO2  in  arterial  and  venous  blood,  in  the  atmosphere,  and  in  the  air  of  the 
alveoli : — 

I.  IV. 

OTension    in   arterial    blood ^=29.6   mm.    Hg  :  CO^-Tension   in  venous  blood ^41   mm.    Hg 

(corresponding   to  a  mixture   containing  3.9  I       (corresponding  105.4  vol.  per  cent.). 

vol.  per  cent,  of  O). 

0-Tension  in  the  air  of  the  alveoli  of  the  cathe- 
terized  lung  =  27.44  mm.  Hg  (correspond- 
ing to  3.6  vol.  per  cent.). 


II. 
COj-Tension    in   arterial   blood  =  21  mm.  Hg 
(corresponding  to  2.9  vol.  per  cent.). 

III. 
O-Tension    in  venous     blood  =  22    mm.    Hg 
(corresponding  to  2.9  vol.  per  cent.) 


VI. 
CO, -Tension   in  the   air  of  the  alveoli   of  the 
catheterized   lung  =  27  mm.  Hg  (correspond- 
ing to  3.56  vol.  per  cent.). 


ABSORPTION  OF  OXYGEN  IN  THE  LUNGS.  217 

VII.  I  V[II. 

0-Tension  in  the    atmosphere  :=  158   mm.  Ilg  !   C02^-Tension  in  the  atmosphere  =0.38  mm.  Hg 

(corresponding  to  20.8  vol.  per  cent.),  1       (corresponding  to  0.03-0.05  vol.  per  cent.). 

When  we  compare  the  tension  of  the  O  in  the  air  (¥11  =  158  mm.  Hg)  with 
the  tension  of  the  O  in  venous  blood  (111=22  mm.  Hg,  or  V=  27.44  mm. 
,Hg),  we  might  be  inclined  to  assume  that  the  passage  of  the  O  from  the  air  of 
the  air  vesicles  into  the  blood  was  due  solely  to  diffusion  of  the  gases;  and  simi- 
larly, we  might  assume  that  the  CO.j  of  the  venous  blood  (IV  or  VI)  diffused 
into  the  air  vesicles,  because  the  tension  of  the  CO.j  in  the  air  is  much  less  (VIII). 
There  are  a  number  of  facts,  however,  which  prove  that  the  exchange  of  the 
gases  in  the  lungs  is  chiefly  due  to  chemical  forces. 

Absorption  of  O. — With  regard  to  the  absorption  of  O  from  the  air  in  the 
alveoli  into  the  venous  blood  of  the  lung  capillaries,  whereby  the  blood  is  arterial- 
ized,  it  is  proved  that  this  is  a  chemical  process.  The  gas-free  (reduced) 
haemoglobin  takes  up  O  to  form  oxyha;moglobin  (i;  15,  I).  That  this  absorption 
has  nothing  to  do  directly  with  the  diffusion  of  gases,  but  is  due  to  a  chemical 
combination  of  the  atomic  compounds,  is  shown  by  the  fact  that,  when  pure  O 
is  respired,  the  blood  does  not  take  up  more  O  than  when  atmospheric  air  is 
respired  ;  further,  that  animals  made  to  breathe  in  a  limited  closed  space  can 
absorb  almost  all  the  O — even  to  traces — into  their  blood  before  suffocation 
occurs.  Of  course,  if  the  absorption  of  O  were  due  to  diffusion,  in  the  former 
case  more  O  would  be  absorbed,  while  in  the  latter  case  the  absorption  of  O  could 
not  possibly  occur  to  such  an  extent  as  it  does.  The  law  of  diffusion  comes  into 
play  in  connection  with  the  absorption  of  O  to  this  extent,  viz.,  that  the  O  diffuses 
from  the  air  cells  of  the  lung  into  the  blood  plasma,  where  it  reaches  the  blood 
corpuscles  floating  in  the  plasma.  The  haemoglobin  of  the  blood  corpuscles  forms 
at  once  a  chemical  compound  (oxyhemoglobin)  with  the  O. 

Even  in  very  rarefied  air,  such  as  is  met  with  in  the  upper  regions  of  the  atmosphere  during  a 
balloon  ascent,  the  absorption  of  O  still  remains  independent  of  the  partial  pressure  [Loth.  Meyer, 
Fernet).  But  a  much  lunger  time  is  required  for  this  process  at  the  ordinary  temperature  of  the 
body,  so  that  in  rarefied  air  the  absorption  of  O  is  greatly  delayed,  but  is  not  diminished.  This  is 
the  cause  of  death  in  aeronauts  who  have  ascended  so  high  that  the  atmospheric  pressure  is  dimin- 
ished to  one-third  {.Setsc/ienoTi/j. 

Excretion  of  COo. — With  regard  to  the  excretion  of  COo  from  the  blood,  we 
must  remember  that  the  CO.^  in  the  blood  exists  in  two  conditions.  Part  of  the 
CO..,  forms  a  loose  or  feeble  chemical  compound,  while  another  portion  is  more 
firmly  combined.  The  former  is  obtained  by  those  means  which  remove  gases 
from  fluids  containing  them  in  a  state  of  absorption,  so  that  in  removing  the  CO.^ 
from  the  blood  it  is  difficult  to  determine  whether  the  COj  so  removed  obeyed 
the  law  of  diffusion,  or  if  it  was  expelled  by  chemical  means. 

Although  it  is  convenient  to  represent  the  excretion  of  CO^  from  the  blood  into 
the  air  vesicles  of  the  lung,  as  due  to  equilibration  of  the  tension  of  the  CO,  on 
opposite  sides  of  the  alveolar  membrane,  /.  e.,  to  diffusion — nevertheless,  chemi- 
cal processes  play  an  important  part  in  this  act.  The  absorption  of  O  by  the 
colored  corpuscles  acts,  at  the  same  time,  in  expelling  CO_,.  This  is  proved  by 
the  fact  that  the  expulsion  of  COj  from  the  blood  takes  place  more  readily  when 
O  is  simultaneously  admitted  {Lu.hc/g  and  Holmgren). 

The  free  supply  of  O  not  only  favors  the  removal  of  the  CO,,  which  is  loosely 
coiTibined,  but  it  also  favors  the  expulsion  of  that  portion  of  the  CO..,  which  is  more 
firmly  combined,  and  which  can  only  be  expelled  by  the  addition  of  acids  to  the 
blood  (^Ludivig,  Schoffer  and  Sczilkoui).  That  the  oxygenated  blood  corpuscles 
(/.  e.,  their  oxyhemoglobin)  are  concerned  in  the  removal  of  CO,  is  proved  by 
the  fact  that  CO.^  is  more  easily  removed  from  serum  which  contains  oxygenated 
blood  corpuscles  than  from  serum  charged  with  O. 

[The  following  scheme  may  serve  to  illustrate  the  extent  to  which  diffusion 
comes  into  play.     The  O  must  pass  through  the  alveolar  membrane,  AB — including 


218        .  DISSOCIATION    OF    GASES. 

the  alveolar  epithelium  and  the  wall  of  the  capillaries — as  well  as  the  blood  plasma, 
to  reach  the  hasmoglobin  of  the  blood  corpuscles.  Similarly,  the  CO^  must  leave 
the  salts  of  the  plasma  with  which  it  is  in  combination,  and  diffuse  in  the  opposite 
direction,  through  the  wall  of  the  capillaries,  the  alveolar  membrane  and  epithe- 
lium, to  reach  the  air  vesicles.     Let  AB  represent  the  alveolar  membrane  ;  on  the 

Partial  pressure  of  air  in  J      ^^2       ^ 

alveoli  of  lung.  1         ^7       2744 

A — y-^ ?— B 

Tension  of  gases  in  venous        J         ^[       22 

blood  of  lung.  1        cq, O 

one  side  of  it  is  represented  the  partial  pressure  of  the  COj  and  O  in  the  air 
vesicles ;  and  on  the  other,  the  partial  pressure  of  the  CO-^  and  O  in  the  venous 
blood  entering  the  lung.     The  indexes  indicate  the  direction  of  diffusion.] 

Theories. — Various  theories  have  been  proposed  to  account  for  the  expulsion  of  the  COj  from 
its  state  of  chemical  combination  in  (he  blood  due  to  the  action  of  the  oxygenated  blood  corpuscles. 
{a)  It  is  possible  that  the  CO,  in  the  blood  corpuscles  (perhaps  united  with  paraglobulin? — 
Setschinow)  is  expelled  by  the  O  taken  up;  [b)  the  acid  reaction  of  the  hsemoglobin  (Preyer)  may 
act  so  as  to  expel  the  CO,  out  of  the  corpuscles  and  the  plasma ;  (<:}  by  the  absorption  of  O  volatile 
fatty  acids  may  be  formed  from  the  haemoglobin  [Hoppe-Seyler).  These  acids  may  act  so  as  to 
expel  the  CO,. 

Nature  of  the  Process. — The  exchange  of  gases  between  the  blood  and  the 
air  in  the  lungs  has  been  represented  by  Bonders  as  due  to  the  process  of  disso- 
ciation. 

130.  DISSOCIATION  OF  GASES. — Many  gases  form  true  chemical 
compounds  with  other  bodies  (/.  c,  they  combine  according  to  their  equivalents), 
when  the  contact  of  these  bodiies  is  effected  under  conditions  such  that  the  partial 
pressure  of  the  gases  is  high.  The  chemical  compound  formed  under  these  con- 
ditions is  broken  up,  whenever  the  partial  pressure  is  diminished,  or  when  it 
reaches  a  certain  minimum  level,  which  varies  with  the  nature  of  the  bodies 
forming  the  compound.  Thus,  by  increasing  and  diminishing  the  partial  pressure 
alternately,  a  chemical  compound  of  the  gas  may  be  formed  and  again  broken  up. 
This  process  is  called  dissociation  of  the  gases.  The  minimal  partial  pressure 
is  constant  for  each  of  the  different  substances  and  gases,  but  temperature,  as  in 
the  case  of  the  absorption  of  gases,  has  a  great  effect  on  the  partial  pressure ;  with 
increase  of  temperature  the  partial  pressure,  under  which  dissociation  occurs, 
diminishes. 

As  an  example  of  the  dissociation  of  a  gas,  take  the  case  of  calcium  carbonate.  When  it  is  heated 
in  the  air  to  440°  C,  CO,  is  given  off  from  its  state  of  chemical  combination,  but  is  taken  up  again 
and  a  chemical  compound  formed,  which  is  changed  into  chalk  when  it  cools. 

Dissociation  in  the  Blood. — The  chemical  combinations  containing  CO, 
and  those  containing  O  within  the  blood  stream  behave  in  a  similar  manner,  viz., 
the  salts  of  the  plasma,  which  are  combined  with  CO,,  and  the  oxyhaemoglcbin. 
If  these  compounds  of  O  and  CO,  are  placed  under  conditions  where  the  partial 
pressure  of  these  gases  is  very  low — /.  e.,'m  a  medium  containing  a  very  small 
amount  of  these  gases,  the  compounds  are  dissociated,  /.  e.,  they  give  off  CO,  or 
O.  If  after  being  dissociated  they  are  placed  under  conditions  where,  owing  to 
the  large  amount  of  these  gases,  the  partial  pressure  of  O  or  of  COj  is  high,  these 
gases  are  taken  up  again,  and  enter  into  a  condition  of  chemical  combination. 

The  hemoglobin  of  the  blood  in  the  pulmonary  capillaries  finds  plenty  of  O  in 
the  alveoli ;  hence,  it  unites  with  the  O  owing  to"  the  high  partial  pressure  of  the 
O  in  the  lung,  and  so  forms  the  compound  oxyhsemoglobin.  On  its  course  through 
the  capillaries  of  the  systemic  circulation,  the  oxyhjemoglobin  of  the  blood  comes 
into  relation  with  tissues  poor  in  O  ;  the  oxyhsemoglobin  is  dissociated,  the  O  is 
supplied  to  the  tissues,  and  the  blood  freed  from  this  O  returns  to  the  right  heart, 
and  passes  to  the  lungs,  where  it  takes  up  the  new  O. 


INTERNAL    RESPIRATION.  219 

The  blood  while  circulating  meets  with  most  CO,  in  the  tissues;  the  high  partial 
pressure  of  the  CO,  in  the  tissues  causes  the  CO,  to  unite  with  certain  constituents 
in  the  blood  so  as  to  form  chemical  compounds,  which  carry  the  COj  from  the 
tissues  to  the  lungs.  In  the  air  of  the  lungs,  however,  the  partial  pressure  of  the 
CO2  is  very  low,  dissociation  of  these  chemical  compounds  occurs  under  the  low 
partial  pressure,  and  the  COj  passes  into  the  air  cells  of  the  lung,  from  which  it  is 
expelled  during  expiration.  It  is  evident  that  the  giving  up  of  O  from  the  blood 
to  the  tissues,  and  the  absorption  of  CO.,  from  the  tissues,  go  on  side  by  side  and 
take  place  simultaneously,  while  in  the  lungs  the  reverse  processes  occur  almost 
simultaneously. 

131.  CUTANEOUS  RESPIRATION.— Methods.— If  a  man  or  an  animal  be  placed  in  the 
chamber  of  a  respiratory  apparatus  [Sckarling's,  or  -'.  Pettenkofer' s),  and  if  tubes  be  so  arranged 
that  the  respiratory  gases  do  not  enter  the  chamber,  of  course  we  obtain  only  the  ^'■perspiration''^  of 
the  skin  in  the  chamber.  It  is  less  satisfactory  to  leave  the  head  of  the  person  outside  the  chamber 
while  the  neck  is  fixed  air  tight  in  the  wall  of  the  chamber.  The  extent  of  the  cutaneous  respiration 
of  a  limb  may  be  ascertained  by  enclosing  it  in  an  air-tight  vessel  i^Rbkrig)  similar  to  that  used  for 
the  arm  in  the  plethysmograph  (^  loi). 

Loss  by  Skin. — A  healthy  man  loses  by  the  skin,  in  24  hours,  ^V  of  his  body 
weight  {Segitin),  which  is  greater  than  the  loss  by  the  lungs,  in  the  ratio  of  3  :  2 
{^Valentin,  184J).  Only  10  grammes — 150  grains  {Scharling),  or  it  may  be  3.9 
grammes — 60  grains  (^Aiibert),  of  the  entire  loss  is  due  to  the  CO,  given  off  by  the 
skin.  The  remainder  of  the  excretion  from  the  skin  is  due  to  water  [j-^-2  lbs. 
daily]  containing  a  few  salts  in  solution.  When  the  surrounding  temperature  is 
raised,  the  CO.,  is  increased  (^Gcrlach'),  in  fact  it  may  be  doubled  {Auhert); 
violent  muscular  exercise  has  the  same  effect. 

O  Absorbed. — The  O  taken  up  by  the  skin  is  either  equal  to  {Rcgnault  and 
Reiset),  or  slightly  less  than,  the  CO2  given  off.  As  the  CO..,  excreted  by  the  skin 
is  only  -^\~^  of  that  excreted  by  the  lungs,  while  the  O  taken  in  =  -^\^  of  that 
taken  in  by  the  lungs,  it  is  evident  that  the  respiratory  activity  of  the  skin  is  very 
slight.  Animals  whose  skin  has  been  covered  by  an  impermeable  varnish  die,  not 
from  suffocation,  but  from  other  causes  (§  225). 

In  animals  with  a  thin,  moist  epidermis  (frog)  the  exchange  of  gases  is  much  greater,  and  in 
them  the  skin  so  far  supports  the  lungs  in  their  function,  and  may  even  partly  replace  them  function- 
ally. In  mammals  with  thick,  dry,  cutaneous  appendages,  the  exchange  of  gases  is,  again,  much 
less  than  in  man, 

132.  INTERNAL    RESPIRATION.— Where   CO,   is    formed.— By 

the  term  "  internal  respiration  "  is  understood  the  exchange  of  gases  between 
the  capillaries  of  the  systemic  circulation  and  the  tissues  of  the  various  organs 
of  the  body.  As  organic  constituents  of  the  tissues,  during  their  activity,  undergo 
gradual  oxidation,  and  form,  among  other  products  CO.,,  we  may  assume — (i) 
that  the  chief  focus  for  the  absorption  of  O  and  the  formation  of  CO,  is  to  be 
sought  for  within  the  tissues  themselves.  That  the  O  from  the  blood  in  the 
capillaries  rapidly  penetrates  or  diffuses  into  the  tissues  is  shown  by  the  fact  that 
the  blood  in  the  capillaries  rapidly  loses  O  and  gains  CO.,,  while  blood  containing 
O,  and  kept  warm  outside  the  body,  changes  very  slowly  and  incompletely.  If 
portions  of  fresh  tissues  be  placed  in  defibrinated  blood  containing  O,  then  the  O 
rapidly  disappears  {^Hoppe-Seyler).  Frogs  deprived  of  their  blood  exhibit  an  ex- 
change of  gases  almost  as  great  as  normal.  This  shows  that  the  exchange  of  gases 
must  take  place  in  the  tissues  themselves  {Pfliigcr  and  Oertmann).  If  the  chief 
oxidations  took  place  in  the  blood  and  not  in  the  tissues,  then,  during  suffocation, 
when  O  is  excluded,  the  substances  which  use  up  O,  /.  e.,  those  substances  which 
act  as  reducing  agents,  ought  to  accumulate  in  the  blood.  But  this  is  not  the 
case,  for  the  blood  of  asphyxiated  animals  contains  mere  traces  of  reducing  mate- 
rials {Ffliiger).  It  is  difficult  to  say  how  the  O  is  absorbed  by  the  tissues,  and 
what  becomes  of  it  immediately  it  comes  in  contact  with  the  living  elements  of 
the  tissues.   Perhaps  it  is  temporarily  stored  up,  or  it  may  form  certain  intermediate 


220  TENSION    OF   THE    GASES    IN    CAVITIES   AND    LYMPH. 

less  oxidized  compounds.  This  may  be  followed  by  a  period  of  rapid  formation 
and  excretion  of  CO,.  On  this  supposition,  it  is  evident  that  the  absorption  of  O 
and  the  excretion  of  CO,  need  not  occur  to  the  same  extent,  so  that  the  amount 
of  CO.,  given  off  at  any  period  is  not  necessarily  an  index  of  the  amount  of  O 
absorbed  during  the  same  period  (§  127). 

[There  are  two  views  as  to  where  the  CO.,  is  formed  as  the  blood  passes  through 
the  tissues.  One  view  is  that  the  seat  of  oxidation  is  in  the  blood  itself,  and  the 
other  IS  that  it  is  formed  in  the  tissues.  If  we  knew  the  tension  of  the  gases  in 
the  tissues  the  problem  would  be  easily  solved,  but  we  can  only  arrive  at  a  knowl- 
edge of  this  subject  indirectly,  in  the  following  ways]  :  — 

CO,  in  Cavities. — That  the  CO  j  is  formed  in  the  tissues  is  supported  by  the  fact  that  the  amount 
of  CO',  in  the  fluids  of  the  cavities  of  the  body  is  greater  than  the  COj  in  the  blood  of  the 
capillaries. 

Pfliiger  and  Strassburger  found  the  tension  of  COj  to  be,  in 


Arterial  blood  .    .    .    2 1. 28  Hg   tension 
Peritoneal  cavity  .    .     58.5       "         " 
Acid  urine     ....    68.0       "         •' 


Bile 50.8  Hg  tension. 

Hydrocele  fluid    .    .    46.5     "  " 


The  large  amount  of  CO^  in  these  fluids  can  only  arise  from  the  C0„  of  the  tissues  passing  into 
them. 

Gases  of  Lymph. — In  the  lymph  of  the  ductus  thoracicus  the  tension  of  COj  =33.4  to  37.2 
mm.  Hg,  which  is  greater  than  in  arterial  blood,  but  considerably  less  than  in  venous  blood  (41.0 
mm.  Hg).  \_Ludwig  and  Hammarstcn,  Tschiriew.']  This  does  not  entitle  us  to  conclude  that  in 
the  tissues  from  which  the  lymph  comes  only  a  small  quantity  of  CO,  is  formed,  but  rather  that  in 
the  lymph  there  is  less  attraction  for  the  CO,  formed  in  the  tissues  than  in  the  blood  of  the  capil- 
laries, where  chemical  forces  are  active  in  causing  it  to  combine,  or  that  in  the  course  of  the  long 
lymph  current  the  CO  2  is  partly  taken  back  to  the  tissues,  or  that  CO^  is  formed  in  the  blood  itself. 
Further,  the  muscles,  which  are  by  far  the  largest  producers  of  CO,,  contain  few  lymphatics,  never- 
theless  they  supply  much  CO,  to  the  blood.  The  amount  of  free  "  non-fixed  "  CO,  contained  in 
the  juices  and  tissues  indicates  that  the  CO,  passes  from  the  tissues  into  the  blood  ;  still,  Preyer 
believes  that  in  venous  blood  CO,  undergoes  chemical  combination.  The  change  of  O  and  COj 
varies  much  in  the  dift'erent  tissues.  The  muscles  are  the  most  important  organs,  for  in  their  active 
condition  they  excrete  a  large  amount  of  CO,,  and  use  up  much  O.  The  O  is  so  rapidly  used  up 
by  them  that  no  free  O  can  be  pum|)ed  out  of  muscular  tissue  (Z.  Hermann).  The  exchange  of 
gases  is  more  vigorous  during  the  activity  of  the  tissues.  Nor  are  the  salivary  glands,  kidneys,  and 
pancreas  any  exception,  for  although  when  these  organs  are  actively  secreting,  the  blood  flows  out 
of  the  dilated  veins  in  a  bright  red  stream,  still  the  relative  diminution  of  CO,  is  more  than  com- 
pensated by  the  increased  volume  of  blood  which  passes  through  these  organs. 

Reductions  by  the  Tissues. — The  researches  of  Ehrlich  have  shown  that  in  most  tissues  very 
energetic  reductions  take  place.  If  coloring  matters,  such  as  alizarin  blue,  indophenol  blue,  or 
methyl  blue,  be  introduced  into  the  blood  stream,  the  tissues  are  colored  by  them.  Those  tissues 
or  organs  which  have  a  particular  affinity  for  O  {e.g.,  liver,  cortex  of  the  kidney, .and  lungs),  absorb 
O  from  these  pigments,  and  render  them  colorless.  The  pancreas  and  submaxillary  gland  scarcely 
reduce  them  at  all. 

(2)  In  the  blood  itself,  as  in  all  tissues,  O  is  used  up  and  CO,  is  formed.  This 
is  proved  by  the  following  facts  :  That  blood  withdrawn  from  the  body  becomes 
poorer  in  O  and  richer  in  CO, ;  that  in  the  blood  of  asphyxia,  free  from  O,  and 
in  the  blood  corpuscles  {Afaiiassieff),  there  are  slight  traces  of  reducing  agents, 
which  become  oxidized  on  the  addition  of  O  {A.  Schmidt).  .Still,  this  process  is 
comparatively  insignificant  as  against  that  which  occurs  in  all  the  other  tissues. 
That  the  walls  of  the  vessels — more  especially  the  muscular  fibres  in  the  walls  of 
the  small  arteries — use  O  and  produce  CO,  is  unquestionable,  although  it  is  so 
slight  that  the  blood  in  its  whole  arterial  course  undergoes  no  visible  change. 

Ludwig  and  his  pupils  have  proved  that  CO,  is  actually  formed  in  the  blood.  If  the  easily  oxi- 
dizable  lactate  of  soda  be  mixed  with  blood,  and  this  blood  be  caused  to  circulate  in  an  excised  but 
still  living  organ,  such  as  a  lung  or  kidney,  more  O  is  used  up  and  more  COj  is  formed  than  in 
unmixed  blood  similarly  transfused. 

(3)  That  the  tissues  of  the  living  limgs  use  O  and  give  off  COj  is  probable. 
When  C.  Ludwig  and  Miiller  passed  arterial  blood  through  the  blood  vessels  of  a 
lung  deprived  of  air,  the  O  was  diminished  and  the  COj  increased. 


RESPIRATION    IN    A   CLOSED    SPACE.  221 

As  the  total  amount  of  COj  and  O  found  in  the  entire  blood,  at  any  one  time, 
is  only  4  grammes,  and  as  the  daily  excretion  of  CO,  ==  900  grammes,  and  the 
O  absorbed  daily  ^=  744  grammes,  it  is  clear  that  exchange  of  gases  must  go  on 
with  great  rapidity,  that  the  O  absorbed  must  be  used  quickly,  and  the  CO,  must 
be  rapidly  excreted. 

.  Still,  it  is  a  striking  fact  that  oxidation  processes  of  such  magnitude,  as,  e.g.,  the  union  of  C  to 
form  COj,  occur  at  the  relatively  low  temperature  of  the  blood  and  the  tissues.  It  has  been 
assumed  that  the  blood  acts  as  an  ozone  producer,  and  transfers  this  active  form  of  O  to  the  tissues. 
Liebig  showed  that  the  alkaline  reaction  of  most  of  the  juices  and  tissues  favors  the  process  of  oxi- 
dation. Numerous  organic  substances,  which  are  not  altered  by  O  alone,  become  rapidly  oxidized 
in  the  presence  of  free  alkalies,  e.  g.,  gallic  acid,  pyrogallic  acid  and  sugar;  while  many  organic 
acids,  which  are  unaffected  by  ozone  alone,  are  changed  into  carbonates,  when  in  the  form  of  alka- 
line salts  (  Corup-Besanez] ;  and  in  the  same  way  when  they  are  introduced  into  the  body  in  the 
form  of  acids,  they  are  partly  or  wholly  excreted  in  the  urine,  but  when  they  are  administered  as 
alkaline  compounds  they  are  changed  iiuo  carbonates. 

133.  RESPIRATION  IN  A  CLOSED  SPACE.— Respiration  in  a  closed 
or  limited  space  causes — (i)  a  gradual  diminution  of  O  ;  (2)  a  simultaneous  increase 
of  CO2 ;  (3)  a  diminution  in  the  volume  of  the  gases.  If  the  space  be  of  moderate 
dimensions,  the  animal  uses  up  almost  all  the  O  contained  therein  {Ahslen),  and 
dies  ultimately  from  spasms  caused  by  the  asphyxia.  The  O  is  absorbed,  there- 
fore—independently of  the  laws  of  absorption — by  chemical  means.  The  O  in 
the  blood  is  almost  completely  used  up  {Setschenow,  §  129).  In  a  larger  closed 
space,  the  CO.j  accumulates  rapidly,  before  the  diminution  of  O  is  such  as  to 
affect  the  life  of  the  animal.  As  C0._,  can  only  be  excreted  from  the  blood  when 
the  tension  of  the  CO,  in  the  blood  is  greater  than  the  tension  of  CO^  in  the 
air,  as  soon  as  the  CO,  in  the  surrounding  air  in  the  closed  space  becomes  the 
same  as  in  the  blood,  the  CO.^  will  be  retained  in  the  blood,  and  finally  CO,  may 
pass  back  into  the  body.  This  occurs  in  a  large  closed  space,  when  the  amount 
of  O  is  still  sufficient  to  support  life,  so  that  death  occurs  under  these  circum- 
stances (in  rabbits)  through  poisoning  with  CO^  causing  diminished  excitability, 
loss  of  consciousness  and  lowering  of  temperature,  but  no  spasms  (  Worm  Miiller). 
In  pure  O,  animals  breathe  in  a  normal  way ;  the  quantity  of  O  absorbed  and 
the  CO.;  excreted  is  quite  independent  of  the  percentage  of  O,  so  that  the  former 
occurs  through  chemical  agency  independent  of  pressure  {Regnau/t  and  Reiset, 
Herter,  Lukjanoiv).  In  closed  spaces  filled  withO,  animals  died  by  reabsorption 
of  the  CO,  excreted.  Worm  Miiller  found  that  rabbits  died  after  absorbing  CO.^ 
equal  to  half  the  volume  of  their  body,  although  the  air  still  contained  50  per 
cent.  O.  Animals  can  breathe  quite  quietly  a  mixture  of  air  containing  14.8  per 
cent.  (20.9  jiei^  cent,  normal)  ;  with  7  per  cent,  they  breathe  with  difficulty  ;  with 
4.5  per  cent,  there  is  marked  dyspnoea;  with  3  per  cent.  O  there  is  tolerably 
rapid  asphyxia  ( /f'  Aliiller).  The  air  expired  by  man  normally  contains  14  to 
18  per  cent.  O.  According  to  Hempner,  mammals  placed  in  a  mixture  of  gases 
poor  in  O,  use  slightly  less  O. 

Dyspncea  occurs  when  the  respired  air  is  deficient  in  O,  as  well  as  when  it  is  overcharged  with 
CO2,  but  the  dyspncea  in  the  former  case  is  prolonged  and  severe  ;  in  the  latter,  the  respiratory 
activity  soon  ceases.  The  want  of  O  causes  a  greater  and  more  prolonged  increase  of  the  blood 
pressure  tlian  is  caused  by  excess  of  CO^.  Lastly,  the  consumption  of  O  in  the  body  is  less  affected 
when  the  O  in  the  air  is  diminished  than  when  there  is  excess  of  CO,.  If  air  containing  a  dimin- 
ished amount  of  O  be  respired,  death  is  preceded  by  violent  phenomena  of  excitement  and  spasms, 
which  are  absent  in  cases  of  death  caused  by  breathing  air  overcharged  with  CO,.  In  poisoning 
with  CO,,  the  excretion  of  CO^  is  greatly  diminished,  while  with  diminution  of  O,  it  is  almost 
unchanged  ( C.  Friealdnder  and  E.  Herter). 

If  animals  be  supplied  with  a  mixture  of  gases  similar  to  the  atmosphere,  in 
which  N  is  replaced  by  H,  they  breathe  quite  normally  {Lavoisier  and  Segiiin)  ; 
the  H  undergoes  no  great  change. 

CI.  Bernard  found  that,  when  an  animal  breathed  in  a  closed  space,  it  became  partially  accus- 
tomed to  the  condition.     On  placing  a  bird  under  a  bell-jar,  it  lived  several  hours;  but  if  several 


222  PHENOMENA   OF    ASPHYXIA. 

hours  before  its  death  another  bird  fresh  from  the  outer  air  were  placed  under  the  same  bell-jar,  the 
second  bird  died  at  once,  with  convulsions. 

Frogs,  when  placed  for  several  hours  in  air  devoid  of  O,  give  off  just  as  much  CO,  as  in  air 
containing  O,  and  they  do  this  without  any  obvious  disturbance  (Pfliigcr,  Aubert).  Hence,  it 
appears  that  the  formation  of  CO,  is  independent  of  the  absorption  of  O,  and  the  CO^  must  be 
formed  from  the  decomposition  of  other  compounds.  Ultimately,  however,  complete  motor  paraly- 
sis occurs,  while  the  circulation  remains  undisturbed  (Atiberl). 

[134.  DYSPNCEA  AND  ASPHYXIA.]— [The  causes  of  dyspnoea  have 
already  been  referred  to  (§  iii),  and  those  of  asphyxia  are  referred  to  in  detail 
in  §  368.  If  from  any  cause  an  animal  be  not  supplied  with  a  due  ainount  of  air, 
normal  respiration  becomes  greatly  altered,  passing  through  the  phases  of  hyper- 
pnoea,  or  increased  respiration,  dyspnoea  or  difficulty  of  breathing  to  the  final 
condition  of  suffocation  or  asphyxia.  The  phenomena  of  asphyxia  may  be 
developed  in  an  animal  by  closing  its  trachea  by  means  of  a  clamp,  and  in  fact 
by  any  means  which  prevent  the  entrance  of  air  or  blood  into  the  lungs. 

The  phenomena  of  asphyxia  are  usually  divided  into  several  stages:  i. 
During  the  first  stage  there  is  hyperpntea,  the  respirations  being  deeper,  more 
frequent  and  labored.  The  extraordinary  muscles  of  respiration — both  those  of 
inspiration  and  expiration — referred  to  in  §  118  are  called  into  action,  the  condi- 
tion of  dyspnoea  being  rapidly  produced,  and  the  struggle  for  air  becomes  more 
and  more  severe.  During  this  time  the  oxygen  of  the  blood  is  being  used  up,  the 
blood  itself  is  becoming  more  and  more  venous.  This  venous  blood  circulating 
in  the  medulla  oblongata  and  spinal  cord  stimulates  the  respiratory  centres,  thus 
causing  these  violent  respirations.  This  stage  usually  lasts  about  a  minute,  and 
gradually  gives  place  to — 

2.  The  second  stage,  when  the  inspiratory  muscles  become  less  active,  while 
those  concerned  in  labored  expiration  contract  energetically,  and,  indeed,  almost 
every  muscle  in  the  body  may  contract ;  so  that  this  stage  of  violent  expiratory 
efforts  ends  in  general  convulsions.  The  convulsions  are  due  to  stimulation  of  the 
respiratory  centres  by  the  venous  blood.  The  convulsive  stage  is  short,  and  is 
usually  reached  in  a  little  over  one  minute.     This  storm  is  succeeded  by — 

3.  The  third  stage,  or  stage  of  exhaustion,  the  transition  being,  usually, 
somewhat  sudden.  This  condition  is  brought  about  by  the  venous  blood  acting 
on  and  paralyzing  the  respiratory  centres.  The  pupils  are  widely  dilated,  con- 
sciousness is  abolished,  and  the  activity  of  the  reflex  centres  is  so  depressed  that 
it  is  impossible  to  discharge  a  reflex  act,  even  from  the  cornea.  The  animal  lies 
alinost  motionless,  with  flaccid  muscles,  and,  to  all  appearance,  dead  ;  but  every 
now  and  again,  at  long  intervals,  it  makes  a  few  deep  inspiratory  efforts,  showing 
that  the  respiratory  centres  are  not  quite,  but  almost,  paralyzed.  Gradually,  the 
pauses  become  longer  and  the  inspirations  feebler  and  of  a  gasping  character.  As 
the  venous  blood  circulates  in  the  spinal  cord,  it  causes  a  large  number  of  muscles 
to  contract,  so  that  the  animal  extends  its  trunk  and  limbs.  It  inakes  one  great 
inspiratory  spasm,  the  mouth  being  widely  open  and  the  nostrils  dilated,  and 
ceases  to  breathe.  After  this  stage,  which  is  the  longest  and  most  variable,  the 
heart  becomes  paralyzed,  partly  from  being  over-distended  with  venous  blood, 
and  partly,  perhaps,  from  the  action  of  the  venous  blood  on  the  cardiac  tissues, 
so  that  the  pulse  can  hardly  be  felt.  To  this  pulseless  condition  the  term 
"  asphyxia"  ought  properly  to  be  applied.  In  connection  with  the  resuscitation 
of  asphyxiated  persons,  it  is  important  to  note  that  the  heart  continues  to  beat 
for  a  few  seconds  after  the  respiratory  movements  have  ceased. 

The  whole  series  of  phenomena  occupies  from  3  to  5  minutes,  according  to  the 
animal  operated  on,  and  depending,  also,  upon  the  suddenness  with  which  the 
trachea  was  closed.  If  the  cause  of  suffocation  act  more  slowly,  the  phenomena 
are  the  same,  only  they  are  developed  more  slowly. 

The  Circulation. — The  post-mortem  appearances  in  man  or  in  an  animal  are 
generally  well   marked.     The  right  side  of  the  heart,  the  pulmonary  artery,  the 


THE   CHANGES  OF  THE   CIRCULATION   DURING  ASPHYXIA.  223 

venae  cavse  and  the  veins  or  the  neck  are  engorged  with  dark  venous  blood.  The 
left  side  is  comparatively  empty,  because  the  rigor  mortis  of  the  left  side  of  the 
heart,  and  the  elastic  recoil  of  the  systemic  arteries,  force  the  blood  toward  the 
systemic  veins.  The  blood  itself  is  almost  black,  and  is  deprived  of  almost  all 
its  oxygen,  its  haemoglobin  being  nearly  all  in  the  condition  of  reduced  haemo- 
globin, while  ordinary  venous  blood  contains  a  considerable  amount  of  oxyhae- 
moglobin  as  well  as  reduced  Hb.  The  blood  of  an  asphyxiated  animal,  practically, 
contains  none  of  the  former  and  much  of  the  latter. 

It  is  important  to  study  the  changes  in  the  circulation  in  connection  with  the 
outward  phenomena  exhibited  by  an  animal  during  suffocation. 

We  may  measure  the  blood  pressure  in  any  artery  of  an  animal  while  it  is  being 
asphyxiated,  or  we  may  open  its  chest,  maintain  artificial  respiration,  and  place  a 
manometer  in  a  systemic  artery,  e.g.,  the  carotid,  and  another  in  a  branch  of  the 
pulmonary  artery.  In  the  latter  case,  we  can  watch  the  order  of  events  in  the 
heart  itself,  when  the  artificial  inspiration  is  interrupted.  It  is  well  to  study  the 
events  in  both  cases. 

If  the  blood  pressure  be  measured  in  a  systemic  artery,  e.g.,  the  carotid,  it  is 
found  that  the  blood  pressure  rises  very  rapidly  and  to  a  great  extent  during  the 
first  and  second  stages ;  the  pulse  beats  at  first  are  quicker,  but  soon  become 
slower  and  more  vigorous.  During  the  third  stage  it  falls  rapidly  to  zero.  The 
great  rise  of  the  blood  pressure  during  the  first  and  second  stages  is  chiefly  due 
to  the  action  of  the  venous  blood  on  the  vasomotor  centre,  causing  constriction 
of  the  small  systemic  arteries.  The  peripheral  resistance  is  thus  greatly  increased, 
and  it  tends  to  cause  the  heart  to  contract  more  vigorously  ;  but  the  slower  and 
more  vigorous  beats  of  the  heart  are  also  partly  due  to  the  action  of  the  venous 
blood  on  the  cardio-inhibitory  centre  in  the  medulla. 

If  the  second  method  be  adopted — viz.,  to  open  the  chest— keep  up  artificial 
respiration,  and  measure  the  blood  pressure  in  a  branch  of  the  pulmonary  artery, 
as  well  as  in  a  systemic  artery — e.g.,  the  carotid — we  find  that  when  the  artificial 
respiration  is  stopped,  in  addition  to  the  rise  of  the  blood  pressure  indicated  in 
the  carotid  manometer,  the  cavities  of  the  heart  and  the  large  veins  near  it  are 
engorged  with  venous  blood.  There  is,  however,  but  a  slight  comparative  rise  in 
the  blood  pressure  in  the  pulmonary  artery.  This  may  be  accounted  for  either  by 
the  pulmonary  artery  not  being  influenced  to  the  same  extent  as  other  arteries,  by 
the  vasomotor  centre,  or  by  its  greater  distensibility  {Lichtheim — compare  §  88). 
But  as  the  heart  itself  is  supplied  through  the  coronary  arteries  with  venous  blood,  its 
action  soon  becomes  weakened  ;  each  beat  becomes  feebler,  so  that  soon  the  left 
ventricle  ceases  to  contract,  and  is  unable  to  overcome  the  great  peripheral  resist- 
ance in  the  systemic  arteries,  although  the  right  ventricle  may  still  be  contracting. 
As  the  blood  becomes  more  venous,  the  vasomotor  centre  becomes  paralyzed,  the 
small  systemic  arteries  relax,  and  the  blood  flows  from  them  into  the  veins,  while 
the  blood  pressure  in  the  carotid  manometer  rapidly  falls.  The  left  ventricle, 
now  relieved  from  the  great  internal  pressure,  may  execute  a  few  feeble  beats,  but 
they  can  only  be  feeble,  as  its  tissues  have  been  subjected  to  the  action  of  the  very 
impure  blood.  More  and  more  blood  accumulates  in  the  right  side,  from  the 
causes  already  mentioned.  The  violent  inspiratory  efforts  in  the  early  stages 
aspirate  blood  from  the  veins  toward  the  right  side  of  the  heart,  but,  of  course, 
this  factor  is  absent  when  the  chest  is  opened.] 

[Convulsions  during  asphyxia  occur  only  in  warm-blooded  animals,  and 
not  in  frogs.  If  a  drug  when  injected  into  a  mammal  excites  convulsions, 
but  does  not  do  so  in  the  frog,  then  it  is  usually  concluded  that  the  convulsions 
are  due  to  its  action  on  the  circulation  and  respiration,  and  not  to  any  direct 
stimulating  effect  upon  the  motor  centres.  But  if  the  drug  excite  convulsions 
both  in  the  mammal  and  frog,  then  it  probably  acts  directly  on  the  motor 
centres  {Brunton).'] 


224  ARTIFICIAL    RESPIRATION    IN    ASPHYXIA. 

[Recovery  from  the  Condition  of  Asphyxia. — If  the  trachea  of  a  dog  be  closed  suddenly 
and  completely,  the  average  duration  of  the  respiratory  movements  is  4  minutes,  5  seconds,  while 
the  heart  continues  to  beat  for  about  7  minutes.  Recovery  may  be  obtained  if  proper  means  be 
adopted  before  the  heart  ceases  to  beat;  but  after  this,  never.] 

[If  a  dog  be  drowned,  the  result  is  difl'erent.  After  complete  submersion  for  ij'^  minutes, 
recovery  did  not  take  place.  In  the  ca.se  of  drowning,  air  passes  out  of  the  chest,  and  water  is 
inspired  into  and  fills  the  air  vesicles.  It  is  rare  for  recovery  to  take  place  in  a  person  deprived  of 
air  for  more  than  five  minutes.  If  the  statements  of  sponge  divers  are  to  be  trusted,  a  person  may 
become  accustomed  to  the  deprival  of  air  for  a  longer  time  than  usual.  In  cases  where  recovery 
takes  place  after  a  much  longer  period  of  submersion,  it  has  been  suggested  that,  in  these  cases, 
syncope  occurs,  the  heart  beats  but  feebly  or  not  at  all,  so  that  the  oxygen  in  the  blood  is  not  used 
up  with  the  same  rapidity.  It  is  a  well-known  fact  that  newly-born  and  young  puppies  can  be  sub- 
merged for  a  long  time  before  they  are  suffocated.] 

Artificial  Respiration  in  Asphyxia. — In  cases  of  suspended  animation,  artificial  respiration 
must  be  performed.  The  first  thing  to  be  done  is  to  remove  any  foreign  substance  from  the 
respiratory  passages  (mucus  or  cedematous  fluids)  in  the  newly-born  or  asphyxiated.  In  doubtful 
cases,  open  the  trachea  and  suck  out  any  fluid  by  means  of  an  elastic  catheter  (v.  Hiiter).  Recourse 
must  in  all  cases  be  had  to  artificial  re.spiration.  There  are  several  methods  of  dilating  and  com- 
pressing the  chest  so  as  to  cause  an  exchange  of  gases.  One  method  is  to  compress  the  chest 
rhythmically  with  the  hands. 

[Marshall  Hall's  Method. — "After  clearing  the  mouth  and  throat,  place  the  patient  on  the 
face,  raising  and  supporting  the  chest  wall  on  a  folded  coat  or  other  article  of  dress.  Turn  the 
body  very  gently  on  the  side  and  a  little  beyond,  and  then  briskly  on  the  face,  back  again,  repeat- 
ing these  measures  cautiously,  efficiently  and  perseveringly,  about  fifteen  times  in  the  minute,  or  once 
every  four  or  five  seconds,  occasionally  varying  the  side.  By  placing  the  patient  on  the  chest,  the 
weight  of  the  body  forces  the  air  out ;  when  turned  on  the  side,  this  pressure  is  removed,  and  air 
enters  the  chest.  On  each  occasion  that  the  body  is  replaced  on  the  face,  make  uniform  but  effi- 
cient pressure  with  bri^k  movement  on  the  back  between  and  below  the  shoulder-blades  or  bones  on 
each  sid'e,  removing  the  pressure  immediately  before  turning  the  body  on  the  side.  During  the 
whole  of  the  operations  let  one  person  attend  solely  to  the  movements  of  the  head  and  of  the  arm 
placed  under  it."'] 

[Sylvester's  Method. — "Place  the  patient  on  the  back  on  the  flat  surface,  inclined  a  little 
upward  from  the  feet  ;  raise  and  support  the  head  and  shoulders  on  a  small,  firm  cushion  or  folded 
article  of  dress  placed  under  the  shoulder-blades.  Draw  forward  the  patient's  tongue,  and  keep  it 
projecting  beyond  the  lips;  an  elastic  band  over  the  tongue  and  under  the  chin  will  answer  this 
purpose,  or  a  piece  of  string  or  tape  may  be  tied  around  them,  or  by  raising  the  lower  jaw,  the 
teelh  may  be  made  to  retain  the  tongue  in  that  position.  Remove  all  tight  (flothing  from  about  the 
neck  and  chest,  especially  the  braces." 

"7(1  Itnilate  the  Movements  0/  Breathing. — Standing  at  the  patient's  head,  grasp  the  arms  just 
above  the  elbows,  and  draw  the  arms  gently  and  steadily  upward  above  the  head,  and  keep  them 
stretched  upward  for  two  seconds.  By  this  means  air  is  drawn  into  the  lungs.  Then  turn  dow-n 
.  the  patient's  arms  and  press  them  gently  and  firmly  for  two  seconds  against  the  sides  of  the  chest. 
By  this  means  air  is  pressed  out  of  the  lungs.  Repeat  these  measures  alternately,  deliberately  and 
perseveringly,  about  fifteen  times  in  a  minute,  until  a  spontaneous  effort  to  respire  is  perceived, 
immediately  upon  which  cease  to  imitate  the  movements  of  breathing,  and  proceed  to  induce  circu- 
lation and  7i'arjiithy] 

Howard  advises  rhythmical  compression  of  the  chest  and  abdomen  by  sitting  like  a  rider  astride 
of  the  body,  while  SchiiUer  advises  that  the  lower  ribs  be  seized  from  above  with  both  hands  and 
raised,  whereby  the  chest  is  dilated,  especially  when  the  thigh  is  pressed  against  the  abdomen  to 
compress  the  abdominal  walls.  The  chest  is  compressed  by  laying  the  hands  flat  upon  the  hypo- 
chondria. Artificial  respiration  acts  favorably  by  supplying  O  to,  as  well  as  removing  CO.^  from, 
the  blood ;  further,  it  aids  the  movement  of  the  blood  within  the  heart  and  in  the  large  vessels  of 
the  thorax.  If  the  action  of  the  heart  has  ceased,  recovery  is  impossible.  In  asphyxiated  newly- 
born  children,  we  must  not  cease  to  perform  artificial  respiration  Loo  soon.  Even  when  the  result 
appears  hopeless,  we  ought  to  persevere.  Pfliiger  and  Zuntz  observed  that  the  reflex  excitability  of 
the  foetal  heart  continued  for  several  \ionrs  after  the  death  of  the  mother. 

Resuscitation  by  compressing  the  heart. — Bohm  found  that  in  the  case  of  cats  poisoned  with 
potash  salts  or  chloroform,  or  asphyxiated,  so  as  to  arrest  respiration  and  the  action  of  the  heart — 
even  for  a  period  of  forty  minutes — and  even  when  the  pressure  within  the  carotid  had  fallen  lo 
zero,  he  could  restore  animation  by  rhythmical  compression  of  the  heart,  combined  with  artificial 
respiration.  The  compression  of  the  heart  causes  a  slight  movement  of  the  blood,  while  it  acts  at 
the  same  time  as  a  rhythmical  cardiac  stimulus.  After  recovery  of  the  respiration,  the  reflex  excit- 
ability is  restored,  and  gradually  also  voluntary  movements.  The  animals  are  blind  for  several 
days,  the  brain  acts  slowly,  and  the  urine  contains  sugar.  These  experiments  show  how  important 
it  is  in  cases  of  a.sphyxia  to  act  at  the  same  time  U|ion  ihe  heart. 

For  physiological  purposes,  artificial  respiration  is  ofien  made  use  of,  especially  after  poisoning 


ACCIDENTAL    IMPURITIES   OF   THE    AIR.  225 

with  curara.  Air  is  forced  into  the  lungs  by  means  of  an  elastic  bag  or  bellows,  attached  to  a 
cannula  tied  in  the  trachea.  The  cannula  has  a  small  opening  in  the  side  of  it  to  allow  the  expired 
air  to  escape. 

Pathological. — After  the  lungs  have  once  been  properly  distended  with  air,  it  is  impossible  by 
any  amount  of  direct  compression  of  them  to  get  rid  of  all  the  air.  This  is  probably  due  to  the 
pressure  acting  on  the  small  bronchi,  so  a<  to  squeeze  them,  before  the  air  can  be  forced  out  of  the 
air  vesicles.  If,  however,  a  lung  be  filled  with  CO,,  and  be  suspended  in  water,  the  COj  is 
absorbed  by  the  water,  and  the  lungs  become  quite  free  from  air  and  are  atelectic  ( Hermann  and 
Keller).  The  atelectasis  which  sometimes  occurs  in  the  lung  may  thus  be  explamed  :  If  a  bron- 
chus is  stopped  with  mucus  or  exudation,  an  accumulation  of  CO2  in  the  air  vesicles  belonging  to 
this  bronchus  occurs.  If  this  COj  is  absorbed  by  the  blood  or  lymph,  the  corresponding  area  of  the 
lung  will  become  atelectic.  Sometimes  there  is  spasm  of  the  respiratory  muscles,  brought  about 
by  direct  or  reflex  stimulation  of  the  respiratory  centre. 

135.  RESPIRATION  OF  FOREIGN  GASES,  AND  ABSORPTION  BY  THE 
LUNGS. — -No  gas  without  a  sufficient  admixture  of  O  can  support  life.  Even  with  completely 
innocuous  and  ineiifferent  gases,  if  no  O  be  mixed  with  them,  they  cause  suffocation  in  2  to  3 
minutes. 

I.  Completely  indifferent  Gases  are  N,  H,  CH^.  The  living  blood  of  an  animal  breathing 
these  gases  yields  no  (J  to  them  [Pfliiger). 

II.  Poisonous  Gases. — {a)  Those  that  displace  O,  and  form  a  permanent  stable  compound 
with  the  hoemoglobin — (I)  CO  (\  16  and  17).  (2)  CNH  (hydrocyanic  acid)  displaces  (?)  O  from 
haemoglobin,  with  which  it  forms  a  more  stable  compound  and  kills  exceedingly  rapidly.  It  prevents 
O  being  changed  into  ozone  in  the  blood.  Blood  corpuscles  charged  with  hydrocyanic  acid  lose 
the  property  of  decomposing  hydric  peroxide  into  water  and  O  (§  17,  5). 

(/'j   Narcotic  Gases. — (l)  COj — v.  Pettenkofer  characterizes  air  containing  O  with  i  per  cent. 


Fig.  143. 

Ciliated  epitheliu] 

1  V                                      ^ Clear  disk. 

^1-             eJ 

Debove's  membran 

^'.4;,^M^— 

efoi 

Ciliated  epithelium  from  the  larynx  of  a  horse  (  Toldt),  (see  Fig.  125). 

CO  2  as  "  bad  air ;"  still,  air  in  a  room  containing  this  amount  of  CO .,  produces  a  disagreeable  feeling 
rather  from  the  impurities  mixed  with  it  than  from  the  actual  amount  of  CO^  itself.  A\x  containing 
I  per  cent.  CO^  produces  decided  discomfort,  and  with  10  per  cent,  it  endangers  life,  while  larger 
amounts  cause  death  with  symptoms  of  coma.  (2)  X,0  (nitrous  oxidej  respired,  mixed  with  i 
volume  O,  causes,  after  i  to  2  minutes,  a  short  tempor.iry  stage  of  excitement  ("Laughing  gas"  of 
H.  Davy),  which  is  succeeded  by  unconsciousness,  and  afterward  by  an  increased  excretion  of  COj. 
(3}  Ozonized  air  causes  similar  effects  (Binz). 

(c)  Reducing  Gases. — (i)  H,S  (sulphuretted  hydrogen)  rapidly  robs  blood  corpuscles  of  O, 
S  and  H,0  being  formed,  and  death  occurs  rapidly  before  the  gas  can  decompose  the  haemoglobin 
(HoppeSeyler). 

(2)  PH3 — Phosphuretted  hydrogen  is  oxidized  in  the  blood  to  form  phosphoric  acid  and  water, 
with  decomposition  of  the  haemoglobin  [Dybkowski,  Koscklakoff,  and  Popoff). 

(3)  AsHj,  arseniuretted  hydrogen  and  SbHj,  antimoniuretted  hydrogen,  act  like  PHj,  but,  in 
addition,  the  haemoglobin  passes  out  of  the  stroma  and  appears  in  the  urine. 

(4)  C2N2,  cyanogen,  absorbs  O,  and  decomposes  the  blood  (Kosenthal and Lasckke^vitsch). 
III.  Irrespirable  Gases,  i.e.,  gases  which,  on  entering  the  larjmx,  cause  reflex  spasm  of  the 

glottis.  When  introduced  into  the  trachea  they  cause  inflammation  and  death.  Under  this  category 
come  hydrochloric,  hydrofluoric,  sulphurous,  nitrous,  and  nitric  acids,  ammonia,  chlorine,  fluorine, 
and  ozone. 

Absorption  takes  place  almost  immediately  through  the  lungs  (strychnia,  curara,  potassic  nitrate), 
and  far  more  rapidly  than  by  injection  under  the  skin.     Colloids  are  absorbed  more  slowly  [Peiper). 

136.  ACCIDENTAL  IMPURITIES  OF  THE  AIR.— Dust  Particles.— Among  these 

are  dust  particles,  which  occur  in  enormous  amount  suspended  in  the  air,  and  thereby  act  injuriously 

upon  the  respiratory  organs.     The  ciliated  epithelium  of  the  respiratory  passages  eliminates  a  large 

number  of  them  (Fig.  143).     Some  of  them,  however,  reach  the  air  vesicles  of  the  lung,  where  thev 

15 


226  VENTILATION    OF   ROOMS. 

penetrate  the  epithelium,  reach  the  interstitial  lung  tissue  and  lymphatics,  and  so  pass  with  the  lymph 
stream  into  the  bronchial  glands.  Particles  of  coal  or  charcoal  ate  found  in  the  lungs  of  all  elderly 
individuals,  and  blacken  the  alveoli.  In  moderate  amount  these  black  particles  do  not  seem  to  do 
any  harm  in  the  tissues,  but  when  there  are  large  accumulations  they  give  rise  to  lung  affections, 
which  lead  to  disintegration  of  these  organs.  [In  coal  miners,  for  example,  the  lung  tissues  along 
the  track  of  the  lymphatics  and  in  the  bronchial  glands  are  quite  black,  constituting  "coal  miners' 
lung."]  In  many  trades  various  particles  occur  in  the  air;  miners,  grinders,  stone-masons,  tile- 
makers,  weavers,  spinners,  tobacco  manufacturers,  millers,  and  bakers,  suffer  from  lung  affections 
caused  by  the  introduction  of  particles  of  various  kinds  inhaled  during  the  time  they  are  at  work. 

Germs. — There  seems  no  doubt  that  the  seeds  of  some  contagious  diseases  may  be  inhaled. 
Diphtheritic  bacteria  (Micrococcus  diphtheriticus — Berlcl)  become  localized  in  the  pharynx  and  in 
the  larynx — glanders  in  the  nose  (.Sc/i/V/a  and  Loflle?-) — measles  in  the  bronchi  — whooping  cough 
in  the  bronchi — hay  monads  in  the  nose — the  cocci  of  pulmonary  inflammation  (K'lebs,  Lcichtcn- 
stern)  in  the  pulmonary  alveoli.  Tuberculosis,  according  to  R.  Koch,  is  due  to  the  introduction 
and  development  of  the  Bacillus  tuberculosis  in  the  lungs ;  the  bacillus  being  derived  from  the  dust 
of  tuberculous  sputa.  The  same  seems  to  be  the  case  with  the  Bacillus  of  leprosy  (Hansen),  and 
with  Bacillus  malariae,  which  is  the  cause  of  malaria  {A'ld's  and  Tumasl-Cihdeli).  The  latter 
organism  thus  reaches  the  blood  ;  it  changes  the  Hb  within  the  red  blood  corpuscles  into  melanin 
[\  10,3),  and  causes  them  to  break  up  [iMarchiafava  and  Celli).  The  exciter  of  smallpox  (Micro- 
coccus vaccinte)  gains  access  to  the  blood  in  the  same  way  (Kcbei;  iSbS),  also  the  Spirillum  of 
remittent  fever  (Fig.  20 — Obermeier,  iSy^,  the  microbe  of  scarlet  fever,  etc. 

Seeds  of  disease  pass  into  the  mouth  along  with  air,  and  also  with  the  food,  are  swallowed,  and 
undergo  development  in  the  intestinal  tract,  as  is  probably  the  case  in  cholera  (Comma  bacillus  of 
K.  A'och),  [although  that  this  bacillus  is  the  cause  of  cholera  is  questioned  by  Klein  and  Uibbes]  ; 
dysentery  and  typhoid  (Eberth,  A'lcbs),  and  in  anthrax  which  is  due  to  Bacterium  anthracis  (Fig. 
21— Follcnder,  1SJ4). 

137.  VENTILATION  OF  ROOMS.— Fresh  Air  and  Cubic  Space. — Fresh  air  is  as 
necessary  for  the  healtliy  as  for  the  sick.  Every  healthy  person  ought  to  have  a  cubic  space  of,  at 
the  very  least,  800  cubic  feet,  and  every  sick  person  at  the  very  least  1000  cubic  feet  of  space.  [The 
cubic  space  allowed  per  individual  varies  greatly,  but  1000  cubic  feet  is  a  fair  average.  If  the  air 
in  this  space  is  to  be  kept  sweet,  so  that  the  CO,  does  not  exceed  .06  per  cent.,  3000  cubic  feet  of 
air  per  hour  must  be  supplied,  i.  e.,  the  air  in  the  space  must  be  renewed  three  times  per  hour.] 

In  Prussia,  in  barracks,  420-500  cubic  feet  are  allowed  for  every  soldier,  for  hospital,  600-720; 
in  England  600  cubic  feet  per  head. 

[Floor  Space. — It  is  equally  important  to  secure  sufficient  floor  space,  and  this  is  especially  the 
case  in  hospitals.  If  possible,  100-120  square  feet  of  floor  space  ought  to  be  provided  for  each 
patient  in  a  hospital  ward,  and  if  it  is  obtainable  a  cubic  space  of  1500  cubic  feet  (Parkes).  In  all 
cases  the  minimum  floor  space  should  not  be  less  than  yV  of  the  cubic  space.] 

Overcrowding. — When  there  is  overcrowding  in  a  room  the  amount  of  CO2  increases,  v.  Pet- 
tenkofer  found  the  normal  amount  of  CO,  (.04  to  .05  per  looo)  increased  in  comfortable  rooms  to 
0.54-0.7  per  1000  ;  in  badly  ventilated  sick  chambers  =  2.4  ;  in  overcrowded  auditoriums,  3.2  ;  in 
pits  ^  4.9 ;  in  school  rooms,  7.2  per  1000.  Although  it  is  not  the  quantity  of  COj  which  makes  the 
air  of  an  overcrowded  room  injurious,  but  the  excretions  from  the  outer  and  inner  surfaces  of  the 
body,  which  give  a  distinct  odor  to  the  air,  quite  recognizable  by  the  sense  of  smell,  still  the  amount 
of  CO2  is  taken  as  an  index  of  the  presence  and  amount  ol  these  other  deleterious  substances. 
The  question  as  to  whether  the  ventilation  of  a  room  or  ward  occupied  by  persons  is  sufficient,  is 
ascertained  by  estimating  the  amount  of  COj.  A  room  which  does  not  give  a  disagreeable,  some- 
what stuffy,  odor  has  less  than  0.7  per  1000  of  COj,  while  the  ventilation  is  certainly  insufficient  if 
the  CO2  =  I  per  1000. 

As  the  air  contains  only  0.0005  cubic  metre  COj  in  I  cubic  metre  of  air,  and  as  an  adult  produces 
hourly  0.0226  cubic  metre  COj,  calculation  shows  that  every  person  requires  1 13  cubic  metres  of 
fresh  air  per  hour,  if  the  CO,  is  not  to  exceed  0.7  per  1000:  for  0.7:  1000  ^  (0.0226  4- jrX 
0.0005 )  :  .r,  /.  e.,  .1-  =  1 13. 

[Vitiating  Products. — In  a  state  of  repose,  an  adult  man  gives  off  from  12  to  16  cubic  feet  of 
CO2  in  twenty- four  hours,  or  on  an  average  .6  cubic  feet  per  hour.  To  this  must  be  added  a  certain 
quantity  of  organic  matter,  which  is  extremely  deleterious  to  health.  While  the  COj  diffuses 
readily  and  is  easily  disposed  of  by  opening  the  windows,  this  is  not  the  case  with  the  organic 
matter,  which  adheres  to  clothing,  curtains,  and  furniture ;  hence,  to  get  rid  of  it,  a  room,  and  espe- 
cially a  sleeping  ap.irtment,  requires  to  be  well  aired  for  a  long  time,  together  with  the  free  admission 
of  sunlight.  In  considering  the  problem  of  ventilation,  we  must  also  remember  that  an  adult  gives 
off  from  25  to  40  oz.  of  virater  by  the  skin  and  lungs.  The  nature  of  the  organic  matters  is  not 
precisely  known,  but  some  of  it  is  particulate,  consisting  of  epithelium,  fatty  matters,  and  organic 
vapors  from  the  lungs  and  mouth  (Paries).  It  blackens  sulphuric  aciil,  and  decolorizes  a  weak 
solution  of  potassic  permanganate.  As  a  test,  if  we  expire  through  distilled  water,  and  this  water 
be  set  aside  for  some  time  in  a  warm  place,  it  will  soon  l)ecoiTie  lojtid.] 

[We  must  also  take  into  consideration  the  products  of  combustion  ;  thus  i  cubic  foot  of  coal 
gas,  when  burned,  destroys  all  the  O  in  S  cubic  feet  of  air  (Parkes).^ 


THE    SPUTUM.  227 

Methods. — In  ordinary  rooms,  where  every  person  is  allowed  the  necessiry  cubic  space  (looo 
cubic  feet)  the  air  is  sufficiently  renewed  by  means  of  the  pores  in  the  walls  of  the  room,  by  the 
opening  and  shutting  of  doors,  and  by  the  fireplace,  provided  the  damper  is  kept  open. 

It  is  most  important  to  notice  that  the  natural  ventilation  be  not  interlered  with  by  dampness  of  the 
walls,  for  this  influences  the  pores  very  greatly.  At  the  same  time,  damp  walls  are  injurious  to 
health  by  conducting  away  heat,  and  in  them  the  germs  of  infectious  diseases  may  develop  (Liiiii- 
winfn). 

[Natural  Ventilation. — By  this  term  is  meant  the  ventilation  brought  about  by  the  ordinary 
forces  acting  in  nature;  such  as  diffusion  of  gases,  the  action  of  winds,  and  the  movements  excited 
owing  to  the  different  densities  of  air  at  unef|ual  temperatures.] 

[Artificial  Ventilation. — Various  methods  are  in  use  for  ventilating  public  buildings  and  dwell- 
ing houses.  Two  principles  are  adopted  for  the  former,  viz.,  extraction  and  propulsion  of  air. 
In  the  former  method  the  air  is  suclvcd  out  of  the  rooms  by  a  fan  or  other  apparatus,  while  in  the 
latter  air  is  forced  into  the  rooms,  the  air  being  previously  heated  to  the  necessary  temperature.] 

[A  very  convenient  method  of  introducing  air  into  a  room,  is  by  means  of  Tobin's  tubes, 
placed  in  the  walls.  The  air  enters  through  these  tubes  from  the  outside  near  the  floor,  and  is 
carried  up  si.\  or  more  feet,  to  an  opening  in  the  wall ;  the  cool  air  thus  descends  slow'ly.  For  a 
sitting  room  a  convenient  plan  of  window  ventilation  is  that  of  H.  Bhd,  viz.:  Raise  the  lower 
sash  and  place  under  it,  so  as  to  fill  up  the  opening,  a  piece  of  wood  3  or  4  inches  high.  Air  will 
then  pass  in,  in  an  upward  direction,  between  the  upper  part  of  the  lower  sash  frame  and  the  lower 
part  of  the  upper  one.] 

138.  FORMATION  OF  MUCUS  IN  THE  RESPIRATORY  PAS 
SAGES — SPUTUM. — Tlie  respiratory  mucous  membrane  is  covered  normally 
with  a  thin  layer  of  mucus  (Fig.  125).  By  its  presence  this  substance  so  far  inhib- 
its the  formation  of  new  mucus  by  protecting  the  mucous  glands  from  the  action 
of  cold  or  other  irritative  agents.  New  mucus  is  secreted  as  that  already  formed 
is  removed.  An  increased  secretion  accompanies  congestion  of  the  respiratory 
mucous  membrane  [or  any  local  irritation].  Division  of  the  nerves  on  one  side  of 
the  trachea  (cat)  causes  redness  of  the  tracheal  mucous  membrane  and  increased 
secretion  (^Rossl>ach),  [but  the  two  processes  do  not  stand  in  the  relation  of  cause 
and  effect].  [The  secretion  cannot  be  e.xcited  by  stimulating  the  nerves  going  to 
the  mucous  membrane.  This  merely  causes  anaemia  of  the  mucous  membrane, 
while  the  secretion  continues.] 

Effects  of  Reagents  on  the  Mucous  Secretion. — If  ice  be  placed  on  the  belly  of  an  animal 
so  as  to  cause  the  aniirial  to  "  ta/:c  a  to/u,"  the  respiratory  mucous  membrane  first  becomes  pale, 
and  afterward  there  is  a  copious  mucous  secretion,  the  membrane  becoming  deeply  congested.  The 
injection  of  sodium  carbonate  and  ammonium  chloride  mto  the  blood  limits  the  secretion.  The 
local  application  of  alum,  silver  nitrate,  or  tannic  acid,  makes  the  mucous  membrane  turbid,  and  the 
epithelium  is  shed.  The  secretion  is  excited  by  apomorphin,  emetin,  pilocarpin,  and  ipecacuanha 
when  given  internally,  while  it  is  limited  by  atropin  and  morphia  [Rosshach). 

[Expectorants  favor  the  removal  of  the  secretions  from  the  air  passages.  This  they  may  do 
eitiier  by  {a)  altering  the  character  and  qualities  of  the  secretion  itself,  or  {/>)  by  affecting  the  expul- 
sive mechanism.  Some  of  the  drugs  already  mentioned  are  examples  of  the  first  class.  The  second 
class  act  chiefly  by  influencing  the  respiratory  centre,  such  as  ipecacuanha,  strychnia,  ammonia, 
senega;  emetics  also  act  energetically  as  expectorants,  as  in  some  cases  of  chronic  bronchitis; 
warmth  and  moisture  of  the  air  are  also  powerful  adjuncts.] 

Normal  Sputum. — Under  normal  circumstances  some  mucus — mixed  with  a 
little  saliva — may  be  coughed  up  from  the  back  of  the  throat.  In  catarrhal  con- 
ditions of  the  respiratory  mucous  membrane,  the  sputum  is  greatly  increased  in 
amount,  and  is  often  mixed  with  other  characteristic  products.  Microscopic- 
ally, sputum  contains — 

I.  Epithelial  Cells — chiefly  squames  from  the  mouth  and  pharynx  (Fig.  144), 
more  rarely  alveolar  epithelium  and  ciliated  epithelium  (7)  from  the  respiratory 
passages.  The  epithelial  cells  are  often  altered,  having  undergone  maceration  or 
other  changes.     Thus  some  cells  may  have  lost  their  cilia  (6). 

The  epithelium  of  the  alveoli  (2)  is  .squamous  epithelium,  the  cells  beingtwo  to  four  times  the 
breadth  of  a  colorless  blood  corpuscle.  These  cells  occur  chiefly  in  the  morning  sputum  in  indi- 
viduals over  30  years  of  age.  In  younger  persons  their  presence  indicates  a  pathological  condition 
of  the  pulmonary  parenchyma  {Gtitiman,U.  Schmidt,  and  Bizzosero).  They  often  undergo  fatty 
degeneration,  and  they  may  contain  pigment  granules  (3) ;  or  they  may  present  the  appearance  of 


228 


THE    SPUTUM. 


what  Buhl  has  called  "  myelin  degeneraieJ  cells"  i.  e.,  cells  filled  with  clear  refractive  drops  of  vari- 
ous sizes,  some  colorless,  others  colored  particles,  the  latter  having  been  absorbed  (4).  Mucin  in 
the  form  of  myelin  drops  (5)  is  always  present  in  sputum. 

2.  Lymphoid  cells  (9)  are  to  be  regarded  as  colorless  blood  corpuscles  which 
have  wandered  out  of  the  blood  vessels  ;  they  are  most  numerous  in  yellow  sputum, 
and  less  numerous  in  the  clear,  mucus-like  excretion.  The  lymph  cells  often  pre- 
sent alterations  in  their  characters ;  they  may  be  shriveled  up,  fatty,  or  present  a 
granular  ajipearance. 

'Y\\t  jiutil  siihstance  oi  X\\^  sputum  contains  much  ////^c«j  arising  from  the  mucous 
glands  and  goblet  cells;  together  with  nuclein,  and  lecithin,  and  the  constituents 
of  saliva  according  to  the  amount  of  the  latter  mixed  with  the  secretion.  Albu- 
min occurs  only  during  inflammation  of  the  respiratory  passages,  and  its  amount 
increases  with  the  degree  of  inflammation.  Urea  has  been  found  in  cases  of 
nephritis. 

Fig.  144. 


Various  objects  found  in  sputum,  i,  Detritus  and  particles  of  dust :  2,  alveolar  epithelium  with  pigment;  3,  fatty 
anci  partly  pigmented  alveolar  epithelium  ;  4,  alve-ilar  epithelium  containing  myelin  forms  ;  5,  free  myelin  forms  ; 
6,  7,  ciliated  epithelium,  some  changed,  others  without  cilia;  8,  squamous  epitheluim  from  the  mouth;  9,  leu- 
cocytes ;  10,  elastic  fibres  ;  11,  fibrin  cast  of  a  small  bronchus;  12,  leptothrix  buccalis  with  cocci,  bacteria,  and 
spirochastae ;  a,  fatty  acid  crystals  and  free  fatty  granules ;  ^,  haematoidin  ;  c,  Charcot's  crystals  ;  rf,  Cholesterin. 

Pathological. — In  cases  of  ca/tirrA,  the  sputum  is  at  first  usually  sticky  and  clear  (sputa  cruda),  but 
later  it  becomes  more  firm  and  yellow  (sputa  cocta).  Under  pathological  conditions  there  may  be 
found  in  the  sputum — (a)  red  blood  corpuscles,  from  rupture  of  a  bloodvessel,  [b)  Elastic 
fibres  (10)  from  disintegration  of  the  alveoli  of  the  lung;  usually  the  bundles  are  fine,  curved,  and 
the  fibres  branched.  [In  certain  cases  it  is  well  to  add  a  solution  of  caustic  potash,  which  dissolves 
most  of  the  other  elements,  leaving  the  elastic  fibres  untouched.]  Their  presence  always  indicates 
destruction  of  the  lung  tissue,  (c)  Colorless  plugs  of  fibrin  (11),  casts  of  the  smaller  or  larger 
bronchi,  occur  in  some  cases  of  fibrinous  exudation  into  the  finer  air  passages.  (</)  Crystals  of 
various  kinds — crystals  oi  fatty  acids  (Fig.  144,  u)  in  bundles  of  fine  needles.  They  indicate  great 
decomposition  of  the  stagnant  secretion.  Leucin  and  tyrosin  cry.stals  are  rare  (J  269).  Tyrosin 
occurs  in  considerable  amount  when  an  old  abscess  breaks  into  the  lungs  [Leyden,  Kannenberg\. 
Colorless,  sharp-pointed,  octagonal  or  rhombic  plates — Charcot's  crystals  (c) — have  been  found 
in  the  expectoration  in  asthma,  and  exudative  affections  of  the  bronchi.  Hcematoidin  {/>}  and 
cholesterin  crystals  ((/)  occur  much  more  rarely. 

Fungi  and  other  lowly  organisms  are  taken  in  during  inspiration  {\  136).  The  threads 
of  I^eptothrix  buccalis  (12)  detached  from  the  teeth,  are  frequently  found  (\  147).     Mycelium  and 


ACTION   OF    DIMINISHED    ATMOSPHERIC    PRESSURE.  229 

spores  are  found  in  thrush  (Oiclium  albicans),  especially  in  the  mouths  of  sucking  infants.  In  mal- 
odorous expectoration  rod-shaped  bacteria  are  present.  In  pulmonary'  gangrene  are  found  monads, 
and  cercomonad  (A'annenbdi-i;) ;  in  pulmonary  phthisis  the  tubercle  bacillus  {R.  Koch)  \  very  rarely 
sarcina,  which,  however,  is  often  found  in  gastric  catarrh  in  the  stomach,  and  also  in  the  urine  (Fig. 
in  \  270). 

Physical  Characters. — Sputum,  with  reference  to  its  physical  characters,  is  described  as 
mucous,  miico-ptirnlent,  ox  purulent. 

Abnormal  coloration  of  the  sputum — red  from  blood.  When  the  blood  remains  long  in  the 
lung  it  undergoes  a  regular  series  of  changes,  and  tinges  the  sputum  dark  red,  bluish  brown,  brown- 
ish yellow,  deep  yellow,  yellowish  green,  or  grass  green.  The  sputum  is  sometimes  yellow  in  jaun- 
dice.   The  sputum  may  be  tinged  by  what  is  inspired  [as  in  the  case  of  the  "black  spit"  of  miners]. 

The  odor  of  the  sputum  is  more  or  less  unpleasant.  It  becomes  very  disagreeable  v.'hen  it  has 
remained  long  in  pathological  lung  cavities,  and  it  is  stinking  in  gangrene  of  the  lung. 

139.   ACTION    OF   THE  ATMOSPHERIC  PRESSURE.— At  the 

normal  pressure  of  the  atmosphere  (height  of  the  barometer,  760  millimetres  Hg), 
pressure  is  e.xerted  upon  the  entire  surface  of  the  body  ^  15,000  to  20,000  kilos., 
according  to  the  extent  of  the  superficial  area  {^Galileo).  This  pressure  acts  equally 
on  all  sides  upon  the  body,  and  occurs  also  in  all  internal  lavities  containing  air, 
both  those  that  are  constantly  filled  with  air  (the  respiratory  pa.ssages  and  the 
spaces  in  the  superior  maxillary,  frontal  and  ethmoid  bones),  and  those  that  are 
temporarily  in  direct  communication  with  the  outer  air  (the  digestive  tract  and 
tympanum).  As  \\\t  fluids  of  tlie  body  (blood,  lymph,  secretions,  parenchymatous 
juices)  are,  practically,  incompressible,  their  volume  remains  practically  unchanged 
under  the  pressure  ;  but  they  will  absorb  gases  from  the  air  corresponding  to  the 
prevailing  pressure  (/.  e.,  the  partial  pressure  of  the  individual  gases),  and  accord- 
ing to  their  temperature  (compare  §33.) 

The  solids  consist  of  elementary  parts  (cells  and  fibres),  each  of  which  presents 
only  a  microscopic  surface  to  the  pressure,  so  that  for  each  cell  the  prevailing 
pressure  of  the  air  can  only  be  calculated  at  a  few  millimetres — a  pressure  under 
which  the  most  delicate  histological  tissues  undergo  development.  As  an  example 
of  the  action  of  the  pressure  of  the  atmospheric  pressure  upon  large  masses,  take 
that  brought  about  by  the  adhesion  of  the  smooth,  sticky,  moist,  articular  surfaces 
of  the  shoulder  and  hip  joints.  In  these  cases,  the  arm  and  the  leg  are  supported 
without  the  action  of  muscles.  The  thigh  bone  remains  in  its  socket  after  section 
of  all  the  muscles  and  its  capsule  {Brothers  Weber').  Even  when  the  cotyloid 
cavity  is  perforated,  the  head  of  the  femur  does  not  fall  out  of  its  socket.  The 
ordinary  barometric  variations  affect  the  respiration — a  rise  of  the  barometric 
pressure  excites,  while  a  fall  diminishes,  the  respirations.  The  absolute  amount 
of  CO...  remains  the  same  (§  127,  8). 

A  Great  Diminution  of  the  Atmospheric  Pressure,  such  as  occurs  in  ballooning  (highest 
ascent,  8600  metres),  or  in  ascending  mountains,  causes  a  series  of  characteristic  phenomena:  (I) 
In  consequence  of  the  diminution  of  the  pressure  upon  the  parts  directly  in  contact  with  the  air, 
they  become  greatly  congested ;  hence,  there  is  redness  and  swelling  of  the  skin  and  free  mucous 
membranes;  there  may  be  hemorrhage  from  the  nose,  lungs,  gums,  turgidity  of  the  cutaneous  veins, 
copious  secretion  of  sweat,  great  secretion  of  mucus.  (2)  A  feeling  of  weight  in  the  limbs,  a  press- 
ing outward  of  the  tympanic  membrane  (until  the  tension  is  equilibrated  by  opening  the  Eustachian 
tube),  and,  as  a  consequence,  noises  in  the  ears  and  difficulty  of  hearing.  (3)  In  consequence  of 
the  diminished  tension  of  the  O  in  the  air  (\  129),  there  is  difficulty  of  breathing,  pain  in  the  chest, 
whereby  the  respirations  (and  pulse)  become  more  rapid,  deeper  and  irregular.  When  the  atmo- 
spheric pressure  is  diminished  \--\,  the  amount  of  O  in  the  blood  is  diminished  (Bert,  Friinkel  and 
Geppert),  the  CO^  is  imperfectly  removed  from  the  blood,  and,  in  consequence,  there  is  diminished 
oxidation  within  the  body.  When  the  atmospheric  pressure  is  diminished  to  one-half,  the  amount 
of  CO .2  in  arterial  blood  is  lessened ;  and  the  amount  of  N  diminishes  proportionplly  with  the  de- 
crease of  the  atmospheric  pressure  (Friinkel  and  Geppert).  The  diminished  tension  of  the  air 
prevents  the  vibrations  of  the  vocal  cords  from  occurring  so  forcibly,  and,  hence,  the  voice  is  feeble. 
(5)  In  consequence  of  the  amount  of  blood  in  the  skin,  the  internal  organs  are  relatively  anojmic ; 
hence,  there  is  diminished  secretion  of  urine,  muscular  weakne.ss,  disturbances  of  digestion,  dullness 
of  the  senses,  and.  it  may  be,  unconscimisness,  and  all  these  phenomena  are  intensified  by  the  con- 
ditions mentioned  under  (3).  Some  of  ihe'^e  phenomena  are  modified  by  usage.  The  highest  limit 
at  which  a  man  may  still  retain  his  senses  is  placed  by  Tissandier  at  an  elevation  of  Scxx)  metres 


230  HISTORICAL. 

(2S0  mm.  Hg).  In  dogs,  the  blood  pressure  falls,  and  the  pulse  becomes  small  and  diminished  in 
frequency  when  the  atmospheric  prssure  falls  to  200  mm.  Hg. 

Those  who  live  upon  high  mountains  sufter  from  a  disease,  mal  de  montagne,  which  consists, 
essentially,  in  tlie  above  symptoms,  although  it  is  sometimes  complicated  with  anaimiaof  the  internal 
organs.  Al.  v.  Humboldt  found  that  in  those  who  lived  on  the  Andes  the  thorax  was  capacious. 
At  6000  to  Sooo  feet  above  sea  level,  water  contains  only  one-third  of  the  absorbed  gases,  so  that 
fishes  cannot  live  in  it  {Boussiiigaii/l).  Animals  may  be  sulijected  to  a  further  diminution  of  the 
atmospheric  pressure  by  being  placed  under  the  receiver  of  an  air  pump.  Birds  die  when  the 
pressure  is  reduced  to  120  mm.  Hg;  mammals,  at  40  mm.  Hg;  frogs  endure  repeated  evacuations 
of  the  receiver,  whereby  they  are  much  distended,  owing  to  the  escape  of  gases  and  water  ;  but  after 
the  entrance  of  air,  they  become  greatly  compressed.  The  cause  of  death  in  mammals  is  ascribed 
by  Hoppe-Seyler  to  the  evolution  of  bubbles  of  gas  in  the  blood;  these  bubbles  stop  up  the  capilla- 
ries and  the  circulation  is  arrested.  Local  Jiminiition  of  the  atmospheric  pressure  causes  marked 
congestion  and  swelling  of  the  part,  as  occurs  when  a  cupping  glass  is  used. 

Great  Increase  of  the  Atmospheric  Pressure. — The  phenomena  which  are,  for  the  most 
part,  the  reverse  of  the  foregoing,  have  been  observed  in  pneumatic  cabinets  and  in  diving  bells, 
where  men  may  work  even  under  4^  atmospheres  pressure.  The  phenomena  are :  (i)  Paleness 
and  dryness  of  the  external  surfaces,  collapse  of  the  cutaneous  veins,  diminution  of  perspiration 
and  mucous  secretions.  (2)  The  tympanic  membrane  is  pressed  inward  (until  the  air  escapes 
through  the  Eustachian  lube,  after  causing  a  sharp  sound),  acute  sounds  are  heard,  pain  in  the  ears, 
and  difficulty  of  hearing.  (3)  A  feeling  of  lightness  and  freshness  during  respiration,  the  respira- 
tion becomes  slower  (by  2-4  per  minute),  inspiration  easier  and  shorter,  e.vpiration  lengthened,  the 
pause  distinct.  The  capacity  of  the  lungs  increases,  owing  to  the  freer  movement  of  the  diapliragm, 
in  consequence  of  the  diminution  of  the  intestinal  gases.  Owing  to  the  more  rapid  oxidations  in 
the  body,  muscular  movement  is  easier  and  more  active.  The  O  absorbed  and  the  CO^  excreted 
are  increased.  The  venous  blood  is  reddened.  (4)  Difficulty  of  speaking,  alteration  of  the  tone 
of  the  voice,  inability  to  whistle.  (5)  Increase  of  the  urinary  secretion,  more  muscular  energy, 
more  rapid  metabolism,  increased  appetite,  subjective  feeling  of  warmth,  pulse  beats  slower,  and 
pulse  curve  is  lower  (compare  ^  74).  In  animals  subjected  to  excessively  high  atmospheric  pressure, 
P.  Bert  found  that  the  arterial  blood  contained  30  vols,  per  cent.  O  (at  760  mm.  Hg) ;  when  the 
ainount  rose  to  35  vols,  per  cent,  death  occurred,  with  convulsions.  Compressed  air  has  been  used 
for  therapeutical  purposes,  but  in  doing  so  a  too  rapid  increase  of  the  pressure  is  to  be  avoided. 
Waldenburg  has  constructed  such  an  apparatus,  which  may  be  used  for  the  respiration  of  air  under 
a  greater  or  less  pressure. 

Frogs,  when  placed  in  comprfssed  O  (at  14  atmospheres),  exhibit  the  same  phenomena  as  if 
tliey  were  in  a  vacuum,  or  pure  N.  There  is  paralysis  of  the  central  nervous  system,  sometimes 
preceded  by  convulsions.  The  heart  ceases  to  beat  (not  the  lymph  hearts),  while  the  excitability 
of  the  motor  nerves  is  lost  at  the  same  time,  and,  lastly,  the  direct  muscular  excitability  disappears 
(A'.  £.  Lchniann],  An  excised  frog's  heart  placed  in  O,  under  a  very  high  pressure  (13  atmo- 
spheres), scarcely  beats  one-fourth  of  the  time  during  which  it  pulsates  in  air.  If  the  heart  be 
exposed  to  the  air  again,  it  begins  to  beat ;  so  that  compressed  O  renders  the  vitality  of  the  heart 
latent  before  abolishing  it. 

Phosphorus  retains  its  luminosity  under  a  high  jjressure  in  O  {Schonbeiit),  but  this  is  not  the  case 
with  the  luminous  organisms,  e.g.,  I.ampyris,  and  luminous  bacteria  (A'.  B.  Lehmann).  A  very 
high  atmospheric  pressure  is  also  injurious  to  plants. 

140.  COMPARATIVE  AND  HISTORICAL  —Mammals  have  lungs  similar  to  those  of 
man.  The  lungs  of  birds  are  spongy,  and  united  to  the  chest  wall,  while  there  are  openings  on 
their  surface  communicating  with  thin  walled  "  air  sacs,"  which  are  placed  among  the  viscera.  The 
air  sacs  communicate  with  cavities  in  the  bones,  which  give  the  latter  great  lightness  [.Aristotle). 
The  diaphragm  is  absent.  In  reptiles  the  lungs  are  divided  into  greater  and  smaller  compartments ; 
in  snakes  one  lung  is  abortive,  while  the  other  has  the  elongated  form  of  the  body.  The  amphibians 
(frog)  possess  two  simple  lungs,  each  of  which  represents  an  enormous  infuiidibulum  with  its  alveoli. 
The  frog  pumps  air  into  its  lungs  by  the  contraction  of  its  throat,  the  nostrils  being  closed  and  the 
glottis  opened.  When  young  — until  their  metamorphosis — frogs  breathe  like  fishes,  by  means  of 
gills.  The  perennibranchiate  amphibians  (Proteus)  retain  their  gills  throughout  life.  Among 
fishes,  which  breathe  by  gills  and  use  the  O  absorbed  by  the  water,  the  Dipnoi  have,  in  addition 
to  gills,  a  swim  bladder,  provided  with  afferent  and  eft'erent  vessels,  which  is  comparable  to  the  lung. 
The  Cobitis  respires  also  with  its  intestine  [Erman,  180S).  Insects  and  centipedes  respire  by 
"trachea;,"  which  are  branched  canals  distributed  throughout  the  body;  they  open  on  the  surface 
of  the  body  by  openings  (stigmata),  which  can  be  closed.  Spiders  respire  by  means  of  trachcc^ 
and  tracheal  sacs;  crabs,  by  gills.  The  molluscs  and  cephalopods  have  gills;  some  gasteropods 
have  gills  and  others  luni;s.  Among  the  lower  invertebrata  some  breathe  by  gills,  others  by  means 
of  a  special  "  water  vascular  .system,"  and  others  again  by  no  special  organs. 

Historical. — Aristotle  (384  B.  c. )  regarded  the  object  of  respiration  to  be  the  cooling  of  the  body, 
so  as  to  moderate  the  internal  warmth.  He  ob.served  correctly  that  the  warmest  animals  breathe 
most  actively,  but  in  interpreting  the  fact  he  reversed  the  cause  and  effect.  Galen  ( 131-203  A.  D.) 
thought  that  the  "soot  "  was  removed  from  the  body  along  with  the  expired  water.     The  most  im- 


HISTORICAL.  231 

portant  experiments  on  the  mechanics  of  respiration  date  from  Galen  ;  he  observed  that  the  lungs 
passively  follow  the  movements  of  the  chest;  that  the  diaphragm  is  the  most  important  muscle  of 
inspiration;  that  the  external  intercostals  are  inspiratory,  and  the  internal,  expiratory.  He  divided 
the  intercostal  ner\'es  and  muscles,  and  observed  that  loss  of  voice  occurred.  On  dividing  the  spinal 
cord  higher  and  higher,  he  found  that  as  he  did  so  the  muscles  of  the  thorax  lying  higher  up  became 
paralyzed.  Oribasius  (360  A.  D.)  observed  that  in  double  pneumothorax  both  lungs  collapsed. 
Ve^alius  (1540)  first  described  artificial  respiration  as  a  means  of  restoring  the  beat  of  the  heart. 
Malpighi  (1661)  described  the  structure  of  the  lungs.  J.  A.  Borelli  (f  1679)  gave  the  first  funda- 
mental description  of  the  mechanism  of  the  respiratory  movements.  The  chemical  processes  of 
respiration  could  only  be  known  after  the  discovery  of  the  individual  gases  therein  concerned.  Van 
Helmont  (t  1644)  detected  COj.  [Joseph  Black  (1757)  discovered,  by  the  following  experiment, 
that  COj  or  "  fixed  air  "  is  given  out  during  expiration  :  Take  two  jars  of  lime  water,  breathe  into 
one  through  a  bent  glass  tube,  and  force  ordinary  air  through  the  other,  when  a  white  precipitate  of 
calcium  carbonate  will  be  found  to  occur  in  the  former.]  In  1 774  Priestley  discovered  O.  Lavoisier 
delected  N  (1775),  and  ascertained  the  composition  of  atmospheric  air,  and  he  regarded  the  forma- 
tion of  COj  and  H^O  of  the  breath  as  a  result  of  a  combustion  within  the  lungs  themselves.  J. 
Ingen-Houss  (1730-1790)  discovered  the  respiration  of  plants.  Vogel  and  others  proved  the  exist- 
ence of  CO,  in  venous  blood,  and  Hoffmann  and  ethers  that  of  O  in  arterial  blood.  The  more 
complete  conception  of  the  exchange  of  gases  was,  however,  only  possible  after  Magnus  had 
extracted  and  analyzed  the  gases  of  arterial  and  venous  blood  (J  36). 


Physiology  of  Digestion. 


141.  THE  MOUTH  AND  ITS  GLANDS.— The  mucous  membrane  of  the  cavity  of  the 
mouth,  which  becomes  continuous  with  the  skin  at  the  red  margin  of  the  lips,  has  a  number  of 
sebaceous  glands  in  the  region  of  the  red  part  of  the  Hp.  The  buccal  mucous  membrane  consists 
of  bundles  of  fine  fibrous  tissue  mixed  with  elastic  fibres,  which  traverse  it  in  every  direction. 
Papillae — simple  or  compound — occur  near  the  free  surfaces.  The  submucous  tissue,  which  is 
directly  continuous  with  the  fibrous  tissue  of  the  mucous  membrane  itself,  is  thickest  where  the 
mucous  membrane  is  thickest,  and  densest  where  it  is  firmly  fixed  to  the 
Fig.    145.  periosteum  of  the  bone  and  to  the  gum  ;  it  is  thinnest  where  the  mucous 

membrane  is  most  movable,  and  where  there  are  most  folds.  The  cavity 
of  the  mouth  is  lined  by  stratified  squamous  epithelium  (Fig.  145), 
which  is  thickest,  as  a  rule,  where  the  longest  papillce  occur. 

All  the  glands  of  the  mouth,  including  the  salivary 
glands,  may  be  divided  into  different  classes,  according  to 
the  nature  of  their  secretions. 

1.  The  serous  or  albuminous  glands  [t>-ue  salh'aiy'], 
whose  secretion  contains  a  certain  amount  of  albumin,  e.  g., 
the  human  parotid. 

2.  The  mucous  glands,  whose  secretion,  in  addition  to 
some  albumin,  contains  the  characteristic  constituent 
mucin. 

3.  The  mixed  [or  miu-o-saliran']  glands,  some  of  the 
acini  secreting  an  albuminous  fluid  and  other  mucin,  e.g., 
the  human   maxillary  gland  {HciJcnhaifi).     The  structure 

tach1:'d"from  of  these  glands  is  referred  to  under  the  salivary  glands. 


fied    squamous 


epitheliun 

Numerous  mucous  glands  (labial,  buccal,  palatine,  lingual,  molar) 
have  the  appearance  of  small  macroscopic  bodies  lying  in  the  sub-mucosa.  They  are  branched 
tubular  glands,  and  the  contents  of  their  secretory  cells  consist  partly  of  mucin,  which  is  expelled 
from  them  during  secretion.  The  excretory  ducts  of  these  glands,  which  are  lined  by  cylindrical 
epithelium,  are  constricted  where  they  enter  the  mouth.  Not  unfrequently  one  duct  receives  the 
secretion  of  a  neighboring  gland. 

The  glands  of  the  tongue  form  two  groups  which  differ  morphologically  and  physiologically, 
(i)  The  mucous  glands  (  Iledfr's  glands),  occurring  chiefly  near  the  root  of  the  tongue,  are 
branched  tubular  glands  lined  with  clear,  transparent,  secretory  cells  whose  nuclei  are  placed  near  the 
attached  end  of  the  cells.  The  acini  have  a  distinct  membrana  propria.  (2)  The  serous  glands 
(£bners)  are  acinous  glands  occurring  in  the  region  of  the  circumvallate  papilla-  (and  in  animals 
near  the  papiihe  foliatae).  They  are  lined  with  turljid  granular  epithelium  with  a  central  nucleus, 
and  they  secrete  saliva  [HenU).  (3)  The  glands  of  Blandin  and  Nuhn  are  placed  near  the  tip  of 
the  tongue,  and  consist  of  mucous  and  serous  acini,  so  that  they  are  mixed  glands  {Podunsotzky). 

The  blood  vessels  are  moderately  abundant,  and  the  larger  trunks  lie  in  the  sub  muco-sa,  while 
the  finer  twigs  penetrate  into  the  papillre,  where  they  form  either  a  capillary  network  or  simple 
loops. 

The  larger  lymphatics  lie  in  the  sub-mucosa,  while  the  finer  branches  form  a  fine  network 
placed  in  the  mucosa.  The  lymph  follicles  also  belong  to  the  lymphatic  system  (§  197).  On  the 
dorsum  of  the  posterior  part  of  tlie  tongue  they  form  an  almost  continuous  layer.  They  are  round 
or  oval  (1-1.5  mm.  in  diameter),  and  placetl  in  the  sub-mucosa.  They  consist  of  adenoid  tissue 
loaded  with  lyniph  corpuscles.  The  outer  part  of  the  adenoid  reticulum  is  compressed  so  as  to  form 
a  kind  of  capsule  for  each  follicle.  Similar  follicles  occur  in  the  intestine  as  solitary  follicles;  in 
the  small  intestine  they  are  collected  together  into  Peyer's  patches,  and  in  the  spleen  they  occur  as 
Malpighian  corpuscles.  On  the  dorsum  of  the  tongue  several  of  these  follicles  form  a  slightly 
oval  elevation,  wliich  is  surrounded  by  connective  tissue.  In  the  centre  of  this  elevation  there  is  a 
depression,  into  which  a  mucous  gland  opens,  which  fills  the  small  crater  with  mucus  (Fig.  146). 

232 


THE    SALIVARY    GLANDS. 


233 


The  Tonsils  have  fundamentally  the  same  structure.  On  their  surface  are  a  number  of  depres- 
sions into  which  the  ducts  of  small  mucous  glands  open.  These  depressions  are  surrounded  by 
groups  (10-20)  of  lymph  follicles,  and  the  whole  is  environed  by  a  capsule  of  connective  tissue. 
After  E.  H.  Weber  discovered  lymphatics  in  the  neighborhood  of  the  tonsils,  Briicke  referred  these 
structures  to  the  lymphatic  system.  Large  lymph  spaces,  communicating  with  lymphatics,  occur  m 
the  neighborhood  of  the  tonsils,  but  as  yet  a  direct  connection  between  the  spaces  in  the  follicles 
and  the  lymph  vessels  has  not  been  proved  to  exist.  Similar  structures  occur  in  the  tubal  and 
pharyngeal  tonsils.  [Slohr  asserts  that  an  enormous  number  of  leucocytes  wander  out  of  the 
tonsils,  solitary  and  Peyer's  glands,  and  the  adenoid  tissue  of  the  bronchial  mucous  membrane.  The 
cells  pass  out  between  the  epithelial  cells,  but  do  not  pass  in'o  the  interior  of  the  latter.] 

Nerves. — Numerous  medullaled  nerve  fibres  occur  in  the  sub-mucosa,  pass  into  the  mucosa,  and 
terminate  partly  in  the  individual  papillae  in  Krause's  end  bulbs,  which  are  most  abundant  in  the  hps 
and  soft  palate,  and  not  so  numerous  in  the  cheeks  and  in  the  floor  of  the  mouth.  The  nerves  ad- 
minister not  only  to  common  sensation,  but  they  also  are  the  organs  of  transmission  for  tactile  (heat 
and  pressure)  impressions.  It  is  highly  probable,  however,  that  some  nerve  fibres  end  in  fine  ter- 
minal fibrils,  between  the  epithelial  cells,  such  as  occur  in  the  cornea  and  elsewhere. 

142.    THE  SALIVARY  GLANDS.— Structure  of  the  Ducts.— The 

three  pairs  of  salivary  glands,  sub-maxillary,  sublingual,  and  parotid,  are  com- 
pound tubular  glands.  Fig.  148,  A,  shows  a  fine  duct,  terminating  in  the  more  or  less 
flask-shaped  alveoli  or  acini.     [Each  gland  consists  of  a  number  of  lobes,  and 

Fig.  146. 


Closed  follicles. 


i- 


-^- 


Section  of ; 


follicle  from  the  dorsum  of  the  tongue  {Schenk). 


each  lobe  in  turn  of  a  number  of  lobules,  which  again  are  composed  of  acini. 
All  these  are  held  together  by  a  framework  of  connective  tissue.  The  larger 
branches  of  the  duct  lie  between  the  lobules,  and  constitute  the  interlobular 
ducts,  giving  branches  to  each  lobule  which  they  enter,  constituting  the  intra- 
lobular ducts.  These  intralobular  ducts  branch  and  finally  terminate  in  connection 
with  the  alveoli,  by  means  of  an  intermediary  or  intercalary  part.  The  larger 
interlobar  and  interlobular  ducts  consist  of  a  membrana  propria,  strengthened 
outside  with  fibrous  and  elastic  tissue,  and  in  some  places  also 
by  non-striped  muscle,  while  the  ducts  are  lined  by  columnar 
epithelial  cells.  In  the  largest  branches  there  is  a  second  row  ^>^^V' .'■.:fl'/;"//'^'/>, 
of  stnaller  cells,  lying  between  the  large   cells  and  the  mem-     vV  ' 

brana  propria.  The  intralobular  ducts  are  lined  by  a  single  £;;' 
layer  of  large  cylindrical  epithelium.  As  is  shown  in  Fig.  147.  ^;.-; 
the  nucleus  occurs  about  the  middle  of  the  cell,  while  the  outer    \:-. 

half,  /.  e.,  ne.\t  the  basement  membrane  of  the  cell,  is  finely      V  

striated  longitudinally,  which  is  due  to  fibrillas  ;  the  inner  half  ""iin\'i\\\ii-^ 
next  the  lumen  is  granular.  The  intermediary  part  is  narrow,  Rodded  epiiheiii 
and  is  lined  by  a  single  layer  of  flattened  cells,  each  with  an         glffid""'"  "' 


Fig.  147. 


234 


THE    STRUCTURE    OF   THE    SALIVARY    GLANDS. 


elongated  oval  nucleus.  There  is  usually  a  narrow  "  neck,"  where  the  intra- 
lobular duct  becomes  continuous  with  the  intermediary  part,  and  here  the  cells 
are  polyhedral  (A'A-Zn). 

The  acini,  or  alveoli,  are  the  parts  where  the  actual  process  of  secretion  takes 
place.  They  vary  somewhat  in  shape  ;  some  are  tubular,  others  branched,  some 
are  dilated  and  resemble  a  Florence  flask,  and  several  of  them  usually  open  into 
one  intermediary  part  of  a  duct.  Each  alveolus  is  bounded  by  a  basement  mem- 
brane, with  a  reticulate  structure  made  up  of  nucleated,  branched,  and  anastomos- 
ing cells,  so  as  to  resemble  a  basket  (D).  There  is  a  homogeneous  membrane 
bounding  the  alveoli  in  addition  to  this  basket-shaped  structure.  Immediately 
outside  this  membrane  is  a  lymph  space  {Giaiunzi),  and  outside  this  again  the  net- 
work of  capillaries  is  distributed.  [The  extent  to  which  this  lymph  space  is  filled 
with  lymph  determines  the  distance  of  the  capillaries  from  the  membrana  propria. 
The  inter-alveolar  lymph  spaces  communicate  with  large  lymph  spaces  between 
the  lobules,  which  in  turn  communicate  with  perivascular  lymphatics  around  the 
arteries  and  veins.]     The  lymphatics  emerge  from  the  gland  at  the  hilum. 

The   secretory  cells   vary  in  structure,   according   as  the  salivary  gland  is 


A,  duct  and  acini  of  the  parotid  gland  of  a  dog:  B.  acini  of  the  sub-maxillary  gland  of  a  dog  :  c,  refractive  mucous 
cells  ;  ti,  g'-anular  half-moons  of  Gianuzzi ;  C,  similar  alveoli  after  prolonged  secretion  ;  D,  basket-shaped  tissue 
"  :  of  a  non-meduUated  nerve  fibre  into  a  secretory  cell. 


mucous  [sub-maxillary  and  sublingual  of  the  dog  and  cat],  a  serous  [parotid 
of  man  and  mammals,  and  sub-maxillary  of  rabbit],  or  a  mixed  gland  [human 
sub-maxillary  and  sublingual]. 

Mucous  Acini. — The  secretory  cells  of  mucous  glands,  and  the  mucous 
acini  of  mixed  glands  (Fig.  149),  are  lined  by  a  single  layer  of  "  mucin  cells  " 
(^Hcidenhain)  (Fig.  148,  B,  <-),  which  are  large  cells  distended  with  mucin-,  or,  at 
least,  with  a  hypothetical  substance,  mucigen,  which  yields  mucin.  The  mucin 
cells  are  more  or  less  spheroidal  in  shape,  clear,  shining,  highly  refractive,  and 
nearly  fill  the  acinus.  The  flattened  nucleus  is  near  the  wall  of  the  acinus.  Each 
cell  has  a  fine  process  which  overlaps  the  fixed  parts  of  the  cell  next  to  it.  Owing 
to  the  fact  that  the  body  of  each  cell  is  infiltrated  with  mucin,  these  cells  do  not 
stain  with  carmine,  although  the  nucleus  and  its  immediately  investing  protoplasm 
do.  Another  kind  of  cell  occurs  in  the  sub-maxillary  gland  of  the  dog.  It 
ioxxm  z.  half-moon-shaped  structure  lying  in  direct  contact  with  the  wall  of  the 
acinus  {Gianuzzi).  Each  "  half-moon  "  or  "  crescent "  consists  of  a  number 
of  small,  closely  packed,  angular,  strongly  albuminous  cells  with  small  oval 
nuclei,  which,  however,  are  separated  only  with  difficulty.     Hence,  Heidenhain 


HISTOLOGICAL    CHANGES    IN   THE    SALIVARY    GLANDS.  235 

has  called  them  "composite  marginal  cells"  (B,  d).  They  are  granular, 
darker,  devoid  of  mucin,  and  stain  readily  with  pigments.  [In  the  sub-maxillary 
gland  of  the  cat  there  is  a  complete  layer  of  these  "  marginal  "  carmine-staining 
cells  lying  between  the  mucous  cells  and  the  membrana  propria.] 

[Serous  Acini. — In  true  serous  glands  (parotid  of  man  and  mammals)  and 
in  the  serous  acini  of  mixed  glands,  the  acini  are  lined  by  a  single  layer  of  secre- 
tory, columnar,  finely  granular  cells,  which,  in  the  quiescent  condition,  completely 
fill  the  acinus,  so  that  scarcely  any  lumen  is  left.  Just  before  secretion,  or  when 
these  cells  are  quiescent,  Langley  has  shown  that  they  are  large  and  filled  with 
numerous  granules,  which  obscure  the  presence  of  the  nucleus.  As  secretion 
takes  place,  these  granules  seem  to  be  used  up  or  discharged  into  the  lumen  ;  at 
least,  the  outer  part  of  each  cell  gradually  becomes  clear  and  more  transparent, 
and  this  condition  spreads  toward  the  inner  part  of  the  cell.] 

[In  the  mixed  or  muco-salivary  glands  {Klein)  {e.g.,  human  sub-maxillary), 
some  of  the  alveoli  are  mucous  and  others  serous  in  their  characters,  but  the 
latter  are  always  far  more  numerous,  and  the  one  kind  of  acinus  is  directly 
continuous  with  the  others  (Fig.  149)] 

P"iG.  149. 


Section  of  part  of  the  human 

143.  HISTOLOGICAL  CHANGES  DURING  THE  ACTIVITY 
OF  THE  SALIVARY  GLANDS.— [The  condition  of  physiological  activity 
of  the  gland  cells  is  accompanied  by  changes  in  the  histological  characters  of  the 
secretory  cells.] 

[Serous  Glands. — The  changes  in  the  secretory  cells  have  been  carefully 
studied  in  the  parotid  of  the  rabbit.  The  histological  appearances  vary  some- 
what, according  as  the  glands  are  examined  in  the  fresh  condition  or  after  harden- 
ing in  various  reagents,  such  as  absolute  alcohol.  When  the  gland  is  at  rest,  in 
a  preparation  hardened  in  alcohol,  and  stained  with  carmine,  the  cells  consist  of 
a  pale,  almost  uncolored  sulistance,  with  a  few  fine  granules,  and  a  small,  irregu- 
lar, red-stained,  shriveled  nucleus,  devoid  of  nucleolus.  The  appearance  of  the 
nucleus  suggests  the  idea  of  its  being  shriveled  by  the  action  of  the  harden- 
ing reagent  (Fig.  150).] 

[During  activity,  if  the  gland  be  caused  to  secrete  by  stimulating  the  sym- 
pathetic, all  parts  of  the  cells  undergo  a  change  (Fig.  150,  151).  (i)  The  cells 
diminish  somewhat  in  size;    (2)  the  nuclei  are  no  longer   irregular,  but  round. 


236 


HISTOLOGICAL   CHANGES    IN    THE    SALIVARY    GLANDS. 


with  a  sharp  contour  and  nucleoli;  (3)  the  substance  of  the  cell  itself  is  turbid, 
owing  to  the  diminution  of  the  clear  substance,  and  the  increase  of  the  granules, 
especially  near  the  nuclei;  C4)  at  the  same  time,  the  whole  cell  stains  more  deeply 
with  carmine  {Heideii/iain).'\ 

[On  studying  the  changes  which  occur  in  a  living  serous  gland,  Langley 
found  that,  during  rest,  the  substance  of  the  cells  of  the  parotid  is  pervaded  by 
fine  granules,  which  are  so  numerous  as  to  obscure  the  nucleus,  while  the  outlines 
of  the  cells  are  indistinct.  No  lumen  is  visible  in  the  acini  during  activity,  the 
granules  disappear  frotn  the  outer  zone  of  the  cells,  the  cells  themselves  becoming 
more  distinct  and  smaller.  After  prolonged  secretion,  the  granules  largely  dis- 
appear from  the  cell  substance  except  quite  near  the  inner  margin.  The  cells  are 
smaller,  their  outlines  more  distinct,  their  round  nuclei  apparent,  and  the  lumen 
of  the  acini  is  wide  and  distinct.  Thus,  it  is  evident  that,  during  rest,  granules 
are  manufactured,  which  disappear  during  the  activity  of  the  cells,  the  disappear- 
ance taking  place  from  without  inward.  Similar  changes  occur  in  the  cells  of 
the  pancreas.] 

[Mucous  Glands. — More  complex  changes  occur  in  the  mucous  glands,  such 
as  the  sub-maxillary  or  orbital  glands  of  the  dog  {Lavdovsky).  The  appearances 
vary  according  to   the  intensity  and  duration  of  the  secretory  activity.     The 

Fig   151. 

3^ 


Fig,  151,  after  stimulatit 


nmcous  cells  at  rest  are  large,  clear,  and  rf'fractive,  containing  a  flattened  nucleus 
(Fig.  148,  B,  c),  surrounded  with  a  small  amount  of  protoplasm,  and  jilaced  near 
the  basement  membrane.  The  clear  substance  does  not  stain  with  carmine,  and 
consists  of  mucigen  lying  in  the  wide  spaces  of  an  intracellular  plexus  of  fibrils. 
After  prolonged  secretion,  produced,  it  may  be,  by  strong  and  continued 
stimulation  of  the  chorda,  the  mucous  cells  of  the  sub-maxillary  gland  of  the  dog 
undergo  a  great  change.]  The  distended,  refractive,  and  "mucous  cells,"  which 
occur  in  the  quiescent  gland,  and  which  do  not  stain  with  carmine,  do  not  appear 
after  the  gland  has  been  in  a  state  of  activity.  Their  place  is  taken  by  small,  dark, 
protoplasmic  cells  devoid  of  mucin  (Fig.  148,  C).  These  cells  readily  stain  with 
carmine,  while  their  nucleus  is  scarcely,  if  at  all,  colored  by  the  dye.  The 
researches  of  R.  Heidenhain  ( 1S68)  have  shed  much  light  on  the  secretory  activity 
of  the  salivary  glands. 

The  change  may  be  produced  in  two  ways.  Either  it  is  due  to  the  "mucous  cells"  during 
secretion  becoming  broken  up,  so  that  they  yield  their  mucin  directly  to  the  saliva ;  in  saliva  rich 
in  mucin,  small  microscopic  pieces  of  mucin  are  found,  and  sometimes  mucous  cells  themselves  are 
pre--ent.  Or,  we  must  assume  that  the  mucous  cells  simply  eliminate  the  mucin  from  their  bodies 
\Ewald,  St'dhr) ;  while,  after  a  period  of  rest,  new  mucin  is  formed.  According  to  this  view,  the 
dirk  granular  cells  of  the  glands,  after  active  secretion,  are  simply  mucous  celN,  which  have  given 
out  their  mucin.     If  we  assume,  with   Heidenhain,  that   the   mucous  cells  break  up,  then  these 


ACTION    OF    NERVES   ON    THE    SECRETION    OF    SALIVA.  237 

granular  non  mucous  cells  must  be  regarded  as  new  formations  produced  by  the  proliferation  and 
growth  of  the  composite  marginal  cells,  ;'.  e.,  the  crescents,  or  half-moons  of  Gianuzzi. 

[During  rest,  the  protoplasm  seems  to  manufacture  mucigen,  which  is  changed 
into  and  discharged  as  mucin  in  the  secretion,  when  the  gland  is  actively  secreting. 
Thus,  the  cells  become  smaller,  but  the  protoplasm  of  the  cell  seems  to  increase, 
,  new  mucigen  is  manufactured  during  rest,  and  the  cycle  is  repeated.] 

144.  THE  NERVES  OF  THE  SALIVARY  GLANDS.— The  nerves 
are  for  the  most  part  medullated,  and  enter  at  the  hilum  of  the  gland,  where  they 
form  a  rich  plexus  provided  with  ganglia  between  the  lobules.  [According  to 
Klein,  there  are  no  ganglia  in  the  parotid  gland.]     {^Krause,  Reich,  Schliiter.) 

All  the  salivary  glands  are  supplied  by  branches  from  two  different  nerves — 
from  the  sympathetic  and  from  a  cranial  nerve. 

1.  The  sympathetic  nerve  gives  branches  to  {a)  the  sub-maxillary  and  the 
sublingual  glands,  derived  from  the  plexus  on  the  external  maxillary  artery ;  (^) 
to  the  parotid  gland  from  the  carotid  plexus. 

2.  The  facial  nerve  gives  branches  to  the  sub-maxillary  and  sublingual  glands 
from  the  chorda  tympani  which  accompanies  the  lingual  branch  of  the  fifth  nerve. 
The  branches  to  the  parotid  reach  it  in  a  roundabout  way.  They  arise  from  the 
tympanic  branch  of  the  glosso-pharyngeal  nerve  (dog).  The  tympanic  plexus 
sends  fibres  to  the  small  superficial  petrosal  nerve  (Eckhard),  and  with  it  these 
fibres  run  to  the  anterior  surface  of  the  pyramid  in  the  temporal  bone,  emerging 
from  the  skull  through  a  fissure  between  the  petrous  and  great  wing  of  the  sphenoid, 
and  then  joining  the  otic  ganglion.  This  ganglion  sends  branches  to  the  auriculo- 
temporal nerve  (itself  derived  from  the  third  branch  of  the  trigeminus),  which,  as 
it  passes  upward  to  the  temporal  region,  under  cover  of  the  parotid,  gives  branches 
to  this  gland  (?'.  Wittich). 

The  sub-maxillary  ganglion,  v/hich  gives  branches  to  the  sub-maxiUary  and 
sublingual  glands,  receives  fibres  from  the  tympanico-lingual  nerv'e  (Chorda  tym- 
pani), as  well  as  sympathetic  fibres  from  the  plexus  on  the  external  maxillary 
artery. 

Termination  of  the  Nerve  Fibres. — With  regard  to  the  ultimate  distribu- 
tion of  these  nerves  we  can  distinguish  (i )  the  vasomotor  nerves,  which  give 
branches  to  the  walls  of  the  blood  vessels,  and  (2)  the  secretory  nerves  proper. 
Pfliiger  states,  with  regard  to  the  latter,  that  {a)  medullated  nerve  fibres  penetrate 
the  acini;  the  sheath  of  Schwann  (gray  sheath)  unites  with  the  membrana  propria 
of  the  acinus  ;  the  medullated  fibre — still  medullated — passes  between  the  secre- 
tory cells,  where  it  divides  and  becomes  non-medullated,  and  its  axial  cylinder 
terminates  in  connection  with  the  nucleus  of  a  secretory  cell.  [This,  however, 
is  not  proved]  (Fig.  148,  F). 

(J))  According  to  Pfliiger,  some  of  the  nerve  fibres  end  in  multipolar  ganglion  cells,  which  lie  out- 
side the  wall  of  the  acinus,  and  these  cells  send  branches  to  the  secret'jry  cells  of  the  acini.  [These 
cells  probably  correspond  to  the  branched  cells  of  the  basket-shaped  structure.] 

(c)  Again,  he  describes  medullated  fibres  which  enter  the  attached  end  of  the  cylindrical  epithe- 
lium lining  the  excretory  ducts  of  the  glands  i^E).  Pfliiger  thmks  that  those  fibres  entering  the 
acini  directly  are  cerebral,  while  those  witli  ganglia  in  their  course  are  derived  from  the  sympathetic 
system. 

[(«)  The  direct  termination  of  nerve  fibres  has  been  observed  in  the  salivary  glands  of  the  cock- 
roach by  Kupffer.] 

145.  ACTION  OF  THE  NERVOUS  SYSTEM  ON  THE  SECRE- 
TION OF  SALIVA.— (A)  Submaxillary  Gland.— Stimulation  of  the  facial 
nerve  at  its  origin  {Li/divig  and  Rahn)  causes  a  profuse  secretion  of  a  thin 
watery  saliva,  which  contains  a  very  small  amount  of  specific  constituents 
(Eckhard).  Simultaneously  with  the  act  of  secretion,  the  blood  vessels  of  the 
glands  become  dilated,  and  the  capillaries  are  so  distended  that  the  pulsatile 
movement  in  the  arteries  is  propagated  into  the  veins.  Nearly  four  times  as  much 
blood  flows  out  of  the  veins  (CV.  Bernard),  the  blood  being  of  a  bright  red  color. 


238  ACTION    OF    NERVES   ON    THE    SECRETION    OF    SALIVA. 

and  contains  one-third  more  O  than  the  venous  blood  of  the  non-stimulated 
gland.  Notwithstanding  this  relatively  high  percentage  of  O,  the  secreting  gland 
uses  more  O  than  the  passive  gland  (§  131,  i). 

[I.  Stimulation  of  Chorda. — If  a  cannula  be  placed  in  Wharton's  duct,  e.g., 
in  a  dog,  and  the  chorda  tympani  be  divided,  no  secretion  flows  from  the  cannula. 
On  stimulating  X\\^ periplicral  end  of  the  chorda  tympani  \\\\.\\  an  interrupted  cur- 
rent of  electricity,  the  same  results — copious  secretion  of  saliva  and  vascular  dila- 
tation, with  increased  flow  of  blood  and  lymph,  through  the  gland — occur  as  when 
the  origin  of  the  seventh  nerve  itself  is  stimulated  The  watery  saliva  is  called 
chorda  saliva.] 

Two  functionally  different  kinds  of  nerve  fibres  occur  in  the  facial  nerve — (i) 
true  secretory  fibres,  (2)  vaso-dilator  fibres.  The  increased  amount  of  secre- 
tion is  not  due  simply  to  the  increased  blood  supply,  as  is  proved  below. 

II.  Stimulation  of  the  sympathetic  nerve  causes  a  scanty  amount  of  a 
very  thick,  sticky,  mucous  secretion  (Eckhard),  in  which  the  specific  salivary 
constituents,  mucin,  and  the  salivary  corpuscles  are  very  abundant.  The  specific 
gravity  of  the  saliva  is  raised  from  1007  to  loio.  Simultaneously  the  blood  ves- 
sels become  contracted,  so  that  the  blood  flows  more  slowly  from  the  veins,  and 
has  a  dark  bluish  color. 

The  sympathetic  also  contains  two  kinds  of  nerve  fibres — (i)  true  secretory 
fibres,  and  (2)  vaso-constrictor  fibres. 

[Electrical  Variations  during  Secretion. — That  changes  in  the  electromotive  properties  of 
glands  occur  during  secretion  was  shown  in  the  frog's  skin  by  Roeber,  Engelinann,  and  Hermann. 
Bayliss  and  Bradford  find  that  the  same  is  true  of  the  sub-ma.\illary  gland  I  dog).  During  secretion 
the  excitatory  change  on  stimulaling  the  chorda  is  s. positive  variation  of  the  current  of  rest  (the 
hilus  of  the  gland  becoming  more  positive),  but  it  is  frequently  followed  by  a  second  phase  of  oppo- 
site sign.  The  latent  period  is  always  very  short,  about  0.37".  Atropin  abolishes  the  chorda 
variation.  On  stimulating  the  sympathetic,  the  excitatory  change  is  of  an  opposite  sign  to  that 
of  the  chorda,  and  the  hilus  becomes  less  positive,  so  that  there  is  a  negative  variation.  It  requires 
a  more  powerful  stimulus,  is  less  in  amount,  and  its  latent  period  is  longer  (2"-4"),  while  atropin 
lessens  but  does  not  abolish  it.] 

Relation  to  Stimulus. — On  stimulating  the  cerebral  nerves,  at  first  with  a  weak  and  gradually 
with  a  stronger  stimulus,  there  is  a  gradual  development  of  the  secretion  in  which  the  solid  constitu- 
ents— occasionally  the  organic — are  increased  (Heidenhain).  If  a  strong  stimulus  be  applied  for  a 
long  lime,  the  secretion  diminishes,  becomes  watery,  and  is  poor  in  specific  constituents,  especially 
in  the  organic  elements,  which  are  more  affected  than  the  inorganic  ( C.  LuJwig  and  Bee  her).  After 
prolonged  stimulation  of  the  sympathetic,  the  secretion  resembles  the  chorda  saliva.  It  would  seem, 
therefore,  that  the  chorda  and  sympathetic  saliva  are  not  specifically  distinct,  but  vary  only  in  de- 
gree. On  continuing  the  stimulation  of  the  nerves  up  to  a  certain  maximal  limit,  tlie  rapidity  of 
secretion  becomes  greater,  and  the  percentage  oi  salts  also  increases  to  a  certain  maximum,  and  this 
independently  of  the  former  condition  of  the  glands.  The  percentage  of  organic  constituents  also 
depends  on  the  strength  of  the  nervous  stimulation,  but  not  on  this  alone,  as  it  is  essentially  contin- 
gent upon  the  condition  of  the  gland  before  the  secretion  took  place,  and  it  also  depends  upon  the 
duration  and  intensity  of  the  previous  secretory  activity.  Very  strong  stimulation  of  the  gland  leaves 
an  "  alter  tffect  "  wiiich  predisposes  it  to  give  off  organic  constituents  into  the  secretion  (Heiden- 
hain). A  latent  period  of  1.2  sec.  {//ering)  to  24  sec.  (Ludwig)  may  elapse  between  the  nerve 
stimulation  and  the  beginning  of  the  secretion. 

[Langley  has  shown  that  in  the  cat  the  sympathetic  saliva  of  the  sub-maxillary  gland  is  less  viscid 
than  the  chorda  saliva.  The  following  table  from  Langley  shows  the  difference  in  percentage  com- 
position between  the  chorda  and  sympathttic  saliva  in  the  cat: — 


*of 


f  Sympathetic  saliva  (weak  1 
stimulation   .    .    .    .    ) 

J  Sympathetic    saliva   after  j 

I  5      mgrm.       atropin  v 

[  (strong   stimulation),  ) 

\  Chorda      saliva      (weak  I 

'  stimulation)  ....    1 


Chorda    saliva    (st 


stimulation) 


stronger  1 


Organic 
Substance, 

?  of  Ash. 

Tot.ll  < 
ot*  builds. 

0-3535 

0.4419 

°-7954 

05250 

0.4540 

0.9790 

0.86566 

0-33978 

1.20544 

0.42598 

0.27568 

0.70161 

ACTION    OF   NERVES    ON    THE    SECRETION    OF   SALIVA.  239 

Relation  to  Blood  Supply. —  The  secretion  of  saliva  is  not  simply  the  result 
of  the  amount  of  blood  in  the  glands;  that  there  is  a  factor  independent  of  the 
changes  in  the  state  of  the  vessels  is  shown  by  the  following  facts : — • 

(I )  The  secretory  aclivity  of  the  glands  when  their  nen'es  are  stimulated  continues  for  some  time 
after  the  blood  vessels  of  the  gland  have  been  ligatured  [Luduiig,  Czermaci,  Giaiiuzzi).  [If  the 
head  of  a  rabbit  be  cut  off,  stimulation  of  the  seventh  nerve,  above  where  the  chorda  leaves  it,  causes 
a  flow  of  saliva,  which  cannot  be  accounted  for  on  the  supposition  that  the  saliva  already  present  in 
the  salivary  glands  is  force  1  out  of  them.  Thus  we  may  have  secretion  without  a  blood  stream. 
The  saliva  is  really  secreted  from  the  lymph  present  in  the  lymph  spaces  of  the  gland  (LuJ7vig.)'\ 

(2)  Atropin  and  Daturin  extinguish  the  activity  of  the  secretory  fibres  in 
the  chorda  tympani  i^Keuchel ),  that  do  not  affect  the  vaso-dilator  fibres  {IJeiden- 
hain).  The  same  results  occur  after  the  injection  of  acids  and  alkalies  into  the 
excretory  duct  {Gianiizzi). 

(3)  The  pressure  in  the  excretory  duct  of  the  salivary  gland- — measured  by 
means  of  a  manometer  tied  into  it — may  be  nearly  twice  as  great  as  the  pressure 
within  the  arteries  of  the  glands  {Ludwig),  or  even  in  the  carotid  itself.  The 
pressure  in  Wharton's  duct  may  reach  200  mm.  Hg. 

(4)  Just  as  in  the  case  of  muscles  and  nerves,  the  salivary  glands  become  fatigued  or  exhausted 
after  prolonged  action.  The  result  may  also  be  brought  about  by  injecting  acids  or  alkalies  into  the 
duct,  which  shows  that  the  secretory  activity  of  the  gland  is  independent  of  the  circulation  [Gian- 

tizzi). 

[Action  of  Atropin. — The  vascular  dilatation  and  the  increased  flow  of 
saliva  due  to  tlie  activity  of  the  secretory  cells,  produced  by  stimulation  of  the 
chorda  tympani,  althougii  they  occur  simultaneously,  do  not  stand  in  the  relation 
of  cause  and  effect.  We  may  cause  vascular  dilatation  without  an  increased  flow 
of  saliva,  as  already  stated  (2).  If  atropin  be  given  to  an  animal,  stimulation  of 
the  chorda  produces  dilatation  of  the  blood  vessels,  but  no  secretion  of  saliva. 
Atropin  paralyzes  the  secretory  fibres,  but  not  the  vaso-dilator  fibres  (Fig.  152). 
The  increased  supply  of  blood,  while  not  causing,  yet  favors  the  act  of  secretion, 
by  placing  a  larger  amount  of  pabulum  at  the  disposal  of  the  secretory  elements, 
the  tells.] 

[Secretory  Pressure. — The  experiment  described  under  (3)  proves,  in  a 
dennite  manner,  that  the  passage  of  the  water  from  the  blood  vessels,  or  at  least 
from  the  lymph  into  the  acini  of  the  gland,  cannot  be  due  to  the  blood  pressure  ; 
that,  in  fact,  it  is  not  a  mere  process  of  filtration  such  as  occurs  in  the  glomeruli  of 
the  kidney.  In  the  case  of  the  salivary  gland,  where  the  pressure  within  the 
gland  may  be  double  that  of  the  arterial  pressure,  the  water  actually  moves  from 
the  lymph  spaces  against  very  great  resistance.  We  can  only  account  for  this 
result  by  ascribing  it  to  the  secretory  activity  of  the  gland  cells  themselves. 
Whether  the  activities  of  the  gland  cells,  as  suggested  by  Heidenhain,  are 
governed  directly  by  two  distinct  kinds  of  nerve  fibres,  a  set  of  solid -secreting 
fibres,  and  a  set  of  water-secreting  fibres,  remains  to  be  proved.] 

All  these  facts  le.ad  us  to  conclude  ih.at  the  nerves  e.xercise  a  direct  effect  upon  the  secretory  cells, 
apart  from  their  action  on  the  blood  vessels.  This  physiological  consideration  goes  hand  in  hand 
with  the  anatomical  fact  of  ihe  direct  continuity  of  nerve  fibres  with  the  secretoiy  cells.  When  the 
chorda  tympani  is  extirpated  on  one  side  in  young  dogs,  the  sub-maxillary  gland  on  that  side  does 
not  develop  so  much— its  weight  is  50  per  cent  less— while  the  mucous  cells  and  the  "  crescents  " 
are  smaller  than  on  the  sound  side  (Bii/alini). 

During  secretion  the  temperature  of  the  gland  rises  1.5°  C.  {Ludwig'),  and 
the  blood  flowing  from  the  veins  is  often  warmer  than  the  arterial  blood.  [The 
electro-motive  changes  are  referred  to  at  p.  238.] 

"  Paralytic  Secretion"  of  Saliva. — By  this  term  is  meant  the  continued 
secretion  oi  a  thin,  watery  saliva  from  the  sub-maxillary  gland,  which  occurs 
twenty-four  hours  after  the  section  of  the  cerebral  nerves  (chorda  of  the  seventh), 
/.  e.,  those  branches  of  them  that  go  to  this  gland,  whether  the  sympathetic  be 
divided  or  not  {CI.  Bernard).     It  increases  until  the  eighth  day,  after  which  it- 


240 


REFLEX   SECRETION    OF   SALIVA. 


gradually  diminishes,  while  the  gland  tissue  degenerates.     The  injection  of  a 
small  quantity  of  curara  into  the  artery  of  the  gland  also  causes  it. 

[Heidenhain  showed  that  section  of  one  chorda  i^  followed  by  a  continuous  secretion  of  saliva 
from  l>o//i  sub-maxillary  glands.  The  term  "  paralytic  "  secretion  is  applied  to  that  which  takes 
place  on  the  side  on  which  the  nerve  is  cut,  and  Langley  proposes  to  call  the  secretion  on  the  oppo- 
site side  the  antilytic.  The  condition  of  apncea  (J  36S)  stops  almost  or  entirely  both  the  para- 
lytic and  antilytic  secretion,  while  dyspncea  increases  the  flow  in  both  cases;  and  as  section  of  the 
sympathetic  fibres  to  the  gland  (where  the  chorda  is  cut)  arrests  the  paralytic  secretion  excited  by 
dyspncea,  it  is  evident  that  both  the  paralytic  secretion  and  the  secretion  following  dyspncea  are 
caused  by  stimuli  traveling  down  the  sympathetic  fibres  (Langley).  In  the  later  stages  of  the  para- 
lytic secretion,  the  cause  is  in  the  gland  itself,  for  it  goes  on  even  if  all  the  nerves  p.assing  to  the 
gland  be  divided,  and  is  probably  due  to  a  local  ner/e  centre.  In  this  stage  the  secretion  is 
arrested  by  a  large  dose  of  chloroform.  The  paralytic  secretion  in  the  first  stage,  according  to 
Langley,  is  owing  to  a  venous  condition  of  the  Ijlood  acting  on  a  centr.il  secretory  centre  whose 
excitability  is  increased;  and  in  the  latter  stages  probably  on  local  nerve  centres  within  the  gland. 
The  fibres  of  the  chorda  in  the  cat  are  only  partially  degenerated  thirteen  days  after  section  (Lang- 

[Histological  Changes. — In  the  gland  during  paralytic  secretion,  the  gland  cells  of  the  alveoli 
(serous,  mucous  and  demilunes),  diminish  in  size  and  show  the  typical  "resting"  appearance,  even 
to  a  greater  extent  than  the  normal  resting  gland  (Langley).'\ 

(B)  Sublingual  Gland. — Very  probably  the  same  relations  obtain  as  in  the 
sub- maxillary  gland. 

Fig.  152. 


VCS^SBLS  vrEtSKD 


(C)  Parotid  Gland. — In  the  dog,  stimulation  of  the  sympathetic  alone  causes 
no  secretion  ;  it  occurs  when  theglosso-pharyngeal  branch  to'  the  parotid  is  simul- 
taneously excited.  This  branch  may  be  reached  within  the  tympanum  in  the  tym- 
panic plexus.  A  thick  secretion  containing  much  organic  matter  is  thereby 
obtained.  Stimulation  of  the  cerebral  branch  alone  yields  a  clear,  thin,  watery 
secretion,  containing  a  very  small  amount  of  organic  substances,  but  a  consider- 
able amount  of  the  salts  of  the  saliva  {Hcidenhahi). 

Reflex  Secretion  of  Saliva. — [If  a  cannula  be  placed  in  Wharton's  duct, 
e.  g.,  in  a  dog,  during  fiisting,  no  saliva  will  flow  out.  If  the  mucous  membrane 
of  the  mouth  hi  stimulated  by  a  sapid  substance  placed  on  the  tongue,  there  is  a 
copious  flow  of  saliva.  If  the  sympathetic  nerve  be  divided,  secretion  still  takes 
place  when  the  mouth  is  stimulated,  but  if  the  chorda  tympani  be  cut,  secretion 
no  longer  takes  place.  Hence,  the  secretion  is  due  to  a  reflex  act ;  in  this  case, 
the  lingual  is  the  afferent,  and  the  chorda  the  efferent  nerve  carrying  impulses  from 
a  centre  situated  in  the  medulla  oblongata  (Fig.  152).]  In  the  intact  body,  the 
secretion  of  saliva  occurs  through  a  reflex  stimulation  of  the  nerves  concerned, 
whereby,  under  normal  circumstances,  the  secretion  is  always  watery  (chorda  or 
facial  saliva).  The  centripetal  or  afferent  nerve  fibres  concerned  are — (i) 
The  nerves  of  taste.     (^2)  The  sensory  branches  of  the  trigeminus  of  the  entire 


THEORY   OF   SALIVARY   SECRETION.  241 

cavity  of  the  mouth  and  the  glosso-pharyngeal  (which  appear  to  be  capable  of 
being  stimulated  by  mechanical  stimuli,  pressure,  tension,  displacement).  The 
movements  of  mastication  also  cause  a  secretion  of  saliva.  Pfliiger  found  that  one- 
third  more  saliva  was  secreted  on  the  side  where  mastication  took  place ;  and  CI. 
Bernard  observed  that  the  secretion  ceased  in  horses  during  the  act  of  drinking. 
(3)  The  nerves  of  smell,  excited  by  certain  odors.  (4)  The  gastric  branches  of 
'  the  vagus  {Frcrichs,  Ochl).  A  rush  of  saliva  into  the  mouth  usually  precedes  the 
act  of  vomiting  (§  158). 

(5)  The  stimulation  of  distant  sensory  nerves,  e.g.,  the  central  end  of  the  sciatic — certainly 
through  a  complicated  reflex  mechanism — causes  a  secretion  of  saliva  ( Owsjannikow  and  Tschier- 
jeti').  Stimulation  of  the  conjunctiva,  e.  g.,  by  applying  an  irritating  fluid  to  the  eye  of  carnivorous 
animals,  causes  a  reflex  secretion  of  saliva  [Aschenbrandt).  Perhaps  the  secretion  of  saliva  which 
sometimes  occurs  during  pregnancy  is  caused  in  a  similar  reflex  manner. 

The  reflex  centre  for  the  secretion  of  saliva  lies  in  the  medulla  oblongata,  at 
the  origin  of  the  seventh  and  ninth  cranial  nerves  (Eckhard  and  Loeh).  The 
centre  for  the  sympathetic  fibres  is  also  placed  here  {Griiizner  and  Ch/apowski). 
This  region  is  connected  by  nerve  fibres  with  the  cerebrum  ;  hence,  the  thought 
of  a  savory  morsel,  sometimes,  when  one  is  hungry,  causes  a  rapid  secretion  of  a 
thin  watery  fluid — [or,  as  we  say,  "  makes  the  mouth  water  "].  If  the  centre  be 
stimulated  directly  by  a  mechanical  stimulus  (puncture),  salivation  occurs,  while 
asphyxia  has  the  same  effect.  The  reflex  secretion  of  saliva  may  be  inhibited  by 
stimulation  of  certain  sensory  nerves,  e.  g.,  by  pulling  out  a  loop  of  the  intestine 
{Pawloic).  Stimulation  of  the  cortex  cerebri  of  a  dog,  near  the  sulcus  cruciatus, 
is  often  followed  by  secretion  of  saliva  (Eulenberg  and Landois,  Bochefontaine, 
Biibnoff  and  Heidenhain').  Disease  of  the  brain  in  man  sometimes  causes  a  secre- 
tion of  saliva,  owing  to  the  effects  produced  on  the  intracranial  centre. 

So  long  as  there  is  no  stimulation  of  the  nerves,  there  is  no  secretion  of  saliva, 
as  in  sleep  {Mitscheriich).  Immediately  after  the  section  of  all  nerves,  secretion 
stops,  for  a  time,  at  least. 

Pathological  Conditions  and  Poisons. — Certain  affections,  as  inflammation  of  the  mouth,  neu- 
ralgia, ulcers  of  the  mucous  membrane,  aftections  of  the  gums,  due  to  teething  or  the  prolonged  ad- 
ministration of  mercury,  often  produce  a  copious  secretion  of  saliva  (or  ptyalism).  Certain  poisons 
cause  the  same  effect  by  direct  stimulation  of  the  nerves,  as  Calabar  bean  (Physostigmin),  din-italin, 
and  especially  pilocarpin.  Many  poisons,  especially  the  narcotics — above  all,  atropin — paralyze  the 
secretory  nerve*,  so  that  there  is  a  cessation  of  the  secretion,  and  the  mouth  becomes  dry ;  while  the 
administration  of  muscarin  in  this  condition  causes  secretion  (Prez'ost).  Pilocarpin  acts  on  the 
chorda  tympani,  causing  a  profuse  secretion,  and,  if  atropin  be  given,  the  secretion  is  again  arrested. 
Conversely,  if  the  secretion  be  arrested  by  atropin,  it  may  be  restored  by  the  action  of  pilocarpin  or 
physostigmin.  Nicotin,  in  small  doses,  excites  the  secretory  nerves,  but  in  large  doaes  paralyzes 
them  (IJiiJinhain).     Daturin,  cicutin,  and  iodide  of  a;thystrychnine,  paralyze  the  chorda. 

[Sialogogues  are  those  drugs  which  increase  the  secretion  of  saliva.  Some  are  topical,  and 
take  eflect  when  applied  to  the  mouth.  They  excite  secretion  reflexly  by  acting  on  the  sensory 
nerves  of  the  moutfi.  They  include  acids,  and  various  pungent  bodies,  such  as  mustard,  ginger, 
pyrethrum,  tobacco,  ether,  and  chloroform ;  but  they  do  not  all  produce  the  same  eflect  ou  the 
amount  or  quality  of  the  saliva ;  others,  the  general  sialogogues,  cause  salivation  when  introduced 
into  the  blood,  physostigmin,  nicotin,  pilocarpin,  muscarin.  The  drugs  named  act  after  all  the 
nerves  going  to  the  gland  are  divided,  so  that  they  stimulate  the  peripheral  ends  of  the  nerves  in 
the  glands.     The  two  former  also  excite  the  central  ends  of  the  secretory  nerves.] 

[Excretion  by  the  Saliva. — Some  drugs  are  excreted  by  the  saliva.  Iodide  of  potassium  is 
rapidly  eliminated  by  the  liidneys,  and  also  by  the  salivary  glands,  and  so  also  is  iodide  of  iron.] 

[Anti-sialics  are  those  substances  which  diminish  the  secretion  of  saliva,  and  they  may  take 
eflect  upon  any  part  of  the  reflex  arc,  i.  e.,  on  the  mouth,  the  afferent  nerves,  the  nerve  centre  and 
afferent  nerves,  or  upon  the  blood  stream  through  the  glands,  or  on  the  glands  themselves.  Opium 
and  morphia  afl'ect  the  centre ;  large  doses  of  physostigmin  affect  the  blood  supply ;  but  atropin  is 
the  most  powerful  of  all,  as  it  paralyzes  the  terminations  of  the  secretory  ner\-es  in  the  glands,  e.  '\, 
the  chorda  tympani,  and  even  the  sympathetic  in  the  cat  (but  not  in  the  dog)  (Brunlo>t).~\ 

Theory  of   Salivary   Secretion. — Heidenhain  has  recently  formulated  the  following  theory 

regarding  the  secretion  of  saliva :  •'  During  the  passive  or  quiescent  condition  of  the  gland,  the 

organic  materials  of  the  secretion  are  formed  from  and  by  the  activity  of  the  protoplasm  of  the 

secretory  cells.     A  quiescent  cell,  which  has  been  inactive  for  some  time,  therefore  contains  little 

16 


242  THE    PAROTID   SALIVA. 

protoplasm,  and  a  large  amount  of  these  secretory  substances.  In  an  actively  secreting  gland,  there 
are  two  processes  occurring  together,  but  independent  of  each  other,  and  regulated  by  t«  o  difierent 
classes  of  nerve  fibres;  secretory  fibres  cause  the  act  of  secretion,  while  trophic  fibres  cause  chemical 
processes  within  the  cells,  partly  resulting  in  the  formation  of  the  soluble  constituents  of  the  secretion, 
and  partly  in  the  growth  of  the  protoplasm.  According  to  the  number  of  both  kinds  of  fibres  present 
in  a  nerve  passing  to  a  gland,  such  nerve  being  stimulated,  the  secretion  takes  place  more  rapidly 
(cerebral  nerve)  or  more  slowly  (sympathetic),  while  the  secretion  contains  less  or  more  solid  con- 
stituents. The  cerebral  nerves  contam  many  secretory  fibres  and  few  trophic  fibres,  while  the 
sympathetic  contains  more  trophic,  but  few  secretory  fibres.  The  rapidity  and  chemical  composition 
of  the  secretion  vary  according  to  the  strength  of  the  stimulus.  During  continued  secretion,  the 
supply  of  secretory  materials  in  the  gland  cells  is  used  up  more  rapidly  than  it  is  replaced  by  the 
activity  of  the  protoplasm;  hence,  the  amount  of  organic  constituents  diminishes,  and  the  microscopic 
characters  of  the  cells  are  altered.  The  microscopic  cliaracters  of  the  cells  are  altered  also  by  the 
increase  of  the  protoplasm,  which  lakes  place  in  an  active  gland.  The  mucous  cells  disappear,  and 
seem  to  be  dissolved  after  prolonged  secretion,  and  their  place  is  taken  by  other  cells  derived  from 
the  proliferation  of  the  marginal  cells.  The  energy  w'hich  causes  the  current  of  fluid  depends  upon 
the  protoplasm  of  the  gland  cells." 

The  saliva  is  diminished  in  amount  in  man  in  case?,  oi  paralysis  of  the  fiacial  or  sympathetic 
nerves,  as  is  observed  in  unilateral  paralysis  of  these  nerves. 

146.  THE  SALIVA  OF  THE  INDIVIDUAL  GLANDS.— (a)  The 
Parotid  Saliva  is  obtained  by  placing  a  fine  cannula  in  Steno's  duct  [^Eckhard) ; 
it  has  an  alkaline  reaction,  but  during  fasting,  the  first  few  drops  may  be  neutral 
or  even  acid  on  account  of  free  COj  (^Oehl) — its  specific  gravity  is  1003  to  1004. 
When  allowed  to  stand  it  becomes  turbid,  and  deposits,  in  addition  to  albuminous 
matter,  calcium  carbonate,  which  is  present  in  the  fresh  saliva  in  the  form  of 
bicarbonate. 

Salivary  calculi  are  formed  in  the  ducts  of  the  salivary  glands  owing  to  the  deposition  of  lime 
salts,  and  they  contain  only  traces  of  the  other  salivary  constituents :  in  the  same  way  is  formed  the 
tartar  of  the  teeth,  which  contains  many  threads  of  leptothrix,  and  the  remains  of  low  organisms 
which  live  in  decomposing  saliva  in  carious  cavities  between  the  teeth. 

It  contains  small  quantities  (more  abundant  in  the  horse)  of  a  globulin-like 
body,  and  never  seems  to  be  without  C  N  K  S  sulphocyanide  of  potassmm  (or 
sodium — Trcviranus,  1814),  which,  however,  is  absent  in  the  sheep  and  dog 
{Brcttel). 

The  sulphocyanide  gives  a  dark  red  color  (ferric  sulphocyanide)  with  ferric  chloride.  It  also 
reduces  iodic  acid  when  added  to  saliva,  causing  a  yellow  color  from  the  liberation  of  iodine,  which 
may  be  detected  at  once  by  starch  [Solera). 

Among  the  organic  substances  the  most  important  are  ptyalin,  and  a  small 
amount  oi  urea  {^Goliltj),  and  traces  of  a  volatile  acid  (^CaproicPj. 

Mucin  is  absent,  hence  the  parotid  saliva  is  fluid,  is  not  sticky,  and  can 
readily  be  poured  from  one  vessel  into  another.  It  contains  1.5  to  1.6  per  cent,  of 
solids  in  man  {Mitschetiich,  van  Setlcn),  of  which  0.3  to  i.o  per  cent,  is  inorganic. 

Of  the  inorganic  constituents — the  most  abundant  are  potassium  and  sodium  chlorides ;  then 
potassium;  sodium,  and  calcium  carbonates,  some  phosphates  and  a  trace  of  an  alkaline  sulphate. 

{fi)  The  Sub-maxillary  Saliva  is  obtained  by  placing  a  cannula  in  Wharton's 
duct ;  it  is  alkaline,  and  may  be  strongly  so.  When  allowed  to  stand  for  a  long 
time,  fine  crystals  of  calcium  carbonate  are  deposited,  together  with  an  amorphous 
albuminous  body.  It  always  contains  mucin  (which  is  precipitated  by  acetic 
acid)  ;  hence,  it  is  usually  somewhat  tenacious.  Further,  it  contains  ptyalin,  but 
in  less  amount  than  in  parotid  saliva;  and,  according  to  Oehl,  only  0.0036  per 
cent,  of  potassium  sulphocyanide. 

Chemical  Composition. — Sub-maxillary  saliva  (dog) : — 

Water 991-45  per  looo. 

Organic  iVIatter     .    .    .      2.89    "       " 

Inorganic  Matter.    .    .       5.66  1 45°  Nad  and  CaCI,. 

=•  ■'J  1. 10  CaCO,,  Calcium  and  Magnesium  phosphates. 


THE    MIXED    SALIVA    IN    THE    MOUTH.  243 

Mixed  Saliva  Parotid  Sub-maxillary 

(Human)  (Human)  (Dog) 

{jMiiim'ilscA).  (Hjppc-SeyUr).  {Herter). 

[Water 99-5'  99-32  99-44 

Solids 0.4S  0.6S  0.59 

Soluble  organic  bodies  (Ptyalin) 0.13    1  f  0.066 

Epithelium,  mucin 0.16    /  •'''  \0.17 

Inorganic  salts 0.182  0.34                          0.43 

Potassic  sulphocyanide o  006  0.03                         .    .    . 

Potassic  and  sodic  chlorides 0.0S4  ...                         •    •    ■  ] 

Gases. — PflUger  found  that  100  cubic  centimetres  of  the  saliva  contained  0.6  O  to  64.7  CO^ 
(part  could  be  pumped  out,  and  part  required  the  addition  of  phosphoric  acid) ;  0.8  N;  or,  in  100 
vol.  gas,  0.91  (3  ;  97.88  CO2,  I.2I  N.     [It  therefore  contains  much  more  COj  than  venous  blood.] 

{/)  The  Sublingual  Saliva  is  obtained  by  placing  a  very  fine  cannula  in  the 
ductus  Rivinianus  (  Ochi),  is  strongly  alkaline  in  reaction,  very  sticky  and  cohesive, 
contains  much  mucin,  numerous  salivary  corpuscles  and  some  potassium  sulpho- 
cyanide {Longei). 

147.  THE  MIXED  SALIVA  IN  THE  MOUTH.— The  fluid  in  the 
mouth  is  a  mixture  of  the  secretions  from  the  salivary  glands  and  the  secretions 
of  the  raucous  and  other  glands  of  the  mouth. 

(ij  Physical  Characters. — The  mixed  saliva  of  the  mouth  is  a  somewhat 
opalescent,  tasteless,  odorless,  slightly  glairy  fluid,  with  a  specific  gravity  of  1004 
to  1009,  and  an  alkaline  reaction.  The  amount  secreted  in  twenty-four  hours 
=  200  to  1500  grammes  (7  to  50  oz.)  ;  according  to  Bidder  and  Schmidt,  how- 
ever, 1000  to  2000  grammes.     The  solid  constituents  ^  5.8  per  1000. 

Composition. — The  solids  are:  Epithelium  and  mucus,  2.2;  ptyalin  and  albumin,  1.4;  salts, 
2.2;  potassium  sulphocyanide,  0.04  per  1000.  The  ash  contains,  chiefly,  potash,  phosphoric  acid 
and  chlorine  [Hammerhacher). 

Decomposition  products  of  epithelium,  salivaiy  corpuscles,  or  the  remains  of  food,  may  render 
\i  acid  temporarily,  a^  after  long  fasting  and  after  much  speaking  (//(y/t'-&)'/e'/-).  Even  outside 
the  body,  saliva  containing  much  epithelium  becomes  acid  before  it  putrefies  [Gorup-Besanez). 
'l"he  reaction  is  acid  in  some  cases  of  dyspepsia  and  in  fever,  owing  to  the  stagnation  and  insuffi- 
cient secretion. 

(2)  Microscopic  Constituents. — {a)  The  salivary  corpuscles  are  slightly 
larger  than  the  white  blood  corpuscles  (8  to  11  //),  and  are  nucleated  protoplasmic 
globular  cells  without  an  envelope.  During  their  living  condition,  the  particles 
in  their  interior  exhibit  molecular  or  Brownian  movements.  The  dark  granules 
lying  in  the  protoplasm  are  thrown  into  a  trembling  movement,  from  the  motion 
of  the  fluid  in  which  they  are  suspended.  This  dancing  motion  stops  when  the 
cell  dies. 

[The  Brownian  movements  of  these  suspended  granules  are  purely  physical,  and  are  exhibited 
by  all  fine  microscopic  particles  suspended  in  a  limpiil  fluid,  e.  g.,  gamboge  rubbed  up  in  water, 
panicles  of  carmine,  charcoal,  etc.] 

[b)  J'avcment  epitltelial  cells  from  the  mucous  membrane  of  the  mouth  and  tongue ;  they  are 
very  abundant  in  catarrh  of  the  mouth  (Fig.  145). 

(<\)  Living  organisms,  which  live  and  thrive  in  the  cavities  of  teeth  nourished  by  the  remains  of 
food.  Among  these  are  Leptolttrix  buaalis  (Fig.  144,  I2j  and  small  bacteria-like  organisms.  The 
threads  of  the  leptothrix  penetrate  into  the  canals  of  the  dentine  and  produce  dental  caries  [Liltcr). 
Cucci,  bacteria,  vibrios,  spirilla  and  spirocha^tce  may  also  be  lound. 

(^3)  Chemical  Properties. — (a)  Organic  Constituents. — Serum  albumin 
is  precipitated  by  heat  and  by  the  addition  of  alcohol.  In  saliva,  mixed  with 
much  water  and  shaken  up  with  CO^,  a.  globulin- like  body  is  precipitated  ;  mucin 
occurs  in  small  amount.  Among  the  extractives,  the  most  important  is  ptyalin 
(Berzelius) ;  fats  and  u>ea  occur  only  in  traces.  In  twenty-four  hours  130  milli- 
grammes of  potassium  or  sodium  sulphocyanide  are  secreted. 

{b)  Inorganic  Constituents. — ^Sodium  and  potassium  chlorides,  potassium 
sulpnatc,  alkaline  and  earthy  phosphates,  ferric  phosphate. 


244  PHYSIOLOGICAL   ACTION   OF   SALIVA. 

Abnormal  Constituents. — In  diabetes  mellitus,  lactic  acid,  derived  from  .i  further  decomposi- 
tion of  grape  sugar,  is  found  (Lchmann).  It  dissolves  the  lime  in  the  teeth,  giving  rise  to  diaL)etic 
dental  caries.  Frerichs  found  /('«(■/«,  and  Vulpian  increase  of  albumin,  in  albuminuria.  Of  foreign 
substances  tal^en  into  the  body,  the  following  appear  in  the  saliva:  Mercury,  potassium,  iodine  and 
bromine. 

Saliva  of  New-born  Children. — In  new-born  children,  the  parotid  alone 
contains  ptyalin.  The  diastatic  ferment  seems  to  be  developed  in  the  sub-maxillary 
gland  and  pancreas  at  the  earliest  after  two  months.  Hence,  it  is  not  advisable  to 
give  starchy  food  to  infants.  No  ptyalin  has  been  found  in  the  saliva  of  infants 
suffering  from  thrush  (Oidiuni  albicans — Zwcifel).  The  diastatic  action  of  saliva 
is  not  absolutely  necessary  for  the  suckling,  feeding,  as  it  does,  upon  milk.  The 
mouth,  during  the  first  two  months,  is  not  moist,  but  at  a  later  period  saliva  is  copi- 
ously secreted  {Konnoin)  ;  after  the  first  six  months,  the  salivary  glands  increase 
considerably.  The  eruption  of  the  teeth — owing  to  the  irritation  of  the  mucous 
membrane — produces  a  copious  secretion  of  saliva. 

148.    PHYSIOLOGICAL   ACTION    OF    SALIVA.  — I.    Diastatic 

Action. — The  most  important  part  played  by  saliva  m  digestion  is  its  diastatic 
or  amylolytic  action  (Leiichs,  iSjl),  i.  e.,  the  transformation  of  starch  into  dextrin 
and  some  form  of  sugar.  This  is  due  to  the  ptyalin — a  hydrolytic  ferment  or 
enzym — which  acts  in  very  minute  quantity,  so  that  starch  takes  up  water  and 
becomes  soluble,  the  ferment  itself  undergoing  no  essential  change  in  the  process. 
[Ptyalin  belongs  to  the  group  of  unorganized  ferments.  Like  all  other  ferments, 
u  acts  only  within  a  certain  range  of  temperature,  being  most  active  about  40°  C. 
Its  energy  is  permanently  destroyed  by  boiling.  It  acts  best  in  a  slightly  alkaline 
or  neutral  medium.] 

Action  on  Starch. — [Starch  grains  consist  of  ^■';-(7«//'/(V^  or  starch  enclosed  by 
coats  of  iiilidose.  Cellulose  does  not  appear  to  be  affected  by  saliva,  so  that  saliva 
acts  but  slowly  on  raw,  unboiled  starch.  If  the  starch  be  boiled  so  as  to  swell  up 
the  starch  grains  and  rupture  the  cellulose  envelopes,  the  amylolytic  action  takes 
place  rapidly.  If  starch  paste  or  starch  mucilage,  made  by  boiling  starch  in 
water,  be  acted  upon  by  saliva,  especially  at  the  temperature  of  the  body,  the  first 
physical  change  observable  is  the  liquefaction  of  the  paste,  the  mixture  becoming 
more  fluid  and  transparent.  The  change  takes  place  in  a  few  minutes.  When  the 
action  is  continued,  important  chemical  changes  occur.] 

According  to  O'Sullivan,  Musculus,  and  v.  Mering,  the  diastatic  ferment  of 
saliva  (and  of  the  pancreas)  by  acting  upon  starch  or  glycogen  forms  dextrin  and 
maltose  (both  soluble  in  water).  Several  closely  allied  varieties  of  dextrin, 
distinguishable  by  their  color  reactions,  seem  to  be  produced  (^Bri/eke).  Ery- 
throdextrin  is  formed  first;  it  gives  a  red  color  with  iodine;  then  a  reducmg 
dextrui — achroodextrin,  which  gives  no  color  reaction  with  iodine.  The  sugar 
formed  by  the  action  of  ptyalin  upon  starch  is  maltose  (Ci.^H„0,i  -\-  H.^O), 
which  is  distinguished  from  grape  sugar  (Ci^Hj^Opj)  by  containing  one  molecule 
less  of  water,  which,  however,  it  holds  as  a  molecule  of  water  of  hydration,  as 
indicated  in  the  formula  given  above  (Ad.  Mayer).  [Maltose  also  differs  from 
grape  sugar  in  its  greater  rotatory  power  on  polarized  light,  and  in  its  less  power 
of  reducing  cupric  oxide.  Thus,  it  will  be  seen  that  between  the  original  starch 
and  the  final  product,  maltose,  several  intermediate  bodies  are  formed.  The 
starch  gives  a  blue  with  iodine,  but  after  it  has  been  acted  on  for  a  time  it  gives  a 
red  or  violet  color,  indicating  the  color  of  erythrodextrin,  there  being  a  simulta- 
neous production  of  sugar;  but  ultimately  no  color  is  obtained  on  adding  iodine — 
achroodextrin,  which  gives  no  color  with  iodine,  and  maltose  being  formed.  The 
presence  of  the  maltose  is  easily  determined  by  testing  with  Fehling's  solution.] 

[Brown  and  Heron  suggest  that  the  final  result  of  the  transformation  may  be 
represented  by  the  equation — 

io(Ci,H,oOi„)  -f  8H20  =  S(C,,H,,0,,)  +  2(C,2Hj(,0,o) 

Soluble  starch.  Water.  Maltose".  Achroodextrin.] 


FUNCTIONS    OF   THE    SALIVA.  245 

[The  ferment  slowly  changes  maltose  into  grape  sugar  or  dextrose.  This  result 
may  be  brought  about  much  more  rapidly  by  boiling  maltose  with  dilute  sulphuric 
or  hydrochloric  acid.]  Achroode.xtrin  ultimately  passes  into  maltose,  and  this 
again  into  dextrose ;  the  other  form  of  dextrin  does  not  seem  to  undergo  this 
change  (Seegen's  Dystropodextrin).  For  the  further  changes  that  maltose  under- 
,  goes  in  the  intestine,  see  §  183,  II,  2. 

[The  formula  of  starch  is  usually  expressed  as  CgHj^Oj,  but  the  researches  already  mentioned, 
and  those  of  Brown  and  Heron,  make  it  probable  that  it  is  more  complex,  which  we  may  provision- 
ally represent  by  «  (Cj^H^gOj;,).  According  to  Musculus  and  Meyer,  erythrodextrin  is  a  mixture 
of  dextrin  and  soluble  starch.] 

Preparation  of  Ptyalin.—  (i)  Like  all  other  hydrolytic  ferments,  it  is  carried  down  with  any 
copious  precipitate  that  is  produced  in  the  fluid  which  contains  it.  It  is  easily  isolated  from  the 
precipitate.  The  saliva  is  acidulated  with  phosphoric  acid,  and  lime-water  is  added  until  the  reac- 
tion becomes  alkaline,  when  a  precijiitate  of  basic  calcium  phosphate  occurs,  which  carries  the 
ptyalin  along  with  it.  This  precipitate  is  collected  on  a  filter  and  washed  with  water,  which  dissolves 
the  ptyalin,  and  from  its  watery  solution  it  is  precipitated  by  alcohol  as  white  powder.  It  is  redis- 
solved  in  water  and  reprecipitaled,  and  is  obtained  pure  (Cohn/ieim). 

(2)  Glycerine  or  v.  WilticKs  Method. —  The  salivary  glands  [rat]  are  chopped  up,  placed  in 
absolute  alcohol  for  twenty-four  hours,  taken  out  and  dried,  and  afterward  placed  in  glycerine  for 
several  days.  The  glycerine  extracts  the  ptyalin.  It  is  precipitated  by  alcohol  from  the  glycerine 
extract. 

(3)  William  Roberts  recommends  the  following  solutions  for  extracting  ferments  from  organs 
which  contain  them  :  (l)  A  3  to  4  per  cent,  solution  of  a  mixture  of  2  parts  of  boracic  acid  and 
I  part  borax,  (i)  Water,  with  12  to  IJ  per  cent,  of  alcohol.  (3)  I  part  chloroform  to  200  of 
water. 

Diastatic  Action  of  Saliva. — (a)  The  diastatic  or  sugar-forming  action  is  known  by— (i)  The 
disappearance  of  the  starch.  When  a  small  quantity  of  starch  is  boiled  with  several  hundred  times 
its  volume  of  water,  starch  mucilage  is  obtained,  which  strikes  a  blue  color  with  iodine.  If  to  a 
small  quantity  of  this  starch  a  sufficient  amount  of  saliva  be  added,  and  the  mixture  kept  for  some 
time  at  the  temperature  of  the  body,  the  blue  color  disappears.  (2)  The  presence  o/sugar  is  proved 
directly  by  using  the  tests  for  sugar  (J  149). 

(d)  The  action  takes  place  more  slowly  in  the  coM  than  at  the  temperature  of  the  body — its  action 
is  enfeebled  at  55°  C,  and  destroyed  at  75°  C.  (Paschutin).  The  most  favorable  temperature  is 
35°  to  39°  C. 

[c)  The  ptyalin  itself  does  not  seem  to  be  changed  during  its  action,  but  ptyalin  which  has  been 
used  for  one  experiment  is  less  active  when  used  the  second  time  (Paschutin). 

Ptyalin  differs  from  di.istase  in  so  far  that  the  latter  first  begins  to  act  at  +  66°  C.  Ptyalin 
decomposes  salicin  into  saligenin  and  grape  sugar  (Frerichs  and  Stddlei ),  but  it  has  no  action  on 
cane  sugar  and  amygdalin. 

[d)  Saliva  acts  best  in  a  slightly  alkaline  medium,  but  it  also  acts  in  a  neutral  and  even  in  a 
slightly  acid  fluid  ;  strong  acidity  prevents  its  action.  The  ptyalin  is  only  active  in  the  stomach 
when  the  acidity  is  due  to  organic  acids  (lactic  or  butyric),  and  not  when  free  hydrochloric  acid  is 
present  [van  de  Velde).  In  both  cases,  however,  dextrin  is  formed.  Ptyalin  is  destroyed  by  hydro- 
chloric acid  or  digestion  by  pepsin  [Chittenden  and  Griswold,  Langley).  Even  butyric  and  lactic 
acids  formed  from  grape  sugar  in  the  stomach  may  prevent  its  action ;  but  if  the  acidity  be  neutral- 
ized, the  action  is  resumed  (  CI.  Bernard). 

[e)  The  addition  of  common  salt,  ammonium  chloride,  or  sodium  sulphate  (4  per  cent,  solution), 
increases  the  activity  of  the  ptyalin,  and  so  do  CO21  acetate  of  quinine,  strychnia,  morphia,  curara, 
0.025  P^f  cent,  sulphuric  acid, 

if)  Much  alcohol  and  caustic  potash  destroy  the  ptyalin ;  long  exposure  to  the  air  weakens  its 
action,  sodium  carbonate  and  magnesium  sulphate  delay  the  action  [P/eiffer).  Salicylic  acid  and 
much  atropin  arrest  the  formation  of  sugar. 

(g)  Ptyalin  acts  very  feebly  and  very  gradually  upon  raw  starch,  only  after  2  to  3  hours 
(Schiff) ;  while  upon  boiled  starch  it  acts  rapidly,  [Hence  the  necessity  for  boiling  thoroughly  all 
starchy  foods.] 

(/i)  The  various  kinds  of  starch  are  changed  more  or  less  rapidly,  according  to  the  amount  of 
cellulose  which  they  contain  ;  raw  potato  starch  after  two  to  three  liours,  raw  maize  starch  after  2  to 
3  minutes  (//ammarsten).  Starch  cellulose  is  dissolved  at  55°  C.  (JVdgeli).  WTien  the  starches  are 
powdered  and  boiled,  they  are  changed  with  ec|ual  rapidity. 

(i)  A  mixture  o!  the  saliva  from  all  the  glands  is  more  active  than  the  saliva  from  any  single 
gland  {Jakuhountsch\.  while  mucin  is  inactive. 

[Effect  of  Tea. — W.  Roberts  finds  that  tea  has  an  intensely  inhibitory  effect  on  salivary  diges- 
tion, which  is  due  to  the  large  quantity  of  tannin  contained  in  the  tea  leaf.  Coffee  and  cocoa  have 
only  a  slight  effect  on  salivary  digestion.  The  only  way  to  mitigate  the  inhibitory  effect  of  tea  on 
salivary  digestion  is  "  not  to  sip  the  beverage  with  the  meal,  but  to  eat  first  and  drink  afterward."] 


246  TESTS   FOR    SUGAR. 

II.  Saliva  dissolves  those  substances  which  are  soluble  in  water  ;  while  the  alka- 
line reaction  enables  it  to  dissolve  some  substances  which  are  not  soluble  in  water 
alone,  but  require  the  presence  of  an  alkali. 

III.  .Saliva  moistens  dry  food  and  aids  the  formation  of  the  "  bolus,"  while  by 
its  mucin  it  aids  the  act  of  swallowing,  the  mucin  being  given  off  unchanged  in 
the  fjeces.     The  ultimate  fate  of  ptyalin  is  unknown. 

[IV.  Saliva  also  aids  articulation,  while  according  to  Liebig,  it  carries  down 
into  the  stomach  small  quantities  of  O.] 

[V.  It  is  necessary  to  the  sense  of  taste,  to  dissolve  sapid  substances,  and  bring 
them  in  relation  with  the  end  organs  of  the  nerves  of  taste.] 

The  presence  of  a  peptone-forming  ferment  has  recently  been  detected  in  saliva  [Hiifmi;  Muni, 
A'ii/nn-).  This  ferment  is  likewise  said  to  occur  in  the  saliva  of  the  horse,  which  can  also  convert 
cane  sugar  into  invert  sugar,  and  slightly  emulsionize  fats  [Ellcnberger  and  v.  Hofmeister).  Ac- 
cording to  Hofmeister,  the  saliva  of  the  sheep  has  a  digestive  action  on  cellulose. 

Saliva  has  no  action  on  proteids  or  on  fats. 

[Perfectly  healthy  human  saliva  has  no  poisonous  properties.  Those  observers  (/"(/^too-,  Vul- 
plan  and  Gautier),  who  obtained  poisonous  results  by  injecting  human  saliva  into  animals  probably 
used  an  unhealthy  saliva.] 

149.  TESTS  FOR  SUGAR.— (i)  Trommer's  Test  depends  upon  the 
fact  that  in  alkaline  solutions  sugar  acts  as  a  reducing  agent ;  in  this  case  a 
metallic  oxide  is  changed  into  a  suboxide.  To  the  fluid  to  be  investigated,  add  j4 
of  its  volume  of  a  solution  of  caustic  potash  (soda),  specific  gravity  1.25,  and  a 
few  drops  of  a  weak  solution  of  cupric  sulphate,  which  causes  at  first  a  bluish  pre- 
cipitate consisting  of  a  hydrated  cupric  oxide,  but  it  is  redissolved,  giving  a  clear 
blue  fluid,  if  sugar  be  present.  Heat  the  upper  stratum  of  the  fluid,  and  a  yellow 
or  red  ring  of  cuprous  oxide  is  obtained,  which  indicates  the  presence  of  sugar  ; 
2CuO  —  O  =  Cu^O. 

The  solution  of  hydrated  cupric  oxide  is  caused  by  other  organic  substances ;  but  the  final  stai^e, 
or  the  production  of  cuprous  oxide,  is  obtained  only  with  certain  sugars — grape,  fruit  and  milk 
(but  not  cane)  sug.ir.  Fluids  which  are  turbid  must  be  previously  filtered,  and  if  they  are  highly 
colored  they  must  be  treated  with  basic  lead  acetate ;  the  lead  acetate  is  afterward  removed  by  the 
addition  of  sodium  phosphate  and  subsequent  filtration.  If  very  small  quantities  of  sugar  are 
present  along  with  compounds  of  ammonia,  a  yellow  color  instead  of  a  yellow  precipitate  may  be 
obtained.     In  doing  the  test,  care  must  be  taken  not  to  add  too  much  cupric  sulphate. 

[(2)  Fehling's  Solution  is  an  alkaline  solution  of  potassio-tartarate  of  copper. 
Boil  a  small  quantity  of  the  deep-blue  colored  Fehling's  solution  in  a  test  tube, 
and  add  to  the  boiling  test  a  few  drops  of  the  fluid  supposed  to  contain  the  sugar. 
If  sugar  be  present  the  copper  solution  is  reduced,  giving  a  yellow  or  reddish  pre- 
cipitate. The  reason  for  boiling  the  test  itself  is,  that  the  solution  is  apt  to  de- 
compose when  kept  for  some  time,  when  it  is  precipitated  by  heat  alone.  This 
is  one  of  the  best  and  most  reliable  tests  for  the  presence  of  sugar.  In  Pavy's 
modification  of  this  test,  ammonia  is  used  instead  of  a  caustic  alkali  (§  267).] 

(3)  Buttger's  Test. — Alkaline  bismuth  oxide  solution  is  best  prepared,  according  to  Nylander, 
as  follows:  2  grms.  bismuth  subnitrate,  4grms.  potassic  and  sodic  tartrate.  loo  grms.  caustic  soda 
of  8  per  cent.  Add  i  c.c.  to  every  lo  c.c  of  the  fluid  to  be  investigated.  When  boiled  for  several 
minutes,  the  sugar  causes  the  reduction  and  deposits  a  black  precipitate  of  metallic  bismuth.  [Ac- 
cording to  Salkowski  the  urine  of  a  person  taking  rhubarb  gives  the  same  reaction  with  this  test.] 

(4)  Moore  and  Heller's  Test. — Caustic  potash  or  soda  is  added  until  the  mixture  is  strongly 
alkaline  ;  it  is  afterward  boiled.  If  sugar  be  present,  a  yellow,  brown,  or  brownish-black  colora- 
tion is  obtained.  If  nitric  acid  be  added,  the  odor  of  burned  sugar  (caramel)  and  formic  acid  is 
obtained. 

(5)  Mulder  and  Neubauer's  Test. — A  solution  of  indigo-carmine,  rendered  alkaline  with 
sodic  carbonate,  is  added  to  the  sugar  solution  until  a  slight  bluish  col^r  is  obtained.  When  the 
mixture  is  heated  the  color  passes  into  purple,  red  and  yellow.  When  shaken  with  atmospheric  air, 
the  fluid  again  becomes  blue. 

Other  tests  are  described  in  Vol.  ii,  \  266. 

In  all  cases  where  albumin  is  present  it  must  be  removed — in  urine  by  acidulating  with  acetic 
acid  and  boiling;  in  blood,  by  adding  four  times  its  volume  of  alcohol  and  afterward  filtering, 
while  the  alcohol  is  expelled  by  heat. 


SOLEIL-VENTZKE  S    POLARIZATION    APPARATUS. 


247 


150.  QUANTITATIVE  ESTIMATION    OF    SUGAR.— I.  By  Fermentation.— Into 
the  glass  vessel  (Fig.  1^3,  (7)  a  measured  quantity  (20cm.)  of 

the  fluid  (sugar)  is  jilaced  along  with  some  yeast,  while  /'  con-  Fig.  i^JJ. 

tains  concentrated  sulphuric  acid.  The  whole  apparatus  is 
weighed.  When  exposed  to  a  sufficient  temperature  ( 10°  to  40° 
C),  the  sugar  splits  into  two  molecules  of  alcohol  and  two  of 
carbon  dio.xide, 

C,H,  ,Oe  =  2{C,U,0}  +  2(C02), 
grape  sugar  =  2  alcohol  -f-  2  carbon  dioxide;  and  in  addi- 
tion there  are  formed  traces  of  glycerine  and  succinic  acid. 
The  COo  escapes  from  d,  and  as  it  passes  through  the  H^SO.j, 
Coj  yields  to  the  latter  its  water.  The  apparatus  is  weighed 
after  two  days,  when  the  reaction  is  ended,  and  the  amount 
of  sugar  is  calculated  from  the  loss  of  weight  in  the  20  cm. 
of  fluid.  100  parts  of  water-free  sugar  =  4S.89  parts  COj,  or  100  parts  CO,  correspond  to  204.54 
parts  of  sugar. 

Fig.  154. 


App 


Soleil-Ventzke's  polarization  apparatus. 

II.  Titration. — By  means  of  Fehling's  solution,  which  consists  of  cupric  sulphate,  tartrate  of 
potash  and  soda,  caustic  soda,  and  water.  It  is  made  of  such  a  strength  that  all  the  copper  in  10 
cubic  centimetres  of  the  solution  is  reduced  by  0.05  gramme  of  grape  sugar  (I  267). 

III.  Circumpolarization. — The  saccharimeter  of  Soleil-Ventzke  may  be  used  to  determine  the 
amount  of  sugar  present.  It  may  also  be  used  for  the  quantitative  estimation  of  albumin.  Sugar 
rotates  the  ray  of  polarized  light  to  the  right  and  albumin  to  the  left.     The  amount  of  rotation,  or 


248  THE    MOVEMENTS   OF    MASTICATION. 

"specific  rotatory  power,"  is  directly  proportional  to  the  amount  of  the  rotating  substance  present 
in  the  solution,  so  that  the  amount  of  rotation  of  the  rays  indicates  the  amount  of  the  substance 
present. 

In  Fig.  154  the  light  from  the  lamp  falls  upon  a  crystal  of  calc-spar.  Two  Nicol's  prisms  are 
placed  at  v  and  s ;  z*  is  movable  round  the  axis  of  vision,  while  s  is  fixed.  In  m  Soleil's  double 
plate  of  quartz  is  placed  ;  so  that  one-half  of  it  rotates  the  ray  of  polarized  light  as  much  to  the 
right  as  the  other  rotates  it  to  the  left.  In  n  the  field  of  vision  is  covered  by  a  plate  of  left  rotatory 
quartz.  At  (5  c  is  the  co7npensator,  composed  of  two  right  rotatory  prisms  of  quartz,  which  can  be 
displaced  laterally  by  the  milled  head,  y,  so  that  the  polarized  light  pissing  through  the  apparatus 
can  be  made  to  pass  through  a  thicker  or  thinner  layer  of  quartz.  When  these  right  rotatory  prisms 
are  placed  in  a  certain  position,  the  rotation  of  the  left  rotatory  quartz  at  n  is  exactly  neutralized.  In 
this  position  the  scale  on  the  compensator  has  its  nonius  exactly  at  0,  and  both  halves  of  the  double 
plate  at  m  appear  to  have  the  same  color  to  the  observer,  who  from  v  looks  through  the  telescope 
placed  at  e.  Rotate  the  Nicol's  prism  at  t'  until  a  bright  rose  colored  field  is  obtained.  In  this 
position  the  telescope  must  be  so  adjusted  that  the  vertical  line  bounding  the  two  halves  shall  be 
distinctly  visible.     The  apparatus  is  now  ready  for  use. 

Fill  a  tube,  I  decimetre  in  length,  with  urine  containing  sugar  or  albumin,  the  urine  being  per- 
fectly clear.  The  tube  is  placed  between  in  and  n  By  rotating  the  Nicol's  prisms,  v,  the  rose- 
color  is  again  obtained.  The  compensator  at  g  is  then  rotated  until  both  halves  of  the  field  of  vision 
have  exactly  the  same  color.  When  this  is  obtained,  read  ofi"  on  tlie  scale  the  number  of  degrees 
the  nonius  is  displaced  to  the  right  (sugar)  or  to  the  left  (albumin)  from  zero.  The  number  of 
degrees  indicates  directly  the  number  of  grammes  of  the  rotating  susbtance  present  in  100  c.  c.  of 
the  fluid.  If  the  fluid  is  very  dark-colored,  it  must  be  decolorized  by  filtering  it  through  animal 
charcoal  {Sccgen)  [or  the  coloring  matter  may  be  precipitated  by  the  addition  of  lead  acetate.]  If 
the  sugary  urine  contains  albumin,  the  latter  must  be  removed  by  boiling  and  filtration.  A  turbidity 
not  removed  by  filtration  may  be  got  rid  of  by  add;ng  a  drop  of  acetic  acid,  or  several  drops  of 
sodic  carbonate  or  milk  of  lime,  and  afterward  filtering. 

151.  MECHANISM  OF  THE  DIGESTIVE  APPARATUS.— This 

embraces  the  following  acts  :  — 

1.  The  introduction  of  the  food  ;  the  movements  of  mastication  and   those  of 

the  tongue  ;  insalivation  and  the  formation  of  the  bolus  of  food. 

2.  Deglutition. 

3.  The  movements  of  the  stomach,  of  the  small  and  large  intestine. 

4.  The  excretion  of  faecal  matters. 

152.  INTRODUCTION  OF  THE  FOOD.— Fluids  are  taken  into  the 
mouth  in  three  ways:  (i)  By  suction,  the  lips  are  applied  air  tight  to  the  vessel 
containing  the  fluid,  while  the  tongue  is  retracted  (the  lower  jaw  being  often 
depressed)  and  acts  like  the  piston  in  a  suction  pump,  that  causes  the  fluid  to  enter 
the  mouth.  Herz  found, that  the  negative  pressure  caused  by  an  infant  while  sucking 
=  3  to  10  mm.  Hg.  (2)  The  fluid  is  lapped  when  it  is  brought  into  direct  con- 
tact with  the  lips,  and  is  raised  by  aspiration  and  mixed  with  air  so  as  to  produce 
a  characteristic  sound  in  the  mouth.  (3)  Fluid  may  be /('«rf(/  into  the  mouth, 
and,  as  a  general  rule,  the  lips  are  applied  closely  to  the  vessel  containing  the 
fluid. 

The  solids  when  they  consist  of  small  particles  are  licked  up  with  the  lips,  aided 
by  the  movements  of  the  tongue.  In  the  case  of  large  masses,  a  part  is  bitten  off 
with  the  incisor  teeth,  and  is  afterward  brought  under  the  action  of  the  molar 
teeth  by  means  of  the  lips,  cheeks,  and  tongue. 

153.  THE  MOVEMENTS  OF  MASTICATION.— The  articulation  of  the  jaw  is  pro- 
vided with  an  interarticular  cartilage  (  Vidius,  ij6y) — the  meniscus — which  prevents  direct  pressure 
being  made  upon  the  articular  surface  when  the  jaws  are  energetically  closed,  and  which  also 
divides  the  joint  into  two  cavities,  one  lying  over  the  other.  The  capsule  is  so  lax  that,  in  addition 
to  the  raising  and  depressing  of  the  lower  jaw,  it  permits  of  the  lower  jaw  being  displaced  for- 
ward upon  the  articular  tubercle,  whereby  the  meniscus  moves  with  it,  and  covers  the  articular 
surface. 

The  process  of  mastication  consists  of  the  following  movements  : — 

{a)  The  elevation  of  the  jaw  is  accomplished  by  the  combined  action  of  the 
temporal,  masseter,  and  internal  pterygoid  muscles.     If  the  lower  jaw  was  pre- 


STRUCTURE   AND    DEVELOPMENT   OF   THE   TEETH.  249 

viously  so  far  depressed  that  its  articular  surface  rested  upon  the  tubercle,  it  now 
passes  backward  upon  the  articular  surface. 

(/')  The  depression  of  the  lower  jaw  is  caused,  by  its  own  weight,  aided  by 
the  action  of  the  anterior  bellies  of  the  digastrics,  the  mylo-  and  genio-hyoid 
and  platysma  {Hallcr).  The  muscles  act  during  forcible  opening  of  the  mouth. 
The  necessary  fixation  of  the  hyoid  bone  is  obtained  through  the  action  of  the 
omo-and  sterno-hyoid,  and  by  the  sterno-thyroid  and  thyro-hyoid. 

When  the  articular  surface  of  the  lower  jaw  passes  forward  on  to  the  tubercle,  the  external 
pterygoids  actively  aid  in  producing  this  (Berard). 

(c)  Displacement  of  both  or  one  articular  surface  forward  or  back- 
^wa^d. — During  rest,  when  the  mouth  is  closed,  the  incisor  teeth  of  the  lower 
jaw  fall  within  the  arch  of  the  upper  incisors.  When  in  this  position  the  jaw  is 
protruded  by  the  external  pterygoids,  whereby  the  articular  surface  passes  on  to 
the  tubercle  (and,  therefore,  downward),  while  the  lateral  teeth  are  thereby 
separated  from  each  other.  The  jaw  is  retracted  by  the  internal  pterygoids  with- 
out any  aid  from  the  posterior  fibres  of  the  temporals.  When  one  articular  sur- 
face is  carried  forward,  the  jaw  is  protruded  and  retracted  by  the  external  and 
internal  pterygoid  of  the  same  side.  At  the  same  time,  there  is  a  transverse 
movement,  whereby  the  back  teeth  of  the  protruded  side  are  separated  from  each 
other. 

During  mastication,  when  the  individual  movements  of  the  lower  jaw  are  vari- 
ously combined,  the  food  to  be  masticated  is  kept  from  passing  outward  by  the 
action  of  the  muscles  of  the  lips  (orbicularis  oris)  and  the  buccinators,  while  the 
tongue  continually  pushes  the  particles  between  the  molar  teeth.  The  energy  of 
the  muscles  of  mastication  is  regulated  by  the  sensibility' of  the  teeth,  and  the 
muscular  sensibility  of  the  muscles  of  mastication,  as  well  as  by  the  general  sensi- 
bility of  the  mucous  membrane  of  the  mouth  and  lips.  At  the  same  time,  the 
mass  is  mixed  with  saliva,  the  divided  particles  cohere,  and  are  formed  into  a  mass 
or  bolus  of  a  long,  oval  shape,  by  the  muscles  of  the  tongue,  ready  to  be  swallowed. 

Nerves  of  Mastication. — The  muscles  of  mastication  and  the  buccinator  receive  their  motor 
nerves  from  the  third  branch  of  the  trigemirus ;  the  mylo-hyoid  and  the  anterior  belly  of  the  digas- 
tric being  supplied  from  the  same  source.  The  genio-,  omo-,  and  sterno-hyoid,  sternothyroid,  and 
thyro-hyoid  are  supplied  by  the  hypoglossal,  while  the  facial  supplies  the  posterior  belly  of  the  di- 
gastric, the  stylo-hyoid,  the  platysma,  and  the  muscles  of  the  lips.  The  general  centre  for  the 
muscles  of  mastication  lies  in  the  medulla  oblongata  (J  367). 

When  the  mouth  is  closed,  the  jaws  are  kept  in  contact  by  the  pressure  of  the  air,  as  the  cavity 
of  the  mouth  is  rendered  free  from  air,  and  the  entrance  of  air  is  prevented  anteriorly  by  the  lips, 
and  posteriorly  by  the  soft  palate.  The  pressure  e.xerted  by  the  air  is  from  2  to  4  mm.  Hg  (Metzger 
and  Danders). 

[The  process  of  mastication  is  also  influenced  by  guiding  contact  sensations  from  the  mouth.] 

[Effect  on  the  Circulation.— Marey  found  that  mastication  trebled  the  velocity  of  the  blood 
current  in  the  carotid  (horse),  while  Frangois  Frank  observed  that  the  circulation  of  the  brain  (in 
man)  is  increased  ;  hence  it  is  evident  that  mastication  implies  an  increased  supply  of  blood  to  the 
nerve  centres.] 

154.  STRUCTURE  AND   DEVELOPMENT  OF  THE  TEETH.— A  tooth  is  just  a 

papilla  of  the  mucous  membrane  of  the  gum  which  has  undergone  a  characteristic  development. 
In  its  simplest  form,  as  in  the  teeth  of  the  lamprey,  the  connective-tissue  basis  of  the  papilla  is 
covered  with  many  layers  of  corneous  epithelium.  In  human  teeth,  part  of  the  papilla  is  trans- 
formed into  a  layer  of  calcified  dentine,  while  the  epithelium  of  the  papilla  produces  the  enamel, 
the  fang  of  the  tooth  being  covered  by  a  thin  accessory  layer  of  bone,  the  crusta  petrosa  or 
cement. 

The  dentine  or  ivory  which  surrounds  the  pulp  cavity  and  the  canal  of  the  fang  (Fig.  155)  is 
very  firm,  elastic  and  brittle.  The  matrix  of  bone,  dentine,  when  treated  in  a  certain  way,  presents 
a  fibrillar  structure  (ta  £/'«£■;■).  It  is  permeated  by  innumerable  long,  tortuous,  wavy  tubes — the 
dentinal  tubules  \LceHwenhoek,  i6yS) — each  of  which  communicates  with  the  pulp  cavity  by 
means  of  a  fine  opening,  and  passes  more  or  less  horizontally  outward  as  far  as  the  outer  layers  of 
the  dentine.  The  tubules  are  bounded  l)y  an  extremely  resistant,  thin,  cuticular  membrane,  which 
strongly  resists  the  action  of  chemical  reagents.  These  tubules  are  filled  completely  by  soft  fibres, 
the  "fibres  of  Tomes"  (1840),  which  are  merely  greatly  elongated  and  branched  processes 
of  the  odontoblasts  of  the  pulp  ( Waldeyer,  l68j). 


250 


STRUCTURE    AND    DEVELOPMENT   OF   THE    TEETH. 


Pulp  Cavity. 


Fig.  155-  The  dentinal  tubules,  as  well  as  the  fibres  of  Tomes, 

anastomose  throughout  their  entire  extent  by  means 
of  fine  processes.  As  the  fibres  approach  the  enamel, 
which  they  do  not  penetrate,  seme  of  tliem  beml  on 
themselves,  and  form  a  loop  (Fig.  15S,  C),  while 
others  pass  into  the  "  interglobular  spaces  "  (Fig. 
157)  which  are  so  abundant  in  the  outer  part  of  the 
dentine  (Czermak,  iSjo),  The  interglobular  spaces 
are  small  spaces  bounded  by  curved  surfaces.  Cer- 
tain curved  lines,  "  Schreger's  lines  "  (iSoo),  may 
be  detected  with  the  naked  eye  in  the  dentine  (c.  ,^., 
of  the  elephant's  tusk)  running  parallel  with  the 
contour  of  the  tooth.  These  are  caused  by  the 
fact  that  at  these  parts  all  the  chief  curves  in  the 
dentinal   tubules   follow   a   similar  course  (Hetzius, 

The  enamel,  the  hardest  substance  in  the  body 
(resembling  apatite),  covers  the  crown  of  the  teeth. 
It  consists  of  hexagonal  flattened  prisms  (Malpighi, 
iSdf)  arranged  side  by  side  like  a  palisade  (Fig.  15S, 
B  and  C).  They  are  3  to  5  !>■  (3555  inch)  broad, 
not  quite  uniform  in  thickness,  curved  slightly  in  dif- 
ferent directions,  and  owing  to  inequalities  of  thick- 
ness, they  exhibit  transverse  markings.  They  are 
elongated,  calcified,  cylindrical,  epithelial  cells  de- 
rived from  the  dental  papilla.  Retzius  described 
dark  brown  lines  running  par.allel  with  the  outer 
boundary  of  the  enamel,  due  to  the  presence  of 
pigment  (Fig.  155).  The  fully-formed  enamel  is 
negatively  doubly  refractive  and  uniaxial,  while  the 
developing  enamel  is  positively  doubly  refractive 
{Hoppe  SeyleA. 

The  cuticula  or  Nastnyth's  membrane  (1839) 
covers  the  free  surface  of  the  enamel  as  a  completely 

structureless  membrane,  I  to  2  /^  thick,  but  in  quite  young  teeth  it  exhibits  an  epithelial  structure, 

and  is  derived  from  the  outer  epithelial  layer  of  the  enamel  organ. 

Fig.  157. 


Fig.  156. 


Longitudinal  section  of  ; 


1  of  dentine— The 
light  rings  are  the  walls  of  the 
dentinal  tubules  ;  the  dark  cen- 
tres with  the  light  points  are 
the  fibres  of  Tomes  lying  in  the 


Interglobular  spaces  in  dentine  {Schenk). 


The  cement  {John  Hunter^  lyyS)  or  crusta  petrosa,  is  a  thin  layer  of  bone  covering  the  fang 
(Fig.  159,  a).  The  bone  lacunce  communicate  directly  with  the  dental  tubules  of  the  fang. 
Haversian  canals  and  lamellce  are  only  found  where  the  layer  of  cement  is  thick,  and  the  former 
may  communicate  with  the  pulp  cavity  {^Salter).     Very  thin   layers  of  cement  may  be  devoid  of 


CHEMISTRY   OF   A   TOOTH. 


251 


bone  corpuscles.  Sharpey's  fibres  occur  in  the  cement  of  the  dog's  tooth  ( IValdeyer)  ;  while  in  the 
horse's  tooth  single  bone  corpuscles  are  enveloped  by  a  capsule  ( Gerber).  In  the  periodontal 
membrane,  which  is  just  the  periosteum  of  the  alveolus,  coils  of  blood  vessels  similar  to  the  renal 
glomeruli  occur.  They  anastomose  with  each  other,  and  are  surrounded  by  a  delicate  capsule  of 
connective  tissue  (C  IVedl). 


Section  of  a  tooth  bet 


and  enamel,    a,  enamel ;  c,  dentinal  tubules:  B,  ( 
magnified  ;  C,  transverse  sections  of  enamel  prisms. 


el  prisms  highly 


Fig.  159. 


Chemistry  of  a  Tooth.  —The  teeth  consist  of  a  gelatin-yielding  matrix  infiltrated  with  calciuin 
phosphate  and  carbonate  (like  bone),  (i)  The  dentine  contains — organic  matter,  27.70;  calcium 
phosphate  and  carbonate,  72.06 ;  magnesium  phosphate,  0.75,  with  traces  of  iron,  fluorine,  and 
sulphuric  acid  {Acby,  Hofpe-Seyler). 

(2)  The  enamel  contains  an  organic  proteid  matrix 
allied  to  the  substance  of  epithelium.  It  contains  3.60 
organic  matter  and  96.00  of  calctum  phosphate  and  car- 
bonate, 1.05  magnesium  phosphate,  with  traces  of  cal- 
cium fluoride  and  an  insoluble  chlorine  compound. 

(3)  The  cement  is  identical  with  bone. 

The  Pulp  in  a  fully  grown  tooth  represents  the  re- 
mainder of  the  dental  papilla  around  which  the  dentine 
was  deposited.  It  consists  of  a  very  vascular,  indis- 
tinctly fibrillar  connective  tissue,  laden  with  cells.  The 
layers  of  cells,  resembling  epithelium,  which  lie  in  direct 
contact  with  the  dentine,  are  called  odontoblasts  ( IVal- 
deyer, iS6^),  i.  e.,  those  cells  which  build  up  the  dentine. 
The  cells  send  off"  longbranched  processes  into  the  den- 
tinal tubules,  while  their  nucleated  bodies  he  on  the  sur- 
face of  the  pulp,  and  form  connections  by  processes  with 
other  cells  of  the  pulp  and  with  neighboring  odonto- 
blasts. Numerous  non-meduUated  nerve  fibres  (.sensory 
from  the  trigeminus)  whose  mode  of  termination  is 
unknown,  occur  in  the  pulp. 

The  periosteum  or  periodontal  membrane  of  the  fang  is,  at  the  same  time,  the  alveolar  peri- 
osteum, and  consists  of  delicate  connective  tissue,  with  few  elastic  fi'Dres  and  many  nerves. 

The  gums  are  devoid  of  mucous  glands,  very  vascular,  and  often  provided  with  long  vascular 
papilla?,  which  are  sometimes  compound. 

Development  of  a  Tooth. — It  begins  at  the  end  of  the  second  month  of  fcetal  life.  Along  the 
whole  length  of  the  fcetal  gum  is  a  thick  projecting  ridge  (Fig.  160,  a'),  composed  of  many  layers 
of  epithelium.  A  depression,  the  denial  groove,  also  filled  with  epithelium,  occurs  in  the  gum,  and 
runs  along  under  the  ridge.  The  dental  groove  becomes  deeper  throughout  its  entire  length,  and, 
on  transverse  section,  presents  the  appearance  of  a  dilated  flask  (b),  while,  at  the  same  time,  it  is 
filled  with  elongated  epithelial  cells,  which  form  the  "  enamel  organ."  A  conical  ])apiUa.>  (the 
"  dentine  germ  "  grows  up  from  the  mucous  tissue,  of  which  the  gum  consists,  toward  the  enamel 
organ  (Fig.  161,  <-),  so  that  the  apex  of  the  papilla  comes  to  have  the  enamel  organ  resting  upon  it, 
like  a  double  cap.     Afterward,  owing  to  the   development  of  connective  tissue,  the  parts  of  the 


ansverse  section  of  the  fang, 
bone  corpuscles  ;  6,  dentini 
tubules  :  c,  boundary  betwe 


252 


ERUPTION    OF   THE   TEETH. 


enamel  organ  lying  between  and  uniting  the  individual  dentine  germs  disappear,  and  gradually 
the  connective  tis'^ue  forms  a  tooth  sac  enclosing  the  papilla  and  its  enamel  organ  (</). 

Those  epithelial  cells  (Fig.  i6i,  3)  of  the  enamel  organ  which  lie  next  the  top  of  the  papilla,  are 
cylindrical,  and  become  calcified  to  form  enamel  prisms.  The  layer  of  cells  of  the  double  cap, 
which  is  directed  toward  the  tooth  sac  (l),  becomes  flattened,  fuses,  undergoes  a  horny  transforma- 
tion, and  becomes  the  cuticula,  while  the  cells  which  lie  between  both  layers  undergo  an  interme- 
diate metamorphosis,  so  that  they  come  to  resemble  the  branched  stellate  cells  of  the  mucous  tissue 
(2),  and  gradually  disappear  altogether. 

The  dentine  is  formed  in  the  most  superficial  layer  of  the  projecting  connective  tissue  of  the 
dental  papilla,  owing  to  the  calcification  of  the  continuous  layer  of  odontoblasts  which  occur  there 
(Figs.  161  and  162,  /').  During  the  process,  fibres  or  branches  of  these  cells  are  left  unaffected, 
and  remain  as  the  fibres  of  Tomes.  Exactly  the  same  process  occurs  as  in  the  formation  of  bone, 
the  odontoblasts  forming  around  themselves  a  calcified  matrix.  The  cement  is  formed  from  the 
soft  connective  tissue  of  the  dental  alveolus. 

Dentition. — During  the  development  of  the  first  (temporary  or  milk)  teeth,  a  special  enamel 
organ  (Fig.  i6r,  e)  is  formed  near  these,  but  it  does  not  undergo  development  until  the  milk  teeth 
are  shed ;  even  the  papilla  is  wanting  at  first.  When  the  permanent  tooth  begins  to  develop,  it 
opens  into  the  alveolar  wall  of  the  milk  teeth  from  below. 

The  tissue  of  this  dental  sac  causes  erosion,  or  eating  away  of  the  fang,  and  even  of  the  body,  of 
the  milk  teeth,  without  its  blood  vessels  undergoing  atrophy.  The  chief  agents  in  the  absorption 
are  the  amreboid  cells  of  the  granulation  tissue.  [Multinuclear  giant  cells  also  erode  the  fangs  of 
the  teeth.] 

Fig.  160.  Fig.  16:.  Fig.  162. 


Dental  ridge ;  i,  enamel 
organ  ;  c,  beginning  of  the 
dentine  germ  ;  d,  first  indi- 
cation of  the  tooth  sac. 


,  Dental  ridge;  ^,  enamel  organ  with  (i) 
outer  epithelium,  (2)  middle  stellate 
layer,  {3)  enamel  prism  cell  layer ;  c, 
dentine  germ  with  blood  vessels  and 
the  long  osteoblasts  on  the  surface  ;  rf, 
tooth  sac  :  e,  secondary  enamel  germ. 


,  Dental  ridge  ; 


5V. ,  .,,  ^......lel  organ  ; 

-, ..J  germ  ;  /,  enamel;  ^, 

dentine;  h,  interval  between 
enamel  organ  and  the  position 
of  the  tooth  ;  k,  layer  of  odon- 
toblasts. 


Eruption  of  the  Teeth. — The  following  is  the  order  in  which  the  twenty  milk  teeth  cut  the 
gum,  /.«'.,  from  the  seventh  month  to  the  second  year:  Lower  central  incisors,  upper  central  incisors, 
upper  lateral  incisors,  lower  lateral  incisors,  first  molar,  canine,  the  second  molars. 

[The  figures  indicate  in  months  the  period  of  eruption  of  each  tooth.] 


Molars. 

Canines. 

Incisors. 

Canines. 

Molars. 

24      12 

18 

9  7  7  9                        "8 

24       12 

[The  permanent  teeth  succeed  the  milk  teeth,  the  process  beginning  about  the  jrew^/Z/wrtr. 
Ten  teeth  in  each  jaw  take  the  place  of  the  milk  teeth,  while  six  teeth  appear  further  back  in  each 
jaw.  Thus,  the  total  number  of  permanent  teeth  is  thirty-two.  As  the  sacs  from  which  the  perma- 
nent teeth  are  developed  are  formed  before  birth,  they  merely  undergo  the  same  process  of  devel- 
opment as  the  teinporary  teeth,  only  at  a  much  later  period.  The  last  of  the  permanent  molars — 
the  -L'isdom  tooth— m:\y  not  cut  the  jaw  until  the  scventectith  to  the  twenty-fifth  year.  At  the  sixth 
year  the  jaw  contains  the  largest  number  of  teeth,  as  all  the  temporary  teeth  are  present,  and.  in 
addition,  the  crowns  of  all  the  pemianent  teeth,  except  the  wisdom  tooth,  making  forty-eight  in  all.] 

[Eruption  of  Permanent  Teeth. — The  age  at  which  each  tooth  cuts  the  gum  is  given  in  years 
in  the  following  table  : — 


MOVEMENTS    OF   THE    TONGUE. 


253 


Molars. 

Bicuspid. 

Canines. 

Incisors. 

Canines. 

Bicuspid. 

Molars. 

17       12 
to      to     6 
25      '3 

10     9 

II   to   12 

8778 

II   to    12 

9      10 

12      17 

6     to     to 

13  25 

[Action  of  Drugs  on  the  Teeth. — All  the  conditions  for  putrefaction  are  evidently  present  in 
the  moulh,  and  when  putrefaction  occurs,  the  products  (often  acid)  attack  the  dentine  of  the  teeth 
and  hasten  their  decay.  Hence,  the  necessity  for  thorough  daily  cleansing  of  the  teeth  and  moulh. 
The  teeth  may  be  cleaned  by  means  of  a  soft  tooth  brush  and  water,  with  or  without  the  use  of  any 
of  the  numerous  dentifrices,  such  as  powdered  chalk  or  charcoal.  Astringents,  such  as  catechu 
and  areca  nut,  are  sometimes  used.  Mineral  acids,  of  course,  attack  the  teeth,  and  ought,  when 
taken,  to  be  sucked  through  a  tube.] 

155.  MOVEMENTS  OF  THE  TONGUE.— The  tongue,  being  a  mus- 
cular organ  (^Arctaeus,  .A..D.  81),  and  extremely  mobile,  plays  an  important  part 
in  the  process  of  mastication  :  (i)  It  keeps  the  food  from  passing  from  between 
the  molar  teeth.  (2)  It  collects  into  a  bolus  the  finely  divided  food  after  it  is 
mixed  with  saliva.  (3)  When  the  tongue  is  raised,  the  bolus  lying  on  its  dorsum 
is  pushed  backward  into  the  pharynx,  whence  it  passes  into  the  oesophagus. 

The  muscular  fibres  of  the  tongue  run  in  three  directions — longifiidinalty,  from 
base  to  tip ;  transversely,  the  fibres  for  the  most  part  proceeding  outward  from  the 
vertically  placed  septum  linguae ;  vertically,  from  below  upward.  Some  of  the 
muscles  are  confined  to  the  tongue  (intrinsic),  while  others  (extrinsic)  are  attached 
beyond  it  to  the  hyoid  bone,  lower  jaw,  the  styloid  process,  and  the  palate. 

Microscopically,  the  fibres  are  transversely  striated,  with  a  delicate  sarcolemma,  and  very  often 
they  are  divided  where  they  are  inserted  into  the  mucous  membrane  [Lt'c-iru'en/wei).  The  muscu- 
lar bundles  cross  each  other  in  various  directions,  and  in  the  interspaces  fat  cells  and  glands  occur. 

On  analyzing  the  lingual  movements,  we  may  distinguish  changes  in  form  and 
changes  in  position  :  — 

(ij  Shortening  and  broadening  by  the  longitudinal  muscle,  aided  by  the  hyo- 
glossus. 

(2)  Elongation  and  narrowing,  by  the  transversus  lingua. 

( 3 )  The  dorsum  rendered  concave  by  the  transversus  and  the  simultaneous  action 
of  the  median  vertical  fibres. 

(4)  Arching  of  the  dorsum — (a)  Transversely,  by  contraction  of  the  lowest 
transverse  bundles ;  {li)  longitudinally,  by  the  action  of  the  lowest  longitudinal 
muscles. 

(5)  Protrusion,  by  the  genio-glossus,  while  at  the  same  time  the  tongue  usually 
becomes  narrower  and  longer  (2). 

(6)  Retraction,  by  the  hyo-glossus  and  stylo-glossus,  and  (i)  usually  occurring 
at  the  same  time. 

(7)  Depression  of  the  tongue  into  the  floor  of  the  mouth,  by  the  hyo-glossus. 
The  floor  of  the  mouth  may  be  made  deeper  by  simultaneously  depressing  the 
hyoid  bone. 

(8)  Elevation  of  the  tongue  toward  the  gums — {a)  At  the  tip  by  the  anterior 
part  of  the  longitudinal  fibres;  {b)  in  the  middle  by  elevating  the  entire  hyoid 
bone  by  the  mylo-hyoid  {N.  trigemhiiis)  ;  {c)  at  the  root  by  the  stylo-glossus  and 
palato-glossus,  as  well  as  indirectly  by  the  stylo-hyoid  {N.  facialis). 

(9)  Lateral  movements,  whereby  the  tip  of  the  tongue  passes  to  the  right  or 
left ;  these  are  caused  by  the  contraction  of  the  longitudinal  fibres  of  one  side. 

Motor  Nerves. — The  proper  motor  nerve  of  the  tongue  is  the  hypoglossal.  When  this  nerve  is 
divided  or  paralyzed  on  one  side,  the  tip  of  the  tongue  lying  in  the  floor  of  the  mouth  is  directed 
toward  the  sound  side,  because  the  tonus  of  the  non- paralyzed  longitudinal  fibres  shortens  the  sound 
side  slightly.  If  the  tongue  be  /;'o/;-«(/f</,  however,  the  tip  passes  toward  \\\^  paralyzed  i\At.  This 
arises  from  the  direction  of  the  genio-glossus  (from  the  middle  downward  and  outward),  and  the 


254  DEGLUTITION. 

tongue  follows  the  direction  of  its  action.     The  tongues  of  animals  which  have  been  killed  exhibit 
fibrillar  conlraclioiis  of  the  muscles,  sometimes  lasting  for  a  whole  day  {^Cardonus,  ^55^)- 

156.  DEGLUTITION. — The  onward  movements  of  the  contents  of  the 
digestive  canal  are  effected  by  a  special  kind  of  action  whereby  the  tube  or  canal 
contracts  upon  its  contents,  and  as  this  contraction  proceeds  along  the  tube,  the 
contents  are  thereby  carried  along.  This  is  the  "  peristaltic  movement,"  or 
peristalsis. 

In  the  first  and  most  complicated  part  of  the  act  of  deglutition,  we  distinguish 
in  order  the  following  individual  movements  : — 

(i)  The  aperture  of  the  mouth  is  closed  by  the  orbicularis  oris  (iV.  facialis). 

(2)  The  jaws  are  pressed  against  each  other  by  the  muscles  of  mastication  \^N. 
trigeminus),  while  at  the  same  time  the  lower  jaw  affords  a  fixed  point  for  the  ac- 
tion of  the  muscles  attached  to  it  and  the  hyoid  bone. 

(3)  The  tip,  middle,  and  root  of  the  tongue,  one  after  the  other,  are  pressed 
against  the  hard  palate,  whereby  the  contents  of  the  mouth  are  propelled  toward 
the  pharynx. 

(4)  When  the  bolus  has  passed  the  anterior  palatine  arch  (the  mucus  of  the 
tonsillar  glands  making  it  slippery  again),  it  is  prevented  from  returning  to  the 
mouth  by  the  palato-glossi  muscles,  which  lie  in  the  anterior  pillars  of  the  fauces, 
coming  together  like  two  side-screens  or  curtains,  meeting  the  raised  dorsum  of 
the  tongue  (Stylo-glossus — Dzoiuii,  i8ji). 

(5)  The  morsel  is  now  behind  the  anterior  palatine  arch  and  the  root  of  the 
tongue,  and  has  reached  the  pharynx,  where  it  is  subjected  to  the  successive  action 
of  the  three  pharyngeal  constrictor  muscles  which  propel  it  onward.  The  action 
of  the  superior  constrictor  of  the  pharynx  is  always  combined  with  a  horizontal 
elevation  (^Levator  veli  palatini  ;  N.  facialis),  and  tension  (Tensor  veli  palatini ; 
N.  trigeminus,  otic  ganglion)  of  the  soft  palate  {Bidder,  l8j8).  The  upper  con- 
strictor presses  (^through  the  pterygo-pharyngeusj  the  posterior  and  lateral  walls  of 
the  pharynx  tightly  against  the  posterior  margin  of  the  horizontal  tense  soft  palate 
{Fassavant),  whereby  the  margins  of  the  posterior  palatine  arches  (palato-pharyn- 
geus)  are  approximated.  The  pharyngo-nasal  cavity  is  thus  completely  shut  off, 
so  that  the  bolus  cannot  be  pressed  backward  into  the  nasal  cavity. 

In  persons  with  congenital  or  acquired  defects  of  the  soft  palate,  or  cleft-palate,  during  swallow- 
ing food  passes  into  the  nose. 

I'he  Elevation  of  the  Soft  Palate  may  be  demonstrated  by  placing  a  light  straw  along  the 
floor  of  the  nose,  so  that  its  posterior  end  rests  on  the  soft  palate. 

During  swallowing,  the  end  projecting  from  the  nose  descends,  because  of  the  elevation  of  the 
end  resting  on  the  soft  palate. 

(6)  Falk  and  Kronecker  assert  that,  by  the  energetic  contraction  of  the  muscles 
which  diminish  the  cavity  of  the  mouth,  especially  the  mylo-hyoid,  the  bolus  is 
projected  into  the  pharynx  and  cesophagus. 

If  we  make  a  series  of  efforts  to  swallow,  one  after  the  other  (as  in  drinking), 
contraction  of  the  pharynx  and  oesophagus  takes  place  only  after  the  last  effort. 

Thus,  each  new  act  of  deglutition  in  the  mouth  inhibits  (by  stimulation  of  the  glossopharyngeal 
nerve)  the  movements  in  the  parts  of  the  esophageal  tube  situated  below  11. 

(7)  The  bolus  is  propelled  onward  by  the  successive  contraction  of  the  upper, 
middle,  and  lower  constrictors  of  the  pharynx  until  it  passes  into  the  ojsophagus. 
At  the  same  time  the  entrance  to  the  glottis  is  closed,  else  the  morsel  would  pass 
into  the  larynx,  or,  as  is  generally  said,  would  "pass  the  wrong  way." 

Duration. — According  to  Meltzer  and  Kronecker,  the  duration  of  deglutition  in  the  mouth  is 
0.3  sec;  then  the  constrictors  of  the  pharynx  contract  0.9  sec;  afterward,  the  upper  part  of  the 
oesophagus;  then  after  I.S  sec.  the  middle;  and  after  another  3  sec  the  lower  constrictor.  The 
closure  of  the  cardia,  after  the  entrance  of  the  bolus  into  the  stomach,  is  the  final  act  in  the  total 
series  of  movements. 

Sounds  during  Deglutition. — If  the  region  of  the  stomach  be  auscultated,  during  the  act  of 
swallowing  two  sounds  may  be  heard;  the  hrst  one  is  produced  when  the  bolus  is  projected  into 


NERVES  CONCERNED  IN  DEGLUTITION.  255 

the  stomach ;  the  second  occurs  when  the  peristalsis,  which  takes  place  at  the  end  of  swallowing, 
squeezes  the  contents  of  the  oesophagus  through  the  cardia  (Meltzer,  Zenker,  Ewald). 

The  closure  of  the  glottis  is  effected  in  the  following  manner:  (<7)  The 
whole  larynx — the  lower  jaw  being  fixed — is  raised  upward  and  forward,  while  at 
the  sime  time  the  root  of  tlie  tongue  hangs  over  it.  The  hyoid  bone  is  raised 
forward  and  upward  by  the  genio-hyoid,  anterior  belly  of  the  digastric  and  mylo- 
hyoid ;  the  larynx  is  approximated  close  to  the  hyoid  bone  by  the  thyro-hyoid 
{Berengar,  ij2i).  {l/)  When  the  larynx  is  raised  so  that  it  comes  to  lie  below 
the  overhanging  root  of  the  tongue,  the  epiglottis  is  pressed  downward  over  the 
entrance  to  the  glottis,  and  the  bolus  passes  over  it.  In  addition,  the  epiglottis 
is  pulled  down  by  the  special  muscular  fibres  of  the  reflector  epiglottidis  and 
aryepiglotticus  {T/iie/c). 

Injury  to  the  Epiglottis. — Intentional  injury  of  the  epiglottis  in  animals,  or  its  destruction  in 
man,  may  cause  fluids  to  "go  the  wrong  way,"  /.  e.,  into  the  glottis,  while  solid  food  can  be  swal- 
lowed without  disturbance.  In  dogs,  at  any  rate,  colored  fluids  placed  on  the  root  of  the  tongue 
have  been  observed  to  pass  directly  into  the  pharynx  without  coming  into  contact  with  it,  so  as  to 
tinge  the  upper  surface  of  the  epiglottis  {Mogcnc/u;  Schiff).  [The  basis  of  the  epiglottis  is  yellow 
elastic  cartilage,  so  that  it  shows  no  tendency  to  ossify,  and  always  retains  its  elasticity.] 

{c)  Lastly,  the  closure  of  the  glottis  by  the  constrictors  of  the  larynx  (§  313, 
II,  2)  also  prevents  the  entrance  of  substances  into  the  larynx  i^Czermak). 

In  order  that  the  descending  bolus  may  be  prevented  from  carrying  the  pharynx 
with  it,  the  stylo-pharyngeus,  salpingo-pharyngeus,  and  baseo-pharyngeus  contract 
upward  when  the  constrictors  act. 

Nerves. — Deglutition  is  voluntary  only  during  the  time  the  bolus  is  in 
the  mouth.  When  the  food  passes  through  the  palatine  arch  into  the  gullet 
the  act  becomes  involuntary,  and  is,  in  fact,  a  well-regulated  reflex  action. 
When  there  is  no  bolus  to  be  swallowed,  voluntary  movements  of  deglutition  can 
be  accomplished  only  within  the  mouth  ;  the  pharynx  only  takes  up  the  move- 
ment provided  a  bolus  (food  or  saliva),  mechanically  excites  the  reflex  act.  The 
afferent  nerves,  which,  when  mechanically  stimulated,  excite  the  involuntary  act 
of  deglutition,  are,  according  to  Schrceder  van  der  Kolk,  the  palatine  branches  of 
the  trigeminus  (from  the  spheno-palatine  ganglion)  and  the  pharyngeal  branches 
of  the  vagus  (^Waller,  Prevost).  The  centre  for  the  nerves  concerned  (for  the 
striped  muscles)  lies  in  the  superior  olives  of  the  medulla  oblongata.  Swallowing 
can  be  carried  out  when  a  person  is  unconscious,  or  after  destruction  of  the  cere- 
brum, cerebellum,  and  pons  (§  367,  6).  [Even  in  the  deep  coma  of  alcoholism, 
the  tube  of  a  stomach  pump  is  readily  carried  into  the  stomach  reflexly,  provided 
the  surgeon  passes  it  back  into  the  pharynx,  to  bring  it  within  the  action  of  the 
constrictors  of  the  pharynx.] 

The  nerves  of  the  pharynx  are  derived  from  the  pharyngeal  plexus,  which 
receives  branches  from  the  vagus,  glosso-pharyngeal,  and  sympathetic  (S  352,  4). 

Within  the  oesophagus,  whose  stratified  epithelium  is  moistened  with  the  mucus 
derived  from  the  mucous  glands  in  its  walls,  the  downward  movement  is  involun- 
tary, and  depends  upon  a  complicated  reflex  movement  discharged  from  the  centre 
for  deglutition.  There  is  a  peristaltic  movement  of  the  outer  longitudinal  and 
inner  circular  non-striped  muscular  fibres. 

In  the  upper  part  of  the  oesophagus,  which  contains  striped  muscular  fibres,  the  peristalsis  takes 
place  more  quickly  than  in  the  lower  part.  The  movements  of  the  oesophagus  never  occur  inde- 
pendently, but  are  always  the  continuation  of  a  foregoing  act  of  deglutition.  If  food  be  introduced 
into  the  cesophagus  through  a  hole  in  its  wall, there  it  hes;  and  it  is  only  carried  downward  when  a 
movement  to  swallow  is  made  {  Volkmann).  The  peristalsis  extends  along  the  whole  length  of  the 
oesophagus,  even  when  it  is  ligatured  or  when  a  part  of  it  is  removed  {jUosso).  If  a  dog  be  allowed 
to  swallow  a  piece  of  flesh  tied  to  a  string,  so  that  the  flesh  goes  half-way  down  the  cesophagus,  and 
if  the  flesh  be  withdrawn,  the  peristalsis  still  passes  downward  (C.  Ludwig  and  iVi/d). 

The  motor  nerve  cf  the  oesophagus  is  the  vagus  (not  the  accessory  fibres) ;  after  it  is  divided, 
the  food  lodges  in  the  lower  part  of  trie  oesophagus,  Very  large  and  very  small  masses  are  swal- 
lowed with  more  difticulty  than  those  of  moderate  size.     Dogs  can  swallow  an  olive-shaped  body 


256 


MOVEMENTS   OF   THE    STOMACH. 


weighted  with  a  counterpoise  of  450  grammes  (Afosso).  When  the  thorax  is  greatly  distended,  as 
in  Miiller's  experiment,  or  greatly  diminished,  as  in  Valsilva's  experiment  (§  60),  deglutition  is 
rendered  more  difficult. 

Gollz  observed  that  the  cesophagus  and  stomach  (frog)  became  greatly  more  excitable,  ;'.  e.,  the 
excitability  of  the  ganglionic  plexuses  in  their  walls  was  increased,  when  the  brain  and  spinal  cord 
or  both  vagi  were  destroyed.  These  organs  contracted  energetically  after  slight  stimulation,  while 
frogs,  whose  central  nervous  system  was  intact,  swallowed  fluids  simply  by  peristalsis.  Females  and 
sometimes  men  also,  with  marked  weakening  of  the  nervous  system,  as  in  hysteria,  not  unfrequently 
have  .similar  spasmodic  contractions  of  the  cesophageal  region  (globus  hysto-icus).  After  section  of 
both  vagi,  Schiff  observed  spasmodic  contraction  of  the  oesophagus. 

Every  time  one  swallows  the  heart's  action  is  accelerated,  the  blood  pressure  falls,  the  necessity 
for  respiration  diminishes,  while  many  movements  (labor  pains,  erection)  are  inhibited.  These 
effects  are  brought  about  reflexly  [Kronecker  and  Meltzer,  \  369). 

[Structure  of  the  (Esophagus. — The  walls  of  the  cesophagus  are  composed  of  three  coats — 
mucous,  submucous,  and  muscular  (Fig.  163). 

The  mucous  coat  is  firm  and  is  thrown  into  longitudinal  folds,  which  disappear  when  the  tube 
is  distended.  It  is  lined  by  several  layers  of  stratified  squamous  epithelium.  The  membrane  itself 
is  composed,  especially  at  its  inner  pari,  of  dense  fibrous  tissue,  which  projects  in  the  form  of  pa- 
pilla;, into  the  stratified  epithelium.  At  its  outer  part  is  a  continuous  layer  of  non-striped  muscle, 
the  muscularis  mucosir. 

The  sub-mucous  coat  is  thicker  than  the  foregoing,  and  consists  of  loose  connective  tissue,  with 


Excretory  duct 


Connective 

witti  papilla:. 


Mucous  gland.      — 


Transverse  section  of  part  of  the  cesophagus  [Schenk). 

the  acini  of  small  compound  tubular  mucous  glands  imbedded  in  it.  The  ducts  pierce  the  muscu- 
laris  mucos£e  to  open  on  the  inner  surface  of  the  tube. 

The  muscular  coat  consists  of  an  inner,  thicker,  circular,  and  an  outer,  thinner,  longitudinal 
layer  of  non-striped  muscle.  In  man  the  upper  third  of  the  gullet  consists  of  striped  muscular 
fibres.     Outside  the  muscular  coat  is  a  layer  of  fibrous  tissue  with  elastic  fibres. 

As  in  the  intestine,  there  are  two  plexuses  of  nerves  with  ganglia;  one  in  the  sub-mucous  coat 
(A/eissnc'i-'s)  and  the  other  between  the  two  muscular  coats  [Aueriac/i's),  which  arecontmuous  with 
those  in  the  stomach  and  intestine.  Blood  vessels  and  numerous  lymphatics  lie  in  the  mucous  and 
sub-mucous  coats.] 

157.    MOVEMENTS  OF  THE   STOMACH.— Position.— When  the 

stomach  is  empty,  the  great  curvature  is  directed  downward  and  the  lesser  up- 
ward ;  but  when  the  organ  is  full,  it  rotates  on  an  axis  running  horizontally 
through  the  pylorus  and  cardia,  so  that  the  great  curvature  appears  to  be  directed 
to  the  front  and  the  lesser  backward. 

Arrangement  of  the  Muscular  Fibres. — The  non-striped  muscular  fibres  of  the  stomach  are 
arranged  in  three  directions  or  layers,  an  outer  longitudinal  continuous  with  those  of  the  oeso- 
phagus. This  layer  is  best  developed  along  the  curvatures,  especially  the  lesser.  At  the  pylorus 
the  fibres  form  a  thick  layer,  and  become  continuous  with  the  longitudinal  fibres  of  the  duodenum. 
The  circular  fibres  form  a  complete  layer,  but  at  the  pylorus  they  are  well  marked,  and  constitute 


VOMITING.  257 

the  pyloric  sphincter  muscle,  or  valve  ;  while  at  the  cardia  (inlet),  such  a  muscular  ring  is  absent 
(Gianuzzi).     The  innermost  oblique  or  diagonal  layer  is  incomplete. 

The  movements  of  the  stomach  are  of  two  kinds — (i)  The  rotatory 
or  churning  movements,  whereby  the  parts  of  the  wall  of  the  stomach  lying  in 
contact  with  the  contents  or  ingesta  glide  to  and  fro  with  a  slow  rubbing  move- 
ment. Such  movements  seem  to  occur  periodically,  every  period  lasting  several 
minutes  {Beaumont).  By  these  movements  the  contents  are  moistened  with  the 
gastric  juice,  while  the  masses  of  food  are  partly  broken  down.  The  formation  of 
hair  balls  in  the  stomach  of  dogs  and  oxen  indicates  that  such  rotatory  movements 
of  the  contents  of  the  stomach  take  place.  (2)  The  other  kind  of  movement 
consists  in  a  periodically  occurring  peristalsis,  whereby,  as  with  a  push,  the  por- 
tions of  the  contents  of  the  stomach  first  dissolved  are  forced  into  the  duodenum. 
They  begin  after  a  quarter  of  an  hour  {Biisch),  and  recur  until  about  five  hours 
after  a  meal  {Beatimonf).  This  peristalsis  is  most  pronounced  toward  the  pyloric 
end,  and  the  muscles  of  the  pyloric  sphincter  relax  to  allow  the  contents  to  pass 
into  the  duodenum.  According  to  Riidinger,  the  longitudinal  muscular  fibres, 
when  they  contract,  especially  when  the  pyloric  end  is  filled,  may  act  so  as  to 
dilate  the  pylorus. 

Gizzard. — The  strongly  muscular  walls  of  the  stomach  of  grain-eating  birds  effect  a  trituration 
of  the  food.  The  mechanical  force  thereby  e.xerted  was  often  experimented  upon  by  the  older 
physiologists,  who  found  that  glass  balls  and  lead  tubes,  which  could  be  compressed  only  by  a 
weight  of  40  kilos.,  were  broken  or  compressed  in  the  stomach  of  a  turkey. 

Influence  of  Nerves  on  the  Movements. — ^[The  stomach  is  supplied  by 
the  vagi  and  by  the  sympathetic,  the  right  vagus  being  distributed  to  the  posterior 
surface,  and  the  left  to  the  anterior  surface,  of  the  organ.]  'Y\\^  ganglionic  plexus 
of  nerve  fibres  and  nerve  cells  {Aucrliaeh' s),  which  lies  between  the  muscular 
coats  of  the  stomach,  must  be  regarded  as  its  proper  motor  centre,  and  to  it  motor 
impulses  are  conducted  by  the  vagi.  Section  of  both  vagi  does  not  abolish,  but  it 
diminishes  the  movements  of  the  stomach.  The  muscular  fibres  of  the  cardia  may 
be  excited  to  action,  or  their  action  inhibited,  by  fibres  which  run  in  the  vagus 
(Nn.  constrictores,  et  dilatator  cardire),  (<'.  Openchowski).  [If  the  vagi  be  divided 
in  the  neck,  there  is  a  short  temporary  spasmodic  contraction  of  the  cardiac  aper- 
ture. On  stimulating  the  peripheral  end  of  the  vagus  with  electricity,  after  a 
latent  period  of  a  few  seconds,  the  cardiac  end  contracts,  more  especially  if  the 
stomach  be  distended,  but  the  movements  are  slight  if  the  stomach  be  empty.  In 
curarized  dogs,  the  pylorus  contracts  with  varying  intensity,  and  irregularly 
whether  the  vagi  and  splanchnics  be  intact  or  divided.  Stimulation  of  the  vagi 
in  the  neck  causes  contraction  of  the  pylorus,  when  the  latent  period  inay  be  seven 
seconds.  Stimulation  of  the  splanchnics  in  the  thorax  arrests  the  spontaneous 
pyloric  contractions,  the  left  splanchnic  being  more  active  than  the  right  ((9j«'). 

Stimulation  of  the  cceliac  plexus  causes  moveinents  in  the  stomach  of  ruminants 
(JEckhard ),  perhaps  indirectly  through  the  effect  upon  the  blood  vessels. 

Local  electrical  stimulation  of  the  surface  of  the  stomach  causes  circular  constrictions  of  the 
organ,  which  disappear  very  gradually,  while  the  movement  is  often  propagated  to  other  parts  of 
the  gastric  wall.  When  heated  to  25°  C,  the  excised  empty  stomach  exhibits  movements  (Calli- 
iurces).  Injury  to  the  pedunculi  cerebri,  optic  thalamus,  medulla  oblongata,  and  even  to  the  cer- 
vical part  of  the  spinal  cord,  according  to  SchifT,  causes  paralysis  of  the  vessels  of  certain  areas  of 
the  stomach,  resulting  in  congestion  and  subsequent  hemorrhage  into  the  mucous  membrane.  [It 
is  no  uncommon  occurrence  to  find  hemorrhage  into  the  gastric  mucous  membrane  of  rabbits,  alter 
they  have  been  killed  by  a  violent  blow  on  the  head.] 

158.  VOMITING. — Mechanism. — Vomiting  is  caused  by  contraction  of 
the  walls  of  the  stoinach,  whereby  the  pyloric  sphincter  is  closed.  It  occurs  most 
easily  when  the  stomach  is  distended — (dogs  usually  greatly  distend  the  stomach 
by  swallowing  air  before  they  vomit ) ;  it  readily  occurs  in  infants,  in  whom  the 
cul-de-sac  at  the  cardia  is  not  developed.  It  is  quite  certain  that  in  children 
vomiting  occurs  through  contraction  of  the  walls  of  the  stomach  without  the 
17 


258  VOMITING. 

spasmodic  action  of  the  abdominal  walls.  When  the  vomiting  is  violent,  the 
abdominal  muscles  act  energetically.  [The  act  of  vomiting  is  generally  preceded 
by  a  feeling  of  nausea,  and  usually  there  is  a  rush  of  saliva  mto  the  mouth,  caused 
by  a  reflex  stimulation  of  afferent  fibres  in  the  gastric  branches  of  the  vagus,  the 
efferent  nerve  being  the  chorda  tympani.  After  this  a  deep  inspiration  is  taken, 
and  the  glottis  closed,  so  that  the  diaphragm  is  firmly  pressed  downward  against 
the  abdominal  contents,  and  it  is  kept  contracted  ;  the  lower  ribs  are  pulled  in. 
The  diaphragm  being  kept  contracted  and  the  glottis  closed,  a  violent  expiratory 
effort  is  made,  so  that  the  contraction  of  the  abdominal  muscles  acts  upon  the 
abdominal  contents  the  stomach  being  forcibly  compressed.  The  cardiac  orifice 
is  opened  at  the  same  time,  and  the  contents  of  the  stomach  are  ejected.  The 
chief  agent  seems  to  be  the  abdominal  compression,  but  the  walls  of  the  stomach 
also  help,  though  only  to  a  slight  extent.] 

The  contraction  of  the  walls  of  the  stomach,  which  causes  a  general  diminution  of  the  gastric 
cavity,  is  not  a  true  anti-peristalsis,  as  can  be  seen  in  the  stomach  when  it  is  exposed  (  Galen).  The 
cardia  is  opened  by  the  longitudinal  muscular  fibres  [Sc/iiff),  which  pull  toward  the  lower  orifice  of 
the  oesophagus,  so  that  when  the  stomach  is  full  they  must  act  as  dilators.  The  act  of  vomiting  is  pre- 
ceded by  a  ructus-like  dilating  movement  of  the  intrathoracic  part  of  the  cesophagus,  which  is 
caused  tfius  :  The  glottis  is  closed,  inspiration  occurs  suddenly  and  violently,  whereby  the  cesophagus 
is  distended  by  gases  proceeding  from  the  stomach  (Liittich).  The  laryn.\  and  hyoid  bone,  by  the 
combined  action  of  the  the  genio-hyoid,  sterno-hyoid,  sternothyroid  and  thyro-hyoid  muscles  are 
forcibly  pulled  forward,  so  that  the  air  passes  from  the  pharynx  downward  into  the  upper  section 
of  the  cesophagus  [Landois).  If  the  abdominal  walls  contract  suddenly,  and  if  this  sudden  im- 
pulse be  aided  by  the  movements  of  the  stomach  itself,  the  contents  of  the  stomach  are  forced 
outward.  During  continued  vomiting,  anti-peristalsis  of  the  duodenum  may  occur,  whereby  bile 
passes  into  the  stomach,  and  becomes  mixed  with  its  contents. 

Children,  in  whom  the  fundus  is  absent,  vomit  more  easily  than  adults.  [In  them  also  the 
nervous  system  is  more  excitable.]  The  capacity  of  the  stomach  of  a  new-born  child  is  35  to  43 
cubic  centimetres;  after  14  days,  153  to  160  c.c. ;  at  2  years,  740  c.c. 

Magendie  was  of  opinion  that  the  abdominal  muscles  alone  were  concerned  in  vomiting,  as  he 
found  that  vomiting  occurred  when  he  replaced  the  stomach  by  a  bag.  This  was  much  too  crude 
an  experiment.  But  it  only  succeeds  when  the  lowest  part  of  the  (esophagus  has  been  removed 
[Fantini,  Schiff).  The  view  of  Gianuzzi,  that  the  aodominal  muscles  are  the  chief  factor, 
because  animals  poisoned  with  curara — in  whom  these  muscles  are  paralyzed,  but  not  the  walls  of 
the  stomach — cannot  vomit,  is  too  wide  a  deduction. 

Influence  of  Nerves. — The  centre  for  the  movements  concerned  in  vomit- 
ing lies  in  the  medulla  oblongata,  and  is  in  relation  with  the  respiratory  centre, 
as  is  shown  by  the  fact  that  nausea  may  be  overcome  by  rapid  and  deep  respira- 
tions. In  anunals,  vomiting  may  be  inhibited  by  vigorous  artificial  respiration. 
On  the  other  h^nd,  the  administration  of  certain  emetics  prevents  the  occurrence 
of  apncea  [while  emetics  quicken  the  respirations]. 

The  act  of  vomiting  is  most  easily  excited  by  stimulation  (chemically  or 
mechanically)  of  the  centripetal  or  afferent  nerves  of  (i)  the  mucous  membrane 
of  the  soft  palate,  pharynx,  root  of  the  tongue  {glosso-phatyngeal  nerve),  as  by 
tickling  the  fauces  with  the  finger  or  a  feather;  (2)  the  nerves  of  the  stomach 
{vagus  and  sympathetic)  ;  (3)  stimulation  of  the  uterine  nerves  (pregnancy)  ;  (4) 
\\^^  mesenteric  nerves  (inflammation  of  the  abdomen  and  hernia);  (5)  nerves  of 
the  urinary  apparatus  (passing  a  renal  calculus)  ;  (6)  nerves  to  the  liver  and  gall 
duct  (vagus')  ;  (7)  nerves  to  the  lungs  in  phthisis  (vagus).  Vomiting  is  also  pro- 
duced by  direct  stimulation  of  the  vomiting  centre.  [The  efferent  impulses  are 
carried  by  the  phrenics  (diaphragm),  vagus  (oesophagus  and  stomach),  and  inter- 
costals  (abdominal  muscles).] 

Vomiting  produced  by  the  thought  of  something  disagreeable  appears  to  be  caused  by  the  con- 
duction of  the  excitement  from  the  cerebrum  to  the  vomiting  centre.  [It  m.ay  also  be  excited 
through  the  brain  by  a  disagreeable  smell,  shocking  sight,  or  by  other  impressions  on  the  nerves  of 
special  sense.]  Vomiting  is  very  common  in  diseases  of  the  brain  [tubercle,  inflammation,  hemor- 
rhage.]    Section  of  both  vagi  generally,  but  not  always,  prevents  vomiting. 

Emetics  act  (i)  partly  by  mechanically  or  chemically  stimulating  the  ends  of  the  centripetal 
(afferent)  nerves  of  the  mucous  membrane.     [These  are  local  emetics.]     Tickling  the  fauces,  touch- 


MOVEMENTS   OF   THE    INTESTINE.  259 

in"  ihe  surface  of  the  exposed  stomach  (dog) ;  and  many  chemical  emetics,  e^.,  mustard,  cupric 
an'd  zinc  sulphate  and  other  metallic  sahs,  act  in  this  way.  (2)  Other  substances  cause  vomiting 
when  they  are  introduced  into  the  blood  (without  being  first  introduced  into  the  stomach  I,  and  act 
directly  upon  the  vomiting  centre,  e.g.,  apomorphin.  [These  are  general  emetics.]  (3)  Lastly, 
there  are  some  substances  which  act  in  both  ways,  e.g.,  tartar  emetic.  Emetics  may  also  remove 
mucus  from  the  lungs,  and  in  this  case  it  is  probable  that  the  emetic  acts  upon  the  rjspiratory  cen- 
tre, and  so  favors  the  respirations.  [According  to  Lauder  Brunton,  cupric  sulphate  acts  even  when 
injected  into  the  blood.]  The  general  emetics  usually  create  considerable  depression,  while  the 
vomiting  lasts  longer  than  with  local  emetics.  The  former  increase  the  salivary,  gastric,  and  respi- 
ratory secretions. 

[Uses  of  Emetics. — Emetics  are  useful  not  only  for  removing  from  the  stomach  any  offending 
body,  be  it  a  poison  or  the  products  of  imperfect  or  perverted  gastric  digestion,  or  bile  which  has 
passed  into  the  stomach,  but  foreign  bodies  impacted  in  the  cesophagus  may  be  got  rid  of  on  exciting 
vomiting  by  the  subcutaneous  injectiou  of  apomorphin.  As  the  diaphragm  contracts  vigorously  dur- 
ing vomiting,  it  compresses  the  liver,  and  thus  bile  is  expelled  into  the  duodenum,  or  the  passage  of 
a  small  calculus  along  the  bile-duct  may  be  aided.  They  also  are  useful  in  removing  mucus  or 
false  membranes  from  the  respiratory  passages.] 

[Anti-Emetics. — Vomiting  may  be  allayed  by  /()i<;/ anti-emetics,  such  as  ice,  and  many  chemical 
substances,  such  as  bismuth,  hydrocyanic  acid,  opium,  and  morphia,  as  well  as  by  n-fHtviz/ remedies 
which  act  on  the  vomiting  centre.  Some  of  the  foregoing  drugs  perhaps  act  both  locally  and  gener- 
ally.] 

V'omiting  is  analogous  to  the  process  of  rumination  in  animals  that  chew  the  cud  \'{,  1S7).  Some 
persons  can  empty  their  stomach  in  this  way. 

159.  MOVEMENTS    OF    THE    INTESTINE.— Peristalsis.— The 

best  example  of  peristaltic  movements  is  afforded  by  the  small  intestine  ;  the  pro- 
gressive narrowing  of  the  tube  proceeds  from  above  downward,  thus  propelling 
the  contents  before  it.  Frequently  after  death,  or  when  air  acts  freely  upon  the 
gut,  we  may  observe  that  the  peristalsis  develops  at  various  parts  of  the  intestine 
simultaneously,  whereby  the  loops  of  intestine  present  the  appearance  of  a  heap 
of  worms  creeping  among  each  other.  The  advance  of  new  intestinal  contents 
again  increases  the  movement.  In  the  large  intestine,  the  movements  are  more 
sluggish  and  less  extensive.  The  peristaltic  movements  may  be  seen  and  felt  when 
the  abdominal  walls  are  very  thin,  and  also  in  hernial  sacks.  They  are  more  lively 
in  vegetable  feeders  than  in  carnivora.  The  peristalsis  is  perhaps  conducted  directly 
through  the  muscular  substance  itself  (as  in  the  heart  and  ureter — Engelmaiin). 

[Rate  of  Motion. — In  a  Thirj'-Vella  fistula  (J  1S3,  II)  Fubini  estimated  the  rate  of  motion  of  a 
smooth  sphere  of  sealing  w^ax.  It  took  55  sec.  to  travel  I  ctm.  [|  in.]  ;  an  induction  current  greatly 
increases  the  motion,  I  ctm.  in  10  seconds  ;  NaCl  does  not  affect  it,  but  excites  secretion  ;  laudanum 
paralyzes  it.] 

Method  of  Observation. —Open  the  abdomen  of  an  animal  under  a  .6  per  cent,  saline  solution, 
to  prevent  the  expo^ure  of  the  gut  to  air  \Sanders  and  Braam-Homkgeest). 

The  ileo-colic  valve  (Bauhin's  valve,  1579,  known  to  Rondelet  in  1554),  as  a 
rule,  prevents  the  contents  of  the  large  intestine  from  passing  backward  into  the 
small  intestine.  The  movements  of  the  stomach  and  intestine  cease  during  sleep 
i^Busch). 

However,  when  fluid  is  slowly  introduced  into  the  rectum  through  a  tube,  it  may  pass  upward 
into  the  intestine,  and  even  go  through  the  ileo-colic  valve  into  the  small  intestine. 

.Muscarin  excites  very  lively  peristalsis  of  the  intestines,  which  may  be  set  aside  by  atropin 
[Silimiedelieyg  and  A'opfe). 

Pathological. — When  any  condition  excites  an  acute  inflammation  of  the  intestinal  mucous 
membrane,  catarrh  is  rapidly  produced,  and  very  strong  contractions  of  the  inflamed  parts  filled 
with  food  take  place.  When  these  parts  of  the  gut  become  empty,  the  movements  are  not  stronger 
than  normal,  if  new  material  parses  into  the  inflamed  part,  the  peristalsis  recurs,  becomes  more 
lively  than  normal,  and  the  result  is  diarrhoea  (Nol/uiagel).  Sometimes,  a  greatly  contracted 
part  of  the  small  intestine  is  pushed  into  the  piece  of  gut  directly  continuous  with  it,  giving 
rise   to  invagination  or  intussusception. 

Anti-peristalsis,  /.  e.,  a  movement  which  sets  in  and  travels  in  an  upward  direction  toward  the 
stomach,  does  not  occur  normally.  That  such  a  condition  takes  place  has  been  inferred  from  the 
fact  that,  in  cases  where  the  intestine  is  occluded,  called  ileus,  fa'cal  matter  is  vomited.  The  most 
recent  experiments  of  Nothnagel  throw  doubt  upon  this  view,  as  he  failed  to  observe  anti-peristalsis 
in  cases  where  the  intestine  was  occluded  artificially.  The  fcecal  odor  of  the  ejecta  may  result  from 
the  prolonged  retention  of  the  material  within  the  small  intestine. 


260 


EXCRETION    OF    F.ECAL    MATTER. 


160.  EXCRETION  OF  F^CAL  MATTER.— The  contents  of  the 
small  intestine  remain  in  it  about  three  hours,  and  about  twelve  hours  in  the  large 
intestine,  where  they  become  less  watery.  The  contents  assume  the  characters  of 
fsces,  and  become  "  formed  "  in  the  lower  part  of  the  great  intestine.  The  freces 
are  gradiially  carried  along  by  the  peristaltic  movement,  until  they  reach  a  point 
a  little  above  that  part  of  the  rectum  which  is  surrounded  by  both  sphincters,  the 
internal  sphincter  consisting  of  non-striped,  and  the  external  of  striped  muscle. 

Immediately  after  the  fsces  have  been  expelled,  the  external  sphincter  (Fig. 
164,  S,  and  Fig.  165)  usually  contracts  vigorously,  and  remains  in  this  condition 
for  some  time.     Afterward  it  relaxes,  when  the  elasticity  of  the  parts  surrounding 

Fig.  164. 


'i'he  perinteum  and  its  muscles,  i,  anus;  2,  coccy.\ ;  3,  tuberosity  4,  S(,i-*tii,  ligament:  5,  cotyloid  cavity;  B, 
bulbo-cavernosus  muscle  ;  Ts,  superficial  tiansverse  perineal  muscle  F,  tascia  ol  the  deep  transverse  perineal 
muscle:  J,  ischio-cavernosus  muscle;  M.  obturator  internus  b,  e\iernal  anal  sphincter;  L,  levator  ani  ;  P, 
pyriformis  {Henle). 

the  anal  opening,  particularly  of  the  two  sphincters,  suffices  to  keep  the  anus 
closed.  In  the  interval  between  two  evacuations,  there  does  not  seem  to  be  a 
continued  tonic  contraction  of  the  sphincters.  As  long  as  the  faeces  lie  above  the 
rectum,  they  do  not  excite  any  conscious  sensations,  but  the  sensation  of  requir- 
ing to  go  to  stool  occurs  when  the  faeces  pass  into  the  rectum.  At  the  same  time, 
the  stimulation  of  the  sensory  nerves  of  the  rectum  causes  a  reflex  excitement  of 
the  sphincters.  The  centre  for  the.se  Inovements  (Budge's  centrum  ano-spinale) 
lies  in  the  lumbar  region  of  the  spinal  cord  ;  in  the  rabbit  between  the  sixth  and 
seventh,  and  in  the  dog  at  the  fifth  lumbar  vertebra  {Masius). 

In  animals,  whose  spinal  cord  is  divided  above  the  centre,  a  slight  touch  in  the  region  of  the  anus 
causes  this  orifice  to  contract,  but  after  this  lively  reflex  contraction,  the  sphincters  relax  again,  and 


DEF.'ECATION. 


261 


the  anus  may  remain  open  for  a  time.  This  occurs,  because  the  voluntary  impulses  which  proceed 
from  the  brain  to  cause  the  contraction  of  the  external  sphincter  are  absent.  Landois  observed  that 
in  dogs  with  the  posterior  roots  of  their  lower  lumliar  and  sacral  nerves  divided  the  anus  remained 
open,  and  not  unfrequently  a  mass  of  fasces  remained  half  ejected.  As  the  sensibility  of  the  rectum 
and  anus  was  abolished  in  these  animals,  the  sphincters  could  not  contract  refle.xly,  nor  could  there 
be  any  voluntary  contraction  of  the  sphincters,  the  result  of  sensory  impulses  from  the  rectum. 

The  external  sphincter  can  be  contracted  voluntarily  from  the  cerebrum,  like 
any  voluntary  muscle,  but  the  closure  of  the  anus  can  only  be  effected  up  to  a 
certain  degree.  When  the  pressure  from  above  is  very  great,  the  energetic  peri- 
stalsis at  last  overcomes  the  strongest  voluntary  impulses.  Stimulation  of  the 
peduncles  of  the  cerebrum  and  of  the  spinal  cord  below  this  point  causes  contrac- 
tion of  the  external  sphincter. 

Defaecation. — The  evacuation  of  the  fasces,  which  in  man  usually  occurs  at 


Fig.  165. 


and  sphincter  ani  extemus. 


certain  times,  begins  with  a  lively  peristalsis  of  the  large  intestine,  which  passes 
downward  to  the  rectum.  In  order  that  the  mass  of  faeces  may  not  excite  reflexly 
the  sphincter  muscles,  in  consequence  of  mechanical  stimulation  of  the  sensory 
nerves  of  the  rectum,  there  seems  to  be  a  centre  which  inhibits  the  reflex  action 
of  the  sphincters,  which  is  called  into  play  owing,  as  it  appears,  to  voluntary  im- 
pulses. Its  seat  is  in  the  brain  ;  Masius  thinks  it  is  in  the  optic  thalami,  from 
whence  fibres  pass  through  the  peduncles  of  the  cerebrum  to  the  lumbar  part  of 
the  spinal  cord.  When  this  inhibitory  apparatus  is  in  action,  the  fcecal  inass  passes 
through  the  anus,  without  causing  it  to  close  reflexly. 

The  strong  peristalsis  which  precedes  defrecation  can  be  aided,  and  to  a  certain 
degree,  excited    by  voluntary  short    movements    of  the   external  sphincter  and 


262  INFLUENCE    OF    NERVES   ON    THE    INTESTINE. 

levator  ani,  whereby  the  plexus  myentericus  of  the  large  intestine  is  stimulated 
mechanically,  thus  causing  lively  peristaltic  movements  in  the  large  intestine. 
The  expulsion  of  the  faeces  is  also  aided  by  the  pressure  of  the  abdominal  muscles, 
and  most  efficiently  when  a  deep  inspiration  is  taken,  so  as  to  fix  the  diaphragm, 
whereby  the  abdominal  cavity  is  diminished  to  the  greatest  extent.  The  soft  parts 
of  the  floor  of  the  pelvis  during  a  strong  effort  at  stool,  are  driven  downward  in 
the  form  of  a  cone,  causing  the  mucous  membrane  of  the  anus,  which  contains 
much  venous  blood,  to  be  everted.  The  function  of  the  levator  ani  (Figs  164, 
165),  is,  to  raise  voluntarily  the  soft  parts  of  the  floor  of  the  pelvis,  and  to  pull 
the  anus  to  a  certain  extent  upward  over  the  descending  fsecal  mass.  At  the  same 
time,  it  prevents  the  distention  of  the  pelvic  fascia.  As  the  fibres  of  both  leva- 
tores  converge  below  and  become  united  with  the  fibres  of  the  external  sphincter, 
they  aid  the  latter,  during  energetic  contraction  of  the  sphincter ;  or,  as  Hyrtl 
puts  it,  the  levatores  are  related  to  the  anus,  like  the  two  cords  of  a  tobacco  pouch. 
During  the  periods  between  the  evacuation  of  the  gut,  the  fceces  appear  only  to 
reach  the  lower  end  of  the  sigmoid  flexure.  As  a  rule,  from  thence  downward, 
the  rectum  is  normally  devoid  of  fa;ces.  It  seems  that  the  strong  circular  fibres 
of  the  muscular  coat,  which  Nelaton  has  called  sphincter  ani  tertius,  when  they 
are  well  developed,  contract  and  prevent  the  entrance  of  the  faeces.  When  the 
tendency  to  the  evacuation  of  the  rectum  is  very  pressing,  the  anus  may  be  closed 
more  firmly  from  without,  by  energetically  rotating  the  thigh  outward,  and  con- 
tracting the  muscles  of  the  gluteal  region. 

161.  INFLUENCE  OF  NERVES  AND  OTHER  CONDITIONS 
ON   THE    INTESTINAL    MOVEMENTS.— Auerbach's   Plexus.— 

The  intestinal  canal  contains  an  automatic  motor  centre  within  its  walls — t\it  plexus 
myentericus  of  Auerbach — which  lies  between  the  longitudinal  and  circular  mus- 
cular fibres  of  the  gut.  It  is  this  plexus  which  enables  the  intestine  when  cut  out 
of  the  body  to  execute,  apparently  spontaneously,  movements  for  some  time. 

[Structure. — The  plexus  of  Auerbach  consists  of  non-meduUated  nerve  fibres  which  form  a 
dense  network,  groups  of  ganglion  cells  occurring  at  the  nodes  (Fig.  i66).  A  similar  plexus 
extends  throughout  the  whole  intestine  between  the  longitudinal  and  circular  muscular  coats  from 
the  cesophagus  to  the  rectum.  Branches  are  given  oft'  to  the  muscular  bundles.  A  .similar,  but  not 
so  rich  a  plexus  lies  in  the  submucous  coat,  Meissner's  plexus,  which  gives  branches  to  supply  the 
muscularis  mucosa,  the  smooth  muscular  fibres  of  the  villi,  and  the  glands  of  the  intestine  (Fig. 
167J.] 

1.  If  this  centre  is  not  affected  by  any  stimulus,  the  movements  of  the  intestine 
cease — comparable  to  the  condition  of  the  medulla  oblongata  in  apncea  {Sig.  Afayer 
and  v.  Bascli).  The  same  is  true — just  as  in  the  case  of  the  respiration — during 
intra-uterine  life,  in  consequence  of  the  fcetal  blood  being  well  supplied  with  O. 
This  condition  may  be  termed  aperistalsis.  It  also  occurs  during  sleep,  perhaps 
on  account  of  the  greater  amount  of  O  in  the  blood  during  that  state. 

2.  When  blood  containing  the  normal  amount  of  blood  gases  passes  through 
the  intestinal  blood  vessels,  the  quiet  peristaltic  movements  of  health  occur 
(euperistalsis),  provided  no  other  stimulus  be  applied  to  the  intestine. 

3.  All  stimuli  applied  to  the  plexus  myentericus  increase  the  peristalsis,  which 
may  become  so  very  violent  as  to  cause  evacuation  of  the  contents  of  the  large 
gut,  and  may  even  produce  spasmodic  contraction  of  the  musculature  of  the  intes- 
tine. This  condition  maybe  termed  dysperistalsis,  corresponding  to  dyspnoea. 
The  comiition  of  the  blood  flowing  through  the  intestinal  vessels  has  a  most  impor- 
tant effect  on  the  peristaltic  movements. 

Condition  of  the  Blood. ^Dysperistalsis  may  be  produced  by  (a)  interrupting  the  circulation  of 
the  blood  in  the  intestines,  no  matter  whether  anreniia  (as  after  compressing  the  aorta — Schiff]  or 
venous  hypera'mia  be  produced.  The  stimulating  condition  is  the  want  of  O.  i.  e  ,  the  increase  of 
CO2-  Very  slight  disturbance  in  the  intestinal  blood  vessels,  e.  ^  ,  venous  congestion  after  copious 
transfusion  into  the  veins,  whereby  the  abdominal  and  portal  veins  become  congested,  cause  increased 
perista'sis.     The  intestines  become  nodulated  .at  one  p.irt  and  narrow  at  another,  and  involuntary 


INFLUENCE   OF   NERVES   ON   THE    INTESTINE. 


263 


evacuation  of  the  f?eces  takes  place  when  there  is  congestion,  owing  to  the  plugging  of  the  intes- 
tinal blood  vessels  when  blood  from  another  species  of  animal  is  used  for  transfusion  (?.  102).  The 
marked  peristalsis  which  occurs  on  the  approach  of  death  is,  undoubtedly,  due  to  the  derangements 
of  the  circulation,  and  the  consequent  alteration  of  the  amount  of  gases  in  the  blood  of  the  intes- 
tine.    The  same   is  true  of  the  increased   movements  of  the  intestines  which  occur  as  a  result  of 

Fig.  166. 


us  of  Auerbach,  prcp.ired  from  the  small  intestine  of  a  dog,  by  the  action  of  gold  chloride.  The  nerve  ceils  are 
.hown  at  the  nodes,  while  the  fibrils  preceding  from  the  ganglia,  and  the  anastomosing  fibres,  lie  between  the 
nuscular  bundles. 


Fig.  167. 


rt,  ganglia;  b,  anastomosing  fib: 


accompanying  c. 


psychical  excitement,  e.  g.,  grief.  The  stimulus,  in  this  ca'se,  passes  from  the  cerebrum,  through 
the  medulla  oblongata  (vasomotor  centre)  to  the  intestinal  nerves,  and  causes  anaemia  of  the  intes- 
tine (corresponding  to  the  pallor  occurring  elsewhere).  When  the  normal  condition  of  the  circula- 
tion is  restored,  the  peristalsis  diminishes,  [b)  Direct  stimulation  of  the  intestine,  conducted  to  the 
plexus  myentericus,  causes  dysperistalsis  ;  direct  exposure  of  the  intestines  to  the  air  (stronger  when 


264  IFFLUENCE    OF    NERVES   ON    THE    INTESTINE. 

CO,  or  CI  is  present),  introduction  of  various  irritating  substances  into  the  intestine,  increased  filling 
of  the  intestine  when  there  is  any  difficulty  in  emptying  the  gut  (often  in  man),  direct  stimulation 
of  various  kinds  (also  inflammation),  all  act  upon  the  intestine,  either  from  without  or  from  within. 
Induction  shocks  applied  to  a  loop  of  intestine  in  a  hernial  sack  cause  lively  peristalsis  in  the  hernia. 
The  intestinal  movements  are  favored  by  heat. 

4.  The  continued  application  of  strong  stimuli  causes  the  dysperistalsis  to  give 
place  to  rest,  owing  to  over-stimulation,  which  may  be  called  "  intestinal  pa- 
resis," or  exhaustion. 

This  condition  is  absolutely  different  from  the  passive  condition  of  the  intestine  in  aperistalsis. 
Continued  congestion  of  the  intestinal  blood  vessels  ultimately  causes  intestinal  panalysis,  ^.g.,  when 
transfusion  of  foreign  blood  causes  coagulation  within  these  vessels  (Lamiois).  P'ilMng  the  blood 
vessels  w-ith  "  indifferent "  fluids,  after  the  peristalsis  has  been  previously  brought  about  by  com- 
pressing the  aorta,  also  causes  cessation  of  the  movements  {O.  JVasse).  The  movements  cease  when 
the  intestines  are  cooled  to  19°  C.  (I/o>~wa/h),  while  severe  inflammation  of  the  intestine  has  a 
similar  effect.  Under  favorable  circumstances,  the  intestine  may  recover  from  this  condition. 
Arterial  blood  admitted  into  the  vessels  of  the  exhausted  intestine  causes  peristalsis,  which  at  first 
is  more  vigorous  than  normal. 

5.  The  continued  application  of  strong  stimuli  causes  complete  paralysis  of 
the  intestine,  such  as  occurs  after  violent  peritonitis,  or  inflammation  of  the  mus- 
culature or  mucous  coat  in  man.  In  this  condition  the  intestine  is  greatly  dis- 
tended, as  the  paralyzed  musculature  does  not  offer  sufficient  resistance  to  the 
intestinal  gases  which  are  expanded  by  the  heat.  This  constitutes  the  condition 
of  meteorism. 

Influence  of  Nerves. — With  regard  to  the  nerves  of  the  intestine,  stimula- 
tion of  the  vagus  increases  the  movements  (of  the  small  intestine),  either  by 
conducting  impressions  to  the  plexus  myentericus,  or  by  causing  contraction  of 
the  stomach,  which  stimulates  the  intestine  in  a  purely  mechanical  manner  \Braam- 
Houckgeest).  The  splanchnic  is  (i)  the  inhibitory  nerve  of  the  small  intestine 
{Pfliiger),  but  only  as  long  as  the  circulation  in  the  intestinal  blood  vessels  is 
undisturbed,  and  the  blood  in  the  capillaries  does  not  become  venous  {Sigm. 
Mayer  and  von  Basch) ;  when  the  latter  condition  occurs,  stimulation  of  the 
splanchnic  increases  the  ijeristalsis.  If  arterial  blood  be  freely  supplied,  the  in- 
hibitory action  continues  for  some  time  {O.  Nasse).  Stimulation  of  tlie  origin  of 
the  splanchnics  of  the  spinal  cord  in  the  dorsal  region  (under  the  same  conditions), 
and  even  when  general  tetanus  has  been  produced  by  the  administration  of 
strychnia,  causes  an  inhibitory  effect.  O.  Nasse  concludes,  from  these  experi- 
ments, that  the  splanchnic  contains — (2)  inhibitory  fibres,  which  are  easily  ex- 
hausted by  a  venous  condition  of  the  blood,  and  also  motor  fibres,  which  remain 
excitable  for  a  longer  time,  because  after  death  stimulation  of  the  splanchnics 
always  causes  peristalsis,  just  like  stimulation  of  the  vagus.  (3)  The  splanchnic 
is  also  the  vasomotor  nerve  of  all  the  intestinal  blood  vessels,  so  that  it  governs 
the  largest  vascular  area  in  the  body.  When  it  is  stimulated,  all  the  vessels  of 
the  intestine  which  contain  muscular  fibres  in  their  walls  contract ;  when  it  is 
divided,  they  dilate.  In  the  latter  case,  a  large  amount  of  blood  accumulates 
within  the  blood  vessels  of  the  abdomen,  so  that  there  is  anaemia  of  the  other 
parts  of  the  body,  which  may  be  so  great  as  to  cause  death — owing  to  the  defi- 
cient supply  of  blood  to  the  medulla  oblongata.  (4)  The  splanchnic  is  the  sensory 
nerve  of  the  intestine,  and  as  such,  under  certain  circumstances,  it  may  give  rise 
to  extremely  painful  sensations. 

As  stimulation  of  the  splanchnic  contracts  the  blood  ve^^sels,  von  Basch  has  raised  the  question 
whether  the  intestine  does  not  come  to  rest,  owing  to  the  want  of  the  blood,  which  acts  as  a  stim- 
ulus. But  when  a  weak  stimulus  is  applied  to  the  splanchnic,  the  intestine  ceases  to  move  before 
the  blood  vessels  contract  (T.ian  Braam-Honckgiest) ;  it  would,  therefore,  seem  that  the  stimulation 
diminishes  the  excitabihty  of  the  plexus  myentericus. 

According  to  Engelmann  and  v.  Brakel,  the  peristaltic  movement  is  chiefly  propagated  by  direct 
muscular  conduction,  as  in  the  heart  and  ureter,  without  the  intervention  of  any  nerve  fibres. 


EFFECT   OF    DRUGS   ON    THE    INTESTINE.  265 

[Effect  of  Nerves  on  the  Rectum. — The  nervi  erigentef,  when  stimulated,  cause  the  longi- 
tudinal muscular  fibres  of  the  rectum  to  contract,  while  the  circular  muscular  fibres  are  supplied  by 
the  hypogastric  nen-es.  Stimulation  of  the  latter  nerves  also  exerts  an  inhibitor)-  effect  on  the  lon- 
gitudinal muscles.  Stimulation  of  the  erigentes  inhibits  not  only  the  spontaneous  movements  of 
the  circular  fibres  of  the  rectum,  but  also  those  movements  excited  by  stimulation  of  the  hypogastric 
nerves  [Fel/ner.)'] 

[Artificial  Circulation  in  the  Intestine. — Ludwig  and  Sah-ioli,  after  exciting  a  loop  of  intes- 
tine from  an  animal,  tied  a  cannula  into  an  artery  and  another  into  a  vein.  The  arterial 
cannula  was  connected  with  a  vessel  containing  defibrinated  blood,  to  which  different  drugs  could 
be  added.  A  lever  rested  on  the  intestine,  and  registered  its  movements  on  a  recording  surface. 
The  intestine  was  kept  in  a  warm  chamber.  As  long  as  arterial  blood  was  transfused,  the  intestine 
was  nearly  quiescent,  but  when  it  was  arrested,  so  that  the  blood  became  venous,  a  series  of  con- 
tractions occurred.  Nicotin  diminished  the  flow  of  blood  and  quickened  the  intestinal  movements, 
while  at  the  same  time  the  circular  muscular  fibres  remained  contracted  or  tetanic. .  Tincture  of 
opium,  in  the  proportion  of  .01  to  .04  in  the  blood,  causes  at  first  contraction  of  the  vessels  and 
lessens  the  amount  of  blood  circulating  in  the  intestine ;  but  it  very  rapidly  increases — even  to  six 
times — the  amount  of  blood  which  transfuses,  while  at  the  same  time  the  movements  of  the  intes- 
tine cease,  the  walls  of  the  intestine  being  contracted.] 

"Effect  of  Drugs. — Among  the  reagents  which  act  upon  the  intestinal  movements,  are :  (l) 
Such  as  diminish  the  excitability  of  the  plexus  myentericus,  i.e.,  which  lessen  or  even  abolish  intes- 
tinal peristalsis,  e.g.,  belladonna.  (2)  Such  as  stimulate  the  inhibitory  fibres  of  the  splanchnic,  and 
in  large  doses  paralyze  them — opium,  morphia  (.AW/;«<7ff/) ;  I  and  2  produce  constipation.  (3) 
Other  agents  excite  the  motor  apoaratus — nicotin  (even  causing  spasm  of  the  intestine),  muscarin, 
caffein  and  many  laxatives,  which  act  as  purgatives.  The  movements  produced  by  muscarin  are 
abolished  by  atropin  (Schmiedeberg  and  Koppe").  These  substances  accelerate  the  evacuation  of  the 
intestine,  and,  owing  to  the  rapid  movement  of  the  intestinal  contents,  only  a  small  amount  of  water 
is  absorbed ;  so  that  the  evacuations  are  frequently  fluid.  (4)  Among  purga/ives,  colocj'nth  and 
croton  oil  act  as  direct  irritants.  With  regard  to  drugs  of  this  sort,  they  seem  to  cause  a  watery 
transudation  into  the  intestine  (  C.  Schmidt,  Moreati),  just  as  croton  oil  causes  vesicles  when  applied 
to  the  skin.  (5)  Calomel  is  said  to  limit  the  absorptive  activity  of  the  intestinal  wall,  and  to  con- 
trol the  decompo.sitions  in  the  intestine.  The  stools  are  thin  and  greenish,  from  the  admixture  of 
biliverdin.  (6)  Certain  saline  purgatives — sodium  sulphate,  magnesium  sulphate,  causes  fluid 
evacuations  by  retaining  the  water  in  the  intestine  (Buchheim) ;  and  it  is  said  that  if  they  be 
injected  into  the  blood  vessels  of  animals,  they  cause  constipation  (Auieri). 

[Nothnagel  finds  that  when  a  crj'stal  of  a  potask  salt  is  applied  to  the  peritoneal  surface  of  the 
intestine  of  an  animal  whose  abdomen  is  opened,  it  causes  merely  a  local  constriction  of  the  mus- 
cular fibres  of  the  gut,  while  a  sodium  salt  on  the  other  hand  excites  a  contraction  which  passes 
upward  toward  the  stomach,  and  never  toward  the  rectum.  Perhaps  this  is  due  to  the  more  power- 
ful stimulant  action  of  the  former.  In  any  case  it  may  serve  as  a  useful  guide  to  the  surgeon,  in 
determining  which  is  the  upper  end  of  a  piece  of  intestine  during  an  operation  on  the  intestines.] 

[Action  of  Saline  Cathartics. — From  an  extended  investigation  recently  made  by  M.atthew 
Hay  on  the  action  of  saline  cathartics,  it  would  appear  certain  that  a  salt  exerts  a  genuine  excito- 
secretory  action  on  the  glands  of  the  intestines,  while  at  the  same  time,  in  virtue  of  its  low  diffusi- 
bility,  it  impedes  absorption.  Thus,  between  stimulated  secretion  and  impeded  absorption  there  is 
an  accumulation  of  fluid  within  the  canal,  which,  partly  from  ordinary  dynamical  laws,  partly  from 
a  gentle  stimulation  of  the  peristaltic  movements  excited  by  distention,  reaches  the  rectum  and 
results  in  purgation.  Purgation  does  not  ensue  when  water  is  withheld  from  the  diet  for  one  or  two 
days  previous  to  the  administration  of  the  salt  in  a  concentrated  form.  This  absence  of  effect  is 
due  to  a  deficiency  of  water  in  the  blood,  so  that  the  blood  cannot,  through  the  intestinal  glands, 
yield  enough  fluid  to  the  salt  in  order  to  produce  purgation.  When  a  concentrated  solution  of  a 
salt  is  administered  to  an  animal  whose  alimentary  canal  is  known,  from  a  few  hours'  preliminary 
fasting,  to  be  empty,  but  whose  blood  is  in  a  natural  state  of  dilution,  the  blood  becomes  rapidly 
very  concentrated,  and  reaches  the  maximum  of  its  concentration  in  from  half  an  hour  to  an  hour 
and  a  half;  within  four  hours  the  blood  has  gradually  returned  to  its  normal  state  of  concentration 
without  having  reabsorbed  fluid  from  the  intestine.  It  apparently  recoups  itself  fi-om  the  tissue 
fluids.  After  a  few  days'  abstention  from  water,  the  tissue  fluids  are  so  much  dimmished  as  not  to 
be  able  any  longer  to  recoup  the  blood,  and  the  blood  itself  gradually  becomes  concentrated ;  hence, 
a  concentrated  saline  solution  fails  to  excite  any  secretion  when  administered.] 

[It  is  also  interesting  in  connection  with  saline  cathartics  that  the  salt — sulphate  of  magnesia  or 
sulphate  of  soda — becomes  split  up  in  the  small  intestine,  and  the  acid  is  more  rapidly  absorbed 
than  the  base.  .\  portion  of  the  absorbed  acid  shortly  afterward  returns  to  the  intestines,  evidently 
through  the  intestinal  glands.  After  the  maximum  of  excretion  of  the  acid  has  been  reached,  the 
salt  begins  very  slowly  and  gradually  to  disappear  by  absorption,  which  is  checked  only  by  the 
occurrence  of  purgation.  The  salt  does  not  purge  when  injected  into  the  blood,  and  excites  no 
intestinal  secretion  ;  nor  does  it  purge  when  injected  subcutaneously,  unless  on  account  of  its  caus- 
ing local  irritation  of  the  abdominal  subcutaneous  tissue,  which  acts  reflexly  on  the  intestines,  dila- 
ting their  blood  vessels,  and  perhaps  stimulating  their  muscular  movements.] 


266  FUNDUS    GLANDS   OF   THE    STOMACH. 

162.  STRUCTURE  OF  THE  STOMACH.— [The  stomach  receives 
the  bolus,  and  secretes  a  juice  which  acts  on  certain  constituents  of  the  food, 
while  by  its  muscular  walls  it  moves  the  latter  within  its  own  cavity,  and  after  a 
time  expels  the  partially  digested  products  toward  the  duodenum.] 

Structure. — [The  walls  of  the  stomach  consist  of  four  coats,  which  are,  from 
without  inward — 

(i)  The  sc'ro7(s  iayer,  from  the  peritoneum. 

(2)  The  miisci//<ir /a}'er,  composed  of  three  layers  of  non-striped  muscular  fibres — (<;),  longi- 
tudinal;   (/S),  circular;   (r),  oblique  (^  15). 

(3)  Tlie  submucous  layer,  of  loose  connective  tissue,  with  larger  blood  vessels,  lymphatics  and 

nerves. 

(4)  The  mucous  layer.~\ 

The  well-developed  mucous  membrane  of  the  stomach  is  thrown  into  a 
series  of  folds  or  rugae,  in  the  contracted  condition  of  the  organ.  With  the  aid 
of  a  hand  lens,  it  is  seen  to  be  beset  with  small,  irregular  depressions  or  pi fs  (Fig. 
169).  Throughout  its  entire  extent  it  is  covered  by  a  single  layer  of  moderately 
tall,  narrow,  r)'//V/i?Vm?/ epithelium,  which  seems  to  consist  of  mucus-secreting 

Fig.  i6g. 


e  Surface  section  of  the  dog's  gastrii 

br.-ine,  showing  the  crater-like  depr* 
pits,  /,/, :  a,  the  elevations  round  i,i. 

goblet  cells  (Fig.  i68).  The  epithelium  is  sharply  defined  at  the  cardia  from 
the  stratified  epithelium  of  the  oesophagus,  and  also  at  the  pylorus,  from  the  true 
cylindrical  epithelium  with  the  striated  disk  in  the  duodenum.  [The  cells  con- 
tain a  plexus  of  fibrils  and  in  the  passive  condition  seem  to  consist  of  two  zones, 
an  outer  clear  part,  next  the  lumen  of  the  organ,  consisting  of  a  substance  (muci- 
gen)  which  yields  mucus,  the  attached  end  of  the  cell  being  granular.]  The  oval 
nucleus  lies  about  the  centre  of  the  cells.  Spindle-shaped,  nucleated  cells,  pro- 
bably for  replacing  the  others,  are  said  by  Ebstein  to  occur  at  their  bases.  All 
the  cells  are  open  at  their  free  ends,  so  that  the  mucus  is  readily  discharged,  leav- 
ing the  cells  empty  (F.  E.  Siiiiiitze).  Numerous  tubular  glands  o{  two  distinct 
kinds  are  placed  vertically,  like  rows  of  test  tubes,  in  the  mucous  membrane. 

Fundus  Glands. — On  making  a  vertical  section  of  the  cardiac  portion  of 
the  gastric  mucous  membrane,  and  submitting  it  to  microscopic  examination,  it  is 
seen  to  consist  of  a  number  of  tubular  glands  placed  side  by  side.  These  are  the 
fundus  glands  of  Heidenhain,  otherwise  called  peptic,  or  cardiac.  Several  gland 
tubes,  which  are  wider  below,  usually  open  into  the  short  duct  (Fig.  172).  Each 
gland  consists  of  a  structureless  membrana  propria  with  anastomosing  branched 


PYLORIC    GLANDS    OF   THE    STOMACH. 


267 


cells  in  relation  with  it.  The  duct  is  lined  by  a  layer  of  cells  like  those  lining 
the  stomach,  while  the  secretory  part  of  the  tubes  is  lined  throughout  by  a 
layer  of  granular,  short,  small,  polyhedral,  or  columnar  nucleated  cells.  These 
cells  border  the  very  narrow  lumen,  and  were  called  chief  or  principal  cells  by 


Fig.  170. 


L  duct  of  .1  fundi 

II,  Transverse  sect 
1  the  gland  tubes;  c,  divided  capillai 


goblet  cells  ;  c,  adeni 
parietal  cells ;  r,  aden 


Heidenhain  ;  they  are  also  known  as  central  cells  (Fig.  170,  II,  a),  or  adelomor- 
phous (rlor^loi,  hidden).  At  various  places  between  these  cells  and  the  membrana 
propria  are  large,  oval  or  angular,   well-defined,   granular,   densely  reticulated. 


nucleated  cells,  the /izr/cAz/cells  of  Heidenhain,  the  ilelo- 
morphoiis  cells  of  Rollett,  or  the  oxyntic  (acid  forming) 
cells  of  Langley  (Fig.  170,  II,  li).  They  are  most 
numerous  in  the  neck  of  the  glands,  and  least  so  in  the 
deep  blind  end  of  the  tubes.  These  cells  are  stained 
deeply  by  osmic  acid  and  aniline  blue,  so  that  they  are 
readily  distinguished  from  the  other  cells.  They  bulge 
out  the  membrana  propria  of  the  gland  opposite  where 
they  are  placed.  The  parietal  cells  in  man  are  said  to 
reach  to  the  lumen  of  the  gland  tubes  (Slohr').  Isolated 
cells  are  sometimes  found  under  the  epithelium  of  the 
surface  of  the  stomach  {Heidenhain),  and  occasionally 
in  individual  pyloric  glands  (Slohr).  The  fundus  glands 
are  most  numerous  (about  five  millions,  according  to  Sap- 
pey),  and  are  of  considerable  size  in  the  fundus. 

2.  The  Pyloric  Glands  occur  only  in  the  region  of 
the  pylorus,  where  the  mucous  membrane  is  more  yellow- 
ish-white in  color  (Fig.  171).  These  glands  are  gen- 
erally branched  at  their  lower  ends,  so  that  several  tubes 
open  into  a  single  duct  [which,  in  contradistinction  to 
the  duct  of  the  other  glands,  is  wide  and  long,  extending 
often  to  half  the  depth  of  the  mucous  membrane.  The 
duct  is  lined  by  epithelium  like  that  lining  the  stomach, 
while  the  secretory  part  is  lined  by  a  single  layer  of 
short,  finely  granular,  columnar  cells,  whose  secretion  is 
quite  different  from  that  of  the  cells  lining  the  duct.  The 
lumen  is  well  defined.  Nussbaum  has  occasionally  found 
other  cells,  which  stain  deeply  with  osmic  acid,  between 
the  bases  of  these.  Ebstein  regards  these  cells  as  form- 
ing pepsin.     It  is  to  be  remembered  that  the  appearance 


Fig.  17 


268 


LYMPHATICS    AND   NERVES   OF   THE    STOMACH. 


of  the  cells  differs  according  to  their  state  of  physiological  activity  (Figs.  173, 
174).  When  they  are  exhausted  they  are  smaller  and  more  granular,  owing  to 
the  denser  reticulation  of  their  network ;  at  any  rate,  they  are  granular  in 
preparations  hardened  in  alcohol  (Fig.  1 74).] 

Muscularis  Mucosae. — The  glands  are  supported  by  very  delicate  connective  tissue  mixed  with 
adenoid  tissue  (Fig.  170).  Below  this  are  two  layers,  circular  and  longitudinal,  of  non-striped 
muscle,  the  muscularis  mucosa,  and  from  it  fine  processes  of  smooth  muscular  fibres  pass  up 
between  groups  of  the  glands  toward  the  free  epithelial  surface  of  the  gastric  mucous  membrane. 
These  muscular  processes  are  said  to  be  concerned  in  emptying  the  glands.     [In  the  gastric  mucous 


large  trunk,  t 


k  of  ;i  fundus  gland  opening  into 
:/,  lymphatics,  emptying  into  a 


membrane  of  the  cat,  there  is  a  clear  homogeneous  layer,  which  is  stained  red  by  picrocarmine,  and 
placed  immediately  internal  to  the  muscularis  mucosre.  It  is  pierced  by  the  processes  passing  from 
the  muscularis  mucosa'.] 

Masses  of  adenoid  tissue  occur  in  the  mucous  membrane,  especially  near  the  pylorus,  constitut- 
ing lytnph  follicles,  which  are  comparable  to  the  solitary  glands  of  the  small  intestine. 

The  Lymphatics  are  numerous,  and  begin  close  under  the  epithelium  by  dilated  extremities 
or  loops  (Fig.  172,  (/) ;  they  run  vertically,  and  anastomose  in  the  mucosa  between  the  gland  tubes, 
which  they  envelop  in  sinus-like  spaces.  They  join  large  trunks  in  the  mucosa;  another  ple.xus  of 
large  vessels  exists  in  the  sub-mucosa  {Loven). 


SECRETION    OF    GASTRIC   JUICE.  269 

[The  Nerves. — A  plexus  of  non-medullated  nerve  fibres  and  a  few  ganglion  cells  exist  in  the 
muscular  coat  [.-liiefliaih's),  and  another  (Meissner" s)  in  the  submucosa.] 

The  Blood  Vessels  are  very  numerous.  Small  arterial  branches,  n,  run  in  the  sub-mucosa  and 
ascend  between  the  glands  to  form  a  longitudinal  capillary  network,  c,  c,  which  forms  a  narrow  net- 
work under  the  epithelium,  and  between  its  meshes  the  gland  ducts  open,^'.  The  veins  gradually 
collect  from  this  horizontal  capillary  network  and  run  toward  the  large  veins  of  the  sub-mucosa,  v. 

163.  THE  GASTRIC  JUICE.— Properties.— The  gastric  juice  is  a 
tolerably  clear,  colorless  fluid,  with  a  .strong  acid  reaction,  sour  taste,  and  peculiar 
characteristic  odor;  it  rotates  the  plane  of  polarized  light  to  the  left  {Hoppc-Sey- 
ler).  It  is  not  rendered  turbid  by  boiling,  and  resists  putrefaction  for  a  longtime. 
Its  specific  gravity  =  1002.5  (dog,  1005),  and  it  contains  only  ]A  per  cent,  of 
solid  constituents.  The  quantity  of  gastric  juice  secreted  in  twenty-four  hours 
was  estimated  by  Beaumont,  from  observations  upon  Alexis  .St.  Martin,  who  had 
a  gastric  fistula  (1834) — at  only  180  grms.  daily  (!)  ;  by  Griinewald  (1853),  in  a 
similar  case,  as  equal  to  26.4  per  cent,  of  the  body  weight;  while  Bidder  and 
Schmidt  (from  corresponding  observations  on  dogs)  estimated  it  as  equal  to  6^ 
kilos,  daily,  corres])onding  to  j'jy  of  the  body  weight.     It  contains : — 

(i)  Pepsin  {I'll.  Schwann,  i8j6),  the  characteristic  nitrogenous  hydrolytic 
ferment  or  enzym,  which  dissolves  proteids.  E.  Schiitz  obtained  0.41  to  1.17  per 
cent,  from  a  fasting  person,  by  means  of  the  oesophageal  sound. 

(2)  Hydrochloric  Acid  {Prout,  1824),  0.2  to  0.3  {Richct,  0.8  to  2.1)  per 
1000  ;  (in  the  dog,  0.52  per  cent.  K  This  occurs  free  in  the  gastric  juice,  as  the 
latter  always  contains  more  free  chlorine  than  bases,  to  which  it  can  be  united 
(C  Schmidt).  Lactic  acid  is  usually  met  with,  but  it  arises  from  the  fermentation 
of  the  carbohydrates  of  the  food.  [A  solution  of  HCl  of  this  strength  is  made 
by  adding  6.5  c.c.  of  the  ordinary  commercial  acid  to  i  litre  of  water.] 

Tests. — Free  hydrochloric  acid  is  detected  by  the  following  reactions: — 0.025  P^f  cent,  solu- 
tion of  mythyl  violet  becomes  blue;  or,  alkaline  solution  of  co-tropa^olin  becomes  lilac;  or,  red 
Bordeaux  wine  is  treated  with  amylic  alcohol  until  its  color  almost  disappears — when,  if  dilute 
hydrochloric  acid  be  added,  a  rose  color  is  obtained. 

Lactic  Acid. — The  freshly  prepared  blue  solution  of  10  c.c.  of  a  4  per  cent,  solution  of  carbolic 
acid,  with  20  c.c.  of  distilled  water,  and  i  drop  of  liquor  ferri  perchloride,  is  changed  \q yellow  by 
lactic  acid  (Ufeliinmn). 

(3)  The  large  amount  of  mucus  which  covers  the  surface  of  the  mucous  mem- 
brane is  to  be  regarded  as  the  secretion  from  the  goblet  cells  of  the  inucous  mem- 
brane (§  162). 

(4)  Mineral  Salts  (2  per  1000). 

They  are  chiefly  sodium  and  potassium  chlorides,  less  calcic  chloride  (ammonium  chloride,  also 
in  animals),  and  the  compounds  of  phosphoric  acid  with  lime,  magnesium,  and  iron. 

Among  foreign  substances,  which  may  be  introduced  into  the  body,  the  following  appear  in  the 
gastric  juice — HI,  after  the  use  of  potassium  iodide — potassium  sulphocyanide,  ferric  lactate,  and 
sugar,  and  ammonium  carbonate  in  uraemia. 

[Composition. — Gastric  juice  (human)  mixed  with  some  saliva  (C  Schmidt) — 

Water 99.44 

Solids 0.56 

Organic  substances  (pepsin  and  peptones) 0.32 

Free  hydrochloric  acid 0.25 

Sodic  chloride 0.14 

Potassic  chloride 0.05 

Calcic  chloride 0.006 

Phosphates  of  lime,  m.agnesia  and  iron 0.015.] 

164.  SECRETION  OF  GASTRIC  JUICE.— After  the  discovery  of  the 

two  kinds  of  glands  in  the  stomach,  and  after  it  was  found  that  the  fundus  glands 
contained  two  different  forms  of  cells,  the  question  as  to  whether  the  different 
constituents  of  gastric  juice  were  formed  by  different  histological  elements  came  to 
be  investigated. 


270 


CHANGES    IN    THE    GLANDS    DURING    SECRETION. 


Changes  of  the  Cells  during  Digestion. — During  the  course  of  digestion  the  cells  of  the  fun- 
dus (and  pyloric  glands,  dog)  undergo  important  changes  {Ht'idt'n/iain,  £/istt'in).  During  hunger 
the  chief  cells  are  clear  and  large,  the  parietal  investing  cells  are  small,  the  pyloric  cells  iiear  and 
of  moderate  size.  During  the  first  six  hours  of  digestion  the  chief  cells  become  enlarged  and 
moderately  turbid  or  granular,  the  parietal  cells  also  enlarge,  while  the  pyloric  cells  remain 
unchanged.  The  chief  cells  become  i/imim's/ied  and  more  turbid  or  granular  until  the  ninth  hour, 
the  parietal  cells  are  still  swollen,  and  the  pyloric  cells  enlarge.  During  the  last  hours  of  digestion 
the  chief  cells  again  become  larger  and  clearer,  the  parietal  cells  diminish,  the  pyloric  cells  decrease 
in  size  and  become  turbid  (I'igs.  173  and  174). 

[Langley  gives  a  different  description  of  the  appearances  presented  by  these  cells  during  different 
phases  of  secretory  activity.  The  results  may  be  reconciled  by  remembering  that  the  gland  cells 
were  examined  under  diflerent  conditions.     The  secretory  cells  consist  of  a  cell  substance  composed 


Fig.  173. 


Fig.  174. 


Section  of  the  pyloric  mucous  membrane 


0\V 


#? 


Pyloric  glands  showing  changes  of  the 
cells  during  digestion  {^hdstem) 


of  [a)  a  framework  of  Uving  protoplasm,  either  in  the  form  of  an  intracellular  fibrillar  network 
(Klein),  or  in  flattened  bands.  The  meshes  of  this  framework  enclose  at  least  two  chemical  sub. 
stances,  viz.,  (b)  a  hyaline  substance  in  contact  with  the  framework,  and  (,-)  spherical  granules  which 
are  embedded  in  the  hyaline  substance  (Langley).  Speaking  generally,  during  active  secretion, 
the  granules  decrease  in  number  and  size,  the  hyaline  substance  increases  in  amount,  the  network 
grows.  This  is  the  reverse  of  what  is  stated  above  as  the  observation  of  Heidenhain,  but  the  gran- 
ular appearance  described  by  Heidenhain  after  secretion  is  very  probably  due  to  the  action  of  the 
hardening  agent,  alcohol.  Langley  found  that  in  the  living  condition,  or  after  the  use  of  osmic 
acid,  in  some  animals  at  least,  the  chief  cells  are  granular  during  rest,  but  during  a  state  of  activity 
two  zones  are  differentiated,  an  outer  one,  which  is  clear,  owing  to  the  disappearance  of  the  gran- 
ules, and  an  inner  more  or  less  granular  one.    Granules  reappear  in  the  outer  part  after  rest.    During 


FORMATION    OF    HYDROCHLORIC    ACID.  271 

digestion,  the  parietal  cells  increase  in  size,  but  do  not  become  granular.  In  all  cells  containing 
much  pepsinogen,  distinct  granules  are  present,  and  the  quantity  of  pepsinogen  varies  directly 
with  the  number  and  size  of  the  granules.  In  the  glands  of  some  animals  there  is  little  difler- 
ence  between  the  resting  and  active  phases  (Langley).  Compare  Serous  GlanJs,  \  143,  and  Pan- 
creas, \   168.] 

The  Pepsin  is  formed  in  the  chief  cells  lyHcidenhaiii).  When  these  are  clear 
and  large  they  contain  much  pepsin,  when  they  are  contracted  and  turbid  the 
amount  is  small  {Grii/ziter).  The  pyloric  glands  are  also  said  to  secrete  pepsin,  but 
only  to  a  small  extent  {^Ebstein,  Griltzner,  Klemensietvicz).  Pepsin  accumulates 
during  the  first  stage  of  hunger,  and  it  is  eliminated  during  digestion  and  also  dur- 
ing prolonged  hunger.  According  to  Ebstein,  Griitzner,  and  Langley,  pepsin,  as 
such,  is  not  present  within  the  cells,  but  only  as  a  "  mother  substance,"  a  pepsin- 
ogen substance  (zymogenj,  or  propepsin  {Schiff),  which  occurs  in  the  gran- 
ules of  the  chief  cells  {Langley).  Tnis  zymogen  or  mother  substance,  by  itself, 
has  no  effect  upon  proteids ;  but  if  it  be  treated  with  hydrochloric  acid  or  sodium 
chloride,  it  is  changed  into  pepsin.  Pepsin  and  pepsinogen  may  be  extracted 
from  the  gastric  mucous  membrane  by  means  of  water  free  from  acids. 

The  pyloric  glands  secrete  pepsin,  but  no  acid.     Klemensiewicz  ex- 
cised in  a  living  dog  the  pyloric  portion  ot  the  stomach,  and  afterward  stitched 
together  the  duodenum  and  the  remaining  part  of  the 
stomach. 

Pyloric  Fistula.  — [In  Fig.  175  P  represents  the  excised 
pyloric  portion,  C  the  cardiac.  The  parts  a,  a,  and  a'  a'  were 
then  stitched  together,  and  the  continuity  of  the  organ  established . 
The  lower  end  {d)  of  P  was  closed  by  sutures,  while  the  edges  of 
P  at  o  were  stitched  to  the  abdominal  walls,  thus  making  a  pyloric 
fistula.] 

The  excised  pyloric  part,  with  its  vessels  intact,  he 
stitched  to  the  abdominal  wall,  after  sewing  its  lower 
end.  The  animals  experimented  on  died,  at  the  latest 
after  six  days.     The  secretion  of  this  part  was  thin,     Diagram  of  Kiemensiewicz's  experi- 
alkaline,  and  contained  2  per  cent,  of  solids,  includ-  ™="'  (Stirling). 

\ng  pepsin. 

In  the  frog  the  alkaline  glands  of  the  cesophagus  contain  only  chief  cells  which 
produce  pepsin ;  while  the  stomach  has  glands  which  secrete  acid  (and  perhaps 
some  pepsin),  and  are  lined  by  parietal  cells  {Fartsc/i,  v.  Swiecicki). 

Among  fishes  the  carps  have  no  fundus  glands  in  the  stomach  (Luchau).  [The  secreting  por- 
tions of  glands  of  the  cardiac  sack  (crop)  ol  the  herring  are  lined  by  a  single  layer  of  polygonal 
cells  ( IV.  Stirling). 

The  hydrochloric  acid  is  formed,  according  to  Heidenhain,  by  the  parietal 
cells.  It  occurs  on  the  free  surface  of  the  gastric  mucous  membrane  as  well  as  in 
the  ducts  of  the  gastric  glands.  The  deep  parts  of  the  glands  are  u.sually  alkaline. 
Free  HCl  is  detected  in  human  gastric  juice,  within  45  minutes  to  i  to  2  hours 
after  a  moderate  meal  {I'an  de  Velde,  and  othersj,  but  in  10  to  15  minutes  in  a 
fasting  condition  after  drinking  water  {E.  Frerichs)  ;  the  amount  gradually  in- 
creases during  the  process  of  digestion  {Kretschy  and  Uffelmann). 

01.  Bernard  injected  potassium  ferrocyanide,  and  afterward  lactate  of  iron,  into  the  veins  of  a  dog. 
After  death,  blue  coloration  occurred  only  in  the  upper  acid  layers  of  the  mucous  membrane.  Never- 
theless, we  must  assume  that  the  hyarochloric  acid  is  secreted  in  the  parietal  cells  of  the  fundus  of 
the  glands,  and  that  it  is  rapidly  carried  to  the  surface  along  with  the  pepsin.  Briicke  neutralized 
the  surface  of  the  gastric  mucous  membrane  with  magnesia  usta,  chopped  up  the  mucous  membrane 
with  water,  and  left  it  for  some  time,  when  the  fluid  had  again  an  acid  reaction. 

With  regard  to  the  formation  of  a  free  acid,  the  following  statements  may 
be  noted  ;  The  parietal  cells  form  the  h}drochloric  acid  from  the  chlorides  which 
the  mucous  membrane  takes  up  from  the  blood.  According  to  Voit,  the  formation 


272  INFLUENCE   OF    NERVES   ON   THE    SECRETION. 

of  acid  ceases  if  chlorides  be  withheld  from  the  food.  The  active  agent  is  lactic 
acid,  which  splits  up  sodium  chloride  and  forms  free  HCl  {Maiy).  The  base  set 
free  is  excreted  by  the  urine,  rendering  it  at  the  same  time  less  acid  (Jones,  Alaly). 
The  formation  of  acid  is  arrested  during  hunger.  According  to  H.  Schulz,  watery- 
solutions  of  alkaline  and  earthy  chlorides  are  decomposed,  even  at  a  low  tempera- 
ture, by  CO,,,  free  hydrochloric  acid  being  formed. 

Secretion. — When  the  stomach  is  empty,  there  is  no  secretion  of  gastric  juice  ; 
this  takes  place  only  after  appropriate  (mechanical,  thermal,  or  chemical)  stimu- 
lation. In  the  normal  condition,  it  takes  place  immediately  on  the  introduction 
of  food,  but  also  of  indigestible  substances,  such  as  stones.  The  mucous  mem- 
brane becomes  red,  and  the  circulation  more  active,  so  that  the  venous  blood 
becomes  brighter.  [That  the  vagi  are  concerned  in  this  vascular  dilatation,  is 
proved  by  the  fact,  that  if  both  nerves  be  divided  during  digestion,  the  gastric 
mucous  membrane  becomes  pale  {Riitherford).'\  The  secretion  is  probably  caused 
reflexly,  and  the  centre  is  perhaps  in  the  wall  of  the  stomach  itself  (Meissner's 
plexus  in  the  sub-mucous  coat).  It  is  asserted  that  the  idea  of  food,  especially 
during  hunger,  excites  secretion.  As  yet  we  do  not  know  the  effect  produced  upon 
the  secretion  by  stimulation  or  destruction  of  other  nerves,  e.  g.,  vagus,  sympa- 
thetic. [There  is  no  nerve  passing  to  the  stomach,  whose  stimulation  causes  a 
secretion  of  gastric  juice,  as  the  chorda  tympani  does  in  the  submaxillary  gland. 
If  the  vagi  be  divided  sufficiently  low  down  not  to  interfere  with  respiration,  the 
introduction  of  food  still  causes  a  secretion  of  gastric  juice;  even  if  the  sympa- 
thetic branches  be  divided  at  the  same  time,  secretion  still  goes  on  (Heidenhain). 
This  experiment  points  to  the  existence  of  local  secretory  centres  in  the  stomach. 
But  there  is  evidence  to  show  that  there  is  some  connection,  perhaps  indirect, 
between  the  central  nervous  system  and  the  gastric  glands.  Richet  observed  a 
case  of  complete  occlusion  of  the  cesophagus  in  a  woman,  produced  by  swallow- 
ing a  caustic  alkali.  A  gastric  fistula  was  made,  through  which  the  person  could 
be  nourished.  On  placing  sugar  or  lemon  juice  in  the  person's  mouth,  Richet 
observed  secretion  of  gastric  juice.  In  this  case  no  saliva  could  be  swallowed  to 
excite  secretion,  so  that  it  must  have  taken  place  through  some  nervous  channels. 
Even  the  sight  or  smell  of  food  caused  secretion.  Emotional  states  also  are  known 
to  interfere  with  gastric  digestion.] 

Effect  of  Absorption. — Heiaenhain  isolated  a  part  of  the  mucous  membrane 
of  \.\\<i  fundus  so  as  to  form  a  blind  sack  of  it,  and  he  found  that  mechanical  stimu- 
lation caused  merely  a  scanty  local  secretion  at  the  spots  irritated.  If,  however, 
at  the  same  time,  absorption  of  digested  matter  also  occurred,  secretion  took  place 
over  larger  surfaces.  [He  distinguishes  a  primary  and  merely  local  secretion 
excited  by  the  mechanical  stimulus  of  the  ingesta,  and  a  secondary  depending  on 
absorption  and  extending  to  the  whole  of  the  mucous  membrane.] 

The  statement  of  Schifi,  that  active  gastric  juice  is  secreted  only  after  absorption  of  the  so-called 
peptogenic  substances  (especially  dextrin),  is  denied. 

Action  of  Alcohol. — Small  doses  of  alcohol,  introduced  into  the  stomach,  increase  the  secretion 
of  ga^itric  juice;  large  doses  arrest  it.  Arliticial  digestion  is  affected  by  lo  per  cent,  of  alcohol 
(Schiitz),  is  retarded  by  20  per  cent,  and  is  arrested  by  stronger  doses.  Beer  and  wine  hinder 
digestion,  and  in  an  undiluted  form  they  interfere  with  artificial  digestion  (Buc/iner). 

The  gastric  juice,  which  passes  into  the  duodenum  after  gastric  digestion  is 
completed,  is  neutralized  by  the  alkali  of  the  intestinal  mucous  membrane  and  the 
pancreatic  juice  [at  the  same  time,  a  precipitate  is  formed  and  deposited  on  the 
walls  of  the  duodenum,  and  it  carries  the  pepsin  down  with  it].  Part  of  the 
pepsin  is  reabsorbed  as  such,  and  is  found  in  traces  in  the  urine  and  muscle  juice 
\Brueke). 

If  the  gastric  juice  be  completely  discharged  externally  through  a  gastric  fistula, 
the  alkalinity  of  the  intestine  is  so  strong  that  the  urine  becomes  alkaline  (Maly). 

The  acid  gastric  juice  of  the  new-born  child  is  already  fairly  active;  casein  is  most  easily  di- 
gested by  it,  then  fibrin  and  the  other  proteids  (Z-weiJcl).     When  the  amount  of  acid  is  loo  great 


METHODS   OF   OBTAINING    GASTRIC    JUICE.  273 

in  the  stomach  of  sucklings,  large,  firm,  indigestible  masses  of  casein  are  apt  to  be  formed  (Simon, 
BicJert — see  Milk,  \  230 ).     This  occurs  more  especially  after  the  use  of  cow's  milk. 

[Action  of  Drugs  on  Gastric  Secretion. — Dilute  alkalies,  if  given  before  food ;  saliva ;  some 
substances  called  peptogens  by  Schiff,  such  as  dextrin  and  peptones,  alcohol  and  ether,  all  excite 
secretion,  the  last  being  very  powerful.  When  the  secretion  is  exces-ively  acid,  antacids  are  given, 
some  diminishing  the  acidity  in  the  stomach,  as  the  carbonates  and  bicarbonates  of  the  alkalies, 
liquor  potassK  and  the  carbonate  of  magnesia;  while  the  citrates  and  tartrates  of  the  alkalies, 
becoming  converted  into  carbonates  in  their  passage  through  the  organism,  diminish  the  acidity  of 
the  urine.] 

165.  METHODS  OF  OBTAINING  GASTRIC  JUICE.— Historical.— Spallanzani  caused 
starving  animals  to  swallow  small  pieces  of  sponge  enclosed  in  perforated  lead  capsules,  and  after 
a  time,  when  the  sponges  had  become  saturated  with  gastric  juice,  he  removed  them  from  the 
stomach.  To  avoid  the  admixture  of  saliva,  the  sponges  are  best  mtioduced  through  an  opening 
in  the  cesophagus  [A/anasseiii).  Starving  animals  were  forced  to  swallow  small  stones,  which 
excited  the  secretion  of  gastric  juice.     After  a  time,  the  animals  were  killed,  and  the  juice  collected. 

Dr.  Beaumont  (1825),  an  American  physician,  was  the  first  to  obtain  human  gastric  juice,  from 
a  Canadian  named  Alexis  St.  Martin,  who  was  injured  by  a  gunshot  wound,  whereby  a  permanent 
gastric  fistula  was  established.  Various  substances  were  introduced  through  the  external  opening, 
which  was  partially  covered  with  a  fold  of  skin,  and  the  time  required  for  their  solution  was  noted. 
Bassow  (1842),  Blondlot  (1843),  and  Bardeleben  (1S49)  ^'ere  thereby  led  to  make  artificial  gastric 
fistulae. 

Gastric  Fistula. — The  anterior  abdominal  wall  is  opened  by  a  median  incision  just  below  the 
ensiform  cartilage,  the  stomach  is  exposed,  and  its  anterior  wall  opened  and  afterward  stitched  to 
the  margins  of  the  abdjminal  walls.  A  strong  cannula  is  placed  in  the  fistula  thus  formed.  A 
silver  cannula,  about  an  inch  wide  and  with  a  flange,  is  introduced  into  the  stomach,  so  that  the 
flange  lies  in  contact  with  the  gastric  mucous  membrane.  The  inner  surface  of  the  tube  of  the 
cannula  is  provided  with  a  screw,  into  which  a  similar  cannula  is  screwed,  and  its  flange  comes  in 
contact  with  the  abdominal  wall.  When  the  two  are  placed  together,  they  have  the  form  of  — ,  where 
a  passes  into  b.  [When  the  two  parts  of  the  cannula  are  screwed  together,  the  flanges  keep  the 
abdominal  walls  and  gastric  walls  in  contact  until  they  become  united  organically.]  As  a  rule,  the 
tube  is  kept  corked.  If  the  ducts  of  the  salivary  glands  be  tied,  a  perfectly  uncomplicated  object 
for  investigation  is  obtained. 

According  to  Leube,  dilute  human  gastric  juice  may  be  obtained  by  means  of  a  siphon-like  tube 
introduced  into  the  stomacti.     Water  is  introduced  first,  and  after  a  time  it  is  withdrawn. 

Artificial  Gastric  Juice. — .\n  important  advance  was  made  when  Eberle  (1S34)  prepared  "  arti- 
ficial gastric  jiiicf,"  by  extracting  the  pepsin  from  the  gastric  mucous  membrane  with  dilute  hydro- 
chloric acid.  A  certain  degree  of  concentration,  however,  is  required  (Sc/iwaiin).  Four  litres  of 
a  watery  solution  of  0.8-1. 0-1.7  °f  pure  hydrochloric  acid  per  1000  [Briicke)  are  sufficient  to 
extract  the  chopped-up  mucous  membrane  of  the  pig's  stomach.  Half  a  litre  is  infused  with  the 
stomach  and  renewed  every  six  hours.  The  collected  fluid  is  afterward  filtered  (Hoppe-SeyUr). 
The  substance  to  be  digested  is  placed  in  this  fluid,  and  the  whole  is  kept  at  the  temperature  of  the 
body,  but  it  is  necessary  to  add  a  little  HCl  from  time  to  time  [Schwann).  The  HCl  may  be  re- 
placed by  ten  times  its  volume  of  lactic  acid  [Lehmann)  and  also  by  nitric  acid  ;  while  oxalic,  sul- 
phuric, phosphoric,  acetic,  formic,  succinic,  tartaric  and  citric  acids  are  much  less  active ;  butyric 
and  salicylic  acids  are  inactive. 

Von  Wittich's  Glycerine  Method. — ^(a)  Glycerine  extracts  pepsin  in  a  very  pure  form.  The 
mucous  membrane  is  rubbed  up  with  powdered  glass  until  it  forms  a  pulp,  mixed  with  glycerine, 
and  allowed  to  stand  for  eight  days.  The  fluid  is  pressed  through  cloth,  and  the  filtrate  mixed  with 
alcohol,  thus  precipitating  the  pepsin,  which  is  washed  with  alcohol,  and  afterward  dissolved  in  the 
dilute  HCl,  to  form  an  artificial  digestive  fluid.  [The  addition  of  a  few  drops  of  the  glycerine 
extract  to  dilute  HCl  is  sufficient  for  experiments  on  artificial  digestion.] 

{b)  Or  the  mucous  membrane  may  be  placed  for  twenty-four  hours  in  alcohol,  and  afterward  dried 
and  extracted  for  eight  days  with  glycerine. 

(f )   \Vm.  Roberts  has  used  other  agents  for  extracting  enzyms  {\  148). 

Prepara'tion  of  Pure  Pepsin. — Briicke  pours  on  the  pounded  mucous  membrane  of  the  pig's 
stomach  a  5  per  cent,  solution  of  phosphoric  acid,  and  afterward  adds  lime  water  until  the  acid 
reaction  is  scarcely  distinguishable.  A  copious  precipitate,  which  carries  the  pepsin  with  it,  is  pro- 
duced. This  precipitate  is  collected  on  cloth,  repeatedly  washed  with  water,  and  afterward  dis- 
solved in  very  dilute  HCl.  A  copious  precipitation  is  caused  in  this  fluid  by  gradually  adding  to  it 
a  mixture  of  cholesterin  in  four  parts  ot  alcohol  and  one  of  ether.  The  cholesterin  pulp  is  col- 
lected on  a  filter,  washed  with  water  containing  acetic  acid,  and  afterward  with  pure  water.  The 
cholesterin  pulp  is  placed  in  ether,  to  dissolve  the  cholesterin,  and  the  ether  is  then  removed.  The 
small  watery  deposit  contains  the  pepsin  in  solution. 

Properties. — Pepsin  so  prepared  is  a  colloid  substance;  it  does  not  react, 
like  albumin,  with  tne  following  tests,  viz.  :   it  does  not  give  the  xanthroprotein 


274  ACTION   ON    PROTEIDS. 

reaction  (§  24S),  is  not  precipitated  by  acetic  acid  and  potassium  ferrocyanide, 
nor  by  tannic  acid,  mercuric  chloride,  silver  nitrate  or  iodine.  In  other  respects, 
it  belongs  to  the  group  of  albumins.  It  is  rendered  inactive  in  an  acid  fluid  by 
heating  it  to  5S°-6o°  C.  {Ad.  ALiver). 

166.  PROCESS  OF  GASTRIC  DIGESTION.— [In  the  process  of  gas- 
tric digestion  we  have  to  consider — 

1.  The  secretion  of  gastric  juice  and  its  action  on  food. 

2.  The  absorption  of  the  products  of  this  digestion. 

3.  The  movement  of  the  stomach  itself.] 

Chyme. — The  finely  divided  mixture  of  food  and  gastric  juice  is  called  chyme. 
The  gastric  juice  acts  upon  certain  constituents  of  chyme. 

I.  Action  on  Proteids. — Pepsin  and  the  dilute  hydrochloric  acid,  at 
the  temperature  of  the  body,  transform  proteids  into  a  soluble  form,  to  which 
Lehmann  (1850)  gave  the  name  of  "  Peptone."  During  this  change,  they  are 
first  transformed  into  a  substance  which  has  the  characters  of  syntonin  {Mulder). 
Syntonin  is  an  acid  albumin  or  albuminate;  when  neutralized  by  an  alkali  \e.g., 
sodium  carbonate],  the  albuminate  is  again  precipitated  (§  249,  III).  Fibrm  or 
coagulated  proteids  first  becomes  clear  and  swollen  up. 

An  intermediate  product  is  then  formed,  a  body  which,  as  it  were,  stands  mid- 
way between  albumm  and  peptone.  This  is  called  propeptone  {Schmidt-Miil- 
heim),  and  is  identical  with  Kiihne's  hemialbumose.  It  is  soluble  in  water, 
acids,  salts,  and  alkalies.  The  solutions  are  not  precipitated  by  boiling  but  by 
acetic  acid  and  ferrocyanide  of  potassium,  by  acetic  acid  and  saturation  with  NaCl 
or  MgSO^.  It  is  precipitated  by  nitric  acid  and  adheres  firmly  to  the  walls  of  the 
reagent  glass;  it  dissolves  in  nitric  acid  with  the  aid  of  heat,  giving  an  intense 
yellow  color,  and  is  again  precipitated  in  the  cold  {E.  Salkowski). 

By  the  continued  action  of  the  gastric  juice,  the  propeptone  passes  into  a  true 
soluble  peptone.  The  unchanged  albumin  behaves  like  an  anhydride  with 
respect  to  the  peptone.  The  formation  of  peptone  is  due  to  the  taking  up  of  a 
molecule  of  water,  under  the  influence  of  the  hydrolytic  ferment  pepsin,  and  the 
action  takes  place  most  readily  at  the  temperature  of  the  body.  Gelatin  is  changed 
into  a  gelatin-peptone. 

According  to  Kiihne,  the  proteid  molecule  contains  two  substances  preformed  ;  anti-alburrin 
and  hemi-albumin.  Gastric  juice  at  first  converts  them  into  antialbiimose  and  hemialhiintose,  and 
Loth  ultimately  into  anti-peptone  and  hemi-peptone  (J  170,  II).  Only  the  latter  issplit  up  by  trypsin 
into  leucin  and  tyrosiu  [Kiihne  and  Chittenden^ 

The  greater  the  amount  of  pepsin  (within  certain  limits)  the  more  rapidly  does 
the  solution  take  place.  The  pepsin  suffers  scarcely  any  change,  and  if  care  be 
taken  to  renew  the  hydrochloric  acid  so  as  to  keep  it  at  a  unit'orm  amount,  the 
pepsin  can  dissolve  new  quantities  of  albumin.  Still,  it  seems  that  some  pepsin  is 
used  up  in  the  process  of  digestion  {Grutzner).  Proteids  are  introduced  into  the 
stomach  either  in  a  solid  (coagulated)  or  fluid  condition.  Casein  alone  of  the  fluid 
forms  is  precipitated  or  coagulated,  and  afterward  dissolved.  The  non  coagulated 
proteids  are  transformed  into  syntonin,  without  being  previously  coagulated,  and  are 
then  changed  into  propeptone  and  directly  peptonized,  i.e.,  actually  dissolved. 

Heat  Disappears. — When  albumin  is  digested  by  pepsin  at  the  temperature 
of  tlie  body,  a  not  inconsiderable  amount  of  heat  disappears,  as  can  be  proved  by 
calorimetnc  experiment  {Maly).  Hence,  the  temperature  of  the  chyme  in  the 
stomach  falls  o°.2-o°.6  C.  in  two  to  three  hours  (/'.  J'i/itsiiigau  and Dietl). 

Coagulated  albumin  may  be  reg;arded  as  the  anhydride  of  the  fluid  form,  and 
the  latter  again  as  the  anhydride  of  peptone.  The  peptones,  therefore,  represent 
the  highest  degree  of  hydration  of  the  proteids. 

Hence,  peptones  may  be  formed  from  proteids  by  those  reagents  which  usually  cause  hydration, 
viz.,  treatment  with  strong  acids  (from  fibrin,  with  0.2  HCl — v.  IVittich),  caustic  alkalies,  putrefac- 
tive, and  various  other  ferments  and  ozone  (Gorup-Besanez). 


ARTIFICIAL    DIGESTION    OF   THE    PROTEIDS.  275 

The  anhydride  proteid  has  been  prepared  from  the  hydrated  form.  Henniger 
and  Hofmeister,  by  boiling  pure  peptone  with  dehydrating  substances  (anhydrous 
acetic  acid  at  So°  C),  have  succeeded  in  decomposing  it  into  a  body  resembling 
syntonin. 

Properties  of  Peptones. — (i)  They  are  completely  soluble  in  water.  (2)  They 
diffuse  very  easily  through  membranes  {Ftinke).  (3)  They  filter  quite  easily 
through  the  pores  of  animal  membranes  {Acker).  (4)  They  are  tiof  precipitated 
by  boiling,  nitric  acid,  acetic  acid  and  potassium  ferrocyanide,  acetic  acid  and 
saturation  with  common  salt.  (5)  They  zx^ precipitated  from  neutral  or  feebly 
acid  solutions  by  mercuric  chloride,  tannic  acid,  bile  acids,  and  phosphoro-wol- 
framic  acid  {Briicke).  (6)  With  jSIillon's  reagent  they  react  like  proteids,  and 
give  a  red  color,  and  with  nitric  acid  give  the  yellow  xanthoprotein  reaction.  (7) 
With  caustic  potash  or  soda  and  a  small  quantity  of  cupric  sulphate  [or  Fehling's 
solution]  they  give  a  beautiful  purplisli-red  color  (Biuret  reaction).  (8)  They 
rotate  the  plane  of  polarized  light  to  the  left. 

The  biuret  reaction  is  obtained  with  propeptone,  as  well  as  with  a  form  of  albumin,  which  is 
formed  during  artificial  digestion  and  is  soluble  in  alcohol.     It  is  called  Alkophyr  by  Briicke. 

[Darby's  fluid  meat  gives  all  the  above  reactions,  and  is  very  useful  for  studying  the  tests  for 
peptones.] 

The  Rapidity  of  Solution  of  fibrin  is  tested  by  placing  fibrin,  which  is  swollen  up  by  the  action 
of  0.2  per  cent.  HCl,  in  a  filter,  and  adding  the  digestive  fluid,  observing  the  rapidity  with  which 
the  fluid,  the  altered  fibrin,  drops  from  the  filter,  and  the  fibrin  disappears  {Gritnhagen).  Or 
the  fibrin  may  be  colored  with  carmine,  swollen  up  in  o.i  per  cent.  HCl,  and  placed  in  the 
digestive  fluid.  The  more  rapidly  the  fluid  is  colored  red,  the  more  energetic  is  the  digestion 
{Griitziler). 

Preparation. — Pure  peptones  are  prepared  by  taking  fluid  which  contains  them  and  neutral- 
izing it  with  barium  carbonate,  evaporating  upon  a  water  bath,  and  filtering.  The  barium  is 
removed  from  the  filtrate  by  the  careful  addition  of  sulphuric  acid,  and  subsequent  filtration 
{Hoppe-Seyler). 

Ptomaines. — Brieger  extracted  from  gastric  peptones  by  amylic  alcohol  a  peptone-free  poison, 
with  actions  like  those  of  curara.  It  belongs  to  the  group  of  ptomaines,  i.  e.,  alkaloids  obtained 
from  dead  bodies  or  decomposing  proteids. 

Peptones  are  undoubtedly  those  modifications  of  albumin  or  proteids  which, 
after  their  absorption  from  the  intestinal  canal  into  the  blood,  are  destined  to 
make  good  the  proteids  used  up  in  the  human  organism.  By  giving  peptones 
(instead  of  albumin)  as  food,  life  cannot  only  be  maintained,  but  there  may  even 
be  an  increase  of  the  body  weight  {F/osz  and  Maty,  Adamkiewicz).  After  [or 
before]  being  absorbed  into  the  blood  stream,  peptones  are  re-transformed,  first 
into  propeptone,  and  then  into  serum  albumin  (§  192). 

Conditions  Affecting  Gastric  Digestion. — The  presence  of  already- formed  peptones  inter 
feres  with  the  action  of  the  gastric  juice,  in  so  far  as  the  greater  concentration  of  the  fluid  interferes 
with  and  limits  ihe  mobility  of  the  fluid  particles  {Hoppe-Scyler).  Boiling  concentrated  acids, 
alum  and  tannic  acid,  allialinity  of  the  gastric  juice  [e.  g.,  by  the  admixture  of  much  saliva;,  abohsh 
the  action,  also  sulphurous  and  arsenious  acids  and  potassic  iodide  {Fubini  and  Mori).  The  salts 
of  the  heavy  metals,  which  cause  precipitates  with  pepsin,  peptone  and  mucin,  interfere  with  gastric 
digestion,  and  so  do  concentrated  solutions  of  alkaline  salts,  common  salt,  magnesium  and  sodium 
sulphates.  A  small  quantity  of  NaCl  increases  the  secretion  (Griitzner)  and  favors  the  action  of 
pepsin  ( ll'olberg).  Alcohol  precipitates  the  pepsin,  but  by  the  subsequent  addition  of  water  it  is 
redissolved,  so  that  digestion  goes  on  as  before.  Any  means  that  prevent  the  proteid  bodies  from 
swelling  up,  as  by  binding  them  firmly,  impede  digestion.  Slightly  over  half  a  pint  of  cold  water 
does  not  seem  to  disturb  healthy  digestion,  but  it  does  so  in  cases  of  disease  of  the  stomach. 
Copious  draughts  of  water  and  violent  muscular  exercise  disturb  digestion ;  while  warm  clothing, 
especially  over  the  pit  of  the  stomach,  aids  it.      Menstruation  retards  gastric  digestion. 

[Artificial  Digestion. — The  action  of  gastric  juice  on  proteids  may  be 
observed  outside  the  body,  and  we  can  prove,  as  is  shown  in  the  following  table, 
after  Rutherford,  that  pepsin  and  an  acid — e.g.,  hydrochloric,  along  with  water — 
are  essential  to  the  formation  of  gastric  peptones  : — 


276 


ACTION    ON    OTHER   CONSTITUENTS   OF    FOOD. 


Beaker  A. 

Beaker  B. 

Beaker  C. 

Water. 

Pepsin,  0.3  per  cent. 

Fibrin. 

Water. 

HCl,  0.2  per  cent. 

Fibrin. 

Water. 

Pepsin,  0.3  per  cent. 

HCl,      0.2 

Fibrin. 

Keep  all  in  water  bath  at  38°  C. 

Unchanged. 

Fibrin    swells  up,  becomes  clear, 
and  is  changed  into  acid  albu- 
min or  syntonin. 

Fibrin     ultimately     changed 
into  peptone. 

The  two  essential  substances  must  also  be  present  in  certain  proportions  and 
the  acid  must  be  present  to  a  certain  amount,  and  not  exceed  certain  limits.  The 
fibrin  is  obtained  by  beating  blood,  and  afterward  washing  and  boiling  it,  to 
destroy  any  traces  of  pepsin.  The  fibrin  may  be  colored  with  carmine,  and  from 
the  rapidity  with  which  the  fibrin  is  dissolved,  /.  e.,  the  depth  of  the  color  of  the 
fluid,  we  may  estimate  the  digestive  power  of  the  gastric  juice.  Similar  experi- 
ments may  be  made  with  unboiled  white  of  egg  mixed  with  nine  volumes  of 
water,  and  filtered  through  muslin.] 

[In  all  animals  gastric  digestion  is  essentially  an  acid  digestion,  and  between 
the  native  proteid,  fibrin,  albumin,  or  any  other  form  of  proteid,  and  the  end- 
product  peptone,  there  are  many  intermediate  substances  or  by-products,  whose 
properties  and  characters  have  still  to  be  investigated.  If  the  peptones  be  decom- 
posed, small  quantities  of  leucin  and  tyrosin  are  produced.  W.  Roberts  obtained 
a  bitter  substance  during  gastric  digestion.] 

[Exclusion  of  the  Stomach. — Ogata  finds  that  if  the  stomach  be  divided  at  the  pyloric  end  .so 
as  to  exclude  the  stomach  from  the  digestive  apparatus,  a  dog  can  be  nourished  for  a  long  time  by 
introducing  food  through  the  pylorus  into  the  duodenum.  Raw  tlesh  so  introduced  is  digested 
more  rapidly  in  the  small  intestine  than  in  the  stomach.  The  stomach  not  only  digests  but  it  acts 
on  the  connective  tissue  of  flesh  so  as  to  prepare  the  latter  for  intestinal  digestion.] 

II.  Action  on  other  Constituents  of  Food. — Milk  coagulates  when  it 
enters  the  stomach,  owing  to  the  precipitation  of  the  casein,  and  in  doing  so  it 
entangles  some  of  the  milk  globules.  Daring  the  process  of  coagulation,  heat  is 
given  off  {Afosso,  Ad.  Mayer).  The  free  hydrochloric  acid  of  the  gastric  juice  is 
itself  sufficient  to  precipitate  it ;  the  acid  removes  from  the  alkali  albuminate  or 
casein  the  alkali  which  keeps  it  in  solution.  Hammarsten  separated  a  special 
ferment  from  the  gastric  juice — quite  distinct  from  pepsin — the  milk-curdling 
ferment  which,  quite  independently  of  the  acid,  precipitates  the  casein  either  in 
neutral  or  alkaline  solutions.  It  is  this  ferment  or  rennet  which  is  used  to 
coagulate  casein  in  the  making  of  cheese.  [Rennet  is  an  infusion  of  the  fourth 
stomach  of  the  calf  in  brine  (§  231).  The  ferment  which  coagulates  milk  is  quite 
distinct  from  pepsin.  If  magnesic  carbonate  be  added  to  an  infusion  of  calf's 
stomach,  a  precipitate  is  obtained.  The  clear  fluid  has  strongly  coagulating  prop- 
erties, while  the  precipitate  is  strongly  peptic] 

The  action  of  the  milk-curdUng  ferment  is  perhaps  like  the  action  of  all  ferments,  a  hydration  of 
casein  (Aii.  Meyer);  it  is  greater  m  the  presence  of  0.2  HCl  [Sc/iumburg). 

One  part  of  the  rennet  ferment  can  precipitate  800,000  parts  of  casein.  When  casein  coagulates, 
two  new  proteids  seem  to  be  formed — the  coagulated  proteid  which  constitutes  cheese,  and  a  body 
resembling  peptone  dissolved  in  the  whey.  The  addition  of  calcium  chloride  accelerated,  while 
water  retarded  the  coagulation  {Hammarsten) — see  Milk,  S  231.  [A  ferment  similar  to  rennet  is 
contained  in  the  seeds  of    IVithania  eoaguhins  (S.  Lea).} 

Casein  is  first  precipitated  in  the  stomach,  then  a  body  like  syntonin  is  formed,  and  finally  peptone. 
During  the  process,  a  substance  containing  phosphorus  and  resembling  nuclein  appears  (Lu/>avin). 


ACTION    OF    GASTRIC    JUICE    ON    THE    VARIOUS   TISSUES.  277 

There  is  a  "  lactic  acid  ferment  "  {Hamtnarstui)  also  present,  which  changes 
milk  sugar  into  lactic  acid.  Part  of  the  milk  sugar  is  changed  in  the  stomach  and 
intestine  into  grape  sugar. 

Action  on  Carbohydrates. — Gastric  juice  does  not  act  as  a  solvent  of 
starch,  imilin,  or  gums.  Cane  sugar  is  slowly  changed  into  grape  sugar  {Boiich- 
anlat  and  Sandras  (iS^j),  Lehmann).  According  to  Uffelmann,  the  gastric 
mucus,  and  according  to  Leube,  the  gastric  acids,  are  the  chief  agents  in  this 
process. 

Albuminoids. — During  the  digestion  of  true  cartilage,  there  is  formed  a 
chondrin  peptone,  and  a  body  which  gives  the  sugar  reaction  with  Trommer's  test. 
Perfectlv  pure  elastin  yields  an  elastin  peptone,  similar  to  albumin  peptone,  and 
hemi-elastin  similar  to  hemi-albumose  (^Horbaczewski) . 

Fats  formerly  were  stated  not  to  be  acted  on,  but  the  recent  researches  of  Cash 
and  Ogata  show  that  a  small  part  of  the  fats  is  broken  up  into  glycerine  and  fatty 
acids.  [On  neutral  olive  oil  being  injected  into  the  stomach  of  a  dog,  after  several 
hours — the  pylorus  being  plugged  with  an  elastic  bag — it  partly  slips  up  and  yields 
oleic  acid  {^Ogata).'\ 

fWe  still  require  further  observations  on  the  gastric  digestion  of  fats.  Richet  observed  in  his  case 
of  fistula  that  fatty  matters  remained  a  long  time  in  the  stomach,  and  Ludwig  found  the  same  result 
in  the  dog.  In  some  dyspeptics,  rancid  eructations  often  take  place  toward  the  end  of  gastric 
digestion.  W.  Roberts  suggests  that  there  may  be  some  slight  decomposition  of  neutral  fats  and 
liberation  of  fatty  acids.  In  this  connection,  it  is  important  to  remember  that  fatty  acids  are  liber- 
ated from  neutral  fats  by  bacteroid  ferments  (zymophytes).] 

III.  Action  of  Gastric  Juice  on  the  Various  Tissues. — (i)  The  gelatin-yielding  sub- 
stance (collagen)  of  all  the  connective  tissues  (connective  tissue,  white  fibro-cartilage,  and  the  matrix 
of  bone),  as  well  as  glutin,  are  dissolve!  and  peptonized  by  the  gastric  juice  (  Uffelmann). 
[Gelatin  when  acted  on  by  gastric  juice  no  longer  solidifies  in  the  cold,  but  a  gelatin  peplone  is 
formed,  which  is  soluble  and  diffusible,  although  it  differs  from  true  peptone.]  In  the  dog,  con- 
nective tissues  are  specially  acted  on  in  the  stomach,  while  the  other  parts  of  organs  used  as  food 
are  prepared  for  digestion  in  the  small  intestine,  where  the  cellular  and  nucle.ar  elements  are 
digested  by  the  pancreatic  juice  (Bikfalvi).']  (2)  The  structureless  membranes  (membranre 
propria;)  of  glands,  sarcolemma,  Schwann's  sheath  of  nerve  fibres,  capsule  of  the  lens,  the  elastic 
laminie  of  the  cornea,  the  membranes  of  fat  cells  are  dissolved,  but  the  true  elastic  (fenestrated) 
membranes  and  fibres  are  not  affected.  (3)  Striped  muscle,  after  solution  of  the  sarcolemma, 
breaks  up  transversely  into  disks,  and,  like  non-striped  muscle,  is  dissolved  and  forms  a  true  soluble 
peptone,  hut  parts  of  the  muscle  always  pass  into  the  intestine.  (4)  The  albuminous  constituents 
of  the  soft  cellular  elements  of  glands,  stratified  epithelium,  endothelium,  and  lymph  cells,  form 
peptones,  but  the  nuclein  of  the  nuclei  does  not  seem  to  be  dissolved.  (5)  The  horny  parts  of 
the  epidermis,  nails,  hair,  as  well  as  chitin,  silk,  conchiolin,  and  spongin  of  the  lower  animals 
are  indigestible,  and  so  are  amyloid  substance  and  wax.  (6)  The  red  blood  corpuscles  are  dis- 
solved, the  haemoglobin  decomposed  into  ha^matin  and  a  globulin-like  substance  ;  the  latter  is  pep- 
tonized, while  the  former  remains  unchanged,  and  is  partly  absorbed  and  transformed  into  bile  pig- 
ment. Fibrin  is  easily  dissolved  to  form  propeptone  and  fibrin  peptone.  (7)  Mucin,  which  is  also 
secreted  by  the  goblet  cells  of  the  stomach,  passes  through  the  intestines  unchanged.  (81  Vege- 
table fats  are  not  affected  by  the  gastric  juice;  these  cells  yield  their  protoplasmic  contents  to  form 
peptones,  while  the  cellulose  of  the  cell  wall,  in  the  case  of  man  at  least,  remains  undigested 
(I  184)- 

Why  the  Stomach  does  not  digest  itself. — That  the  stomach  can  digest  living  things  is 
shown  by  the  following  facts  :  The  limb  of  a  living  frog  was  introduced  through  a  gastric  fistula 
into  the  stomach  of  a  dog  (CI.  Bernard) — The  ear  of  a  rabbit  [Pa-y)  was  also  introduced — and 
both  were  partly  digested.  The  margins  cf  a  gastric  ulcer  and  of  gastric  fistula;  in  man  are  attacked 
by  the  gastric  juice.  John  Hunter  (1772)  discussed  the  question  as  to  why  the  stomach  does  not 
digest  itself.  Not  unfrequently  after  death  the  posterior  wall  of  the  stomach  is  found  dige.'-led  [more 
especially  if  the  person  die  after  a  full  meal  and  the  body  be  kept  in  a  warm  place,  whereby  the 
Contents  of  the  stomach  may  escape  into  the  peritoneum.  CI.  Bernard  showed,  that  if  a  rabbit  be 
killed  and  placed  in  an  oven  at  the  temperature  of  the  body,  the  walls  of  the  stomach  are  attacked 
by  its  own  gastric  juice.  Fishes  are  also  frequently  found  with  their  stomach  partially  digested 
after  death].  It  would  seem,  therefore,  that  so  long  as  the  circulation  continues,  the  tissues  are  pro- 
tected from  the  action  of  the  acid  by  the  alkaline  blood;  this  action  cannot  take  place  if  the  reac- 
tion be  alkaline  (Pavy).  Ligature  of  the  arteries  of  the  stomach,  according  to  Pavy,  causes  diges- 
tive softening  of  the  gastric  mucous  membrane.  The  thick  layer  of  mucus  may  also  aid  in  protect- 
ing the  stomach  from  the  action  of  its  own  gastric  juice  (C/.  Bernard). 


278 


STRUCTURE    OF   THE    PANCREAS. 


167.  GASES  IN  THE  STOMACH.— The  stomach  always  contams  a 
certain  quantity  of  gases,  which  are  derived  partly  from  the  gases  swallowed  with 
the  saliva,  partly  from  gases  which  pass  backward  from  the  duodenum,  and  partly 
from  air  swallowed  directly. 

If  the  lan'nx  and  hyoid  bone  (^  15S)  are  suddenly  and  forcibly  raised  upward  and  forward,  there 
jiasses  into  the  space  behind  the  larynx  a  considerable  amount  of  air.  which  on  the  latter  regaining 
its  position,  is  swallowed,  owing  to  the  peristalsis  of  the  oesophagus.  We  can  feel  the  passage  of  such 
a  mass  of  air  as  it  passes  along  the  oesophagus.  In  this  way  a  considerable  volume  of  air  may  be 
swallowed. 

The  air  in  the  stomach  is  constantly  undergoing  changes,  whereby  its  O  is 
absorbed  by  the  blood,  and  for  i  vol.  of  O  absorbed  2  vols,  of  CO2  are  returned 
to  the  stomach  from  the  blood.  Hence,  the  amount  of  O  in  the  stomach  is  very 
small,  the  CO.  very  considerable  {Flaner). 

Gases  in  the  Stomach. — Vol.  per  cent.  (Planer). 


Human  Subject  after  Vegetable  Diet. 

Dog. 

I. 

II. 

I. 
Alter  Animal  Diet. 

II. 

After   Legumes. 

CO.,,  .    .    .  20.79 
H,'    .    .    .    6.71 
N,     .    .    .  72.50 
0, 

33-83 
27-58 
38-22 
0-37 

25.2 

68.7 
6.1 

32-9 
66.3 

0.8 

Fig.  176. 


By  the  acid  of  the  stomach  a  part  of  the  CO.j  is  set  free  from  the  saliva,  which 
contains  much  CO.j  (§  146).     The  N  acts  as  an  indifferent  substance. 

Abnormal  development  of  gases  in  persons  suffering  from  gastric  catarrh,  only  occurs  when 
the  gastric  contents  are  neutral m  reaction;  during  the  butyric  acid  fermentation  H  and  COj  are 
formed,  while  the  acetic  acid  and  lactic  acid  fermentations  do  not  cause  the  formation  of  gases. 
Marsh  gas  (CH^)  has  also  been  found,  but  it  must  come  from  the  intestine,  as  it  can  only  be  formeil 
when  no  O  is  present  (§  184). 

168.  STRUCTURE  OF  THE  PANCREAS.— The  pancreas  is  built 
on  the  t\  pe  of  compound  tubular  or  acino  tubular  glands,  and  in  its  general 
arrangement  into  lobes,  lobules  and  system  of  ducts  and 
acini',  it  corresponds  exactly  to  the  true  salivary  glands. 
The  epithelium  lining  the  ducts  is  not  at  all,  or  only  faintly, 
striated.  The  acini  are  tubular  or  flask-shaped,  and  often 
convoluted.  They  consist  of  a  membrana  propria,  resem- 
bling that  of  the  .salivary  glands,  lined  by  a  single  layer  of 
somewhat  cylindrical  cells,  with  a  more  or  less  conical  apex 
directed  toward  the  very  narrow  luinen  of  the  acini.  [As 
in  the  salivary  glands,  there  is  a  narrow  intermediary 
part  of  the  ducts  opening  into  the  acini,  and  lined  by  flat- 
tened epithelium.]  The  cells  lining  the  acini  consist  of  two 
zones  (Fig.  176)  : — 

(I)  The  smaller  parietal  layer  (outer)  is  transparent, 
homogeneous,  sometimes  faintly  striated,  and  readily  stained 
with  carmme  and  logwood:  and  (2)  the  inner  layer 
{Bernard's  granular  layer)  is  strongly  granular,  and  stains 
but  slightly  with  carmine  (Fig.  176).  It  undoubtedly  contributes  to  the  secretion 
by  giving  off  material,  the  granules  being  dissolved,  and  this  zone  becoming 
smaller  (^Hcidenhain).  The  spherical  nucleus  lies  between  the  two  zones.  [The 
lumen  of  the  acini  is  very  small,  and  spindle-shaped  or  branched  cells  (centro- 
acinar  cells)  lie  in  it,  and  send  their  processes  between  the  secretory  cells,  thus 


Section  of  the 
pancreas  i 
condition. 


THE    PANCREATIC   JUICE.  279 

acting  as  supporting  cells  for  the  elements  of  the  wall  of  the  acini  {^Langerhans , 
Fotiwisotzky).']  During  secretion  there  is  a  continuous  change  in  the  appearance 
of  the  cell  substance  ;  the  granules  of  the  inner  zone  dissolve  in  the  secretion  ; 
the  homogeneous  substance  of  the  outer  zone  is  reversed  and  transformed  into 
granules,  which  pass  toward  the  inner  zone  {Heidenhain,  Kiihne  and  Lea). 

Changes  in  the  Cells  during  Digestion. — During  theyfri/  stage  (6  to  lo  hours)  the  granular 
inner  zone  diminishes  in  size,  the  granules  disappear,  while  the  striated  outer  zone  increases  in  size 
(Fig  177,  2).  In  the  second  stage  (lo  to  20  hours)  the  inner  zone  is  greatly  enlarged  and  granular, 
while  the  outer  zone  is  small  {Fig.  177,3)-  During  hunger  the  outer  zone  again  enlarges  (Fig. 
177.  l).  In  a  gland  where  paralylic  secretion  takes  place,  the  gland  is  much  diminished  in  size, 
the  cells  are  shriveled  (Fig.  177,  4)  and  greatly  changed  (^Heidenhain).  According  to  Ogata, 
some  cells  actually  disappear  during  secretion. 

Duct. — -The  axially-placed  excretory  duct  consists  of  an  inner  thick  and  an  outer  loose  wall  of 
connective  and  elastic  tissues,  lined  bv  a  single  layer  of  non-striated  columnar  epithelium.  Small 
mucous  glands  lie  in  the  largest  trunk-;.  The  connecti-je  tissue  separates  the  gland  into  lobes  and 
lobules.  Non-meduUated  nerves,  vi\lh  ganglia  in  their  course,  pass  to  the  acini,  but  their  mode  of 
termination  is  unknown.  The  blood  vessels  form  a  rich  capillary  plexus  round  some  acini,  while 
round  others  there  are  very  few.  Kiihne  and  Lea  found  peculiar  small  cells  in  groups  between  the 
alveoli,  and  supplied  with  convoluted  capillaries  like  glomeruli.  Their  significance  is  entirely 
unknown.  [They  are  probably  lymphatic  in  their  nature.]  The  lymphatics  resemble  those  of  the 
salivary  glands.  The  pancreas  contains  water,  proteids,  ferments,  fats  and  salts.  When  a  colored 
injection  is  forced  into  the  ducts  under  a  high  pressure,  fine  intercellular  passages  between  the 
secreting  cells  are  formed  (Saviotti's  canals'),  h\xX  they  are  <2r//^c/«/ products. 

[In  making  experiments  upon  the  pancreatic  secretion,  it  is  important  to  remember  that  the  num- 
ber of  pancreatic  ducts  varies  in  different  animals.     In  man  there  is  just  one  duct  opening  along 

Fir,.  177. 


Changes  of  the  pancreatic  cells  in  varinu-S  stages  of  activity.     I,  During  hunger  :  2,  In  the  first  stage  of  digestion  ;  3 
In  the  second  stage  ;  4,  During  paralytic  secretion. 

with  the  common  bile  duct  at  Vater's  ampulla,  at  the  junction  of  the  middle  and  lower  third  of  the 
duodenum.  The  rabbit  has  two  ducts,  the  larger  opening  separately  about  14  inches  (30  to  35  cm.) 
below  the  entrance  of  the  bile  duct.     The  dog  and  cat  have  each  two  ducts  opening  separately.] 

Chemistry  — The  fresh  pancreas  contains  water,  proteids,  the  ferments,  fats  and  salts.  In  a 
gland  which  has  been  exposed  for  some  time,  leucin,  isoleucin  [Nencki),  butalin,  tyrosin,  often 
xanthin  and  guanin  are  found :  lactic  and  fatty  acids  seem  to  be  formed  from  chemical  decomposi- 
tions taking  place. 

i6g.  THE  PANCREATIC  JUICE.— Method  of  obtaining  the  pancreatic  juice.  Regner 
de  Graaf  (1664)  tied  a  cannula  in  the  pancreatic  duct  of  a  dog,  and  collected  the  juice  in  a  small 
bag  placed  in  the  abdomen.  Other  experimenters  brought  the  tube  through  the  abdominal  wall, 
and  made  a  temporary  fistula,  which  after  some  days  became  inflamed,  so  that  the  cannula  fell 
out-  To  make  a  permanent  fistula,  a  duodenal  fistula  (like  a  gastric  fistula)  is  made,  and  Wir- 
sung's  duct  is  catheierized  with  a  fine  tube;  or  the  abdomen  is  opened  (dog),  and  the  pancreatic 
duct  is  pulled  forward  and  stitched  to  the  abdominal  wall,  with  which,  in  certain  cases,  it  unites. 
Heidenhain  cuts  out  the  part  of  the  duodenum  where  the  duct  opens  into  it,  from  its  continuity  with 
the  intestine,  and  fixes  it  on  the  outside  the  abdominal  wound. 

Variations  in  Secretion. — The  secretion  obtained  from  a  permanent  fistula 
is  a  copious,  slightly  active,  watery  secretion,  containing  much  sodium  carbonate; 
while  the  thick  fluid  obtained  from  the  fistula  before  inflammation  sets  in  acts  far 
more  energetically.  This  thick  secretion,  which  is  small  in  amount,  is  the  normal 
secretion.  The  copious  watery  secretion  is  perhaps  caused  by  the  increased  trans- 
udation from  the  dilated  blood  vessels  (possibly,  in  consequence  of  the  paralysis 
of  the  vasomotor  nerves).  It  is,  therefore,  in  a  certain  sense,  a  "  paralytic  secre- 
tion "  (§  145).     The  quantity  varies   much,  according  as  the  fluid  is  thick  or 


280  DIGESTIVE    ACTION    OF   THE    FANCREATIC   JUICE. 

thin.  During  digestion,  a  large  dog  secretes  i  to  1.5  grammes  of  a  thick  secre- 
tion (C/.  Bernard).  Bidder  and  Schmidt  obtained  in  twenty-four  hours  35  to  117 
grammes  of  a  watery  secretion  per  kilo,  of  a  dog. 

When  the  gland  is  not  secreting,  and  is  at  rest,  it  is  soft  and  of  a  pale  yellowish- 
red  color,  but  during  secretion  it  is  red  and  turgid  with  blood,  owing  to  the  dila- 
tation of  the  blood  vessels. 

The  normal  secretion  is  transparent,  colorless,  odorless,  saltish  to  the  taste, 
and  has  a  strong  alkaline  reaction,  owing  to  the  presence  of  sodium  carbonate, 
so  that  when  an  acid  is  added,  CO^  is  given  off.  It  contains  albumin  and  alkali 
albuminate;  like  thin  white  of  egg,  it  is  sticky,  somewhat  viscid,  flows  with  diffi- 
culty, and  is  coagulated  by  heat  into  a  white  mass.  In  the  cold,  there  separates 
a  jelly-like  albuminous  coagulum.  Nitric,  hydrochloric  and  sulphuric  acids  cause 
a  precipitate,  while  the  precipitate  caused  by  alcohol  is  redissolved  by  water.  CI. 
Bernard  found  in  the  pancreatic  juice  of  a  dog  8.2  per  cent,  of  organic  substances, 
and  0.8  per  cent,  of  ash.  The  juice  (dog)  analyzed  by  Carl  Schmidt  contained  in 
1000  parts  :  — 

f  Sodic  Chloride 7.36 

"       Phosphate 0.45 

[  Organic 81. S4  "      .Sulphate o.io 

Solids.  yo.jS  in    J    Inorganic S.54    ]    Soda 0.32 

1000  parts,        I        (like  those  of  blood  j    Lime 2.22 

[  serum).  Magnesia 0.05 

I    Potassic  Sulphate 0.02 

[   Ferric  Oxide 0.02 

The  more  rapid  and  more  profuse  the  secretion,  the  poorer  it  is  in  organic  substances  ( IVcinmann, 
Bernstein),  while  the  inorganic  remain  almost  the  same;  nevertheless,  the  total  quantity  of  solids 
is  greater  than  when  the  quantity  secreted  is  small  [Bernsic'in\.  Traces  of  leucin  (Radzicje'wski) 
and  soaps  are  contained  in  the  fresh  juice.  [It  usually  contains  few  or  no  structural  elements.  Any 
structural  elements  present  in  the  fresh  juice,  as  well  as  its  proteids,  are  digested  by  the  peptone- 
forming  ferment  of  the  juice,  especially  if  the  juice  be  kept  for  some  time.  If  the  fresh  juice  is 
allowed  to  stand  for  some  time,  and  then  mixed  with  chlorine  water,  a  red  color  is  obtained.] 

Concretions  are  rarely  formed  in  the  pancreatic  ducts ;  they  usually  consist  of  calcic  carbonate. 
Dextrose  has  been  found  in  the  juice  in  diabetes,  and  urea  in  jaundice. 

The  statement  made  by  Schift,  that  the  pancreas  secretes  only  after  the  absorption  of  dextrin,  has 
not  been  confirmed.  The  secretory  activity  of  the  pancreas  is  not  dependent  on  the  presence  of 
the  spleen. 

170.  DIGESTIVE  ACTION  OF  THE  PANCREATIC  JUICE.— 

The  presence  of  at  least /<>///■  hydrolytic  ferments  or  enzymes  makes  the  pancreatic 
juice  one  of  the  most  important  digestive  fluids  in  the  body. 

I.  The  Diastatic  Action  {Valentin,  1844)  is  caused  by  a  diastatic  ferment, 
amylopsin,  a  substance  which  seems  to  be  identical  with  the  saliva  ferment  ;  but 
it  acts  much  more  energetically  than  the  ptyalin  of  saliva,  on  raw  starch  as  well 
as  upon  boiled  starch ;  at  the  temperature  of  the  body  the  change  is  effected 
almost  at  once,  while  it  takes  place  more  slowly  at  a  low  temperature.  Glycogen 
is  changed  into  dextrin  and  grape  sugar,  and  achroode.\trin  {Briieke' s)  into  sugar. 
Even  cellulose  is  said  to  be  dissolved  {Sehmiilewitsch),  and  gum  changed  into 
sugar  by  it  {v.  Voit),  but  inulin  remains  unchanged. 

•According  to  v.  Mering  and  Musculus,  the  starch  {as  in  the  case  of  the  saliva,  ^  14S)  is  changed 
into  maltose,  a  reducing  dextrin,  and  grape  sugar;  so,  also,  is  glycogen.  Amylopsin  changes 
achioodextrin  into  maltose ;  at  40°  C.  maltose  is  slowly  changed  into  dextrose  (Brown  and  Heron), 
but  cane  sugar  is  not  changed  into  invertin. 

The  ferment  is  ]jrecipitated  by  alcohol,  while  it  is  extracted  by  glycerine  without  undergoing  any 
essential  change.  All  conditions  which  destroy  the  diastatic  action  of  saliva  (i,  148)  similarly  affect 
its  action,  but  the  admixture  with  acid  gastric  juice  (its  acid  being  neutralized)  or  bile  does  not  seem 
to  have  any  injurious  influence.  This  ferment  is  absent  from  the  pancreas  of  new-born  children 
(A-orow:n). 

Preparation. — The  ferment  is  isolated  by  the  same  methods  as  obtain  for  the  saliva  ptyalin 
(§  148) ;  but  the  tryptic  ferment  is  precipitated  at  the  same  time.  The  addition  of  neutral  salts  (4 
per  cent,  solution),  e.g.^  potassium  nitrate,  common  salt,  ammonium  chloride,  increases  the  diastatic 
action. 


DIGESTIVE    ACTION    OF   THE    PANCREATIC   JUICE.  281 

II.  The  Tryptic  Action  {CI.  Berttard,  iSjj),  or  the  action  on  proteids, 
depends  upon  the  presence  of  a  hydrolytic  ferment  which  Corvisart  (1858)  called 
pancreatin,  and  W.  Kiihne  (1S76)  termed  trypsin.  Trypsin  acts  upon  proteids 
at  the  temperature  of  the  body,  when  the  reaction  is  alkaline,  and  changes  them 
first  into  a  globulin-like  substance  (serum  globulin,  §249,y.  G.  Oft),  then  into 
propeptone,  and,  lastly,  into  a  true  peptone,  sometimes  called  tryptone.  The 
proteids  do  not  swell  up  before  they  are  changed  into  peptone  [but  they  are 
eroded  or  eaten  away  by  the  action  of  the  juice].  When  the  proteid  has  been 
previously  swollen  up  by  the  action  of  an  acid,  or  when  the  reaction  of  the  medium 
is  acid,  the  transformation  is  interfered  with. 

Substances  yielding  gelatin,  nuclein  (Bokay)  and  Hb  resist  trypsin ;  glutin  and  swollen-up  gelatin- 
yielding  substances  are  changed  into  gelatin  peptone,  but  the  latter  undergoes  no  further  change. 
O-Hb  is  split  up  into  albumin  and  h.'emochromnjen.  In  other  respects,  trypsin  acts  on  tissues  con- 
taining albumins  just  like  pepsin  (?.  167,  III)  [Hop/e-Sey/tr). 

Preparation. — Trypsin  is  never  absent  from  the  pancreas  of  new-born  children  [Ztoeifeh,  and  it 
may  be  extracted  by  water,  which,  however,  also  dissolves  the  albumin.  Kiihne  has  carefully  sepa- 
rated the  albumin  and  obtained  the  ferment  in  a  pure  state.  It  is  soluble  in  water,  insoluble  in 
alcohol.  Pepsin  and  hydrochloric  acid  together  act  upon  tryp.sin  and  destroy  it;  hence  it  is  not 
advisable  to  administer  trypsin  by  the  mouth,  as  it  would  be  destroyed  in  the  stomach  (Ewald, 
Mays).     When  dried  it  may  be  heated  to  l6o°  without  injury  (Sa/iowsii). 

Origin  of  Trypsin. — It  is  formed  within  the  pancreas,  from  a  "  mother  sub- 
stance'^ or  zymogen  (Heidenhain),  \\h\c\-\  takes  up  oxygen.  The  zymogen  is 
found  in  small  amount,  six  to  ten  hours  after  a  meal,  in  the  inner  zone  of  the  se- 
cretory cells,  but  after  sixteen  hours  it  is  very  abundant  in  the  inner  zone  of  the 
cells.  It  is  soluble  in  water  and  glycerine.  Trypsin  is  formed  in  the  watery  solu- 
tion from  the  zymogen,  and  the  same  result  occurs  when  the  pancreas  is  chopped 
up  and  treated  with  strong  alcohol  ( IV.  Kiihne).  The  addition  of  sodium  chlo- 
ride, carbonate,  and  glycocholate,  favors  the  activity  of  the  tryptic  ferment  {ffei- 
denhain).  [The  following  facts  show  that  zymogen  {"^uij.ri,  ferment),  or,  as  it  has 
been  called,  trypsinogen,  is  the  precursor  of  trypsin,  that  it  exists  in  the  gland 
cells,  and  requires  to  be  acted  upon  before  trypsin  is  formed.  If  a  glycerine  ex- 
tract be  made  of  a  pancreas  taken  from  an  animal  just  killed,  and  if  another  extract 
be  made  from  a  pancreas  which  has  been  kept  for  twenty-four  hours,  it  will  be 
found  that  an  alkaline  solution  of  the  former  has  practically  no  effect  on  fibrin, 
while  the  latter  is  powerfully  proteolytic.  If  a  fresh  and  still  warm  pancreas  be 
rubbed  up  with  an  equal  volume  of  a  i  per  cent,  solution  of  acetic  acid,  and  then 
extracted  with  glycerine,  a  powerfully  proteolytic  extract  is  at  once  obtained. 
Trypsin  is  formed  from  zymogen  by  the  action  of  acetic  acid  {Heidcnhaiii). 
There  is  reason  to  believe  that  trypsin  is  formed  from  zymogen  by  oxidation, 
and  that  the  former  loses  its  proteolytic  power  after  removal  of  its  oxygen. 
The  amount  of  zymogen  present  in  the  gland  cells  seems  to  depend  upon 
the  number  and  size  of  the  granules  present  in  the  inner  granular  zone  of  the 
secretory  cells.] 

Disturbing  Conditions. — The  addition  of  NaCl,  sodic  glycocholate,  and  carbonate,  increases 
the  activity  of  the  ferment  (Heidenhniri),  while  MgSO^  diminishes  it  (P/eiff'er). 

[In  dogs  poisoned  with  CO,  the  trypsin  no  longer  has  any  action  on  albumin  and  fibrin.  An  infu- 
sion of  the  CO-pancreas  becomes  active  \\'hen  oxygen  is  driven  through  it  [Herseti).  Poisoning 
with  COo,  however,  does  not  aifect  the  tryptic  activity.] 

Further  Effects. — When  the  trypsin  is  allowed  to  act  upon  the  peptone 
formed  by  its  own  action,  the  peptone  is  partly  changed  into  the  amido  acid,  leu- 
cin,  or  amido- eaproic  acid  {C^Yiu^O.,,  and  tyrosin  (CaHnNO;,),  which  belongs  to 
the  aromatic  series  {Kiihne,  §  252,  IV,  3).  Hypoxanthin,  xanthin  {Salomon),  and 
asparaginic  or  amido-succinic  acid  (C,H;NOi),  are  also  formed  during  the  diges- 
tion of  fibrin  and  gluten,  and  so  are  glutaminic  acid  (CjH.jNO,),  amido-valerianic 
and  (CjHiiNO.^).  Gelatin  is  first  changed  into  a  gelatin  peptone,  and  afterward  is 
decomposed  into  glycin  and  ammonia. 


282 


DIGESTIVE   ACTION    OF   THE    PANCREATIC   JUICE. 


Putrefactive  Phenomena. — If  the  action  of  the  pancreatic  juice  be  still  fur- 
ther |iri)longed,  especially  if  the  reaction  be  alkaline,  a  body  with  a  stron^,  stink- 
ing, disagreeable  fscal  odor,  ///,/<>/  (C,U.N^,  volatile  fatty  acids,  s^-uA?/  (C,,UJ<!), 
3.nd  />/ic'fi(>/  (CgHgO)  and  a  substance  which  becomes  red  on  the  addition  of  chlo- 
rine or  bromine  water  {Bernard)  are  formed,  while,  at  the  same  time,  H,  CO.2, 
HjS,  CHj,  and  N  are  given  off.  The  formation  of  indol  and  the  other  substances 
just  mentioned  depends  upon  putrefaction  (§  184,  III).  Their  formation  is  pre- 
vented by  the  addition  of  calomel,  salicvlic  acid,  or  thymol,  which  kills  the  organ- 
isms upon  which  putrefaction  depends  {Hiifner.  Kiihne). 

[Artificial  Digestion. — If  some  fibrin  be  placed  in  pancreatic  juice,  or  in  a  i 
percent,  solution  of  sodium  carbonate  containing  the  ferment  trypsin,  peptones 
are  rapidly  formed.  When  we  compare  gastric  with  pancreatic  digestion, 
we  find  that  there  are  marked  differences.  The  fibrin  in  pancreatic  digestion  is 
eroded,  or  eaten  away,  and  never  swells  up.  The  process  takes  place  in  an  alka- 
line medium,  and  never  in  an  acid  one.  In  fact,  a  i  per  cent,  solution  of  sodic 
carbonate  seems  to  play  the  same  part  in  assisting  trypsin  that  a  .2  per  cent,  solu- 
tion of  HCl  does  for  pepsin  in  gastric  digestion.  In  gastric  digestion  acid  albu- 
min or  syntonin  is  formed  in  addition  to  the  true  peptones.  In  pancreatic  diges- 
tion a  body  resembling  alkali  albumin,  which  passes  into  a  globulin-like  body,  and 
ultimately  into  a  tryptic  peptone  or  tryptone  is  formed.  Of  the  peptones  so 
formed,  one  is  called  antipeptonc,  and  it  is  not  further  changed,  but  part  of  the 
proteid  is  changed  in  a  by-product,  hemipeptone.  This  body,  when  acted  upon, 
yields  leucin  and  tyrosin.  When  putrefaction  takes  place,  the  bodies  above  men- 
tioned are  also  formed.  We  might  represent  the  action  of  trypsin  thus  :  Proteid 
+  trypsin  -f  i  per  cent,  sodium  carbonate,  kept  at  38°  C.  =  formation  of  a 
globulin-like  body,  and  then  antipeptone  and  hemipeptone  are  formed. 


undergoes  no 
further  change. 


yields. 

Hemip 

yields. 

Normal  Digestive 
Products. 

Putrefactive  Products. 

Leucin, 

Tyrosin, 
Hypoxanthin, 
Asparaginic  Acid. 

Indol. 
Skatol, 
Phenol, 

Volatile  Fattv  Acids, 
H,  CO,,  H,S, 
CH^,  N. 

It  seems  that  trypsin  in  pure  water  can  act  slowly  upon  fibrin  to  produce  pep- 
tone.    Pepsin  cannot  do  this  without  the  aid  of  an  acid.] 

When  proteids  are  boiled  for  a  long;  tim';  with  dilute  H^SO^,  we  obtain  peptone,  then  leucin  and 
tyroiin  {Kuhne);  gelatin  yields  ^/i'«'k.  Hypoxanthin  and  xanthin  are  obtained  in  the  same  way 
by  similarly  boiling  fibrin,  and  the  former  may  even  be  obtained  by  boiling  fibrin  with  water  [Chit- 
tenden), 

Papain. — It  is  very  remarkable  that  the  juice  of  the  green  fruit  of  the  papaya  tree  (Ca?-ica  fapava) 
possesses  digestive  properties  [Roy,  IVittmnci),  and  the  action  is  due  to  an  albuminous  peptonizing 
ferment,  closely  related  to  trypsin,  and  called  caricin  or  papain.  [It  forms  a  true  peptone,  an  inter- 
mediate body,  leucin  and  tyrosin.  It  also  contains  a  milk-coagulating  ferment  \!ilartin).'\  The 
milky  juice  of  the  fig  tree  has  a  similar  action. 

According  to  Gorup-Besanez,  sprouting  malt,  vetch,  hop,  hemp  during  sprouting,  and  the  recep- 
tacle of  the  artichoke,  contain  a  peptonizing  ferment. 

Leucin,  tyrosin,  glutaminic  and  asparaginic  acids,  and  xanthin  are  formed  in  the  seeds  of  some 
plants;  hence  we  may  assume  that  the  processes  of  decomposition  in  some  seeds  are  closely  allied 
to  the  fermentative  actions  that  occur  in  the  intestine  (Salotiion). 

III.  The  action  on  neutral  fats  is  twofold :  (i)  It  acts  upon  fats  so  as  to 
iorxw  z.  fine  permanent  enuihicn  (yEberlc).  (2)  It  causes  neutral  fats  to  take  up  a 
molecule  of  water  and  split  into  glycerine  and  their  corresponding  fitty  acids  :  — 


Tristearin 
(C5:H„<,0, 


Water.  Glycerine.  Stearic  Acid. 

3(H,0)  =  {C3H,03)+3(C,,H3,0J. 


SECRETION    OF   PANCREATIC   JUICE.  283 

The  latter  result  is  due  to  the  action  of  an  easily  decomposable  fat-splitting  fer- 
ment {CI.  Bernard),  zX'io  called  steapsin.  Lecithin  is  decomposed  by  it  into 
glycero-phosphoric  acid,  neurin  and  fatty  acids  (Bokay).  After  the  decomposi- 
tion is  completed,  the  fatty  acids  are  partly  saponified  hy  the  alkali  of  the  pancre- 
atic and  intestinal  juices  and  partly  emulsionized  bv  the  alkaline  intestinal  juice 
{J.  Miink).    Both  the  soaps  and  emulsions  are  capable  of  being  absorbed  (§  191). 

Emulsification. — The  most  important  change  effected  on  fats  in  the  small  intestine  is  the  pro- 
duction of  an  emulsion,  or  their  sulidivision  into  exceedingly  minute  particles  (?  191 ).  This  is  neces- 
sary in  order  that  the  fats  may  be  taken  up  by  the  lacteals.  If  the  fat  to  be  emulsified  contains  a  free 
fatty  acid,  /.  c,  if  it  be  slightly  rancid,  and  if  the  fluid  with  which  it  is  mixed  be  alkaline,  emulsifica- 
tion takes  place  extremely  rapidly  {Brucki).  A  drop  of  cod-liver  oil,  which  in  its  unpurified  condi- 
tion alwavs  contains  fatty  acids,  on  being  placed  in  a  drop  of  0.3  per  cent,  solution  of  soda,  instantly 
gives  rise  to  an  emulsion  ( Gad).  The  excessively  minute  oil  globules  that  compose  the  emulsion 
are  first  covered  with  a  laver  of  soap,  which  soon  dissolves,  and  in  the  process  small  globules  are 
detached  from  the  original  oil  globules.  The  fresh  surface  is  again  covered  by  a  soap  film,  and  the 
process  is  repeated  over  and  over  again  until  an  excessively  fine  emulsion  is  obtained  (  G.  Quincke). 
If  the  fat  contain  much  fatty  acid  and  the  solution  of  soda  be  more  concentrated,  "  myelin  forms" 
are  obtained  similar  to  those  which  are  formed  when  fresh  nerve  fibres  are  teased  in  water  (Briicke). 
Animal  oils  emulsionize  more  readily  than  vegetable  oils;  castor  oil  does  not  emulsionize  (Gad). 

[It  is  extremely  difficult  to  obtain  a  perfectly  neutral  oil,  as  most  oils  contain  a  trace  of  a  fatty 
acid.  In  fact,  if,  on  adding  a  weak  solution  of  sodic  carbonate  to  oil  or  faUy  matters,  fluid  at  the 
temperature  of  the  body,  an  emulsion  is  obtained,  one  may  be  sure  that  the  oil  contained  a  fatty 
acid,  so  that  Bernard's  view  about  an  "  emulsive  ferment  "  being  necessary  is  not  endorsed.  The 
fatty  acid  set  free  by  the  fat-splitting  ferment  enables  the  alkaline  pancreatic  juice  at  once  to  produce 
an  emulsion.] 

Fat-Splitting  Ferment. — This  is  a  very  unstable  body,  and  must  be  prepared  from  the  perfectly 
fresh  gland  by  rubbing  it  up  with  powdered  glass,  glycerine,  and  a  i  per  cent,  solution  of  sodic  car- 
bonate, and  allowing  it  to  stand  for  a  day  or  two  [Griitzner).  [This  ferment  is  said  to  cause  an 
emuKion  of  oil  and  mucilage  tinged  blue  with  litmus  at  40°  C.  to  become  red  (Gamgee).  In  per- 
forming this  experiment  notice  that  the  mucilage  is  perfectly  neutral,  as  gum  arable  is  frequently 
acid  ] 

[Pancreatic  Extracts. — The  action  of  the  pancreas  may  be  tested  by  making  a  watery  extract 
of  a  perfectly  fresh  gland.  Such  an  extract  always  acts  upon  starch  and  generally  upon  fats,  but 
this  extract  and  also  the  glycerine  extract  vary  in  their  action  upon  proteids  at  different  times.  If 
the  extract — watery  or  glycerine — be  made  from  the  pancreas  of  a  fasting  animal,  the  tryptic  action 
is  slight  or  absent,  but  is  active  if  it  be  prepared  from  a  gland  4  to  10  hours  after  a  meal.  The 
pancreatic  preparations  of  Benger,  of  Manchester,  Savory  and  Moore,  or  Burroughs  and  Welcome, 
all  possess  active  diastatic  and  proteolytic  properties.] 

[Pancreas  Salt. — Prosser-James  proposes  to  employ  common  salt  mixed  with  pepsin,  which  he 
calls  peptic  salt ;  and  he  advocates  the  use  of  another  preparation  composed  of  the  pancreatic  fer- 
ments and  common  salt,  pancreatic  salt.] 

The  pancreas  of  nevy-born  children  contains  trypsin  and  the  fat-decomposing  ferment,  but  not 
the  diastatic  one  {Zti-eifel).  A  slight  diastatic  action  is  obtained  after  two  months,  but  the  full  effect 
is  not  obtained  until  after  the  first  year  (A'orowin). 

IV.  According  to  Kiihne  and  W.  Roberts,  the  pancreas  contains  a  milk-curd- 
ling ferment,  which  may  be  extracted  by  means  of  a  concentrated  solution  of 
cornmon  salt. 

171.  THE  SECRETION  OF  THE  PANCREATIC  JUICE.- 
Rest  and  Activity. — .\s  in  other  glands,  we  distniguish  a  quiescent  state,  during 
which  the  gland  is  soft  and  pale,  and  a  state  of  secretory  activity,  during  which 
the  organ  swells  up  and  appears  pale  red.  The  latter  condition  only  occurs  after 
a  meal,  and  is  caused  probably  in  a  reflex  way,  owing  to  stimulation  of  the  nerves 
of  the  stomach  and  duodenum.  Kiihne  and  Lea  found  that  all  the  lobules  of  the 
gland  were  not  active  at  the  same  time.  The  pancreas  of  the  herbivora  secretes 
uninterruptedly  [but  in  the  dog  secretion  is  not  constant]. 

Time  of  Secretion. — .According  to  Bernstein  and  Heidenhain  the  secretion 
begins  to  flow  when  food  is  introduced  into  the  stomach,  and  reaches  its  maximum 
2  to  3  hours  thereafter.  The  amount  falls  toward  the  5th  or  7th  hour,  and  rises 
again  (owing  to  the  entrance  of  the  chyme  into  the  duodenum)  toward  the  9th 
and  nth  hour,  gradually  falling  toward  the  i7th-24th  hour,  until  it  ceases  com- 
pletely.    When   more  food  is  taken   the  same  process  is  repeated.     As  a  general 


284  STRUCTURE  OF  THE  LIVER. 

rule,  when  the  secretion  occurs  rapidly  it  contains  less  sqlids  than  when  it  takes 
place  slowlv. 

Condition  of  Blood  Vessels. — During  secretion,  the  blood  vessels  behave 
like  the  blood  vessels  of  the  salivary  glands  after  stimulation  of  the  chorda — they 
dilate,  and  the  venous  blood  is  bright  red — thus,  it  is  probable  that  a  similar 
nervous  mechanism  exists  [but  as  yet  no  such  mechanism  has  been  discovered]. 
The  secretion  is  excreted  at  a  pressure  of  more  than  17  mm.  Hg  (rabbit). 

Effect  of  Nerves  upon  the  secretion.  The  nerves  arise  from  the  hepatic, 
splenic,  and  superior  mesenteric  plexuses,  together  with  branches  from  the  vagus 
and  sympathetic.  The  secretion  is  excited  by  stimulation  of  the  medulla 
oblongata  {Heiilenhain  and  Landaii),  as  well  as  bv  direct  stimulation  of  the  gland 
itself  by  induction  shocks  {Kiihne  and  Lea).  [It  is  not  arrested  by  section  of 
the  cervical  spinal  cord.]  The  secretion  is  suppressed  by  atropin  [in  the  dog, 
but  not  the  rabbit],  by  producing  vomiting  (C/.  Bernard),  by  stimulation  of  the 
central  end  of  the  vagus  (C.  Liidwig  and  Bernstein),  as  well  as  by  stimulation  of 
other  sensory  nerves,  e.g.,  the  crural  and  sciatic  {Afanassiew  and  Fazvhnu). 
E.vtirpation  of  the  nerves  accompanying  the  blood  vessels  prevents  the  above- 
named  stimuli  from  acting.  Under  these  circumstances  a  thin  "  paralytic 
secretion  "  with  feeble  digestive  powers  is  formed,  but  its  amount  is  not  in- 
fluenced by  the  taking  of  food  {Bernstein).  [Secretion  is  excited  by  the  injection 
of  ether  into  the  stomach.] 

Extirpation  of  the  gland  maybe  performed  [Sctiiff),  or  the  duct  ligatured  in  animals  [Freric/is), 
without  causin ;  any  very  great  change  in  their  nutrition ;  the  absorption  of  fat  from  the  intestme 
does  not  ce.ise.  After  the  duct  is  ligatured  it  may  be  again  restored.  Ligature  of  the  duct  may 
cause  the  f  irmation  of  cysts  in  the  duct  and  atrophy  of  the  gland  substance  (Fawlow).  Pigeons 
soon  die  after  this  operation  (^LangcnJorff). 

[172.  PREPARATION  OF  PEPTONIZED  FOOD.]— [Peptonized 
food  may  be  given  to  patients  whose  digestion  is  feeble.  Sir  Wni.  Roberts,  of 
Manchester,  uses  various  forms  of  this  food.  Food  may  be  peptonized  either  by 
peptic  or  tryptic  digestion,  but  the  former  is  not  so  suitable  as  the  latter,  because 
in  peptic  digestion  the  grateful  odor  and  taste  of  the  food  are  destroyed,  while 
bitter  by-products  are  formed.  Hence,  Dr.  Roberts  employs  pancreatic  diges- 
tion, which  yields  a  more  palatable  and  agreeable  product.  As  tryspin  is  destroyed 
by  gastric  digestion,  obviously  it  is  useless  to  give  extract  of  the  pancreas  to  a 
patient  along  with  his  food.] 

[Peptonized  Milk. — "  A  pint  of  milk  is  diluted  with  a  quarter  of  a  pint  of  water  and  heated 
to  60°  C.  Two  or  three  teaspoonfuls  of  Benger's  liquor  pancreaticus,  together  with  ten  or  twenty 
grains  of  bicarbonate  of  soda,  are  then  mixed  therewith."  Keep  the  nii.xture  at  38°  C.  for  about 
two  hours,  and  then  boil  it  for  two  or  three  minutes,  which  arrests  the  ferment  action.] 

[Peptonized  Gruel,  prepared  from  oatmeal,  or  any  farinaceous  food,  is  more  agreeable  than 
peptonized  milk,  as  the  bitter  flavor  does  not  appear  to  be  developed  in  the  pancreatic  digestion  of 
I'^^^Az/^A' proteids.] 

Peptonized  Milk  Gruel  yielded  Roberts  the  most  satisfactory  results,  as  a  complete  and  highly 
nutritious  food  for  weak  digestions.  Make  a  thick  gruel  from  any  farinaceous  focd,  e.g.,  oatmeal, 
and  while  still  hot  add  to  it  an  equal  volume  of  cold  milk,  when  the  mixture  will  li.ave  a  tempera- 
ture of  52°  C.  (125°  F. ).  To  each  pint  of  this  mixture  add  two  or  three  teaspoonfuls  of  liquor 
pancreaticus  and  20  grains  of  bicarbonate  of  soda.  It  is  kept  warm  for  two  hours  under  a  "  cosey." 
It  is  then  boiled  for  a  few  minutes  and  strained.  The  bitterness  of  the  digested  milk  is  almost 
completely  covered  by  the  sugar  produced  during  the  process  {Roberts).'\ 

[Peptonized  soups  and  beef  tea  have  also  been  made  and  used  with  success,  and  have  been 
administered  both  by  the  mouth  and  rectum.] 

[Peptonizing  powders  containing  the  prouer  proportions  of  ferment  and  sodic  bicarbonate  are 
prepared  by  Benger,  and  Burroughs  and  Welcome.] 

173.  STRUCTURE  OF  THE  LIVER.— The  liver,  the  largest  gland 
in  the  body,  consists  of  inntmierable  small  lobules  or  acini,  i  to  2  millimetres 
(•jV  to  tV  inch)  in  diaineter.  These  lobules  are  visible  to  the  naked  eye.  All  the 
lobules  have  the  same  structure. 


STRUCTURE    OF   THE    UVER. 


285 


1.  The  Connective  Tissue  and  Capsule. — The  liver  is  covered  by  a  thin,  fibrous,  firmly 
adherent  capsule,  which  has  on  its  free  surface  a  layer  of  endothelium  derived  from  the  peritoneum. 
The  capsule  bends  fine  septa  into  the  orj^an  between  the  lobules,  but  it  is  also  continued  into  the 
interior  at  the  transverse  fissure,  where  it  surrounds  the  portal  vein,  hepatic  artery,  and  bile  duct, 
and  accompanies  these  structures  as  the  Capsule  of  Glisson  or  interlobular  connective  tissue. 
The  spaces  in  which  these  three  structures  lie  are  known  as  portal  canals,  in  some  animals  (pi^j, 
camel,  polar  bear),  the  lobules  are  separated  from  each  other  by  the  somewhat  Umellated  connective 
tissue  of  Glisson's  capsule,  but  in  man  this  is  but  slightly  de\  eloped,  so  that  adjoining  lobules  are 
more  or  less  fused.  Very  delicate  connective  tissue,  but  small  in  amount,  is  also  found  within  the 
lobules  {FUischl,  Kiipffer).     Leucocytes  are  sometimes  found  in  the  tissue  of  Glisson's  capsule. 

2.  Blood  Vessels.  —  (a)  Branches  of  the  Venous  System. — If  the  vena  porta  be  traced  from 
its  entrance  into  the  liver  at  the  portal  fissure,  it  will  be  found  to  give  off  numerous  branches  lying 
between  the  lobules,  and  ultimately  forming  small  trunks  which  reach  the  periphery  of  the  lobules. 


Fig.  17S. 


I.  Schem< 
capiU; 
giving  branche! 


lobule,— V.  J,  V.  ;,  interlobular  veins  (portal) ;  V. 
:en  both;  V.  j,  sub-lobular  vein;  V.  j-,  vena  vascularis;  A,  A,  brar 
_  >r,  r,  to  Glisson's  capsule  and  the  larger  vessels,  and  ultimately  forr 

_  opening  into  the  intralobular  capillaries  ;  ff,  branches  of  the  bile  ducts  :  x,  x, 
between  the  liver  cells  ;  rf,  t/,  position  of  the  liver  cells  between  the  meshes  of  the  blood  capillaries.     II,  Isolated 
liver  cells — c,  a  blood  capillary  ;  a,  fine  bile  capillary  channel. 


lobular  vein  (hepatic)  ;  c, 

K  hes  of  the  hepatic  artei 

ning  the  vena:  vasculares 

tralobular  bile  capillar 


where  they  form  a  rich  plexus.  These  are  the  interlobular  veins  (Fig.  178,  V.  ;).  From  these 
Veins  numerous  capillaries  (r,  c)  are  given  oft"  to  the  entire  periphery  of  the  lobule.  The  capillaries 
converge  toward  the  centre  of  the  lobule.  As  they  proceed  inward,  they  form  elongated  meshes, 
and  between  the  capillaries  lie  rows  or  columns  of  liver  cells  (</,  d).  The  capillaries  are  relatively 
wide,  and  are  so  disposed  as  to  lie  between  the  edges  of  the  columns  of  cells,  and  never  between 
the  surfaces  of  two  neighboring  cells.  The  capillaries  converge  toward  the  centre  of  each  lobule, 
where  they  join  to  form  one  large  vein,  the  intralobular  or  central  vein  (V.  c),  which  traverses 
each  lobule,  reaches  its  surface  at  one  point,  passes  out,  and  joins  similar  veins  from  other  lobules  to 
form  the  sublobular  veins  (V.  s\.  These  in  turn  unite  to  form  wide  veins,  the  origins  of  the 
hepatic  veins,  which  open  into  the  vena  cava  inferior. 

lyb]  Branches  of  the  Hepatic  Artery. — The  branches  of  the  hepatic  artery  accompany  the 
branches  of  the  portal  vein  and  bile  duct  in  the  portal  canals  between  the  lobules,  and  in  their 
course  they  give  off  capillaries  to  supply  the  walls  of  the  portal  vein  and  larger  bile  ducts.     The 


286  STRUCTURE  OF  THE  LIVER. 

branches  of  the  hepatic  artery  anastomose  frequently  where  they  lie  between  the  lobules.  On 
reaching  the  periphery  of  the  lobules,  a  certain  number  of  capillaries  are  given  oft',  which  penetrate 
the  lobule  and  terminate  in  the  capillaries  of  the  portal  vein  ^^■,^■).  These  capillaries,  however, 
which  supply  the  walls  of  the  portal  vein  and  large  bile  ducts  (r.  r),  terminate  in  veins  which  end 
in  the  portal  vein  (V.  k — Ft'rn'in).  Several  branches — capsular — pass  to  the  surface  of  the  liver, 
where  they  form  a  wide-meshed  plexus  under  the  peritoneum.  The  blood  is  returned  by  veins 
which  open  into  branches  of  the  portal  vein, 

[Hepatic  Zones. — Pathologists  draw  a  sharp  distinction  between  different  zones  within  a  hepatic 
lobule.  Thus  the  central  area,  capillaries  and  cells  form  the  hepatic  vein  zone,  which  is  specially 
liible  to  cyanotic  changes ;  the  area  next  the  periphery  of  the  lobule  is  the  portal  vein  zone,  whose 
cells  under  certain  circumstances  are  particularly  apt  to  undergo  fatty  degeneration;  while  there  is 
an  area  lying  midway  between  the  two  foregoing — the  hepatic  artery  zone — which  is  specially 
liable  to  amyloid  or  waxy  degeneration.] 

3.  The  Hepatic  Cells  (Fig  17S,  11,  a)  are  inegular  polygonal  cells  of  about  3-555  of  an  inch 
(34  to  45  ."■)  Ill  diameter  (Fig.  179).  The  arrangement  of  the  capillaries  within  a  lobule  deter- 
mines the  arrangement  of  the  liver  cells.  The  liver  cells  form  anastamosing  columns  which  radiate 
from  the  centre  to  the  periphery  of  each  lobule  (Fig.  180).  [The  liver  cells  are  usually  stated  to 
be  devoid  of  an  envelope,  although  Haycraft  states  that  they  possess  one.  They  usually  contain 
a  single  nucleus,  with  one  or  more  nucleoli,  but  sometimes  two  nuclei  occur.  The  protoplasm  and 
nucleus  of  each  cell  contains  a  plexus  of  fibrils,  just  like  other  epithelial  cells.  In  some  animals, 
globules  of  oil  and  pigment  granules  are  found  in  the  cell  protoplasm  (Fig.  179).]  Each  cell  is  in 
relation  with  the  wide-meshed  blood  capillaries  (i/,  </),  and  also  with  the  much  narrower  meshwork 
of  bile  ducts  (I,  .r). 

Effect  of  Foods. — It  is  important  to  observe   that  the  appearance  of  the  cells  varies  with  the 

Fig.   180. 


Fig.  179. 

V- 

^ 

>^' 

/, 

\ 

0  /S  °1 

0. 

Human  liver  cells      The  cell  protoplasm  contains  Appearanceof  the  hverCLlU  after 

biliary  coloring  matter  and  oil  globules,  b;   d  w  itholding   food    for   lhirt> 

has  two  nuclei.  six  hours. 

period  of  digestion.  During  hunger,  the  liver  cells  are  finely  granular  and  very  cloudy  (Fig.  180). 
About  thirteen  hours  after  a  full  meal,  especially  of  starchy  food,  they  contain  coarse  glancing  masses 
of  glycogen  (Fig.  1S2,  2).  The  protoplasm  near  the  surface  of  the  cell  is  condensed,  and  a  fine 
network  stretches  toward  the  centre  of  the  cell,  and  in  it  is  suspended  the  nucleus  {Kupffer,  Hci- 
dcnhain).  [Afanassiew  finds  that  if  the  formation  of  bile  in  the  liver  be  increased  [e.g.,  by  section 
of  the  hepatic  nerves,  or  feeding  with  proteids),  the  cells  are  moderately  enlarged  in  size,  and  con- 
tain numerous  granules  which  are  proteid  in  their  nature;  such  cells  resist  the  action  of  caustic 
potash.  When  there  is  a  great  formation  of  glycogen  (as  after  feeding  with  potatoes  and  sugar), 
all  the  cells  are  very  large  and  sharply  defined,  while  their  bodies  are  loaded  with  granules  of  gly- 
cogen, the  cells  being  so  large  as  to  compress  the  capillaries.  These  cells  dissolve  quickly  in  caustic 
potash.     The  network  within  the  cells  is  best  seen  after  solution  of  the  glycogen.] 

4.  The  Bile  Ducts. — The  finest  bile  capillaries  or  canaliculi  arise  from  the  centre  of  the  lobule, 
and,  indeed,  throughout  the  whole  lobule,  they  form  a  regular  anastomosing  network  of  very  fine 
tubes  or  channels.  Each  cell  is  surrounded  by  a  polygonal — usually  hexagonal — mesh  (Fig.  17S, 
X  x).  The  bile  capillaries  always  lie  in  the  middle  of  the  surface  between  two  adjoining  cells 
(II,  a),  where  they  form  actual  intercellular  passages  (¥\g.  181)  (Hering).  [According  to  some 
observers,  they  are  merely  excessively  narrow  channels  (I  to  2  /-t  wide)  in  the  cement  substance 
between  the  cells,  while  according  to  others,  they  have  a  distinct  delicate  wall  [Fritsc/i,  Aliura). 
The  bile  capillary  network  is  much  closer  than  the  blood  capillary  network.  [Thus,  there  are 
three  networks  within  each  lobule— 

(i)  A  network  of  blood  capillaries; 

(2)  "  hepatic  cells; 

(3)  "  bile  capillaries;   (Fig.  i8i.] 


STRUCTURE    OF   THE    LIVER. 


287 


Excessively  minute  intracellular  passages  are  said  to  pass  from  the  bile  capillaries  into  the 
interior  of  the  liver  cells,  where  they  communicate  with  certain  small  cavities  or  vacuoles  (Asp, 
Kupffer,  Pfliiger — Fig.  182,  3).  As  the  blood  capillaries  run  along  the  edges  of  the  liver  cells, 
and  the  bile  capillaries  between  the  opposed  surfaces  of  adjacent  cells,  the  two  systems  of  canals 
within  the  lobule  are  kept  separate.  Some  bile  capillaries  run  along  the  edges  of  the  liver  cells  in 
the  human  liver,  especially  during  embryonic  \\iit  \Zuckerkandl,  Toldl).     Tow-ard  the   peripheral 

Fig.   181. 


Blood  capillaries,  finest  bile  ducts 


^ Finest  bile  duct. 


{£■.  Htrittg). 


part  of  the  lobule,  the  bile  capillaries  are  larger,  while  adjoining  channels  anastomose  and  leave 
the  lobule,  where  they  become  interlobular  ducts  (g),  which  join  with  other  similar  ducts  to  form 
larger  interlobular  bile  ducts.  These  accompany  the  hepatic  artery  and  portal  vein,  and  leave  the 
liver  at  the  transverse  fissure.  Ihe  finer  interlobular  ducts  frequently  anastomose  in  Glisson's  cap- 
sule (Asp),  possess  a  structureless  basement  membrane,  and  are  lined  by  a  single  layer  of  low, 
polyhedral,  epithelial  cells.     The  larger  interlobular  duels  have  a  distinct  wall  consisting  of  con- 


Fig.  183. 


,  Liver  cell  during  fasting  ;  2.  containing  1 

of  glycogen  ;  3,  a  liver  cell  surrounded  with 
bile  channels,  Irom  which  fine  twigs  proceed 
into  the  cell  substance,  where  they  end  in 
vacuole. like  enlargements.  From  a  rabbit's 
liver  injected  with  Berlin  blue  from  the  bile 
duct. 


Interlobular  bile  duct  (Human) 


nective  and  elastic  tissue,  mixed  with  circularly  disposed,  smooth,  muscular  fibres  (Fig.  183). 
Capillaries  are  supplied  to  the  wall,  which  is  lined  by  a  single  layer  of  columnar  epithehum.  A 
sub.mucosa  occurs  only  in  the  largest  bile  ducts,  and  in  the  gall  bladder.  Smooth  muscular  fibres, 
arranged  in  single  bundles,  occur  in  the  largest  ducts,  and  as  longitudinal  and  circular  layers  in  the 
gall  bladder,  wnose  mucous  membrane  is  provided  with  numerous  folds  and  depressions.  The 
epithelium  lining  the  gall  bladder  is  cylindrical,  with  a  distinct,  clear  disl<,  and  between  these  cells 


288  CHEMICAL   COMPOSITION    OF   THE    LIVER   CELLS. 

are  goblet  cells.     Small  branched  tubular  mucous  glands  occur  in  the  small  bile  ducts  and  in  the 
gall  bladder. 

Vasa  Aberrantia  are  isolated  bile  ducts  which  occur  on  the  surface  of  the  liver,  but  have  no 
relation  to  any  system  of  liver  lobules.  They  occur  at  the  sharp  margin  of  the  liver  in  the  region 
of  the  inferior  vena  cava,  of  the  gall  bladder,  and  of  the  parts  near  the  portal  fissure.  It  seems 
that  the  bver  lobules  to  which  they  originally  belonged  have  atrophied  and  disappeared  [Zucierkandl 
and  ToUt). 

(5)  The  Lymphatics  begin  as  peri-capillary  tubes  around  the  capillaries  within  the  lobules 
[MacGilta-ry).  They  emerge  from  the  lobule  and  run  within  the  wall  of  the  branches  of  the 
hepatic  and  portal  veins,  and  afterward  surround  the  venous  trunks  (J'/eisi/il,  A.  Budge),  thus  form- 
ing the  interlobular  lymphatics.  These  unite  to  form  larger  trunks,  which  leave  the  liver  partly  at 
the  portal  fissure,  partly  along  with  the  hepatic  veins,  and  partly  at  different  points  on  the  surface 
of  the  organ.  There  is  a  narrow  superficial  meshwork  of  lymphatics  under  the  peritoneum — sub- 
peritcmeal — which  communicate  with  the  thoracic  lymphatics  through  the  triangular  ligament  and 
suspensorium,  while  on  the  under  surface  they  communicate  with  the  lymphatics  of  the  interlobular 
connective  tissue. 

(6)  The  Nerves  consist  partly  of  medullated  and  partly  of  non-medullated  fibres  from  branches 
of  the  sympathetic  and  left  vagus  to  the  hepatic  plexus.  They  accompany  the  branches  of  the 
hepatic  artery,  and  ganglia  occur  on  their  branches  within  the  liver.  Some  of  the  nerve  fibres  are 
vasomotor  in  function,  and  according  to  Pliiger,  other  nerve  fibres  terminate  directly  in  connection 
with  liver  cells,  although  this  observation  has  still  to  be  confirmed. 

Pathological. — The  connective  tissue  between  the  lobules  may  undergo  great  increase  in 
amount,  especially  in  alcohol  and  gin  drinkers,  and  thus  the  substance  of  the  lobules  may  be 
greatly  compressed,  owing  to  the  cicatricial  contraction  ot  the  newly-formed  connective  tissue  (cir- 
rhosis of  the  liver).  In  such  interlobular  connective  tissue,  newly-formed  bile  ducts  are  found 
[Cornil,  Charcot  and  others  1. 

Ligature  of  the  ductus  choledochus  [causes  enlargement  of  the  spleen  (rabbit)  and  a  diminu- 
tion in  the  number  of  the  blood  corpuscles  {Mackey)\,  and,  after  a  lime,  interstitial  inflam- 
mation of  the  liver.  In  rabbits  and  guinea  pigs  the  liver  parenchyma  disappears,  and  its  place  is 
taken  by  newly-formed  connective  tissue  and  bile  ducts  (^Charcot  and  Gombault).  In  all  these 
cases  of  interstitial  inflammation,  there  is  proliferation  of  the  epithelium  of  the  bile  ducts  (/brf, 
Salvioli).  According  to  Beloussow,  the  dilated  bile  ducts  partly  burst,  and  partly  (owing  to 
pressure)  undergo  necrosis,  and  thereafter  in  the  neighborhood  of  these  foci  inflammatory  reaction 
sets  in,  v\ith  cell  infiltration,  formation  of  new  connective  tissue,  and  regenerative  new  formation  of 
bile  ducts. 

[Regeneration  of  the  Liver. — Tizzoni  finds  that  there  may  be  partial  regeneration  and  new 
formation  of  liver  lobules  in  the  dog,  the  process  being  the  same  as  that  which  occurs  in  the  embry- 
onic development  of  the  organ,  i.  e.,  the  growth  of  solid  cylinders  of  liver  cells,  formed  by  the  pre- 
existing hver  cells,  which  penetrate  into  the  connective  tissue  uniting  the  edges  of  the  wound.. 
These  cells  ultimately  differentiate  into  hepatic  cells  and  bile  ducts.  Griffini  also  confirms  the  fact 
of  the  regeneration  of  the  hepatic  substance  in  the  dog  and  rabbit,  but  he  thinks  that  the  new  forma- 
tion is  developed  by  the  outgrowth  of  the  epithelial  cells  of  the  bile  cells.] 

174.  CHEMICAL  COMPOSITION  OF  THE  LIVER  CELLS.— 

(i)  Proteids. — The  fresh,  soft  ])arenchyma  of  the  liver  is  alkaline  in  reaction  ; 
after  death,  coagulation  occurs,  the  cell  contents  appear  turbid,  the  tissue  becomes 
friable,  and  gradually  an  acid  reaction  is  developed.  This  process  closely 
resembles  what  occurs  in  muscle,  and  is  due  to  the  coagulation  of  a  myosin-like 
body,  which  is  soluble  during  life,  but  after  death  undergoes  spontaneous  coagula- 
tion lyPlbsz).  The  liver  contains  other  albuminous  bodies;  one  coagulating  at  45^ 
C,  another  at  70°  C,  and  one  which  is  slightly  soluble  in  dilute  acids  and  alkalies. 
The  cell  nuclei  contain  nuclein  {Flbsz).     The  connective  tissue  yields  gelatin. 

(2)  Glycogen  or  Animal  Starch — 1.2  to  2.6  per  cent. — is  most  closely 
related  to  inulin,  is  soluble  in  water,  but  diffuses  with  difficulty,  is  a  true  carbohy- 
drate (C/.  Bernard  and  v.  Hensen,  iSjj),  and  has  the  formula  6(C6H,„05)  -|- 
H^O  l^Kulz  and  Borntrdger).  It  is  stored  up  in  the  liver  cells  {Bock  and  Hoff- 
man'), in  amorphous  granules  around  the  nuclei  (Fig.  182,  2),  but  it  is  not  uni- 
formly distributed  in  all  parts  of  the  liver  {v.  Witticli).  Like  inulin,  it  gives  a 
deep  red  color  with  solution  of  iodine  in  iodide  of  potassium.  It  is  changed  into 
dextrin  and  sugar  by  diastatic  ferments,  and  when  boiled  with  dilute  mineral 
acids,  it  yields  grape  sugar  (§  148,  I  ;  §  170,  I ;   §  252,  IIIj. 

Preparation  of  Glycogen. — Let  a  rabbit  have  a  hearty  meal,  and  kill  it  three  or  four  hours 
therealter.     The  liver  is  removed  immediately  after  death  ;  it  is  cut  into   fine  pieces,  plunged  into 


CHEMICAL    COMPOSITION    OF   THE    LIVER   CELLS.  289 

boiling  water,  and  boiled  for  some  time  in  order  to  obtain  a  watery  extract  of  the  liver  cells.  [It  is 
placed  in  boiling  water  to  de-troy  the  ferment  supposed  to  be  present  in  the  liver,  which  would  trans 
form  the  glycogen  into  grape  sugar.]  To  the  cold  filtrate  are  added  alternately  dilute  hydrochloric 
acid  and  polassio- mercuric  iodide  as  long  as  a  precipitate  occurs.  The  albuminates  or  proteids  are 
precipitated  by  the  iodide  compound  in  the  presence  of  free  HCI.  It  is  then  filtered,  when  a  clear 
opalescent  fluid,  containing  the  glycogen  in  solution,  is  obtained.  The  glycogen  is  precipitated 
from  the  filtrate,  as  a  while  amorphous  powder,  on  adding  an  excess  of  70  to  80  per  cent,  alcohol. 
The  precipitate  is  washed  with  60 per  cent,  and  afterward  with  95  per  cent,  alcohol,  then  with  ether, 
and  lastly,  with  absolute  alcohol ;  it  is  dried  over  sulphuric  acid  and  weighed  {^Briicke). 

Ferment. — [F.  Eves  asserts  that  \\\^ post-mortem  conversion  of  sugar  in  the  liver  is  not  attribut- 
able to  a  ferment  action,  and  the  rapid  appearance  of  sugar  in  the  liver  after  death  is  due  to  the 
specific  metabolic  activity  of  the  dying  cells.] 

Conditions  which  influence  its  amount. — If  large  quantities  of  starch, 
milk-,  fruit-,  or  cane-sugar,  or  glycerine,  but  not  mannite  or  glycol  {Ltichsinger), 
or  inosite  {Kiilz),  be  added  to  the  proteids  of  the  food,  the  amount  of  glycogen 
in  the  liver  is  very  greatly  increased  (to  12  per  cent,  in  the  fowl),  while  a  purely 
albuminous  or  partly  fatty  diet  diminishes  it  enormously.  During  hunger  it  almost 
disappears  {Favy  and  Tscherinoff).  The  injection  of  dissolved  carbohydrates 
into  a  mesenteric  vein  of  a  starving  rabbit  causes  the  liver,  previously  free  from 
glycogen,  to  contain  glycogen  (^Naunyn). 

[Arsenic,  phosphorus,  and  antimony  destroy  the  glycogenic  function  of  the  liver,  no  glycogen 
being  present  in  the  liver  of  animals  poisoned  with  these  drugs,  so  that  puncture  of  the  floor  of  the 
fourth  ventricle  no  longer  causes  glycosuria  in  them.] 

During  life,  under  normal  conditions,  the  glycogen  in  the  liver  is  either  not 
transformed  into  grape  sugar  {Pavy,  Hitter,  Eiilenbcrg),  or,  what  is  more  prob- 
able, only  a  very  small  amount  of  it  is  so  changed.  The  normal  amount  of  sugar 
in  blood  is  0.5  to  i  per  1000,  although  the  blood  of  the  hepatic  vein  contains 
somewhat  more.  A  considerable  amount  is  transformed  into  sugar  only  when 
there  is  a  decided  derangement  of  the  hepatic  circulation,  and  in  these  circum- 
stances the  blood  of  the  hepatic  vein  contains  more  sugar.  The  glycogen  under- 
goes this  change  very  rapidly  after  death,  so  that  a  liver  which  has  been  dead  for 
some  time  always  contains  more  sugar  and  less  glycogen. 

The  Diastatic  ferment  in  the  liver  is  small  in  amount,  and  can  be  obtained 
from  the  extract  of  the  liver  cells  by  the  same  means  as  are  applicable  for  obtain- 
ing other  similar  ferments,  such  as  pytalin  ;  but  it  does  not  seem  to  be  formed 
within  the  liver  cells,  but  only  passes  very  rapidly  from  the  blood  into  them.  The 
ferment  seems  to  be  rapidly  formed  when  the  blood  stream  undergoes  considerable 
derangement  (Hitter,  Schiff).  A  similar  ferment  is  formed  when  red  blood  cor- 
puscles are  dissolved  {  Fiegel),  and,  as  there  is  a  destruction  of  red  blood  corpus- 
cles taking  place  continually  within  the  liver,  this  is  one  source  from  which  the 
ferment  may  be  formed,  whereby  minute  quantities  of  sugar  would  be  continually 
formed  in  the  liver. 

If  glycogen  is  injected  into  the  blood,  achroodextrin  appears  in  the  urine,  and  also  hs^moglobin, 
as  glycogen  dissolves  red  blood  corpuscles  (Bo/im,  Hoffmann). 

Ligature  of  the  bile  duct  causes  decrease  of  the  glycogen  in  the  liver  (y.  Wittich);  it  appears  as 
if,  after  this  operation,  the  liver  loses  the  property  of  forming  glycogen  from  the  materials  supplied 
to  it. 

(3)  The  following  substances  have  also  been  found  in  the  liver  cells :  Fats,  in 
the  form  of  highly  refractive  granules  in  the  liver  cells,  as  well  as  in  the  bile 
ducts  ;  sometimes,  when  the  food  contains  much  fat  (more  abundant  in  drunkards 
and  the  phthisical),  olein,  palmitin,  stearin,  volatile  fatty  acids,  and  sarcolactic 
acid  are  found. 

[Fatty  Degeneration  and  Infiltration. — Fatty  granules  are  of  common  occurrence  within  the 
cells  of  the  liver,  and  when  they  do  not  occur  in  too  great  amount,  do  not  seem  to  interfere  very 
greatly  with  the  functions  of  the  liver  cells.  These  fatty  granules  are  common  in  disease,  constitut- 
ing fatty  infiltration  and  degeneration,  and  in  such  cases  the  cells  within  a  lobule  of  the  liver,  next 
the  portal  vein,  are  usually  most  highly  charged  with  the  fatty  particles.  Fatty  particles  occur  if  too 
19 


290  DIABETES    MELLITUS. 

much  fatty  food  be  taken,  and  they  are  commonly  found  in  the  livers  of  stall  fed  animals,  and  the 
■vit\\-)Lr\o-<iin  pale-de-foie  gras  is  largely  composed  of  the  livers  of  geese  which  have  been  fed  on  large 
amounts  of  farinaceous  food,  and  which  have  been  subjected  to  other  unfavorable  hygienic  condi- 
tions. Fatty  granules  are  recognized  by  their  highly  refractive  appearance,  by  their  solubility  in 
ether,  and  by  being  blackened  by  osmic  acid.] 

There  are  also  found  traces  of  cholejterin,  minute  quantities  of  urea,  uric  acid.  [Leucin  (?  gu- 
anin),  sarkin,  xanthin,  cystin,  and  tyrosin  occur  pathologically  in  certain  diseases  where  marked 
chemical  decompositions  occur.] 

(4)  The  inorganic  substances  found  in  the  human  liver  are — potassium, 
sodium,  calcium,  magnesium,  iron,  manganese,  chlorine,  and  phosphoric,  sul- 
phuric, carbonic,  and  silicic  acids  ;  while  copper,  zinc,  lead,  mercury,  and  ar- 
senic may  be  accidentally  deposited  in  the  hepatic  tissue. 

175.  DIABETES  MELLITUS  AND  GLYCOSURIA.— [Glycosuria 

is  characterized  by  the  presence  of  grape  sugar  in  the  urine.  According  to  Brucke, 
a  trace  of  sugar  exists  normally  in  urine,  and  when  this  amount  is  increased,  we 
have  glycosuria.  When  the  normal  amount  of  grape  sugar  in  the  blood  (0.12  to 
0.33  per  cent.)  is  increased,  grape  sugar  appears  in  the  urine.  In  Diabetes 
Mellitus,  grape  sugar  also  appears  in  the  urine,  but  this  is  really  a  serious  dis- 
ease, involving  the  alteration  of  many  tissues,  and  distinguished  by  profound  dis- 
turbance of  the  whole  metabolic  activity,  which  leads  to  numerous  pathological 
changes  and  often  to  death.  The  appearance  of  grape  sugar  in  urine  does  not, 
necessarily,  mean  that  a  person  is  suffering  from  this  disease]. 

The  formation  of  large  quantities  of  grape  sugar  by  the  liver,  and  its  passage 
into  the  blood,  and  from  the  blood  into  the  urine,  are  related  to  the  above-men- 
tioned normal  conditions.  Extirpation  of  the  liver  in  frogs  (jlA'/esc/ioff),  or 
destruction  of  the  hepatic  cells,  as  by  fatty  degeneration  from  poisoning  with 
phosphorus  or  arsenic  (SalkoTvski)  do  not  cause  this  condition.  It  occurs  for 
several  hours,  however,  after  the  injury  of  a  certain  part — the  centre  for  the  he])atic 
vasomotor  nerves — of  the  floor  of  the  lower  part  of  the  fourth  ventricle  i^Cl.  Ber- 
.nard' s  piqure) ;  also  after  section  of  the  vasomotor  channels  in  the  spinal  cord, 
from  above  down  to  the  exit  of  the  nerves  for  the  liver,  viz.,  to  the  lumbar  region, 

■  and  in  the  frog  to  the  fourth  vertebra  {Schi'ff').  When  the  vasomotor  nerves, 
.which  proceed  from  this  centre  to  the  liver,  are  cut  or  paralyzed  in  any  part  of 
itheir  course,  mellituria  or  glycosuria  is  produced.  All  the  nerve  channels  do  not 
■run  through  the  spinal  cord  alone.    A  number  of  vasomotor  nerves  leave  the  spinal 

■  cord  higher  up,  pass  into  the  sympathetic,  and  thus  reach  the  liver ;  so  that  de- 
struction of  the  superior  (^Pavy),  as  well  as  of  the  inferior  cervical  sympathetic 
ganglion,  and  the  first  thoracic  ganglion  {Eckhard)  of  the  abdominal  sympathetic 
{Klebs,  Aliink),  and  often  of  the  splanchnic  itself  {Hensen,v.  Gracfe),  produces 
diabetes.  The  paralysis  of  the  blood  vessels  causes  the  liver  to  contain  much 
blood,  and  the  intra-hepatic  blood  stream  is  slowed.  The  disturbance  of  the  cir- 
culation causes  a  great  accumulation  of  sugar  in  the  liver,  as  the  blood  ferment 
has  time  to  act  upon  the  glycogen  and  transform  it  into  sugar.  By  stimulation  of 
the  sympathetic  at  the  lowest  cervical  and  first  thoracic  ganglion,  the  hepatic 
■vessels  at  the  periphery  of  the  liver  lobules  become  contracted  and  pale  {Cyon, 
Aladoff).  It  is  remarkable  that  glycosuria,  when  present,  may  be  set  aside  by 
section  of  the  splanchnic  nerves.  This  is  explained  by  supposing  that  the  enor- 
mous dilatation  and  congestion,  or  the  hypersemia,  of  the  abdominal  blood  vessels 
thereby  produced,  renders  the  liver  ansemic. 

A  number  of  poisons  which  paralyze  the  hepatic  vasomotor  nerves  produce  diabetes  in  a  similar 
way;  constantly  after  curara  (when  artificial  respiration  is  not  maintained*,  CO,  amyl  nitrite,  ortho- 
nitro-propionic  acid  and  methyl  delphinin  ;  another  series  of  poisons  in  large  doses  are  not  constant 
intheir  effect — morphia,  chloral  hydrate  HCN,  H^SO^,  mercury,  alcohol  [phlorizin  (-■.  Merhig)'], 
and  such  infectious  diseases  as  cholera,  anthrax,  diphtheria,  typhoid  and  scarlatina.  But  congestion 
of  the  liver  produced  in  other  ways  appears  to  cause  diabetes,  e.g..  after  mechanical  stimulation  of 
the  liver.  To  this  class  belongs  the  injection  of  di'ute  sali  le  solutions  into  the  blood  \Bo(k,  Hoff- 
mann), whereby  either  the  change  in  form  or  the  solution  of  the  colored  blood  corpuscles  causes 


SOURCES   OF    GLYCOGEN.  291 

the  congestion.  The  circumstance  that  repeated  blood  letting  makes  the  blood  richer  in  sugar,  may, 
perhaps,  be  explained  by  the  slowing  of  the  circulation.  [Injection  of  a  solution  of  a  neutral  salt 
into  a  ligatured  loop  of  the  small  intestine  sometimes  causes  mellituria  (/)/.  Hay).'] 

Continued  stimulation  of  peripheral  nerves  may  act  reflexly  upon  the  centre  for 
the  vasomotor  nerves  of  the  liver.  Diabetes  has  been  observed  to  occur  after 
stimulation  of  the  central  end  of  the  vagus  (C/.  Bernard,  Eckhard,  Kiilz,  Lobeck), 
and  also  after  stimulation  of  the  central  end  of  the  depressor  nerve  {Filehne). 
Even  section,  and  subsequent  stimulation  of  the  central  end  of  the  sciatic  nerve, 
causes- diabetes  {Sehiff,  Kiilz,  Bohm  and  Hoffmann,  Froning).  This  may  explain 
the  occurrence  of  diabetes  in  people  who  suffer  from  sciatica. 

[It  may  occur,  also,  after  perverted  nervous  activity,  as  psychical  excitement,  neuralgias  (sciatica, 
trigeminal  or  occipital),  concussion  of  the  brain,  as  well  as  after  certain  injuries  to  the  skull  and 
vertebral  column  and  some  cerebral  diseases.] 

According  to  Sehiff,  the  stagnation  of  blood  in  other  vascular  regions  of  the  body  may  cause  the 
ferment  to  accumulate  in  the  blood  to  such  an  extent  that  diabetes  occurs.  The  glycosuria  that  occurs 
after  compression  of  the  aorta  or  portal  vein  may,  perhaps,  be  ascribed  to  this  cause,  but,  perhaps, 
the  pressure  produced  by  these  procedures  may  paralyze  certain  nerves.  According  to  Eckhard, 
injury  to  the  vermiform  process  of  the  cerebellum  of  the  rabbit  cauies  diabetes.  In  man,  affections 
of  the  above-named  nervous  regions  cause  diabetes. 

[  The  Consequence  of  Disturbances  of  Digestion. — In  most  individuals  the  use  of  a  large  quantity 
of  ^ugar  in  the  food  is  not  followed  by  sugar  in  the  urine ;  but  in  some  exceptional  cases  it  is  often 
present,  e.g.,  in  persons  suffering  from  gastric  catarrh,  especially  if  they  are  gouly.] 

Theoretical. — In  order  to  explain  the  more  immediate  cause  of  these  phenomena,  several  hy- 
potheses have  been  advanced  :  — 

[a)  The  liver  glycogen  may  be  transformed,  unhindered,  into  sugar,  as  the  blood,  in  its  passage 
through  the  liver,  deposits  or  gives  up  the  ferment  to  the  liver  cells  (see  above).  So  that  the  normal 
function  of  the  vasomotor  system  of  the  liver,  and  its  centre  in  the  floor  of  the  fourth  ventricle,  may 
be  regarded  as,  in  a  certain  sense,  an  "  inhibitory  system  "  for  the  formation  of  sugar. 

{b)  If  we  assume  that,  under  normal  conditions,  there  is  continually  a  small  quantity  of  sugar 
passing  from  the  liver  into  the  hepatic  vein,  we  might  explain  the  diabetes  as  due  to  the  disappear- 
ance of  these  decompositions — diminished  burning  up  of  the  sugar  in  the  blood — which  are  con- 
stantly removing  the  sugar  from  the  blood.  In  fact,  diabetic  persons  have  been  found  to  consume 
less  O  {y.  Pettenkofer  and  Veil)  and  to  have  an  increased  for. nation  of  urea. 

Sources  of  Glycogen. — The  "mother  substance"  of  the  glycogen  of 
the  liver  has  been  variously  stated  to  be  the  carbohydrates  of  the  food  {Pavy), 
fats  (olive  oil,  Salomon),  glycerine  {van  Deen,  Weiss),  taurin  and  glycin  (the  latter 
splitting  into  glycogen  and  urea — Heynsius  and Kiithe),  the  proteids  (C/.  Bernard), 
and  gelatin  (Salomon).  If  it  is  derived  from  the  albumins,  it  must  be  formed 
from  a  non-nitrogenous  derivative  thereof. 

According  to  Seegen,  the  blood  of  the  hepatic  vein  contains  twice  as  much  sugar  (0.23  per  cent.) 
as  that  in  the  portal  vein  (0.1 19  per  cent.) ;  observations  on  dogs  showed  that  the  blood  flowing 
through  the  liver  gives  up  over  400  grms.  sugar.  Hence,  in  carnivora,  the  greatest  part  of  the  C  of 
the  animal  food  must  pass  into  sugar,  so  that  the  formation  of  sugar  in  the  liver  and  its  decomposi- 
tion in  the  blood,  or  in  the  organs  traversed  by  the  blood,  must  be  a  very  important  function  of  the 
metabolism.  Seegen  is  also  of  opinion  that  the  liver  glycogen  takes  no  part  in  the  formation  of 
sugar  in  the  liver. 

Rohmann  found  that  the  use  of  ammonia  in  rabbits  considerably  increased  the  formation  of  gly- 
cogen. The  excessive  formation  of  acid  in  diabetes  observed  by  Stadelmann  unites  with  the 
ammonia  and  diminishes  considerably  the  formation  of  glycogen. 

[Injection  of  Grape  Sugar  into  the  Blood. — When  grape  sugar  is  injected  into  the  jugular 
vein  of  a  dog,  only  33  per  cent,  at  most  is  given  off  in  the  urine,  while  usually  within  two  to  five 
hours  the  urine  is  free  from  sugar.  Even  within  a  few  minutes  after  the  injection  only  a  certain 
proportion  {^2-% )  of  the  sugar  is  found  in  the  blood ;  a  part  of  the  sugar  has  been  detected  in  the 
muscles,  liver,  and  kidneys,  but  the  fate  of  the  remainder  is  not  known.  Immediately  after  the 
injection,  the  amount  of  haemoglobin  and  also  of  s;rum  albumin  is  diminished  (50  per  cent.),  which 
is  due  to  increase  ol  the  quantity  of  water  within  the  vessels  ;  but  within  two  hours  this  dispropor- 
tion is  restored  to  the  normal  state  (Srasof).  In  a  curarized  dog  the  injection  of  grape  sugar  into  a 
vein  increases  the  blood  pressure,  but  this  effect  is  not  observed  after  the  injection  of  morphia  and 
Chljral  (.A/ber/oni).] 

Effects  of  Food. — Rabbits  whose  livers  have  been  rendered  free  from  gly- 
cogen by  starvation,  yield  new  glycogen  from  their  livers  when  they  are  fed  with 


292  THE    FUNCTIONS   OF   THE    LIVER. 

cane  sugar,  grape  sugar,  maltose,  or  starch.  Forced  muscular  movements  soon 
make  the  liver  of  dogs  free  from  glycogen,  exposure  to  cold  diminishes  its  amount. 
Dextrin  and  grape  sugar  occur  in  the  dead  liver  {^Limpriiht,  Kiilz),  but  in  addition, 
some  glycogen  is  found  for  a  considerable  time  after  death  in  the  liver  and  in  the 
muscles. 

Other  Situations. — Glycogen  is  by  no  means  confined  to  the  liver  cells ;  it  occurs  during  foetal 
life  ill  all  the  tissues  of  the  bodv  of  the  embryo  [including  the  embryonic  skeleton  [PaschutinW, 
also  in  young  animals  (AliJine),  and  in  the  placenta  (Bernard).  In  the  adult  it  occurs  in  the  tes- 
ticle [A'ii/ine),  in  the  muscles  (Mac  Donnel,  O.  Nasse),  in  numerous  pathological  products,  in  in- 
flamed lungs  (Kilhne),  and  also  in  the  corresponding  tissues  of  the  lower  animals.  [It  also  occurs 
in  the  chorionic  villi  ( 67.  i>V?-««?-a'),  in  colorless  blood  corpuscles,  in  fresh  pus  cells  which  still 
exhibit  amoeboid  movements,  and,  in  fact,  in  all  developing  animal  cells,  with  amceboid  movement; 
it  is  a  never  faihng  constituent  in  cartilage,  and  in  the  muscles  and  liver  of  invertebrata,  such  as  the 
oyster  {Hoppe-Seyler).  There  is  none  in  the  fresh  brain  of  the  dog  or  rabbit,  but  it  is  found  in  the 
brain  in  diabetic  coma  {Abeles).~\ 

Persons  suffering  from  diabetes  require  a  large  amount  of  food  ;  they  suffer 
greatly  from  thirst,  and  drink  much  fluid.  They  exhibit  signs  of  marked  emacia- 
tion, when  the  loss  of  the  body  is  greater  than  the  supply.  [In  advanced  diabetes 
the  glycogenic  function  of  the  liver  is  almost  abolished,  as  was  proved  by  remov- 
ing with  a  trocar  a  small  part  of  the  liver  from  man  i^Ehrlich),  when  almost  no 
glycogen  was  found.  The  absorbed  sugar  in  the  portal  vein  passes  directly  into 
the  general  circulation  without  being  submitted  to  the  action  of  the  liver 
(l<.  Frerichs)^  In  severe  cases,  toward  death,  not  unfrequently  a  peculiar 
comatose  condition — diabetic  coma — occurs,  when  the  breath  often  has  the 
odor  of  acetone,  which  is  also  found  in  the  urine  (Fetters).  But  neither 
acetone  nor  its  precursor,  aceto-acetic  acid,  nor  tethyl-diacetic  acid,  nor  the 
unknown  substance  in  diabetic  urine  which  gives  the  red  color  with  ferric 
chloride  (v.  JakscJi),  is  the  cause  of  the  coma  {Frericlis  and  Brieger).  The 
urinary  tubules  often  show  the  signs  of  coagulation  necrosis,  which  is  recognized 
by  a  clear,  swollen-up  condition  of  the  dead  cells  {Ebstein).  As  yet  there  is 
no  satisfactory  explanation  of  those  rarer  cases  of  "  acetonfemia "  without 
diabetes  (A"(i'///(V/'/,  Cantiiii,  v.  JakscJi). 

176.  THE  FUNCTIONS  OF  THE  LIVER.— [In  order  to  under- 
stand the  functions  of  the  liver,  we  must  remember  its  unique  relation  to  the 
vascular  and  digestive  systems,  whereby  many  of  the  products  of  gastric  and  in- 
testinal digestion  have  to  traverse  it  before  they  reach  the  blood,  and,  in  fact,  as 
some  of  them  traverse  the  liver  they  are  altered.  We  have  still  much  to  learn  re- 
garding these  offices  of  the  liver,  but  it  has  several  distinct  functions — some 
obvious,  others  not.  (i)  The  liver  secretes  bile,  which  is  formed  by  the  hepatic 
cells,  and  leaves  the  organ  by  the  bile  ducts,  to  be  poured  by  them  into  the  duo- 
denum. (2)  But  the  liver  cells  also  form  glycogen,  which  does  not  pass  into  the 
ducts,  but  in  some  altered  and  diffusible  torm  passes  into  the  blood  stream,  and 
leaves  the  liver  by  the  hepatic  veins.  Hence,  the  study  of  the  liver  materially 
influences  our  conception  of  a  secreting  organ.  In  this  case,  we  have  the  pro- 
ducts of  its  secretory  activity  leaving  it  by  two  different  channels — the  one  by  the 
ducts,  and  the  other  by  the  blood  stream.  The  liver,  therefore,  is  a  great  store- 
house of  carbohydrates,  and  it  serves  them  out  to  the  economy  as  they  are 
required.  All  this  points  to  the  liver  as  being  an  organ  intimately  related  to  the 
general  metabolism  of  the  body.  (3)  In  a  certain  period  of  development  it 
IS  concerned  in  the  formation  of  blood  corpuscles  (§  7).  (4)  It  has  some  relation 
to  the  breaking  up  of  blood  corpuscles  and  the  formation  of  urea  and  other 
metabolic  products  (§  20,  §  177,  3)-  Cs)  Brunton  attributes  some  importance  to 
the  liver  in  connection  with  the  arrest  of  certain  substances  absorbed  from  the 
alimentary  canal,  whereby  they  are  either  destroyed,  stored  up  in  the  liver,  or,  it 
may  be,  prevented  from  entering  the  general  circulation  in  too  large  amount.  It 
is  possible  that  ptomains  may  be  arrested  in  this  way  (§  166).] 


THE    BILE    ACIDS.  293 

177.  CONSTITUENTS  OF  THE  BILE.— Bile  is  a  yellowish-brown 
or  dark  green  colored  transparent  fluid,  with  a  sweetish,  strongly  bitter  taste, 
feeble  musk-like  odor  and  neutral  reaction.  The  specific  gravity  of  human  bile 
from  the  gall-bladder  =  1026  to  1032,  while  that  from  a  fistula  =  loio  to  loii 
(^Jacobsi-n).      It  contains — 

(i)  Mucus,  which  gives  bile  its  sticky  character,  and  not  unfrequently  makes 
it  alkaline,  is  the  product  of  the  mucous  glands  and  the  goblet  cells  of  the  mucous 
membrane  of  the  larger  bile  ducts.  When  bile  is  exposed  to  the  air,  the  mucus 
causes  it  to  putrefy  rapidly.     It  is  precipitated  by  acetic  acid  or  alcohol. 

[Bile  from  the  gall  bladder,  when  poured  from  one  vessel  into  another,  shows  the  presence  of 
mucin  in  the  form  of  thin  threads  connecting  the  fluids  in  the  two  vessels.  When  such  bile  is 
treated  with  alcohol,  it  no  longer  exhibits  this  property,  but  flows  like  a  non  viscid  watery  fluid. 
The  bile  formed  in  the  ultimate  bile  duels  does  not  seem  to  contain  mucin  or  mucus,  but  bile  from 
the  gall  bladder  always  does.  It  is  formed  from  the  mucous  glands  in  the  larger  bile  ducts 
(?  «73)-] 

(2)  The  Bile  Acids. — Glycocholic  and  taurocholic  acids,  so-called  conjugate 
acids,  are  united  with  soda  (in  traces  with  potash)  to  form  glycocholate  and 
taurocholate  of  soda,  which  have  a  bitter  taste.  In  human  bile  (as  well  as  in  that 
of  birds,  many  mammals  and  amphibians),  taurocholic  acid  is  most  abundant;  in 
other  mammals  Cpig,  ox)  glycocholic  acid  is  most  abundant.  These  acids  rotate 
the  plane  of  polarized  light  to  the  right. 

[The  bile  from  a  biliarv-  fistula  is  sometimes  not  bitter.] 

(ff)  Glycocholic  acid,  C.jeH^NOs  (first  discovered  and  described  as  cholic  acid 
by  Gmelin,  and  called  by  Lehmann  glycocholic  acid).  When  boiled  with  caustic 
potash,  or  baryta  water,  or  with  dilute  mineral  acids,  it  takes  up  H..0  (Strecke7-^, 
and  splits  into — 

Glycin  (  =  Glycocoll  -.=  Gelatin  Sugar  =  Amido-acetic  acid)  ^  C2H5NO2. 

-f-  CholaUc  acid  (also  called  Cholic  acid) ^=  C^^^aO^. 

=  Glycocholic  acid  +  Water =  C^^H^jNOe  —  H,0. 

{b)  Taurocholic  acid,  CssHjsNSG,,  when  similarly  treated,  takes  up  water 
and  splits  into — 

Taurin  (  ^  Amido-tethyl-sulphuric  acid)  ^  CH.NSOj. 

-I-  Cholalic  acid =  C^^H^pOs. 

=  Taurocholic  acid -1- Water    ....    =  CjeH^^NSO,  +  H^O  {Strecker). 

[Solutions  of  taurocholic  acid  are  antiseptic,  and  if  sufficiently  strong  interfere  with  the  develop- 
ment of  bacteria,  and  prevent  the  alcoholic  and  lactic  fermentations,  as  well  as  the  tryptic  and  dias- 
tatic  action  of  the  pancreas  (iTw/t-/;).] 

Preparation  of  the  Bile  Acids  — Bile  is  evaporated  to  ]^  of  its  volume,  rubbed  up  into  a 
paste  with  excess  of  animal  charcoal,  and  dried  at  100°  C.  The  black  mass  is  extracted  with  abso- 
lute alcohol,  which  is  filtered  until  it  is  clear.  After  a  part  of  the  alcohol  has  been  removed  by 
distillation,  the  bile  sails  are  precipitated  in  a  resinous  form,  and  on  the  addition  of  excess  of  ether 
there  is  formed  immediately  a  crjsialline  mass  of  glancing  needles  [P/alncr's  "  crystallized  bile''). 
The  alkaline  salts  of  the  bile  acids  are  freely  soluble  in  water  or  alcohol,  and  insoluble  in  ether. 
A'eiitial  lead  acetate  precipitates  the  glycocholic  acid — as  lead  glycocholate — from  the  solution  of 
both  salts;  the  precipitate  is  collected  on  a  filter,  dissolved  in  hot  alcohol,  and  the  lead  is  precipi- 
tated as  lead  sulphide  by  H,S ;  after  removal  of  the  lead  sulphide,  the  addition  of  water  precipitates 
the  isolated  glycocholic  acid.  If,  after  precipitating  the  lead  glycocholate,  the  filtrate  be  treated 
with  basic  lead  acetate,  a  precipitate  of  lead  taurocholate  is  formed,  from  which  the  lead  may  be 
obtained  in  the  same  way  as  described  above  (Sirecier). 

When  human  bile  is  similarly  treated,  instead  of  the  "  cr>'stallized  bile,"  a  resinous  non-crystal- 
line precipitate  is  obtained.  Boiling  with  barj-ta  water  isolates  the  cholalic  acid  from  it,  which  is 
obtained  from  its  barium  salt  by  adding  hydrochloric  acid.  When  dissolved  in  ether,  it  occurs  in 
the  form  of  prismatic  crystals  if  petroleum  ether  is  added.  The  anthropocholic  acid  iCi  jH^jO^ 
— H.  Bayer),  so  obtained  is  not  soluble  in  water,  but  readily  so  in  alcohol,  and  rotates  the  ray  of 
polarized  light  to  the  left. 

With  regard  to  the  decomposition  products  of  the  bile  acids,  glycin,  as 
such,  does  not  occur  in  the  body,  but  only  in  the  bile  in  combination  with  cholalic 


294  THE    BILE    ACIDS. 

acid,  in  urine  in  combination  with  benzoic  acid,  as  hippuric  acid,  and  lastly,  in 
gelatin  in  complex  combination. 

Cholalic  acid  rotates  the  ray  of  polarized  light  to  the  right,  and  its  chemical 
composition  is  unknown ;  perhaps  it  is  to  be  regarded  as  benzoic  acid,  in  which  a 
complex  ot"  atoms  similar  to  oleic  acid  is  introduced  (Hoppf-Scykr').  It  occurs 
free  only  in  the  intestine,  where  it  is  derived  from  the  splitting  up  of  taurocholic 
acid,  and  it  passes  in  part  into  the  fasces.  It  is  insoluble  in  water,  soluble  in 
alcohol,  but  soluble  with  difficulty  in  ether,  from  which  it  separates  in  prisms. 
Its  crystalline  alkaline  salts  are  readily  soluble  in  water. 

Cholalic  acid  is  replaced  in  the  bile  of  many  animals  by  a  nearly  related  acid,  e.  g.,  in  pig's  bile, 
by  hyo-cholalic  acid  [Strecker,  Gundlach);  in  the  bile  of  the  goose,  cheno-cholalic  acid  is  present 
[Marsson,  Otto). 


When  cholalic  acid  is  boiled  with  concentrated  HCl,  or  dried  at  200°  C,  it 
becomes  an  anhydride,  thus:  — 

Cholalic  acid    .    .  ^=  Cj^H^pO,,  produces 

Choloidinic  acid  .  =  Co4H3g04  +  H,0,  and  this  again  yields 

Dyslysin   .    .    .    .  =  CJ^Hj^Oj  =  HJO. 

(Choloidinic  acid  is,  however,  improbably  a  mixture  of  cholalic  acid  and  dyslysin;  dyslysin, 
when  fused  with  caustic  potash,  is  changed  into  cholalale  of  potash — Hoppe-Seyler).  If  anthro- 
pochohc  acid  be  heated  to  185°  C,  it  gives  up  I  molecule  of  water,  and  yields  anthropocholdysly- 
sin  \Bayer). 

By  oxidation  cholalic  acid  yields  a  tribasic  acid,  as  yet  uninvestigated,  and  a  fair  amount  of 
oxalic  acid,  but  no  fatty  acids  [Cleve). 

Pettenkofer's  Test. — The  bile  acids,  cholalic  acids,  and  their  anhydrides, 
when  dissolved  in  water,  yield  on  the  addition  of  Ji  concentrated  sulphuric  acid 
(added  in  drops  so  as  not  to  heat  the  fluid  above  70'^  C),  and  several  drops  of  a 
10  per  cent,  solution  of  cane  sugar,  a  redJis/i-piirp/e  transparent  fluid,  which 
shows  two  absorption  bands  at  E  and  F  i^Schenk).  [A  very  good  method  is  to 
mix  a  few  drops  of  the  cane-sugar  solution  with  the  bile,  and  to  shake  the  mix- 
ture until  a  copious  froth  is  obtained.  Pour  the  sulphuric  acid  down  the  side  of 
the  test  tube,  and  then  the  characteristic  color  is  seen  in  the  froth.  Any  albumin 
present  must  be  removed  before  applying  the  test.] 

According  to  Drechsel,  it  is  better  to  add  phosphoric  acid,  instead  of  sulphuric  acid,  until  the  fluid 
is  syrupy,  then  add  the  cane  sugar,  and  afterward  place  the  whole  in  boiling  water.  When  investi- 
gating the  amount  of  bile  acids  in  a  liquid,  the  albumin  must  be  removed  beforehand,  as  it  gives 
a  reaction  similar  to  the  bile  acids,  but  in  that  case  the  red  fluid  has  only  one  absorption  band.  If 
only  small  quantities  of  bile  acids  are  present,  the  fluid  must  in  the  first  place  be  concentrated  by 
evaporation. 

[Hay's  Test  for  the  Bile  Acids. — This  test  depends  on  the  fact,  recently  ascertained  by 
Matthew  Hay  in  the  course  of  an  investigation  which  is  not  yet  completed,  that  the  bile  acids  or 
their  soluble  salts  have  a  remarkable  lowering  effect  on  the  surface  tension  of  fluids  in  which  they 
are  dissolved.  One  part  of  glycoholic  or  taurocholic  acid  in  100,000  or  120,000  parts  of  water,  per. 
ceptibly  lowers  the  surface  tension  of  the  water,  and  the  lowering  is  very  evident  in  a  solution  of  I 
in  10,000,  This  lowering  of  the  surface  tension  can,  of  course,  be  measured  in  the  usual  way  by 
means  of  a  capillary  tube.  But  Hay  proposes,  as  a  much  more  conven  ent  method,  the  throwing  of 
a  small  quantity  of  sulphur  (sublimed  or  precipitated)  on  the  surface  of  the  fluid  containing  bile 
acids.  If  the  bile  acids  are  present  in  greater  proportion  than  I  in  5000  or  10,000,  the  ,sulphur  will 
at  once  begin  to  sink,  and  will  be  wholly  precipitated  within  one  to  two  or  three  minutes.  Precipi- 
tation can  even  be  observed,  though  it  takes  place  much  more  slowly,  in  a  solution  of  I  in  120,000, 
especially  if  the  fluid  is  acidulated  with  a  drop  of  a  dilute  mineral  acid  Thrown  on  water,  sulphur 
does  not  sink,  even  after  a  week.  No  other  substances  in  the  body,  except  soaps,  have  the  same 
action  as  the  bile  acids — at  least  in  anything  like  the  same  degree  ;  and  soaps  can  be  readily  excluded 
from  the  fluid  under  examination,  either  by  precipitation  with  calcic  or  baric  chloride  or  by  decom- 
position with  a  mineral  acid,  the  earthy  .salts  of  the  fatty  acids,  as  also  the  liberated  acids  themselves, 
being  insoluble  in  water.  Even  outside  the  body.  Hay  has  as  yet  found  no  substances,  besides  soaps, 
which  have  the  same  powerful  eflect  on  the  surface  tension  as  the  bile  acids  have.  Hay  has  already 
used  the  sulphur  test  with  success  for  the  detection  of  bile  acids  in  urine.  He  attaches  considerable 
importance  to  this  physical  property  of  the  bile  acids  in  their  role  in  digestion. — (Privately  commu- 
nicated).'] 


THE    BILE    PIGMENTS.  295 

The  origin  of  the  bile  acids  takes  place  within  the  liver.  After  its  extirpa- 
tion there  is  no  accumulation  of  biliary  matters  in  the  blood  (^Joh.  Miiller,  Kunde, 
Moleschott). 

How  the  formation  of  the  nitrogenous  bile  acids  is  effected  is  quite  unknown.  They  must  be 
obtained  from  the  decomposition  of  albuminous  materials,  and  it  is  Important  to  note  that  the  amount 
of  bile  acids  is  increased  by  albuminous  food. 

Taurin  contains  part  of  the  sulphur  of  albumin ;  bile  salts  contain  4  to  4.6  per  cent,  of  sulphur 
{y.  Voit),  which  may  perhaps  be  derived  from  the  stroma  of  the  dissolved  red  blood  corpuscles. 

(3)  The  Bile  Pigments. — The  freshly  secreted  bile  of  man  and  many  ani- 
mals has  a  yellowish-brown  color,  due  to  the  presence  of  bilirubin  {Stddler). 
When  it  remains  for  a  considerable  time  in  the  gall  bladder,  or  when  alkaline  bile 
is  exposed  to  the  air,  the  bilirubin  absorbs  O  and  becomes  changed  into  a  green 
pigment,  biliverdin.  This  substance  is  present  naturally,  and  is  the  chief  pig- 
ment in  the  bile  of  herbivora  and  cold-blooded  animals. 

{a)  Bilirubin  (CajHseN^Og),  is,  according  to  Stiidler  and  Maly,  perhaps  united 
with  an  alkali  ;  it  crystallizes  in  transparent  fox-red  clino-rhombic  prisms.  It  is 
insoluble  in  water,  soluble  in  chloroform,  by  which  substance  it  may  be  separated 
from  biliverdin,  which  is  insoluble  in  chloroform.  It  unites  as  a  monobasic  acid 
with  alkalies,  and  as  such  is  soluble.  It  is  identical  with  Virchow's  hcematoidin 
(§  20). 

Preparation. — It  is  most  easily  prepared  from  the  red  (bilirubin  chalk)  gall  stones  of  man  or  the 
ox.  The  stones  are  pounded,  and  their  chalk  dissolved  by  hydrochloric  acid  ;  the  pigment  is  then 
extracted  with  chloroform. 

Source. — That  bilirubin  is  derived  from  hemoglobin  is  very  probable,  considering  its  identity 
with  hrematoidin.  Very  probably  red  blood  corpuscles  are  dissolved  in  the  liver,  and  their  haemo- 
globin changed  into  bilirubin. 

(1^)  Biliverdin  {Heintz),  CsoHanNjOg,  is  simply  an  oxidized  derivative  of  the 
former,  from  which  it  can  be  obtained  by  various  oxidation  processes.  It  is  readily 
soluble  in  alcohol,  very  slightly  so  in  ether,  and  not  at  all  soluble  in  chloroform. 
It  occurs  in  considerable  amount  in  the  placenta  of  the  bitch.  As  yet  it  has  not 
been  retransformed  by  reducing  agents  into  bilirubin. 

Tests  for  Bile  Pigments. — Bilirubin  and  biliverdin  may  occur  in  other 
fluids,  e.g.,  the  urine,  and  are  detected  by  the  Gmelin-Heintz'  reaction. 
When  nitric  acid  containing  some  nitrous  acid  is  added  to  the  liquid  containing 
these  pigments,  a  play  of  colors  is  obtained,  beginning  with  green  (biliverdin), 
blue,  violet,  red,  ending  with  yellow.  [This  reaction  is  best  done  by  placing  a 
drop  of  the  liquid  on  a  white  porcelain  plate,  and  adding  a  drop  of  the  impure 
nitric  acid.] 

(c)  If  when  the  blue  color  is  reached,  the  oxidation  process  is  arrested,  bilicyanin  (Heynsius, 
Cam/'bcll),  in  acid  solution  blue  (in  alkaline  violet),  is  obtained,  which  shows  two  ill-defined  absorp- 
tion band<  near  D  {faffc). 

[d)  Bilifuscin  occurs  in  small  amount  in  decomposing  bile  and  in  gall  stones  =  bilirubin 
-f  H,0. 

{e^  Biliprasin  {Stddler)  also  occurs  =:  Bilirubin  -|-  HjO  -\-  O. 

(/)  The  yellow  pigment,  which  results  from  the  prolonged  action  of  the  oxidizing  reagent,  is  the 
choletelin  (CjjHjgNjOj)  of  Maly;  it  is  amorphous,  and  soluble  in  water,  alcohol,  acids,  and 
alkalies. 

[Spectrum  of  Bile. — The  bile  of  carnivorous  animals  is  generally  free  from  absorption  bands, 
except  when  acids  are  added  to  it,  in  which  case  the  band  of  bilirubin  is  revealed.  Bilirubin  and 
biliverdin  yield  characteristic  spectra  only  when  they  .are  treated  with  nitric  acid.  The  bile  of  some 
animals  yields  bands,  but  when  this  is  the  case  they  are  due  to  the  presence  of  a  derivative  of 
hsematin,  and  MacMunn  calls  this  body  Cholohaematin,  which  gives  a  three-  or  four-banded  spec- 
trum (ox,  sheep).] 

{g)  Hydro-bilirubin. — Bilrubin  absorbs  H  -|-  H,;0  (by  putrefaction,  or  by  the 
treatment  of  alkaline  watery  solutions  with  the  powerfully  reducing  sodium  amal- 
gam), and  becomes  converted  into  Maly's  hydro-bilirubin  (CjjHuNiO,),  which  is 
slightly  soluble  in  water,  and  more  easily  soluble  in  solutions  of  salts,  or  alkalies. 


296  THE    SECRETION    OF   BILE. 

alcohol,  ether,  chloroform,  and  shows  an  absorption  band  at  b,  F.  This  substance, 
which,  according  to  Hammarsten,  occurs  in  normal  bile,  is  a  constant  coloring 
matter  of  ffeces,  and  was  called  stercobilin  by  Valulair  and  Masius,  but  is  iden- 
tical with  hydro  bilirubin  (Maly).  It  is.  however,  probably  identical  with  the 
urinary  pigment  urobilin  of  Jafle  {Stokvis,  §  20). 

[The  bile  of  invertebrates  contains  none  of  the  bile  pigments  present  in  vertebrates,  although 
hsmochromogen  is  found  in  the  crayfish  and  pulmonate  molluscs.  In  some  organs,  and  in  bile,  a 
pigment-like  vegetable  chlorophyll — entero  chlorophyll — is  found,  but  whether  it  is  derived  from 
without  or  formed  within  the  organism,  is  not  certain. (J/(i£-il/K«K).] 

(4)  Cholesterin,  C26H„0(H20),  is  an  alcohol  which  rotates  the  ray  of  polar- 
ized light  to  the  left,  and  whose  constitution  is  un- 
known ;  it  occurs  also  in  blood,  yelk,  nervous  matter 
and  [gall  stones].  It  forms  transparent  rhombic 
plates,  which,  usually,  have  a  small  oblong  piece  cut 
out  of  one  corner  (Figs.  184,  and  144,  r/).  It  is 
insoluble  in  water,  soluble  in  hot  alcohol,  in  ether 

Crystals  of^choksterin,  regularly  and  chloroform.  It  IS  kept  in  solution  in  the  bile 
by  the  bile  salts. 

Preparation. — It  is  most  easily  prepared  from  so-called  white  gall  stones,  which  not  unfrequently 
consist  almost  entirely  of  cholesterin,  by  extracting  them  with  hot  alcohol  after  they  are  pulverized. 
Crystals  are  excreted  after  evaporation  of  the  alcohol.  Tests. — They  give  a  red  color  with  sul- 
phuric acid  (5  vol.  to  i  vol.  H.,0 — Moiesckotf),  while  they  give  a  blue — as  cellulose  does — with 
sulphuric  acid  and  iodine.  When  dissolved  in  chloroform,  one  drop  of  concentrated  sulphuric  acid 
causes  a  deep  red  color  (//.  Sc/iiff). 

(5)  Among  the  other  organic  constituents  of  bile  are  :  Lecithin  (§  23),  or 
its  decomposition  product,  nei\rin  (cholin),  and  glycero-phosphoric  acid  (into 
which  lecithin  may  be  artificially  transformed  by  boiling  with  baryta)  ;  Palmitin, 
Stearin,  Olein,  as  well  as  their  soda  soaps  ;  Diastatic  Ferment  {Jacobson, 
V.  WitticK);  traces  of  Urea  (Picard);  (in  ox  bile,  acetic  acid  and  propionic  acid, 
united  with  glycerine  and  metals,  Dogiel). 

(6)  Inorganic  constituents  of  bile  (0.6  to  i  per  cent.) : — ■ 

They  are — sodium  chloride,  potassium  chloride,  calcic  and  magnesic  phosphate  and  much  iron, 
which  in  fresh  bile  gives  the  ordinary  reactions  for  iron,  so  that  iron  must  occur  in  one  of  its  oxid- 
ized compounds  in  the  bile  (Ktinkel);  manganese  and  silica.  Gases. — P'reshly  secreted  bile 
contains  in  the  dog  more  than  50  vol.,  and  in  the  rabbit  log  vol.  per  cent.  COj  {Pfliiger,  Bogulju- 
bow,  Charles),  partly  united  in  alkalies,  partly  absorbed,  tlie  latter,  however,  being  almost  com- 
pletely absorbed  within  the  gall  bladder. 

The  mean  composition  of  human  bile  is:  — 

Water 82  to  90  per  cent.       I       Lecithin 0.5  per  cent. 

Bile  Salts 6  to  II        "  |       Mucin i  to  3    " 

Fats  and  Soaps ....    2  "  Ash 0.61       " 

Cholesterin 0.4       •        "  | 

Further,  unchanged  fat,  probably,  always  passes  into  the  bile,  but  is  again  absorbed  tlierefrom 
(  Virc/iozu).  The  amount  of  S  in  dry  dog's  bile  =  2.8  to  3.1  per  cent.,  the  N  ^  7  to  10  per  cent. 
{Spiro) ;  the  sulphur  of  the  bile  is  not  oxidized  into  sulphuric  acid,  but  it  appears  as  a  sulphur 
compound  in  the  urine  {^Kunkel^  v.  VoW). 

178.    SECRETION    OF    BILE.— (i)  The  secretion  of  bile  is  not  a 

mere  filtration  of  substances  already  existing  in  the  blood  of  the  liver,  but  it  is  a 
chemical  production  of  the  characteristic  biliary  constituents,  accompanied  by 
oxidation,  within  the  hepatic  cells,  to  which  the  blood  of  the  gland  only  supplies 
the  raw  material.  The  liver  cells  themselves  undergo  histological  changes  during 
the  process  of  digestion  (/Tf/Vf/z/za///,  Vv'(7iJfr).  It  is  secreted  continually;  but 
part  is  stored  up  in  the  gall  bladder,  and  is  poured  out  copiously  during  digestion. 
The  higher  temperature  of  the  blood  of  the  hepatic  vein,  as  well  as  the  large 
amount  of  CO-^  in  the  bile  (^Pfliiger),  indicate  that  oxidations  occur  within  the 
liver.  The  water  of  the  bile  is  not  merely  filtered  through  the  blood  capillaries, 
as  the  pressure  within  the  bile  ducts  may  exceed  that  in  the  portal  vein. 


CONDITIONS    INFLUENCING   THE    SECRETION    OF    BILE.  297 

(2)  The  quantity  of  bile  was  estimated  by  v.  Witticli,  from  a  biliary  fistula, 
at  533  cubic  centimetres  in  twenty-four  hours  (some  bile  passed  into  the  intestine) ; 
by  Westphalen,  at  453  to  566  grm.  [by  Murchison,  at  40  oz.]  ;  by  Joh.  Ranke, 
on  a  biliary-pulmonary  fistula,  at  652  cubic  centimetres.  The  last  observation 
gives  14  grm.  (with  0.44  grm.  solids)  per  kilo,  of  man  in  twenty  hours. 

,  Analogous  values  for  animals  are— I  kilo,  dog,  32  grm.  (1.2  so\ids)~A'o//iief;  H.  Miiller); 
I  kilo,  rabbit,  137  gnn.  (2-5  solids);  I  kilo  guinea  pig,  176  grm.  (5.2  solids)— (^ioWt-r  and 
Schmidt). 

(3)  The  excretion  of  bile  into  the  intestines  shows  two  maxima  during  one 
period  of  digestion;  the  first,  from  three  to  five  hours,  and  the  second,  from  thir- 
teen to  fifteen  hours  after  food.  The  cause  is  due  to  simultaneous  reflex  excite- 
ment of  the  hepatic  blood  vessels,  which  become  greatly  dilated. 

(4)  The  influence  of  food  is  very  marked.  The  largest  amount  is  secreted 
after  a  flesh  diet,  with  some  fat  added  ;  less  after  vegetable  food  ;  a  very  small 
amount  with  a  pure  fat  diet;1Fstops  during  hunger.  Draughts  of  water  increase 
the  amount,  with  a  corresponding  relative  diminution  of  the  solid  constituents. 
[The  biliary  solids  are  increased  by  food,  reaching  their  maximum  about  one  hour 
after  feeding]. 

(5)  The  influence  of  blood  supply  is  variable  : — 

(a)  Secretion  is  greatly  favored  by  a  copious  and  rapid  blood  supply.  The  blood  pressure  is  not 
the  prime  factor,  as  ligature  of  the  cava  above  the  diaphragm,  whereby  the  greatest  blood  pressure 
occurs  in  the  liver,  arrests  the  secretion  [Heiaenhain). 

{b)  Simultaneous  ligature  of  the  hepatic  artery  (diameter,  5;^  mm.)  and  the  portal  vein  (diameter, 
16  mm.)  abolishes  the  secretion  {RShrig).  These  two  vessels  supply  the  raw  material  for  the  secre- 
tion of  bile. 

(c)  If  the  hepatic  artery  be  ligatured,  the  portal  vein  alone  supports  the  secretion  {Simon,  Schiff, 
Schmulewitsch,  Asf).  According  to  Kottmeier,  Betz,  Cohnheim,  and  Litten,  ligature  of  the  artery 
or  one  of  its  branches  ultimately  causes  necrosis  of  the  parts  supplied  by  that  branch,  and  eventu- 
ally of  the  entire  liver,  as  this  artery  is  the  nutrient  vessel  of  the  liver. 

(</)  If  the  branch  of  the  portal  vein  to  the  lobe  be  ligatured,  there  is  only  a  slight  secretion  in 
that  lobe,  so  that  the  bile  must  be  formed  from  the  arterial  blood  (Schmulnvitsch  and  Asp).  Com- 
plete ligature  of  the  portal  vein  rapidly  causes  death.  [The  blood  pressure  falls  rapidly  and  the 
blood  a'-cumulates  in  the  blood  vessels  of  the  abdomen.  In  fact,  the  accumulation  of  the  blood 
within  the  .nbdomen  takes  place  to  so  great  an  extent,  that  practically  the  animal  is  bled  into  its 
own  abdomen  (§  87).] 

Neither  the  ligature  of  the  hepatic  artery  by  itself  (Schiff,  Betz),  nor  the  ^rarfz/a/ obliteration  of 
the  portal  vein  by  itself,  causes  the  cessation  of  the  secretion,  but  it  is  diminished.  That  sudden 
ligature  of  the  portal  vein  causes  cessation  is  explained  by  the  fact,  that  in  addition  to  diminution  of 
the  secretion,  the  enormous  stagnation  of  blood  in  the  rootlets  of  the  portal  vein  in  the  abdominal 
organs  makes  the  liver  very  aneemic,  and  thus  prevents  it  from  secreting. 

(e)  If  the  blood  of  the  hepatic  artery  is  allowed  to  pass  into  the  portal  vein  (which  has  been  liga- 
tured on  the  peripheral  side),  secretion  continues  (Sehiff). 

(/)  Profuse  loss  of  blood  arrests  the  secretion  of  the  bile,  before  the  muscular  and  nervous  appa- 
ratus become  paralyzed.  A  more  copious  supply  of  blood  lo  other  organs — e.g.,  to  the  muscles  of 
the  trunk — during  vigorous  exercise,  diminishes  the  secretion,  while  the  transfusion  of  large  quan- 
tities of  blood  increases  it  (Landois)  ;  but  if  too  high  a  pressure  is  caused  in  the  portal  vein,  by 
introducing  blood  from  the  carotid  of  another  animal,  it  is  diminished  (Heiden/iain). 

{x  )  The  Influence  of  Nerves. — All  conditions  which  cause  contraction  of  the  abdominal 
blood  vessels,  e.g.,  stimulation  of  the  ansa  Vieussenii,  of  the  inferior  cervical  ganglion,  of  the  hepatic 
nerves  [Afanassieio),  of  the  splanchnics,  of  the  spinal  cord  (either  directly  by  strychnia,  or  reflexly 
through  stimulation  of  sensory  nerves)  affect  the  secretion  ;  and  so  do  all  conditions  which  cause 
stagnation  or  congestion  of  the  blood  in  the  hepatic  vessels  (section  of  the  splanchnic  nerv'es,  diabetic 
puncture,  J!  175),  section  of  the  cervical  spinal  cord  {lleidenhain).  Paralysis  (ligature)  of  the 
hepatic  nerves  causes  at  first  an  increase  of  the  biliary  secretion  (Afanassiew). 

{h)  Portal  and  Hepatic  Veins. — With  regard  to  the  raw  material  supplied  to  the  liver  by  its 
blood  vessels,  it  is  important  to  note  the  difference  in  the  composition  of  the  blood  of  the  hep.atic 
and  portal  veins.  The  blood  of  the  hrpatic  vein  contains  more  .sugar  (?),  lecithin,  cholesterin 
(Drosdoff),  and  blood  corpuscles,  but  less  albumin,  fibrin,  ha:moglobin,  fat,  water,  and  salts. 

\_{i)  Uffelmann  observed  that  the  flow  of  bile  from  a  person  with  a  biliary  fistula  was  arrested 
during  fever.] 

(6)  The  formation  of  bile  is  largely  dependent  upon  the    decomposition  of 


298 


EXCRETION    OF   BILE. 


red  blood  corpuscles,  as  they  supply  the  material  necessary  for  the  formation 
of  some  of  its  constituents. 

Hence,  all  conditions  which  cause  solution  of  the  colored  blood  corpuscles  are  accompanied  by 
an  increased  formation  of  bile  (^  i8o). 

(7)  Of  course  a  normal  condition  of  the  hepatic  cells  is  required  for  a  normal 
secretion  of  bile. 

Biliary  Fistulae. — The  mechanism  of  the  biliary  secretion  is  studied  in  animals  by  means  of 
biliary  fistulie.  Schwann  opened  the  belly  by  a  vertical  incision  a  little  to  the  right  of  the  ensiform 
process,  cut  into  the  fundus  of  the  gall  bladder,  and  sewed  its  margins  to  the  edges  of  the  wound  in 
the  abdomen,  and  afterward  introduced  a  cannula  into  the  wound  (Fig.  1S5).  As  a  rule,  all  the 
bile  is  discharged  externally;  but  to  be  quite  certain  that  this  is  so,  the  common  bile  duct  ought  to 
be  tied  between  two  ligatures,  and  divided.  After  a  fistula  is  freshly  made  the  secretion  falls.  This 
depends  upon  the  removal  of  the  bile  from  the  body.  If  bile  be  supplied  the  secretion  is  increased. 
Regeneration  of  the  divided  bile  duct  may  occur  in  dogs.  v.  Wittich  observed  a  biliary  fistula  in 
man.  [A  temporary  biliary  fistula  may  also  be  made.  The  abdomen  is  opened  in  the  same  way 
as  described  above.  A  long,  bent  glass  cannula  is  introduced  and  tied  into  the  common  bile  duct, 
and  the  cystic  duct  is  ligatured  or  clamped  (Fig.  185).  The  tube  is  brought  out  through  the  wound 
in  the  abdomen.      Necessarily  all  the  bile  must  be  discharged  by  the  tube.] 

[Influence  of  the  Liver  on  Metabolism. — If  the  liver  be  excluded  from  the  circulation, 
remarkable  changes  must  necessarily  occur  in  the  metabolism.  In  birds  (the  goose  especially), 
there  is  an  anastomosis  between  the  portal  system  of  the  liver  and  that  of  the  kidneys,  so  that  when 
the  portal  circulation  is  interrupted  in  these  animals,  there  is  never  any  great  congestion  in  the 
abdominal  organs.     The  goose  dies  generally  eight  to  ten  hours  after  the  operation.     The  uric  acid 


i  permanent  fistula, 

INT,  intest 


nporary  fistula.     Abd,  ahdomina 
,  T,  lube  in  temporary  fistula  l^Sciriing). 


in  the  urine  rapidly  falls  to  a  minimum  (j'j  to  ^  of  normal) ;  the  chief  constituent  of  the  urine  is 
then  sarcolactic  acid,  while  in  normal  urine  there  is  none;  the  ammonia  is  increased  [Alinkinuski). 
This  experiment  goes  to  indicate  that  uric  acid  is  formed  in  the  liver.] 

[Dog. — If  the  liver  be  excluded  from  the  portal  circulation  by  connecting  the  portal  vein  with  the 
inferior  vena  cava,  and  ligaturing  the  hepatic  artery,  a  dog  will  live,  in  the  former  case  three  to  six 
days  and  in  the  latter  one  to  two.  The  liver  does  not  undergo  necrosis,  nor  does  bile  cease  to  be 
secreted.  The  liver  is  nourished  by  the  blood  in  the  hepatic  vein,  the  reflux  in  this  vein  being  prob- 
ably caused  by  the  respiratory  movements  (Slolnitow).  Noel  Paton  finds  that  in  dogs,  in  a  condi- 
tion of  nitrogenous  balance,  some  drugs  which  increase  the  flow  of  bile  (c.^.,  salicylate  and  benzoate 
of  soda,  colchicum,  perchloride  of  mercury,  and  euonymin),  also  increase  the  production  of  urea  ; 
hence,  he  concludes  that  the  formation  of  urea  in  the  liver  bears  a  very  direct  relationship  to  the 
secretion  of  bile  (§  256).] 

179.  EXCRETION  OF  BILE.— In  connection  with  the  excretion  of  bile, 
we  must  keep  in  view  two  distinct  mechanisms,  (i)  The  bile-secreting  mech- 
anism dependent  upon  the  liver  cells,  which  are  always  in  a  greater  or  less  degree 
of  activity  ;  (2)  the  bile-expelling  mechanism,  which  is  specially  active  at  cer- 
tain periods  of  digestion  (§  178). 

Excretion  of  Bile  occurs — (i)  owing  to  the  continual  pressure  of  the  newly- 
formed  bile  within  the  interlobular  bile  ducts  forcing  onward  the  bile  in  the  ex- 
cretory ducts. 

(2)  Owing  to   the  mttrrwpttA  periodic  compression  of  the  liver  hoxa  above,  by 


REABSORPTION    OF    BILE  ;    JAUNDICE.  299 

the  diaphragm,  at  every  inspiration.  Further,  every  inspiration  assists  the  flow  of 
blood  in  the  hepatic  veins,  and  every  respiratory  increase  of  pressure  within  the 
abdomen  favors  the  current  in  the  portal  vein. 

It  is  probable  that  the  diminution  of  the  secretion  of  bile,  which  occurs  after  bilateral  division  of 
the  vagi,  is  to  be  explained  in  this  way  ;  still  it  is  to  be  remembered,  that  the  vagus  sends  branches 
to  the  hepatic  plexus.  It  is  not  decided  whether  the  biliary  excretion  is  diminished  after  section 
of  the  phrenic  nerves  and  paralysis  of  the  abdominal  muscles. 

(3)  Owing  to  the  contraction  of  the  smooth  muscles  of  the  larger  bile  ducts  and 
the  gall-bladder.  Stimulation  of  the  spinal  cord,  from  which  the  motor  nerves 
for  these  structures  pass,  causes  acceleration  of  the  outflow,  which  is  afterward 
followed  by  a  diminished  outflow  {Hcidenliain,  J.  Miink).  Under  normal  condi- 
tions, this  stimulation  seems  to  occur  reflexly,  and  is  caused  by  the  passage  of  the 
ingesta  into  the  duodenum,  which,  at  the  same  time,  excites  movement  of  this 
part  of  the  intestine. 

(4)  Direct  stimulation  of  the  liver  {Ffliiger~),  and  reflex  stimulation  of  the 
spinal  cord  {Hohrig),  diininish  the  excretion  ;  while  extirpation  of  the  hepatic 
plexus  {Ffluger),  and  injury  to  the  floor  of  the  fourth  ventricle  do  not  exert  any 
disturbing  influence  {He!denhai!i). 

(5)  A  relatively  small  amount  of  resistance  causes  bile  to  stagnate  in  the  bile 
ducts. 

Secretion  Pressure. — A  manometer,  tied  into  the  gall-bladder  of  a  guinea  pig,  supports  a 
column  of  200  millimetres  of  waUr ;  and  secretion  can  take  place  under  this  pressure  [^Hcidenliain^ 
Friedlander,  Barisrh).  If  this  pressure  be  increased,  or  too  long  sustained,  the  watery  bile  passes 
from  the  liver  mto  the  blood,  even  to  the  amount  of  four  times  the  weight  of  the  liver,  thus  caus- 
ing solution  of  the  red  blood  corpuscles  by  the  absorbed  bile  ;  and  very  soon  thereafter  heemoglobin 
appears  in  the  urine.  [This  fact  is  of  practical  importance,  as  duodenitis  may  give  rise  to  symptoms 
of  jaundice,  the  resistance  of  the  inflamed  mucous  meinbrane  being  sufficient  to  arrest  the  outflow 
of  bile.] 

180.  REABSORPTION  OF  BILE;   JAUNDICE.-I.  Absorption   Jaundice.— When 

an  impediment  or  resistance  is  offered  to  the  outflow  of  bile  into  the  intestine,  e.  g.,  by  a  plug  of 
mucus,  or  a  gall-stone  which  occludes  the  bile  duct,  or  where  a  tumor  or  pressure  from  without 
makes  it  impervious — the  bile  ducts  become  filled  with  bile  and  cause  an  enlargement  of  the  liver. 
The  pressure  within  the  bile  ducts  is  increased.  As  soon  as  the  pressure  has  reached  a  certain 
amount,  which  it  soon  does  when  the  bile  duct  is  occluded  (in  the  dog  275  mm.  of  a  column  of 
bile — Afanassie-cv) — reabsorption  of  bile  from  the  distended  larger  bile  ducts  takes  place  into  the 
lymf'/iatics  (not  the  blood  vessels)  of  the  liver  {Sauni/ers,  /ygS)  J  '^"2  ti''^  acids  pass  into  the  lym- 
phatics of  the  liver.  [The  lymphatics  can  be  seen  at  the  portal  fissure  filled  with  a  deep  yellow- 
colored  lymph.]  The  lymph  passes  into  the  thoracic  duct,  and  so  into  the  blood  [^Fleischl,  Kutiket, 
Kufferalh\.  Even  when  the  pre.ssure  is  very  low  within  the  portal  vein,  bile  may  pass  into  the 
blood  without  any  obstruction  to  the  bile  duct  being  present.  This  is  the  case  in  /ctenis  neona- 
loium,  as  after  ligature  of  the  umbilical  cord  no  more  blood  passes  through  the  umbilical  vein ; 
further,  in  the  ictt  rus  of  hunger,  "  hunger  jaundice  "  as  the  portal  vein  is  relatively  empty,  owing 
to  the  feeble  absorption  from  the  intestinal  canal  (C7.  Bernard,   Voit,  Naunyn). 

II.  Cholaemia  may  also  occur,  owing  to  the  excessive  production  of  bile  (hypercholia),  the  bile 
not  being  all  excreted  into  the  intestine,  so  that  part  of  it  is  reabsorbed.  This  takes  place  when 
there  is  solution  of  a  great  number  of  blood  corpuscles  (J  178,  6),  which  yield  material  for  the  for- 
mation of  bile.  Thick,  inspissated  bile  accumulates  in  the  bile  ducts,  .so  that  stagnation,  with  sub- 
sequent reabsorption  of  the  bile,  takes  place  (A/anassiew).  The  transfusion  of  heterogeneous 
blood  by  dissolving  colored  blood  corpuscles  acts  in  this  direction.  Icterus  is  a  common  phe- 
nomenon after  too  copious  transfusion  of  the  same  blood.  The  blood  corpuscles  are  dissolved  by 
the  injection  into  the  blood  of  heterogeneous  blood  serum  (Landois)  by  the  injection  of  bile  acids 
into  the  vessels  [Frerir/is),  and  by  other  salts,  by  phosphoric  acid,  water  (Hermann),  chloral, 
inhalation  of  chloroform  and  ether  (A'o/kiiage/,  Bernstein) ;  the  injection  of  dissolved  ha-moglobin 
into  the  arteries  (A'iiiine),  or  into  a  loop  of  the  small  intestine,  acts  in  the  same  way  (A'aiaiyn). 

Icterus  Neonatorum. — When,  owing  to  compression  of  the  placenta  within  the  uterus,  too 
much  blood  is  forced  into  the  blood  vessels  of  the  newly-born  infant,  a  part  of  the  surplus  blood 
during  the  first  few  days  becomes  dissolved,  part  of  the  haemoglobin  is  converted  into  bilirubin, 
thus  causing  jaundice  (  Virchow,   Violet). 

Absorption  Jaundice. — When  the  jaundice  is  caused  by  the  absorption  of 
bile  already  formed  in  the  liver,  it  is  called  hepatogenic  or  absorption  jaundice. 
The  following  are  the  symptoms: — 


300  INFLUENCE    OF    DRUGS   ON   THE    SECRETION    OF   BILE. 

Phenomena. — (i)  Bile  pigments  and  bile  aci<ls  pass  into  the  tissues  of  the  body;  hence,  the 
most  pronounced  extemarsymjjtom  is  the  yellowish  tmt  or  jaundice.  The  skin  and  the  sclerotic 
become  deeply  colored  yellow.     In  pregnancy  the  fcetus  is  also  tinged. 

(2)  Bile  pigments  and  bile  acids  pass  mto  the  urine  (not  into  the  saliva,  tears  or  mucus),  and 
their  presence  is  ascertained  by  the  usual  tests  (J  I77).  When  there  is  much  bile  pigment,  the 
urine  is  colored  a  deep  yellowish  brown,  and  its  froth  is  citron-yellow;  white  strips  of  gelatin  or 
paper  dipped  into  it  also  become  colored.  Occasionally  bilirubin  (=  hjematoidin)  crystals  occur  in 
the  urine  (J  266). 

(3)  The  faeces  xnt  "clay-colored"  (because  the  hydro-bilirubin  of  the  bile  is  absent  from  the 
fsecal  matter) — very  hard  (because  the  fluid  of  the  bile  does  not  pass  into  the  intestine);  contain 
much  fat  (in  globules  and  crystals),  because  the  fat  is  not  sufficiently  digested  in  the  intestine  with- 
out bile,  so  that  more  than  60  per  cent,  of  the  fat  taken  with  the  food  reappears  in  the  fieces  (v. 

Voit);  they  have  a  very  disagreeable  odor,  because  bile  normally  greatly  limits  the  putrefaction  in 
the  intestine,  [v.  Voit  finds  that  putrefaction  does  not  take  place  if  fats  be  withheld  from  the 
food.]  The  eTaciiation  of  the  fa-ces  occurs  slowly,  partly  owing  to  the  hardness  of  the  fjeces, 
partly  because  of  the  absence  of  the  peristaltic  movements  of  the  intestine,  owing  to  the  want  of 
the  stimulating  action  of  the  bile. 

(4)  The  heart  beats  are  generally  diminished,  e.  g.,  to  40  per  minute.  This  is  due  to  the 
action  of  the  bile  salts,  which  at  first  stimulate  the  cardiac  ganglia,  and  then  weaken  them.  The 
injection  of  bile  sails  into  the  heart  produces  at  first  a  temporary  acceleration  of  the  pulse  (Lan- 
doij),  and  afterward  slowing  (fiohrig).  The  same  occurs  when  they  are  injected  into  the  blood, 
but  in  this  case  the  stage  of  excitement  is  very  short.  The  phenomenon  is  not  affected  by  section 
of  the  vagi.  It  is  probable,  that  when  the  action  of  the  bile  salts  is  long  continued  they  act  upon 
the  heart  muscle  (  Traube).  In  addition  to  the  action  on  the  heart,  there  is  slowing  of  the  respi- 
ration and  diminution  of  temperature. 

(5)  That  the  nervous  system,  and  perhaps  also  the  muscles,  are  affected,  either  by  the  bile 
salts  or  by  the  accumulation  of  cholesterin  in  the  blood  (flint,  K.  Miiller),  is  shown  by  the  very 
general  relaxation,  sensation  of  fatigue,  weakness  and  drowsiness,  lastly  deep  coma — sometimes 
there  is  sleeplessness,  itchiness  of  the  skin,  even  mania,  and  spasms.  Lowit,  after  injecting  bile 
into  animals,  observed  phenomena  referable  to  stimulation  of  the  respiratory,  cardio-inhibitory,  and 
vasomotor  nerve  centres. 

(6)  In  very  pronounced  jaundice  there  may  be  ''yellow  vision  "  (Lucretius  Cams),  owing  to  the 
impregnation  of  the  retina  and  macula  lutea  with  the  bile  pigment. 

(7)  The  bile  acids  in  the  blood  dissolve  the  red  blood  corpuscles.  The  haemoglobin  is  changed 
into  new  bile  pigment,  and  the  globulin-like  body  of  the  hiemoglobin  may  form  urinary  cylinders 
or  casts  in  the  urinary  tubules,  which  are  ultimately  washed  out  of  the  tubules  by  the  urine  (Noth- 
nagel). 

Passage  of  Substances  into  the  Bile.— -Various  substances  pass  into  the  bile,  such  substances 
being  in  the  blood,  viz.,  the  metals  (v.  Sartoris,  Mohnheim,  Orjila] — copper,  lead,  zinc,  nickel, 
silver,  bismuth  [ll'ichert),  arsenic,  antimony,  iron;  these  substances  are  also  deposited  in  the 
hepatic  tissues.  Potassium  iodide,  bromide,  and  sulphocyanide  (Pei/ier),  and  turpentine  also  pass 
into  the  bile,  and,  to  a  less  degree,  cane  sugar  and  grape  sugar  {A/osler) ;  sodium  salicylate,  and 
carbolic  acid  (Peiper).  If  a  large  amount  of  water  be  injected  into  the  blood,  the  bde  becomes 
albuminous  (Moster);  mercuric  and  mercurous  chlorides  cause  an  increase  of  the  water  of  the  bile 
{C  Scott).  Sugar  has  been  found  in  the  bile  in  diabetes;  leucin  and  tyrosin  in  typhus,  lactic  acid 
and  albumin  in  other  pathological  conditions  of  this  fluid. 

[Influence  of  Drugs  on  the  Secretion  of  Bile. — Two  methods  are  adopted,  one  by  means 
of  permanent  fistuUe.  and  the  other  by  establishing  temporary  fislulfe.  The  latter  is  the  most  satis- 
factory method,  and  the  experiments  are  usually  made  on  fasting  curarized  dogs.  A  suitable  cannula 
IS  introduced  into  the  common  bile  duct  (Fig.  185).  the  animal  is  curarized,  artificial  respiration  being 
kept  up,  while  the  drug  is  injected  into  the  stomach  or  intestine.  Rohrig  used  this  method,  which 
was  improved  by  Rutherford  and  Vignal.  Rohrig  found  that  some  purgatives,  croton  oil,  colocynth, 
jalap,  aloes,  rhubarb,  senna,  and  other  substances,  increased  the  secretion  of  bile.  Rutherford  and 
Vignal  investigated  the  action  of  a  large  number  of  drugs  on  the  bile-secreting  mechanism. 
They  found  that  croton  oil  is  a  feeble  hepatic  stimulant,  while  podopbyllin,  aloes,  colchicum, 
euonymin,  iridin,  sanguinarin,  ipecacuanha,  colocynth,  sodium  phosphate,  phytolaccin,  sodium  ben- 
zoale,  sodium  salicylate,  dilute  nitrohydrochloric  acid,  ammonium  phosphate,  mercuric  chloride  (cor- 
rosive sublimate),  are  all  powerful,  or  very  considerable,  hepatic  stimulants.  They  found  that  some 
substances  stimulate  the  intestinal  glands,  but  not  the  liver,  e.  g.,  magnesium  sulphate,  castor  oil, 
gamboge,  ammonium  chloride,  manganese  sulphate,  calomel.  (Dther  substances  stimulate  the  liver 
a-i  well  as  the  intestinal  glands,  although  not  to  the  same  extent,  e.  g.,  scammony  (powerful  intes- 
tinal, feeble  hepatic  stimulant) ;  colocynth  excites  both  powerfully  ;  jalap,  sodium  sulphate,  baptisin, 
act  with  considerable  power  both  on  the  liver  and  the  intestinal  glands.  Calabar  bean  stimulates 
the  liver,  and  the  increased  secretion  caused  thereby  may  be  reduced  by  sulphate  of  atropin, 
although  the  Latter  drug,  when  given  alone,  does  not  notably  alTect  the  secretion  of  the  bile.  The 
injection  of  water  or  bile  slightly  increases  the  secretion.  In  all  cases  where  purgation  was  pro- 
duced by  purely  intestinal  stimulants,  such  as  magnesium  sulphate,  gamboge,  and  castor  oil,  the 


FUNCTIONS    OF   THE    BILE.  301 

secretion  of  bile  was  dimiiiished.  In  all  such  experimenls  it  is  most  important  that  the  temperature 
of  the  animal  be  kept  up  by  covering  it  with  cotton  wool,  else  the  secretion  of  bile  diminishes. 
Paschkis's  results  on  dogs  differ  considerably  from  those  of  Rutherford.  He  asserts  that  only  the  bile 
acids  (salts),  of  all  the  sul)Stances  he  investigated,  excite  a  prompt  and  distinct  cholagogue  action.] 

[As  yet  we  cannot  say  definitely  whether  these  substances  stimulate  the  secretion  of  bile,  by  ex- 
citing the  mucous  membrane  of  the  duodenum  or  other  part  of  the  small  intestine,  and  thereby 
inducing  reflex  excitement  of  the  liver.  Their  action  does  not  seem  to  be  due  to  increase  of  the 
blood  stream  through  the  liver.  More  probably,  as  Rutherford  suggests,  these  drugs  act  directly  on 
the  hepatic  cells  or  their  nerves.  Acetate  of  lead  directly  depresses  the  biliary  secretion,  while  some 
substances  affect  it  indirectly.] 

Cholesteraemia. — Flint  ascribes  great  importance  to  the  excretion  of  cholesterin  by  the  bile, 
with  reference  to  the  metabolism  of  the  nervous  system.  Cholesterin,  which  is  a  normal  ingredient 
of  nervous  tissue,  is  excreted  by  the  bile ;  and  if  it  be  retained  in  the  blood  "  cholesteraemia,"  with 
grave  nervous  symptoms,  is  said  to  occur.  This,  however,  is  problematical,  and  the  phenomena 
described  are  probably  referable  to  the  retention  of  the  bile  acids  in  the  blood. 

i8i.  FUNCTIONS  OF  THE  BILE.— [(ij  Bile  is  concerned  in  the 
digestion  of  certain  food-stuffs;  (2)  part  of  it  is  absorbed;  (3)  part  is  excreted.] 

(A)  Bile  plays  an  important  part  in  the  absorption  of  fats  : — 

(ij  It  emulsionizes  neutral  fats  (§  170,  III),  whereby  the  fatty  granules  pass 
more  readily  through  or  between  the  cylindrical  epithelium  of  the  small  intestine 
into  the  lacteals.  It  does  tiot  decompose  neutral  fats  into  glycerine  and  a  fatty 
acid,  as  the  pancreas  does. 

When,  however,  fatty  acids  are  dissolved  in  the  bile  (Lenz)  the  bile  salts  are  decomposed,  the 
bile  acids  being  set  free,  while  the  soda  of  the  decomposed  bile  salts  readily  forms  a  soluble  soap 
with  the  fatty  acids.  These  soaps  are  soluble  in  the  bile,  and  increase  considerably  the  emulsifying 
power  of  this  fluid.  Bile  can  dissolve  directly  fatty  acids  to  form  an  acid  fluid,  which  has  hiyh 
emulsionizing  properties  [Steiner).  Emulsification  is  influenced  by  a  i  per  cent  solution  of  NaCl,  or 
Na^SO,  {Pje,ffer). 

(2)  As  fluid  fat  flows  more  rapidly  through  capillary  tubes  when  they  are  mois- 
tened with  bile,  it  is  concluded  that  when  the  pores  of  the  absorbing  wall  of  the 
small  intestine  are  moistened  with  bile,  the  fatty  particles  pass  more  easily  through 
them. 

(3)  Filtration  of  fat  takes  place  through  a  membrane  moistened  with  bile  or 
bile  salts  under  less  pressure  than  when  it  is  moistened  with  water  or  salt  solutions 
{v.   Wistinghausen). 

(4)  As  bile,  like  a  solution  of  soap,  has  a  certain  relation  to  watery  solutions, 
as  well  as  to  fats,  it  permits  effusion  to  take  place  between  these  two  fluids,  as  the 
membrane  is  moistened  by  both  fluids  {v.   Wistinghausen'). 

It  is  clear,  therefore,  that  the  bile  is  of  great  importance  in  the  preparation  and  in  the  absorption  of 
fats.  This  is  forcibly  illustrated  by  experiments  on  animals,  in  which  the  bile  is  entirely  discharged 
externally  through  a  fistula.  Dogs  under  these  conditions,  absorbed  at  most  40  per  cent,  of  the  fat 
taken  with  the  food  [60  per  cent,  being  given  off  by  the  faeces,  while  a  normal  dog  absorbs  99  per 
cent,  of  the  fat.  The  digestion  of  flesh  and  gelatine  is  not  interfered  with  in  dogs  by  the  removal 
of  the  bile  {v.  Voit).'\  The  chyle  of  such  animals  is  very  poor  in  fat,  is  not  white,  but  transparent ; 
the  fa.-ces,  however,  contain  much  fat,  and  are  oily.  Such  animals  are  voracious  [iVasse) ;  the  tissues 
of  the  body  contain  little  fat,  even  when  the  nutrition  of  the  animals  has  not  been  much  interfered 
with.  Persons  suffering  from  disturbances  of  the  biliary  secretion,  or  from  liver  aflfections,  ought, 
therefore,  to  abstain  from  fatty  food. 

(B)  Fresh  bile  cpntains  a  diastatic  ferment  which  transforms  starch  into 
sugar  (Nasse,  Jacobson,  v.  IVittich),  and  also  glycogen  into  sugar  {Bufa/ini). 

(C)  Bile  excites  contractions  of  the  muscular  coats  of  the  intestine,  and 
contributes  thereby  to  absorption. 

(1)  The  bile  acids  act  as  a  stimulus  to  the  muscles  of  the  villi,  which  contract  from  time  to 
time,  so  that  the  contents  of  the  lymph  spaces  [origins  of  the  lacteals]  are  emptied  toward  the  larger 
lymphatics,  and  the  villi  are  thus  in  a  position  to  absorb  more  [Sc/nff).  [The  villi  act  like  numerous 
small  pumps,  and  expel  their  contents,  which  are  prevented  from  returning  by  the  presence  of  valves 
in  the  larger  lymphatics.] 

(2)  The  musculature  of  the  intestine  itself  seems  to  be  excited,  perhaps  through  the  agency 
of  the  plexus  myentericus.     In  animals  with  a  biliary  fistula,  and  in  which  the  bile  duct  is  obstructed. 


302  FATE   OF   THE    BILE    IN    THE    INTESTINE. 

the  intestinal  peristalsis  is  greatly  diminislied,  while  the  salts  of  the  bile  acids  administered  by  the 
mouth  cause  diarrhcea  and  vomiting  (Leyden,  Sc/iiilein).  As  contraction  of  the  intestine  aids  absorp- 
tion, bile  is  also  necessary,  in  this  way,  for  the  absorption  of  the  dissolved  food  stuffs. 

(D)  The  presence  of  bile  seems  to  be  necessary  to  the  vital  activity  of  the  in- 
testinal epithelium  in  its  supposed  function  of  being  concerned  in  the  absorption 
of  fatty  particles  (v.   Thanhoffer,  Rohinanu).      Compare  (§190). 

(E)  The  bile  moistens  the  walls  of  the  intestine,  as  it  is  copiously  excreted. 
It  gives  to  the  feeces  their  normal  amount  of  water,  so  that  they  can  be  readily 
evacuated.  Animals  with  biliary  fistula,  or  persons  with  obstruction  of  the  bile 
ducts,  are  very  costive.  The  mucus  of  the  bile  aids  the  forward  movement  of  the 
ingesta  through  the  intestinal  canal.  [Thus,  in  a  certain  sense,  bile  is  a  natural 
purgaiwe.'\ 

(F)  The  bile  diminishes  putrefactive  decomposition  of  the  intestinal  con- 
tents {Bidder  and  Schmidt),  especially  with  a  fatty  d\tii{RShmann,  v.  Vait),  §  190. 
[Thus,  It  is  an  antiseptic,  although  this  is  doubted  by  v.  Voit,  p.  300).] 

(G)  When  the  strongly  acid  contents  of  the  stomach  pass  into  the  duodenum, 
the  glycocholic  acid  is  precipitated  by  the  gastric  acid,  and  carries  the  pepsin 
with  it  {Biirkart').  Some  of  the  albumin,  which  has  been  simply  dissolved,  but 
as  yet  not  peptonized,  is  also  precipitated,  but  it  does  not  seem  that  peptone  or 
propeptone  are  precipitated  by  the  mixture  of  the  bile  acids  (Maly  and  EmicK). 
The  bile  salts  are  decomposed  by  the  action  of  the  gastric  juice.  When  the  mix- 
ture is  rendered  alkaline  by  the  pancreatic  juice  and  the  alkali  derived  from  the 
decomposition  of  the  bile  salts,  the  pancreatic  juice  acts  energetically  in  this  alka- 
line medium  {Molesehott). 

[Taurocholic  acid  and  its  soda  salts  precipitate  albumin,  but  not  peptone ;  glycocholic  acid  does 
not  precipitate  albumin,  so  that  in  the  intestine  the  peptone  is  separated  from  the  albumin  (and  syn- 
tonin),  and  may,  therefore,  be  more  readily  al>sorbed,  while  the  precipitate  adhering  to  the  intestinal 
wall  can  be  further  digested  [Maly  and  Emich).  Taurocholic  acid  behaves  in  the  same  way  toward 
gelatine  peptone.] 

Bilious  Vomit. — When  bile  passes  into  the  stomach,  as  in  vomiting,  the  acid  of  the  gastric  juice 
unites  with  the  bases  of  the  bile  salts;  so  that  sodium  chloride  and  free  bile  acids  are  formed,  and 
the  acid  reaction  is  thereby  somewhat  diminished.  The  bile  acids  are  not  effective  for  carrying  on 
gastric  digestion;  the  neutralization  also  causes  a  precipiiation  of  the  pepsin  and  mucin.  As  soon, 
however,  as  the  walls  of  the  stomach  secrete  new  acid,  the  pepsin  is  redissolved.  The  bile  which 
passes  into  the  stomach  deranges  gastric  digestion,  by  shriveling  the  proteids,  which  can  only  be 
peptonized  when  they  are  swollen  up. 

182.  FATE  OF  THE  BILE  IN  THE  INTESTINE.— Some  of  the 

biliary  constituents  are  completely  evacuated  with  the  fa;ces,  while  others  are  re- 
absorbed by  the  intestinal  walls. 

(i)   Mucin  passes  unchanged  into  the  faeces. 

(2)  The  bile  pigments  are  reduced,  and  are  partly  excreted  with  the  faeces 
as  hydro- bilirubin  (§  177,  3  g),  and  partly  as  the  identical  end  product,  urobilin,  by 
the  urine. 

From  Meconium  hydro-bilirubin  is  absent,  while  crystalline  bilirubin  and  biliverdin  and  an 
unknown  red  oxidation  product  of  it  are  present  [bile  acids,  even  taurocholic,  and  small  traces  of 
fatty  acids],  [Zioeifel).  [So  that  it  gives  Gmelin's  reaction.]  Hence,  no  reduction — but  rather 
oxidation — processes  occur  in  the  fcetal  intestine  (Hoppe-Seyler). 

(Composition. — Dary  gives  72.7  per  cent,  water,  23.6  mucus  and  epithelium,  i  per  cent,  fat  and 
cholesterin,  and  3  per  cent,  bile  pigments.  Zweifel  gives  79.78  per  cent,  water,  and  solids  20.22 
per  cent.  It  does  not  contain  lecithin,  but  so  much  bilirubin  that  Hoppe-Seyler  uses  it  as  a  good 
source  whence  to  obtain  this  pigment.  It  gives  a  spectrum  of  a  body  related  to  urobilin  (  Vaulair, 
MacMuiin).] 

(3)  Cholesterin  is  given  off  with  the  fasces. 

(4)  The  bile  salts  are,  for  the  most  part,  reabsorbed  by  the  walls  of  the  jeju- 
num and  ileum,  to  be  reemployed  in  the  animal's  economy.  Tappeiner  found 
them  in  the  chyle  of  the  thoracic  duct;  minute  quantities  pass  normally  from  the 
blood   into  the   urine.     Only  a  very  small  amount   of  glycocholic   acid   appears 


THE   INTESTINAL   JUICE.  303 

unchanged  in  the  feces.  The  taurocholic  acid,  as  far  as  it  is  not  absorbed,  is 
easily  decomposed  in  the  intestine,  by  the  putrefactive  processes,  into  cholalic 
acid  and  taurin  ;  the  former  of  these  is  found  in  the  faces,  but  the  taurin,  at  least, 
seems  not  to  be  constantly  present.  Part  of  the  cholalic  acid  is  absorbed,  and 
may  unite  in  the  liver  either  with  glycin  or  taurin  (  Weiss). 

As  putrefactive  decomposition  does  not  occur  in  the  fcetal  intestine,  unchanged  taurocholic  acid  is 
found  in  meconium  (Zwei/el).  The  anhydride  stage  of  cholalic  acid  (the  artificially. prepared 
choloidinic  acid?},  dyslysin,  is  an  artificial  product,  and  does  not  occur  in  the  fs:ces  (/Joppe- 
SeyUr). 

(5)  The  faeces  contain  mere  traces  of  Lecithin  {Wegscheiiier,  Bokay). 

Impaired  Nutrition. — The  greatest  part  of  the  most  important  biliary  constituents,  the  bile  acids, 
re-enter  the  blood,  and  thus  is  explained  why  animals  with  a  biliary  fistula,  where  all  the  bile  is  re- 
moved (without  the  animal  being  allowed  to  lick  the  bile),  rapidly  lose  weight.  This  depends 
partly  upon  the  digestion  of  the  fats  being  interfered  with,  and  also  upon  the  direct  loss  of  the  bile 
salts.  If  such  dogs  are  to  maintain  their  weight,  they  must  eat  twice  as  much  food.  In  such  cases, 
carbohydrates  most  beneficially  replace  the  fats.  If  the  digestive  apparatus  is  otherwise  intact,  the 
animals,  on  account  of  their  voracity,  may  even  increase  in  weight,  but  the  flesh  and  not  the  lat  is 
increased. 

Bile  partly  an  Excretion. — The  fact  that  bile  is  secreted  during  the  foetal 
period,  while  none  of  the  other  digestive  fluids  are,  proves  it  is  an  excretion. 

The  cholalic  acid  which  is  reabsorbed  by  the  intestinal  walls  passes  into  the  body,  and  seems 
ultimately  tu  be  burned  to  form  CO2  and  H^O.  The  glycin  (with  hippuric  acid)  forms  urea,  as  the 
urea  is  increased  after  the  injection  of  glycin  {^Horsford,  Schultsen,  A'encki).  The  fate  of  taurin  is 
unknown.  When  large  quantities  are  introduced  into  the  human  stomach,  it  reappears  in  the  urine, 
as  tauro-carbamic  acid,  along  with  a  small  quantity  of  unchanged  taurin.  When  injected  subcuta- 
neously  into  a  rabbit,  nearly  all  of  it  reappears  in  the  urine. 

[Practical. — In  practice  it  is  important  to  remember  that  bile  once  in  the  intestine  is  liable  to 
be  absorbed  unless  it  be  carried  down  the  intestine  ;  hence,  it  is  one  thing  to  give  a  drug  which  will 
excite  the  secretion  of  bile,  i.  e.,  a  hepatic  stimulant,  and  another  to  have  the  bile  so  secreted  ex- 
pelled. It  is  wise,  therefore,  to  give  a  drug  which  will  do  both,  or  at  least  to  combine  a  hepatic 
stimulant  with  one  which  will  stimulate  the  musculature  of  the  intestine  as  well.  Active  exercise, 
whereby  the  diaphragm  is  vigorously  called  into  action  to  compress  the  liver,  will  aid  in  the  ex- 
pulsion of  the  bile  from  the  liver  (Brunton).'] 

183.  THE  INTESTINAL  JUICE.— Length  of  Intestine.— The  human  intestine  is  ten 
times  longer  than  the  length  of  tlie  body,  as  measured  from  the  vertex  to  the  anus.  It  is  longer 
comparatively  than  that  of  the  omnivora  IHenning).  Its  minimum  length  is  507,  its  maximum 
1149  centimetres  [17  to  35  feet];  its  capacity  is  relatively  greater  in  children  {Beneke).  [The 
average  length  is  30  feet;  25  feet  (small),  and  5  to  6  feet  large  intestine.]  In  childhood  the  ab- 
sorptive elements,  in  adults  the  secreto-chemical  processes,  appear  to  be  most  active  {Baginsky). 

The  succus  entericus  is  the  digestive  fluid  secreted  by  the  numerous  glands 
of  the  intestinal  mucous  membrane.  The  largest  amount  is  produced  by  Lieber- 
kiihn's  glands,  while  in  the  duodenum  there  is  added  the  scanty  secretion  of  the 
small  compound  Brunner's  glands. 

Brunner's  glands  are  small,  convoluted,  branched,  tubular  glands,  lying  in  the  sub-mucosa  of 
the  duodenum.  Their  fine  ducts  run  inward,  pierce  the  mucous  membrane,  and  open  at  the  bases 
of  the  villi.  The  acini  are  lined  by  cylindrical  cells,  like  those  lining  the  pyloric  glands.  In  fact, 
Brunner's  glands  are  structurally  and  anatomically  identical  with  the  pyloric  glands  of  the  stomach. 
During  hunger,  the  cells  are  turbid  and  small,  while  during  digestion  they  are  large  and  clear. 
The  glands  receive  nerve  fibres  from  Meissner's  plexus  [Drasch). 

I.  The  Secretion  of  Brunner's  Glands. — The  granular  contents  of  the 
secretory  cells  of  these  glands,  which  occur  singly  in  man,  but  form  a  continuous 
layer  in  the  duodenum  of  the  sheep,  besides  albuminous  substances,  consist  of 
mucin  and  a  ferment  substance  of  unknown  constitution.  The  watery  extract  of 
the  glands  causes — (i)  Solution  of  proteids  at  the  temperature  of  the  body 
{Kroiow).  (2)  It  also  has  a  diastatic  (?)  action.  It  does  not  appear  to  act  upon 
fats.  [Brown  and  Heron  have  shown  that  the  secretion  of  Brunner's  glands, 
more  actively  than  any  other  glands  of  the  intestines,  converts  maltose  into 
glucose.] 


304 


LIEBERKUHN  S    GLANDS. 


On  account  of  the  smallness  of  the  objects,  such  experiments  are  only  made  with  great  difficulty, 
and,  therefore,  there  is  a  considerable  uncertainty  with  regard  to  the  action  of  the  secretion. 

Lieberkhiin's  glands  are  simply  tubular  glands  resembling  the  finger  of  a  glove  [or  a  test-tube], 
which  lie  closely  packed,  vertically  near  each  other,  in  the  mucous  membrane  (Fig.  iS6) ;  they  are 
most  numerous  in  the  large  intestine,  owing  to  the  absence  of  the  villi  in  this  region.  They  consist 
of  a  structureless  membrana  propria  lined  by  a  layer  of  low  cylindrical  epithelium,  between  which 
numerous  goblet  cells  occur,  the  goblet  cells  being  fewer  in  the  small  intestine  and  much  more 
numerous  in  the  large  (Fig.  201).  The  glands  of  the  small  intestine  yield  a  thin  secretion,  while 
those  of  the  large  intestine  yield  a  large  amount  of  sticky  mucus  from  their  goblet  cells  (A'/ose  and 
Heidenhain'].  [In  a  vertical  section  of  the  small  intestine  they  lie  at  the  base  of  villi  (Fig.  186). 
In  transverse  section  they  are  shown  in  Fig.  187.] 

II.  The  Secretion  of  Lieberkuhn's  Glands,  from  the  duodenum  onward, 
is  the  chief  source  of  the  intestinal  juice. 


_  Villi  with  epitbdit 


Lieberkuhn's  glands. 
Muscularis  mucosae 


:!  Longitudinal  r 


Longitudinal  section  of  the  small  intestine  of  a  dog,  through  a  Peyer's  patch. 


Intestinal  Fistula. — The  intestinal  juice  is  obtained  by  making  a  Thiry's  Fistula  (1S64).  A 
loop  of  the  intestine  of  a  dog  is  pulled  forward  (Fig.  1S8,  i),  and  a  piece  about  4  inches  in  length 
is  cut  out,  so  that  the  continuity  of  the  intestinal  tube  is  broken,  but  the  mesentery  and  its  blood  ves- 
sels are  not  divided.  One  end  of  this  tube  is  closed,  and  the  other  end  is  left  open  and  stitched  to 
the  abdominal  wall  (Fig.  188,  3),  After  the  two  ends  of  the  intestine  from  which  this  piece  was 
taken  have  been  carefully  brought  together  with  sutures,  so  as  to  establish  the  continuity  of  the 
intestinal  canal,  animals  still  continue  to  live  (Fig.  1S8,  2).  The  excised  piece  of  intestine  yields 
a  secretion  which  is  uncontaminated  with  any  other  digestive  secretion.  [Thiry's  method  is  very 
unsatisfactory,  as  judged  from  the  action  of  the  separated  loop  in  relation  to  medicaments,  probably 
owing  to  its  mucous  membrane  becoming  atrophied  from  disuse,  or  injured  by  inflammation.] 


ACTIONS    OF   THE    INTESTINAL   JUICE. 


305 


[Meade  Smith  has  lately  used  a  better  method,  in  which  he  makes  a  small  opening  in  the  intes- 
tine, through  which  he  introduces  two  small,  hollow  and  collapsed  India-rubljer  balls,  one  above  and 
the  other  below  the  opening,  which  are  then  distended  by  inflation  until  they  completely  block  a 
certain  length  of  the  intestine.  The  loop  thus  blocked  off  having  been  previously  well  washed  out,  is 
allowed  to  become  filled  with  succus,  which  is  secreted  on  the  application  of  various  stimuli.  By  means 
of  Bernard's  gastric  cannula  (§  165)  inserted  into  the  fistula  in  the  loop,  the  secretion  can  be  re- 
moved when  desired.] 

[Valla's  Fistula. — Open  the  belly  of  a  dog,  and  pull  out  a  loop  (30  to  50  ctm.)  [l  to  lyi  feet] 
of  small  intestine  and  ligature  it ;  dividing  it  above  and  below,  re-establish  the  continuity  of  the 
rest  of  the  intestine.  Stitch  both  ends  of  the  loop  of  intestine  into  the  wound  in  the  linea  alba 
(Fig.  1S8,  4)  so  that  there  is  a  loop  of  intestine  supplied  by  its  blood  vessels  and  nerves,  isolated  and 
with  an  upper  and  lower  aperture.] 

Fig.  187. 

Crypt. 


-Glandular  epithelium. 


Cavity  of  the  gland. 


Transverse  section  of  Lieberkiihn's  follicles. 

The  intestinal  juice  of  such  fistula  flows  spontaneously  in  very  small  amount, 
and  is  increased  during  digestion  ;  it  is  increased — especially  its  mucus — by  me- 
chanical, chemical,  and  electrical  stimuli  ;  at  the  same  time,  the  mucous  mem- 
brane becomes  red,  so  that  100  centimetres  yield  13  to  iS  grammes  of  this  juice 
in  an  hour  (  Thiry,  Masloff^. 

Characters.— The  juice  is  light  yellow,  opalescent,  thin,  strongly  alkaline, 
specific  gravity  loii,  evolves  CO.,  when  an  acid  is  added;  it  contains  albiitnin 
and  ferments  ;  mucin  occurs  in  the  juice  of  the  large  intestine.  Its  composition 
is — proteids  =  0.80  per  cent.  ;  other  organic  substances  ^  0.73  per  cent. ;  salts, 
0.88  per  cent.  ;  among  these — sodium  carbonate,  0.32  to  0.34  per  cent.  ;  water, 
07.  SO  per  cent. 

Fig.  188. 


of  Thiry 's  fistula 


Ahd.  Abdominal  wall  {Stirling), 


stitched  together ; 


[The  intestinal  juice  obtained  by  Meade  Smith's  method  contained  only  0.39  per  cent,  of  organic 
matter,  and  in  this  respect  agreed  closely  with  the  juice  which  A.  Moreau  procured  by  dividing  the 
mesenteric  nerves  of  a  ligatured  loop  of  intestine.  The  secretion  of  the  large  intestine  is  much 
more  viscid  than  that  of  the  small  intestine.] 

Actions  of  Succus  Entericus. — The  digestive  functions  of  the  fluid  of  the 
small  intestine  are — 

(i)  It  has  less  diastatic  action  than  either  the  saliva  or  the  pancreatic  juice 
{Schiff,  Busch,  Quincke,  Garland),  but  it  does  not  form  maltose  ;  while  the  juice 
of  the  large  intestine  is  said  to  possess  this  property  {Eickhorsi).  v.  Wittich  ex- 
tracted the  ferment  with  a  mixture  of  glycerine  and  water. 


306  ACTIONS   OF   THE    INTESTINAL   JUICE. 

[The  diastatic  action  of  the  small  intestine  is  incomparably  weaker  than  that  of  the  saliva,  or  pan- 
creatic juice,  and  barely  exceeds  that  of  the  tissues  and  fluids  of  the  bodies  generally.  A  similarly 
weak  diastatic  action  is  possessed  by  the  secretion  of  the  colon.] 

(2)  It  converts  maltose  into  grape  sugar.  It  seems,  therefore,  to  continue  the 
diastatic  action  of  the  saliva  (§  148)  and  pancreatic  juice  (§  170)  which  usually 
form  only  maltose.  Thus  maltose  seems  to  be  transformed  into  grape  sugar  by 
the  intestinal  juice. 

According  to  Bourquelot  this  action  is  due  to  the  intestinal  schizomycetes  and  not  to  the  intestinal 
juice  as  such,  the  saliva,  the  gastric  juice,  or  invertin.  The  greater  part  of  the  maltose  appears, 
however,  to  be  absorbed  unchanged. 

(3)  Fibrin  is  slowly  (by  the  trypsin  and  pepsin — Kiihne)  peptonized  (  Thiry, 
Leube);  less  easily  albumin  {Masloff),  i'r?.%\\,  casein,  flesh,  raw  or  cooked,  vege- 
table albumin  {Ko/liker,  Schiff  )  ;  probably  gelatin  is  also  changed  by  a  special 
ferment  into  a  solution  which  does  not  gelatinize  (^Eichhorsf). 

[The  ferment  for  this  purpose  is  mainly  contained  in  Brunner's  glands,  and  in  Peyer's  patches 
[Brown  and  Heron') ^ 

(4)  Fats  are  only  partly  emulsionized  {Si/iiff),  and  afterward  decomposed 
(  Vella). 

[M.  Hay  has  never  observed  any  emulsifying  action.  The  appaifnt  emulsification  in  certain 
instances  is  due  to  shaking  the  alkaline  juice  with  a  rancid  oil,  containing  free  fatty  acids,  when  a 
certain  quantity  of  a  soap  is  at  once  formed.] 

(5)  According  to  CI.  Bernard,  invertin  occurs  in  intestinal  juice  (this  ferment 
can  also  be  extracted  from  yeast),  whereby  cane  sugar  (CioH.jOn)  takes  up  water 
(-f  H.,0)  and  becomes  converted  into  invert  sugar,  which  is  a  mixture  of  left 
rotating  sugar  (laevulose,  CsHioO^)  and  of  grape  sugar  (dextrose,  CeHuOs).  Heat 
seems  to  be  absorbed  during  the  process  {Leiibe).  (See  Carbohydrates,  §  252,  for 
the  various  kinds  of  sugar.) 

[Hoppe-Seyler  has  suggested  that  this  ferment  is  not  a  natural  product  of  the  body,  but  is  intro- 
duced from  without  with  the  food.  Matthew  Hay  has  recently  disproved  this  theory  by,  among 
other  reasons,  finding  it  to  be  invariably  present  in  the  intestine  of  the  foetus.  It  is  found  in  every 
portion  of  the  small  inte;^tine,  but  not  in  the  large  intestine,  nor  in  any  other  part  of  the  body,  and 
IS  much  less  Jiftusible  than  diastase.] 

[Effect  of  Drugs. — -The  subcutaneous  injection  of  pilocarpin  causes  the  mucous  membrane  of  a 
Vella's  fistula  [dog)  to  be  congested,  when  a  strongly  alkaline,  opalescent,  watery,  and  slightly  albu- 
minous secretion  is  obtained.  Ihis  secretion  produces  a  reducing  sugar,  converts  cane  sugar  into 
invert  sugar,  emulsifies  neutral  fats,  ultimately  splitting  them  up,  peptonizes  proteids,  and  coagulates 
milk,  even  although  alkaline.  The  juice  auacks  the  sarcous  substance  of  muscle  before  the  con- 
nective tissues — the  reverse  of  the  gastric  juice.  The  mucous  membrane  in  a  Vella's  fistula  does 
not  atrophy.  K.  B.  Lehmann  finds  that  the  succus  entericus  obtained  from  the  intestine  of  k  goat 
by  a  Thiry- Vella  fistula  has  no  digestive  action  ( ?>//«).] 

[Fate  of  the  Ferments. — With  regard  to  the  digestive  ferments,  Langley  is  of  opinion  that 

they  are  destroyed  in  the  intestinal  canal ;  the  diastatic  ferment  of  saliva  is  destroyed  by  the  free  HCl 

of  the  gastric  juice;  pepsin  and  rennet  are  acted  upon  by  the  alka- 

FiG.  189.  line  salts  of  the  pancreatic  and  intestinal  juices,  and  by  trypsin;  while 

P  the  diastatic  and  peptic  fennents  of  the  pancreas  disappear  under  the 

influence  of  the  acid  fermentation  in  the  large  intestine.] 

The  Action  of  the  Nervous  System  on  the  secretion  of  the  in- 
testinal juice  is  not  well  determined.  Section  or  stimulation  of  the 
vagi  has  no  apparent  eft'ect ;  while  extirpation  of  the  large  sympathetic 
abdominal  ganglia  causes  the  intestinal  canal  to  be  filled  with  a  watery 
fluid,  and  gives  rise  to  diarrhcea  [Budge).  This  may  be  explained  by 
the  paralvsis  of  the  vasomotor  nerves,  and  also  by  the  section  of  large 
lymphatic  vess-els  during  the  operation,  whereby  absorption  is  inter- 
fered with  and  tiansud.nion  is  favored. 

Moreau's  Experiment. — A  similar  result  is  caused  by  extirpation 
of  the  nerves  which  accompany  the  blood  vessels  going  to  a  loop  of 
intestine  (.l/ormw),  the  bloodvessels  tliemselves  being  intact.  [Moreau 
placed  four  ligatures  on  a  loop  of  intestine  at  equal  distances  from  each  other  (Fig.  189).  The  liga- 
tures were  tied  so  that  three  loops  of  intestine  were  shut  oft'.     The  nerves  (N)  to  the  middle  loop 


FUNGI    AS    EXCITERS   OF    FERMENTATION. 


307 


were  divided,  and  the  intestine  was  replaced  in  the  abdominal  cavity.  After  a  time,  a  very  small 
amount  of  secretion,  or  none  at  all,  was  found  in  two  of  the  ligatured  compartments  of  the  gut, 
/.  <•.,  in  those  with  the  nerves  and  blood  vessels  intact  (1,3),  but  the  compartment  (2)  whose  nerves 
had  been  divided  contained  a  watery  secretion.  Perhaps  the  secretion  which  occurs  after  section  of 
the  mesenteric  nerves  is  a  paralytic  secretion.] 

The  secretion  of  the  intestinal  and  gastric  juices  is  diminished  in  man  in  certain  nervous  affec- 
tions (hysteria,  hypochondriasis,  and  various  cerebral  diseases);  while  in  other  conditions  these 
secretions  are  increased. 

Excretion  of  Drugs. — If  an  isolated  intestinal  fistula  be  made,  and  various  drugs  administered, 
experiment  shows  that  the  mucous  membrane  excretes  iodine,  bromine,  lithium,  sulphocyanides,  but 
HI)/  potassium  ferrocyanide,  arsenious  or  boracic  acid  (Quincke),  or  iron  salts  (Glaevecke). 

In  sihk/iiigs,  not  unfrequently  a  large  amount  of  acid  is  formed  when  the  fungi  in  the  intestine 
split  up  milk  sugar  or  grape  sugar  into  lactic  acid  (Leii/v).  .Starch  changed  into  grape  sugar  may 
undergo  the  same  abnormal  process;  hence,  infants  ought  not  to  be  fed  with  starchy  food. 

184.    FERMENTATION   PROCESSES   IN  THE   INTESTINE. 

— Those  processes  wiiich  are  to  be  regarded  as  fermentations  or  putrefactive  pro- 
cesses, are  quite  different  from  those  caused  b)-  the  action  of  distinct  ferments 
{Frerichs,  Hoppe-Sey/er).  The  putrefactive  changes  are  connected  with  the 
presence  of  lower  organisms,  so-called  fermentation  or  putrefaction  producers 
{Nencki ) :  and  they  may  develop  in  suitable  media  outside  the  body.  The  lower 
organisms  which  cause  the  intestinal  fermentation  are  swallowed  with  the  food  and 
the  drink,  and  also  with  the  saliva.  When  they  are  introduced,  fermentation  and 
putrefaction  begin,  and  gases  are  evolved. 

Intestinal  Gases. — During  the  whole  of  the  fcetal  period,  until  birth,  this 
fermentation  cannot  occur  ;  hence,  gases  are  never  present  in  the  intestine  of  the 
newly  born  {Brcslau).  The  first  air  bubbles  pass  into  the  intestine  with  the  saliva 
which  is  swallowed,  even  before  food  has  been  taken.  The  germs  of  organisms 
are  thus  introduced  into  the  intestinal  tract,  and  give  rise  to  the  formation  of  gases. 
The  evolution  of  intestinal  gases  goes  hand-in-hand  with  the  fermentations.  At- 
mospheric air  is  also  swallowed,  and  an  exchange  of  gases  takes  place  in  the  intes- 
tine, so  that  the  composition  of  the  intestinal  gases  depends  upon  various  condi- 
tions. 

Kolbe  and  Ruge  collected  the  gases  from  the  anus  of  a  man,  and  found  in  100 
vols. — 


Food. 

CO.. 

H. 

CH,. 

N. 

HoS. 

Milk, 

Flesh,  

Peas 

16.8 
12.4 
21.0 

43-3 
2.1 
4.0 

0.9 

27.5 
55-9 

38.3 
57.S 
18.9 

Quantity 
not  estimated. 

With  regard  to  the  formation  of  gas  and  the  processes  of  fermentation,  we 
note — 

1.  Air  bubbles  are  swallowed  when  the  food  is  taken.  The  O  thereof  is 
rapidly  absorbed  by  the  walls  of  the  intestinal  tract,  so  that  in  the  lower  part  of 
the  large  intestine,  even  traces  of  O  are  absent.  In  exchange,  the  blood  vessels 
in  the  intestinal  wall  give  off  COj  into  the  intestine,  so  that  a  part  of  the  CO,  in 
the  intestine  is  derived  by  diffusion  from  the  blood. 

2.  H  and  C0j,NH3,  and  CH,  are  also  formed  from  the  intestinal  contents  by 
fermentation,  which  takes  place  even  in  the  small  intestine  {Planer'). 

Fungi  as  Exciters  of  Fermentation. — The  chief  agents  in  the  production  of  fermentations, 
putrefaction,  and  other  similar  decompositions  are  undoubtedly  the  group  of  the  fungi  called 
Schizomycetes.  They  are  small  unicellular  organisms  of  various  forms,  globular  {.Micrococcus), 
short  rods  (Bacterium),  long  rods  (Bacillus),  or  spiral  threads  (  Vibrio,  Sfirillum,  Spirocliieta,  Fig. 
20).  The  mode  of  reproduction  is  by  division,  and  they  may  either  remain  single  or  unite  to  form 
colonies.  Each  organism  is  usually  capable  of  some  degree  of  motion.  They  produce  profound 
chemical  changes  in  the  fluids  or  media  in  which  they  grow  and  multiply,  and  these  changes  depend 


308 


FERMENTATION    OF   THE   CARBOHYDRATES. 


upon  the  vital  activity  of  their  protoplasm.  These  minute  microscopic  organisms  take  certain  con- 
stituents from  the  "  nutrient  fluids"  in  which  they  live,  and  use  them  partly  for  building  up  their 
own  tissues  and  partly  for  their  own  metabolism.  In  these  processes,  some  of  the  substances  so 
absorbed  and  assimilated  undergo  chemical  changes,  some  fernwnli  seem  thereby  to  be  produced, 
which  in  their  turn  may  act  upon  material  present  in  the  nutritive  fluid. 

These  fungi  consist  of  a  capsule  or  envelope  enclosing  protoplasmic  contents.  Many  of  them 
are  provided  with  excessively  delicate  cilia,  by  means  of  which  they  move  about.  The  new  organ- 
isms produced  by  the  division  of  pre-existing  ones,  sometimes  fortn  large  colonies  visible  to  the 
naked  eye,  the  individual  fungi  being  united  by  a  jelly-like  mass,  the  whole  constituting  zoogloea 
In  some  fungi,  reproduction  takes  place  by  spores  ;  more  especially  when  the  nutrient  fluids  are 
poor  in  nutritive  materials.  The  bacteria  form  longer  rods  or  threads  which  are  jointed,  and  in 
each  joint  or  segment  small  (1-2  /j)  highly  refractive  globules  or  spores  zxt  developed  (Fig.  191,  7). 
In  some  cases,  as  in  the  butyric  acid  fermentation,  the  rods  become  fusiform  before  spores  are 
formed.  When  the  envelope  of  the  mother  cell  is  ruptured  or  destroyed,  the  spores  are  liberated, 
and  if  they  fall  upon  or  into  a  suitable  medium,  they  germinate  and  reproduce  organisms  similar  to 
those  from  which  they  sprung.  The  process  of  spore  production  is  illustrated  in  Fig.  igo,  7,  8,  9, 
and  in  i,  2,  3,  4  is  shown  the  process  of  germination  in  the  butyric  acid  fungus.  The  spores  are 
very  tenacious  of  life;  they  may  be  dried,  when  they  resist  death  for  a  very  long  time  ;  some  of 
them  are  killed  by  being  boiled.  Some  fungi  exhibit  their  vital  activiiiesonly  in  the  presence  of  O 
(Aerobes),  while  others  require  the  exclusion  of  O  (Anaerobes,  Pasteur).  According  to  the 
products  of  their  action,  they  are  classified  as   follows:  Those  that  \>rm\\ict  fermentations  (zymo- 

FiG.  I  go. 


V5 


l.Z 


8  %a 


I  accii.  in  the  form  of^cocci  (l) ;  dipli 
icus — (i)  isolated  spo 
8,  9J  formation  of  spores  withii 


rods  (3),  and  jointed  tlireads  (4,  5).     B,  Baal- 
3n  of  tlie  spores;  (5,  6j  stiort  and  long  rods  ;  (7, 


genie  schizomycetes) ;  those  that  produce  pigments  (chromogenic) ;  those  that  produce  disagreeable 
odors,  as  during  putrefaction  (bromogenic) ;  and  those  that,  when  introduced  into  the  living  tissues 
of  other  organisms,  \>xo&mq.&  pathological  conditions,  and  even  death  (pathogenic).  All  these  differ- 
ent kinds  occur  in  the  human  body. 

When  we  consider  that  numerous  fungi  are  introduced  into  the  intestinal  canal  with  the  food  and 
drink — that  the  temperature  and  other  conditions  within  this  tube  are  specially  favorable  for  their 
development ;  that  there  also  they  meet  with  sufiicient  pabulum  for  their  development  and  repro- 
duction— we  cannot  wonder  that  a  rich  crop  of  these  organisms  is  met  witli  in  the  intestine,  and 
that  they  produce  there  numerous  fermentations. 

I.  Fermentation    of  the    Carbohydrates. — (i)    Bacterium    lacticum 

(^Cohii),  (^Ferment  lactique,  Pashur)  are  biscuit-shaped  cells,  1.5-3  //.  in  length, 
arranged  in  groups  or  isolated.     They  split  up  sugar  into  lactic  acid  ; 
I  grape-sugar  =  QHi-^Ob  =  2(C3H603)  =  2  lactic  acid. 
Milk  sugar  (Ci.jHjjOn)  may  be  split  up  by  the  same  ferment  causing  it  to  take  up 
H^O,  and  fonning  2  molecules  of  grape  sugar,  2(CoH,.iOc),  which  are  again  split 
up  into  4  molecules  of  lactic  acid,  4(C3H|;03). 

The  fungi  which  occur  everywhere  in  the  atmosphere  are  the  cause  of  the  spontaneous  acidifica. 
tion,  and  subset^uent  coagulation  of  milk  {^Milk  (^  230).) 


FERMENTATION    OF   THE    FATS.  309 

(2)  Bacillus  butyricus  (B.  amylobacter,  Vii/i  Tieghcm ;  Clostridium  buty- 
ricum,  Vibrion  biityrique,  Pasteur),  which  ill  the  presence  of  starch  is  often 
colored  blue  by  iodine,  changes  lactic  acid  into  butyric  acid,  together  with  CO2 
and  H  {Frazmowski). 

(    C,H„0;j  =  I  butyric  acid. 
2(C3H603)  lactic  acid  =  -|  2(C02)     =  2  carbon  dioxide. 
(^  4  H  =  4  hydrogen. 

This  fungus  (Fig.  190,  B)  is  a  true  anaerobe,  and  grows  only  in  the  absence  of  O.  The  lactic 
acid  fungus  uses  O  verj'  largely,  and  is,  therefore,  its  natural  precursor.  The  butyric  acid  fermenta- 
tion is  the  last  change  undergone  by  many  carbohydrates,  especially  by  starch  and  inulin.  It  takes 
place  constantly  in  the  fa;ces. 

(3)  A  fungus,  whose  nature  is  not  yet  determined,  causes  alcohol  to  be  formed 
from  carbo-hydrates  {Fitz).  The  presence  of  yeast  may  cause  the  formation  of 
alcohol  in  the  intestine,  and  in  both  cases  also  from  milk  sugar,  which  first 
becomes  changed  into  dextrose. 

(4)  Bacterium  aceti  (Fig.  190,  A)  converts  alcohol  into  acetic  acid  outside  the  body.  Alcohol 
(CjHgO)  +  O  =  C,,H_,0  (Al(lehyd)  +  H^O.  Acetic  acid(C2H^O,)  is  formed  from  aldehyd  by 
oxidation.  According  to  Nageli,  the  same  fungus  causes  the  formation  of  a  small  amount  of  CO, 
and  H^O.  As  the  acetic  fermentation  is  arrested  at  35°  C,  this  fermentation  cannot  occur  in  the 
intestine,  and  the  acetic  acid  which  is  constantly  found  m  the  feces  must  be  derived  from  another 
source.     During  putrefaction  of  the  proteids  with  exclusion  of  air  acetic  acid  is  produced  i^Nencki). 

Fig.  191. 


BaciUus  sttbtilis.  i,  spore  ;  2,  3,  4,  germination  of  the  spore  :  5.  6,  short  rods  :  7,  jointed  thread,  with  the  formation 
of  spores  in  each  segment  or  ctU  ;  8,  short  rods,  some  of  them  containing  spores  ;  9,  spores  in  single  short  rods  ; 
10,  fungus  with  a  cilium. 

(5)  Starch  and  cellulose  are  partly  dissolved  by  the  schizomycetes  of  the 
intestine.  If  cellulose  be  mixed  with  cloacal  mucus  (Hoppe-Seylcr),  or  with  the 
contents  of  the  intestine  {^Tappeincr),  n  molecules,  [//(CeHjoOj)],  take  up  n  mole- 
cules of  water,  +  «(H,0),  and  produce  three  times  n  molecules  CO..,  and  three 
times  n  molecules  of  marsh  gas  3  ^(CHi). 

During  the  solution  of  cellulose,  volatile  acids  (acetic  and  butyric)  are  evolved.  When  the  cel- 
lulose capsule  is  dissolved,  the  digestive  juices  can  act  upon  the  enclosed  digestible  parts  of  the 
vegetable  (  Tappeiner,  v,  Knierieiti). 

(6)  Fungi  whose  nature  is  unknown  can  partly  transform  y/(7/-t7/ (?  and  cellulose) 
into  sugar  ;  others  excrete  invertin  e.  g.,  the  Leukonostoc  mesenteriodes,  which 
develops  in  the  juice  of  turnips.  Invertin  changes  cane  sugar  into  invert  sugar 
(§  183,  II,  5). 

II.  Fermentation  of  the  Fats  (§  251). — In  certain  putrefactive  conditions, 
organisms  of  an  unknown  nature  cause  natural  fats  to  take  up  water  and  split  into 
glycerine  and  their  corresponding  fatty  acid  (§  170").  Glycerine — C3H5(HO)3 — 
is  a  triatomic  alcohol,  and  is  capable  of  undergoing  several  fermentations,  accord- 
ing to  the  fungus  which  acts  upon  it  (§  251 ).  With  a  neutral  reaction,  in  addition 
to  succinic  acid,  a  number  of  fatty  acids,  H  and  CO,  are  formed. 


310  REACTION    FOR    INDUL. 

Fitz  found,  under  the  influence  of  the  hay  (ia <-///;«  (Bacillus  subtilis.  Fig.  191)  alcohol  with 
caproic,  butyric,  and  acetic  acids;  in  other  cases  butylic  alcohol  is  the  chief  product;  van  de  Velde 
found  butyric,  lactic,  and  traces  of  succinic  acid  with  CO.,,  H2O,  N. 

The  fatty  acids,  especially  as  chalk  soaps,  form  an  excellent  material  for  fer- 
mentation. Calcium  formiate  mixed  with  cloacal  mucus  ferments  and  yields  cal- 
cium carbonate,  CO.2  and  H  ;  calcium  acetate,  under  the  same  conditions,  produces 
calciimi  carbonate,  CO2  and  CH,.  Among  the  oxy-acids,  we  are  acquainted 
with  the  fermentations  of  lactic,  glycerinic,  malic,  tartaric,  and  citric  acids. 

According  to  Fitz,  lactic  acid  (in  combination  with  chalk),  produces  propionic  and  acetic  acids, 
CO,,  HjO.  Other  ferments  cause  the  formation  of  valerianic  acid.  Glycerinic  acid,  \xv  addition 
to  alcohol  and  succinic  acid,  yields  chiefly  acetic  acid ;  malic  acid  forms  succinic  and  acetic  acid. 
The  other  acids  above  enumerated  yield  somewhat  similar  products. 

III.  Fermentation  of  the  Proteids  (§  249). — There  do  not  seem  to  be 
fungi  of  sufficient  activity  in  the  intestine  to  act  upon  undigested  proteids  and 
their  derivatives.  Many  schizomycetes,  however,  can  produce  a  peptonizing  fer- 
ment. We  have  already  seen  that  pancreatic  digestion  acts  upon  the  proteids 
(§  170,  II),  forming,  among  other  products,  amido  acids,  leucin,  tyrosin,  and 
other  bodies.  Under  normal  conditions,  this  is  the  greatest  decomposition  pro- 
duced by  the  pancreatic  juice.  The  putrefactive  fermentation  of  the  large  intes- 
tine causes  further  and  more  profound  decompositions  {Hiiffner,  Nencki).  Leu- 
cin (CeHuNO.j),  takes  up  two  molecules  of  water,  and  yields  valerianic  acid 
iCjCi.iO^)  ammonia,  CO,  and  2(H.i)  ;  glycin,  behaves  in  a  siinilar  manner. 
Tyrosin  (CgHnNOa)  is  decomposed  into  indol  (C„H,N),  which  is  constantly 
present  in  the  intestine  {Kiihne)  along  with  CO,,  H,0,  H,  (^Nencki).  If  O  be 
present,  other  decompositions  take  place.  These  putrefactive  products  are  absent 
from  the  intestinal  canal  of  the  foatus  and  the  newly  born  (Senator).  During  the 
putrefactive  decomposition  of  proteids,  CO^.HS,  also  H  and  CH,,  are  formed  ; 
the  same  result  is  obtained  by  boiling  them  with  alkalies.  Gelatin,  under  the 
same  conditions,  yields  much  leucin  and  ammonia,  CO,,  acetic,  butyric,  and  vale- 
rianic acids,  and  glycin  (JVencki).  Mucin  and  nuclein  undergo  no  change.  Arti- 
ficial pancreatic  digestion  experiments  rapidly  tend  to  undergo  putrefaction. 

The  substance  which  causes  the  peculiar  faecal  odor  is  produced  by  putrefaction,  but  its  nature  is 
not  known.  It  clings  so  firmly  to  indol  and  skatol  that  these  sub>tances  were  formerly  regarded  as 
the  odorous  bodies,  but  when  they  are  prepared  pure  they  are  odorless  {Bayer).-  The  above  men- 
tioned putrefactive  processes  which  also  occur  in  pancreas  undergoing  decomposition,  may  be  inter- 
rupted by  antiseptics  (salicylic  acid).  The  putrefactive  products  of  the  pancreas  give  a  red  color 
or  precipitate  with  chlorine  water. 

Indol.  - —  Among  the  solid  substances  in  the  large  intestine  formed  only  by 
putrefaction  is  indol  (CgHjN),  a  substance  which  is  also  formed  when  proteids  are 
heated  with  .alkalies,  or  by  overheating  them  with  water  to  200°  C.  It  is  the  stage 
preceding  the  indican  in  the  urine.  If  the  products  of  the  digestion  of  the  pro- 
teids— the  peptones — are  rapidly  absorbed,  there  is  only  a  slight  formation  of 
indol  ;  but  when  absorption  is  slight,  and  putrefaction  of  the  products  of  pan- 
creatic digestion  occurs,  much  indol  is  formed,  and  indican  appears  in  the  urine. 

Jafie  found  much  indican  in  the  urine  in  strangulated  hernia,  and  when  the  small  intestine  was 
obstructed.     Landois  observed  the  same  after  the  transfusion  of  heterogeneous  blood  (§  262,  i). 

Reactions  for  Indol. — Acidulate  strongly  with  HCl,  and  shake  vigorously  after  adding  a  few 
drops  of  turpentine.  If  there  be  an  intense  red  color,  the  ])igment  is  removed  by  ether.  The  sub- 
stance which,  after  the  digestion  of  fibrin  by  trypsin,  and  which  gives  a  violet  color  with  bromine 
water  [\  170,  2),  can  be  removed  by  chloroform.  In  addition  to  the  last  pigment,  there  is  a  second 
one,  which  passes  over  during  distillation,  and  which  can  be  extracted  from  the  distillate  by  ether. 
Both  substances  seem  to  belong  to  the  indigo  group  (Kriikenberg). 

A.  Bayer  prepared  indigo-blue  artificially  from  ortho  phenyl-propionic  ncid,  by  boiling  it  with  dilute 
caustic  soda,  after  the  adthtion  of  a  little  grape  sugar.  He  obtained  indol  and  skatol  from  indigo 
blue.  Hoppe-Seyler  found  that  on  feeding  rabbits  with  ortho-nitrophenyl-propionic  acid,  much 
indican  was  present  in  the  urine.  . 


PROCESSES    IN    THE    LARGE    INTESTINE.  311 

Phenol  (CcH^O)  is  formed  by  putrefaction  in  the  intestine,  and  it  is  also 
formed  when  fibrin  and  pancreatic  juice  putrefy  outside  the  body  {Baumann), 
while  Brieger  found  it  constantly  in  the  fajces.  It  seems  to  be  increased  by  the 
same  circumstances  that  increase  indol  {Sa/kcnas/ci ),  as  an  excess  of  indican  in 
the  urine  is  accompanied  by  an  increase  of  phenyl  sulphuric  acid  in  that  fluid 
(§  262). 

From  putrefying  flesh  and  fibrin  amiilo-phenyl  propionic  acid  is  obtained,  as  a  decomposition 
product  of  tyrosin.  A  part  of  this  is  transformed  by  putrefactive  ferments  into  hydrocinnamic  acid 
(phenyl  propionic  acid).  The  latter  is  completely  oxidized  in  the  body  into  benzoic  acid,  and 
appears  as  hippuric  acid  in  the  urine.  Thus  is  explained  the  formation  of  hippuric  acid  from  a 
purely  albuminous  diet  {£.  and  H.  Salkowski). 

Skatol  (CjHgN)  =  methyl  indol — {Brieger'),  is  a  constant  human  faecal  sub- 
stance, and  has  been  prepared  artificially  by  Nencki  and  Secretan  from  egg 
albumin,  by  allowing  it  to  putrefy  for  a  long  time  under  water.  It  also  appears 
in  the  urine  as  a  sulphuric  acid  compound.  The  excretin  of  human  faeces, 
described  by  Marcet,  is  related  to  cholesterin,  but  its  history  and  constitution  are 
unknown. 

According;  to  the  Brothers  Salkowski,  skatol  and  indol  are  both  formed  from  a  common  substance 
which  exists  preformed  in  albumen,  and  which,  when  it  is  decomposed,  at  one  time  yields  more 
indol,  at  another  skatol,  according  as  the  hypothetical  "  ;'«(/«/y««^'-K.;"  or  "  skalol-fungiis"  m  the 
more  abundant. 

It  is  of  the  utmost  importance,  in  connection  with  the  processes  of  putrefac- 
tion, to  determine  whether  they  take  place  when  oxygen  is  excluded  or  not  {Pas- 
teur). When  O  is  absent,  reductions  take  place  ;  oxy-acids  are  reduced  to 
fatty  acids,  and  H,CHj  and  H,S  are  formed  ;  while  the  H  may  produce  further 
reductions.  If  O  be  present  the  nascent  H  separates  the  molecule  of  free  ordi- 
nary oxygen  (  =^  O,)  into  two  atoms  of  active  oxygen  (  =  O).  Water  is  formed 
on  the  one  hand,  while  the  second  atom  of  O  is  a  powerful  oxidizing  agent  {Hoppe- 
Seyler). 

[It  is  not  improbable  that  some  substances,  as  sulphur,  are  in  part  rendered  soluble  and  absorbed 
by  the  action  of  the  nascent  hydrogen  evolved  by  the  schizomycetes,  forming  a  soluble  hydrogen 
compound  with  the  substance  (Mat/hew  Hay).] 

It  is  remarkable  that  the  putrefactive  processes,  after  the  development  of  phenol,  indol,  skatol, 
cresol,  phenyl  propionic  and  phenyl  acetic  acids  are  afterward  limited,  and  after  a  certain  concentra- 
tion is  reached  tliey  cease  altogether.  The  putrefactive  process  produces  antiseptic  substances 
which  kill  the  micro-organisms  [IVeniic/i),  so  we  may  assume  that  these  substances  limit  to  a  cer- 
tain extent  the  putrefactive  processes  in  the  intestine. 

The  reaction  of  the  intestine  immediately  below  the  stomach  is  acid,  but  the 
pancreatic  and  intestinal  juices  cause  a  neutral  and  afterward  an  alkaline  reaction, 
which  obtains  along  the  whole  small  intestine.  In  the  large  intestine,  the  re- 
action is  generally  acid,  on  account  of  the  acid  fermentation  and  the  decomposi- 
tion of  the  ingesta  and  the  faeces. 

185.  PROCESSES    IN   THE    LARGE  INTESTINE.— Within    the 

large  intestine,  the  fermentative  and  putrefactive  processes  are  certainly  more 
prominent  than  the  digestive  processes  proper,  as  only  a  very  small  amount  of  the 
intestinal  juice  is  found  in  it  {Kilhne).  The  absorptive  function  of  the  large 
intestine  is  greater  than  its  secretory  function,  as  at  the  beginning  of  the  colon  its 
contents  are  thin  and  watery,  but  in  the  further  course  of  the  intestine  they 
become  rnore  solid.  Water  and  the  products  of  digestion  in  solution  are  not  the 
only  substances  absorbed,  but  under  certain  circumstances  unchanged  fluid  egg- 
albumin  {Voit  and  Bauer,  Czerny  and  Latschenberger),  milk  and  its  proteids 
{Eichlwrst),  flesh  juice,  solution  of  gelatin,  myosin  with  common  salt,  may  also 
be  absorbed.  Experiments  with  acid  albumin,  syntonin,  or  blood  serum  gave  no 
result.  Toxic  substances  are  certainly  absorbed  more  rapidly  than  from  the 
stomach    {Savoiy).     [In    the   dog    the  secretion  of  the    large    intestine  has   no 


312  CHARACTERS   OF   THE    F.-ECES. 

digestive  properties,  but  fats  are  absorbed  in  it.  Klug  and  Koreck  regard  its 
Lieberkiihnian  glands  not  as  secreting,  but  as  absorbing  structures.]  The  fecal 
matters  sxt  formed  ox  rather  j//(?/c(/ in  the  lower  part  of  the  gut.  The  crecum  of' 
many  animals,  e.  g.,  rabbit,  is  of  considerable  size,  and  in  it  fermentation  seems 
to  occur  with  considerable  energy,  giving  rise  to  an  acid  reaction.  In  man,  the 
chief  function  of  the  caecum  is  absorption,  as  is  shown  by  the  great  number  of 
lymphatics  in  its  walls.  From  the  lower  part  of  the  small  intestine  and  the 
crecum  onward,  the  ingesta  assume  the  faecal  odor. 

The  amount  of  faeces  is  about  [5  oz.]  or  170  grms.  f6o  to  250  grms.)  in 
twenty-four  hours;  but  if  much  indigestible  food  be  taken,  it  may  be  as  much  as 
500  grms.  The  amount  is  less,  and  the  absolute  amount  of  solids  is  less,  after  a 
diet  of  flesh  and  albumin,  than  after  a  vegetable  diet.  The  fsces  are  rendered 
lighter  by  the  evolution  of  gases,  and  hence  they  float  in  water. 

The  consistence  of  the  fseces  depends  on  the  amount  of  water  present — it  is 
usually  about  75  per  cent.  The  amount  of  water  depends  partly  on  the  food — 
pure  flesh  diet  causes  relatively  dry  faeces,  while  substances  rich  in  sugar  yield 
faeces  with  a  relatively  large  amount  of  water.  The  quantity  of  water  taken  has 
no  effect  upon  the  amount  of  water  in  the  faeces.  But  the  energy  of  the  peristal- 
sis has  this  effect,  that  the  more  energetic  it  is,  the  more  watery  the  faeces  are, 
because  sufficient  time  is  not  allowed  for  absorption  of  the  fluid  from  the  ingesta. 
Paralysis  of  the  blood  and  lymph  vessels,  or  section  of  the  nerves,  leads  to  a 
watery  condition  of  the  faeces  (§  183). 

The  reaction  is  often  acid  in  consequence  of  lactic  acid  being  developed  from 
the  carbohydrates  of  the  food.  Numerous  other  acids  produced  by  putrefaction 
are  also  present  (§  1S4).  If  much  ammonia  be  formed  in  the  lower  part  of  the 
intestine,  a  neutral  or  even  alkaline  reaction  may  obtain.  A  copious  secretion  of 
mucus  favors  the  occurrence  of  a  neutral  reaction. 

The  odor,  which  is  stronger  after  a  flesh  diet  than  after  a  vegetable  diet,  is 
caused  by  some  ffecal  products  of  putrefaction,  which  have  not  yet  been  isolated  ; 
also  by  volatile  fatty  acids  and  by  sulphuretted  hydrogen,  when  it  is  present. 

The  color  of  the  faeces  depends  upon  the  amount  of  altered  bile  pigments 
mixed  with  them,  whereby  a  bright  yellow  to  a  dark  brown  color  is  obtained. 

The  color  of  the  food  is  also  of  niiportance.  If  much  blood  be  present  in  the  food,  the  f:eces 
are  almost  brownish  black,  from  h;i;matin  ;  green  vegetables  =  brownish  green,  from  chlorophyll  ; 
bones  (dog)  =  white,  from  the  amount  of  lime;  preparations  of  iron  =  black,  from  the  formation 
of  sulphide  of  iron. 

The  faeces  contain — 

(i)  The  unchanged  residue  of  animal  or  vegetable  tissues  used  as  food;  hairs, 
horny  and  elastic  tissues;  most  of  the  cellulose,  woody  fibres,  spiral  vessels  of 
vegetable  cells,  gum. 

(2)  Portions  of  digestible  substances,  especially  when  these  have  been  taken  in 
too  large  amount,  or  when  they  have  not  been  sufficiently  broken  up  by  chewing. 
Portions  of  muscular  fibres,  ham,  tendon,  cartilage,  particles  of  fat,  coagulated 
albumin — vegetable  cells  from  potatoes  and  vegetables,  raw  starch,  etc. 

All  food  yields  a  certain  amount  of  residue — white  bread,  3.7  per  cent. ;  rice,  4.1  per  cent. ;  flesh, 
4.7  per  cent. ;  potatoes,  9.4  per  cent. ;  cabbage,  14.9  per  cent. ;  black  bread,  15  per  cent. ;  yellow 
turnip,  20.7  per  cent.  [Kubner). 

(3)  The  decomposition  products  of  the  bile  pigments,  which  do  not  now  give 
the  Gmelin-Heintz  reaction  ;  as  well  as  the  altered  bile  acids  (§  177,  2).  This 
reaction,  however,  may  be  obtained  in  pathological  stools,  especially  in  those  of 
a  green  color  ;  unaltered  bilirubin,  biliverdin,  glycocholic  and  taurocholic  acids 
occur  in  meconium  {^Zweifel,  Hoppe-Seyler,  §  182). 

[MacMunn  found  no  unchanged  bile  pigments  in  the  fisces.  A  substance  called  stercobilin  is 
obtained  from  the  fxces,  and  it  closely  resembles  what  has  been  called  "  febrile  "  urobilin,  but  it  is 
certainly  different  from  normal  urobilin.] 


COMPOSITION    OF   THE    F^CES.  313 

(4)  Unchanged  mucin  and  nuclein — the  latter  occasionally  after  a  diet  of  bread, 
together  with  partially  disintegrated  cylindrical  epithelium  from  the  intestinal 
canal,  and  occasionally  drops  of  oil.  Cholesterin  is  very  rare.  [Ten  grains  of  a 
substance,  stercorin,  said  to  be  a  modification  of  cholesterin,  occur  in  the  faeces 
{Flint).~\  The  less  the  mucus  is  mixed  with  the  faeces,  the  lower  the  part  of  the 
intestine  from  which  it  was  derived  {Nothnagel). 

(5)  After  a  milk  diet,  and  also  after  a  fatty  diet,  crystalline  needles  of  lime 
combined  with  fatty  acids  and  chalk  soaps  constantly  occur,  even  in  sucklings 
(  Wegscheider).  Even  unchanged  masses  of  casein  and  fat  occur  during  the  milk 
cure.  Compounds  of  ammonia  with  the  acids  mentioned  as  the  result  of  putre- 
faction (§  184,  III)  belong  to  the  fKcal  matters  {Brieger). 

(6)  Among  inorganic  residues,  soluble  salts  rarely  occur  in  the  faeces,  because 
they  diffuse  readily,  e.  g.,  common  salt,  and  the  other  alkaline  chlorides,  the  com- 
pounds of  phosphoric  acid,  and  some  of  those  of  sulphuric  acid.  The  insoluble 
compounds,  of  which  ammoniaco-magnesic  or  triple  phosphate,  neutral  calcic 
phosphate,  yellow-colored  lime  salts,  calcium  carbonate,  and  magnesium  phos- 
phate are  the  chief,  form  70  per  cent,  of  the  ash.  Some  of  these  insoluble  sub- 
stances are  derived  from  the  food,  as  lime  from  bones,  and  in  part  they  are 
excreted  after  the  food  has  been  digested,  as  ashes  are  eliminated  from  food  which 
has  been  burned. 

Fig.  192. 


a 

I,  Bacterium  coli  commune  ;  2,  bacterium  lactis  aerogenes  ;  3  and  4,  the  large  bacilli  of  Bie 
genous  spore  formation ;  5,  the  various  stages  in  the  development  of  the  bacillus  whicl 


-Si-  IDH:- 


Concretions. — The  excretion  of  inorganic  substances  is  sometimes  so  great,  that  they  form  in- 
crustations around  other  fivcal  matters.  Usually  ammoniaco-magnesic  phosphate  occurs  in  large 
crystals  by  itself,  or  it  may  be  mixed  with  magnesium  phosphate. 

(7)  Micro-organisms. — A  considerable  portion  of  normal  faecal  matter  con- 
sists of  micrococci  and  micro-bacteria  (Bacterium  termo — Woodward,  Nothnagel^. 
Bacillus  subtilis  is  not  very  plentiful,  while  yeast  is  seldom  absent  {Frerichs, 
Nothnagel). 

To  isolate  the  individual  fungi,  Escherich  has  made  pure  cultivations  from  the  intestinal  con- 
tents of  sucklinijs,  and  Bienstock  from  adults.  In  the  intestine  of  sucklings  which  have  been 
nourished  entirely  on  their  mother's  milk,  the  Bacteriitm  laclis  aerogenes  (Y\^.  192,  2)  causes  the 
lactic  acid  fermentation  with  the  evolution  of  CO2  and  H,  in  the  upper  part  of  the  canal  where 
still  some  milk  sugar  is  unabsorbed.  In  the  evacuations  is  the  characteristic  slender  Bacterium 
coli  commune  (Fig.  192,  I).  In  addition,  occasionally  there  are  other  bacilli,  cocci,  spores  of  yeast, 
and  a  mould  [Escherich). 

In  the  fieces  of  an  adult,  Bienstock  detected  two  large  forms  of  Bacilli  (Fig.  192,  3,  4I,  closely 
resembling  Bacillus  subtilis  in  form  and  size,  but  distinguished  only  from  it  by  the  form  of  its  pure 
cultivation,  by  the  mode  of  growth  of  its  spores,  and  by  the  absence  of  movements.  These  two 
forms  can  be  distinguished  microscopically  by  the  mode  of  their  cultivation,  which  is  either  in  the 
form  of  a  grape  or  a  flat  membrane.  These  two  do  not  excite  a  fermentative  action.  A  third 
micrococcusdike,  small,  very  slowly  developing  bacillus  occurs  in  three-fourths  of  all  stools.  A 
fourth  kind  (ab.sent  in  sucklings)  is  the  specific  bacillus  (^  184,  III),  causing  the  decomposition  of 
albumin,  resulting  in  the  products  of  putrefaction  and  a  fsecal  odor.  This  is  the  only  bacillus  that 
excites  these  processes  in  the  intestine;  but  it  does  not  decompose  casein  and  alkali-albumin.  In 
Fig.  192,  5,  a-g,  the  stages  in  the  development  of  this  bacillus  are  represented,  but  the  stages  from 
c  and  g  are  absent  in  the  faeces,  and  are  found  only  in  artificial  cultivations. 


314  PATHOLOGICAL   VARIATIONS   OF   DIGESTION. 

If  the  feces  are  simply  investigated  microscopically  and  without  special  precautions,  there  are 
other  fungi,  some  of  which  may  be  introduced  through  the  anus.  In  stools  that  contain  much 
starch,  the  bacillus  amylobacter,  which  is  tinged  blue  with  iodine,  occurs  (J  1S4),  and  other  small, 
globular  or  rod-like  fungi,  which  give  a  similar  reaction  [A^othnagel,  Uffelmann). 

The  changes  of  the  intestinal  contents  have  been  studied  on  persons  with  an  accidental  intestinal 
fistula,  or  an  artificial  anus. 

186.  PATHOLOGICAL  VARIATIONS.— (A)  The  taking  of  food  may  be  interfered  with 
by  spasm  of  the  muscles  of  mastication  (usually  accompanied  by  general  spasms),  stricture  of  the 
cesoph.agus.  by  cicatrices  after  swallowing  caustic  fluids  (e.g.,  caustic  potash,  mineral  acids),  or  by 
the  presence  of  a  tumor,  such  as  cancer.  Inflammation  of  all  kinds  in  the  mouth  or  pharynx  inter- 
feres with  the  taking  of  food.  Impossibility  of  swallowing  occurs  as  part  of  the  general  phenomena 
in  disease  of  the  medulla  oblongata,  in  consequence  of  paralysis  of  the  motor  centre  (superior  olives) 
for  the  facial,  vagus,  and  hypoglossal  nerves,  and  also  for  the  aft'erent  or  sensory  fibres  of  the  glosso- 
pharyngeal, vagus  and  trigeminus.  Stimulation  or  abnormal  excitation  of  these  parts  causes  spas- 
modic swallowing  and  the  disagreeable  feeling  of  a  constriction  in  the  neck  (globus  hystericus). 

(Bl  The  secretion  of  saliva  is  a'/«;«/.i/iC(/ during  inflammation  of  the  salivary  glands;  occlusion 
of  their  ducts  by  concretions  (salivary  calculi) ;  also  by  the  use  of  atropin,  daturin,  and  during  fever, 
whereby  the  secretory  (not  the  vasomotor)  fibres  of  the  chorda  appear  to  be  paralyzed  (§145). 
Wlien  the  fever  is  very  high,  no  saliva  is  secreted.  The  saliva  secreted  during  moderate  fever  is 
turbid  and  thick,  and,  usually,  acid.  .'\s  the  fever  increases,  the  diastatic  action  of  the  saliva  dimin- 
ishes (Ufft/»ia?iii).  The  secretion  is  increased  by  stimulation  of  the  buccal  nerves  (inflammation, 
ulceration,  trigeminal  neuralgia),  so  that  the  saliva  is  secreted  in  great  quantity.  Mercury  and  jabo- 
randi  cause  secretion  of  .saliva,  the  former  causing  stomatitis,  which  excites  the  secretion  of  saliva 
reflexly.  Even  diseases  of  the  stomach  accompanied  by  vomiting  cause  secretion  of  saliva.  A 
very  thick,  tenacious,  sympathetic  saliva  occurs  when  there  is  violent  stimulation  of  the  vascular 
system  during  sexual  excitement,  and  also  during  certain  psychical  conditions.  The  reaction  of  the 
saliva  is  acid  in  catarrh  of  the  mouth,  in  fever,  in  consequence  of  decomposition  of  the  buccal 
epithelium,  and  in  diabetes  mellitus,  in  consequence  of  acid  fermentation  of  the  saliva,  which 
contains  sugar.  Hence,  diabetic  persons  often  suffer  from  carious  teeth.  Unless  the  mouth  of  an 
infant  be  kept  scrupulously  clean,  the  saliva  is  apt  to  become  acid. 

(C)  Disturbances  in  the  activity  of  the  musculature  of  the  stomach  may  be  due  to  paralysis 
of  the  muscular  layers,  whereby  the  stomach  becomes  distended,  and  the  ingesta  remain  a  long 
time  in  it.  A  special  form  of  paralysis  of  the  stomach  is  due  to  non-closure  of  the  pylorus  [Ebstein). 
This  may  be  due  to  disturbances  of  innervation  of  a  central  or  peripheral  nature,  or  there  may  be 
actual  paralysis  of  the  pyloric  sphincter,  or  an.i;sthesia  of  the  pyloric  mucous  membrane,  which 
acts  reflexly  upon  the  sphincter  muscle;  and,  lastly,  it  may  be  due  to  the  reflex  impulse  not  being 
transferred  to  the  efferent  fibre  within  the  nerve  centre.  Abnormal  activity  of  the  gastric  muscula- 
ture hastens  the  passage  of  the  ingesta  into  the  intestine  ;  vomiting  often  occurs. 

Gastric  digestion  is  delayed  by  violent  bodily  or  mental  exercise,  and  sometimes  it  is  arrested 
altogether.  Sudden  mental  excitement  may  have  the  same  effect.  These  effects  are,  very  probably, 
caused  through  the  vasomotor  nerves  of  the  stomach,  p'eeble  and  imperfect  digestion  may  be  of  a 
purely  nervous  nature  (Dyspepsia  nervosa — Leiibe ;  Neurasthenia  gastrica — Burkart),  An  exces- 
sive formation  of  acid  may  be  due  to  nervous  disturbance,  and  is  called  "nervous  gastroxynsis," 
by  Rossbach. 

[Action  of  Alcohol,  Tea,  etc.,  in  Digestion. — According  to  J.  W.  Fraser,  all  infused  beverages, 
tea,  coffee,  cocoa,  retard  the  peptic  digestion  of  proteids,  with  few  exceptions.  The  retarding  action 
is  less  with  cofi"ee  than  with  lea.  The  tannic  acid  and  volatile  oil  seem  to  be  the  retarding  ingiedi- 
ents  in  teas.  Distilled  Spirits — brandy,  whisky,  gin — have  but  a  trifling  retarding  effect  on  the 
digestive  processes ;  and  when  one  considers  their  action  on  the  secretory  glands,  it  follows  that  in 
moderate  dietetic  doses  they  promote  digestion.  Wines  are  highly  inimical  to  salivary  digestion, 
but  this  is  due  to  their  acidity;  and  this  effect  can  be  removed  by  the  addition  of  an  alkali.  Wines 
retard  peptic  digestion,  the  sparkling  less  than  the  still  wines.  Tea  has  an  intensely  inhibitory 
action  on  salivary  digestion  — in  fact,  a  small  quantity  paralyzes  the  action  of  salive — while  coff'ee 
has  only  a  slight  effect.  This  action  of  tea  is  due  to  the  tannin.  Tea,  coffee  and  cocoa  all  retard 
peptic  digestion  when  they  form  20  per  cent,  of  the  digestive  mixture  ( \V.  Roberts,  p.  245).] 

Inflammatory  or  Catarrhal  Affections  of  the  stomach,  as  well  as  ulceration  and  new  forma- 
tions, interfere  with  digestion,  and  the  same  result  is  caused  by  eating  too  much  food  which  is  diffi- 
cult of  digestion,  or  taking  too  much  highly-spiced  sauces  or  alcohol.  In  the  case  of  a  dog  suffer- 
ing from  chronic  gastric  catarrh,  Griitzner  observed  that  the  secretion  took  place  continuously,  and 
that  the  gastric  juice  contained  little  pepsin,  was  turbid,  sticky,  feebly  acid,  and  even  alkaline.  The 
introduction  of  food  did  not  alter  the  secretion,  so  that  in  this  condition  the  stomach  really  obtains 
no  rest.  The  chief  cells  of  the  gastric  glands  were  turbid.  Hence,  in  gastric  catarrh  we  ought  to 
eat  frequently.  l)ut  take  little  at  a  time,  while,  at  the  same  time,  dilute  (0.4  per  cent.)  hydrochloric 
acid  ought  to  be  administered.     Small  doses  of  common  salt  seem  to  aid  digestion. 

[Absence  of  HCl. — HCl  is  always  absent  in  carcinoma  of  the  stomach  {van  de  Veide);  amyloid 
degeneration  of  the  gastric  mucous  membrane  { Edingej'),  a.nd  sometimes  in  fever.  In  all  these 
cases  the  aciil  reaction  is  due  to  lactic  or  butyric  acid.    The  absence  of  HCl  in  cancer  of  the  stomach 


DIGESTION    DURING    FEVER    AND    AN.'EMIA.  315 

is  an  important  diagnostic  and  prognostic  symptom.  It  is  not  alisent  in  simple  dilatation  of  the 
stomacli.  Test  the  contents  of  the  stomach  for  free  HCl  with  tropjeolin  (red  colon,  methyl  violet 
(blue),  and  with  ferric  chloride  and  carbolic  acid  {i'ffelmann).  4-^  percent,  of  free  HCl  causes 
the  amethyst-blue  of  the  last  to  become  steel-gray,  while  somewhat  more  discharges  the  color 
altogether.] 

[In  testing  for  the  presence  of  free  lactic  acid  in  the  gastric  contents,  use  a  freshly  prepared 
solution  of  10  c.  c.  of  4  per  cent,  carbolic  acid,  20  c.  c.  distilled  water,  and  one  drop  of  the  officinal 
liquor  of  the  perchloride  of  iron.  The  amethyst-blue  color  is  made  yellow  by  adding  ^A  to  J^  of 
its  volume  of  dilute  lactic  acid  (i  per  1000).  The  lactic  acid  is  easily  e.\tracted.  by  ether,  from 
the  gastric  contents,  and  the  reaction  can  then  be  performed  with  the  residue  obtained  after  evapo- 
rating the  ether.  A  solution  of  I  drop  of  the  liquor  perchloride  in  50  c.  c.  of  water  is  made  yellow 
by  lactic  acid  {Vffelmann].'\ 

Feeble  Digestion  may  be  caused  either  by  imperfect  formation  of  acid  or  pepsin,  so  that  both 
substances  may  be  administered  in  such  a  condition.  [It  may  also  be  due  to  deficient  muscular 
power  in  the  wall  of  the  stomach].  In  other  cases,  lactic,  butyric  and  acetic  acids  are  formed, 
owing  to  the  presence  of  lowdy  organisms.  In  such  cases,  small  doses  of  salicylic  acid,  together 
with  some  hydrochloric  acid,  are  useful  {Hoppe-Seyhr).  Pepsin  need  not  be  given  often,  as  it  is 
rarely  absent,  even  from  the  diseased  gastric  mucous  membrane.  Albumin  has  been  found  in  the 
gastric  juice  in  cases  of  gastric  catarrh  and  cholera. 

(Dl  Digestion  during  Fever  and  Anaemia. — Beaumont  found  that  in  the  case  of  Alexis  St. 
Martin,  when  fever  occurred,  a  small  amount  of  gastric  juice  was  secreted;  the  mucous  membrane 
was  dry,  red,  and  irritable.  Dogs  suffering  from  septica^mic  fever,  or  rendered  anaemic  by  great  loss 
of  blood.  Secrete  gastric  juice  of  feeble  digestive  power  and  containing  little  acid  1  Mmiasscin).  [In 
acute  diseases  accompanied  by  fever,  the  inner  cells  of  the  fundus  glands  of  the  human  stomach 
may  disappear  (C.  Kupffer.W  Hoppe-Seyler  investigated  the  gastric  juice  of  a  typhus  patient,  in 
which  van  de  Velde  found  no  free  acid,  and  he  found  the  same  in  gastric  catarrh,  fever,  and  in  can- 
cer of  the  stomach.  The  gastric  juice  of  the  typhus  patient  did  not  digest  artificially,  even  after  the 
addition  of  hydrochloric  acid.  The  diminution  of  acid,  under  these  circumstances,  favors  the  occur- 
rence of  a  neutral  reaction,  so  that,  on  the  one  hand,  digestion  cannot  proceed,  and  on  the  other, 
fermentative  processes  (lactic  and  butyric  acid  fermentations  with  the  evolution  of  gases)  occur. 
These  results  are  associated  with  the  presence  of  micro-organisms  and  Sarciiia  ventriculi  {  Good- 
sjr^.  He  advises  the  administration  of  hydrochloric  acid  and  pepsin,  and  when  there  are  symp'onis 
of  fermentation,  small  doses  of  salicylic  acid.  Ufielmann  found  that  the  secretion  of  a  peptone- 
forming  gastric  juice  ceased  in  fever,  when  the  fever  is  severe  at  the  outset,  when  a  feeble  condition 
occurs,  or  when  the  temperature  is  very  high.  The  amount  of  juice  secreted  is  certainly  diminished 
during  fever.  The  excitability  of  the  mucous  membrane  is  increased,  so  that  vomiting  readily 
occurs.  The  increased  excitability  of  the  vasomotor  nerves  during  fever  (Hcidcnhahi)  is  disadvan- 
tageous for  the  secretion  of  the  digestive  fluids.  Beaumont  obser\'ed  that  fluids  are  rapidly  ab- 
sorbed from  the  stomach  during  fever,  but  the  absorption  of  peptones  is  diminished  on  account  of 
the  accompanying  catarrhal  condition  of  the  stomach,  and  the  altered  functional  activity  of  the 
muscularis  mucosa;  [Lciibe). 

Many  salts,  when  given  in  lars;e  amount,  disturb  gastric  digestion,  «•..?■.,  the  sulphates.  While 
the  alkaloids,  morphia,  strychnia,  digitalin.  narcotin,  veratria,  have  a  similar  action;  quinine  favors 
it  ( IVolberg).  In  some  ner\'ous  individuals  a  "  peristaltic  unrest  of  the  stomach,"  conjoined  with  a 
dyspeptic  condition,  occurs  (Kussmatih.  [Professor  James  directs  attention  to  the  value  of  peptic 
and  pancreatic  salts,  which  are  preparations  of  common  salt  mixed  with  pepsin  and  the  ferments  of 
the  pancreas  respectively.] 

[Artificial  Digestion  is  affected  by  various  salts  according  to  their  nature  and  dilution.  The 
digestion  oi  fibrin  by  pepsin  goes  on  best  without  the  addition  of  salts,  being  diminished  by  magnesic 
sulphate,  sodic  carbonate  and  sulphate.  The  digestion  of  fibrin  by  pancreatic  extract  is  accelerated 
by  sodic  carbonate  (Heidenhain^.  and  retarded  by  MgSO^  and  Na2SO.j.  The  diastatic  action 
of  the  saliva  and  pancreas  on  starch  is  greatly  accelerated  by  NaCl  (2  per  cent.)  while  Na2C03, 
NajSO^,  MgSO^  slow  it  {Pfeiffer).'\ 

According  to  .Schiitz,  artificial  gastric  digestion  is  retarded  by  a  2  per  cent,  solution  of  alcohol, 
and  also  by  a  solution  of  salicylic  acid  (.06  to  .1  per  cent.).  Buchner,  however,  finds  that  10  per 
cent,  of  alcohol  does  not  afiect  artificial  gastric  digestion,  while  above  20  per  cent,  arrests  it.  Beer 
hinders  digestion. 

(E)  In  acute  diseases,  the  secretion  of  bile  is  affected  ;  it  becomes  less  in  amount  and  more 
watery,  i.  e.,  it  contains  less  specific  constituents.  If  the  liver  undergoes  great  structural  change,  the 
secretion  may  be  arrested. 

(F)  Gallstones When  decomposition  of  the  bile   occurs,  gall  stones  are   formed  in  the  ^vz// 

b/adder  or  in  the  bi/e  diiols.  .Some  are  luhile,  and  consist  almost  entirely  of  stratified  layers  of  crys- 
tals of  cholesterin.  The  brown  forms  consist  of  bilirubin,  lime  and  calcium  carbonate,  often 
mixed  with  iron,  copj^er,  and  manganese.  The  gall  stones  in  the  gall  bladder  become  faceted  by 
rubbing  against  each  other.  The  nucleus  of  the  white  stones  often  consists  of  chalk  and  bile  color- 
ing matters,  together  with  nitrogenous  residues,  derived  from  shed  epithelium,  mucin,  bile  salts  and 
fats.     Gall  stones  may  occlude  the  bile  duct   and  cause   cholxmia.     When  a  small  stone  becomes 


316  COMPARATIVE    PHYSIOLOGY   OF    DIGESTION. 

impacted  in  a  duct,  it  gives  rise  to  excessive  pain,  constituting  hepatic  colic,  and  may  even  cause 
rupture  of  the  bile  duct  with  its  sharp  edges. 

(G)  Nothing  certain  has  been  determined  regarding  the  pancreatic  secretion  in  disease,  but  in 
fever  it  appears  to  be  diminished  in  amount  and  digestive  activity.  The  suppression  of  the  pancre- 
atic secretion  [as  by  a  cancerous  tumor  of  the  head  of  the  pancreas]  is  often  accompanied  by  the 
appearance  of  fat  in  the  form  of  globules  or  groups  of  crystals  in  the  fa'ces. 

(H)  Constipation  is  a  most  important  derangement  of  the  digestive  tract.  It  may  be  caused  by 
— ( I )  Conditions  which  obstruct  the  normal  channely  e.g.,  constriction  of  the  gut  from  stricture — in 
the  large  gut  after  dysentery,  tumors, rotation  on  its  axis  of  a  loop  of  intestine  (volvulus),  or  invagina- 
tion, occlusion  of  a  coil  of  gut  in  a  hernial  sac,  or  by  the  pressure  of  tumors  or  exudations  from 
without,  or  congenital  absence  of  the  anus.  (2)  Too  great  drviiess  of  the  contents,  caused  by  too 
little  water  in  the  articles  of  diet,  diminution  of  the  amount  of  the  digestive  secretions,  e.g.,  of  bile 
in  icterus;  or  in  consequence  of  much  fluid  being  given  off  by  other  organs,  as  after  copious  secre- 
tion of  saliva,  milk,  or  in  fever.  (3)  Variations  in  the  functional  activity  of  the  miise/es  and  motor 
7ieitious  apparatus  of  the  gut  may  cause  constipation,  owing  to  imperfect  peristalsis.  This  condition 
occurs  in  inflammations,  degenerations,  chronic  catarrh,  diaphragmatic  inflammation.  Affections  of 
the  spinal  cord,  and  sometimes  also  of  the  brain,  are  usually  accompanied  by  slow  evacuation  of  the 
intestine.  Whether  diminished  mental  activity  and  hypochondriasis  are  the  cause  of,  or  are  caused 
by  constipation  is  not  proved.  Spasmodic  contraction  of  a  part  of  the  intestine  may  cause  tempo- 
rary retention  of  the  intestinal  contents,  and,  at  the  same  time,  give  rise  to  great  pain  or  colic;  the 
same  is  true  of  spasm  of  the  anal  sphincter,  which  may  be  excited  reflexly  from  the  lower  part  of 
the  gut.  The  faecal  masses  in  constipation  are  usually  hard  and  dry,  owing  to  the  water  being  ab- 
sorbed ;  hence  they  form  large  masses  or  scybala  within  the  large  intestine,  and  these  again  give 
rise  to  new  resistance. 

Among  the  reagents  which  prevent  evacuation  of  the  bowels,  some  paralyze  the  motor  apparatus 
temporarily,  e.g.,  opium,  morphia  ;  some  diminish  the  secretion  of  the  intestinal  mucous  membrane, 
and  cause  constriction  of  the  blood  vessels,  as  tannic  acid,  vegetables  containing  tannin,  alum,  chalk, 
lead  acetate,  silver  nitr,ate,  bismuth  nitrate. 

(I)  Increased  ei'aeuation  of  the  intestinal  contents  is  usually  accompanied  by  a  watery  condition 
of  the  faeces,  constituting  diarrhcea. 

The  causes  are  : — 

1.  A  too  rapid  movement  of  the  contents  through  the  intestine,  chiefly  through  the  large  intestine, 
so  that  there  is  not  time  for  the  normal  amount  of  absorption  to  take  place.  The  increased  peristal- 
sis depends  upon  stimulation  of  the  motor  nervous  apparatus  of  the  intestine  usually  of  a  reflex 
nature.  Rapid  transit  of  the  contents  through  the  inte.stine,  causes  the  evacuation  of  certain  sub- 
stances, which  cannot  be  digested  in  so  short  a  time. 

2.  The  stools  become  thinner,  from  the  presence  of  much  water,  mucus,  and  the  admixture  with 
fat,  and  by  eating  fruit  and  vegetables.  In  rare  cases,  w-hen  the  evacuations  contain  much  mucin, 
Charcot's  crystals  occur  (Fig.  144,  c).  In  ulceration  of  the  intestine  leucocytes  (pus)  are  present 
{Nothnagel). 

3.  Diarrhoea  may  occur  as  a  consequence  of  disturbance  of  the  diffusion  processes  through  the 
intestinal  walls,  as  in  affections  of  the  epithelium,  when  it  becomes  swollen  in  inflammatory  or 
catarrhal  conditions  of  the  intestinal  mucous  membrane.  [Irritation  over  the  abdomen,  as  from  the 
subcutaneous  injection  of  small  quantities  of  saline  solutions,  causes  diarrhcea  [Af.  Hay)^ 

4.  It  may  also  be  due  to  increased  secretion  into  the  intestine,  as  in  capillary  diffusion,  when 
magnesium  sulphate  in  the  intestine  attracts  water  from  the  blood. 

The  same  occurs  in  cholera,  when  the  stools  are  copious  and  of  a  rice-water  character,  and  are 
loaded  with  epithelial  cells  from  the  villi.  The  transudation  into  the  intestine  is  so  great  that  the 
blood  in  the  arteries  becomes  very  thick,  and  may  even  on  this  account  cease  to  circulate. 

Transudation  into  the  intestine  also  takes  place  as  a  consequence  of  paralysis  of  the  vasomotor 
nerves  of  the  intestine.  This  is  perhaps  the  case  in  diarrhcea  following  upon  a  cold.  Certain  sub- 
stances seem  directly  to  excite  the  secretory  organs  of  the  intestines  or  their  nerves,  such  as  the 
drastic  purgatives  [\  iSo).     Pilocarpin  injected  into  the  blood  causes  great  secretion  (Mas/off). 

During  febrile  conditions,  the  secretion  of  the  intestinal  glands  seems  to  be  altered  quantita- 
tively and  qualitatively,  with  simultaneous  alteration  of  the  functional  activity  of  the  musculature 
and  the  organs  of  absorption,  while  the  excitability  of  the  mucous  membrane  is  increased  (  i'ffel- 
niann).  It  is  important  to  note  that  in  many  acute  febrile  diseases  the  amount  of  common  salt  in  the 
urine  diminishes,  and  increases  again  as  the  fever  subsides. 

187.  COMPARATIVE. — Salivary  Glands. — Among  Mammals  the  herbivora  have  larger 
salivary  glands  than  the  carnivora;  while  midway  between  both  are  the  omnivora.  The  whale  has 
no  salivary  glands.  The  pinnipedia  have  a  small  parotid,  w'hich  is  absent  in  the  echidna.  The 
dog  and  many  carnivora  have  a  special  gland  lying  in  the  orbit,  the  orbita/  or  zygomatic  gland.  In 
Birds  the  salivary  glands  open  at  the  angle  of  the  mouth  ;  in  them  the  parotid  is  absent.  Among 
Reptiles  the  parotid  of  some  species  is  so  changed  as  to  form  poison  glands  ;  the  tortoise  has  sub- 
lingual glands;  reptiles  have  labial  glands.  The  Amphibia  and  Fishes  have  merely  small  glands 
scattered  over  the  mouth.     The  salivary  glands  are  large  in  Insects;  some  of  them  secrete  formic 


HISTORICAL   ACCOUNT   OF    DIGESTION.  317 

acid.  The  salivary  glands  are  well  developed  in  molluscs,  and  the  saliva  of  Dolium  galea  contains 
more  than  3  per  cent,  of  free  sulphuric  acid  (?).     The  cephalopods  have  double  glands. 

A  Crop  is  not  present  in  any  manmial;  the  stomach  is  either  simple^  as  in  man,  or,  as  in  many 
rodents,  it  is  divided  into  two  halves,  into  a  cardiac  and  a  pyloric  portion.  The  intestine  is  short  in 
flesh-eating  animals  and  long  in  herbivora.  The  stomach  of  ruminants  is  compound,  and  consists 
of  four  cavities.  The  first  and  largest  is  the  paunch  or  rumen,  then  the  reticulum.  In  these 
two  cavities,  especially  the  former,  the  ingesta  are  softened  and  undergo  fermentation.  They  are 
then  returned  to  the  mouth  by  the  action  of  the  voluntary  muscular  fibres,  which  reach  to  the 
stomach.  This  is  the  process  of  rumination.  The  ingesta  are  chewed  again  in  the  mouth,  and 
are  again  swallowed,  but  this  time  they  enter  the  third  cavity  or  psalterium— (which  is  absent  in 
the  camel) — -and  thence  into  the  fourth  stomach  or  abomasum  in  which  the  fermentative  digestion 
takes  place.  The  cjecum  is  a  very  large  and  important  digestive  organ  in  herbivora,  and  in  most 
rodents;  it  is  small  in  man,  and  absent  in  carnivora.  The  cesophagus  in  grain-eating  Birds  not 
unfrequently  has  a  blind  diverticulum  or  crop  for  softening  the  food.  In  the  crop  of  pigeons  during 
the  breeding  season,  there  is  formed  a  peculiar  secretion — "pigeon's  milk,"  which  is  used  to  feed 
the  young  (J.  Hunter).  The  stomach  consists  of  a  glandular  proventriculus  and  a  strong  muscu- 
lar stomach  which  is  covered  with  horny  epithelium  and  triturates  the  food.  There  are  usually  two 
fluid  diverticula  on  the  small  intestine  near  where  it  joins  the  large  gut.  In  Fishes  the  intestinal 
canal  is  usually  simple;  the  stomach  is  merely  a  dilatation  of  the  tube;  and  at  the  pylorus  there 
may  be  one,  but  usually  many,  blind  glandular  appendages  (the  appendices  pyloricse).  There  are 
usually  longitudinal  folds  in  the  intestinal  mucous  membrane,  but  in  some  fishes,  <■.  i,'.,  the  shark, 
there  is  a  spiral  valve.  [It  is  curious  to  find  that  the  inversive  (cane-sugar)  ferment  is  wanting  in 
the  herbivora,  as  the  cow,  horse  and  sheep,  but  is  present  in  the  carnivora,  as  the  dog  and  cat.  It 
is  also  met  with  in  birds  and  reptiles,  and  in  many  of  the  invertebrates,  as  the  ordinary  earthworm 
{Matthew  //ay).] 

In  Amphibia  and  Reptiles  the  stomach  is  a  simple  dilatation ;  the  gut  is  larger  in  vegetable 
feeders  than  in  flesh  feeders.  The  liver  is  never  absent  in  vertebrates,  although  the  gall  bladder 
frequently  is.     The  pancreas  is  absent  in  some  fishes. 

Digestion  in  Plants. — The  observations  on  the  albumin-digesting  power  of  some  plants  {Candy, 
t86g  ;  Ch.  Darwin,  iSjj)  are  extremely  interesting.  The  sun  dew  or  drosera  has  a  series  of  ten- 
tacles on  the  surface  of  its  leaves,  and  the  tentacles  are  provided  with  glands.  As  soon  as  an  insect 
alights  upon  a  leaf  it  is  suddenly  seized  by  the  tentacles,  the  glands  pour  out  an  acid  juice  over  the 
prey,  which  is  gradually  digested ;  all  e.'icept  the  chitinous  structures.  The  secretion,  as  well  as 
the  subsequent  absorption  of  the  products  of  digestion,  are  accomplished  by  the  activity  of  the  pro- 
toplasm of  the  cells  of  the  leaves.  The  digestive  juice  contains  a  pepsin-like  ferment  and  formic 
acid.  Similar  phenomena  are  manifested  by  the  Venus  fly  trap  (Diona:a),  by  pinguicula,  as  well  as 
by  the  cavity  of  the  altered  leaves  of  nepenthes.  About  fifteen  species  of  these  "  insectivorous  " 
or  carnivorous  plants  are  known.  [The  action  of  papain,  and  other  ferments  analogous  in  their 
action  to  trypsin,  are  referred  to  in  |  170.] 

188.  HISTORICAL. — Digestion  in  the  Mouth. — -The  Hippocratic  school  was  acquainted 
with  the  vessels  of  the  teeth  ;  Aristotle  ascribed  an  uninterrupted  growth  to  these  organs,  and  he 
further  noticed  that  animals  that  were  pro\  ided  with  horns  and  had  cloven  hoofs,  had  an  imperfect 
set  of  teeth — the  upper  incisors  were  absent.  It  is  curious  to  note  that  in  some  cases  where  men 
have  had  an  excessive  formation  of  hairy  appendages,  the  incisor  teeth  have  been  found  to  be  badly 
developed.  The  muscles  of  mastication  were  known  at  an  early  period;  Vidius  (f  1567)  described 
the  temporo-maxillary  articulation  with  its  meniscus.  The  older  observers  regarded  the  saliva  as 
a  solvent,  and  in  addition,  many  bad  qualities,  especially  in  starving  animals,  were  ascribed  to  it. 
This  arose  from  the  knowledge  of  the  saliva  of  mad  animals,  and  the  parotid  saliva  of  poisonous 
snakes.  Human  saliva,  without  organisms,  is  poisonous  \.o\>\x&s  {Gautier).  The  salivary  glands 
have  been  known  for  a  long  time.  Galen  (131--203  A. D.)  was  acquainted  with  Wharton's  duct, 
and  Aetius  (270  a.d.)  with  the  sub-maxillary  and  sublingual  glands.  Hapel  de  la  Chenaye  (17S0) 
obtained  large  quantities  of  saliva  from  a  horse,  in  which  he  was  the  first  to  make  a  salivary  fistula. 
Spallanzani  (17S6)  asserted  that  food  mixed  with  saliva  was  more  easily  dige-.ted  than  food  moist- 
ened with  water.  Hamberger  and  Sieliold  investigated  the  reaction,  consistence  and  specific  gravity 
of  saliva,  and  found  in  it  mucus,  albumin,  common  salt,  calcium  and  sodium  phosphates.  Berzelius 
gave  the  name  ptyalin  to  the  characteristic  organic  constituent  of  saliva,  but  Leuchs  (1831  j  was 
the  first  to  detect  its  diastatic  action. 

Gastric  Digestion. — Digestion  was  formerly  compared  to  boiling,  whereby  solution  was  effected. 
According  to  Galen,  only  substances  that  have  been  dissolved  passed  through  the  pylorus  into  the 
intestine.  He  described  the  movements  of  the  stomach  and  the  peristalsis  of  the  intestines. 
Aelian  gave  names  to  the  four  stomachs  of  the  ruminants.  Vidius  (■)■  1567)  noticed  the  numerous 
small  apertures  of  the  gastric  glands.  Van  Helmont  (f  1644)  expressly  notices  the  acidity  of  the 
stomach.  Reaumur  (1752)  knew  that  a  juice  was  secreted  by  the  stomach,  which  effected  solution, 
and  with  which  he  and  Spallanzani  performed  experiments  on  digestion  outside  the  body.  Car- 
minati  (17S5)  found  that  the  stomachs  of  carnivora  during  digestion  secreted  a  very  acid  juice. 
Prout  (1S24)  discovered  the  hydrochloric   acid  of  the  gastric  juice,  Sprott  and  Boyd  (1836)  the 


318  HISTORICAL. 

glands  of  the  gastric  mucous  membrane,  while  Wasmann  and  Bischoff  noted  the  two  kinds  of 
gastric  glands.  After  Beaumont  (1834)  had  made  his  observations  upon  Alexis  St.  Martin,  who 
had  a  gastric  fistula  caused  by  a  gunshot  wound,  Bassow  ( 1842)  and  Blondlot  (1843)  made  the  first 
artificial  gastric  fistulas  upon  animals.  Eberle  (1834)  prepared  artificial  gastric  juice.  Mialhe 
called  albumin,  when  altered  by  gastric  digestion,  albuminose  ;  Lehmann,  who  investigated  this 
substance  more  carefully,  gave  it  the  nxmt  peptone.  Schwann  isolated  ^i?/««  (1836),  and  estab- 
lished the  fact  of  its  activity  in  the  presence  of  hydrochloric  acid. 

Pancreas,  Bile,  Intestinal  Digestion. — The  Pancreas  was  known  to  the  Hippocratic  School ; 
Maur.  Hoffmann  (1642)  demonstrated  its  duct  ifowl),  and  Wirsung  described  it  in  man.  Regner 
de  Graaf  (1664)  collected  the  pancreatic  juice  from  a  fistula,  and  Tiedemann  and  Gmelin  found  it 
to  be  alkaline,  while  Lauret  and  Lassaigne  found  that  it  resembled  saliva.  Valentin  discovered  its 
diastatic  action,  Eberle  its  emulsionizing  power,  and  CI.  Bernard  (1846)  its  tryptic  and  fat  .splitting 
properties.     The  last  mentioned  function  was  referred  to  by  Purkinje  and  Pappenheim  {1836). 

Aristotle  characterized  the  bile  as  a  useless  secretion;  according  to  Erasistratus  (304  B.  c. ),  fine 
invisible  channels  conduct  the  bile  from  the  liver  into  the  gall  bladder.  Aretaeus  ascribed  icterus 
to  obstruction  of  the  bile  duct.  Benedetti  (1493)  described  gall  stones.  According  to  Jasolinus 
(1573),  the  gall  bladder  is  emptied  by  its  own  contractions.  Sylvius  de  la  Boe  noticed  the  lymph- 
atics of  the  liver  (1640) ;  Walaeus,  the  connective  tissue  of  the  so-called  capsule  of  Glisson  (1641). 
Haller  indicated  the  uses  of  bile  in  the  digestion  of  fats. 

The  liver  cells  were  described  by  Henle,  Purkinje,  and  Dutrochet  (1838).  Heynsius  discovered 
the  urea,  and  CI.  Bernard  (1853)  the  sugar  in  the  liver,  and  he  and  Hensen  (1857)  found  glycogen 
in  the  liver.  Kiernan  gave  a  more  exact  description  of  the  hepatic  blood  vessels  (1834).  Beale 
injected  the  lymphatics,  and  Gerlach  the  finest  bile  ducts.  Schwann  (1844)  made  the  first  biliary 
fi-tula ;  Demarcay  particularly  referred  to  the  combination  of  the  bile  acids  with  soda  (1838); 
Strecker  discovered  the  soda  compounds  of  both  acids,  and  isolated  them. 

Corn.  Celsus  mentions  nutrient  enemata  (3-5  A.  D.).  Fallopius  (1561)  described  the  valvulae 
conniventes  and  villi  of  the  intestinal  mucous  membrane,  and  the  nervous  plexus  of  the  mesentery. 
The  agminated  glands  or  patches  of  Peyer  were  known  to  Seveiinus  (1645). 


PHYSIOLOGY  OF  ABSORPTION. 


leme  of  intestinal  absorption 
teal;  T.  D.,  thoracic  duct; 
v.,  portal  and  hepatic  vein? 


LAC,  lac- 
.  V.  and  H. 
INT.,  intcs- 


189.  THE  ORGANS  OF  ABSORPTION.— [As  most  substances  in 
the  state  in  whicli  tht;y  are  used  for  food  are  either  insoluble  or  diffuse  but  imper- 
fectly through  membranes,  the  whole  drift  of  the  complicated  digestive  processes 
is  to  render  these  substances  soluble  and  diffusible,  and  thus  fit  them  for  absorp- 
tion ;  while  most  of  the  fats  are  emulsionized.] 

The  mucous  membrane  of  the  whole  intestinal  tract,  as  far  as  it  is  covered  by  a 
single  layer  of  columnar  epithelium,  /.  e.,  from  the  cardiac  orifice  of  the  stomach 
to  the  anus — is  adapted  for  absorption.  The 
mouth  and  cesophagus,  lined  as  they  are  by 
stratified  squamous  epithelium,  are  much  less 
adapted  for  this  purpose.  Still,  poisoning  is 
caused  by  placing  potassium  cyanide  in  the 
mouth. 

The  channels  of  absorption  in  the  intestinal 
tract  are  (Fig.  193) — ( i)  the  capillaries 
\_clirect'\,  and  (2)  the  lacteals  [/>/<///y(/]  of  the 
mucous  membrane.  Almost  the  whole  of  the 
substances  absorbed  by  the  former  pass  into 
the  rootlets  of  the  portal  vein,  and  traverse  the 
liver,  while  those  that  enter  the  lacteals  really 
pass  into  lymphatics,  so  that  the  chyle  passes 
through  the  thoracic  duct,  and  is  poured  by  it 
into  the  blood,  where  the  thoracic  duct  joins 
the  subclavian  vein. 

Absorption  in  the  Stomach. — Watery  solutions  of  salts,  grape  sugar,  pep- 
tone, poisons,  and  in  a  still  higher  degree  alcoholic  solutions  of  poisons  are 
absorbed.  The  empty  stomach  absorbs  more  rapidly  than  one  filled  with  food  ; 
gastric  catarrh  delays  absorption  i^Qiietsch).  After  a  copious  diet  of  milk,  fatty 
granules  have  been  found  in  the  protoplasm  of  the  goblet  cells  {Ko/tiker)  ;  so  that 
according  to  this  view,  the  goblet  cells  have  a  double  function,  to  secrete  mucus 
and  to  absorb  nutrients. 

Small  Intestines. — The  greatest  area  of  absorption  is  undoubtedly  the  small 
intestine,  especially  \\.?,  upper  \\a.\i  ( Landois  and  Lepine),  owing  to  the  presence 
of  the  valvulae  conniventes  and  the  villi. 

190.  STRUCTURE  OF  THE  SMALL  AND  LARGE  INTES- 
TINES.—[The  wall  of  the  small  intestine  consists  of  four  coats;  which  from 
without  inward  are  named  serous,  muscular,  submucous,  and  mucous. 

The  serous  coat  has  the  same  structure  as  the  peritoneum,  ;'.  c,  a  thin  basis  of  fibrous  tissue 
covered  on  its  outer  surface  by  endothelium. 

The  muscular  coat  consists  of  a  tliin  oii/er  longitudinal  and  an  inner  tliicker  circular  layer  of 
non-striped  muscular  fibres  (Fig.  iS6j. 

The  submucous  coat  consists  of  loose  connective  tissue  containing  large  blood  vessels  and 
nerves,  ami  it  connects  the  muscular  with  the  mucous  coat.] 

The  mucous  coat  is  the  most  internal  coat,  and  its  absorbing  surface  is  largely  increased  by  the 
presence  of  the  valvule  conniventes  and  villi.  [The  valvulx  conniventes  are  permanent  folds 
of  the  mucous  membrane  of  the  small  intestine,  arranged  across  the  long  axis  of  the  gut.     They 

oiy 


320 


STRUCTURE    OF   A    VILLUS. 

Fig    194 


Mucous  membrane  of  the  small  intestine  of  the  dog ;   the  lacteals  are  black,  and  the  blood-vessels  lighte; 
artery;  b^  lymphatic;  c,  plexus  of  capillaries  in  the  villi ;  d^  lacteal;  f,  Lieberkuhn's  glands. 


leme  of  an  intestinal  villus.     A,  transverse  section  of  part  of  a  villus  ;  a.  columnar  epiihcHi 
c,  goblet  cell ;  i,  j,  adenoid  reticulum  ;  d,  d,  spaces  within  the  same  and  containing  leucocytt 
the  central  lacteal ;  B,  scheme  of  a  cell  with  processes  supposed  to  be  projected  from  its  intcri 
thelium  after  the  absorption  of  fatty  granules  ;    D,  the  columnar  epithelium  of  a  villus  seer 
goblet  cell  in  the  centre. 


6,  clear  disk  ; 
:/,  section  of 
columnar  epi- 


STRUCTURE    OF   A   VILLUS. 


321 


pass  round  a  half  or  more  of  the  inner  surface  of  the  gut.  They  begin  a  little  below  the  com- 
mencement of  the  duodenum,  and  are  large  and  well  marked  in  the  duodenum,  and  remain  so  as 
far  as  the  upper  half  of  the  jejunum,  where  they  begin  to  become  smaller,  and  finally  disappear 
about  the  lower  part  of  the  ileum.]  The  villi  are  characteristic  of  the  small  intestine,  and  are 
confined  to  it;  they  occur  everywhere  as  closely-set  projections  over  and  between  the  valvulse  con- 
niventes  (Fig.  194).  When  the  inner  surface  of  the  mucous  membrane  is  examined  in  water,  it 
has  a  velvety  appearance  owing  to  their  presence.  [They  vary  in  length  from  ^\  to  -^^  of  an  inch, 
are  most  numerous  and  largest  in  the  upper  part  of  the  intestine,  duodenum,  and  jejunum,  where 
absorption  is  most  active,  but  they  are  less  abundant  in  the  ileum.  Their  total  number  has  been 
calcidated  at  four  millions,  by  Krause.]  Each  villus  is  a  projection  of  the  entire  mucous  membrane, 
so  that  it  contains  within  itself  representatives  of  all  the  tissue  elements  of  the  mucosa.  The  orifices 
of  the  glands  of  Lieberkiihn  open  between  the  bases  of  villi  (Fig.  197). 

Each  villus,  be  it  cylindrical  or  conical  in  shape,  is  covered  by  a  single  layer  of  columnar 
epithelium,  whose  protoplasm  is  reticulated,  and  contains  a  well-defined  nucleus  with  an  intra- 
nuclear plexus  of  fibrils.  The  ends  of  the  epithelial  cells  directed  toward  the  gut  are  polygonal, 
and  present  the  appearance  of  a  mosaic  (Fig.  195,  D).  When  looked  at  from  the  side,  their  free 
surface  is  seen  to  be  covered  with  a  clear,  highly  refractive  disk  or  "  cuticula,"  which  is  marked 
with  vertical  strice.     These  stria;  were  supposed  by  Kolliker  to  represent  pores  for  the  absorption  of 


FiG.  196. 


Cylindrical  epithelii 


Disk  on  the  epithelii 


Injected  blood  vessels  of  a  villus. 


fatty  particles,  but  this  has  not  been  confirmed,  while  Brettauer  and  Steinach  regarded  them  as  pro- 
duced by  prisms  placed  side  by  side. 

According  to  some  observers  {v.  Thanhoffer),  however,  this  clear  disk  is  the  optical  expression 
of  a  thinning  of  the  cell  membrane,  comparable  to  the  thickened  flange  around  the  bottom  of  a 
vessel,  such  as  is  used  for  collecting  gases.  On  this  supposition,  the  upper  end  of  each  cell  is  open, 
and  from  it  there  projects  pseudopodia-like  bundles  of  protoplasmic  processes  (Fig.  195,  B).  These 
processes  are  supposed  to  be  extended  beyond  the  margin  of  the  cell  and  again  rapidly  retracted, 
and  in  so  acting  they  are  said  to  carry  the  fatty  particles  into  the  interior  of  the  cells,  much  as  the 
pseudopodia  of  an  amceba  entangles  its  food.  [This  view  has  not  been  confirmed  by  a  sufficient 
number  of  observers.]  Between  the  epithelial  cells  are  the  so-called  goblet  cells  (Fig.  195,  C). 
[Each  goblet  cell  is  more  or  less  like  a  chalice,  narrower  above  and  below,  and  broad  in  the  middle, 
with  a  tapering  fixed  extremity.  The  outer  part  of  these  cells  is  filled  with  a  clear  substance  or 
mucigen,  which,  on  the  addition  of  water,  yields  mucus.  The  mucigen  lies  in  the  intervals  of  a 
fine  network  of  fibrils,  which  pervades  the  cell  protoplasm,  while  the  protoplasm,  containing  a  glob- 
ular or  triangular  nucleus,  is  pushed  into  the  lower  part  of  the  cell.  These  goblet  cells  are  simply 
altered  columnar  epithelial  cells,  which  secrete  mucus  in  their  interior.  They  are  more  numerous 
under  certain  conditions.  Not  unfrequenily  in  sections  of  the  mucous  membrane  of  the  gut,  after 
it  is  stained  with  logwood,  we  may  see  a  deep  blue  plug  of  mucus  partly  exuded  from  these   cells. 


322 


STRUCTURE    OF    A    VILLUS. 


When  looked  at  from  above  they  give  the  appearance  seen  in  Fig.  195,  D.]  The  epithelial  cells 
are  shed  in  enormous  numbers  in  cholera,  and  in  poisoning  with  arsenic  and  muscarin  [Bo/tni). 

[The  epithelial  cells  covering  the  villus  are  placed  upon  a  layer  of  squamous  epithelium  (base- 
ment membrane) — the  sub-epithelial  membrane  of  D6bove.  This  basement  membrane  is  said 
to  be  connected  by  processes  with  the  so-called  branched  cells  of  the  adenoid  tissue  of  the  villus, 
while  it  also  sends  up  processes  between  the  epithelial  covering.] 

Adenoid  Tissue  of  Villus. — The  villus  itself  consists  of  a  basis  of  adenoid  tissue,  containing  in 
its  centre  one  or  more  lacteals,  closely  invested  with  a  few  longitudinal,  snnoth  muscular  fibres, 
derived  from  the  muscularis  mucosa?,  and  a  plexus  of  blood  vessels.  The  adenoid  tissue  of  the 
villus  consists  of  a  reticulum  of  fibrils  with  endothelial  plates  at  its  nodes.  The  spaces  of  the  ade- 
noid tissue  form  a  spongy  network  of  intercommunicating  channels,  containing  stroma  cells  or  leu'o- 
cytes  (Fig.  195,  A,  c,  e).  These  leucocytes,  or  lymph  corpuscles,  have  been  seen  to  contain  fatty 
granules,  and  they  may,  perhaps,  play  an  important  part  in  the  absorption  of  fatty  particles. 

The  lymphatic,  or  lacteal,  lies  in  the  axis  of  the  villus  (Fig.  194,  d).  By  some  observers  the 
lacteal  is  regarded  merely  as  a  space  in  the  centre  of  the  villus,  but,  more  probably,  it  has  a  distinct 
wall  composed  of  endothelial  cells,  with  apertures  or  stomata  here  and  there  between  the  cell  plat'-s. 


Fig.   iqy. 


Section  ol  the 


These  stomata  place  the  interior  of  the  lacteal  in  direct  communication  with  the  spaces  of  the  adenoid 
tissue.  It  is  very  probable  that  white  blood  corpuscles  wander  out  of  the  blood  vessels  of  the  villi 
into  the  spaces  of  the  adenoid  tissue,  where  they  become  loaded  with  fatty  granules,  and  pass  into 
the  central  lacteal.  Zuwarykin  and  Weidersheim  suppose  that  the  leucocytes  pass  from  the  paren- 
chyma of  the  villus  toward  the  epithelial  layer,  and  even  between  the  epithelial  cells,  from  which 
they  return  toward  the  axis  of  the  villus,  laden  with  substances  which  they  have  taken  into  their 
interior  (?  192,  II). 

A  small  artery,  placed  eccentrically,  passes  into  each  villus  (Fig.  196).  In  man,  it  begins  to 
divide  about  the  middle  of  the  villus,  but  in  animals  it  usually  runs  to  the  apex  before  it  divides. 
The  capillaries  resulting  from  the  division  of  the  artery  form  a  fine,  dense  network,  placed  super- 
ficially, immediately  under  the  epithelium  of  the  surface.  The  blood  is  carried  out  of  a  villus  by 
one  or  two  veins  (Figs.  194,  196). 

Non-striped  Muscular  Fibres  are  present  in  villi  [Henle).  Some  are  arranged  longitudinally 
from  base  to  apex,  immediately  outside  the  central  lacteal.  When  they  contract,  they  tend  to  empty 
the  lacteal  (Brihie).  A  few  muscular  fibres  are  placed  more  superficially,  and  run  in  a  more 
transverse  direction.     [The   longitudinal   bundles  of  non-striped  muscle  in  the  villi  are  connected 


STRUCTURE    OF   A    VILLUS. 


323 


together  by  oblique  strands;  while  the  longitudinal  bundles  shorten  the  villus,  the  oblique  fibres 
keep  the  lacteal  open;  thus,  the  parenchyma  of  the  villus  is  also  compressed  transversely,  whereby 
the  products  of  absorption  are  forced  into  the  lacteal.  The  muscles  are  fixed,  by  cement,  to  the 
subepithelial  basal  membrane.  The  muscular  fibres  of  the  villi  are  direct  prolongations  of  the 
muscularis  mucosa;.] 

Nerves  pass  into  the  villi  from  Meissner's  plexus,  lying  in  the  submucous  coat.     The  nerves  to 


Section  of  a  solitary  fo        e  of    he     ma       n         ne  (h   man)     how  ng — a       mph  fo  1  cle  covered  with  epithelium  (^) 
which  has  fallen  fr  m    he  d   L  ebe  kuhn     fo        e         mu     u  a      mu  o  ae    _/,  submucous  tissue. 

Fig.  199. 


dog,  showing  the  closed  follicle' 


the  villi  are  said  to  have  small  granular  ganglionic  cells  in  their  course,  and  they  terminate  partly  in 
the  muscular  fibres  and  partly  in  the  arteries  of  the  villi. 

[On  making  a  vertical  section  of  the  mucous  membrane  of  the  small  intestine,  it  is  seen  to 
consist  of  a  network  of  adenoid  tissue  loaded  with  leucocytes.  This  tissue  forms  its  basis,  and  in  it 
are  placed  vertically,  side  by  side — like  test  tubes  in  a  stand — immense  numbers  of  simple  tubular 


324 


SOLITARY    FOLLICLES. 


glands — the  Crypts  of  LieberkUhn  (Fig.  ig?).]  [Kultschitzki  finds  that  the  connective  tissue 
framework  of  the  mucous  membrane  of  the  small  intestine  is  not  true  adenoid  tissue,  but  a  transi- 
tion form  between  the  latter  and  loose  fibrous  tissue.]  They  open  above,  at  the  bases  of  the  villi, 
while  their  closed  lower  extremity  reaches  almost  to  the  muscularis  mucosa;.  Each  tube  consists  of 
a  basement  membrane,  lined  by  a  single  layer  of  columnar  epithelium,  leaving  a  wide  lumen,  the 
cells  lining  them  being  continuous  with  those  that  cover  the  mucous  membrane.     Some  goblet  cells 

Fig.   200. 


Auerbach's   pie 


n  (human),     rt,  ganglionic  cells;  b,  nerve  1 
ular  fibres  ;  d,  longitudinal  muscular  fibres. 


are  often  found  between  the  columnar  epithelium.  Immediately  below  the  bases  of  the  follicles  of 
Lieberkiihn  is  the  muscularis  mucosae,  consisting  of  two  or  three  narrow  layers  of  non-striped 
muscular  fibres,  arranged  circularly  and  longitudinally.  [It  is  continuous  with  the  muscularis 
mucosae  of  the  stomach,  and  extends  throughout  the  whole  intestine — not  as  a  continuous  layer, 
but  as  a  close  network  of  bundles  of  smooth  muscle  (A'u//!c/iit:ki\.  It  sends  fibres  upward  into 
the  villi  (Fig.  19S,  e).] 

Fig.  201. 


Epitheli  111 


Mucous  ineindran 


Solitary  follicle 


Lieberkiihn's  elands 


-S 


A 


Circular  fibres.    -  -     -1 

Muscular  emit '      \ 


Longitudinal 


of  the  large  intestin 


[Brunner's  Glands  are  compound  tubular  glands  lying  in  and  confined  to  the  .submucous  coat 
of  the  duodenum.  Their  ducts  perforate  the  muscularis  mucosa  to  open  on  the  surface.  They 
seem  to  be  the  homologues  of  the  pyloric  glands  of  the  stomach.] 

[Solitary  Follicles  are  small  round  or  oval  white  masses  of  adenoid  tissue,  with  their  deeper 
parts  embedded  in  the  sub-mucosa,  and   their  apices  projecting  into  the   mucosa  of  the  intestine. 


ABSORPTION    OF   THE    DIGESTED    FOOD. 


325 


They  begin  at  the  pyloric  end  of  the  stomach  and  are  found  throughout  the  whole  intestine.  They 
consist  of  small  masses  of  adenoid  tissue  loaded  with  leucocytes  (Fig.  198).  They  are  well  sup- 
plied with  blood  vessels  (J  197),  although  no  lymphatic  vessels  enter  them.  They  are  surrounded 
by  lymphatics,  and,  in  fact,  they  may  be  said  to  hang  into  a  lymph  stream.  The  distribution  of 
solitary  follicles  is  fairly  uniform  in  the  small  intestine;  their  number  generally  increases  from  the 
stomach  to  the  large  intestine  ;  although  there  are  considerable  variations  in  different  individuals, 
there  seems  to  be  the  same  number  of  solitary  follicles  and  Peyer's  patches  in  the  infant  as  in  the 
adult  (/'iisso-u').} 

[Peyer's  glands,  or  agminated  glands,  consist  of  groups  of  lymph  follicles  like  the  foregoing 
(Figs.  186,  199).  The  masses  are  often  more  or  less  fused  together,  their  bases  lie  in  the  sub-mucosa, 
while   their  summits  project  into   the  mucosa,  where  they  are 

covered  merely  by  the  columnar  epithehum  of  the  intestine.    The  FiG.  202. 

lymph  corpuscles  often  project  between  the  epithelium.  The 
patches  so  formed  have  their  long  axis  in  the  axis  of  the  intestine, 
and  they  are  ahvays  placed  opposite  the  attachment  of  the  mesen- 
tery. Like  the  solitary  glands,  they  are  well  supplied  with  blood 
vessels,  while  around  them  is  a  dense  plexus  of  lymphatics  or 
lacteals.  They  are  most  abundant  in  the  lower  part  of  the  ileum. 
These  glands  are  specially  aftected  in  typhoid  fever.] 

Nerves  of  the  Intestine. — Throughout  the  whole  intestinal 
tract  there  exists  the  plexus  of  Auerbach  (Fig.  200),  lying  be- 
tween the  longitudinal  and  circular  muscular  coats.  This  plexus 
consists  of  non-meduUated  nerves  with  groups  of  ganglionic  cells 
at  the  nodes.  Fibres  are  given  off  by  it  to  the  muscular  coats. 
Connected  by  branches  with  the  foregoing,  and  lying  in  the  sub. 
mucosa,  is  the  plexus  of  Meissner,  which  is  much  finer,  the 
meshes  being  wider,  the  nodes  smaller,  but  al>o  provided  with 
ganglionic  cells.  It  supplies  the  muscular  fibres  and  arteries  of 
the  mucosa,  including  those  of  the  villi.  It  also  supplies  branches 
to  Lieberkuhn's  glands  (Drasck).     Compare  Figs.  166  and  167. 

[Structure  of  the  Large  Intestine. — It  has  four  coats  like 
those  of  the  small  intestine.  The  serous  coat  has  the  same 
structure  as  that  of  the  small  intestine.  The  muscular  coat  has 
external  longitudinal  fibres  occurring  all  round  the  gut,  but  they 
form  three  Hat,  ribbon-like,  longitudinal  bands  in  the  csecum  and 
colon  (Fig.  201).  Inside  this  coat  are  the  ciiciilar  fibres.  The 
sub-mucosa  is  practically  the  same  as  that  of  the  small  intes- 
tine. Tlie  mucosa  is  characterized  by  negative  characters.  It 
has  no  villi  and  no  Peyer's  patches,  but  otherwise  it  resembles 
structurally  the  small  intestine,  consisting  of  a  basis  of  adenoid 
tissue  with  the  simple  tubular  glands  of  Lieberkiihn  (Fig.  202). 
These  glands  are  very  numerous  and  somewhat  longer  than  those 
of  the  small  intestine,  and  they  always  contain  far  more  goblet 
cells — about  ten  times  as  many.  The  cells  lining  them  are  de 
void  of  a  clear  disk.  Solitary  glands  occur  throughout  the 
entire  length  of  the  large  intestine.  At  the  bases  of  Lieberkuhn's 
glands  is  the  muscularis  mucosae.  The  blood  vessels  and 
nerves  have  a  similar  arrangement  to  those  in  the  stomach.] 

[Blood  Vessels. — On  looking  down  on  an  opaque  injection 
of  the  mucous  membrane  of  the  stomach,  one  sees  a  dense  meshwork  of  polygonal  areas  of 
unequal  size,  with  depressions  here  and  there.  The  orifices  are  the  orifices  of  the  gastric  glands, 
each  surrounded  by  a  capillary.  A  somewhat  similar  appearance  is  seen  in  an  opaque  injection  of 
the  mucous  membrane  of  the  large  intestine,  but  in  the  latter  the  meshwork  is  uniform,  all  the 
orifices  (of  Lieberkuhn's  glands)  being  of  the  same  size.] 

191.  ABSORPTION  OF  THE  DIGESTED  FOOD.— The  physical 
forces  concerned  are,  endosinosis,  diffusion  and  filtration. 

All  the  constituents  of  the  food,  with  the  exception  of  the  fats,  which  in  part  are  changed  into  a 
fine  emulsion,  are  brought  into  a  state  of  solution  by  the  digestive  processes.  These  substances 
pass  through  the  walls  of  the  intestinal  tract,  either  into  the  blood  vessels  of  the  mucous  membrane 
or  into  the  beginning  of  the  lymphatics.  In  this  passage  of  the  fluids  two  physical  processes  come 
into  play  — c-mlosmosis  and  diffusion,  as  well  as  filtration. 

I.  Endosinosis  and  diffusion  occur  between  two  fluids  which  are  capable  of  foniiing  an  inti- 
mate mixture  with  each  other,  e.  g.,  hydrochloric  acid  and  water,  but  never  between  two  fluids 
which  do  not  form  a  perfect  mixture,  such  as  oil  and  water.  If  two  fluids  capable  of  mixing  with 
each  other,  but  of  dift'erent  compositions,  be  separated  from  each  other  by  means  of  a  septum  with 
physical  pores  (which  occur  even  in  a  homogeneous  membrane),  an  exchange  of  the  constituents 


ntestlne  (.dog). 


large 


326 


FORCES   CONCERNED    IN    ABSORPTION. 


in  the  fluids  occurs  until  both  fluids  have  the  same  composition.     This  exchange  of  fluids  is  termed 
endosniosis  or  diosinosis. 

If  we  remember  that  within  the  intestinal  tract  there  are  relatively  concentrated  solutions  of  those 

substances  which  have  been  brought  into  solution  by  the  digestive  juices — peptone,  sugar,  soaps  and 

solutions   of    the   sails — while  separated  from    these  ijy  the   porous  mucous 

Fig.  203.  membrane   and  the   walls  of  the   blood   and  lymph  capillaries  is  the  blood, 

^  which   contains  relatively  less  of  these  substances,  it  is  clear  that  an  endos- 

molic  current  must  set  in  toward  the  blood  and  lymph  vessels. 

Diffusion.— If  the  two  mixible  fluids  are  placed  in  a  vessel,  the  one  fluid 
over  the  other,  but  without  being  separated  by  a  porous  septum,  an  exchange 
of  the  particles  of  the  fluids  also  occurs,  until  the  whole  mi.\ture  is  of  uniform 
composition.     This  process  is  called  diffusion. 

Conditions  Influencing  Diffusion. — Graham's  investigations  showed 
that  the  rapidity  of  diffusion  is  influenced  by  a  variety  of  conditions:  (I) 
The  nature  of  the  fluids  themselves  is  of  importance  ;  acids  diffuse  most 
rapidly  ;  the  alkaline  salts  more  slowly ;  and  most  slowly,  fluid  albumin,  gela- 
tin, gum,  dextrin.  These  last  do  not  crystallize,  and  do  not  form  true  solu- 
tions. (2)  The  more  concentrated  the  solutions,  the  greater  the  diffusion. 
(3)  Heat  accelerates,  while  coal  retards,  the  process.  (4)  If  a  solution  of  a 
body  which  diff'uses  with  difficulty  be  mixed  with  an  easily  diffusible  one,  the 
former  diffuses  with  still  greater  difficulty.  (5)  Dilute  solutions  of  several 
substances  diffuse  into  each  other  without  any  difficulty,  but  if  concentrated 
solutions  are  employed,  the  process  is  retarded.  (6)  Double  salts,  one  con- 
stituent of  which  diff'uses  more  readily  than  the  other,  may  be  chemically 
separated  by  diffusion. 

Endosmometer. — The  exchange  of  the  fluid  particles  takes  place  inde- 
pendently of  the  Jiydrostatic  pressure.  Fig.  203  represents  an  endosmometer. 
A  glass  cyhnder  is  filled  with  distilled  water,  and  into  this  is  placed  a  flask, 
J,  without  a  bottom,  instead  of  which  a  membrane,  vi,  is  tied  on.  A  glass 
tube,  R,  is  fixed  firmly  by  means  of  a  cork  into  the  neck  of  the  flask.  The 
flask  is  filled  up  to  the  lower  end  of  the  tube  with  a  concentrated  salt  solu- 
tion, and  is  then  placed  in  the  cylindrical  vessel  until  both  fluids  are  on  the 
same  level,  x.  The  fluid  in  the  tube,  R,  soon  begins  to  rise,  because  water 
passes  through  the  membrane  into  the  concentrated  solution  in  the  flask,  and 
'  this  independently  of  the  hydrostatic  pressure.     Particles  of  the  concentrated 

Endosmome^ter  for  os-  j^|j  solution  pass  into  the  cylinder  and  mix  with  the  water,  F.  These  out- 
going and  ingoing  currents  continue  until  the  fluids  without  and  within  J  are 
of  uniform  composition,  whereby  the  fluid  in  R  always  stands  higher  (^e.  g.,  at_)'),  while  it  is  lowered 
in  the  cylinder.  The  circumstance  of  the  level  of  the  fluid  within  the  tube  being  so  high  and 
remaining  so,  is  due  to  the  fact  that  the  pores  in  the  membrane  are  too  fine  to  allow  the  hydrostatic 
pressure  to  act  through  them. 

Endosmotic  Equivalent. — Experiment  has  shown  that  equal  weights  of  different  soluble  sub- 
stances attract  different  amounts  of  distilled  water  through  the  membrane,  /.  e.,  a  known  weight  of 
a  soluble  substance  (in  the  flask)  can  be  exchanged  by  endosmosis  for  a  definite  weight  of  water. 
The  term  endosmotic  equivalent  indicates  the  weight  of  distilled  water  that  passes  into  the  flask  of 
the  endosmometer,  in  exchange  for  a  known  weight  of  the  soluble  substance  (Jolly').  For  I  grm. 
alcohol  4.2  grins,  water  were  exchanged  ;  while  for  I  grm.  NaCl  4.3  grms.  water  passed  into  the 
endosmometer.     The  following  numbers  give  the  endosmotic  equivalent  of — 


Magnesium  sulphate =:    11.7 

Potassium  sulphate =    12.0 

Sulphuric  acid =      0.39 

Potassium  hydrate =  215.0 

ugh  the  membrane  into  the  water  of  the  cylinder 
(  Vierordt).     If  the  water  in  the  cylinder,  there- 


Acid  potassium  sulphate =  2.3 

Common  salt =^  4.3 

Sugar       =  7-1 

Sodium  sulphate =11.6 

The  amount  of  the  substance  which  passes  thn 
is  proportional  to  the  concentration  of  the  solutio 

fore,  be  repeatedly  renewed,  the  endosmosis  takes  place  more  rapidly  and  the  process  of  equilibra- 
tion is  accelerated.  The  larger  the  pores  of  the  membrane,  and  the  smaller  the  molecules  of  the 
substance  in  solution,  the  more  rapid  is  the  endosmosis.  Hence,  the  rapidity  of  the  endosmosis  of 
different  substances  varies — thus,  the  rapidity  of  sugar,  sodium  sulphate,  common  salt,  and  urea  is 
in  the  ratio  of  I  :  I.I  :  5  :  9.5  {Eckhard,  Hoffmann). 

The  endosmotic  equivalent  is  not  eonstant /or  each  substance.  It  is  influenced  by — { I )  The  tem- 
perature, which,  as  it  increases,  generally  increases  the  endosmotic  equivalent.  (2)  It  also  varies 
with  the  degree  of  concentration  of  the  osmotic  solutions,  being  greater  for  dilute  solutions  of  the 
substances  (C  Ltidwig  and  Cloetta). 

If  a  substance  other  than  water  be  placed  in  the  cylinder,  an  endosmotic  current  occurs  on  both 
sides  until  complete  equality  is  obtained.  In  this  case,  the  currents  in  opposite  directions  disturb 
each  other.     If  two  substances  be  dissolved  in  the  water  in  the  flask  at  the  same  time,  they  diffuse 


ABSORPTIVE    ACTIVITY   OF   THE    INTESTINAL   WALL.  327 

into  water  without  afl'ecting  each  other.  (3)  It  also  varies  with  membranes  of  varying  porosity. 
Common  salt,  which  gives  an  endosmotic  equivalent  with  a  pig's  bladder  =  4.3,  gives  6.4  when  an 
ox  bladder  is  used;  2.9  with  a  swimming  bladder;  and  20.2  with  a  collodion  membrane  (Hmzer). 
Colloids. — There  is  a  number  of  fluid  substances  which,  on  account  of  the  great  size  of  their 
molecules,  do  not  pass,  or  pass  only  with  difficulty,  through  the  pores  of  a  membrane  impregnated 
with  gelatinous  bodies,  which  diffuse  slowly.  These  substances  are  not  actually  in  a  true  state  of 
solution,  but  exist  in  a  very  dilute  condition  of  imbibition.  Such  substances  are  the  fluid  proteids, 
starches,  dextrin,  gum,  and  gelatin.  These  diffuse  when  no  septum  is  present,  but  difi'use  with 
difficulty  or  not  at  all  through  a  porous  septum.  Graham  called  these  substances  colloids,  because 
when  concentrated,  they  present  a  glue  like  or  gelatinous  appearance  ;  further,  they  do  not  crystal- 
lize, while  those  substances  which  diffuse  readily  are  crystalline,  and  are  called  crystalloids. 
Crystallizable  substances  may  be  separated  from  non-crystallizable  by  this  process,  which  Graham 
called  dialysis.     Mineral  salts  favor  the  passage  of  colloids  through  membranes  (Baranetziy). 

That  Endosmosis  takes  place  in  the  intestinal  tract,  through  the  mucous 
membrane  and  the  delicate  membranes  of  the  blood  and  lymph  capillaries,  can- 
not be  denied.  On  the  one  side  of  the  membrane,  within  the  intestine,  are  the 
highly  diffusible  peptones,  sugar,  and  soaps,  and  within  the  blood  vessels  are  the 
colloids  which  are  scarcely  diffusible,  e.g.,  the  proteids  of  blood  and  lymph. 

II.  Filtration  is  the  passage  of  fluids  through  the  coarse  intermolecular  pores  of  a  membrane, 
owing  to  pressure.  The  greater  the  pressure,  and  the  larger  and  more  numerous  the  pores,  the 
more  rapidly  does  the  fluid  pass  through  the  membrane  ;  increase  of  temperature  also  accelerates  it. 
Those  substances  which  are  imbibed  by  the  membrane  filter  most  rapidly,  so  that  the  same  sub- 
stance filters  through  different  membranes  with  varying  rapidity.  The  filtration  is  usually  slower, 
the  greater  the  concentration  of  the  fluid.  The  filter  has  the  property  of  retaining  some  of  the  sub- 
stances from  the  solution  passing  through  it,  e.  g.,  colloid  substances — or  water  (in  dilute  solutions 
of  nitre).  In  the  former  case,  the  filtrate  is  more  dilute,  in  the  latter  more  concentrated  than  before 
filtration.  Other  substances  filter  without  undergoing  any  change  of  concentration.  Many  mem- 
branes behave  differently,  according  to  which  surface  is  placed  next  to  the  fluid;  thus  the  shell- 
membrane  of  an  egg  permits  filtration  only  from  without  inward ;  [and  the  same  is  true  to  a  much  less 
extent  with  filter  paper  ;  the  smooth  side  of  the  filter  paper  ought  always  to  be  placed  next  the  fluid 
to  be  filtered.  The  intact  skin  of  the  grape  prevents  the  entrance  of  fungi].  There  is  a  similar 
difference  with  the  gastric  and  intestinal  mucous  membrane. 

[Filtration  of  Albumin. — Runeberg  finds  that  the  amount  of  albumin  in  pathological  transuda- 
tions varies  with  (I)  the  capillary  area,  being  least  in  cedema  of  the  subcutaneous  tissue.  (2)  The 
presence  or  absence  of  inftammatory  processes  in  the  vascular  wall,  non  inflammatory  pleuritic  effu- 
sion containing  2  per  cent.,  and  inflammatory  6  per  cent.,  of  albumin.  (3)  The  condition  and 
amount  of  albumin  in  the  blood.  The  amount  of  albumin  in  the  transudate  never  reaches,  although 
it  sometimes  approaches,  that  in  blood.  In  ascites  in  general  dropsy  the  amount  is  .03  to  .04  per 
cent.  (4)  l^ie  duration  oi  the  transudation.  (5)  Perhaps  the  blood  pressure  and  the  condition 
of  the  circulation.] 

[By  using  numerous  layers  of  filter  paper,  many  colloids  and  crystalloids  are  retained  in  the  filter, 
e.g.,  ha;moglobin,  albumin,  and  many  coloring  matters,  especially  anilin  colors,  the  last  being 
arrested  by  glass-wool  (^Krysinski).'\ 

Filtration  of  the  soluble  substance  may  take  place  from  the  canal  of  the  digest- 
ive tract  when — (i)  The  intestine  contraets  and  thus  e.\erts  pressure  upon  its 
contents.  This  is  possible  when  the  tube  is  narrowed  at  two  points,  and  the  mus- 
culature between  these  two  points  contracts  upon  the  fluid  contents.  (2)  Filtra- 
tion, under  negative  pressure,  may  be  caused  by  the  villi  {Briieke).  When 
the  villi  contract  energetically,  they  empty  their  contents  toward  the  blood  and 
lymph  vessels.  The  lymph  vessels  remain  empty,  as  the  chyle  is  prevented  from 
passing  backward  into  the  origin  of  the  lacteal  within  the  villi,  owing  to  the 
presence  of  numerous  valves  in  the  lymphatics.  When  the  villi  pass  again  into 
the  relaxed  condition,  they  again  become  filled  with  fluids  from  the  intestinal 
contents. 

192.  ABSORPTIVE     ACTIVITY     OF    THE    INTESTINAL 

WALL.^The  process  of  digestion  produces  from  the  food  partly  solutions  and 
partly  finely  divided  emulsions,  whose  fine  particles  are  said  to  be  surrounded  by 
an  albuminous  envelope,  the  haptogen  membrane  [of  Ascherson],  whereby  these 
particles  become  more  stable.  Unchanged  colloid  substances  may  also  be  present 
in  the  intestinal  tract. 


328        ABSORPTION    OF    SOLUBLE    CARBOHYDRATES    AND    PEPTONES. 

I.  Absorption  of  Solutions. — True  solutions  undoubtedly  pass  by  endos- 
mosis  into  the  blood  vessels  and  lymphatics  of  the  intestinal  walls,  but  numerous 
facts  indicate  that  the  protoplasm  of  the  cells  of  the  tube  take  an  active  part  in 
the  process  of  absorption.  The  forces  concerned  have  not  as  yet  been  referred 
simply  to  physical  and  chemical  processes. 

(i)  The  Inorganic  substances. — Water  and  the  soluble  salts  necessary 
for  nutrition  are  easily  absorbed,  the  latter  especially  by  the  blood-  and  lymph 
vessels.  When  saline  solutions  pass  by  endosmosis  into  the  vessels,  water  must 
pass  from  the  intestinal  vessels  into  the  intestine.  The  amount  of  water,  however, 
is  small,  owing  to  the  small  endosmotic  equivalent  of  the  salts  to  be  absorbed. 
More  salts  are  absorbed  from  concentrated  than  from  dilute  solutions  (Fu>ike).  If 
large  quantities  of  salts,  with  a  high  endosmotic  equivalent,  are  introduced  into 
the  intestine,  e.g.,  magnesium  or  sodium  sulphate,  these  salts  retain  the  water  ne- 
cessary for  their  solution,  and  thus  diarrhcea  is  caused  {Foiscuine,  Biichhcini). 
Conversely,  when  these  substances  are  injected  into  the  blood  a  large  quantity  of 
water  passes  from  the  intestine  into  the  blood,  so  that  constipation  occurs,  owing 
to  dryness  of  the  intestinal  contents  {^Aiibcrt).  [M.  Hay  concludes  from  his  ex- 
periments ($)  i6i),  that  salts,  when  placed  in  the  intestines,  do  not  abstract  water 
from  the  blood,  or  are  themselves  absorbed,  in  virtue  of  an  endosmotic  relation 
being  established  between  the  blood  and  the  saline  solution  in  the  intestines.  Ab- 
sorption is  probably  due  to  the  filtration  and  diffusion,  or  processes  of  inhibition 
other  than  endosmosis,  as  yet  little  understood.  The  result  obtained  by  Aubert, 
which  is  not  constant,  is  mostly  caused  by  the  great  diuresis  which  the  injected 
salts  excites.] 

Numerous  inorganic  substances,  which  do  not  occur  in  the  body,  are  absorbed  by  endosmosis 
from  the  intestine,  f.^.,  dilute  sulphuric  acid,  potassium  iodide,  chlorate,  and  bromide,  and  many 
other  salts. 

(2)  The  soluble  carbohydrates,  such  as  the  sugars,  of  which  the  chief  rep- 
resentatives are  dextrose  and  maltose,  with  a  relatively  high  endosmotic  equiva- 
lent. Cane  sugar  is  changed  by  a  special  ferment  into  invert  sugar  (§  183,  5). 
Absorption  appears  to  take  place  somewhat  slowly,  as  only  very  small  quantities 
of  grape  sugar  are  found  in  the  chyle  vessels  or  the  portal  vein,  at  any  time. 
.\ccording  to  v.  Merings  the  suga}-  passes  from  the  intestine  into  the  rootlets  of  the 
portal  vein  ;  dextrin  also  occurs  in  the  portal  vein.  When  the  blood  of  the  portal 
vein  is  boiled  with  dilute  sulphuric  acid,  the  amount  of  sugar  is  increased  i^Nau- 
nyii).  The  amount  of  sugar  absorbed  depends  upon  the  concentration  of  its  solu- 
tion in  the  intestine ;  hence  the  amount  of  sugar  in  the  blood  is  increased  after  a 
diet  containing  much  of  this  substance  (C.  Schmidt  and  v.  Becker'),  so  that  it  may 
appear  in  the  urine;  in  which  case  the  blood  must  contain  at  least  0.6  per  cent, 
of  sugar  {Lehinann  and  Uhle).  A  small  amount  of  cane  sugar  has  also  been 
found  in  the  blood  (C7.  Bernard,  Hoppc-Seylcr).  The  sugar  is  used  up  in  the 
bodily  metabolism  ;  some  of  it  is,  perhaps,  oxidized  in  the  muscles  {Ziminer). 
[Compare  effects  of  injecting  grape  sugar  into  the  blood  (§  176).] 

(3)  The  peptones  have  a  small  endosmotic  equivalent  tyFunke),  a  2  to  9  per 
cent  solution  ^  7  to  ro.  Owing  to  their  great  diffusibility  they  are  readily  absorbed, 
and  they  are  the  chief  representatives  of  the  proteids  which  are  absorbed.  The 
amount  absorbed  depends  upon  the  concentration  of  the  solution  in  the  intestine. 
They  pass  into  the  bloodvessels  {Schmidt- Miilheim).  When  animals  are  fed  on 
peptones  (with  the  necessary  fat  or  sugar),  they  serve  to  maintain  the  body  weight 
(Maly,  Ftbsz  and  Gybrgyai).  Only  minute  quantities  of  peptone  have  as  yet  been 
found  in  the  blood  {Drosdorjf )  ;  hence,  it  is  assumed,  either  that  they  are  rapidly 
converted  into  true  albuminous  bodies,  or  that,  in  part  at  least,  they  undergo 
further  decompositions,  with  which  we  are  as  yet  unacquainted.  As,  however, 
they  can  compensate  for  the  total  metabolism  of  the  proteids  within  the  body,  we 
must  assume  that  they  are  converted  into  proteids.     Hofmeister  supposes  that  the 


ABSORPTION    OF    FATTY    PARTICLES.  329 

leucocytes  absorb  the  peptones  and  act  as  their  carriers,  much  as  the  red  corpus- 
cles are  oxjgen  carriers.  They  carry  the  peptones  into  the  mucous  membrane  of 
the  stomach  and  small  intestine,  which  are  very  rich  in  peptone  at  the  fourth  hour 
of  digestion.  It  is  asserted  by  Salivoli  that  tiie  mucous  membrane  possesses  the 
property  of  changing  peptone  into  albumin.  Only  a  part  of  the  peptone  passes 
unchanged  into  the  blood,  and  disappears  from  it  after  its  passage  through  the 
tissues. 

[Injection  of  Peptone  into  Blood  — When  peptone  is  injected  into  the  blood  of  an  animal, 
within  twenty  minutes  thereafter  no  trace  of  the  peptone  is  lo  be  found  in  the  blood,  although  it  has 
not  been  excreted  by  any  of  the  organs.  Peptone  so  injected  prevents  the  blood  of  the  dog  (not  of 
the  rabbit  or  pig)  from  coagulating  (p.  48).  Faiio  asserts  that  the  peptone  is  taken  up  by  the  red 
blood  corpuscles,  which  thus  become  of  greater  specific  gravity,  and  change  it  into  globulin.  After 
three  or  more  hours  the  corpuscles  return  the  globulin  to  the  blood,  so  that  the  corpuscles  represent 
a  reserve  store  of  proteid.] 

(4)  Unchanged  true  proteids  filter  with  great  difficulty,  and  much  albumin 
remains  upon  the  filter.  On  account  of  their  high  endosmotic  equivalent  they 
pass  with  extreme  difficulty,  and  only  in  traces,  through  membranes.  Neverthe- 
less, it  has  been  conclusively  proved  that  unchanged  proteids  can  be  absorbed 
{Briicke),  e.g.,  casein,  soluble  myosin,  alkali  albuminate,  albumin  mixed  with 
common  salt,  gelatin  {Fc?//,  Bauer,  Eiehhorst).  They  are  absorbed  even  from  the 
large  intestine  (Czer/ty  and  La/se/te//ierger),  although  the  human  large  intestine 
cannot  absorb  more  than  6  grms.  daily.  But  the  amount  of  unchanged  proteids 
absorbed  is  always  very  much  less  than  the  amount  of  peptone. 

Egg  albumin  without  common  salt,  syntonin,  serum  albumin,  and  fibrin  are  not  absorbed  (Eieh- 
horst). Landois  observed  in  the  case  of  a  young  man  who  took  the  whites  of  14  to  20  eggs  along 
with  NaCl,  that  albumin  was  given  off  Ijy  the  urine  for  4  to  10  hours  thereafter.  The  amount  of 
albumin  given  off  rose  until  the  third  day  and  ceased  on  the  fifth  day.  The  more  albumin  that  was 
taken  the  sooner  the  albuminuria  appeared  and  the  longer  it  lasted.  The  unchanged  egg  albumin 
reappeared  in  the  urine.  If  egg  albumin  be  injected  into  the  blood,  part  of  it  reappears  in  the 
urine  (J  41,  2)  [Stoivis,  I.ehnianii). 

(5)  The  soluble  fat  soaps  represent  only  a  fraction  of  the  fats  of  the  food 
which  are  absorbed  ;  the  greater  part  of  the  neutral  fats  being  absorbed  in  the 
form  of  very  fine  jjarticles — as  an  emulsion  (§  192,  11).  The  absorbed  soaps  have 
been  found  in  the  chyle,  and  as  the  blood  of  the  portal  vein  contains  more  soaps 
during  digestion  than  during  hunger,  it  has  been  assumed  that  the  soaps  pass  into 
the  intestinal  blood  capillaries.  The  investigations  of  Lenz,  Bidder  and  Schmidt 
render  it  probable  that  the  organism  can  absorb  only  a  limited  amount  of  fat 
within  a  given  period  ;  the  amount  perhaps  bears  a  relation  to  the  amount  of  bile 
and  pancreatic  juice.  The  maximum  per  i  kilo,  (cat)  was  0.6  grm.  of  fat  per 
hour. 

It  appears  as  if  the  soaps  reunite  with  glycerine  in  the  parenchyma  of  the  villi, 
to  form  neutral  fats,  as  Perewoznikoff  and  Will  found,  after  injecting  these  two 
ingredients  into  the  intestinal  canal.  C.  A.  Ewald  found  that  fat  was  formed 
when  soaps  and  glycerine  were  brought  into  contact  with  the  fresh  intestinal 
mucous  membrane.  Perhaps  this  is  the  explanation  of  the  observation  of  Bruch, 
who  found  fatty  particles  within  the  blood  vessels  of  the  villi. 

Absorption  of  other  Substances. — Of  soluble  substances  which  are  introduced  into  the  intes- 
tinal canal,  some  are  absorbed  and  others  are  not.  The  following  are  absorbed  :  alcohol,  part  of 
which  appears  in  the  urine  (not  in  the  expired  air),  viz.,  that  part  which  is  not  changed  into  COj 
and  HjO,  within  the  body;  tartaric,  citric,  malic,  and  lactic  acids;  glycerine,  inulin  (Komanos); 
gum  and  vegetable  mucin,  which  give  rise  to  the  formation  of  glycogen  in  the  liver. 

Among  coloring  matters,  alizarin  (from  madder),  alkannet,  indigo-sulphuric  acid,  and  its  soda 
salt  are  absorbed  ;  h;ematin  is  partly  absorbed,  while  chlorophyll  is  not.  Metallic  salts  seem  to 
be  kept  in  solution  by  proteids,  are  perhaps  absorbed  along  with  them,  and  are  partly  carried  by 
the  blood  of  the  portal  vein  to  the  liver  (ferric  sulphate  has  been  found  in  chyle).  Numerous 
poisons  are  very  rapidly  absorbed,  e.  g.,  hydrocyanic  acid  after  a  few  seconds  ;  potassium  cyanide 
has  been  found  in  the  chyle.     [If  salts  (IvI,  sulphocyanide  of  ammonium)  be  injected   into  a  liga- 


330  ABSORPTION    OF    FATTY    PARTICLES. 

tured  loop  of  intestine  (dog,  cat,  rabbit),  these  substances  are  absorbed  both  by  the  blood  and  lymph 
vessels,  and  in  both  nearly  simultaneously  (A'.  B.  Leii??innn).~\ 

II.  Absorption  of  the  smallest  particles. — The  largest  amount  of  the  fats 
is  absorbfd  in  the  form  of  a  milk  like  emulsion,  formed  by  the  action  of  the 
bile  and  the  ])ancreatic  juice,  and  consisting  of  excessively  sinall  granules  of  uni- 
form size  (i^  170,  III  ;  §  181).  The  fats  themselves  are  not  chemically  changed, 
but  remain  as  undecomposed  neutral  fats.  The  particles  seem  to  be  surrounded 
by  a  delicate  albuminous  envelope,  or  haptogen  membrane,  partly  derived  from 
the  pancreatic  juice  [probably  froin  its  alkali  albuminate].  The  villi  of  the  small 
intestine  are  the  chief  organs  concerned  in  the  absorption  of  the  fatty  emulsion, 
but  the  epithelium  of  the  stomach  and  that  of  the  large  intestine  also  take  a  part. 
The  fatty  granules  are  recognized  in  the  villi — (i)  Within  the  delicate  canals? 
(§  190)  in  the  clear  band  of  the  epithelium  {Ko/likcr).  [It  is  highly  doubtful  if 
the  vertical  lines  seen  in  the  clear  disk  of  the  epithebum  of  the  intestine  are  due 
to  pores.]  (2)  The  protoplasm  of  the  epithelial  cells  is  loaded  with  fatty  granules 
of  various  sizes  during  the  time  of  absorption,  while  the  nuclei  of  the  cells  remain 
free,  although,  from  the  amount  of  fat  within  the  cells,  it  is  often  difficult  to  dis- 
tinguish them.  (3)  The  granules  pass  into  the  spaces  of  the  parenchyma  of  the 
villi ;  these  spaces  communicate  freely  with  each  other.  (4)  The  origin  of  the 
lacteal  in  the  axis  of  the  villus  is  found  to  be  filled  with  fatty  granules.  The 
amount  of  fat  in  the  chyle  of  a  dog,  after  a  fatty  meal,  is  8  to  10  per  cent.,  while 
the  fat  disappears  from  the  blood  within  thirty  hours. 

Forces  concerned. — With  regard  to  the  forces  concerned  in  the  absorp- 
tion of  fats,  V.  Wistinghausen  proved,  that  when  a  porous  membrane  is  moist- 
ened with  bile,  the  passage  of  fatty  particles  through  it  is  thereby  facilitated,  but 
this  fact  alone  does  not  explain  the  copious  and  rapid  absorption  of  fats.  It  is 
possible  that  the  protoplasm  of  the  epithelial  cells  is  actively  concerned  in  the 
process,  and  that  it  takes  the  particles  into  its  interior.  Perhaps  a  fine  proto- 
plasmic process  is  thrown  out  by  these  cells,  just  as  pseudopodia  are  thrown  out 
and  retracted  by  lower  organisms.  It  is  possible  that  absorption  may  take  place 
through  the  open  mouths  of  the  goblet  cells.  The  protoplasm  of  the  epithelial 
cells  is  in  direct  communication  with  the  numerous  protoplasmic  lymph  cells  within 
the  reticulum  of  the  villi,  so  that  the  particles  may  pass  into  these,  and  from  them 
through  the  stomata  (?)  between  the  endothelial  cells  into  the  central  lacteal  of  the 
villus.  According  to  this  view,  the  absorption  of  tatty  particles,  and  perhaps  also 
the  absorption  of  true  proteids,  is  due  to  an  active  vital  process,  as  indicated  by 
the  observations  of  Briicke  and  v.  Thanhoffer.  This  view  is  suported  by  the  ob- 
servation of  Griinhagen,  that  the  absorption  of  fatty  particles  in  the  frog  is  most 
active  at  the  temperature  at  which  the  motor  phenomena  of  protoplasm  are  most 
lively.  That  it  is  due  to  simple  filtration  alone  is  not  a  satisfactory  explanation, 
for  the  amount  of  fatty  particles  in  the  chyle  is  independent  of  the  amount  of 
water  in  it.  If  absorption  was  chiefly  due  to  filtration,  we  would  expect  that  there 
would  most  probably  be  a  direct  relation  between  the  amount  of  water  and  fat 
{Luihvig  and  Zawi/sky).  [The  observations  of  Watney  have  led  him  to  suppose 
that  the  fatty  particles  do  not  pass  through  the  cell  protoplasm  to  reach  the  lacteal, 
but  that  they  pass  through  the  cement  siibstaiiee  between  the  epithelial  cells  cover- 
ing a  villus.  If  this  view  be  correct,  the  absorbing  surface  is  thereby  greatly  di- 
minished.] 

[Zuwarykin,  and  also  .Schafer,  suggest  that  the  leucocytes,  which  have  been 
observed  between  the  columnar  cells  of  the  villi  of  the  small  intestine,  are  carriers 
of  at  least  part  of  the  fat  from  the  lumen  of  the  gut  to  the  lacteal ;  they  also, 
perhaps,  alter  it  for  further  use  in  the  economy  (p.  322).  According  to  Zuwa- 
rykin, Peyer's  patches,  in  the  rabbit,  seem  to  be  especially  active  in  the  absorp- 
tion of  fat,  so  that  he  attaches  great  importance  to  the  leucocytes  of  the  adenoid 
tissue  in  the  absorption  of  fat.] 


FEEDING    WITH    "NUTRIENT    ENEMATA."  331 

The  activity  of  the  cells  of  the  intestine  with  pseudopodial  processes  may  be  studied  in  the  intes- 
tinal canal  of  Distomum  hepaticum.  Sommer  has  figured  these  pseudopodial  processes  actively 
engaged  in  the  absorption  of  panicles  from  the  intestine.  Spina  observed  that  the  intestinal  epi- 
thehum  of  the  larva;  of  flies  shortened  when  they  were  stimulated  with  electricity,  and  absorbed 
fluid  from  the  intestinal  canal.  The  cells  of  the  villi  of  the  frog  also  react  to  electrical  stimulation. 
The  increase  in  the  size  of  the  cells  occurs  simultaneously  with  the  contraction  of  the  intestine. 
Spina  also  supports  the  view  that  the  cells,  by  virtue  of  their  activity,  possess  the  property  of  absorb- 
ing fluid  from  the  intestinal  contents,  and  again  giving  it  up.  An  exchange  of  fluids  in  the  opposite 
direction  never  takes  place. 

The  statements  of  former  observers,  that  particles  of  charcoal,  pigments,  and  even  mammalian 
blood  corpuscles  (in  the  frog),  were  absorbed  by  the  epithelial  cells  of  the  intestine,  and  passed  into 
the  blood,  are  erroneous.  Even  for  the  absorption  of  completely  fluid  substances,  endosmosis  and 
filtration  seem  to  be  scarcely  sufficient.  An  active  participation  of  the  protoplasm  of  the  cells  seems 
here  also — in  part,  at  least — to  be  necessary,  else  it  is  difficult  to  explain  how  very  slight  disturbances 
in  the  activity  of  these  cells — e.^.,  from  intestinal  catarrh — cause  sudden  variations  of  absorption, 
and  even  the  passage  of  fluids  into  the  mtestine. 

If  absorption  was  due  to  diffusion  alone,  when  alcohol  is  injected  into  the  intestine,  water  ought 
to  pass  into  the  intestine,  but  this  does  not  occur.  Brieger  found  that  the  injection  of  a  0.5  to  I 
per  cent,  solution  of  salts  into  a  ligatured  loop  of  intestine  did  not  cause  water  to  pass  into  the  intes- 
tine ;  but  it  appeared  when  a  20  per  cent,  solution  was  injected. 

193.  INFLUENCE  OF  THE  NERVOUS  SYSTEM.— With  regard 

to  the  influence  of  the  nervous  system  upon  intestinal  absorption  we  know  very- 
little.  After  extirpation  of  the  semilunar  ganglion  {Budge),  as  well  as  after  sec- 
tion of  the  mesenteric  nerves  (jl/frfaw),  the  intestinal  contents  become  more  fluid 
and  are  increased  in  amount  (§  183).  This  may  be  partly  due  to  diminished 
absorption.  V.  Thanhoffer  states  that  he  observed  the  protrusion  of  threads  from 
the  epithelial  cells  of  the  small  intestine  only  after  the  spinal  cord,  or  the  dorsal 
nerves,  had  been  divided  for  some  time. 

[Matthew  Hay  injected  saline  solutions  directly  into  the  exposed  intestine.  He  found  that  a  20 
per  cent,  solution  of  sulphate  of  .soda  always  excites  a  profuse  secretion,  but  that  a  10  per  cent, 
solution  only  does  so — or,  rather,  that  it  only  increases  in  bulk,  when  injected  in  sufficient  quantity 
— a  certain  weight  of  salt  failing  to  increase  the  bulk  of  the  fluid  secretion  when  dissolved  as  a  10 
per  cent,  solution,  but  exciting  a  profuse  secretion  when  forming  a  20  per  cent,  solution.  Secretion, 
he  has  reason  to  believe,  is  active  in  both — perhaps,  almost  equally  active;  but  absorption  is  greatly 
impeded  in  the  case  of  the  concentrated  salt,  by  its  injurious  action  on  the  absorptive  mechanism  of 
the  mucous  membrane.  Moreau  has  recently  maintained  that,  under  .such  circumstances,  there  is, 
actually,  no  absorption  ;  but  Hay  has  disproved  this,  by  observing  that  strychnia  injected  into  a  loop 
of  intestine  containing  the  concentrated  salt,  still  causes  death,  although  after  an  interval  three  times 
longer  than  when  the  loop  contains  a  10  per  cent,  solution  of  the  salt.  Hay  has  also  observed  that 
the  local  effect  of  a  ligature  applied  to  the  intestine  is  to  excite  secretion  from  the  mucous  membrane 
in  its  immediate  vicinity,  and,  therefore,  add  to  the  bulk  of  the  saline  solution;  whereas,  the 
reflex  effect  of  a  ligature,  as  exercised  through  the  nervous  system,  is  to  diminish  the  quantity  of 
the  secreted  fluid  in  a  remote  portion  of  the  intestine,  probably  by  stimulating  and  accelerating 
absorption.     Division  of  the  vagi  does  not  affect  the  nature  or  the  quantity  of  the  secretion.] 

194.  FEEDING  WITH  "  NUTRIENT  ENEMATA."— In  cases  where  food  cannot  be 
taken  by  the  mouth,  e.  g.^  in  stricture  of  the  oesophagus,  continued  vomiting,  etc.,  food  is  given  per 
rectum  (Cdstis,  3-5  a. I).).  As  the  digestive  activity  of  the  large  intestine  is  very  slight,  fluid  food 
ought  to  be  given  m  a  condition  ready  to  be  absorbed,  and  this  is  best  done  by  introducing  it  into 
the  rectum  through  a  tube  with  a  funnel  attached,  and  allowing  the  food  to  pass  in  slowdy  by  its 
own  weight.  The  patient  must  endeavor  to  retain  the  enema  as  long  as  possible.  When  the  fluid 
is  slowly  and  gradually  mtroduced,  it  may  pass  above  the  ileo-caecal  valve. 

Solutions  of  grape  sugar,  and,  perhaps,  a  small  amount  of  soap  solution,  are  useful ;  and  among 
nitrogenous  substances,  the  commercial  flesh-,  bread-  or  mdk  peptones  of  Sanders-Ezn,  Adam- 
kiewicz,  in  Germany,  and  Darby's  fluid  meat,  and  Carnrick's  beef  peptonoids  in  this  country, 
are  to  be  recommended.  The  amount  of  peptone  required  is  I. II  grms.  per  kilo,  of  body  weight 
[Catillon)  \  less  useful  are  buttermilk,  egg  albumin,  with  common  salt.  Leube  uses  a  mixture  of 
150  grms.  flesh,  with  50  grms.  pancreas  and  100  grms.  water,  which  he  slowly  injects  into  the  rectum, 
where  the  proteids  are  peptonized  and  absorbed.  [Peptonized  food  prepared  after  the  method  of 
Roberts  is  very  useful  (§  172).]  The  method  of  nutrient  enemata  only  permits  imperfect  nutrition, 
and,  at  most,  only  %  of  the  proteids  necessary  for  maintaining  the  metabolism  of  the  body  is  ab- 
sorbed (y.  Voit,  Bauer).  [Horace  Dobell  recommends  that  a  %  11)  of  cooked  beef  or  mutton  be 
grated,  and  to  it  added  20  grms.  of  pancreas  powder  and  the  same  of  pepsin.  Mix  the  whole  in  a 
warm  mortar,  and  add  a  tablespoonful  of  brandy  and  warm  water,  sufficient  to  make  a  semi-fluid 
mass,  which  is  to  be  injected  into  the  rectum.] 


332  ORIGIN    OF   THE    LYMPHATICS. 

195.  CHYLE  VESSELS  AND  LYMPHATICS.— Lymphatics— Within  the  tissues  of 
the  body,  and  even  in  those  tissues  which  do  not  contain  blood  vessels,  e.g ,  the  cornea,  or  in  those 
which  contain  few  blood  vesseU,  there  exists  a  system  of  vessels  or  channels  which  contain  the 
juices  of  the  tissues,  and  within  these  vessels  the  fluid  always  moves  in  a  centripetal  direction. 
These  canals  arise  within  the  tissues  in  a  variety  of  ways,  and  unite  in  their  course  to  form  delicate, 
and  afterward  thicker,  tubes,  which,  ultimately,  terminate  in  two  large  trunks  which  open  at  the 
junction  of  the  jugular  and  subclavian  veins;  that  on  the  left  side  is  the  thoracic  duct,  and  that  on 
the  right,  the  right  lymphatic  trunk. 

Lymph. — With  regard  to  the  lymph  and  its  movements  in  different  organs,  it 
is  to  be  noticed  that  this  occurs  in  different  ways  in  different  places,  (i)  In 
many  tissues,  the  lymphatics  represent  the  nutrient  channels,  by  which  the 
fluid  which  transudes  through  the  neighboring  vessels  is  distributed,  as  in  the 
cornea  and  in  many  connective  tissues.  (2)  In  many  tissues,  as  in  glands,  e.g., 
the  salivary  glands  {Gianiizzi)  and  the  testis,  the  lymph  spaces  are  the  chief 
reservoirs  for  fluid,  from  which  the  cells,  during  the  act  of  secretion,  derive 
the  fluid  necessary  for  that  process.  (3)  The  lymphatics  have  the  general  func- 
tion of  collecting  the  fluid  which  saturates  the  tissues,  and  carrying  it  back  again 
to  the  blood.  The  capillary  blood  system  may  be  regarded  as  an  irrigation 
system,  which  supplies  the  tissues  with  nutrient  fluids,  while  the  lymphatic  system 
may  be  regarded  as  a  drainage  apparatus,  which. conducts  away  the  fluids  that 
have  transuded  through  the  capillary  walls.  Some  of  the  decomposition  products 
of  the  tissues — proofs  of  their  retrogressive  metabolism — become  mixed  with  the 
lymph  stream,  so  that  the  lymphatics  are,  at  the  same  time,  absorbing  vessels. 
Substances  introduced  into  the  parenchyma  of  the  tissues  in  other  ways — e.g.,  by 
subcutaneous  injection — are  partly  absorbed  by  the  lymphatics.  A  study  of  these 
conditions  shows  that  the  lymphatic  system  represents  an  appendix  of  the  blood- 
vascular  system,  and,  further,  that  there  can  be  no  lymph  system  when  the 
blood  stream  is  completely  arrested ;  it  acts  only  as  a  part  of  the  whole,  and  with 
the  whole. 

Lacteals. — When  we  speak  of  the  lymphatics  proper  as  against  the  chyle  ves- 
sels or  lacteals,  we  do  so  from  anatomical  reasons,  because  the  important  and  con- 
siderable lymphatic  channels  coming  from  the  whole  of  the  intestinal  tract  are, 
in  a  certain  sense,  a  fairly  independent  province  of  the  lymphatic  vascular  area, 
and  are  endowed  with  a  high  absorptive  activity,  which,  from  ancient  times,  has 
attracted  the  notice  of  observers.  The  contents  of  the  chyle  vessels  or  lacteals 
are  mi.xed  with  a  large  amount  of  fatty  granules,  giving  the  chyle  a  white  color, 
which  distinguishes  them  at  once  from  the  clear,  watery  contents  of  the  true 
lymphatics.  From  a  physiological  point  of  view,  however,  the  lacteals  must  be 
classified  with  the  lymphatics,  for,  as  regards  their  structure  and  function,  they  are 
true  lymphatics,  and  their  contents  consist  of  true  lymph  mixed  with  a  large 
amount  of  absorbed  substances,  chiefly  fatty  granules.  [The  contents  of  the  lac- 
teals are  white  only  during  digestion,  at  other  times  they  are  clear,  like  lymph.] 

196.  ORIGIN  OF  THE  LYMPHATICS.— The  mode  of  origin  of  the 
lymphatics  varies  within  the  different  tissues.    The  following  modes  are  known  : — 

I.  Origin  in  Spaces. — Within  the  connective  tissues  (connective  tissue  proper,  bone)  are 
numerous  stellate,  irregular,  or  branched  spaces,  which  communicate  with  each  other  by  numerous 
tubular  processes  (Fig.  204,  s) ;  in  these  communicating  spaces  lie  the  cellular  elements  of  these 
tissues.  These  spaces,  however,  are  not  completely  filled  by  the  cells,  but  an  interval  exists  be- 
tween the  body  of  the  cell  and  the  \\'all  of  the  space,  which  is  greater  or  less  according  to  the  con- 
dition of  movement  of  the  protoplasmic  cell.  These  spaces  are  the  so-called  "juice  canals  "  or 
"  saft  canalchen,"  and  they  represent  the  origin  of  the  lymphatic  vessels  {v.  Recklinghausen).  As 
they  communicate  with  neighboring  spaces,  the  movement  of  the  lymph  is  provided  for.  The  cells 
which  lie  in  the  spaces,  and  which  were  formerly  but  erroneously  regarded  by  Virchow  as  the  ori- 
gins of  the  lymphatics,  exhibit  amceboid  movements.  Some  of  these  cells  remain  permanently  each 
in  its  own  space,  within  which,  however,  it  may  change  its  fomr — these  are  the  so-called  "  fixed  " 
connective-tissue  corpuscles,  and  bone  corpuscles — while  others  merely  \a  ander  or  pass  into  these 
spaces,  and  are  called  "wandering  cells,"  or  "leucocytes ;"  but  the  latter  .are  merely  lymph  cor- 
puscles, or  colorless  blood  corpuscles  which  have  passed  out  of  the  blood  vessels  into  the  origin  of 


ORIGIN    OF   THE    LYMPHATICS. 


333 


the  lymphatics.  These  cells  exhibit  amoeboid  movements.  These  spaces  communicate  %vith  the  small 
tubular  lymphatics — the  so-called  lymph  capillaries  (L).  The  spaces  lie  close  together  where  they 
pass  into  a  lymph  capillary  (a).  The  lymph  capillary,  which  is  usually  of  greater  diameter  than 
the  blood  capillary,  generally  lies  in  the  middle  of  the  space  within  the  capillary  arch  (B).  The 
finest  lymphatics  are  lined  by  a  layer  of  delicate,  nucleated  endothelial  cells  (c,^),  with  characteristic 
sinuous  margins,  whose  characters  are  easily  revealed  by  the  action  of  silver  nitrate  (Fig.  205, 
L).  This  substance  blackens  the  cement  substance  which  holds  the  endothelial  cells  together.  Be- 
tween the  endothelial  cells  are  small  holes,  or  stomata,  by  means  of  which  the  lymph  capillaries 
communicate  (at  j)  with  the  juice  canals. 

It  is  assumed  that  the  blood  vessels  communicate  with  the  juice  canals  (J.  Ar- 
nold, Thoma,  Uskoff),  and  that  fluid  passes  out  of  the  thin-walled  capillaries, 
through  their  stomata,  into  these  spaces  (§  65).  This  fluid  nourishes  the  tissues, 
the  tissues  take  up  the  substances  appropriate  to  each,  while  the  effete  materials 
pass  back  into  the  spaces,  and  from  these  reach  the  lymphatics,  which  ultimately 
discharge  them  into  the  venous  blood. 

Whether  the  cells  within  these  spaces  are  actively  concerned  in   the   pouring  out  of  the   blood 
Fig.  204. 


Origin  of  lymphatics  from  the  central  tendon  of  the  diaphragm  of  a  rahbit  (semi-diagrammatic) ;  f,  the  juice 
canals,  communicating  at  x  with  the  lymphatics  :  a,  origin  of  the  lymphatics  by  the  confluence  of  several  juice 
canals.    The  tissue  has  been  stained  witli  nitrate  of  silver. 


plasma,  or  take  part  in  its  movement,  is  matter  for  conjecture.  We  can  imagine  that  by  contracting 
their  body,  after  it  has  been  impregnated  with  fluid,  this  fluid  may  be  propelled  from  space  to  space 
toward  the  lymphatics.  The  leucocytes  wander  through  these  spaces  until  they  pass  into  the 
lymphatics.  Fine  particles  which  are  contained  in  these  spaces — e.g.,  after  tattooing  the 
skin,  and  even  fatty  particles  after  inunction — are  absorbed  by  the  leucocytes,  and  carried  by  them 
to  other  parts  of  the  body.  [The  pigment  particles  used  to  tattoo  the  finger  are  usually  found  within 
the  first  lymphatic  gland  at  the  elbow.] 

After  what  has  been  said  regarding  the  passage  of  colorless  blood  corpuscles 
through  the  stomata  of  the  blood  capillaries,  or  through  the  walls  of  the  smaller 
blood  vessels  (§  95),  the  passage  of  cellular  elements  from  the  blood  vessels  into 
the  origin  of  the  lymphatics  is  to  be  considered  as  a  normal  process  {E.  Hering). 
Granular  coloring  matter  passes  from  the  blood  into  the  protoplasmic  body  of  the 
cells  within  the  lymph  spaces ;  and  only  when  the  granular  pigment  is  in  large 
amount,  does  it  appear  as  a  granular  injection  in  the  branches  of  the  juice  spaces 
(^Uskoff). 


334 


PERIVASCULAR    SPACES. 


(2)  The  origin  of  lymphatics  within  villi — /.  e.,  of  the  chyle  vessel  or  lacteal — has  been  de- 
scribed [\  190).  The  central  lacteal  communicates  with  the  lacunar  interstitial  spaces  in  the  ade- 
noid tissue  of  the  villus,  and  this  again  with  the  protoplasmic  body  of  the  epithelial  cells.  It  is 
assumed  that  the  lymph  corpuscles,  which  lie  in  the  meshes  of  the   adenoid   tissue,  pass  into  the 

Fig.  205. 


Central  tendon  of  the  diaphragm  of   the 
lymphatic  with  its  sinuous  endothel 


ewed  from  the  pleural  side 
brought  into  view  by  the  ; 


central  lacteal  {His),  while  new  cells  are  continually  passing  out  of  the  blood   capillaries  of  the 
villi  into  the  tissue,  where  they  perhaps  undergo  increase  through  division. 

(3)  Origin  of  lymphatics  in  perivascular  spaces  (Fig.  206). — The  smallest  blood  vessels  of 
bone,  the  central  nervous  system,  retina,  and  the  liver,  are  completely  surrounded  by  wide  lymph- 


FlG.  207. 


Perivascular  lymphatics.     A,  aorta  of  tortoise ; 
B,  artery  from  the  brain. 


atic  tubes,  so  that  the  blood  vessels  are  completely  bathed  by  a  lymph  stream.  In  the  brain  these 
lymphatics  are  partly  composed  of  delicate  connective-tissue  fibres,  which  traverse  the  lymph  space 
and  become  attached  to  the  wall  of  the  included  blood  vessel  (Roth).  Fig.  206,  B,  represents  a 
transverse  section  of  a  small  blood  vessel,  B,  from  the  brain;  /  is  the  divided  perivascular  space. 


LYMPH    FOLLICLES. 


335 


This  space  is  called  the  perivascular  space  of  His,  but  in  addition  to  it  the  blood  vessels  of  the  brain 
have  a  lymph  space  within  the  adventitia  of  the  blood  vessels  (  Virchom- Robin' s  space).  It  is  partly 
lined  by  a  well  defined  endothelium.  Where  the  blood  vessels  begin  to  increase  considerably  in 
diameter,  they  pass  through  the  wall  of  the  lymphatics,  and  the  two  vessels  afterward  take  sepa- 
rate courses.  In  all  cases,  where  there  is  a  perivascular  space,  the  passage  of  lymph  and  blood 
corpuscles  into  the  lymphatics  is  greatly  facilitated.  In  the  tortoise  the  large  blood  vessels  are  often 
surrounded  with  perivascular  lymphatics.  Fig.  206,  A,  gives  a  representation  of  the  aorta  sur- 
rounded by  a  perivascular  space  ( Gegenbaur)  which  is  visible  to  the  unaided  eye.  In  mammals  the 
perivascular  spaces  are  microscopic. 

(4)  Origin  in  the  form  of  interstitial  slits  within  organs. — Within  the  testis  the  lymphatics 
begin  simply  in  the  form  of  numerous  slits,  which  occur  between  the  coils  and  twists  of  the  seminal 
tubules.  They  take  the  form  of  elongated  spaces  bounded  by  the  curved  cylindrical  surfaces  of  the 
tubules.  The  surfaces,  however,  are  covered  with  endothelium.  The  lymphatics  of  the  testis  get 
independent  walls  after  they  leave  the  parenchyma  of  the  organ.  In  many  other  glands  the  gland 
substance  is  similarly  surrounded  by  a  lymph  space.  The  blood  vessels  pour  the  lymph  into  these 
spaces,  and  from  them  the  secreting  cells  obtain  the  materials  necessary  for  the  formation  of  their 
secretion. 

(5)  Origin  by  means  of  free  stomata  on  the  walls  of  the  larger  serous  cavities  (Fig.  207,  a). 
— The  investigations  of  v.  Recklinghausen,  Ludwig,  Dybkowsky,  Schweigger-Seidel,  Dogiel,  and 
others  have  shown  that  the  old  view  of  Mascagni,  that  the  serous  cavities  freely  communicate  with 
the  lymphatics,  is  correct.  The  investigation  of  the  serous  surfaces  is  most  easily  accomplished  on 
the  septum  of  the  great  abdominal  lymph  sack  of  the  frog.  Silver  nitrate  distinctly  reveals  the 
presence  of  relatively  large  free  openings  or  stomata  lying  between  the  endothelium.     Each  stoma 


Two  lymph  follicles.     A,  ; 


small  follicle  highly  magnified,  showing  the  adenoid  r 
magnified,  showing  injected  blood  vessels. 


B,  a  follicle  less  highly 


is  bounded  bv  several  germinating  cells,  which  have  a  granular  appearance,  and  undergo  a  change 
of  shape,  so  that  the  size  of  the  stoma  depends  upon  the  degree  of  contraction  of  these  cells ;  thus 
the  stoma  maybe  open  (o),  half  open,  (i>),or  completely  closed  (c).  These  stomata  are  the  origin  of 
the  lymphatics.  The  serous  cavities  belong  therefore  to  tlie  lymphatic  sy»tem,and  fluids  placed  in 
the  serous  cavities  readily  pass  into  the  lymphatics.  The  cavities  of  the  peritoneum,  pleura,  peri- 
cardium, tunica  vaginalis  testis,  arachnoid  space,  aqueous  chambers  of  the  eye  (Sc/iwa/be),  and  the 
labyrinth  of  the  ear,  are  true  lymph  cavities,  and  the  fluid  they  contain  is  to  be  regarded  as  lymph. 

(6)  Free  open  pores  have  been  observed  on  some  n27icoiis membranes^which  are  regarded  as  the 
origin  of  lymphatics,  e.  g.,  in  the  bronchi  (Klein) — the  nasal  mucous  membrane  [Njalmar-Neiberg), 
in  the  trachea  and  larynx. 

Structure. — The  larger  lymphatics  resemble  in  structure  the  veins  of  corresponding  size.  The 
valves  are  particularly  numerous  in  the  lymphatics,  so  that  a  distended  lymphatic  resembUs  a 
chain  of  pearls.     [Lymphatics  have  dilatations  here  and  there  in  their  course  (Fig.  205).] 

197.  LYMPH  GLANDS.— The  so-called  lymphatic  glands  belong  to 
the  lymph  apparatus.  They  are  incorrectly  terined  glands,  as  they  are  merely 
much  branched  lacunar  labyrinthine  spaces  composed  of  adenoid  tissue,  and  inter- 
calated in  the  course  of  the  lymphatic  vessels. 

They  are  simple  and  compound  lymph  glands. 

(1)  The  simple  lymph  glands,  or,  more  correctly,  lymph  follicles,  are  small,  rounded  bodies, 
about  the  size  of  a  pin  head.  They  consist  of  a  mass  of  ailenoid  tissue  (Fig.  208,  A),  ;'.  c,  of  a 
very  delicate  network  of  fine  recticular  fibres  with  nuclei  at  their  points  of  intersection,  and  in  the 


336 


LYMPHATIC    GLANDS. 


spaces  of  the  meshwork  lie  the  lymph  and  the  lymph  corpuscles.  Near  the  surface,  the  tissue  is 
somewhat  denser,  where  it  forms  a  capsule,  which  is  not  however  a  true  capsule,  as  it  is  permeated 
with  numerous  small,  sponge-like  spaces.  Small  lymphatics  come  directly  into  contact  with  these 
lymph  follicles,  and  often  cover  their  surface  in  the  form  of  a  close  network.  The  surface  of  the 
lymph  follicles  is  not  unfrequently  placed  in  the  wall  of  a  lymph  vessel,  so  that  it  is  directly  bathed 
by  the  lymph  stream.  Although  no  direct  canal  like  opening  leads  from  the  follicle  into  the 
lymphatic  stream  in  relation  with  it,  a  communication  must  exist,  and  this  is  obtained  by  the  numer- 
ous spaces  in  the  follicle  itself,  so  that  a  lymph  follicle  is  a  true  lymphatic  apparatus  whose  juices 
and  lymph  corpuscles  can  pass  into  the  nearest  lymphatic  (Briukc).  The  follicles  are  surrounded 
by  a  network  of  blood  vessels  which  send  loops  of  capillaries  into  their  interior  (Fig.  208,  B).  We 
may  assume  that  lymph  corpuscles  pass  from  these  capillaries  into  the  follicle. 

In  connection  with  these  follicles,  including  those  of  the  back  of  the  tongue,  the  solitary  glands 
of  the  intestine  and  the  adenoid  tissue  in  the  bronchial  tract,  the  tonsils,  Peyer's  patches,  it  is  import- 
ant to  remember  that  enormous  numbers  of  leucocytes  pass  out  between  the  epithelial  cells  cover- 
ing  these  follicles.     The  extruded  leucocytes  undergo  disintegration  subsequently  (PJi.  Stdhr). 

(2)  The  compound  lymph  glands — the  so-called  lymphatic  glands— represent  a  collection 
of  lymph  follicles,  whose  form  is  somewhat  altered.  Every  lympli  gland  is  covered  externally  with 
a  connective-tissue  capsule  (Fig.  209,  c),  which  contains  numerous  non-striped  muscular  fibres  (O. 
Heyfelder).  From  its  inner  surface,  numerous  septa  and  trabeculae  (tr)  pass  into  the  interior  of  the 
gland,  so  that  the  gland  substance  is  divided  into  a  large  number  of  compartments.     These  com- 


FiG.  209. 


,  lymph  s 


,  /,  efferent  lymphatics  ;  C,  cortical  substance ;  M , 
capsule,  with  trabecule,  tr.  {Sharpey) 


partments  in  the  cortical  portion  of  the  gland  have  a  somewhat  rounded  form,  and  constitute  the 
alveoli,  while  in  the  medullary  portion  they  have  a  more  elongated  and  irregular  form.  [On  making 
a  section  of  a  lymph  gland  we  can  readily  distinguish  the  cortical  from  the  medullary  portion  of 
the  gland.]  All  the  compartments  are  of  equal  dignity,  and  they  all  communicate  with  each  other 
by  means  of  openings,  so  that  the  septa  bound  a  rich  network  of  spaces  within  the  gland,  which 
communicate  on  all  sides  with  each  other. 

These  spaces  are  traversed  by  the  follicular  threads  (Fig.  2\o,f,f).  These  represent  the  contents 
of  the  spaces,  but  they  are  smaller  than  the  spaces  in  which  they  lie,  and  do  not  come  into  contact 
anywhere  with  the  walls  of  the  spaces.  If  we  imagine  the  spaces  to  be  injected  with  a  mass,  which 
ultimately  shrinks  to  one-half  of  its  original  volume,  we  obtain  a  conception  of  the  relation  of  these 
follicular  threads  to  the  spaces  of  the  gland.  The  blood  vessels  of  the  gland  {l>)  lie  within  these 
follicular  threads.  They  are  surrounded  by  a  tolerably  thick  crust  of  adenoid  tissue,  with  very  fine 
meshes  (x,  x)  filled  with  lymph  corpuscles,  and  with  its  surface  (0,  0)  covered  by  the  cells  of  the 
adenoid  reticulum,  in  such  a  way  as  to  leave  free  communications  through  the  narrow  meshes. 

Between  the  surface  of  the  follicular  threads  and  the  inner  wall  of  all  the  spaces  of  the  gland, 
lies  the  lymph  channel  or  lymph  path  1  B,  B),  which  is  traversed  by  a  reticulum  of  adenoid  tissue, 
containing  relatively  few  lymph  corpuscles.  It  is  very  probable  that  these  lymph  paths  are  lined 
by  endothelium  (v.  Recklinghausen). 

The  vasa  afferentia  (Fig.  209,  n,  /),  of  which  there  are  usually  several,  expand  upon  the  surface 


LYMPHATIC    GLANDS. 


337 


of  the  gland,  perforate  the  outer  capsule,  and  pour  their  contents  into  the  lymph  paths  (C)  of  the 
gland.  The  vasa  efferentia,  which  are  less  numerous  than  the  afiTerentia,  and  come  out  at  the 
hilum,  form  large,  wide,  almost  cavernous  dilatations,  and  they  anastomose  near  the  gland  (c,/). 
Through  them  the  lymph  passes  out  at  the  opposite  surface  of  the  gland.  The  lymph  percolates 
through  the  gland,  and  passes  along  the  lymph  paths,  which  represent  a  kind  of  rete  mirabile  inter- 
posed between  the  afferent  and  efferent  lymph  vessels. 

During  its  passage  through  this  complicated  branched  system  of  spaces,  the  movement  of  the 
lymph  through  the  gland  is  retarded,  and,  owing  to  the  numerous  resistances  which  occur  in  its 
path,  it  has  very  little  propulsive  energy.  The  lymph  corpuscles  which  lie  in  the  meshes  of  the 
adenoid  reticulum  are  washed  out  of  the  gland  by  the  lymph  stream  (Briicke).  The  lymph  cor- 
puscles lying  within  the  follicular  threads  pass  through  the  narrow  meshes  (O)  into  the  lymph 
paths.  The  formation  of  lymph  corpuscles  occurs  either  locally,  from  division  of  the  pre-existing 
cells,  or  new  leucocytes  wander  out  into  the   follicular  threads.     The  movement  of  the  lymph 


Part  of  a  lymphatic  gland.  A,  Vas  afferens;  B,  B.  lymph  paths  within  the  gla 
edge  :  y,y,  follicular  strand  from  the  medulla;  x,x,\is  adenoid  reticulun 
meshed  part  limiting  the  follicular  strands  from  the  lymph  path. 


througl  the  gland  is  favored  by  the  muscular  action  of  the  capsule.  When  the  capsule  contracts 
energetically,  it  must  compress  the  glard  like  a  sponge,  and  the  direction  in  which  the  fluid  moves 
is  regulated  by  the  position  and  arrangement  of  the  valves.  The  researches  of  Teichmann,  His, 
Frey,  Ilriicke  and  v.  Recklinghausen  have  chiefly  contributed  to  the  elucidation  of  the  morpho- 
logical and  physiological  relations  of  the  lymph  glands. 

Chemistry. — In  addition  to  the  constituents  of  lymph,  the  following  chemical  substances  have 
been  fjund  in  lymphatic  glands:   Leucin  (Frericlis  and  Stddeler)  and  Xanthin. 

193.  PROPERTIES  OF  CHYLE  AND  LYMPH.— Chyle  and 
Lymph  are  albuniinous,  colorless,  clear  juices,  containing  lymph  corpuscles, 
which  are  identical  with  the  colorless  blood  corpuscles  (S  9).  In  some  places, 
e.g.-  in  the  Ij'mphatics  of  the  spleen,  especially  in  starving  animals  (^Nasse),  and 


338  COMPOSITION    OF   CHYLE. 

in  the  thoracic  duct,  a  few  colored  blood  corpuscles  have  been  found.  The 
lymph  corpuscles  are  supplied  to  the  lymph  and  chyle  from  the  lymphatic  glands 
and  the  adenoid  tissue.  As  to  their  source  see  §  200,  2.  They  also  pass  out  of 
the  blood  vessels  and  wander  into  the  lymphatics.  As  red  blood  corpuscles  have 
also  been  seen  to  pass  out  of  the  blood  vessels  {^Slricker,  J.  Arnold),  this  explains 
the  occasional  presence  of  these  corpuscles  in  some  lymphatics;  but  when  the 
pressure  within  the  veins  is  high  near  the  ireiUra/  orifice  of  the  thoracic  duct,  red 
blood  corpuscles  may  pass  into  the  thoracic  duct.  But  we  are  not  entitled  to  con- 
clude from  their  pressure  that  lymph  cells  form  red  blood  corpuscles.  In  addi- 
tion, the  chyle  contains  numerous  fatty  granules  each  surrounded  with  an  albu- 
minous envelope.  [Thus  the  chyle,  m  addition  to  the  constituents  of  the  lymph, 
contains,  especially  during  digestion,  a  very  large  amount  of  fat,  in  the  form  of 
the  finely  emulsionized  fat  of  the  food,  which  gives  it  its  characteristic  w/ii/t'  or 
milky  appearance.  During  hunger,  the  fluid  in  the  lacteals  resembles  ordinary 
lymph.  The  fine  fat  granules  constitute  the  so-called  "molecular  basis"  of 
the  chyle.] 

Composition  of  Lymph. — The  lymph  consists  of  a  plasma  with  lymph 
corpuscles  suspended  in  it.  The  corpuscles — for  the  most  part  investigated  in 
the  form  oi  pus  cells — consist  of  a  swollen-up  /ra/c'/f/ and  soluble paraglobulin, 
together  with  lecithin,  cerebri)!,  cholesterin  a.nd/i7l,  while  their  nuclei  }ield  nuclein. 
Nuclein  contains  P,  and  is  prepared  by  the  artificial  digestion  of  pus,  as  it  alone 
remains  undigested  ;  it  is  soluble  in  alkalies,  and  is  precipitated  from  this  solution 
by  acids.  It  gives  a  feeble  xanthoproteic  reaction.  When  subjected  to  the  pro- 
longed action  of  alkalies  and  acids,  it  yields  substances  allied  to  albumin  and 
syntonin.  Miescher  found  glycogen  in  the  lymph  corpuscles  of  serous  fluids  (§ 
24).  The  lymph  plasma  contains  the  three  so-called  fibrin  factors  (§  29), 
derived  very  probably  from  the  breaking  up  of  lymph  corpuscles.  When  lymph 
is  withdrawn  from  the  body,  these  substances  cause  it  to  coagulate.  Coagula- 
tion occurs  slowly,  owing  to  the  formation  of  a  soft,  jelly-like,  small  "lymph 
clot,"  which  contains  most  of  the  lymph  corpuscles.  The  exuded  fluid  or 
lymph  serum  contains  alkali  albuminate  (precipitated  by  acids),  serum  albumin 
(coagulated  by  heat),  ^.wd  paraglobulin- — the  two  latter  occurring  in  the  same  pro- 
portion as  in  blood  serum  ;  37  per  cent,  of  the  coagulable  proteids  is  paraglobu- 
lin iSalvioli).  Peptone  has  been  found  in  chyle  (?  and  perhaps  also  in  lymph)  ; 
also  urea  (  Il'urtz),  leucin  and  sugar. 

(2)  Chyle,  which  occurs  within  the  lacteals  of  the  intestinal  tract,  can  only 
be  obtained  in  very  small  amount  before  it  is  mixed  with  lymph,  and  hence 
the  difficulty  of  investigating  it.  A  few  lymph  corpuscles  occur  even  in  the 
origin  of  lacteals  within  the  villi,  but  their  number  increases  in  the  vessels 
beyond  the  intestine,  more  especially  after  the  chyle  has  passed  through  the 
mesenteric  glands.  The  amount  of  solids  which  undergoes  a  great  increase 
during  digestion,  on  the  contrary,  diminishes  when  chyle  mixes  with  lymph. 
After  a  diet  rich  in  fatty  matters,  the  chyle  contains  innumerable /«//)' ^iJ7-(?««/« 
(2-4 /JL  in  size).  [This  is  the  so-called  "molecular  basis"  of  the  chyle.]  The 
amount  of  fibrin  factors  increases  with  the  increase  of  lymph  corpuscles,  as 
they  are  formed  from  the  breaking  up  of  the  lymph  corpuscles.  Grohe  found 
a  iliastatic  ferment  in  chyle,  which  was  probably  absorbed  from  the  intestine, 
occasionally  sugar,  to  2  per  cent.  i^Colin);  after  much  starchy  food,  lactates 
have  been  found  {Lehmann),  peptone  in  the  leucocytes  (§  192,  I,  3),  and  traces 
of  urea  and  leucin  {JVurts). 

The  Chyle  of  a  person  who  was  executed  contained : — 


Water 90.5  per  cent. 

Solids 95        " 


f  Fibrin trace. 

j  Albumin 7.1 

■j  Fats 0.9 

Extractives I.o 

[  Salts 0.4 


QUANTITY  OF  LYMPH  AND  CHYLE. 


339 


Cl.  Schmidt  found  the  following  inorganic  substances  in  looo  parts  of  chyle  (horse) : — 

Sodic  chloride    ....  5.84     I     Sulphuric  acid    ....  0.05     I     Magnesic  phosphate  .    .  0.05 

Soda 1. 1 7         Phosphoric  acid  .    .    .    .0.05         Iron trace. 

Potash 0.13    I     Calcic  pho.sphate    .    .    .0.20    | 

(3)  The  lymph  obtained  from  the  beginning  of  the  lymphatic  .system  also 
contains  very  few  lymph  corpuscles ;  it  is  clear,  transparent  and  colorless,  and 
closely  resembles  the  fluids  of  serous  cavities.  That  the  lymph  coming  from  dif- 
ferent tissues  varies  somewhat,  is  highly  probable,  but  this  has  not  been  proved. 
After  lymph  has  passed  through  lymphatic  glands,  it  contains  more  corpuscles, 
and  also  more  solids,  especially  albumin  and  fat.  Ritter  counted  8200  lymph 
corpuscles  in  one  cubic  centimetre  of  the  lymph  of  a  dog. 

Hensen  and  Diihnhardt  obtained  pure  lymph  in  considerable  quantity  from  a 
lymphatic  fistula  in  the  leg  of  a  man.  It  had  an  alkaline  reaction  and  a  saline 
taste.  It  had  the  following  composition,  which  may  be  cornpared  with  the  com- 
position of  serous  transudations:  — 


Cerebro-spinal  Fluid 
(Hoppe-Seyler). 


Water 98.63 

Solids 1.37 

Fibrin o.ii 

Albumin 0.14 

Alkali  albuminate  ....    0.09 

Extractives 

Urea,  Leucin 1.05 

Salts 0.88 

70V0I.J4  of  CO,,  50%  of  which 
could  be  pumped  out,  and  20  fc 
by  the  addition  of  an  acid. 


9S.74 
'•25 


The  cerebro-spinal  fluid  and  ab- 
dominal lymph  contain  a  kind  of 
sugar  (without  the  property  of  rotat- 
ing polarized  light — 'Hoppe-Seyter). 


Pericardial  Fluid, 
(z*.  Gorup-Besanez) 


9551 
4.48 
0.08 
2.46 

1.26 


100  parts  of  the  Ash  of  Lymph  contained  the  following  substances: — 


Sodium  chloride     .    .    .  74.48 

Soda 10.36 

Potash 3.26 


Lime 0.98 

Magnesia 0.27 

Phosphoric  acid     ...  1 .09 


Sulphuric  acid 1.28 

Carbonic  acid S.21 

Iron  oxide 0.06 


Just  as  in  blood,  potash  and  phosphoric  acid  are  most  abundant  in  the 
corpuscles,  while  soda  (chiefly  sodium  chloride)  is  most  abundant  in  the 
lymph  serum.  The  potash  and  phosphoric  acid  compounds  are  most  abundant 
111  cerebro-spinal  fluid,  according  to  C.  Schmidt.  The  amount  of  icater  in  the 
lymph  rises  and  falls  with  that  of  the  blood.  Gases. — Dog's  lymph  contains 
much  COj — more  than  40  vols,  per  cent.,  of  which  17  per  cent,  can  be  pumped 
out,  and  23  per  cent,  expelled  by  acids,  while  there  are  only  traces  of  O  and  1.2 
vols,  per  cent.  N  {Ludwig,  Hammersten). 

The  observation  that  when  lymph  is  collected  from  large  vessels  and  exposed  to  the  air,  it  becomes 
red  [Funke),  is,  as  yet,  unexplained ;  but  it  is  certainly  not  due  to  the  formation  of  colored  corpus- 
cles from  colorless  ones,  owing  to  contact  with  the  (.1  of  the  air. 

199.  QUANTITY  OF  LYMPH  AND  CHYLE.— When  it  is  stated 
that  the  total  amount  of  the  lymph  and  chyle  passing  through  the  large  vessels 
in  twenty-four  hours  is  equal  to  the  amount  of  the  blood  (^Bidder  and  C.  Schmidt), 
it  must  be  remembered  that  this  is  merely  a  conjecture.  Of  this  amount  one-half 
may  be  lymph  and  the  other  half  chyle.  The  formation  of  lymph  in  the  tissues 
takes  place  continually,  and  without  interruption.  Nearly  6  kilos,  of  lymph  were 
collected  in  twenty-four  hours  from  a  lymphatic  fistula  in  the  arm  of  a  woman, 
by  Gubler  and  Quevenne ;  70  to  100  grms.  were  collected  in  i^4  to  2  hours  from 
the  large  lymph  trunk  in  the  neck  of  a  young  horse.  The  following  conditions 
affect  tlie  amount  of  chyle  and  lymph  : — 


340  ORIGIN    OF    LYMPH. 

(i)  The  amount  of  chyle  undergoes  very  considerable  increase  during  diges- 
tion, more  especially  after  a  full  meal,  so  that  the  lacteals  of  the  mesentery  and 
intestine  are  distended  with  white  or  milky  chyle.  During  hunger,  the  lymph 
vessels  are  collapsed,  so  that  it  is  difficult  to  see  the  large  trunks. 

(  2)  The  amount  of  blood  iiicirases  with  the  activity  of  the  organ  from  which 
it  proceeds.  Active  or  passive  muscular  movements  greatly  increase  its  amount. 
Lesser  obtained  in  this  way  300  cubic  centimetres  of  lymph  from  a  fasting  dog, 
whereby  its  blood  became  so  inspissated  as  to  cause  death. 

(3)  All  conditions  which  increase  the  pressure  upon  the  juices  of  the  tissues 
increase  the  amount  of  lymph,  and  vice  versa.     These  conditions  are  : — 

(a)  An  increase  of  the  blood  pressure,  not  only  in  the  whole  vascular  system,  but  also  in  the 
vessels  of  the  corresponding  organ,  augments  tlie  amount  of  lymph  and  vice  versa  {Luiiwig,  Tomsa). 
This,  however,  is  doubtful,  as  has  been  shown  by  Paschutin  and  Emminghaus.  [In  order  to  increase 
the  amount  of  lymph  depending  upon  pressure  within  the  vessels,  what  must  happen  is  increased 
pressure  within  the  capillaries  and  veins.] 

(/')  Ligature  or  obstruction  of  the  efferent  veins  greatly  increases  the  amount  of  lymph  which 
flows  from  the  corresponding  parts  (Bidder,  Kmminjrhaus).  It  may  be  doubled  in  amount  (  ll'eiss). 
Tight  bandages  cause  a  swelling  of  the  pans  on  the  peripheral  side  of  the  bandage,  owing  to  a 
copious  effusion  of  lymph  into  the  tissue  (congestive  oedema). 

[c]  An  increased  supply  of  arterial  blood  acts  in  the  same  way,  but  to  a  less  degree.  Paralysis 
of  the  vasomotor  nerves  (/,«</«'/<.'),  or  stimulation  of  vasodilator  fibres  (Gianuzzi),hy  increasing  the 
supply  of  blood,  increases  the  amount  of  lymph  ;  while  diminution  ot  the  blood  supply,  owing  to 
stimulation  of  vasomotor  fibres  or  other  causes,  diminishes  the  amount.  Even  after  ligature  of  both 
carotids,  as  the  head  is  still  supplied  with  blood  by  the  vertebrals,  the  lymph  stream  in  the  large 
cervical  lymphatic  does  not  cease  ( //'.  A'rause). 

(4)  When  the  total  amount  of  the  blood  is  increased,  by  the  injection  of  blood,  serum,  or  milk 
into  the  arteries,  much  fluid  passes  into  the  tissues  and  increases  the  formation  of  lymph. 

(5)  The  formation  of  lymph  still  goes  on  for  a  short  time  after  death,  and  after  complete  cessation 
of  the  action  of  the  heart,  but  only  to  a  slight  extent.  If  fresh  blood  be  caused  to  circulate  in  the 
body  of  an  animal,  while  it  is  still  warm,  more  lymph  flows  from  the  lymphatics  (Geiiersit/i).  It 
appears  as  if  the  tissues  obtained  plasma  from  the  blood  for  a  time  after  the  stoppage  of  the  circula- 
tion. This,  perhaps,  explains  the  circumstance  that  some  tissues — e.g.,  connective  tissues — contain 
more  fluid  alter  death  than  during  life,  while  the  blood  vessels  have  given  out  a  considerable  amount 
of  their  plasma  after  death. 

(6)  The  amount  of  lymph  is  increased  under  the  influence  of  curara  {Lesser,  Paschutin),  and  so 
is  the  amount  of  lolids  in  the  lymph.  A  large  amount  of  lymph  collects  in  the  lymph  sacs  [especially 
the  sublingual]  of  frogs  poisoned  with  curara,  which  is  partly  explained  by  the  fact  that  the  lymph 
hearts  are  paralyzed  by  curara  (Bidder).  The  miiount  of  Jymph  is  also  increased  in  inflamed  parts 
(Lassar). 

200.  ORIGIN   OF   LYMPH.— ( I)  Origin  of  the  Lymph  Plasma.— 

The  lymph  plasma  may  be  regarded  as  fluid  which  has  been  pressed  through  the 
walls  of  the  blood  vessels  by  the  blood  pressure,  /.  e.,  by  filtration  into  the  tissues. 
The  salts  which  pass  most  readily  through  membranes,  go  through  nearly  in  the 
same  proportion  as  they  exist  in  blood  plasma — the  fibrin  factors  to  about  two- 
thirds,  and  alluiwin  to  about  one-half  of  that  in  the  blood.  As  in  the  case  of  other 
filtration  processes,  the  amount  of  lymph  must  increase  with  increasing  pressure. 

This  was  proved  by  Ludwig  and  Tomsa,  who  found  that  when  they  passed  blood  serum  under 
varying  pressures  through  the  blood  vessels  of  an  excised  testis,  the  amount  of  transuded  fluid  which 
flowed  from  the  lymphatics  varied  with  the  pressure.  This  "  artificial  lymph  "  had  a  composition 
similar  to  that  of  the  natural  lymph.  Even  the  amount  of  albumin  increased  with  increasing  pressure. 
The  lymph  plasma  is  mixed  in  the  difterent  tissues  with  the  decomposition  products,  the  results  of 
the  metabolism  of  the  tissues. 

When  the  muscles  are  in  action,  not  only  is  the  lymph  poured  out  more  rapidly, 
but  more  lymph  is  formed.  The  tendons  and  fiiscias  of  the  muscles  of  the  skeleton, 
which  are  provided  with  numerous  small  stomata,  absorb  the  lymph  from  the 
muscles.  By  the  alternate  contraction  and  relaxation  of  these  fibrous  structures, 
they  act  like  suction  pumps,  whereby  the  lymphatics  are  alternately  filled  and 
emptied,  while  the  lymph  is  propelled  onward.  Even  passive  movements  act  in 
the  same  way.     If  solutions  be  injected  under  the  fascia  lata,  they  may  be  propelled 


MOVEMENT  OF  CH VLE  AND  LYMPH.  341 

onward  to  the  thoracic  duct  by  passive  movements  of  the  limb  (Ludwig,  Schweigger- 
Seidel,  and  Genersich). 

(2)  The  Origin  of  the  Lymph  Corpuscles  varies. — (i)  A  very  consider- 
able number  of  the  lymph  corpuscles  are  derived  from  the  lymphatic  glands  ; 
they  are  washed  out  of  these  glands  into  the  vas  efiferens  by  the  lymph  stream, 
hence,  the  lymph  always  contains  more  corpuscles  after  it  has  passed  through  a 
lymph  gland.  Small,  isolated  lymph  follicles  permit  corpuscles  to  pass  through 
their  limiting  layer  into  the  lymph  stream.  (2)  A  second  source  is  those  organs 
whose  basis  consists  of  adenoid  tissue,  and  in  whose  meshes  numerous  lymph 
corpuscles  occur,  e.g.,  the  mucous  membrane  of  the  entire  intestinal  tract,  red 
marrow  of  bone,  and  the  spleen  (§  103).  In  these  cases  the  cells  reach  the  origin 
of  the  lymph  stream  by  their  own  amojboid  movements.  (3)  As  lymph  corpuscles 
are  returned  to  the  blood  stream,  where  thev  appear  as  colorless  blood  corpuscle;., 
so  they  again  pass  out  of  the  blood  capillaries  into  the  tissues,  partly  owing  to 
their  amceboid  movements  {Cohnheim),  and  they  are  partly  expelled  by  the  blood 
pressure  {Heri/ig).  In  rare  cases  lym})h  corpuscles  wander  from  lymphatic  spaces 
back  again  into  the  blood  vessels  {v.  Recklinghauseii). 

Fine  particles  of  cinnabar  or  milk  globules  introduced  into  the  blood  soon  pass  into  the  lymphatics, 
and  the  vasomotor  nerves  do  not  aft'ect  the  process.  The  e.xtrusion  of  particles  is  greater  during 
venous  congestion  than  when  the  circulation  is  undisturbed,  just  as  with  diapedesis  {\  95) ;  inflam- 
matory affections  of  the  vascular  wall  also  favor  their  passage.  The  vessels  of  the  portal  system  are 
especially  pervious  {^Riltimeyer). 

(4")  By  division  of  the  lymph  corpuscles,  and  also  by  proliferation  of 
the  fixed  connective-tissue  corpuscles  {His).  This  process  certainly  occurs 
during  inflammation  of  many  organs.  This  has  been  proved  for  the  excised  cor- 
nea kept  in  a  moist  chamber  {v.  Recklinghausen,  Hoffmann)  ;  the  nuclei  of  the 
cornea  corpuscles  proliferate  also  {Strieker,  Morris). 

That  the  connective-tissue  corpuscles  proliferate  is  shown  by  the  enormous  production  of  lymph 
corpuscles  in  acute  inflammations  (with  the  formation  of  pus),  e.g.,  in  extensive  erysipelas,  and  in- 
flammatory purulent  effusions  into  serous  cavities,  where  the  number  of  corpuscles  is  too  great  to  be 
explained  by  the  wandering  of  blood  corpuscles  out  of  the  blood  vessels. 

Decay  of  Lymph  Corpuscles. — The  lymph  corpuscles  disappear  partly 
where  the  lymphatics  arise.  The  occurrence  of  the  fibrin  factors  in  the  lymph — 
formed  as  they  are  from  the  breaking  up  of  lymph  corpuscles — would  seem  to  in- 
dicate this.  In  inflammation  of  connective  tissue,  in  addition  to  the  formation  of 
numerous  new  lymph  corpuscles,  a  considerable  number  seems  to  be  dissolved  ; 
hence  the  lymph,  and  also  the  blood,  in  this  case  contains  more  fibrin.  Lymph 
corpuscles  are  also  dissolved  within  the  blood  stream,  and  help  to  form  the 
fibrin  factors. 

201.  MOVEMENT  OF  CHYLE  AND  LYMPH.— The  ultimate 
cause  of  the  movement  of  the  chyle  and  lymph  depends  upon  the  difference  of 
the  pressure  at  the  origin  of  the  lymphatics,  and  the  pressure  where  the  thoracic 
duct  opens  into  the  venous  system. 

( i)  The  forces  which  are  active  at  the  origin  of  the  lymphatics  are  con- 
cerned in  moving  the  lymph,  but  these  must  vary  according  to  the  place  of  origin 
— {a)  The  lacteals  receive  the  first  impulse  toward  the  movements  of  their  con- 
tents— the  chyle — from  the  contraction  of  the  muscular  fibres  of  the  villi  (pp. 
322,  327).  When  these  contract  and  shorten  the  axial  lacteal  is  compressed,  and 
its  contents  forced  in  a  centripetal  direction  toward  the  large  lymphatic  trunks. 
When  the  villi  relax,  the  numerous  valves  prevent  the  return  of  the  chyle  into  the 
villi,  {b)  Within  those  lymphatics  which  take  the  form  of  perivascular  spaces, 
every  time  the  contained  /dood  vessel  is  dilated  the  surrounding  lymph  will  be 
pressed  onward,  (c)  In  the  case  of  the  pleural  lymphatics  with  open  mouths, 
every  inspiratory  movement  acts  like  a  suction  pump  upon  the  lymph  {Dyh- 
kowsky),  and  the  same  is  the  case  with  the  openings  (stomata)  of  the  lymphatics 


342 


MOVEMENT   OF   THE    LYMPH. 


on  the  abdominal  side  of  the  diaphragm  {Liuhcig,  Sc/iweiggfr-Se-iden.  (,f)  In 
the  case  of  those  vessels  which  begin  by  means  of  fine  juice  canals,  the  movement 
of  the  lymph  must  largely  depend  upon  the  tension  of  the  juices  of  the  par- 
enchyma, and  this  again  must  depend  upon  the  tension  or  pressure  in  ike  blood 
capillaries,  so  that  the  blood  pressure  acts  like  a  vis  a  tergo  in  the  rootlets  of  the 
lymphatics. 

[In  some  organs  peculiar  pumping  arrangements  are  brought  into  action.  As  already  men- 
tioned, the  abdominal  surface  of  the  central  tendon  of  the  diaphragm  is  provided  with  stomata,  or 
open  communications  between  the  peritoneal  cavity  and  the  lymphatics  in  the  substance  of  the  ten- 
don.    V.  Recklinghausen  found  that  milk   put  upon  the  peritoneal  surface  of  the  central  tendon 


nlral  tendon  of  diaphragm.  The  injected  lymph  spaces,  h  and  h,  are  black.  At  /  the  walLs  of 
the  space  are  collapsed  {Brunton,  after  Ludivig  ami Schweigger-^eidt-l). 

showed  little  eddies  caused  by  the  milk  globules  passing  through  the  stomata  and  entering  the  lym- 
phatics. The  central  tendiin  consists  of  two  layers  of  fibrous  tissue  arranged  in  different  directions 
(Fig.  211,  b,  c).  When  (he  diaphragm  moves  during  respiration,  these  layers  are  alternately  pressed 
together  and  pulled  apart.  Thus  the  spaces  are  alternately  dilated  and  contracted,  lymph  being 
drawn  into  the  lymphaiics  (Fig.  211,  h\  through  the  stomata.] 

[Ludwig's  Experiment. — Tie  a  re.spiration  cannula  in  the  trachea  of  a  dead  rabbit ;  cut  across 
the  body  of  the  animal  immediately  below  the  diaphragm  ;  remove  the  viscera,  and  ligature  the 
vessels  passing  between  the  thorax  and  abdomen  ;  tie  the  thorax  to  a  ring,  and  hang  it  up  with  the 
head  downward  ;  pour  a  solution  of  Berlin  blue  upon  the  peritoneal  surface  of  the  diaphr.agm ;  con- 
nect the  respiration  cannula  either  with  a  pair  of  bellows  or  an  apparatus  for  artificial  respiration, 

Fig.  212. 


Injected  lymph  spaces  from  the  fascia  lata  of  the  dog.     The  injected  spaces  are  black  in  the  figure 
{Brunton^  after  Luduuig  and  Schvjeigger-Seidel), 

and  imitate  the  respiratory  movements.     After  a  few  minutes  the  lymphatics  are  filled  with  a  blue 
injection  showing  a  beautiful  plexus.] 

[The  same  kind  of  pumping  mechanism  exists  over  the  costal  pleura.  The  fascia  covering  the 
muscles  is  another  similar  mechanism.  The  fascia  consists  of  two  layers  of  fibrous  tissue,  with  in- 
tervening lymphatics  (Fig.  212).  When  a  muscle  contracts,  lymph  is  forced  out  from  between  the 
layers  of  the  fascia,  while  when  it  relaxes,  the  lymph  from  the  muscle,  carrying  with  it  some  of  the 
waste  products  of  muscular  action,  passes  out  of  the  muscle  into  the  fascia,  between  the  now  partially 
separated  layers.] 

(2)  Within  the  lymph  trunks  themselves,  the  independent  contraction  of 
their  muscular  fibres  partly  aids  the  lymph  stream.  Heller  observed  in  the 
mesentery  of  the  guinea  pig  that  the  peristaltic  movements  of  the  lymphatic  wall 


LYMPH    HEARTS. 


343 


passed  in  a  centripetal  direction.  Tiie  numerous  valves  prevent  any  reflux. 
The  conlrarfion  of  the  surroumling  muscles,  and  every  pressure  upon  the  vessels 
and  the  tissues  aid  the  current  (Liithvig,  NoH).  If  the  outflow  of  blood  from 
the  veins  is  interfered  with,  lymph  flows  copiously  from  the  corresponding  tissues 
{Nasse,  Tomsa).  [If  a  cannula  be  tied  in  a  lymphatic  of  a  dog,  a  few  drops  of 
lymph  flow  out  at  long  intervals.  But  if  even  passive  movements  of  the  limb  be 
made,  e.  g. ,  simply  flexing  and  extending  the  limb,  the  outflow  becomes  very  con- 
siderable and  continuous.] 

(3)  The  lymph  glands,  which  occur  in  the  course  of  the  lymphatics,  offer 
very  considerable  resistance  to  the  lymph  stream,  which  must  pass  through  the 
lymph  paths,  whose  spaces  are  traversed  by  adenoid  tissue,  and  contain  a  few 
lymph  corpuscles.  But  this  is,  to  a  certain  extent,  comiiensated  by  the  non-striped 
muscle  which  exists  in  the  capsule  and  trabecule  of  the  glands.  When  they  con- 
tract they  force  on  the  lymph,  while  the  valves  prevent  its  reflux.  Enlarged 
lymphatic  glands  have  been  seen  to  contract  when  stimulated  electrically.  [Bot- 
kin  has  stimulated  enlarged  lymphatic  glands  with  electricity  in  cases  of  leu- 
kaemia.] 

(4)  As   the  lymph  vessels  gradually  join  and  form  larger  vessels,  and  finally 


Fig.  213. 


Posterior  paii 


al  lymph  hearts  (L)  of  the  frog  {Ecker), 


form  one  trunk,  the  transverse  section,  or  sectional  area,  diminishes,  so  that  the 
velocity  of  the  current  and  the  pressure  are  increased.  Nevertheless,  the  velo- 
city is  always  small  ;  it  varied  from  230  to  300  millimetres  per  minute  in  the  large 
lymphatic  in  the  neck  of  a  horse  (  Weiss),  a  fact  which  enables  us  to  conclude 
that  the  movement  must  be  very  slow  in  small  vessels.  The  lateral  pressure  at 
the  same  place  was  10  to  20  mm.,  and  in  the  dog  5  to  10  mm.  of  a  weak  solution 
of  soda  {Ifeiss,  Noll),  although  it  was  found  to  be  12  mm.  Hg  in  the  thoracic 
duct  of  a  horse  ( IVeiss). 

(5)  The  respiratory  movements  exercise  a  considerable  influence  upon  the 
lymph  stream  in  the  thoracic  duct,  and  in  the  right  lymjjhatic  duct  ;  every  inspira- 
tion favors  the  passage  of  the  venous  blood,  and  also  of  the  lymph  toward  the 
heart,  whereby  the  tension  in  the  thoracic  duct  may  even  become  negative  {Bid- 
der). [The  diastolic  suction  of  the  heart,  by  diminishing  the  pressure  in  the  sub- 
clavian vein,  also  favors  the  inflow  of  lymph  into  the  thorax.] 

(6)  Lymph  hearts  exist  in  certain  cold-lilooded  an\ma.\%  [Panizza,Jok.  Miil/er).  The  frog 
has  two  axillary  hearls  (aliove  the  shoulder  near  the  vertebral  column,  and  two  sacral  hearts,  one 
on  each  side  of  tlie  coccyx  near  the  anus  (Fig.  213,  L).  [If  the  skin  covering  them  be  retlected 
they  are   brought   into  view   at  once.]     They  beat,  but  not  synchronou.sly,  about  sixty  times   per 


344  CEDEMA,    DROPSY,    AND    SEROUS   EFFUSIONS. 

minute,  and  contain  lo  cubic  centimetres  of  lymph.  They  have  transversely-striped  muscular 
fibres  in  their  walls,  and  are  also  provided  with  nerve  ^^ang/ia  ( IValJeyer),  The  posterior  pair 
pump  the  lymph  into  the  branch  of  the  vena  iliaca  communicans,  and  the  anterior  pair  into  the 
vena  subscapularis.  Their  pulsation  depends  partly,  but  not  exclusively,  upon  the  spinal  cord,  for 
if  the  cord  be  rapidly  destroyed,  they  may  cease  to  pulsate  (  Vo/kmann),  but  not  unfrequently  they 
continue  to  pulsate  after  removal  of  the  cord  (  Valentin^  Luc/isinger).  A  second  source  of  their 
pulsatile  movements  is  to  be  sought  for  in  Waldeyer's  ganglia.  Stimulation  of  the  skin,  intestine 
or  blood  heart  influences  them  reflexly — partly  accelerating  and  partly  retarding  them.  If  the 
coccygeal  nerve,  which  connects  the  sacral  hearts  to  the  spinal  cord,  be  divided,  these  eflects  do  not 
occur  (;>.  Wittic/i).  Strychnia  accelerates  their  movements  (Scherhcj),  and  so  does  heating  of  the 
spin.al  cord,  but  if  the  cord  be  cooled  they  are  retarded  (Fubiiii  and  Spalitta).  A  lymph  heart 
arrested  by  being  exposed,  or  after  the  action  of  muscarin,  can  be  caused  to  beat  by  filling  it  under 
pressure,  but  this  is  not  the  case  when  the  arrest  is  caused  by  destruction  of  its  nerves  (Boll,  Lan- 
gerdorff).  Antiarin  paralyzes  the  lymph  heart  and  the  blood  heart  at  the  same  time  (  Vintschgau), 
while  curara  paralyzes  the  former  alone  (Bidder).  In  other  ani|)hibians,  there  are  two  lymph 
hearts;  in  the  ostrich  and  cassowary  and  some  swimming  birds  (Panizza),3.nd  in  the  embryo  chick 
[A.  Budge)  I  or  2.     They  occur  in  some  fishes,  e.  g.,  near  the  caudal  vein  of  the  eel. 

(7)  The  nervous  system  has  a  direct  effect  upon  the  lymph  stream)  on 
account  of  its  connection  with  the  muscles  of  the  lymphatics  and  lymph  glands, 
and  with  the  lymph  hearts,  where  these  exist.  Further,  Kiihne  observed  that  the 
cornea  corpuscles  contracted  when  the  corneal  nerves  were  stimulated.  Goltz 
also  observed  that  when  a  dilute  solution  of  common  salt  was  injected  under  the 
skin  of  a  frog,  it  was  rapidly  absorbed,  but  if  the  central  nervous  system  was 
destroyed  it  was  not  absorbed. 

If  inflammation  be  produced  in  the  posterior  extremities  of  a  dog,  and  if  the  sciatic  nerve  be 
divided  on  one  side,  cedema  and  a  simultaneous  increase  of  the  lymph  stream  occur  on  that  .side 
(Jankozi'ski).  [A  combination  of  congestion  and  inflammation  greatly  increases  the  lymph  stream, 
and  this  is  still  more  the  case  when  the  nerves  are  divided  at  the  same  time.] 

Ligature  the  leg  of  a  frog,  except  the  nerves,  so  as  to  arrest  the  circulation,  and  place  the  leg  in 
water  ;  it  swells  up  very  rapidly,  but  a  dead  limb  does  not  swell  up.  So  that  absorption  is  inde- 
pendent of  the  continuance  of  the  circulation.  Section  of  the  sciatic  nerve,  or  destruction  of  the 
spinal  cord  (but  not  section  of  the  brain),  arrests  absorption  (Laii/cn/iack). 

202.  ABSORPTION  OF  PARENCHYMATOUS  EFFUSIONS.— Fluids  which  pass 
from  the  blood  vessels  into  the  spaces  in  the  tissues,  or  those  injected  subcutaneously,  are  absorbed 
chiefly  by  the  blood  vessels,  but  also  by  the  lymphatics.  Small  particles,  as  after  tattooing  with  cin- 
nabar or  China  ink,  may  pass  from  the  tissue  spaces  into  the  lymplvitics — and  so  do  blood  cor- 
puscles from  extravasations  of  blood,  and  fat  granules  from  the  marrow  of  a  broken  bone.  If  all 
the  lymphatics  of  a  part  are  ligatured,  absorption  takes  place  quite  as  rapidly  as  before  (Magendie) ; 
hence,  .ibsorbed  fluid  must  pass  through  the  thin  membranes  of  the  blood  vessels.  The  correspond- 
ing experiment  of  ligaturing  all  the  blood  vessels,  when  no  absorption  of  the  parenchymatous  juices 
taiies  place  (Emmerl,  Henle,  v.  Diisc/i),  does  not  prove  that  the  lymphatics  are  not  concerned  in 
absorption,  for,  alter  ligaturing  the  blood  vessels  of  a  part,  of  course,  the  formation  of  lymph,  and 
also  the  lymph  stream,  must  cease. 

When  fluids  are  injected  under  the  skin  absorption  takes  place  very  rapidly — ^more  rapidly 
than  when  the  substance  is  given  by  the  mouth.  The  subcutaneous  injection  of  many  drugs  is 
now  extensively  used,  but,  of  course,  the  substances  used  must  not  corrode,  irritate,  or  coagulate 
the  tissues.  Some  substances  do  not  act  when  given  by  the  mouth,  as  snake  poison,  poisons 
from  dead  bodies,  or  putrid  things,  altliough  they  act  rapidly  when  introduced  subcutaneously.  If 
emulsin  be  given  by  the  mouth,  and  amygdalin  be  injected  into  the  veins  of  an  animal,  hydro- 
cyanic acid  is  not  formed,  as  the  emulsin  seems  to  be  destroyed  in  the  alimentary  canal.  If  the 
emulsin,  however,  be  injected  into  the  blood,  and  the  amygdalin  be  given  by  the  mouth,  the  animal 
is  rapidly  poisoned,  owing  to  the  formation  of  hydrocyanic  acid,  as  the  amygdalin  is  rapidly  absorbed 
from  the  intestinal  canal.  The  amygdalin,  a  glucoside  (CjdH,-NOi  ,),  is  acted  upon  by  fresh 
emulsin  like  a  ferment ;  it  takes  up  21  Hot))  ^"<i  yields  hydrocyanic  acid  (CHX).  +  oil  of  bitter 
almonds  (C-H5O), -|- sugar  2(CgHj20j) — (C7.  Bernard).  When  serum  is  mjected  subcuta- 
neously, it  is  rapidly  absorbed  ;  it  is  decomposed  within  the  blood  stream,  and  increases  the  amount 
of  urea.     Albuminous  solutions,  oil,  peptones,  and  sugars  are  also  absorbed  (Eichhorsl). 

203.  CEDEMA,  DROPSY,  AND  SEROUS  EFFUSIONS.— [Dropsy.  As  aptly  illus- 
trated by  I.auder  Hrunton,  the  lymph  spaces  may  be  represented  by  cisterns,  each  of  which  is  pro- 
vided with  supply  pipes — the  arteries  and  capillaries;  while  there  are  two  exit  pipes— the  veins  and 
lymphatics.  In  health,  the  balance  between  the  inflow  and  outflow  is  such  that  the  spaces  are 
merely  moistened  with  fluid.  When  a  cannula  is  placed  in  a  lymphatic  vessel  in  a  dog,  only  a  few 
drops  of  lymph  flow  out  at  long  intervals.      Emniinghaus  found  that  if  the  veins  of  the  limb  be 


CEDEMA,    DROPSY,    AND    SEROUS    EFFUSIONS.  345 

ligatured  the  lymph  flows  much  more  quickly.  This  is  in  part  due  to  the  increased  transudation  of 
fluid  from  the  small  blood  vessels,  but,  as  Brunton  suggests,  it  may  also  be  due  to  fluid  passing  away 
by  the  lymphatics  when  it  can  no  longer  be  carried  away  by  the  veins.  We  cannot  say  what  is  the 
relative  share  of  the  veins  and  lymphatics,  nor  in  the  above  experiment  do  we  know  how  much  is 
due  to  increased  transudation  or  diminished  absorption.  When  there  is  an  undue  accumulation  of 
fluid  more  or  less  like  serum  in  the  lymph  spaces,  we  have  the  condition  termed  dropsy.  When 
there  is  general  dropsy  it  is  called  anasarca.] 

CEdema. — If  the  efferent  veins  and  lymphatics  of  an  organ  be  ligatured,  or  if  resistance  be 
offered  to  the  outflow  of  their  contents,  congestion  and  a  copious  transudation  of  lymph  into  the 
tissues  take  place.  These  are  most  marked  in  the  skin  and  subcutaneous  cellular  tissue.  The  soft 
parts  swell  up,  without  pain  or  redness,  and  a  doughy  swelling,  which  pits  on  pressure  with  the 
finger,  results.  These  are  the  signs  of  lymph  congestion,  which  is  called  cedema  when  the  fluid 
is  ~xiatery  and  localized. 

Under  similar  circumstances,  lymph  is  effused  in  the  serous  cavities.  [In  the  peritoneum  it  is 
ascites — thorax,  hyjrolhorax — pericardium,  hydro-pericardium — cranium,  hydrocephalus — tunica 
vaginalis,  hydrocele — ^joints,  hydrarthrosis,  etc.]  If,  at  the  same  time,  a  large  number  of  colorless 
blood  corpuscles  pass  out  of  the  blood  vessels  into  the  cavity,  the  fluid  becomes  more  and  more 
like  pus.  In  order  that  these  corpu.scles  may  proliferate,  a  considerable  percentage  of  albumin  is 
necessary.  When  the  pressure  within  the  serous  cavity  rises  above  that  in  the  small  blood  vessels, 
water  may  pass  into  the  blood.  These  sero-purulent  effusions  not  unfrequently  undergo  changes, 
and  yield  decomposition  products,  such  as  leucin,  tyrosin,  xanthin,  kreatin,  krealinin  (?),  uric  acid 
(?),  urea.  Endothelium  from  the  serous  cavity  (Quincke],  sugar  in  pleuritic  effusions  (Eichhorst) 
and  in  oedemas  with  little  albumin  {Rosetibach),  cholesterin  frequently  in  hydrocele  fluid,  and  suc- 
cinic acid  in  the  fluid  of  echinococci,  have  all  been  found  in  these  efliusions. 

The  effusion  of  lymph  may  arise  not  only  from  pressure  upon  the  lymphatics,  but  also  from  in- 
flammation and  thrombosis  of  the  lymphatics  themselves,  in  which  cases  not  unfrequently  new- 
lymphatics  are  formed,  so  that  the  communication  is  re-established.  Sometimes  the  ductus  tho- 
racicus  bursts,  and  lymph  is  poured  directly  into  the  abdomen  or  thorax.  [Ligature  of  the  thoracic 
duct  results  in  rupture  of  the  receptaculum  chyli  and  escape  of  chyle  and  lymph  into  the  large 
serous  cavities  {Liid'd<ii;').'\ 

When  dropsy  or  effusion  of  fluids  occurs  into  serous  cavities,  there  is  always  a  greater  transuda- 
tion of  fluid  through  the  blood  vessels.  The  abdominal  blood  vessels,  and  those  which  yield  a 
watery  effusion  under  normal  circumstances,  are  those  most  liable  to  be  affected. 

Transudation  is  favored  by — (i )  Venous  congestion,  so  as  to  raise  the  blood  pressure,  in 
which  case  the  effusion  usually  contains  little  albumin  and  few-  lymph  corpuscles,  while  the  colored 
corpuscles,  on  the  contrary,  are  more  numerous  the  greater  the  venous  obstruction.  Ranvier  pro- 
duced oedema  artificiaily  by  ligaturing  the  vena  cava  in  a  dog,  and  at  the  same  time  dividing  the 
sciatic  nerve.  The  paralytic  dilatation  of  the  blood  ve-sels  thereby  produced  caused  an  increased 
amount  of  blood  to  pass  to  the  limb,  while  the  blood  pressure  w-as  raised,  and  both  factors  favored 
the  transudation  of  fluid.  [Ranvier's  experiment  proves  that  mere  ligature  of  the  venous  trunk  of 
a  limb  by  itself  is  not  sufficient  to  cause  oedema.  The  oedema  is  due  to  the  concomitant  paralysis  of 
the  vasomotor  ners-es.  If  the  motor  roots  of  the  sciatic  nerve  alone  be  divided  along  with  ligature  of 
the  vena  cava,  no  cedema  occurs,  but  if  the  vasomotor  fibres  are  divided  at  the  same  time,  the  limb 
rapidly  becomes  redemalous.  There  is  such  an  increased  transudation  through  the  vascular  walls 
that  the  veins  and  lymphatics  cannot  remove  it  with  sufficient  rapidity,  and  cedema  occurs.  If  there 
be  weakness  of  the  vasomotor  nerves,  slight  obstruction  is  sufficient  to  prcjduce  <xitma.  (Lauder 
Brunton).']  When  the  leg  veins  are  occluded  with  an  injection  of  gypsum,  cedema  occurs 
(Sotnischeu'shy).  (2)  .Some  unknown  physical  changes  occur  in  the  protoplasm  of  the  endo- 
thelium of  the  capillaries  and  blood  vessels,  which  favor  the  transudation  of  albumin,  ha;moglobin, 
and  even  blood  corpuscles.  This  occurs  when  abnormal  substances  accumulate  in  the  blood — e.i;., 
dissolved  hcemoglobin — and  when  the  blood  contains  little  O  or  albumin.  The  same  has  been  ob- 
served after  exposure  to  too  high  temperatures,  and  the  swelling  of  soft  parts  in  the  neighborhood 
of  an  inflammatory  focus  seems  due  to  the  transudation  of  fluid  through  the  altered  vascular  wall. 
It  is  probable  that  a  nervous  influence  may  affect  particular  areas  through  its  action  on  the  blood 
vessels  of  the  part  (it  may  be  upon  the  protoplasm  of  the  blood  capillaries).  The  transudations  of 
this  nature  usually  contain  much  albumin  and  many  lymph  corpuscles.  (3)  When  the  blood  con- 
tains a  very  large  amount  of  water  the  tendency  lo  transudation  of  fluid  is  increased.  After  a 
lime  it  may  produce  the  changes  indicated  in  (21,  and  when  long  continued  may  increase  the  permea- 
bility of  the  vascular  wall  (Cohnlieim).  Watery  lymphatic  effusions,  from  watery  blood — "  cachec- 
tic oedema" — occur  in  feeble  and  badly  nourished  individuals.  [One  of  the  commonest  forms  of 
dropsy  is  the  slight  cedema  of  the  legs  in  ana-mic  persons  in  whom  the  heart  and  lungs  are  healthy. 
Many  factors  are  involved — the  blood  pressure,  watery  condition  of  the  blood,  the  condition  of 
nutrition  of  the  capillaries,  and  probably  a  tendency  10  vasomotor  paresis  (Brunton).'] 

[The  fl>iid  poured  out  varies  according  to  the  rapidity  with  which  this  occurs.  In  acute  inflamma- 
tion, effusion  or  exudation  takes  place  rapidly,  and  the  fluid  contains  the  fibrin  factors,  so  that  it 
tends  to  coagulate  spontaneously.  There  is  every  gradation  between  the  non-coagulable  hydrocele 
fluid  and  the  coagulable  exudation  in  inflammation.     The  fluids  in  different  dropsies  vary  in  com- 


346  COMPARATIVE    AND    HISTORICAL. 

position,  and  some  have  more  cells  in  them,  depending  on  local  causes,  as  in  some  situations  absorp- 
tion is  more  active  than  in  others  (James).  The  pleural  fluid  contains  most  solids,  then  ascitic, 
cerebrospinal,  and,  lastly,  that  in  the  subcutaneous  tissue.] 

[(4)  Ostroumoff  found  that  stimulation  of  the  lingual  nerve  not  only  causes  the  blood  vessels  of 
the  tongue  to  dilate,  but  the  corresponding  side  of  the  tongue  becomes  cedematous.  If  a  solution 
of  dilute  hydrochloric  acid  or  quinine  (^  145)  be  injected  into  the  duct  of  the  submaxillary  gland, 
and  the  chorda  tynipani  stimulated,  there  is  no  secretion  of  saliva,  but  the  gland  becomes  cedema- 
tous. In  an  animal  poisoned  with  atropin,  stimulation  of  the  chorda  causes  dilatation  of  the  blood 
vessels,  although  there  is  no  secretion  of  saliva ;  nevertheless,  the  gland  does  not  become  cedema- 
tous (Heidenhain).  As  Brunton  suggests,  this  experiment  points  to  some  action  of  atropin  on  the 
blood  vessels  which  has,  hitherto,  been  entirely  overlooked.] 

204.  COMPARATIVE  PHYSIOLOGY.— In  the  frog  large  lymph  sacs,  lined  with  endo- 
thelium,  exist  under  the  skin,  while  large  lymph  sacs  lie  in  relation  with  the  vertebral  column — one 
on  each  side — separated  from  the  abdominal  cavity  by  a  thin  membrane,  perforated  with  stomata. 
This  is  the  cysterna  lymphatica  magna  of  Panizzi.  Some  amphibians,  and  many  reptiles,  have 
large  lymph  spaces  under  the  skin,  which  occupy  the  whole  of  the  dorsal  region  of  the  body.  All 
reptiles  and  the  tailed  amphibians  have  large  elongated  reservoirs  for  lymph  along  the  course  of  the 
aorta.  The  lymph  apparatus  of  the  tortoise  (Fig.  206)  is  very  extensive.  The  osseous  fishes 
have  in  the  lateral  parts  of  their  backs  an  elongated  lymph  trunk,  which  reaches  from  the  tail  to 
the  anterior  fins,  and  is  connected  with  the  dilated  lymphatic  rootlets  in  the  base  of  the  tail  and  in 
the  fins.  The  largest  internal  lymph  sinus  is  in  the  region  of  the  (esophagus.  Many  birds  possess 
a  sinus-like  dilatation  or  lymph  space  in  the  region  of  the  tail.  The  lymph  spaces  communicate 
with  the  venous  system — with  valves  properly  arranged — usually  in  connection  with  the  upper  vena 
cava.  Lymph  hearts  have  already  been  referred  to  (^  20[,  6).  In  carnivora  the  lymph  glands  of 
the  mesentery  are  united  into  one  large,  compact  mass,  the  so-called  "  pancreas  Asellii." 

205.  HISTORICAL. — Although  the  Hippocratic  School  was  acquainted  with  the  lymph  glands, 
from  their  becoming  swollen  from  time  to  time,  and  although  Herophilus  and  Erasistratus  had  seen 
the  mesenteric  glands,  yet  Aselli  (1662)  was  the  first  who  accurately  described  the  lacteals  of  the 
mesentery  with  their  valves.  Pecquet  (1648)  discovered  the  receptaculum  chyli;  Rudbeck  and 
Thorn.  Bartholinus,  the  lymphatic  vessels  (1650-52) ;  Eustachius  (1563)  was  acquainted  with  the 
thoracic  duct,  which  Gassendus  (1654)  maintained  that  he  was  the  first  to  see;  Lister  noticed  that 
the  chyle  became  blue  when  indigo  was  injected  into  the  intestine  (167 1) ;  Sommering  observed 
the  separation  of  fibrin  when  lymph  coagulated;  Reuss  and  Emmert  discovered  the  lymph  corpus- 
cles. The  chemical  investigations  date  from  the  first  quarter  of  this  century ;  they  were  carried  out 
by  Lassaigne,  Tiedemann,  Gmelin  and  others.  The  last  two  observers  noticed  that  the  white  color 
of  chyle  was  due  to  the  presence  of  small,  fatty  granules. 


Physiology  of  Animal  Heat. 


206.  SOURCES  OF  HEAT.— Heat.— The  heat  of  the  body  is  an  unin- 
terrupted evolution  of  kinetic  energy,  which  we  must  represent  to  ourselves  as  due 
to  vibrations  of  the  corporeal  atoms.  The  ultimate  sou7-ce  of  the  heat  is  contained 
in  the  potential  energy  taken  into  the  body  with  the  food,  and  with  the  O  of  the 
air  absorbed  during  respiration.  The  (7otot/«/ of  heat  formed  depends  upon  the 
amount  of  energy  liberated  (see  Introduction). 

The  energy  of  the  food  stuffs  may  be  called  "  latent  heat,"  if  we  assume  that 
when  they  are  used  up  in  the  body — chiefly  by  a  process  of  combustion — kinetic 


Water  calorimeter  of  Favre  and  Silberm.inii. 

energy  is  liberated  only  in  the  form  of  heat.  As  a  matter  of  fact,  however, 
mechanical  energy  and  electrical  energy  are  developed  from  the  potential  energy. 
In  order  to  obtain  a  unit  measure  for  the  energy  liberated,  it  is  advisable  to  ex- 
press all  the  potential  energy  as  heat  units. 

The  Calorimeter.— This  instrument  enables  us  to  transform  the  jiotential 
energy  of  the  food  into  heat,  and,  at  the  same  time,  to  measure  the  number  of 
heat  units  produced. 

347 


348  CHEMICAL   SOURCES   OF    HEAT. 

Favre  and  Silbermann  used  a  water  calorimeter  (Fig.  214).  The  substance  to  be  burned  is 
placed  in  a  large  cylindrical  combustion  chamber  (K),  suspended  in  a  large  cylindrical  vessel  (L) 
filled  with  water  (-n'),  so  that  the  combustion  chamber  is  completely  surrounded  by  the  water.  Three 
tubes  open  into  the  upper  part  of  the  chamber;  one  of  them  lO)  supplies  the  a  r  which  is  necessary 
for  ombustion ;  it  reaches  almost  to  the  bottom  of  the  chamber;  the  second  tube  (^71  is  lixed  in  the 
middle  of  the  lid,  and  is  closed  above  with  a  thick  glass  plate,  and  on  this  is  placed,  at  an  angle,  a 
small  mirror  (j),  which  enables  an  observer  to  see  into  the  interior  of  the  chamber,  and  to  observe 
the  process  of  combustion  at  c.  The  third  tube  ((/)  is  used  only  when  combustible  gases  are  to  be 
burned  in  the  chamber.  It  can  be  closed  by  means  of  a  stop-cock.  A  lead  tube  (»-,  e)  with  many 
twists  on  it,  passes  from  the  upper  part  of  the  ciiamber  through  the  water,  and  finally  opens  at  ^. 
The  gaseous  products  of  combustion  pass  out  through  this  tube,  and  in  doing  so  help  to  heat  the 
water.  The  cylindrical  vessel  with  the  water  is  closed  with  a  lid  which  transmits  tlie  four  tubes. 
The  w.iter  cylinder  stands  on  four  feet  within  a  large  cylinder  (M).  which  is  filled  with  some  good 
non-conductor  of  heat,  and  this  again  is  placed  in  a  large  vessel  filled  with  water  (W).  This  is  to 
prevent  any  heat  reaching  the  inner  cylinder  from  without.  A  weighed  quantity  of  the  substance 
(c)  to  be  investigated,  is  placed  in  the  combustion  chamber.  When  combustion  is  ended,  during 
which  the  inner  water  must  be  repeatedly  stirred,  the  temperature  of  the  water  is  ascertained  by 
means  of  a  delicate  thermometer.  If  the  increase  of  the  temperature  and  the  amount  of  water  are 
known,  then  it  is  easy  to  calculate  the  number  of  heat  units  produced  by  the  combustion  of  a 
known  weight  of  the  substance  (see  Introduction). 

The  ice  calorimeter  may  also  be  used.  The  inner  cylinder  is  filled  with  ice  and  not  with  water, 
and  ice  is  also  placed  in  the  outer  cylinder,  to  prevent  any  heat  from  without  from  acting  upon  the 
inner  ice.  The  heat  given  off  from  the  combustion  chamber  causes  a  certain  amount  of  the  ice  to 
melt,  and  the  water  thereby  produced  is  collected  and  measured.  It  requires  79  heat  units  to  melt 
I  grm.  of  ice  to  i  grm.  of  water  at  0°  C. 

Just  as  in  a  calorimeter,  although  much  more  slowly,  the  food  stuffs  within  our 
body  are  burned  up,  oxygen  being  supplied,  and  thus  potential  energy  is  trans- 
formed into  kinetic  energy,  which  in  the  case  of  a  person  at  res/,  i.  e.,  when  the 
muscles  are  inactive,  almost  completely  appears  in  the  form  of  heat  (see  Introduc- 
tion). 

Heat  Units. — Favre,  Silbermann,  Frankland,  Rechenberg,  B.  Danilewsky.  and  others  have 
made  calorimetric  experiments  on  the  heat  produced  by  food.  Thus,  I  gramme  of  the  following 
dry  substances  yields  heat  units  : — 

Peptone  .    .    .  4914 
Glutin      .    .    .   5493 
Chondrin     .    .  4909 
Flesh     extract 
(Liebig)  .    .3216 


As  albumin  is  only  oxidized  to  the  stage  of  urea,  we  must  deduct  the  heat  units  obtainable  from 
urea  from  those  of  albumin,  and  as  i  part  of  albumin  yields  in  round  numbers  about  \  of  urea,  we 
pbtain  about  5100  calories  [^=  2170  kilogram  metres]  for  I  grm.  of  albumin. 

Isodynamic  foods,  i.  e.,  those  that  produce  a  similar  amount  of  heat ;  100  grms.  animal  albumin 
(after  deducting  the  heat  units  of  urea)  ^=  52  fat,  ^114  starch  =  129  dextrose  ;  100  grms.  of  vege- 
table albumin  :=  55  fat,  =  121  starch  ^  137  dextrose  (Dani/e-u'sky\.  Rubner  calculated  that  in 
man,  with  a  mixed  diet,  the  avai/able  heat  units  for  I  grm.  of  albumin  r^4IOO;  I  grm.  fat  =  9300  ; 
and  for  I  grm.  carbohydrate  ^4100  calories. 

When  we  know  the  weight  of  any  of  the  above-named  substances  consumed  by 
a  man  in  twenty-four  hours,  a  simple  calculation  enables  us  to  determine  how  many 
heat  units  are  formed  in  the  body  by  oxidation,  /.  e.,  provided  the  substance  is 
completely  oxidized. 

Sources  of  Heat. — The  individual  sources  of  heat  are  to  be  found  in  the 
following : — 

(i)  In  the  transformation  of  the  chemical  constituents  of  the  food,  endowed  with  a 
large  amount  of  potential  energy,  into  such  substances  as  have  little  or  no  energy. 
The  organic  substances  used  as  food  consist  of  C,  H,  O,  N,  so  that  there  takes 
place — {a)  Combustion  of  C  into  CO.j,  of  H  into  H.X),  whereby  heat  is  pro- 
duced ;  I  grm.  C  burned  to  produce  COj  yields  80S0  heat  units,  while  i  grm.  H 
oxidized  to  H^O  yields  34,460  heat  units.  The  O  necessary  for  these  purposes  is 
absorbed  during  respiration,  so  that,  to  a  certain  extent  at  least,  the  amount  of 


Casein      .    . 

.   578s 

Alcohol    . 

.   8958 

Grape  sugar    . 

3939 

Potatoes  .    . 

.   3752 

Stearin     . 

•   9036 

Cane  sugar 

4173 

Milk     .    .    . 

.   5093 

Palmitin  . 

.   8883 

Milk  sugar  .    . 

4162 

Bread  .    .    . 

•   3984 

Olein    .    . 

.   8958 

Vegetable  fibrir 

6231 

pice     .    .    . 

.   3813 

Glycerin  . 

.  4t79 

Glutin      .    .    . 

6141 

Starch  .    .    . 

.   4479 

Leucin     . 

.   6141 

Legumin      .    . 

5573 

Velk  of  egg 

.   6460 

Creatin    . 

.  4118 

Blood  fibrin     . 

5709 

PHYSICAL    SOURCES    OF    HEAT.  349 

heat  produced  may  be  estimated  from  the  amount  of  O  consumed.  The  same 
consumption  of  O  gives  rise  to  the  same  amount  of  heat  whether  it  is  used  to 
oxidize  H  or  C  (Pfli/ger).  There  is  a  relation,  amounting  to  cause  and  effect, 
between  the  amount  of  heat  produced  in  the  body  and  the  O  consumed.  The 
cold-blooded  animals,  which  consume  little  O,  have  a  low  temperature  ;  among 
warm-blooded  animals,  i  kilo,  of  a  living  rabbit  takes  up  within  a  hour  0.914  grm. 
O,  and  its  body  is  heated  to  a  mean  of  38°  C.  i  kilo  of  a  living  fowl  uses  i.i85 
grms.  O,  and  gives  a  mean  temperature  of  43.9°  C.  (Rcgnaiilt  and  Reiset).  The 
amount  of  heat  produced  is  the  same  whether  the  combustion  occurs  slowly  or 
quickly;  the  rapidity  of  the  metabolism,  therefore,  affects  the  rapidity,  but  not 
the  absolute  amount  of  heat  production.  The  combustion  of  inorganic  substances 
in  the  body,  such  as  the  sulphur  into  sulphuric  acid,  the  phosphorus  into  phosphoric 
acid,  is  another,  although  very  small,  source  of  heat. 

(^)  In  addition  to  the  processes  of  combustion  or  oxidation,  all  those  chemical 
processes  in  our  body,  by  which  the  amount  of  the  available  potential  energy 
which  is  present  is  diminished,  in  consequence  of  a  greater  satisfaction  of  atomic 
affinities,  lead  to  the  production  of  heat.  In  all  cases  where  atoms  assume  more 
stable  positions  with  their  affinities  satisfied,  chemical  energy  passes  into  kinetic 
thermal  energy,  as  in  the  alcoholic  fermentation  of  grape  sugar,  and  other  similar 
processes. 

Heat  is  .-ilso  developed  during  the  following  chemical  processes : — 

(«)  During  the  union  of  bases  with  acids  {Andrews).  The  nature  of  the  base  determines  the 
amount  of  heat  produced,  while  the  nature  of  the  acid  is  without  effect.  Only  in  those  cases  where 
the  acid,  e.g.,  COj,  is  unable  to  set  aside  the  alkaline  reaction,  the  amount  of  heat  produced  is  less. 
The  formation  of  compounds  of  chlorine  {e.g.,  in  the  stomach)  produces  heat. 

{b)  When  a  neutral  salt  is  changed  into  a  basic  one  {AnJrcujs).  In  the  blood  the  sulphuric  and 
phosphoric  acids  derived  from  the  combustion  of  S  and  P  are  united  with  the  alkalies  of  the  blood 
to  form  basic  salts.  The  decomposition  of  the  carbonates  of  ihe  blood  by  lactic  and  phosphoric 
acids  forms  a  double  source  of  heat,  on  the  one  hand,  by  the  formation  of  a  new  salt,  as  well  as  by 
the  liberation  of  CO,,  which  is  partly  absorbed  by  the  blood. 

(f)  The  combination  of  haemogloiJin  with  O  (j  36). 

In  connection  with  those  chemical  processes,  whereby  the  heat  of  the  body  is 
produced,  heat-absorbing  intermediate  compounds  are  not  unfrequently  formed. 
Thus,  in  order  that  the  final  stage  of  more  complete  saturation  of  the  affinities  be 
reached,  intermediary  atomic  groups  are  formed,  whereby  heat  is  absorbed.  Heat 
is  also  absorbed  when  the  solid  aggregate  condition  is  dissolved  during  retrogres- 
sive processes.  But  these  intermediary  processes,  whereby  heat  is  lost,  are  very 
small  compared  with  the  amount  of  heat  liberated  when  the  end  products  are 
formed. 

(2)  Certain  physical  processes  are  a  second  source  of  heat :  (a)  The 
transformation  of  the  kinetic  mechanical  energy  of  internal  organs,  when 
the  work  done  is  not  transferred  outside  the  body,  produces  heat.  Thus  the  whole 
of  the  kinetic  energy  of  the  heart  is  changed  into  heat,  owing  to  the  obstructions 
which  are  opposed  to  the  blood  stream  (S  93).  The  same  is  true  of  the  mechanical 
energy  evolved  by  many  muscular  viscera.  The  torsion  of  the  costal  cartilages, 
the  friction  of  the  current  of  air  in  the  respiratory  organs  and  the  ingesta  in  the 
digestive  tract,  all  yield  heat. 

An  CNcessively  minute  amount  of  the  mechanical  energy  of  the  heart  is  transferred  to  surrounding 
bodies  by  the  cardiac  impulse  and  the  superficial  pulse  beats,  but  this  is  infinitesimally  small.  During 
respiration,  when  the  respiratory  gases  and  other  substances  are  expired,  a  very  small  amount  of 
energy  disappears  externally,  which  does  not  become  changed  into  heat.  If  we  assume  that  the 
daily  work  of  the  circulation  exceeds  86,cxx>  kilogram  metres,  the  heat  evolved  is  equal  to  204.000 
calories,  in  twenty-four  hours  {\  93),  which  is  sufficient  to  raise  the  temperature  of  a  person  of 
medium  size  2°  C. 

(J?)  When,  owing  to  muscular  activity,  the  body  produces  work  which  is  trans- 
ferred to  e.xternal  objects,  e.  g.,  when  a  man  ascends  a  tower  or  mountain,  or 
throws  a  heavy  weight,  a  portion  of  the  kinetic  energy  passes  into  heat,  owing  to 


350 


HOMOIOTHERMAL    AND    POIKILOTIIERMAL    ANIMALS. 


friction  of  the  muscles,  tendons,  and  the  articular  surfaces,  as  well  as  to  the  shock 
and  pressure  of  the  ends  of  the  bones  against  each  other. 

((■)  The  electrical  currents  which  occur  in  muscles,  nerves,  and  glands  very 
probably  are  changed  into  heat.  The  chemical  processes  which  produce  heat 
evolve  electricity,  which  is  also  changed  into  heat.  This  source  of  heat,  however, 
is  very  small. 

(li)  Other  processes  are  the  formation  of  heat  from  the  ahsorption  of  C0„  {Henry'),  by  the  con- 
centration of  water  as  it  passes  through  membranes  {^Regnault  and  Pouillet),  in  imbibition  (A/at- 
teiicci,  i8j4),  formation  of  the  solids,  e.  g.,  of  chalk  in  the  bones.  After  death,  and  in  some  patho- 
logical processes  during  life,  the  coagulation  of  blood  (  Valentin,  Schiffer)  and  the  production  of 
rigor  mortis  are  sources  of  heat. 

207.  HOMOIOTHERMAL  AND  POIKILOTHERMAL  ANI- 
MALS.— In  place  of  tlie  old  classification  of  animals  into  "  cold  blooded  " 
and  "  warm  blooded,"  another  basis  of  classification  seems  desirable,  viz.,  the 
relation  of  the  temperature  of  the  body  to  the  temperature  of  the  surrounding 
medium. 

Bergmann  introduced  the  word  homoiothermal  for  the  warm-blooded  ani- 
mals (mammals  and  birds),  because  these  anitnals  can  maintain  a  very  uniform 
temperature,  even  although  the  surrounding  temperature  be  subject  to  considerable 
variations.  The  so-called  cold-blooded  animals  are  called  poikilothermal, 
because  the  temperature  of  their  bodies  rises  or  falls,  within  wide  limits,  with  the 
heat  of  the  surrounding  medium. 

When  homoiothermal  animals  are  kept  for  a  long  time  in  a  cold  medium, 
their  heat  production  is  increased,  and  when  they  are  kept  for  a  long  time  in  a 
warm  medium  it  is  diminished. 

Fordyce  gave  a  proof  of  the  nearly  uniform  temperature  in  man.  .^  man  remained  ten  minutes 
in  an  oven  containing  very  dry  hot  air  (\  21S),  and  yet  the  temperature  of  the  palm  of  his  hand, 
mouth,  and  urine  was  increased  only  a  few  tenths  of  a  degree.  Becquerel  and  Brechet  investigated 
the  temperature  of  the  human  biceps  (Ijy  means  of  thermo-electric  needles),  when  the  arm  had  been 
one  hour  in  ice,  and  yet  the  temperature  of  the  muscular  tissue  was  cooled  only  0.2°  C.  The  same 
muscle  did  not  undergo  any  increase  in  temperature,  or  at  most  0.2°  C,  when  the  man's  arm  was 
placed  for  a  quarter  of  an  hour  in  water  at  42°  C. 

If  heat  be  rapidly  abstracted  (§  225)  or  rapidly  supplied  (§  221)  to  the  body, 
so  as  to  produce  rapid  variation  of  the  temperature,  life  is  endangered. 

Poikilothermal  animals  behave  very  differently  ;  the  temperature  of  their 
bodies  generally  follows,  although  with  considerable  variations,  the  temperature  of 
the  surroundings.  When  the  temperature  of  the  surroundings  is  increased,  the 
arnount  of  heat  produced  is  increased,  and  when  the  surrounding  temperature 
falls,  the  amount  of  heat  evolved  within  the  body  also  falls. 

The  following  table  shows  very  clearly  the  characters  of  poikilothermal  animals,  e.  g.,  frogs 
(Rana  esculenta),  which  were  placed  in  air  and  water  of  varying  temperatures.  The  frogs  were 
fixed  to  an  iron  .support,  and  immersed  up  to  the  mouth.  The  temperature  was  measured  by  means 
of  a  thermometer  introduced  through  the  mouth  into  the  stomach. 


In  Water. 

In  Air. 

Temperature  of  the 

Temperature  of  Frog's 

Temperature  of  the 

TemperaUire  of  Frog's 

Water. 

Stomach. 

Stomach. 

41.0°  C. 

38.0°  c. 

40.4°  C. 

31.7°  c. 

35-2 

34-3 

35.8 

24.2 

30.0 

29.t> 

27.4 

19.7 

23.0 

22.6 

19.8 

15.6 

"20.6 

20.7 

.6.4 

14.6 

"•S 

12.9 

14.7 

10.2 

5-9 

8.0 

6.2 

7.6 

2.8 

5-3 

5-9 

8.6 

THERMO-ELECTRIC    MEASUREMENT    OF    HEAT. 


351 


Birds. 

T=mp. 
Thalassidroma    .  .    .  40.30 

Procellaria 40.S0 

Goose 41-70 

Sparrow    ....    |  ^9'°^ 

Pigeon    .    .    .  41.80-42.50 

Turkey 42.70 

Guinea  fowl  ....  43.90 

^-^ {^^ 

Crow 4l->7 


[Temperature  of  Different  Animals. 

Temp. 

Panther 38.90 

Mouse 41 


44-03 
J7.8 


■Swallow 

Gull 

Mammals. 

Tiger 37.20 

Horse    .    .    .  36.80-37.50 

Rat 38  80 

Hare 37  80 

Cat    ...    .  38.30-3S.90 
Guinea  pig  ....  38.80 

3740 
Dog \  39.00 

39.60 


Fig.  215. 


Dolphin 35.5 

(  37-30-40-00 

Sheep  ...   J  39.50-40.00 

(  40.00-40.50 

Ape 35.50 

Guinea  pig  .  .  35.76-38.00 
Rabbit    .    .    .  37.50-38.00 

Ox 37-50- 

Ass 36.95 

( Gavarret and  Rosenthal)^ 


Reptiles. — Snakes,  lo°-i2°,  but  higher  when  incubating.  Amphibians  and  fishes — 
°-S°~3°  above  the  temperature  of  the  surroundings.  Arlhropoda — o.i°-5.8°  above  the 
surroundings.  Bees  in  a  hive,  30°-32°,  and  when  swarming,  40°.  The  following 
animals  have  a  temperature  higher  than  the  surrounding  temperature :  Cephalopods, 
0.57°;  molluscs,  0.46°  ;  echinoderms,  0.40°  :   medusae,  0.27  ;  polyps,  0.21°  C. 

208.  ESTIMATION  OF  TEMPERATURE— THERMOMETRY.— 
Thermometry. — liy  using  thermometric  apparatus,  we  are  enabled  to  obtain  informa- 
tion regarding  the  degree  of  heat  of  the  body  to  be  investigated.  For  this  purpose  the 
following  methods  are  employed  : — 

(A)  The  Thermometer  {^Galileo,  1603). — Sanctorius  made  the  first  thermometric 
observations  on  man  (1626).  Celsius  (1701-1744)  divided  his  thermometer  into  100 
part*,  and  each  part  was  again  divided  into  10  parts,  so  that  ^5°  C.  could  be  easily 
read  off.  All  thermometers  which  have  been  used  for  a  long  time  give  too  high  read- 
ings [Bellani),  hence  they  should  be  compared,  from  time  to  time,  with  a  normal 
thermometer.  When  taking  the  temperature,  the  bulbs  ought  to  be  surrounded  for  fif- 
teen minutes,  and  during  the  last  five  minutes  the  mercury  column  ought  not  to  vary. 
A  very  sensitive  therinometer  will  indicate  the  temperature  after  seven  seconds  if  the 
urine  stream  be  directed  upon  its  bulb  (Oertmann).  Minimal  and  Maximal  ther- 
mometers are  often  of  use  to  the  physician. 

Walferdin's  metastatic  thermometer  (Fig.  215)  is  specially  useful  for  compara- 
tive observation.  The  tube  is  very  narrow  in  comparison  with  the  bulb,  and  in  order 
that  the  stem  be  not  too  long,  it  is  constructed  so  that  the  amount  of  mercury  can  be 
varied.  A  quantity  of  mercury  is  taken,  so  that  with  the  temperature  expected  the 
thread  of  mercury  will  stand  about  the  middle  of  the  Stem.  A  small  bulb  at  the  upper 
part  of  the  stem  receives  the  excess  of  Hg.  Suppose  a  temperature  between  37°-40° 
C.  is  to  be  measured,  the  bulb  is  first  heated  a  little  over  40°  C,  it  is  then  suddenly 
cooled,  and  shaken  at  the  same  time,  so  that  the  thread  of  mercury  is  thereby  suddenly 
broken  above  40°.  The  tube  is  so  narrow  that  1°  C.  is  equal  to  about  10  centimetres 
of  the  length  of  the  tube,  so  that  -^^°  C.  is  still  i  millimetre  in  length.  The  scale  is 
divided  empirically,  but  the  valve  of  the  divisions  must  be  compared  with  a  normal 
thermometer. 

Kronecker  and  Meyer  used  very  small  maximal  "  outflow  thermometers  "  [Duhng 
and  Petit\,  and  caused  them  to  pass  through  the  intestinal  canal,  or  through  large  blooil 
vessels.  The  mercury  flows  out  of  the  short  open  tube,  and,  of  course,  more  flows  out 
the  higher  the  temperature.  After  these  small  tubes  have  passed  through  the  animal, 
a  comparison  is  instituted  with  a  normal  thermometer,  to  determine  at  what  tempera- 
ture the  mercury  reaches  the  free  margin  of  the  tube. 

(B)  Thermo.electric  Method. — This  method  enables  us  to  determine  the  metas- 
tatic temperature  accurately  and  rapidly  (Fig.  216,  I).  The  thermo-electric  galvano- 
meter of  Meissner  and  Meyerstein  consists  of  a  circular  magnet  («),  suspended  by  a 
thread  of  silk  (c),  to  which  a  small  mirror  (S)  is  attached.  A  large  stationary  bar 
magnet  (M)  is  placed  near  the  magnet  (>n),  so  that  the  north  poles  (h  and  N|  or  both 
magnets  point  in  the  same  direction,  and  it  is  so  arranged  that  the  suspended  magnet  is 
caused  to  point  to  the  north  by  a  minimal  action  of  M.  A  thick  copper  wire  (b,  b)  is 
coiled  several  times  round  m  (although  in  the  figure  it  is  represented  as  a  single  coil), 
and  the  ends  of  the  wire  are  soldered  to  two  thermo  elements,  each  composed  of  two 
different  metals,  iron  and  German  silver,  the  two  similar  free  elements  being  united 
by  a  wire  (A,),  so  that  the  two  thermoelements  form  part  of  a  closed  circuit.  A 
horizontal  scale  (K,  K)  is  placed  at  a  distance  of  3  metres  from  the  mirror,  so  that  the 
the  scale  are  seen  in  the  mirror.  The  scale  itself  rests  upon  a  telescope  (F)  directed 
mirror.     The  observer  (B)  who  looks  through  the  telescope  can  see  the  divisions  of  the 


divisions  of 
toward  the 
scale  in  the 


352 


THERMO-ELECTRIC    MEASUREMENT   OF   HEAT. 


mirror.  When  the  magnet,  and  with  it  the  mirror,  swing  out  of  the  magnetic  meridian,  the 
observer  notices  other  divisions  of  the  scale  in  the  mirror.  When  one  of  the  thermo  elements  is 
heated,  an  electrical  current  is  produced,  which  passes  from  the  iron  to  the  German  silver  in  the 
heated  couple,  and  causes  a  deviation  of  the  suspended  magnet.  Suppose  a  person  were  swimming 
in  the  direction  of  the  current  in  the  conducting  wire,  then  the  north  pole  of  the  magnet  goes  to 
the.  north  (Amfive).  The  tangent  of  the  angle  y,  through  which  the  freely  movable  magnet  is 
diverted  by  a  galvanic  current,  from  its  position  of  rest  or  zero,  in  the  magnetic  meridian,  is  the  same 

as  the  galvanic  stream;  G  is  proportional  to  the  magnetic  energy  D,  /.  e..  tang.  «  ^  -  •     If    G  is 


Scheme  of  the 


:  arrangements  fo: 


ng  the  temperature. 


to  remain  the  same,  and  the  tang.  <f  to  be  as  large  as  possible,  the  magnetic  energy  must  be  dimin- 
ished as  much  as  possible.  If  the  magnetism  of  the  suspended  magnet  be  indicated  by  m,  and  that 
of  the  earth  by  T,  the  magnetic  directing  energy  D  ^  Tot,  so  that  D  can  be  diminished  in  two 
ways:  (i)  by  diminishing  the  magnetic  moment  of  the  suspended  magnet,  as  may  be  done  by  using 
a  pair  of  astatic  needles,  such  as  are  used  in  Nobili's  galvanometer  ;  (2)  and  also  by  weakening 
the  magnetism  of  the  earth,  by  placing  an  accessory  stationary  magnet  (Hauy's  rod)  in  the  same 
direction,  and  near  the  suspended  magnet.  An  important  arrangement  for  rapidly  getting  the  mag- 
net to  zero  is  the  dead-beat  arrangement  of  Gauss  (not  figured  in  the  scheme).  It  consists  of  a  thick 
copper  cylinder,  on  which  the  wire  of  the  coil  is  wound.     This  mass  of  copper  may  be  regarded  as 


TEMPERATURE   TOl'OGRAPIIV.  353 

a  closed  multiplicator  with  a  very  large  transverse  section.  Tlie  vibrating  magnet  induces  a  current 
of  electricity  in  this  closed  circuit,  whose  intensuy  is  greatest  when  the  velocity  of  the  excursion  of 
the  magnet  is  greatest,  and  which  takes  the  opposite  direction  as  soon  as  the  magnet  returns  toward 
zero.  These  induced  currents  cause  a  diminution  of  the  vibrations  of  the  magnet  in  this  way,  that 
the  arc  of  vibration  of  the  magnet  diminishes  very  rapidly,  almost  in  a  geometrical  progression. 
The  induced  damping  current  is  stronger,  the  less  the  resistance  in  the  closed  circuit,  and  in  the 
damper  or  dead-beat  arrangement  itself,  the  greater  the  section  of  the  copper  ring.  This  damping 
arrangement  limits  the  oscillation  of  the  magnet,  and  it  comes  to  rest  rapidly  and  promptly  afttr 
three  or  four  small  vibrations,  so  that  much  time  is  saved.  The  angle  of  deviation  is  so  small  that 
the  angle  itself  may  be  taken  instead  of  the  tangent. 

The  thermo-electric  needles  of  Dutrochet  (II)  may  be  placed  in  the  circuit.  They  consist  of 
iron  and  German  silver  soldered  at  their  points ;  or  the  needles  of  Becquerel  (III)  may  be  used. 
They  consist  of  the  same  metals  soldered  in  a  straight  line,  one  behind  the  other.  The  needles 
must  always  be  covered  by  a  varnish,  which  will  prevent  the  parenchymatous  juices  from  acting 
upon  them,  and  so  causing  a  current.  Before  the  experiment  we  must  determine  what  extent  of  ex- 
cursion on  the  scale  is  obtained  with  a  certain  temperature.  In  order  to  determine  this,  a  delicate 
thermometer  is  fixed  to  each  of  the  thermo  couples,  and  both  are  placed  in  oil  baths,  which  dift'er  in 
temperature — say  by  i°  C. — as  can  be  determined  by  the  thennometer.  When  the  current  is  closed, 
the  excursion  on  the  scale  will  indicate  i°  C.  Suppose  the  excursion  was  150  mm.,  then  each  mm. 
of  the  scale  would  be  equal  to  jl^°  C.  When  this  is  determined,  the  two  thermo  needles  may  be 
placed  in  the  different  tissues  or  organs  of  animals,  and,  of  course,  we  obtain  the  diflference  of  tem- 
perature in  these  places.  Or  one  thermo  couple  may  be  placed  in  a  bath  of  constant  temperature 
(nearly  that  of  the  body),  in  which  is  placed  a  deHcate  thermometer,  while  the  other  needle  is  intro- 
duced into  the  organ  to  be  investigated.  In  this  case,  we  obtain  the  difference  of  temperature  be- 
tween the  tissue  and  the  source  of  the  constant  heat.  The  electric  current  pas^es  in  the  warmer 
needle  from  the  iron  to  the  German  silver,  and  thus  through  the  wires  of  the  apparatus.  For  small 
differences  of  temperature,  such  as  occur  in  the  body,  the  thermo  electric  energy  is  always  propor- 
tional to  the  difference  of  temperature  of  the  two  needles  or  couples.  In  place  of  a  single  pair  of 
needles  several  may  be  used,  whereby  the  sensitiveness  of  the  apparatus  is  greatly  increased.  Helm- 
holtz  found  that  by  using  sixteen  antimony-bismuth  couples  he  could  detect  an  increase  of  :f^jj^°  C. 
Schiffer  prepared  a  simple  thermo  pile  (IV)  by  soldering  together  alternately  four  pairs  of  wires  of 
iron  {/)  and  German  silver  (a).  These  are  placed  in  the  two  organs  (A  and  B),  which  are  to  be 
investigated,  whereby  a  very  high  degree  of  exactness  is  obtained. 

209.  TEMPERATURE  TOPOGRAPHY.— Although  the  blood,  in 
virtue  of  its  continual  motion,  completing,  as  it  does,  the  circulation  in  twenty- 
three  seconds,  must  exercise  a  very  considerable  influence  on  the  equilibration  of 
the  temperature  in  different  organs,  nevertheless  a  completely  uniform  temperature 
does  not  exist,  and  the  temperature  varies  in  different  parts : — 

I.  Temperature  of  the  Skin. 

Middle  of  the  sole  of  the  foot  .    .  32.26°  C.  ] 

Near  tendo-Achillis 33-85  t   i-,  j     .1.  u  .■         j-      .1      r. 

At'       u  fir      fl  3'^  oc  \  J'  ^^^y  "i^de  these  observations  directly  after 

\VuM\Tn(  Lu^  °     ^^ 7,  Xc  standing    while   naked,  with  the  tempera 


Middle  of  calf 33.85  | 

Bend  of  knee 3S-00  j 

Middle  of  upper  arm 35-40  I 

Inguinal  fold 35-So  | 

Near  cardiac  impulse 34-4°  J 


ture  of  the  room  at  21°  C.  Only  the  under 
surface  of  the  thermometer  touched  the 
skin. 


In  the  closed  axilla,  36.49  (mean  of  505  individuals) ;  — 36.5  to  37.25  (  Wunderlich) ;  — 36.89°  C. 

[Liebervteister). 

The  temperature  of  the  skin  of  the  head  is  higher  in  the  forehead  and  parietal  region  than  in  the 
occipital  region;  the  left  side  is  warmer  than  the  ngh\.  (Maragliano).  Dyspnoea  increases  the 
temperature  of  the  skin  [Heidinhain,  Frankel). 

Method. — Liebermeister  determines  the  temperature  of  free  cutaneous  surfaces  thus :  The 
bulb  of  the  thermometer  is  heated  slightly  above  the  temperature  expected;  after  the  mercury  begins 
to  fall,  the  bulb  is  placed  on  the  skin,  and  if  the  bulb  has  the  same  temperature  as  the  skin,  the 
mercury  remains  stationary.     This  experiment  must  be  repeated  several  times. 

2.  Temperature  of  the  Cavities. 

Mouth  under  the  tongue 37- '9°  C, 

Rectum 38.01 

Vagina 3S.30 

(Uterine  cavity  somewhat  warmer;  cervical  canal  somewhat  cooler.) 
Urine 37.03 

23 


854         CONDITIONS   AFFECTING   THE   TEMPERATURE    OF   ORGANS. 

The  temperature  falls  in  the  stomach  during  digestion  (§  i66,  i).  Cold  in- 
jections (ii°  C.)  into  the  rectum  rapidly  lower  the  temperature  in  the  stomach  i° 
C.  {Wintcrnitz). 

3.  The  temperature  of  the  Blood  is,  as  a  mean,  39°  C.  The  venous  blood 
in  internal  viscera  is  warmer  than  the  arterial,  but  it  is  cooler  in  peripheral 
parts: — 


Blood  of  the  right  lieart 38.8° 

"  left  heart 38. 6 

"  aorta 38.7 

"         hepatic  veins    ....  39.7 
{CI.  BtvnarJ). 


Blood  of  the  superior  vena  cava  .    .  36  78° 
"         inferior  vena  cava    .    .38.11 
"         crural  vein    .    .        .    .  37.20 
V.  LicOig. 


The  lower  temperature  of  the  blood  in  the  left  heart  may  be  explained  by  the  blood  becoming 
cooled  in  its  pa-saje  through  the  lungs  during  respiration.  According  to  Heidenhain  and  Korner, 
the  right  heart  is  slightly  warmer  because  it  lies  in  relation  with  the  warm  liver,  while  the  left  heart 
is  suriounded  by  the  lung  which  contains  air.  This  observation  of  Malgaigne  (1832),  Berger,  and 
G.  V.  Liebig  is  disputed  by  others,  who  say  that  the  left  heart  is  slightly  warmer  (_/<7,-(j/«()«  oHa' 
Bernha)-(it)  because  the  combustion  processes  are  more  active  in  arterial  blood,  and  heat  is  evolved 
during  the  formation  of  oxyhaemoglobin  (  Ganigei).  The  blood  in  the  veins  is  usually  cooler  than 
in  the  corresponding  arteries  [Hallcr),  owing  to  the  superficial  position  of  the  former,  whereby  they 
give  off  heat  during  their  long  course  ;  thus  the  blood  of  Vcie  Jugular  vein  is  i^  to  2°  C.  lower  than 
the  blood  in  the  carotid  (Coliti) ;  the  crural  vein  3^  to  1°  cooler  than  in  the  crural  artery  (Becque- 
rcl  and  Brechet).  Superficial  veins,  more  especially  than  those  of  the  skin,  give  off  much  heat, 
and  their  blood  is,  therefore,  somewhat  cooler.  The  warmest  blood  is  that  of  the  hepatic  vein, 
39.7°  C.  (CI.  Bernard),  partly  owing  to  the  great  chemical  changes  which  occur  within  the  liver 
owing  to  its  .secretory  activity  (?  210,  a),  and  partly  to  its  protected  situation. 

(4)  Temperature  of  the  Tissues. — The  individual  tissues  are  warmer — (i) 
the  greater  the  transformation  of  kinetic  energy  into  heat,  i.  e.,  the  greater  the 
tissue  metabolism  ;  (2)  the  more  blood  they  contain  ;  (3)  and  the  more  protected 
their  situation.  According  to  Heidenhain  and  Korner,  the  cerebrum  is  the  warm- 
est organ  in  the  body. 

Berger  measured  the  temperature  of  the  tissues  of  a  sheep,  and  found — 

Subcutaneous  tissue 37.35°  C.  ~\  While  the  temperature  was  in — 

Brain 40.25  I  Rectum 40.67°  C. 

Liver 41.25  [  Right  heart 41.60 

Lungs 4' .50         J  Lett  heart 40.90 

Becquerel  and  Brechet  found  the  temperature  of  the  human  subcutaneous  tissue  to  be  2.1°  C. 
lower  than  that  of  the  neighboring  muscles.  The  horny  tissues  do  not  produce  heat,  and  their 
low  temperature  is  due  to  the  conduction  of  heat  from  the  parts  on  which  they  grow.  The  tem- 
perature of  tne  cornea  partly  depends  on  that  of  the  iris,  and  the  more  contracted  the  pupil  is,  it 
receives  more  heat  from  the  blood  vessels  of  the  iris. 

210.  CONDITIONS  AFFECTING  THE  TEMPERATURE  OF 
ORGANS. — 'I'he  temperature  of  the  individual  organs  is  by  no  means  constant ; 
It  is  influenced  by  many  conditions  ;  among  these  are  the  following : — 

(i)  The  more  heat  that  is  produced  iiidtpendettt/y  within  a  part,  the  liighcr  is  its 
temperature.  As  the  amount  of  heat  produced  within  a  part  depends  upon  its 
metabolism,  therefore,  when  the  metabolism  is  increased,  the  amount  of  heat  pro- 
duced is  similarly  increased. 

(a)  Glands  produce  more  heat  during  the  act  of  secretion,  as  is  proved  by 
the  higher  temijerature  of  their  secretion,  or  by  the  higher  temperature  of  the 
venous  blood  flowing  out  of  their  veins. 

Ludwig  found  that  when  he  stimulated  the  chorda  tyinpani,  the  saliva  of  the  submaxillary  gland 
was  1.5°  C.  warmer  than  the  blood  in  the  carotid,  which  supplied  the  gland  with  blood  [y.  239). 
The  blood  in  the  renal  vein  in  a  kidney  which  is  secreting  is  warmer  than  the  blood  in  the  renal 
artery.  The  secreting  liver  produces  much  heat  (^  178).  CI.  Bernard  investigated  the  tempera- 
ture of  the  blood  o!  the  portal  and  hepatic  veins  during  hunger,  at  the  begmning  of  digestion, 
and  when  digestion  was  most  active,  and  he  found  : — 

Temperature  of  portal  vein 37-8°  C.  I      After  .f  days      f  Blood  of  right  heart,  38  8°. 

*'  iiepatic  vein  .         ...  36.4         J        starvation.        \  (Hunger  period. j 


CONDITIONS   AFFECTING    THE   TEMPERATURE    OF    ORGANS.         355 

Temperature  of  portal  vein 39-9°  C.  1       Beginning  of 

"  hepatic  vein 39  5         J  digesticni. 

Temperature  of  portal  vein    .....  39.7         1     Digestion  most    (  Blood  of  right  heart  during 

"  hepatic  vein 41.3        J  active.  \      digestion,  39.2°. 

In  the  dog  a  moderate  diet,  chemical  or  mechanical  stimulation  of  the  gastric  mucous  membrane, 
or  even  the  sight  of  food,  raises  the  temperature  in  the  stomach  and  intestine. 

{b)  When  the  muscles  contract  they  evolve  heat  {Bunsen,  1805).  Davy 
found  that  an  active  muscle  became  0.7°  C.  warmer;  while  Becquerel  (1835),  ^Y 
means  of  a  thermo-galvanometer,  found  that  human  muscles,  when  kept  con- 
tracted for  five  minutes,  became  1°  C.  warmer  (§  302). 

This  is  one  of  the  reasons  why  the  temperature  may  rise  above  40°  during  rapid  running  A 
temperature  obtained  by  energetic  muscular  action  usually  does  not  fall  to  the  normal  until  after 
resting  for  I Y^  hours  {Billroth).  The  low  temperature  of  paralyzed  limbs  depends  partly  upon  the 
absence  of  the  muscular  contractions. 

((-)  With  regard  to  the  effect  of  sensory  nerves  upon  the  temperatures,  some 
of  the  chief  points  to  ascertain  are  whether  the  circulation  is  accelerated  or  re- 
tarded by  their  stimulation,  or  whether  the  respiration  is  increased  or  diminished 
(§  214,  II,  3),  and  whether  the  muscles  of  the  skeleton  are  relaxed  or  contracted 
reflexly  (§  214,  I,  3).  In  the  former  case  the  temperature  of  the  interior  and 
rectum  is  increased ;  in  the  latter,  diminished. 

That  there  are  heat-regulating  nerve  centres  has  not  been  definitely  proved  ;  with  regard  to  the 
influence  of  vasomotor  nerves  (\  371). 

((/)  The  temperature  of  the  body  rises  during  mental  exertion.  Davy  ob- 
served an  increase  of  0.3°  C.  after  vigorous  mental  exertion. 

Lombard  observed  that  the  temperature  of  the  forehead  rose  0.5°  C.  during  mental  activity  and 
emotional  disturbances.  The  part  of  the  forehead  corresponded  to  the  posterior  region  of  both 
upper  frontal  convolutions,  to  the  anterior  central  convolution,  and  (?)  to  the  anterior  part  of  the 
posterior  central  convolution.     The  temperature  was  higher  on  the  left  side. 

{e)  The  parenchymatous  fluids,  serous  fluids,  and  lymph  produce  little  heat, 
owing  to  their  feeble  metabolism,  hence  they  have  the  same  temperature  as  their 
surroundings  ;  the  epidermal  and  horny  tissues  do  not  produce  heat,  they  merely 
conduct  it  from  subjacent  structures. 

(2)  The  temperature  depends,  to  a  large  extent,  upon  the  amount  of  blood  in  an 
organ,  and  also  upon  the  rapidity  with  which  blood  is  renewed  by  the  circulation. 
This  is  best  observed  in  the  difference  of  the  temperature  between  a  cold,  pale, 
bloodless  hand  and  a  warm,  red,  congested  one. 

Becquerel  and  Brechet  found  that  the  temperature  of  the  human  biceps  fell  several  tenths  of  a 
degree,  when  the  axillary  artery  was  compressed.  Ligature  of  the  iliac  artery  in  a  dog  caused  a  fall 
of  ^°  C.  within  eighteen  minutes;  while  the  removal  of  the  ligature  caused  the  temperature  to  rise 
rapidly  to  normal.  Ligature  of  the  crural  artery  and  vein  in  a  dog  causes  a  fall  of  several  tlegrees 
(Landois).     If  the  extremities  be  kept  suspended  in  the  air,  they  become  bloodless  and  cold. 

Liebermeister  has  pointed  out  a  difference  with  regard  to  the  external  and  internal  parts  of  the 
body.  The  external  parts  give  off  more  heat  than  they  produce,  so  that  they  become  cooler  the 
more  slowly  new  blood  flows  into  them,  and  warmer  the  greater  the  rapidity  of  the  blood  stream 
through  them.  Acceleration  of  the  blood  stream,  therefore,  causes  the  temperature  of  peripheral 
parts  to  approximate  more  and  more  to  the  temperature  of  internal  organs,  while  retardation  of  llie 
blood  slream  causes  them  to  approach  the  temperature  of  the  surrounding  medium.  Exactly  the 
reverse  is  the  case  with  internal  parts,  where  a  large  amount  of  heat  is  produced,  and  heat  is  given 
up  almost  alone  to  the  blood  which  flows  through  them.  Their  temperature  must  fall  when  the 
blood  stream  through  them  is  accelerated,  and  it  is  raised  when  the  blood  stream  is  retarded  [Hei- 
denhain).  Hence  it  follows,  that  the  greater  the  difference  of  the  temperature  between  peripheral 
and  internal  parts,  the  slower  must  be  the  velocity  of  the  circulation. 

(3)  If  the  position  of  an  organ  be  such,  or  if  other  conditions  cause  it  to 
give  off  heat  by  conduction  or  radiation,  then  its  temperature /a/A. 

A  good  example  of  this  is  the  skin,  which  varies  greatly  in  temperature  according  to  the  tempera- 
ture of  the  surrounding  medium,  whether  it  is  covered  or  uncovered,  whether  it  is  dry  or  moist  with 
sweat  (which  abstracts   heat  when  it  evaporates).     When   much   cold   food  or  drink   is  taken  the 


356 


SPECIFIC    HEAT   OF   THE   BODY. 


stomach  is  cooled,  and  when  ice  cold  air  is  breathed  the  respiratory  passages  as  far  as  the 
bronchi  are  cooled. 

211.   ESTIMATION  OF  HEAT— CALORIMETRY.— Calorimetry 

is  the  method  of  determining  the  amount  of  heat  possessed  by  any  body,  or  what 
amount  of  heat  it  is  capable  of  producing.  The  unit  of  measurement  is  the 
"heat  unit,"  /.  e.,  the  amount  of  heat  (or  potential  energy)  required  to  raise 
the  temperature  of  i  gramme  of  water,  i°  C.  (see  Introduction). 

Experiment  has  shown  that  equal  quantities  of  differefit  substances  require  very  unequal  amounts 
of  heat  to  raise  them  to  the  same  temperature^  e.  ^j,^.,  I  kilo,  water  requires  nine  times  as  much  heat 
as  I  kilo,  iron  to  raise  it  to  the  same  temperature.  In  the  human  body,  therefore,  which  is  com- 
posed of  very  different  substances,  unequal  amounts  of  heat  will  be  required  to  raise  them  all  to  the 
same  temperature.  The  same  amount  of  heat  transferred  to  two  different  substances  will  raise  them 
to  different  temperatures.  Hence,  bodies  of  different  temperatures  may  contain  equal  amounts  of 
heat.  The  amount  of  heat  required  to  raise  a  definite  quantity  {e.^.,  I  grm.)  of  a  substance  to  a 
certain  higher  degree  (e.  g.,  i°  C.)  is  called  "  specific  heat  "  ( IVilkie,  lySo).  The  specific  heat 
of  water  (which  of  all  bodies  has  the  highest  specific  heat)  is  taken  as  =  i.  By  "  heat  capacity  " 
is  meant,  that  property  of  bodies  in  virtue  of  which  they  must  absorb  a  given  amount  of  heat  in 
order  to  have  a  certain  temperature  [Cra^vford). 

Calorimetry  is  employed  :   I.    To  determine  the  specific  heat  of  the  different  organs 
Fig.  217. 


iimiiiiTiiiiiiiiniiiiiiiimimimiiiiiiiii 


Kopp's  apparatus  for  the  estimation  of  specific  heat. 


of  the  body.     Only  a  few  observations  have  been  made.     The  mean  specific 
heat  of  the  following  animal  parts  (water  ^  i)  is — 


Human  blood 

= 

1.02 

(?) 

Compact  bone 

=            0.3 

Arterial  blood 

= 

1-031 

(?) 

Spongy  bone 

=            0.71 

Venous  blood 

= 

0.892 

(?) 

Fat  tissue 

=            0.712 

Cow's  milk 

= 

0.992 

Striped  muscle 

=           0.825 

Human  muscle 

:= 

0.741 

Defibrinated  blood 

=           0.927 

Ox  muscle 

= 

0.787 

(/.  Rosenthal) 

The  specific  heat  of  the  human  body,  as  a  whole,  is  about  that  of  an  equal 
volume  of  water. 

Method. — Kopp  has  estimated  the  specific  heat  of  solids  and  fluids  thus  (Fig.  217)  :  The  solid 
to  be  investigated  is. broken  in  pieces  about  the  size  of  a  pea,  and  placed  in  a  test  tube,  A,  with  thin 
walls,  which  is  closed  above  with  a  cork,  from  which  a  copper  wire  with  a  hook  on  it  projects. 
The  test  tube  contains  a  certain  quantity  of  fluid  which  does  not  dissolve  the  substance,  but  which 
lies  between  its  pieces  and  covers  it.  It  is  weighed  three  times,  to  ascertain  the  weight,  (I)  of  the 
empty  glass,  (2)  after  it  is  filled  with  the  solid  substance,  (3)  after  the  fluid  is  added,  so  that  we 
obtain  the  weight  of  the  solid  substance,  nt,  and  that  of  the  fluid  /.  The  test  tube  and  its  contents 
are  placed  in  a  mereury  bath,  BB,  and  this  again  in  an  oil  bath,  CC,  and  the  whole  is  raised  to  a 
high  temperature.  Into  BB  there  is  introduced  a  fine  thermometer,  T.  When  the  tube,  A,  has 
reached  the  necessary  temperature  (say  40°)  it  is  rapidly  placed  in  the  water  of  the  accompanying 


THERMAL   CONDUCTIVITY   OF   ANIMAL   TISSUES.  357 

calorimeter  box,  DD.  The  water  in  this  box,  which  also  contains  a  thermometer,  D,  is  kept  in 
motion  until  it  has  completely  absorbed  all  the  heat  given  off  by  A.  Let  T  represent  the  tempera- 
ture to  which  A  and  its  contents  were  raised  in  the  mercury  bath,  and  T,  the  temperature  to  which 
it  fell  in  the  calorimeter;  let  s  be  the  specific  heat,  and  m  the  weight  of  the  solid  substance  in  the 
test  tube,  while  "  and  ,«  represent  the  specific  heat  of  the  weight  of  the  interstitial  fluid  in  the  test 
tube  ;  and  lastly,  let  w  equal  the  amount  of  water  in  contact  with  A,  which  absorbs  and  gives  off 
heat ;  then  W  represents  the  amount  of  heat  which  the  test  tube  and  its  contents  give  off  during 
cooling. 

W  =  {s.  m  +  2v  +  a.  II)  T  —  TJ. 

The  amount  of  heat,  Wj,  absorbed  by  the  calorimeter  is 

Wi  =  M  [t^  —  t), 

where  M  represents  the  amount  of  water  in  the  calorimeter,  and  /  the  original  temperature  of  the 

water  in  the  calorimeter,  and  /j  the  temperature  to  which  it  is  raised  by  placing  A  in  it.    If  W  and 

Wj  are  equal,  then 

,**•/;*/           M  (/.  —  ^)  —  (w  +  <r.  II)  (T  —  T,) 
the  specific  heat,  s  =  — !^J m(T  —  1  )       ' 

If  a  fluid  substance  is  placed  in  the  test  tube,  and  its  weight  ^  ?«,  and  its  specific  heat  :=  s,  the 
formula  for  the  specific  heat  of  the  fluid  to  be  investigated  is— 

M  (/,  —t)  —  a-(T  — T,) 
'  —  /«(T  — Ti)  ■ 

This  is  a  subject  which  has  been  very  slightly  investigated.  J.  Rosenthal,  in  his  researches,  used 
an  ice  calorimeter  (J  206). 

II.  Calorimetry  is  more  important  for  determining  the  amount  of  heal  produced 
in  a  given  time  by  the  body  as  a  whole,  or  by  its  individual  parts. 

Lavoisier  and  Laplace  made  the  first  calorimetic  observations  on  animals  in  17S3,  by  means  of 
an  ice  calorimeter;  a  guinea  pig  melted  13  oz.  of  ice  in  ten  hours.  Crawford,  and  afterward 
Dulong  and  Despretz  (1824),  used  Rumford's  water  calorimeter,  which  is  similar  to  the  one  already 
described,  viz.,  of  Favre  and  Silbermann.  Small  animals  are  placed  in  the  inner  thin-walled  copper 
chamber  (K),  which  is  placed  in  a  water  bath  surrounded  on  all  sides  by  some  non-conducting 
material.  We  require  to  know  the  amount  of  water,  and  its  original  temperature.  The  number 
of  calories  is  obtained  from  the  increase  of  the  temperature  at  the  end  of  the  experiment,  which 
lasts  several  hours.  The  air  is  supplied  to  the  animal  through  a  special  apparatus  resembling  a 
gasometer.     The  amount  of  COj  in  the  gases  evolved  is  estimated  chemically. 

According  to  Despretz,  a  bitch  forms  14,610  heat  units  per  hour — /.  e.,  393,000 
in  twenty-four  hours.  Other  things  being  equal,  a  man  seven  times  heavier  than 
this  would  produce  in  twenty-four  hours  about  2,750,000  calories.  Senator  found 
that  a  dog  weighing  6330  grms.  produced  15,370  calories,  and  excreted  at  the 
same  time  367  grms.  CO^.  The  first  calorimetric  experiments  on  man  were  made 
by  Scharling  (1849).  Liebermeister  estimated  the  amount  of  heat  given  off  by 
a  man  placed  in  a  cold  bath,  which  was  surrounded  with  a  woolen  covering. 
Leyden  placed  a  lower  limb  in  the  calorimeter,  whereby  6000  grms.  water  were 
raised  1°  C.  in  an  hour.  If  we  assume  that  the  total  superficial  area  of  the  body 
is  fifteen  times  greater  than  that  of  the  leg,  the  human  body  would  produce 
2,376,000  calories  in  twenty-four  hours. 

212.  THERMAL  CONDUCTIVITY  OF  ANIMAL  TISSUES.— The  thermal  con- 
ductivity of  animal  tissues  is  of  special  interest  in  connection  with  the  skin  and  subcutaneous  fatty 
tissue.  The  fatty  layer  under  the  skin,  more  especially  in  the  whale,  walrus,  and  seal,  forms  a  pro- 
tective covering,  whereby  the  conduction  of  heat  from  internal  organs  is  rendered  almost  impossible. 
Investigations  upon  this  subject,  however,  are  few.  Griess  (1870)  attempted  to  estimate  the  thermal 
conductivity  by  heating  one  part  of  the  tissue,  and  determining  when  and  in  what  direction  pieces 
of  wax  placed  on  the  tissue  to  be  investigated  began  to  melt.  He  investigated  the  stomach  of  the 
sheep,  the  bladder,  skin,  hoof,  horn,  and  bones  of  an  ox,  deer's  horn,  ivory,  mother-of-pearl,  shell 
of  haliotis.  He  found  that  fibrous  tissues  conducted  heat  more  readily  in  the  direction  of  their 
fibres  than  at  right  angles  to  the  course  of  the  fibres.  Hence,  the  figures  obtained  from  the  melted 
wax  were  usually  elliptical.  Landois  has  made  similar  observations,  and  he  finds  that  tissues  con- 
duct better  in  the  direction  of  their  fibres.  After  bones,  blood  clot  was  the  best  conductor,  then 
followed  spleen,  liver,  cartilage,  tendon,  muscle,  elastic  tissue,  nail  and  hair,  bloodless  skin,  gastric 
mucous  membrane,  washed  fibrin.  It  is  specially  interesting  to  note  how  much  better  skin  con- 
taining blood m  its  blood  vessels  conducts,  compared  with  bloodless  skin.  Hence  little  heat  is  given 
off  from  a  bloodless  skin,  while  congested  skin  conducts  and  gives  off  much  more  heat. 


358 


VARIATIONS   OF   THE    MEAN    TEMPERATUKE. 


Like  all  other  substances,  the  human  body  is  enlarged  by  heat.  A  man  weighing  60  kilos.,  and 
whose  temperature  is  raised  from  37°  C.  to  40°  C,  is  enlarged  about  62  cubic  centimetres.  Con- 
nective tissue  (tendon)  is  extended  by  heat,  while  elastic  tissue  and  the  skin,  like  caoutchouc,  are 
contracted  (^Lombard  and  IVallon). 

213.  VARIATIONS  OF  THE  MEAN  TEMPERATURE.— (i) 
General  Climatic  and  Somatic  Influences. — In  the  tropics  the  mean  tem- 
perature of  the  body  is  about  ] 2°  C.  higher  than  in  temperate  climates,  where 
again  it  is  several  tenths  of  a  degree  warmer  than  in  cold  clirriates  {J.  Davy)  ; 
but  this  has  recently  been  denied  by  Boileau  and  Pinkerton.  This  difference  is 
comparatively  trivial,  when  we  remember  that  a  man  is  subjected  to  a  variation  of 
over  40°  C.  in  passing  from  the  equator  to  the  poles.  Observations  on  more  than 
4000  persons  show  that  when  a  person  goes  from  a  warm  to  a  cold  climate  his 
temperature  is  but  slightly  diminished,  but  when  he  goes  from  a  cold  to  a  warm 
climate  his  temperature  rises  relatively  considerably  more.  In  the  temperate  zone, 
the  temperature  of  the  body  during  a  cold  winter  is  usually  0.1°  to  0.3°  C.  lower 
than  it  is  on  a  warm  summer  day.  The  elevation  of  a  place  above  sea-level  has 
no  obvious  effect  on  the  temperature  of  the  body.  There  seems  to  be  no  difference 
in  different  races,  nor  in  the  sexes,  other  conditions  being  the  same.  Persons 
of  powerful  physique  and  constitution  are  said  to  have  generally  a  slightly 
higher  temperature  than  feeble,  weak,  anremic  persons. 

(2)  Influence  of  the  General  Metabolism. — As  the  formation  of  heat  de- 
pends upon  the  transformation  of  chemical  compounds,  whose  chief  final  pro- 
ducts, in  addition  to  H./J,  are  CO.2  and  urea,  the  amount  of  heat  formed  must 
go  pari  passu  with  the  amount  of  these  excreta.  The  more  rapid  metabolism 
which  sets  in  after  a  full  meal  causes  a  rise  of  temperature  to  several  tenths  of  a 
degree  ("  Digestion  fever").  As  the  metabolism  is  much  diminished  during 
hunger,  this  explains  why  the  mean  temperature  in  a  fasting  man  is  36.6°,  while 
it  is  37.17°  on  ordinary  days  {Lich/enfeis  and  Frchlich)  (§  237). 

Jiirgensen  also  found  that  the  temperature  fell  on  the  first  day  of  inanition  (although  there  was  a 
temporary  rise  on  the  second  day).  In  experiments  made  upon  starving  animals,  the  temperature  at 
first  fell  rapidly,  then  remained  const.ant  for  a  considerable  time,  while  during  the  last  days  it  fell 
considerably.  Schmidt  starved  a  cat;  on  the  15th  day  the  temperature  was  38°. 6 ;  on  the  i6th, 
38°.3;  17th,  37°.64;  i8th,  35°.8  ;  19th  (death)  =  33°.o.  Chossat  found  that  starving  mammals 
and  birds  had  a  temperature  16°  C.  below  normal  on  the  day  of  their  death. 

(3)  Influence  of  Age. — Age  has  a  decided  effect  upon  the  temperature  of  the 
body.  The  extent  of  the  general  metabolism  is  in  part  an  index  of  the  heat  of 
the  body  at  different  ages,  but  it  is  possible  that  other  as  yet  unknown  influences 
are  also  active. 


Age. 

Mean  Temperature  at  the 
Ordinary  Temperature. 

Normal  Limits. 

Where  Measured. 

Newly-born, 

37-45°  C. 

37-35-37-55°  C. 

Rectum. 

5-9    year. 

37-72 

36.87-37.62 

Mouth  and  Rectum. 

15-20      " 

37-37 

36. 1 2-38. 1 

Axilla. 

21-30      " 

37.22 

" 

25-30      " 

36.91 

" 

31-40      " 

37-1 

36-25-37-5 

" 

41-50      " 

36.87 

" 

51-60      " 

36.83 

" 

So      " 

37-46 

Mouth. 

Newly-born  Animals  exhibit  peculiarities  owing  to  the  sudden  change  in 
their  conditions  of  existence.  Immediately  after  birth,  the  infant  is  0.3°  warmer 
than  the  vagina  of  the  mother,  viz.,  37.86°.  A  short  time  after  birth,  the  tem- 
perature falls  0.9°,  while  twelve  to  twenty-four  hours  afterward  it  has  risen  to  the 
normal   temperature  of  an  infant,  which  is  37.45°-     Several  irregular  variations 


VARIATIONS   OF   THE    MEAN    TEMPERATURE. 


55U 


occur  during  the  first  weeks  of  life.  During  sleep,  the  temperature  of  an  infant 
falls  0.34°  to  0.56°,  while  continued  crying  may  raise  it  several  tenths  of  a  degree. 
Old  people,  on  account  of  their  feeble  metabolism,  produce  little  heat;  they 
become  cold  sooner,  and  hence  ought  to  wear  warm  clothing  to  keep  up  their 
temperature. 

Fig.  218. 


10     11     12     1    •  2     3 


i  of  the  daily  temperature  in  health  during  twenty-tour  houn 
Jiirgensen. 


L ,  after  Liebe 


(4)  Periodical  Daily  Variations. — In  the  course  of  twenty-four  hours  there 
are  regular  periodic  variations  in  the  mean  temperature,  and  these  occur  at  all  ages. 
As  a  general  rule,  the  temperature  continues  to  rise  during  the  day  (maximum  at  5  to 
8  P.M.),  while  It  continues  K.o  fall  during  the  /«^/// (minimum  2  to  6  a.m.).  The  mean 
temperature  occurs  at  the  third  hour  after  breakfast  {Lichtenfels  and  Frohlich). 


Time. 

Barensprung. 

J.  Davy. 

Kallmann. 

Gierse. 

Jiirgensen. 

Jager. 
36-9 

Morning 

•  S 

36.7 

366 

6 

36.68 

36.7 

36-4 

37-1 

7 

36-94* 

36-63 

36.98 

36.7* 

,6.,* 

37-5* 

8 

37.16* 

36.80* 

37-08* 

36.S 

36.7 

37-4 

9 

36.89 

36-9 

36-8 

37-5 

10 

37-26 

io>^  =  37-36 

37-23 

37-0 

37-0 

37-5 

II 

36.89 

37-2 

37-2 

37-3 

Mid-day. 

.  12 

36.87 

37-.S* 

37-3* 

37-5* 

I 

36.83 

37-21 

37-13 

373 

37-3 

37.4 

2 

37-05 

37-5°* 

37-4 

37-4 

37-5 

3 

37-15* 

37-43 

37-4* 

37-3* 

37-5 

4 

37-17 

37-4 

37-3 

37-5* 

5 

37-48 

37-05* 

5^^=37-21 

37-43 

37-5 

37-5 

37-5 

b 

6K  =  36.83 

37-29 

37-5 

^7-b 

37-4 

7 

37-43 

lYz  =  36-50* 

37-31* 

37-5* 

37-6* 

37-3 

8 

37-4 

37-7 

,S7-i* 

9 

37.02* 

37-4 

37-5 

36-9 

10 

37-29 

37-3 

37-4 

36.8 

II 

36.8s 

36.72 

36.70 

36.81 

37-2 

S7-I 

36.8 

Night.  . 

.  12 

-    - 

37-1 

36.9 

36-9 

I 

36.65 

36-44 

37-0 

36-9 

36-9 

2 

369 

36.7 

36.8 

.3 

36.8 

36.7 

36.7 

4 

36-31 

36-7 

36-7 

36-7 

[*  Indicates  taking  of  food.] 


3(J0  CONDITIONS    AFFECTING   THE    MEAN    TEMPERATURE. 

The  mean  height  of  all  the  temperatures  taken  during  a  day  in  a  patient  is 
called  the  "daily  mean,"  and  according  to  Jaeger,  it  is  37- 13°  in  the  rectum 
in  health.  A  daily  mean  of  more  than  37.8°  is  a  "fever  temperature,"  while  a 
mean  under  37.0°  C.  is  regarded  as  a  "collapse  temperature." 

According  to  I.ichtenfels  and  Frohlich,  the  morning  temperature  rises  four  to  six  hours  after 
breakfast  until  its  first  maximum,  then  it  falls  until  dinner  time ;  and  it  rises  again  within  two  hours 
to  a  second  maximum,  falls  again  toward  evening,  while  supper  does  not  appear  to  cause  any 
obvious  increase.  The  daily  variation  of  the  temperature  is  given  in  Fig.  218,  according  to  Lieber- 
meister  and  Jiirgensen.  According  to  Bonnal,  the  minimum  occurs  between  12  and  3  A.M.  (in 
winter  36.05,  in  summer  36.45°  C. ),  the  maximum  between  2  and  4  p.m. 

As  the  variations  occur  when  a  person  is  starved  for  a  day — although  those  that  occur  at  the 
periods  at  which  food  ought  to  have  been  taken  are  less — it  is  obvious  that  the  variations  are  not 
due  entirely  to  the  taking  of  food. 

The  daily  variation  in  the  frequency  of  the  pulse  often  coincides  with  variation  of  the  tem- 
perature. Barensprung  found  that  the  mid-day  temperature  maximum  slightly  preceded  the  pulse 
maximum  (?  70,  3,  C). 

If  we  sleep  during  the  day,  and  do  all  our  daily  duties  during  the  night,  the 
above  described  typical  course  of  the  temperature  is  inverted  {Kiiegcr).  With 
regard  to  the  effect  of  activity  or  rest,  it  appears  that  the  activity  of  the  muscles 
during  the  day  tends  to  increase  the  mean  temperature  slightly,  while  at  night  the 
mean  temperature  is  less  than  in  the  case  of  a  person  at  rest  (^Liehermeister). 

The  peripheral  parts  of  the  body  exhibit  more  or  less  regular  variations  of  their  temperature. 
In  the  palm  of  the  hand,  the  progress  of  events  is  the  following  :  After  a  relatively  high  night 
temperature  there  is  a  rapid  fall  at  6  a.m.,  which  reaches  its  minimum  at  g  to  10  a.m.  This  is  fol- 
lowed by  a  slow  rise,  which  reaches  a  high  maximum  after  dinner;  it  falls  between  i  and  3  p.m.,  and 
after  two  or  three  hours  reaches  a  minimum.  It  rises  from  6  to  8  p.m.,  and  falls  again  toward 
morning.  A  rapid  fall  of  the  temperature  in  a  peripheral  part  corresponds  to  a  rise  of  temperature 
in  internal  parts  [Komer). 

(5)  Many  operations  upon  the  body  affect  the  temperature.  After  hemor- 
rhage, the  temperature  falls  at  first,  but  it  rises  again  several  tenths  of  a  degree, 
and  is  usually  accompanied  by  a  shiver  or  slight  rigor;  several  days  thereafter  it 
falls  to  normal,  and  may  even  fall  somewhat  below  it.  The  sudden  loss  of  a  large 
amount  of  blood  causes  a  fall  of  the  temperature  ^4  to  2°  C.  Very  long-continued 
hemorrhage  (dog)  causes  it  to  fall  to  31°  or  29°  C.  (^Marshall  Hall). 

This  is,  obviously,  due  to  the  diminution  of  the  processes  of  oxidation  in  the  anaemic  body,  and 
to  the  enfeebled  circulation.  Similar  conditions,  causing  diminished  metabolism,  effect  the  same 
result.  Continued  stimulation  of  the  peripheral  end  of  the  vagus,  so  that  the  heart's  action  is  enor- 
mously slowed,  diminishes  the  temperature  several  degrees  in  rabbits  (Landois  and  Ammon). 

The  transfusion  of  a  considerable  quantity  of  blood  raises  the  temperature 
about  half  an  hour  after  the  operation.  This  gradually  passes  into  a  febrile  attack, 
which  disappears  within  several  hours.  When  blood  is  transfused  from  an  artery  to 
a  vein  of  the  same  animal  a  similar  result  occurs  {Albert  ami  Strieker)  (§  102). 

(6)  Many  poisons  diminish  the  temperature,  e.g.,  chloroform  {Selieinesson), 
and  the  anaesthetics,  as  also  alcohol  (§  235),  digitalis,  quinin,  aconitin,  muscarin. 
These  appear  to  act,  partly,  by  rendering  the  tissues  less  liable  to  undergo  molecu- 
lar transformations  for  the  production  of  heat.  In  the  case  of  the  anaesthetics, 
this  effect,  perhaps,  occurs,  and  is  due,  possibly,  to  a  semi-coagulation  of  the 
nervous  substance  (?).  They  may  also  act  partly  by  influencing  the  giving  off 
of  heat  (§  214,  II).    Other  poisons  increase  the  temperature,  for  opposite  reasons. 

The  temperature  is  increased  by  strychnin,  nicotin,  picrotoxin,  veratrin  (Hoi^yes),  laudanin 
{F.  A.  Fakk).     Curara  (muscarin — //i.\^yes),  laudanosin  [F.  .4.  Fa/ck),  cause  an  uncertain  effect. 

(7)  Various  diseases  diminish  the  temperature,  which  may  be  due  either  to  lessened  produc- 
tion of  heat  (diminution  of  the  metabolism),  or  to  increased  expenditure  of  heat.  Loewenhardt 
found  that  in  paralytics  and  in  insane  persons,  several  weeks  before  their  death,  the  rectal  tempera- 
ture was  30°  to  31°  C. ;  Bechterew  found  in  dementia  paralytica,  before  death,  27.5°  C.  (rectum); 
the  lowest  temperature  obser\'ed,  and  life  retained,  in  a  drunken  person,  was  24°  C.  (Kfinie, 
A'iiolaysen). 


REGULATION  OF  THE  TEMPERATURE.  361 

The  temperature  is  increased  in  fe-jer,  and  the  highest  point  reached  just  before  death,  and  re- 
corded by  Wunderlich,  was  44.65°  C.  (compare  \  220).  Increase  of  temperature,  constituting  fever, 
is  treated  of  in  \  220. 

214.  REGULATION  OF  THE  TEMPERATURE.— As  the  bodily 
temperature  of  man  and  similar  animals  is  nearly  constant — notwithstanding 
great  variations  in  the  temperature  of  their  surroundings — it  is  clear  that  some 
mechanism  must  exist  in  the  body  whereby  the  heat  economy  is  constantly 
regulated.  This  may  be  brought  about  in  two  ways:  either  by  controlling  the 
transformation  of  potential  energy  into  heat,  or  by  affecting  the  amount  of  heat 
given  off  according  to  the  amount  produced,  or  to  the  action  of  external  agencies. 

I.  Regulatory  Arrangements  Governing  the  Production  of  Heat. — 
Liebermeister  estimated  the  amount  of  heat  produced  by  a  healthy  man  at  1.8 
calories  per  minute.  It  is  highly  probable  that,  within  the  body,  there  exist 
mechanisms  which  determine  the  molecular  transformations,  upon  which  the  evo- 
lution of  heat  depends  {Hoppe-Seyler,  Liebermeister).  This  is  accomplished, 
chiefly,  in  a  reflex  manner.  The  peripheral  ends  of  cutaneous  nerves  (by 
thermal  stimulation),  or  the  nerves  of  the  intestine  and  the  digestive  glands  (by 
inechanical  or  chemical  stimulation  during  digestion  or  inanition)  may  be  irri- 
tated, whereby  impressions  are  conveyed  to  the  heat  centre,  which  sends  out 
impulses,  through  efferent  fibres,  to  the  depots  of  potential  energy,  either  to 
increase  or  diminish  the  extent  of  the  transformations  occurring  in  them.  The 
nerve  channels  herein  concerned  are  entirely  unknown.  Many  considerations, 
however,  go  to  support  such  an  hypothesis  (§  377). 

Heat  Centre. — So  far,  the  investigations  as  to  the  existence  of  such  a  centre  are  not  quite  con- 
clusive. Tschetschechin  and  Naunyn,  Ott  and  Wood,  assume  that  there  is  a  cerebral  heat  centre, 
which  inhibits  the  comlsustion  processes  in  the  body  by  means  of  fibres  descending  through  the 
pons,  medulla  oblongata  and  spinal  cord,  so  that  destruction  of  this  centre,  or  its  conducting  paths, 
increases  the  production  of  heat.  Aronsohn  and  Sachs  observed  that  puncture  of  a  rabbit's  brain, 
several  millimetres  to  the  side  of  and  behind  the  large  fontanelle,  was  followed  by  a  temporary  rise 
of  the  temperature.  Richet  noted  a  similar  result,  but  he  referred  it  to  increased  production  of  heat ; 
the  animals  ate  more  and  lost  flesh.  Repeated  puncture  of  the  brain  finally  caused  emaciation, 
diminution  of  temperature  (26°  C.)  and  death. 

The  following  phenomena  indicate  the  existence  of  mechanisms  regulating  the 
production  of  heat : — 

(i)  The  temporary  application  of  moderate  cold  raises  ike  bodilv  temperature, 
while  heat,  similarly  applied  to  the  external  surface,  lowers  it  (§222  and  224). 

(2)  Cooling  of  the  surroundings  increases  the  amount  of  COj  excreted,  by 
increasing  the  production  of  heat  {Liebermeister,  Gildermeister),  while  the  O 
consumed  is  also  increased  simultaneously ;  heating  the  surrounding  medium  di- 
minishes the  COj  (§  127,  5). 

D.  Finkler  found,  from  experiments  upon  guinea  pigs,  that  the  production  of  heat  was  more  than 
doubled  when  the  surrounding  temperature  was  diminished  24°  C.  The  metabolism  of  the  guinea 
pig  is  increaseil  in  winter  23  per  cent.,  as  compared  with  summer ;  so  that  the  same  relation  obtains 
as  in  the  case  of  a  diminution  of  the  surrounding  temperature  of  short  duration. 

C.  Ludwig  and  Sanders- Ezn  found  that  in  a  rabbit  there  was  a  rapid  increase  in  the  amount  of 
COj  given  off,  when  the  surroundings  were  cooled  from  38°  to  6°  or  7°  C. ;  while  the  excretion  was 
diminished  when  the  surrounding  temperature  was  raised  from  4°-9°  to  35°-37°,.so  that  the  thermal 
stimulation,  due  to  the  temperature  of  the  surrounding  medium,  acted  upon  the  combustion  within 
the  body.  Pfluger  found  that  a  rabbit  which  was  dipped  in  cold  water  used  more  O  and  excreted 
more  CO  2. 

If  the  cooling  action  was  so  great  as  to  reduce  the  bodily  temperature  to  30°,  the  exchange  of 
gases  diminished,  and  where  the  temperature  fell  to  20°,  the  exchange  of  gases  was  diminished  one- 
half.  It  is  to  be  remembered,  however,  that  the  excretion  of  CO,  does  not  go  hand  in  hand  with 
the  formation  of  CO,,  so  that  the  increased  excretion  of  CO,  in  a  cold  bath  is,  perhaps,  due  to  more 
complete  expiration,  and  Berthelot  has  proved  that  the  formation  of  CO^  is  not  a  certain  test  of  the 
amount  of  heat  produced.  If  mammals  be  placed  in  a  warm  bath,  which  is  2°  to  3°  higher  than 
their  own  temperature,  the  excretion  of  CO,  and  the  consumption  of  O  are  increased,  owing  to  the 
stimulation  of  their  metabolism  (P/lii^er),  while  the  excretion  of  urea  is  also  increased  in  animals 
{Xaiinyn)  and  in  man  (Schleieh)  (|  133,  5). 


362  REGULATION  OF  THE  TEMPERATURE. 

(3)  Cold  acting  upon  the  skin  causes  involuntary  muscular  movements 
(shivering,  rigors),  and  also  voluntary  movements,  both  of  which  produce  heat. 

The  cold  excites  the  action  of  the  muscles,  which  is  connected  with  processes  of  oxidation 
(Pfliii^fr).  After  poisoning  with  cui%ra,  which  paralyzes  voluntary  motion,  this  rejjulation  of  the 
heat  falls  to  a  minimum  (ke/irig  and  Ziin/:)  [while  tlie  bodily  temperature  rises  and  falls  with  a 
rise  or  fall  in  the  temperature  of  the  surrounding  medium]. 

(4)  Variations  in  the  temperature  of  the  surroundings  affect  the  appetite 

for  food  ;  in  winter,  and  in  cold  regions,  the  sensation  of  hunger  and  the  appetite 
for  the  fats,  or  such  substances  as  yield  much  heat  when  they  are  oxidized,  are 
increased  ;  in  summer,  and  in  hot  climates,  they  are  diminished.  Thus  the  mean 
temperature  of  the  surroundings,  to  a  certain  extent,  determines  the  amount  of 
the  heat-producing  substances  to  be  taken  in  the  food.  In  winter  the  amount  of 
ozone  in  the  air  is  greater,  and  thus  the  oxidizing  power  of  the  inspired  air  is 
increased. 

II.  Regulatory  Mechanisms  Governing  the  Excretion  of  Heat. — 
The  mean  amount  of  heat  given  off  by  the  human  skin  in  twenty-four  hours,  by  a 
man  weighing  82  kilos.,  is  2092  to  2592  calories,  /.  e.,  1.36  to  1.60  per  minute. 

(i)  Increased  temperature  causes  dilatation  of  the  cutaneous  vessels; 
the  skin  becomes  red,  congested,  and  soft;  it  contains  more  fluids,  so  that  it 
becomes  a  better  conductor  of  heat ;  the  epithelium  is  moistened,  and  sweat 
appears  upon  the  surface.  Thus  increased  excretion  of  heat  is  provided  for,  while 
the  evaporation  of  the  sweat  also  abstracts  heat. 

The  amount  of  heat  necessary  to  convert  into  vapor  I  grm.  of  water  at  100°  C,  is  equal  to  that 
required  to  heat  10  grms.  from  0°  to  53.67°  C.  The  sweat  as  secreted  is  .it  the  temperature  of  the 
body;  if  it  were  completely  changed  into  vapor,  it  would  require  the  heat  necessary  to  raise  it  to  the 
boiling  point,  and  also  that  necessary  to  convert  it  into  vapor. 

Cold  causes  contraction  of  the  cutaneous  vessels ;  the  skin  becomes 
pale,  less  soft,  poorer  in  juices,  and  collapsed  ;  the  epithelium  becomes  dry,  and 
does  not  permit  fluids  to  pass  through  it  to  be  evaporated,  so  that  the  excretion  of 
heat  is  diminished.  The  excretion  of  heat  from  the  periphery,  and  the  transverse 
thermal  conduction  through  the  skin,  are  diminished  by  the  contraction  of  the 
vessels  and  muscles  of  the  skin,  and  by  the  expulsion  of  the  well-conducting  blood 
from  the  cutaneous  and  subcutaneous  ve,ssels.  The  cooling  of  the  body  is  very 
much  affected,  owing  to  the  diminution  of  the  cutaneous  blood  stream,  just  as 
occurs  when  the  current  through  a  coil  or  worm  of  a  distillation  apparatus  is  greatly 
diminished  (  Winternitz).  If  the  blood  vessels  dilate,  the  temperature  of  the  surface 
of  the  body  rises,  the  difference  of  temperature  between  it  and  the  surrounding 
cooler  medium  is  increased,  and  thus  the  excretion  of  heat  is  increased.  Tomsa 
has  shown  that  the  fibres  of  the  skin  are  so  arranged  anatomically,  that  the  tension 
of  the  fibres  produced  by  the  erector  pili  muscles  causes  a  diminution  in  the 
thickness  of  the  skin,  this  result  being  brought  about  at  the  expense  of  the  easily 
expelled  blood. 

Landois  and  Hauschild  ligatured  the  arteries  alone,  or  the  arteries  and  veins  (dog),  e.g.,  the 
axillary  artery  and  vein,  the  crurals,  the  carotids  and  the  jugular  veins,  and  found  that  in  a  short 
time  the  temperature  rose  several  tenths  of  a  degree. 

By  the  systemiitic  application  of  stimuli,  e.g.,  cold  baths,  and  washing  with  cold  water,  the 
muscles  of  the  skin  and  its  blood  vessels  may  be  caused  to  contract,  and  become  so  vigorous  and 
excitable  that,  when  cold  is  suddenly  applied  to  the  body,  or  to  a  part  of  it,  the  excretion  of  heat  is 
energetically  prevented,  so  that  cold  baths  and  washing  with  cold  water  are,  to  a  certain  extent, 
"  gymnastics  of  the  cutaneous  muscles,"  which,  under  the  above  circumstances,  protect  the  body 
from  cold  (^Rosenthal,  Jit  Bois  Reymond). 

(2)  Increased  temperature  causes  increased  heart  beats,  while 
diminished  temperature  diminishes  the  number  of  contractions  of  the 
heart  (§  58,  II,  a).  The  relatively  warm  blood  is  pumped  by  the  action  of  the 
heart  from  the  internal  organs  of  the  body  to  the  surface  of  the  skin,  where  it 
readily  gives  off  heat.     The  more  frequently  the  same  volume  of  blood  passes 


CLOTHING.  363 

through  the  skin — twenty-seven  heart  beats  being  necessary  for  the  complete 
circuit  of  the  blood — the  greater  will  be  the  amount  of  heat  given  off  and  con- 
versely. Hence,  the  frequency  of  the  heart  beat  is  in  direct  relation  to  the 
rapidity  of  cooling  (Walther).  In  very  hot  air  (over  ioo°  C.)  the  pulse  rose  to 
over  1 60  per  minute.  The  same  is  true  in  fever  (§  70,  3,  c).  Liebermeister  gives 
the  following  numbers  with  reference  to  the  temperature  in  an  adult : — 

Pulse  beats,  per  min. 78.6 — 91.2 — 99.8 — 10S.5 — no— 137.5. 

Temperalure  in  C.° 37° — 38° — 39° —    40° — 41° —    42°. 

(3)  Increased  Temperature  increases  the  Number  of  Respirations. 

— Under  ordinary  circumstances,  a  much  larger  volume  of  air  passes  through  the 
lungs  when  it  is  warmed  almost  to  the  temperature  of  the  body.  Further,  a  cer- 
tain amount  of  watery  vapor  is  given  off  with  each  expiration,  which  must  be 
evaporated,  whereby  heat  is  abstracted.  Energetic  respiration  aids  the  circula- 
tion, so  that  respiration  acts  indirectly  in  the  same  way  as  (2).  According  to 
other  observers,  the  increased  consumption  of  O  favors  the  combustion  in  the 
body  (§  127,  8),  whereby  the  increased  respiration  must  act  in  producing  an 
amount  of  heat  greater  than  normal.  This  excess  is  more  than  compensated  by 
the  cooling  factors  above  mentioned.  Forced  respiration  produces  cooling,  even 
when  the  air  breathed  is  heated  to  54°  C,  and  saturated  with  watery  vapor. 
(^Lombard). 

(4)  Covering  of  the  Body. — Animals  become  clothed  in  winter  with  a  winter 
fur  or  covering,  while  in  summer  their  covering  is  lighter,  so  that  the  excretion  of 
heat  in  surroundings  of  different  temperatures  is  thereby  rendered  more  constant. 
Many  animals  which  live  in  very  cold  air  or  water  (whale)  are  protected  from  too 
rapid  excretion  of  heat  by  a  thick  layer  of  fat  under  the  skin.  Man  provides  for 
a  similar  result  by  adopting  summer  and  winter  clothing. 

(5)  The  position  of  the  body  is  also  important ;  pulling  the  parts  of  the  body 
together,  approximation  of  the  head  and  limbs,  keep  in  the  heat ;  spreading  out 
the  limbs,  erection  of  the  hairs,  pluming  the  feathers,  allow  more  heat  to  be 
evolved.  If  a  rabbit  be  kept  exposed  to  the  air  with  its  legs  extended  for  three 
hours,  the  rectal  temperature  will  fall  from  39°  C.  to  37°  C.  Man  may  influence 
his  temperature  by  remaining  in  a  warm  or  cold  room — by  taking  hot  or  cold 
drinks,  hot  or  cold  baths — remaining  in  air  at  rest  or  air  in  motion,  e.  g.,  by  using 
a  fan. 

Stimulation  of  the  central  end  of  a  sensory  nerve  (sciatic)  increases  the  surface  temperature  and 
diminishes  the  internal  temperature  (  Ostroumo-v,  Mitropo/siv). 

Clothing — Warm  Clothing  is  the  Equivalent  of  Food. — As  clothes  are  intended  to  keep  in 
heat  of  the  body,  and  heat  is  produced  by  the  combustion  and  oxidation  of  the  food,  we  may  say 
the  body  takes  in  heat  directly  in  the  food,  while  clothing  prevents  it  from  giving  off  too  much  heat. 
Summer  clothes  weii;h  3  to  4  kilos  ,  and  winter  ones  6  to  7  kilos. 

In  connection  with  clothes,  the  following  considerations  are  of  importance  : — 

( I )  Their  capacity  for  conduction. — Those  substances  which  conduct  heat  badly  keep  us  warmest. 
Hare  skin,  down,  beaver  skin,  raw  silk,  taffeta,  sheep's  wool,  cotton  wool,  flax,  spun  silk,  are  given 
in  order,  from  the  worst  to  the  best  conductors.  (2)  The  capacity  for  radiation. — Coarse  materials 
radiate  more  heat  than  smooth,  but  color  has  no  effect.  (3)  Relation  to  the  sun's  rays. — Dark 
materials  absorb  more  heat  than  light  colored  ones.  (4)  Their  hygroscopic  properties  are  important, 
whether  they  can  absorb  much  moisture  from  the  skin  and  gradually  give  it  off  by  evaporation,  or 
the  reverse.  The  same  weight  of  wool  takes  up  twice  as  much  as  linen  ;  hence,  the  latter  gives  it 
off  in  evaporation  more  rapidly.  Flannel  next  the  skin  is  not  so  easily  moistened,  nor  does  it  so 
rapidly  become  cold  by  evaporation ;  hence  it  protects  against  the  action  of  cold.  (5)  The/^>-- 
vteability  for  air  is  of  importance,  but  does  not  stand  in  relation  with  the  heat  conducting  capacity. 
The  following  substances  are  arranged  in  order  from  the  most  to  the  least  permeable — flannel,  buclc- 
skin,  linen,  silk,  leather,  wax  cloth. 

215.  INCOME,  EXPENDITURE,  AND  BALANCE  OF  HEAT. 

— As  the  temperature  of  the  body  is  maintained  within  narrow  limits,  the  amount 
of  heat  taken  in  must  balance  the  heat  given  off,  /.  c,  exactly  the  same  amount  of 
potential  energy  must  be  transformed  in  a  given  time  into  heat,  as  heat  is  given  off 
from  the  body. 


364       INCOME,  EXPENDITURE,  AND  BALANCE  OF  HEAT. 

An  adult  produces  as  much  heat  in  half  an  hour  as  will  raise  the  temperature  of 
his  body  i°  C.  If  no  heat  was  given  off,  the  body  would  become  very  hot  in  a 
short  time  ;  it  would  reach  the  boiling  point  in  thirty-six  hours,  supposing  the 
production  of  heat  continued  uninterruptedly. 

The  following  are  the  most  important  calculations  on  the  subject : — 

(A)  According  to  Helmholtz,  who  was  the  first  to  estimate  numerically  the  amount  of  heat 
produced  by  a  man. 

(1)  Heat  Income. — (a)  A  heahhyaduh,  weighing  82  kilos.,  expires  in  twenty- 

four  hours  878.4  grms.  CO;   [Scharling).     The  combustion  of  the 

C  therein  into  CO^  produces 1,730,760  cal. 

[b)  But  he  takes  in  more  O  than  reappears  in  the  COj ;  the  excess  is  used 

in  oxidation  processes,*'.^.,  for  the   formation  of  H^O,  by  union 
with  H,  so  that   13,615  grms.  H  will  be  oxidized  by  the  excess  of 

O,  which  gives 318.600  cal. 

2,049,360  cal. 

[c)  About  25  per  cent,  of  the  heat  must  be  referred  to  sources  other  than 

combustion  {Du!ong),  so  that  the  total =  2,732,000  cal. 

2,732,000  calories  are  actually  sufficient  to  raise  the  temperature  of  an 
adult  weighing  80  to  90  kilos.,  from  10°  to  38  or  39°  C,  /.  e.,  to  a 
normal  temperature. 

(2)  Heat  expenditure. — (a)  Heating  the  food  and  drink,  which  have  a  mean 

temperature  of  12°  C.     70, 157  cal =^  2.6  per  cent. 

[b)  Heating  the  air  respired  =  16,400  grms.,  with  an  initial  temperature  of 

20°  C.      70,032  cal ^2.6  per  cent. 

(  IV/ien  the  temperature  of  the  air  is  0°,  140,064  cal.  =  5.2  per  rent.) 

(c)  Evaporation  of  656  grms.  water  by  the  lungs,  397.536  cal. ^  14.7  per  cent. 

(i/)  The  remainder  given  off  by  radiation  and  evaporation  of  water  by  the 

s,k\n,  (yj .$  per  eeiti.  to) =80.1  per  cent. 

(B)  According  to  Dulong. — (i)  Heat  income. — Dulong,  and  after  him  Boussingault,  Liebig, 
and  Dumas,  sought  to  estimate  the  amount  of  heat  from  the  C  and  H  contained  in  the  food.  As 
we  know  that  the  combustion  of  I  grm.  C  =  8040  heat  units,  and  I  grm.  H  ^  34.460  heat  units, 
it  would  be  easy  to  determine  the  amount  of  heat  were  the  C  simply  converted  into  CO^  and  the 
H  into  HjO.  But  Dulong  omitted  the  H  in  the  carbohydrates  {e.  g.,  grape  sugar  =  C^H,  jO,;)  as 
producing  heat,  because  the  H  is  already  combined  with  O,  or  at  least  is  the  proportion  in  which  it 
exists  in  water.  This  assumption  is  hypothetical,  for  the  atoms  of  C  in  a  carbohydrate  may  be  so 
firmly  united  to  the  other  atoms,  that  before  oxidation  can  take  place  their  relations  must  be  altered, 
so  that  potential  energy  is  used  up,  i.  e.,  heat  must  be  rendered  latent;  so  that  these  considerations 
rendered  the  following  example  of  Dulong's  method  given  by  Vierordt  very  prolilematical. 

An  adult  eats  in  twenty- four  hours,  120  grms.  proteids,  90  grms.  fat  and  340  grms,  starch  (carbo- 
hydrates).    These  contain  : — 

Grms.  C.  H. 

Proteids 120  contain     64.18  and     8.60 

Fat 90         "         70.20     "     10.26 

Starch 330         "       146.82     "       .    . 

281.20  and  18.86 
The  urine  and  fs;ces  contain  still  unconsumed  ...  29  8       "       6.3 

Remainder  to  be  burned 251.4     and   12.56 

As  I  grm.  C  =8040  heat  units  and  I  grm.  H  =  34,460  heat  units,  we  have  the  following  calcu- 
lation : — 

251.4    X    8.040  =  2,031,312  (from  combustion  of  C). 
12.56  X  34.460  =     432.818  (     "  "  H). 

2.464,130  heat  units. 
(2]  Heat  expenditure  : —  Per  cent,  of 

^    '  ^  Heat  units.  the  excreta. 

1.  1900  grms.  are  excreted  daily  by  the  urine  and  f;tces,  and 

they  are  25°  warmer  than  the  food 47,500  1.8 

2.  13,000  grms.  air  are  heated  (from   12°  to  27°  C.)  (heat 

capacity  of  the  air  =  0.26) 84. 500  3.5 

3.  330  grms.  water  are  evaporated  by  the  respiration  ( i  grm. 

=  582  heat  units) 192,060  7.2 

4.  660  grms.  water  are  evaporated  from  the  skin 384,1^0  14.5 

Total 708,180 

Remainder  radiated  and  conducted  from  the  skin 1,791,810  72 

Total  amount  of  heat  units  given  oft' 2,500,000  *  100 


RELATION   OF   HEAT   PRODUCTION   TO   WORK.  365 

(C)  Heat  income. — Frankland  burned  the  food  directly  in  a  calorimeter,  and  found  that  l  grm. 
of  the  following  substances  yielded — 

Albumin 4998  heat  units 

Grape  sugar 3277         " 

Ox  fat 9069         " 

The  albumin,  however,  is  only  oxidized  to  the  stage  of  urea,  hence  the  heat  units  of  urea  must  be 
deducted  from  4998,  which  gives  4263  heat  units  obtainable  from  I  grm.  albumin.  When  we  know 
the  number  of  grammes  consumed,  a  simple  multiplication  gives  the  number  of  heat  units. 

The  heat  units  will  vary,  of  course,  with  the  nature  of  the  food.     J.  Ranke  gives  the  following  : — 

With  animal  diet 2,779,524  heat  units. 

"     food  free  from  N 2,059,506 

"     mixed  diet 2,200,000        " 

"     during  hunger 2,012,816        " 

216.  VARIATIONS  IN  HEAT  PRODUCTION.— According  to  Helmholtz,  an  adult 
weighing  82  kilos,  produces  2,732,000  calories  in  twenty-four  hours. 

(1)  Influence  of  the  Body  Weight. — Accepting  the  above  number,  Immermann  has  given  the 
following  formula  for  the  heat  production  in  living  tissues  : — 

3  3 

w:   W  =  y'p':   y  P^ 

(where  W  =  2,732,000;  P  ^  82  kilos.     [W:  y^/'-  =  144,75]  >  /  =  body  weight  of  the  person 
to  be  investigated,  and  w  represents  the  heat  production  which  is  required). 
3 — 
It  is  highly  desirable  that  W:  ^//^  (=  ot)  was  ascertained  as   a  mean   from  a  large   number  of 
observations,  that  the  heat  production  for  any  body  weight/  would  be 

s — 
TV  =  m  Y/>^. 

(2)  Age  and  Sex. — The  heat  production  is  less  in  infancy  and  in  old  age,  and  it  is  less  in  pro- 
portion in  the  female  than  in  the  male. 

(3)  Daily  Variation. — The  heat  production  shows  variations  in  twenty-four  hours  correspond- 
ing with  the  temperature  of  the  body  (J  213,  4). 

(4)  The  heat  production  is  greater  in  the  waking  condition,  during  physical  and  mental  exer- 
tion, and  during  digestion,  than  in  the  opposite  conditions. 

217.   RELATION  OF  HEAT    PRODUCTION  TO  WORK.— The 

potential  energy  supplied  to  the  body  may  be  transformed  into  heat  and  kinetic 
energy  (see  Introduction).  In  the  passive  condition,  almost  all  the  potential 
energy  is  changed  into  heat ;  the  workman,  however,  transforms  potential  energy 
into  work — mechanical  work — in  addition  to  heat.  These  two  may  be  com- 
pared by  using  an  equivalent  measurement,  thus  i  heat  unit  (energy  required  to 
raise  i  gramme  of  water  1°  C.)  =  425.5  gramme  metres. 

Relation  of  Heat  to  Work. — The  following  example  may  serve  to  illustrate  the  relation  between 
heat  production  and  the  production  of  work  :  Suppose  a  small  steam  engine  to  be  placed  within  a 
capacious  calorimeter,  and  a  certain  quantity  of  coal  to  be  burned,  then  as  long  as  the  engine  does 
not  perform  any  mechanical  work,  heat  alone  is  produced  by  the  burning  of  the  coal.  Let  this 
amount  of  heat  be  estimated,  and  a  second  e.xperiment  made  by  burning  the  same  amount  of  coal, 
but  allow  the  engine  to  do  a  certain  amount  of  work — say,  raise  a  weight — by  a  suitable  arrange- 
ment. This  work  must,  of  course,  be  accomplished  by  the  potential  energy  of  the  heating  material. 
At  the  end  of  this  experiment,  the  temperature  of  the  water  will  be  much  less  than  in  the  first  ex- 
periment, i.  t.,  fewer  heat  units  have  been  transferred  to  the  calorimeter  when  the  engine  was  heated 
than  when  it  did  no  work. 

Comparative  experiments  of  this  nature  have  shown  that  in  the  second  experiment  the  useful 
work  is  very  nearly  proportional  to  the  decrease  of  the  heat  (Hirn).  In  good  steam  engines  only 
j'j,  and  in  the  very  best  's,  of  the  potential  energy  is  changed  into  mechanical  energy,  while  \l  to 
^  passes  into  heat. 

Compare  this  with  what  happens  within  the  body  :  A  man  in  a  passive  con- 
dition forms  from  the  potential  energy  of  the  food  between  zyi  and  2^  million 
calories.  The  work  done  by  a  workman  is  reckoned  at  300,000  kilogramme 
metres  (§  300). 

If  the  organism  were  entirely  similar  to  a  machine,  a  smaller  amount  of  heat, 
corresponding  to  the  work  done,  would  be  formed  in  the  body.  .A.s  a  matter  of 
fact,  the  organism  produces  less  heat  from  the  same  amount  of  potential  energy 


366  ACCOMMODATION    FOR   VARYING   TEMPERATURES. 

when  mechanical  work  is  done.  There  is  one  point  of  difference  between  a  work- 
man and  a  working  machine.  The  workman  consumes  much  more  potential 
energy  in  the  same  time  than  a  passive  person  ;  much  more  transformed  in  his 
body,  and  hence  the  increased  consumption  is  not  only  covered,  but  even  over- 
compensated.  Hence,  the  workman  is  warmer  than  the  passive  person,  owing  to 
the  increased  muscular  activity  (§  210,  i,  b).  Take  the  following  example  :  Him 
(1858)  remained /aj-JW^',  and  absorbed  30  grm.  O  per  hour  in  a  calorimeter,  and 
produced  155  calories.  When  in  the  calorimeter  he  did  work  equal  to  27,450 
kilogramme  metres,  which  was  transferred  beyond  it;  he  absorbed  132  grm.  O, 
and  produced  only  251  calories. 

In  estimating  the  work  done,  we  must  include  only  the  heat  equivalent  of  the  work  transferred 
beyond  the  body ;  lifting  weights,  pushing  anything,  throwing  a  weight,  and  lifting  the  body,  are 
examples.  In  ordinary  walking  there  is  no  loss  of  heat  (apart  from  overcoming  the  resistance  of 
the  air);  when  descending  from  a  height  there  may  be  increased  warmth  of  the  body. 

The  organism  is  superior  to  a  machine  in  as  far  as  it  can,  from  the  same  amount 
of  potential  energy,  produce  more  work  in  proportion  to  heat.  While  the  very 
best  steam  engine  gives  \  of  the  potential  energy  in  the  form  of  work,  and  \  as 
heat,  the  body  produces  \  as  work  and  ^  as  heat.  Chemical  energy  can  never  do 
work  alone,  in  a  living  or  dead  motor,  without  heat  being  formed  at  the  same 
time. 

218.  ACCOMMODATION  FOR  VARYING  TEMPERATURES. 

— All  substances  which  possess  high  conductivity  for  heat,  when  brought  into  con- 
tact with  the  skin,  appear  to  be  very  much  colder  or  hotter  than  bad  conductors 
of  heat.  The  reason  of  this  is  that  these  bodies  abstract  far  more  heat,  or  con- 
duct more  heat  than  other  bodies.  Thus  the  water  of  a  cool  bath,  being  a  better 
conductor  of  heat,  is  always  thought  to  be  colder  than  air  at  the  same  tempera- 
ture.    In  our  climate  it  appears  to  us  that — 


Air,  at  iS°  C.  is  moderately  warm; 
"    at  25°-28°  C,  hot ; 
"    above  28°,  very  hot. 


Water,  at  18°  C.  is  cold; 
"       from  i8°-29°  C,  cool ; 
"  "     29°-35°  C,  warm  ; 

"  "     37.5°  and  above,  hot. 


Warm  Media. — As  long  as  the  temperature  of  the  body  is  higher  than  that 
of  the  surrounding  medium,  heat  is  given  off,  and  that  the  more  rapidly  the 
better  the  conducting  power  of  the  surrounding  medium.  As  soon  as  the  tem- 
perature of  the  surrounding  medium  rises  higher  than  the  temperature  of  the 
body,  the  latter  absorbs  heat,  and  it  does  so  the  more  rapidly  the  better  the  con- 
ducting power  of  the  medium.  Hence,  hot  water  appears  to  be  warmer  than  air 
at  the  same  temperature.  A  person  may  remain  eight  minutes  in  a  bath  at  45.5° 
C.  (dangerous  to  life  !)  ;  the  hands  may  be  plunged  into  water  at  50.5°  C,  but 
not  at  51.65°  C,  while  at  60°  violent  pain  is  produced. 

A  person  may  remain  for  eight  minutes  in  hot  air  at  127°  C,  and  a  tempera- 
ture of  132°  C.  has  been  borne  for  ten  minutes  (Tillett,  ij6f).  The  body  tem- 
perature rises  only  to  38.6°  or  38.9°  {Fordyce,  Blagden,  1774)-  This  depends 
upon  the  air  being  a  bad  conductor,  and  thus  it  gives  less  heat  to  the  body  than 
water  would  do.  Further,  and  what  is  more  important,  the  skin  becomes  covered 
with  sweat,  which  evaporates  and  abstracts  heat,  while  the  lungs  also  give  off  more 
watery  vapor.  The  enormously  increased  heart  beats — over  160 — and  the  dilated 
Hood  vessels,  enable  the  skin  to  obtain  an  ample  supply  of  blood  for  the  formation 
and  evaporation  of  sweat.  In  proportion  as  the  secretion  of  sweat  diminishes, 
the  body  becomes  unable  to  endure  a  hot  atmosphere ;  hence  it  is  that  in  air  con- 
taining  much  watery  vapor  a  person  cannot  endure  nearly  so  high  a  temperature  as 
in  dry  air,  so  that  heat  must  accumulate  in  the  body.  In  a  Turkish  vapor  bath 
of  53°  to  60°  C,  the  rectal  temperature  rises  to  40.7°  or  41.6°  C.  (Barthels, 
Jiirgensen  Krishaber).  A  person  may  work  continuously  in  air  at  31°  C.  which 
is  almost  saturated  with  moisture  {Stapff). 


FEVER  AND  ITS  PHENOMENA.  367 

If  a  person  be  placed  in  water  at  the  temperature  of  the  body,  the  normal 
temperature  rises  i°  C.  in  one  hour,  and  in  1J2  hours  about  2°  C.  {Lieben/ieister). 
A  gradual  increase  of  the  temperature  from  38.6°  to  40.2°  C.  causes  the  axillary 
temperature  to  rise  to  39.0°  within  fifteen  minutes. 

Rabbits  placed  in  a  warm  box  at  36°  C.  acquire  a  constant  temperature  of  42°  C,  and  lose 
weight ;  but  if  the  temperature  of  the  box  be  raised  to  40°,  death  occurs,  the  body  temperature 
rising  to  45°  C.  (_/.  Rosenthal). 

219.  STORAGE  OF  HEAT  IN  THE  BODY.— As  the  uniform  tem- 
perature of  the  body,  under  normal  circumstances,  is  due  to  the  reciprocal  rela- 
tion between  the  amount  of  heat  produced  and  the  amount  given  off,  it  is  clear 
that  heat  must  be  stored  up  in  the  body  when  the  evolution  of  heat  is  diminished. 
The  skin  is  the  chief  organ  regulating  the  evolution  of  heat ;  when  it  and  its 
blood  vessels  contract  the  heat  evolved  is  diminished,  when  they  dilate  it  is  in- 
creased.    Heat  may  be  stored  up  when — 

(a)  The  skin  is  extensively  stimulated,  whereby  the  cutaneous  vessels  are  temporarily  contracted 
{Rohrig).  (b)  Any  other  circumstances  preventing  heat  from  being  given  off  by  the  skin  (  Win- 
ternitz).  (r)  When  the  7'asonictor  centre  is  excited,  causing  all  the  blood  vessels  of  the  body — 
those  of  the  skin  mcluded — to  contract.  This  seems  to  be  the  cause  of  the  rise  of  temperature 
after  the  transfusion  of  blood  (Laiidois),  and  the  rise  of  temperature  after  the  sudden  removal  of 
water  from  the  body  seems  to  admit  of  a  similar  explanation  ;  as  the  inspissated  blood  occupies  less 
space,  and  the  contracted  vessels  of  the  skin  admit  less  blood,  [d)  When  the  circulation  in  the 
cutaneous  vessels  of  a  large  area  is  mechanically  slowed,  or  when  the  smaller  vessels  are  plugged 
by  the  injection  of  some  sticky  substance,  or  by  the  transfusion  of  foreign  blood,  the  temperature 
rises  {\  102).  Landois  found  that  ligature  of  both  carotids,  and  the  axillary  and  crural  arteries, 
caused  a  rise  of  1°  C.  within  two  hours. 

It  is  also  obvious  than  when  a  normal  amount  of  heat  is  given  off,  an  increased 
production  of  heat  must  raise  the  temperature.  The  rise  of  the  temperature  after 
muscular  or  mental  exertion,  and  during  digestion,  seems  to  be  caused  in  this 
way.  The  rise  which  occurs  several  hours  after  a  cold  bath  is  probably  due  to  the 
reflex  excitement  of  the  skin  causing  an  increased  production  ( Jiirgensen). 

When  the  temperature  of  the  body,  as  a  whole,  is  raised  6°  C,  death  takes 
place,  as  in  sunstroke.  It  seems  as  if  there  was  a  molecular  decomposition  of  the 
tissues  at  this  temperature ;  while,  if  a  slightly  lower  temperature  be  kept  up  con- 
tinuously, fatty  degeneration  of  many  tissues  occurs  {Litten).  If  animals  which 
have  been  exposed  artificially  to  a  temperature  of  over  42°  to  44°  C.  be  transferred 
to  a  cooler  atmosphere,  their  temperature  becomes  subnormal  (36°  C.)  and  may 
remain  so  for  several  days. 

220.  FEVER. — Cause. — Fever  consists  in  a  greatly  increased  tissue  metabolism  (especially  in 
the  muscles — Finkler,  Zuntz),  with  simultaneous  increase  of  the  temperature.  Of  course,  the 
mechanism  regulatmg  the  balance  of  formation  and  expenditure  of  heat  is  disturbed.  During  fever 
the  body  is  greatly  mcapacitated  for  performing  mechanical  work.  It  is  evident,  therefore,  that  the 
large  amount  of  potential  energy  transformed  is  almost  all  converted  into  heat,  so  that  the  non- 
transformation  of  the  energy  into  mechanical  work  is  another  important  factor. 

We  may  take  intermittent  fever  or  ague  as  a  type  of  fever,  in  which  violent  attacks  of  fever  of 
several  hours'  duration  alternate  with  periods  free  from  fever.  This  enables  us  to  analyze  the 
symptoms.     The  symptoms  of  fever  are: — 

(I)  The  increased  temperature  of  the  body  {38°  to  39°  C,  slight;  from  39°  to  41°  C.  and 
upward,  severe).  The  high  temperature  occurs  not  only  in  cases  where  the  skin  is  red,  and  has  a 
hot,  burning  feeling  (calor  mordax),  but  even  during  the  rigor  or  the  shivering  stai;e,  the  tempera- 
ture IS  raised  i^Anl.  de  Haen,  1760).  The  congested,  red  skin  is  a  good  conductur  of  heat,  while 
the  pale,  bloodless  skin  conducts  badly ;  hence,  the  former  feels  hot  to  the  touch  {v.  Bdrcnsprung 
—compare  ^212). 

The  following  table  in  °C  and  °F  indicates  generally  the  degree  of  fever : — 


3S°C.  =    95°  F.     .    . 
36        =    96.8         .    . 

.    .    Collapse. 
.    .    Low. 

39°  C.  =  102.2°  F. 
39.5      =  103. 1 

}■ 

Moderate  fever. 

l(^-S     =    97-7 

37        =    98.6         .    . 

.    .    .    Subnormal. 
.    .    .    Normal. 

40        =  104 
40.5      =  104.9 

}^ 

High  fever. 

37-5     =    99-5) 

41          =  105. 8 

Hyperpyretic. 

3S        =  100.4  >      .    ■ 

.    .    Sub-febrile. 

J-'inlafson.} 

38.S     =101.3  J 

1 

368  FEVER   AND    ITS   PHENOMENA. 

(2)  The  increased  production  of  heat  (assumed  by  Lavoisier  and  Crawford)  is  proved  by 
calonmetric  observations.  This  is,  in  small  part,  due  to  the  increased  activity  of  the  circulation 
being  changed  into  heat  (§  206,  2,  a),  but  for  the  most  part  it  is  due  to  increased  combustion  withm 
the  body. 

(3)  The  increased  metabolism  gives  rise  to  the  "  consuming"  or  "wasting"  character  of  fever, 
which  was  known  to  Hippocrates  and  Galen,  and,  in  1852,  v.  Barensprung  asserted  that  "all  the 
so-called  febrile  symptoms  show  that  the  metabolism  is  increased."  The  increase  of  the  metabolism 
is  shown  in  the  increased  excretion  of  COj  =  70  to  80  per  cent.  (LeyJen  and  J-ianie/),  while 
more  O  is  consumed,  although  the  respiratory  quotient  remains  the  same  [Zuii/z  and  Lilicnfeld). 
According  to  Dr.  Kinkier,  the  COj  excreted  shows  greater  variations  than  the  O  consumed.  The 
excretion  of  urea  is  increased  \  to  |.  In  dogs  suffering  from  septic  fever,  Naunyn  observed  that 
the  urea  began  to  increase  before  the  temperature  rose,  " f  re-febrile  rise."  Part  of  the  urea, 
however,  is  sometimes  retained  during  the  fever,  and  appears  after  the  fever  is  over,  "  epi-critical 
excretion  of  urea"  (^Naunyn).  The  uric  acid  is  also  increased;  the  urine  pigment  (^  19), 
derived  from  the  haemoglobin,  may  be  increased  twenty  times,  while  the  excretion  of  potash 
may  be  sevenfold. 

It  is  important  to  observe  that  the  oxidation  or  combustion  processes  within  the  body  of  the  fever 
patient  are  greatly  increased  when  he  is  placed  in  a  warmer  atmosphere.  The  oxidation  processes 
in  fever,  however,  are  also  increased  under  the  influence  of  cooler  surroundings  (J  214,  1,  2),  but 
the  increase  of  the  oxidation  in  a  warm  medium  is  very  much  greater  than  in  the  cold  {D.  Finkler). 
The  amount  of  COj  in  the  blood  is  diminished,  but  not  at  once  after  the  onset  even  of  a  very  severe 
k^^r  (Geppert). 

(4)  The  diminished  excretion  of  heat  varies  in  different  stages  of  a  fever.  We  distinguish 
several  stages  in  a  fever — (a)  The  cold  stage,  when  the  loss  of  heat  is  greatly  diminished,  owing 
to  the  pale,  bloodless  skin,  but  at  the  same  time  the  heat  production  is  increased  i'/^  to  2yi  times. 
The  sudden  and  considerable  rise  of  the  temperature  during  this  stage  shows  that  the  diminished 
excretion  of  heat  is  not  the  only  cause  of  the  rise  of  the  temperature.  (/>)  During  the  hot  stage 
the  ileal  given  off'  from  the  congested,  red  skin  \s  greatly  increased,  but  at  the  same  time  more  heat 
is  produced.  Liebermeister  assumes  that  a  rise  of  1,2,  3,  4°  C.  corresponds  to  an  increased  pro- 
duction of  heat  of  6,  12, 18,  24  per  cent,  (c)  In  the  sweating  stage  the  excretion  of  heat  through 
the  red,  moist  skin  and  evaporation  are  greatest,  more  than  two  to  three  times  the  normal  [Leyden). 
The  heat  production  is  either  increased,  normal,  or  subnormal,  so  that  under  these  conditions  the 
temperature  may  also  be  subnormal  (36°  C). 

(5)  The  heat-regulating  mechanism  is  injured.  A  warm  temperature  of  the  surroundings 
raises  the  temperature  of  the  fever  patient  more  than  it  does  that  of  a  non-febrile  person.  The 
depression  of  the  heat  production,  which  enables  normal  animals  to  maintain  their  normal  tempera- 
ture in  a  warm  medium  (^  214),  is  much  less  in  fever  (D.  Fintler). 

The  accessory  phenomena  of  fever  are  very  important :  Increase  in  the  intensity  and  number 
of  the  heart  beats  (§  214,  II,  2)  and  respirations  (in  adults  40,  and  children  60  per  min.),both  being 
compensatory  phenomena  of  the  increased  temperature;  further,  dnninished  digestive  activity  (J  1 86, 
D)  and  intestinal  movements;  disturbances  of  the  cerebral  activities;  of  secretion;  of  muscular 
activity;  slower  excretion,  e.g.,  of  potassium  iodide  through  the  urine  (Bachrach,  Scholze).  In 
severe  fever,  molecular  degenerations  of  the  tissues  are  very  common. 

For  the  condition  of  the  blood  corpuscles  in  fever,  see  ^  10;  the  vascular  tension,  §  69;  the 
saliva,  ^  146. 

Quinine,  the  most  important  febrifuge,  causes  a  decrease  of  the  temperature-  by  limiting  the 
production  of  heat  (I.ewisky,  Binz,  Naunyn,  Quincke,  Arniz)  (§  213,  6).  Toxic  doses  of  the 
metallic  salts  act  in  the  same  way,  while  there  is  at  the  same  time  diminished  formation  of  CUj 
{Lucksinger). 

[Antipyretics  or  Febrifuges. — All  methods  which  diminish  abnormal  temperature  belong  to 
this  group.  As  the  constant  temperature  of  the  body  depends  on  (l )  the  amount  of  heat  production, 
and  (2)  the  loss  of  heat,  we  may  lower  the  temperature  either  in  the  one  way  or  the  other.  When 
cold  water  is  applied  to  the  body,  it  abstracts  heat,  /.  e.,  it  affects  the  results  of  fever,  so  that  Lieber- 
meister calls  such  methods  antithermic.  But  those  remedies  which  diminish  the  actual  heat 
production  are  true  antipyretic.  In  practice,  however,  both  methods  are  usually  employed,  and 
spoken  of  collectively  as  antipyretics.] 

[Among  the  methods  which  are  used  to  abstract  heat  from  the  body  are  the  application  of  colder 
fluids,  such  as  the  cold  bath,  affusion,  douche,  spray,  ice,  or  cold  mixtures,  etc.  A  person  suffering 
from  high  fever  requires  to  be  repeatedly  placed  in  a  cold  bath,  to  produce  any  permanent  reduc- 
tion of  the  temperature.  Some  remedies  act  by  favoring  the  radiation  of  heat,  by  dilating  the 
cutaneous  vessels  (alcohol),  while  others  excite  the  sweat  glands — i,  e.,  are  sudorifics — so  that  the 
water,  by  its  evaporation,  removes  some  heat.  Among  the  drugs  which  influence  tissue  changes 
and  oxidation — and  thereby  lessen  heat  production — are  quinine,  salicylic  acid,  some  of  the  salicy- 
lates, digitalis  and  veratrin.  Blood  letting  was  formerly  used  to  diminish  abnormal  temperature. 
Among  the  newer  antipyretic  remedies  are  hydrochlorate  of  kalrin  and  antipyrin,  both  of  which 
belong  to  the  aromatic  group  (derivatives  of  benzol),  which  includes,  also,  many  of  our  best 
antiseptics.] 


INCREASE    OF    TEMPERATURE    POST-MORTEM.  369 

221.  ARTIFICIAL  INCREASE  OF  THE  BODILY  TEMPERA- 
TURE.— If  mammals  are  kept  constantly  in  air  at  40°  C,  the  excretion  of  heat 
from  the  body  ceases,  so  that  the  heat  produced  is  stored  up.  At  first,  the  tem- 
perature falls  somewhat  for  a  very  short  time  (Obcrnicr),  but  soon  a  decided 
increase  occurs.  The  respirations  and  pulse  are  increased,  while  the  latter  becomes 
irregular  and  weaker.  The  O  absorbed  and  CO,  given  off  are  diminished  after 
six  to  eight  hours  {IJtfen),  and  death  occurs  after  great  fatigue,  feebleness,  spasms, 
secretion  of  saliva  and  loss  of  consciousness,  when  the  bodily  temperature  ha.s 
been  increased  4°,  or,  at  most,  6°  C.  Death  does  not  take  place,  owing  to  rigidity 
of  the  muscles  ;  for  the  coagulation  of  the  myosin  of  mammals'  muscles  occurs  at 
49°  to  50°  C.  ;  in  birds,  at  53°  C,  and  in  frogs,  at  40°  C.  If  mammals  are 
suddenly  placed  in  air  at  100°  C,  death  occurs  (in  15  to  20  min.)  very  rapidly, 
and  with  the  same  phenomena,  while  the  bodily  temperature  rises  4°  to  5°  C.  In 
rabbits,  the  body  weight  diminishes  i  grm.  per  min.  Birds  bear  a  high  tempera- 
ture somewhat  longer ;  they  die  when  their  blood  reaches  48°  to  50°  C. 

Even  man  may  remain  for  some  time  in  air  at  100-110-132°  C,  but  in  ten  to 
fifteen  minutes  there  is  danger  to  life.  The  skin  is  burning  to  the  touch,  and  red ; 
a  copious  secretion  of  sweat  bursts  forth,  and  the  cutaneous  veins  are  fuller  and 
redder  {Crawford).  The  pulse  and  respirations  are  greatly  accelerated.  Violent 
headache,  vertigo,  feebleness,  stupefaction,  indicate  great  danger  to  life.  The 
rectal  temperature  is  only  1°  to  2°  C.  higher.  The  high  temperature  of  fever  may 
even  be  dangerous  to  human  life.  If  the  temperature  remains  for  any  length  of 
time  at  42.5°  C,  death  is  almost  certain  to  occur.  Coagulation  of  the  blood  m  the 
arteries  is  said  to  occur  at  42.6°  C.  (  Weikart).  If  the  artificial  heating  does  not 
produce  death,  fatty  infiltration  and  degeneration  of  the  liver,  heart,  kidneys  and 
muscles  begin,  after  thirty-si.\  to  forty-eight  hours  {Litten). 

Cold-blooded  Animals,  if  placed  in  hot  air  or  warm  water,  soon  have  their  temperature  raised 
6°  to  10°  C.  The  highest  temperature  compatible  with  life  in  a  frog  must  be  below  40°  C,  as  the 
frog's  heart  and  muscles  begin  to  coagulate  at  this  temperature.  Death  is  preceded  by  a  stage 
resembling  death,  during  which  life  may  be  saved. 

Most  of  the  juicy  plants  die  in  half  an  hour  in  air  at  52°  C,  or  in  water  at  46°  C.  (Sachs). 
Dried  seeds  of  corn  may  still  germinate  after  long  exposure  to  air  at  120°  C.  Lowly-organized 
plants,  such  as  algae,  may  live  in  water  at  60°  C.  {Hoppe-Seyler).  Several  bacteria  withstand  a 
boiling  temperature  (  Tyndall,  Chambertand). 

222.  EMPLOYMENT  OF  HEAT.— Action  of  Heat.— The  short,  but  not  intense,  action 
of  heat  on  the  surface  causes,  in  the  first  place,  a  transient  slight  decrease  of  the  bodily  temperature, 
partly  because  it  retards  retlexly  the  production  of  heat  [JCernii^),  and  partly  because,  owing  to  the 
dilatation  of  the  cutaneous  vessels  and  the  stretching  of  the  skin,  more  heat  is  given  off  (Scnalor). 
A  warm  bath  above  the  temperature  of  the  blood  at  once  increases  the  bodily  temperature. 

Therapeutic  Uses. — The  application  of  heat  to  the  entire  body  is  used  where  the  bodily  tem- 
perature has  fallen— or  is  likely  to  fall — -very  low,  as  in  the  algid  stage  of  cholera,  and  in  infants 
born  prematurely.  The  gentral  application  of  heat  is  obtained  by  the  use  of  warm  baths,  packing, 
vapor  baths,  and  the  copious  use  of  hot  drinks.  The  local  application  of  heat  is  obtained  by  the  use 
of  warm  wrappings,  partial  baths,  plunging  the  parts  in  warm  earth  or  sand,  or  placing  wounded 
parts  in  chambers  filled  with  heated  air.  After  removal  of  the  heating  agent,  care  must  be  taken  to 
prevent  the  great  escape  of  heat  due  to  the  dilatation  of  the  blood  vessels. 

223.  INCREASE  OF  TEMPERATURE  POST-MORTEM.— Phenomena.— Heiden- 

hain  found  that  in  a  dead  dog,  before  the  body  cooled,  there  was  a  constant  temporary  rise  of  the 
temperature,  which  slightly  exceeded  the  normal.  The  same  observation  had  been  occasionally 
made  on  human  bodies  immediately  after  their  death,  especially  when  death  was  preceded  by  mus- 
cu'ar  spasms  [also  in  yellow  fever.]  Thus,  Wunderlich  measured  the  temperature  fifty-seven  min- 
utes after  death  in  a  case  of  tetanus,  and  found  it  to  be  45.375°  C. 

Causes. — (i)  A  temporary  increased  production  of  heat  after  death,  due,  chiefly,  to  the  change 
of  the  semi-solid  myosin  of  the  muscles  into  a  solid  form  (rigor  mortis),  ."^s  the  muscle  coagulates, 
heat  is  produced  (yi.  Wather,  Fick).  All  conditions  which  cause  rapid  and  intense  coagulation  of 
the  muscles — e.g.,  spasms — favor  a. post-mortem  rise  of  temperature  (see  J  295) ;  a  rapid  coagulation 
of  the  blood  has  a  similar  result  (^  28,  5). 

(2)  Immediately  after  death,  a  series  of  chemical  processes  occur  within  the  body,  whereby  heat 
is  produced.  Valentin  placed  dead  rabbits  in  a  chamber,  so  that  no  heat  could  be  given  off  from 
the  body,  and  he  found  that  the  internal  temperature  of  the  animal's  body  was  increased.  The 
24 


370  ARTIFICIAL    LOWERING    OF   THE    TEMPERATURE, 

processes  which  cause  a  rise  of  temperature  post-mortem  are  more  active  during  the  first  than  the 
second  hour;  and  the  higher  the  temperature  at  the  moment  of  death,  the  greater  is  the  amount  of 
heat  evolved  after  death  (Quincke  and  Brieger). 

(3)  Another  cause  is  the  diminished  excretion  of  heat  postmortem.  After  the  circulation  is 
abolished,  within  a  few  minutes  little  heat  is  given  off  from  the  surface  of  the  liody,  as  rapid  excre- 
tion implies  that  the  cutaneous  vessels  must  be  continually  filled  with  warm  blood. 

224.  ACTION  OF  COLD  ON  THE  BODY.— Phenomena.— A  short, 
temporary,  slight  cooling  of  the  skin  (removing  one's  clothes  in  a  cool  room,  a 
cool  bath  for  a  short  time,  or  a  cool  douche)  causes  either  no  change  or  a  slight 
rise  in  the  bodily  temperature  {Liehcniieister).  The  slight  rise,  when  it  occurs,  is 
due  to  the  stimulation  of  the  skin  causing  reflexly  a  more  ra])id  molecular  trans- 
formation, and  therefore  a  greater  production  of  heat  {Lichenneister),  while  the 
amount  of  heat  given  off  is  diminished,  owing  to  contraction  of  the  small  cuta- 
neous vessels  and  the  skin  itself  {Jiirgcnscn,  Senator).  The  continuous  and 
intense  application  of  cold  causes  a  decrease  of  the  temperature  {Citrn'e),  chiefly 
by  conduction,  notwithstanding  that  at  the  same  time  there  is  a  greater  produc- 
tion of  heat.     After  a  cold  bath  the  temperature  may  be  34°,  32°,  and  even  30°  C. 

As  an  after-effect  of  the  great  abstraction  of  heat,  the  temperature  of  the 
body  after  a  time  remains  lower  than  it  was  before  (^'primary  after-effect" — 
Liebermeister)  ;  thus  after  an  hour  it  was  —  0.22°  C.  in  the  rectum.  There  is  a 
"secondary  after-effect"  which  occurs  after  the  first  after-effect  is  over,  when  the 
temperature  rises  (Jiirgensen).  This  effect  begins  five  to  eight  hours  after  a  cold 
bath,  and  is  equal  to  -1-  0.2°  C.  in  the  rectum.  Hoppe-Seyler  found  that  some 
time  after  the  application  of  heat  there  was  a  corresponding  lowering  of  the  tem- 
perature. 

Taking  Cold. — If  a  rabbit  be  taken  from  a  surrounding  temperature  of  35°  C,  and  suddenly 
cooled,  it  shivers,  and  there  may  be  temporary  diarrhoea.  After  two  days  the  temperature  rises  1.5° 
C,  and  albuminuria  occurs.  There  are  microscopic  traces  of  interstitial  inflammation  in  the  liidneys, 
liver,  lungs,  heart  and  nerve  sheaths,  the  dilated  arteries  of  the  liver  and  lung  contain  thrombi,  and 
in  the  neighborhood  of  the  veins  are  accumulations  of  leucocytes.  In  pregnant  animals  the  fcetus 
shows  the  same  conditions  (Lassar).  Perhaps  the  greatly  cooled  blood  acts  as  an  irritant,  causing 
inflammation  (Rosenthal). 

Action  of  Frost.— The  continued  application  of  a  high  degree  of  cold  causes  at  first  contrac- 
tion of  the  blood  vessels  of  the  skin  and  its  muscles,  so  that  it  becomes  pale.  If  continued  paraly- 
sis of  the  cutaneous  vessels  occurs,  the  skin  becomes  red,  ow-ing  to  congestion  of  its  vessels.  As  the 
passage  of  fluids  through  the  capillaries  is  rendered  more  difficult  by  the  cold,  the  blood  stagnates, 
and  the  skin  assumes  a  lii'id  appearance,  as  the  O  is  almost  completely  used  up.  Thus  the  peri, 
pheral  circulation  is  slowed.  If  the  action  of  the  cold  be  still  more  intense,  the  peripheral  circula- 
tion stops  completely,  especially  in  the  thinnest  and  most  exposed  organs — ears,  nose,  toes  and 
fingers.  The  sensory  nerves  are  paralyzed,  so  that  there  is  numbness  and  loss  of  sensibility,  and 
the  parts  may  even  be  frozen  through  and  through.  As  the  slowing  of  the  circulation  in  the 
superficial  vessels  gradually  affects  other  areas  of  the  circulation,  the  pulmonary  circulation  is 
enfeebled,  and  diminished  oxidation  of  the  blood  occurs,  notwithstanding  the  greater  amount  of  O 
in  the  cold  air,  so  that  the  nerve  centres  are  aff'ected.  Hence  arise  great  dislike  to  making  move- 
ments or  any  muscular  effort,  a  painful  sensation  of  fatigue,  a  peculiar  and  almost  irresistible  desire 
to  sleep,  cerebral  inactivity,  blunting  of  the  sense  organs,  and  lastly,  coma.  The  blood  freezes  at 
— 3.9°  C,  while  the  juices  of  the  superficial  parts  freeze  sooner.  Too  rapid  movements  of  the 
frost-bitten  parts  ought  to  be  avoided.  Rubbing  with  snow,  and  the  very  gradual  application  of 
heat,  produce  the  best  results.  Partial  death  of  a  part  is  not  unfrequently  produced  by  the  pro- 
longed action  of  cold. 

225.  ARTIFICIAL  LOWERING  OF  THE  TEMPERATURE. 
— Phenomena. — The  artificial  cooling  of  warm-blooded  animals,  by  placing 
them  in  cold  air  or  in  a  freezing  mi.xture,  gives  rise  to  a  series  of  characteristic 
phenomena  (A.  IVa/ther).  If  the  animals  (rabbits)  are  cooled  so  that  the  tem- 
perature (rectum)  falls  to  18°,  they  suffer  great  depression,  without,  however,  the 
voluntary  or  reflex  movements  being  abolished.  The  pulse  falls  from  100  or  150 
to  20  beats  per  minute,  and  the  blood  pressure  falls  to  several  millimetres  of  Hg. 
The  respirations  are  few  and  shallow.  Suffocation  does  not  cause  spasins  (Hor- 
vath),  the  secretion  of  urine  stops,  and  the  liver  is  congested.     The  animal  iTiay 


HYBERNATION  AND  USE  OF  COLD.  371 

remain  for  twelve  hours  in  this  condition,  and  when  the  muscles  and  nerves  show 
signs  of  paralysis,  coagulation  of  the  blood  occurs  after  numerous  blood  cor- 
puscles have  been  destroyed.  The  retina  becomes  pale,  and  death  occurs  with 
spasms  and  the  signs  of  asphyxia.  If  the  bodily  temperature  be  reduced  to  17° 
and  under,  the  voluntary  movements  cease  before  the  reflex  acts  {Richet  and  Ron- 
deau). An  animal  cooled  to  18°  C,  and  left  to  itself,  at  the  same  temperature  of 
the  surroundings,  does  not  recover  of  itself,  but  if  artificial  respiration  be 
employed,  the  temperature  rises  10°  C.  If  this  be  combined  with  the  application 
of  external  warmth,  the  animals  may  recover  completely,  even  when  they  have 
been  apparently  dead  for  forty  minutes.  Walther  cooled  adult  animals  to  9°  C, 
and  recovered  them  by  artificial  respiration  and  external  warmth  ;  while  Horvath 
cooled  I'cwwo- animals  to  5°  C.  Mammals  which  are  born  blind,  and  birds  which 
come  out  of  the  egg  devoid  of  feathers,  cool  more  rapidly  than  others.  Mor- 
phia, and  more  so,  alcohol,  accelerate  the  cooling  of  mammals,  at  the  same 
time  the  exchange  of  gases  falls  considerably  {Rump/)  ;  hence,  drunken  men  are 
more  liable  to  die  when  exposed  to  cold. 

Artificial  Cold-blooded  Condition. — CI.  Bernard  made  the  important 
observation,  that  the  muscles  of  animals  that  had  been  cooled  remained  irritable 
for  a  long  time,  both  to  direct  stimuli  and  to  stimuli  applied  to  their  nerves; 
and  the  same  is  the  case  when  the  animals  are  asphyxiated  for  want  of  O.  An 
'^  artificial  cold-blooded  condition,^'  i.  e.,  a  condition  in  which  warm-blooded 
animals  have  a  lower  temperature,  and  retain  muscular  and  nervous  excitability 
(C7.  Bernard),  may  also  be  caused  in  warm-blooded  animals,  by  dividing  the  cer- 
vical spinal  cord  and  keeping  up  artificial  respiration  ;  further,  by  moistening  the 
peritoneum  with  a  cool  solution  of  common  salt  (IFegner). 

Hybernation  presents  a  series  of  similar  phenomena.  Valentin  found  that  hybernating  animals 
become  half  awake  when  their  bodily  temperature  is  28°  C. ;  at  18°  C  they  are  in  a  somnolent 
condition,  at  6°  they  are  in  a  gentle  sleep,  and  at  1.6°  C.  in  a  deep  sleep.  The  heart  beats  and  the 
blood  pressure  fall, the  former  to  8  to  10  per  minute.  The  respiratory,  urinary  and  intestinal  move- 
ments cease  completely,  and  the  cardio-pneumalic  movement  alone  sustains  the  slight  exchange  of 
gases  in  the  lungs  (?  59).  They  cannot  endure  cooling  to  0°  C,  and  awake  before  the  tempera- 
ture falls  so  low.  Hybernating  animals  may  be  cooled  to  a  greater  degree  than  other  mammals ; 
they  give  off  heat  rapidly,  and  they  become  warm  again  rapidly,  and  even  spontaneously.  New- 
bom  mammals  resemble  hybernating  animals  more  closely  in  this  respect  than  do  adults. 

Cold-blooded  Animals  may  be  cooled  to  0°.  Even  when  the  blood  has  been  frozen  and  ice 
formed  in  the  lymph  of  the  peritoneal  cavity,  frogs  may  recover.  In  this  condition  they  appear  to 
be  dead,  but  when  placed  in  a  warm  medium  they  soon  recover.  A  frog's  muscle  so  cooled  will 
contract  again  (A'iihne).  The  germs  and  ova  of  lower  animals,  e.g.,  insects'  eggs,  survive  con- 
tinued frost;  and  if  the  cold  be  moderate,  it  merely  retards  development.  Bacteria,  e.g..  Bacillus 
anthracis,  survive  a  temperature  of —  130°  C.  (Pictet  and  Young);  yeast,  even  —  100°  C.  (Frisch  ). 

Varnishing  the  Skin  causes  a  series  of  similar  phenomena.  The  varnished  skin  gives  off  a 
large  amount  of  heat  by  radiation  {A'rieger),  and  sometimes  the  cutaneous  vessels  are  greatly  dilated 
(LaschkeT.uilsch).  Hence  the  animals  cool  rapidly  and  die,  although  the  consumption  of  O  is  not 
diminished.  If  cooling  be  prevented  (  Valentin,  Schiff,  Brttnton)  by  warming  them  and  keeping 
them  in  warm  wool,  the  animals  live  for  a  longer  time.  The  blood  post-mortetn  does  not  contain 
any  poisonous  substances,  nor  even  are  any  materials  retained  in  the  blood  which  can  cause  death, 
for  if  the  blood  be  injected  into  other  animals,  these  remain  healthy.  Varnishing  the  human  skin 
does  not  seem  to  be  dangerous  (^Senator). 

226.  EMPLOYMENT  OF  COLD.— Cold  may  be  applied  to  the  whole  or  part  of  the  sur- 
face of  the  body  in  the  following  conditions  : — 

(a)  By  placing  the  body  for  a  time  in  a  cold  bath,  to  abstract  as  much  heat  as  possible,  when  the 
bodily  temperature  in  fever  rises  so  high  as  to  be  dangerous  to  life.  This  result  is  best  accomplished 
and  lasts  longest  when  the  bath  is  gradually  cooled  from  a  moderate  temperature.  If  the  body  be 
placed  at  once  in  cold  water,  the  cutaneous  vessels  contract,  the  skin  becomes  bloodless,  and  thus 
obstacles  are  placed  in  the  way  of  the  excretion  of  heat.  A  bath  gradually  cooled  in  this  way  is 
borne  longer  (f.  Ziemssen).  The  addition  of  stimulating  substances,  e.g.,  salts,  which  cause  dila- 
tation of  the  cutaneous  vessels,  facilitates  the  secretion  of  heat ;  even  salt  water  conducts  heat  better. 
If  alcohol  be  given  internally  at  the  same  time,  it  lowers  the  temperature. 

(b)  Cold  may  be  ap|)Ued  locally  by  means  of  ice  in  a  bag,  which  causes  contraction  of  the 
cutaneous  vessels  and  contraction  of  the  tissues  (as  in  inflammation),  while  at  the  same  time  heat 
is  abstracted  locally. 


372 


HISTORICAL   AND    COMPARATIVE. 


(<-)  Heat  may  be  abstracted  locally  by  the  rapid  evaporation  of  volatile  substances  (ether,  car- 
bon disulphide),  which  causes  numbness  of  the  sensory  nerves.  The  introduction  of  media  of  low 
temperature  into  the  body,  respiring  cool  air,  taking  cold  drinks,  and  the  injection  of  cold  fluids 
into  the  intestine  act  locally,  and  also  produce  a  more  general  action.  In  applying  cold  it  is  im- 
portant to  notice  that  the  initial  contraction  of  the  vessels  and  the  contraction  of  the  tissues  are 
followed  by  a  greater  dilatation  and  turgescence,  ;'.  *".,  by  a  healthy  reaction. 

227.  HEAT  OF  INFLAMED  PARTS.— "Calor,"  or  heat,  is  reckoned  one  of  the  funda- 
mental phenomena  of  intiammaiion,  in  addition  to  rubor  (redness),  tumor  (swelling),  and  dolor 
(pain).  But  the  apparent  increase  in  the  heat  of  the  inflamed  parts  is  not  above  the  temperature  of 
the  blood.  Simon,  in  i860,  asseited  that  the  arterial  blood  flowing  to  an  inflamed  part  was  cooler 
than  the  part  itself;  but  v.  Baren.sprung  denies  this,  as  J.  Hunter  did,  and  so  does  facobson,  Bern- 
hardt, and  Laudien.  The  outer  parts  of  the  skin  in  an  inflamed  part  are  warmer  than  usual,  owing 
to  the  dilatation  of  the  vessels  (rubor)  and  the  consequent  acceleration  of  the  blood  stream  in  the 
inflamed  part, and  owing  to  the  swelling  (tumor)  from  the  presence  of  good  heat-conducting  fluids; 
but  the  heat  is  not  greater  than  the  heat  of  the  blood.  It  is  not  proved  that  an  increased  amount 
of  heat  is  produced  owing  to  increased  molecular  decompositions  within  an  inflamed  part. 

228.  HISTORICAL  AND  COMPARATIVE.— According  to  Aristotle,  the  heart  prepares 
the  heat  within  itself,  and  sends  it  along  with  the  blood  to  all  parts  of  the  body.  This  doctrine 
prevailed  in  the  time  of  Hippocrates  and  Galen,  and  occurs  even  in  Cartesius  and  Bartholinus 
(1667,  "  flammula  cordis" ).  The  iatro-mechanical  school  {Boerhaave,  van  Swieten)  ascribed  the 
heat  to  the  friction  of  the  blood  on  the  walls  of  the  vessels.  The  iatro-chetnical  school,  on  the 
other  hand,  sought  the  .source  of  heat  in  the  fermentations  that  arose  from  the  passage  of  the  ab- 
sorbed substances  into  the  blood  i^van  Helmont,  Svlvius,  E/tmiiller).  Lavoisier  (1777)  was  the 
first  to  ascribe  the  heat  to  the  combustion  of  carbon  in  the  lungs. 

After  the  construction  of  the  thermometer  by  Galileo,  Sanctorius  (1626)  made  the  first  ther- 
mometric  observations  on  sick  persons,  while  the  first  ca/onmetric  observations  were  made  by 
Lavoisier  and  Laplace. 

Comparative  observations  are  given  at  §  207,  and  also  under  Hybernation  y\  225). 


Physiology- Metabolic  Phenomena 


By  the  term  metabolism  are  meant  all  those  phenomena,  whereby  all — even 
the  most  lowly — living  organisms  are  capable  of  incorporating  the  substances 
obtained  from  their  food  into  their  tissues,  and  making  them  an  integral  part  of 
their  own  bodies.  This  part  of  the  process  is  known  as  assimilation.  Further, 
the  organism  in  virtue  of  its  metabolism  forms  a  store  of  potential  energy,  which 
it  can  transform  into  kinetic  energy,  and  which,  in  the  higher  animals  at  least, 
appears  most  obvious  in  the  form  of  muscular  work  and  heat.  The  changes  of 
the  constituents  of  the  tissues,  by  which  these  transformations  of  the  poten- 
tial energy  are  accompanied,  result  in  the  formation  of  excretory  products, 
which  is  another  part  of  the  process  of  metabolism.  The  normal  metabolism 
requires  the  supply  of  food  quantitatively  and  qualitatively  of  the  proper  kind, 
the  laying  up  of  this  food  within  the  body,  a  regular  chemical  transformation  of 
the  tissues,  and  the  preparation  of  the  effete  products  which  have  to  be  given  out 
through  the  excretory  organs.  [Synthetic  or  constructive  metabolism  is  spoken  of  as 
Anabolic,  and  destructive  or  analytical  metabolism  as  Katabolic  metabolism.] 

229.  THE  MOST  IMPORTANT  SUBSTANCES  USED  AS 
FOOD. — Water. — When  we  remember  that  58.5  per  cent,  of  the  body  con- 
sists of  water,  that  water  is  being  continually  given  off  by  the  urine  and  fsces,  as  well 
as  through  the  skin  and  lungs,  that  the  processes  of  digestion  and  absorption 
require  water  for  the  solution  of  most  of  the  substances  used  as  food,  and  that 
numerous  substances  excreted  from  the  body  require  water  for  their  solution,  e.g., 
in  the  urine,  the  great  importance  of  water  and  its  continual  renewal  within  the 
organism  are  at  once  apparent.  As  puf  by  Hoppe-Seyler,  all  organisms  live  in 
water,  and  even  in  running  water,  a  saying  which  ranks  with  the  old  saying — 
"  Corpora  non  agunt  nisi  fluida." 

Water^as  far  as  it  is  not  a  constituent  of  all  fluid  foods — occurs  in  different  forms  as  drink :  (l) 
Rain  water,  which  most  closely  resembles  distilled  or  chemically  pure  water,  always  contains 
minute  quantities  of  CO,,  NHj,  nitrous  and  nitric  acids.  (2)  Spring  water  usually  contains 
much  mineral  substance.  It  is  formed  from  the  deposition  of  watery  vapor  or  rain  from  the  air, 
which  permeates  the  soil,  containing  much  CUj, ;  the  COj  is  dissolved  by  the  water,  and  aids  in 
dissolving  the  alkalies,  alkaline  earths  and  metals  which  appear  in  solution  as  bicarbonates,  e.g.,  of 
lime  or  iron  oxide.  The  water  is  removed  from  the  spring  by  proper  mechanical  appliances,  or  it 
bubbles  up  on  the  surface  in  the  form  of  a  "spring."  13)  The  running  water  of  rivers  usually 
contains  much  less  mineral  matter  than  spring  water.  Spring  water  floating  on  the  surface  rapidly 
gives  off'  its  COj,  whereby  many  substances — e.g.,  lime — are  thrown  out  of  solution  and  deposited 
as  insoluble  precipitates. 

Gases. — Spring  water  contains  little  O,  but  much  COj,  the  latter  giving  to  it  its  fresh  taste. 
Hence,  vegetable  organisms  flourish  in  spring  water,  while  animals  requiring,  as  tliey  do,  much  t), 
are  but  poorly  represented  in  such  water.  Water  flowing  freely  gives  up  CO.j,  and  absorbs  O  from 
the  ail,  and  thus  affords  the  necessary  conditions  for  the  existence  of  fishes  and  other  marine  ani- 
mals. River  water  contains  j'j  to  ,'5  of  its  volume  of  absorbed  gases,  which  may  be  expelled  by 
boiling  or  freezing. 

Drinking  water  is  chiefly  obtained  from  springs.  River  water,  if  used  for  this  purpose,  must  be 
filtered,  to  get  rid  of  mechanically  suspended  impurities.  For  household  purposes  a  charcoal  filter 
may  be  used,  as  the  charcoal  acts  as  a  disinfectant.  Alum  has  a  remarkable  action;  if  o.oooi  per 
cent,  be  added,  it  makes  turbid  water  clear. 

Investigation  of  Drinking  Water. — Drinking  water,  even  in  a  thick  layer, 
ought  to  be  completely  colorless,  not  turbid,  and  without  odor.     Any  odor  is  best 

373 


374  SALTS   AND   OTHER    SUBSTANCES    IN    WATER. 

recognized  by  heating  it  to  50°  C,  and  adding  a  little  caustic  soda.     It  ought  not 
to  be  too  hard,  i.e.,  it  ought  not  to  contain  too  much  lime  (and  magnesia)  salts. 

By  the  term  "  degree  of  hardness  "  of  a  water  is  meant  the  unit  amount  of  lime  (and  magne- 
sia) in  100,000  parts  of  water;  a  water  of  20  degrees  of  hardness  contains  20  parts  of  hme  (cal- 
cium oxide)  combined  with  COj,  sulphuric  or  hydrochloric  acids  (the  small  amount  of  magnesia 
may  be  neglected).  A  good  drinking  luater  ought  not  to  exceed  20  degi-ees  of  hardness.  The 
hardness  is  determined  by  titrating  the  water  with  a  standard  soap  solution,  the  result  being  the  for- 
mation of  a  scum  of  lime  soap  on  the  surface.  The  hardness  of  unboiled  water  is  called  its  total 
hardness,  while  that  of  boiled  water  is  called  permanent  hardness.  Boiling  drives  off  the  CO^, 
and  precipitates  the  calcium  carbonate,  so  that  the  water  at  the  same  time  becomes  softer. 

The  presence  of  sulphuric  acid,  or  sulphates,  is  determined  by  the  water  becoming  turbid  on 
adding  a  solution  of  barium  chloride  and  hydrochloric  acid. 

Chlorine  occurs  in  small  amount  in  pure  spring  water,  but  when  it  occurs  there  in  large  amount 
^apart  from  its  being  derived  from  saline  springs,  near  the  sea  or  manufactories — we  may  conclude 
that  the  water  is  contaminated  from  water  closets  or  dunghills,  so  that  the  estimation  of  chlorine 
is  of  importance.  For  this  purpose  use  a  solution  (A)  of  17  grms.  of  crystallized  silver  nitrate  in  i 
litre  of  distilled  water;  I  cubic  centimetre  of  this  solution  precipitates  3.55  milligrammes  of  chlor- 
ine as  silver  chloiide.  Use  also  (B)  a  cold  saturated  solution  of  neutral  potassium  chromate.  Take 
50  cubic  centimetres  of  the  water  to  be  investigated,  and  place  it  in  a  beaker,  add  to  it  2  to  3  drops 
of  B,  and  allow  the  fluid  A  to  run  into  it  from  a  burette  until  the  while  precipitate  first  formed 
remains  red,  even  after  the  fluid  has  been  stirred.  Multiply  the  number  of  cubic  centimetres  of  A 
used  by  7.1,  and  this  will  give  the  amount  of  chlorine  in  100,000  parts  of  the  water.  Example — 
50  c.cmtr.  requires  2.9  c.cnur.  of  the  silver  solution,  so  that  100,000  parts  of  the  water  contain  2.9 
X  7-1  ^  20.59  parts  chlorine  (A'ubel,  Tiemann).  Good  water  ought  not  to  contain  more  than  15 
milligrammes  of  chlorine  per  litre. 

The  presence  of  lime  may  be  ascertained  by  acidulating  50  cubic  centimetres  of  the  water  with 
HCl  and  adding  ammonia  in  excess,  and  afterward  adding  ammonia  oxalate  ;  the  white  precipitate 
is  lime  oxalate.  According  to  the  degree  of  turbidity  we  judge  whether  the  water  is  "soft  "  (poor 
in  lime),  or  "  hard  "  (rich  in  lime). 

Magnesia  is  determined  by  taking  the  clear  fluid  of  the  above  operation,  after  removing  the 
precipitate  of  lime,  and  adding  to  it  a  solution  of  sodium  phosphate  and  some  ammonia ;  the  crys- 
talline precipitate  which  occurs  is  magnesia. 

The  more  feeble  all  these  reactions  are  which  indicate  the  presence  of  sulphuric  acid,  chlorine, 
lime  and  magnesia,  the  better  is  the  water.  In  addition,  good  water  ought  not  to  contain  more  than 
traces  of  nitrates,  nitrites,  or  compounds  of  ammonia,  as  their  presence  indicates  the  decomposition 
of  nitrogenous  organic  substances. 

For  nitric  acid,  take  100  cubic  centimetres  of  water  acidulated  with  two  to  three  drops  of  concen- 
trated sulphuric  acid,  add  several  pieces  of  zinc,  together  with  a  solution  of  potassium  iodide,  and  starch 
solution ;  a  blue  color  indicates  nilric  acid.  The  following  test  is  very  delicate :  Add  to  half  a  drop  of 
water,  in  a  capsule,  two  drops  of  a  watery  solution  of  Brucinum  sulphuricum,  and  afterward  several 
drops  of  concentrated  sulphuric  acid;  a  rose-red  coloration  indicates  the  presence  of  nitric  acid. 

The  presence  of  nitrous  acid  is  ascertained  by  the  blue  coloration  which  results  from  the  addi- 
tion of  a  solution  of  potassium  iodide,  and  solution  of  starch,  after  the  water  has  been  acidulated 
with  sulphuric  acid. 

Compounds  of  ammonia  are  detected  by  Nessler's  reagent,  which  gives  a  yellow  or  reddish 
coloration  when  a  trace  of  ammonia  is  present  in  water;  while  a  large  amount  of  these  compounds 
gives  a  brown  precipitate  of  the  iodide  of  mercury  and  ammonia. 

The  contamination  of  water  by  decomposing  animal  substance  is  determined  by  the  amount  of 
N  it  contains.  In  most  cases  it  is  sufficient  to  determine  the  amount  of  nitric  acid  present.  F'or 
this  purpose  we  require  (A)  a  solution  of  1.S71  grms.  potassium  nitrate  in  i  litre  distilled  water;  i 
cubic  centimetre  contains  I  milligramme  nitric  acid;  (B)  a  dilute  solution  of  indigo,  which  is  pre- 
pared by  rubbing  together  one  part  of  pulverized  indigotin  with  six  parts  H2SO4,  and  allowing  the 
deposit  to  subside,  when  the  blue  fluid  is  poured  into  forty  times  its  volume  of  distilled  water,  and 
filtered.  This  fluid  is  diluted  with  distilled  water  until  a  layer,  12  to  15  mm.  in  thickness,  begins  to 
be  transparent. 

To  lest  the  activity  of  B,  place  I  cubic  centimetre  of  A  in  24  cubic  centimetres  water ;  add  some 
common  sail  and  50  cubic  centimetres  concentrated  sulphuric  acid,  and  allow  B  to  flow  from  a 
burette  into  this  mixture  until  a  faint  green  mixture  is  obtained.  The  number  of  cubic  Cintimetres 
of  B  used  coi-respond  to  I  milligramme  of  nitric  acid. 

25  cubic  centimetres  of  the  water  to  be  investigated  are  mixed  with  50  cubic  centimetres  of  con- 
centrated Hj.SO^,  and  titrated  with  B  until  a  green  color  is  obtained.  This  process  must  be  repeated, 
and  on  the  second  occasion  the  solution  B  must  be  allowed  to  flow  in  at  once,  when,  usually,  some- 
what more  indigo  solution  is  required  to  obtain  the  green  solution.  The  number  of  cubic  centi- 
metres of  B  (corresponding  to  the  strength  of  B,  as  determined  above)  indicates  the  amount  of 
nitric  acid  present  in  25  c.  cmtr.  of  the  water  investigated.  .\s  much  .is  10  milligrammes  nitric  acid 
have  been  found  in  spring  water  i^Marx,  Trommsdorff). 


MAMMARY    GLANDS.  375 

Sulphuretted  Hydrogen  is  recognized  by  its  odor,  also  by  a  piece  of  blotting  paper  moistened 
witli  alkaline  solution  of  lead  becoming  brown  when  it  is  held  over  the  boiling  water.  If  it  occurs 
as  a  compound  in  the  water,  sodium  nitro-prusside  gives  a  reddish-violet  color 

It  is  of  the  greatest  importance  that  drinking  water  should  be  free  from  the  presence  <?/"  organic 
matter  in  a  state  of  decomposition.  Organic  matter  in  a  state  of  decomposition,  and  the  organisn^s 
therewith  associated,  when  introduced  into  the  body,  may  give  rise  to  fatal  maladies,  e.  g.,  cholera 
and  typhoid  fever.  This  is  the  case  when  the  water  supply  has  been  contaminated  from  water 
which  has  percolated  from  water  closi.ts,  privies  and  dung  pits.  'J'/te  presence  of  organic  matter  may 
lie  delected  thus  :  ( I )  A  considerable  amount  of  the  water  is  evaporated  to  dryness  in  a  porcelain 
vessel ;  if  the  residue  be  healed  again,  a  brown  or  black  color  indicates  the  presence  of  a  consider- 
able amount  of  organic  matter;  and  if  it  contain  N,  there  is  an  odor  of  ammonia.  Good  water 
treated  in  this  way  gives  only  a  light-brown  stain.  The  presence  of  micro-organisms  may  be 
determined  microscopically  after  evaporating  a  small  quantity  of  water  on  a  glass  slide.  (2)  The 
addition  o( potassio-go/d  chloride  added  to  the  water  gives  a  black  frothy  precipitate  after  long  stand- 
ing. (3)  A  solution  of  potassium  permanganate,  added  to  the  water  in  a  covered  jar,  gradually 
becomes  decolorized,  and  a  brownish  precipitate  is  formed. 

Water  containing  much  organic  matter  should  never  be  used  as  drinking  water,  and  this  is  espe- 
cially the  case  when  there  is  an  epidemic  of  typhoid  fever,  cholera  or  diarrhcea.  In  all  such  cir- 
cumstances the  water  ought  to  be  boiled  for  a  long  time,  whereby  the  organic  germs  are  killed. 
The  insipid  taste  of  the  water  after  boiling  may  be  corrected  by  adding  a  little  sugar  or  lime  juice. 

230.  THE  MAMMARY  GLANDS  AND  MILK.— Milk  Duct.— About  20 galactophorous 
ducts  open  singly  upon  the  surface  of  the  nipple.  Each  of  these,  just  before  it  opens  on  the  surface, 
is  provided  with  an  oval  dilatation — the  sinus  lacteus.  When  traced  into  the  gland,  the  galacto- 
phorous ducts  di\ide  like  the  branches  of  a  tree,  and  a  large  branch  of  the  duct  passes  to  each  lobe 
of  the  gland — all  the  lobes  being  held  together  by  loose  connective  tissue.  Only  during  lactation 
do  all  the  fine  terminations  of  the  ducts  communicate  with  the  globular  glandular  acini.  Every 
gland  acinus  consists  of  a  membrana  propria,  surrounded  externally  with  a  network  of  branched 
connective-tissue  corpuscles,  and  lined  internally  with  a  somewhat  flattened,  polyhedral  layer  of 
nucleated  secretory  cells  (Fig.  219).     The  size  of  the  lumen  of 

the  acini  depends  upon  the  secretory  activity  of  the  glands;  when  pj^    210 

it  is  large,  it  is  filled  with  milk  containing  numerous  refractive  fatty 
granules.  The  milk  ducts  consist  of  fibrillar  connective  tissue. 
Some  fibres  are  arranged  longitudinally,  but  the  chief  mass  are 
disposed  circularly,  and  are  permeated  externally  with  elastic  fibres, 
wdiile  in  the  finer  ducts  there  is  a  membrana  propria  continuous 
with  that  of  the  gland  acini.  The  ducts  are  lined  by  cylindrical 
epithelium. 

During  the  first  few  days  after  delivery,  the  breasts  secrete  a 
small  amount  of  milk  of  greater  consistence  and  of  a  yellow  color 
— the  colostrum — in  wdiich  large  cells,  filled  with  fatty  granules, 
occur — the  colostrum  corpuscles  (Fig.  221).  Sometimes  a  nucleus 
is  observable  within  them,  and  rarely  they  exhibit  amoeboid  move- 
ments (Fig.  220,  c,  d,  e).  The  regular  secretion  of  milk  begins  Acmi  of  the  . 
after  three  to  four  days.     It  was  formerly  supposed  that  the  cells  brana  propria ;  i,  sec'rctoryepi- 

of  the  acini  underwent  a  fatty  degeneration,  and  thus  produced  the  thelium. 

fatty  granules  of  the  milk.     It  is  more  probable,  from  the  observa- 
tions of  Strieker,  Schvvarz,  Partsch  and  Heidenhain,  that  the   cells  of  the  acini  manufacture  the 
fatty  granules,  and  their  protaplasm  eliminates  them,  at  the  same  time  forming  the  clear  fluid  part 
of  the  milk. 

Changes  during  Secretion. — Partsch  and  Heidenhain  found  that  the  secretory 
cells  in  the  passive  non-secreting  gland  (Fig.  220,  l)  were  flat,  polyhedral  and 
uni  nucleated,  while  the  secreting  cells  (Fig.  220,  II)  often  contained  several  nuclei, 
were  more  allmminous,  higher,  and  cylindrical  in  form.  The  edge  of  the  cell 
directed  toward  the  lumen  of  the  acinus  undergoes  changes  during  secretion. 
Fatty  grannies  are  formed  in  this  part  of  the  cell,  and  are  afterward  extruded. 
The  decomposed  portion  of  the  cell  is  dissolved  in  the  milk,  and  the  fatty  gran- 
ules become  free  as  milk  globules  (Fig.  220,  II,  a).  If  nuclei  are  present  in  that 
part  of  the  cell  which  are  broken  up,  they  also  pass  into  the  milk,  and  give  rise 
to  the  presence  of  nuclein  in  the  secretion. 

Besides  the  milk  globules  and  colostrum  corpuscles,  Rauber  has  found  leucocytes  undergoing 
fatty  degeneration  and  single  pale  cells  (/).  Occasionally  milk  globules  are  found  with  traces  of 
the  cell  substance  adhering  to  their  surface  [i). 

Formation  of  Milk. — Concerning  the  formation  of  the  individual  constituents  of  milk,  H. 
Thicrfelder,  who  digested  fiesh  mammary  glands  directly  after  death,  found  that  during  the  diges- 


376 


STRUCTURE   OF   THE    MAMMA. 


tion  of  the  glands,  at  the  temperature  of  the  body,  a  reducing  substance,  probably  lactose,  was 
formed  by  a  process  of  fermentation.  Tlie  mother  substance  (saccharogen)  is  soluble  in  water,  but 
not  in  alcohol  or  ether,  is  not  destroyed  by  boiling,  and  is  not  identical  with  glycogen.  The  ferment 
which  forms  the  lactose  is  connected  with  the  gland  cells ;  it  does  not  pass  into  the  milk,  nor  into  a 
watery  extract  of  the  gland.  During  the  digestion  of  the  mammary  glands  at  the  temperature  of 
the  body,  casein  is  formed,  probably  from  serum  albumin,  by  a  process  of  fermentation.  This 
ferment  occurs  in  the  milk. 

The  nipple  and  its  areola  are  characterized  by  the  presence  of  pigment — more  abundant  during 
pregnancy — in  the  rete  Malpighii  of  the  skin,  and  by  large  papillre  in  the  cutis  vera.  Some  of  the 
papilUe  contain  touch  corpuscles.  Numerous  non  striped  muscular  fibres  surround  the  milk  ducts 
in  the  deep  layers  of  the  skin  and  in  the  subcutaneous  tissue,  which  contains  no  fat.  These  muscular 
fibres  can  be  traced  following  a  longitudinal  course  to  the  termination  of  the  ducts  on  the  surface. 
The  small  glands  of  Montgomery,  which  occur  on  the  areola  during  lactation,  are  just  small  milk 
glands,  each  with  a  special  duct  opening  on  the  surface  of  the  elevation. 

Arteries  proceed  from  several  sources  to  supply  the  mamma,  but  their  branches  do  not  accom- 
pany the  milk  ducts ;  each  gland  acinus  is  surrounded  by  a  network  of  capillaries.,  which  commu- 
nicate with  those  of  adjoining  acini  by  small  arteries  and  veins.  The  veins  of  the  areola  are 
arranged  in  a  circle  (cMrculus  Halleri).  The  nerves  are  derived  from  the  supraclavicular,  and  the 
II-IV-VI  intercostals ;  they  proceed  to  the  skin  over  the  gland,  to  the  very  sensitive  nipple,  to  the 
blood  vessels  and  non-striped  muscle  of  the  nipple,  and  to  the  gland  acini,  where  the  mode  of  ter- 
mination is  still  unknown.  Lymphatics  surround  the  alveoli,  and  they  are  often  full.  The  milk 
appears  to  be  prepared  from  the  lymph  contained  in  the  lymphatics  surrounding  the  acini. 

The  comparative  anatomy  of  the  mamma.  The  rodents,  insectivora,  and  carnivora  have  lo 
to  12  teats,  wlide  some  of  them  have  only  4.  The  pachydermata  and  ruminantia  have  2  to  4 
abdominal  teats ;   the  whale  has  2  near  the  vulva.     The  apes,  bats,  vegetable-feeding  whales,  ele- 


phants, and  sloths  have  2,  like  man.  In  the  marsupials  the  tubes  are  arranged  in  groups,  which 
open  on  a  patch  of  skin  devoid  of  hair,  without  any  nipple.  The  young  animals  remain  within  the 
mother's  pouch,  and  the  milk  is  expelled  into  their  mouths  by  the  action  of  a  muscle — the  compressor 
mammie. 

The  development  of  the  human  mamma  begins  in  both  sexes  during  the  third  month  ;  at  the 
fourth  and  fifth  months  a  few  simple  tubular  gland  ducts  are  arranged  radially  around  the  position 
of  the  future  nipple,  which  is  devoid  of  hair.  In  the  new-born  child  the  ducts  are  branched  twice 
or  thrice,  and  are  provided  with  dilated  extremities,  the  future  acini.  Up  to  the  twelfth  year,  in 
both  sexes,  the  ducts  continue  to  divide  dendritically,  but  without  any  proper  acini  being  formed. 

In  the  girl  at  puberty  the  ducts  branch  rapidly  ;  birt  the  acini  are  formed  onlv  at  the  periphery  of 
the  gland,  while  Aviiwi^  pregnancy  acini  are  also  formed  in  the  centre  of  the  gland,  while  the  con- 
nective tissue  at  the  same  time  becomes  somewhat  more  opened  out.  At  the  climacteric  period, 
or  menopause,  all  the  acini  and  numerous  fine  milk  ducts  degenerate.  In  the  aditlt  male  the  gland 
remains  in  the  non-developed  infantile  condition.  Accessory  or  supernumerary  glands  upon  the 
breast  and  abdomen  are  not  uncommon;  sometimes  the  mamma  occurs  in  the  axilla,  on  the  back, 
over  the  acromion  process,  or  on  the  leg.  A  slight  secretion  of  milk  in  a  newly-born  infant  is 
normal. 

During  the  evacuation  of  the  milk  (500-1500  cubic  centimetres  daily),  there  is  not  only  the 
mechanical  action  of  sucking,  but  also  the  activity  of  the  gland  itself  [\  152).  This  consists  in  the 
erection  of  the  nipple,  whereby  its  non-striped  muscular  fibres  compress  the  sinuses  on  the  milk 
ducts,  and  empty  them,  so  that  the  milk  may  How  out  in  streams.  The  gland  acini  are  also  excited 
to  secretion  reflexly  by  the  stimulation  of  the  sensory  nerves  of  the  nipple.  The  vessels  of  the 
gland  are  dilated,  and  there  is  a  copious  transudation  into  the  gland,  the  transuded  fluid  being 
manufactured  into  milk  under  the  influence  of  the  secretory  protoplasm.     The  amount  of  secretion 


MILK   AND    ITS    PREPARATIONS. 


377 


depends  upon  the  blood  pressure  {HS/iyig).  During  sucking,  not  only  is  the  milk  in  the  gland 
extracted,  but  new  milk  is  formed,  owing  to  the  accelerated  secretion.  Emotional  disturbances — 
anger,  fear,  etc. — arrest  the  secretion.  Laffont  found  that  stimulation  of  the  mammary  nerve  (bitch) 
caused  erection  of  the  teat,  dilatation  of  the  vessels,  and  secretion  of  milk.  After  section  of  the 
cerebro-spinal  nerves  going  to  the  mamma,  Eckhard  observed  that  erection  of  the  teat  ceased, 
although  the  secretion  of  milk  in  a  goat  was  not  interrupted.  The  rarely  observed  galactorrhcea 
is  perhaps  to  be  regarded  as  a  paralytic  secretion  analogous  to  the  paralytic  secretion  of  saliva. 
Heidenhain  and  Partsch  found  that  the  secretion  (bitch)  was  increased  by  injecting  strychnine  or 
curara  after  section  of  the  nerves  of  the  gland.  The  "  milk  fever,"  which  accompanies  the  first 
secretion  of  milk,  probably  depends  on  stimulation  of  the  vasomotor  nerves,  but  this  condition  must 
be  studied  in  relation  with  the  other  changes  which  occur  within  the  pelvic  cavity  after  birth. 
[Some  substances,  such  as  atropin,  arrest  the  secretion  of  milk.] 

231.  MILK  AND  ITS  PREPARATIONS.— Milk  represents  a  com- 
plete or  typical  food  in  which  are  present  all  the  constituents  necessary  for 
maintaining  the  life  and  growth  of  the  body  [of  an  infant  (§  236).  If  an  adult 
were  to  live  on  milk  alone,  to  get  the  23  oz.  of  dry  solids  necessary,  he  would 
have  to  take  9  pints  of  milk  daily,  which  would  give  far  too  much  water,  fat,  and 
proteids.]  To  every  10  parts  of  proteids  there  are  10  parts  fat  and  20  parts  sugar. 
Relatively  more  fat  than  albumin  is  absorbed  from  the  milk  {Ruiner)  ;  while  a 
part  of  both  is  excreted  in  the  fsces. 

Fig.  221. 


Microscopic  .ippearance  of  milk  (M)  upper  half  of  the  figure,  and  colostrum  (C)  lower  half. 


Characters. — Milk  is  an  opaque,  bluish-white  fluid  with  a  sweetish  taste  and  a 
characteristic  odor,  probably  due  to  the  peculiar  volatile  substances  derived  from 
the  cutaneous  secretions  of  the  glands,  and  it  has  a  specific  gravity  of  1026  to 
1035  {Radeii!uiiisi-/t).  When  it  stands  for  a  time,  numerous  milk  globules,  butter 
globules,  or  cream,  collect  on  its  surface,  under  which  there  is  a  bluish  watery 
fluid.  Human  milk  is  zXw&ys  alkaline ;  cow's  milk  may  be  alkaline,  acid,  or 
amphoteric ;  while  the  milk  of  carnivora  is  always  acid. 

Milk  Globules. — When  milk  is  examined  microscopically,  it  is  seen  to  contain 
numerous  small,  highly  refractive  oil  globules,  floating  in  a  clear  fluid — the  milk 
plasma  (Figs.  220,  a,  h,  221);  while  colostrum  corpuscles  and  epithelium  from 
the  milk  ducts  are  not  so  numerous.  The  white  color  and  opacity  of  the  milk  are 
due  to  the  presence  of  the  milk  globules  which  reflect  the  light ;  the  globules  con- 
sist of  a  fat,  or  butter,  and  are  apparently  surrounded  with  a  very  thin  envelope  of 
casein  or  haptogen  membrane.  [This,  however,  is  denied  ;  it  is  more  probable 
that  the  casein  exists  in  a  swollen-up  condition  rather  than  in  a  state  of  true  solu- 
tion.] 

If  acetic  acid  be  added  to  a  microscopic  preparation  of  milk,  this  caseous  envelope  is  dissolved, 
the  fatty  granules  are  liberated,  and  they  run  together  to  form  irregular  masses.     If  cow's  milk  be 


378  FATS  AND  PLASMA  OF  MILK. 

shaken  with  caustic  potash,  the  casein  envelopes  are  dissolved,  and  if  ether  be  added  the  milk  be. 
conies  clear  and  transparent,  as  the  ether  dissolves  out  all  the  fatty  particles  in  the  solution.  Ether 
cannot  extract  the  fat  from  cow's  milk  until  acetic  acid  or  caustic  potash  is  added  to  liberate  the 
fats  from  their  envelopes ;  but  shaking  with  ether  is  sufficient  to  extract  the  fats  from  human  milk 
(/iaJenhaiisen).  Some  observers  deny  that  an  envelope  of  casein  exists,  and  according  to  them 
milk  is  a  simple  emulsion,  kept  emulsionized  owing  to  the  colloid,  swollen-up  casein  in  the  milk 
plasma  (A'ekrer).  The  treatment  of  milk  with  potash  and  ether  makes  the  casein  unable  any 
longer  to  preserve  the  emulsion  (Soxhlet). 

The  fats  of  the  milk  globules  are  the  triglycerides  of  stearic,  pahnitic,  oleic 
(very  little),  myristic,  arachinic  ( butinic),  capric,  caprylic,  caproic,  and  butyric 
acids,  with  traces  of"  acetic  and  formic  acids  {^Heintz),  and  cholesterin. 

Butter. — When  milk  is  beaten  or  stirred  for  a  long  time  {i.  c,  churned),  the  fat  of  the  milk 
globules  is  ultimately  obtained  in  the  form  of  butter,  owing  to  the  rupture  of  the  envelopes  of  casein. 
Butter  is  soluble  in  alcohol  and  ether,  and  it  is  clarified  by  heat  (90°  C),  or  by  washing  in  water  at 
40°  C.  When  allowed  to  stand  exposed  to  the  air  it  fir^t  becomes  sour,  owing  to  the  formation  of 
lactic  acid,  and  afterward  becomes  rancid,  owing  to  the  glycerine  of  the  neutral  fats  being  decom- 
posed  by  fungi  into  acrolein  and  formic  acid,  while  the  volatile  fatty  acids  give  it  its  rancid  odor. 

The  milk  plasma,  obtained  by  filtration  through  clay  filters  or  membranes,  is 
a  clear,  slightly  opalescent  fluid,  and  contains  casein  (§  249,  III,  3),  some  serum 
albumin  (§32),  peptone  (o.  13  per  cent.),  nuclein,  and  a  trace  of  diastatic 
ferment  (in  human  milk — Bechamp). 

Whether  other  peculiar  chemical  bodies,  such  as  proteids  are  present  in  milk,  e.g.,  fetoprotein 
(Milton  and  Comaille,  Liebermann),  globulin,  albumose,  galactin,  etc.,  is  disputed  by  some  chem- 
ists (Hoppe-Seyler). 

When  milk  is  boiled  the  albumin  coagulates,  while  the  surface  also  becomes 
covered  with  a  thin  scum  or  layer  of  casein,  which  has  become  insoluble  [the  rest 
of  the  milk  remaining  fluid]. 

Casein. — When  milk  is  filtered  through  fresh  animal  membranes  (Hoppe-SeyUr),  or  through  a 
clay  filter,  the  casein  does  not  ])ass  through  (Netmholtz,  Zii/in,  A'elirer). 

Precipitation. — It  is  precipitated  by  adding  crystals  of  MgSO_,  to  saturation.  [If  to  milk  twice 
its  volume  of  a  saturated  solution  of  NaCl  and  crystals  of  NaCl  be  added,  and  the  whole  shaken 
thoroughly,  casein  is  precipitated,  and  carries  down  with  it  fat,  so  that  the  clear  filtrate  contains  the 
lactose  and  coagulable  proteids.] 

The  plasma  contains  milk  sugar  (§  252)  ;  a  carbohydrate  resembling  dextrin 
(Jiitthaust'n),  (?  lactic  acid),  lecithin,  urea,  extractives,  kreatin,  sarkin,  (potassic 
sulphocyanide  in  cow's  milk),  sodic  and  potassic  chlorides,  alkaline  phosphates, 
calcium  and  magnesium  sulphates,  alkaline  carbonates,  traces  of  iron,  fluorine,  and 

silica  (CO.,  N,  O). 

The  coagulation  of  milk  depends  upon  the  coagulation  of  its  casein.  In  milk,  casein  is  com- 
bined with  calcium  phosphate,  which  keeps  it  in  solution  ;  acids  which  act  on  the  calcium  phosphate 
cause  coagulation  ol  the  casein  (acetic  and  tartaric  acids  in  excess  redissolve  it).  All  acids  do  not 
coagulate  human  milk  [Simon  and  Lehmann).  It  is  coagulated  with  two  or  more  drops  of  hydro- 
chloric acid  (o.i  percent.)  or  acetic  acid  (0.2  percent.).  The  spo/itaneous  coagulation  of  milk  after 
it  has  stood  lor  a  time,  especially  in  a  warm  place,  is  due  to  the  formation  of  lactic  acid,  which  is 
formed  from  the  milk  su^ar  in  the  milk  by  the  action  of  bacterium  lacticum  [which  is  introduced 
from  without  (Pasteur,  Colin,  Lister)\  (ji  184,  I).  It  changes  the  neutral  alkaline  phosphate  in 
the  acid  phosphate,  takes  the  casein  from  the  calcium  phosphate,  and  precipitates  the  casein.  The 
sugar  is  decomposed  into  lactic  acid  and  COj. 

Rennet  (}  250,  9,  d,  \  166,  II)  coagulates  milk  with  an  alkaline  reaction  (sweet  whey).  This 
ferment  deio>i:poses  the  casein  into  the  precipitated  cheese,  and  also  into  the  slightly  soluble  whey 
albumin  (Unmmersten,  Korstcr),  so  that  the  coagulation  by  rennet  is  a  process  quite  distinct  from 
the  coagulation  of  milk  by  the  gastric  and  pancreatic  juices  [and  also  from  the  precipitation  pro- 
duced by  acids.  The  presence  of  calcium  phosphate  seems  to  be  necessary  for  the  complete  action 
of  the  rennet  (Hammersten).'\ 

[Experiments. — Warm  a  little  milk  to  40°  C,  and  add  a  few  drops  of  commercial  rennet,  set- 
ting aside  the  mixture  in  a  warm  place;  a  solid  coagulum  is  soon  formed,  and  by  and  by  the  whey 
separates  from  it  If  the  milk  be  previously  diluted  with  water,  no  coagulum  is  formed  ;  and  if  the 
rennet  be  boiled  before,  it,  like  other  ferments,  is  destroyed.  A  solution  of  rennet  may  be  prepared 
by  extracting  the  fourth  stomach  of  the  calf  with  glycerine.] 


COMPOSITION    OF    MILK.  379 

[A  milk-coagulating  ferment  is  found  in  certain  plants  (artichokes,  figs,  Carica  papays),  and 
causes  milk  to  coagulate  in  neutral  or  alkaline  solution  (Baginsky).  It  is  also  found  in  the  small 
intestine  of  the  calf,  while  a  5  per  cent.  NaCl  solution  of  the  seeds  of  H^ithania  coagulans  coagu- 
lates milk  in  an  alkaline  medium  (Ailchison  and  Lea).'\ 

[When  the  milk  is  coagulated  we  obtain  the  curd,  consisting  of  casein  with  some  milk  globules 
entangled  in  it ;  the  whey  contains  some  soluble  albumin  and  fat,  and  the  great  proportion  of  the 
salts  and  milk  sugar,  together  with  lactic  acid.] 

BoiUng  (by  killing  all  the  lower  organisms),  sodium  bicarbonate  (jtj'jj),  ammonia,  salicyUc  acid 
(jjijjj),  glycerine,  and  ethereal  oil  of  mustard  prevent  the  spontaneous  coagulation.  Fresh  milk 
makes  tincture  of  guaiacura  blue,  but  boiled  milk  does  not  do  so  (Sc/iacAl,  C.  ArnoU).  When 
milk  is  exposed  to  the  air  for  a  long  time,  it  gives  off  COj  and  absorbs  O;  the  fats  are  increased 
(?  owing  to  the  development  of  fungi  in  the  milk),  and  so  are  the  alcoholic  and  ethereal  extracts, 
from  the  decomposition  of  the  casein  (^Hoppe-Scyler,  Kemmericli).  According  to  Schmidt-Miil- 
heim,  some  of  the  casein  becomes  converted  into  peptone,  but  this  occurs  only  in  unboiled  milk. 
Composition. — too  parts  of  milk  contain — 

Human.  Cow.  Goat.  Ass. 

Water 87.24  to  90.5S  86.23  86.85  S9.01 

Solids 9.42  "  12.39  '3-77  "352  '0-99 

Casein 2.91  "     3.92  1  .  „„  ,     ,  ,.  f    3.23  2.53  ) 

,,.        .  ^    ..     ■' '     >  1. 90  to  2.21  <     -■  ,-'  'i>  1=^7 

Albumm "         .     /  I    0.50  1.26  j  ^^' 

Butter 2.67  "     4.30  4-50  4-34  I  85 

Mdk  sugar     .    .    .    3.15"     609  4.93  3.78 1 

Sahs 0.14  "     0.2S  0.6  0.65  /  -> ^^ 

Human  milk  contains  less  albumin;  which  is  more  soluble  than  the  albumin  in  the  milk  of 
animals. 

Colostrum  contains  much  serum  albumin,  and  very  little  casein,  while  all  the  other  substances, 
and  especially  the  fats,  are  more  abundant. 

Gases. — Plliiger  and  Setschenow  found  in  100  vols,  of  milk  5.01  to  7.60  CO,  ;  o  09  to  0.32  O; 
0.70  to  1. 41  N,  according  to  volume.     Only  part  of  the  CO2  is  expelled  by  phosphoric  acid. 

Salts. — 'Wit polash  salts  (as  in  blood  and  muscle)  are  more  abundant  than  the  soda  compounds, 
while  there  is  a  considerable  amount  of  calcium  phosphate,  which  is  necessary  for  forming  the 
bones  of  the  infant.  Wildenstein  found  in  100  parts  of  the  ash  of  human  milk — sodium  chloride, 
10.73;  potassium  chloride,  26.33 ;  potash,  21.44;  lime,  18.78;  magnesia,  0.87 ;  phosphoric  acid, 
19;  ferric  phosphate,  0.21  ;  sulphuric  acid,  2.64;  silica,  traces.  The  amount  ot  salts  present  is 
affected  by  the  salts  of  the  food. 

Conditions  Influencing  the  Composition. — The  more  frequently  the  breasts  are  emptied,  the 
richer  the  mdk  becomes  in  casein.  The  last  milk  obtained  at  any  time  is  always  richer  in  butter, 
as  it  comes  from  the  most  distant  part  of  the  gland — viz.,  the  acini  {Rtiset,  Heynsius,  Forster,  ae 
Leon)  Some  substances  are  diminished  and  others  increased  in  amount,  according  to  the  time 
after  delivt'fv.  The  following  are  increased :  Until  the  2d  month  after  delivery,  casein  and  fat;  until 
the  5th  month,  the  salts  (which  diminish  progressively  from  this  time  onward);  from  8-ioth 
month,  the  sugar.  The  following  are  diminished :  From  io-24th  month,  casein;  from  5-6th 
and  lo-iith  months,  fat;  during  ist  month,  the  sugar;  from  the  5th  month,  the  salts. 

[Influence  of  Drugs. — That  cow's  milk  is  influenced  by  the  pasture  and  food  is  well  known. 
Turnip  as  food  gives  a  peculiar  odor,  taste  and  flavor  to  milk,  and  so  do  the  fragrant  grasses.  The 
mental  state  of  the  nurse  influences  the  quantity  and  quality  of  milk,  while  many  substances  given 
as  medicines  reappear  in  the  milk,  such  as  ddl,  copaiba,  conium,  aniseed,  garlic  ;  especially  those 
containing  aromatic  volatile  oils,  as  the  umbellifene  and  cruciferje ;  also  some  of  the  following 
drugs:  potassium  iodide,  arsenic,  mercury,  opium,  rhubarb,  or  its  active  principle,  the  purgative 
principle  of  castor  oil,  and  the  cathartic  principle  of  senna.  Jaborandi  is  the  nearest  approach  to  a 
galactagogue,  but  its  action  is  temporary.  Alropin  is  a  true  anti-galactagogue.  The  composition 
of  the  milk  may  be  affected  by  using  faity  food,  by  the  use  of  salts,  and  above  all,  by  the  diet 
(  Dolan).'\ 

[Milk  may  be  a  vehicle  for  communicating  disease — by  direct  contamination  from  the  water 
used  for  adulterating  it  or  cleansing  the  vessels  in  which  it  is  kept;  by  the  milk  absorbing  delete- 
rious gases;  by  the  secretion  being  altered  in  diseased  animals.] 

The  greater  the  amount  of  milk  that  is  secreted  (woman),  the  more  casein  and  sugar,  and  the  less 
butter  it  contains.  The  milk  of  a  primipara  is  less  watery.  Rich  feeding,  especially  proteids 
(small  amount  of  vegetable  food),  increase  the  amount  of  milk  and  the  casein,  sugar,  and  fat  in  it ; 
a  large  amount  of  carbohydrates  ^not  fats)  increases  the  amount  of  sugar. 

Substitutes. — If  other  than  human  milk  has  to  be  used,  ass's  milk  most  closely  resembles  human 
milk.  Cow's  milk  is  best  when  it  contains  plenty  of  fatty  matters — it  must  be  diluted  with  its  own 
volume  of  water  at  first,  and  a  little  milk  sugar  added.  The  casein  of  cow's  milk  differs  qualita- 
tively from  that  of  human  milk  (Biedert) ;  its  coagulated  flocculi  or  curd  are  much  coarser  than 
the  tine  curd  of  human  milk,  and  they  are  only  I4'  dissolved  by  the  digestive  juices,  while  human 
milk  is  completely  dissolved.     Cow's  milk  when  boiled  is  less  digestible  than  unboiled  (E.  Jessen). 

Milk  ought  not  to  be  kept  in  zinc  vessels,  owing  to  the  formation  of  zinc  lactate. 


380  TESTS    FOR    MILK. 

[Milk  exposed  to  light  becomes  sour  more  rapidly,  and  the  cream  separates  quicker;  after  a 
time  there  is  a  very  acid  reaction,  an  evolution  of  gases,  and  few  bacteria  are  present,  while  in 
milk  kept  in  the  d,irk  the  former  processes  go  on  more  slow  ly,  while  there  is  a  putrid  fermentation 
without  the  evolution  of  gas,  but  with  many  bacteria  and  a  feeble  acid  reaction  [Albitii  and 
Ma/I'crla).'] 

Tests  for  Milk. — The  amount  of  cream  is  estimated  by  placing  the  milk  for  twenty-four  hours 
in  a  tall  cylindrical  glass  graduated  into  a  hundred  parts,  or  creamometer ;  the  cream  collects  on 
the  surface,  and  ought  to  form  from  lo  to  24  vols,  per  cent.  [The  cream  is  generally  about  j§j.] 
The  specitic  gravity  (fresh  cow's  milk,  1029  to  1034  ;  when  creamed,  1032  to  1040)  is  estimated 
with  an  acroiiwter  or  lactometer  at  15°  C.  The  sugar  is  estimated  by  titration  with  Fchling's 
solution  (§  150,  II).  but  m  this  case  r  cubic  centimetre  of  this  solution  corresponds  to  0.0067  gfm- 
of  milk  sugar;  or  its  amount  may  be  estimated  with  X\\^  polariscopic  apparatus  (\  150).  The  pro- 
teids  are  precipitated  and  the  fats  extracted  with  ether.  The  fats  in  Iresh  milk  form  about  3  per 
cent.,  and  in  skimmed  milk  i  'i  per  cent.  The  amount  of  water  in  relation  to  the  milk  globules 
is  estimated  by  the  lactoscope  or  the  diaphanometer  of  Donne  (modified  by  Vogel  and  Hoppe- 
Seyler),  which  consists  of  a  glass  vessel  with  plane  parallel  sides  placed  i  centimetre  apart.  A 
measured  quantity  of  milk  is  taken,  and  water  is  added  to  it  from  a  burette  until  the  outline  of  a 
candle  tlame  placed  at  a  distance  of  I  metre  can  be  distinctly  seen  through  the  diluted  milk.  This 
is  done  in  a  dark  room.  For  i  cubic  centimetre  of  good  cow's  milk,  70  to  85  centimetres  water 
are  required.  [Other  forms  of  lactoscope  are  used',  all  depending  on  the  same  principle  of  an 
optical  test,  viz.,  that  the  opacity  of  milk  varies  with  and  is  proportional  to  the  amount  of  butter  fats 
present,  ;'.  e.,  the  oil  globules.  Bond  uses  a  shallow  cyhndrical  vessel  with  the  bottom  covered  by 
black  lines  on  a  white  surface.  A  measured  quantity  of  water  is  placed  in  this  vessel,  and  milk 
is  added,  drop  by  drop,  until  the  parallel  lines  on  the  pattern  at  the  bottom  of  the  dish  cease 
to  be  visible.  On  counting  the  number  of  drops,  a  table  accompanying  the  appliance  gives 
the  percentage  of  fats.  This  method  gives  approximate  results.  In  all  cases  it  is  well  to  use 
fresh  milk.] 

Various  substances  pass  into  the  milk  liihen  they  are  aJministered  to  the  mother — many 
ouoriferous  vegetable  bodies,  e.g.^  anise,  vermuth,  garlic,  etc. ;  opium,  indigo,  salicylic  acid,  iodine, 
iron,  zinc,  mercury,  lead,  bismuth,  antimony.  In  osteomalacia  the  amount  of  lime  in  the  milk  is 
increased  (  Giisserow).  Potassium  iodide  diminishes  the  secretion  of  milk  by  afi'ecting  the  secretory 
function  (Stump/).  Among  abnormal  constituents  are — haemoglobin,  bile  pigments,  mucin,  blood 
corpuscles,  pus,  fibrin.  Numerous  fungi  and  other  low  organisms  develojj  in  evacuated  milk,  and 
-the  rare /'/«t' milk  is  due  to  the  development  of  Bacterium  cyanogeneum  (Fuchs,  A'ee/sen).  The 
milk  serum  is  blue,  not  the  fungus.  Blue  milk  is  unhealthy,  and  causes  diarrhoea  (Mosler).  There 
are  fungi  which  make  milk  hluish-black  ox  green.  Red  &\\A  yellow  milk  are  produced  by  a  similar 
action  of  chromogenic  fungi  \\  1 84).  The  former  is  produced  by  Micrococcus prodigiosus,  which 
is  colorless.  The  color  seems  to  be  due  to  fuchsin.  The  yellow  color  is  produced  by  Bacterium 
synxanthum  (Ehrenherg).  Some  of  the  pigments  seem  to  be  related  to  the  aniline,  and  others  to 
the  phenol  coloring  matters  (Hiippe). 

The  rennet- like  action  of  bacteria  is  a  widely  diffused  property  of  these  organisms;  they 
coagulate  and  peptonize  casein  and  may  ultimately  produce  further  decompositions.  The  butyric 
acid  bacillus  (^  184)  first  coagulates  casein,  then  peptonizes  it,  and  finally  splits  it  up,  with  the  evo- 
lution of  ammonia  [Hiippe). 

Milk  becomes  stringy,  owing  to  the  action  of  cocci  [Schmidt,  MUlheim),  which  form  a  stringy 
substance  [  =  de.xtran,  CjjHjdO,^  (Scheibler)'],]ns\.  as  beer  or  wine  undergoes  a  similar  or  ropy 
change.     [The  milk  of  diseased  animals  may  coniain  or  transmit  directly  infectious  matter.] 

Preparations  of  Milk — (i)  Condensed  milk — 80  grms.  cane  sugar  are  added  to  i  litre  of 
milk  ;  the  whole  is  evaporated  to  i  ;  and  while  hot  sealed  up  in  tin  cans  [Lignac).  For  children 
one  teaspoonful  is  dissolved  in  a  pint  of  cold  water,  and  then  boiled. 

(2)  Koumiss  is  prepared  by  the  Tartars  from  mare's  milk.  Koumiss  and  sour  milk  are  added 
to  milk,  the  whole  is  violently  stirred,  and  it  undergoes  the  alcoholic  fermentation,  whereby  the 
milk  sugar  is  first  changed  into  galactose,  and  then  into  alcohol;  so  that  koumiss  contains  2  to  3  per 
cent,  of  alcohol ;  while  the  casein  is  at  first  precipitated,  but  is  afterward  partly  redissolved  and 
changed  into  acid  albumin  and  peptone  [Dochmann).  Tartar  koumiss  seems  to  be  produced  by 
the  action  of  a  special  bacterium  (Diaspora  caucasia,  A'ern). 

(3)  Cheese  is  prepared  by  coagulating  milk  with  rennet,  allowing  the  whey  to  separate,  and 
adding  salt  to  the  curd.  When  kept  for  a  long  time,  cheese  "ripens,"  the  casein  again  liecomes 
soluble  in  water,  probably  from  the  formation  of  soda  albuminate  ;  in  many  cases  it  becomes  semi- 
fluid when  it  takes  the  characters  of  peptones.  When  further  decomposition  occurs,  leucin  and 
tyrosin  are  formed.  The  fats  increase  at  the  exjiense  of  the  casein,  and  they  again  undergo  further 
change,  the  volatile  fatty  acids  giving  the  characteristic  odor.  The  formation  of  peptone,  leucin, 
tyrosin  and  the  decomposition  of  fat  recalls  the  digestive  processes. 

[Cheese  is  coagulated  casein  entangling  more  or  less  fat,  so  that  the  richness  of  the  cheese  will 
depend  upon  the  kind  of  milk  from  which  it  is  made.  There  are,  in  this  sense,  three  kinds  of 
cheese,  wlwle  milk,  skim  milk,  and  cream  cheese,  the  last  being  represented  by  Stilton,  Roquefort, 
Cheshire,  etc. 


FLESH    AND   ITS    PREPARATIONS. 
The  composition  is  shown  in  the  following  table,  after  Bauer : — 


381 


Water. 

Nitrogeneous 
Matter. 

Fat. 

Extractives. 

Ash. 

Cream  cheese 

Whole  milk 

Skim  milk 

35-75 
46.S2 
48.02 

7.16 
27.62 
32-65 

30.43 

20.54 

8.41 

2-53 
2-97 
6.80 

4-13 

305 

4-12 

Cream  cheese,  especially  if  it  be  made  from  goat  milk,  acquires  a  verj'  high  odor  and  strong 
flavor  when  it  is  kept  and  "  ripens ;"  the  casein  is  partly  decomposed  to  yield  ammonia  and  ammo- 
nium sulphide,  while  the  fats  yield  butyric,  caproic  and  other  acids.] 

232.  EGGS. — Eggs  must  be  regarded  as  a  complete  food,  as  the  organism  of 
the  young  chick  is  developed  from  them.  The  yelk  contains  a  characteristic 
proteid  body — vitellin  (§  249),  and  an  albuminate  in  the  envelopes  of  the  yellow 
yelk  spheres — niiilein,  from  the  white  yelk  ;  fats  in  the  yellow  yelk  (palmitin, 
olein),  cholesterin,  much  lecithin;  and  as  its  decomposition  product,  glycerin- 
phosphoric  acid — grape  sugar,  pigments  (lutein),  and  a  body  containing  iron  and 
related  to  hsemoglobin  ;  lastly,  salts  qualitatively  the  same  as  in  blood — quantita- 
tively as  in  the  blood  corpuscles — and  gases.  The  chief  constituent  of  the  white 
of  egg  is  egg  albumin  (§  249),  together  with  a  small  amount  of  palmitin  and 
olein  partly  saponified  with  soda  :  grape  sugar,  extractives  ;  lastly,  salts,  qualita- 
tively resembling  those  of  blood,  but  quantitatively  like  those  of  jvr//w  and  a  trace 
of  fluorine. 

[The  shell  is  composed  chiefly  of  mineral  matter  (91  per  cent,  of  calcic  carbonate,  6  per  cent,  of 
calcic  phosphate,  and  3  per  cent,  of  organic  matter).  .^  hen's  egg  weighs  about  1^4  oz.,  of  which 
the  shell  forms  about  j'^. 

Composition  :— 

White  of  Egg.  Yelk. 

Water 84.8  51.5 

Proleids 12.0  15.0 

Fats,  etc 2.0  30.0 

Mineral  matter 1.2  1.4 

Pigment  extractives 2.1 

This  shows  the  large  amount  oi  fatty  matter  in  the  yelk.] 

Relatively  more  of  the  nitrogenous  constituents  than  the  fatty  constituents  of 
eggs  are  absorbed  {Rubncr). 

233.  FLESH  AND  ITS  PREPARATIONS.— Flesh,  in  the  form  in 
which  it  is  eaten,  contains,  in  addition  to  the  muscle  substance  proper,  more  or 
less  of  the  elements  of  fat,  connective  and  elastic  tissue  mixed  with  it  (§  293). 
The  following  results  refer  to  flesh  freed  as  much  as  possible  from  the  constituents. 
The  chief  proteid  constituent  of  the  contractile  muscular  substance  is  myosin 
{Kuhne')  ;  serum  albumin  occurs  in  the  fluid  of  the  fibres,  in  the  lymph  and  blood 
of  muscle.  'Y\\efais  are  for  the  most  part  derived  from  the  interfibrillar  fat  cells, 
while  lecithin  and  cholesterin  come  from  the  nerves  of  the  muscles  ;  the  gelatin  is 
derived  from  the  connective  tissue  of  the  perimysium,  perineurium,  and  the  walls 
of  blood  vessels  and  tendons.  The  red  color  of  the  flesh  is  due  to  the  hemo- 
globin present  in  the  sarcous  substance  {Kiihne,  Gscheidlen),  but  in  some  muscles, 
e.g.,  the  heart,  there  is  a  special  pigment,  myo-hsematir.  {MacMunn^.  Elastin 
occurs  in  the  sarcolemma,  neurilemma,  and  in  the  elastic  fibres  of  the  perimysium 
and  walls  of  the  vessels  ;  the  small  amount  of  keratin  is  derived  from  the  endo- 
thelium of  the  vessels.  The  chief  muscular  substance,  the  result  of  the  retrogres- 
sive metabolism  of  the  sarcous  substance,  is  kreatin  (  —  0.25  per  cent.,  Chevreul, 
Perls) ;  kreatinin.  the  inconstant  inosinic  acid,  then  lactic,  or  rather  sarcolactic 
acid  (§  293I.  Further,  taurin,  sarkin,  xanthin,  uric  acid,  carnin,  inosit  (most 
abundant  in  the  muscles  of  drunkards),  urea  (.01  per  cent.),  dextrin  (in  horse  and 


382 


FLESH    AND    ITS    PREPARATIONS. 


rabbit,  not  constant — Sanson,  Limpricht)  ;  grape  sugar  i^Meissner'),  but  it  is  very 
probably  derived  /<?jrAOT(;/Viv«  from  glycogen  (0.43  per  cent.),  which  occurs  in 
considerable  amount  in  fa'tal  muscles  (O.  Nasse);  lastly,  volatile /<?//>'  acids. 
Among  the  salts,  potash  and  phosphoric  acid  compounds  {Braconnof)  are  most 
abundant  ;  magnesium  phosphate  exceeds  calcium  phosphate  in  amount.  [The 
composition  varies  somewhat  even  in  different  muscles  of  the  same  animal.] 
In  icxD  parts  Flesh  there  is,  according  to  Schlossberger  and  v.  Bibra — 


Ox. 

Calf. 

Deer. 

Pig. 

Man. 

Fowl. 

Carp. 

Frog. 

Water 

Solids 

77-5° 
22.50 

1  2.20 

1.30 

1.50 

7820 
21.80 

2.60 

1.60 

1.40 

74.63 

2537 

1.94 

0.50 

4-75 

78.30 
21.70 

2.40 

0.80 
1.70 

74.45 
25.55 

•■93 
2.07 
3.71 
2.30 

15.54 

77.30 
22.7 

3-0  { 

1.2 

1.4 

16.5 

79.78 

20.22 

2.35 

80.43 

»9-57 
1.86 

Soluble  albumin 

Coloring  matter 

Glutin 

Alcoholic  extract 

Fats 

.    .     . 
1.98 
3.47 
I. II 

II.31 

2.48 
3.46 

O.IO 

11.67 

Insoluble  albumin,  Blood  vessels, 
etc 

17.50 

162 

16.81 

i6.8i 

In  100  parts  Ash  there  is- 


Horse. 

Ox. 

Calf. 

Pig. 

Potash 

39-40 

4.S6 
3.88 
1.80 

35-94 

3.31 
'•73 
536 

4.S6' 
0.98 
34.36 
3.37 
2.07 
8.02 
0.15 

34.40 

2-35 
1:45 
1.99 

37-79 
4.02 
4.81 
7.54 

Chalk 

I.IO 

46.74 

0.30 

}  >o.59   { 
0.27 
48.13 

0.40 
0.62 
0.35 
44.47 

Chlorine 

Iron  oxiJe 

Phosphoric  acid 

0.81 

The  amount  of  fat  in  flesh  varies  very  much,  according  to  the  condition  of  the  animal.  After 
removal  of  the  visible  fat,  human  flesh  contains  7.15;  ox,  II. 12;  calf,  10.4;  sheep,  3.9;  wild  goose, 
8.8 ;  fowl,  2.5  per  cent. 

The  amount  of  extractives  is  most  abundant  in  those  animals  which  exhibit  energetic  muscular 
action;  hence  it  is  largest  in  wild  animals.  The  extract  is  increased  after  vigorous  muscular  action, 
when  sarcolactic  acid  is  developed,  and  the  flesh  becomes  more  tender  and  is  more  palatable.  Some 
of  the  extractives  excite  the  nervous  system,  e.  g.,  kreatin  and  kreatinin  ;  and  others  give  to  flesh  its 
characteristic  agreeable  flavor  ["  osmasome,"]  but  this  is  also  partly  due  to  the  different  fats  of  the 
flesh,  and  is  best  developed  when  the  flesh  is  cooked.  The  extractives  in  100  parts  of  flesh  are  in 
man  and  pigeon,  3  ;  deer  and  duck,  4 ;  swallow,  7  per  cent. 

Preparation,  or  Cooking  of  Flesh. — As  a  general  rule,  the  flesh  of  young  animals,  owing  to 
the  sarcolemma,  connective  tissue,  and  elastic  constituents  being  less  tough,  is  more  tender  and  more 
easily  digested  than  the  flesh  of  old  animals  ;  after  flesh  has  been  kept  for  a  time  it  is  more  friable 
and  tender,  as  the  inosit  becomes  changed  into  sarcolactic  acid  and  the  glycogen  into  sugar,  and  this 
.-igain  into  lactic  acid,  whereby  the  elements  of  the  flesh  undergo  a  kind  of  maceration.  Finely 
divided  flesh  is  more  digestible  than  when  it  is  eaten  in  large  pieces.  In  cooking  meat,  the  heat 
ought  not  to  be  too  intense,  and  ought  not  to  be  continued  too  long,  as  the  muscular  fibres  thereby 
become  hard  and  shrink  very  much.  Those  parts  are  most  digestible  which  are  obtained  from  the 
centre  of  a  roast  where  they  have  been  heated  to  60°  to  70°  C  ,  as  this  temperature  is  sufticient, 
with  the  aid  of  the  acids  of  the  flesh,  to  change  the  connective  tissue  into  gelatin,  whereby  the  fibres 
are  loosened,  so  that  the  ga>itric  juice  readily  attacks  them.  In  roasting  beef,  apply  heat  suddenly 
at  first,  to  coagulate  a  layer  on  the  surface,  which  prevents  the  exit  of  the  juice. 


VEGETABLE    FOODS. 


383 


Meat  Soup  is  best  prepared  by  cutting  the  flesh  into  pieces  and  placing  them  for  several  hours 
in  cold  waier,  and  afterward  boiling.  Liebig  found  that  6  parts  per  too  of  ox  flesh  were  dissolved 
by  cold  water.  When  this  cold  extract  was  boiled,  2.95  parts  were  precipitated  as  coagulated 
albumin,  which  is  chiefly  removed  by  "skimmini;,"  so  that  only  3.05  parts  remain  in  solution.  From 
100  parts  of  flesh  of  fowl,  8  parts  were  extracted,  and  of  these  4.7  coagulated  and  3.3  remamed 
dissolved  in  the  soup.  By  boiling  for  a  very  long  time,  part  of  the  albumin  may  be  redissolved  (Mulder]. 
The  dissolved  substances  are  :  ( i )  Inorganic  salts  of  the  meat,  of  which  82. 27  per  cent,  pass  into  the 
soup  ;  the  earthy  phosphates  chiefly  remain  in  the  cooked  meat.  (2)  Kreatin,  kreatinin,  the  inosin- 
ates  and  lactates  which  give  to  broth  or  beef  tea  their  stiniulatinc:  qualities,  and  a  small  amount  of 
aromatic  extractives.  (3)  Gelatin,  more  abundantly  extracted  from  the  flesh  of  young  animaN. 
According  to  these  facts,  therefore,  flesh,  brolh  or  beef-tea  is  a  powerful  stimulant,  supplying  muscle 
with  restoratives,  but  is  not  a  food  in  the  ordinary  sense  of  the  term,  as  kreatin  (-■.  Voil)  in  general 
leaves  the  body  unchanged.  The  flesh,  especially  if  it  be  cooked  in  a  large  mass,  after  the  extrac- 
tion of  the  broth  is  still  available  as  a  food. 

Liebig's  Extract  of  Meat  is  an  extract  of  flesh  evaporated  to  a  thick  syrupy  consistence.  It 
contains  no  fat  or  gelatin,  and  is  chiefly  a  solution  of  the  extractives  and  salts  of  flesh. 

[Extract  of  Fish. — A  similar  extract  is  now  prepared  from  fish,  and  such  extract  has  no  fishy 
flavor,  but  presents  much  the  same  appearance,  odor,  and  properties  as  extract  of  flesh.] 

234.  VEGETABLE  FOODS.— The  nitrogenous  constituents  of  plants 
are  not  so  easily  absorbed  as  animal  food  {Rubner').  Carbohydrates,  starch,  and 
sugar  are  very  completely  absorbed,  and  even  a  not  inconsiderable  proportion  of 
cellulose  may  be  digested  (yU'ciske,  Konig).  The  more  fits  that  are  contained  in 
the  vegetable  food,  the  less  are  the  carbohydrates  digested  and  absorbed. 

I.  The  cereals  are  most  important  vegetable  foods;  they  contain  proteids, 
starch,  salts,  and  water  to  14  per  cent.  The  nitrogenous  glutin  is  most  abundant 
under  the  husk  (Fig.  222,  c).  The  use  of  whole  meal  containing  the  outer  layers 
of  the  grain  is  highly  nutritive,  but  bread  containing  much  bran  is  somewhat  in- 
digestible (^Rubner).     Their  composition  is  the  following  : — 


100  Parts  of  the  Dry  Meal  contain 

100  Parts  of  Ash  contain 

Of 

Albumin. 

Starch. 

Red        1 
Wheat.      1 

White 
Wheat. 

Wheat     .... 

Rye 

Barley      .... 

Maize 

Rice 

Buckwheat     .    . 

16.52  % 

11.92 

17.70 

13-65 
7.40 

6.8-io.s 

56.25  % 

60.91 

3831 

77-74 
86.21 
65.05 

27.87 

IS-7S 
1-93 
9.60 
1.36 

49-36 
O.IS 

Potash 

Soda 

Lime 

Magnesia       .... 
Iron  oxide    .... 
Phosphoric  Acid  . 
Silica 

33.84 

309 
13-54 

0.31 
59-21 

It  is  curious  to  observe  that  soda  is  absent  from  white  wheat,  its  place  being  taken  by  other 
alkalies.  Rye  contains  more  cellulose  and  dextrin  than  wheat,  but  less  sugar;  rye  bread  is  usually 
less  porous. 

In  the  preparation  of  bread  the  meal  is  kneaded  with  water  until  dough  is  formed,  and  to  it 
is  added  salt  and  yeasl  (Saccharomycetes  cerevisioe).  When  placed  in  a  warm  oven,  the  proteids 
of  the  meal  begin  to  decompose  and  act  as  a  ferment  npon  the  swollen-up  starch,  which  becomes  in 
part  changed  into  sugar.  The  sugar  is  further  decomposed  into  CO2  and  alcohol,  the  CO,  forms 
bubbles,  which  make  the  bread  to  "rise"  and  thus  become  spongy  and  porous.  The  alcohol  is 
driven  off  by  the  baking  (200°),  while  much  soluble  dextrin  is  formed  in  the  crust  of  the  bread. 
[But  COj  may  be  set  free  within  the  dough  by  chemical  means  without  yeast  or  leaven,  thus  forming 
unfermented  bread.  This  is  done  by  mixing  with  the  dough  an  alkaline  carbonate  and  then 
adding  an  aciti.  Baking  powders  consist  of  carbonate  of  soda  and  tartaric  acid.  In  Dauglish's 
process  for  aerated  bread,  the  CO,  is  forced  into  water, and  a  dough  is  made  with  this  water  under 
pressure,  and  when  the  dough  is  heated,  the  CO2  expands  and  forms  the  spongy  bread.  Bread  as 
an  article  of  food  is  deficient  in  N,  while  it  is  poor  in  fats  and  some  salts.  Hence  the  necessity  for 
using  some  form  of  fat  with  it  (butter  or  bacon).] 

[Oatmeal  contains  more  nitrogenous  substances  (gliadin  and  glutincasein)  than  wheaten  flour, 
but  owing  to  the  want  of  adhesive  properties  it  cannot  be  made  into  bread.  The  amount  of  fat  and 
salts  is  large.] 

2.  The  Pulses  contain  tnuch  albumin,  especially  vegetable  casein  i^r  legumin  : 
together  with  starch,  lecithin,  cholesterin,  and  9  to  19  per  cent,  water.     Peas 


384  PULSES,  POTATOES,  FRUITS. 

contain  18.02  proteids,  and  38. Si  starch  ;  beans,  28.54,  and  37.50  ;  lentils,  29.31, 
and  40,  and  more  cellulose.  Owing  to  the  absence  of  glutin  they  do  not  form 
dough,  and  bread  cannot  be  prepared  from  them.  On  account  of  the  large 
amount  of  proteids  which  they  contain,  they  are  admirably  adapted  as  food  for 
the  poorer  classes. 

[3.  The  whole  group  of  farinaceous  substances  used  as  "pudding  stuiTs,"  such  as  com  flour, 
arrowroot,  rice,  hominy,  are  really  very  largely  composed  of  starchy  substance.] 

4.  Potatoes  contain  70  to  81  per  cent,  water.  In  the  fresh,  juicy  cellular 
tis.sue,  which  has  an  acid  reaction,  from  the  presence  of  phosphoric,  malic,  and 
hydrochloric  acids,  there  is  16  to  23  per  cent,  of  starch,  2.5  soluble  albumin, 
globulin  {Zoller),  and  a  trace  of  asparagin.  The  envelopes  of  the  cells  swell  up 
by  boiling,  and  are  changed  into  sugar  and  gums  by  dilute  acids.  The  poisonous 
solanin  occurs  in  the  sprouts.  In  100  parts  o{ potato  ash.  May  found  46.96  potash, 
2.41  sodium  chloride,  8. 11  potassium  chloride,  6.50  sulphuric  acid  derived  from 
burned  proteids,  7.17  silica. 

5.  In  Fruits  the  chief  nutrient  ingredients  are  sugar  and  salts;  the  organic 
acids  give  them  their  characteristic  taste ;  the  gelatinizing  substance  is  the  soluble 


Microscopic  characters  of  wheat  (,<  200).     a,  cells  of  the  bran  ;  3,  cells  of  tliin  cuticle  ;  c,  glutin  cells  ;  d,  starch 
cells;  B,  wheat  starch  (X  350). 

so-called  pectin  (Cs^H^hO,,"),  which  can  be  prepared  artificially  by  boiling  the 
very  insoluble  pectose  of  unripe  fruits  and  mulberries. 

6.  Green  Vegetables  are  especially  rich  in  salts  which  resemble  the 
salts  of  the  blood  ;  thus,  dry  salad  contains  23  per  cent,  of  salts  which 
closely  resemble  the  salts  of  the  blood.  Of  much  less  importance  are  the 
starch,  cell  substance,  de.xtrin,  sugar,  and  the  small  amount  of  albumin  which 
they  contain. 

[Vegetables  are  chiefly  useful  for  the  salts  they  contain,  while  many  of  them  are  antiscorbutic. 
Their  value  is  attested  by  the  serious  defects  of  nutrition,  such  as  scurvy,  which  result  when  they 
are  not  supplied  in  the  food.  In  Arctic  expeditions  and  in  the  navy,  lime  juice  is  served  out  as  an 
antiscorbutic] 

[Preserved  Vegetables. — The  dried  and  compressed  vegetables  of  Messrs.  Chollet  &  Company 
are  an  excellent  substitute  for  fresh  vegetables,  and  are  used  largely  in  naval  and  military  expe- 
ditions.] 

Utilization  of  Food. — As  regards  what  percentage  of  the  food  swallowed  is 
actually  absorbed,  we  know  that,  stated  broadly,  vegetable  food  is  assimilated  to 
a  much  less  extent  than  animal  food  in  man.  Fr.  Hofmann  gives  the  following 
table  as  showing  this  ;  — 


CONDIMENTS,  COFFEE,  TEA,  ALCOHOL. 


385 


Weight  of  Food, 

Vegetable. 

Animal. 

Digested.           Undigested. 

Digested. 

Undigested. 

Of  loo  parts  of  solids 

"    loo        "        albumin 

"    100        "        fats  or  carbohyd  .    . 

90-3 

24.5 
S3-4 
9-7 

89.9 
81.2 
96.9 

II. I 

18,8 

3-1] 

[The  following  table,  abridged  from  Parkes,  shows  the  composition  of  the  chief  articles  of  diet,  and 
is  also  used  for  calculating  diet  tables  : — 


Beefsteak 

Fat  pork 

Smoked  hain  .    .    .    , 

White  fish 

Poultry 

White  wheaten  bread 
Wheat  flour    .    .    .    . 

Biscuit 

Rice 

Oatmeal      

Maize      

Macaroni 

Arrow  root     .    .    .    . 

Peas  (dry)  

Potatoes 


Carrots 

Cabbage      .... 

Butter 

Egg  (tV  for  shell) 

Cheese 

Milk  (sp.  gr. 
Cream      .    .    . 
Skimmed  milk 
Sugar  .... 


032) 


744 
39-0 
27.8 
78.0 
74.0 
40.0 
15.0 

8.0 
100 
15.0 
>3-5 
'31 
'5-4 
15.0 
74.0 
85.0 
91.0 

6.0 

73-5 
36.8 
86.8 
66.0 
88.0 
30 


20.5 
9.8 
24.8 
18.1 
21.0 
8.0 

II.O 

15.6 

50 
12.6 
1 0.0 
9.0 
0.8 
22.0 
2.0 
1.6 
1.8 
0-3 
13s 
33-5 
40 
2.7 
4.0 


Fats.  Carbohyd] 


s-s 

48.9 

36-5 

2.9 

3-« 

■•5 

2.0 

>  3 

0.8 

S.6 

b-7 

0-3 

2.0 

0.16 

0.25 

5.0 

91.0 

11.6 

243 

,v7 

20  7 

i.S 

96. 


1.6 

2-3 


■•3 

'•7 

1-7 

o-S 

30 

1-4 

0.8 

0.27 

2.4 

i.o 

i.o 

0,7 

2.7 

1.0 

5-4 

0.7 

1.8 

0.8 

0.5] 


235.  CONDIMENTS,  COFFEE,  TEA,  ALCOHOL.— Some  substances  are  used  along 
with  food,  not  so  much  on  account  of  their  nutritive  properties  as  on  account  of  their  stimulating 
effects  and  agreeable  qualities,  which  are  exerted  partly  upon  the  organ  of  taste  and  partly  upon 
the  nervous  system.     These  are  called  condiments. 

Coffee,  Tea,  and  Chocolate  are  prepared  as  infusions  of  certain  vegetables  [the  first  of  the 
roasted  berry,  the  second  of  the  leaves,  and  the  third  of  the  seeds].  The  chief  active  ingredients 
are  respectively  caffein,  thein  (CgH,(,N402  +  H^O,)  and  theobromin  (C,HgN_,02),  which  are 
regarded  as  alkaloids  of  the  vegetable  bases,  and  which  liave  recently  been  prepared  artificially 
from  xanthin  (E.  Fischer).  [Guarana,  or  Brazilian  cocoa,  is  made  of  the  seeds  ground  into  a 
paste  in  the  form  of  a  sausage.  Mate  or  Paraguay  tea,  the  leaves  of  a  species  of  holly,  are  used  in 
.South  America,  and  so  also  is  the  coca  of  the  Andes  (Erythroxylon  Coca).] 

These  "alkaloids  "  occur  as  such  in  the  plants  containing  them  ;  they  behave  like  ammonia; 
they  have  an  alkaline  reaction,  and  form  crystalline  salts  with  acids.  All  thesa  vegetable  bases  act 
upon  the  nervous  system;  some  more  feebly  (as  the  above),  others  more  powerfully  (quinine)  ;  some 
stimulate  powerfully,  or  com|)letely  paralyze  (morphia,  atropin,  strychnin,  curarin,  nicotin,  mus- 
carin). 

Effects. — All  these  substances  act  on  the  nervous  system  ;  they  quicken  thought, 
accelerate  movement,  and  stir  one  to  greater  activity.  In  these  respects  they  re- 
semble the  stimulating  extractives — kreatin  and  kreatinin — of  beef  tea.  Coffee 
contains  about  y'l  per  cent,  of  caffein,  part  of  which  is  only  liberated  by  the  act 
of  roasting.  Tea  has  6  per  cent,  of  thein  ;  while  green  tea  contains  i  per  cent, 
ethereal  oil,  and  black  tea  j/   per  cent.  ;  in   green  tea  there  is  18  per  cent.,  in 


386  PREPARATION    OF   ALCOHOLIC    DRINKS. 

black,  15  per  cent,  tannin  ;  green  tea  yields  about  46  per  cent.,  and  the  black 
scarcely  30  per  cent,  of  extract.  The  inorganic  salts  present  are  also  of  im- 
portance ;  tea  contains  3.03  per  cent,  of  salts,  and  among  these  are  soluble  com- 
pounds of  iron,  manganese,  and  soda  salts.  In  coffee,  which  yields  3.41  per  cent. 
of  ash,  potash  salts  are  most  abundant ;  in  all  three  substances  the  other  salts  which 
occur  in  the  blood  are  also  present. 

Alcoholic  Drinks  owe  their  action  chiefly  to  the  alcohol  which  they  contain. 
The  alcohol,  when  taken  into  the  body,  undergoes  certain  changes  and  produces 
certain  effects:  (i)  About  95  per  cent,  of  it  is  oxidized  chiefly  into  CO.j  and 
H2O,  so  that  it  is  so  far  a  source  of  heat.  .\s  it  undergoes  this  change  very  read- 
ily, when  taken  to  a  certain  extent,  it  may  act  as  a  substitute  for  the  consumption 
of  the  tissues  of  the  body,  especially  when  the  amount  of  food  is  insufficient. 
[Hammond  found  that  when  he  lived  on  an  insufficient  amount  of  food,  alcohol, 
if  given  in  a  certain  quantity,  supplied  the  place  of  the  deficiency  of  food,  and  he 
even  gained  in  weight.  If,  however,  sufficient  food  was  taken,  alcohol  was  unnec- 
essary. As  it  interferes  with  oxidation,  and  where  there  is  a  sufficient  amount  of 
other  food,  in  health,  it  is  unnecessary,  for  dietetic  reasons.]  Small  doses  dimin- 
ish the  decomposition  of  the  proteids  to  the  extent  of  6  to  7  per  cent.  Only  a 
very  small  part  of  the  alcohol  is  excreted  in  the  urine  ;  the  odor  of  the  breath  is 
not  due  to  alcohol,  but  to  other  volatile  substances  mixed  with  it,  e.  g.,  fusel  oil, 
etc.  (2)  In  small  doses  it  excites,  while  in  large  doses  it  paralvzes  the  ner- 
vous system.  By  its  stimulating  qualities  it  excites  to  greater  action,  which, 
however,  is  followed  by  depression.  (3)  It  diminishes  the  sensation  of  hunger. 
(4)  It  e.xcites  the  vascular  system,  accelerates  the  circulation,  so  that  the  muscles 
and  nerves  are  more  active,  owing  to  the  greater  supply  of  blood.  It  also  gives  rise 
to  a  subjective  feeling  of  warmth.  In  large  doses,  however,  it  paralyzes  the  ves- 
sels, so  that  they  dilate,  and  thus  much  heat  is  given  off"  (S  213,  7,  §  227).  The 
action  of  the  heart  also  becomes  affected,  the  pulse  becomes  smaller,  feebler,  and 
more  rapid.  In  high  altitudes  the  action  of  alcohol  is  greatly  diminished,  owing 
to  the  diminished  atmospheric  pressure  whereby  it  is  rapidly  given  off  from  the 
blood. 

Alcohol  in  small  doses  is  of  great  use  in  conditions  of  temporary  want,  and 
where  the  food  taken  is  insufficient  in  quantity.  When  alcohol  is  taken  regularly, 
more  especially  in  large  doses,  it  affects  the  nervous  system,  and  undermines  the 
psychical  and  corporeal  faculties,  partly  from  the  action  of  the  impurities  which  it 
may  contain,  such  as  fusel  oil,  which  has  a  poisonous  effect  upon  the  nervous  sys- 
tem, partly  by  the  direct  effects,  such  as  catarrh  and  inflammation  of  the  digestive 
organs,  which  it  produces,  and  lastly,  by  its  effect  upon  the  normal  metabolism. 

[The  action  of  alcohol  in  lowering  the  temperature,  even  in  moderate  doses,  is  most  important. 
By  dilating  the  cutaneous  vessels,  it  thus  permits  of  the  radiating  of  much  heat  from  the  blood. 
When  the  action  of  alcohol  is  pushed  too  far — and  especially  when  this  is  combined  with  the  action 
of  great  cold — its  use  is  to  be  condemned.] 

[Brunton  has  pointed  out  that,  as  regards  its  action  on  the  nervous  system,  it  seems  to  induce 
progressive  paralysis,  affecting  the  nervous  tissues  "  in  the  mverse  order  of  their  development,  the 
highest  centres  being  affected  first  and  the  lowest  last."  The  judgment  is  aflected  first,  although 
the  imagination  and  "emotions  maybe  more  than  usually  active."  'Y\\^  motor  centres  znA  speeck 
are  aflected,  then  the  cerebellum  is  influenced,  and  afterward  the  cord,  while,  by  and  by,  the  centres 
essential  to  life  are  paralyzed,  provided  the  dose  be  sufficiently  large.] 

Preparation. — .Mcoholic  drinks  are  prepared  by  the  fermentation  of  various  carbohydrates, 
such  as  sugar  derived  from  starch.  The  alcoholic  fermentation,  such  as  occurs  in  the  manufacture 
of  beer,  is  caused  by  the  development  of  the  yeast  plant,  Saccharomycetes  cerevisise  ;  while  in 
the  fermentation  of  the  grape  (wine),  S.  ellipsoideus  is  the  species  present  (Fig.  223).  The  yeast 
tal<es  the  substances  necessary  for  the  maintenance  of  its  organic  processes  directly  from  the  mixture 
of  the  sugar,  viz.,  carbohydrates,  proteids  and  salts,  especially  calcium  and  potassium  phosphates 
and  magnesium  sulphate.  These  substances  undergo  decomposition  within  the  cells  of  the  yeast 
plant,  which  multiply  during  the  process,  and  there  are  produced  alcohol  and  CO^  (|  150),  together 
with  glycerine  (3.2  to  3.6  per  cent.)  and  succinic  acid  (0.6  to  0.7  per  cent.).  Veast  is  either  added 
intentionally  or  it  reaches  the  mixture  from  the  air,  which  always  contains  its  spores.  When  yeast 
is  completely  excluded,  or  if  it  be  killed  by  boiling  [or  if  its  action  be  prevented  by  the  presence  of 


CONDIMENTS.  387 

some  germicide],  the  fermentation  does  not  occur.  The  alcoholic  fermentation  is  due  to  the  vital 
activity  of  a  low  organism  {Si^iiOiiii/i^  Mitscherluh^  Pash'ity]. 

In  the  preparation  of  brandy,  the  starch  of  the  grain  or  potatoes  is  first  changed  into  sugar  by 
the  action  of  diastase  or  maltin.  Veast  is  added,  and  fermentation  thereby  produced  ;  the  mixture 
is  distilled  at  78.3°  C.  The  fusel  oil  is  prevented  from  mixing  with  the  alcohol  by  passing  the  vapor 
through  heated  charcoal.     The  distillate  contains  50  to  55  per  cent,  of  alcohol. 

In  the  preparation  of  wine,  the  saccharine  juice  of  the  grape — the  must — after  being  expressed 
from  the  grapes,  is  exposed  to  the  air  at  10°  to  15°  C,  and  the  yeast  cells,  which  are  floating  about, 
drop  into  it  and  excite  fermentation,  which  lasts  ten  to  fourteen  days,  when  the  yeast  sinks  to  the 
bottom.  The  clear  wine  is  drawn  off  into  casks,  where  it  becomes  turbid  by  undergoing  an  after- 
fermentation,  until  the  sugar  is  converted  into  alcohol  and  CO^,  which  is  accompanied  by  the  deposi- 
tion of  some  yeast  and  tartar.  If  all  the  sugar  is  not  decomposed — which  occurs  when  there  is  not 
sufficient  nitrogenous  matter  present  to  nourish  the  yeast — a  S7i'eet  wine  is  obtained.  Wine  contains 
89  to  90  per  cent,  water,  7  to  S  per  cent,  alcohol,  together  with  ;ethylic,  propylic  and  butylic  alcohol. 
1  he  red  color  of  some  wines  is  due  to  the  coloring  matter  of  the  skin  of  the  grapes,  but  if  the  skins 
be  removed  before  fermentation,  red  grapes  yield  white  wine.  When  wine  is  stored,  it  develops  a 
fine  flavor  or  bouquet.  The  characteristic  vinous  odor  is  due  to  cenanthic  ether.  The  salts  of 
wine  closelj'  resemble  the  salts  of  the  blood. 

In  the  preparation  of  beer  the  grain  is  moistened,  and  allowed  to  germinate,  when  the  tempera- 
ture rises,  and  the  starch  (68  per  cent,  in  barley)  is  changed  into  sugar.     Thus,  "  malt "  is  formed, 

Fig.  223. 


which  is  dried,  and  afterward  pulverized,  and  extracted  with  water  at  70°  to  75°,  the  watery  extract 
being  the  "  wort."  Hops  are  added  to  the  wort,  and  the  whole  is  evaporated,  when  the  proteids  are 
coagulated.  Hops  give  beer  its  bitter  taste,  make  it  keep,  while  their  tannic  acid  precipitates  any 
starch  that  may  be  present,  and  clarifies  the  wort.  .After  being  boiled,  it  is  cooled  rapidly  (12°  C.)  ; 
yeast  is  added,  and  fermentation  goes  on  rapidly  and  with  considerable  effervescence  at  10°  to  14°. 
lieer  contains  75  to  95  per  cent,  water;  alcohol,  2  to  5  per  cent,  (porter  and  ale,  to  8  per  cent.) ; 
CUj,  0.1  to  0.8  per  cent.;  sugar,  2  to  8  per  cent.;  gum,  dextrin,  2  to  10  per  cent.;  the  hops  yield 
traces  of  protein,  fat,  lactic  acid,  ammonia  compounds,  the  salts  of  the  grain  and  of  the  hops.  In 
the  ash  there  is  a  great  preponderance  of  phosphoric  acid  and  potash,  both  of  which  are  of  great 
importance  for  the  formation  of  blood.  In  ICX3  parts  of  ash  there  are  40.8  potash,  20.0  phosphorus, 
magnesium  phosphate,  20,  calcium  phosphate,  2.6,  silica,  16.6  per  cent.  The  formation  of  blood, 
muscle  and  other  tissues  from  the  consumption  of  beer  is  due  to  the  phosphoric  acid  and  potash, 
while  if  too  much  be  taken,  the  potash  produces  fatigue. 

Condiments  are  taken  with  food,  partly  on  account  of  their  taste,  and  partly 
because  they  e.xcite  secretion.  Common  salt,  in  a  certain  sense,  is  a  condiment. 
We  may  also  include  many  substances  of  unknown  constitution  which  act  upon 
the  gustatory  organs,  e.  g.,  substances  in  the  crust  of  bread  [dextrin]  and  in  meat 
which  has  been  roasted. 


PHENOMENA  AND  LAWS  OF  METABOLISM. 


236.  EQUILIBRIUM  OF  THE  METABOLISM.— Ry  this  term  is 
meant  that,  under  normal  physiological  conditions,  just  as  much  material  is  absorbed 
and  assimilated  from  the  food  as  is  removed  from  the  body,  by  the  excretory 
organs,  in  the  form  of  effete  or  end  products,  the  result  of  the  retrogressive  tissue 
changes.  The  income  must  always  balance  the  expenditure  ;  wherever  a  tissue  is 
used  up,  it  must  be  replaced  by  the  formation  of  new  tissue.  During  the  period 
of  growth,  the  increase  of  the  body  corresponds  to  a  certain  increase  of  forma- 
tion, whereby  the  metabolism  of  the  growing  parts  of  the  body  is  2.5  to  6.3  times 
greater  than  that  of  the  parts  already  formed  (Cn/s/us).  Conversely,  during 
senile  decay,  there  is  an  excess  of  expenditure  from  the  body. 

Methods. — The  normal  equilibrium  of  the  metabolism  of  the  body  is  investigated — (l)  By 
determining  chemically  that  the  sum  of  all  the  substances  passing  into  the  body  is  equal  to  the  sum 
of  all  the  substances  given  off  from  it.  Thus  the  C,  H,  N,  O,  salts  and  water  of  the  food,  and  the 
O  inspired,  must  be  equal  to  the  C,  N,  H,  O,  salts  and  water  given  oft"  in  the  excreta  (urine,  faeces, 
air  expired,  water  excreted).  (2)  The  physiological  equilibrium  is  determined  empirically  by 
observing  that  the  body  retains  its  normal  weight  with  a  given  diet;  so  that,  by  simply  weighing  a 
person,  a  physician  is  enabled  to  determine  exactly  the  .state  of  convalescence  of  his  patient.  The 
tedious  process  of  making  an  elementary  analysis  of  the  metabolic  substances  was  first  under- 
taken in  the  Munich  School  by  v.  Bischoft,  v.  Voit,  v.  Pettenkofer,  and  others. 

Circulation  of  C. — In  the  circulation  of  materials  the  total  amount  of  C  taken 
in  the  food,  if  the  metabolism  be  in  a  condition  of  physiological  equilibrium, 
must  be  equaled  by  the  C  in  the  CO^  given  off  by  the  lungs  and  skin  (90  per 
cent.),  together  with  the  relatively  small  amount  of  C  in  the  organic  excreta  of 
the  urine  and  faeces  fio  per  cent.). 

Circulation  of  N. — Nearly  all  the  7\^  taken  in  with  the  food  is  excreted  within 
twenty-four  hours  in  the  form  of  urea.  A  very  small  amount  of  nitrogenous 
matter  is  excreted  in  the  fa;ces,  while  the  other  nitrogenous  urinary  constituents 
(uric  acid,  kreatinin,  etc.)  represent  about  2  per  cent,  of  N.  A  trace  of  the  N 
is  given  off  by  the  breath  (§  124),  and  a  minute  proportion  in  combination, 
in  the  epidermal  scales  (50  milligrammes  daily  in  the  hair  and  nails),  and 
in  the  sweat. 

Deficit  of  N. — That  nearly  all  the  N  taken  in  the  food  reajipears  in  the  urine 
and  ftEces,  as  was  stated  by  v.  Voit  to  be  the  case  in  the  carnivora,  by  Henneberg, 
Stohman,  and  Grouven  in  the  herbivora,  and  v.  Ranke  in  man,  is  contradicted 
partly  by  old  and  partly  by  new  observations,  which  go  to  show  that  the  whole  of 
the  N  cannot  be  recovered  from  these  excretions,  but  on  the  contrary  there  is  a 
considerable  deficit. 

According  to  Leo,  only  0.55  per  cent,  of  the  albumin  transformed  within  the  body  (assuming  15 
per  cent.  N.  in  albumin)  gives  off  its  N  in  the  form  of  gaseous  N  (according  to  Seegen  and  Nowak 
12  times  more).  In  every  exact  analysis  of  the  metabolism  of  N  this  gaseous  excretion  of  N  must 
be  taken  into  account. 

The  Excretion  of  N  after  food  does  not  take  place  regularly  from  hour  to  hour,  but  it  increases 
at  once  and  distinctly,  reaches  its  maximum  in  five  to  six  hours,  and  then  gradually  falls.  The  same 
is  true  of  the  excretion  of  S  and  P ;  but  in  these  cases  the  maximum  of  excretion  is  reached  at  the 
fourth  hour.  When  fat  is  added  to  a  diet  of  flesh,  the  excretion  of  N  and  S  is  uniformly  distributed 
o\'er  the  individual  hours  of  the  day  C?'.   Voil  and  Feder). 

The  nitrogenous  constituents  in  the  body  during  metabolism  become  poorer  in  C,  and  richer  in  N 
and  O.  Thus  in  albumin  to  i  atom  of  N  there  are  4  atoms  C;  in  gelatin,  3}<  C;  in  glycocoU, 
2  C;  in  kreatin,  I'j  C;  in  uric  acid,  i '4  C;  in  allantoin,  i  C;  in  urea,  oiilv  '^  atom  of  C. 

388 


EQUILIBRIUM    OF   THE    METABOLISM.  389 

The  H  leaves  the  body  chiefly  in  the  form  of  water — a  part,  however,  is  in  the 
combination  in  other  excreta ;  the  O  is  chiefly  excreted  as  CO,  and  water  ;  a  little 
is  given  off"  in  combination  in  other  excreta  ;  water  is  given  off"  by  evaporation 
from  the  lungs  and  skin,  and  also  in  the  urine  and  faeces.  As  H  is  oxidized  to 
form  H2O,  more  water  is  excreted  than  is  taken  in.  With  regard  to  the  salts, 
most  of  the  readily  soluble  salts  are  given  off  by  the  urine  ;  the  less  soluble  salts, 
especially  those  of  potash,  and  the  insoluble  salts,  in  the  fa;ces  ;  while  others  e.  g., 
common  salt,  are  given  off  in  the  sweat.  Of  the  sulphur  of  albumin,  about  one- 
half  is  excreted  in  the  sulphur  compounds  in  the  urine,  and  the  other  half  in  the 
fseces  (taurin),  and  in  the  epidermal  tissues. 

Every  organism  has  a  minimum  and  a  maximum  limit  of  metabolism, 
according  to  the  amount  of  work  done  by  the  body,  and  its  weight.  If  less  food 
be  given  than  is  necessary  to  maintain  the  former,  the  body  loses  weight ;  while, 
if  more  be  given  after  the  maximum  limit  is  reached,  the  food  so  given  is  not 
absorbed,  but  remains  as  a  floating  balance,  and  is  given  off"  with  the  fseces.  When 
food  is  liberally  supplied  and  the  weight  increases,  of  course  the  minimum  limit 
rises;  hence,  during  the  process  of  "feeding"  or  "fattening,"  the  amount  of 
food  necessary  is  very  much  greater  than  in  poorly  fed  animals,  for  the  same 
increase  of  the  body  weight.  By  continuing  the  process,  a  condition  is  at  last 
reached,  in  which  the  digestive  organs  are  just  sufficient  to  maintain  the  existing 
condition,  but  cannot  act  so  as  to  admit  of  new  additions  being  made  to  the  body 
weight  {v.  Bisclwff,  v.   Voit,  v.  Pcttenkofcr). 

By  the  term  "  luxus  consumption  "  is  meant  the  direct  combustion  or  oxi- 
dation of  the  superfluous  food  stufts  absorbed  into  the  blood.  This,  however,  does 
not  exist  ;  on  the  contrary,  the  material  in  the  juices  is  always  being  used  for 
building  up  the  tissues.  The  albumin  found  in  the  fluids  which  everywhere  per- 
meate the  tissues  has  been  called  "  circulating  albumin,"  and  according  to 
v.  Voit  it  undergoes  decomposition  sooner  than  the  organized  "  organic  albu- 
min "  which  forms  an  integral  part  of  the  tissues. 

[Liebig  lauglit  that  the  nitrogenous  metabolism  of  the  body  depended  on  a  corresponding  decom- 
position of  the  proteids  of  the  organs,  so  that  the  proteids  in  the  food  supplied  the  place  of  the 
proteids  of  the  organs  thus  used  up.  He  called  the  proteids  "  plastic  foods  "  or  "  tissue  for- 
mers," while  he  regirded  the  fats  and  carbohydrates  as  respiratory  foods,"  as  he  supposed  that 
they  alone  were  concerned  in  the  evolution  of  heat.  .\s  a  matter  of  fact,  experiment  proved  that 
the  N  metabolism  is  to  a  large  extent  independent  of  the  proteids  of  the  food.  The  luxus-con- 
sumption  theory  was  invented  to  explain  this.  It  simply  means,  that  proteids  taken  with  the  food 
not  only  replace  the  amount  of  proteids  which  have  been  decomposed  during  the  activity  of  organs 
and  tissues,  but  any  excess  is  immediately  consumed  without  being  converted  into  tissue,  and  thus 
this  surplus  amount  giving  rise  to  heat,  being  oxidized,  to  a  certain  extent  it  replaced  the  fats  and 
carbohydrates.  But  Voit  showed  that  nitrogenous  metabolism  is  not  influenced  by  the  activity  of 
the  organism,  and  he  proved  that  in  ordinary  conditions  only  a  small  amount  of  the  organic  albumin, 
i.  e.,  that  composing  tissues  and  organs,  undergoes  decomposition,  while,  owing  to  the  action  of  the 
cellular  elements  of  the  tissues,  a  large  amount  of  the  circulating  albumin  is  split  up,  so  that  under 
ordinary  conditions  the  organic  albumin  is  comparatively  stable.  This  he  demonstrated  from  a 
comparison  of  the  urea  excreted,  for  the  urea  may  be  taken  as  an  index  of  the  N  metabolism 
in  well-fed,  fasting,  and  starving  anitnals.  But  in  certain  pathological  conditions  the  organic 
albumin  may  undergo  rapid  change,  having  become  less  stable,  as  in  fevers,  and  poisoning 
with  phosphorus.] 

.According  to  v.  Voit  only  i  per  cent,  of  the  organic  albumin  present  in  the 
body,  while  70  per  cent,  of  the  circulating  albumin,  is  transferred  in  twenty-four 
hours. 

Quality  and  Quantity  of  the  Income  in  a  Healthy  Adult. — As  far  as 
his  organization  is  concerned,  man  belongs  to  the  omnivorous  animals,  i.  e., 
those  that  can  live  upon  a  mixed  diet. 

For  an  adequate  diet  man  requires  for  his  existence  and  to  maintain  health  a 
mixture  of  the  following  four  chi€f  groups  of  food  stuffs,  along  with  the  necessary 
relishes ;  none  of  them  mu^t  be  absent  from  the  food  for  any  length  of  time. 
They  are  :  — 


390  REQUISITES    FOR    A    PERFECT   DIET. 

1.  Water — for  an  adult,  in  his  food  and  drink,  2700  to  2S00  grms.  [70  to  90 
oz.]  daily  (§  229  and  §  247,  i). 

[Thirst. —  The  needs  of  tlie  economy  for  water  are  expressed  by  the  sensation  of  thirst.  The 
sensation  of  heat  and  dryness  may  be  confined  to  the  tongue,  mouth,  and  fauces,  and,  indeed,  may 
be  excited  by  inhaling  dry  air.  This  local  thirst  may  be  allayed  by  swallowing  waler  or  by  eating 
substances  which  excite  the  secretion  of  saliva.  More  frequently,  however,  the  sensation  is  the 
expression  of  a  general  condition  indicating  the  diminution  of  water  in  the  tissues  ;  or  it  may  be  due 
to  excess  of  saline  matters  in  the  blood.  In  some  diseases  this  sensation  is  very  intense,  e.g.,  dia- 
betes, and  there  seems  to  be  a  thirst  centre  in  the  brain  (AWhntigel).  If  water  be  injected  into  the 
blood  vessels,  or  stomach,  both  the  general  and  local  thirst  are  abolished,  even  although  no  water 
enters  the  mouth  In  some  diseased  conditions  the  sensation  of  thirst  is  not  perceived,  owing  to 
the  diminution  of  the  excitability  of  the  perceptive  centre,  and  in  some  cases  excessive  thirst  is 
complained  of  even  although  the  body  does  not  seem  to  be  unduly  deficient  in  fluids.] 

2.  Inorganic  Substances  are  the  integral  part  of  all  tissues,  and  without 
them  the  tissues  cannot  be  formed.  They  occur  in  ordinary  food.  The  addition 
of  too  much  salt  increases  the  consumption  of  water,  and  this  in  turn  increases 
the  transformation  of  N  in  the  body  ( Jl^eisi'e).  If  an  animal  be  deprived  of  salts, 
nutrition  is  interfered  with  ;  food  deprived  of  its  lime  affects  the  formation  of  the 
bones  ;  deprival  of  common  salts  causes  albuminuria  (§  247,  A,  III).  The  alkaline 
salts  serve  to  neutralize  the  sulphuric  acid  formed  by  the  oxidation  of  the  sulphur 
of  the  proteids  (E.  Sa!ko7iiski).  Iron,  which  is  so  essential  for  the  formation  of 
blood,  exists  in  animals  and  plants  in  combination  with  complex  organic  bodies 
{Bunge). 

[The  uses  of  mineral  salts  are  referred  to  in  J  247,  .\.  Salts  form  an  essential  ingredient  in 
soups  and  broth.  Some  salts  exist  in  combination  with  the  organized  tissues,  while  others  are 
merely  dissolved  in  the  fluids.     Forster  thinks  that  it  is  the  latter  which  are  chiefly  excreted.] 

Only  in  times  of  famine  is  man  driven  to  eat  large  quantities  of  inorganic  subslances,  to  extract 
the  organic  matler  mixed  therewith.  A.  v.  Humboldt  states,  in  regard  to  the  inhabitants  of  the 
Orinoco,  that  they  eat  a  kind  of  earth  which  contains  innumerable  infusoria. 

3.  At  least  one  animal  or  vegetable  albuminous  body  or  proteid  (§§  248,  250). 
The  proteids  are  required  to  replace  the  used-up  nitrogenous  tissues,  e.  g.,  for 
muscles.     They  contain  15.4  to  16.5  per  cent.  N. 

The  proteids  are  in  blood  :^  20.56  per  cent.;  muscles,  19.9  per  cent. ;  liver,  11.74  per  cent.  ; 
brain,  8.63  per  cent.;  blood  plasma,  7.5  per  cent.;  milk,  3.94  per  cent.;  lymph,  2.46  per  cent. 
According  to  Pfliiger  and  Bohland,  a  youth  of  full  stature,  and  62  kilos.  [136  lbs],  decomposes 
89.9  grms.  of  albumin  daily. 

Asparagin,  in  combination  with  gelatin,  can  replace  albumin  in  the  food  (H'7iske),  while  aspara- 
gin  alone  limits  the  decomposition  of  albumin  in  herbivora  but  not  in  camivora  {J.  Munk). 
Amraoniacal  salts,  glycocoU,  sarkosin,  and  benzamid,  increase  the  amount  of  albumin  in  the  body. 

4.  At  least  one  fat  (§  251),  or  a  digestible  carbohydrate  (§  252).  These 
chiefly  serve  to  replace  the  transformed  fats  and  non-nitrogenous  constituents. 
Owing  to  the  large  amount  of  C  which  they  contain,  when  they  undergo  oxida- 
tion, they  form  the  chief  source  of  the  heat  of  the  body  (S  206).  Fats  and  car- 
bohydrates may  replace  each  other  in  the  food,  and  in  inverse  proportion  too, 
corresponding  to  the  amount  of  C  which  each  contains.  As  far  as  the  mere  evo- 
lution of  heat  is  concerned,  100  parts  of  fat  ^  256  of  grape  sugar  =  234  of  cane 
sugar  =  221  of  dry  starch  {Ruhner^.  A  man  consumes  210  grms.  fat  daily. 
(v.  Voit  and  v.  Pettenkofer).  According  to  v.  Voit,  in  the  economy  175  parts  of 
starch  by  weight  are  equal  to  1 00  parts  of  fat. 

[5.  Every  proper  diet  ough'  to  have  a  certain  degree  of  sapidity  or  flavor. 
The  substances  which  give  this  are  not  useful  in  the  evolution  of  energy  or  build- 
ing up  the  tissues,  but  they  stimulate  the  nervous  system  and  excite  secretion. 
They  are  called  "  Genussmittel  "  (means  of  enjoying  food)  by  the  Germans,  but 
we  have  no  exact  equivalent  for  this  word  in  English,  though  the  articles  them- 
selves are  included  under  our  expression  "condiments."  These  substances  are 
the  aromatic  matter  in  roast  meat  (osmasome),  tea,  vinegar,  salt,  mustard,  pepper, 
etc.] 


PROPORTION    OF    FOODS. 


391 


[Condition  of  Diet  for  Health. — In  an  adequate  diet,  not  only  (i)  should 
the  total  quantity  be  sufficient  and  not  more  than  sufficient,  but  (2)  the  constitu- 
ents should  exist  in  proper  proportions,  (3)  be  digestible,  and  (4)  the  whole 
should  be  in  good  condition,  wholesome,  and  not  adulterated  with  any  substance 
prejudicial  to  health.] 

Fig.  224. 
explanation  of  the  signs. 


Beef. 

Pork. 
Fowl. 


Egg. 


^•^t;;r 


] 


73,5 


I' 


MssM 


Animal  Foods. 
EXPLANATION    OF   THE    SIGNS. 


Whcaten  bread 


41,3          ^y| 

::li|ll;iillilllllill!illi|lillllll!|||l!|li|| 

14 

I-'-      H      . 

53,5'',  ;^                       ■'■    '^ 

i        '3      1 

rtli  lll|||i!llliiliiiiiiV'iiiiii:i 

,.„,^: 

--'     "III 

75 

^,:,i,.,.ii-j„l ,;J:::M 

1 

90,5 

■IN 

1 

80 

^€ilil 

1 

30 

iiiiiil 

Vegetable  Foods. 

Relative  Proportion. — With  regard  to  the  relative  proportions  of  the  various 
kinds  of  food  which  ought  to  be  taken,  experience  has  shown  that  the  diet  best 
suited  for  the  body  must  contain  i  part  of  nitrogt-noiis  foods  to  3'^  or,  at  most,  41^ 
of  the  no n- nitrogenous.  Looking  at  ordinary  foods  from  this  point  of  view,  we  see 
how  far  they  correspond  to  this  requirement,  and  how  several  substances  may  be 
combined  to  produce  a  satisfactory  diet. 


392 


DAILY    QUANTITY   OF   FOOD    REQUIRED. 


1.  Veal   .    .    . 

2.  Hare's  flesh 

3.  Beef   .    .    . 


Lentils 10       2t 

5.  Beans 10       22 

6.  Peas 10       23 


7.  Mutton     .    .    .    . 

8.  Pork 

9.  Cow's  milk    .    . 

10.  Human  milk    .    . 

11.  Wheaten  flour . 

12.  Oatmeal   .    .    .    . 


13.  Rye  meal     .    . 

14.  Barley  meal 

15.  White  potatoes 

16.  Blue 

17.  Rice     .... 

18.  Buckwheat  meal 


57 
57 
86 

"5 
123 

130 

An  examination  of  this  table  shows  that,  in  addition  to  human  milk,  wheat  flour  has  the  right 
proportion  of  nitrogenous  to  non-nitrogenous  substances.  A  man  who  tries  to  nourish  himself  on 
beef  alone,  commits  as  great  a  mistake  as  one  who  would  feed  himself  with  potatoes  alone. 
Experience  has  taught  people  that  man  may  live  upon  milk  and  eggs,  but  that  in  addition  to  flesh 
we  must  eat  bread  or  potatoes,  while  pulses  require  fat  or  bacon. 

Effect  of  Cold. — The  diet  varies  with  the  climate  and  with  the  season  of  the  year.  As  the 
organism  must  produce  more  heat  in  cold  latitudes,  the  inhabitants  of  northern  climates  must  eat 
more  non-nitrogenous  foods,  such  as  fats  and  sugar  or  starches,  which,  on  account  of  the  large 
amount  of  C  they  contain,  are  admirably  adapted  for  producing  heat  (§  214,  I,  4). 

The  graphic  representation  of  the  composition  of  foods  (Fig.  224),  taken  from 
Fick,  shows  at  once  the  relative  proportions  of  the  most  important  food  stuffs, 
and  how  they  vary  from  the  standard  of  i  nitrogenous  to  3J2  or  4J2  non-nitro- 
genous. 

The  absolute  amount  of  food  stuffs  required  by  an  adult  in  twenty-four  hours 
depends  upon  a  variety  of  conditions.  As  the  food  represents  the  chemical 
reservoir  of  potential  energy,  from  which  the  kinetic  energy  (in  its  various  forms) 
and  the  heat  of  the  body  are  obtained,  the  absolute  amount  of  food  must  be 
increased  when  the  body  loses  more  heat,  as  in  winter,  and  when  more  muscular 
activity  (work )  is  accomplished.  As  a  general  rule,  <?//  aJu//  requires  daily  130 
grammes  proteids,  84  grammes  fats,  404  grammes  carbohydrates. 

The  following  tables  express  the  mean  of  numerous  single  observations : — 

A  Healthy  Adult  Requires  in  24  Hours,  of  Water-free  solids — 


Food  in  Grammes. 

At  Rest. 
iPUy/air.) 

Moderate  Work, 
(Moleschott.) 

Laborious  Work. 

(Play/air.) 

(v.  Pttttnkofer 
aiidv.  Volt.) 

Proteids 

Fats 

Carbohydrates  (Sugar,  Starch,  etc.)  . 
Salts 

70.87 

28.35 

340.20 

14.00 

130 
84 

404 
30 

155.92^ 
70.87 

567-50 
40.00 

"37 
117 

352 
40 

[When  we  record  these  numbers  in  ounces  we  get  the  following  results  as 
■water-free  solids  required  by  any  average  man  {Parkes) : — 


At  Rest. 

Ordinary  Work. 

Laborious  Work. 

Proteids 

Fats  ,   - 

2-5 
I.O 
12.0 
0.5 

4.6 

3-0 
14.4 
1.0 

6  to    7 

3-5 '0    4  5 
16  to  18 

1.2  to       1.5 

Salts 

Total  water-free  food    ...  - 

16.0 

23.0 

26.7  to  31.0 

During  ordinary  work  the  proportion  is  about : — 

Proteids,  i  :   fats,  0.6:  carbohydrates,  3.0, 
i.e.,  I  Nitrogenous  to  3.6  non-nitrogenous.] 
[In  a  diet  for  ordinary  work  (23  oz.  of  dry  solids)  a  man  takes  about  y^^  part  of 
his  own  weight  daily ;  ordinary  food,  however,  as  it  is  consumed,  contains  between 


DAILY    QUANTITY   OF    FOOD    REQUIRED. 


393 


50  and  60  per  cent,  of  water ;  if  we  add  this  proportion  of  water  to  the  actually 
dry  food  we  get  48  to  60  oz.  of  ordinary  food  (exclusive  of  liquids).  But  we 
consume  50  to  80  oz.  of  water  in  some  liquid  form,  making  the  total  amount  of 
water  70  to  90  oz.  {Farkes).~\ 

In  an  analogous  example  from  Vierordt,  the  elementary  substances  in  the  food  are  given  (J  215, 
B),  and  compared  with  the  income  and  expenditure. 

An  Adult  doing  a  Moderate  Amount  of  Work  takes  in : — 


c. 

H.             N.       !        0. 

i 

64.18 
70.20 
146.82 

8.60         18.88  1      28.54. 

10.26 
20-33 

.    .     1       9-54 
.    .     1   162.85 

281.20 

3919 

18.88  .  200.73 

Add    744.1 1  grm.  O  from  the  air  by  respiration. 
"     2818  "     HjO. 

"         32  "     Inorganic  compounds  (salts). 

The  whole  is  equal  to  t,\  kilos  [7  Itjs.],  /.  e.,  about  ^V  '^^  the  body  weight  ;  so 
that  about  6  per  cent,  of  the  water,  about  6  per  cent,  of  the  fat,  about  i  per  cent, 
albumin,  and  about  0.4  per  cent,  of  the  salts  of  the  body  are  daily  transformed 
within  the  organism. 

An  Adult  doing  Moderate  Work  gives  off,  in  grammes : —  , 


Water. 

c. 

H. 

N. 

0. 

330 

660 

1700 

128 

248.8 
2.0 

9.8 

20.0 

3-3 
3-0 

.' 

i"s.8 
3° 

651.15 
7.2 
II. I 
12.0 

Urine 

2818 

201.2 

6.3 

18.8 

681.45 

Add  to  this  (besides  28 1 S  grammes  water,  as  drink)  296  grammes  water  formed  in  the  body  by 
the  oxidation  of  H.  These  296  grammes  of  water  contain  3289  grammes  H,  and  263.41  grammes 
O ;  26  grammes  of  salts  are  given  off  in  the  urine,  and  6  by  the  fixces. 

Effect  of  Age. — The  investigations  of  the  Munich  School  have  shown  that  the 
following  numbers  represent  the  minimum  amount  of  food  necessary  for  dif- 
ferent ages : — 


Child  until  ij^  years    .    .    .    , 

"      from  six  to  fifteen  years 

Man  (moderate  work)  .    .    .    . 

Woman .    

Old  man 

Old  woman 


Nitrogenous. 

Fat. 

Carbohydrates. 

20-36  grms. 
70-80     " 
118       " 
92       " 
100       " 
80       " 

30-45  grms. 

37-50     " 
56        " 
44 

68       " 
50       " 

60-90  grms. 
250-400  " 
500       " 
400       " 
350       " 
260       " 

[Not  only  do  muscular  movements  and  age  influence  the  amount  of  food  taken,  but  climate  anil 
individual  peculiarities,  such  as  size  and  the  activity  of  certain  organs,  also  affect  it.] 

Small  animals  have  a  more  lively  metabolism  than  large  ones  {Regnatilt  and  Reiset).  In  small 
animals  the  decomposition  of  albumin  per  unit  weight  of  body  is  greater  than  in  large  animals 
[V.  Voit).  Small  animals,  a3  a  rule,  consume  more  proteids  than  larger  ones,  because  they  generally 
have  less  bodily  fat  {Rubner). 


394 


METABOLISM    DURING    HUNGER   AND    STARVATION. 


Relation  of  N  to  C. — In  most  of  the  ordinary  articles  of  diet,  nitrogenous 
and  non-nitrogenous  substances  are  present,  but  in  very  varying  proportion,  in 
the  difterent  foods.  Man  requires  that  these  shall  be  in  the  proportion  of  i  :  3)4 
to  I  :  4>4. 

If  food  be  taken  in  which  this  proportion  is  not  observed,  in  order  to  obtain 
the  necessary  amount  of  that  substance  which  is  contained  in  too  small  proportion 
in  his  food,  he  must  consume  far  too  much  food.  Moleschott  finds  that  a  person, 
in  order  to  obtain  the  130  grammes  of  proteids  necessary,  must  use 

Cheese 338  grms.    I    Beef. 614  grms.    I    Rice 2562  grms. 

Lentils 491    "  Epgs 96S     "  Rye  bread     .    .    .  2875     " 

Peas 5S2    "         I    Wiieat  bread  .    .     1444     "         |    Potatoes     .    .    .   10,000     " 

provided  he  were  to  take  only  one  of  these  substances  as  food  ;  so  that  it  is  per- 
fectly obvious  that,  if  a  workman  were  to  live  on  potatoes  alone,  m  order  to  get 
the  necessary  amount  of  N,  he  would  have  to  consume  an  altogether  preposterous 
amount  of  this  kind  of  food. 

To  obtain  the  448  grammes  of  carbohydrates,  or  the  equivalent  amount  of 
fat  necessary  to  support  him,  a  man  must  eat 

Rice 572  grms.    I    Peas 819  grms.    I    Cheese 201 1  grms. 

Wheat  bread    .    .    .  626    "  Eggs 902     "  Potatoes     ....  2039     " 

Lentils 806    "         ]    Rye  bread  ....  930     "         |    Beef 2261     " 

so  that  if  he  were  to  live  upon  cheese  or  flesh  alone,  he  would  require  to  eat  an 
enormous  amount  of  these  substances. 

In  the  case  of  the  herbivora,  the  proportion  of  nitrogenous  to  non-nitrogenous  food  necessary  is 
I  of  the  former  to  8  or  9  parts  of  the  latter. 

237.  METABOLISM  DURING  HUNGER  AND  STARVATION. 

— If  a  warm-blooded  animal  be  deprived  of  all  food,  it  must,  in  order  to 
maintain  the  temperature  of  its  body  and  to  produce  the  necessary  amount  of  me- 
chanical work,  transform  and  utilize  the  amount  of  potential  energy  of  the  con- 
stituents of  its  own  body.  The  result  is  that  its  body  weight  diminishes  from 
day  to  day,  until  death  occurs  from  starvation. 

The  following  table,  from  Bidder  and  Schmidt,  shows  the  amounts  of  the  diflerent  excreta  in  the 
case  of  a  starved  cat : — 


Day. 

Body 
Weight. 

Water 
taken. 

Urine. 

Urea. 

Inorganic 

Substances 

in  Urine. 

Dry 

Faces. 

Expired 

Water  in 

Urine 

and  Faeces. 

I. 

2464 

98 

7-9 

1-3 

1.2 

13-9 

91.4 

2. 

2297 

II.5 

54 

5-3 

0.8 

1.2 

12.9 

50.5 

3- 

2210 

45 

4.2 

0.7 

I.I 

12 

42.9 

4. 

2172 

68.2 

45 

3-8 

0-7 

I.I 

12.3 

43 

5- 

2129 

55 

4-7 

0.7 

1-7 

11.9 

54.1 

6. 

2024 

44 

4-3 

0.6 

0.6 

11.6 

41. 1 

7- 

1946 

40 

3-8 

°S 

0.7 

II 

37-5 

8. 

1873 

42 

3-9 

0.6 

I.I 

10.6 

40 

9- 

1782 

15.2 

42 

4 

0-5 

1-7 

10.6 

41.4 

10. 

I717 

35 

.    3-3 

0.4 

1-3 

lo.s 

34 

II. 

169s 

4 

32 

2.9 

0.5 

I.I 

10.2 

3°-9 

12. 

1634 

22.5 

30 

2-7 

0.4 

I.I 

10.3 

29.6 

'3- 

1570 

7-1 

40 

3-4 

0.5 

0.4 

lO.I 

36.6 

14. 

1518 

3 

41 

3-4 

0.5 

0-3 

9-7 

3^ 

'5- 

"434 

41 

2.9 

0.4 

0-3 

9-4 

38-4 

16. 

1389 

48 

3 

0.4 

0.2 

8.8 

45-5 

'7- 

'335 

28 

1.6 

0.2 

0-3 

7.8 

26.6 

i8.t 

1267 
-1197 

13 

0.7 

0.1 

03 

6.1 

12.9 

«3i-5 

775 

659 

9.8 

158 

190.8 

737-4 

LOSS    OF    WEIGHT   OF    ORGANS    DURING    STARVATION.  395 

The  cat  lost  1197  grms.  in  weight  before  it  died,  and  this  amount  is  apportioned 
in  the  following  way:  204.43  grms.  (  =  17.01  per  cent.)  loss  of  albumin; 
132.75  grms.  (:=  11.05  Psr  cent.)  loss  of  fat;  863.82  grms.  loss  of  water  (  = 
71.91  per  cent,  of  the  total  body  weight). 

Methods. — In  order  to  investigate  the  condition  of  inanition  it  is  necessarj- — (i)  to  weigh  the 
a'pinial  daily ;  (2)  to  estimate  daily  all  the  C  and  N  given  oft'  from  the  body  in  the  feces,  urine  and 
expired  air.  The  N  and  C,  of  course,  can  only  be  obtained  from  the  decomposition  of  tissues  con- 
taining them. 

Among  the  general  phenomena  of  inanition,  it  is  found  that  strong,  well-nourished  dogs  die 
after  4  weeks,  man  after  21-24  days  {MoUschott)  —  (6  melancholies  who  took  water  died  after  41 
days);  small  mammals  and  birds,  9  days,  and  frogs  9  months.  Vigorous  adults  die  when  they 
lose  y't,  of  their  body  weight,  but  ynung  individuals  die  much  sooner  than  adults.  The  symptoms 
are  obvious:  The  mouth  is  dry,  the  walls  of  the  alimentary  canal  become  thin,  and  the  digestive 
secretions  cease  to  be  formed  ;  pulse  beats  and  respirations  are  fewer;  urine  very  acid  from  the 
presence  of  an  increased  amount  of  sulphuric  and  phosphoric  acids,  while  the  chlorine  compounds 
rapidly  diminish  and  almost  disappear.  The  blood  contains  less  water  and  the  plasma  less  albumin, 
the  gall  bladder  is  distended,  which  indicates  a  contmuous  decomposition  of  blood  corpuscles  within 
the  liver.  The  liver  is  small  and  very  dark-colored,  the  muscles  are  very  brittle  and  dry,  so  that 
there  is  great  muscular  weakness,  and  death  occurs,  with  the  signs  of  great  depression  and  coma. 
The  relations  of  the  metabolism  are  givn  in  the  foregoing  table,  the  diminution  in  the  excretion  of 
urea  is  much  greater  than  that  of  CO^,  which  is  due  to  a  larger  amount  of  fats  than  proteids  being 
decomposed. 

According  to  the  calculation,  there  is  daily  a  tolerably  constant  amount  of  fat 
used  up,  while,  as  the  starvation  continues,  the  proteids  are  decomposed  in  much 
smaller  amounts  from  day  to  day,  although  the  drinking  of  water  accelerates  their 
decomposition.  The  excretion  of  CO..,  therefore,  falls  more  slowly  than  the  total 
body  weight,  so  that  the  unit  weight  of  the  living  animal  from  day  to  day  may 
even  show  an  increased  production  of  CO^.  The  amount  of  O  consumed  depends, 
of  course,  upon  the  oxidation  of  proteids  (which  require  less  O),  and  of  fats 
(which  require  more  O). 

According  to  D.  Finkler,  starving  animals  consume  nearly  as  much  O  as  well-nourished  animals, 
so  that  the  energy  of  oxidation  is  scarcely  altered  during  inanition.  Corresponding  to  this,  the  tem- 
perature of  a  starving  animal  is  the  same  as  normal.  The  respiratory  quotient  {\  124)  then  falls 
from  0.9  to  0.7,  and  the  excretion  of  CO,  diminishes  more  rapidly  than  the  consumption  of  O.  It 
would  be  wrong,  however,  to  conclude,  i'rom  the  diminished  excretion  of  CO,,  that  the  oxidation 
also  was  diminished,  as  the  simultaneous  consumption  of  O  is  the  only  guide  to  the  energy  of  the 
metabolism.  As  starving  animals  use  up  their  own  flesh  and  fat,  they  form  less  CO2  than  well- 
nourished  animals,  which  oxidize  carbohydrates  chiefly. 

Loss  of  Weight  of  Organs. — It  is  of  importance  to  determine  to  what  extent 
the  individual  organs  and  tissues  lose  weight  ;  some  undergo  simple  loss  of  weight, 
e.g.,  the  bones,  the  fat  undergoes  very  considerable  and  rapid  decomposition, 
while  other  organs,  as  the  heart,  undergo  little  change,  because  they  seem  to  be 
able  to  nourisii  themselves  from  the  transformation  products  of  other  tissues. 

A  starving  cat,  according  to  v.  Voit,  lost — 
Per  cent, 
originally 
present. 

1.  fat 97 

2.  Spleen     ....    66.7 
3-  Liver 53.7 

4.  Testicles      .    .    .  40.0 

5.  Muscles    ....  30.5 

6.  Blood 27.0 

7.  Kidneys  ....  25.9 

8.  Skin 20.6 

9.  Intestine      .    .    .  18.0 

There  is  a  very  important  difference  according  as  the  animals  before  inanition 
have  been  fed  freely  on  flesh  and  fat  [/.  e.,  if  they  have  a  surplus  store  of  food 
within  themselves],  or  as  they  have  merely  had  a  subsistence  diet.  Well-fed  ani- 
mals lose  weight  much   more  rapidly  during  the  first  few  days  than  on  the  later 


Per  cent 

of 

Percent. 

Pe 

r  cent,  of 

ttie  total  1 

«sof 

originally 

the 

otal loss  of 

body  weight. 

present. 

body  weight. 

26.2 

10. 

Lungs  .    .   .   . 

17.7 

0-3 

0.6 

II. 

Pancreas  .    .    . 

17.0 

0.1 

4.8 

12. 

Bones   .    .    .    . 

13-9 

5-4 

O.I 

«3- 

Central    Nerv- 

42.2 

ous  System 

3-2 

0.1 

3-7 

14. 

Heart   .    .    .    . 

2.6 

0.02 

0.6 

IS- 

Total    loss    of 

8.8 

the    rest    of 

2  0 

the  body    .    . 

36.8 

50 

396  METABOLISM    OF   PEPTONES. 

days.  V.  Voit  thinks  that  the  albumin  derived  from  the  excess  of  food  occurs  in 
a  state  of  loose  combination  in  the  body  as  "  circulating  "  or  "  storage  albumin,'" 
so  that  during  hunger  it  must  decompose  more  readily  and  to  a  greater  extent  than 
the  "  organic  albumin,"  which  forms  an  integral  part  of  the  tissues  (§  236). 
Further,  in  fat  individuals,  the  decomposition  of  fat  is  much  greater  than  in 
slender  persons. 

238.  METABOLISM  ON  A  PURELY  FLESH  DIET— ALBU- 
MIN OR  GELATIN,  PROTEID  METABOLISM.— A  man  is  not  able 
to  maintain  his  metabolism  in  equilibrium  on  a  purely  flesh  diet ;  if  he  were  com- 
pelled to  live  on  such  a  diet,  he  would  succumb.  The  reason  is  obvious.  In  beef, 
the  proportion  of  nitrogenous  to  non-nitrogenous  elementary  constituents  of  food 
is  I  :  1.7  (p.  392).  A  healthy  person  excretes  280  grammes  [8  to  90Z.]  of  carbon, 
in  the  form  of  COj,  in  the  expired  air,  and  in  the  urine  and  fasces.  If  a  man  is 
to  obtain  2S0  grammes  C  from  a  flesh  diet,  he  must  consume — digest  and  assimilate 
— more  than  2  kilos.  [4.4  fts.]  of  beef  in  twenty-four  hours.  I3ut  our  digestive 
organs  are  unequal  to  this  task  for  any  length  of  time.  The  person  is  soon 
obliged  to  take  less  beef,  which  would  necessitate  the  using  of  his  own  tissues,  at 
first  the  fatty  parts  and  afterward  the  proteid  substances. 

A  carnivorous  animal  (dog),  whose  digestive  apparatus,  being  specially  adapted  for  the  diges- 
tion of  flesh,  has  a  short  intestine  and  powerfully  active  digestive  flu'ds,  can  only  maintain  its  meta- 
bolism in  a  state  of  equilibrium  when  fed  on  a  tiesh  diet  free  from  fat,  provided  its  body  is  already 
well  supplied  with  fat,  and  is  muscular.  It  consumes  ^-^  to  ^L  part  of  the  weight  of  its  body  in 
flesh,  so  that  the  excretion  of  urea  increases  enormously.  If  it  eats  a  larger  amount,  it  may  "  put 
on  flesh,"  when,  of  course,  it  requires  to  eat  more  to  maintain  itself  in  this  condition,  unless  the  limit 
of  its  digestive  activity  is  reached.  If  a  well-nourished  dog  is  fed  on  less  than  4^  to  ^^  of  its  body 
weight  of  tlesh.  it  uses  part  of  its  own  fat  and  muscle,  gradually  diminishes  in  weight,  and  ulti- 
mately succumbs.  Poorly-fed  non-muscular  dogs  are  unable  from  the  very  beginning  to  maintain 
their  metabolism  in  equilibrium  for  any  length  of  time  on  a  purely  flesh  diet,  as  they  must  eat  so 
large  a  quantity  of  flesh  that  their  digestive  organs  cannot  digest  it.  The  herbivora  cannot  live 
upon  flesh  f  jod,  as  their  digestive  apparatus  is  adapted  solely  for  the  digestion  of  vegetable  food. 

[The  proteid  metabolism  depends  (i)  on  the  amount  of  proteids  ingested, 
for  the  great  mass  of  these  becomes  changed  into  circulating  albumin  {v.  Voit)  ; 

(2)  upon  the  previous  condition  of  nutrition  of  the  organism,  for  we  know  that  a 
certain  amount  of  proteid  may  produce  very  different  results  in  the  same  individual 
when  he  is  in  good  health,  and  when  he  has  suffered  from  some  exhausting  disease  ; 

(3)  it  is  also  influenced  by  the  use  of  other  foods,  c.  g.,  fats  and  carbohydrates. 
If  a  certain  amount  of  fat  be  added  to  a  diet  of  flesh,  much  less  flesh  is  required, 
so  that  the  N  metabolism  is  reduced  by  fat.  This  is  spoken  of  as  the  "  albumin- 
sparing  action"  of  fats.] 

Exactly  the  same  result  occurs  with  other  forms  of  proteids  as  with  flesh.  It 
has  been  proved  that  gelatin  may,  to  a  certain  extent,  replace  proteids  in  the 
food,  in  the  proportion  of  2  of  gelatin  to  i  of  albumin.  The  carnivora,  which  can 
maintain  their  metabolism  in  equilibriutn  by  eating  a  large  amount  of  flesh,  can 
do  so  with  less  flesh  when  gelatin  is  added  to  their  food.  A  diet  of  gelatin  alone, 
which  produces  much  urea,  is  not  sufficient  for  this  purpose,  and  animals  soon  lose 
their  appetite  for  this  kind  of  food  {i>.  Bischoff,  v.  Voit,  v.  Pcttetikofer,  Oerum). 

[Voit  has  shown  that  gelatin  readily  undergoes  metabolism  in  the  body  and  forms  urea,  and  if  a 
small  quantity  be  taken  it  is  completely  and  rapidly  metabolized.  When  administered,  it  acts,  just 
like  fats  and  carbohydrates,  as  an  "albumin-sparing"  substance.  It  seems  that  gelatin  is  not  avail- 
able directly  for  the  growth  and  repair  of  tissues  (jS(7«.?;-).] 

Owing  to  the  great  solubility  of  gelatin,  the  value  of  gelatin  as  a  food  used  to  be  greatly  discussed, 
and  now,  again,  the  addition  of  gelatin  in  the  form  of  calf's-foot  jelly  is  recommended  to  invalids. 
[When  a  large  amount  of  gelatin  is  given  as  food,  owing  to  the  large  and  rapid  excretion  of  urea 
the  latter  excites  diuresis.]  When  chondrin  is  given  along  with  flesh  for  a  time,  grape  sugar  is 
found  in  the  urine  (Bodeker). 

[The  Metabolism  of  Peptones. — Most  of  the  proteids  absorbed  into  the 
blood  are  previously  converted  into  peptones  by  the  digestive  juices.     It  has  been 


FLESH    AND    CARBOHYDRATES.  397 

asserted,  more  especially  by  Briicke,  that  some  albumin  is  absorbed  unchanged 
(§  192,  4),  and  that  only  this  is  capable  of  forming  organic  albumin,  while  the 
jieptones,  after  undergoing  a  reconversion  into  albumin,  undergo  decomposition  as 
such.  This  view  is  opposed  by  many  observers  {Adamkiewicz,  Plbsz,  Maly),  who 
maintain  that  peptones  perform  all  the  functions  of  proteids,  so  that  peptones, 
with  the  other  necessary  constituents  of  an  adequate  diet,  form  an  adequate  diet.] 

239.  A  DIET  OF  FAT  OR  OF  CARBOHYDRATES.— If  fat  alone 

be  given  as  a  food,  the  animal  lives  but  a  short  time.  The  animal  so  fed  secretes 
even  less  urea  than  when  it  is  starving  ;  so  that  the  consumption  of  fat  limits  the 
decomposition  of  the  animal's  own  proteids.  This  depends  upon  the  fact  that 
fat,  being  an  easily  oxidized  body,  yields  heat  chiefly,  and  becomes  sooner  oxi- 
dized than  the  nitrogenous  proteids  which  are  oxidized  with  more  difficulty.  If 
the  amount  of  fat  taken  be  very  large,  all  the  C  of  the  fat  does  not  reappear,  e.  g., 
in  the  CO^  of  the  expired  air;  so  that  the  body  must  acquire  fat,  while  at  the  same 
time  it  decomposes  proteids.  The  animal  thus  becomes  poorer  in  proteids  and 
richer  in  fats  at  the  same  time. 

[The  Metabolism  of  Fats  is  not  dependent  on  the  amount  of  fats  taken  with 
the  food.  I.  It  is  largely  influenced  by  work,  i.  e.,  by  the  activity  of  the  tissues, 
and,  in  fact,  with  muscular  work  CO..  is  excreted  in  greatly  increased  amount 
(§  127,  6).  2.  By  the  temperature  of  the  surroundings,  as  more  CO^  is  produced 
in  the  cold  (§  214,  2),  and  far  more  fatty  foods  are  required  in  high  latitudes.] 

[In  their  action  on  the  organism,  proteids  and  fats  so  far  oppose  each  other,  as 
the  former  increases  the  waste,  and  therefore  oxidation,  while  the  latter  diminish 
it,  probably  by  affecting  the  metabolic  activity  of  the  cells  themselves  {Bauer). 
As  a  matter  of  fact,  fat  animals  or  persons  bear  starvation  better  than  spare  indi- 
viduals. In  the  latter,  the  small  store  of  fat  is  soon  used  up,  and  then  the  albumin 
is  rapidly  decomposed.  For  the  same  reason,  corpulent  persons  are  very  apt  to 
become  still  more  so,  even  on  a  very  moderate  diet.] 

When  carbohydrates  alone  are  given,  they  must  fir.st  be  converted  by  the 
act  of  digestion  into  sugar.  The  result  of  such  feeding  coincides  pretty  nearly 
with  the  results  of  feeding  with  fat  alone.  But  the  sugar  is  more  easily  burned  or 
oxidized  within  the  body  than  the  fat,  and  1 7  parts  of  carbohydrate  are  equal  to 
10  parts  of  fat.  Thus  the  diet  of  carbohydrates  limits  the  excretion  of  urea  more 
readily  than  a  purely  fat  diet.  The  animals  lose  flesh,  and  appear  even  to  use  up 
part  of  their  own  fat. 

[The  Metabolism  of  Carbohydrates. — They  also  serve  to  diminish  the 
proteid  metabolism,  a.s  they  are  rapidly  burned  up  and  thus  "spare"  the  circu- 
lating albumin.  But  Pettenkofer  and  Voit  assert  that  they  are  rapidly  destroyed 
in  the  body,  even  when  given  in  large  amount,  so  that  they  differ  from  fats  in  this 
respect.  They  are  more  easily  oxidized  than  fats,  so  that  they  are  always  con- 
sumed first  in  a  diet  of  carbohydrates  and  fat.  By  being  consumed,  they  protect 
the  proteids  and  fats  from  consumption.] 

The  direct  introduction  of  grape  sugar  and  cane  sugar  into  the  blood  does  not  increase  the  amount 
of  o.vygen  used,  although  the  amount  of  CO2  formed  is  increased  (IVo/fers). 

[The  doctrine  of  Liebig,  that  the  oxygen  taken  in  was  a  measure  of  the  metabolic  processes,  is 
refuted  by  these  and  other  experiments.  It  would  seem  that  fat  is  not  directly  oxidized  by  O,  but 
that  it  is  split  up  into  other  simpler  compounds  whidi  are  slowly  and  gradually  oxidized;  in  fact, 
fat  may  lessen  the  amount  of  (J  taken  in,  as  it  diminishes  waste.] 

240.  FLESH  AND  FAT,  OR  FLESH  AND  CARBOHYDRATES. 

— Since  an  amount  of  flesh  equal  to  ^'3-  to  -i,'^  of  the  weight  of  the  body  is  required 
to  nourish  a  dog  which  is  fed  on  a  purely  flesh  diet,  if  the  necessary  amount  of 
fat  or  carbohydrates  be  added  to  the  diet,  a  smaller  quantity  of  flesh  is  required 
[v.  Voit  and  Grubei-).  For  100  parts  of  fat  added  to  the  flesh  diet,  245  parts  of 
dry  fle.sh  or  227  of  syntonin  can  be  dispensed  with.  If  instead  of  fats  carbohy- 
drates are  added,  then    100   parts  of    fat  =^   230-250  of    the   latter  {Riibner). 


398  ORIGIN    OF    FAT    IN    THE    BODY. 

When  the  amount  of  flesh  is  insufficient,  the  addition  of  fat  or  carbohydrates  to  the 
food  always  limits  the  decomposition  of  the  animal's  own  substance.  Lastly, 
when  too  much  flesh  is  given  along  with  these  substances,  the  weight  of  the  body 
increases  more  with  them  than  without  them.  Under  these  circumstances,  the 
animal's  body  puts  on  more  fat  than  flesh. 

The  consumption  of  O  in  the  body  is  regulated  by  the  mixture  of  flesh  and 
non-nitrogenous  substances,  rising  and  falling  with  the  amount  of  flesh  consumed. 
It  is  remarkable  that  more  O  is  consumed  when  a  given  amount  of  flesh  is  taken, 
than  when  the  same  amount  of  flesh  is  taken  with  the  addition  of  fat  (v.  Pctten- 
kofer  and  v.   Voit). 

It  seems  that,  instead  of  fat,  the  corresponding  amount  of  fatty  acids  has  the  same  effect  on  the 
metabolism.  [If  a  dog  be  fed  with  fatty  acids  and  a  sufficient  amount  of  proteid,  no  fatty  acids  are 
found  in  the  chyle,  while  fat  is  formed  synthetically,  the  glycerin  for  the  latter  probably  being  pro- 
duced in  the  body.]  They  are  abs  prbed  as  an  emulsion,  just  like  the  fats.  When  so  absorbed, 
they  seem  to  be  reconverted  into  fats  in  their  passage  from  the  intestine  to  the  thoracic  duct,  probably 
by  the  action  of  the  leucocytes  (_/.  Muni,  U'i/l).  Glycerin  does  not  diminish  the  decomposition 
of  albumin  within  the  body  (Lewin,  Tscliirwinsky,  J.  Munk).  Accordmg  to  Lebedeff  and  v.  Voit, 
it  diminishes  the  decomposition  of  the  fats,  and  is  therefore  a  food. 

241.  ORIGIN  OF  FAT  IN  THE  BODY.— I.  Part  of  the  fat  of  the 

body  is  derived  directly  from  the  fat  of  the  food,  /.  e.,  it  is  absorbed  and  depos- 
ited in  the  tissues.  This  is  shown  by  the  fact  that,  with  a  diet  containing  a  small 
amount  of  albumin,  the  addition  of  more  fat  causes  the  deposition  of  a  larger 
amount  of  fat  in  the  body  (v.  Voit,  Hofmann). 

Lebedeff  found  that  dogs,  which  were  starved  for  a  month,  so  as  to  get  rid  of  all  their  own  fat, 
on  being  fed  with  linseed  oil,  or  mutton  suet  and  Hesh,  had  these  fats  restored  to  their  tissues.  These 
fats,  therefore,  must  have  been  absorbed  and  deposited.  J.  Munk  found  the  same  on  feeding 
animals  with  rape-seed  oil.  Fatty  acids  may  also  contribute  to  the  formation  of  fats,  as  glycerin 
when  formed  in  the  body  must  be  stored  up  during  metabolism  ( J.  Muni). 

II.  A  second  source  of  the  fats  is  their  formation  from  albuminous  bodies 
{Liebig  and  others).  In  the  case  of  the  formation  of  fat  from  proteids  which 
may  yield  11  per  cent,  of  fat  (according  to  Henneberg  100  parts  of  dry  albumin 
can  form  51.5  parts  of  fat),  these  proteids  split  up  into  a  non-nitrogenous  and  a 
nitrogenous  atomic  compound.  The  former,  during  a  diet  containing  much  al- 
bumin, when  it  is  not  completely  oxidized  into  C0„  and  H-^O  is  the  substance 
from  which  the  fat  is  formed — the  latter  leaves  the  body  oxidized  chiefly  to  the 
stage  of  urea. 

Examples. — That  f<its  are  formed  from  proteiJs  is  shown  by  the  following  :  i.  A  cow  which 
produces  I  lb.  of  butter  daily  does  not  take  nearly  this  amount  of  fatty  matter  in  its  food,  so  that 
the  fat  would  appear  to  be  formed  from  vegetable  proteids.  2.  Carnivora  giving  suck,  when  fed  on 
plenty  of  flesh  and  some  fat,  yield  milk  rich  in  fat.  3.  Dogs  fed  with  plenty  of  flesh  and  some  fat, 
add  more  fat  to  their  bodies  than  the  fat  contained  in  the  food.  4.  Fatty  degeneration,  c.^.,  of 
nerve  and  muscle,  is  due  to  decomposition  of  proteids.  5.  The  transformation  of  entire  bodies,  <'.^'., 
such  as  have  lain  for  a  long  time  surrounded  with  water,  into  a  mass  consisting  almost  entirely  of 
palmitic  acid  or  adipocere  i^Fourcroy),  is  also  a  proof  of  the  transformation  of  part  of  the  proteids 
into  fats.  6.  Fungi  are  also  able  to  form  fat  from  albumin  during  their  growth  (w.  Naegeti,  and  O. 
Low). 

Fats  not  merely  absorbed. — Experiments  which  go  to  show  that  the  fat  of  animals,  during 
the  fattening  process,  is  not  absorbed  as  such  from  the  food:  i.  Fattening  occurs  with  flesh  and 
soaps ;  it  is  most  improbable  that  the  soaps  are  re-transformed  into  neutral  fats  by  taking  up  glycerin 
and  giving  up  ,^Hiali  [A'ii/ine  and  Radzieje-wski).  2.  If  a  lean  dog  be  fed  with  flesh  and  palmitin- 
and  stearin. soda  soap,  the  fat  of  its  body  contains,  in  addition  to  palmitin  and  stearin,  olein  fat,  so 
that  the  last  must  be  formed  by  the  organism  from  the  proteids  of  the  flesh.  T'urther,  Ssubotin 
found  that  when  a  lean  dog  was  fed  on  lean  meat  and  spermaceti  fat,  a  very  small  amount  of  the 
latter  was  found  in  the  fat  of  the  animal.  Although  these  experiments  show  that  the  fat  of  the  body 
must  be  formed  from  the  decomposition  of  proteids,  they  do  not  prove  that  all  the  fat  arises  in  this 
way,  and  that  none  of  it  is  absorbed  and  ledeposited. 

III.  According  to  v.  Voit,  no  fat  is  formed  in  the  body  directly  from  carbo- 
hydrates, e.g.,  by  reduction.     As  fattening  occurs  on  a  diet  of  pure  flesh  with 


CORPULENCE.  399 

the  addition  of  carbohydrates,  we  must  assume  that  the  carbohydrates  are  con- 
sumed or  oxidized  in  the  body,  and  that  thereby  a  non-nitrogenous  body  derived 
from  the  proteids  is  prevented  from  being  burned  up,  and  that  it  is  changed  into 
fat,  and  stored  up  as  such.  No  doubt  fat  is  formed  indirectly  in  the  blood  in  this 
way  (§  240). 

From  experiments  upon  fattening  animals,  however,  Lawes  and  Gilbert,  Leh- 
mann,  Heiden,  v.  Wolff,  think  they  are  entitled  to  conclude  that  the  carbo- 
hydrates absorbed  are  directly  concerned  in  the  formation  of  fats,  a  view  which  is 
supported  by  Henneberg,  B.  Schulze,  Soxhlet.  According  to  Pasteur,  glycerine 
(the  basis  of  neutral  fats)  may  be  formed  from  carbohydrates. 

Formerly  it  was  believed  that  bees  could  prepare  wax  from  honey  alone ;  this  is  a  mistake — an 
equivalent  of  albumin  is  required  in  addition — the  necessary  amount  is  found  in  the  raw  honey 
itself. 

242.  CORPULENCE.— The  addition  of  too  much  fat  to  the  body  is  a  pathological  phe- 
nomenon which  is  attended  with  disagreeable  consequences.  With  regard  to  the  causes  of 
obesity,  without  doubt  there  is  an  inherited  tendency  (in  33  to  56  per  cent,  of  the  cases — Bou- 
chard, Chalmers)  in  many  families — and  in  some  breeds  of  cattle,  to  lay  up  fat  in  the  body,  while 
other  families  may  be  richly  supplied  with  fat,  and  yet  remain  lean.  Ttie  chief  cause,  however,  is 
taking  too  much  food,  i.e.,  more  than  the  amount  required  for  the  normal  metabolism ;  corpulent 
people,  in  order  to  maintain  their  bodies,  must  eat  absolutely  and  relatively  more  than  persons  of 
spare  habit,  under  analogous  conditions  of  nutrition  (\  236). 

Conditions  favoring  Corpulence. — The  following  conditions  favor  the  occurrence  of  corpu- 
lence :  (l )  .-^  diet  rich  '\v\  froteids,  with  a  corresponding  addition  ai  fatox  carhnhydrates.  As  flesh  or 
muscle  IS  formed  from  proteids,  and  part  of  the  fat  of  the  body  is  also  formed  from  albumin  (p.  398), 
the  assumption  that  fats  and  carbohydrates  fatten,  or  when  taken  alone,  act  as  fattening  agents,  is 
completely  without  foundation.  Xo  one  ever  becomes  fat  without  takmg  plenty  of  albumin.  (2) 
Diminished  disintegration  of  materials  within  the  body,  e.g.,  (a)  diminished  muscular  activity 
(much  sleep  and  little  exercise) ;  (/*)  abrogation  of  the  se.vual  functions  (as  is  shown  by  the  rapid 
fattening  of  castrated  animals,  as  well  as  by  the  fact  that  some  women,  after  cessation  of  the  menses, 
readily  become  corpulent)  ;  (c)  diminished  mental  activity  (the  obesity  of  dementia),  phlegmatic 
temperament.  On  the  contrary,  vigorous  mental  work,  excitable  temperament,  care  and  sorrow, 
counteract  the  deposit  of  fat ;  [d)  diminished  extent  of  the  respiratoiy  activity,  as  occurs  when 
there  is  a  great  deposition  of  fat  in  the  abdomen,  limiting  the  action  of  the  diaphragm  (breathless- 
ness  of  corpulent  people),  whereby  the  combustion  of  the  fatty  matters,  which  become  deposited  in 
the  body  is  limited  ;  \e)  a  corpulent  person  requires  to  use  relatively  less  heat-diving  substances  in 
his  body,  partly  because  he  gives  oft'  relatively  less  heat  from  his  compact  body,  than  is  done  by  a 
slender,  long-bodied  individual,  and  partly  because  the  thick  layer  of  fat  retards  the  conduction  of 
heat  (J  214,  4).  Thus,  corresponding  to  the  relatively  diminished  production  of  heat,  more  fat 
may  be  stored  up;  (/)  a.  diminution  of  the  red  blood  corf uscles,  vi\nch  are  the  great  exciters  of 
oxidation  in  the  body,  is  generally  followed  by  an  increase  of  fat — fat  people,  as  a  rule,  are  fat 
because  they  have  relatively  less  blood  (|  41) — women  with  fewer  red  blood  corpuscles  are  usually 
fatter  than  men;  (g)  the  consumption  of  alcohol  favors  the  conservation  of  fat  in  the  body;  the 
alcohol  is  easily  oxidized,  and  thus  prevents  the  fat  from  being  burned  up  {\  235). 

Well  nourished  individuals  are  usually  at  first  both  muscular  and  endowed  with  a  fair  amount  of 
fatty  tissue.  When  they  begin  to  put  on  fat,  the  development  of  the  muscular  system  lags  behind, 
partly  because  the  increasing  corpulence  leads  to  diminished  activity  of  the  muscular  system,  so 
that  this  system  is  involved  secondarily.  Some  lively  corpulent  people,  nevertheless,  retain  their 
muscular  energy.  When  those  conditions  which  favor  corpulence  are  especially  active,  corpulence 
may  ultimately  pass  into  a  condition  of  great  obesity. 

Disadvantages. — Besides  the  inconvenience  of  the  great  size  and  weight  of  the  body,  corpu- 
lent people  suffer  from  breathlessness — they  are  easily  fatigued,  are  liable  to  intertrigo  between  the 
folds  of  the  skin,  the  heart  becomes  loaded  with  fat,  and  they  not  unfrequently  are  subject  to 
apoplexy. 

In  order  to  counteract  corpulence  we  ought  to— (l)  Reduce  uniformly  all  articles  of  diet. 
The  diet  and  body  ought  to  be  weighed  from  week  to  week,  and  as  long  as  there  is  no  diminution 
in  the  body  weight,  the  amount  of  food  ought  to  be  gradually  and  uniformly  reduced  (notwithstand- 
ing the  appetite).  This  must  be  done  very  gradually  and  not  suddenly.  A  moderate  reduction  of 
fat  and  carbohydrates  in  a  normal  diet,  at  the  same  time  leads  to  a  diminution  of  the  fat  of  the 
body  itself.  Let  a  person  who  is  capable  of  muscular  exertion  take  156  grms.  proteid,  43  grms.  fat, 
and  1 14  grms.  carbohydrates ;  but  in  those  where  congestions,  hydrasmia,  breathlessness  have  taken 
place,  take  1 70  grms.  proteid,  25  grms.  fat,  and  70  grms.  carbohydrates  ( Oertel).  It  is  not  advisable 
to  limit  the  amount  of  fat  and  carbohydrates  alone,  as  is  done  in  the  Banting  cure  or  Bantingism. 
Apart  altogether  from  the  fact  that  fat  is  formed  from  proteids,  if  too  little  non-nitrogenous  food  be 
taken,  severe  disturbance  of  the  bodily  metabolism  is  apt  to  occur.     (2)   It  is  advisable  during  the 


400  METABOLISM  OF   THK   TISSUES. 

chief  meal  to  limit  the  consumption  of  fluids  of  all  sorts  (even  until  three-quarters  of  an  hour  there- 
after), and  thus  render  the  absorption  and  digestive  activity  of  the  intestine  less  active  (Oev-/*'/). 
(3)  The  muscular  activi/y  OM^l  to  be  greatly  developed  by  doing  plenty  of  muscular  work,  or 
taking  plenty  of  exercise,  both  physical  and  mental.  (4)  Favor  the  cvolulion  of  heat  by  taking 
cold  baths  of  considerable  duration,  and  afterward  rubbing  the  skin  strongly  so  as  to  cause  it  to 
become  red  ;  further,  dress  lightly,  and  at  night  use  light  bed  clothing;  tea  and  coffee  are  useful, 
as  they  excite  the  circulation.  (5)  Use  gentle  laxatives;  acid  fruits,  cider;  alkaline  carbonates 
[A/arieytbad^  Carlsbad^  I'ichy^  Neuenahr,  Ems,  etc.),  act  by  increasing  the  intestinal  evacuations 
and  diminishing  absorption.  (6)  If  from  accumulation  of  fat  there  is  danger  of  failure  of  the 
heart's  action,  Oertel  recommends  hill  climbing,  whereby  the  cardiac  muscle  is  exercised  and 
strengthened.  At  the  same  time  the  circulation  becomes  more  lively  and  the  metabolism  is 
increased. 

[Oertel's  Method  goes  on  the  idea  of  strengthening  the  cardiac  musculature,  which  is  sought 
to  be  accomplished  by  (i)  limiting  the  amount  of  fluids  consumed,  and  (2)  carefully  regulated  mus- 
cular exertion.  The  amount  of  food  is  first  reduced  one  half,  and  the  water  to  a  still  lower  amount, 
while  the  nitrogenous  elements  in  food  are  increased,  the  non-nitrogenous  are  decreased.  The  per- 
son is  then  instructed  to  take  exercise  under  certain  medical  precautions,  first,  on  level  ground,  and 
then  on  gr.idually  increasing  gradients.  Oertel  has  opened  several  establishments  in  Germany 
(Terrain  Curorte)  for  conducting  what  he  calls  his  Terrain  Cur.] 

Fatty  Degeneration. — The  process  of  fattening  consists  in  the  deposition  of  drops  of  fat  within 
the  fat  cells  of  the  panniculus  and  around  the  viscera,  as  well  as  in  the  marrow  of  bone  (but  they 
are  never  deposited  in  the  subcutaneous  tissue  of  the  eyelids,  of  the  penis,  of  the  red  part  of  the 
lips,  in  the  ears  and  nose).  This  is  quite  different  from  the  fatty  atrophy  or  fatty  degeneration 
which  occurs  in  the  form  of  fatty  globules  or  granules  in  altjuminous  tissues,  e.g.,  in  muscular  fibres 
(heart),  gland  cells  (liver,  kidney),  cartilage  cells,  lymph  and  pus  corpuscles,  as  well  as  in  nerve 
fibres  separated  from  their  nerve  centres.  The  fat  in  these  cases  is  derived  from  albumin,  much  in 
the  same  way  as  fat  is  formed  in  the  gland  cells  of  the  mammary  and  sebaceous  glands.  Marked 
fatty  degeneration  not  unfrequenlly  occurs  after  severe  fevers,  and  after  artificial  heating  of  the  tis- 
sues ;  when  a  too  small  amount  of  O  is  supplied  to  the  tissues,  as  occurs  in  cases  of  phosphorus 
^OKordng  [Bauer);  in  drunkards;  after  poisoning  with  arsenic  and  other  substances;  and  after 
some  disturbances  of  the  circulation  and  innervation.  .Some  organs  are  especially  prone  to  undergo 
fatty  degeneration  during  the  course  of  certain  diseases. 

243.  METABOLISM  OF  THE  TISSUES.— The  blood   stream    is 

the  chief  medium  whereby  new  material  is  supplied  to  the  tissues  and  the  effete 
products  removed  from  them.  The  lymph  which  passes  through  the  thin  capil- 
laries comes  into  actual  contact  with  the  tissue  elements.  Those  tissues  which 
are  devoid  of  blood  vessels  in  their  own  substance,  such  as  the  cornea  and  cartil- 
age, receive  nutrient  fluid  or  lymph  from  the  adjacent  capillaries,  by  means  of 
their  cellular  elements,  which  act  as  juice-conducting  media.  Hence,  when  the 
normal  circulation  is  interfered  with,  as  by  atheroma  or  calcification  of  the  walls 
of  the  blood  vessels,  these  tissues  are  secondarily  affected  [this,  for  example,  is 
the  case  in  arcus  senilis  of  the  cornea,  due  to  a  fatty  degeneration  of  the  corneal 
tissue,  owing  to  some  affection  of  the  blood  vessels  on  which  the  cornea  depends 
for  its  nutrition].  Total  compression  or  ligature  of  all  the  blood  vessels  results 
in  necrosis  of  the  parts  supplied  by  the  ligatured  blood  vessels. 

Atrophies  caused  by  diminution  of  the  normal  supply  of  blood  gradually,  in  the  course  of  time, 
become  less  and  less  [Samuel ). 

Hence,  there  must  be  a  ilotible  current  of  the  tissue  juices ;  the  afferent  or 
supply  current,  which  supplies  the  new  material,  and  the  efferent  stream, 
which  removes  the  effete  products.  The  former  brings  to  the  tissues  the  proteids, 
fats,  carbohydrates,  and  salts  from  which  the  tissues  are  formed.  It  is  evident 
that  any  interruption  of  the  arterial  supply  to  the  tissues  will  diminish  this  supply. 

That  such  a  current  exists  is  proved  by  injecting  an  indifferent,  easily  recognizable  substance  into 
the  blood,  e.g.,  ]:)otassium  ferrocyanide,  when  its  presence  may  be  detected  in  the  tissues,  to  which 
it  has  been  carried  by  the  outgoing  current. 

The  efferent  stream  carries  away  the  decomposition  products^)-;?;;/  the  various 
tissues,  more  especially  urea,  CO.,,  H.O,  and  salts,  and  these  are  transferred  as 
quickly  as  possible  to  the  organs  through  which  they  are  excreted. 

That  such  a  current  exists  is  proved  by  injecting  such  a  substance  as  potassium  ferrocyanide  into 
the  tissues,  e.g.,  subcutaneously,  when  its  presence  may  be  detected  in  the  urine  within  two  to  five 
minutes. 


METABOLISM    OF   THE   TISSUES.  401 

If  the  current  from  the  tissues  to  the  blood  is  so  active  that  the  excretory  organs 
cannot  eliminate  all  the  effete  products  from  the  blood,  then  ihese  products  are 
found  in  the  tissues.  This  occurs  when  certain  poisons  are  injected  subcutaneously, 
when  they  pass  rapidly  into  the  blood  and  are  carried  in  great  quantity  to  other 
tissues,  e.g.,  to  the  nervous  system,  on  which  they  act  with  fatal  effect,  before 
they  are  eliminated  to  any  great  e.xtent  from  the  blood  by  the  action  of  the 
excretory  organs.  The  effete  materials  are  carried  away  from  the  tissues  by  (7vo 
channels,  viz.,  by  the  veins  and  by  the  lymphatics,  so  that  if  these  be  inter- 
fered with,  the  metabolism  of  the  tissues  must  also  suffer.  When  a  limb  is  ligatured 
so  as  to  compress  the  veins  and  the  lymphatics,  the  efferent  stream  stagnates  to 
such  an  extent  that  considerable  swelling  of  the  tissues  or  oedema  may  occur 
(§  203).  The  action  of  the  muscles  and  fasciae  are  very  important  in  removing 
these  effete  matters  (Ifasse). 

H.  Nasse  found  that  the  blood  of  the  jugular  vein  is  0.225  P^r  1000  specifically  heavier  than  the 
blood  of  the  carotid,  and  contains  0.9  parts  per  1000  more  solids;  1000  cubic  centimetres  of  blood 
circulating  through  the  head  yield  about  5  cubic  centimetres  of  transudation  into  the  tissues. 

The  extent  and  intensity  of  the  metabolism  of  the  tissues  depend  upon 
a  variety  of  factors. 

1.  Upon  their  activity.  The  increased  activity  of  an  organ  is  indicated  by 
the  increased  amount  of  blood  going  into  it,  and  by  the  more  active  circulation 
through  it  (,§  100).  When  an  organ  is  completely  inactive,  such  as  a  paralyzed 
muscle,  or  the  peripheral  end  of  a  divided  nerve,  the  amount  of  blood  and  the 
nutritive  exchange  of  fluids  diminish  within  these  parts.  The  parts  thus  thrown 
out  of  activity  become  pale,  relaxed,  and  ultimately  undergo  fatty  degeneration. 
The  increased  metabolism  of  an  organ  during  its  activity  has  been  proved  experi- 
mentally in  the  case  of  muscle,  and  [(§  263)  also  in  the  brain  {SpiY/:).~\  Langley 
and  Sewell  have  recently  observed  directly  the  metabolic  changes  within  sufficiently 
thin  lobules  of  glands  during  life.  The  cells  of  serous  glands  (§  143),  and  those 
of  mucus-  and  pepsin-forming  glands  (§  164),  during  quiescence,  become  filled 
with  coarse  granules,  which  are  dark  in  transmitted  light  and  white  in  reflected 
light,  which  granules  are  consumed  or  disappear  during  granular  activity.  During 
sleep,  when  most  organs  are  at  rest,  the  metabolism  is  limited  ;  darkness  also 
diminishes  it,  while  light  excites  it,  obviously  owing  to  nervous  influences.  The 
variations  in  the  total  metabolism  of  the  body  are  reflected  in  the  excretion  of 
CO2  (§  127,  9)  and  urea  (§  257),  which  may  be  expressed  graphically  in  the  form 
of  a  curve  corresponding  with  the  activity  of  the  organism  ;  this  curve  corresponds 
very  closely  with  the  daily  variations  in  the  respirations,  pulse,  and  temperature 

(P-  359)- 

2.  The  composition  or  quality  of  the  blood  has  a  marked  effect  upon  the 
current  on  which  the  metabolism  of  the  tissues  depends.  Very  concentrated 
blood,  which  contains  a  small  amount  of  water,  as  after  profuse  sweating,  severe 
diarrhoea — e.g.,  in  cholera — makes  the  tissues  dry,  while  if  much  water  be  absorbed 
into  the  blood,  the  tissues  become  more  succulent  and  even  ledema  may  occur. 
When  much  common  salt  is  present  in  the  blood,  and  when  the  red  blood  cor- 
puscles contain  a  diminished  amount  of  O,  and  especially  if  the  latter  condition 
be  accompanied  by  muscular  exertion  causing  dyspnoea,  a  large  amount  of  albumin 
is  decomposed,  and  there  is  a  great  formation  of  urea.  Hence,  exposure  to  a 
rarefied  atmosphere  is  accompanied  by  increased  excretion  of  urea.  Certain 
abnormal  conditions  of  the  blood  produce  remarkable  results;  blood  charged  with 
carbonic  oxide  cannot  absorb  O  from  the  air,  and  does  not  remove  CO^  from  the 
tissues  (§  16).  The  presence  of  hydrocyanic  acid  in  the  blood  (§  16)  is  said  to 
interrupt  at  once  the  chemical  oxidation  processes  in  the  blood,  so  that  rapid 
asphyxia,  owing  to  cessation  of  the  ////cT/za/ respiration,  occurs.  Fermentation  is 
interrupted  by  the  same  substance  in  a  similar  way.  A  diminution  of  the  total 
amount  of  the  blood  causes  more  fluid  to  pass  from  the  tissues  into  the  blood ;  but 

26 


402  REGENERATION    OF   ORGANS    AND   TISSUES. 

the  absorption  of  substances,  such  as  poisons  or  pathological  effusions,  from  the 
tissues  or  intestines  is  delayed.  If  the  substances  which  pass  from  the  tissues  into 
the  blood  be  rapidly  eliminated  from  it,  absorption  takes  place  more  rapidly. 

3.  The  blood  pressure  is  of  importance,  in  so  far,  that  when  it  is  greatly  in- 
creased, the  tissues  contain  more  fluid,  while  the  blood  itself  becomes  more  con- 
centrated, to  the  extent  of  3  to  5  per  1000  (AviJiV).  We  may  convince  ourselves 
that  blood  plasma  easily  passes  through  the  capillary  wall,  by  pressing  upon  the 
efferent  vessel  coming  from  the  chorium  deprived  of  its  epidermis,  e.  g.,  by  a  burn 
or  a  blister,  when  the  surface  of  the  wound  becomes  rapidly  suffused  with  plasma. 
Diminution  of  the  blood  pressure  produces  the  opposite  result.  The  o.vidation 
processes  in  the  body  are  diminished  after  the  use  of  P,  Cu,  ether,  chloroform, 
chloral  {Nencki  and  S/rfier). 

4.  Increased  temperature  of  the  tissues  (several  hours  daily)  does  not 
increase  the  breaking  up  of  albumin  and  fats  (A'oc/i,  S/ockvis,  Simanowsky,  and 
V.  Voit).  (See  also  Artificial  Elevation  of  the  Temperature,  §  221  ;  Fever,  §  220  ; 
and  Artificial  Cooling,  §  225.) 

5.  The  influence  of  the  nervous  system  on  the  metabolism  is  twofold.  On 
the  one  hand,  it  acts  indirectly  through  its  effect  upon  the  blood  vessels,  by  caus- 
ing them  to  contract  or  dilate  through  the  agency  of  vaso-motor  nerves, 
whereby  it  influences  the  amount  of  blood  supplied,  and  also  affects  the  blood 
pressure.  But  in  addition  to  this,  and  quite  independently  of  the  blood  vessels, 
it  is  probable  that  certain  special  nerves — the  so-called  trophic  nerves,  influence 
the  metabolism  or  nutrition  of  the  tissues  (§  342,  i).  That  nerves  do  influence 
directly  the  transformation  of  matter  within  the  tissues  is  shown  by  the  secretion 
of  saliva  resulting  from  the  stimulation  of  certain  nerves,  after  cessation  of  the 
circulation  (§  145),  and  by  the  metabolism  during  the  contraction  of  bloodless 
muscles.  Increased  respiration  and  apnoea  are  not  followed  by  increased  oxida- 
tion ^Pfliiger)  {%  127,  8). 

[Gaskell  has  raised  the  question  as  to  the  existence  of  katabolic  and  anabolic  nerves  control- 
ling respectively  the  analytic  and  synthetic  metabolism  of  the  tissues  (p.  373).] 

244.    REGENERATION    OF   ORGANS   AND   TISSUES.— The  extent  to  which  lost 

parts  are  replace<l  varies  greatly  in  dift'erent  organs.  Among  the  Imucr  animals  the  parts  of  organs 
are  replaced  to  a  far  greater  extent  than  among  warm-blooded  animals.  When  a  hydra  is  divided 
into  two  parts,  each  part  lurms  a  new  individual — n.iy,  if  the  body  of  the  animal  be  divided  into 
several  parts  in  a  particular  way,  then  each  part  gives  rise  to  a  new  individual  (S/>a/lanzani).  The 
Plananans  also  show  a  great  capability  of  reproducing  lost  parts  (Du^i-s).  .Spiders  and  crabs  can 
^reproduce  lost  feelers,  limbs,  and  claws;  snails,  part  of  the  heart,  feelers,  and  eyes,  provided  the 
central  nervous  system  is  not  injured.  Many  fishes  reproduce  fins,  even  the  tail  fin.  Salamanders 
and  lizards  can  produce  an  entire  tail,  including  bones,  muscles,  and  even  the  posterior  part  of  the 
spinal  cord;  while  the  triton  reproduces  an  amputated  limb,  the  lower  jaw  and  the  eye.  This  re- 
production necessitates  that  a  small  stump  be  left,  while  total  expiration  of  the  parts  prevents  repro- 
duction [Philtppiaux). 

In  amphibians  and  reptiles  the  regeneration  of  organs  and  tissues,  as  a  whole,  takes  place  after 
the  type  of  the  embryonic  development  (Fraisse,  GSlte),  and  the  same  is  true  as  regards  the  histo- 
logical processes  which  occur  in  the  regenerated  tail  and  other  parts  of  the  body  of  the  earthworm 
(BiiUnv). 

The  extent  to  which  regeneration  can  take  place  in  mammals  and  in  man  is  very 
slight,  and  even  in  these  cases  it  is  chiefly  confined  to  young  individuals.  A  true 
regeneration  occurs  in — 

1.  The  blood  (compare  §  7  and  §  41),  including  the  plasma,  the  colorless  and 
colored  corpuscles. 

2.  The  epidermal  appendages  (§  2S3)  and  the  epithelium  of  the  mucous 
membranes  are  reproduced  by  a  proliferation  of  the  cells  of  the  deeper  layers  of 
the  epithelium,  with  simultaneous  division  of  their  nuclei.  Epithelial  cells  are 
reproduced  as  long  as  the  matrix  on  which  they  rest  and  the  lowest  layer  of  cells 
are  intact.  When  these  are  destroyed  cell-regeneration  from  below  ceases,  and 
the  cells  at  the  margins  are  concerned  in  filling  up  the  deficiency.    Regeneration, 


REGENERATION   OF  TISSUES.  403 

therefore,  either  takes  place  from  below  or  from  the  margins  of  the  wound  in  the 
epithelial  covering  ;  leucocytes  also  wander  into  the  part,  while  the  deepest  layer 
of  cells  forms  large  multi-nucleated  cells,  which  reproduce  by  division  polygonal, 
flat,  nucleated  cells  (Kiel's,  Heller').  [In  the  process  of  division  of  the  cells,  the 
nucleus  plays  an  important  part,  and  in  so  doing  it  shows  the  usual  karyokinetic 
figures  (§  431  )•]  The  nails  grow  from  the  root  forward  ;  those  of  the  fingers  in 
four  to  five  months,  and  that  of  the  great  toe  in  about  twelve  months,  although 
growth  is  slower  in  the  case  of  fracture  of  the  bones,  The  matrix  is  co-extensive 
with  the  liinule,  and  if  it  be  destroyed  the  nail  is  not  reproduced  (§  284).  The 
eyelashes  are  changed  in  100  to  i5odays(Z'(i;/(zVr^),  the  other  hairs  of  the  body 
somewhat  more  slowly.  If  the  papilla  of  the  hair  follicle  be  destroyed,  the  hair 
is  not  reproduced.  Cutting  the  hair  favors  its  growth,  but  hair  which  has  been 
cut  does  not  grow  longer  than  uncut  hair.  After  hair  has  grown  to  a  certain  length 
it  falls  out.  The  hair  never  grows  at  its  apex.  The  epithelial  cells  of  mucous 
membranes  and  secretory  glands  seem  to  undergo  a  regular  series  of  changes  and 
renewal.  The  presence  of  secretory  cells  in  the  milk  (§  231)  and  in  the  sebaceous 
secretion  (§  285)  proves  this  ;  the  spermatozoa  are  replaced  by  the  action  of  sper- 
matoblasts. In  catarrhal  conditions  of  mucous  membranes,  there  is  a  great 
increase  in  the  formation  and  excretion  of  new  epithelium,  while  many  cells  are 
but  indifferently  formed  and  constitute  mucous  corpuscles.  The  crystalline 
lens,  which  is  just  modified  epithelium,  is  reorganized  just  like  epithelium  ;  its 
matrix  is  the  anterior  wall  of  its  capsule,  with  the  single  layer  of  cells  covering  it. 
If  the  lens  be  removed  and  this  layer  of  cells  retained,  these  cells  proliferate  and 
elongate  to  form  lens  fibres,  so  that  the  whole  cavity  of  the  empty  lens  capsule  is 
refilled.  If  much  water  be  withdrawn  from  the  body,  the  lens  fibres  become 
turbid  {Kunde,  Koehiihorn).  [A  turbid  or  opaque  condition  of  the  lens  may  occur 
in  diabetes,  or  after  the  transfusion  of  strong  common  salt  or  sugar  solution  into 
a  frog.] 

3.  The  blood  vessels  undergo  extensive  regeneration,  and  they  are  regener- 
ated in  the  same  way  as  they  are  formed  (§  7,  B).  Capillaries  are  always  the  first 
stage,  and  around  them  the  characteristic  coats  are  added  to  form  an  artery  or  a 
vein.  When  an  artery  is  injured  and  permanently  occluded,  as  a  general  rule 
the  part  of  the  vessel  up  to  the  nearest  collateral  branch  becomes  obliterated, 
whereby  the  derivatives  of  the  endothelial  lining,  the  connective-tissue  corpuscles 
of  the  wall,  and  the  leucocytes  change  into  spindle-shaped  cells,  and  form  a  kind 
of  cicatricial  tissue.  Blind  and  solid  outshoots  are  always  found  on  the  blood 
vessels  of  young  and  adult  animals,  and  are  a  sign  of  the  continual  degeneration 
and  regeneration  of  these  vessels  {Sigm.  Mayer). 

Lymphatics  behave  in  the  same  way  as  blood  vessels ;  after  removal  of  a  lym- 
phatic gland,  a  new  one  may  be  formed  (Bayer). 

4.  The  contractile  substance  of  muscle  may  undergo  regeneration  after  it 
has  become  partially  degenerated.  This  takes  place  after  amyloid  or  wax-like 
degeneration,  such  as  occurs  not  unfrequently  after  typhus  and  other  severe  fevers. 
This  is  chiefly  accomplished  by  an  increase  of  the  muscle  corpuscles.  After  being 
compressed,  the  muscular  nuclei  disappear,  and  at  the  same  time  the  contractile 
contents  degenerate  (T/rtV/f-Z/^ifr^).  After  several  days,  the  sarcolemma  contains 
numerous  nuclei  which  reproduce  new  muscular  nuclei  and  the  contractile  sub- 
stance (^Kraske,  Erhkam).  In  fibres  injured  by  a  subcutaneous  wound,  Neumann 
found  that,  after  five  to  seven  days,  there  was  a  bud-like  elongation  of  the  cut 
ends  of  the  fibres,  at  first  without  transverse  striation  ultimately.  If  a  large  extent 
of  a  muscle  be  removed,  it  is  replaced  by  cicatricial  connective  tissue.  Non- 
Striped  muscular  fibres  are  also  reproduced  ;  the  nuclei  of  the  injured  fibres  divide 
after  becoming  enlarged,  and  exhibit  a  well-marked  intranuclear  plexus  of  fibrils. 
The  nuclei  divide  into  two,  and  from  each  of  these  a  new  fibre  is  formed,  prob- 
ably by  the  differentiation  of  the  perinuclear  protoplasm. 


404  REGENERATION    OF    BONE. 

5.  After  a  nerve  is  divided,  the  two  ends  do  not  join  at  once  so  as  to  permit 
the  function  of  the  nerve  to  be  established.  On  the  contrary,  marked  changes 
occur.  If  a  piece  be  cut  out  of  a  nerve  trunk,  the  peripheral  end  of  the  divided 
nerve  degenerates,  the  axial  cylinder  and  the  white  substance  of  Schwann  disap- 
pear. The  interval  is  filled  up  at  first  with  juicy,  cellular  tissue.  The  subsequent 
changes  are  fully  described  in  §  325,  4.  There  seems  to  be  in  peripheral  nerves  a 
continual  disappearance  of  fibres  by  fatty  degeneration,  accompanied  by  a  con- 
secutive formation  of  new  fibres  {S/gm.  Afavfr).  The  regeneration  of  peripheral 
ganglionic  cells  is  unknown,  v.  Voit,  however,  observed  that  a  pigeon,  part  of 
whose  bram  was  removed,  had  within  five  months  reproduced  a  nervous  mass 
within  the  skull,  consisting  of  niedullated  nerve  fibres  and  nerve  cells.  Eichhorst 
and  Naunyn  found  that  in  young  dogs,  whose  spinal  cord  was  divided  between  the 
dorsal  and  lumbar  regions,  there  was  an  anatomical  and  physiological  regeneration, 
to  such  an  extent  that  voluntary  movements  could  be  executed  (§  33S,  3).  Vau- 
lair,  in  the  case  of  frogs,  and  Masius  in  dogs,  found  that  mobility  or  motion  was 
first  restored,  and  afterward  sensibility.  Regeneration  of  the  spinal  ganglia  did 
not  occur. 

6.  If  a  portion  of  a  secretory  gland  be  removed,  as  a  general  rule,  it  is  not 
reproduced.  But  the  bile  ducts  (§  173)  and  the  pancreatic  duct  may  be 
reproduced  (§  171)-  According  to  Phihppeaux  and  Griffini,  if  part  of  the 
spleen  be  removed  it  is  reproduced  (§  103I.  Tizzoni  and  CoUucci  observed 
the  formation  of  new  liver  cells  and  bile  ducts  after  injury  to  the  liver  (§  173), 
and  Pisenti  makes  the  same  statement  as  regards  the  kidney.  After  me- 
chanical injury  to  the  secretory  cells  of  glands  (liver,  kidney,  salivary. 
Meibomian)  neighboring  cells  undergo  proliferation  and  aid  in  the  restoration 
of  the  cells  ( IF.  Podwisotzky). 

7.  Among  connective  tissues,  cartilage,  provided  its  perichondrium  be  not  in- 
jured, reproduces  itself  by  division  of  its  cartilage  cells  {ReJfern)  ;  but  usually 
when  a  part  of  a  cartilage  is  removed,  it  is  replaced  by  connective  tissue. 

8.  When  a  tendon  is  divided,  proliferation  of  the  tendon  cells  occurs,  and  the  cut 
ends  are  united  by  connective  tissue. 

9.  The  reproduction  of  bone  takes  place  to  a  great  extent  under  certain  con- 
ditions. If  the  articular  end  be  removed  by  excision,  it  may  be  reproduced, 
although  there  is  a  considerable  degree  of  shortening.  Pieces  of  bone  which  have 
been  broken  off  or  sawed  oft"  heal  again,  and  become  united  with  the  original  bone 
{Jakiiiiowitsch).  If  a  piece  of  periosteum  be  transplanted  to  another  region  of 
the  body,  it  eventually  gives  rise  to  the  formation  of  new  bone  in  that  locality. 
If  part  of  a  bone  be  removed,  provided  the  periosteum  be  left,  new  bone  is  rapidly 
reproduced  ;  hence  the  surgeon  takes  great  care  to  preserve  the  periosteum  intact 
in  all  operations  where  he  wishes  new  bone  to  be  reproduced.  Even  the  marrow 
of  bone,  when  it  is  transplanted,  gives  rise  to  the  formation  of  bone.  This  is  due 
to  the  osteoblasts  adhering  to  the  osseous  tissue  {F.  Burns,  AlaiEweii). 

In  fracture  of  a  long  bone  the  periosteum  deposits  on  the  surface  of  the  ends  of  the  broken 
bones  a  ring  of  substance  which  forms  a  temporary  support,  the  external  callus.  At  first  this 
callus  is  jelly-like,  soft,  and  contains  many  corpuscles,  but  afterward  it  becomes  more  solid  and 
somewhat  like  cartilage.  A  similar  condition  occurs  within  the  bone,  where  an  internal  callus  is 
formed.  The  formation  of  this  temporary  callus  is  due  to  an  inflammatory  proliferation  of  the 
marrow.  According  to  Rigal  and  Vignal,  the  internal  callus  is  always  osseous,  and  is  derived  from 
the  marrow  of  the  bone.  The  outer  and  inner  callus  become  calcified  ami  ultimately  ossified, 
whereby  the  broken  ends  are  reunited.  Toward  the  fortieth  day,  a  thin  layer  of  bone  is  formed 
(intermediary  callus)  between  the  ends  of  the  bone.  Where  this  begins  to  be  definitely  ossified, 
the  outer  and  inner  callus  begm  to  be  absorbed,  and  ultimately  the  intermediary  callus  has  the  same 
structure  as  the  rest  of  the  bone. 

There  are  many  interesting  observations  connected  with  the  growth  and  metabolism  of  bones. 
I.  The  addition  of  a  very  small  amount  Qi  phosphorus  (  Wagner)  or  arseniotts  acid  [A/aas)  to  the 
food  causes  considerable  thickening  of  the  bones.  This  .seems  to  be  due  to  the  non-absorption  of 
those  parts  of  the  bones  which  are  usually  absorbed,  while  new  growth  is  continually  taking  place. 


INCREASE    IN    SIZE    AND   WEIGHT   DURING    GROWTH.  405 

2.  When  food  dezwid  of  lime  salts  is  given  to  an  animal,  the  growth  of  the  bones  is  not  arrested 
[v.  Poll),  but  the  bones  become  thinner,  whereby  all  parts,  even  the  organic  basis  of  tlie  bone, 
undergo  a  nnifoTm  diminution  (dossal,  A.  A/ilne-Eihitii ids).  3.  Feeding  with  madder  makes  the 
bones  red,  as  the  coloring  matter  is  deposited  with  the  bone  salts  in  the  bone,  especially  in  the  grow- 
ing and  last-formed  parts.  In  birds  the  shell  of  the  egg  becomes  colored.  4.  The  continued  use  of 
lacliir  acid  dissolves  the  bones  (Siedamgrotzky  and  J/o/mcister).  The  ash  of  bone  is  thereby  dimin- 
ished. If  lime  salts  be  withheld  at  the  same  time,  the  effect  is  greatly  increased,  so  that  the  bones 
come  to  resemble  rachitic  bones.     (Development  of  Bone,  J  447.) 

When  a  lost  tissue  is  not  replaced  by  the  same  kind  of  tissue,  its  place  is  always 
taken  by  cicatricial  connective  tissue. 

When  this  is  the  case,  the  part  becomes  inflamed  and  swollen,  owing  to  an  exudation  of  plasma. 
The  blood  vessels  become  dilated  and  congested,  and  notwithstanding  the  slower  circulation,  the 
amount  of  blood  is  greater.  The  blood  vessels  are  increased,  owing  to  the  formation  of  new  ones. 
Colorless  blood  corpuscles  pass  out  of  the  vessels  and  reproduce  themselves,  and  many  of  them 
undergo  falty  degeneration,  while  others  take  up  nutriment  and  become  converted  into  large  uni- 
nucleated  protoplasma  cells,  from  which  giant  cells  are  developed  (ZiegUr,  Cohnheim).  The 
newly-formed  blood  vessels  supply  all  these  elements  with  blood. 

245.  TRANSPLANTATION  OF  TISSUES.— The  nose,  ear,  and  even  a  finger,  after 
having  been  severed  from  the  body  by  a  clean  cut,  have,  under  certain  circumstances,  become  united 
to  the  part  from  which  they  were  removed.  The  skin  is  frequently  transplanted  by  surgeons,  as, 
for  example,  to  fomi  a  new  nose.  The  piece  of  skin  is  cut  from  the  forehead  or  arm.  to  which  it 
is  left  attached  by  a  bridge  of  skin.  The  skin  is  then  stitched  to  the  part  which  it  is  desired  to 
cover  in,  and  when  it  has  become  attached  in  its  new  situation,  the  bridge  of  skin  is  severed.  Re- 
verdin  cut  a  piece  of  skin  into  pieces  about  the  size  of  a  pea  and  fixed  them  on  an  ulcerated  sur- 
face, where  they,  as  it  were,  took  root,  grew%  and  sent  off  from  their  margins  epithelial  outgrowths, 
so  that  ultimately  the  whole  surface  was  covered  with  epithelium.  The  excised  spiir  of  a  cnck  was 
transplanted  and  fixed  in  the  comb  of  the  same  animal,  where  it  grew  (John  Hunter).  P.  Bert  cut 
off  the  tail  and  legs  of  rats  and  transplanted  them  under  the  skin  of  the  back  of  other  rats,  where 
they  united  witli  the  adjoining  parts.  Oilier  found  that,  when  periosteum  was  transplanted,  it  grew 
and  reproduced  bone  in  its  new  situation.  Even  blood  and  Ivmph  may  be  transfused  (Transfusion, 
§  102).  [Small  portions  (1.5  mm.)  of  epiphyses,  costal  cartilage,  of  a  rabbit  or  kitten,  when  trans- 
planted quite  fresh  into  the  anterior  chamber  of  the  eye,  testis,  submaxillary  gland,  kidney,  and 
under  the  skin  of  a  ralibit,  attach  themselves  and  grow,  and  the  growth  is  more  rapid  the  more  vas- 
cular the  site  on  which  the  tissue  is  transplanted.  The  cartilage  is  not  essentially  different  from 
hyaline  cartilage,  but  the  cells  are  fewer  in  the  centre,  while  the  matrix  tends  to  become  fibrous. 
Small  pieces  of  epiphyseal  cartilage  introduced  into  the  jugular  vein  were  found  as  cartilaginous 
foci  in  the  lungs  (Zahn,  Leopold).  Tissues  transplanted  from  embryonic  structures  grow  far  better 
than  adult  tissues  [Zahn]. 

Many  of  these  results  seem  only  to  be  possible  between  individuals  of  the  same  species,  although 
Helferich  has  recently  found  that  a  piece  of  dog's  muscle,  w-hen  substituted  for  human  muscle, 
united  to  the  adjoining  muscle,  and  became  functionally  active.  [J.  R.  Wolfe  has  transplanted  the 
conjunctiva  of  the  rabbit  to  the  human  eye.]  Most  tissues,  however,  do  not  admit  of  transplantation, 
e.g.,  glands  and  the  sense  organs.  They  may  be  removed  to  other  parts  of  the  body,  or  into  the 
peritoneal  cavity,  without  exciting  any  inflammatory  reaction;  they,  in  fact,  behave  like  inert  foreign 
matter. 

246.  INCREASE  IN  SIZE  AND  WEIGHT  DURING  GROWTH.— The  length  of 
the  body,  which  at  birth  is  usually  ^^  of  the  adult  body,  undergoes  the  greatest  elongation  at  an 
early  period  :  in  the  first  year,  20  ;  in  the  second,  10  ;  in  the  tliird,  about  7  centimetres;  while  from 
five  to  sixteen  years  the  annual  increase  is  about  5J.<  centimetres.  In  the  twentieth  year  the  increase 
is  very  slight.  From  fifty  onward  the  size  of  the  body  diminishes,  owing  to  the  intervertebral 
disks  becoming  thinner,  and  the  loss  may  be  6-7  centimetres  about  the  eightieth  year.  The  weight 
of  the  body  (j'j  of  an  adult)  sinks  during  the  first  five  to  seven  days,  owing  to  the  evacuation  of 
the  meconium  and  the  small  amount  of  food  which  is  taken  at  first.  Only  on  the  tenth  day  is  the 
weight  the  same  as  at  birth. 

The  increase  of  weight  is  greater  in  the  same  time  than  the  increase  in  length.  Within  the  first 
year  a  child  trebles  its  weight.  The  greatest  weight  is  usually  reached  about  forty,  while  toward 
sixty  a  decrease  begins,  which  at  eighty  may  amount  even  to  6  kilos.  The  results  of  measurements, 
chiefly  by  Quetelet,  are  given  in  the  following  table ; — 


406 


INCREASE    IN    SIZE    AND    WEIGHT    DURING    GROWTH. 


Length  (Cmtr.). 

Weight  (Kilo.). 

Length  (Cmtr.). 

Weight 

(Kilo.). 

Age 

Age 

Man. 

Woman. 

Man. 

Woman. 

Man. 

Woman. 

Man. 

Woman. 

O 

49.6 

48.3 

3.20 

2.91 

15 

"55-9 

147-5 

46.41 

41-30 

I 

69.6 

69.0 

10.00 

930 

16 

161.0 

150.0 

53-39 

44-44 

2 

79.6 

78.0 

12.00 

11.40 

17 

167.0 

154-4 

57.40 

49.08 

3 

86.0 

85. 0 

13.21 

12.45 

18 

170.0 

.56.2 

61.26 

53-'o 

4 

93-2 

91.0 

15.07 

14.18 

19 

170.6 

63-32 

5 

99.0 

97.0 

16.70 

1550 

20 

171. 1 

157.0 

6i;.oo 

54-46 

6 

104.6 

103.2 

1 8. 04 

16.74 

25 

172.2 

157-7 

68.29 

55.08 

7 

III. 2 

109.6 

20. 1 6 

18.45 

30 

172.2 

'57-9 

68.90 

55-14 

8 

II7.0 

II3-9 

22.26 

19.82 

40 

i7>-3 

155-5 

6S.81 

56.65 

9 

122.7 

120.0 

24.09 

22.44 

50 

166.4 

153-6 

67-45 

58-45 

lO 

128.2 

124.8 

26.12 

24.24 

60 

163-9 

151.6 

65-50 

56.73 

II 

1327 

127-5 

27-85 

26.25 

70 

162.3 

151.4 

6303 

53-72 

12 

«35-9 

132-7 

31.00 

30-54 

80 

161.3 

150.6 

61.22 

51.52 

'3 

140.3 

138-6 

35-32 

34-65 

90 

57-83 

49-34 

H 

14S.7 

144.7 

40.50 

38-10 

(Chiefly  from 

Quetelet.) 

Between  the  twelfth  and  fifteenth  years  the  weight  and  size  of  the  girl  are  greater  than  of  the 
boy.  Growth  is  most  active  in  the  last  months  of  foetal  life,  and  afterward  from  the  sixth  to  ninth 
year  until  the  thirteenth  to  sixteenth.  The  full  stature  is  reached  about  thirty,  but  not  the  greatest 
weight  [T/wiiia). 


CHEMICAL  CONSTITUENTS  OF  THE  ORGANISM. 


247.  (A)  INORGANIC  CONSTITUENTS.— I.  Water  forms  58.5  per  cent,  of  the  whole 
body,  but  it  occurs  in  different  quantity  in  the  different  tissues.  The  kidneys  contain  the  most 
water,  82.7  per  cent. ;  bones,  22  per  cent. ;  teeth,  10  per  cent. ;  while  enamel  contains  the  least,  0.2 
per  cent. 

[  Waler  is  of  the  utmost  importance  in  the  economy,  and  it  is  no  paradox  to  say  that  all  organisms 
live  in  water,  for  though  the  entire  animal  may  not  live  in  water,  all  its  tissues  are  bathed  by  watery 
fluids,  and  the  essential  vital  processes  occur  in  water  (^  229).  A  constant  stream  of  water  may  be 
said  to  be  passing  through  organisms;  a  certain  quantity  of  water  is  taken  in  with  the  food  and  drink, 
which  ultimately  reaches  the  blood,  while  from  the  blood  a  constant  loss  is  taking  place  by  the  urine, 
the  sweat,  and  breath.  The  greater  quantity  of  the  water  in  our  bodies  is  derived  from  without, 
but  it  is  probable  that  a  small  amount  is  formed  within  our  bodies  by  the  action  of  free  oxygen  on 
certain  organic  substances.  According  to  some  observers,  peroxide  of  hydrogen  (HjOj)  is  also 
present  in  the  body.] 

II.  Gases. —  [Oxygen  is  absorbed  from  the  air,  and  enters  the  blood,  where  it  forms  a  loose 
chemical  comjround,  with  the  coloring  matter  or  haemoglobin,  while  a  small  amount  exists  in  a  free 
state,  or  is  simply  absorbed.]  Hydrogen  is  found  in  the  alimentary  canal.  Nitrogen,  [like 
oxygen,  is  absorbed  from  the  atmosphere  by  the  blood,  in  which  it  is  dissolved,  and  from  which  it 
passes  into  other  fluids  of  the  body.  It  is  probable  that  a  very  small  quantity  is  formed  within  the 
body.] 

The  presence  of  marsh  gas  (CH^)  (?  124),  ammonia  (NH3),  CO2  (?  38),  sulphuretted  hydrogen 
(HjS)  (5  184),  and  ozone  (?  37)  has  been  referred  to  already. 

III.  Salts. — Sodium  chloride  [is  one  of  the  most  important  inorganic  substances  present  in 
the  body.  It  occurs  in  all  the  tissues  and  fluids  of  the  body,  and  it  plays  a  most  prominent  part  in 
connection  with  the  diffusion  of  fluids  through  membranes,  and  its  presence  is  necessary  for  the 
solution  of  the  globulins  (^  4091.  In  some  cases  it  exists  in  a  state  of  combination  with  albuminous 
bodies,  as  in  the  blood  pl.isma.  Common  salt  is  absolutely  necessary  for  one's  existence ;  if  it  be 
withdrawn  entirely,  life  soon  comes  to  an  end.  .-Vbout  15  grammes  are  given  off  in  twenty-four 
hours,  the  great  part  being  excreted  by  the  urine.  Boussingault  showed  that  the  addition  of  a  certain 
amount  of  common  salt  to  the  daily  food  of  cattle  greatly  improved  their  condition.] 

[Calcium  phosphate  (CajP^O, )  is  the  most  abundant  salt  in  the  body,  as  it  forms  more  than 
one-half  of  our  bones,  liut  it  also  occurs  in  dentine,  enamel,  and,  to  a  much  less  extent,  in  the  other 
solids  and  fluids  of  the  body.  Among  secretions,  milk  contains  relatively  the  largest  amount  (2.72 
per  cent.).  In  milk,  it  is  necessary  for  forming  the  calcareous  matter  of  the  bones  of  the  infant. 
It  gives  bones  their  hardness,  solidity,  and  rigidity.  It  is  chiefly  derived  from  the  food,  and,  as 
only  a  small  quantity  is  given  off  in  the  excretions,  it  seems  not  to  undergo  rapid  removal  from 
the  body,] 

[Sodium  phosphate  (PNajO,),  acid  sodium  phosphate  (VUdL^O^,  acid  potassium  phosphate 
(PKjHOj).  The  sodium  phosphate  and  the  corresponding  potash  salt  give  most  of  the  fluids  of 
the  body  their  alkaline  reaction.  The  alkaline  reaction  of  the  blood  plasma  is  partly  due  to  alkaline 
phosphates,  which  are  chiefly  derived  from  the  food.  The  acid  sodium  phosphate  is  the  chief  cause 
of  the  acid  reaction  of  the  urine.  A  small  quantity  of  phosphoric  acid  is  formed  in  the  body  owing 
to  the  oxidation  of  "lecithin,"  which  contains  phosphorus,  and  also  forms  an  important  constituent 
of  nerve  tissue.] 

[Sodium  carbonate  (Na,C03)  and  sodium  bicarbonate  fNaHC03)  exist  in  small  quantities 
in  the  food,  and  are  chiefly  formed  in  the  body  from  the  decomposition  of  the  .salts  of  the  vegetable 
acids.  They  occur  in  the  blood  plasma,  where  they  play  an  important  part  in  carrying  the  CO2 
from  the  tissues  to  the  lungs.] 

[Sodium  and  potassium  sulphates  (Na^SO^  and  K^SO.,)  exist  in  very  small  quantity  in  the 
body,  and  are  introduced  with  the  food,  but  part  is  formed  in  the  body  from  the  oxidation  of  organic 
bodies  containing  sulphur.] 

[Potassium  chloride  (KCl)  is  pretty  widely  distributed,  and  it  occurs  specially  in  muscle, 
colored  blood  corpuscles,  and  milk.  Calcium  fluoride  (CaFlj)  occurs  in  small  quantity  in  bones 
and  teeth.  Calcium  carbonate  (CaCO,)  is  associated  with  calcium  phosphate  in  bone,  tooth, 
and  in  some  fluids,  but  it  occurs  in  relatively  much  smaller  amount.  It  is  kept  in  solution  by  alka- 
line chlorides,  or  by  the  presence  of  free  carbonic  acid.] 

[Ammonium  chloride  (NH^Cl). — Minute  traces  occur  in  the  gastric  juice  and  the  urine.] 

407 


408  THE    ALBUMINOUS   OR    PROTEID    SUBSTANCES. 

[Magnesium  phosphate  (Mga^O^)  occurs  in  the  tissues  and  fluids  of  the  body,  along  with 
calcium  ]>hospliate,  but  in  very  much  smaller  quantity.] 

IV.  Free  Acids. — flydrochloric  acid  ( HCl)  [occurs yVc?  in  the  gastric  juice,  but  in  combination 
with  the  alkalies  it  is  widely  distributed  as  chlorides].  Sulphuric  acid  (HjSO^)  [is  said  to  occur 
free  in  the  saliva  of  certain  gasteropods,  as  Dolium  galea.  In  the  body  it  forms  sulphates,  being 
chiefly  in  combination  with  soda  and  potash]. 

V.  Bases. — Silicon  as  silicic  acid  (SiOj) ;  manganese,  iron,  the  last  forms  an  integral  constituent 
of  the  blood  pigment;  copper  (?),  (§  174)' 

248.  (B)  ORGANIC  COMPOUNDS.— I.  THE  ALBUMINOUS  OR  PROTEID 
SUBSTANCES.— I.  True  Proteids  and  their  Allies.— Proteids  or  Albumins  and  their 
allies  are  composed  of  C,  H,  O,  N.  aiul  S,  and  are  derived  from  plants  (see  Introduction). 

[According  to  Hoppe-Seyler  their  general  percentage  composition  is — 

O.  H.         N,  C.  S. 

From      20.9       6.9       15.2       51.5       0.3 

To 23.5  to  7.3  to  17.0  to  54.5  to  2.O.] 

They  exist  in  all  animal  fluids,  and  in  nearly  all  the  tissues.  They  occur  partly  in  the  fluid 
form,  although  Briicke  maintains  that  the  molecule  of  albumin  e.\ists  in  a  condition  midway 
between  a  state  of  imbibition  and  a  true  solution,  and  partly  in  a  more  concentrated  condition. 
Besides  forming  the  chief  part  of  muscle,  nerve,  and  gland,  they  occur  in  nearly  all  the  fluids 
of  the  body,  including  the  blood,  lymph,  and  serous  fluids;  but  in  lictillh  mere  traces  occur  in 
the  sweat,  while  they  are  absent  from  the  bile  and  the  urine.  Unboiled  white  of  egg  is  the 
type.  In  the  alimentary  canal  they  are  changed  into  peptones.  The  chief  products  derived  from 
their  o.xidation  within  the  body  are  COj,  H,0,  and  especially  urea,  which  contains  nearly  all 
the  N  of  the  proteids. 

Constitution. — Their  chemical  constitution  is  quite  unknown.  The  N  seems  to  exist  in  two 
distinct  conditions,  partly  loosely  combined,  so  as  to  yield  ammonia  readily  when  they  are  decom- 
posed, and  partly  in  a  more  fixed  condition.  According  to  Pfliiger,  part  of  the  N  in  living  proteid 
bodies  exists  in  the  form  of  cyanogen.  The  proteid  molecule  is  very  large,  and  is,  very  probably, 
a  complex  one ;  a  small  part  of  the  molecule  is  composed  of  substances  from  the  group  of  aromatic 
bodies  (which  become  conspicuous  during  putrefaction),  the  larger  part  of  the  molecule  belongs  to 
the /(j/Zj  bodies  (during  the  oxidation  of  albumin,  fatty  acids  especially  are  developed).  Carbo- 
hydrates may  also  appear  as  decomposition  products  (A'rukenberg).  For  the  decompositions  during 
digestion,  see  ?  170,  and  during  putrefaction,  J  184.  The  proteids  form  a  large  group  of  closely- 
related  substances,  all  of  which  are,  perhaps,  modifications  of  the  same  body.  When  we  remember 
that  the  infant  manufactures  most  of  the  proteids  of  its  ever-growing  body  from  the  casein  in  milk, 
this  last  view  seems  not  improbable. 

Characters. — Proteids,  the  anhydrides  of  peptones  (§  166),  are  colloids  (|  191),  and,  therefore, 
do  not  diffuse  easily  through  animal  membranes ;  they  are  amorphous,  and  do  not  crystallize,  and, 
hence,  are  isolated  with  difficulty;  some  are  soluble,  others  are  insoluble,  in  water;  are  insoluble  in 
alcohol ;  rotate  the  ray  of  polarized  light  to  the  left ;  in  a  flame,  they  give  the  odor  of  burned  horn. 
Various  metallic  salts  and  alcohol  precipitate  tliem  from  their  solution ;  they  are  coagulated  by 
heat,  mineral  acids,  and  the  prolonged  action  of  alcohol.  Caustic  alkalies  dissolve  them  (yellow), 
and  from  this  solution  they  are  precipitated  by  acids.  By  powerful  oxidizing  agents  they  yield 
carbamic  acid,  guanidin  and  volatile  fatty  acids. 

Decompositions. — When  acted  upon  in  a  suitable  manner  by  acids  and  alkalies,  they  give  rise 
to  the  decomposition  products — leucin  (10-18  per  cent.),  tyrosin  (0.25-2  per  cent  ),  asparaginic  acid, 
glutamic  acid,  and  also  volatile  fatty  acids,  benzoic  and  hydrocyanic  acids,  and  aldehydes  of  benzoic 
and  fatty  acids;  also,  indo  (Hlasiwetz,  Habermann).  Similar  products  are  formed  during  pan- 
creatic digestion  (^  170),  and  during  putrefaction  [\  184). 

Reactions. — ( i)  They  are  coagulated  by  nitric  acid,  and  when  boiled  therewith,  give  2. yellow, 
the  xanthoproteic  reaction ;  the  addition  of  ammonia  gives  a  deep  orange  color. 

(2)  Millon's  reagent  (nitrate  of  mercury  with  nitrous  acid);  when  heated  with  this  reagent 
above  60°  C,  they  give  a  red,  probably  owing  to  the  formation  of  tyrosin.  [If  the  proteids 
are  present  in  large  amount,  a  red  precipitate  occurs;  but  if  mere  traces  are  present,  only  the 
fluid  becomes  red.] 

(3)  The  addition  of  a  few  drops  of  solution  of  cupric  sulphate,  and  the  subsequent  addition  of 
caustic  potash  or  soda,  give  a  violet  color,  which  deepens  on  boiling  [the  same  color  is  obtained  by 
adding  a  few  drops  of  Fehling's  solution  (biuret  reaction).] 

(4)  They  are  precipitated  by  acetic  acid  and  potassium  ferrocyanide. 

(5)  When  boiled  with  concentrated  hydrochloric  acid,  they  give  a  violet-red  color. 

(6)  Sulphuric  acid  containing  molybdic  acid  gives  a  blue  color  [Frohde]. 

(7)  Their  solution  in  acetic  acid  is  colored  violet  with  concentrated  sulphuric  acid,  and  shows  the 
absorption  band  of  hydrobilirubin  (.-Idamiie-uncz). 

(8)  Iodine  is  a  good  microscopic  reagent,  which  strikes  a  brownish-yellow,  while  sulphuric  acid 
and  cane  sugar  give  a  purplish- violet  [E.  Schultze). 


NATIVE    ALBUMINS,   GLOBULINS    AND    ALBUMINATES.  409 

[(g)  When  boiled  with  acetic  acid  and  an  equal  volume  of  a  concentrated  solution  of  sodic  sul- 
phate, they  are  precipitated.  This  method  is  used  for  removing  proteids  from  other  liquids,  as  it 
does  not  interfere  with  the  presence  of  other  substances.  Saturation  with  sodio-magne^ic  sulphate 
precipitates  the  proteids,  but  not  peptones.] 

249.  THE  ANIMAL  PROTEIDS  AND  THEIR  CHARACTERS.— They  have  been 
divided  into  classes  : — 

Class  I. — Native  Albumins. — Native  albumins  occur  in  a  natural  condition  in  the  solids 
and  fluids  of  the  body.  They  are  soluble  in  water,  and  are  not  precipitated  by  alkaline  carbonates, 
NaCl,  or  by  very  dilute  acids.  Their  solutions  are  coagulated  by  heat  at  65°-73°  C.  Dried  at  40° 
C,  they  yield  a  clear,  yellow,  amber-colored,  friable  mass,  "  soluble  albumin,"  which  is  soluble  in 
water. 

(1)  Serum  albumin,  whose  chemico-physical  characters  are  given  in  ?  32,  and  its  physiological 
properties  at  ?,4i.  Almost  all  its  salts  may  be  removed  from  it  by  dialysis,  when  it  is  no  longer 
coagulated  by  heat  {Sc/imiii/).  It  is  coagulated  by  strong  alcohol,  and  is  easily  dissolved  in  strong 
hydrochloric  acid.  When  precipitated,  it  is  readily  soluble  in  strong  nitric  acid.  It  is  not  coagulated 
when  shaken  up  with  ether.  The  addition  of  water  to  the  hydrochloric  solution  precipitates  acid 
albumin.     For  its  presence  in  urine,  ^  264. 

(2)  Egg  albumin.  When  injected  into  the  bloodvessels  or  under  the  skin,  or  even  when 
introduced  in  large  quantity  into  the  intestine,  part  of  it  appears  unchanged  in  the  urine  (^  192,  4, 
and  ^  264).  When  shaken  with  ether,  it  is  precipitated.  These  two  reactions  serve  to  distinguish 
it  from  (i).     The  specific  rotation  is  37.8°.     Amount  of  S,  1.6  per  cent. 

(Metalbumin  and  Paralbumin  have  been  found  by  Scherer  in  ropy  solutions  in  ovarian  cysts; 
they  are  only  partially  precipitated  by  heat.  The  precipitate  thrown  down  by  the  action  of  strong 
alcohol  is  soluble  in  water.  They  are  not  precipitated  by  acetic  acid,  by  acetic  acid  and  potassium 
ferrocyanide,  by  mercuric  chloride,  or  by  saturation  with  magnesium  suljihate.  Concentrated  sul- 
phuric acid  and  acetic  acid  give  a  violet  color  (Atiamkiewicz).  According  to  Hammarsten,  met- 
albumin is  a  mixture  of  paralbumin  and  other  proteid  substances.  On  being  boiled  with  dilute  sul- 
phuric acid,  they  yield  a  reduciuij  substance  (?  sugar)). 

Class  II.— Globulins. — They  are  native  proteids,  which  are  insoluble  in  distilled  water,  but 
soluble  in  dilute  saline  solutions,  sodium  chloride  of  i  per  cent.,  and  in  magnesium  sulphate. 
These  solutions  are  coagulated  by  heat,  and  are  precipitated  by  the  addition  of  a  large  quantity  of 
water.  Most  of  them  z.k  precipitated  ito^a  their  sodium  chloride  solution  by  the  addition  of  crystals 
of  sodium  chloride,  and  also  bv  satiiratini^  their  neutral  solution  at  30°  7uith  crystals  of  magnesium 
sulphate.  When  acted  upon  by  dilute  acids,  they  yield  acid  albumin,  and  by  dilute  alkalies,  alkali 
albumin. 

(1)  Globulin  (Crystallin)  is  obtained  by  passing  a  stream  of  CO2  through  a  watery  extract  of  the 
cry.stalline  lens. 

(2)  Vitellin  is  the  chief  proteid  in  the  yelk  of  egg.  It  is  also  said  to  occur  in  the  chyle  (?)  and 
in  the  amniotic  fluid  ( IVeyl).  Both  the  foregoing  are  not  precipitated  from  their  neutral  solutions 
by  saturalinn  with  sodium  chloride. 

(3)  Paraglobulin  or  Serum  globulin  (|  29),  and  in  urine,  |  264. 

(4)  Fibrinogen  (  J  291. 

(5)  Myosin  is  the  chief  proteid  in  dead  muscle.  Its  coagulation  in  muscle  post  mortem  consti- 
tutes rigor  mortis.  If  muscle  be  repeatedly  washed,  and  afterward  treated  wiih  a  10  per  cent, 
solution  of  sodium  chloride,  it  yields  a  viscid  fluid,  which,  when  dropped  into  a  large  quantity  of 
distilled  water,  gives  a  white  flocculent  precipitate  of  myosin.  It  is  also  precipitated  from  its  NaCl 
solution  by  cry.stals  of  NaCl.     For  Kiihne's  method  of  preparation,  see  ^  293. 

(6)  Globin  (Preyer),  the  proteid  residue  of  hemoglobin,  ^  18. 

Class  III. — Derived  Albumins  (Albuminates). — (i)  Acid  Albumin  or  Syntonin. — When 
proteids  are  dissolved  in  the  stronger  acids,  e.i^.,  hydrochloric,  they  become  changed  into  acid 
albumins.  They  are  precipitated  from  solution  by  the  addition  of  many  salts  (NaCl,  Na^SOj),  or 
by  neutralization  with  an  alkali,  e.g.,  sodic  carbonate,  but  they  are  not  precipitated  by  heat.  The 
concentrated  solution  gelatinizes  in  the  cold,  and  is  redissolved  by  heat.  Syntonin,  which  is 
obtained  by  the  prolonged  action  of  dilute  hydrochloric  acid  (2  per  1000)  upon  minced  muscle,  is 
also  an  acid  alliumin.  It  is  formed  also  in  the  stomach  during  digestion  (J  166, 1).  According  to 
Soyka,  the  alkali-  and  acid  albumins  differ  from  each  other  only  in  so  far  as  the  proteid  in  the  one 
case  is  united  with  the  base  (metal)  and  in  the  other  with  the  acid. 

(2)  Alkali  Albumin. — If  egg-  or  serum  albumin  be  acted  upon  by  dilute  alkalies,  a  solution  of 
alkali  albumin  is  obtained.  Strong  caustic  potash  acts  upon  white  of  egg,  and  yields  a  thick  jelly 
{Liebt-rkiVin).  The  solution  is  not  precipitated  by  heat,  but  it  is  precipitated  by  the  addition  of  an 
acid.  ' 

(3)  Casein  is  the  chief  proteid  in  milk  [\  231).  It  is  precipitated  by  acids  and  by  rennet  at  40° 
C.  In  its  characters  it  is  closely  related  to  alkali  albuminate,  but,  according  to  O.  Nasse,  it  contains 
more  N.  It  contains  a  large  amount  of  phosphorus  (0.S3  per  cent.).  It  may  be  precipitated  from 
milk  by  diluting  it  with  several  times  its  volume  of  water  and  adding  dilute  acetic  acid,  or  by  adding 
magnesium  sulphate  crystals  to  milk  and  shaking  vigorously.     Owing  to  the  large  amount  of  phos- 


410  VEGETABLE    PROTEID    BODIES. 

phorus  which  it  contains,  it  is  sometimes  referred  to  the  nucleoalbumins.  When  it  indigested  with 
dilute  HC!  lo. i  ]ier  cent.)  and  pepsin  at  the  temperature  of  the  body,  it  gradually  yields  nuclein. 

Class  IV. — Fibrin. — For  fibrin,  see  ^  27,  and  for  the  fibrin  factors,  '^  29. 

Class  V. — Peptones. — For  peptones  and  propeptone  [hemialbumose],  see  J  166,  I,  and 
in  urine,  ?  264. 

Class  VI. — Lardacein  and  Other  Bodies. — There  fall  to  be  mentioned  the  "  yelk  plates." 
which  occur  in  the  yelk:  Ichthin  (cartilaginous  fishes,  frog);  Ichthidin  (osseous  fishes); 
Ichthulin  (salmon);  Emydin  (tortoise — Valenciennes  and  Fremy);  also  the  indigestible  amy- 
loid substance  (  Virehoui)  or  lardacein,  which  occurs  chiefly  as  a  palhological  infiltration  into 
various  organs,  as  the  liver,  spleen,  kidneys  and  blood  vessels.  It  gives  a  blue  with  iodine  and 
sulphuric  acid  (like  cellulose),  and  a  mahogany  brown  with  iodine.  It  is  difificult  to  change  it  into 
an  albuminate  by  the  action  of  acids  and  alkalies. 

Class  VII. — Coagulated  Proteids. — When  any  native  albumins  or  globules  are  coagulated, 
e.g,^  at  70°  C.  they  yield  bodies  with  altered  characters,  insoluble  in  water  and  saline  solutions,  but 
soluble  in  boiling  strong  acids  and  alkalies,  when  they  are  apt  to  split  up.  They  are  dissolved 
during  gastric  and  pancreatic  digestion,  to  produce  peptones. 

Appendix :  Vegetable  Proteid  Bodies. — Plants,  like  animals,  contain  proteid  bodies, 
although  in  less  amount.  They  occur  either  in  solution  in  the  juices  of  living  plants  or  in  the 
solid  form.      In  composition  and  reaction  they  resemble  animal  proteids. 

[The  characters  of  the  proteids  occurring  in  plants  have  not  been  sufficiently  investigated  to 
generalize  on  the  nature  of  the  bodies  themselves.  As  far  as  our  knowledge  at  present  extends, 
they  have  a  great  resemblance  to  animal  proteids.  They  have  frequently  been  obtained  in  a 
crystalline  form  [RaJlkofer),  e.g.,  from  the  seeds  of  the  gourd  (Grii/>ler)  and  various  oleaginous 
seeds  {Jii/tkausen).  Theyoccurin  greatest  bulk  in  the  seeds  of  plants,  aleurone  grains  being  for 
the  most  part  composed  of  them.] 

[As  regards  the  kinds  of  proteid,  the  researches  of  late  years  (since  1S77)  have  shown  that  in 
seeds,  globulins  and  "  vegetable  peptone"  form  the  greater  proportion  of  the  proteid  constituents. 
The  existence  of  this  "  peptone,"  however,  is  denied  (  Vines],  and  other  bodies  similar  in  some  par- 
ticulars to  peptones  have  been  described,  viz.,  albumoses  (  Vines,  Martin).'] 

[Globulins. — Three  varieties  have  been  described  as  occurring  in  the  seeds  of  plants  :  vegetable 
myosin  (Hof^pe- Sevier),  vitellin  (  Weyl),  and  paraglobulin  (Martin).  They  have  practically  the 
same  properties  as  those  found  in  the  animal  kingdom :  vegetable  vitellin  has.  however,  not  been 
sufficiently  studied.  Paraglobulin  has  been  found  in  papaw  juice  {^Martin).  Myosin  occurs  in  the 
seeds  of  leguminos-T:,  in  flour  and  in  the  potato.] 

[Albumin. — The  existence  of  a  body  corresponding  to  egg-  or  serum  albumin  in  the  vegetable 
kingdom  is  douljtful  { Rittliausen).     Such  a  body  has  been  described  in  papaw  juice  (Martin).'] 

[Vegetable  Peptone :  Albumoses. — A  true  peptone  has  not  yet  been  recognized  in  plants  : 
what  has  been  described  as  such  is  hemialbumose  (  Vines).  The  existence  of  albumoses  in  the 
vegetable  kingdom  is  probably  widespread  ;  up  to  the  present  date  they  have  been  described  as 
occurring  in  the  seeds  of  leguminosie,  in  flour,  and  in  papaw  juice.  In  the  last,  two  forms  occur, 
called  respectively  a-  and  ^-phytalbumose.  The  former,  a  phytalbumose,  agrees  with  the 
hemialbumose  described  by  Vines,  being  soluble  in  cold  and  boiling  water ;  giving  also  a  biuret 
reaction,  and  a  precipitate  by  saturation  with  sodium  chloride  only  in  an  acid  solution.  The  latter, 
/3-phytalbumose,  is  soluble  in  cold,  but  not  in  boiling,  distilled  water;  hence  it  is  precipitated  by 
heat.  It  is  also  readily  thrown  down  by  saturation  with  sodium  chloride,  and  gives  a  faint  biuret 
reaction  (Martin).] 

[Vegetable  Casein  is  said  to  occur  in  the  seeds  of  leguminosse;  and  it  is  slightly  soluble  in 
water,  hut  readily  so  in  weak  alkalies  and  in  solutions  of  basic  calcic  phosphate.  A  solution  of 
this  body  is  precipitated  by  acids  and  rennet.  Two  varieties  have  been  described  :  (a)  legumin, 
in  peas,  beans,  lentils  (1805);  acid  in  reaction,  soluble  in  weak  alkalies  and  very  dilute  IICl  or 
acetic  acid  (Ernhof,  iSoj);  (i>)  conglutin,  a  very  similar  body  occurring  in  hops  and  almonds 
{Ritthaiisen).  The  existence  of  vegetable  casein  is  denied  (  W'<y'/,  /<?77  ,•  Vines,  1S7S  io  iSSo). 
Vines  states  that  both  legumin  and  conglutin  are  artificial  products,  being  formed  from  the  globulins 
present  by  the  dilute  alkali  used  in  extraction  of  the  proteids.     This  is  denied  by  Ritthausen.] 

[Gluten  and  Glutin. — Gluten  is  readily  prepared  from  flour  by  washing  and  kneading  it  in  a 
muslin  bag  under  a  stream  of  water.  So  prepared  it  is  yellowish-brown  in  color,  very  sticky,  and 
capable  of  being  drawn  out  into  long  shreds.  It  is  insoluble  in  water,  soluble  (but  not  completely) 
by  prolonged  action  in  dilute  acids  and  alkalies  (.2  per  cent.  KHO  and  HCl).  The  prolonged 
action  of  alcohol  (80  to  85  per  cent.)  dissolves  part  of  the  substance  of  gluten  (  Taddei,  Liebig), 
leaving  a  residue,  called  by  Liebig  plant  fibrin  and  by  Ritthausen  gluten  casein.  The  alcohol  con. 
tains  gliadin  (glutin),  gluten  fibrin  and  mucedin  (Ritthausen).  Gluten  casein  is  readily  soluble 
in  dilute  alkalies,  almost  insoluble  in  dilute  acetic  acid,  and  quite  insoluble  in  cold -and  boiling 
water;  the  products  of  its  decomposition,  by  heating  with  H2SO2,  are  leucin,  tyrosin,  glutamic  and 
asparaginic  acids.  The  three  bodies  dissolved  from  glutin  by  alcohol  differ  chiefly  in  their  solubility 
in  alcohol  and  water.  Gluten  fibrin,  the  least  soluble,  is  coagulated  by  the  action  of  absolute 
alcohol;  it  is  readily  soluble  in  dilute  acids  and  alkalies,  being  precipitated  by  neutralization. 
Gliadin  (gluten,  plant  gelatin)  may  be  prepared  by  boiling  gluten  with  water:  it  deposits  on  cool- 


ALBUMINOIDS.  411 

in<r  the  solution.  Though  soluble  in  water  at  ioo°  C.  at  first,  it  becomes  insoluble  by  the  prolonged 
action  of  water  at  that  temperature.  It  is,  like  gluten  fibrin,  soluble  in  dilute  acids  and  alkalies. 
Mucedin  differs  from  gliadin  in  being  less  soluble  in  strong  alcohol;  it  is  considered  by  Ritthausen 
as  a  modification  of  gluten  fibrin.  The  existence  of  these  several  constituents  of  gluten  has  not 
been  definitely  proved:  they  were  first  described  by  Ritthausen  (1872).  The  formation  of  gluten 
has  been  ascribed  by  Weyl  to  a  ferment  action  similar  to  the  formation  of  blood  fibrin  ;  all  attempts, 
however,  to  isolate  a  ferment  have  proved  fruitless.  The  water  used  in  washing  the  Bour  in  the 
preparation  of  gluten  contains  hemialbumose  f  ?'/««)  and  a  globulin  ( IViyl).  Rye  flour,  as  well  as 
wheaten,  yields  gluten  under  similar  treatment  with  water.] 

[Nitrogenous  Crystalline  Principles. — Leucin,  tyrosin,  asparagin,  and  glutamic  acid,  have 
been  found  in  the  seeds  of  plants.] 

250.  (2)  THE  ALBUMINOIDS. — These  substances  closely  resemble  true  proteids  in  their 
composition  and  origin,  and  are  amorjjhou^  non-crystalline  colloids;  some  of  them  do  not  contain 
S,  but  the  most  of  them  have  not  been  prepared  free  from  ash.  Their  reactions  and  decomposition 
products  closely  resemble  those  of  the  proteids ;  some  of  them  produce,  in  addition  to  leucin  and 
tyrosin,  glycin  and  alanin  (amido-propionic  acid).  They  occur  as  organized  constituents  of  the 
tissues  and  also  in  fluid  form.  It  is  unknown  whether  they  are  formed  by  oxidation  from  proteid 
bodies  or  by  synthesis. 

1.  Mucin  is  the  characteristic  substance  present  in  mucus.  It  contains  no  S.  That  obtained  from 
the  submaxillary  gland  contains— C  52.31,  H  7.22,  N  11  84,  O  28.63.  It  dissolves  in  water,  mak- 
ing it  sticky  or  slimy,  and  can  be  filtered.  It  is  precipitated  by  acetic  acid  and  alcohol ;  and  the 
alcohol  precipitate  is  again  soluble  in  water.  It  is  not  precipitated  by  acetic  acid  and  ferrocyanide 
of  potassium,  but  HNO3  and  other  mineral  acids  precipitate  it  (Sc/ieyer).  It  occurs  in  saliva  (§  146), 
in  bile,  in  mucous  glands,  secretions  of  mucous  membranes,  in  mucous  tissue,  in  synovia,  and  in 
tendons  [A.  Rollett).  Pathologically  it  occurs  not  unfrequently  in  cysts;  in  the  animal  kingdom, 
especially  in  snails  and  in  the  skin  of  holothurians  (Eich-uald).  It  yields  leucin  and  7  per  cent,  of 
tyrosin  when  it  is  decomposed  by  prolonged  boiling  with  sulphuric  acid.  [The  precipitate  called 
mucin  has  not  always  the  same  characters,  and,  in  fact,  it  differs  according  to  the  animal  from  which 
it  is  obtained  (LanJwehr)  ] 

2.  Nuclein  (Miescher,  \  19S) — (C  29,  H  49,  N  9,  P  3,  O  22) — contains  phosphoric  acid,  and  is 
slightly  soluble  in  water,  easily  in  ammonia,  alkaline  carbonates,  strong  HNO,;  it  gives  the  biuret  re- 
action; no  reaction  with  Millon's  reagent;  when  decomposed  it  yields  phosphorus.  It  occurs  in  the 
nuclei  of  pus  and  blood  corpuscles  (|  22),  in  spermatozoids.yelk-spheres,  liver,  brain,  and  milk, yeast, 
fungi,  and  many  seeds.  It  has  resemblances  to  mucin,  and  is  perhaps  an  intermediate  product  between 
albumin  and  lecithin  {Hoppe-Seylci).  It  is  prepared  by  the  artificial  digestionof  pus  when  it  remains  as 
an  indigestible  residue;  acids  precipitate  it  from  an  alkaline  solution.  It  gives  a  feeble  xanthoproteic  re- 
action; after  the  prolonged  action  of  alkalies  and  acid,  substances  similar  to  albumin  and  syntonin  are 
formed.     Hypoxanthin  and  guanin  have  been  obtained  as  decomposition  products  from  it  {Kossel). 

3.  Keratin  occurs  in  all  horny  and  epidennic  tissues  (epidermic  scales,  hairs,  nails,  feathers) — 
C  50.3-52.5,  H  6.4-7,  N  15. 2-17,  O  20.8-25,  S  0.7-5  percent. — is  soluble  in  boiling  caustic  alka- 
lies, but  swells  up  in  cold  concentrated  acetic  acid.  When  decomposed  by  HjSO^  it  yields  10  per 
cent,  leucin  and  3.6  percent,  tyrosin.     Neuro-keratin,  \  321. 

4.  Fibroin  is  soluble  in  strong  alkalies  and  mineral  acids,  in  ammonia-sulphate  of  copper;  when 
boiled  with  H^SO^  it  yields  5  per  cent,  tyrosin,  leucin,  and  glycin.  It  is  the  chief  constituent  of 
the  cocoons  of  insects  and  threads  of  spiders. 

5.  Spongin,  allied  to  fibroin,  occurs  in  the  bath  sponge,  and  yields,  as  decomposition  products, 
leucin  and  glycin  {Stiidekr). 

6.  Elastin,  the  fundamental  substance  in  elastic  tissue,  is  soluble  only  when  boiled  in  concen- 
trated caustic  potash — C  55-55.6,  H  7.1-7.7,  N  16.1-17.7,  O  19. 2-21. 1  per  cent.  It  yields  36-45 
per  cent,  of  leucin  and  j^  per  cent,  of  tyrosin. 

7.  Gelatin  (Glutin),  obtained  from  connective  tissues  by  prolonged  boiling  with  water;  it  gela- 
tinizes in  the  cold — C  52.2-50.7,  H  6.6-7.2,  N  17.9-18.S,  S  +  O  23.5-25,  (S  0.7  per  cent.).  [The 
ordinary  connective  tissues  are  supposed  to  contain  the  hypothetical  anhydride  collagen,  while  the 
organic  basis  of  bone  is  called  ossein.]  It  rotates  the  ray  of  polarized  light  strongly  to  the  left. 
By  prolonged  boiling  and  digestion  it  is  converted  into  a  peptone-like  body  (gelatin  peptone), 
which  does  not  gelatinize  (\  161,  I).  [It  swells  up,  but  does  not  dissolve  in  cold  water  ;  when  dis- 
solved in  warm  water,  and  tinged  with  Berlin  blue  or  carmine,  it  forms  the  usual  colored  mass 
which  is  employed  by  histologists  for  making  fine  transparent  injections  of  blood  vessels.]  A  body 
re-embling  gelatin  is  found  in  leuka;mic  blood  and  in  the  juice  of  the  spleen  (\  103,  1).  When 
decomposed  with  sulphuric  acid  it  yields  glycin,  ammonia,  leucin,  but  no  tyrosin.  It  gives  insoluble 
precipitates  with  mercuric  chloride,  and  tannin. 

8.  Chondrin  (yoh.  Miiller)  occurs  in  the  matrix  of  hyaline  cartilage  and  between  the  fibres  in 
fibro-cartilage.  It  is  obtained  from  hyaline  cartilage  and  the  cornea  by  boiling.  It  occurs  also  in 
the  mantle  of  molluscs — C  49.5-50.9,  H  6.6-7.1,  N  14.4-14.9,  S  +0  27.2-29  (S  0.4  per  cent). 
When  boiled  viith  sulphuric  acid  it  yields  leucin;  with  hydrochloric  acid,  and  when  digested, 
chondro-glucose  ( J/ifm^^f-r)  ;  it  belongs  to  the  glucosides,  which  contain  N.  When  acted  upon  by 
oxidizing  reagents  it  is  converted  into  gelatin  [Brame).     The  substance  which  yields  chondrin   is 


412 


ORGANIZED   AND    UNORGANIZED   FERMENTS. 


called  chondrogen,  which  is  perhaps  an  anhydride  of  chondrin.  The  following  properties  of  gelatin 
and  chondrin  are  to  be  noted  :  Gelatin  is  precipitated  by  tannic  acid,  mercuric  chloride,  chlorine 
water,  platinic  chloride,  and  alcohol,  but  not  by  acids,  alum,  or  salts  of  silver,  iron,  copper,  or  lead  ; 
its  specific  rotation  is  =  —  130°.  [Compare  these  precipitants  with  those  of  albumin.]  Chondrin 
is  precipitated  by  acetic  acid  and  dilute  sulphuric  and  hydrochloric  acids,  by  alum,  and  by  salts  of 
silver,  iron,  and  lead  ;  its  specific  rotation  =:  —  213°. 

9.  The  hydrolytic  ferments  have  recently  been  called  Enzymes  by  W.  Kiihne,  in  order  to 
distinguish  them  from  organized  ferments,  such  as  yeast.  The  enzymes,  hydrolytic  or  organic  fer- 
ments, act  only  in  the  presence  of  water.  They  act  upon  certain  bodies,  causing  them  to  take  up  a 
molecule  of  water.  They  all  decompose  hydric  pero.\ide  into  water  and  O.  They  are  most  active 
between  30  and  35°  C,  and  are  destroyed  by  boiling,  but  when  dry  they  may  be  subjected  to  a  tem- 
perature of  100°  without  being  destroyed.  Their  solutions,  if  kept  for  a  long  time,  gradually  lose 
their  properties  and  undergo  more  or  less  decomposition. 

{<!)  Sugar  forming  or  diastatic  ferment  occurs  in  saliva  (^  148),  pancreatic  juice  (?  170), 
intestinal  juice  (?  1S3),  bile  (§  iSo),  blood  (|  22),  chyle  (§  189),  liver  (g  174),  in  human  milk  (j  231). 
Invertin  in  intestinal  juice  (?  183). 

.Mmost  all  dead  tissues,  organic  fluids,  and  even  proteids,  although  only  to  a  slight  degree,  may 
act  diastaticallv.     Diastatic  ferments  are  very  generally  distributed  in  the  vegetable  kingdom. 

\b^  Proteolytic,  or  Ferments  luhich  act  upon  Proteids. — Pepsin  in  gastric  juice  and  in  muscle 
(?  166),  in  vetches,  myxomycetes  [Krtckenberg],  trypsin  in  the  pancreatic  juice  (J  170),  a  similar 
ferment  in  the  intestinal  juice  (\  183),  and  urine  (?  264). 

(i)   Fat-decomposing  in  pancreatic  juice  (§  170),  in  the  stomach  (J  166). 

(,/)  Milk-coagulating  in  the  stomach  (§  166),  pancreatic  juice  {\  170),  and  perhaps  also  in  the 
intestinal  juice  (?) — (W.  Roberts). 

[The  importance  of  fermentive  processes  has  already  been  referred  to  in  detail  under 
"Digestion."  Ferments  are  bodies  which  excite  chemical  changes  in  other  matter  with  which 
they  are  brought  into  contact.     They  are  divided  into  two  classes  : — 

(1)  Unorganized;  soluble  or  non-living. 

(2)  Organized,  or  living.] 


[Table  showing  the  unc 

jrganized  ferments  present  in  the 

body,  and  their  actions. 

Fluid  or  Tissues. 

Ferment. 

Actions. 

Saliva, 

I.  Ptyalin,  (|  148) 

Converts  starch  chiefly  into  maltose. 

f 
Gastric  juice \ 

1.  Pepsin -j 

2.  Milk  curdling 

3.  Lactic-acid  ferment,    .    . 

4.  Fat  splitting, \ 

Converts  proteids  into  peptones  in  an 
acid  medium,  certain  by-products 
being  formed  (\  166). 

Curdles  casein  of  milk. 

Splits  up  milk  .sugar  into  lactic  acid. 

Splits  up  fats  into  glycerine  and  fatty 
acids. 

Pancreatic  juice,  .    .    .   ■ 
Intestinal  juice,    .    .    .   ■ 

1.  Diastatic  or  amylopsin,    .        Converts  starch  chiefly  into  maltose. 

C  Changes  proteids  into  peptones  in  an 

2.  Trypsin \       alkaline    medium,  certain    by-pro- 

(       ducts  being  formed  [\  170). 

3.  Emulsive,  (?) iEmulsifies  fats. 

4.  Fat  splitting  or  steapsin,  .   {  ^^'^'f^^^'^    '"'°   S'^'""""   ^"'^    *'""'' 
J.  Milk  curdling, iCurdles  casein  of  milk. 

1.  Diastatic i. 

2.  Proteolytic 

3.  Invertin 

4.  Milk  curdling, 

Does  not  form  m.altose,  but  maltose  is 

changed  into  glucose  (§  183). 
Fibrin  into  peptone  (?). 
Changes  cane-  into  grape  sugar. 
(?  in  small  intestine). 

Blood,  

Chyle 

I'iver,(?) 

Milk 

Most  tissues,    .... 

\  Diastatic  ferments. 

Muscle 

Urine 

Blood 

\  Pepsin  and  other  ferments. 

Fibrin- forming  ferment. 

(\fodified  from  W.  Roberts).] 

FATS.  413 

[(l)  The  Unorganized  Ferments  are  those  mentioned  in  the  preceding  table.  They  seem  to 
be  nitrogenous  bodies,  although  their  exact  composition  is  unknown,  and  it  is  doubtful  if  they 
have  ever  been  obtained  perfectly  pure.  They  are  produced  within  the  body,  in  many  secretions, 
by  the  vital  activity  of  the  protoplasm  of  cells.  They  are  termed  soluble  because  they  are 
soluble  in  water,  glycerine,  and  some  other  substances  (^  148),  while  they  can  be  precipitated  by 
alcohol  and  some  other  reagents.  They  do  not  multiply  during  their  activity,  nor  is  their 
activity  prevented  by  a  certain  proportion  of  salicylic  acid.  They  are  not  aflTected  by  oxygen 
subjected  to  the  compression  of  many  atmospheres  {/".  Bert).  They  are  non-living.  Their 
other  properties  are  referred  to  above.] 

[(2)  The  Organized  or  living  ferments  are  represented  by  yeast  (\  235).  Other  living  ferments 
belonging  to  the  schizomycetes,  occurring  in  the  intestinal  canal,  are  referred  to  in  \  184.  Veast 
causes  fermentation  by  splitting  up  sugar  into  CO,  and  alcohol  (\  156),  but  this  result  only  occurs 
so  long  as  the  yeast  is  living.  Hence,  its  activity  is  coupled  with  the  vitality  of  the  cells  of  the 
yeast.  If  yeast  be  boiled,  or  if  it  be  mixed  with  carbolic  or  salicylic  acid,  or  chloroform,  all  of 
which  destroy  its  activity,  it  cannot  produce  the  alcoholic  fermentation.  As  yet  no  one  has  suc- 
ceeded in  extracting  from  yeast  a  substance  which  will  excite  the  alcoholic  fermentation.  All  the 
organized  ferments  grow  and  multiply  during  their  activity  at  the  expense  of  the  substances  in 
which  they  occur.  Thus  the  alcoholic  fermentation  depends  upon  the  "  life  "  of  the  yeast.  They 
are  said  to  be  killed  by  oxygen  subjected  to  the  compression  of  many  atmospheres  i^P.  Bert).  But 
it  is  important  to  note  that  Hoppe-Seyler  has  extracted  from  dead  yeast  (killed  by  ether)  an  unor- 
ganized ferment  which  can  change  cane  sugar  into  grape  sugar.] 

10.  Haemoglobin,  the  coloring  matter  of  blood,  which,  in  addition  to  C,  H,  O,  N,  and  S,  con- 
tains iron,  may  be  taken  with  the  albuminoids  (|  11). 

(3)  Glucosides  containing  Nitrogen. — In  addition  to  chondrin,  the  following  glucosides  con- 
taining nitrogen,  when  subjected  to  hydrolytic  processes,  may  combine  with  water,  and  form  sugar 
and  other  substances  : — 

Cerebrin  (^  322)  =  C^HuoN^Oj^  {Geoghegan). 

Protagon — C  66.29,  H  10.69,  ^  2.39,  P  1.06S  per  cent. — occurs  in  nerves,  and  contains  phos- 
phorus (I  322";. 

Chitin,  2(C,5H25N20jo),  is  a  glucoside,  containing  nitrogen,  and  occurs  in  the  cutaneous  cov- 
erings of  arthropoda,  and  also  in  their  intestine  and  trachea  ;  it  is  soluble  in  concentrated  acids,  e.g., 
hydrochloric  or  nitric  acid,  but  insoluble  in  other  reagents.  According  to  Sandwick.  chitin  is  an 
amin-derivative  of  a  carbohydrate  with  the  general  formula  n(Ci2H2(,Oi„).  The  hyalin  of  worms 
is  closely  related  to  chitin.  (Solanin,  amygdalin  (§  202),  and  salicin,  etc.,  are  glucosides  of  the 
vegetable  kingdom. ) 

(4)  Coloring  Matters  containing  Nitrogen. — Their  constitution  is  unknown,  and  they  occur 
only  in  animals.  They  are  in  all  probability  derivatives  of  ha-moglobin.  They  are — ( i )  haematin 
(§  18,  A),  myo-h£Ematin  (^  232,  \  292,  a),  and  haematoidin  \\  20).  (2)  Bile  pigments  ({  177, 
3).  (3J  Urine  pigments  (except  Indican).  (4)  Melanin — C  44.2,  H  3,  N  9.9,  O  42.6 — or  the 
black  pigment,  which  occurs  partly  in  epithelium  (choroid,  retina,  iris,  and  in  the  deep  layers 
of  epidermis  in  colored  races)  and  partly  in  connective-tissue  corpuscles  (Lamina  fusca  of 
the  choroid). 

11.  ORGANIC  ACIDS  FREE  FROM  NITROGEN.— (l)  The  fatty  acids,  with  the  for- 
mula C„H2„.iO(OH),  occur  in  the  body  partly  free  and  partly  in  combination.  Free  volatile  fatty 
acids  occur  in  decomposing  cutaneous  secretions  (sweat).  In  combination,  acetic  acid  and  caproic 
acid  occur  as  amido-compounds  in  glycin  (  =  amido-acetic  acid),  and  leucin  (  =  amido-caproic 
acid).  More  especially  do  they  occur  united  with  glycerine  to  form  neutral  fats,  from  which  the 
fatty  acid  is  again  set  free  by  pancreatic  digestion  [\  170,  111). 

(2)  The  acids  of  the  acrylic  acid  series,  with  the  formula  C„H2o.30(HO),  are  represented 
in  the  Ixidy  by  one  acid,  oleic  acid,  which  in  combination  with  glycerine  yields  the  neutral 
fat  olein. 

251.  FATS. — (i)  Neutral  fats  occur  very  abundantly  in  animals,  but  they  also  occur  in  all 
plants;  in  the  latter  more  especially  in  the  seeds  (nuts,  almonds,  cocoanut,  poppy),  more  rarely 
in  the  pericarp  (olive)  or  in  the  root.  They  are  obtained  by  pressure,  melting,  or  by  extracting 
thein  with  eiiicr  or  boiling  alcohol.  They  \eg.,  tristearin,  Cj^HjjjOg]  contain  much  less 
O  than  the  carbohydrates,  such  as  sugar  and  starch  ;  they  give  a  greasy  spot  on  paper,  and 
when  shaken  with  colloid  substances,  such  as  albumin,  they  yield  an  emulsion.  When 
treated  with  superheated  steam,  or  with  certain  ferments  (p.  412,  c),  they  take  up  water 
and  yield  glycerine  and  fatty  acids,  and  if  the  latter  be  volatile  they  have  a  rancid  odor. 
Treated  with  caustic  alkalies  they  also  take  up  water,  and  are  decomposed  into  glycerine  and 
fatty  acids ;  the  fatty  acid  unites  with  the  alkali  and  forms  a  soap,  while  glycerine  is  set  free. 
The  soap  solution  dissolves  fats. 

Glycerine  is  a  tri-atomic  alcohol,  €3115(011)3,  and  unites  with  (i)  the  following  monobasic 
fatty  acids  (those  occurring  in  the  body  are  printed  in  italics) : — 


414 


ACIDS. 


Acids. 
[Margaric,    .    .  C, 


IS  a  mixture  of 
13  and  14.] 

14.  Stearic  ....  CjgHggOj 

15.  Arachinic      .    .  Q^^^W^ffd^ 

16.  Hyanic      .    .    .  Cj^H^^Oj 

17.  Cerotinic  .    .    .  C2  7H5^02 


Acids.  Acids. 

1.  Formic   ....  CH^O,  7.  CEnanthylic  .  .  CjHuOj 

2.  Acetic      .    .  .  .  CjH^Oj  8.   Caprylic    .    .  .CjHi^Oj 

3.  Propionic  .  .  .  C^HjOj  9.  Pelavgonic    .  .C,jH,j02 

4.  Butyric.    .  .  .  C^HjOj  10.    Capric  .    .    .  .C-^^W-^^O^ 
[Isobutyric  .  .  C^HjO^]  II.  Laiirostearic  ,  Cj2H2j02 

5.  Valerianic  .  .  C5H15O2  12.  A/yristic    .    .  .  Cj^H^gOj 

6.  Caproic  .    .  .  .C^HjjO,  13.   Palmitic  .    .  .CigH'jOj 

The  acids  form  a  homologous  series  with  the  formula  C„H2o.iO(OH).  With  every  CHj  added 
their  boiling  point  rises  19°.  Those  containing  most  carbon  are  solid  and  non-volatile;  those  con- 
taining less  C  (up  to  and  including  10)  are  fluid  like  oil,  have  a  burning  acid  taste,  and  a  rancid 
odor. 

The  earlier  members  of  the  series  may  be  obtained  by  oxidation  from  the  latter,  by  CH,  being 
removed,  while  COj  and  HjO  are  formed;  thus,  butyric  acid  is  obtained  from  propionic  acid. 

Nos.  13  and  14  are  found  in  human  and  animal  fat,  less  abundant  and  more  inconstant  are  12, 
II,  6,  8,  10,  4.  .Some  occur  in  sweat  {\  2S7)  and  in  milk  (§  231).  Many  of  them  are  developed 
during  the  decomposition  of  albumin  and  gelatin.  Most  of  the  above  (except  15  to  17)  occur  in 
the  contents  of  the  large  intestine  {\  185). 

(2)  Glycerine  also  unites  with  the  monobasic  oleic  acid,  which  also  forms  a  series,  whose  gen- 
eral formula  is  C[,Hv„.30(0H) ;  and  they  all  contain  2H  less  than  the  corresponding  members  of  the 
fatty  acid  series.  The  corresponding  fatty  acids  can  be  olxained  from  the  oleic  acid  series,  and  vice 
versa.  Oleic  acid  (olein-elainic  acid),  CjgHj^Oj,  is  the  only  one  found  in  the  organism;  united 
with  glycerine,  it  forms  the  fluid  fat,  olein.  The  fat  of  new-born  children  contains  more  glycerine 
of  palmitic  and  stearic  acid  than  that  of  adults,  which  contains  more  glyceride  of  oleic  acid.  Oleic 
acid  also  occurs  united  with  alkalies  (in  soaps),  and  (like  some  fatty  acids)  in  the  lecithins  (§  23). 
If  lecithin  be  acted  on  with  barium  hydrate,  we  obtain  insoluble  stearic,  or  oleic,  or  palmitic  acids 
and  barium  oleate,  together  with  dissolved  neurin  (J  322,  b)  and  baric  glycerin  phosphate.  It  ap- 
pears as  if  there  were  several  lecithins,  of  which  the  most  abundant  are  the  one  with  stearic  acid 
and  that  with  palmitin  -f-  oleic  acid  radicle  (Diakonaw).  Lecithin  occurs  in  the  blood  corpuscles 
(§  23),  semen,  nerves,  while  neurin  is  constantly  present  in  fungi. 

The  neutral  fats  [palmitin,  stearin  (both  solid),  and  olein  (fluid)],  the  glycerides  of  fatty  acids, 
and  of  oleic  acid,  are  triple  ethers  of  the  tri-atomic  alcohol  glycerine. 

With  the  neutral  fats  may  be  associated  glycerin  phosphoric  acid,  and  acid  glycerin  ether, 
formed  by  the  union  of  glycerine  and  phosphoric  acid,  with  the  giving  otT  of  a  molecule  of  water 
(CjHjPOg) ;  It  is  a  decomposition  product  of  lecithin  {\  23). 

(3)  The  glycolic  acids  (acids  of  the  lactic  acid  series)  have  the  formula  C„H2„.20(OH)2. 
They  are  formed  by  oxidation  from  the  fatty  acid  series  by  substituting  OH  (hydroxyl)  for  one  atom 
of  H  of  the  fatty  acids.  Conversely,  fatty  acids  may  be  obtained  from  the  glycolic  acids.  The  fol- 
lowing acids  of  this  series  occur  in  the  body  :  — 

{a)  Carbonic  acid  (oxy-formic  acid),  CO(OH)2 ;  in  this  form,  however,  it  only  makes  salts. 
Free  carbonic  acid  or  carbon  dioxide  is  an  anhydride  of  the  same  =  CO^. 

(b)  Glycolic  acid  (oxy-acetic  acid),  C2H20(OH)2,  does  not  occur  free  in  the  body.  One  of 
its  compounds,  glycin  (glycocoll,  amido-acetic  acid,  or  gelatin  sugar)  occurs  as  a  conjugate  acid, 
viz.,  as  glycocholic  acid  in  the  bile  (g  177,  2),  and  as  hippuric  acid  in  the  urine  (|  260).  Glycin 
exi^ts  in  complex  combination  in  gelatin. 

(c)  I^actic  Acid  (o.\y-propionic  acid),  C3H40(0H)2,  occurs  in  the  body  in  two  isomeric  forms : 
I.  The  etiiylidene-lactic  acid,  which  occurs  in  two  modihcations — as  the  right  rotary  sarcclactic  acid 
(paralactic),  a  metabolic  product  of  muscle;  and  as  the  ordinary  optically  inactive  product  of 
'•  lactic  fermentation,"  which  occurs  in  gastric  juice,  in  sour  milk  (sauerkraut,  acid  cucumber),  and 
can  be  obtained  by  fermentation  from  sugar  {\  184).  2.  The  isomer,  ethylene- lactic  acid,  occurs  in 
the  watery  extract  of  muscles  {\  293). 

(d)  Leucic  Acid  (oxy-caproic  acid),  CjHjjOj,  does  not  occur  as  such,  but  only  in  the  form  of 
one  of  its  derivatives,  leucin  (amido  caproic  acid),  as  a  product  of  the  metabolism  m  many  tissues, 
and  is  formed  during  pancreatic  digestion  \\  170,  II).  Leucic  acid  may  be  prepared  from  leucin, 
and  glycolic  acid  from  glycin,  by  the  action  of  nitrous  acid. 

(4)  Acids  of  the  Oxalic  Acid  or  Succinic  Acid  Series, having  the  formula  CiH2„.402 (OH),, 
are  bi-ba-ic  acids,  which  are  formed  as  completely  oxidized  products  by  the  oxidation  of  fatty  acids 
and  glycolic  acid,  water  being  removed ;  and  it  is  important  to  note  their  origin  from  substances 
rich  in  carbon,  e.  g.,  fats,  carbohydrates,  and  proteids. 

((?)  Oxalic  Acid,  C202(OH),,  arises  from  the  oxid.ition  of  glycol,  glycin,  cellulose,  sugar, 
starch,  glycerine,  and  many  vegetable  acids — it  occurs  in  the  urine  as  calcium  oxalate  (^  260). 

(b)  Succinic  Acid,  C4H^02(OH)2,  has  been  found  in  small  amount  in  animal  solids  and 
fluids  ;  spleen,  liver,  thymus,  thyroid  ;  in  the  fluids  of  echinococcus,  of  hydrocephalus,  and  of  hydro- 
cele, and  more  abundantly  in  dog's  urine  .after  fatty  and  flesh  food;  in  rabbit's  urine  after  feeding 
with  yellow  turnips.     It  is  also  formed  in  small  amount  during  alcoholic  fermentation  (\  150). 


THE    CARBOHYDRATES.  415 

(5)  Cholalic  Acids  in  the  bile  (|  177)  and  in  the  intestine  (§  182). 

(6)  Aromatic  Acids  contain  tiie  radicle  of  benzol.  Benzoic  acid  (=  phenylformic  acid) 
occurs  in  urine  united  with  glycin,  as  hippuric  acid  (J  260). 

III.  ALCOHOLS. — Alcohols  are  those  bodies  which  originate  from  carbohydrates,  in  which 
the  radicle  hydroxyl  (HO)  is  substituted  for  one  or  more  atoms  of  H.     They  may  be  regarded  as 

water,  „  >  O,  in  which  the  half  of  the  H  is  replaced  by  a  CH  compound.     Thus,  C^Hj  (ethyl- 
hydrogen)  passes  into    2     5  lo  (ethylic  alcohol). 

(«)  Cholesterin,      ^^u^^  l   O,  is  a  true  mon  atomic  alcohol,  and  occurs  in  blood,  yelk,  brain, 

bile  (§  177,  4),  and  generally  in  vegetable  cells. 
(OH 

(i)  Glycerine,  C3H5  \  OH,  is  a  tri-atomic  alcohol.     It  occurs  in  neutral  fats  united  with  fatty 
(OH 
acids  and  oleic  acid ;  it  is  formed   by  the  splitting  up   of  neutral  fats  during  pancreatic  digestion 
(g  170,  III),  and  during  alcoholic  fermentation  (J  150). 

(c)   Phenol  (^  phenylic  acid,  carbolic  acid,  oxybenzol)  (?  184,  III). 

(t/ j  Pyrokatechin  (^  dioxybenzol)  [^  252). 

(<r)  The  Sugars  are  closely  related  to  the  alcohols,  and  they  may  be  regarded  as  polyatomic 
alcohols.  Their  constitution  is  unknown.  Together  with  a  series  of  closely-related  bodies  they 
form  the  great  group  of  the  carbohydrates,  some  of  which  occur  in  the  animal  body,  while  others 
are  widely  distributed  in  the  vegetable  kingdom. 

252.  THE  CARBOHYDRATES.— These  substances,  which  occur  in  plants  and  animals, 
have  received  their  name,  because  in  addition  to  C  (at  least  6  atoms),  they  contain  H  and  O,  in  the 
proportion  in  which  these  occur  in  water.  They  are  all  solids,  chemically  indifferent,  and  without 
odor.  They  have  either  a  sweet  taste  (sugars),  or  can  be  readily  changed  into  sugars  by  the  action 
of  dilute  acids  ;  they  rotate  the  ray  of  polarized  light  either  to  the  right  or  left;  as  far  as  their  con-" 
stitution  is  concerned,  they  may  be  regarded  as  fatty  bodies,  as  hexatonic  alcoliols,  in  which  2H  are 
wanting. 

They  are  divided  into  the  following  group  : — 

1.  Division. — Glucoses  (CgHj20g)—(i)  Grape  sugar  (glucose,  dextrose,  or  diabetic  sugar) 
occurs  in  minute  quantities  in  the  blood,  chyle,  muscle,  liver  (?),  urine,  and  in  large  amount  in  the 
urine  in  diabetes  mellitus  (|  175).  It  is  formed  by  the  action  of  diastatic  ferments  upon  other 
carbohydrates,  during  digestion.  In  the  vegetable  kingdom,  it  is  extensively  distributed  in  the 
sweet  juices  of  many  fruits  and  flowers  (and  thus  it  gets  into  honey).  It  is  formed  from  cane  sugar, 
maltose,  dextrin,  glycogen,  and  starch,  by  boiling  with  dilute  acids.  It  crystallizes  in  warty  masses 
with  one  molecule  of  water  of  crystallization  ;  unites  w'lth  bases,  salts,  acids,  and  alcohols,  but  is 
easily  decomposed  by  bases;  it  reduces  many  metallic  oxides  (|  149).  Fresh  solutions  have  a 
rotatory  power  of  -|-  106°.  By  fermentation  with  yeast  it  splits  up  into  alcohol  and  CO,  (J  150) ; 
with  decomposing  proteids  it  splits  into  tw'O  molecules  of  lactic  acid  (^  184,  I);  the  lactic  acid  splits 
up,  under  the  same  conditions  in  alkaline  solutions,  into  butyric  acid,  COj  and  H.  For  the  qualita- 
tive and  quantitative  estimation  of  glucose,  see  ^  149  and  §  150.  In  alcoholic  solution,  it  forms 
very  insoluble  compounds  with  chalk,  barium,  and  potassium,  and  it  also  forms  a  crystalline  com- 
pound with  common  salt  (Estimation,  §  150). 

(2)  Galactose,  obtained  by  boiling  milk  sugar  (lactose)  with  dilute  mineral  acids;  it  crystallizes 
readily,  is  very  fermentable,  and  gives  all  the  reactions  of  glucose.  When  oxidized  with  nitric  acid 
it  becomes  transformed  into  mucic  acid.     Its  specific  rotatory  power  =  -]-  SS.o8°. 

(3)  Laevulose  (Icft-fruit-,  invert-,  or  mucin  sugar)  occurs  as  a  colorless  syrup  in  the  acid  juices 
of  some  fruits  and  in  honey ;  is  non-crystallizable,  and  insoluble  in  alcohol ;  specific  rotatory  power 
=  —  106°.  It  is  formed  normally  in  the  intestine  (^  183),  and  occurs  rarely  as  a  pathological  pro- 
duct in  urine. 

II.  Division  contains  carbohydrates  with  the  formula  C12H22O1  j,  and  which  may  be  regarded 
as  anhydrides  of  the  first  division — i.  Milk  sugar  or  lactose  occurs  only  in  milk,  crystallizes  in 
cakes  (with  i  molecule  of  water)  from  the  syrupy  concentrated  whey;  it  rotates  polarized  liglit  to 
the  right  =  -|-  59.3,  and  is  much  less  soluble  in  water  and  alcohol  than  grape  sugar.  When  boiled 
with  dilute  mineral  acids  it  passes  into  galactose,  and  can  be  'directly  transformed  into  lactic  acid 
only  by  fermentation  ;  the  galactose,  however,  is  capable  of  undergoing  the  alcoholic  fermentation 
with  yeast  (Kouniis  preparation,  J  232).  For  its  quantitative  estimation,  see  A/i/i  (^  231).  Rare 
in  urine  (^  267). 

2.  Maltose  (Cj  jH^oOjj)  -|-  H2O  (O'Sulliz'an)  has  I  molecule  of  water  less  than  grape  sugar 
(CjjH240,;),is  lomicd  during  the  action  of  a  diastatic  ferment,  such  as  saliva  upon  starch  (§  148) ; 
is  soluble  in  alcohol,  right  rotatory  power  =:  150°  ;  it  is  crystalline,  while  its  reducing  power  is  only 
two-thirds  that  of  dextrose. 

(3.  Saccharose  (cane  sugar)  occurs  in  sugar  cane  and  some  plants,  it  does  not  reduce  a  solution 
of  copper,  is  insoluble  in  alcohol,  is  right  rotatory,  and  not  capable  of  fermentation.     When  boiled 


416 


THE    CARBOHYDRATES. 


with  dilute  acids,  it  becomes  changed  into  a  mixture  of  easily  fermentable  glucose  (right  rotatory) 
and  laevulose  (invert  sugar,  |  183,  5,  and  ^  184,  I,  6),  which  ferments  with  difficulty  and  is  left 
rotatory  (|  183).     When  oxidized  with  nitric  acid,  it  parses  into  glucic  acid  and  oxalic  acid.) 

(4.  Meiitose,  from  Eucalyptus-manna  ;  Melezitose,  from  Larch-manna  ;  Trehalose  (Mycose), 
from  Ergot:  are  all  right  rotatory,  and  do  not  reduce  alkaline  cupric  solutions.) 

III.  Division  contains  carbohydrates,  with  the  formula,  CgHjoOj,  which  may  be  regarded  as 
anhydrides  of  the  second  division. 

1.  Glycogen,  with  a  rotatory  power  of  211°  [Bokm,  Hofmann,  Kiilz),  does  not  reduce  cupric 
oxide.  It  occurs  in  the  liver  (\  174),  muscles,  many  embryonic  tissues,  the  embryonic  area  of  the 
chick  {A'iih),  in  normal  and  pathological  epithelium  [Schiele) ;  in  diabetic  persons  it  is  widely  dis- 
tributed;  brain,  pancreas,  and  cartilage;  and  in  the  spleen,  pancreas,  kidney,  ovum,  brain,  and 
blood,  together  with  a  small  amount  of  glucose  (Pavy).  It  also  occurs  in  the  oyster  and  some  of 
the  molluscs  (Bizio),  and  indeed  in  all  tissues  and  classes  of  the  animal  kingdom. 

2.  Dextrin  was  discovered  by  Limpricht  in  the  muscles  of  the  horse.  It  is  right  rotatory  =  -|- 
138°,  soluble  in  water,  and  forms  a  very  sticky  solution,  from  which  it  is  precipitated  by  alcohol  or 
acetic  acid  ;  it  is  tinged  slightly  red  with  iodine.  It  is  formed  in  roasted  starch  (hence  it  occurs  in 
large  quantity  in  the  crust  of  bread — see  Bread,  \  234),  by  dilute  acids,  and  in  the  body  by  the 
action  of  ferments  (§  148).  It  is  formed  from  cellulose  by  the  action  of  dilute  sulphuric  acid.  It 
occurs  in  beer,  and  is  found  in  the  juices  of  most  plants. 

(3.  Amylum  or  Starch  occurs  in  the  "  mealy  "  parts  of  many  plants,  is  formed  within  vegetable 
cells,  and  consists  of  concentric  layers  with  an  excenlric  nucleus  (Fig.  2251.  The  diameter  and 
characters  of  starch  grains  vary  greatly  with  the  plant  from  which  they  are  derived,  as  indicated  in 
the  above  illustration.  At  72°  C.  it  swells  up  in  water  and  forms  mucilage  ;  in  the  cold,  iodine 
colors  it  blue.  Starch  grains  always  contain  more  or  less  cellulose  and  a  substance  which  is  colored 
red  with  iodine  (erythrogranuloss)  (J  14S).     It  sxiA  glycogen  are  transformed  into  dextrose  by  cer- 

FlG.  225. 


,  West  Indian  arrowroot  ; 


d.  Potato  starch. 


tain  digestive  ferments  in  the  saliva,  pancreatic  and  intestinal  juices,  and  artificially  by  boiling  with 
dilute  sulphuric  acid.) 

(4.  Gum,  CigH^oOjo,  occurs  in  veeetable  juices  (specially  in  acacias  and  mimosa),  is  partly 
soluble  in  water  (arabin),  partly  swells  up  like  mucin  (bassorin),  also  in  the  salivary  glands,  mucous 
tissue,  lungs,  and  urine.  Alcohol  precipitates  it.  It  is  fermentable,  and  when  boiled  with  dilute 
acids  yields  a  reducing  sugar.) 

(5.  Inulin,  a  crystalline  powder  occurring  in  the  root  of  chicory,  dandelion,  and  specially  in  the 
bulbs  of  the  dahlia  ;  it  is  not  colored  blue  by  iodine.) 

(6.  Lichenin  occurs  in  the  intercellular  substance  of  Iceland  moss  (Cetraria  islandica)  and  algre; 
is  transformed  into  glucose  by  dilute  sulphuric  acid.) 

(7.  Paramylum  occurs  in  the  form  of  granules  resembling  starch,  in  the  infusorian,  Euglena 
viridis.) 

(8.  Cellulose  occurs  in  the  cell  walls  of  all  plants  (in  the  exo-skeleton  of  arthropoda,  and  the 
skin  of  snakes) ;  soluble  only  in  ammonio-cupric  oxide ;  rendered  blue  by  sulphuric  acid  and  iodine. 
Boiled  with  dilute  sulphuric  acid,  it  yields  dextrin  and  glucose.  Concentrated  nitric  acid  mixed 
with  sulphuric  .acid  changes  it  (cotton)  into  nitro-cellulose  (gun  cotton)  C5H-(N02)305,  which 
dissolves  in  a  mixture  of  ether  and  alcohol  and  forms  coUodoin.) 

(9.  Tunicin  is  a  substance  resembling  cellulose,  and  occurs  in  the  integument  of  the  Tunicata 
or  Ascidians. ) 

IV.  Division  contains  the  carbohydrates  which  do  not  ferment. 

I.  Inosit  (phaseo-mannit,  muscle  sugar)  occurs  in  muscle  {Scherer^,  lung,  liver,  spleen,  kidney, 
brain  of  ox,  human  kidney ;  pathologically  in  urine  and  the  fluid  of  echinococcus.  In  the  vegetable 
kingdom,  in  beans  (leguminoss),  and  the  juice  of  the  grape.  It  is  an  isomer  of  grape  sugar; 
optically  it  is  inactive,  crystallizes  in  warts  with  two  molecules  of  water,  in  long  monoclinic  crystals; 
it  has  a  sweet  taste,  is  insoluble  in  water,  does  not  give  Trommer's  reaction,  is  capable  of  undergoing 


HISTORICAL.  417 

only  the  sarcolactic  acid  fermentation.     (Nearly  allied  are  Sorbin,  from  sorbic  acid — Scyllit,  from 
the  intestines  of  the  hag-fish  and  skate — and  Eukalyn,  arising  from  the  fermentation  of  melitose.) 

IV.  DERIVATIVES  OF  AMMONIA  AND  THEIR  COMPOUNDS.— The  am- 
monia derivatives  are  obtained  from  the  proteids,  and  are  decomposition  products  of  their  meta- 
bolism. 

(i)  Amines,  i.e.,  compound  ammonias  which  can  be  obtained  from  ammonia  (NHj),  or  from 
ammonium  hydroxide  (NH^ — OH  I,  by  replacing  one  or  all  the  atoms  of  H  by  groups  of  carbo- 
hydrates (alcohol  radicals).  The  amine  derived  from  cue  molecule  of  ammonia  is  called  monamine. 
\Ve  are  only  acquainted  with — 

H    )  CH3] 

H     I      X         Methylamine  and  Tri-Methylamine         CH3  V      N, 

chJ  chJ 

as  decomposition  products  of  cholin  (neurin)  and  of  kreatin.     Neurin  occurs  in  lecithin  in  a  very 
complex  combination  (see  Lecithin,  p.  414,  and  also  \  23). 

(2I  Amides,  i.  e.,  derivatives  of  acids,  which  have  exchanged  the  hydroxy!  (HO)  of  the  acids 
for  NHj.  Urea,  C0(XH2).,,  the  biamid  of  CO,,  is  the  chief  end  product  of  the  metabolism  of 
the  nitrogenous  constiluents  of  our  bodies  (see  Urine,  5  256).  Carbon  dioxide  containing  water 
=  CO(OH)2 :  in  it  both  OH  are  replaced  by  NH,— thus  we  get  COiNH^U,  urea. 

(3)  Amido  acids,  ;'.(■.,  nitrogenous  compounds,  which  show  partly  the  character  of  an  acid  and 
partly  that  of  a  weak  base,  in  which  the  atoms  of  H  of  the  acid  radicle  are  replaced  by  NH,,  or  by 
the  substituted  ammonia  groups. 

(«)  Glycin  (or  amido-acetic  acid,  glycocoll,  gelatin  sugar,  \  177,  2)  is  formed  by  boiling  gelatin 
with  dilute  sulphuric  acid.  It  has  a  sweet  taste  (gelatin  sugar),  behaves  as  a  weak  acid,  but  also 
unites  with  acids  as  an  amine  base.  It  occurs  as  glycin  4-  benzoic  acid  =  hippuric  acid  in  urine 
(|  260);  and  also  as  glycin  -f  cholalic  acid  =  glycocholic  acid  in  bile  (?  177).  {b)  Leucin — 
(I  170)  =  amido-caproic  acid,  (c)  Serin — (  ^  ?  amido-lactic  acid),  obtained  from  silk  gelatin. 
(d)  Asparaginic  acid— (amido-succinic  acid) ;  and  (c)  Glutaminic  acid,  obtained  by  the  splitting 
up  of  proteids  (\  170).  Other  amido  acids  are — if)  Cystin  =  amido-lactic  acid,  in  which  O  is 
replaced  by  S  (\  26S).  {g)  Taurin — {\  177),  amido-ethyl-sulphuric  acid  occurs  (except  in  certain 
glands)  chiefly  in  combination  with  cholalic  acid,  as  taurocholic  acid  in  bile.  Tyrosin  (parahydro- 
oxyphenylamido-propionic  acid),  an  amido  acid  of  unknown  constitution,  occurs  along  with  leucin 
during  pancreatic  dige.'-tion  (§  170),  is  a  decomposition  product  of  proteids,  and  occurs  plentifully 
in  the  urine  in  acute  yellow  atrophy  of  the  liver  [\  269). 

To  the  amido  acids  are  related  —  (al  Kreatin  in  muscle,  brain,  blnod,  urine,  regarded  as  methyl- 
uramido-acetic  acid  (C^HgNjO^).  It  has  been  prepared  artificially.  When  boiled  with  baryta 
water,  it  takes  up  H^O,  and  splits  into  urea — and  [b]  Sarkosin  (C3H-NO2),  methyl-amido-acetic 
acid.  When  boiled  with  water,  heated  with  strong  acids,  in  the  presence  of  putrefying  substances, 
kreaiin  gives  off  water,  and  is  changed  into  kreatinin  (C^HjNjO).  This  strong  base  can  be 
rechanged  by  alkalies  into  kreatin. 

(4)  Ammonia  Derivatives  of  Unknown  Constitution. — Uric  acid  (J  258) ;  allantoin 
(?  260)  is  formed  by  the  oxidation  of  uric  acid  by  means  of  potassium  permanganate;  cyanuric 
acid  in  dog's  urine;  inosinic  acid  in  muscle;  guanin  in  traces  in  the  liver  and  pancreas,  in 
guano,  the  excrements  of  spiders,  in  the  skin  of  amphibia  and  reptiles,  in  the  silver  .'^heen  of  many 
fishes  i^A.  E-vatd  and  Kriikenberg) ;  by  oxidation  it  yields  urea ;  hypoxanthin  or  sarkin  occurs 
along  with  xanthin  in  many  organs  and  in  urine.  Kossel  prepared  hypoxanthin  from  nuclein  by 
prolonged  boiling  of  the  latter.  It  may  be  obtained  from  fibrin  by  putrefaction,  by  gastric  and 
pancreatic  digestion,  and  by  dilute  acids  \SaIomon,  H.  Kratise,  Chittenden);  xanthin  is  prepared 
by  oxidation  from  hypoxanthin.  It  occurs  very  rarely  in  the  form  of  a  urinary  calculus.  Para- 
xanthin  in  urine,  and  a  similar  body,  carnin,  in  flesh  (J  233). 

Aromatic  Substances. —  i.  Monatomic  phenols — [a)  Phenol  (hydroxyl  of  benzol)  in  the 
intestine  (J  184).  Phenyl-sulphuric  acid  in  urine  {\  262).  (b)  Kresol,  in  the  form  of  orthokresol 
and  parakresol,  united  with  sulphuric  acid,  occur  in  urine  (^  262).  2.  Diatomic  phenols — («) 
pyrokatechin  united  with  sulphuric  acid  in  urine  (|  262).  3.  Aromatic  oxyacids — \a)  Hydyo- 
paracumaric  acid;  (b)  Paraoxyphenylacetic  acid  in  urine  (|  562).  4.  Indol  and  skatol  in  the 
intestine  (J  1S4),  conjoined  with  sulphuric  acid  in  urine  (^  262). 

253.  HISTORICAL  — According  to  Aristotle,  the  organism  requires  food  for  three  purposes — 
for  growth,  for  the  production  of  heat,  and  to  compensate  for  the  loss  of  the  bodily  excreta.  The 
formation  of  heat  takes  place  in  the  heart  by  a  process  of  concoction,  the  heat  so  formed  being 
distributed  to  all  parts  of  the  body  by  means  of  the  blood,  while  the  respiration  is  regarded 
as  an  act  whereby  the  body  i»  cooled.  Galen  accepted  this  view  in  a  somew  hat  modified  form ; 
according  to  him,  the  metabolic  processes  may  be  compared  to  the  processes  going  on  in  a  lamp  ; 
the  blood  represents  the  oil ;  the  heart,  the  wick  ;  the  lungs,  the  fanning  apparatus.  .According  to 
the  view  of  the  iatrochemical  school  {van  Helmont),  the  metabolic  processes  of  the  body  are  fer- 
mentations, whereby  the  food  is  mixed  with  the  juices  of  the  body.  Since  the  middle  of  the  seven- 
teenth century  (Boyle),  the  knowledge  of  the  metabolic  processes  has  followed  the  development  of 
chemistry.     A.  v.  Haller  regarded  heat  as  due  to  chemical  processes — the  food  continually  supplying 

27 


418  HISTORICAL. 

the  waste  which  is  excreted  from  the  body.  After  the  discovery  of  oxygen  (1774,  by  Priestley  and 
Scheele),  Lavoisier  formulated  the  theory  of  combustion  in  the  lungs,  whereby  carbonic  acid  and 
water  were  formed.  Mitscherlich  compared  the  decomposition  processes  in  the  living  body  with 
putrefactive  processes.  Magendie  was  the  first  to  emphasize  the  difference  between  nitrogenous 
and  non-nitrogenous  foods,  and  he  showed  that  the  latter  alone  were  not  able  to  support  life.  Even 
gelatin  alone  is  not  sufficient  for  this  purpose.  The  greatest  advance  in  the  theory  of  nutrition  was 
made  by  J.  v.  Liebig,  who  laid  the  foundation  of  our  present  knowledge  of  this  subject.  According 
to  Liebig,  foods  may  be  divided  into  two  classes,  viz.,  the  "plastic,"  suitable  for  the  construction 
of  the  organism,  and  the  "respiratory,"  for  the  maintenance  of  the  temperature;  to  the  former 
class  he  referred  the  albuminates  or  proteids,  to  the  latter,  the  non-nitrogenous  carbohydrates  and 
fats  (p.  3S9).  Among  recent  observers,  the  Munich  School,  as  represented  by  v.  Bischoff,  v.  Petten- 
kofer,  and  v.  Voit,  has  done  most  to  give  us  an  exact  knowledge  of  this  department  of  physiology. 


The  Secretion  of  Urine. 


254.  STRUCTURE  OF  THE  KIDNEY.— [Capsule.— The  kidney  is 

a  compound  tubular  gland,  and  is  invested  by  a  thin,  tough,  fibrous  capsule,  easily 
stripped  off  from  the  substance  of  the  organ,  to  which  it  is  attached  by  fine  pro- 
cesses of  connective  tissue  and  blood  vessels.] 

[Naked  Eye  Appearances. — On  dividing  the  kidney  longitudinally  from  the  hilum  to  its  outer 
border,  and  examining  the  cut  surface  with  the  naked  eye,  we  observe  the  parenchyma  of  the 


Boundary   layer 

of  medulla. 
Papillary  portion 

of  medulla.        j 


!;: 


section"! 
of      tubules       in  I  -. 
boundary  layer,    j 


1"  Labyrinth. 

i'  Medullary  rays. 


2        MEDULLA. 


isversely  "| 

iing  medullary  \ 


Longitudinal 


,gh  the  kidney  {Tyson,  after Henle). 


kidney,  consisting  of  an  outer  cortical  and  an  inner  medullary,  or  pyramidal  portion,  the  latter 
composed  of  about  twelve  conical  papillce,  or  Pyramids  of  Malpighi,  with  their  apices  directed 
toward  the  pelvis  of  the  organ,  and  embraced  by  the  calices  of  the  pelvis  of  the  kidney  (Fig.  226). 
The  medullary  portion  is  further  subdivided  into  the  boundary  layer  of  Ludwig  and  the  papillary 
portion.  According  to  Klein,  the  relative  proportions  of  these  three  parts  are — cortex,  3.5 ; 
boundary  layer,  2.5 ;  and  papillary  portion,  4.  The  cortex  has  a  light-brown  color,  and  when  torn, 
it  presents  a  slightly  granular  aspect,  with  radiating  lines  or  stri*  running  at  regular  distances.  The 
granules  are  due  to  the  presence  of  the  Malpighian  corpuscles,  and  the  stria;  to  the  medullary  rays.  The 

419 


420 


COURSE  AND  STRUCTURE  OF  THE  TUBULES. 


boundary  zone  is  darker,  and  often  purplish  in  color.  It  is  striated  with  clear  and  red  lines  alternating 
with  opaque  ones,  the  former  being  blood  vessels  and  the  latter  uriniferous  tubules.  The  papillary  zone 
is  nearly  white  and  uniformly  striated,  the  stri.c  converging  to  the  apex  of  the  pyramid.  The  me- 
dulla is  much  denser  and  less  friable  than  the  cortex,  owing  to  the  presence  of  a  large  amount  of 
connective  tissue  between  the  tubules.  The  bundles  of  straight  tubes  of  the  medulla  may  be  traced 
at  regular  intervals,  running  outward  into  the  cortex,  constituting  medullary  rays,  which  become 
smaller  as  they  pass  outward  in  the  cortical  zone,  so  that  they  are  conical,  and  form  the  pyramids 
of  Ferrein  (Kig.  227,  PF).  The  portion  of  the  cortex  lying  between  the  medullary  rays  is  known 
as  the  labyrinth,  from  the  complicated  arrangement  of  its  tubules.] 

[Size,  Weight. — The  adult  kidney  is  about  II  centimetres  (4.4  inches)  in  length,  5  centimetres 
(2  inches)  wide,  and  .75  centimetres  (.3  inches)  in  thickness,  It  weighs,  in  the  male,  1 13.5  to 
170  grms.  (4  to  6  oz.),  in  the  female,  113.  5  to  156  grms.  (4  to  Sj4  oz.).  The  width  of  the  cortex 
is  usually  5  to  6  millimetres  (^  to  ^  inch — Tyson).'] 

I.  The  uriniferous  tubules  all  arise  within  the  labyrinth  of  the  cortex  by 
means  of  a  globular  enlargement,  200   to   300  ix  \_Yhs  '°  tts  inch]  in  diameter, 


7l>     Correx 


Papillary  z 


Longitudinal  section  of  a  Malpighian  pyramid.  PF,  pyramids  of  Ferrein  ;  R.4,  branch  of  renal  artery;  RV,  lumen 
of  a  renal  vein  receiving  an  interlobular  vein  ;  VR,  vasa  recta  ;  PA,  apex  of  a  renal  papilla ;  6^  b,  embrace  the 
bases  of  the  renal  lobules. 

called  Bowman's  capsule  (^Figs.  228,  229),  and,  after  pursuing  a  complicated 
course,  altering  their  direction,  diameter  and  structure,  and  being  joined  by  other 
tubules,  they  ultimately  form  large  collecting  tubes,  which  terminate  by  minute 
apertures — visible  with  the  aid  of  a  hand  lens — on  the  apices  of  the  papilhu  pro- 
jecting into  the  calices  of  the  kidney.  Each  urinary  tubule  is  composed  of  a 
homogeneous  membrana  propria,  lined  by  epithelial  cells,  so  as  to  leave  a 
lumen  for  the  passage  of  the  urine  from  the  Malpighian  corpuscles  to  the  pelvis 
of  the  kidney.  The  diameter  and  direction  of  the  tubules  vary,  and  the  epithe- 
lium differs  in  its  characters  at  different  parts  of  the  tube,  while  the  lumen  also 
undergoes  alterations  in  its  diameter. 

Course  and  Structure  of  the  Tubules. — In  the  labyrinth  of  the  cortex, 
tubules  arise  in  the  spherical  enlargement  known  as  Bowman's  capsule  (Fig. 


COURSE    OF   THE   TUBULES. 


421 


228,  i),  which  invests  (in  the  manner  presently  to  be  described^  the  tuft  of  capil- 
lary blood  vessels  called  a  glomerulus  or  Malpighian  corpuscle.  By  means 
of  a  short  and  narrow  neck  (2)  the  capsule  becomes  continuous  with  a  convoluted 
tubule,  X  in  Fig.  229  {Bowinati).  This  tubule  is  of  considerable  length,  forming 
many  windings  in  the  cortex  (Fig.  228,  3) ;  the  first  part  of  it  is  4.5  /i  wide,  con- 
stituting \}iie.  proximal  ox  first  convoluted  tubule.  It  becomes  continuous  with  the 
spiral  tubule  of  Schachowa  (4),  which  lies  in  a  medullary  ray,  where  it  pursues  a 
slightly  wavy  or  spiral  course.     On  the  boundary  line  between  the  cortical  and 


13.  Straight  part  of  col- 
lecting tube. 

9.  Wavy  part  of  ascend- 
ing limb  of  Henle's 
loop. 

Inner  stratum  of  cortex 
without  Malpighian 
Corpuscles. 


nd  8.  Ascending  limb 
of  Henle's  loop 
tube. 


Sub-capsular  layei 
out  Malpighic 
puscles. 


First  part  of  <: 
ing  tube. 


CORTEX. 

Irregular  tubule 


Wavy  part  of  as- 
cending limb. 
Constriction  or  neck 
Spiral  tubule. 
Malpighian  tuft  sur- 
rounded by  Bow- 
man's capsule. 


8.  Spiral  part  of 
cending  limb 
Henle's  loop. 


B.  BOUNDARY 
ZONE. 

5.  Descending  limb  of 
Henle's  loop  tube. 


6.  Henle's  loop. 


Diagram  of  the  course  of  two 


boundary  zone,  the  spiral  tubule  suddenly  becomes  smaller  {Isaacs)  and  passes 
into  the  descending  portion  of  Henle's  loop  (5),  which  is  14  //  in  breadth,  and  is 
continued  downward  through  the  boundary  zone  into  the  medulla,  where  it  forms 
the  narrow  loop  of  Henle  (6),  which  runs  backward  in  the  medullary  part  to  the 
boundary  zone.  Here  it  becomes  wider  (  20-26  /i),  and  as  it  continues  its  undu- 
lating course,  it  enters  a  medullary  ray,  where  it  constitutes  the  ascending  loop 
////v  (7),  which  becomes  narrower   in    the  cortex.     Leaving   the   medullary   ray 


422 


COURSE   OF   THE   TUBULES. 


again,  it  passes  into  the  labyrinth,  where  it  forms  a  tube  with  irregular  angular 
outlines — the  irregular  tubule  (lo),  which  is  continuous  with  (Fig.  229,  n,  n)  the 
second  ox  distal  convoluted  tubule  or  intercalated  tubule  ("  Schaltstiick  "  of  Schweig- 
ger-Seidel)   (11),  which  resembles  the  proximal  tubule  of  the  same  name.     Its 


Fig.  229. 


I,  Blood  vessels  and  uriniferous  tubules  of  the  kidney  (semi-diagrammatic) ;  A,  capillaries  of  the  cortex,  B,  of  the 
medulla;  <i,  interlobular  artery;  t,  vas  afferens;  2.  vas  efferens ;  r,  e,  vasa  recta;  c,  venae  recta;  7',  »,  inter- 
lobular vein  ;  S,  origin  of  a  vena  stellata;  i,  i,  Bowman's  capsule  and  glomenilus  ;  X,  X,  convoluted  tubules;  t,  t, 
Henle's  loop  ;  «,  n,  junctional  piece  ;  o,  0,  collecting  tubes  ;  O,  excretory  tube. 

diameter  is  40  ix.  A  short,  narrow,  wayy  junctional  or  curved  collecting  tubule 
(12)  connects  the  latter  with  one  of  the  straight  collecting  tubes  (13)  of  a  medul- 
lary ray.  As  the  collecting  tubule  proceeds  through  the  boundary  zone,  it  receives 
numerous  junctional  tubes,  and  when  it  reaches  the  boundary  zone,  it  forms  one 


STRUCTURE  OF  THE  TUBULES. 


423 


of  the  collecting  tubes  (Fig.  229,  O),  which  unite  with  one  another  at  acute  angles 
to  form  the  larger  straight  excretory  tubes  or  ducts  of  Bellini  ( 15 ),  which  open  on 
the  summit  of  the  Malpighian  pyramids  into  a  calyx  of  the  pelvis  of  the  kidney. 
In  the  cortex  the  collecting  tubules  are  45  p.  in  diameter,  but  where  they  have 
formed  an  excretory  tube  (O),  their  diameter  is  200  to  300  n;  24  to  80  of  these 
tubes  open  on  the  apex  of  each  of  the  12  to  15  Malpighian  pyramids.  In  the 
lowest  and  broadest  part,  the  membrana  propria  is  strengthened  by  the  presence 
of  a  thick  supporting  framework  of  connective  tissue. 

Structure  of  the  Tubules. — [Below  the  neck,  the  tubules  are  lined  every- 
where by  a  single  layer  of  nucleated  epithelium.]  Bowman's  capsule, 
which  is  about  -j^^  inch  in  diameter  (Fig.  230,  II),  consists  of  a  homogeneous 
basement  membrane  lined  internally  by  a  smgle  continuous  layer  of  flattened 
cells  {li).  According  to  Roth,  the  basement  membrane  itself  is  composed  of 
endothelial  cells.  [In  the  fcjetus  the  lining  cells  are  more  polyhedral.]  Within 
the  capsule  lies  the  glomerulus  or  tuft  of  blood  vessels.  The  cells  lining  the  cap- 
sule are  reflected  over  and  between  the  lobules  of  which  the  glomerulus  consists. 
The  glomerulus  may  not  completely  fill  the  capsule,  so  that,   according  to  the 


11,  Bowman's  capsule  and  glomerulus,  t 
thelium  of  the  capsule;  k,  origin  of  a 
from  the  side,  with^,  inner  granular 
of  a  collecting  tube. — VI,  section  of  ; 


vas  afferens  ;  tf,  vas  efferens  ;  c,  capillary  network  of  the  cortex  ;  k,  endo- 
:onvoluted  tubule. — III,  '*  rodded"  cells  from  a  convoluted  tubule — 2,  seen 
jne  ;  i,  from  the  surface. — IV,  cell  lining  Henle's  looped  tubule. — V,  cells 
1  excretory  tube. 


activity  of  the  kidney,  there  may  be  a  larger  or  smaller  space  between  the 
glomerulus  and  the  capsule  into  which  the  filtered  urine  passes.  The  neck  is 
lined  by  cubical  cells.  These  cells,  in  some  animals,  e.g.,  the  rabbit,  sheep 
(^Hassal),  mouse  (Klein),  and  frog  are  ciliated. 

The  proximal  convoluted  tubule  is  lined  by  characteristic  epithelium.  The 
cells,  which  are  short  or  polyhedral,  form  a  single  layer,  with  a  turbid  or  cloudy 
protoplasm  (Fig.  230,  III,  i  and  2),  which  not  unfrequently  contains  oil  globules. 
The  cells  consist  of  two  parts  ;  the  inner,  containing  the  spherical  nucleus,  is 
next  the  lumen,  and  granular  (III,  2,  i,'),  while  the  outer  part,  next  the  membrana 
propria,  appears  fibrillated,  or  "rodded"  lyHeidenhain),  from  the  presence  of 
rods  (Stabchen)  or  fibrils  placed  vertically  to  the  basement  membrane  (Fig. 
231).  These  appear  like  the  hairs  of  a  brush  pressed  upon  a  plate  of  glass 
(III,  2).  The  cells  are  not  easily  separated  from  each  other,  as  neighboring 
cells  interlock  by  means  of  the  branched  ridges  on  their  surfaces  (III,  i) — {^Hci- 
denhain,  Schacliotva).  The  lumen  is  well  defined,  but  its  size  seems  to  depend 
upon  the  state  of  imbibition  of  the  cells  bounding  it. 


424 


BLOOD    VESSELS   OF   THE   CORTEX. 


Convoluted  tubule  (afte 


The  spiral  tubule  has  similar  epithelium  and  a  correspond- 
ing lumen,  altliough  the  epithelium  becomes  lower  and  somewhat 
altered  in  its  characters  at  the  lower  part  of  the  tube. 

The  descending  limb  of  Henle's  loop,  and  the  loop  itself 
with  a  relatively  wide  lumen,  are  bounded  by  clear,  flattened 
epithelial  cells,  with  a  bulging  nucleus  (IV,  .S) ;  the  cells  lying 
on  one  side  of  the  tube  being  so  jilaced  that  the  bulging  part  of 
tlie  bodies  of  the  cells  is  opposite  the  thin  part  of  the  cells  on 
the  opposite  side  of  the  tube.  [These  tubes  might  be  mistaken 
tor  blood  capillaries,  but  in  addition  to  their  squamous  lining, 
they  have  a  basement  membrane,  which  capillaries  have  not.] 
In  the  ascending  limb,  the  lumen  is  relatively  wide,  while 
Its  epithelium  agrees  generally  with  that  in  the  convoluted 
tubule,  e.xcepting  that  the  "rods"  are  shorter.  Sometimes 
the  cells  are  arranged  in  an  "  imbricate"  manner. 

In  the  irregular  tubule,  which  has  a  very  small  lumen, 
the  polyhedral  cells  lining  it  contain  oval  nuclei,  and  are 
shorter  than  those  of  the  convoluted  tubules.  The  cells, 
again,  are  very  irregular  in  size,  while  their  "rodded"  character 
is  much  coarser  and  more  defined  (Fig.  232). 

The    distal    convoluted    tubule    closely  resembles   in    its 

structure  the  proximal  convoluted  tubule,  and  is  lined  by  similar 

cells.     The  curved  collecting  or  junctional  tubule,  although 

narrow,  has  a  relatively  wide  lumen,  as  it  is  lined 

by  clear,  somewhat  flattened  cells. 

The  collecting  tubes  have  a  distinct  lumen, 
and  are  lined  by  clear,  somewhat  irregular,  cubi- 
cal cells  (Fig.  230,  V),  which,  in  the  larger  c.v- 
cretory  tubes,  are  distinctly  columnar  (^Vlj.  The 
basement  membrane  is  said  to  be  absent  in  the 
larger  tubes. 

[Klein  describes  a  tliir,  delicate,  nucleated  centro-tubiilar 
membrane  lining  ihe  surfaceof  the  epitlielium  next  the  lumen.] 

II.  The  Blood  Vessels. — The  renal  artery  (Fig.  226)  divides  into  four  or 

five  branches,  which  pass  into  the  kidney  at  the  hilum.  These  branches,  sur- 
rounded by  connective  tissue  continuous  with  that  of  the  capsule,  continue  to 
divide,  and  pass  between  the  papillae,  to  reach  the  bases  of  the  pyramids  on  the 
limits  between  the  cortical  and  boundary  zones,  where  they  form  incomplete 
arches.  From  these  horizontal  trunks  the  interlobular  arteries  (Fig.  229,  a) 
run  vertically  and  singly  into  the  cortex,  between  each  two  medullary  rays,  and 
in  their  course  they  give  off  on  all  sides  the  short,  undivided  vasa  afferentia 
(i),  each  of  which  enters  a  Malpighian  capsule  at  the  opposite  pole  from  which 
the  urinary  tubule  is  given  off.  Within  the  capsule,  each  afferent  artery  breaks 
up  into  capillaries  arranged  in  lobules  and  supported  by  connective  tissue,  the 
whole  forming  a  tuft  of  capillary  blood  vessels,  or  a  glomerulus.  Each  glom- 
erulus is  covered  on  its  surface,  directed  toward  the  wall  of  the  capsule  by  a  layer 
of  flat,  nucleated  epithelial  cells  (Fig.  230,  II),  which  also  dip  down  between  the 
capillaries  {Heidenliain,  Runeberg).  A  vein,  the  vas  efferens  (2),  which  is 
always  smaller  than  the  afferent  arteriole,  proceeds  from  the  centre  of  the  glom- 
erulus, and  leaves  the  capsule  close  to  the  point  at  which  the  afferent  vessel  enters 
it  (Fig.  230,  II).  In  their  structure  and  distribution  all  the  efferent  vessels  re- 
semble arteries,  as  they  divide  into  branches  to  form  a  dense,  narrow-meshed 
capillary  network  (Fig.  229,  A,  and  Fig.  230,  II,  c'),  which  surrounds  and 
ramifies  over  the  convoluted  tubules.  The  meshes  are  elongated  around  the  tubules 
of  the  medullary  rays,  and  more  polygonal  around  the  convoluted  tubules  (^Fig. 


LYMPHATICS,  NERVES,  CONNECTIVE   TISSUE.  425 

229).  Some  of  the  lowest  efferent  vessels  split  up  into  vasa  recta,  which  run 
toward  the  medulla.  The  interlobular  arteries  become  smaller  as  they  pass  toward 
the  surface  of  the  kidney,  and  some  of  their  terminal  capillaries  communicate 
with  the  capillaries  of  the  external  capsule  itself.]  Venous  trunks  proceed  from 
the  capillary  network,  to  terminate  in  the  interlobular  veins  (V).  These  veins 
begin  close  under  the  external  capsule  by  venous  radicles  arranged  in  a  stellate 
manner  (constituting  the  stelluls  Verheynii,  or  venae  stellatae),  and  accompany 
the  corresponding  artery  to  the  limit  between  the  cortex  and  boundary  zone, 
where  they  communicate  with  the  large  venous  trunks  in  that  situation. 

The  blood  vessels  of  the  medulla  arise  from  the  vasa  recta  (Fig.  229,  r). 
The  latter  begin  on  the  limit  of  the  cortex  and  medulla,  either  as  single,  direct, 
muscular  branches  (/')  of  the  large  arterial  trunks,  or  from  those  efferent  vessels 
(<")  which  lie  next  to  the  medulla.  The  latter  are  said  to  be  devoid  of  muscle; 
while,  according  to  Huschke,  a  few  vasa  recta  are  formed  by  the  union  of  the 
capillaries  of  the  medullary  rays.  All  the  vasa  recta  enter  the  boundary  layer, 
where  they  split  up  into  a  leash  or  pencil  of  small  arterioles,  which  pass  between 
the  straight  tubules  toward  the  pelvis,  and  form  in  their  course  a  capillary  network 
with  elongated  meshes.  From  these  capillaries  there  arise  venous  radicles,  which, 
as  they  proceed  toward  the  limit  between  the  cortex  and  medulla,  form  the  venae 
recta  (<},  and  open  into  the  concave  side  of  the  venous  trunks  in  this  region. 
At  the  apex  of  the  papillre,  the  capillaries  of  the  medulla  form  connections  with 
the  rosette-like  capillaries  surrounding  the  excretory  ducts  (at  I).  [The  circula- 
tion through  the  vasa  recta  is  most  important.  The  cortical  system  of  blood 
vessels  communicates  with  the  medullary,  but  as  most  of  the  vasa  recta  are  derived 
from  the  same  vessel  as  the  interlobular  arteries,  it  is  evident  that  they  may  form 
a  side  stream  through  which  much  of  the  blood  may  pass  without  traversing  the 
vessels  of  the  cortex.  Very  probably  the  "short  cut  "  is  useful  in  congestions  of 
the  kidney.  The  amount  of  distention  of  these  vessels,  also,  will  influence  the 
size  of  the  tubules  lying  between  them.  There  are  two  other  channels  by  which 
blood  can  pass  through  the  renal  arteries  without  traversing  the  glomeruli — (i) 
The  anastomoses  between  the  terminal  twigs  of  the  renal  artery  and  the  sub- 
capsular venous  plexus  ;  (2)  small  branches  given  off,  either  by  the  interlobular 
arteries,  or  by  the  afferent  vessels  before  entering  the  glomeruli  (^Bninton).'\ 

The  blood  vessels  of  the  external  capsule  are  derived  partly  from  the  terminal  twigs  of  the 
interlobular  arteries,  partly  from  branches  of  the  supra-renal,  phrenic  and  lumbar  arteries,  which 
anastomose  with  each  other.  The  capillary  network  has  simple  meshes.  The  origins  of  the  veins 
pass  partly  into  the  ven^  stellatai  and  partly  into  the  veins  of  the  same  name  as  the  arteries.  The 
connection  of  the  area  of  the  renal  artery  with  the  other  arteries  of  the  capsule  explains  why,  after 
ligature  of  the  renal  artery  within  the  kidney,  the  blood  still  circulates  in  the  external  capsule  (C. 
Liidwig,  M.  Herrmann)  ;  in  fact,  these  blood  vessels  still  supply  the  kidney  with  a  small  amount 
of  blood,  which  may  suffice  to  permit  a  slight  secretion  of  urine  to  take  place  (Li/len,  Pautynski). 

III.  The  lymphatics  form  a  wide-meshed  plexus  in  the  capsule  of  the  kidney,  while  under  it 
they  form  large  spaces  (Heidenliain).  In  the  parenchyma  of  the  kidney,  the  lymphatics  are  said 
to  be  represented  by  large  slits,  devoid  of  a  wall,  in  the  tissues,  and  are  more  numerous  around  the 
convoluted  than  the  straight  tubules.  The  slits  pass  to  the  surface  of  the  kidney,  and  expand  under 
the  capsule.  When  the  lymphatics  are  greatly  distended,  they  tend  to  compress  the  uriniferous  tubules 
and  the  blood  vessels  (C.  Lmiung  and  Zawarykin).  According  to  Ryndowsky,  the  uriniferous 
tubules  are  surrounded  by  true  lymphatics  with  an  endothelial  lining,  and  they  even  penetrate  into 
the  capsule  of  Bowman,  along  with  the  vas  aflerens.  [The  large  blood  vessels  are  also  surrounded 
by  lymphatics.]  Large  lymphatics,  provided  wiih  valves,  pass  out  of  the  kidney  at  the  hilum,  while 
others  emerge  through  the  capsule ;  both  sets  are  connected  with  the  lymph  spaces  of  the  capsule  of 
the  kidney  (.-?.  Budge). 

IV.  The  nerves  form  small  trunks  provided  with  ganglia  [Beale],  and  accompany  the  blood 
vessels.  [They  are  derived  from  the  renal  plexus  and  the  lesser  splanchnic  nerve.]  They  contain 
medullated  and  non-medullated  fibres,  and  the  latter  have  been  traced  by  \V.  Krause  as  far  as  the 
apices  of  the  papillce.  Their  mode  of  termination  is  unknown.  Physiologically,  we  are  certain  that 
they  contain  both  vaso-motor  and  sensory  fibres;  perhaps  there  may  be  also  vaso-dilator  and  secretory 
fibres. 

V.  The  connective  tissue,  or  interlobular  stroma,  forms  in  the  papillae,  especially  at  their 
pices,  fibrous,  concentric  layers  of  considerable  thickness  between  the  excretory  tubules  (Fig.  233). 


426 


PHYSICAL   CHARACTERS   OF   URINE. 


Further  outward,  the  fibrillar  character  becomes  less  distinct,  while  at  the  same  time  branched 
connective-tissue  corpuscles  occur  in  greater  numbers  (Beer).  In  the  cortex,  the  interstitial  stroma 
consists  almo^t  entirely  of  branched  corpuscles,  which  anastomose  with  each  other  ( Gooi/siy).  [There 
is  also  a  small  quantity  of  delicate  fibrous  tissue  around  Bowman's  capsule,  and  along  the  course  of 
the  arteries.  The  connective  tissue  often  plays  an  important  role  in  pathological  conditions  of  the 
kidney,  as  in  interstitial  nephritis.]  The  outer  layers  of  the  capsule  of  the  kidney  are  composed 
of  dense  bundles  of  fibrous  tissue,  while  the  deeper  layers  are  more  loose,  and  send  processes  into 
the  cortical  layers.  The  deeper  layers  also  contain  non-striped  muscular  fibres  [EliertJi,  IT.  A'raiise). 
The  capsule  is  easily  stripped  off.  None  of  the  secretory  substance  is  removed  with  it.  Under  the 
capsule  in  the  human  kidney,  there  is  a  thin  ple.\us  of  nonslriped  muscular  fibres.  At  the  hilum 
it  becomes  continuous  with  the  outer  fibrous  coat  of  the  dilated  upper  end  of  the  ureter.  The  faf 
surrounding  the  kidney  is  united  to  the  kidney  partly  by  blood  vessels  and  partly  by  bands  of 
connective  tissue.  [The  sub-capsular  layer  of  the  corte.x,  and  a  thin  layer  next  the  boundary  zone 
(Fig.  228,  a,  a),  are  devoid  of  Malpighian  corpuscles.] 

[Development  of  a  Malpighian  Capsule. — The  upper  end  of  the  urinary  tubule  is  dilated 
and  closed,  and  into  it  there  grows  a  tuft  of  blood  vessels  (a),  pushing  one  layer  of  the  tube  before 
it  (b) ;  hence  the  capillaries  become  invested  by  it,  just  as  an  organ  is  surrounded  by  a  serous  sac, 
so  that  one  layer — the  reflected  one  (b)- — of  the  tubule  is  closely  applied  to  the  blood  vessels,  while 
the  other  [c)  lies  loosely  over  it  with  a  space  between  the  two  (Fig.  234).] 


Fig.  2J3. 


.'^^,^^ 


^^ 


/ 


^\ 


section  of  apex  of  aMa,lpighian  pyramid.     «,  large  collecting 
tubes;  i,  c,  d,  tubules  of  Henle;  e^/,  blood  capillaries. 


Fig.  234. 


Development  of  a  glomerulus  and 
Malpighian  capsule,  a,  capil- 
lary; (^.visceral;  c, parietal  layer 
of  capsule. 


255.  THE  URINE.— Physical  Characters.— A  knowledge  of  the  com- 
position of  this  secretion  is  of  the  greatest  value  to  the  physician  and  surgeon. 

I.  The  quantity  of  urine  passed  by  an  adult  man  in  twenty-four  hours  is 
between  1000  and  1500  cubic  centimetres,  or  about  50  02s.,  and  in  the  female 
900  to  1200  c.c.  The  minimum  is  secreted  between  2-4  a.m.,  and  the  maximum 
between  2-4  p.m.  {IVeigelin). 

The  amount  is  diminished  by  profuse  sweating,  diarrhoea,  thirst,  non-nitrogenous  food,  diminu- 
tion of  the  general  blood  pressure,  after  severe  hemorrhage,  and  in  some  diseases  of  the  kidneys. 
The  minimum,  which  may  be  normal,  is  400  to  500  c.c.  It  is  increased  by  increase  of  the  general 
blood  pressure,  or  of  the  pressure  within  the  area  of  the  renal  artery,  by  copious  drinking,  contrac- 
tion of  the  cutaneous  vessels  through  the  action  of  cold,  the  passage  of  a  large  amount  of  soluble 
substances  (urea,  salts,  and  sugar)  into  the  urine,  a  large  amount  of  nitrogenous  food,  as  well  as  by 
various  drugs,  such  as  digitalis,  alcohol,  squills.  After  taking  fluids  charged  with  CO^,  the  amount 
of  urine  is  increased  during  the  following  hours  f  Quincke). 

The  secretion  is  influenced  directly  by  the  nervous  system,  as  in  the  sudden  polyuria  following 
nervous  excitement,  such  as  hysteria  [when  the  person  usually  passes  a  large  amount  of  very  pale- 
colored  urine];  after  an  epileptic  attack,  and  also  after  pleasurable  excitement  (Beneii-).     Lastly, 


ESTIMATION   OF   SOLIDS. 


427 


we  have  the  polyuria  unaccompanied  by  the  presence  of  sugar  in  the  urine,  which  follows  injur)-  to 
a  certain  pari  of  the  floor  of  the  fourth  ventricle  (C/.  BeritaiJ).  The  urine  is  measured  in  tall, 
graduated,  cylindrical  vessels  (P"ig.  235,  A).  [In  estimating  the  quantity  of  urine  passed,  the  patient 
must,  of  course,  be  directed  always  to  empty  his  bladder  at  a  particular  hour,  and  collect  the  urine 
passed  during  the  next  twenty-four  hours.] 

2.  The  specific  gravity  varies,  as  a  mean,  between  1015  and  1025  ;  the 
minimum,  after  copious  draughts  of  water,  may  be  1002  ;  while  the  maximum, 
after  profuse  perspiration  and  great  thirst,  may  be  1040.  The  mean  specific  gravity 
is  about  1020.  In  newly-born  children,  the  specific  gravity  falls  very  considerably 
during  the  first  three  days,  which  is  due  to  the  ingestion  of  a  large  amount  of 
food  (^Martin  and  Huge).  [The  specific  gravity  of  the  urine  in  infants  is  about 
1003  to  1006.]  A  healthy  adult  excretes  about  50  grms.  \_1j2  oz.]  daily  of  solids 
by  the  urine,  or  about  i  grm.  of  solids  per  i  kilo,  of  body  weight. 

The  specific  gravity  is  estimated  by  means  of  a  urinometer  (Fig.  235,  B),  the  urine  being  at 
the  temperature  of  16°  C.  [The  urinometer,  when  placed  in  distilled  water,  ought  to  float  at  the 
mark  0°  or  zero,  which  is  conventionally  spoken  of  as  1000.  The  urine  itself  ought  to  be  tested  in  an 
tall  cylindrical  glass,  of  such  width  that  the  urinometer,  when  placed  in  it,  may  float  freely  and  not 
touch  the  sides.  Take  care  that  no  air  bubbles  adhere  to  the  instrument.  When  reading  oft'  the 
mark  on  the  stem,  raise  the  vessel  to  the  eye  and  bring  the  eye  on  a  level  with  the  surface  of  the 
water,  noting  the  number  which  corresponds  to  this.  This  rule  is  adopted,  because  the  water  rises 
on  the  stem  in  virtue  of  capillarity.  It  is  essential  that  a  sample  of  the  mixed  urine  of  the  twenty- 
four  hours  be  used  for  ascertaining  the  mean  specific  gravity.] 

Cbristison's  Formula. — To  estimate  the  amount  of 
solids   in   the   urine.     This  maybe  done  approximately  clG.  235. 

by  means  of  the  formula  of  Trapp  or  Haeser,  or,  as  it 
is  called  in  this  country,  "  Cbristison's  formula,"  viz  , 
"  Multiply  the  two  last  figures  of  a  specific  gravity  ex- 
pressed in  four  figures  by  2.33  "  (  Christison  and  Haeser), 
or  by  2  [Trapp),  or  2.2  yLoebisch).  This  gives  the 
amount  of  solids  in  every  1000  parts.  [Suppose  a  person 
passes  1200  c.  c.  urine  in  twenty-four  hours,  and  specific 
gravity  is  1022,  then 

22  X  '^■H  =  51.26  grms.  in  locxj  c.  c. 
To  ascertain  the  amount  in  1200  c.  c. 

51.26  X  1200 


1000:  1200:  :  51.26  :  X  = 


=  61.51  grms.] 


1000 

Direct  estimation  to  determine  the  exact  amount 
of  solids.  Place  15  c.  c.  of  urine  in  a  capsule  of  known 
weight,  and  evaporate  it  over  a  water  bath,  afterward 
completely  dry  the  residue  in  an  air  bath  at  100°  C, 
and  then  cool  it  over  concentrated  sulphuric  acid. 
During  the  process,  a  small  amount  of  urea  is  decom- 
posed, so  that  the  value  obtained  is  slightly  too  small. 
Of  course,  the  specific  gravity  varies  with  the  amount  of 
water  in  the  urine.  The  mos/  concentra/eJ  (highest  spe- 
cific gravity)  urine  is  the  morning  urine  (Urina  noctis), 
especially  after  being  retained  in  the  t)ladder,  e.g.,\n 
prolonged  sleep  a  certain  amount  of  water  is  absorbed,  so 
that  the  urine  becomes  more  concentrated.  The  most 
dilute  urine  is  secreted  after  copious  drinking  (Urina 
potus).  Under  pathological  conditions,  as  in  diabetes 
mellitus  (J  '75),  the  urine  is,  at  the  same  time,  very 
copious  (as  much  as  10,000  c.  c),  and  very  concentrated, 
while  the  specific  gravity  varies  from  1030  to  1060.  [The 
high  specific  gravity  in  this  case  is  due  to  the  presence  of 
a  large  amount  of  grape  sugar.]  In  fever  the  urine  is 
concentrated,  and  small  in  amount.  In  polyuria,  due  to 
certain  nervous  conditions,  the  urine  is  very  dilute  and 
copious,  while  the  specific  gravity  may  be  as  low  as 
lOOI. 

3.  The  color  of  the  urine  depends  on  the 
coloring  matters  present  in  it,  and  varies 
greatly,  but  the  differences  in   color  are  due 


toot 


_10l» 


lOlil 


lOSI 


428 


AMOUNTS   OF   URINARY   CONSTITUENTS. 


chiefly  to  the  variations  in  the  amount  of  water.  Normally,  it  has  a  pale  straw 
color,  but  if  it  contains  more  water  than  usual  it  has  a  very  pale  tint,  and  in 
certain  cases  (as  in  the  sudden  polyuria  occurring  after  an  attack  of  hysteria),  it 
may  be  as  clear  as  water.  Concentrated  urine,  as  after  meals,  or  the  first  urine 
passed  in  the  morning,  has  a  darker  color ;  it  is  a  dark-yellow  or  brownish-red  ; 
while  it  is  usually  dark  colored  in  fever. 

Foetal  urine,  and  also  the  urine  first  passed  after  birth,  are  as  clear  and  colorless  as  water.  The 
admixture  of  various  substances  with  the  urine  alters  its  color.  When  mixed  with  blood,  according 
to  the  degree  of  decomposition  of  the  haemoglobin,  the  urine  is  red  or  dark  brownish-red 
[more  frequently  it  is  jwoir],  especially  if  the  blood  comes  from  the  kidneys  and  the  urine  is 
acid.  When  mixed  with  bile  pigments,  it  is  of  a  deep  yellowish-brown,  with  an  intense  yellow 
froth ;  senna  taken  internally  makes  it  intensely  red,  rhubarb  brownish-yellow,  and  carbolic  acid 
black.  Urine  undergoing  the  ammoniacal  fermentation  may  present  a  dirty,  bluish  appearance 
owing  to  the  formation  of  indigo.  The  color  of  urine  is  estimated  by  Neubauer  and  Vogel  by 
means  of  an  empirical  "  color  scale." 


[Amounts  i 


Urinary  Constituents  {Loebisck). 


Quantity, 

Specific  gravity, 

Water, 

Solids, 

Urea,       

Uric  acid, 

Sodium  chloride, 

Phosphoric  acid, 

Sulphuric  acid, 

Phosphorus,  Calcium 

Magnesium   phosphate,    .    .    . 
Total  quantity   of    earthy  phos- 
phates,     

Ammonia, 

Free  acid 


Man,  28  years  of  age,  weight  72  kilos.,  observations 
over  8  days  (Kernes). 


1099 
lOIS 


32.00 
0.69 

15.00 
3.00 
2.26 
0.25 
0.67 

0.92 
0.74 

1-74 


43  4 
1-37 

19.20 
4.07 
2.84 
0.51 
1.29 

I. So 


1491 
1021 


38.1 
0.94 

16.8 
3-42 
2.48 
0.38 
0.97 

1-35 
0.83 

••95 


Means  of 
analyses  in 

different 
individuals. 

{.yogel.) 


In  24  hours. 


C.  C. 

1500 

1020 

1440 

60 

35 
0.73 
16.S 

3-S 
2.0 


0.65 
3      ] 


[Amounts  of  the  Several  Urinary  Co 


24  Hours  {Parkes). 


Constituents. 


Water, 

Total  solids, 

Urea, 

Uric  acid, , 

Hippuric  acid, , 

Kreatinin, , 

Pigment  and  other  substances, 

Sulphuric  acid, 

Phosphoric  acid, , 

Chlorine, 

Ammonia, 

Potassium, 

Sodium, 

Calcium, , 

Magnesium, 


By  an  average   man  of 

Per  I  kilo,  of  body 

66  kilos. 

weight. 

grms. 

grms. 

1500.000 

23.000 

72.000 

1. 100 

33- '80 

0.500 

0-55S 

0.0084 

0.400 

0.0060 

0.910 

0.0140 

10.300 

0.1510 

2.012 

0.0305 

3.164 

0.048b 

7.000(8.12) 

0.1260 

0.770 

2.500 

1 1 .090 

0.260 

0.207 

.    .    .    ] 

REACTION    OF    URINE. 


429 


Fig.  256. 


Fluorescence. — Urine,  but  especially  ammoniacal  urine,  exhibits  fluorescence,  which  disappears  on 
the  additiun  uf  an  acid,  and  reappears  after  the  addition  of  an  alkali  [Sc/ioiilifin,  Scileiss,v.  L'dwenffld  ). 

Mucous  Cloud. — Normal  urine,  after  standing  for  several  hours,  deposits  a  fine  cloud  of  vesical 
mucus  [like  delicate  cotton  wool].  The  froth  of  normal  urine  is  white,  and  disappears  pretty  rap- 
idly, while  that  on  an  albuminous  urine  persists  much  longer.  The  urine  not  unfrequently  contains 
some  epithelial  cells  from  the  bladder  and  urethra. 

4.  Consistence. — Normal  urine,  like  water,  is  a  freely  mobile  fluid. 

Large  quantities  of  sugar,  albumin,  or  mucus  make  it  less  mobile;  while  the  so-called  chylous 
urine  of  warm  climates  may  be  like  a  white  jelly. 

5.  The  taste  is  a  saline  bitter,  the  odor  is  characteristic  and  aromatic. 
Ammoniacal  urine  has  the  odor  of  ammonia.     Turpentine  taken  internally  gives  rise  to  the  odor 

of  violets,  copaiba  and  cubebs  a  strongly  aromatic,  and  asparagus  an  unpleasant  odor.  Valerian, 
assafoetida,  and  castoreum  [but  not  camphor]  also  produce  a  characteristic  odor.  [The  odor  of 
diabetic  urine  is  described  as  "  sweet."  ] 

6.  The  reaction  of  normal  urine  is  acid,  owing  to  the  presence  of  acid  salts, 
chiefly  acid  sodic  phosphate,  which  seems  to  be  derived  from  basic  sodic  phos- 
phate, owing  to  the  uric  acid,  hippuric  acid,  sulphuric  acid,  and  CO,  taking  to 
themselves  part  of  the  soda,  so  that  the  phosphoric  acid  forms  an  acid  salt. 
After  a  diet  of  flesh,  acid  potassic  phosphate  is  the  cause  of  the  acidity.  That 
the  urine  contains  no  free  acid  is  proved  by  the  fact  that  it  gives  no  precipitate 
with  sodic  hyposulphite  {v.   Voif,  Huppert^. 

The  acid  reaction  is  increased  after  the  use  of 
acids,  <'.^.,  hydrochloric  and  ])hosphoric,  also  by 
ammoniacal  salts,  which  are  changed  within  the 
body  into  nitric  acid  ;  lastly,  after  prolonged  mus- 
cular exertion  {Kliipfel,  Fustier).  The  morning 
urine  is  strongly  acid. 

The  urine  becomes  less  acid  or  alkaline — 
fl)  By  the  use  of  caustic  alkalies,  alkaline  car- 
bonates, or  alkaline  salts  of  the  vegetable  acids, 
the  last  being  oxidized  within  the  body  into  car- 
bonates. (2)  By  the  presence  of  calcic,  or  roag- 
nesic  carbonate.  {3)  By  admixture  with  alkaline 
blood,  or  pus.  (4)  By  removing  the  gastric  juice 
through  a  gastric  fistula  (p.  272 — Maly) ;  further, 
from  one  to  three  hours  after  a  meal  [The  reac- 
tion of  urine  passed  during  digestion  may  be 
neutral,  or  even  alkaline.  This  is  due  either  to 
the  formation  of  acid  in  the  stomach  (Hence 
Jones),  or  to  a  fixed  alkali  derived  from  the  basic 
alkaline  phosphates  taken  with  the  food  ( /T.  Jfob- 
erts).'\  (5)  The  urine  is  rarely  alkaline  in  anxmia, 
owing  to  a  deficiency  of  phosphoric  and  sulphuric 
acids.  [(6)  The  nature  of  the  food — vegetable 
food  makes  it  alkaline.  (7)  By  profuse  sweating 
(Jos.  Hofmann).  (8)  By  absorption  of  alkaline 
transudations  (blood  serum),  Quincke.'\ 

Method. ^[The  reaction  of  urine  is  tested  by 
means  of  litmus  paper.  Normal  urine  turns  blue 
litmus  paper  red,  and  does  not  affect  red  litmus. 
An  alkaline  urine  makes  red  litmus  paper  blue, 
while  a  neutral  urine  docs  not  alter  either  blue  or 
red  litmus  paper.]  Sometimes  violet  litmus  paper 
is  used,  which  becomes  red  in  acid,  and  blue  in 
alkaline  urine. 

Estimation  of  the  Acidity. — This  is  done  by 
determining  the  amount  of  caustic  soda  necessary 
to  produce  a  neutral  reaction  in  100  c.c.  of  urine. 
A  soda  solution  containing  0.0031  grm.  of  soda    ~-^^ 
in  each  c.c.  is  used  ;   i  c.c.  of  this  solution  exactly      ^ 
neutralizes  0.0063  g''™'  oxalic  acid.     To  the   lot' 
c.c.  of  urine  in  a  beaker,  soda  solution  is  added, 
drop  by  drop,  from  a  graduated  burette  (Fig.  236),  === 
until  violet  litmus  paper  becomes  neither  red  nor 


Graduated  burette. 


430 


QUANTITY   OF   UREA. 


blue.  The  number  of  c.c.  of  soda  solution  is  now  read  off  on  the  burette,  and  as  each  c.c.  corres- 
ponds to  0.0063  grm.  oxalic  acid,  we  can  easily  calculate  the  amount  of  oxalic  acid  which  is  equiv- 
alent to  the  degree  of  acidity  in  100  c.c.  of  urine.  So  that  the  degree  of  acidity  of  the  urine  is 
expressed  by  the  equivalent  amount  of  oxalic  acid,  which  is  completely  neutralized  by  the  same 
amount  of  caustic  soda. 

Urine  of  Mammals. — The  urine  of  carnivora  is  pale,  passing  into  a  golden  yellow  ;  its  specific 
gravity  is  high,  and  its  reaction  strongly  acid.  The  urine  of  herbivora  is  alkaline  ;  it  shows  a  pre- 
cipitate of  earthy  carbonates  (hence,  it  effervesces  on  the  addition  of  an  acid),  and  of  basic  earthy 
phosphates.  During  hunger,  the  urine  presents  the  character  of  that  of  carnivora,  as  the  animal  in 
this  case  practically  lives  upon  its  o\\n  flesh  and  tissues. 

256.— I.  THE  ORGANIC  CONSTITUENTS  OF  URINE.— Urea 
=  CO(NH2\. — Urea,  the  diamide  of  CO.,,  or  carbamide,  is  the  chief  end 
product  of  the  o.xidation  of  the  nitrogenous  constituents  of  the  body.  Its  com- 
position is  comparatively  simple  :  1  carbonic  acid  -)-  2  ammonia  —  i  water.  It 
crystallizes  in  silky,  four-sided  prisms  with  oblique  ends  (rhombic  system),  with- 
out water  of  crystallization  (Fig.  237,  a),  but  when  it  crystallizes  rapidly  it  forms 
delicate  white  needles.  It  has  no  action  on  litmus,  is  odorless,  and  has  a  weak, 
bitter,  cooling  taste,  like  saltpetre  ;  is  readily  soluble  in  water  and  alcohol,  but 
insoluble  in  ether.     It  is  an  isomer  of  amnionic   cyanate,  from  which  it  may  be 


Fig 


a.  Urea ;  i,  hexagonal  plates  ;  and 


prepared  by  evaporation  (  IVohler,  1828),  whereby  the  atoms  rearrange  themselves. 
It  can  be  prepared  artificially  in  many  other  ways. 

Decomposition. — When  heated  above  120°,  it  gives  off  ammonia  vapor,  while  a  glassy  mass  of 
biuret  and  cyanic  acid  is  left.  When  urine  undergoes  the  alkaline  fermentation  (J  263),  or  when 
urea  is  treated  with  strong  mineral  acids,  or  boiled  with  the  hydrates  of  the  alkalies,  or  superheated 
with  water  (240°  C),  it  takes  up  two  molecules  of  water  and  produces  ammonium  carbonate, 

'"''~  CO(NH2)2  +  2Hi,0  =  CO(NH^O)o. 

When  brought  into  relation  with  nitrous  acid,  it  splits  up  into  water,  COj,  and  N.  The  Iwo  last 
decompositions  are  made  the  basis  of  methods  for  the  quantitative  estimation  of  urea  (§  257). 

Quantity. — In  normal  urine,  urea  occurs  to  the  extent  of  2.5  to  3.2  per  cent. 
An  adult  man  excretes  daily  from  30  to  40  grms.  [500  grains,  or  a  little  over  i 
oz.]  ;  women  excrete  less,  while  children  excrete  relatively  more  ;  owing  to  the 
relatively  greater  metabolism  in  children,  the  unit  weight  of  body  produces  more 
urea  than  the  unit  weight  of  an  adult,  in  the  proportion  of  1.7  :  i.  If  the  meta- 
bolism of  the  body  is  in  a  condition  of  equilibrium  (§  236),  the  urea  excreted  con- 
tains almost  as  much  N  as  is  taken  in  with  the  nitrogenous  constituents  of  the  food. 


QUANTITY   OF   UREA.  431 

Variations  in  the  Quantity. — The  amount  of  urea  increases  when  the 
amount  of  proteids  in  the  food  is  increased  ;  and  also  when  there  is  a  more  rapid 
breaking  up  of  the  nitrogenous  tissues  of  the  body  itself  As  this  breaking  up  is 
increased  by  diminution  of  O  {Frdnkel,  Penzoldf,  and  Fleischer'),  and  by  loss  of 
blood  (Bauer)  ;  so  these  conditions  also  increase  the  urea  (§  41).  It  is  also  in- 
creased by  drinking  large  draughts  of  water,  by  various  salts,  by  frequent  urina- 
tion, and  by  exposure  to  compressed  air.  In  diabetic  persons,  who  eat  very  large 
quantities  of  food,  it  may  exceed  100  grms.  [over  3  oz.]  per  day  ;  during  hunger 
it  sinks  to  6.  i  grms.  [90  grains]  per  day  {Seegen).  During  inanition,  the  maximum 
amount  is  excreted  toward  mid-day,  and  the  minimum  in  the  morning.  The 
daily  amount  of  urea  varies  with  the  quantity  of  urine  ;  three  to  five  hours  after  a 
meal,  the  formation  of  urea  is  at  a  maximum,  when  it  sinks  and  reaches  its  mini- 
mum during  the  night.  Muscular  exercise,  as  a  rule,  does  not  increase  it 
{v.  Voit,  Fick,  and  WisHceniis — §  295),  but  only  when  deficiency  of  O,  causing 
dyspnoea,  occurs  at  the  same  time  (Oppenheim). 

Pathological. — In  acute  febrile  inflammations,  and  in  fevers  generally  (J  22,  3),  the  urea  in- 
creases until  the  crisis  is  reached,  and  afterward  it  diminishes  (  Vogel].  After  the  fever  has  passed 
off,  the  amount  excreted  is  often  under  the  normal.  In  some  cases  of  high  fever,  although  the 
amount  of  urea  formed  is  increased,  it  may  not  be  excreted  ;  ihere  is  a  retention  of  the  urea,  while, 
later  on,  this  may  lead  to  an  increased  excretion  [A^uiiityn).  In  chronic  diseases,  the  amount 
depends  largely  upon  the  stale  of  the  nutrition,  the  metabolism,  and  also  upon  the  degree  of  fever 
present.  Degenerative  changes  in  the  liver,  e.  g.,  due  to  poisoning  with  phosphorus,  may  be  ac- 
companied by  diminished  excretion  of  urea  and  increased  excretion  of  ammonia  [Stm/elmann).  It 
is  increased  in  man  by  morphia,  narcotin,  marcein,  papaverin,  codein,  thebain  (Fubini),  arsenic 
[Gathgens),  compounds  of  antimony,  and  small  doses  of  phosphorus  (Bauer),  which  favor  the  de- 
composition of  proteids.     Quinine  which  "spares"  the  proteids  diminishes  it. 

Occurrence.— Urea  occurs  in  the  blood  (i  :  10,000),  lymph,  chyle  (2  •  1000),  liver,  lymph 
glands,  spleen,  lungs,  brain,  eye,  bile,  saliva,  amniotic  fluid,  and  pathologically  in  sweat,  f.^.,  in 
cholera,  in  the  vomit  and  sweat  of  urjemic  patients,  and  in  dropsical  fluids. 

Formation.— It  is  certain  that  it  is  the  chief  end  product  of  the  metabolism 
of  the  proteids.  Less  oxidized  products  are  uric  acid,  guanin,  xanthin,  hypo- 
xanthin,  alloxan,  allantoin.  Uric  acid  administered  internally  appears  in  the  urine 
as  urea ;  alloxan  and  hypoxanthin  can  be  changed  directly  into  urea.  The  urea 
excretion  is  increased  by  the  administration  of  leucin,  glycin,  aspartic  acid,  or 
ammonia  salts.  {Schiilzen,  Nencki.)  As  yet,  it  has  not  been  definitely  determined 
where  urea  is  formed,  but  the  liver  and,  perhaps,  the  lymph  glands  are  organs 
where  it  is  produced  (§  178). 

In  birds,  the  liver  forms  uric  acid  from  ammonia.  The  liver  can  be  readily  excluded  from  the 
circulation  in  birds,  and  Minkowski  found  that  after  this  operation  the  uric  acid  was  diminished  and 
the  ammoniacal  salts  increased  (\  178). 

Antecedents. — During  digestion,  the  proteids  are  converted  into  leucin,  tyrosin,  glycin,  and  as- 
paraginic acid.  If  the  amido  acids,  glycin,  leucin,  or  asparaginic  acid,  or  ammoniacal  salts,  be 
given  to  an  animal,  the  amount  of  urea  excreted  is  increased.  As  the  molecule  of  the  amido  acids 
contains  only  one  atom  of  N,  and  the  molecule  of  urea  contains  two  of  N,  it  is  probable  that  urea 
may  be  formed  synthetically  from  these  acids.  It  is  possible  that  the  amido  acids  meet  with  nitro- 
genous residues  in  the  juices  of  the  body,  e.g.,  carbamic  acid 
or  cyanic  acid.  The  union  of  these  may  produce  urea. 
According  to  Salkowski,  feeding  with  these  substances 
causes  the  breaking  up  of  the  proper  proteids  of  the  body 
so  as  to  provide  the  necessary  components.  Schmiedeberg 
is  of  opinion  that  urea  is  formed  in  the  body  from  ammonia 
carbonate  by  the  removal  of  water ;  and  v.  Schroder  found 
that,  when  he  passed  blood  containing  ammonia  carbonate  4% 
through  a  fresh  liver,  the  urea  in  the  blood  was  greatly  in-  '• 
creased,  Drechsel  succeeded  in  producing  urea  at  ordinary 
temperatures  by  the  rapid  alternating  oxidation  and  reduc- 
tion of  a  watery  solution  of  ammonia  carbonate.  [We 
know  that  the  greater  part  of  the  urea  exists  in  the  blood, 
and  that  the  renal  epithelium  removes  it  from  the  blood. 
Although  it  is  surmised  that  some  of  the  proteid  bodies 
named    above,    more    especially  leucin,   and   perhaps,  also.  Perfect  crystals  of  oxalate  of  1 


432         QUALITATIVE    AND    QUANTITATIVE   ESTIMATION    OF   UREA. 

krealin,  are  the  precursors  of  urea,  yet  we  cannot  say  definitely  how  or  where  the  transformation 
takes  place.     Perhaps  this  is  effected  in  the  liver,  and,  it  may  be,  also  in  the  spleen  (^  103)-] 

Preparation. — Urea  is  readily  prepared  from  dog's  urine  (especially  after  a  diet  of  flesh)  by 
evaporating  it  to  a  syrupy  consistence,  extracting  it  with  alcohol,  and  again  evaporating  the  filtrate 
to  a  syrupy  consistence.  The  crystals  which  separate  are  washed  with  water  to  remove  any 
extractives  that  may  be  mixed  with  them,  and  dis.sclved  in  absolute  alcohol  It  is  then  filtered  and 
allowed  to  crystallize  slowly.  Or,  human  urine  may  be  evaporated  to  one-sixth  of  its  volume 
and  cooled  to  0°,  and  excess  of  strong  nitric  acid  added,  which  precipitates  urea  nitrate  mixed 
with  coloring  matter.  This  prec  pilate  is  pressed  in  blotting  paper,  then  dissolved  in  boiling  water 
containing  animal  charcoal,  and  filtered  while  hot.  When  it  cools,  colorless  crystals  of  urea  nitrate 
sep.irale  (Fig.  237,  c).  These  crystals  are  redissolved  in  warm  water,  and  barium  carbonate  added 
until  effervescence  ceases ;  urea  and  barium  carbonate  are  formed.  Evaporate  to  dryness,  extract 
with  absolute  alcohol,  filter,  and  allow  evaporation  to  take  p'ace,  when  urea  separates. 

Compounds  of  Urea. — Urea  combines  with  acids,  bases  and  salts.  The 
following  are  the  most  important  combinations:  — 

1.  Urea  nitrate  (CH^N,0,  HNO3)  is  easily  soluble  in  water,  and  not  so  soluble  in  water  con- 
taining nitric  acid.  It  forms  characteristic  rhombic  crystals  (Fig.  237,  b  and  r).  Sometimes  the 
formation  of  these  crystals  is  used  to  determine  microscopically  the  presence  of  urea  in  a  fluid. 
If  a  fluid  is  suspected  to  contain  minute  traces  of  urea,  it  is  concentrated  and  a  drop  of  the  fluid 
is  put  on  a  microscopic  slide.  A  thread  is  placed  in  the  fluid,  and  the  whole  is  covered  with  a 
cover  glass.  A  drop  of  concentrated  nitric  acid  is  allowed  to  flow  under  the  cover  glass,  and  after 
a  time  crystals  of  urea  nitrate  adhering  to  the  thread  may  be  detected  with  the  microscope. 

2.  Urea  oxalate  (CH^N^O),,  C^HjO^  +  H^O,  is  made  by  mixing  a  concentrated  solution  of 
urea  with  oxalic  acid.  The  crj'Stals  form  groups  of  rhombic  tables,  often  of  irregular  shape.  It  is 
only  slightly  soluble  in  cold  water,  and  still  less  so  in  alcohol  (Fig.  238). 

3.  Urea  phosphate  (CH^N^O,  HjPO^)  forms  large,  glancing  rhombic  crystals,  very  easily 
soluble  in  water.      It  is  obtained  by  evaporating  the  urine  of  pigs  fed  on  dough. 

4.  Sodic  chloride  -j-  urea  (CH^NjO,  NaCl  -f-  H^Oj  forms  rhombic,  shining  prisms,  which 
are  sometimes  deposited  in  evaporated  human  urine. 

5.  Urea  -f  mercuric  nitrate  is  obtained  as  a  white,  cheesy  precipitate,  when  mercuric  nitrate 
is  added  to  a  solution  of  urea.  Liebig's  titration  method  for  urea  depends  on  this  reaction  (\  257, 
II). 

257.  QUALITATIVE    AND    QUANTITATIVE    ESTIMATION    OF    UREA.— I. 

The  Qualitative  Estimation  of  Urea.  —  ( I )  //  may  he  isolatcJ  as  such.  If  allnimin  be  present, 
add  to  the  fluid  three  to  four  times  its  volume  of  alcohol,  and,  after  several  hours,  filter.  Evapo- 
rate the  fillrate  over  a  water  bath,  and  dissolve  the  residue  in  a  few  drops  of  water. 

(2)   The  crystals  of  urea  nitrate  may  be  detected  microscopically  (Fig.  237). 

II.  Quantitative  Estimation. —  (t )  Sodic  hypobromite  decomposes  urea  intoCOj.  HjO  and 
N.  On  this  reaction  depends  the  Knop-HUfner  method  of  quantitative  estimation.  The  N  rises 
in  the  form  of  small  bubbles  in  the  mixed  fluid,  while  the  COj  is  absorbed  by  the  caustic  soda. 
[The  reaction  is  the  following  : — 

N^H^CO  +  3NaBrO  =  3  NaBr  -f-  CO^  +  2H2O  +  N. 
The  nitrogen  is  collected  and  estimated  in  a  graduated  tube,  and  the  amount  of  urea  calculated 
from  the  volume  of  nitrogen.     The  uric  acid  is  also  decomposed,  but  that  can  be  estimated  sepa- 
rately and  a  correction  made.     We  may  use  the  apparatus  of  Russell  and  W^est,  or  Dupre,  or  that 
of  Charteris  (Fig.  239).] 

[Ureameter. — Make  a  solution  of  hypobromite  of  soda  by  mixing  100  grammes  NaHO  in  250 
c.c.  of  water,  and  adding  25  c.c.  of  bromine.  It  is  better  to  be  made  fresh,  as  it  decomposes  by 
keeping.  The  graduated  tube  is  placed  in  a  cylindrical  vessel,  filled  with  water,  and  depressed 
until  the  zero  on  the  tube  coincides  with  the  level  of  the  water.  Introduce  15  c.c.  of  the  hypo. 
1  romite  solution  into  the  pyramidal-shaped  bottle,  while  into  a  short  test  tube  are  placed  5  c.c.  of 
urine.  The  te>t  tube  with  the  urine  is  introduced  into  the  bottle  by  means  of  a  pair  of  forceps  in 
such  a  way  that  it  does  not  spill.  Close  the  bottle  tightly  with  the  caoutchouc  stopper,  through 
which  passes  a  glass  tube  to  connect  it  with  the  graduated  burette.  Incline  the  bottle  so  as  to 
allow  the  urine  to  mix  with  the  hypobromite  solution,  when  the  gases  are  given  off,  and  pa-ss  into 
the  collecting  tube,  which  is  gradually  raised  until  the  surfaces  of  the  liquids  outside  and  in  coin- 
cide. Time  should  be  allowed  to  permit  the  whole  apparatus  to  have  the  same  temperature.  Read 
off  the  amount  of  gas  N  evolved,  for  the  CO,  is  alisorbed  by  the  caustic  soda.  The  collecting 
tube  is  usually  graduated  beforehand,  so  that  each  division  of  the  tube  is  ^  o.i  per  cent,  of  urea, 
or  0.44  gr.  per  fluid  oz.  Thus,  suppose  50  03.  of  urine  are  passed  in  twenty-four  hours,  and  that  5 
c.c.  of  urine  evolve  18  measures  of  N,  then  0.44  X  18  X  5°  =  39^  grs.  of  urea.  If,  however, 
the  tube  be  graduated  into  c.c,  then  30.3  c.c.  of  N  =rT  o.i  grm.  of  urea  at  the  ordinary  temperature 
and  pres.sure.] 

[Squibb's  Method  is  simple  and  expeditious.  Measure  off  i^  oz.  of  liquor  sodje  chlor. 
(U.  S.),  and  place  it  in  A  (Fig.  240),  together  with  a  glass  thimble  D,  containing  4  c  c.  of  urir.e. 


QUANTITATIVE    ESTIMATION    OF   UREA. 


433 


B  is  filled  with  water,  connected  by  an  India-rubber  tube  with  A,  and  so  adjusted  that  when  it  is 
in  the  position  shown,  no  water  escapes  into  C.  Filter  A,  and  mix  the  urine  in  D  with  the  chlorin- 
ated solution,  when  N  is  given  off,  displacing  water  from  Binto  C.  All  the  N  escapes  in  about  ten 
minutes.  When  the  pressure  in  A  and  B  is  restored,  the  contents  of  C  are  measured  by  a  pipette 
(J),  so  graduated  that  each  measure  is  =  .0027  grm.  urea,  from  which  the  calculation  is  easily 
made  (Afar/im/ale).'] 

III.  Volumetric  Method  {Liehig).  By  means  of  a  graduated  pipette  (Fig.  241),  40  cubic  cen- 
timetres of  the  urine  are  taken  up  and  placed  in  a  beaker.  To  this  is  added  20  cubic  centimetres 
of  barium  mixture  to  precipitate  the  sulphuric  and  phosphoric  acids.     T  he  barium  mixture  consists 


Fig.  239. 


Fig.  241. 


of  I  vol.  of  a  cold  saturated  solution  of  barium  nitrate  and  2  vols,  of  a  cold  saturated  solution  of 
barium  hydrate.  Filter  through  a  i/r^' filter,  and  take  15  cubic  centimetres  of  the  filtrate,  tfi/«V/< 
correspond  to  10  c.c.  of  urine,  and  place  in  a  beaker.  Allow  a  titrated  standard  solution  of 
mercuric  nitrate  to  drop  from  a  burette  into  the  urine  until  a  precipitate  no  longer  occurs.  The 
mercuric  nitrate  is  made  of  such  a  strength  that  I  cubic  centimetre  of  it  will  combine  with  10 
milligrammes  of  urea.  Test  a  drop  of  the  mixture  from  time  to  time  in  a  watch  glass  or  piece 
of  glass  blackened  on  its  under  surface,  with  a  solution  of  sodic  carbonate,  which  is  called  the 
indicator.  Whenever  the  slightest  excess  of  mercuric  nitrate  is  added,  the  mixture  strikes  a  yello-a< 
color  with  the  soda.  The  standard  solution  must  be  added  drop  by  drop  until  this  result  is 
28 


434 


PROPERTIES    OF    URIC    ACID. 


obtained.  Read  off  the  number  of  cubic  centimetres  of  the  standard  solution  used  ;  as  each  centi- 
metre corresponds  to  lo  milligrammes  of  urea,  just  multiply  by  ten,  and  the  amount  of  urea  in  10 
cubic  centimetres  of  urine  is  obtained. 

This  method  does  not  give  quite  accurate  results  even  in  normal  urine.  To  urine  containing 
much  phosphates  is  added  an  equal  volume  of  the  barium  mixture.  Very  acid  urines  may  require 
several  volumes  to  be  added.  Urine  containing  albumin  or  blood  must  be  boiled,  after  the  addition 
of  a  few  drops  of  acetic  acid,  to  remove  the  albumin.  The  sodic  chloride  in  the  urine  also  inter- 
feres with  the  accuracy  of  the  process,  as  on  adding  mercuric  nitrate  to  urine  mercuric  chloride  and 
sodic  nitrate  are  formed,  so  that  the  urea  does  not  combine  until  the  sodic  chloride  is  decomposed. 
When  the  urine  contains,  as  is  usually  the  case,  1  to  I  jj  per  cent.  NaCl,  deduct  2  c.c.  from  the 
number  of  c.c.  of  the  S.S.  added  to  lo  c.c.  of  urine. 

258.  URIC  ACID  =  CsH^N.Oj.— Quantity.— Uric  acid  is  the  nitro- 
genous substance  which,  next  to  urea,  carries  off  most  of  the  N  from  the  body  ; 
in  twenty-four  hours  0.5  grm.  (7  to  10  grains);  during  hunger,  0.24  grm.  (4 
grains);  after  a  strongly  animal  diet,  2. 11  grm.  (30  to  35  grains)  are  e.xcreted. 
The  proportion  of  urea  to  uric  acid  is  45  :  i. 

It  is  the  chief  nitrogenous  product  in  the  urine  of  birds,  reptiles,  and  insects,  while  it  is  absent 
from  herbivorous  urine. 


Fig.  242. 


Fig.  243 


Fig.  242  — Uric  acid,  ti,  rhombic  tables  (whetstone  form) ;  6,  barrel  form  ;  c,  sheaves ;  rf,  rosettes  of  whetstone  crys- 
tals. Fig.  243. — Uric  acid,  a,  rhomboidal,  truncated,  hexahedral,  and  laminated  crystals  ;  ir,  rhombic  prism, 
liorizontally  truncated  angles  of  the  rhombic  prism,  imperfect  rhomljic  prisms  :  c,  prism  with  a  hexahedral  basic 
surlace,  barrel-shaped  figure,  prism  with  a  hexahedral  basal  surface;  ti,  cylindrical  figure,  stellate  and  superim- 
posed groups  of  crystals. 

If  a  mammal  be  fed  with  uric  acid,  part  of  it  becomes  more  highly  oxidized 
into  urea,  while  the  oxalic  acid  in  the  urine  is  also  increased  (§  260 — IViih/er,  v. 
Frerichs) ;  in  fowls,  feeding  with  leucin,  glycin,  or  asparaginic  acid  (v.  Knien'cm), 
or  ammonia  carbonate  {Schroeder'),  increases  the  amount  of  uric  acid.  When 
urea  is  administered  to  fowls,  it  is  reduced  chiefly  to  uric  acid  {Cee/i,  H.  Mayer, 

Me). 

Properties. — Uric  acid  is  dibasic,  colorless,  and  crystallizes  in  various  forms 
(Figs.  242  and  243),  belonging  to  the  rhombic  system.  When  the  angles  are 
rounded,  the  whetstone  form  (a)  is  produced,  and  if  the  long  surfaces  be  flattened 
six-sided  tables  occur.  Not  unfrequently  diabetic  urine  deposits  spontaneously 
large,  yellow,  transparent  rosettes  (//).  If  20  c.c.  of  HCl,  or  acetic  acid,  be 
added  to  i  litre  of  urine,  crystals  {b)  are  deposited,  like  cayenne  pepper,  on  the 
surface  and  sides  of  the  glass,  after  several  hours.  [The  HCl  decomposes  the 
urates,  and  liberates  the  acid,  which  does  not  crystallize  at  once,  owing  to  the 
presence  of  the  phosphates  in   the   urine  {Erilcke).     Crystals  of  uric  acid  are 


ESTIMATION    OF   URIC    ACID.  435 

usually  yellowish  in  color  from  the  pigment  of  the  urine,  and  they  are  soluble  in 
caustic  potash.] 

Solubility. — It  is  tasteless  and  odorless  ;  reddens  litmus  ;  is  soluble  in  iS.ooo  parts  of  cold,  and 
in  15,000  of  boiling  water,  and  insoluble  in  alcohol  and  ether.  Horbaczewski  prepared  it  synthetic- 
ally by  melting  together  glycin,  or,  as  it  is  also  called  glycocin,  and  urea. 

it  IS  freely  solulile  in  alkaline  carbonates,  borates,  phosphates,  lactates,  and  acetates,  these  salts 
at  the  same  time  removing  a  part  of  the  base  ;  thus  there  are  formed  acid  urates  and  acid  salts  from 
the  neutral  salts.  It  is  soluble  in  concentrated  sulphuric  acid,  from  which  it  may  be  precipitated  by 
the  addition  of  water.  During  dry  distillation  it  decomposes  into  urea,  cyanuric  acid,  hydrocyanic 
acid,  and  ammonium  carbonate.  Supero.side  of  lead  converts  it  into  urea,  allantoin,  oxalic  acid,  and 
CO,  ;  while  ozone  forms  the  same  bubstances,  with  the  addition  of  allo.xan.  When  it  is  reduced 
by  H  in  slain  iiascendi,  as  by  sodium  amalgam,  it  forms  xanthin  and  sarkin.  It  is  a  less  oxidized 
metabolic  product  than  urea,  but  it  is  by  no  means  proved  that  uric  acid  is  a  precursor  of  urea. 

Occurrence. — Uric  acid  occurs  dissolved  in  the  urine  in  the  form  of  acid 
urates  of  soda  and  potash.  These  salts  occur  also  in  urinary  calculi,  gravel, 
and  in  goutv  deposits.  Ammonium  urate  occurs  in  very  small  quantity  in  a 
deposit  of  "  urates,"  but  is  formed  in  considerable  amount  when  urine  becomes 
ammoniacal  from  decomposition  (Fig.  250).  Free  uric  acid  occurs  in  normal 
urine  only  in  the  very  smallest  amount.  It  is  sometimes  deposited  after  a  time 
(Fig.  249).  It  frequently  forms  urinary  calculi,  being  sometimes  deposited 
around  a  speck  of  albumin  as  a  nucleus  (^El'stein).  [It  has  also  been  found  in  the 
blood,  liver,  and  spleen.  It  is  remarkable  that  it  has  been  found  in  the  spleen  of 
herbivora,  although,  as  stated  above,  it  is  absent  from  herbivorous  urine.  In  gout, 
it  accumulates  in  the  blood  {Garrod).'\ 

The  urine  of  newly-lwrn  children  contains  much  uric  acid.  Uric  acid  and  its  salts  are  increased 
after  severe  muscular  exertion,  accompanied  by  perspiration,  in  catarrhal  and  rheumatic  fevers,  and 
such  conditions  as  are  accompanied  by  disturbance  of  the  respiration ;  in  leukaemia  and  tumors  of 
the  spleen,  cirrhotic  liver,  and,  generally,  m  cases  of  catarrh  of  the  stomach  and  intestinal  tract,  fol- 
lowing the  excessive  use  of  alcohol.  [It  is  also  increased  during  ague  and  fevers,  and  perhaps  this 
has  some  relation  to  the  congestion  of  the  spleen  which  accompanies  these  conditions.]  It  is 
diminished  after  copious  draughts  of  water,  after  large  doses  of  quinine,  caffein,  polassic  iodide, 
common  salt,  sodic  and  lithic  carbonates,  sodic  sulphate,  inhalation  of  O,  slight  muscular  exertion. 
In  gout,  the  amount  excreted  in  the  urine  is  small.  In  chronic  tumors  of  the  spleen,  ana;mia  and 
chlorosis,  when  the  respiration  is  not  at  the  same  time  embarrassed,  it  is  also  diminished. 

Urates. — Uric  acid  forms  salts — chiefly  acid  urates — with  several  bases,  which 
dissolve  with  difficulty  in  cold  w-ater,  but  are  easily  soluble  in  warm  water.  Neu- 
tral urates  are  changed  by  CO.,  into  acid  salts.  Hydrochloric  and  acetic  acids 
break  up  the  compounds,  and  crystals  of  uric  acid  separate. 

(i)  Acid  sodic  urate  usu.ally  appears  as  a  brick-red  deposit,  more  rarely  gray  or  white  (lateri- 
tious  deposit),  tinged  with  uroerythrin,  in  urine,  in  catarrhal  conditions  of  the  digestive  organs,  and 
in  rheumatic  and  febrile  affections.  Microscopically,  it  is  completely  amorphous,  consisting  of 
granules,  sometimes  disposed  in  groups  (Fig.  249,  h");  sometimes  the  granules  have  spines  on  them. 
The  corresponding  potash  salt  occurs  not  unfrequently  under  the  same  conditions,  and  presents  the 
same  characters. 

(2)  Acid  ammonium  urate  (Fig.  250,  a)  always  occurs  as  a  sediment  in  ammoniacal  urine,  either 
with  (l),  or  mixed  with  free  uric  acid,  accompanied  by  triple  phosphate.  Microscopically,  it  is  the 
same  as  (I).  (I)  and  {2)  are  distitii^nished  by  the  sediment  dissotvin^  "uhen  the  urine  is  heated. 
If  a  drop  of  hydrochloric  acid  be  added  to  a  microscopic  preparation  of  the  sediment,  crystals  of 
uric  acid  separate. 

(3)  Acid  calcic  urate  occurs  sometimes  in  calculi,  and  is  a  white,  amorphous  powder,  but  slightly 
soluble  in  water.  When  heated  on  platinum,  it  leaves  an  ash  of  calcium  carbonate.  Magnesia 
rarely  occurs  in  urimry  calculi. 

259.  ESTIMATION  OF  URIC  ACID.— I.  Qualitative.— i.  Micro- 
scopic Characters. — The  appearances  presented  by  uric  acid  and  its  salts  under 
the  microscope.  It  is  deposited  from  urine  after  several  hours,  on  adding  acetic 
or  hydrochloric  acid. 

2.  Murexide  Test. — Gently  heat  a  urate  or  uric  acid  in  a  porcelain  vessel, 
along  with  nitric  acid.  Decomposition  takes  place,  and  the  color  changes  to 
yellow.     N  and  CO.  are  given  off;  urea  and  allo.xan  (C^H-^NiO,)  remain.     F>apo- 


436  KREATININ    AND    OTHER    SUBSTANCES. 

rate  slowly,  and  allow  the  yellowish-red  stain  to  cool ;  on  adding  a  drop  of  dilute 
ammonia,  a  purplish-red  color  of  murexide  is  obtained  ;  it  becomes  blue  on  the 
addition  of  caustic  potash.  If  potash  or  soda  be  added,  instead  of  ammonia,  a 
violet  color  is  obtained. 

3.  Schiff' s  Test. — If  a  little  uric  acid  or  a  urate  be  dissolved  in  a  solution  of  an  alkaline  car- 
bonate, and  this  be  dropped  upon  blotting  paper  saturated  with  a  solution  of  siiver  nitrate.,  reduction 
of  the  silver  takes  place  at  once,  and  a  black  spot  is  formed  (H.  Schiff). 

4.  On  boiling  a  solution  of  uric  acid  or  a  urate  in  an  alkali,  with  Fehling's  solution  (§  149,  2), 
at  first  white  urate  of  the  suboxide  of  copper  is  deposited,  while  later,  red  copper  suboxide  is 
formed. 

II.  The  Quantitative  estimation  may  be  made  by  adding  5  cubic  centimetres  of  concentrated 
HCl  to  100  c.  c.  of  urine,  and  allowing  it  to  stand  for  forty-eight  hours  in  the  dark,  when  the  uric 
acid  is  precipitated  like  fine  cayenne  pepper  crystals.  Salkowski  and  Fokker  have  improved  the 
method.  All  the  uric  acid  is  not  precipitated  by  the  HCl,  even  after  standing  for  a  time.  [E.  A. 
Cook  uses  sulphate  of  zinc  to  precipitate  the  uric  acid  as  urate  of  zinc.  Caustic  soda  is  added  to 
precipitate  the  phosphates,  and  then  to  the  clear  fluid  zinc  sulphate  solution,  which  precipitates  urate 
of  zinc  as  a  white  gelatinous  deposit.] 

[Haycraft's  method  depends  on  the  fact  that  uric  acid  forms  a  compound  with  silver — urate  of 
silver,  which  is  very  insoluble  in  water.  The  solutions  required  are  :  i.  Centinormal  ammonic  sul- 
phocyanate,  made  by  dissolving  8  grms.  of  crystals  in  i  litre  of  water,  and  adjust  to  decinormal  silver 
solution.  Dilute  with  9  vols,  of  water,  i  c.  c.  =  0.0016S  uric  acid.  2.  Saturated  solution  of  iron 
alum  (the  indicator).  3.  Pure  HNO3  (20  to  30  per  cent.).  4.  .Strong  ammonia.  Ammoniacal 
silver  solution  made  by  dissolving  5  grms.  AgNOj  in  100  c.  c.  water,  and  add  NH^HO  until  the 
solution  becomes  clear.  Process. — Place  25  c.  c.  of  urine  in  a  beaker,  and  add  i  grm.  sodic  bicar- 
bonate; then  add  2  to  3  c.  c.  of  ammonia  to  precipitate  ammonio-magnesic  phosphate.  Add  I  to 
2  c.  c.  of  ammoniacal  silver  solution,  which  precipitates  silver  urate  in  a  white  gelatinous  form. 
The  precipitate  is  then  thoroughly  washed  on  an  asbestos  filter,  anil  then  dissolved  from  this  by  nitric 
acid,  after  which  the  silver  is  estimated  (Volhard's  method).  In  doing  so,  add  a  few  drops  of  the 
indicator,  and  drop  in  the  centinormal  solution  of  ammonic  sulphocyanate.  A  white  precipitate, 
with  a  transient  reddish  coloration,  will  be  formed ;  as  soon  as  the  red  color  is  permanent,  the 
process  is  at  an  end.  The  uric  acid  j>resent  is  ascertained  by  multiplying  the  number  of  cubic  centi- 
metres of  the  sulphocyanate  used  by  0.0016S.] 

260.  KREATININ  AND    OTHER   SUBSTANCES.— Quantity.— 

Kreatinin,  CjHaNjO.,  (LicMg),  is  derived  from  the  kreatin  of  muscle,  from  which 
it  can  be  otitained  by  heating  in  a  watery  solution,  a  molecule  of  water  being  given 
off;  and,  conversely,  kreatinin  may  take  up  water  and  form  kreatin.  The  amount 
excreted  daily  is  0.6  to  1.3  grammes  (8  to  18  grains). 

It  is  diminished  in  progressive  muscular  atrophy,  tetanus,  anemia,  marasmus,  chlorosis,  con- 
sumption, paralysis ;  and  is  increased  in  typhus,  inflammation  of  the  lung ;  it  is  absent  from  the 
urine  of  sucklings. 

Properties. — Kreatinin  is  alkaline  in  reaction,  easily  soluble  in  water  and  hot  alcohol.  It  occurs 
in  the  form  of  colorless,  oblique,  rhombic  columns.  It  forms  compounds  with  acids  and  salts,  with 
silver  nitrate,  mercuric  chloride,  and  especially  with  zinc  chloriJe.  Kreatinin-zinc  chloride  ( Fig. 
244)  is  used  to  detect  its  presence.  Test. — Add  to  urine  a  few  drops  of  a  slightly-brownish  solu- 
tion of  nitro-prusside  of  soda,  and  then  weak  caustic  soda  solution,  which  cause  a  Burgundy  red 
color,  which  soon  disappears  (  77;.  W'cyl).  When  heated  with  acetic  acid,  the  color  changes  to 
green  or  blue  [Salkowski).  Kreatinin  has  been  prepared  artificially.  When  boiled  with  baryta 
water,  it  decomposes  into  urea  and  sarkosin.  When  administered  by  the  mouth,  or  when  injected 
into  the  blood,  the  greater  part  of  it  reappears  unchanged  in  the  urine. 

Xanthin  (^  C^H^N^Oj)  (Marcet)  occurs  only  to  the  amount  of  I  gramme  in  300  kilos,  of  urine. 
It  is  a  substance  intermediate  between  sarkin  and  uric  acid.  Guanin  and  hypoxanthin  may  be 
changed  into  xanthin ;  in  contact  with  water  and  ferments  it  passes  into  uric  acid.  When  evapo- 
rated with  nitric  acid,  it  gives  a  yellow  stain,  which  becomes  yellowish-red  on  adding  potash,  and 
violet-red  on  applying  more  heat.  It  is  an  amorphous,  yellowish- white  powder,  fairly  soluble  in 
boiling  water.  It  has  also  been  found  in  traces  in  muscles,  brain,  liver,  spleen,  pancreas,  and 
thymus.  The  crystalhne  body  paraxanthin,  and  the  amorphous  heteroxanthin,  occur  in  traces 
in  the  urine  (Salomon). 

Sarkin  (=:  Hypoxanthin),  C5H4N4O. — As  yet  this  substance  has  been  found  only  in  the  urine 
of  leukfemic  patients  (Jakubasck),  and  it  has  been  prepared  in  the  form  of  needles  or  llattened 
scales  [Scherer)  from  muscle,  spleen,  thymus,  brain,  bone,  liver,  and  kidney.  In  normal  urine  a 
body  nearly  related  to,  and  possibly  identical  with,  hypoxanthin  occurs  [E.  Salko-cski).  Hypo- 
xanthin closely  resembles  xanthin,  and  can  be  changed  into  it  by  oxidation.  Nascent  hydrogen,  on 
the  other  hand,  reduces  uric  acid  to  xanthin  and  hypoxanthin.     When  evaporated  with  nitric  acid 


OXALIC    ACID    AND    OXALURIA. 


437 


it  gives  a  light  yellow  stain,  which  becomes  deeper,  but  not  reddish  yellow,  on  adding  caustic  soda. 
It  is  more  easily  soluble  in  water  than  xanthin,  and  by  this  means  the  two  substances  can  be  sepa- 
rated from  each  other.     Guanin  is  insoluble  in  water. 

Oxaluric  acid  (CjH^N.O^)  occurs  in  very  small  quantity  comhmeA  with  ammonia  in  urine. 
Physiologically,  it  is  interesting  on  account  of  its  relation  to  uric  acid.  It  is  a  white  powder,  slightly 
soluble  in  water.     Ammonia  oxalurate  can  be  prepared  from  uric  acid. 

Oxalic  Acid  (€21^204). — The  series  of  chemical  decompositions  of  oxaluric 
acid  leads  to  oxalic  acid.     It  occurs,  but  not  constantly,  to  the  amount  of  20 

Fig.  244. 


milligrammes  daily  as  oxalate  of  lime,  which  is  known  by  the  ■"envelope" 
shape  of  the  crystals  (Figs.  245  and  246)  ;  insoluble  in  acetic  acid,  and  forming 
transparent  octahedra.  More  rarely  it  assumes  a  biscut  or  sand-glass  form  (Fig. 
259,  c).  According  to  Neiibauer,  soluble  oxalate  of  lime  occurs  in  urine,  being 
kept  in  solution  by  acid  sodic  phosphate.  This  substance  is  excreted  in  a  crys- 
talline form,  the  more  the  reaction  of  the  urine  becomes  neutral. 

The  genetic  relation  of  oxalic  acid  to  uric  acid  is  shown  by  the  fact,  that  dogs 


Fig.  245. 


Fig.  246. 


a,  oclahedr.i ;  b,  basal  plane  of  an  octahedn 
angle  ;  c,  compound  forms  ;  d,  dumb  belts. 


1  forming 


fed  with  uric  acid  e.xcrete  much  oxalate  of  lime  {v.  FrcrUhs,  lllihler).  Oxalic 
acid  may  also  be  produced  by  the  oxidation  of  products  derived  from  the  fatty 
acid  series  (p.  414). 

Oxaluria. — The  eating  of  substances  containing  oxalate  of  lime  (rhubarb)  increases  the  excretion. 
Increased  excretion  is  called  oxaluria;  it  is  regarded  as  a  sign  of  retarded  metabolism  (Beiiel-e], 
and  it  m.iy  give  rise  to  the  formation  of  a  calculus.  In  oxaluria  the  uric  acid  is  also  often  increased 
in  amount.  Perhaps,  in  the  first  instance,  there  is  an  increased  formation  of  uric  acid,  from  which 
oxalic  acid,  urea,  and  CO^  may  be  formed.  The  amount  of  oxalic  acid  is  increased  after  the  use 
of  wine  and  sodic  bicarbonate. 


438 


HIPPURIC   ACID. 


Hippuric  Acid  =  CgHjiNO^  (Benzoylamidoacetic  acid)  occurs  in  large  amount 
in  the  urine  of  herbivora  (Liehig),  and  in  them  it  replaces  uric  acid,  and  is  one  of 
the  chief  end  products  of  the  metabolism  of  nitrogenous  substances ;  in  human 
urine  the  daily  amount  is  small,  0.3  to  3.8  grms.  (5  to  50  grains).  It  is  an  odor- 
less monobasic  acid  with  a  bitter  taste,  and  crystallizes  m  colorless,  four-sided 
prisms  (Fig.  247 j.  It  is  readily  soluble  in  alcohol,  and  only  soluble  in  600  parts 
of  water. 

It  is  a  conjugated  acid,  and  is  formed  in  the  body  from  benzoic  acid,  or  some 
nearly  related  chemical  body,  such  as  the  cuticular  substance  of  plants,  or  from 
oil  of  bitter  almonds,  cinnamic  or  chinic  acid,  which  easily  pass  by  reduction 
(chinic  acid)  or  by  oxidation  (cinnamic  acid)  into  benzoic  acid  ;  glycin  uniting 
with  it,  and  water  being  given  off — 

CjHeO,     +  C.HsNOj   =     C,H,,N03     +    H,0 

Benzoic  acid    -\-       Glycin        =   Hippuric  acid    -|-  Water. 

[Formation. — When  benzoic  acid  is  introduced  into  the  alimentary  canal  of 
an  animal  (rabbit  or  dog),  it  appears  in  the  urine  as  hippuric  acid  ;  while  nitro- 

FlG.  247. 


benzoic  acid  appears  as  nitro-hippuric  acid.  As  the  benzoic  acid  passes  through 
the  body  it  becomes  conjugated  with  glycin  or  glycocin,  chiefly  in  the  kidneys. 
The  hippuric  acid  in  the  urine  of  herbivora  is  chiefly  derived  from  some  substance 
with  a  benzoic  acid  residue  present  in  the  cuticular  coverings  of  the  food.  That 
hippuric  acid,  in  part  at  least,  is  formed  in  the  kidneys  is  shown  by  the  follow- 
ing considerations  :  If  arterialized  blood,  containing  benzoic  acid  and  glycin,  or 
even  benzoic  acid  alone,  be  passed  through  the  blood  vessels  of  a  fresh  living 
excised  kidney,  hippuric  acid  is  found  in  the  blood  after  it  is  perfused.  Even 
after  forty-eight  hours,  if  the  kidney  be  kept  cool,  the  synthesis  takes  place.  If 
the  kidney  be  kept  too  long,  the  conjugation  does  not  take  place.  If  the  fresh 
kidney  be  chopped  up,  and  kept  at  the  temperature  of  the  body  with  benzoic  acid 
and  glycin,  hippuric  acid  is  formed.  Oxygen  seems  to  be  necessary  for  the  pro- 
cess, for,  if  blood  or  serum  containing  carbonic  oxide  be  used,  there  is  no  forma- 
tion of  hippuric  acid.] 

According  to  this  view,  it  is  derived  chiefly  from  the  food  of  herbivorous  animals,  and  hence  it  is 
absent  from  the  urine  of  sucking  calves.  But  it  is  also  formed  in  the  body  from  the  proleids.  In 
the  dog,  the  formation  of  hippuric  acid  occurs  in  the  kidney  [Sc/imiedeberg  and  Bttnge"),  and  in  the 


COLORING    MATFERS   OF   URINE.  439 

frog  also  outside  the  kidney.  Kiihne  and  Halhvachs  thought  it  was  formed  in  the  liver,  and  Jaars- 
veld  and  Stockvis  in  the  kidney,  liver,  and  intestine.  The  observation  of  Salomon  that,  after  excision 
of  the  kidneys  in  rabbits,  and  injection  of  benzoic  acid  into  the  blood,  hippuric  acid  was  found  in 
the  muscles,  blood,  and  liver,  goes  to  show  that  it  must  be  formed  in  other  organs  beside  the 
kidneys.  The  power  of  changing  benzoic  acid  introduced  into  the  human  body  into  hippuric  acid, 
may  even  be  abolished  in  disease  of  the  kidney  {^Jaarsveld  and  Stockvis,  Fr.  Kronecker).  Under 
certain  circumstances  it  seems  that  hippuric  acid,  already  formed,  may  be  again  decomposed  in  the 
tissues. 

It  is  greatly  increased  after  eating  pears,  plums,  and  cranberries;  and  it  is  also  increased  in 
icterus,  some  liver  affections,  and  in  diabetes.  When  boiled  with  strong  acid  or  alkalies,  or  with 
putrid  substances,  it  takes  up  H,0  and  splits  into  benzoic  acid  and  glycin. 

[Crystals  of  hippuric  acid  when  heated  in  a  test  tube  are  decomposed,  and  a  sublimate  of  benzoic 
acid  and  ammonic  benzoate  condenses  on  the  upper  cool  part  of  the  tube,  while  there  is  an  odor  of 
new  hay,  and  oily  drops  remain  in  the  tube.]  It  is  freely  soluble  in  water,  with  difficulty  in  alcohol, 
and  insoluble  in  ether. 

Preparation. — .\dd  milk  of  lime  to  \\^t  fresh  urine  of  horses  or  cows  to  form  calcic  hippurate. 
Filler,  evaporate  the  filtrate  to  a  small  bulk,  and  precipitate  the  hippuric  acid  with  excess  of  hydro- 
chloric acid.     To  purify  the  hippuric  acid,  crystallize  it  several  times  from  a  hot  watery  solution. 

Cynuric  Acid. — C^^Hj ^NjOg  -|-  HjO  occurs  in  the  urine  of  dogs  (y.  v.  Liebig). 

AUantoin,  CjHgNjOa,  which  occurs  in  the  amniotic  fluid  of  the  cow,  is  found 
in  minute  traces  in  normal  urine  after  flesh  food,  and  is  more  abundant  during  the 
first  weeks  of  life,  and  during  pregnancy. 

After  large  doses  of  tannic  acid,  the  amount  is  increased  (Sc/wllin),  while  in  dogs  feeding  with 
uric  acid  also  increases  it  (Sa/kowsii). 

Properties. — It  forms  shining,  prismatic  crystals ;  from  the  urine  of  sucking  calves  it  crystallizes 
in  transparent  prisms.  It  is  decomposed  by  ferments  into  urea,  ammonium  oxalate,  and  carbonate, 
and  another  as  yet  unknown  body. 

Preparation. — (a)  The  urine  is  precipitated  with  basic  lead  acetate,  the  lead  in  the  filtrate  is  re- 
moved by  sulphuretted  hydrogen,  and  the  filtrate  itself  is  then  evaporated  to  a  syrup,  from  which 
the  crystals  separate,  after  standing  for  several  days.  They  are  then  washed  with  water,  and  re- 
crystallized  from  that  water  (Salko-uiski). 

261.    COLORING    MATTERS    OF    THE    URINE.— i.  Urobilin 

(Jafff)  is  most  abundant  in  the  highly  colored  urine  of  fevers,  but  it  also  occurs 
in  normal  urine.  It  is  a  derivative  of  hKmatin,  or  of  the  bile  pigments  (§  177)  de- 
rived from  the  latter.  It  is  identical  with  the  hydrobilirubin  of  Maly  (§117,  T„g). 
It  gives  a  red,  or  reddish  yellow  color  to  urine,  which  becomes  yellow  on  the  addi- 
tion of  ammonia. 

Preparation. — Prepare  a  chloroform  extract  of  urine  containing  urobilin  —add  iodine  to  the 
extract,  and  remove  the  iodine  by  shaking  the  mixture  with  dilute  caustic  potash,  which  forms 
potassic  iodide.  This  potash  solution  becomes  yellow  or  brownish  yellow,  and. exhibits  beautifu 
green  fttorcscence  [Gerhardt). 

Urobilin  may  be  extracted  from  many  urines  by  ether  [Suiko'uski).  When  subjected  to  the 
action  of  reducing  agents,  ^.^.,  sodium  amalgam,  a  colorless  product  is  obtained,  which  on  exposure 
to  the  air  absorbs  O,  and  becomes  retransformed  into  urobilin.  This  colorless  body  is  identical  with 
the  chromogen  which  Jaffe  found  in  urine. 

If  urine  is  treated  with  soda  or  potash,  the  characteristic  absorption  band  lying  between  d  and  F, 
passes  nearer  to  l>,  becomes  darker  and  more  sharply  defined.  According  to  Hoppe-Seyler,  urobilin 
is  formed  in  urine  after  it  is  voided,  from  another  urobilin-forming  body  (Jaffe's  chromogen)  absorb- 
ing oxygen.  If  urine  containing  urobilin  be  made  alkaline  with  ammonia,  and  zinc  cliloride  be 
added,  it  exhibits  marked  fluorescence  ;  it  has  a  green  shimmer  by  reflected  light.  When  urobilin 
is  isolated,  it  fluoresces  without  the  addition  of  zinc  chloride.  In  cases  of  jaundice  {\  1 80),  where 
Gmelin's  test  sometimes  fails  to  reveal  the  presence  of  bile  pigments,  urobilin  occurs.  This  "  uro- 
bilin icterus"  { Gerhardt)  occurs  chiefly  after  the  absorption  of  large  extravasations  of  blood.  Ac- 
cording to  Cazeneuve,  the  urobilin  is  increased  in  all  diseases  where  there  is  increased  disintegration 
of  colored  blood  corpuscles. 

2.  Urochrome  (  Thudichtim)  is  regarded  as  the  chief  coloring  matter  of  urine.  It  may  be  iso- 
lated in  the  form  of  yellow  scales,  soluble  in  water,  and  in  dilute  acids  and  alkalies.  The  watery 
solution  oxidizes,  and  when  exposed  to  air  becomes  red  owing  to  the  formation  of  uroerythrin 
(  Thitdichunt)  When  acted  on  by  acids,  new  decomposition  products  are  formed,  e.  g.,  urome- 
lanin.     Uroerythrin  gives  the  red  color  to  deposits  of  urates  (?  258). 

3  .-V  brown  pigment  containing  iron  is  carried  down  with  uric  acid,  which  is  precipitated  on  the 
addition  of  hydrochloric  acid  {\  258).  By  repeatedly  addmg  sodic  urate  to  the  urine,  and  precipi- 
tating the  uric  acid  by  hydrochloric  acid,  a  considerable  amount  may  be  obtained  (JCiinkel). 


440  INDICAN,   PHENOL   AND    PARAKRESOL. 

In  cases  nf  melanotic  tumors,  there  has  been  occasionally  observed  urine,  which  becomes  dark, 
owing  to  melanin  (^  250,  4),  or  to  a  coloring  matter  containing  iron  [A'unki'i). 

262.  INDIGO— PHENOL— KRESOL—PYROKATECHIN— AND 
SKATOL-FORMING    SUBSTANCES.  — i.     Indican    [CH^NSOJ    or 

indigo-forming  substance  (Siht/iick),  is  derived  from  indol,  CjiH.N  {Jcjfc),  the 
basis  of  indigo  (Bayer),  and  is  formed  in  the  intestine  by  the  pancreatic  diges- 
tion of  proteids  (§  170,  II),  but  it  also  arist?S  as  a  putrefactive  product  (§  184,  61. 
Indol,  when  united  with  the  radical  of  sulphuric  acid,  HSOj,  and  combined  with 
jiotassium,  forms  the  so-called  iitdigogen  or  indican  of  urine  (Briegcr,  Baumann). 
This  substance  (CgHgNSO^K  ;=  indoxyl-sulphate  of  potash )  forms  white  glancing 
tablets  and  plates  ;  readily  soluble  in  water  and  less  so  in  alcohol.  By  oxidation 
at  forms  indigo-blue — 2  indican  +  O,  ^  C,6H,„N.j02  (indigo-blue)  -f  2HKS0j 
(acid  potassic  sulphate).  It  is  more  abundant  in  the  urine  in  the  tropics,  and  it 
is  absent  from  the  urine  of  the  newly-born  {Senator). 

Tests.-  (l)  Add  to  40  drops  of  urine,  3  to  4  c.c.  of  strong  fuming  hydrochloric  acid,  and  2  to  3 
drops  of  nitric  acid.  Boil,  a  violet-red  color  with  the  deposition  of  true  ciystallme  indigo-blue 
(rhombic)  and  indigo-red  attest  its  presence.  Putrefaction  causes  a  similar  decomposition  in 
indican ;  hence,  we  not  unfrequently  obser\'e  a  bluish-red  pellicle  of  microscopic  crystals  of  indigo- 
blue,  or  even  a  precipitate  of  the  same  {Hill  Hassal,  /Sjs)'  (2)  Mix  in  a  beaker  equal  quantities 
of  urine  and  hydrochlorous  acid,  and  add  two  drops  of  a  solution  of  chloride  of  lime;  the  mixture 
at  first  becomes  clear,  then  blue  [Jaffi:).  Add  chloroform,  and  shake  the||mixture  vigorously  for 
some  time;  the  chloroform  dissolves  the  blue  coloring  matter,  which  is  obtained  as  a  deposit,  when 
the  chloroform  evaporates  (Senator,  Salkowski).  (3)  Heat  to  70°  one  part  of  urine  with  two  pans 
of  nitric  acid,  and  shake  up  with  chloroform;  the  chloroform  dissolves  the  indigo  which  is  formed, 
assumes  a  violet  color  and  gives  an  absorption  band  between  C  and  D,  slightly  nearer  D  (Hoppe- 
Seyler).  Jaffe  found  in  1500  c.c.  of  normal  human  urine,  4.5  to  19.5  milligrammes  of  indigo  ; 
horse's  urine  contains  23  times  as  much.  The  subcutaneous  injection  of  indol  increases  the  indican 
in  the  urine  {J'lffe)-  E.  Ludwig  obtained  indican  by  heating  hiematin  or  urobilin  with  a  caustic 
alkali  and  zinc  dust.     It  has  also  been  found  in  the  sweat  [Bizio), 

Pathological  — The  indican  in  the  urine  is  increased  when  much  indol  is  formed  in  the  intes- 
tine (^  172,  II),  e.g.,  in  typhus,  lead  colic,  trichinosis,  catarrah  and  hemorrhage  of  the  stomach, 
cholera,  carcinoma  of  the  liver  and  stomach;  obstruction  of  the  bowel  or  ileus,  peritonitis  and 
diseases  of  the  small  intestine — in  cachexia?,  longstanding  suppuration,  paraplegia — after  taking 
creosote,  oil  of  bitter  almonds,  turpentine  or  nux  vomica. 

2.  Phenol,  C„HjO,  carbolic  acid,  monohydroxylbenzol,  §  252),  was  discovered 
by  Stadeler  in  human  urine  (more  abundant  in  horse's  urine).  It  does  not  occur 
as  carbolic  acid,  but  in  combination  with  a  substance  from  which  it  is  separated 
by  distillation  with  dilute  mineral  acids.  The  "  phenol-forming  substance  "  is, 
according  to  Baumann,  "  phenolsulphuric  acid"  (CeHjG,  SO3H),  which  in 
urine  is  united  with  potash. 

Phenol  is  derived  from  the  decomposition  of  proteids  by  pancreatic  digestion  (J  172,  II),  and 
also  from  putrefaction  (^  184,  6),  the  mother  substance  being  tyrosin.  Hence,  the  formation  of 
phenolsulphuric  acid  is  analogous  to  the  formation  of  indican. 

If  in  the  employment  of  carbolic  acid  it  be  absorbed,  the  phenolsulphuric  acid  becomes  greatly 
increased  in  z^raount  [Alirten,  .Salko7uski),so  that  sulphuric  acid  must  be  united  with  it ;  hence, 
alkaline  sulphates  are  decomposed  in  the  body,  so  that  the  latter  may  be  absent  from  the  urine 
{Baumann).  Living  muscle  or  liver,  when  digested  in  a  stream  of  air  for  several  hours  with 
blood  to  which  phenol  and  sodic  sulphate  are  added,  yields  phenolsulphuric  acid;  while,  under 
the  same  circumstances,  pyrokatechin  forms  ethersulphuric  acid. 

Carbolic  Urine. — When  carbolic  acid  is  used  externally  or  internally,  and  it  is  absorbed,  it 
causes  a  deep,  dark-colored  urine,  due  to  the  oxidation  of  phenol  into  hydrochinon  (orthobioxy- 
benzol  =  CgHgOj),  which,  for  the  most  part,  appears  in  the  urine  as  ethersulphuric  acid  {Baii- 
fnann  and  others). 

3.  Parakresol,  (hydroxyltoluol,  CyHgO)  with  its  isomers  ortho-  and  meta- 
kresol  (the  latter  in  traces),  is  more  abundant  in  urine  {Baumann,  Preusse).  It 
also  occurs  in  combination  with  sulphuric  acid. 

Test  for  phenol  (and  also  kresol)  :  Distil  150  c.c.  urine  with  dilute  sulphuric  acid.  The  distillate 
gives  a  brown  crystalline  deposit  of  tribromophenol  with  bromine  water,  as  well  as  a  red  color  with 
MiUon's  reagent. 

Hydroxylbenzol  (pyrokatechin,  hydrochinon)  is  obtained  from  urine,  when  it  is  heated  for  a 
long  time  with  hydrochloric  acid. 


INORGANIC    CONSTITUENTS   OF   THE    URINE.  441 

Resorcin  which  is  an  isomer  of  hydrochinon,  when  administered  internally,  also  appears  in  the 
urine  as  ethersulphuric  acid.     Toluol  and  naphthalin  behave  similarly. 

4.  Pyrokatechin  ^  CeHeO..  (metadihydroxylbenzol)  is  formed  along  with 
hydrochinon  from  jjhenol,  and  is  an  isomer  of  the  former.  It  behaves  like  indol 
and  phenol,  for  when  united  with  sulphuric  acid,  it  forms  the  pyrokatechin-form- 
ing  substance  (Bauinann,  Herier).  Small  quantities  sometimes  occur  in  human 
urine;  it  is  more  abundant  in  the  urine  of  children  {Ebstcin  and Milller)  ;  it 
becomes  darker  when  the  urine  putrefies. 

Perhaps  pyrokatechin  is  formed  in  the  body  from  decomposed  carbohydrates,  from  which  Hoppe- 
Seyler  obtained  it  by  heating  them  with  water  under  a  high  pressure,  as  well  as  by  acting  on  them 
with  alkalies. 

5.  Skatol  (§  252),  which  is  crystalline,  and  is  formed  during  putrefaction  in 
the  intestine,  also  appears  in  the  urine  as  a  compound  of  sulphuric  acid.  On 
feeding  a  dog  with  skatol,  Brieger  found  much  potassic  skatol-oxysulphate. 

Test. — Skatol  compounds  are  recognized  by  adding  dilute  nitric  acid,  which  causes  a  violet 
color,  or  of  fuming  nitric  acid,  which  precipitates  red  flakes  [Ncncki).  Its  quantity  is  regulated 
by  the  same  conditions  as  indican. 

The  aromatic  oxyacids,  hyjroparacumaric  acid  and  paraoxyphenylacetic  acid  (the  former  a 
putrefactive  product  of  flesh,  the  latter  obtained  by  E  and  H — Salkowski,  from  putrid  albumin), 
occur  in  the  urine  [Baumann,  \  252).  Shake  the  urine  treated  with  a  mineral  acid  with  ether, 
evaporate  the  latter,  and  dissolve  the  residue  in  water.  If  aromatic  oxyacids  are  present,  they  give 
a  red  color  with  Millon's  reagent. 

Baumann  gives  the  following  series  of  bodies,  which  are  formed  from  tyrosin  by  decomposition 
and  oxidation ;  most  of  the  sutistances  are  formed  both  during  the  decomposition  of  albumin,  and 
also  in  the  intestine,  whence  they  pass  into  the  urine:  Tyrosin,  C<,Hj  jNOj  -[-  H,  =  C^HijOj 
(hydroparacumaric  acid)  -j-  NH,.  CgHj^Oj  r=  C,Hj(|0  (paraethylphenol,  not  yet  proved)  -)- 
COj.  CjHjoO  +  03  =  CgHgO,  (paraoxyphenylaceticacid)  +  H^O.  CgHgOj  =  C^HjO 
(parakresol)  -1-  CO,.  CjHgO  -|-  O3  =  CjH^Oj  (paroxy benzoic  acid,  not  yet  proved)  -\-  HjG. 
C,H,0  =  C5H5O' (phenol)  +  CO,. 

Potassium  sulphocyanide,  derived  from  the  saliva,  also  occurs  in  urine.  After  acidulation 
with  hydrochloric  acid,  its  presence  may  be  detected  by  the  ferric  chloride  test  (\  146 — Gscheidlen 
and  J.  Muni).     One  litre  of  human  urine  contains  0.02  to  0.08  gramme  combined  with  an  alkali. 

Succinic  acid,  C^H^O^  [A/eissncr  and  Shepard ),  occurs  chiefly  after  a  diet  of  flesh  and  fat,  and 
almost  disappears  after  a  vegetable  diet.  It  is  a  decomposition  product  of  asparagin,  and  therefore 
occurs  in  considerable  amount  in  the  urine  after  eating  asparagus.  It  is  also  a  product  of  the  alco- 
holic fermentation  (|  150),  and  as  it  passes  out  of  the  body  unchanged,  it  occurs  in  the  urine  of 
those  who  imbibe  spirituous  liquors.     It  passes  unchanged  into  the  urine  (Neuliauei'). 

Lactic  acid  (C3H5O3)  is  a  constant  constituent  of  urine  (Lehmann,  Briicke].  Other  observers 
have  found  fermentative  lactic  acid  in  diabetic  urine;  sarcolactic  acid  after  poisoning  with  phos- 
phorus and  in  trichinosis.  Occasionally  traces  of  volatile  fatty  acids  are  present.  Some  atiimal 
gum  occurs  in  urine  (p.  416),  and  Bechamp's  "  Nephrozymose  "  consists  for  the  most  part  of 
gum  (Landwehr).  This  substance  is  precipitated  from  urine  by  adding  to  it  three  times  its  volume 
of  90  per  cent,  alcohol.  It  is  not  a  simple  body,  but  at  60°  to  70°  C.  it  transforms  starch  into  sugar 
(v.   Vintsc/igau). 

Ferments. — Traces  of  diastatic,  peptic,  tryptic,  and  rennet  ferment  have  been  found,  especially 
in  urine  of  high  specific  gravity. 

Traces  of  sugar  (Briicke,  Bence  Jones)  to  the  amount  of  0.05  to  o.oi  per  cent.,  and  less,  occur 
in  normal  urine.  After  the  ingestion  of  milk-,  cane-,  or  grape  sugar  (50  grms.)  these  varieties  of 
sugar  appear  in  small  quantity  m  the  urine  ( ll'orm  Mi'dler—  \  267,  7). 

Krytophanic  acid  (CjHgNOj),  according  to  Thudichum,  occurs  as  a  free  acid  in  urine,  but 
Landwehr  regards  it  as  an  animal  gum. 

Aceton  (C^H^O)  is  formed  when  normal  urine  is  oxidized  with  potassic  bichromate  and  sul- 
phuric acid,  and  it  is  formed  from  a  reducing  substance  present  in  normal  urine  (apparently  derived 
from  the  grape  sugar  of  the  blood).  Aceton  occurs  in  traces  as  a  normal  urinary  constituent, 
which  is  increased  during  increased  decomposition  of  the  tissues,  e.g.,  carcinoma,  inanition.  It 
has  also  been  found  in  the  blood  in  {^\ex  {v.  Jacksch).  Test. — Acidulate  half  a  litre  of  urine 
with  ACl  and  distil ;  when  treated  with  tincture  of  iodine  and  ammonia  there  is  a  turbidity  due  to 
iodoform. 

II.  THE  INORGANIC  CONSTITUENTS  OF  THE  URINE.— 

The  inorganic  constituents  are  either  taken  into  the  body  as  such  with  the  food 
and  pass  off  unchanged  in  the  urine,  or  they  are  formed  in  the  body  owing  to  the 
sulphur  and  phosphorus  of  the  food  being  oxidized  and  the  products  uniting  with 


442 


PHOSPHORIC    ACID    AND    EARTHY   PHOSPHATES. 


bases  to  form  salt.     The  quantity  of  salts  excreted  daily  in  the  urine  is  9  to  25 
grammes  [i^'  to  3^  oz.]. 

1.  Sodic  chloride — to  the  amount  of  12  (10  to  13)  grammes  [180  grains] — 
is  excreted  daily.  It  is  increased,  after  a  meal,  by  muscular  exercise,  drinking 
of  water,  and  generally,  when  the  quantity  of  urine  is  increased,  by  the  free  use 
of  large  quantities  of  common  salt,  but  by  potash  salts  also  ;  while  it  is  dimin- 
ished under  the  opposite  conditions. 

In  disease  it  is  greatly  diminished  ;  in  pneumonia  and  other  inflammations  accompanied  by 
effusions,  in  continued  diarrhoea  and  profuse  sweating,  constantly  in  albuminuria  and  in  dropsies. 
[In  cases  of  pneumonia,  sodic  chloride  may,  at  a  certain  stage,  almost  disappear  from  the  urine,  and 
it  is  a  good  sign  when  the  chlorides  begin  to  reappear.]  In  other  chronic  diseases,  the  amount  of 
NaCl  excreted  runs  nearly  parallel  with  the  amount  of  urine  passed.  In  conditions  of  excitement 
the  amount  of  sodic  chloride  is  diminished,  and  potassic  chloride  increased;  in  conditions  of  de- 
pression the  reverse  is  the  case  (Zeiilzfr). 

Test. — Add  to  the  urine  nitric  acid  and  then  nitrate  of  silver  solution,  which  gives  a  white,  curdy 
precipitate  of  chloride  of  silver.  In  albuminous  urine  the  albumin  must  first  be  removed.  Alicro- 
Siopically  look  for  the  step  like  forms  of  the  common  salt,  and  also  for  the  crystals  of  sodic  chloride 
urea  (§  256,  4). 

2.  Phosphoric   acid  occurs  in  urine  as  acid  sodic  phosphate  and  acid 

Fig.  248. 


h,  crystalline  magnesic  phosphate. 


calcic  and  magnesic  phosphates  (Fig.  248,  h),  to  the  amount  of  about  2 
grammes  daily  [30  grains],  but  it  is  more  abundant  after  a  flesh  than  after  a  vege- 
table diet.  The  amount  uicreases  after  a  mid-day  meal  until  evening,  and  falls 
during  night  until  next  day  at  noon.  It  is  partly  derived  from  the  alkaline  and 
earthy  phosphates  of  the  food,  and  it  is  partly  a  decomposition  product  of  lecithin 
and  nuclein.  As  phosphorus  is  an  important  constituent  of  the  nervous  system, 
the  relative  increase  of  phosphoric  acid  is  due  to  increased  metabolism  of  the 
nervous  substance. 

Pathological. — In  fevers,  the  increased  excretion  of  potassic  phosphate  is  due  to  a  consumption  of 
blood  and  muscle  (|  220,  3).  It  is  also  increased  in  inflammation  of  the  brain,  softening  of  the 
bones,  diabetes,  and  oxaluria;  and  after  the  administration  of  lactic  acid,  morphia,  chloral,  or  chloro- 
form. It  is  diminished  during  pregnancy,  owing  to  the  formation  of  the  fcetal  bones;  also  after 
the  use  of  ether  and  alcohol,  and  in  inflammation  of  the  kidney. 

Test. — Earthy  phosphates  are  precipitated  by  heat.  This  precipitate  is 
distinguished  from  albumin,  which  is- also  precipitated  by  heat,  by  being  soluble 
in  nitric  acid,  which  precipitated  albumin  is  not.  [The  earthy  phosphates  are 
not  precipitated  until  near  the  boiling  point.] 


SULPHURIC    ACID    AND    OTHER    BASES.  443 

Quantitative. — The  amount  of  phosphoric  acid  is  estimated  by  tritation  with  a  standnid solulion 
of  tiraniutit  actlnte  ;  ferrocyanidi:  of  potassitim  being  the  ittJitalor.  The  indicator  gives  a  brown- 
ish-red color  when  there  is  an  excess  of  free  uranium  acetate. 

In  addition  to  phosphoric  acid,  phosphorus  occurs  in  an  incompletely  oxidized  form  in  the  urine, 
e.  g..  glycerinphosphoric  acid  (J  251,  2)  (Sotnilzsclie~u<sky),  which  occurs  to  the  amount  of  15  milli- 
grammes in  a  litre  of  urine,  is  increased  in  nervous  diseases  [Lipine],  and  after  chloroform  narcosis 
(Ziiher). 

3.  Sulphuric  acid  occurs  in  the  urine,  the  greater  part  in  combination  with 
the  alkalies,  and  the  remainder  united  with  indol,  skatol,  and  pyrokatechin,  in  the 
form  of  aromatic  cthcrsiilphiiric  compounds  (Baiimann),  the  ratio  being  i  :  o  1045. 
All  conditions  which  favor  the  formation  of  indol,  skatol,  or  pyrokatechin,  in- 
crease the  amount  of  combined  sulphuric  acid.  The  total  daily  amount  of  sul- 
phuric acid  is  2.5  to  3.5  grammes  [37  to  52  grains].  It  is  increased  by  the 
administration  of  sulphur  {Krause).  The  sulphuric  acid  is  chiefly  derived  from 
the  decomposition  of  proteids,  and  hence  its  amount  runs  parallel  with  the  amount 
of  urea  excreted.  The  amouht  of  alkaline  sulphates  in  the  food  is,  as  a  rule,  very 
small. 

An  increased  excretion  of  sulphuric  acid  in  fevers  indicates  an  increased  metabolism  of  the 
tissues  of  the  body.  In  renal  inflammation  it  has  been  observed  to  be  diminished,  and  in  eczema 
it  is  greatly  increased.  Feeding  with  taurin  (which  contains  sulphur),  in  the  case  of  rabbits  (but 
not  in  carnivora  nor  man),  increases  the  sulphuric  acid  in  the  urine  [Snlkoiusii).  According  to 
Ziilzer,  a  copious  secretion  of  bile  lessens  the  relative  amount  of  sulphuric  acid  in  the  urine. 

Test. — Barium  chloride  gives  a  copious,  white,  heavy  precipitate  of  barium  sulphate,  insoluble  in 
nitric  acid. 

In  addition  to  sulphuric  acid,  sulphur  (i)  occurs  in  an  incompletely  oxidized  form  in  the  urine 
(potassium  sulphocyanide,  sulphurous  acid,  cystin,and  .sulphur-bearing  compounds  derived  from  the 
bile — Kitnkel^t'.  Voit — \  177,6).  /fyposn/phicrous  acid,  2iS  an  alkaline  salt,  is  an  abnormal  con- 
stituent  in  typhus;  and  so  is  sulphuretted  hydrogen,  which  is  recognized  by  the  blackening  of  a 
piece  of  paper  moistened  with  lead  acetate  and  ammonia  held  over  the  urine. 

4.  Excessively  minute  traces  of  silicic  acid  and  nitric  acid  derived  from  drinking  water  have 
been  found  in  urine.  Organic  acids,.e.  g.,  citric  and  tartaric,  when  taken  internally,  increase  the 
amount  of  carbonates  in  the  urine.     The  urine  may  effervesce  on  the  addition  of  an  acid. 

The  sodium  in  the  urine  is  chiefly  combined  with  chlorine,  but  a  small  part  of 
it  is  united  with  phosphoric  and  uric  acids  ;  potassium  (which  is  about  I3  of  the 
sodium)  is  chiefly  combined  with  chlorine.  In  fevers  more  potash  is  excreted  than 
soda,  and  during  convalescence,  the  reverse  is  the  case  ;  calcium  and  magne- 
sium exist  in  normal  acid  urine  as  chlorides  or  acid  phosphates.  If  the  urine  is 
neutral,  neutral  calcium  phosphate  and  magnesium  phosphate  are  precipitated. 
Ebstein  found  the  latter  in  alkaline  urine  as  large,  clear,  four-sided  prisms  in  diseases 
of  the  stomach.  If  the  urine  is  alkaline,  calcium  carbonate  (Fig.  248,  c)  or 
tribasic  calcic  phosphate  are  deposited  as  such,  while  the  magnesium  is  precipitated 
in  the  form  of  ammonio-magnesium  phosphate,  or  triple  phosphate.  The  calcium 
is  derived  from  the  food,  and  dejiends  upon  the  amount  of  lime  salts  absorbed 
from  the  intestine.  Free  ammonia  is  said  to  occur  (0.72  gramme,  or  7  grains 
daily)  in  perfectly  fresh  urine  (^Neuhciuer  and  Briickc),  and  the  amount  is  greater 
with  an  animal  than  with  a  vegetable  diet  {Coranda).  The  amount  of  fixed  am- 
monia is  increased  by  the  administration  of  mineral  acids  (  Walter,  Schtniedeberg, 
Gat/igcns).  Iron  (i  to  11  milligrammes  per  litre)  is  never  absent.  There  is  a 
trace  of  hydric-peroxide  i  Sc/ionlu-in),  which  is  detected  by  its  decolorizing 
indigo  solution  on  the  addition  of  iron  sulphate. 

Gases. — 24.4  c.c.  of  gas  was  obtained  from  one  litre  of  urine — 100  volumes  of  the  gases  pumped 
out  consisted  of  65.40  vol.  CO,,  2.74  O,  13  86  N.  After  severe  muscular  action,  the  amount  of 
CO2  may  lie  doubled;   digestion  also  increases  it. 

263.  SPONTANEOUS  CHANGES  IN  URINE— FERMENTA- 
TIONS.— Acid  Fermentation. — When  perfectly  fresh  urine  is  set  aside  in  a 
cool  jjlace,  it  gradually  becomes  more  acid  from  day  to  day.  This  is  called  the 
"  acid  fermentation."  It  seems  to  be  due  to  the  development  of  special  fungi 
(Fig.  249,  a),  and  the  process  is  accompanied  by  the  deposition  of  uric  acid  {c). 


444 


ACID    FERMENTATION    OF   URINE. 


acid  sodium  urate,  in  amorphous  grains  (*/'),  and  calcium  oxalate  (d).  According 
to  Scherer,  the  fungus  and  the  mucus  from  the  bladder  decompose  part  of  the 
urinary  pigment  into  lactic  and  acetic  acids.  The  latter  sets  free  uric  acid  from 
neutral  sodium  urate,  so  that  free  uric  acid  and  sodium  urate  must  be  formed. 
Butyric  and  formic  acids  have  been  found  as  abnormal  decomposition  products  of 
other  urinary  constituents.    When  the  acid  fermentation  begins,  the  urine  absorbs 


Fig.  249. 


Deposit  in  "acid  fermentatio! 

b,  amorphous  sodium  urate;  ■ 
cium  oxalate. 


Fig.  251 


cal  urine  (alkaline  fermentation). 
(7,  acid  ammonium  urate  ;  b,  ammonio-niagnesiiun 
phosphate  ;  c,  bacterium  ureze. 


Fir,.   252. 


Deposit  from  a  case  of  catarrh  of  the  urinary  bladder  (ammoniacal  The  more  usual  forms  of  triple  phosphate 

fermentation),    a,  detached  epithelium  ;  6,  pus  corpuscles  ;  c,  ;<  300. 

triple  phosphate  ;  tf,  micro-organisms. 

oxygen  (^Pasteur).  According  to  Briicke,  it  is  the  lactic  acid  formed  from  the 
minute  traces  of  sugar  present  in  urine,  which  causes  the  acidity.  According  to 
Rohmann,  who  recognizes  the  acid  fermentation  as  an  exceptional  phenomenon, 
the  acids  are  formed  from  the  decomposition  of  sugar,  and  from  alcohol  which 
may  be  present  accidentally.  While  the  urine  is  still  acid,  it  becomes  turbid  and 
contains  nitrous  acid,  whose  source  is  entirely  unknown.     According  to  v.  Voit 


ALBUMIN    IN    URINE.  445 

and  Hofmann,  phosphoric  acid  and  a  basic  salt  are  formed  from  acid  sodium 
phosphate,  whereby  part  of  the  uric  acid  is  displaced  from  sodium  urate,  thus 
causing  the  formation  of  an  acid  urate. 

Alkaline  Fermentation. — When  urine  is  exposed  for  a  still  longer  time, 
more  especially  in  a  warm  place,  it  becomes  neutral  and  ultimately  ammoniacal, 
/.  e.,  it  undergoes  the  alkaline  fermentation  (Fig.  250). 

This  condition  is  accompanied  by  the  formation  of  the  micrococcus  ureae 
{Pasteur,  Colui)  and  Bacterium  ures  (Fig.  251),  which  cause  the  urea  to  take  up 
water,  and  decompose  into  COj  and  ammonia. 

Urea  [CO(HN2).,]2(H,Oj  =  ammonium  carbonate  f(NH,),C03]. 

The  property  of  decomposing  urea  belongs  to  many  different  kinds  of  bacteria,  including  even  the 
sarcina  of  the  lungs — whose  genns  seem  to  be  universally  diffused  in  the  air.  These  organisms  pro- 
duce a  soluble  ferment  (AJtiscu/iis),  which,  however,  only  passes  from  the  body  of  the  cells  into 
the  fluid  after  the  cell  or  organism  has  been  killed  by  alcohol  [Sheridan  Lea). 

The  presence  of  ammonia  causes  the  urine  to  become  turbid,  and  those  sub- 
stances which  are  insoluble  in  an  alkaline  urine  are  precipitated — earthy  phos- 
phates, consisting  of  the  amorphous  calcic  phosphate,  acid  ammonium 
urate  (Fig.  250,  a)  in  the  form  of  small,  dark  granules  covered  with  spines  ;  and, 
lastly,  the  large,  clear,  knife-rest  or  "coffin-lid"  form  of  ammoniomagnesic 
phosphate,  or  triple  phosphate  (Fig.  252).  [The  last  substance  does  not 
e-xist  as  such  in  normal  urine,  but  it  is  formed  when  ammonia  is  set  free  by  the 
decomposition  of  urea,  the  ammonia  uniting  with  the  magnesium  phosphate.  Its 
presence,  therefore,  always  indicates  ammoniacal  fermentation  of  the  urine.]  In 
cases  of  catarrh  or  inflammation  of  the  bladder,  this  decomposition  may 
take  place  within  the  bladder,  when  the  urine  always  contains  pus  cells  (Fig.  251, 
b)  and  detached  epithelium  {a).  When  much  pus  is  present,  the  urine  contains 
albumin.  Ammoniacal  urine  forms  white  fumes  of  ammonium  chloride,  when  a 
glass  rod  dipped  in  hydrochloric  acid  is  brought  near  it. 

[Significance  of  Triple  Phosphate. — If  urine  be  alkaline  when  it  is  passed,  and  the  alkalinity 
be  due  to  a  vola/iie  alkali,  i.e.,  to  NH.,,  then  decomposition  of  the  urine  has  taken  place,  and  this 
kind  of  urine  is  a  sure  sign  that  there  is  disease  of  the  genito-urinary  mucous  membrane.] 

[When  ammonia  is  added  to  normal  urine,  triple  phosphate  is  precipitated  in  a 
feathery  form.] 

264.  ALBUMIN  IN  URINE  (ALBUMINURIA).— Serum  albumin 
is  the  most  important  abnormal  constituent  in  urine  which  engages  the  attention 
of  the  physician.  It  is  the  albumin  which  occurs  in  blood  (§  32),  and  whose 
characters  are  described  in  §  249. 

Causes  of  Albuminuria.^!.  Serum  albumin  may  appear  in  urine  without  any  apparent  ana- 
tomical or  structural  change  of  the  renal  tissues.  This  condition  has  been  called  by  v.  Bamberger 
*'J/ir»iatogenous  albumimti'ia.^''  It  occurs  but  rarely,  however,  and  sometimes  in  healthy  individu- 
uals  when  there  is  an  excess  of  albumin  in  the  blood  plasma  {e.g.,  after  suppression  of  the  secre- 
tion of  milk),  and  after  too  free  use  of  albuminous  food.  2.  As  a  result  of  increased  blood  pressure 
in  the  renal  vessels,  e.g.,  after  copious  drinking.  It  may  be  temporary,  or  it  may  be  persistent,  as  in 
cases  of  congestion  following  heart  disease,  emphysema,  chronic  pleural  effusions,  inHltrations  of  the 
lungs,  and  after  compression  of  the  chest,  causing  congestion  in  the  pulmonary  circuit,  which  extends 
even  into  the  renal  veins  (Sehreil'er),  etc.  3.  After  section  or  paralysis  of  the  vasomotor  nerves  of 
the  kidneys,  which  causes  great  congestion  of  these  organs.  The  albuminuria,  which  accompanies 
intense  and  long-continued  abdominal  pain,  is  brought  about  owing  to  a  reflex  paralysis  of  the  renal 
vessels  [Fisehel).  4.  After  violent  muscular  exercise.  [Senator  found  that  forced  marches  in  young 
recruits  were  very  frequently  followed  by  the  appearance  of  albumin  in  the  urine,  which  persisted 
for  several  days.]  Convulsive  disorders,  e.g.,  epilepsy,  the  spasms  of  dyspnoea  after  strychnin  poi- 
soning (Huppert);  in  shock  of  the  brain,  apoplexy,  spinal  paralysis,  and  violent  emotions;  the 
excessive  use  of  morphia,  which,  perhaps,  acts  on  the  vasomotor  centres.  5.  It  may  accompany 
many  acute  febrile  diseases,  e.g.,  the  exanthemata  (scarlet  fever),  typhus,  pneumonia  and  pyaemia. 
In  these  cases  it  may  be  due  to  the  increase  of  temperature  paralyzing  the  vessels,  but  more  prob- 
ably the  secretory  apparatus  of  the  kidney  is  so  changed  (e.g.,  cloudy  swelling  of  the  renal  epithe- 
lium) that  the  albumin  can  pass  through  the  renal  membranes.  6.  Certain  degenerations  and 
inflammations  of  the  kidneys  at  several  of  their  stages.    7.  Inflammation  or  suppuration  in  the  ureter 


446  TESTS   FOR    ALBUMIN    IN    URINE. 

or  urinary  passages.  8.  Certain  chemical  substances  which  irritate  the  renal  parenchyma,  (*. ,i,^., 
cantharides,  carbolic  acid.  9.  The  complete  withdrawal  of  common  salt  from  the  food.  The  albu- 
min disappears  when  the  common  salt  is  given  again  (  IVufidt^  Ji.  J^osenihai ),  lo.  'Y\\t  epilhelium 
may  be  in  such  a  condition  that  it  cannot  retain  the  albumin  wit/iin  the  vessels,  due  to  imperfect 
nourishment  and  functional  weakness  of  the  secretory  elements.  This  includes  the  albuminuria  of 
ischajmia,  and  that  after  hemorrhage  (Quincke),  in  anaemia,  scorbutus,  icterus,  diabetes. 

[Besides  being  derived  from  the  secreting  parenchyma  of  the  kidney,  albumin  may  be  derived 
by  admixture  with  the  secretions  from  any  part  of  the  urinary  tract,  including  the  vagina  and 
uterus  in  the  female.  In  some  cases  the  transudation  of  albumin  is  favored  by  changes  in  the 
capillary  walls,  the  albumin  being  forced  through  by  the  intravascular  pressure.  Sometimes  albu- 
minuria occurs  during  the  course  of  severe  typhoid  fever,  and  in  acute  fevers  generally  where  the 
temperature  is  persistently  above  40°  C.  (104°  F.).  The  high  temperature  alters  the  filtering  mem- 
brane and  permits  the  filtration  of  albumin.] 

[Physiological  Albuminuria. — This  term  has  been  applied  to  that  condition  of  the  urine  where 
traces  of  albumin  are  found  in  individuals  apparently  in  perfect  health.  Johnson  and  Pavy  cite 
such  cases,  while  Posner  asserts  that  all  urine — even  healthy  urine — contains  traces  of  proteids, 
who.se  presence  is  ascertained  after  concentrating  the  urine.  It  is  safe  to  assume  that  normal  urine 
should  give  no  reaction  for  albumin.] 

The  tests  for  albumin  in  urine  depend  upon  the  fact  that  it  is  precipitated 

by  various  reagents. 

[((?)  Heller's  Test. — Place  10  c.c.  of  the  urine  in  a  test  glass,  and  pour  in  pure  colorless  HNO3 
so  as  to  run  down  the  side  of  the  glass,  forming  a  layer  beneath  the  urine.  A  white  zone  of 
coagulated  albuinm  indicates  the  presence  of  albumin.  In  this  test  it  is  important  to  wait  a  certain 
time  for  the  development  of  the  reaction.  In  urines  of  high  specific  gravity,  a  haziness  due  to  acid 
urates  may  be  formed  above,  where  the  two  fluids  meet,  but  its  upper  edge  is  not  circumscribed. 
The  acid  decomposes  the  neutral  urates  and  forms  a  more  insoluble  acid  salt.  This  cloud  of  acid 
urates  is  readily  dissolved  by  heat,  while  the  albumin  is  not ;  the  latter. is  always  a  sharply-defined 
zone  between  the  two  fluids.  In  very  concentrated  urine  (rare),  nitric  acid  may  gradiially  precipitate 
crystalline  urea  nitrate.  In  patients  taking  copaiba,  nitric  acid,  by  acting  on  the  resin,  causes  a 
shght  niilkine-->s.] 

[{b)  Boiling  and  Nitric  Acid. — Place  10  c.c.  of  urine  in  a  test  tube  and  boil.  If  albumin  be 
present  in  small  quantity,  a  faint  haziness,  which  may  be  detected  in  a  proper  light,  will  be 
produced.  -\dd  10  or  12  drops  of  HNO^.  If  the  turbidity  disappears  it  is  due  to  phosphates, 
while  if  any  remains  it  is  due  to  albumin.  If  albumin  be  present  in  large  quantity,  a  copious 
whitish  coagulum  is  obtained.] 

\_Precautions. — (a)  In  all  cases,  if  the  urine  be  turbid,  filter  it  before  applying  any  test.  (^) 
How  to  Boil. — Boil  the  upper  strata  of  the  liquid,  and  take  care,  if  any  coagulum  be  formed,  that 
it  does  not  adhere  to  the  side  of  the  tube,  else  the  tube  is  liable  to  break,  {c)  In  performing  this 
test  with  a  neutral  solution,  note  when  the  precipitate  falls,  for  albumin  is  precipitated  about  70° 
C,  phosphates  not  till  about  the  boiling  point,  [d]  Amount  of  Acid. — If  too  little  (2  or  3  drops) 
HNO3  be  added,  or  too  much  (30  or  40  drops),  we  may  fail  to  detect  albumin,  although  present.] 

(i)  Ferrocyanide  Test. — By  the  addition  of  acetic  acid  and  potassium  ferrocyanide  [If  albu- 
min be  present,  a  white  flocculent  precipitate  separates  in  the  cold.  Dr.  Pavy  has  introduced  pel- 
lets, consisting  of  a  mixture  of  citric  acid  and  sodic  ferrocyanide.  All  that  is  required  is  to  add 
a  pellet  to  the  suspected  urine.  Oliver's  papers. — Dr.  Oliver  uses  papers,  one  saturated  with 
citric  acid  and  another  with  ferrocyanide  of  potassium.  The  two  papers  are  added  to  the  clear 
filtered  urine.  (Jther  precipitants  of  albumin,  such  as  small  pieces  of  paper  impregnated  with 
polassio-mercuric  iodide,  are  used  by  Oliver.] 

(</)  By  boiling  Acid  Urine. — If  the  urine  be  alkaline,  although  albumin  may  be  present,  it 
is  not  precipitated  by  heat  alone.  We  require  to  add  acetic  acid  until  a  slightly  acid  reaction  is 
obtained. 

Boiling  may  give  a  precipitate  of  earthy  phosphates  in  an  alkaline  urine,  owing  to  the  CO^ 
being  driven  off.  This  precipitate  might  be  mistaken  for  albumin,  but  on  adding  acetic  or  nitric 
acid,  the  earthy  precipitate  is  dissolved,  while  the  precipitate  of  albumin  is  not  dissolved.  In  test- 
ing for  albumin,  always  use  clear  urine.     If  it  is  turbid,  filter  it. 

\_(e)  Metaphosphoric  acid  is  dissolved  in  water  just  before  it  is  to  be  used  and  added  to  clear 
xinne  (Hindcnlang).  Graham  pointed  out  that  metaphosphoric  acid  precipitated  albumin.  A  20 
per  cent,  solution  of  the  ordinary  glacial  phosphoric  acid  is  a  good  test  for  albumin,  but  it  also  pre- 
cipitates peptones.  It,  however,  changes  into  ordinary  phosphoric  acid  by  keeping,  and  then  it  no 
longer  precipitates  albumin.] 

[(/)  Acidulate  10  c.c.  of  urine  with  acetic  acid,  and  add  ]/(,  of  its  volume  of  a  concentrated 
solution  of  sulphate  of  soda  or  magnesia.  On  heating,  if  albumin  be  present,  a  distinct  cloudiness 
is  obtained.] 

[\g)  In  picric  acid,  according  to  Dr.  Johnson,  we  have  a  more  delicate  test  for  minute  traces 
of  albumin  than  either  heat  or  nitric  acid,  or  than  both  these  tests  combined.  It  is  used  either  in 
the  form  of  crystals  or  powder,  or  as  a  saturated  aqueous  solution.     Take  a  four-inch  column  of 


H.EMATURIA   AND    H.EMOGLOBINURIA.  447 

urine  in  a  test  tube,  hold  the  tube  in  a  slanting  direction,  and  pour  an  inch  of  the  picric  acid  solu- 
tion on  the  surface  of  the  urine,  where,  in  consequence  of  its  low  specific  gravity  (1005),  it  mixes 
only  with  the  upper  layer  of  the  urine.  It  coagulates  any  albumin  present.  The  precipitate  occurs 
at  once,  and  is  increased  by  heat,  while  the  urate  of  soda,  which  is  sometimes  precipitated,  is 
soluble  on  heating.] 

[Dr.  Roberts  regards  any  test  for  albumin  which  requires  strong  acidulalion  with  an  organic  acid, 
citric,  acetic  or  lactic,  as  unsatisfactory,  since  it  precipitates  mucin.  For  this  reason  he  rejects  the 
tungstate,  mercuric  iodide,  and  potassic  ferrocyanide  tests.  Dr.  Roberts  regards  the  heat  test,  with 
the  addition  of  a  small  definite  quantity  of  acetic  acid,  as  the  best  test  for  the  detection  of  small 
quantities  of  albumin.] 

1.  Quantitative  Estimation  of  albumin. — 100  c.c.  of  urine  are  boiled  in  a  capsule,  some 
acetic  acid  being  ultimately  added,  whereby  the  albumin  is  precipitated  in  flakes.  The  precipitate 
is  collected  on  a  weighed,  dried  (110°),  and  ash  free  filter,  and  repeatedly  washed  with  hot  water, 
then  with  alcohol,  and  completely  dried  in  an  air  bath  at  110°.  Lastly,  the  dried  filter  with  the 
albumin  is  burned  in  a  weighed  platinum  capsule,  and  the  weight  of  the  ash  also  deducted  from  it. 
[This  method  is  not  available  for  the  busy  practitioner  on  account  of  the  time  it  takes.  Practically, 
it  is  sufficient  to  compare  from  day  to  day  the  proportion  that  the  precipitated  albumin  bears  to  the 
bulk  of  the  urine  tested.  A  graduated  tube  may  be  used,  so  that  after  the  precipitate  has  subsided 
the  ph}sician  may  see  whether  it  occupies  one-fourth  or  one-tenth  of  the  fluid,  as  the  case  may  be.] 

2.  Globulin  occurs  only  in  albuminous  urine  (Senator,  Edlefsen'),&TiA  is  frequently  present.  Its 
presence  is  ascertained  by  adding  powdered  magnesium  sulphate  in  excess  to  the  urine;  when  it 
is  present  it  is  precipitated  (J  32).  The  more  globulin  there  is  in  the  presence  of  albumin,  the 
more  difficult  it  is  to  precipitate  it.  [Sometimes,  when  an  albuminous  urine  is  dropped  into  a  large 
cylinder  of  water,  each  drop  as  it  sinks  is  followed  by  a  milky  train,  and  when  a  sufficient  number 
of  drops  has  been  added,  the  water  becomes  opalescent,  the  opalescence  disappearing  on  adding  an 
acid.  The  globulin  is  kept  in  solution  by  common  salt  and  other  neutral  salts,  but  when  these  are 
largely  diluted,  the  globulin  is  precipitated  {Roberts).'\ 

3.  Peptone  (v.  Frerichs,  iSji)  occurs  in  some  specimens  of  albuminous  urine,  but  also  in  non- 
albuminous  urine  (Ger/tardt).  Maixner  found  it  constantly  in  the  urine  in  all  cases  where  suppu- 
ration is  present,  f.^.,  in  exudations,  abscesse.--,  resolution  of  pneumonia,  and  in  articular  rheumatism, 
when  the  attack  is  passmgofi  [v.  Jaisc/i).  feptone  occurs  in  pus,  and  the  peptonuria  in  these 
cases  is  a  sign  of  the  breaking  up  of  the  pus  cells  [No/meister).  Also  when  many  leucocytes  are 
broken  up  in  the  blood,  or  when  large  quantities  of  peptone  are  absorbed  from  the  intestinal  canal. 
It  is  frequently  found  after  childbirth. 

Test. — Separate  the  albumin  by  boiling  and  the  addition  of  acetic  acid.  Treat  the  filtrate  with 
three  volumes  of  alcohol;  this  precipitates  the  peptone,  which,  when  dissolved  in  water,  gives  the 
characteristic  reactions  for  peptone  (^  166,  I). 

4.  Propeptone  occurs  very  rarely  in  osteomalacia  and  intestinal  tuberculosis  (Macynter  and Bence 
Jones).  The  urine  is  treated  to  saturation  with  NaCl  and  a  large  quantity  of  acetic  acid  added,  and 
riltereii  while  hot,  to  separate  the  albumin  and  globulin.  In  the  cold  filtrate  propeptone  forms  a 
turbidity,  which  is  redissolved  by  heat.  The  precipitate  thrown  down  by  HCl  and  HNO3  is  soluble 
by  heat  (Kuhne).  The  precipitate  is  isolated  by  filtration,  and  dissolved  in  a  little  warm  water, 
when  it  gives  with  HNO3  a  yellow  reaction;  like  peptone,  the  solution  gives  the  biuret  reaction. 

5.  Egg  albumin  appears  in  the  urine  wdien  much  egg  albumin  is  taken  in  the  food,  and  also 
when  it  is  injected  into  the  blood  vessels  (§  192,  4).  According  to  Semmola,  the  albumin  present 
in  the  urine  in  Bright's  disease  has  undergone  a  molecular  change  (similar  to  egg  albumin),  and 
hence  it  is  excreted. 

6.  Mucus  is  present  in  large  amount,  especially  in  catarrh  of  the  bladder.  It  contains  numerous 
mucus  corpuscles,  which  are  scarcely  distinguishable  from  pus  corpuscles.  They  contain  albumin, 
so  that  urine  containing  much  mucus  is  albuminous ;  mucin  is  not  precipitated  by  heat,  but  acetic 
acid  gives  a  fiocculent  precipitate  in  clear  urine.  [Minute  traces  of  mucin  occur  normally  in  urine. 
If  clear,  normal  urine  be  set  aside  for  a  short  time,  a  flocculent  haziness,  like  a  cloud  of  cotton  wool, 
is  seen  floating  in  the  urine.  This  is  mucus  entangling  a  few  epithelial  cells  from  the  genito-urinary 
tract.  Mucin  Reaction. — According  to  \V.  Roberts,  the  addition  of  a  concentrated  solution  of 
citric  acid  to  urine,  as  in  Heller's  test  {\  264,  a),  where  the  two  fluids  meet,  causes  an  opalescent 
zone  gradually  to  be  formed  above  the  layer  of  acid.] 

265.   BLOOD    IN    URINE   (H.,EMATURIA)— H.ff;MOGLOBINURIA.— I.  Source 

of  the  Blood.  —  (i  )  In  haematuria,  the  blood  may  come  from  any  part  of  the  urinary  apparatus. 
I.  In  hemorrhage  from  the  kidney,  the  amount  of  blood  is  usually  small  and  well  mixed  with  the 
urine.  The  presence  of  ■•  blood  cylinders,"  long,  microscopic  blood  coagula,  casts  of  the  uriniferous 
tubules,  washed  out  of  them  by  the  urine,  are  characteristic  when  they  are  found  in  the  urine  (Fig. 
263).  The  urine  usually  has  a  smoky  appearance.  [The  urine  slowly  dissolves  out  the  coloring 
matter,  the  stroma  of  the  corpuscles  after  a  time  being  deposited  as  a  brownish  sediment.  The 
smoky  hue  occurs  only  in  acid  urine;  if  the  urine  becomes  alkaline, the  hue  becomes  brighter  red.] 
The  blood  corpuscles  show  peculiar  changes  of  form  [they  become  crenated]  ( Fig.  253),  and  exhibit 
evidence  of  division,  due  to  the  action  of  urea  on  them  \\  5).     Large  coagula  are  never  found  in 


448  H.EMATURIA    AND    H.EMOGLOBINURIA. 

urine  mixed  with  blood  derived  from  the  kidney.  2.  In  hemorrhage  from  the  ureter,  we  occa- 
sionally find  worm-like  masses  of  clotted  blood,  casts  of  the  canal  of  the  ureter.  3.  The  relatively 
largest  coagula  occur  in  hemorrhage  from  the  bladder.  In  all  cases  where  blood  is  present,  we 
must  examine  microscopically  for  the  blood  corpuscles,  and  it  may  be  for  coagula  of  fibrin  In  acid 
urine,  blood  corpuscles,  but  never  in  rouleaux,  may  be  found  after  two  to  three  days  in  urine.     The 

Fig.  253. 


Crenated  red  blood  corpuscles  in  urine  X  35°. 
Fir,.  254. 


Peculiar  ch.inges  of  the  red  blood  corpuscles  in  renal  haeniaturia  {Friedreich). 

blood  corpuscles  settle  as  a  red  sediment  at  the  bottom.     If  the  hemorrhage  is  copious,  many  retain 
their  original  shape;  but  if  the  urine  is  very  concentrated,  they  may  become  crenated. 

When  there  is  a  small  and  slow  hemorrhage  from  ruptured,  small  capillaries,  the  red  blood  cor. 
puscles  are  of  unequal  size,  many  J4  to  y^  the  size  of  normal,  while  the  pigment  has  become  brownish 
yellow  (Fig.  255). 


BLOOD    IN    URINE. 


449 


If  a  hemorrhage  of  this  kind  is  accompanied  by  catarrhal  inflammation  of  the  bladder,  there 
is  found  between  the  red,  numerous  shriveled  leucocytes  (Fig.  255),  which  in  freshly-passed  urine 
often  exhibit  lively  amceboid  movements.  If  the  urine  be  alkaline,  as  it  usually  is,  crystals  of  triple 
phosphate  also  occur. 

If  the  remains  of  the  red  blood  corpuscles  become  very  pale,  their  presence  may  be  frequently 
ascertained  by  adding  iodine  in  a  solution  of  KI  (Fig.  254).  Blood  is  constantly  present  in  the 
urine  during  menstruation. 

Fig.  255. 


Colored  and  {a)  colorless  blood  corpuscles  of 

Fig.  256. 


f^::^^% 


Shriveled  blood  corpuscles  in  urine  (catarrh  of  the  bladder),  with  numerous  lymph  corpuscles, 
and  crj'stals  of  triple  phosphate,  X  35o. 

II.  Haemoglobinuria  is  quite  distinct  from  hsematuria.  It  depends  upon  the  excretion  of 
haemoglobin  as  such  through  the  kidneys,  and  it  is  produced  when  haemoglobin  occurs  free 
within  the  blood  vessels,  as  in  cases  where  the  colored  blood  corpuscles  have  been  dissolved  inside 
the  blood  vessels  (hsmocytolysisl.  It  occurs  when  foreign  blood  is  transfused,  i;.g.,  when  lamb's 
blood  is  transfused  into  man.  The  foreign  blood  corpuscles  are  dissolved  in  the  blood  of  the 
recipient,  and  the  hiemoglobin  appears  in  the  urine  (J  I02).  In  addition,  microscopic  "cyHnders," 
29 


450 


BILE    IN    URINE. 


consisting  of  a  globulin-like  body  tinged  yellow  with  haemoglobin,  may  likewise  be  found  in  the 
urine.  It  also  occurs  in  cases  of  severe  burns  (^  lo,  3) ;  after  decomposition  of  the  blood  in  pycemia, 
scorbutus,  purpura,  severe  typhus,  after  respiring  arseniuretted  hydrogen,  and  after  the  passage  of 
azobenzol  [Baiimann  and  Her/er),  of  naphtol  [A'aposi],  pyrogallic  acid,  potassic  chlorate,  chloral, 
phosphorus,  or  carbolic  acid  into  the  circulation.  [The  injection  of  laky  blood,  water,  ether, 
glycerine  (Adnms),  or  toluylendiamin  (Af'anassiew),  also  causes  it,  and  in  such  cases  Afanassiew 
asserts  that  the  Hb  passes  out  through  the  glomeruli,  while  brown  degeneration  products  of  the  red 
blood  corpuscles,  which  are  dissolved  by  these  agents,  were  found  in  the  convoluted  tubules.] 
These  substances  dissolve  the  red  blood  corpuscles.  Sometimes  it  occurs  periodically  from  causes 
and  conditions,  as  yet  but  little  understood,  f,  g.,  the  application  of  cold  to  the  skin. 

Tests  for  Blood  in  Urine. — I.  The  color  of  bloody  urine  shows  every  tint,  from  a  faint  red  to 
a  dark,  blackish  brown,  according  to  the  amount  of  blood  present.     The  urine  is  often  turbid. 

2.  Urine  containing  blood  or  blood  pigment  contains  albumin. 

3.  Heller's  Blood-test. — Add  to  urme  half  its  volume  of  solution  of  caustic  potash,  and  heat 
gently.  The  earthy  phosphates  are  precipitated,  and  they  carry  the  htematin  with  them,  falling  as 
garnet-red  tlocculi.     [This  is  not  a  relialile  test.] 

4.  Haemin  Test. — The  colored  earthy  phosphates  may  be  collected  on  a  filter,  and  from  them 
hoemin  may  be  prepared  as  directed  in  J  19. 

Fig.  257. 


Spectroscope  for  investing  the  pn 


;  of  haemoglobin  i 


5.  AlmiJn's  Test. — Add  to  urine,  freshly-prepared  tincture  of  guaiacum  and  ozonized  ether;  a 
blue  color  iiulicates  the  presence  of  blood  (§  37). 

6.  Spectroscope  (see  ^  14).  Fig.  257  shows  the  arrangement  of  the  apparatus.  The  urine  is 
placed  in  a  glass  vessel,  D,  with  parallel  sides,  I  centimetre  apart  (hoematinometer).  Light 
from  a  lamp,  E,  passes  through  the  fluid.  The  lamp,  F,  illuminates  the  scale,  which  is  seen  by  the 
observer  through  the  telescope,  A.  (a)  Fresh  urine  containing  blood  gives  the  spectrum  of 
oxyhaemoglobin  ( Fig.  14).  (/>)  When  bloody  urine  is  exposed  for  some  time,  especially  in  a  warm 
place,  it  becomes  more  acid,  and  assumes  a  dark,  brownish-black  color.  The  ha;moglobin  becomes 
changed  into  methsemoglobin  (^  15).  It  is  precipitated  by  lead  acetate,  which  does  not  precipi- 
tate oxyhccmoglobin ;  the  spectrum  of  methsemoglobin  resembles  that  of  hncmatin  in  an  acid  solu- 
tion (§  15,  Fig.  14).  The  two  spectra  may  be  combined,  (c)  The  microscopic  investigation 
must  never  be  omitted.  The  shape  of  the  corpuscles  may  vary  considerably,  as  is  shown  in  Figs. 
253  to  255. 

266.  BILE  IN  URINE  (CHOLURIA).— The  physiological  condhions  which  cause  the 
bile  constituents  to  appear  in  the  urine  are  mentioned  in  part  at  ^  iSo. 

Haematogenic,  or  Anhepato^jenic  Icterus  ( yK!«<-/i"i;),  occurs  when  bilirubin  {§  20)  is  formed 
from  extravasated  blood  by  the  action  of  the  connective-tissue  corpuscles,  so  that  bile  pigments,  in 
addition  to  coloring  the  tissues,  pass  into  the  urine. 


SUGAR   IN    URINE.  451 

I.  Bile  Pigments. — Their  presence  is  ascertained  by  Gmelin-Heintz's  test.  Green  (Bili- 
verdin)  is  the  characteristic  hue  in  the  play  of  colors  obtained  with  this  test,  which  is  fully  described 
in  I  in- 

Modifications  of  the  Test. — i.  If  icteric  urine  be  filtered  through  filtering  or  blotting  paper, 
a  drop  of  nitric  acid  containing  nitrous  acid,  when  applied  to  the  inner  surface  of  the  spread-out 
filter,  gives  a  yellowish  colored  ring  [Rosenbaih).  2.  In  order  that  the  reaction  may  not  take  place 
too  rapidly,  add  a  concentrated  solution  of  sodic  nitrate,  and  then  slowly  pour  in  sulphuric  acid 
(FUischl).  3.  On  shaking  50  c.c.  of  icteric  urine  with  10  c.c.  of  chloroform,  the  bilirubin  is  dis- 
solved by  the  latter.  On  adding  bromide  water,  a  beautiful  ring  of  colors  is  obtained  (^/aly).  If 
the  chloroform  extract  be  treated  with  ozonized  turpentine  and  dilute  caustic  potash,  a  green  color, 
due  to  biliverdin,  occurs  in  the  watery  fluid  [Gerhardt). 

In  slight  degrees  of  jaundice,  urobilin  alone  may  be  found  (§  261,  i)  [Quincke). 

In  persistent  high  fever,  the  urine  contains  especially  biliprasin  [Huppert).  If  it  contains 
choletelin  alone,  add  to  the  urine  some  hydrochloric  acid,  and  examine  it  with  the  spectroscope, 
which  gives  a  pale  absorption  band  between  b  and  F  (J  177,  3,/). 

Haematoidin. — Sometimes  crystals  of  Au-ma/oidin  (|  20,  Fig.  14)  appear  in  the  urine,  especially 
when  blood  corpuscles  are  dissolved  within  the  blood  stream  ;  occasionally  in  scarlet  fever  and 
typhus,  and  sometimes  in  cases  of  periodic  linemoglobinuria.  The  breaking  up  of  old  blood  clots 
in  the  urinary  passages,  as  in  pyonephrosis  (Ebstein),  or  during  the  dissolution  of  necrotic  areas 
[Hofmann  and  Ultzmann')  produces  them,  and  similar  crystals  occur  in  analogous  cases  in  the 
sputum  (5  13S).  In  jaundice  due  to  congestion  {\  180),  the  identical  crystalline  substance,  bilirubin, 
is  found. 

II.  Bile  acids  occur  in  largest  amount  in  absorption  jaundice,  but  they  are  never  present  to  any 
extent. 

The  test  is  described  at  ^177,  2,  the  cane-sugar  solution  consisting  of  0.5  grm.  to  i  litre  of 
water.  If  the  urine  be  dilute,  it  is  advisable  to  concentrate  it  on  a  water  bath.  v.  Pettenkofer's 
test  may  be  used  with  the  alcoholic  extract  of  the  nearly  dry  residue,  but  no  albumin  must  be  present. 
Dragendorft'  found  o.S  grm.  in  100  litres  of  normal  urine. 

Strassburg's  Modification. — Dip  filter  paper  into  the  urine,  to  which  a  little  cane  sugar  has 
been  added  ;  dry  the  paper,  and  apply  to  it  a  drop  of  sulphuric  acid.  A  violet-red  color  is  obtained 
after  a  short  time. 

[Hay's  Reaction. — The  effect  of  bile  salts  in  lessening  the  surface  tension  of  a  liquid,  and  thus 
rapidly  causing  the  precipitation  of  a  dry  powder  like  sulphur,  when  placed  in  the  liquid,  is  the 
basis  of  this  test  (\  177)-] 

267.  SUGAR  IN  URINE  (GLYCOSURIA).  —  Diabetes  Mellitus.— The  excessively 
minute  trace  of  grape  sugar,  or  dextrose,  which  is  constantly  present  in  normal  urine,  sometimes 
becomes  greatly  increased,  and  constitutes  the  conditions  of  diabetes  mellitus  and  glycosuria. 
The  physiological  conditions  which  determine  this  result  are  given  at  J  175.  In  this  condition,  the 
quantity  of  urine  is  greatly  increased;  it  may  reach  10  or  more  litres.  Many  pints  may  be  passed 
daily.  [The  usual  abnormal  amount  of  sugar  is  from  i  to  8  per  cent.,  although  15  per  cent,  has 
been  found,  i.  <?.,  found  from  5  to  50  grs.  per  fluid  oz.,  or  300  to  4000  grs.  in  twenty-four  hours 
(7}'j<!«).]  The  specific  gravity  is  also  increased  (1030  to  1040).  [In  a  case  where  a  large 
amount  of  urine  is  passed  of  a  pale  color  and  a  specific  gravity  above  1030,  always  suspect  sugar.] 
A  diabetic  person  gives  oft"  relatively  more  water  by  the  kidneys  and  less  by  the  skin  (and  lungs  ?) 
than  a  healthy  person.  The  color  is  very  pale  yellow,  although  the  amount  of  pigment  is,  by  no 
means,  diminished  ;  it  is  only  diluted  [the  depth  of  the  color  being  inversely  as  the  quantity  passed]. 
The  amount  of  the  nitrogenous  urinary  excreta  is  increased.  The  sugar  is  increased  by  a  diet  of 
carbohydrates  and  diminished  by  an  albuminous  diet.  The  uric  acid  and  oxalate  of  lime  are  often 
increased  at  the  commencement  of  the  disease,  while  yeast  cells  are  constantly  present  after  the 
urine  has  been  exposed  to  the  air  for  some  time. 

Sugar  has  been  found  occasionally  after  poisoning  with,  or  after  the  use  of,  morphia,  CO,  chloral, 
chloroform,  curara;  after  the  injection  of  ether  and  amyl-nitrite  into  the  blood;  and  in  gout,  inter- 
mittent fever,  cholera,  cerebro-spinal  meningitis,  hepatic  cirrhosis,  and  cardiac  and  pulmonary 
affections. 

Tests. — Any  of  the  tests  described  at  \  149  may  be  used,  but  the  urine  must  be  free  from  albumin. 
Tlie  quantitative  estimation  by  fermentation  and  the  titration  methods  are  described  in  \  149.  [The 
tests  for  grape  sugar  described  in  \  149  are  (i)  Trommer's;  (2)  Fehling's ;  (3)  Moore  &  Heller's; 
(4)  Bottger's;   (5)  .Mulder  and  Neubauer's  ;  (6)  Fermentation  test.] 

7.  Worm  Miiller  recommends  the  following  modification  of  Fehling's  test:  Use  a  2.5  per  cent, 
solution  of  cupric  sulphate  solution,  and  another  of  10  parts  of  sodio-polassic  tartarate  in  100  parts 
of  a  4  per  cent,  solution  of  soda.  Boil  5  c.  cm.  of  urine  in  a  test  tube,  while  in  a  second  test  tube 
is  boiled  i  to  3  c.  cm.  of  the  copper  solution  and  2.5  c.  cm.  of  the  potassio-tartrate  solution.  The 
boiling  of  both  fluids  is  stopped  simultaneously,  and  after  20  to  25  seconds,  the  contents  of  one  test 
tube  are  added  to  those  of  the  other,  but  without  shaking  the  mixture,  the  reduction  taking  place 
spontaneously. 

S.  Nylander's  modification  of  Bottger's  test  is  also  good  (^149). 


452  TESTS    FOR    SUGAR    IN    URINE. 

[9.  Picric  Acid  and  Potash  Test. — Braun  showed  ihat  grape  sugar,  when  hoiled  with  picric 
acitl  and  potash,  rei-hices  the  yellow  picric  acid  to  the  deep-red  picramic  acid,  the  depth  of  the  color 
depending  on  the  amount  of  sugar  present.  Dr.  Johnson  uses  this  test  for  detecting  the  presence  of 
sugar  in  urine,  and  also  for  estimating  the  amount  of  sugar  present,  the  depth  of  the  red  color 
obtained  in  boiling  being  compared  with  a  standard  dilution  of  ferric  acetate.  In  doing  the  test, 
use  I  drachm  of  urine,  I2  ^  drachm  of  liquor  potassfe,  and  10  minims  of  picric  acid  solution  ;  make 
up  to  2  drachms  with  distilled  water,  and  boi!  the  mixture  for  one  minute.  This  test  indicates  the 
presence  of  0.6  grain  of  sugar  per  fluidounce  of  normal  urine.  Dr.  Johnson  claims  for  this  lest 
that  it  possesses  all  the  advantages  of  the  other  tests,  while  it  is  not  aflfected  by  uric  acid  or  any 
other  normal  ingredient  of  urine;  neither  does  the  presence  of  albumin  interfere  with  the  action  of 
the  test  as  it  does  with  all  the  forms  of  copper  testing.] 

[10.  Indigo-carmine  Test. — A  blue  solution  of  this  substance,  when  boiled  with  diabetic  urine 
containing  sodic  carbonate,  changes  from  a  blue  to  a  violet,  purple-red,  yellow,  and,  finally,  straw- 
yellow  color.  After  cooling  and  expo.sure  to  the  air,  the  various  colors  are  obtained  in  the  reverse 
order  until  the  mi.vture  becomes  blue  again.  Dr.  Oliver  uses  this  test  in  the  form  of  test  papers. 
One  bibulous  paper  is  impregnated  with  the  indigo  carmine  and  the  other  witli  sodic  carbonate. 
Drop  one  of  the  test  papers  and  a  sodic  carbonate  paper  into  a  test  tube  containing  lyi  inches  of 
water;  heat  gently,  when  a  blue  solution  is  obtained.  Add  the  urine  slowly,  one  drop  at  a  time, 
and  boil  the  mixture,  ol)serving  any  change  of  color  by  holding  the  tube  against  a  white  surface 
below  the  level  of  the  eye.  Uric  acid  and  urates,  which  reduce  Fehling's  solution,  do  net  affect 
the  carmine  test,  nor  does  krealinin,  although  it  reacts  with  the  picric  acid  test.] 

[Quantitative  Estimation — (<;)  Fermentation  Test  (ji  150).  Take  4  oz.  (120  c.  c.)  of  the 
urine;  add  a  lump  of  Oerman  yeast  about  the  size  of  a  walnut,  lightly  cork  the  bottle,  and  place  it 
aside  for  twenty-four  hours  in  a  moderately  warm  place,  e.g.,  on  the  mantelpiece.  Take  the  spe- 
cific gravity  before  and  after  the  fermentation.  Thus,  if  the  specific  gravity  be  1038  before  and 
1013  afterward,  the  difl'erence,  or  "  density  lost,"  is  25,  which  gives  25  grs.  of  sugar  per  fluid  oz. 
(Rol'erts).  If  it  be  desired  to  get  the  percentage,  multiply  the  density  lost  by  0.23  ;  thus,  25  X  0'23 
^  5.69  in  100  parts.] 

\_(b)  Volumetric  Analysis. — 10  c.  c.  of  Fehling's  solution  :=  .05  gramme  of  sugar. 

I.  Ascertain  the  tjuantity  of  urine  passed  in  twenty-four  hours.  2.  Filter  the  urine,  and  remove 
any  albumin  present  by  boiling  and  filtration.  3.  Dilute  10  c.  c.  of  Fehling's  solution  with  about 
twenty  times  its  volume  of  distilled  water,  and  place  it  in  a  white  porcelain  capsule  on  a  wire  gauze 
support,  under  a  burette.  (It  is  diluted  because  any  change  of  color  is  more  easily  observed.)  4. 
Take  5  c.  c.  of  the  urine  and  95  c.  c.  of  distilled  water,  and  place  the  diluted  urine  in  a  burette. 
5.  Gradually  boil  the  diluted  Fehling's  solution,  and  while  it  is  boiling,  gradually  add  the  diluted 
urine  from  the  burette,  until  all  the  cuprous  oxide  is  precipitated  as  a  reddish  powder,  and  the  super- 
natent  fluid  has  a  straw-yellow  color,  not  a  trace  of  blue  remaining.  Read  off  the  number  of  c.  c. 
of  dilute  urine  employed.  Say  36  c.  c.  were  used — that,  of  course,  represents  i  .8  c.  c.  of  the 
original  urine.  Suppose  the  patient  passes  1550  c.c,  and  as  1.8  c.  c.  of  urine  reduced  all  the  cupric 
oxide  in  the  10  c.  c.  of  Fehling's  solution,  it  must  contain  .05  gramme  sugar;  hence, 

1.8  :  1550  :  :  .05  :  _i5 — ^^l_lJ=  237.5  grammes  of  sugar  passed  in  24  hours.] 

(c)  According  to  Worm  MUller,  the  polarization  method  is  almost  valueless  for  diabetic  urine. 

If  large  quantities  of  dextrose  are  taken  in  the  food,  a  part  of  it  (and  more  in  diabetic  persons) 
appears  in  the  urine.  Laevulose,  when  taken  internally,  does  not  increase  the  amount  of  sugar  in 
diabetes.  The  free  use  of  starch  does  not  cause  glycosuria  in  health,  but  in  diabetes  it  increases 
the  amount  of  sugar.  A  large  consumption  of  cane-  or  milk  sugar  causes  the  passage  of  small 
c|iiantilies  of  both  of  these  sugars  into  the  urine  in  health,  while  in  diabetes  the  amount  of  dextrose 
is  increased  (  Worm  Miiller').  According  to  Kiilz,  in  diabetic  persons  cane  sugar  is  split  up  into 
grape-fruit  sugar,  the  latter  being  used  up  in  the  body,  the  former  partly  excreted ;  and  the  same  is 
the  case  with  milk  sugar. 

In  severe  cases  of  diabetes  mellitus,  Kiilz  found  the  left  rotatory  ^-oxybutyric  acid  ( the  next  highest 
analogue  of  lactic  acid)  in  the  urine,  from  which  acetic  acid  is  formed  by  oxidation  (\  175)  which 
in  its  turn  readily  yields  CO^  and  aceton.  (7-crotonic  acid  is  formed  in  urine  by  the  removal  of 
water  from  oxybut)ric  acid  in  the  urine  in  diabetes  [Siade/mann).  The  administration  of  aceton 
causes  albuminuria,  and  this  may  in  part  explain  in  some  cases  the  complication  of  albuminuria  in 
diabetes  [Albertoiti  and  Pisenti). 

[Preparation  of  Fehling's  Solution. — 34.64  grammes  of  pure  crystalline  cupric  sulphate  are 
powdered  and  dissolved  in  200  c.c.  of  distilled  water;  in  another  vessel  dissolve  1 73  giammes  of 
Rochelle  salts  in  4S0  c.c.  of  pure  caustic  soda,  specific  gravity  1.14.  Mix  the  two  solutions,  and 
dilute  the  deep  colored  fluid  which  results  to  I  litre.  yV.  B. — Fehling's  solution  ought  not  to  be 
kept  too  long;  it  is  apt  to  decompose,  and  should  therefore  be  preserved  from  the  light,  or  protected 
with  opaque  paper  pasted  on  the  bottle.  Some  other  substances  in  urine,  e.g.,  urates  and  uric  acid, 
reduce  cupric  oxide.] 

Aceton,  or  Aceton-yielding  substance,  probably  aceto-acetic  acid,  is  sometimes  found  in  diabetic 
urine.  It  has  a  peculiar  venous  odqr,  and  it  has  been  detected  in  the  urine  during  fever.  Gerhardt 
described  a  peculiar  substance  in  di.ibetic  urine,  which  gave  a  deep  red  color  with  perchloride  of 


MILK,  SUGAR   AND    OTHER    SUBSTANCES   IN    URINE. 


453 


iron.  This  substance  is  probably  diacetic  ether,  and  he  considered  it  to  be  the  source  of  aceton ; 
but  it  is  more  probably  derived  from  aceto-acetic  acid.  Tests  for  Aceton. — (l)  Perchloride  of 
iron  =  Burgundy- red  color  ;  but  this  is  not  reliable.  {2)  Lieben  suggested  an  iodoform  test.  Dis- 
solve 20  grains  of  KI  in  fluidrachm  of  liq.  potassje,  and  boil  the  fluid.  Pour  the  suspected  urine 
on  the  surface,  when  a  ring  of  phosphates  is  deposited  from  the  urine  by  the  hot  alkaline  solution. 
If  aceton  be  present,  after  a  time  the  deposit  becomes  yellow,  and  yellow  granules  of  iodoform 
appear  and  sink  to  the  bottom  of  the  test  tube  (Jialfe).  The  only  other  substance  which  may  be 
met  with  in  the  urine  giving  this  reaction  is  lactic  acid.] 

[Picro-Saccharimeter. — G.  Johnson  uses  a  stoppered  bottle  12  inches  long  and  }(  inch  wide, 
graduated  in  y'j  and  yj^  (Fig.  257,  n).  To  it  is  fixed  a  shorter  bottle  containing  the  standard 
iron  solution  for  comparison,  a  standard  solution,  composed  of  liquor  ferri  perchloride  gj,  liq. 
amnion,  acetatis  jiv,  glacial  acetic  acid  giv,  liq.  ammoni.^  ^\,  and  water  to  make  up  ^giv.  All 
B.  P.  preparations  give  a  color  identical  with  a  solution  containing  i  gr.  of  grape  sugar  per  oz., 
reduced  by  picric  acid  and  afterward  diluted  four  times,  so  that  this  tint  =  y(  gr.  of  sugar  per  oz. 


Fig.  257  a. 


Fig.  258. 


t  crj'Stallized  partly  from  alcohol  and  partly 
from  water  (after  Futtke). 


G.  Johns. 


After  reducing  the  sugar  with  the  picric  acid,  pour  into  the  tall  tube  the  dark,  saccharine  liquid  pro- 
duced by  boiling  to  occupy  ten  divisions  of  the  tube,  and  add  distilled  water  cautiously  until  the  color 
approaches  that  of  the  standard  ;  read  off  the  level  of  the  fluid.  The  amount  of  sugar  present  is 
determined  from  the  amount  of  water  added.  In  making  the  test,  the  picric  acid  must  be  added  in 
proportion  to  the  amount  of  sugar  added.] 

Milk  sugar  is  sometimes  found  in  the  urine  of  women  who  are  nursing;  when  the  secretion  of 
milk  is  arrested,  absorption  taking  place  from  the  breasts  (A'irsten,  Spiegelherg).  Laevulose  is 
sometimes  found  in  diabetic  urine  y\  252). 

Dextrin  h<is  also  been  found  in  diabetic  urine.  Inosit,  or  muscle  sugar  (\  252),  is  sometimes 
found  in  diabetes,  in  polyuria  (A/<).(/ev),  and  albuminuria.  It  is  found  in  traces,  even  in  normal 
urine.  Occasionally,  after  the  piqure  in  animals  (\  175),  inosit,  instead  of  grape  sugar,  appears  in 
the  urine  (Fig  258).  In  testing  for  inosit,  remove  the  grape  sugar  by  fermentation,  and  the  allniinin 
by  heat,  after  the  addition  of  a  few  drops  of  acetic  acid  and  sodic  sulphate.  Some  of  the  filtrate 
is  evaporated  nearly  to  dryness  on  a  capsule.     To  the  residue  add  two  drops  of  mercuric  nitrate 


454 


CVSTIN,   LEUCIN    AND    T\'ROSIN. 


(Liebig's  titration  fluid  for  urea),  which  gives  a  yellow  precipitate.  When  this  colored  residue  is 
spread  out  and  carefully  heated,  a.  dark-red  color,  which  disappears  on  cooling,  is  obtained  ( Gallois, 
A'i'ih).     [Inosit  gives  a  green  when  boiled  with  Fehling's  solution.] 

268.  CYSTIN. — This  left  rotatory  body,  CgHj  ^N^S.^O^  (A'iilz,  Haiimunri),  occurs  very  seldom 
in  large  amount  in  urine,  although  it  seems  to  i)e  a  constituent  of  normal  urine.  It  may  be  in  solu- 
tion or  in  the  form  of  hexagonal  crystals  (Fig.  259,  A).  It  is  insoluble  in  water,  alcohol,  and  ether, 
but  easily  soluble  in  ammonia,  from  which  solution  it  may  be  crystallized.     According  to  Baumann 

Fig.  259. 


A,  Crystals  of  cystin ;  B,  oxalate  of  lime :  c,  hourglass  forms  of  , 

Fig.  260. 


a  a,  Leucin  balls  ;  *  t,  ty 


and  Preusse,  there  are  intermediate  products  of  the  metabolism,  from  which  are  furnished  the 
materials  necessary  for  the  formation  of  cystin.  During  normal  metabolism  these  materials  undergo 
further  changes,  and  the  sulphur  appears  oxidized  in  the  unne  as  sulphuric  acid.  In  rare  cases 
these  oxidations  do  not  take  place,  and  then  the  sulphur  appears  in  the  cystin  of  the  urine 
(Stadlhagen). 

269.  LEUCIN=CeHj3NO,.     TYROSIN=C,,H,  jNOj.— Both  bodies  occur  in  the  urine 

in  acute  yellow  atrophy  of  the   liver,  and   in  poisoning   by  phosphorus.      (Their  formation   during 


DEPOSITS    IN    URINE. 


455 


pancreatic  digestion  has  been  referred  to  in  §  170,  II.)  As  the  urea  excreted  is  usually  diminished 
at  the  same  time,  it  is  assumed  that,  in  these  diseases,  the  further  oxidation  of  the  derivatives  of  the 
proteids  is  interfered  with.  Leucin,  which  is  either  precipitated  spontaneously  or  obtained  after 
evaporating  an  alcoholic.extract  of  the  concentrated  urine,  occurs  in  the  form  of  yellowish,  brown 
balls  (Fig.  260,  a  a],  often  with  concentric  markings,  or  with  fine  spines  on  their  surface.  When 
heated,  it  sublimes  without  fusing. 

Tyrosin  forms  silky,  colorless  sheaves  of  needles  (F'ig.  260,  //  b).  When  boiled  with  mer- 
curic nitrate  and  nitric  acid  it  gives  a  red  color,  and  afterward  a  brownish- red  precipitate.  When 
slightly  heated  with  a  few  drops  of  concentrated  sulphuric  acid,  it  dissolves  with  a  temporary  deep 
red  color.  On  diluting  with  water,  adding  barium  carbonate  until  it  is  neutralized,  boiling,  filter- 
ing, and  adding  dilute  ferric  chloride,  a  violet  color  is  obtained  (Piria,  Stddeler). 

270.  DEPOSITS  IN  URINE. — Deposits  may  occur  in  normal  as  well  as 
in  pathological  urine,  and  they  are  either  "organized"  or  "unorganized." 

I.  ORGANIZED  DEPOSITS.— A.  Blood:  red  and  white  blood  corpuscles  and  sometimes 
fibrin  (Figs.  253-255). 

B.  Pus,  in  greater  or  less  amount,  in  catarrh  or  inflammation  of  the  urinary  passages.  Pus  cells 
exactly  resemble  colorless  blood  corpuscles  (Figs.  7,  256).     Donne's  Test. — Pour  off  the  super- 

FiG.  261. 


an  urethr.i ;  b,  vagii 
glands  ;  /,  female  i 


,  prostate  :  d,  Cowper's  glands  ;  e,  Littre's 
-a  ;  g,  bladder. 


natent  fluid  and  add  a  piece  of  caustic  potash  to  the  deposit ;  if  it  be  pus  it  becomes  gelatinous, 
ropy,  and  more  viscid  (alkali-albuminate).  Mucus,  when  so  acted  on,  becomes  more  fluid  and 
mixed  with  flocculi. 

C.  Epithelium  of  various  forms  occurs,  but  it  is  not  always  possible  to  say  whence  it  is  derived 
(Fig.  261). 

D.  Spermatozoa  may  be  present  (Fig.  248,  «). 

E.  Lower  organisms  occur  in  the  urinary  passages  very  seldom,  but  they  may  be  present,  e.g., 
in  the  bladder,  when  germs  are  introduced  from  without  by  means  of  a  dirty  catheter.  [Before 
introducing  a  catheter  into  the  bladder  one  ought  always  to  make  sure  that  the  instrument  is  perfectly 
aseptic]  Micrococci  are  found  in  the  urine  in  certain  diseases,  e.g.,  diphtheria.  The  following 
forms  are  distinguished  : — 

1.  Schizomycetes  (^  1S4).  Normal  human  urine  contains  neither  schizomycetes  nor  their 
spores.  In  pathological  conditions,  however,  fungi  may  pass  from  the  blood  into  the  urinary  tubules 
and  thus  reach  the  urine  (Letibe).  During  the  alkaline  fermentation  of  urine,  micrococci,  rod- 
shaped  bacteria  or  bacilli  (Figs.  250,  251,  may  occur).  Sarcinae  belong  to  the  above  group 
{I  1S6). 

2.  Saccharomycetes  (fermentation  fungi)  :  (r?)  The  fungus  of  the  acid  urine  fermentation  (S. 
urina:)  consists  of  small,  bladder-like  cells  arranged  either  in  chains  or  in  groups  (Figs.  251,1/; 


456 


TUBE    CASTS    IX    URINE. 


262,  i).  {/>)  Yeast  (S.  fermenlum)  occurs  in  diabetic  urine, as  oval  cells  with  a  doited,  eccentrically 
placed  nucleus  (Fig.  262,  rf). 

3.  Phytomycetes  (moulds)  occur  in  putrid  urine  (Fig.  262,  e).  They  are  without  clinical  sig- 
nificance. 

F.  Tube  Casts. — The  occurrence  of  tube  casts,  !.«•.,  casts  of  the  uriniferous  tubules  {//en/e, 
jSjy)  is  of  great  importance  in  connection  with  the  diagnosis  of  renal  diseases.     If  these  structures 

Fig.  262. 


,  micrococci  in  short  chains  and  groups  ;  i,  sarcinse :  c,  fungi  from  acid  fermentation ;  ^,  yeast 
cells  from  diabetic  urine;  e,  mycelium  of  a  fungus. 

Fig.  263. 


yl.._._ . 


a,  blood 


are  relatively  thick  and  straight,  they  probably  come  from  the  collecting  tubules,  but  if  they  are 
sinaller  and  twisted,  they  probably  come  from  the  convoluted  tubules.  There  are  various  forms  of 
tube  casts  :  I.  Epithelial  casts,  consisting  of  the  actual  cells  of  the  uriniferous  tubules.  They 
indicate  that  there  is  no  very  great  change  going  on,  but  only  that,  as  in  catarrhal  inflammation  of 
any  mucous  membrane,  the  epithelium  is  in  process  of  desquamation.  2.   Hyaline  casts  (Fig.  264) 


DETECTION    OF   URINARY   DEPOSITS. 


457 


are  quite  clear  and  homogeneous,  usually  long  and  small;  sometimes  they  are  " finely  granular," 
from  the  presence  of  fat  or  other  particles.  They  are  best  seen  after  the  addition  of  a  solution  of 
iodine.  They  are  probably  formed  from  albumin,  which  passes  into  the  uriniferous  tubules.  They 
are  dissolved  in  alkaline  urine,  while  acid  urine  favors  their  formation.  They  usually  occur  in  the 
late  stages  of  renal  disease,  after  the  tubular  epithelium  has  been  shed.  3.  Coarsely  granular 
casts  (Fig.  263,  b),  brownish-yellow  opaque,  and  granular,  usually  broader  than  2.  There  are  vari- 
ous forms.  Not  unfrequently  there  are  fatty  granules,  and,  it  may  be,  epithelial  cells  in  them.  4. 
Amyloid  casts  occur  in  amyloid  degeneration  of  the  kidneys  (Fig.  263,  c).  They  are  refractive 
and  completely  homogeneous,  and  give  a  blue  color  (amyloid  reaction)  with  sulphuric  acid  and 
iodine.  5.  Blood  casts  occur  in  capillary  hemorrhage  of  the  kidney,  and  consist  of  coagulated 
blood  entangling  blood  corpuscles  (Fig.  263,  a).  When  tube  casts  are  present,  the  urine  is  always 
allmminous. 

II.  Unorganized  Deposits. — Some  of  these  are  crystalline  and  others  are  amorphous,  and 
they  have  been  referred  to  in  treating  of  the  urinary  constituents. 

271.  SCHEME  FOR  DETECTING  URINARY  DEPOSITS.— I.  In  acid  urine  there 
may  occur  : — 

I.  An  amorphous  granular  deposit : 

(a)  Which  is  dissolved  by  heat  and  reappears  in  the  cold  ;  the  deposit  is  often  reddish  in  color 

^=  urates  (Fig.  249). 
[l>)  Which  is  not  dissolved  by  heat,  but  is  dissolved  by  acetic  acid,  but  without  effervescence 
=  probably  tribasic  calcic  phosphate. 


Fig.  264. 


Hyal 


(c)  Small,  bright,  refractive  granules,  soluble  in  ether  =  fat  or  oil  granules  (?.  41)  (Lipjemia). 
Fat  occurs  in  the  urine,  especially  when  the  round  worm,  Filaria  sanguinis  honiinis,  is 
present  in  the  blood ;  sometimes,  along  with  sugar,  in  phthisis,  poisoning  with  phos- 
phorus, yellow  fever,  pyaemia,  after  long-continued  suppuration,  and  lastly,  after  the 
injection  of  fat  or  milk  into  the  blood  (J  102).  It  occurs  also  in  fatty  degeneration  of 
the  urinary  apparatus,  admixture  with  pus  from  old  abscesses,  and  after  severe  injuries  to 
bones.  In  these  cases  attention  ought  to  be  directed  to  the  presence  of  cholesterin  and 
lecithin.  Very  rarely  is  the  fat  present  in  such  amount  in  the  urine  as  to  form  a  cream 
on  the  surface  (chyluria). 
2.  A.  crystalline  deposit  may  be — 

(a)   Uric  acid  (Figs.  242,  243,  249). 

(/')  Calcium  oxalate  (Figs.  249,  259) — octahedra  insoluble  in  acetic  acid. 

(<-)  Cystin  (Fig.  2591. 

(J)  Leucin  and  tyrosin — very  rare  (Fig.  260). 
I.   In  alkaline  urine  there  may  occur — 

1.  A  compUtely  amorphous  granular  deposit,  soluble  in   acids   without  effervescence  ^=  tri- 

basic calcic  phosphate. 

2.  Sediment  crystalline,  or  with  a  characteristic  form. 

(o)  Triple  phosphate  (Figs.  250,  251,  252,  and  256),  soluble  at  once  in  acids. 


458  URINARY    CALCULI. 

{i)  Acid  ammonium  urate — dark -yellowish,  small  balls  often  beset  with  spines,  also  amor- 
phous (I'iss.  250  and  260). 
(1)  Calcium  carbonate — small  whitish  balls  or  biscuit-shaped  bodies.     Acids  dissolve  them 

with  eft'ervescence  (Fig.  248). 
(i/)   Leucin  and  tyrosin  (I'ig.  260) — very  rare. 

(e)   Neutral  calcic  phosphate  and  long  plates  of  tribasic  magnesic  phosphate  (Fig.  24S). 
Organized  deposits  njay  occur  both  in  alkaline  and  in  acid  urine;  pus  cells  are  more  abundant 
in  alkaline  urine,  and  so  are  the  lower  vegetable  organisms. 

272.  URINARY  CALCULI. — Urinary  concretions  may  occur  in  granules  the  size  of  sand,  or 
in  masses  as  large  as  the  list.  According  to  their  size  they  are  spoken  of  as  sand,  gravel,  stone  or 
calculi.     They  occur  in  the  pelvis  of  the  kidney,  ureters,  bladder  and  sinus  prostaticus. 

We  may  classify  them  as  follows  (  Ullz/nann)  : — 

1.  Calculi,  whose  nucleus  consists  of  the  sedimentary  forms  that  occur  in  acid  urine  (primary 
formation  of  calculi).  They  are  all  formed  in  the  kidney,  and  pass  into  the  bladder,  w-here  they 
enlarge  according  to  the  growth  of  the  crystals  in  the  urine. 

2.  Calculi,  which  are  either  sedimentary  forms  from  alkaline  urine,  or  whose  nucleus  consists 
of  2.  foreign  body  (secondary  formation  of  calculil.     They  are  formed  in  the  bladder. 

The  primary  formation  of  calculi  begins  with  free  uric  acid  in  the  form  of  sheaves  (Fig.  242,  c) 
which  form  a  nucleus,  with  concentric  layers  of  oxalate  of  lime.  The  secondary  formation  occurs 
in  neutral  urine  by  the  deposition  of  calcic  carbonate  and  crystalline  calcic  phosphate  ;  in  alkaline 
urine,  by  the  deposition  of  acid  ammonium  urate,  triple  phosphate  and  amorphous  calcic  phosphate. 

Chemical  Investigation. — Scrape  the  calculus,  burn  the  scrapings  on  platinum  foil  to  ascertain 
if  they  are  burned  or  not. 

I.  Combustible  concretions  can  consist  only  of  organic  substances. 

((7)  Apply  the  murexide  test  [\  259,  2),  and  if  it  succeeds  uric  acid  is  present.  Uric  acid  cal- 
culi are  very  common,  often  of  considerable  size,  smooth,  fairly  hard,  and  yellow  to  reddish-brown 
in  color. 

(('<)  If  another  portion,  on  being  boiled  with  caustic  potash,  gives  the  odor  of  ammonia  (or  when 
the  vapor  makes  damp  turmeric  paper  brown,  or  if  a  glass  rod  dipped  in  HCl  and  held  over  it  gives 
white  fumes  of  ammonium  chloride),  the  concretion  contains  ammonium  urate.  If  b  gives  no 
result,  pure  uric  acid  if  present  Calculi  of  ammonium  urate  are  rare,  usually  small,  of  an  earthy 
consistence,  i.e.,  soft  and  pale  yellow  or  whitish  in  color. 

(c)  If  the  xanthin  reaction  succeeds  (J  260),  this  substance  is  present  (rare).  Indigo  has  been 
found  on  one  occasion  in  a  calculus  (Ord). 

(d)  If,  after  solution  in  ammonia,  hexagonal  plates  (Fig.  259,  A)  are  found,  cystin  is  present. 

(e)  Concretions  of  coagulated  blood  or  fibrin,  without  any  crystals,  are  rare.  When  burned 
they  give  the  odor  of  singed  hair.  They  are  insoluble  in  water,  alcohol  and  ether;  but  are  soluble 
in  caustic  potash,  and  are  precipitated  therefrom  by  acids. 

(f)  Urostealith  is  applied  to  a  caoutchouc  like,  soft  elastic  substance,  and  is" very  rare.  When 
dry  it  is  brittle  and  hard,  brown  or  black.  When  warm  it  softens,  and  if  more  heat  be  applied 
it  melts.  It  is  soluble  in  ether,  and  the  residue  after  evaporation  becomes  violet  on  being  heated. 
It  is  soluble  in  warm  caustic  potash,  with  the  formation  of  a  soap. 

II.  If  the  concretions  are  only  partly  combustible,  thus  leaving  a  residue,  they  contain  organic 
and  inorganic  constituents. 

(a)  Pulverize  a  part  of  the  stone,  boil  it  in  water,  and  filter  while  hot.  The  urates  are  dissolved. 
To  test  if  the  uric  acid  is  united  with  soda,  potash,  lime  or  magnesia,  the  filtrate  is  evaporated  and 
burned.  The  ash  is  investigated  with  the  spectroscope  (J  14),  when  the  characteristic  bands  of 
sodmm  or  potash  are  observed.  Magnesic  urate  and  calcic  urate  are  changed  into  carbonate  by 
burning.  To  separate  them  dissolve  the  ash  in  dilute  hydrochloric  acid  and  filter.  The  filtrate  is 
neutralized  with  ammonia,  and  again  redissolved  by  a  few  drops  of  acetic  acid.  The  addition  of 
ammonium  oxalate  precipitates  calcic  oxalate.  Filter  and  add  to  the  filtrate  sodic  phosphate  and 
ammonia,  when  the  magnesia  is  precipitated  as  ammonio-magnesic  phosphate. 

{I')  Calcic  oxalate  (especially  in  children,  either  as  small,  smooth  pale  stones,  or  in  dark,  warty, 
hard  "  mulberry  calculi  ")  is  not  affected  by  acetic  acid,  is  dissolved  by  mineral  acids  without  effer- 
vescence, and  again  precipitated  by  ammonia.  Heated  on  platinum  foil  it  chars  and  blackens,  then 
it  becomes  white,  owing  to  the  formation  of  calcic  carbonate,  which  effervesces  on  the  addition  of  an 
acid. 

(f)  Calcic  carbonate  (chiefly  in  whitish-gray,  earthy,  chalk-like  calculi,  somewhat  rare)  dis- 
solves with  effervescence  in  hydrochloric  acid.  When  burned  it  first  becomes  black,  owing  to 
admixture  with  mucus,  and  then  white. 

[d]  Ammonio- magnesic  phosphate  and  basic  calcic  phosphate  usually  occur  together  in 
soft,  white,  earthy  stones,  which  occasionally  are  very  large.  These  stones  show  that  the  urine  has 
been  ammoniacal  for  a  very  long  time.  The  first  substance  when  heated  gives  the  odor  of  ammo- 
nia, which  is  more  distinct  when  heated  with  caustic  potash;  is  soluble  in  acetic  acid  without  effer 
vescence.  and  is  again  precipitated  in  a  crystalline  form  from  this  solution  on  the  addition  of  am 
monia.    When  heated  it  fuses  into  a  white,  enamel-like  mass  [hence,  it  is  called  "  fusible  calculus  "] 


GLOMERULAR    EPITHELIUM.  459 

Basic  calcic  phosphate  does  not  effervesce  with  acids.  The  solution  in  hydrochloric  acid  is  pre- 
cipitated by  ammonia.  When  ammonium  oxalate  is  added  to  the  acetic  acid  solution,  it  yields 
calcic  oxalate. 

(f)  Neutral  calcic  phosphate  is  rare  in  calculi,  while  it  is  frequent  in  the  form  of  gravel. 
Physically  and  chemically,  these  concretions  resemble  the  earthy  phosphates,  only  they  do  not  con- 
tain magnesia. 

273.  THE  SECRETION  OF  URINE.— [The  functions  of  the  kidney 
are — • 

1.  To  excrete  waste  products,  chiefly  nitrogenous  bodies  and  salts ; 

2.  To  excrete  water  ; 

3.  -\nd  perhaps  also  to  reabsorb  water  from  the  uriniferous  tubules,  after  it 

has  washed  out  the  waste  products  from  the  renal  epithelium. 

The  chief  parts  of  the  organs  concerned  in  i,  are  the  epithelial  cells  of  the 
convoluted  tubules  ;  the  glomeruli  permit  water  and  some  solids  to  pass  through 
them,  while  the  constrictions  of  the  tubules  may  prevent  the  too  rapid  outflow  of 
water,  and  thus  enable  part  of  it  to  be  reabsorbed  (Bnuifon)^ 

Theories. — The  two  chief  older  theories  regarding  the  secretion  of  urine  are 
the  following  :  i.  .According  to  Bowman's  view  ( 1842),  through  the  glomeruli 
are  filtered  only  the  water  and  some  of  the  highly  diffusible  and  soluble  salts 
present  in  the  blood,  while  the  specific  urinary  constituents  are  secreted  by  the 
activity  of  the  epithelium  of  the  urinary  tubules,  and  are  extracted  or  removed 
from  the  epithelium  by  the  water  flowing  along  the  tubules.  This  has  been  called 
the  "vital"  theory.  2.  C.  Ludwig  (1844)  assumes  that  very  dilute  uri/ie  is 
secreted  or  filtered  through  the  glomerulus.  As  it  passes  along  the  urinary 
tubules  it  becomes  more  concentrated,  owing  to  endosmosis.  It  gives  back  some 
of  its  water  to  the  blood  and  lymph  of  the  kidney,  thus  becoming  more  concen- 
trated, and  assuming  its  normal  character.  [This  is  commonly  known  as  the 
"  mechanical"  theory.] 

The  secretion  of  urine  in  the  kidneys  does  not  depend  upon  definite  physical  forces 
on/v.  A  great  number  of  facts  force  us  to  conclude  that  the  vital  activity  of  certain 
secretory  cells  plays  a  foremost  part  in  the  process  of  secretion  (J?.  Heidenhaiii). 

The  secretion  of  urine  embraces — (i)  The  water,  and  (2)  the  urinary  con- 
stituents therein  dissolved;  both  together  form  the  urinary  secretion.  The 
amount  of  urine  depends  chiefly  upon  the  amount  of  water  which  is  filtered 
through  or  secreted  by  the  glomeruli ;  the  amount  of  solids  dissolved  in  the 
urine  determines  its  concentration. 

(A)  The  amount  of  urine,  which  is  secreted  chiefly  within  the  Malpighian 
capsules,  depends  primarily  upon  the  blood  pressure  in  the  area  of  the  renal  artery, 
and  follows,  therefore,  the  laws  of  filtration  [§  191,  II]  (Ludicig  and  Goll). 
[In  this  respect  the  secretion  of  urine  differs  markedly  from  that  of  saliva,  gastric 
juice,  or  bile.  We  may  state  it  more  accurately  thus,  that  the  amount  of  urine 
depends  very  closely  upon  the  difference  of  pressure  between  the  blood  in  the 
glomeruli  and  the  pressure  within  the  renal  tubules.  If  the  ureter  be  ligatured, 
the  secretion  of  urine  is  ultimately  arrested,  even  although  the  blood  pressure  be 
high.  The  secretion  may  also  be  arrested  by  ligature  of  the  renal  vein  ;  ar.d  in 
some  cases  of  cardiac  or  pulmonary  disease  the  venous  congestion  thereby  pro- 
duced may  bring  about  the  same  result.] 

Glomerular  Epithelium. — The  amount  of  urine  secreted  does  not  depend 
upon  the  hydrostatic  pressure  alone,  but  it  seems  that  the  epithelial  cells  covering 
the  glomerulus  also  participate  aetively  in  the  process  of  secretion.  Besides  the 
water,  a  certain  amount  of  the  salts  present  in  the  urine  is  excreted  through  the 
glomeruli.  The  serum  albumin  of  the  blood,  however,  is  prevented  from  passing 
through.  With  regard  to  the  secretory  activity  of  these  cells,  the  quantity  of 
water  must  also  depend  upon  the  amount  and  rate  at  which  the  material  to  be 
secreted  is  carried  to  the  glomeruli  by  the  blood  stream,  and  also  upon  the  amount 
of  the  urinary  constituents  and  water  present  in  the  blood  ( Ji.  Heidenhain). 


460  RELATION    TO   THE    BLOOD    PRESSURE, 

Only  when  the  vitality  of  the  secretory  cells  is  intact  is  there  independent  activity  of  these 
secretory  cells  {Ileidenhain),  When  the  renal  artery  is  closed  temporarily,  their  activity  is  para- 
lyzed, so  that  the  kidneys  cease  to  secrete,  and  even  after  the  compression  is  removed  and  the  circu- 
lation re-established,  secretion  does  not  take  place  for  some  time  (Oz'erlieik). 

That  the  secretion  depends  in  part  upon  the  blood  pressure  is  proved  by 
the  following  considerations  : — 

1 .  Increase  of  the  total  contents  of  the  vascular  system,  so  as  to  increase  the  blood 
pressure,  increases  the  amount  of  water  which  filters  through  the  glomeruli.     The 

injection  of  water  into  the  blood  vessels,  or  drinking  copious  draughts  of  water, 
acts  partly  in  this  way.  If  the  blood  pressure  rises  above  a  certain  height,  albu- 
min may  pass  into  the  urine.  The  active  participation  of  the  cells  of  the  glom- 
eruli is  rendered  probable  by  the  fact  that,  after  very  copious  drinking,  the  blood 
pressure  is  not  always  raised  {Pawlow)  ;  further,  after  profuse  transfusion,  the 
quantity  of  urine  is  not  increased.  Conversely,  the  excretion  of  water,  owing  to 
profuse  sweating  or  diarrhoea,  copious  hemorrhage,  or  prolonged  thirst,  dimin- 
ishes the  secretion  of  urine. 

2.  Diminution  of  t/ie  capacity  of  the  vascular  system,  jjrovided  the  jjressure  within 
the  renal  area  be  thereby  increased,  acts  in  a  similar  manner.  This  may  be  pro- 
duced by  contraction  of  the  cutaneous  vessels,  owing  to  the  action  of  cold,  stim- 
ulation of  the  vasomotor  centre,  or  large  vasomotor  nerves,  ligature,  or  com- 
pression of  large  arteries  (§  85,  e),  or  enveloping  the  extremities  in  tight  bandages. 
All  these  conditions  cause  an  increase  in  the  amount  of  urine,  and,  of  course,  the 
opposite  conditions  bring  about  a  diminution  of  urine,  e.g.,  the  action  of  heat 
on  the  skin  causing  redness  and  dilatation  of  the  cutaneous  vessels,  weakening  of 
the  vasomotor  centre,  or  paralysis  of  a  large  number  of  vasomotor  nerves. 

3.  Increased  action  of  the  heart,  whereby  the  tension  and  rapidity  of  the  blood 
in  the  arteries  are  increased  (§  85,  c),  augments  the  amount  of  urine  ;  conversely, 
feeble  action  of  the  heart  (paralysis  of  motor  cardiac  nerves,  disease  of  the  cardiac 
musculature,  certain  valvular  lesions),  diminishes  the  amount.  Artificial  stimula- 
tion of  the  vagi  in  animals,  so  as  to  slow  the  action  of  the  heart,  and  thus  dimin- 
ish the  mean  blood  pressure  from  130  to  100  mm.  Hg,  causes  a  diininution  in  the 
amount  of  urine  to  the  extent  of  one-fifth  {Goll,  CI.  Bernard)  ;  when  the  pres- 
sure in  the  aorta  falls  to  40  mm.  the  secretion  of  urine  ceases.  [If  the  medulla 
oblongata  be  divided  (dog)  there  is  an  immediate  fall  of  the  general  blood 
pressure,  and  although,  as  a  general  rule,  the  secretion  of  urine  is  arrested  when 
the  pressure  falls  to  40  to  50  mm.  Hg,  yet  secretion  has  been  observed  to  take 
place  with  a  lower  pressure  than  this.] 

4.  The  amount  of  urine  secreted  rises  or  falls  according  to  the  degree  of  fulness 
of  the  renal  artery  (Ludwig,  Max  Herrmann)  ;  even  when  this  artery  is  moderately 
constricted  in  animals,  there  is  a  decided  diminution  in  the  amount  of  urine. 

Pathological. — In  fever  the  renal  vessels  are  less  full,  and  there  is  consecutive  diminution  of 
urine  {Mendetsotin).  It  is  most  important,  in  connection  with  certain  renal  diseases,  to  note  that 
ligature  of  the  renal  artery,  even  when  it  is  obliterated  for  only  two  hours,  causes  necrosis  of  the 
epithelium  of  the  uriniferous  tubules.  When  the  arterial  anjemia  is  kept  up  for  a  long  time,  the 
whole  renal  tissue  dies  [Litten).  After  long-continued  ligation  of  the  renal  artery,  the  epithelium 
of  the  glomeruli  becomes  greatly  changed  (Ribbert). 

5.  Most  diuretics  act  in  one  or  other  of  the  above-mentioned  ways. 

[.Some  diuretics  act  by  increasing  the  general  blood  pressure  (digitalis  and  the  action  of  cold  on 
the  skin),  others  mny  increase  the  blood  pressure  loaiUy  within  the  kidney,  and  this  they  may  do 
in  several  ways.  The  nitrites  are  said  to  paralyze  the  muscular  fibres  in  the  vasa  afferentia,  and 
thus  raise  the  blood  pressure  within  the  glomeruli.  But  some  also  act  on  the  secretory  epithelittm, 
such  as  urea  and  caft'ein.  Brunton  recommends  the  combination  of  diuretics  in  appropriate  cases, 
and  the  diuretics  must  be  chosen  according  to  the  end  in  view — as  we  wish  to  remove  excess  of 
fluids  from  the  tissues  and  serous  cavities,  or  as  we  wish  to  remove  injurious  waste  products,  or 
merely  to  dilute  the  urine.] 

[6.  The  amount  of  urine  also  depends  upon  the  composition  of  the  blood.    Drink- 


SECRETORY   ACTIVITY   OF   THE    RENAL    EPITHELIUM.  461 

ing  a  large  quantity  of  water — whereby  the  blood  becomes  more  watery — increases 
the  amount  of  urine,  but  this  is  true  only  within  certain  limits.  It  is  not  merely 
the  increase  of  volume  of  the  blood  acting  mechanically  which  causes  this  increase, 
as  we  know  that  large  quantities  of  blood  may  be  transfused  without  the  general 
blood  pressure  being  materially  raised  thereby.] 

[Heidenhain  argues  that  it  is  not  so  much  the  pressure  of  the  blood  in  the 
glomeruli  as  its  velocity,  which  determines  the  process  of  the  secretion  of  water 
in  the  kidney.  He  contends  that,  while  increase  of  the  pressure  in  the  renal 
artery  causes  an  increased  flow  of  urine,  ligature  of  the  renal  vein,  whereby  the 
pressure  in  the  glomeruli  is  also  increased,  arrests  the  secretion  altogether.  In 
both  cases  the  pressure  is  increased  within  the  glomeruli,  and  the  two  cases  differ 
essentially  in  the  velocity  of  the  blood  current  through  the  glomeruli.] 

Pressure  in  the  Vas  Afferens. — The  pressure  in  each  vas  afferens  must  be 
relatively  great,  because  (i)  the  double  set  of  capillaries  in  the  kidney  offers  con- 
siderable resistance,  and  because  (2)  the  lumen  of  the  vas  efferens  is  narrower  than 
that  of  the  vas  afferens.  Hence,  owing  to  the  high  blood  pressure  in  the  capilla- 
ries of  the  renal  glomeruli,  filtration  must  take  place  from  the  blood  into  the 
Malpighian  capsules.  When  the  vasa  afferentia  are  dilated,  e.  g.,  through  the 
action  of  the  nervous  system  on  their  smooth  muscular  fibres,  the  filtration  pressure 
is  increased,  while,  when  they  are  contracted,  the  secretion  is  lessened.  When 
the  pressure  becomes  so  diminished  as  to  retard  greatly  the  blood  stream  in  the 
renal  vein,  the  secretion  of  urine  begins  to  be  arrested.  Occlusion  of  the  renal 
vein  completely  suppresses  the  secretion  (/f.  Meyer,  v.  Frerichs).  Ludwig  con- 
cluded, from  this  observation,  that  the  filtration  or  excretion  of  fluid  could  not 
take  place  through  the  renal  capillaries />rc;/«-,  as,  owing  to  occlusion  of  the  renal 
vein,  the  blood  pressure  in  these  capillaries  must  rise,  which  ought  to  lead  to 
increased  filtration.  Such  an  experiment  points  to  the  conclusion  that  the  filtra- 
tion must  take  place  through  the  capillaries  of  the  glomeruli.  The  venous  stasis  dis- 
tends the  vas  efferens,  which  springs  from  the  centre  of  the  glomerulus,  and 
compresses  the  capillary  loops  against  the  wall  of  the  Malpighian  capsule,  so  that 
filtration  cannot  take  place  through  them.  It.  is  not  decided  whether  any  fluid 
is  given  off  through  the  convoluted  urinary  tubules. 

Pressure  in  Ureter. — As  the  blood  pressure  in  the  renal  arlery  is  about  120  to  140  mm.  Hg, 
and  the  urine  in  the  ureter  is  moved  along  by  a  very  shj^ht  propelling  force,  so  that  a  counter-pressure 
of  from  10  (LSI/ell)  to  40  mm.  of  Hg  is  sufficient  to  arrest  its  flow,  it  is  clear  that  the  blood  pressure 
can  also  act  as  a  vis  a  lergo  to  propel  the  urine  stream  through  the  ureter.  The  pressure  in  the 
ureter  is  measured  by  dividing  the  ureter  transversely  and  placing  a  manometer  in  it. 

(B)  Secretory  Activity  of  the  Renal  Epithelium.— The  degree  of 
concentration  of  the  urine  depends  upon  the  quantity  of  the  dissolved  constit- 
uents which  has  passed  from  the  blood  into  the  water  of  the  urine.  The  secretory 
cells  of  the  convoluted  tubules,  by  their  own  proper  vital  activity,  seem  to  be 
able  to  take  up,  or  secrete,  some,  at  least,  of  these  substances  from  the  blood 
{Bowi/ian,  Heidenhain).  The  watery  part  of  the  urine,  containing  only  easily 
diffusible  salts,  as  it  flows  along  the  tubules  from  the  glomeruli,  extracts  or  washes 
out  these  substances  from  the  secretory  epithelium  of  the  convoluted  tubules. 

Experiments. — i.  Sulphindigotate  of  soda  and  sodium  urate,  when  injected 
into  the  blood,  pass  into  the  urine,  and  are  found  within  the  protoplasm  of  the 
cells  o{t\it  convoluted  tubules  [only  in  those  parts  lined  by  "rodded"  epithelium], 
but  not  in  the  Malpighian  capsules  (^Heidenhain).  A  little  later,  these  substances 
are  found  in  the  lumen  of  the  urinary  tubules,  from  which  they  are  washed  out  by 
the  watery  part  of  the  urine  coming  from  the  glomeruli.  If,  however,  two  days 
before  the  injection  of  these  substances  into  the  blood,  the  cortical  part  of  the 
kidney  containing  the  Malpighian  capsules  be  cauterized  \_e.  g. ,  by  nitrate  of  silver] 
(Heidenhain),  or  simply  be  removed  with  a  knife  (Hoegyes),  the  blue  pigment 
remains  within  the  convoluted  tubules.     It  cannot  be  carried  onward,  as  the  water 


462  nussbaum's  experiments. 

which  should  carry  it  along  has  ceased  to  be  secreted,  owing  to  the  destruction  of 
the  glomeruli.  This  experiment  also  goes  to  show  that,  through  the  gAu/ifru//  the 
7vatery  part  of  the  urine  is  chiefly  excreted,  while  through  the  convcli(ted  tubules  the 
specific  urinary  constituents  are  excreted.  Uric  acid  salts,  injected  into  the  blood, 
were  observed  by  Heidenhain  to  be  excreted  by  the  convoluted  tubules.  Von 
Wittich  had  previously  observed  that  in  birds,  crystals  of  uric  acid  were  excreted 
by  the  epithelium  of  the  convoluted  tubules.  [The  presence  of  crystals  of  uric 
acid  in  the  renal  epithelium  was  observed  by  Bowman,  and  used  as  an  argument 
to  support  his  theory.]  Nussbaum,  in  1878,  stated  that  urea  is  secreted  by  the 
urinary  tubules,  and  not  by  the  glomeruli. 

The  same  is  true  for  the  bile  pigments  {Mobius,  fSyy),  for  the  iron  salts  of  the  vegetable  acids 
when  injected  subcutaneously  {Glaevecke'),  and  for  hLiemoglobin  {Landois).  After  the  injection  of 
7nilk  into  the  blood  vessels,  numerous  fatty  granules  occur  within  the  epithelium  of  the  urinary 
tubules  {\  102). 

[Nussbaum's  Experiments. — In  the  frog  and  newt,  the  kidney  is  supplied 
with  blood  in  a  different  manner  frotii  that  obtaining  in  mammals.  The  glomeruli 
are  supplied  by  branches  of  the  renal  artery.  The  tubules  are  supplied  by  the 
renal-portal  vein.  The  vein  coming  from  the  posterior  extremities  divides  at  the 
upper  end  of  the  thigh  into  two  branches,  one  of  which  enters  the  kidney,  and 
breaks  up  to  form  a  capillary  plexus  which  surrounds  the  uriniferous  tubules,  but 
this  plexus  is  also  joined  by  the  efferent  vessels  of  the  glomeruli.  These  two  systems 
are  partly  independent  of  each  other.  By  ligaturing  the  renal  artery,  Nussbaum 
asserted  that  the  circulation  in  the  glomeruli  was  cut  off,  while  ligature  of  the 
renal-portal  vein  excluded  the  functional  activity  of  the  tubules.  By  injecting  a 
substance  into  the  blood  after  ligaturing  either  the  artery  or  renal-portal  vein,  and 
observing  whether  it  occurs  in  the  urine,  he  infers  that  it  is  given  off  either  by  the 
glomeruli  or  the  tubules.  Sugar,  peptones,  and  1?^^  albumin  rapidly  pass  through 
an  intact  kidney,  but  if  the  renal  artery  be  tied  they  are  not  excreted.  Urea  when 
injected  into  the  circulation  is  excreted  after  the  artery  is  tied,  so  that  it  is  excreted 
through  the  tubules,  but  at  the  same  time  it  takes  with  it  a  considerable  quantity 
of  water.  Thus  water  is  excreted  in  tioo  ways  from  the  kidney,  by  the  glomeruli 
and  also  from  the  venous  plexus  around  the  tubules  along  with  the  urea.  Indigo 
carmine  merely  passes  into  the  tubular  epithelium  of  the  convoluted  tubules,  but 
it  does  not  cause  a  secretion  of  urine.  Albumin  passes  through  the  glomeruli,  but 
only  after  their  membranes  have  been  altered  in  some  way,  as  by  clamping  the 
renal  artery  for  a  time.] 

[Adami's  Experiments  on  the  kidney  of  the  frog  clearly  show  that  Nuss- 
baum's conclusions  are  not  justified,  for  Adami  found  that  if  the  renal  arteries  in 
the  frog  be  ligatured,  within  a  few  hours  a  collateral  circulation  is  established,  and 
a  certain  amount  of  blood  flows  through  the  kidney.  He  proved  this  by  injecting 
into  the  blood  carmine  or  painter's  vermilion,  in  a  state  of  fine  suspension,  and 
after  ligature  of  the  renal  arteries  he  found  it  in  many  of  the  glomeruli,  while  laky 
blood  similarly  injected  revealed  its  presence  as  menisci  of  Hb  in  the  Malpighian 
capsules.  Even  secretion  of  some  urine  may  go  on  after  ligature  of  the  renal 
arteries.  It  is  evident,  then,  that  Nussbaum's  method  is  not  a  reliable  one  for 
locating  the  parts  of  the  kidney  through  which  certain  substances  are  excreted.] 

[Adami's  experiments  also  give  some  support  to  Heidenhain's  view  that  tne 
glomerular  epithelium  "  possesses  powers  of  a  selective  secretory  nature  ;"  for  he 
finds  that  in  frogs,  after  ligature  of  the  renal  arteries,  where,  of  course,  the  pres- 
sure in  the  glomeruli  is  just  nearly  that  in  the  veins,  and  in  the  dog  after  section 
of  the  spinal  cord,  so  that  the  blood  pressure  has  fallen  below  40  mm.  Hg,  whereby 
the  secretion  of  urine  is  arrested  ;  the  injection  of  laky  blood  causes  Hb  to  appear 
in  the  capsules,  although  there  is  no  simultaneous  excretion  of  water.] 

Excretion  of  Pigments. — Only  during  very  copious  excretion  does  the  capsule  participate. 
After  the  introduction  of  a  large  amount  of  sodic   sulphinciigotate,  and  when  the  experiment  has 


FORMATION    OF   THE    URINARY   CONSTITUENTS.  463 

lasfed  for  a  long  time,  the  epithelium  of  the  capsule  becomes  blue  (Arnold  and  Pautynski).  In 
albuminuria  the  abnormal  excretion  of  urine  takes  place  first  in  the  urinary  tubules,  and  after- 
ward in  \.\\t  ca^isMXes  [Senator);  Hb  is  partly  found  in  the  capsules  {Griitzner,  Bridges  Adams'). 
According  to  Xussbaum,  egg  albumin  passes  out  through  the  capsule. 

2.  Even  when  the  secretion  of  the  watery  part  of  the  urine  is  completely 
arrested,  either  by  ligature  of  the  ureter,  or  after  a  very  great  fall  of  the  blood 
pressure  in  the  renal  artery  [as  after  section  of  the  cervical  spinal  cord],  the  before- 
mentioned  substances,  when  injected  into  the  blood,  are  found  in  the  cells  of  the 
convoluted  tubules.  The  injection  of  urea  under  these  circumstances  causes  re- 
newed secretion.  These  facts  show  that,  independently  of  the  filtration  pressure, 
the  secretory  activity  of  these  cells  is  still  maintained  {Heidenhain,  Neisser,  Ustimo- 
witsch,  Griitzner'). 

The  independent  vital  activity  of  the  secretory  cells  of  the  urinary  tubules,  which  as  yet  we 
are  unable  to  explain  on  purely  physical  grounds,  renders  it  probable  that  the  tubules  are  not  to  be 
compared  to  an  apparatus  provided  with  physical  membranes.  This  is  proved  by  the  following  ex- 
periment :  Abeles  caused  arterial  blood  to  circulate  through  freshly  excised  living  kidneys.  A  pale, 
urine-like  fluid  dropped  from  the  ureter.  On  adding  some  urea  or  sugar  to  the  blood,  the  secretion 
became  more  concentrated.  Thus  the  excised  living  kidney  also  excretes  substances  in  a  more  con- 
centrated form  than  when  supplied  to  it  in  the  diluted  blood  streaming  through  it. 

Salts  and  Gases. — The  vital  activity  explains  why  the  serum  albumin  of  the  blood  does  not 
pass  into  the  urine,  while  egg  albumin  and  dissolved  haemoglobin  readily  do  so.  Among  the  salts 
which  occur  in  the  blood  and  blood  corpuscles,  of  course  only  those  in  solution  can  pass  into  the 
urine.  Those  which  are  united  with  proteid  bodies,  or  are  fixed  in  the  cellular  elements,  cannot 
pass  out,  or  at  least  only  after  they  have  been  split  up.  Thus  we  may  explain  the  difference  between 
the  salts  of  the  urine  and  those  of  the  blood.  Similarly,  the  urine  can  only  contain  the  absorbed 
and  not  the  chemically  united  gases. 

Ligature  of  the  Ureter. — [f  the  secretion  be  arrested  by  compression  or  by  ligature  of  the 
ureter,  the  lymph  spaces  of  the  kidney  become  filled  with  fluid,  which  may  pass  into  the  blood,  so 
that  the  organ  becomes  cedematous,  owing  to  the  passage  of  fluid  into  its  lymph  spaces.  The  secre- 
tion undergoes  a  change,  as  first  water  passes  back  into  the  blood,  then  the  sodic  chloride,  sulphuric, 
and  phosphoric  acids  diminish,  and  lastly  the  urea  (C  Ludvjig,  Max  Herrmann).  Kreatinin  is 
still  present  in  considerable  amount.     There  is  no  longer  secretion  of  proper  urine  (Lobell). 

Non-Symmetrical  Renal  Activity. — It  is  remarkable  that  both  kidneys  do  not  secrete  sym- 
metrically— there  is  an  alternate  condition  of  hypersemia  and  secretory  activity  on  opposite  sides 
{\  too).  One  kidney  secretes  a  more  watery  urine,  which  at  the  same  time  contains  more  XaCl 
and  urea  [I.udwig,  M.  Herrmann).  \'on  Wittich  observed  that  the  excretion  of  uric  acid  was  not 
uniform  in  all  the  urinary  tubules  of  the  same  bird.  Extirpation  of  one  kidney,  or  disease  of  one 
kidney  in  man,  does  not  seem  to  diminish  the  secretion  (Rosenstein).  The  remaining  kidney 
becomes  more  active  and  larger. 

Reabsorption  in  the  Kidney. — In  discussing  the  secretion  of  the  kidney,  we  must  attach  con- 
siderable importance  to  the  variations  in  the  calibre  of  the  renal  tubules  in  their  course.  Perhaps 
in  the  narrowing  of  the  descending  part  of  the  looped  tubule  of  Henle  there  may  be  either  a  reab- 
sorption of  water,  so  that  the  urine  becomes  more  concentrated,  or  there  may  be  absorption  even  of 
albumin,  which  may,  perphaps.  pass  through  the  glomeruli  in  small  amount.  [That  reabsorption 
of  fluid  takes  place  within  the  kidney  was  part  of  Ludwig's  theory,  which  is  practically  a  process  of 
filtration  and  reabsorption.  Hiifner  pointed  out  that  the  structure  of  the  kidneys  of  various  classes 
of  vertebrates  corresponded  closely  with  the  requirements  for  reabsorption  of  water.  The  experi- 
ments of  Ribbert  show  that  the  urine  actually  secreted  in  the  cortex  of  the  kidney  is  more  watery 
than  that  secreted  normally  by  the  entire  organ.  He  extirpated  the  medullary  portion  in  rabbits, 
leaving  the  cortical  part  intact,  and  in  this  way  collected  the  dilute  urine  from  the  Malpighian  cor- 
puscles before  it  passed  through  Henle's  loops.] 

274.  FORMATION    OF  THE    URINARY   CONSTITUENTS.— 

The  question  has  often  been  discussed,  whether  all  the  urinary  constituents  are 
merely  excreted  through  the  kidneys,  /.  e.,  that  they  exist  pre-formed  in  the 
blood;  or  whether  some  of  them  do  not  exist  pre-formed  in  the  blood,  but  are 
formed  within  the  kidneys,  as  a  result  of  the  activity  of  the  renal  epithelium. 

Seat  of  Urea  Formation.  Urea  formed  outside  the  Kidney. — In 
considering  the  formation  of  urea,  we  have  to  ascertain  if  it  is  formed  within  the 
kidney  or  outside  of  it.  Urea  exists  pre-formed  in  the  blood,  from  which  it  is 
separated  by  the  activity  of  the  kidney.  This  is  proved  by  the  following  con- 
siderations : — 


464  FORMATION    OF   URIC   ACID. 

1.  The  blood  contains  one  part  of  urea  in  3000  to  5000  parts  (Fr.  Simon,  1S41),  but  the  renal 
vein  contains  less  urea  than  the  blood  of  the  corresponding  artery  [Picara,  i8j6 ;  Grehant). 
This  fact  is  in  favor  of  the  excretion  of  urea  from  the  blood. 

2.  After  extirpation  of  the  kidneys,  or  nephrotomy  {Prevost  and  Dumas),  or  after  ligature  of 
the  renal  vessels,  the  amount  of  urea  accumulates  in  the  blood  {Meissner,  v.  I'oit),  and  increases 
with  the  duration  of  the  experiment  to  jj^  to  ;f^j  (Gre/iant).  At  the  same  time  there  is  vomiting 
and  diarrhcea,  and  the  fluids  so  voided  contain  urea  [CI.  Bernard,  Bareswill).  Animals  die  in 
from  one  to  three  days  after  the  operation. 

3.  After  ligature  of  the  ureters,  the  secretion  of  urine  is  soon  arrested.  Urea  accumulates  in  the 
blood,  but  not  to  a  greater  extent  than  after  nephrotomy.  It  is  possible,  however,  that  the  kidneys, 
like  other  organs,  may  form  a  small  amount  of  urea,  due  to  the  metabolism  of  their  own  tissues. 

[Urea  exists  in  the  blood  ;  whence  does  the  blood  derive  it  ?  It  can  only  obtain  it  from  one 
or  more  of  several  organs — (l)  muscle;  (2)  nervous  system;  and  (3)  glands,  of  which  the  Hver  is 
the  most  prominent.     This  is  best  stated  by  the  method  of  exclusion.! 

[l.  That  urea  is  not  formed  in  muscle  is  shown,  among  other  considerations,  by  the  fact  that  only 
a  trace  of  urea  occurs  in  muscle  (^  293).  and  that  amount  is  not  increased  by  exercise.  Blood 
which  has  been  transfused  through  a  muscle,  or  the  blood  after  circulating  in  a  muscle  during  violent 
exercise,  does  not  contain  an  increase  of  urea,  nor  does  the  addition  of  ammonia  carbonate  to  blood 
circulating  through  muscle  show  any  increase  of  urea  [Grehant,  Quinquand,  Salomon).  Again, 
muscular  exertion  does  not  (as  a  rule)  increase  the  amount  of  urea  in  the  urine,  as  shown  by  the 
experiments  of  Fick  and  VVislicenus  (\  294),  Parkes,  and  others.  The  excretion  chiefly  increased 
by  muscular  exertion  is  pulmonary  CO,  (|  127).] 

[2.  From  what  we  know  of  the  nervous  system,  it  is  not  formed  there.  We  are  therefore  forced 
to  consider  the  evidence  as  to  the  liver  as  the  organ,  or,  at  least,  the  chief  organ  in  which  it  is 
formed.  This  evidence  is  in  some  respects  contradictory,  but  it  is  partly  experimental  and  partly 
clinical.  Although  Hoppe-Seyler  denies  the  existence  of  urea  in  the  liver,  its  existence  there  is 
proved  by  Gscheidlen;  and  Cyon,  on  passing  blood  through  an  excised  liver  by  the  "perfusion" 
or  "  Durchstromung  "  method  of  Ludwig,  found  that  blood,  after  being  passed  several  times  through 
the  organ,  contained  an  increased  amount  of  urea.  The  objection  to  these  experiments  is,  that 
Cyon's  method  of  estimating  the  urea  was  unreliable.  But  von  Schrceder,  using  a  similar  method, 
finds  that  if  blood  be  perfused  though  the  liver  of  a  dog  in  full  digestion,  there  is  a  great  increase  in 
the  amount  of  urea,  while  there  is  none  in  the  liver  of  a  fasting  dog.  If  ammonia  carbonate  be 
added  to  the  blood,  there  is  a  very  much  greater  amount  of  urea  in  the  blood  of  the  hepatic  vein. 
This  last  fact  is  confirmed  by  Salomon.  The  experiments  of  Minkowski  on  the  liver  of  the  goose 
(\  386)  show  that  when  the  liver  is  excluded  from  the  circulation,  lactic  acid  takes  the  place  of  uric 
acid  in  this  bird.  Brouardel  further  states,  that  if  the  region  of  the  liver  be  so  beaten  as  to  cause 
congestion  of  that  organ,  there  is  an  increase  of  the  urea  in  the  urine.] 

[The  clinical  evidence  points  strongly  to  the  formation  of  urea  in  the  liver.  Parkes  pointed  out 
that  in  hepatic  abscess,  during  the  early  congestive  stage,  the  urea  in  the  urine  is  increased,  while  it 
is  diminisiied  in  the  suppurative  stage,  when  the  hepatic  parenchyma  is  destroyed.  The  urea  is  also 
diminished  in  cancer  of  the  liver,  phthisis,  and  some  forms  of  hepatic  cirrhosis,  while  it  is  increased 
during  hepatic  congestion,  and  specially  so  in  some  cases  of  diabetes  mellitus.  The  most  striking 
fact  of  all  is  that,  in  acute  yellow  atrophy  of  the  liver,  the  urea  is  enormously  diminished  in  the 
urine,  and  may  even  disappear  from  it,  while  its  place  is  taken  by  the  intermediate  products,  leucin 
and  tyrosin  {v.  Frerichs).  In  poisoning  by  phosphorus,  coincident  with  the  atrophy  of  the  liver, 
there  is  a  fall  in  the  urea  excretion.  Noel-Paton  finds  that  some  drugs  which  increase  the  quantity 
of  bile  in  dogs  in  a  state  of  N  equilibrium  (§  lySl.sodic  salicylate  and  benzoate,colchicum,  mercuric 
chloride  and  euonymin  also  increase  the  urea  in  the  urine;  he  therefore  concludes  "that  the  forma- 
tion of  urea  in  the  liver  bears  a  very  direct  relationship  to  the  secretion  of  bile  by  that  organ."] 

As  to  the  antecedents  of  urea  there  is  the  greatest  doubt  (§  256). 

Seat  of  Uric  Acid  Formation.     Uric  acid  formed  outside  the  kidneys. 


I.  Birds'  blood  normally  contains  uric  acid  (Meissner).  Ligature  of  their  ureters  or  blood  vessels 
(Pawlinoff),  or  the  gradual  destruction  of  their  secretory  parenchyma  by  the  subcutaneous  injection 
of  neutral  potassium  chromate  (Fbstein),  is  followed  by  the  deposition  of  uric  acid  in  the  joints  and 
tissues,  and  it  may  even  form  a  white  incrustation  on  the  serous  membranes.  The  brain  remains  free 
(  Gahani,  ijby ;  ZaJesky,  Opplcr).  Acid  urates  of  ammonia,  soda,  and  magnesia  are  also  similarly 
deposited  (  Colasanli).     Extirpation  of  a  snake's  kidneys  gives  the  same  result,  but  to  a  less  degree. 

[2.  Minkowski  found  that,  after  excluding  the  liver  from  the  circulation,  lactic  acid  took  the  place 
of  uric  acid  in  the  urine  (p.  298).] 

[The  latter  experiments  point  to  the  formation  of  uric  acid  in  the  liver  in  birds, 
and  this  is  supposed  to  be  strengthened  by  the  appearance  of  the  deposition  of 
urates  in  the  urine  in  certain  disorders  of  digestion.]  Von  Schrceder  and  Cola- 
santi,  however,  as  the  result  of  their  experiments  upon  snakes,  come  to  the  con- 
clusion that  there  is  no  special  organ  concerned  in  the  formation  of  uric  acid. 


PASSAGE   OF   VARIOUS    SUBSTA^XES    INTO   THE    URINE.  465 

Hippuric  acid  is  partly  formed  in  the  kidney,  for  the  blood  of  herbivora  does  not  contain  a 
trace  of  it  ( Meissner  and  Shepard  ).  In  rabbits,  perhaps  it  is  formed  synthetically,  in  other  tissues 
as  well  as  in  the  kidney.  If  blood  containing  sodic  benzoate  and  glycin  be  passed  through  the 
blood  vessels  of  a  fresh  kidney,  hippuric  acid  is  formed  (\  260)  (Bunge,  S-hmiedeberg,  Kochs). 
[The  other  evidence  is  given  in  \  260.]  Kreatinin  ha^  intimate  relations  to  kreatin  of  muscle,  but 
where  it  is  formed  is  not  known.  If  phenol  3.nA  pyrokatechinare  digested  along  with  fresh  renal 
substance,  a  compound  of  sulphuric  (7«'a' similar  to  that  occurring  in  urine  (^  262)  is  formed.  The 
latter  substance,  however,  is  also  formed  by  similarly  digesting  liver,  pancreas,  and  muscle.  It  is 
concluded  from  these  experiments  that  these  substances  are  formed  in  the  body  within  the  kidneys, 
and  the  other  organs  mentioned  y/Coc/is). 

Chemistry  of  the  Kidney. — The  kidneys  contain  a  very  large  amount  of  ij/aCi?r.  Besides  serum 
albumin,  globulin,  albumin  soluble  in  sodium  carbonate  (Gotlwalt),  gelatin-yielding  substances,  fat 
in  the  epithelium,  elastic  substance  derived  from  the  membrana  propria  of  the  tubules,  the  kidneys 
contain  leucm,  xanthin,  hypoxanthin,  kreatin,  taurin,  inosit,  cystin  (the  last  in  no  other  tissue),  but 
only  in  very  small  amount.  The  occurrence  of  these  substances  points  to  a  lively  metabolism  in 
the  kidneys,  which  is  also  proved  by  the  liberal  supply  of  blood  they  receive. 

Blood  Vessels. — The  kidneys  receive  a  very  large  supply  of  blood,  and  dur- 
ing secretion  of  the  blood  of  the  renal  vein  is  bright  red  {Cl.  Bernard'].  [In 
the  dog  the  diameter  of  the  renal  artery  may  be  diminished  to  .5  mm.  without  the 
amount  of  blood  flowing  through  the  kidney  being  thereby  greatly  interfered  with. 
Hence,  within  wide  limits,  the  amount  of  blood  is  independent  of  the  size  of  the 
arterial  lumen,  and  is,  therefore,  dependent  on  the  blood  pressure  in  the  aorta, 
and  the  resistance  to  the  blood  current  within  and  beyond  the  kidney  {Heiden- 
hain)r\ 

The  reaction  of  the  kidney  is  acid^  even  in  those  animals  whose  urine  is  alkaline.  Perhaps  this 
fact  is  connected  with  the  retention  of  the  albumin  in  the  vessels  {Heynsius). 

275.  PASSAGE  OF  VARIOUS  SUBSTANCES  INTO  THE  URINE.— I.  The  fol- 
lowing substances  pass  unchanged  into  the  urine  :  Sulphate,  borate,  silicate,  nitrate,  and  carbon- 
ate of  the  alkalies ;  alkaline  chlorides,  bromides,  iodides ;  potassium  sulphocyanide  and  ferrocyanide  ; 
bile  salts,  urea,  kreatinin  ;  cumaric,  oxalic,  camphoric,  pyrogallic,  and  carbolic  acids.  Many  alka- 
loids, e.g.,  morphia,  strychnia,  curara,  quinine,  caffein ;  pigments,  sulphindigotate  of  soda,  carmine, 
madder,  logwood,  colormg  matter  of  cranberries,  cherries,  rhubarb  ;  santonin ;  lastly,  salts  of  gold, 
silver,  mercury,  antimony,  arsenic,  bismuth,  iron  (but  not  lead),  although  the  greatest  part  of  these 
is  excreted  by  the  bile  and  the  feces. 

2.  Inorganic  acids  reappear  in  man  and  carnivora  as  neutral  salts  of  ammonia  [Sckmeideberg  and 
IValter,  Hallen'orden) ;  in  herbivora,  as  neutral  salts  of  the  alkalies  (E.  Salkowski). 

3.  Certain  substances  which,  when  injected  in  small  amount,  seem  to  be  decomposed  in  the 
blood,  pass  in  part  into  the  urine,  when  they  occur  in  such  large  amount  in  the  blood  that  they  can- 
not be  completely  decomposed — sugar,  haemoglobin,  egg  albumin,  alkaline  salts  of  the  vegetable 
acids,  alcohol,  chloroform. 

4.  Many  substances  appear  in  an  oxidized  form  in  the  urine — moderate  quantities  of  vegetable 
alkaline  salts  as  alkaline  carbonates  (  IVohler),  uric  acid  in  part  as  allantoin  [Salkowski),  sulphides 
and  sulphites  of  soda,  in  part  as  sodium  sulphate,  potassium  sulphide  as  potassium  sulphate,  some 
oxyduls  as  o.xides,  benzol  as  phenol  {Naumyn  and  Schulzen). 

5.  Those  bodies  which  are  completely  decomposed,  as  glycerin,  resins,  give  rise  to  no  special 
derivatives  in  the  urine. 

6.  Many  substances  combine  and  appear  as  conjugated  compounds  in  the  urine,  e.g.,  the  origin 
of  hippuric  acid  by  conjugation  (ji  260),  the  conjugation  of  sulphuric  acid  (^  262),  and  the  forma- 
tion of  urea  by  synthesis  from  carbamic  acid  and  ammonia  (Drec/isel)  [i,  256).  After  the  use  of 
camphor,  chloral,  or  butylchloral,  a  conjugated  compound  with  glycuronic  acid  (an  acid  nearly 
related  to  sugar)  appears  in  the  urine.  Taurin  and  sarcosin  unite  with  sulphaminic  acid.  When 
bromphenol  is  given,  it  unites  with  mercapturic  acid,  a  body  nearly  related  to  cystin  (f,  26S). 

7.  Tannic  acid,  C]jHj„Og,  takes  up  H,0,  and  is  decomposed  into  two  molecules  of  gallic  acid 

8.  The  iodates  of  potash  and  soda  are  reduced  to  iodides  ;  malic  acid  (C4H5O5)  partly  to  suc- 
cinic acid  (C^HgO^)  ;  indigo  blue  (CigH^NjO^)  takes  up  hydrogen  and  becomes  indigo  white 
(C,,H,,N3(),). 

9.  Some  substances  do  not  pass  into  the  urine  at  all,  e.g.,  oils,  insoluble  metallic  salts  and 
metals. 

276.  INFLUENCE  OF  NERVES  ON  THE  RENAL  SECRE- 
TION.— .\t  the  present  time  we  are  acquainted  merely  with  the  influence  of  the 
vasomotor  nerves  on  the  filtration  of  the  urine  through  the  renal  vessels.  Each 

30 


466  INFLUENCE    OF    NERVES   ON    THE    RENAL    SECTION. 

kidney  seems  to  be  supplied  with  vasomotor  nerves,  which  spring  from  both  halves 
of  the  spinal  cord  (^Nicolaidcs).  As  a  general  rule,  dilatation  of  the  branches  of 
the  renal  artery,  chiefly  the  vasa  afferentia,  must  raise  the  pressure  within  the  glom- 
eruli, and  thus  increase  the  amount  of  water  filtered  through  them.  The  more  the 
dilatation  is  confined  to  the  area  of  the  renal  artery  alone,  the  greater  is  the 
amount  of  the  urine.  [As  yet  we  only  know  that  the  nervous  system  influences 
the  secretion  of  urine  only  in  so  far  as  it  modifies  the  pressure  and  velocity  of  the 
blood  current  in  the  kidney.  We  have  no  satisfactory  evidence  of  the  existence 
of  direct  secretory  nerves  in  the  kidney.] 

1.  Renal  Plexus  and  its  Centre. — Section  of  the  nerves  of  the  renal  plexus 
— the  nerves  around  the  renal  artery — generally  causes  an  increase  in  the  secretion 
of  urine  [hydruria  or  polyuria]  ;  sometimes,  on  account  of  the  great  rise  of  the 
pressure  within  the  glomeruli,  albumin  passes  into  the  urine  (and  there  may  be 
rupture  of  the  vessels  of  the  glomeruli),  leading  to  the  passage  of  blood  into  the 
urme.  The  nerve  centre  for  these  renal  nerves  lies  in  the  floor  of  the  fourth 
ventricle,  in  front  of  the  origin  of  the  vagus.  Injury  to  this  part  of  the  floor  of 
the  fourth  ventricle,  e.  g.,  by  puncture  (piqure),  may  increase  the  amount  of 
urine  (diabetes  insipidus ),  which  is  sometimes  accompanied  by  the  simulta- 
neous appearance  of  albumin  and  blood  in  the  urine  {CI.  Beniard~).  Section  of 
the  parts  which  lie  directly  in  the  course  of  these  fibres,  as  they  pass  from  the 
centre  in  the  medulla  to  the  kidney,  produces  the  same  effects.  Close  to  this 
centre  in  the  medulla,  there  lies  the  centre  for  the  vasomotor  nerves  of  the  liver, 
whose  injury  causes  diabetes  mellitus  (§  175).  Eckhard  found  that  stimulation 
of  the  vermiform  process  of  the  cerebellum  produced  hydruria.  In  man,  stimula- 
tion of  these  parts  by  tumors  or  inflammation,  etc.,  produces  similar  results. 

2.  Paralysis  of  Limited  Vascular  Areas. — If,  simultaneously  with  the 
paralysis  of  the  nerves  of  the  renal  artery,  the  nerves  of  a  neighboring  large  vas- 
cular area  be  paralyzed,  necessarily  the  blood  pressure  in  the  renal  artery  area 
will  not  be  so  high,  as  more  blood  flows  into  the  other  paralyzed  province. 
Under  these  circumstances,  there  may  be  only  a  temporary,  or,  indeed,  no  increase 
of  urine,  provided  the  paralyzed  area  be  sufficiently  large.  There  is  a  moderate 
increase  of  urine  for  several  hours  after  section  of  the  splanchnic  nerve.  This 
nerve  contains  the  renal  vasomotor  nerves  (which,  in  part,  at  least,  leave  the  spinal 
cord  at  the  first  dorsal  nerve  and  pass  into  the  sympathetic  nerve),  but  it  also  con- 
tains the  vasomotor  nerves  for  the  large  area  of  the  intestinal  and  abdominal 
viscera.  Stimulation  of  this  nerve  has  the  opposite  effect  (C/.  Bernard,  Eckhard). 
[The  polyuria  thus  produced  is  not  so  great  as  after  section  of  the  renal  nerves, 
because  the  splanchnic  supplies  such  a  large  vascular  area,  that  much  blood  accu- 
mulates in  that  area,  and  also  because  all  the  renal  nerves  do  not  run  in  the 
splanchnics.] 

3.  Paralysis  of  Large  Areas. — If,  simultaneously  with  paralysis  of  the 
renal  nerves,  the  great  majority  of  the  vasomotor  nerves  of  the  body  be  paralyzed 
[as  by  section  of  the  medulla  oblongata],  then,  owing  to  the  great  dilatation  of 
all  these  vessels,  the  blood  pressure  falls  at  once  throughout  the  entire  arterial 
system.  The  result  of  this  may  be,  provided  the  pressure  is  sufficiently  low,  that 
there  is  a  great  decrease,  or,  it  may  be,  entire  cessation  of  the  secretion  of  urine. 
The  secretion  is  arrested  when  the  cervical  cord  is  completely  divided,  down  even 
as  far  as  the  seventh  cervical  vertebra  (EcMard).  The  polyuria  caused  by  injury 
to  the  floor  of  the  fourth  ventricle  at  once  disappears  when  the  spinal  cord  (even 
down  to  the  twelfth  dorsal  nerve)  is  divided. 

[As  already  stated,  section  of  the  renal  nerves  is  followed  by  polyuria,  owing  to  the 
increased  pressure  in  the  glomeruli,  but  this  polyuria  may  be  increased  by  stimu- 
lating the  spinal  cord  below  the  medulla  oblongata,  because  the  contraction  of  the 
blood  vessels  throughout  the  body  still  further  raises  the  blood  pressure  within  the 
glomeruli.  If,  however,  the  spinal  cord  be  divided  below  the  medulla  oblongata 
— the  renal   nerve  being  also  divided — the  polyuria  ceases,  because  of  the  fall  of 


RENAL  ONCOGRAPH  AND  ONCOMETER. 


467 


the  general  blood  pressure  thereby  produced.  Merely  dividing  the  spinal  cord  in 
the  dorsal  region  also  diminishes  or  arrests  the  secretion  of  urine,  owing  to  the 
fall  of  the  blood  pressure,  but  animals  recover  from  this  operation,  the  general 
blood  pressure  rises,  and  with  it  the  secretion  of  urine.  Stimulation  of  the  cord 
below  the  medulla  arrests  the  secretion,  as  it  causes  contraction  of  the  renal 
arteries  along  with  the  other  arteries  of  the  body.] 

[Volume  of  the  Kidney — Oncometer. — By  means  of  the  plethysmograph 
(§  loi)  we  can  measure  the  variations  in  the  size  of  a  limb,  while  by  the  oncograph 
(f<yz«j,  volume)  similar  variations  in  the  volume  of  the  spleen  are  measured  (§  103 ). 
Roy  and  Cohnheim  have  measured  the  variations  in  the  volume  of  the  kidney  bv 
means  of  an  instrument  which  consists  of  two  parts,  one  termed  the  oncometer 
or  renal plethysmoineter,  in  which  the  organ  is  enclosed,  while  the  other  part  is 
the  registering  portion  or  oncograph.  The  kidney  is  enclosed  in  a  metallic 
capsule  shaped  like  the  kidney  (Fig.  265),  and  it  is  composed  of  two  halves  which 
move  on  a  hinge,  h,  to  introduce  the  organ.  The  renal  vessels  pass  out  at  a,  v. 
The  kidney  is  surrounded  with  a  thin  membrane,  and  between  this  membrane  and 
the  inner  surface  of  the  capsule  is  a  space  filled  with  warm  w7  through  the  tube, 
I,  which  is  closed  by  means  of  a  stopcock  after  the  space  is  filled  with  oil.  The 
tube,  T,  can  be   made  to  communicate  with  another   tube,    T,,  leading  into  a 


Fig.  265. 


ra~^^ 


■"ttO 


Oncometer.     K.  kidney  :  the  thick  line  is  the  metal-    Oncograph.    C,  chamber  filled  with  oil,  communicating  by  Ti 
lie  capsule  :  h,  hinge  ;  I,  tube  for  filling  appa-  with  T ;  /,  piston ;  /,  writing  lever  ^Stirling,  after  Roy). 

ratus  ;  T,  tube  to   connect   with   Tj  ;  a,  -v,  u, 
artery,  vein,  ureter  {Stiriing,  after  J?oy). 

metallic  chamber,  C,  of  the  oncograph  (Fig.  266),  which  is  provided  with  a 
movable  piston,  /,  attached  by  a  thread  to  the  writing  lever,  /.  Any  increase  in 
the  size  of  the  organ  expels  oil  from  the  chamber,  O,  into  C,  and  thus  the  piston 
is  raised,  while  a  diminution  in  the  size  of  the  kidney  diminishes  the  fluid  in  C 
and  the  lever  falls.  The  actual  volume  of  the  living  kidney  depends  upon  the 
state  of  distention  of  its  structural  elements,  upon  the  amount  of  lymph  in  its  lymph 
spaces,  but  chiefly  upon  the  amount  of  blood  in  its  blood  vessels,  and  this  again 
must  depend  upon  the  condition  of  the  non-striped  muscles  in  the  renal  arteries. 
When  the  vessels  dilate,  the  kidney  will  increase  in  size,  and  when  they  contract 
it  contracts,  so  that  we  can  register  on  the  same  revolving  cylinder  the  variations 
of  the  volume  at  the  same  time  that  we  record  the  general  arterial  blood  pressure.] 
[In  the  normal  circulation  through  the  kidney,  the  kidney  curve,  /.  e.,  the 
curve  of  the  volume  of  the  kidney,  runs  quite  parallel  with  the  blood-pressure 
curve,  and  shows  exactly  the  large  respiratory  undulations,  as  well  as  the  smaller 
elevations  due  to  the  systole  of  the  heart  (Fig.  267).  Usually,  when  the  blood 
pressure  falls,  the  kidney  curve  sinks,  and  when  the  blood  pressure  rises,  the  volume 
of  the  kidney  increases.  When  the  blood-pressure  curve  is  complicated  by  Traube- 
Hering  waves  (§85),  the  opposite  effect   is  produced   on  the  kidney  curve  ;   the 


468  CONDITIONS    AFFECTING   THE   VOLUME    OF   THE    KIDNEY. 

highest  blood  pressure  corresponds  to  the  smallest  size  of  the  kidney,  and  con- 
versely. This  is  due  to  the  fact  that,  when  these  curves  occur,  all  the  small  arte- 
rioles— including  those  in  the  kidney — are  contracted.  A  kidney  placed  in  an 
oncometer  secretes  tirine  like  a  kidney  under  natural  conditions.] 

[Arrest  of  the  respiration  in  a  curarized  animal  produces  a  rapid  and  great 
diminution  of  the  volume  of  the  kidney,  caused  by  the  venous  blood  stimulating 
the  vasomotor  centres,  and  thus  contracting  the  small  arterioles,  including  those 
of  the  kidney.  This  result  occurs  whether  one  or  both  splanchnics  are  divided, 
proving  that  all  the  vasomotor  nerves  of  the  kidney  do  not  reach  it  through  the 
splanchnics.  When  all  the  renal  nerves  at  the  hilum  are  divided,  arrest  of  the 
respiration  causes  dilatation  of  the  organ,  which  condition  runs  parallel  with  the 
rise  of  the  blood  pressure.  Stimulation  of  a  sensory  nerve,  e.  g.,  the  central  end 
of  the  sciatic  nerve,  while  causing  an  increase  of  the  blood  pressure,  makes  the 
kidney  shrink.] 

[In  poisoning  with  strychnin,  the  kidney  shrinks  while  the  blood  pressure 
rises.  Stimulation  of  the  central  or  peripheral  end  of  the  splanchnics,  divided 
at  the  diaphragm,  causes  contraction  of  the  renal  vessels  of  Mh  sides  ;  the  former 
is  a  refle.x,  the  latter  a  direct  effect.  Stimulation  of  the  peripheral  end  of  one 
splanchnic  sometimes  affects  both  kidneys.  Stimulation  of  the  peripheral  end  of 
the  renal  nerves  always  causes  a  diminution  in  the  volume  of  the  kidney,  so  that 

Fig.  267. 


ve  ;   K,  cuire  of  the  volume  of  the  kidney  ;  T,  time  curve,  intervals  indicate  a  quarter  of  a 
minute  ;  A,  abscissa  {Sliriing,  after  Roy). 

Cohnheim  and  Roy  were  forced  to  conclude  that,  although  there  was  evidence  ot 
the  existence  of  vasomotor  and  sensory  nerves  to  the  kidney,  they  found 
none  of  the  vasodilator  nerves.  By  the  same  method,  Cohnheim  and  Roy  con- 
firmed absolutely  the  independent  action  of  the  two  kidneys.  The  sudden  com- 
pression of  one  renal  artery  had  not  the  slightest  effect  upon  the  blood  current 
of  the  other  kidney.  If  a  kidney  be  exposed  in  an  animal,  by  making  an  incision 
in  the  lumbar  region,  on  stimulating  the  medulla  oblongata  directly  with  elec- 
tricity, we  may  observe  the  kidney  itself  becoming  paler,  the  pallor  appearing  in 
a  great  many  small  spots  on  the  surface  of  the  organ,  corresponding  to  the  distri- 
bution of  the  interlobular  arteries  ] 

[The  researches  of  Cohnheim  have  shown  that  the  composition  of  the  blood 
has  a  remarkable  effect  on  the  renal  circulation.  Some  substances  (water  and 
urea),  when  injected  into  the  blood,  cause  the  kidney  first  to  shrink  and  then  to 
expand,  while  sodic  acetate  dilates  the  kidney,  even  after  all  the  renal  nerves  are 
divided — an  operation  which  is  very  difficult  indeed.  Provided  all  the  renal 
nerves  be  divided,  these  effects  would  indicate  the  existence  of  some  local  intra- 
renal  vasomotor  mechanism  governing  the  renal  blood  vessels.  The  general 
blood  pressure  is  not  thereby  modified  ;  nor  need  we  wonder  at  this,  as  ligature 
of  one  renal  artery  does  not  increase  the  pressure  in  the  aorta.] 

[Mosso  also  showed  that  the  blood  stream  through  an  excised  organ  was  mate- 


UR.EMIA   AND   AMMONI.^MIA.  469 

rially  influenced  by  the  substances  mixed  with  the  blood  perfused.  This  effect 
may,  in  part,  be  due  to  the  action  of  these  chemical  ingredients  upon  the  nuclei 
of  the  endothelial  lining  of  the  blood  vessels,  especially  the  capillaries.] 

[The  reciprocal  relation  between  the  skin  and  the  kidneys  is  known  to 
every  one.  On  a  cold  day,  when  the  skin  is  pallid,  owing  to  contraction  of  the 
cutaneous  vessels,  the  amount  of  urine  secreted  is  great,  and,  conversely,  in 
summer  less  urine  is  passed  than  in  winter.  Washing  the  skin  of  a  dog  for  two 
minutes  with  ice-cold  water  causes  a  great  contraction  of  the  kidney.] 

[Strychnin  seems  to  be  able  to  cause  contraction  of  the  renal  vessels,  independently  of  its  action 
on  the  general  vasomotor  centre.  Brunton  and  Power  found  that  digitalis  caused  an  increase  of  the 
blood  pressure  (dog),  but  the  secretion  of  urine  was  either  at  the  same  time  diminished,  or  it  ceased 
altogether.  The  latter  result  was  due  to  contraction  of  the  renal  blood  vessels ;  but  when  the  aortc 
blood  pressure  began  to  fall,  the  amount  of  urine  secreted  rose  much  above  normal,  i.  e.,  when  the 
arteries  had  begun  to  relax.] 

During  fever  the  renal  vesiels  are  probably  contracted  in  consequence  of  the  stimulation  of  the 
renal  centre  by  the  abnormally  warm  blood  [Mendelsohn). 

The  repeated  respiration  of  CO  is  said  to  produce  polyuria,  perhaps  in  consequence  of  paralysis 
of  the  renal  vasomotor  centre. 

Action  of  the  Vagus. — According  to  CI.  Bernard,  stimulation  of  the  vagus  at  the  cardia  in- 
creases the  urinary  secretion,  while  at  the  same  time  the  blood  of  the  renal  vein  becomes  red.  It 
is  possible  that  this  nerve  may  contain  vasodilator  nerve  fibres  corresponding  to  the  fibres  in  the 
facial  nerve  for  the  salivary  glands  (^  145). 

277.  URAEMIA— AMMONIiEMIA. — Symptoms  of  Uraemia. — .\fter  e.xcision  of  the  kid- 
neys (nephrotomy),  or  ligature  of  the  ureter, .whereby  the  secretion  of  urine  is  arrested;  in  man, 
also,  as  a  result  of  certain  diseased  conditions  of  the  kidney,  leading  to  the  suppression  of  the 
secretion  of  urine,  there  is  developed  a  series  of  characteristic  symptoms  which  are  followed  by 
death.  The  condition  is  called  uroemic  intoxication  or  urirmia.  Besides  marked  brain  phenomena, 
drowsiness,  and  even  deep  coma,  there  are  occasional  local  or  more  general  spasms.  Sometimes 
there  is  delirium  ;  Cheyne-Stokes  phenomenon  is  often  observed  (\  III,  II),  and  there  may  be 
vomiting  and  diarrhoea,  while  in  the  fluids  voided,  as  well  as  in  the  expired  air,  ammonia  may  some- 
times be  detected. 

The  cause  of  these  phenomena  has  been  ascribed  to  the  retention  in  the  blood  of  those  sub- 
stances which  normally  are  excreted  by  the  urine,  but  as  yet  it  has  not  been  definitely  ascertained 
which  of  these  substances  causes  the  phenomena  : — 

1.  The  first  thought  is  to  ascribe  them  to  the  retention  of  the  urea.  v.  Voit  found  that  dogs  ex- 
hibited ur;emic  symptoms  if  they  were  fed  for  a  long  time  on  food  containing  urea  and  little  water. 
Meissner  found  that  in  nephrotomized  animals,  the  urxmic  symptoms  were  hastened  by  the  iniection 
of  urea  into  the  blood.  The  injection  of  a  moderate  amount  of  urea  in  perfectly  sound  animals  is 
not  followed  by  urjemic  symptoms,  probably  because  the  urea  is  rapidly  excreted  by  the  kidneys ; 
I  to  2  grms.  [15  to  30  grains]  so  injected  produce  comatose  symptoms  in  rabbits. 

2.  The  injection  of  ammonium  carbonate  produces  symptoms  resembling  those  of  uraemia,  so 
that  v.  Frerichs  and  Stannius  thought  that  the  urea  wai  decomposed  in  the  blood,  yielding  ammo- 
nium carbonate — ammoniaemia.  Demjankow  observed  ursemic  phenomena  after  nephrotomy, 
when  at  the  same  time  he  injected  the  urea  ferment  into  the  blood  (^  263).  Feltz  and  Ritter  ob- 
tained urajmic  symptoms  in  dogs  by  injecting  salts  of  ammonia. 

3.  As  ligature  of  the  ureters  produces  a  comatose  condition  in  those  animals  which  excrete  chiefly 
uric  acid  in  the  urine — c.  f  ,  birds  and  snakes  1  Zrt/fj-,<y) —it  is  possiule  that  other  substances  may 
produce  the  poisonous  symptoms.  The  injection  of  kreatin  causes  feebleness  and  contraction  of  the 
muscles  in  dogs  (Meissner).  Bernard,  Traube,  and  more  recently  Feltz  and  Ritter,  ascribe  the 
symptoms  to  an  accumulation  of  the  neutral  potassium  salts  in  the  blood  (J  54).  The  injection  of 
kreatin,  succinic  acid  (J/«>s«t'/-),  uric  acid,  and  sodic  urale  (Ranie)  is  without  effect.  Schottin 
and  Oppler  ascribe  the  results  to  an  accumulation  of  normal  or  abnormal  exlractives.  It  is  pos- 
sible that  several  substances  and  their  decomposition  products  (v.  Voit,  Perls)  contribute  to  produce 
the  result,  so  that  there  is  a  combined  action  of  several  factors,  but  perhaps  the  retention  of  the 
potash  stilts  plays  the  most  important  part. 

[Alkaloids  in  Urine  (rouchet,iSSo). — Human  urine, and  especially  febrile  urine,  when  injected 
under  the  .skin  of  frogs  or  rabbits,  acts  as  a  poison,  and  even  causes  death,  by  the  arrest  of  the  res- 
piration (CV.  Bernard,  Boeci,  Bouchard).  The  alkaloids  seem  to  be  formed  by  the  action  of  vege- 
table organisms  in  the  intestine,  whence  they  are  absorbed  into  the  blood  and  pass  into  the  urine 
(J  116).  LIrine  rendered  colorless  by  charcoal  loses  half  its  toxic  power,  and  the  poisonous  sub- 
stance IS  not  volatile,  and  even  resists  boiling.  These  alkaloids  are  increased  in  the  urine  in 
typhoid  fever,  pneumonia,  but  not  in  diabetes  [Lepine  and  Guerin).'^ 

Ammoniaemia. — When  urine  undergoes  the  alkaline  fermentation  within  the  bladder,  and  am- 
monium carbonate  is  formed,  the  ammonia  may  be  absorbed  and  produce   this  condition.     The 


470  STRUCTURE    AND    FUNCTIONS   OF   THE    URETER. 

lire.ith  and  excretions  smell  strongly  of  ammonia ;  the  mouth,  pharynx,  and  skin  are  very  dry  j 
there  is  vomiting,  with  diarrhoea  or  constipation,  while  ulcers  may  form  in  the  intestine  [Treilz). 
The  patient  rapidly  loses  flesh,  and  death  occurs  without  any  disturbance  of  the  mental  faculties. 

Uric  Acid  Diathesis.  —  When  too  much  nitrogenous  food,  too  much  alcoholic  fluids  are  persist- 
ently used,  and  little  muscular  exercise  taken,  especially  if  the  respiratory  organs  are  interfered 
with,  uric  acid  may  not  unfrequently  accumulate  in  the  blood  (  Gan-oJ).  It  may  be  deposited  in 
the  joints  and  their  ligaments,  especially  in  the  foot  and  hand,  giving  rise  to  painful  inflammation, 
and  forming  gout  stones  or  chalk  siones.  The  heart,  liver,  and  kidneys  are  rarely  affected.  The 
tissues  near  tliese  deposits  undergo  necrosis. 

278.  STRUCTURE  AND  FUNCTIONS  OF  THE  URETER.— Mucous  Membrane. 

— The  pelvis  of  the  kidney  and  the  ureter  are  lined  by  a  mucous  membrane^  consisting  of  connect- 
ive tissue,  and  covered  with  several  layers  of  stratified  "  transitional  "epithelium  (Fi".  268). 
The  cells  are  of  various  shapes,  those  of  the  lowest  layer  being  usually  more  or  less  spherical  and 
small,  while  many  of  the  cells  in  the  upper  layers  are  irregular  in  shape,  often  with  long  processes 
passing  into  the  deeper  layers. 

Submucosa. — Under  the  epithelium  there  is  a  layer  of  adenoid  tissue  [Hamburger,  Chiari), 
which  may  contain  small  lymph  follicles  [embedded  in  loose  connective  tissue].  There  are  a  few 
small  mucous  glands  in  the  pelvis  of  the  kidney, and  also  in  the  ureter  [Unruh,  £gli).  [They  are 
lined  by  a  single  layer  of  columnar  epithelium.] 

The  muscular  coat  consists  of  an  inner  somewhat  stronger  layer  of  longitudinal,  non-striped 
fibres,  and  an  outer  circular  layer.  In  the  lowest  third  of  the  ureter  there  are  in  addition  a  num- 
ber of  scattered  muscular  fibres.  All  these  layers  are  surrounded  and  supported  by  connective 
tissue.  The  outer  layers  of  the  connective  tissue  form  an  outer  coat  or  adventitia,  which  contains 
the  large  vessels  and  nerves  [with  small  ganglia].  The  various  coats  of  the  ureter  can  be  followed 
up  to  the  pelvis  of  the  kidney,  and  to  its  calices.  The  papillae  are  covered  only  by  the  mucous 
membrane,  while  the  muscular  layer  ceases  at  the  apex  of  the  pyramids,  where  they  are  disposed 
circularly  to  form  a  kind  of  sphincter  muscle  for  each' papilla  (Hcnle). 

The  blood  vessels  supply  the  various  coats,  and  form  a  capillary  plexus  under  the  epithelium. 

The  nerves  .are  not  very  numerous,  but  they  contain  medullated  (few)  and  non-medullateil  fibres, 
with  numerous  ganglia  scattered  in  their  course.  They  are  partly  motor  and  supply  the  muscular 
layers,  and  some  pass  toward  the  epithelium,  and  are  sensory  and  excito-reflex  in  function.  It  is 
these  nerves  which  are  excited  when  a  calculus,  passing  along  the  ureter,  gives  rise  to  severe  pain. 
The  ureter  perforates  the  wall  of  the  bladder  obliquely.  The  inner  opening  is  a  narrow  slit  in  the 
mucous  membrane,  directed  downward  and  inward,  and  provided  with  a  pointed,  valve  like  pro- 
cess (Fig.  269). 

Movement  of  the  Urine. — The  urine  is  propelled  along  the  ureter  thus  : 
(i )  The  secretion,  which  is  continually  being  formed  under  a  high  pressure  in  the 
kidney,  propels  onward  the  urine  in  front  of  it,  as  the  urine  is  under  a  low  pressure 
in  the  ureter.  (2)  Grcwily  aids  the  passage  of  the  urine  when  the  person  is  in 
the  erect  posture.  (3)  The  muscles  of  the  ureter  contract  rhythmically  and  peri- 
staltically,  and  so  propel  it  toward  the  bladder.  This  movement  is  reflex,  and 
is  due  to  the  presence  of  the  urine  in  the  ureter.  Every  three-quarters  of  a  min- 
ute several  drops  of  urine  pass  into  the  bladder  (Mu/Jer).  But  the  fibres  may  also 
be  excited  directly.  The  contraction  passes  along  the  tube  at  the  rate  of  20  to  30 
mm  per  second,  always  from  above  downward.  The  greater  the  tension  of  the 
ureter  due  to  the  urine,  the  more  rapid  is  the  peristaltic  movement  {Sokoleff  and 
Luchsinger). 

Local  Stimulation. — On  applying  a  stimulus  to  the  ureter  directly,  the  contraction  passes  both 
upward  and  downward.  Engelmann  observed  that  these  movements  occur  in  parts  of  the  ureter 
where  neither  nerves  nor  ganglia  were  to  be  found,  and  he  concluded  that  the  movement  was 
propagated  by  "  muscular  conduction."  If  this  be  so,  then  an  impulse  may  be  propagated  from 
one  non-striped  muscular  cell  to  another  without  the  intervention  of  nerves  (compare  the  same 
result  in  the  heart,  \  58,  I,  3). 

Prevention  of  Reflux. — The  urine  is  prevented  from  exerting  a  backward 
pressure  toward  the  kidneys,  thus:  i.  The  urine  which  collects  in  the  pelvis  of 
the  kidney  is  under  a  high  pressure,  and  thus  tends  uniformly  to  compress  the 
pyramids,  so  that  the  urine  cannot  pass  into  the  minute  orifices  of  the  urinary 
tubules  {E.  H.  Weber').  2.  When  there  is  a  considerable  accumulation  of  urine 
in  a  ureter,  f.  _§. ,  from  the  presence  of  an  impacted  calculus  or  other  cause, 
there  is  also  more  energetic  peristalsis,  and,  at  the  same  time,  the  circular  mus- 
cular fibres  round  the  apices  of  the  pyramids  compress  the  pyramids  and  prevent 


URINARY  BLADDER  AND  URETHRA. 


471 


the  reflux  of  urine  through  the  collecting  tubules.  The  urine  is  prevented  from 
passing  back  from  the  bladder  into  the  ureter,  by  the  fact  that,  when  the  bladder 
is  greatly  distended  with  urine,  the  wall  of  the  bladder  itself,  and  the  part  of  the 
ureter  which  passes  through  it,  are  compressed,  so  that  the  edges  of  the  slit-like 
opening  of  the  ureter  are  rendered  more  tense,  and  are  thus  approximated  toward 
each  other  (Fig.  269). 

279.  URINARY  BLADDER  AND  URETHRA.— Structure.— The  mucous  mem- 
brane of  the  bladder  resembles  that  of  the  ureter  ;  the  upper  layers  of  the  stratified  transitional 
epithelium  are  flattened.  It  is  obvious  that  the  form  of  the  cells  must  vary  with  the  state  of  dis- 
tention or  contraction  of  the  bladder.  [The  mucous  membrane  and  muscular  coats  are  thicker 
than  in  the  ureter.  There  are  mucous  glands  in  the  mucous  membrane,  especially  near  the  neck 
of  the  bL-idder.] 

Submucous  Coat. — There  is  a  layer  of  delicate  fibrillar  connective  tissue  mixed  with  elastic 
fibres  between  the  mucous  and  muscular  layers. 

[The  Serous  Coat  is  continuous  with,  and  has  the  same  structure  as,  the  peritoneum,  and  it 
covers  only  the  posterior  and  upper  half  nf  the  organ.] 

Musculature. — The  non-striped  muscular  fibres  are  arrange  1  in  bundles  in  several   layers,  an 


Fig.  269. 


insilionnl  epithelium  from  the  bhdder. 
of  the  large  cells  lie  upon  the  summit 
columnar  and  caudate  cells,  and  depn 
are  seen  on  their  under  surface. 


Lower  part  of  the  human  bladder  laid  open,  with  the  lower  ends  of  the 
ureters.  Note  the  clear  part,  the  trigone,  the  slit-like  openings  of  the 
ureters,  the  divided  ureters,  and  vesiculae  seminales  :  the  sinus  prostati- 
cus,  and  on  each  side  of  it  the  round  openings  of  the  ejaculatory  ducts, 
and  hi  low  both  the  numerous  small  apertures  of  the  ducts  of  the  pros- 


external  hngitudinal  layer,  best  developed  on  the  anterior  and  posterior  surfaces,  and  an  inner 
circular  \?iyer.  [Hetween  these  two  is  an  ohliqiie  layer.]  There  are  other  bundles  of  muscular 
fibres  arranged  in  different  directions.  Physiologically,  the  musculature  of  the  bladder  represents 
a  single  or  common  hollow  muscle,  whose  function  when  it  contracts  is  to  diminish  uniformly  the 
size  of  the  bladder,  and  thus  to  expel  it^  contents  [\  306). 

The  blood  vessels  resemble  those  of  the  ureter.  The  nerves  form  a  plexus,  and  are  placed 
partly  in  the  mucous  membrane  and  partly  in  the  muscular  coat,  and,  like  all  the  extra  renal  parts 
of  the  urinary  apparatus,  are  provided  with  ganglia,  some  of  these  lying  in  the  mucosa,  others  in 
the  submucosa,  and  connected  to  each  other  by  fibres  (Maier).  Ganglia  occur  in  the  course  of 
the  motor  nerve  fibres  in  the  bladder  ( ]V.  IVo/ff).  Their  functions  are  motor,  sensory,  excitomotor 
and  vasomotor.     [Sympathetic  nerve  ganglia  also  exist  underneath  the  serous  coat  {/".  Darzuin).'] 

A  too  minute  dissection  of  the  several  layers  and  bundles  of  the  musculature  of  the  bladder  has 
given  rise  to  erroneous  inferences.  Thus,  we  speak  of  a  special  detrusor  urinae,  which,  how- 
ever, consists  chiefly  of  fibres  running  on  the  anterior  and  posterior  surfaces,  from  the  vertex  to  the 
fundus.  There  does  not  seem  to  be  a  special  sphincter  vesicae  internus ;  it  is  merely  a  thicker 
circular  (6  to  12  mm.)  layer  of  non-striped  muscle  which  surrounds  the  beginning  of  the  urethra, 
and  which,  from  its  shape,  helps  to  form  the  funnel-like  exit  of  the  bladder.  Numerous  muscular 
bundles,  connected  partly  with  the  longitudinal  and  partly  with  the  circular  fibres  of  the  bladder 
exist,  especially  in  the  trigone,  between  the  orifices  of  the  ureters. 


472  ACCUMULATION    OF   URINE MICTURITION. 

Sphincter  Urethrae. — The  projier  sphincter  urethrte  is  a  Iransversely  striped 
muscle  subject  to  the  will,  and  consists  of  completely  circular  fibres  which  extend 
downward  as  far  as  the  middle  of  the  urethra,  and  partly  of  longitudinal  fibres, 
which  extend  only  on  the  posterior  surface  toward  the  base  of  the  bladder,  where 
they  become  lost  between  the  fibres  of  the  circular  layer  {Henle). 

In  the  male  urethra,  the  epithelium  of  the  prostatic  part  is  Ihe  same  as  that  in  the  bladder;  in 
the  membranous  portion  it  is  stratified,  and  in  the  cavernous  part  the  simple  cylindrical  form.  The 
mucous  membrane,  under  the  epithelium  itself,  is  beset  'nXih papillcc,  chiefly  in  the  posterior  part  of 
the  urethra,  and  contains  the  mucous  glands  of  Littre. 

Non-Striped  muscle  occurs  in  the  prostatic  part  arranged  longitudinally,  chiefly  at  the  colUculus 
seminalis;  in  the  membranous  portion  the  direction  of  the  fibres  is  chiefly  circular,  with  a  few  lon- 
gitudinal fibres  intercalated  ;  the  cavernous  part  has  a  few  circular  fibres  posteriorly,  but  anteriorly 
the  muscular  fibres  are  single  and  placed  obliquely  and  longitudinally. 

Closure  of  the  Bladder. — As  to  the  means  by  which  the  male  urethra  is  kept 
closed,  it  must  be  remembered  that  the  so-called  internal  vesical  sphincter  of  the 
anatomists,  which  consists  of  non-striped  muscle,  is  in  reality  an  integral  part  of 
the  muscular  coat  of  the  bladder,  and  surrounds  the  orifice  of  the  urethra  as  far 
down  as  the  prostatic  portion,  just  above  the  colliculus  seminalis.  It  is,  however, 
not  the  sphincter  muscle.  The  proper  sphincter  urethrae  (sph.  vesica;  externusj 
lies  below  the  latter.  It  is  a  completely  circular  inuscle  disposed  around  the 
urethra,  close  above  the  entrance  of  the  urethra  into  the  septum  urogenitale  at  the 
apex  of  the  prostate,  where  it  exchanges  fibres  with  the  deep  transverse  muscle  of 
the  perinaium  which  lies  under  it. 

Some  longitudinal  fibres,  which  run  along  the  upper  margin  of  the  prostate  from  the  bladder, 
belong  to  this  sphincter  muscle.  Single  transverse  bundles  passing  forward  from  the  surface  of  the 
neck  of  the  bladder,  the  transverse  bands  which  lie  within  the  prostate  opposite  the  ape.\  of  the 
colliculus  seminalis,  and  a  strong  transverse  bundle  passing  in  front  of  the  origin  of  the  urethra, 
into  the  substance  of  the  prostate — all  belong  to  the  sphincter  muscle  (He)ile').  In  the  male  urethra, 
the  blooii  vi^sst'h  form  a  rich  capillary  plexus  under  the  epithelium,  below  which  is  a  wide-meshed 
lyiiiphatit  plexus. 

[Tonus  of  Sphincter  Urethrae. — Open  the  abdomen  of  a  rabbit,  ligature  one  ureter,  tie  a 
cannula  in  the  other,  and  j)our  water  into  the  bladder  until  it  runs  out  through  the  urethra,  which  is 
usually  under  a  pressure  of  1 6  to  20  inches.  If  the  spinal  cord  be  divided  between  the  fifth  and 
seventh  lumbar  vertebrae,  a  column  of  six  inches  is  suflicient  to  overcome  the  resistance  of  the 
sphincter,  while  section  at  the  fourth  lumbar  vertebra  has  no  efl'ect  on  the  height  of  the  pressure. 
In  such  an  animal  the  bladder  becomes  distended,  but  in  one  with  its  cord  divided  between  the  fifth 
and  seventh  lumbar  vertebrre,  there  is  incontinence  of  urine  (Fig.  270).  In  the  former  case  because 
the  excito-motor  impulses  are  cut  ofif  from  the  centre  (5  to  7  vert.),  and  in  the  latter  because  the 
tonus  of  the  sphincter  is  destroyed  (JCupressow).     This  tonus  is  denied  by  Landois  and  others.] 

280.     ACCUMULATION     OF    URINE— MICTURITION.— After 

emptying  the  bladder,  the  urine  slowly  collects  again,  the  bladder  being  thereby 
gradually  distended.  [A  healthy  bladder  may  be  said  to  be  full  when  it  contains 
20  oz.  (^/ai?ics).'\  As  long  as  there  is  a  moderate  amount  of  urine  in  the  bladder, 
the  elasticity  of  the  elastic  fibres  surrounding  the  urethra,  and  that  of  the  sphincter 
of  the  urethra  (and  in  the  male  of  the  prostate)  suffice  to  retain  the  urine  in  the 
bladder.  This  is  shown  by  the  fact  that  the  urine  does  not  escape  from  the  bladder 
after  death.  If  the  bladder  be  greatly  distended  (1.5  to  1.8  litre),  so  that  its  apex 
projects  above  the  pubes,  the  sensory  nerves  in  its  walls  are  stimulated  and  cause  a 
feeling  of  a  full  bladder,  while  at  the  same  time  the  urethral  opening  is  dilated,  so 
that  a  few  drops  of  urine  pass  into  the  beginning  of  the  urethra.  Besides  the  sub- 
jective feeling  of  a  full  bladder,  this  tension  of  the  walls  of  the  bladder  causes  a 
reflex  effect,  so  that  the  urinary  bladder  contracts  periodically  upon  its  fluid  con- 
tents, and  so  do  the  sphincter  of  the  urethra  and  the  muscular  fibres  of  the  urethra, 
and  thus  the  urethra  is  closed  against  the  passage  of  these  drops  of  urine.  As 
long  as  the  pressure  within  the  bladder  is  not  very  high,  the  reflex  activity  of  the 
transversely  striped  sphincter  overcomes  the  other  (as  during  sleep)  ;  but,  as  the 
jiressure   rises  and   the   distention   increases,   the  contraction  of  the  walls  of  the 


EFFECT   OF    NERVES   ON    MICTURITION.  473 

bladder  overcomes  the  closure  produced  by  the  sphincter,  and  the  bladder  is 
emptied,  as  occurs  normally  in  young  children. 

As  age  advances,  the  sphincter  urethra;  comes  under  the  control  of  the  will,  so 
that  it  can  be  contracted  voluntarily,  as  occurs  in  man  when  he  forcibly  contracts 
the  bulbo  cavernosus  muscle  to  retain  urine  in  the  bladder.  The  sphincter  ani 
usually  contracts  at  the  same  time.  The  reflex  activity  of  the  sphincter  may  also 
be  inhibited  voluntarily,  so  that  it  may  be  completely  relaxed.  This  is  the  condi- 
tion when  the  bladder  is  emptied  voluntarily. 

Slight  movements,  confined  to  the  bladder,  occur  during  psychical  or  emotional  disturbances 
(e.g.,  anger,  fear),  [the  bladder  may  be  emptied  involuntarily  during  a  fright],  after  stimulation  of 
sensory  nerves  {P.  Bert,  v.  Basclt,  A/t'ver),  auditory  impressions,  restraining  the  respiration,  and  by 
arrest  of  the  heart's  action.  There  are  slight  periodic  variations  coincident  with  variations  in  the 
blood  pressure.  The  contractions  of  the  bladder  cease  after  deep  inspiration,  and  also  during  apnoea 
(Mosso  and  Pe/lacjni).  The  excised  bladder  of  the  frog,  and  even  portions  free  from  ganglia, 
exhibit  rhythmical  contractions,  which  are  increased  by  heat  [Pfah). 

Nerves. — The  nerves  concerned  in  the  retention  and  evacuation  of  the  urine 
are  :  i.  The  motor  nerves  of  the  sphincter  urethra;,  which  lie  in  the  pudendal 
nerve  (anterior  roots  of  the  third  and  fourth  sacral  nerves).  When  these  nerves 
are  divided,  as  soon  as  the  bladder  becomes  so  distended  as  to  dilate  the  urethral 
opening,  the  urine  begins  to  trickle  away  (incontinence  of  urine).  2.  The  sen- 
sory nerves  of  the  urethra,  which  excite  these  reflexes,  leave  the  spinal  cord  by 
the  posterior  roots  of  the  third,  fourth,  and  fifth  sacral  nerves.  Section  of  these 
nerves  also  causes  incontinence  of  urine.  The  centre  in  dogs  lies  opposite  the 
fifth,  and  in  rabbits,  opposite  the  seventh,  lumbar  vertebra  {BiiJge).  3.  Fibres 
pass  from  the  cerebrum  —  those  that  convey  voluntary  impulses  through  the 
peduncles,  and  the  anterior  columns  of  the  spinal  cord  (according  to  Mosso  and 
Pellacani,  through  the  posterior  columns  and  the  posterior  part  of  the  lateral  col- 
umns), to  the  motor  fibres  of  the  sphincter  urethra.  4.  The  inhibitory  fibres 
concerned  in  the  reflex  inhibition  of  the  sphincter  urethra,  take  the  same  course 
(perhaps  from  the  optic  thalamus?)  downward  through  the  cord  to  where  the  third, 
fourth,  and  fifth  sacral  nerves  leave  it.  5.  Sensory  nerves  proceed  from  the 
urethra  and  bladder  to  the  brain,  but  their  course  is  not  known.  Some  of  the 
motor  and  sensory  fibres  lie  for  a  part  of  their  course  in  the  sympathetic. 

Transverse  section  of  the  spinal  cord  above  where  the  nerves  leave  it,  is 
always  followed  in  the  first  instance  by  retention  of  urine,  so  that  the  bladder 
becomes  distended.  This  occurs  because — (i)  the  section  of  the  spinal  cord 
increases  the  reflex  activity  of  the  urethral  sphincter;  and  (2)  because  the  inhi- 
bition of  this  refiex  can  no  longer  take  place.  As  soon,  however,  as  the  bladder 
becomes  so  distended  as  in  a  purely  mechanical  manner  to  cause  dilatation  of 
the  urethral  orifice,  then  the  urine  trickles  away,  but  the  amount  of  urine  which 
trickles  out  in  drops  is  small.  Thus  the  bladder  becomes  more  and  more  dis- 
tended, as  the  continuously  distended  walls  of  the  organ  yield  to  the  increased 
tension,  so  that  the  bladder  may  become  distended  to  an  enormous  extent.  The 
urine  very  frequently  becomes  ammoniacal,  and  there  results  catarrh  and  inflam- 
mation of  the  bladder  (§  263). 

Voluntary  Micturition. — Observers  are  not  agreed  as  to  the  mechanism 
concerned  in  emptying  the  bladder  when  it  is  only  partially  full.  It  is  stated  by 
some  that  a  voluntary  impulse  passes  from  the  brain  along  a  cerebral  peduncle, 
the  anterior  columns  of  the  cord  and  the  anterior  roots  of  the  third  and  fourth 
sacral  nerves,  and  partly  through  motor  fibres  from  the  second  to  the  fifth  lumbar 
nerves  (specially  the  third),  to  act  directly  upon  the  smooth  muscular  fibres  of  the 
bladder.  This  is  assumed,  because  electrical  stimulation  of  any  part  of  this  nervous 
channel  causes  contraction  of  the  bladder.  This  view,  however,  does  not  seem  to 
be  the  true  one.  It  is  to  be  remembered  that  Budge  showed  that  the  sensory 
nerves  of  the  wall  of  the  bladder  are  contained   in  the  first,  second,  third,  and 


474 


VOLUNTARY    MICTURITION. 


fourth  sacral  nerves,  and  also  in  part  in  the  course  of  the  hypogastric  plexus, 
whence  they  ultimately  pass  by  the  rami  communicantes  into  the  spinal  cord. 

According  to  Landois,  the  smooth  musculature  of  the  bladder  cannot  be  excited 
directly  by  a  voluntary  imp\ilse,  but  is  always  caused  to  contract  reflexly.  If  we 
wish  to  micturate  when  the  urinary  bladder  contains  a  small  quantity  of  urine,  we 
first  excite  the  sensory  nerves  of  the  opening  of  the  urethra,  either  by  causing  slight 
contractions  of  the  sphincter  urethrte,  or  by  means  of  slight  abdominal  pressure, 
and  thus  force  a  little  urine  into  the  urethral  orifice.  This  sensory  stimulation 
causes  a  reflex  contraction  of  the  walls  of  the  urinary  bladder.  At  the  same  time, 
this  condition  is  maintained  voluntarily,  by  the  action  of  the  intracranial  reflex 
inhibitory  centre  of  the  sphincter  urethrae.  The  centre  for  the  reflex  stimulation 
of  the  movements  of  the  walls  of  the  urinary  bladder  is  placed  somewhat  higher  in 
the  spinal  cord  than  that  for  the  sphincter  urethrre.  In  dogs,  it  is  opposite  the 
fourth  lumbar  vertebra  {Gianuzzi,  Budge). 

Po\\er  gives  the  following  account  of  ihe  probable  mechanism  involved  : — 

"  In  the  first  place,  looking  at  the  ordinary  sensations  that  are  experienced  as  the  bladder  fills,  we 


Nervous  mechanism  of  the  bladder  {PoTver^.     a,  afferent  nerve  ot  the  sphincters  ;  S  and  M,  sensory  and  motor 
centres  ;  X,  sensory  fibres  to  brain  ;  Z,  motor  fibres  from  brain  ;  Y,  inhibitory  fibres. 

may  conclude  that  sensory  impressions,  rising  gradually  in  intensity,  are  conveyed  (through  P)  to 
the  sensory  ganglia  (S),  from  whence  they  are  reflected  (through  b)  to  the  motor  centre  (M),  and 
from  thence  to  the  sphincter,  causing  this  to  contract  more  firmly  (Fig.  270). 

"  If  the  bladder  becomes  greatly  distended,  the  impression  is  no  longer  wholly  reflected,  but 
passes  onward  and  upward  to  the  brain  (through  S  and  along  X),  and  excites  conscious  uneasiness 
or  pain.  If  it  be  desired  to  retain  the  water,  an  impulse  is  transmitted  by  motor  fibres  (through  Z) 
to  the  motor  ganglion,  M,  and  the  excito-motor  influence  (of  S)  on  the  sphincter  is  intensified  by 
the  will. 

"  But  suppose  that,  instead  of  holding  the  water,  it  be  desired  to  discharge  it ;  what  happens  ? 
The  phenomena  that  are  then  presented  seem  to  necessitate  the  admission  of  an  inhibitory,  restraining, 
or  regulating  centre,  which  must  be  in  close  proximity  with  the  excito-motor  centre,  and,  therefore, 
at  the  lower  part  of  the  .spinal  cord,  for  the  action  of  the  will  in  this  matter  is  not,  like  its  own 
voluntary  muscles,  rapid  and  instantaneous,  but  is  exerted  only  after  the  lapse  of  a  distinct  interval, 
and  the  result  is  a  relaxation  of  the  sphincter. 

"  We  may  conceive  this  impulse  to  pass  down  special  fibres,  Y,  to  an  inhibitory  centre,  I,  which 
may  either  act  directly  (through  L)  on  the  motor  centre,  M,  or  possibly  may  send  branches  directly 
to  the  sphincter  muscles." 

Painful  stimulation  of  sensory  nerves  causes  reflex  contraction  of  the  bladder  and  evacuation  of 


RETENTION    AND    INCONTINENCE    OF    URINE.  475 

the  urine  fin  children  during  teething).  Reflex  contraction  of  the  bladder  can  be  brought  about  in 
cats  by  stimulation  of  the  inferior  mesenteric  ganglion.  After  section  of  all  the  nerves  going  to 
the  bladder,  hemorrhage  and  asphyxia  cause  contraction  by  a  direct  effect  upon  the  structures  in  the 
wall  of  the  bladder.  As  yet  no  one  has  succeeded  in  e.xciting  artificially  the  inhibitory  centre  in 
the  brain  for  the  sphincter  muscle  (So/;oiLnn  and  Kowalesky). 

It  seems  probable  that,  as  in  the  case  of  the  anal  sphincter  {\  l6o),  there  is  not  a  continuous  tonic 
reflex  stimulation  of  the  sphincter  urethroe;  the  reflex  is  excited  each  time  by  the  contents.  The 
sphincier  vesic.-e  of  the  anatomists,  which  consists  of  smooth  muscular  tissue,  does  not  seem  to  take 
part  in  closing  the  bladder.  Budge  and  Landois  found  that,  after  removal  of  the  transversely-striped 
sphincter  urethr.e,  stimulation  of  the  smooth  sphincter  did  not  cause  occlusion  of  the  bladder,  nor 
could  L.  Rosenthal  or  v.  \Vitticli  convince  themselves  of  the  presence  of  tonus  in  this  muscle. 
Indeed,  its  very  exi^tence  is  questioned  by  Henle. 

Changes  of  the  Urine  in  the  Bladder. — -When  the  urine  is  retained  in  the  bladder  for  a  con- 
siderable time,  according  to  Kaupp,  there  is  an  increase  in  the  sodium  chloride  and  a  decrease  in 
the  urea  and  water.  Urine  which  remains  for  a  long  time  in  the  bladder  is  prone  to  undergo 
ammoniacal  decomposition. 

Absorption. — The  mucous  membrane  of  the  bladder  is  capable  of  absorbing  substances — potas- 
sium iodide  and  other  soluble  salts — very  slowly. 

As  the  ureters  enter  near  the  base  of  the  bladder,  the  last  secreted  urine  is  always  lowest.  If  a 
person  remain  perfectly  quiet,  strata  of  urine  are  thus  formed,  and  the  urine  may  be  voided  so  as  to 
prove  this  (Edlc/sen). 

The  pressure  within  the  bladder,  when  in  the  supine  position  =  13  to  15  centimetres  of  water. 
Increase  of  the  intra-abdominal  pressure  (by  inspiration,  forced  expiration,  coughing,  bearing  down) 
increases  the  pressure  within  the  bladder.  The  erect  posture  also  increases  it,  owing  to  the  pressure 
of  the  viscera  from  above  (.StV/rt/s, /^Kiim).  [James  obtained  4  to  4.5  inch  Hg  as  the  highest 
expulsive  power  of  the  bladder,  including  the  abdominal  pressure,  voluntary  and  involuntary.  In 
paraplegia,  where  there  is  merely  the  expulsive  power  of  the  bladder,  he  found  20  to  30  inches  of 
water.] 

[Hydronephrosis  occurs  when  the  ureters  and  pelvis  of  the  kidney  become  dilated,  owing  to 
partial  and  gradual  obstruction  of  the  outflow  of  urine  from  the  ureters;  if  the  obstruction  become 
complete,  there  is  cessation  of  the  urinary  secretion.  James  has  shown  that  the  bbidder  remains 
contracted  for  several  seconds  after  it  is  emptied,  and  this  is  specially  the  case  in  irritable  bladder; 
so  that  this  condition  m.iy  also  give  rise  to  hydronephrosis,  by  damming  up  the  urine  in  the  ureters.] 

During  micturition,  the  amount  of  urine  voided  at  first  is  small,  but  it  increases  with  the  time, 
and  toward  the  end  of  the  act  it  again  diminishes.  In  men,  the  last  drops  of  urine  are  ejected 
from  the  urethra  by  voluntary  contractions  of  the  buibo-cavernosus  muscle.  Adult  dogs  increase 
the  stream  rhythmically  by  the  action  of  this  muscle. 

281.  RETENTION  AND  INCONTINENCE  OF  URINE.— Retention  of  urine,  or 
ischuria,  occurs:  i.  When  there  is  obstruction  of  the  urethra,  from  foreign  bodies,  concretions, 
stricture,  swelling  of  the  prostate.  2.  Paralysis  or  exhaustion  of  the  musculature  of  the  bladder; 
the  litter  sometimes  occurs  after  delivery,  in  consequence  of  the  pressure  of  the  child  against  the 
bladder.  3.  After  section  of  the  spinal  cord  (p.  473).  4.  Where  the  voluntary  impulses  are  unable 
to  act  upon  the  inhibitory  apparatus  of  the  sphincter  urethrse  reflex,  as  well  as  when  the  sphincter 
urethras  reflex  is  increased. 

Incontinence  of  urine  (stillicidium  urinae)  occurs  in  consequence  of — i.  Paralysis  of  the 
sphincter  urethr.!;.  2.  Loss  of  sensibility  of  the  urethra,  which,  of  course,  abolishes  the  reflex  of 
the  sphincter.  3.  Trickling  of  the  urine  is  a  secondary  consequence  of  section  of  the  spinal  cord, 
or  of  its  degeneration. 

Strangury  is  an  excessive  reflex  contraction  of  the  walls  of  the  bladder  and  sphincter,  due  to 
stimulation  of  the  bladder  and  urethra;  it  is  observed  in  inflammation,  neuralgia  [and  after  the  use 
of  some  poisons,  e.  i;.,  cantharides].  • 

Enuresis  nocturna,  or  involuntary  emptying  of  the  bladder  at  night,  may  be  due  to  an  increased 
reflex  excitability  of  the  wall  of  the  bladder,  or  weakness  of  the  sphincter. 

282.  COMPARATIVE  AND  HISTORICAL.— Among  vertebrates,  the  urinary  and 
genital  organs  are  frequently  combined,  except  in  the  osseous  fishes.  The  Wolffian  bodies,  which 
act  as  organs  of  excretion  during  the  embryonic  period,  remain  throughout  life  in  fishes  and  amphi- 
bians, and  continue  to  act  as  such  (Gcgenl'aur).  Fishes. — The  myxineids  (cyclostomatal  have 
the  simplest  kidneys;  on  each  side  is  a  long  ureter,  with  a  series  of  short-stalked  glomeruli,  with 
capsules  arranged  along  it  Both  ureters  open  at  the  genital  pore.  In  the  other  fishes,  the  kidneys 
lie  often  as  elongated,  compact  masses  along  both  sides  of  the  vertebral  column.  The  two  ureters 
unite  to  form  a  urethra,  which  always  opens  behind  the  anus,  either  united  with  the  opening  of  the 
genital  organs  or  behind  this.  In  the  sturgeon  and  hag  fish,  the  anus  and  orifice  of  the  urethra 
together  form  a  cloaca.  Bladder-like  formations,  which,  however,  are  morphologically  homologous 
with  the  urinary  bladder  of  mammals,  occur  in  fishes,  either  on  each  ureter  (ray,  hag  fish),  or  where 
both  join.     In  amphibians,  the  vasa  efferentia  of  the  testicles  are  united  with  the  urinary  tubules  ; 


476 


COMPARATIVE    AXD    HISTORICAL. 


the  duct  in  the  frog  unites  with  the  one  on  the  other  side,  and  both  conjoined  open  into  the  cloaca, 
while  the  capacious  urinary  bladder  opens  through  the  anterior  wall  of  the  cloaca.  From  reptiles 
upward,  the  kidney  is  no  longer  a  persistent  Wolffian  body,  but  a  new  organ.  In  reptiles,  it  is 
usually  tlattened  and  elongated;  the  ureters  open  singly  into  the  cloaca,  ^aurians  and  tortoises 
have  a  urinary  bladder.  In  birds,  the  isolated  ureters  open  into  the  urogenital  sinus,  which  opens 
into  the  cloaca,  internal  to  the  excretory  ducts  of  the  genital  apparatus.  The  urinary  bladder  is 
always  absent.     In  mammals,  the  kidneys  often  consist  of  many  lobules,  e.  g.,  dolphin,  ox. 

Among  invertebrates,  the  mollusca  have  excretory  organs  in  the  form  of  canals,  which  are 
provided  with  an  outer  and  an  inner  opening.  In  the  mussel,  this  canal  is  provided  with  a  spongy- 
like  organ,  often  with  a  central  cavity,  and  consisting  of  ciliated  secretory  cells,  placed  at  the  base  of 
the  gills  (organ  of  Bojanus).  In  gasteropods,  with  analogous  organs,  uric  acid  has  been  found. 
Insects,  spiders  and  centipedes  have  the  so-called  .Malpighian  vessels,  which  are  partly  excretory 
organs  for  uric  acid  and  partly  for  bile.  These  vessels  are  long  tubes,  which  open  into  the  first  part 
of  the  large  intestine.  In  crabs,  blind  tubes,  connected  with  the  intestinal  tube,  perhaps  have  the 
same  functions.     The  vermes  also  have  renal  organs. 

Historical. — Aristotle  directed  attention  to  the  relatively  large  size  of  the  human  bladder;  he 
named  the  ureters.  Massa  (1552)  found  lymphatics  in  the  kidney.  Eustachius  (f  15S01  ligatured 
the  ureters,  and  found  the  bladder  empty.  Cusanus  ( 1565)  investigated  the  color  and  weight  of  the 
urine.  Rousset  (15S1)  described  the  muscular  nature  of  the  walls  of  the  bladder.  Vesling  de- 
scribed the  trigone  (1753).  The  first  important  chemical  investigations  on  the  urine  date  from  the 
time  of  van  Helmont  (1644).  He  isolated  the  solids  of  the  urine,  and  found  among  them  common 
salt ;  he  ascertained  the  higher  specific  gravity  of  fever  urine,  and  ascribed  the  origin  of  urinary 
calculi  to  the  solids  of  the  urine.  Scheele  (1766)  discovered  uric  acid  and  calcium  phosphate. 
Arand  and  Kunckel,  phosphorus;  Rouelle  (1773),  urea;  and  it  got  its  name  from  Fourcroy  and 
Vauquelin  (1799).  Berzelius  found  lactic  acid;  Seguin,  albumin  in  pathological  urine;  Liebig, 
hippuric  acid;  Heintz  and  v.  Pettenkofer,  kreatin  and  kreatinin  ;  WoUaston  (1810),  cystin.  Marcet 
found  xanthin ;  and  Lindbergson,  magnesia  carbonate. 


FUNCTIONS  OF  THE  Skin. 


Fig 


283.  STRUCTURE  OF  THE  SKIN.— Theskin  (3.3  to  2.7  mm.  thick; 
specific  gravity,  1057)  consists  of — 
[i.  The  epidermis  ; 
2.  The  chorium,  or  cutis  vera,  with  the  papillae  (Fig.  272).] 

The  epidermis  (o.oS  to  0.12  mm.  thick)  consists  of  many  layers  of  stratified  epithelial  cells 
united  to  each  other  by  cement  substance.  The  superficial  layers — stratum  corneum  (Figs.  272,  />, 
and  271,  c) — consist  of  several  layers  of  dry,  horny,  non-nucle- 
ated squames,  which  swell  up  in  solution  of  caustic  soda 
(Fig.  272,  E).  [It  is  always  thickest  where  intermittent 
pressure  is  applied,  as  on  the  sole  of  the  foot  and  palm  of  the 
hand.]  The  next  layer  is  the  stratum  lucidum  {Oelii)  — 
it  is  clear  and  transparent  in  a  section  of  skm,  hence  the 
name.  It  consists  of  compact  layers  of  clear  cells  with  ves- 
tiges of  nuclei  (Fig.  271,  I]-  Under  this  is  the  rete  muco- 
sum  or  rete  Malpighii  (Fig.  272,  d),  consisting  of  many 
layers  of  nucleated  protoplasmic  epithelial  cells.  These  cells 
contain  pigment  in  the  dark  races,  and  in  the  skin  of  the 
scrotum,  and  around  the  anus.  [The  superficial  cells  are 
more  fusiform  and  contain  granules  which  stain  deeply  wuh 
carmine.  They  constitute,  3,  the  stratum  granulosum 
(Fig.  271,^).  In  these  cells  the  formation  of  keratin  is 
about  to  begin,  and  the  granules  have  been  called  eleidin 
granules  by  Ranvier.  They  are  chemically  on  the  way  to  be 
transformed  into  keratin  (Fig.  271).  All  corneous  structures 
contain  similar  granules  in  the  area  where  the  cells  are  be- 
coming corneous.  I'hen  follow  several  layers  of  more  or 
less  polyhedral  cells,  softer  and  more  pLi,stic  in  their  nature, 
and  exhibiting  the  characters  of  so  called  "prickle  cells" 
(Figs.  271,  m,  and  272,  R).  The  deepest  layers  of  cells  are 
more  or  less  columnar  and  the  cells  are  placed  vertically 
upon  the  papillce  (Fig.  273,^).  Granular  leucocytes  or 
wandering  cells  are  sometimes  found  between  these  cells 
(Biesiadecki).  This  layer,  4,  has  been  called  the  stratum 
Malpighii  (Fig.  271,  /«).  The  rete  Malpighii  dips  down 
between  adjacent  papillre  and  forms  interpapillary  processes. 
According  to  Klein,  a  delicate  basement  membrane  sepa- 
rates the  epidermis  from  the  true  skin.]  The  superficial 
layers  of  tlie  epidermis  are  continually  being  thrown  oft', 
while  new  cells  are  continually  being  formed  in  the  deeper 
layers  of  the  skin  by  proliferation  of  the  cells  of  the  rete 
Malpighii.  There  is  a  gradual  change  in  the  microscopic 
and  chemical  characters  of  the  cells  as  we  pass  from  the 
deepest  to  the  most  superficial  layer  of  the  epidermis. 

(1)  Stratum  corneum, 

(2)  Stratum  lucidum, 

(3)  Stratum  granulosum,  \  „   .    m  t 
i,\    o,  ,/„.„   !/■  /*■  L-      >  Rete  Mucosum. 

(4)  ^ytt atum  MalpigkiJ,      j  -^ 

[In  a  vertical  section  of  the  skin  stained  writh  picrocarmine,  the  S.  granulosum  is  deeply  stained 
red,  and  is  thus  readily  distinguished  among  the  other  layers  of  the  epidermis.] 

No  pigment  is  formed  within  the  epidermis  itself;  when  it  is  present,  it  is  carried  by  leucocytes 
from  the  subcutaneous  tissue  {Riehl,  Ehrmann,  Aeby). 

The  chorium  (Fig.  272,  I,  C)  is  beset  throughout  its  entire  surface  by  numerous  (0.5  to  o.l  mm. 
high)  papillae  (Fig.  273,  b),  the  largest  being  U])on  the  volar  surface  of  the  hand  and  foot,  on  the 


-'^:r- 


c,  Stratum  corneutr 
granulosum  :  /« 
nerve  fibrils. 


1 


S.    lucidum: 
Malpighii; 


[Epidermis  (Fig.  271 


478 


STRUCTURE    OF   THE    SKIN. 


nipple  and  glans  penis.  Most  of  the  papilUi.'  contain  a  looped  capillary  (j^),  while  in  limited  area 
some  of  them  contain  a  touch  corpuscle  (Fig.  273,1').  The  p.ipillEe  are  disposed  in  groups, 
whose  arrangement  varies  in  ditlerent  parts  of  the  body.  In  the  palm  of  the  hand  and  sole  of  the 
foot  they  occur  in  rows,  which  are  marked  out  by  the  existence  of  delicate  furrows  on  the  surface 
visible  to  the  naked  eye.  The  chormm  consists  of  a  dense  network  of  bundles  of  white  fibrous 
tissue  mixed  with  a  network  of  elastic  fibres,  which  are  more  delicate  in  the  papillae.  The  con- 
nective tissue  contains  many  connective  tissue  corpuscles  and  numerous  leucocytes.     The  deeper 


Fig.  272. 


If 


H 

I.  Vertical  section  of  the  skin,  with  a  hair  and  sebaceous  gland,  T.  Epidermis  and  chorium  shortened— i,  outer;  2, 
inner  fibrous  layer  of  tlie  hair  follicle  ;  3,  hyaline  layer  of  the  hair  follicle  ;  4,  outer  root  sheath  ;  5,  Hu,\ley's 
layer  of  the  inner  root  sheath  :  6,  Henle's  layer  of  the  same  ;  /,  root  of  the  hair,  with  its  papilla :  A,  arrector 
pili  muscle  ;  C,  chorium  ;  a,  subcutaneous  fatty  tissue  ;  6,  epidermis  (horny  layer) :  ci,  rete  Malpighii  ;  g,  blood 
vessels  of  papillae  ;  z',  lymphatics  of  the  same  ;  h.  horny  or  corneous  substance  ;  /,  medulla  or  pith  ;  k,  epider- 
mis or  cuticle  of  hair  ;  K,  coil  of  sweat  gland  ;  E,  epidermal  scales  (seen  from  above  and  en  /ace)  from  the 
stratum  corneum :  R,  prickle  cells  from  the  rete  Malpighii;  «,  superticial,  and  w,  deep  cells  from  the  nail; 
H,  hair  magnified;  r?,  cuticle  ;  c.  medulla,  with  cells  ;/,/,  fusiform  fibrous  cells  of  the  substance  of  the  hair  ; 
X,  cells  of  Huxley's  layer ;  I,  those  of  Henle's  layer ;  S,  transverse  section  of  a  sweat  gland  from  the  axilla  ; 
a,  smooth  muscular  fibres  surrounding  it;  /,  cells  from  a  sebaceous  gland,  some  of  them  containing  granules 
of  oil. 


connective-tissue  layers  of  the  chorium  gradually  pass  into  the  subcutaneous  tissue,  where  they 
form  a  trabecular  arrangement  of  bundles,  leaving  between  them  elongated  rhomboidal  spaces  filled 
for  the  most  part  with  groups  of  fat  cells  (Fig.  272,  (?,  r?).  [In  microscopic  sections,  after  the 
action  of  alcohol,  the  fat  cells  not  unfrequently  contain  crystals  of  margarin  (Fig,  275).]  The 
long  axis  of  the  rhomb  corresponds  to  the  greater  tension  of  the  skin  at  that  part  (C  Latiger).  In 
some  situations  the  subcutaneous  tissue  is  devoid  of  fat  [penis,  eyelids].     In  many  situations,  the 


NAILS    AND    HAIR. 


479 


skin  is  fixed  by  solid  fibrous  bands  to  subjacent  structures,  as   fasciae,  ligaments  or  bones  (tenacula 
cutis),  in  other  parts,  as  over  bony  prominences,  burs;e,  filled  with  synovial  fluid,  occur. 

Smooth  muscular  fibres  occur  in  the  chorium  in  certain  situations  on  extensor  surfaces  (Xeu- 
mann) ;  nipple,  areola  mamma;,  prepuce,  perineum,  and  in  special  abundance  in  the  tunica  dartos 
of  the  scrotum. 


Fig.  273. 


F^rA^' 


/i2 


Vertical  section  of  the  cutis  vera  and  part  of  the  epidermis,    g;  cells  of  the  rete  Vlalpighii :  a, 
c,  blood  vessels  ;  J^  nerve  fibre  entering  a  Wagner's  touch  corpuscle,  e  ;  y,  section  of  i 


apiUary  ;  6,  papilla  : 


Fig.  275. 


Fig.  274. 


PapillfC  of  the  skin,  ctjijirims  removed,  blood  vessi 
jected  :  some  contain  a  Wagner's  touch  corpuscle 
others  a  capillary  loop. 


ning  crystals  of  margari 


284.  NAILS  AND  HAIR. — The  nails  (specific  gravity  1. 19)  consist  of  numerous  layers  of 
solid,  horny,  homogeneous,  epidermal  or  nail  cells,  which  may  be  isolated  with  a  solution  of  caustic 
alkalies,  when  ihey  swell  up  and  exhibit  the  remains  of  an  elongated  nucleus  (Fig.  272,  «,  m). 
The  whole  under  surface  of  the  nail  rests  upon  the  nail  bed  ;  the  lateral  and  posterior  edges  lie  in 
a  deep  groove,  the  nail  groove  (Fig.  276,  e).  The  chorium  under  the  nail  is  covered  throughout 
its  entire  extent   by  longitudinal  rows  of  papillae  (Fig.  276,  a").     Above  this  there  lies,  as  in  the 


480 


DEVELOPMENT   OF   THE    NAILS   AND    HAIR. 


skin,  many  layers  of  prickle  cells  like  those  in  the  rete  Malpighii  (Fig.  272,  c),  and  above  this  again 
is  the  substance  of  the  nail  (Fig.  276,  a).  [The  stratum  granulosum  is  rudimentary  in  the  nail  bed. 
The  substance  of  the  nail  represents  the  stratum  lucidum,  there  being  no  stratum  corneum  (A7«'«).] 
The  posterior  part  of  the  nail  groove  and  the  half  moon,  brighter  part  or  lunule,  form  the  root  of 
the  nail.  They  are,  at  the  same  time,  the  matrix,  from  which  growth  of  the  nail  takes  place.  The 
lunule  is  present  in  an  isolated  nail,  and  is  due  to  diminished  transparency  of  the  posterior  part  of 
the  nail,  owing  to  the  special  thickness  and  uniform  distribution  of  the  cells  of  the  rete  Malpighii 
( Toldt). 

Growth  of  the  NaiL — According  to  Unna,  the  matrix  extends  to  the  front  part  of  the  lunule. 
The  nail  grows  continually  from  behind  forward,  and  is  formed  by  layers  secreted  or  formed  by  the 
matrix.  These'layers  run  parallel  to  the  surface  of  the  matrix.  They  run  obliquely  from  above 
and  behind,  downward  and  forward,  through  the  thickness  of  the  substance  of  the  nail.  The  nail 
is  of  the  same  thickness  from  the  anterior  margin  of  the  lunule  forward  to  its  free  margin.  Thus 
the  nail  does  not  grow  in  thickness  in  this  region.  In  the  course  of  a  year  the  fingers  produce  about 
2  grms.  of  nail  substance,  and  relatively  more  in  summer  than  in  winter  [A/nlesc/iott,  Benecke). 

Development. — Unna  makes  the  following  .statements  regarding  the  development  of  the  nails  ; 
I.  From  the  second  to  the  eighth  month  of  fcetal  life  the  position  of  the  nail  is  indicated  by  a 
partial  but  marked  horny  condition  of  the  epidermis  on  the  back  of  the  first  phalanx,  the  "  epony- 
chium."  The  remainder  of  this  substance  is  represented  during  life  by  the  normally-formed  epidermal 
layer,  which  separates  the  future  nail  from  the  surface  of  the  furrow.  2.  The  future  nail  is  fonned 
under  the  eponychium,  with  its  first  nail  cells  still  in  front  of  the  nail  groove  ;  then  the  nail  grows 
and  pushes  forward  toward  the  groove.     At   the  seventh  month,  the  nail  (itself  covered  by  the 


Fig.  276. 


b    ,.    d 


:  section  of  one-half  of  a  nail. 
Malpighii  of  the  nail  bed  ;  d,  transv 
the  nail ;  g^  papillae  of  the  skin  on  the  back  of  the  finger. 


t,  nail  substance ; 
ely  divided  papil 


open  layer  of  cells  of  the  nail  bed;  c,  stratum 
ail  groove  :  y,  homy  layer  of  /projecting  over 


eponychium)  covers  the  whole  extent  of  the  nail  bed.  3.  When,  at  a  later  period,  the  eponychium 
splits  oft",  the  nail  is  uncovered.  After  birth  the  papillae  are  formed  on  the  bed  of  the  nail,  while 
simultaneously  the  matrix  passes  backward  to  the  most  posterior  part  of  the  groove. 

Absence  of  Hairs. — The  whole  of  the  skin,  with  the  exception  of  the  palmar  surface  of  the 
hand,  sole  of  the  foot,  dorsal  surface  of  the  third  phalanx  of  the  fingers  and  toes,  outer  surface  of 
the  eyelids,  glans  penis,  inner  surface  of  the  prepuce,  and  part  of  the  labia,  is  covered  with  hairs, 
which  may  be  strong  or  fine  (lanugo). 

A  Hair  (specific  gravity  1,26)  is  fixed  by  its  lower  extremity  (root)  in  a  depression  of  the  skin 
or  a  hair  follicle  (Fig.  272,  \, p)  which  passes  obliquely  through  the  thickness  of  the  skin,  some- 
thnes  as  far  as  the  subcutaneous  tissue.  The  structure  of  a  hair  follicle  is  the  following:  I.  The 
outer  fibrous  layer  (Figs.  272,  i,  278),  composed  of  interwoven  bundles  of  connective  tissue, 
arranged  for  the  most  part  longitudinally,  and  provided  with  numerous  blood  vessels  and  nerves. 
[It  is  just  the  connective  tissue  of  the  surrounding  chorium.]  2.  The  inner  fibrous  layer  (Figs. 
272,  2,  277)  consists  of  a  layer  of  fusiform  cells  (?  smooth  muscular  fibres)  arranged  circularly. 
[It  does  not  extend  throughout  the  whole  length  of  the  follicle]  3.  Inside  this  layer  is  a  trans- 
parent, hyaline,  glass-like  basement  membrane  (Figs.  272,  3,  277),  which  ends  at  the  neck  of 
the  hair  follicle;  while  above  it  is  continued  as  the  basement  membrane  which  exists  between  the 
epidermis  and  chorium.  In  addition  to  these  coverings,  a  hair  follicle  has  epithelial  coverings 
which  must  be  regarded  in  relation  to  the  layers  of  the  epidermis.  Immediately  within  the  glass- 
like membrane  is  the  outer  root  sheath  (Figs.  272,  4,  277,  278),  which  consists  of  so  many  layers 
of  epithelial  cells  that  it  forms  a  conspicuous  covering.     It  is,  in  fact,  a  direct  continuation  of  the 


DEVELOPMENT  OF  THE  NAILS  AND  HAIR. 


481 


Stratum  Malpighii,  and  consists  of  many  layers  of  soft  cells,  the  cells  of  the  outer  layer  being  cylin- 
drical. Toward  the  base  of  the  hair  follicle  it  becomes  narrower,  and  is  united  to,  and  continuous 
witli,  the  cells  of  the  root  of  the  hair  itself,  at  least  in  fully-developed  hairs.  The  horny  layer  of 
the  epidermis  continues  to  retain  its  properties  as  far  down  as  the  orifice  of  the  sebaceous  follicle, 
below  this  point,  however,  it  is  continued  as  the  inner  root  sheath.  This  consists  of  (I )  a  single 
layer  of  elongated.  Hat,  homogeneous,  non-nucleated  cells  (Figs.  272,  6,  277, y- — Henle's  layer) 
placed  next  and  within  the  outer  root  sheath.  Within  this  lies  (2)  Huxley's  layer  (Figs.  272,  5, 
^77'g)<  consisting  of  nucleated,  elongated,  polygonal  cells  (Fig.  272,  x,  and  3),  while  the  citticle  of 
the  hair  follicle  is  composed  of  cells  analogous  to  those  of  the  surface  of  the  hair  itself.  Toward 
the  bulb  of  the  hair  these  three  layers  become  fused  together. 

Fig.  278. 


Fig.  277. 


lion  of  a  hair  below  the  neck  of  a  hair 
follicle,  rt,  outer  fibrous  coat  with  b,  blood  vessels  ; 
c,  inner  circularly  disposed  layer ;  d^  glass-like  layer ; 
e,  ovXzT,f^g,  inner  root  sheath  ;/,  outer  layer  of  the 
same  (Henle's  sheath);  ^,  inner  layer  of  the  same 
(Huxley's  sheath) ;  h,  cuticle  ;  /,  hair. 


ction  of  a  hair  follicle  wViile  a  hair  is  being  shed,  a,  outer 
and  middle  sheaths  of  hair  follicle  ;  b,  hyaline  membrane  ; 
c,  papilla,  with  a  capillary;  d,  outer,  e,  inner  root  sheath; 
/,  cuticle  of  the  latter ;  g,  cuticle  of  the  hair  ;  h,  young 
non-medullated  hair;  /,  tip  of  new  hair  ;  /,  hair  knob  of 
the  shed  hair,  with  k^  the  remainder  of  the  cast-otf  outer 
root  sheath. 


[Coverings  of  a  hair  follicle  arranged  from  without  inward: — 

1.  Fibrous  layers,    \  f^'   Longitudinally  arranged  fibrous  tissue. 

'  \.\p)  Circularly  arranged  spintUe  cells. 

2.  Glass-like  (hyaline)  membrane. 

!{a)  Outer  root  sheath.     ,  ,,     ,  ,    , 
(b\  Inner  root  sheath.    {  [|^^!^  ^  '^y^'- 
(<-)   Cuticle  of  the  hair,  '■ 
4.  The  hair  itsell. 

31 


axley's  layer. 


482  THE    GLANDS   OF   THE    SKIN. 

The  arrector  pili  muscle  (Fig.  272,  A)  is  a  faiilike  arrangement  of  a  layer  of  smooth  muscular 
6bres,  which  is  attached  below  to  the  side  of  a  hair  follicle  and  extends  toward  the  surface  of  the 
chorimii;  as  it  stretches  obliquely  upward,  it  subtends  the  obtuse  angle  formed  by  the  hair  follicle 
and  the  surface  of  the  skin,  [or,  in  other  words,  it  forms  an  acute  angle  with  the  hair  follicle,  and 
between  it  and  the  follicle  lies  the  sebaceous  gland].  When  these  muscles  contract,  they  raise 
and  erect  the  hair  follicles,  producing  the  condition  of  cutis  anserina  or  goosf  siin.  As  the 
sebaceous  gland  lies  in  the  angle  between  the  muscle  and  the  hair  follicle,  contraction  of  the  muscle 
compresses  the  gland  and  favors  evacuation  of  the  sebaceous  secretion.  It  also  compresses  the 
blood  vessels  of  the  papilla  (i'nna). 

The  hair  with  its  enlarged  bulbous  extremity — hair  bulb — sits  upon,  or  rather  it  embraces,  the 
papilla.  It  consists  of— (l)  the  marrow  or  medulla  (Fig.  272,  i)  which  is  absent  in  woolly  hair 
and  in  the  hairs  formed  during  the  first  years  of  life.  It  consists  of  two  or  three  rows  of  cubical 
cells  (H,  c).  (2)  Outside  this  lies  the  thicker  cortex  (.4|,  which  consists  of  elongated, rigid,  horny, 
fibrous  cells  (H,/,/!,  while  in  and  between  these  cells  lie  the  pigment  granules  of  the  hair.  (3) 
The  surface  of  the  hair  is  covered  with  a  cuticle  {k),  consisting  of  imbricated  layers  of  non- 
nucleated  squames. 

Gray  Hair. — When  the  hair  becomes  gray,  as  in  old  age,  this  is  due  to  a  defective  formation  of 
pigment  in  the  cortical  part.  The  silvery  appearance  of  white  hair  is  increased  when  small  air 
cavities  are  developed,  especially  in  the  medulla  and  to  a  less  extent  in  the  cortex,  where  they  re- 
flect the  light.  Landois  records  a  case  of  the  hair  becoming  stidiienly  gray  in  a  man  whose  hair 
became  gray  during  a  single  night,  in  the  course  of  an  attack  of  delirium  tremens.  Numerous  air 
spaces  were  found  throughout  the  entire  marrow  of  the  (blond)  hairs,  while  the  hair  pigment  still 
remained. 

Development  of  Hair. — According  to  KoUiker,  from  the  12th  to  13th  week  of  intra-uterine 
hfe,  solid  finger-like  processes  of  the  epidermis  are  pushed  down  into  the  chorium.  The  process 
becomes  flasked  shaped,  while  the  central  cells  of  the  cylinder  become  elongated  and  form  a  conical 
body,  arising  as  it  were  from  the  depth  of  the  recess.  It  soon  dilTerentiates  into  an  inner  darker 
part,  which  becomes  the  hair,  and  a  thinner,  clearer,  layer  covering  the  former,  the  inner  root 
sheath.  The  outer  cells,  /.  e  ,  those  lying  next  the  wall  of  the  sac,  form  the  outer  root  sheath. 
Outside  this,  again,  the  fibrous  tissue  of  the  chorium  forms  a  rudimentary  hair  follicle,  while  one  of 
the  papilla:  grows  up  against  it,  indents  it,  and  becomes  embraced  by  the  bulb  of  the  hair.  This  is 
the  hair  papilla,  which  contains  a  loop  of  blood  vessels.  The  cells  of  the  bulb  of  the  hair  prolif- 
erate rapidly,  and  thus  the  hair  grows  in  length.  The  point  of  the  hair  is  thereby  gradually  pushed 
upward,  pierces  the  inner  root  sheath,  and  passes  obliquely  through  the  epidermis.  The  hairs  ap- 
pear upon  the  forehead  at  the  igth  week;  at  the  23d  to  25th  week  the  lanugo  hairs  appear  free, 
and  they  have  a  characteristic  arrangement  on  different  parts  of  the  body. 

Physical  Properties. — Hair  has  very  considerable  elasticity  (stretching  to  0,33  of  its  length), 
considerable  cohesion  (carrying  3  to  5  lbs.),  resists  putrefaction  for  a  long  time,  and  is  highly  hygro- 
scopic. The  last  property  is  also  possessed  by  epidermal  scales,  as  is  proved  by  the  pains  that  occur 
in  old  wounds  and  scars  during  damp  weather. 

Growth  of  a  hair  occurs  by  proliferation  of  the  cells  on  the  surface  of  the  hair  papilla,  these  cells 
representing  the  matrix  of  the  hair.  Layer  after  layer  is  formed,  and  gradually  the  hair  is  raised 
higher  within  its  follicle. 

Change  of  the  Hair. — The  results  are  by  no  means  uniform.  According  to  one  view,  when 
the  hair  has  reached  its  full  length,  the  process  of  formation  on  the  surface  of  the  hair  papilla  is  in- 
terrupted ;  the  root  of  the  hair  is  raised  from  the  papilla,  becomes  horny,  remains  almost  devoid  of 
pigment,  and  is  gradually  more  and  more  lifted  upward  from  the  surface  of  the  papilla,  while  its 
lower  bulbous  end  becomes  split  up  like  a  brush.  The  lower  empty  part  of  the  hair  follicle  becomes 
smaller,  while  on  the  old  papilla  a  new  formation  of  a  hair  begins,  the  old  hair  at  the  same  time 
falling  out  {KoUiker,  C.  Lunger).  According  to  Stieda,  the  old  papilla  disappears,  while  a  new  one 
is  formed  in  the  hair  follicle,  and  from  it  the  new  hair  is  developed. 

According  to  Gotte,  in  addition  to  the  hair  which  grows  on  the  papilla,  other  hairs  developed  from 
the  outer  root  sheath  are  formed  in  the  same  hair  follicle.  Unna  agan  describes  the  growth  and 
change  of  the  hair  differently.  He  believes  that  each  hair  grows  for  a  time  from  the  surface  of  the 
papilla.  It  then  frees  itself,  and  with  its  brush-like  lower  end  or  bulb  is  transplanted  anew  on  the 
outer  root  sheath,  about  the  middle  of  the  hair  follicle.  The  free  papilla  can  thus  produce  a  new 
hair,  which  may  even  grow  alongside  the  former,  until  the  former  falls  out.  New  recesses  with  new 
papilla:  are  formed  latterly  in  the  hair  follicle,  and  from  them  new  hairs  arise. 

285.  THE  GLANDS  OF  THE  SKIN.— The  sebaceous  glands  (Fig.  272,  I.  T)  are 
simple  acinous  glands,  which  open  by  a  duct  into  the  hair  follicles  of  large  hairs  near  their  upper 
'  pait;  in  the  case  of  small  hairs,  they  may  project  from  the  duct  of  the  gland  (Fig.  279).  In  some 
situations,  the  ducts  of  the  glands  open  free  upon  the  surface,  e.  g.,  the  glands  of  labia  minora, 
glans,  prepuce  (Tyson's  glands),  and  the  red  margins  of  the  lips.  The  largest  glands  occur  in  the 
nose  and  in  the  labia ;  they  are  absent  only  from  the  vola  manus  and  planta  pedis.  The  oblong 
alveoli  of  the  gland  consist  of  a  basement  membrane  lined  with  small  polyhedral  nucleated  granular 
secretory  cells  (Fig.  272,/).  Within  this  are  other  polyhedral  cells,  whose  substance  contains  numer- 


SKIN    AS    A    PROTECTIVE    COVERING. 


483 


ous  oil  globules ;  the  cells  become  more  fatty  as  we  pro-  Fig,  279. 

ceed  toward  the  centre  of  the  alveolus.  The  cells  lining 
the  duct  are  continuous  with  those  of  the  outer  root  sheath. 
The  detritus  formed  Iiythe  fatty  metamorphosis  of  the  cells 
constitutes  the  sebum  or  sebaceous  secretion. 

The  sweat  glands  (Fig.  272,  I,  i),  sometimes  called 
sudoriparous  glands,  consist  of  a  long  blind  tube,  whose 
lower  end  is  .irranged  in  the  form  of  a  coil  placed  in  the 
areolar  tissue  under  the  skin,  while  the  somewhat  smaller 
upper  end  or  excretory  portion  winds  in  a  vertical,  slightly 
wave-like  manner,  through  the  chorium,  and  in  a  cork- 
screw or  spiral  manner  through  the  epidermis,  where  it 
opens  with  a  free,  somewhat  trumpet  shaped  mouth.  The 
glands  are  both  very  numerous  and  large  in  the  palm  of 
the  hand,  sole  of  the  foot,  a.xilla,  forehead,  and  around  the 
nipple;  few  on  the  back  of  the  trunk,  and  are  absent  on 
the  glans,  prepuce,  and  margin  of  the  lips.  The  circum- 
anal glands  and  the  ceruminous  glands  of  the  external 
auditory  meatus,  and  Moll's  glands,  which  open  into  the 
hair  follicles  of  the  eyelashes,  are  modifications  of  the 
sweat  glands. 

Each  gland  tube  consists  of  a  basement  membrane  lined 
by  cells;  the  excretory  part  or  sweat  canal  of  the  tube 
is  lined  by  sfveral  layers  of  cubical  cells,  whose  surface  is 
covered  by  a  delicate  cuticular  layer,  a  small  central  lumen 
being  left.  Within  the  coil  the  structure  is  different.  The 
first  part  of  the  coil  resembles  the  above,  but  as  the  coil  is 
the  true  secretory  part  of  the  gland,  its  structure  differs 
from  the  sweat  canal.  This,  the  so  called  dislal  portion  of 
the  tube,  is  lined  by  a  single  layer  of  moderately  tall,  clear 
nucleated  cylindrical  epithelium  (Fig.  272,  S),  often  con- 
taining oil  globules  (Ranvier).  Smooth  muscular  fibres 
(fColliter)  are  arranged  longitudinally  along  the  tube  in  Sebaceous  gland,  with  a  lanugo  hair.  ii,granu- 
the   large   glands  (Fig.  272,  S,  a).      There   is   a   distinct  o^s^^ljlir'a"; '*fa[r-%d?s''L^n'd'free''fa"' 

lumen   present  in  the   tube.     As  the  duct  passes  through  rf"^adni:  "'  hair' follicle^  with  a^^snuili 

the  epidermis,  it  winds  its  way  between  the  epidermal  cells  hair,/, 

without  any  independent  membrane  lining  it  {Heynold). 

A  network  of  capillaries  surrounds  the  coil.  Before  the  arteries  split  up  into  capillaries,  they 
form  a  true  rete  mirabile  around  the  coil  (Briicke).  This  is  comparable  to  the  glomerulus  of  the 
kidney,  which  may  also  be  regarded  as  a  rete  mirabile.  Numerous  nerves  pass  to  form  a  plexus, 
and  terminate  in  the  glands  (  Tomsa). 

The  total  number  of  sweat  glands  is  estimated  by  Krause  at  2  •<  millions,  which  gives  a  secretory 
surface  of  nearly  loSo  square  metres.  These  glands  secrete  sweat.  Nevertheless,  an  oily  or  fatty 
substance  is  often  mixed  with  the  sweat.  In  some  animals  (glands  in  the  sole  of  the  foot  of  the 
dog,  and  in  birds)  this  oily  secretion  is  very  marked. 

Lymphatics. — Numerous  lymphatics  occur  in  the  cutis;  some  arise  by  a  blind  end,  and  others 
from  loops  within  the  papilla,  on  a  plane  lower  than  the  vascular  capillary.  [These  open  into  more 
or  less  horizontal  networks  of  tubular  lymphatics  in  the  cutis,  and  these  again  into  the  wide  lym- 
phatics of  the  subcutaneous  tissue,  which  are  well  provided  with  valves.]  Special  lymphatic  spaces 
are  disposed  in  relation  with  the  hair  follicles  and  their  glands  (Xeumann),  [and  also  with  the  fat 
(A'lein).     The  lymphatics  of  the  skin  are  readily  mjected  with  Berlin  blue  by  the  puncture  method.] 

The  blood  vessels  of  the  skin  are  arranged  in  several  systems.  There  is  a  superficial  system, 
from  which  proceed  the  capillaries  for  the  papilUe.  There  is  a  deeper  system  of  vessels  which 
supplies  special  blood  vessels  to  (a)  the  fatty  tissue;  (6)  the  hair  follicles,  each  of  which  has  a 
special  vascular  arrangement  of  its  own,  and  in  connection  with  this  each  sebaceous  gland  receives 
a  special  artery ;  (e)  an  artery  goes  also  to  each  coil  of  a  sweat  gland,  where  it  forms  a  dense  plexus 
of  capillaries  (  Tomsa). 

286.  THE  SKIN  AS  A  PROTECTIVE  COVERING.— The  sub- 
cutaneous fatty  tissue  fills  up  the  depression  between  adjoining  parts  of  the 
body  and  covers  projecting  parts,  so  that  a  more  rounded  ajipearance  of  the  body  . 
is  thereby  obtained.  It  also  acts  as  a  soft,  elastic  pad  and  protects  delicate  parts 
from  external  pressure  (sole  of  the  foot,  palm  of  the  hand),  and  it  often  surrounds 
and  protects  blood  vessels,  nerves,  etc.  It  is  a  bad  conductor  of  heat,  and  thus 
acts  as  one  of  the  factors  regulating  the  radiation  of  heat  (§  214,  II,  4),  and,  there- 
fore, the  temperature  of  the  body.     The  epidermis  and  cutis  vera  also  act  in  the 


484  CUTANEOUS    respiration:    sebum SWEAT. 

same  manner  (§  212).  Klug  found  that  the  heat  conduction  is  less  through  the 
skin  and  subcutaneous  fatty  tissue  than  through  the  skin  alone ;  the  epidermis 
conducts  heat  less  easily  than  the  fat  and  the  chorium. 

The  solid,  elastic,  easily  movable  cutis  affords  a  good  protection  against  external, 
mechanical  injuries;  while  the  dry,  impermeable,  horny  epidermis,  devoid  of 
nerves  and  blood  vessels,  affords  a  further  protection  against  the  absorption  of 
poisons,  and  at  the  same  time  it  is  capable  of  resisting,  to  a  certain  degree,  thermal 
and  even  chemical  actions.  A  thin  layer  of  fatty  matter  protects  the  free  surface 
of  the  epidermis  from  the  macerating  action  of  fluids,  and  from  the  disintegrating 
action  of  the  air.  The  epidermis  is  important  in  connection  with  \\\^  fluids  of  the 
body.  It  exerts  a  certain  pressure  upon  the  cutaneous  capillaries,  and,  to  a  limited 
extent,  prevents  too  great  diffusion  of  fluid  from  the  cutaneous  vessels.  Parts  of 
the  skin  robbed  of  their  epidermis  are  red  and  are  always  moist.  When  dry,  the 
epidermis  and  the  epidermal  appendages  are  bad  conductors  of  electricity  (§  326). 
Lastly,  we  may  say  that  the  existence  of  uninjured  epidermis  prevents  adjoining 
parts  from  growing  together. 

As  the  epidermis  is  but  slightly  extensile,  it  is  stretched  over  the  folds  and  papilL-e  of  the  cutis 
vera,  which  becomes  level  when  the  skin  is  stretched,  and  the  papilUi;  may  even  disappear  with 
strong  tension  {Leiujtiski). 

287.  CUTANEOUS    RESPIRATION:    SEBUM— SWEAT.— The 

skin,  with  a  surface  of  more  than  I'j  square  metres,  ha^  the  following  secretory 
functions :  — 

1.  The  respiratory  excretion  ; 

2.  The  secretion  of  sebaceous  matter  ;  and 

3.  The  secretion  of  sweat. 

[Besides  this  the  skin  is  protective,  contains  sense  organs,  is  largely  con- 
cerned in  regulating  the  temperature,  and  may  be  concerned  in  absorption.] 

I.  Respiration  by  the  skin  has  been  referred  to  already  (§  131)-  The  organs  therein  con- 
cerned  are  the  tubes  of  the  sweat  glands,  moistened  as  they  are  with  fluids,  and  surrounded  by  a 
rich  network  of  capillaries.  It  is  uncertain  whether  or  not  the  skin  gives  olT  a  small  amount  of  N 
or  ammonia.  Rohrig  made  experiments  upon  an  arm  placed  in  an  air-tight  metal  box.  .According 
to  him,  the  amount  of  CO,  and  HjO  excreted  is  subject  to  certain  daily  variations ;  it  is  increased 
l)v  digestion,  increased  temperature  of  the  .surroundings,  the  application  of  cutaneous  stimuli,  and 
by  impeding  the  pulmonary  respiration.  The  exchange  of  gases  also  depends  upon  the  vascularity 
of  certain  parts  of  the  skin,  while  the  cutaneous  absorption  of  O  also  depends  upon  the  number  of 
colored  corpuscles  in  the  blood. 

In  frogs  and  other  amphibians,  with  a  thin,  always  moist  epidermis,  the  cutaneous  respiration  is 
more  considerable  than  in  warm-blooded  animals  In  winter  frogs,  the  skin  alone  yields  i^  of  the 
total  amount  of  CO,  excreted  ;  in  summer  frogs,  ='3  of  the  same  (Bidder)  ;  thus,  in  these  animals  it 
is  a  more  important  respiratory  organ  than  the  lungs  themselves. 

Suppression  of  the  cutaneous  activity,  e.g.,  by  varnishing  or  dipping  the  skin  in  oil,  causes 
death  by  asphyxia  sooner  than  ligature  of  the  lungs.  Varnishing  the  Skin. — When  the  skin  of 
a  warm. blooded  animal  is  covered  with  an  impermeable  varnish  [such  as  gek^tin]  [Fourcault, 
Becquerel,  Brechet),  death  occurs  after  a  time,  probably  owing  to  the  loss  of  too  much  heat.  The 
formation  of  crystalline  ammonio-magnesic  phosphate  in  the  cutaneous  tissues  of  such  animals 
[Edenlmizeti),  is  not  suflicient  to  account  for  death,  nor  are  congestion  of  internal  organs  and  serous 
effusions  satisfactory  explanations.  The  retention  of  the  volatile  substances  (acids)  present  in  the 
sweat  is  not  sutlicient.  Strong  animals  live  longer  than  feeble  ones;  horses  die  after  several  days 
( Gcrlacli) ;  they  shiver  and  lose  flesh.  The  larger  the  cutaneous  surface  left  unvarnished,  the  later 
does  death  take  place.  Rabbits  die  when  ^s  of  'heir  surface  is  varnished.  When  the  entire  surface 
of  the  animal  is  v.arnished,  the  temperature  rapidly  falls  (to  19°) ;  the  pulse  and  respirations  vary; 
usually  they  fall  when  the  varnishing  process  is  limited;  increased  frequency  of  respiration  has  been 
observed  ( j  225).  Pigs,  dogs,  horses,  when  one-half  of  the  body  is  varnished,  exhibit  only  a  tem- 
porary fall  of  the  temperature,  and  show  signs  of  weakness,  but  do  not  die  (Elleiiherger  and  Hof- 
meisler).  [In  extensive  burns  of  the  skin,  not  only  is  there  disintegration  of  the  colored  blood 
corpuscles  [v.  Lesser),  but  in  some  cases  ulcers  occur  in  the  duodenum.  The  cause  of  the  ulcera- 
tion,  however,  has  not  been  ascertained  satisfactorily  (Curling).'] 

2.  Sebaceous  Secretion. — The  fatty  matter  as  it  is  excreted  from  the  acini 
of  the  sebaceous  glands  is  fluid,  but  even  within  the  excretory  duct  of  the  gland 


CHEMICAL   COxMPOSITION.  485 

it  stagnates  and  forms  a  white,  fat-like  mass,  which  may  sometimes  be  expressed 
(at  the  side  of  the  nose)  as  a  worm-like,  white  body,  the  so-called  comedo.  The 
sebaceous  matter  keeps  the  skin  supple,  and  prevents  the  hair  from  becoming  loo 
dry.  Microscopically,  the  secretion  is  seen  to  contain  innumerable  fatty 
granules,  a  few  gland  cells  filled  with  fat,  visible  after  the  addition  of  caustic 
soda,  crystals  of  cholesterin,  and  in  some  men  a  microscopic,  mite-like  animal 
(Demodex  foUiculorumj. 

Chemical  Composition. — The  consiituent^  are,  for  the  most  part,  fatty ;  chiefly  olein  (fluid )  and 
pahnitin  (solid)  fat,  soaps  and  some  cholesterin  ;  a  small  amount  of  albumin  and  unknown  ex- 
tractives. Among  the  inorganic  constituents,  the  insoluble  earthy  phosphates  are  most  abundant ; 
while  the  alkaline  chlorides  and  phosphates  are  less  abundant. 

The  vernix  caseosa,  which  covers  the  skin  of  a  new-born  child,  is  a  greasy  mixture  of  sebaceous 
matter  and  macerated  epidermal  cells  (containing  47.5  per  cent.  fat).  A  similar  product  is  the 
smegma  prseputialus  (52.8  per  cent,  fat),  in  which  an  ammonia  soap  is  present. 

The  cerumen,  or  ear  wax,  is  a  mixture  of  the  secretions  of  the  ceruminous  glands  of  the  ear 
(similar  in  structure  to  the  sweat  glands)  and  the  sebaceous  glands  of  the  auditory  canal.  Besides 
the  constituents  of  sebum,  it  contains  yellow  or  brownish  particles,  a  bitter  yellow  extractive  sub- 
stance derived  from  the  ceruminous  glands,  potash  soaps  and  a  special  lat  (Berztliiis).  The  secre- 
tion of  the  Meibomian  glands  is  sebum. 

[Lanoline. — Liebreich  finds  in  feathers,  hairs,  wool,  and  keratin  tissues  generally,  a  cholesterin 
fat,  which,  however,  is  not  a  true  fat,  although  it  saponifies,  but  an  ethereal  compound  of  certain 
fatty  acids  with  cholesterin.  In  commerce  it  is  obtained  from  wool,  and  is  known  by  the  above 
name;  it  forms  an  admirable  basis  for  ointments,  and  it  is  ver\' readily  absorbed  by  the  skin.]  Thus, 
the  fat-like  substance  for  protecting  the  epidermis  is  partly  formed  along  with  keratin  in  the  epi- 
dermis itself. 

3.  The  Sweat. — The  sweat  is  secreted  in  the  coil  of  the  sweat  glands.  .\s 
long  as  the  secretion  is  small  in  amount,  the  water  secreted  is  evaporated  at  once 
from  the  skin,  along  with  the  volatile  constituents  of  the  sweat  ;  as  soon,  how- 
ever, as  the  secretion  is  increased,  or  evaporation  is  prevented,  drops  of  sweat 
appear  on  the  surface  of  the  skin.  The  former  is  called  insensible  perspira- 
tion, and  the  latter  sensible  perspiration.  [Broadly,  the  quantity  is  about  2 
lbs.  in  twenty-four  hours.] 

The  sensible  perspiration  varies  greatly  ;  as  a  rule,  the  right  side  of  the  body  perspires  more 
freely  than  the  left.  The  palms  of  the  hands  secrete  most,  then  follow  the  soles  of  the  feet,  check, 
breast,  upper  arm  and  forearm  (Peiper).  It  falls  from  morning  to  mid-day,  and  rises  s^ain  toward 
evening  (  Tanssen). 

Method. — .Sweat  is  obtained  from  a  man  by  placing  him  in  a  metallic  vessel  in  a  warm  bath  ; 
the  sweat  is  rapidly  secreted  and  collected  in  the  vessel.  In  this  way  Favre  collected  2560  grammes 
of  sweat  in  i  '•<  hours.  An  arm  may  be  inclosed  in  a  cylindrical  vessel,  which  is  fixed  air  tight 
round  the  arm  with  an  elastic  bandage  (Schottin). 

Among  animals,  the  horse  sweats,  so  does  the  ox,  but  to  a  less  extent;  the  vola  and  planta  of 
apes,  cats  and  the  hedgehog  secrete  sweat;  the  snout  of  the  pig  sweats  (?),  while  the  goat,  rabbit, 
rat,  mouse  and  dog  are  said  not  to  sweat  [Luchsin<;er).  [The  skin  over  the  body  and  the  pad  on 
the  dog's  foot  contain  numerous  sweat  glands,  which  open  free  on  the  surface  of  the  pad  and  into 
the  hair  follicles  on  the  general  surface  of  the  skin  (  IV.  Stirling).'^ 

Microscopically. — The  sweat  contains  only  a  few  epidermal  scales  accidentally  mixed  with  it, 
and  fine  fatty  granules  from  the  sebaceous  glands. 

Chemical  Composition. — Its  reaction  is  alkaline,  although  it  frequently  is 
acid,  owing  to  the  admixture  of  fatty  acids  from  decomposed  sebum.  During 
profuse  secretion  it  becomes  neutral,  and,  lastly,  alkaline  again  {Triimpy  and 
Luchsinger').  The  sweat  is  colorless,  slightly  turbid,  of  a  saltish  taste,  and  has  a 
characteristic  odor,  varying  in  different  parts  of  the  body;  the  odor  is  due  to  the 
presence  of  volatile  fatty  acids.  The  constituents  are — water,  which  is  increased 
by  copious  draughts  of  that  fluid.  The  solids  amount  to  1.180  per  cent.  (0.70 
to  2.66  per  cent. — Funke),  and  of  these  0.96  per  cent,  is  organic  and  0.33  inor- 
ganic. Among  the  organic  constituents  are  neutral  fats  (palmitin,  stearin),  also 
present  in  the  sweat  of  the  palm  of  the  hand,  which  contains  no  sebaceous  glands 
(^Krause),  cholesterin,  volatile  fattv  acids  (chiefly  formic,  acetic,  butyric,  propionic, 
caproic,  capric  acids),  varying  qualitatively  and  quantitatively  in  different  parts 


486  INFLUENCE    OF    NERVES   ON    THE    SECRETION    OF    SWEAT. 

of  the  body.  These  acids  are  most  abundant  in  the  sweat  first  (acid)  secreted. 
There  are  also  traces  of  albumin  (similar  to  casein),  and  urea,  about  o  i  per  cent. 
{Funke,  Picard').  In  uraemic  conditions  (anuria  in  cholera),  urea  has  been  found 
crystallized  on  the  skin  {Schottin,  Drasche).  When  the  secretion  of  sweat  is 
greatly  increased,  the  amount  of  urea  in  the  urine  is  diminished  both  in  health 
and  in  uremia  (Lcube).  The  nature  of  the  reddish-yellow  pigment,  which  is 
extracted  from  the  residue  of  sweat  by  alcohol,  and  colored  green  by  oxalic  acid, 
is  unknown.  Among  inorganic  constituents,  those  that  are  easily  soluble  are  more 
abundant  than  those  that  are  soluble  with  difficulty,  in  the  proportion  of  17 
to  I  {Scho/tin);  sodium  chloride,  0.2  ;  potassium  chloride,  0.2  ;  sulphates,  0.0 1 
per  1000,  together  with  traces  of  earthy  phosphates  and  sodium  phosphate.  Sweat 
contains  COj  in  a  state  of  absorption  and  some  N.  When  decomposed  with  free 
access  of  air,  it  yields  ammonia  salts  {Gorup-Bcsanes). 

Excretion  of  Substances.— Some  substances  when  introduced  into  tlie  body  reappear  in  tiie 
sweat;  benzoic,  cinnamic,  tartaric  and  succinic  acids  are  readily  excreted ;  quinine  and  potassium 
iodide  with  more  difficulty.  Mercuric  chloride,  arsenious  and  arsenic  acids,  sodium  and  potassium 
arseniate  have  also  been  found.  After  taking  arseniate  of  iron,  arsenious  acid  has  been  found  in 
the  sweat,  and  iron  in  the  urine.  Mercury  iodide  reappears  as  a  chloride  in  the  sweat,  while  the 
iodine  occurs  in  the  sahva. 

Formation  of  Pigment. — The  leucocytes  furnish  the  material,  and  the  pig- 
ment is  deposited  in  granules  in  the  deeper  layers,  and,  to  a  less  extent,  in  the 
upper  layers  of  the  rete  Malpighii.  This  occurs  in  the  folds  around  the  anus, 
scrotum,  nipple  [especially  during  pregnancy],  and  everywhere  in  the  colored 
races.  There  is  a  diffuse,  whitish-yellow  pigment  in  the  stratum  corneum,  which 
becomes  darker  in  old  age.  The  pigmentation  depends  on  chemical  processes, 
reduction  taking  place,  and  these  processes  are  aided  by  light.  Granular  pig- 
ment lies  also  in  the  layers  of  prickle  cells.  The  dark  coloration  of  the  skin  may 
be  arrested  by  free  O  [hydric  peroxide],  while  the  corneous  change  is  prevented 
at  the  same  time  {Uniia). 

Pathological. — To  this  belongs  the  formation  of  liver  spots  or  chloasma,  freckles,  and  the 
pigmentation  of  Addison's  disease  [pigmentation  round  old  ulcers,  etc.,  ]  {J  103,  IV).  [The 
curious  cases  of  pigmentation,  especially  in  neurotic  women,  eg.,  in  the  eyelids,  deserve  further 
study  in  relation  to  the  part  played  by  the  nervous  system  in  this  process.] 

288.  INFLUENCE  OF  NERVES  ON  THE  SECRETION  OF 
SWEAT. — The  secretion  of  the  skin,  which  averages  about  Jy  of  the  body 
weight,  i.e.,  about  double  the  amount  of  water  excreted  by  the  lungs,  maybe 
increased  or  diminished.  The  liability  to  perspire  varies  much  in  different  indi- 
viduals. The  following  conditions  influence  the  secretion  :  i.  Increased  tem- 
perature of  the  surroundings  causes  the  skin  to  become  red,  while  there  is  a  pro- 
fuse secretion  of  sweat  (§  214,  II,  i).  Cold,  as  well  as  a  temperature  of  the  skin 
about  50°  C,  arrest  the  secretion.  2.  A  very  watery  condition  of  the  blood, 
e.g.,  after  copious  draughts  of  warm  water,  increases  the  secretion.  3.  Increased 
cardiac  and  vascular  activity,  whereby  the  blood  pressure  within  the  cuta- 
neous capillaries  is  increased,  has  a  similar  effect  ;  increased  sweating  follows 
increased  muscular  activity.  4.  Certain  drugs  favor  sweating,  e.g.,  pilo- 
carpin,  Calabar  bean,  strychnin,  picrotoxin,  muscann,  nicotin,  camphor,  ammonia 
compounds,  while  others,  as  atropin  and  morjjhia,  in  large  doses,  diminish  or 
paralyze  the  secretion.  [Drugs  which  excite  copious  perspiration,  so  that  it  stands 
as  beads  of  sweat  on  the  skin,  are  called  sudorifics,  while  those  that  excite  the 
secretion  gently  are  diaphoretics,  the  difference  being  one  of  degree.  Those 
drugs  which  lessen  the  secretion  are  called  antihydrotics.]  5.  It  is  important 
to  notice  the  a/itagonism  which  exists,  probably  upon  mechanical  grounds,  between 
the  secretion  of  sweat,  the  urinary  secretion,  and  the  evacuation  of  the  intestine. 
Thus,  copious  secretion  of  urine  (^..i,'. ,  in  diabetes)  and  watery  stools  coincide 
with  dryness  of  the  skin.     If  the  secretion  of  sweat  be  increased,  the  percentage 


INFLUENCE  OF  NERVES  ON  THE  SECRETION  OF  SWEAT.    487 

of  salts,  urea  {Funke),  and  albumin  is  also  increased  {Leube),  while  the  other 
organic  substances  are  diminished.  The  more  saturated  the  air  is  with  watery 
vapor,  the  sooner  does  the  secretion  appear  in  drops  upon  the  skin,  while  in  dry 
air  or  air  in  motion,  owing  to  the  rapid  evaporation,  the  formation  of  drops  of 
sweat  is  prevented,  or  at  least  retarded.  [The  complementary  relation  between 
the  skin  and  kidneys  is  known  to  every  one.  In  summer,  when  the  skin  is 
active,  the  kidneys  separate  less  water;  in  winter,  when  the  skin  is  less  active,  it 
is  cold  and  comparatively  bloodless,  while  the  kidneys  excrete  more  water,  so  that 
the  action  of  these  two  organs  is  in  inverse  ratio.] 

The  influence  of  nerves  upon  the  secretion  of  sweat  is  very  marked. 

I.  Just  as  in  the  secretion  of  saliva  (§  145),  vasomotor  nerves  are  usually  in 
action  at  the  same  time  as  the  proper  secretory  nerves ;  the  vaso-dilator 
nerves  (sweating  with  a  reJ  congested  skin)  are  most  frequently  involved.  The 
fact  that  secretion  of  sweat  does  occasionally  take  place  when  the  skin  is />a/e 
(fear,  death  agony)  shows  that,  when  the  vasomotor  nerves  are  excited,  so  as  to 
constrict  the  cutaneous  blood  vessels,  the  sweat-secretory  nerve  fibres  may  also  be 
active. 

Under  certain  circumstances  the  amount  of  blood  in  the  skin  seems  to  determine  the  occurrence 
of  sweating;  thus  Dupuy  found  that  section  of  the  cervical  sympathetic  caused  secretion  on  that 
side  of  the  necli  of  a  horse  ;  while  Nitzelnadel  found  that  percutaneous  electrical  stimulation  of 
the  cervical  sympathetic  in  man  limited  the  sweating.! 

[We  may  draw  a  parallel  between  the  secretion  of  saliva  and  that  of  sweat.  Both  are  formed 
in  glands  derived  from  the  outer  layer  of  the  embryo.  Both  are  formed  from  lymph  supplied  by 
the  blood  stream,  and  if  the  lymph  be  in  sufficient  quantity,  secretion  may  take  place  when  there  is 
no  circulation,  although  in  both  cases  secretion  is  most  lively  when  the  circulation  is  most  active 
and  the  secretory  nerves  of  both  are  excited  simultaneously;  both  have  secretory  nerves  distinct 
from  the  nerves  of  the  blood  vessels;  both  may  be  paralyzed  by  the  action  of  the  nervous  system, 
or  in  disease  (fever),  or  conversely,  both  are  paralyzed  by  atropine  and  excited  by  other  drugs,  e.g-., 
pilocarpin.  in  the  gland  cells  of  both  histological,  changes  accompany  the  secretory  act,  and  no 
doubt  similar  electro-motor  phenomena  occur  in  both  glands.] 

II.  Secretory  nerves,  altogether  independent  of  the  circulation,  control  the 
secretion  of  sweat.  Stimulation  of  these  nerves,  even  in  a  limb  which  has  been 
amputated  in  a  kitten,  causes  a  temporary  secretion  of  sweat,  i.e.,  after  complete 
arrest  of  the  circulation  {Goltz,  Kendall  and  Luchsinger,  Ostroumoiv).  In  the 
intact  condition  of  the  body,  however,  profuse  perspiration,  at  all  events,  is 
always  associated  with  simultaneous  dilatation  of  the  blood  vessels  (just  as,  in 
stimulation  of  the  facial  nerve,  an  increased  secretion  of  saliva  is  associated  with 
an  increased  blood  stream — §  145,  A,  I).  The  secretory  nerves  and  those  for 
the  blood  vessels  seem  to  lie  in  the  same  nerve  trunks. 

The  secretory  nerves  for  the  hind  limbs  (cat)  lie  in  the  sciatic  nerve.  Luch- 
singer  found  that  stimulation  of  the  peripheral  end  of  this  nerve  caused  renewed 
secretion  of  sweat  for  a  period  of  half  an  hour,  provided  the  foot  was  always  wiped  to 
remove  the  sweat  already  formed.  If  a  kitten,  whose  sciatic  nerve  is  divided  on 
one  side,  be  placed  in  a  chamber  filled  with  heated  air,  all  the  three  intact  limbs 
soon  begin  to  sweat,  but  tlie  limb  whose  nerve  is  divided  does  not,  nor  does  it  do 
so  when  the  veins  of  the  limb  are  ligatured  so  as  to  produce  congestion  of  its 
blood  vessels.  [The  cat  sweats  only  on  the  hairless  soles  of  the  feet.]  As  to  the 
course  of  the  secretory  fibres  to  the  sciatic  nerve,  some  pass  directly  from  the 
spinal  cord  {Vulpi an),  some  pass  into  the  abdominal  sympathetic  (Z«ir/w«^dv-, 
Nawrocki,  Ostroumow),  through  the  rami  communicantes  and  the  anterior  spinal 
roots  from  the  upper  lumbar  and  lower  dorsal  spinal  cord  (9th  to  13th  dorsal  ver- 
tebras— cat)  where  the  sweat  centre  for  the  lower  limbs  is  situated. 

The  sweat  centre  may  be  excited  directly:  fi)  By  a  strongly  venous  con- 
dition of  the  blood,  as  during  dyspnoea,  e.g.,  in  the  secretion  of  sweat  that  some- 
times precedes  death;  (2)  by  overheated  blood  (45°  C.)  streaming  through  the 
centre;  (3)  by  certain  poisons  (see  p.  486).  The  centre  may  be  also  excited 
reflexly,  although  the  results  are  variable,  e.g.,  stimulation  of  the  crural  and 


488  PATHOLOGICAL   VARIATIONS   OF    SWEATING. 

peroneal  nerves,  as  well  as  the  central  end  of  the  opposite  sciatic  nerve  excites  it 
{Liuksinger).  [The  pungency  of  mustard  in  the  mouth  may  excite  free  perspira- 
tion on  the  face.] 

Anterior  Extremity. — The  secretory  fibres  lie  in  the  ulnar  and  median  nerves, 
for  the  fore  limbs  of  the  cat ;  most  of  them,  or  indeed  all  of  them  {Ncnarocki) 
pass  into  the  thoracic  sympathetic  (Ggl.  stellatum"),  and  part  (?)  runs  in  the  nerve 
roots  direct  from  the  spinal  cord  {Luchsingcr,  Vulpian,  Ott).  A  similar  sweat 
centre  for  the  upper  limbs  lies  in  the  lower  part  of  the  cervical  spinal  cord.  Stim- 
ulation of  the  central  ends  of  the  brachial  plexus  causes  a  reflex  secretion  of  sweat 
upon  the  foot  of  the  other  side  {Adamkiewicz).  At  the  same  time  the  hind  feet 
also  perspire. 

Pathological. — Degeneration  of  the  motor  ganglia  of  the  anterior  horns  of  the  spinal  cord  causes 
loss  of  the  secretion  of  sweat,  in  addition  to  paralysis  of  the  voluntary  muscles  of  the  trunk.  The 
perspiration  is  increa-ied  in  paralyzed  as  well  as  in  cedamatous  limbs.  In  nephritis,  there  are  great 
variations  in  the  amount  of  water  given  off  by  the  skin. 

Head. — The  secretory  fibres  for  this  part  (horse,  man,  snout  of  pig)  lie  in  the 
thoracic  sympathetic,  pass  into  the  ganglion  stellatum,  and  ascend  in  the  cervical 
sympathetic.  Percutaneous  electrical  stimulation  of  the  cervical  sympathetic  in 
man,  causes  sweating  of  that  side  of  the  face  and  of  the  arm  {M.  Meyer).  In  the 
cephalic  portion  of  the  sympathetic,  some  of  the  fibres  pass  into,  or  become 
ap[)lied  to,  the  branches  of  the  trigeminus,  which  explains  why  stimulation  of 
the  infraorbital  nerve  causes  secretion  of  svveat.  Some  fibres,  however,  arise 
directly  from  the  roots  of  the  trigeminus  {Liic/i singer),  and  the  facial  (  Vulpian, 
Adamkiewicz).  Undoubtedly  the  cerebrum  has  a  direct  effect  either  upon  the 
vasomotor  nerves  (p.  487,  I)  or  upon  the  sweat-secretory  fibres  (11),  as  in  the 
sweating  produced  by  psychical  excitement  (pain,  fear,  etc.).  • 

Adamkiewicz  and  Senator  found  that,  in  a  man  suffering  from  abscess  of  the  motor  region  of  the 
cortex  cerebri  for  the  arm,  there  were  spasms  and  perspiration  in  the  arm. 

Sweat  Centre. — According  to  Adamkiewicz,  the  medulla  oblongata  contains 
the  dominating  sweat  centre  (§  t,it,— Marine,  JVawrocki).  When  this  centre 
is  stimulated  in  a  cat,  all  the  four  feet  sweat,  even  three-quarters  of  an  hour  after 
death  (Adamkie^cicz). 

III.  The  nerve  fibres  which  terminate  in  the  smooth  muscular  fibres  of  the  sweat 
glands  act  upon  the  excretion  of  the  secretion. 

[Changes  in  the  Cells  during  Secretion. — In  the  resting  glands  of  the 
horse,  the  cylindrical  cells  are  clear  with  the  nucleus  near  their  attached  ends,  but 
after  free  perspiration  they  become  granular,  and  their  nucleus  is  more  central 
{^Renaut^!\ 

If  the  sweat  nerves  be  divided  (cat),  injection  of  pilocarpin  causes  a  secretion  of  sweat,  even  at 
the  end  of  three  days.  After  a  longer  period  than  six  days  there  may  be  no  secretion  at  all.  This 
observation  coincides  with  the  phenomenon  of  dryness  of  the  skin  in  paralyzed  limbs.  Dieffenbach 
found  that  transplanted  portions  of  skin  first  began  to  sweat  when  their  sensibility  was  restored.  If 
a  motor  nerve  (tibial,  median,  facial)  of  a  man  be  stimulated,  sweat  appears  on  the  skin  over  the 
muscular  area  supplied  by  the  nerve,  and  also  upon  the  corresponding  area  of  the  opposite  non- 
stimulated  side  of  the  body.  This  result  occurs  when  the  circulation  is  arrested  as  well  as  when  it 
is  active.  Sensory  and  thermal  stimulation  of  the  skin  always  cause  a  bilateral  reflex  secretion  inde- 
pendently of  the  circulation.  The  area  of  sweating  is  independent  of  the  part  of  the  skin  stimu- 
lated (Adamkiewicz). 

289.  PATHOLOGICAL  VARIATIONS. — I.  Anidrosis  or  diminution  of  the  secretion  of 
sweat  occurs  in  diabetes  and  the  cancerous  cachexia,  and  along  with  other  disturbances  of  nutrition 
of  the  skin  in  some  nervous  diseases,  <■.,?■.,  in  dementia  paralytica ;  in  some  limited  regions  of  the  skin 
it  has  occurred  in  certain  trophoneuroses  ,  1'.^.,  in  unilateral  atrophy  of  the  face  and  in  paralyzed 
parts.  In  many  of  these  cases  it  depends  upon  paralys:s  of  the  corresponding  nen'es  (Eulsnburg)  or 
their  spitial  sweat  cetitrt's. 

2.  Hyperidrosis,  or  increase  of  the  secretion  of  sweat,  occurs  in  easily  excitable  persons,  in 
consequence  of  the  irritation  of  the  nerves  concerned  (?  288),  ^. y.,  the  sweating  which  occurs  in 
debilitated  conditions  and  in  the  hysterical  (sometimes  on  the  head  and  hands),  and  the  so  called 


CUTANEOUS   ABSORPTION.  489 

epileptoid  sweats  {Eulenhurg).  Sometimes  the  increase  is  confined  to  one  side  of  the  head  (H.uni- 
lateralis).  This  condition  is  often  accompanied  with  other  nervous  phenomena,  partly  with  the 
symptoms  of  paralysis  of  the  cervical  sympathetic  (redness  of  the  face,  narrow  pupil),  partly  with 
symptoms  of  stimulation  of  the  sympathetic  (dilated  pupil,  exophthalmos).  It  may  occur  without 
these  phenomena,  and  is  due,  perhaps,  to  stimulation  of  the  proper  secretory  fibres  alone.  [Increased 
sweating  is  very  marked  in  certain  fevers,  both  during  their  course  and  at  the  crisis  in  some  ;  while 
the  sweat  is  not  only  copious,  but  acid  in  acute  rheumatism.  The  "  night  sweats"  of  phthisis  are 
very  marked  and  disagreeable.] 

3.  Paridrosis  or  qualitative  changes  in  the  secretion  of  sweat,  e.  g.,  the  rare  case  of  '■^ sweat- 
ing of  blood"  (Haematohidrosis),  is  sometimes  unilateral.  According  to  Hebra,  in  some  cases 
this  condition  represents  a  vicarious  form  of  menstruation.  It  is,  however,  usually  one  of  many  phe- 
nomena of  nervous  affections.  Bloody  sweat  sometimes  occurs  in  yellow  fever.  Bile  pigments 
have  been  found  in  the  sweat  in  jaundice;  blue  sweat  from  indigo  {Bizio^,  from  pyocyanin  (the 
rare  blue  coloring  matter  of  pus),  or  from  phosphate  of  the  oxide  of  iron  [Osc.  Kollniann)  i.s  ex- 
tremely rare.  Such  colored  sweats  are  called  chromidrosis.  Bacteria  are  frequently  found,  both 
in  normal  and  in  abnormal  sweat,  in  yellow,  blue,  and  red  sweat.  Grape  sugar  occurs  in  the  sweat 
in  diabetes  mellitus;  uric  acid  and  cystin  very  rarely ;  and  in  the  sweat  of  stinking  feet,  leucin, 
tyrosin,  valerianic  acid  and  ammonia.  Stinking  sweat  (Bromidrosis)  is  due  to  the  decomposition 
of  the  sweat,  from  the  presence  of  a  special  micro-organism  (Bacterium  fcetidum — Thin\.  In  the 
sweating  stage  of  ague  butyra'e  of  lime  has  been  found,  while  in  the  sticky  sweat  of  acute  articular 
rheumatism  there  is  more  albumin  {Anseiniino)^  and  the  same  is  the  case  in  artificial  sweating 
{Leube);  lactic  acid  is  present  in  the  sweat  in  puerperal  fever. 

The  sebaceous  secretion  is  sometimes  increased,  constituting  Seborrhoea,  which  may  be  local  or 
general.  It  may  be  diminished  (Asteatosis  cutis).  The  sebaceous  glands  degenerate  in  old 
people,  and  hence  the  glancing  of  the  skin  (Remy).  If  the  ducts  of  the  glands  are  occluded  the 
sebum  accumulates.  Sometimes  the  duct  is  occluded  by  black  particles  or  ultramarine  {C'nna)  from 
the  blue  used  in  coloring  the  Imen.  When  pressed  out,  the  fatty,  worm-shaped  secretion  is  called 
"  comedo." 

290.  CUTANEOUS  ABSORPTION— GALVANIC  CONDUCTION.— After  long  im- 
mersion in  water  the  superficial  layers  of  the  epidermis  become  moist  and  swell  up.  The  skin  is 
unable  to  absorb  any  substances,  either  salts  or  vegetable  poisons,  from  watery  solutions  of  these. 
This  is  due  to  the  fat  normally  present  on  the  epidermis  and  in  the  pores  of  the  skin.  If  the  fat  be 
removed  from  the  skin  by  alcohol,  ether,  or  chloroform,  absorption  may  occur  in  a  few  minutes 
(Parisot).  According  to  Rohrig,  all  volatile  substances,  e.  g.,  carbolic  acid  and  others,  which  act 
upon  and  corrode  the  epidermis,  are  capable  of  absorption.  While  according  to  Tuhl,  such  watery 
solutions  as  impinge  on  the  skin,  in  a  finely  divided  spray,  are  also  capable  of  absorption,  which  very 
probably  takes  place  through  the  interstices  of  the  epidermis. 

[Inunction. — When  ointments  are  rubbed  into  the  skin  so  as  to  press  the  substance  into  the 
pores,  absorption  occurs,  e.  g.,  potassium  iodide  in  an  ointment  so  rubbed  in  is  absorbed,  so  is  mer- 
curial ointment.  v.  Voit  found  globules  of  mercury  between  the  layers  of  the  epidermis,  and  even 
in  the  chorium  of  a  person  who  was  executed,  into  whose  skin  mercurial  ointment  had  been  previ- 
ously rubbed.  The  mercury  globules,  in  cases  of  mercurial  inunction,  pass  into  the  hair  follicles 
and  ducts  of  the  glands,  wher^  they  are  aft'ected  by  the  secretion  of  the  glands  and  transformed  into 
a  compound  capable  of  absorption.  An  abraded  or  inflamed  surface  {e.g.,  after  a  blister),  where 
the  epidermis  is  removed,  absorbs  very  rapidly,  just  like  the  surface  of  a  wound  (Endermic 
method).] 

[Drugs  may  be  applied  locally  where  the  epidermis  is  intact — Epidermic  method — as  when 
drugs  which  aflect  the  sensory  nerves  of  a  part  are  painted  over  a  painful  area  to  diminish  the  pain. 
Another  method,  the  hypodermic,  now  largely  used,  is  that  of  injecting,  by  means  of  a  hypodermic 
.syringe,  a  non-corrosive,  non-irritant  drug,  in  solution,  into  the  subcutaneous  tissue,  where  it  prac- 
tically passes  into  the  lymph  spaces  and  conies  into  direct  relation  with  the  lymph  and  blood  stream, 
absorption  takes  place  with  great  rapidity,  even  more  so  than  from  the  stomach.] 

Gases. — Under  normal  conditions,  minute  traces  of  O  are  absorbed  from  the  air  ;  hydrocyanic 
acid,  sulphuretted  hydrogen— CO,  CO 2,  the  vapor  of  chloroform  and  ether  may  be  absorbed  (Chans- 
sier,  Ger/aeh,  Rohrig).  In  a  bath  containing  sulphuretted  hydrogen,  this  gas  is  absorbed,  while  CO, 
is  given  off  into  the  water  [Rohrig). 

Absorption  of  watery  solutions  takes  pkace  rapidly  through  the  skin  of  the  hog  (Guttmann, 
W.  .Stirling,  V.  iVittieh).  Even  after  the  circulation  is  excluded  and  the  central  nervous  system 
destroyed,  much  water  is  absorbed  through  the  skin  of  the  frog,  but  not  to  such  an  extent  as  when 
the  circulation  is  intact  (.Spina). 

Galvanic  Conduction  through  the  Skin. — If  the  two  electrodes  of  a  constant  current  be 
impregnated  with  a  watery  solution  of  certain  substances  and  applied  to  the  skin,  and  if  the  direc- 
tion of  the  current  be  changed  from  time  to  time,  strychnin  may  be  caused  to  pass  through  the  skin 
of  a  rabbit  in  a  few  minutes,  and  that  in  sufficient  amount  to  kill  the  animal  (H.  Munk).  In  man, 
quinine  and  potassium  iodide  have  been  introduced  into  the  body  in  this  way,  .and  their  presence 
detected  in  the  urine.  This  process  is  called  the  cataphoric  action  of  the  constant  current  (I  328). 


490  COMPARATIVE HISTORICAL. 

2gi.  COMPARATIVE  — HISTORICAL.— In  all  vertebrates,  the  skin  consists  of  chorium 
and  epidermis.  In  some  reptiles,  the  ej^iderniis  becomes  horny,  and  forms  large  plates  or  scales. 
Similar  structures  occur  in  the  edentata  among  mammals.  The  epidermal  appendages  assume 
various  forms  -  such  as  hair,  nail,  spines,  bristles,  feathers,  claws,  hoof,  horns,  spurs,  etc.  The 
scales  of  some  fishes  are  partly  osseous  structures.  Many  glands  occur  in  the  skin  ;  in  some  am- 
phibia they  secrete  mucus,  in  others  the  secretion  is  poisonous.  *  Snakes  and  tortoises  are  devoid  of 
cutaneous  glands  ;  in  lizards  the  *'  leg  glands  "  extend  from  the  anus  to  the  bend  of  the  knee.  In 
the  crocodile,  the  glands  open  under  the  margins  of  the  cutaneo-osseous  scales.  In  birds,  the 
cutaneous  glands  are  absent;  the  "coccygeal  glands"  form  an  oily  secretion  for  lubricating  the 
feathers.  [This  is  denied  by  O.  Liebreich,  as  he  finds  no  cholesterin  fats  in  their  secretion.]  The 
chvl glands,  at  the  anus  of  the  civet  cat,  the  preputial  glands  of  the  musk  deer,  the  glands  of  the 
hare,  and  the  pedal  glands  of  ruminants,  are  really  greatly  developed  sebaceous  glands.  In  some 
invertebrata,  the  skin,  consisting  of  epidermis  and  chorium,  is  intimately  united  with  the  subj.acent 
muscles,  forming  a  musculo-cutaneous  tube  for  the  body  of  the  animal.  The  cephalopoda  have 
chromatophores  in  their  skin,  ;'.  e.,  round  or  irregular  spaces  filled  with  colored  granules.  Mus- 
cular fibres  are  arranged  radially  around  these  spaces,  so  that  when  these  muscles  contract  the 
colored  surface  is  increased.  The  change  of  color  in  these  animals  is  due  to  the  play  or  contraction 
of  these  muscles.  (Brihkc\)  Special  glands  are  concerned  in  the  production  of  the  shells  of  the 
snail.  The  annulosa  are  covered  with  a  chitinous  investment,  which  is  continued  for  a  certain 
distance  along  the  digestive  tract  and  the  trachea.  It  is  thrown  off  when  the  animal  sheds  its  cover- 
ing. It  not  only  protects  the  animal,  but  it  forms  a  structure  for  the  attachment  of  muscles.  In 
echinodermata,  the  cutaneous  covering  contains  calcareous  masses ;  in  the  holothurians,  the  calca- 
reous structures  assume  the  form  of  calcareous  spicules. 

Historical. — Hippocrates  (born  460  li.  c.)  and  Theophrastus  (born  371  B.C.)  distinguished  the 
perspiration  from  the  sweat;  and,  according  to  the  latter,  the  secretion  of  sweat  stands  in  a  certain 
antagonistic  relation  to  the  urinary  secretion  and  to  the  water  in  the  fceces.  According  to  Cassius 
Felix  (97  A.  D.),  a  person  placed  in  a  bath  absorbs  water  through  the  skin;  Sanctorius  (1614) 
measured  the  amount  of  sweat  given  off;  Albert!  (1581)  was  acquainted  with  the  hair  bulb  ;  Donatus 
(1588)  described  hair  becoming  gray  suddenly;  Riolan  (1626)  showed  that  the  color  of  the  skin 
of  the  negro  was  due  to  the  epidermis. 


Physiology  ™e  motor  Apparatus. 


292.    CILIARY    MOTION  — PIGMENT    CELLS.— f^?)   Muscular 

Movement. — By  far  the  greatest  number  of  the  movements  occuring  in  our 
bodies  IS  accomplished  through  the  agency  of  muscular  fibre,  which,  when  it 
is  excited  by  a  stimulus,  contracts — /.  e.,  it  forcibly  shortens — and  thus  brings  its 
two  ends  nearer  together,  while  it  bulges  to  a  corresponding  extent  laterally.  In 
muscle,  the  contraction  takes  ])lace  in  a  definite  direction. 

(b)  Amoeboid  Movement. — Motion  is  also  exhibited  by  colorless  blood 
corpuscles,  lymph  corpuscles,  leucocytes,  and  some  other  corpuscles.  In  these 
structures  we  have  examples  of  amoeboid  movement  (§  9),  which  is  movement  in 
an  indefinite  direction. 

[((•)  Ciliary  Movement. — There  is  also  a  peculiar  form  of  movement,  known 
as  ciliary  movement.  There  is  a  gradual  transition  between  these  different  forms  of 
movement.  The  cilia,  which  are  attached  to  the  ciliated  epithelium,  are  the 
motor  agents  (Fig.  280,1.] 

[Ciliated  epithelium,  and  where  found. — In  the  nasal  mucous  membrane,  except  the  olfactorj' 
region;  the  cavities  accessory  to  the  nose;  the  upper  half  of  the  pharynx,  Eustachian  tube,  larynx, 
trachea  and  bronchi;   in  the  ulerui,  except  the   lower  half  of  the  cervix;   Fallopian  tubes;  vasa 


Ciliated  epitlicliii 


efferentia  to  the  lower  end  of  epididymis  ;  ventricles  of  brain  (child) ;  and  the  central  canal  of  the 
spinal  cord.] 

[The  cilia  are  flattened,  blade-like  or  hair-like  appendages  attached  to  the  free  end  of  the  cells. 
They  are  about  3t)Vij  inch  in  length,  and  are,  apparently,  homogeneous  and  structureless.  They 
are  planted  upon  a  clear,  non-contractile  disk  on  the  free  end  of  the  cell,  and  some  observers  state 
that  they  pass  through  (his  disk  to  become  continuous  with  the  protoplasm  of  the  cell,  or  with  the 
plexus  of  fibrils  which  pervades  the  protoplasm  ;  so  that  by  some  observers  [Klein )  they  are  regarded 
as  prolongations  of  the  intraepithelial  plexus  of  fibrils.  They  are  specially  modified  parts  of  an 
epithelial  cell,  and  are  contractile  and  elastic.  They  are  colorless,  tolerably  strong,  not  colored  by 
staining  reagents,  and  are  possessed  of  considerable  rigidity  and  flexibility.  They  are  always  con- 
nected with  the  protoplasm  of  ce'ls,  and  are  never  outgrowths  of  the  solid  cell  membranes.  There 
may  be  lo  to  20  cilia  distributed  uniformly  on  the  free  surface  of  a  cell  (Fig.  280).] 

[In  the  large  ciliated  cells  in  the  intestine  of  some  molluscs  (mussel)  the  cilia  perforate  the  clear 
retractile  disk,  which  appears  to  consist  of  small  globules — basal  pieces — united  by  their  edge,  so 
that  a  cilium  seems  to  spring  from  each  of  these,  while  continued  downward  into  the  protoplasm 
of  the  cell,  but  not  attached  to  the  nucleus,  there  is  a  single  varicose  fibril — rootlet,  and  the  leash 
of  these  fibrils  passes  through  the  substance  of  the  cell,  and  may  unite  toward  its  lower-tailed 
extremity  [Enge!maiin).'\ 

[Ciliary  motion  mav  be  studied  in  the  gill  of  a  mussel,  a  small  part  of  the  gill  being  teased  in 

491 


492  FUNCTIONS   OF   CILIA. 

sfa  water  ;  or  the  hard  palate  of  a  frog,  newly  killed,  may  be  scraped,  and  the  scraping  examined 
in  3^  p.  c.  salt  solution.  On  analyzing  the  movement,  all  the  cilia  will  be  observed  to  execute  a 
regular,  periodic,  toand-fro  rhythmical  movement  in  a  plane  usually  vertical  to  the  surface  of  the 
cells,  the  direction  of  the  movement  being  parallel  to  the  long  axis  of  the  organ.  The  appearance 
presented  by  the  movements  of  the  cilia  is  sometimes  described  as  a  lashing  movement,  or  like  a 
field  of  corn  moved  by  the  wind.  Each  vibration  of  a  cilium  consists  of  a  rapid  forward  move- 
ment or  flexion,  the  tip  moving  more  than  the  base,  and  a  slower  backward  movement,  the  cilium 
again  straiglitening  itself.  The  forward  movement  is  about  twice  as  rapid  as  the  backward  move- 
ment. The  ainplitude  of  the  movement  varies  according  to  the  kind  of  cell  and  other  conditions, 
being  less  when  the  cells  are  about  to  die;  but  it  is  the  same  for  all  the  cilia  attached  to  one  cell, 
and  is  seldom  more  than  20°  to  50°.  There  is  a  certain  periodicity  in  their  movement ;  in  the 
frog  they  contract  about  12  times  per  second  [Enge/niaun).  The  result  of  the  rapid  forward 
movement  is  that  the  surrounding  fluid,  and  any  particles  it  may  contain,  are  moved  in  the  direction 
in  which  the  cilia  bend.  All  the  cilia  of  adjoining  cells  do  not  move  at  once,  but  in  regular  suc- 
cession, the  movement  traveling  from  one  cell  to  the  other;  but  how  this  coordination  is  brought 
about  we  do  not  know.  At  least,  it  is  quite  independent  of  the  nervous  system,  as  ciliary  move- 
ment goes  on  in  isolated  cells,  and  in  man  it  has  been  observed  in  the  trachea  two  days  after  death. 
Conditions  for  Movement. — In  order  that  the  ciliary  movement  may  go  on,  it  is  essential  that 
— (i)  the  cilia  be  connected  with  part  of  a  cell ;  (2)  moisture ;  (3)  oxygen  be  present ;  and  {4)  the 
temperature  is  within  certain  limits.] 

[A  ciliated  epithelial  cell  is  a  good  example  of  the  physiological  division  of  labor.  It  is 
derived  from  a  cell  which  originally  held  motor,  automatic  and  nutritive  functions  all  combined  in 
one  mass  of  protoplasm  ;  but  in  the  fully-developed  cell  the  nutritive  and  regulative  functions  are 
confined  to  the  protoplasm,  while  the  cilia  alone  are  contractile.  If  the  cilia  be  separated  from  the 
cell,  they  no  longer  move.  If,  however,  a  cell  be  divided  so  that  part  of  it  remains  attached  to  the 
cilia,  the  latter  still  move.  The  nucleus  is  not  essential  for  this  act.  It  would  seem,  therefore, 
that  though  the  cilia  are  contractile,  the  motor  impulse  probably  proceeds  from  the  cell.  Each 
cell  can  regulate  its  own  nutrition,  for  during  life  they  resist  the  entrance  of  certain  colored 
fluids.] 

[Effect  of  Reagents. — Gentle  heat  accelerates  the  number  and  intensity  of  the  movements, 
cold  retards  them.  A  temperature  of  45°  C.  causes  coagulation  of  their  proteids,  makes  them 
permanently  rigid,  and  kills  them,  just  in  the  same  way  as  it  acts  on  muscle,  causing  heat  stiffening 
(p.  5*^5)-  Weak  alkalies  may  cause  them  to  contract  after  their  movement  is  arrested  or  nearly  so 
( I'irchinc),  and  any  current  of  fluid,  in  fact,  may  do  so.  Lister  showed  that  the  vapor  of  ether 
and  chloroform  arrests  the  movements  as  long  as  the  narcosis  lasts,  but  if  the  vapor  be  not  applied 
for  too  long  a  time,  the  cilia  may  begin  to  move  again.  The  prolonged  action  of  the  vapor  kills 
them.  As  yet.  we  do  not  know  any  specific  poison  for  cilia,  atropin,  veratrin  and  curara  acting 
like  other  substances  with  the  same  endosmotic  equivalent  [Engelmann).'\ 

[Functions  of  Cilia. — The  moving  cilia  propel  fluids  or  particles  along  the 
passages  which  they  line.  By  carrying  secretions  along  the  tubes  which  they  line 
toward  where  these  tubes  open  on  the  surface,  they  aid  in  excretion.  In  the 
respiratory  passages,  they  carry  outward  along  the  bronchi  and  trachea  the  mucus 
formed  by  the  mucous  glands  in  these  regions.  When  the  mucus  reaches  the 
larynx  it  is  either  swallowed  or  coughed  up.  That  the  cilia  carry  particles  upward 
in  a  spiral  direction  in  the  trachea  has  been  proved  by  actual  laryngoscopic  inves- 
tigation, and  also  by  excising  a  trachea  and  sprinkling  a  colored  powder  on  its 
mucous  membrane,  when  the  colored  particles  (IJerlin  blue  or  charcoal)  are  slowly 
carried  toward  the  upper  end  of  the  trachea.  In  bronchitis,  the  ciliated  epi- 
thelium is  shed,  and  hence  the  mucus  tends  to  accumulate  in  the  bronchi.  They 
remove  mucus  from  cavities  accessory  to  the  nose,  and  from  the  tympanum,  while 
the  ova  are  carried,  partly  by  their  agency,  from  the  ovary  along  the  Fallopian 
tube  to  the  uterus.  In  some  of  the  lower  animals  they  act  as  organs  of  locomo- 
tion, and  in  others  as  adjuvants  to  respiration,  by  creating  currents  of  water  in 
the  region  of  the  organs  of  respiration.] 

[The  Force  of  Ciliary  Movement. — Wynian  and  Bowditch  found  that  the  amount  of  work 
that  can  be  done  by  cilia  is  very  considerable.  The  work  was  estimated  by  the  weight  which  a 
measured  surface  of  the  mucous  membrane  of  the  frog's  hard  palate  was  able  to  carry  up  an 
inclined  plane  of  a  definite  slope  in  a  given  time.] 

[Pigment  cells  belong  to  the  group  of  contractile  tissues,  and  are  well  developed  in  the  frog, 
and  many  other  animals  where  their  characters  have  been  carefully  studied.  They  are  generally 
regarded  as  comparable  to  branched  connective-tissue  corpuscles,  loaded  with  pigmented 
granules  of  melanin.     The   pigment  granules  may  be  diff'used  in  the  cell,  or  aggregated  around 


STRUCTURE    AND    ARRANGEMENT   OF   THE    MUSCLES.  493 

the  nucleus;  in  the  former  case,  the  skin  of  the  frog  appears  dark  in  color,  in  the  latter,  it 
is  Ijut  slightly  pigmented.  The  question  has  been  raised  whether  they  are  actual  cells  or  merely 
spaces,  branched,  and  containing  a  fluid  with  granules  in  suspension.  In  any  case,  they  undergo 
marked  changes  of  shape  under  various  influences.  If  the  motor  nerve  to  one  leg  of  a  frog  be 
divided,  the  skin  of  the  leg  on  that  side  becomes  gradually  darker  in  color  than  the  intact  leg.  A 
similar  result  is  seen  in  the  curara  experiment,  when  all  parts  are  ligatured  except  the  nerve. 
Local  applications  aft'ect  the  state  of  diffusion  of  the  pigment,  as  v.  Wittich  found  that  turpentine 
or  electricity  caused  the  cells  of  the  tree-frog  to  contract,  and  the  same  effect  is  produced  by  light. 
In  Rana  temporaria  local  irritation  has  little  effect,  but  light,  on  the  contrary,  has,  although  the 
effect  of  light  seems  to  be  brought  about  through  the  eye  (Lister),  probably  by  a  reflex  mechanism. 
A  pale  colored  frog,  put  in  a  dark  place,  assumes,  after  a  time,  a  diflTerent  color,  as  the  pigment  is 
diffused  in  the  dark  ;  but  if  it  be  exposed  to  a  bright  light  it  soon  becomes  pale  again.  The  same 
phenomenon  may  be  seen  on  studying  the  web  of  a  frog's  leg  under  the  microscope.  The  marked 
variations  of  color— within  a  certain  range — in  the  chameleon  is  due  to  the  condition  of  the  pig- 
ment cells  in  its  skin,  covered  as  they  are  by  epidermis,  containing  a  thin  stratum  of  air  [Briicie). 
When  it  is  poisoned  with  strychnin,  its  whole  body  turns  pale;  if  it  be  ill,  its  body  becomes  spotted 
in  a  dendritic  fashion,  and  if  its  cutaneous  neri'es  be  divided,  the  area  supplied  by  the  nerve  changes 
to  black.  The  condition  of  its  skin,  therefore,  is  readily  affected  by  the  condition  of  its  nervous 
system,  for  psychical  excitement  also  alters  its  color.  If  the  sympathetic  nerve  in  the  neck  of  a 
turbot  be  divided,  the  skin  on  the  dorsal  part  of  the  head  becomes  black.  It  is  notorious  that  the 
color  of  fishes  is  adapted  to  the  color  of  their  environment.  If  the  nerve  proceeding  from  the  stellate 
ganglion  in  the  mantle  of  a  cuttle  fish  be  divided,  the  skin  on  one.half  of  the  body  becomes  pale.] 

292  a.  STRUCTURE  AND  ARRANGEMENT  OF  THE  MUS- 
CLrES. — Muscular  Tissue  is  endowed  with  contractility,  so  that  when  it  is 
acted  upon  by  certain  forms  of  energy  or  stimuli,  it  contracts.  There  are  two 
varieties  of  this  tissue — 

(i)  Striped,  striated  or  (voluntary)  ; 

(2)  Non-striped,  smooth,  organic,  or  (involuntary). 

Some  muscles  are  completely  under  the  control  of  the  will,  and  are  hence  called 
"  voluntary,"  and  others  are  not  directly  subject  to  the  control  of  the  will,  and 
are  hence  called  "involuntary;"  the  former  are  for  the  most  part  striped,  and  the 
latter  non-striped  ;  but  the  heart  muscle,  although  striped,  is  an  involuntary  muscle. 

I.  Striped  Muscles. — The  surface  of  a  muscle  is  covered  with  a  connective-tissue  envelope  or 
perimysium  externum,  from  which  septa,  carrying  blood  vessels  and  nerves,  the  perimysium 
internum,  pa<^s  into  the  substance  of  the  muscle,  so  as  to  divide  it  into  bundles  of  fiijres  or  fasci- 
culi, which  are  fine  in  the  eye  muscles  and  coarse  in  the  glutei.  In  each  such  compartment  or 
mesh  there  lie  a  number  of  miisiulnr  Jilires  arranged  more  or  less  parallel  to  each  other.  [The 
filires  are  held  together  by  delicate  connective  tissue  or  endomesium,  which  surrounds  groups  of 
the  fibres;  each  fibre  being,  as  it  were,  separated  from  its  neighbor  by  excessively  delicate  fibrillar 
connective  tissue.]  Each  muscular  fibre  is  surrounded  with  a  rich  plexus  of  capillaries  [which 
form  an  elongated  meshwork,  lying  between  adjacent  fibres,  but  never  penetrating  the  fibres,  which, 
however,  they  cross  (Fig.  2S4).  In  a  contracted  muscle  the  capillaries  may  be  slightly  sinuous  in 
their  course,  but  when  a  muscle  is  on  the  stretch  thde  curves  disappear.  The  capillaries  lie  in  the 
endomysium,  and  near  them  are  lymphatiis.'\  Each  muscular  fibre  receives  a  nerve  fibre.  [Where 
found.  — Striped  muscular  fibres  occur  in  the  skeletal  muscles,  heart,  diaphragm,  pharynx,  upper 
part  of  cesophagus,  muscles  of  the  middle  ear  and  pinna,  the  true  sphincter  of  the  urethra,  and 
external  anal  sphincter.] 

A  muscular  fibre  (Fig.  2S1,  1)  is  a  more  or  less  cylindrical  or  polygonal 
fibre,  II  to  67  ;i.  [y^  to  ^j-Lj  in.]  in  diameter,  and  never  longer  than  3  to  4  centi- 
metres [i  to  ija  in.].  Within  short  muscles,  e.g.,  stapedius,  tensor  tympani, 
or  the  short  muscles  of  a  frog,  the  fibres  are  as  long  as  the  muscle  itself;  within 
longer  muscles,  however,  the  individual  fibres  are  pointed,  and  are  united  obliquely 
by  cement  substance  with  a  similar  beveled  or  pointed  end  of  another  fibre  lying 
in  the  same  direction.  Muscular  fibres  may  be  isolated  by  maceration  in  nitric 
acid  with  excess  of  potassic  chlorate  i^Budge),  or  by  a  35  per  cent,  solution  of 
caustic  potash  (Mo/eschott). 

[Each  muscular  fibre  consists  of  the  following  parts  :  — 

1.  Sarcolemma,  an   elastic  sheath,   with  transverse  partitions,  stretching 
across  the  fibre  at  regular  intervals — the  membranes  of  Kraiise  ; 

2.  The  included  sarcous  substance; 

3.  The  nuclei  or  muscle  corpuscles.] 


494 


bTRUCTURE   OF   STRIPED    MUSCLES. 


Sarcolemma.— Each  muscular  fibre  is  completely  enclosed  by  a  colorless,  structureless,  trans- 
parent elastic  sheath  (Fig.  281,  i.  Si,  which,  chemically,  is  midway  between  connective  and  elastic 
tissue,  and  within  it  is  the  contractile  substance  of  the  muscle.  [It  has  much  more  cohesion  than 
the  sarcous  substance  which  it  encloses,  so  that  sometimes,  when  teasing  fresh  muscular  tissue  under 
the  microscope,  one  may  observe  the  sarcous  substance  torn  across,  with  the  unruptured  sarcolemma 
stretching  between  the  ends  of  the  ruptured  sarcous  substance.  If  muscular  fibres  be  teased  in 
distilled  water,  sometimes  fine,  clear  blebs  are  seen  along  the  course  of  the  fibre,  due  to  the  sarco- 
lemma being  raised  by  the  fluid  dilTusing  under  it.  The  sarcous  substance,  but  not  the  sarcolemma, 
may  be  torn   across  by  plunging  a  muscle  in  water  at  55°  C,  and  keeping  it  there  for  some  time 


Fig.  28 


Histology  of  muscular  tissue,  i,  Diagram  of  part  of 
F,  fibrillae;  K,  the  muscle  nuclei ;  N,  a  nerve  fib 
plate,  e,  seen  in  profile;  2,  transverse 
muscular  fibrillae  ;  4,  part  of  an  insect 
cases  ;  i,  the  doubly- refractive  substa 
transversely  into  disks  ;  6,  muscular  fi 
human  foetus  at  the  third  month  ;  8, 
puscles  ;  10,  smooth  "muscular  fibres  ; 


fibre  ;  S,  sarcolemma  ;  Q,  transverse  stripes  ; 
:  ntire  entering  it  witn  «,  its  axis  cylinder  and  Kuhne's  motorlal  end 
of  part  of  a  muscular  fibre,  showing  Cohnheim's  areas,  c  ;  3,  isolated 
[luscle  greatly  magnified  ;  a,  Krause-Amici's  line  limiting  the  muscular 
;  f,  Hensen's  disk  ;  d,  the  singly-refractive  substance  ;  5,  fibre  cleaving 
:  from  the  heart  of  a  frog;  7,  development  of  a  striped  muscle  from  a 
muscular  fibres  of  the  heart  ;  c,  capillaries  ;  " 
transverse  section  of  smooth  muscular  fibres. 


Stripes. — The  sarcous  substance  is  marked  transversely  by  alternate  light 
and  dim  layers,  bands,  stripes  or  disks  (Fig.  2S1,  i,  Q),  so  that  each  fibre 
is  said  to  be  *' transversely  striped.**  [The  stripes  do  not  occur  in  the 
sarcolemma,  but  are  confined  to  the  sarcous  substance,  and  they  involve  its 
whole  thickness.] 

[The  animals  most  suited  for  studying  the  structure  of  the  sarcous  substance  are  some  of  the 
insects.  The  muscles  of  the  water  beetle,  Dytiscus  marginalis.  and  the  Hydrophilus  piceus  are  well 
suited  for  this  purpose.  So  is  the  crab's  muscle.  In  examining  a  living  muscle  microscopically, 
no  fluid  except  the  muscle  juice  should  be  added  to  the  preparation,  and  very  high  powers  of  the 
microscope  are  required  to  make  out  the  finer  details.] 


STRUCTURE    OF    A    MUSCULAR    FIBRILLA. 


495 


Fig.  2S2. 


Bowman's  Disks. — If  a  muscular  fibre  be  subjected  to  the  action  of  hydro- 
chloric acid  (i  per  1000),  or  if  it  be  digested  by 
gastric  juice,  or  if  it  be  frozen,  it  tends  to  cleave 
transversely  into  disks  (Bowman),  which  are  arti- 
ficial products,  and  resemble  a  pile  of  coins  which 
has  been  knocked  over  (Fig.  281,  5). 

Fibrillse. — Under  certain  circumstances,  a  fibre 
may  exhibit  longitudinal  striation.  This  is  due  to 
the  fact  that  it  may  be  split  up  longitudinally  into 
an  immense  number  of  (i  to  1.7  p.  in  diameter) 
fine,  contractile  threads,  the  primitive  fibrillae 
(Fig.  281,  I,  F),  placed  side  by  side,  each  of  which 
is  also  transversely  striped,  and  they  are  so  united 
to  each  other  by  semi-fluid  cement  substance,  that 
the  transverse  markings  of  all  the  fibrillae  lie  at  the 
same  level.  These  fibrillae,  owing  to  nmtual  pres- 
sure, are  prismatic  in  form,  so  that  when  a  trans- 
verse section  of  a  perfectly  fresh  muscular  fibre  is 
observed  after  it  is  frozen,  the  end  of  each  fibre  is 
mapped  out  into  a  number  of  small  polygonal  areas 
called  Cohnheim's  areas  (Fig.  281,  2). 

Fibrillffi  are  easily  obtained  from  insects'  mus- 
cles, while  those  from  a  mammal's  muscle  are  readily 
isolated  by  the  action  of  dilute  alcohol,  Miiller's       portion  of  a  human  mu^cuUr  fibre 
fluid  [or,  best  of  all,  \  per  cent,  solution  of  chro-  x  300- 

mic  acid]  (Fig.  281,  3). 

[When  a  living,  unaltered  muscular  fibre  is  examined  microscopically,  in  its 
own  juice,  we  observe  the  alternate  dim  and  light  transverse  disks.  A  high  power 
reveals  the  presence  of  a  line  running  across  the  light  disk,  and  dividing  it  into 
two  (Fig.  2S2).  It  has  been  called  Dobie's  line  (Rutherford),  and  by  others  it  is 
regarded  as  due  to  the  existence  of  a  membrane,  called  Krause's  membrane, 
which  runs  transversely  across  the  fibre,  being  attached  all  round  to  the  sarco- 
lemma,  thus  dividing  each  fibre  into  a  series  o{  compartments  placed  end  to  end. 

These  muscular  compartments  contain  the  sarcous  substance,  and  in  each 
compartment  we  find  (i)  a  broad,  dim  disk,  which  is  the  contractile  part  of  the 
sarcous  substance.  It  is  doubly  refractive  (anisotropous),  and  is  composed  of 
Bowman's  sarcous  elements.  (2)  On  each  end  of  this  disk,  and  between  it  and 
Krause's  membranes,  is  a  narrower,  clear,  homogeneous,  and  but  singly  refractile 
(isotropous),  soft  or  fluid  substance,  which  forms  the  lateral  disk  of  Engel- 
mann.  In  some  insects  it  contains  a  row  of  refractive  granules,  constituting  the 
granular  layer  of  Flogel.  If  a  muscular  fibre  be  stretched  and  stained  with 
logwood,  the  central  part  of  the  dim  di'.k  appears  lighter  in  color  than  the  two 
ends  of  the  same  disk.  This  has  been  described  as  a  separate  disk,  and  is  called 
the  median  disk  of  Hensen  (Fig.  281,  4,  c).] 

[In  an  unaltered  fibre,  the  dim,  broad  stripe  appears  homogeneous,  but  after  a 
time  it  cleaves  throughout  its  entire  extent  in  the  long  axis  of  the  fibre  into  a 
number  of  prismatic  elements  or  fibrils,  the  sarcous  elements  of  Bowman 
(Fig.  281).  These  at  first  are  prismatic,  but  as  they  solidify  they  shrink  and 
seem  to  squeeze  out  of  them  a  fluid,  becoming  at  the  same  time  more  constricted  in 
the  centre.  This  separation  into  fibrils  with  an  interstitial  matter  gives  rise  to  the 
appearance  seen  on  transverse  section  of  a  frozen  muscle,  and  known  as  Cohn- 
heim's areas  (Fig.  281,  2,  c).  In  all  probability  the  cleavage  also  extends  through 
the  lateral  disks,  and  thus  fibrils  are  formed  by  longitudinal  cleavage  of  the  fibre.] 

[According  to  Haycraft,  a  muscular  fibre  is  moniliform,  being  narrowest  at  the  part  opposite 
Krause's  memlirane,  and  thicker  in  the  interval,  so  that  Haycraft  attributes  the  transverse  striation 
to  these  differences,  the  surface  being  undulating.] 


496 


MUSCLE    RODS. 


[Muscle  Rods. — Scliafcr  describes  the  appearance  differently:  "  Double  rows  of  granules  are 
seen  lying  in  or  at  the  boundaries  of  the  light  streaks  (disks),  and  very  tine,  longitudinal  lines  may 
be  detected  running  through  the  dark  streak  (dim  disk)  and  uniting  the  minute  granules.  These 
fine  lines,  with  their  enlarged  extremities,  are  muscle  rods."  They  are  most  conspicuous  in  in- 
sects. During  the  contraction  of  a  living  muscular  fibre,  Schafer  describes  the  "  reversal  of  the 
stripes"  (^  297)  as  follows:  "When  the  fibres  contract  the  light  stripes  are  seen,  as  the  fibre 
shortens  and  thickens,  to  become  dark,  an  apparent  reversal  being  thereby  produced  in  the  stri^. 
This  reversal  is  due  to  the  enlargement  of  the  rows  of  dark  dots  and  the  formation  by  their  juxta- 
position and  blending  of  dark  disks,  while  the  muscular  substance  between  these  disks  has  by  con- 
trast a  bright  appearance."] 

[With  polarized  light  in  a  living  muscular  fibre,  all  the  sarcous  substance,  except  the  muscle 
rod,  is  doubly  refractive  or  anisotropous,  so  that  it  appears  bright  on  a  dark  field  when  the  Nicol's 
prisms  are  crossed,  while  under  the  same  conditions  contracted  muscle  and  dead  muscle  show 
alternate  dark  and  light  bands  (Sc/idfer).'\ 

The  nuclei  or  muscle  corpuscles  are  found  immediately  under  the  sarcolemma  in  all  mammals, 
and  their  long  axis  lies  in  the  long  axis  of  the  fibre  (8  to  13  /'  long,  3  to  4  /*  broad).  [In  the  mus- 
cles of  the  frog  and  some  other  animals,  e.g.,  the  red  muscles  of  the  rabbit  and  hare,  they  lie  in  the 


Injected  blood  vessels  of  a  human  muscle,    a,  small  artery  : 
vein  :  c,  capillaries.     X  250  {^KoUiker). 


substance  of  the  fibre  surrounded  by  a  small  amount  of  protoplasm.]  When  they  occur  immediately 
under  the  sarcolemma  they  are  more  or  less  flattened,  and  lie  embedded  in  a  small  amount  of  pro- 
toplasm (Fig.  281,  I  and  2,  K).  They  contain  one  or  two  nucleoli,  and  it  is  said  that  the  proto- 
plasm sends  out  fine  processes  which  unite  with  similar  processes  from  adjoining  corpuscles,  so  that, 
according  to  this  view,  a  branched  protoplasmic  network  exists  under  the  sarcolemma.  [Each 
nucleus  has  a  reticulated  appearance  due  to  the  presence  of  a  plexus  of  fibrils.  The  nuclei  are  not 
seen  in  a  perfectly  fresh  muscle,  because,  until  they  have  undergone  some  change,  their  refractive 
index  is  the  same  as  that  of  the  sarcous  substance.]  They  become  specially  evident  after  the  addi- 
tion of  acetic  acid.  Histogenetically,  they  are  the  remainder  of  the  cells  from  which  the  muscular 
fibres  were  developed  (Fig.  2S1,  7).  According  to  M.  Schultze,  the  sarcous  substance  is  an  inter- 
cellular substance  differentiated  and  formed  by  their  activity.  Perhaps  they  are  the  centres  of  nutri- 
tion for  the  muscular  fibres.  In  amphibians,  birds,  fishes,  and  reptiles,  they  lie  in  the  axis  of  the 
fibres  between  the  fibrils. 

It  is  said  that  tlie  protoplasm  of  the  muscle  corpuscles  forms  a  fine  network  throughout  the  whole 
muscular  fibre,  the  transverse  branches  taking  the  course  of  the  lines  of  Krause  or  Dobie,  and  the 
longitudinal  branches  running  in  the  interstices  between  Cohnheim's  areas  [A'e/ztus,  Bremer). 


NERVES   OF    A    MUSCLE. 


497 


Relation  to  Tendons. — According  to  Toldt,  the  delicate  connective-tissue  elements,  which 
cover  the  several  muscular  fibres,  pass  from  the  ends  of  the  latter  directly  into  the  connective-tissue 
elements  of  the  tendon.  The  end  of  the  muscular  fibre  is  perhaps  united  to  the  smooth  surface  or 
hollow  end  of  the  tendon  by  means  of  a  special  cement  ( PVasmaim — Fig.  283,  Si.  In  arlhropoda, 
the  sarcolemma  passes  directly  into  and  becomes  continuous  with  the  tendon  {Leydio^  Reichert). 
The  tendon  itself  consists  of  longitudinally  arranged  bundles  of  white  fibrous  tissue  with  cells — 
tendon  cells — embracing  them.  There  is  a  loose  capsule  or  sheath  of  connective  tissue— the  peri- 
tendineum of  KoUman — surrounding  the  whole  and  carrying  the  blood  vessels,  lymphatics,  and 
nerves.  The  tendons  move  in  the  tendon  sheaths,  which  are  moistened  by  a  mucous  fluid.  In 
most  situations,  muscular  fibres  are  attached  by  means  of  tendons  to  some  fixed  point,  but  in  other 
situations  (face)  the  ends  terminate  between  the  connective-tissue  elements  of  the  skin. 

[Blood  Vessels. — Muscles,  being  very  active  organs,  are  richly  supplied  with  blood.  The 
blood  supply  of  a  muscle  differs  from  some  organs  in  not  constituting  an  actual  vascular  unit,  sup- 
plied only  by  one  artery  and  one  vein,  thus  being  unlike  the  kidney,  spleen,  etc.  Each  muscle 
usually  receives  several  branches  from  different  arteries,  and  branches  enter  it  at  certain  distances 
along  its  whole  length.  The  artery  and  vein  usually  lie  together  in  the  connective  tissue  of  the 
perimysium,  while  the  capillaries  lie  in  the  endomysium.  The  capillaries  lie  between  the  muscular 
fibres,  but  outside  the  sarcolemma,  where  they  form  an  elongated,  rich  plexus  with  numerous 
transverse  branches  (Fig.  284).  The  lymph  to  nourish  the  sarcous  substance  must  traverse  the 
sarcolemma  to  reach  the  former.  In  the  red  muscles  of  the  rabbit  |c.^.,  semitendinosus),  the 
capillaries  are  more  wavy,  while  on  the  transverse  branches  of  some  of  the  capillaries,  and  on  the 
veins  (Manvier),  there  are  small,  oval,  saccular  dilatations,  which  act  as  reservoirs  for  blood.] 

[Lymphatics. — We  know  very  little  of  the  lymphatics  of  muscle,  although  the   lymphatics  of 


Fig.  285. 


—       Muscle  nucleus. 


d  plate 


tendon  and  fascia  have  been  carefully  studied  by  Ludwig  and  Schweigger  Seidel.  There  are  lym- 
phatics in  the  endomysium  of  the  heart,  which  are  continuous  with  those  under  the  pericardium. 
This  subject  still  requires  further  investigation.  Compare  the  lymphatics  of  the  fascia  lata  of  the 
dog  (Fig.  212,  i,  201).] 

Entrance  of  the  Nerve. — The  trunk  of  the  motor  nerve,  as  a  rule,  enters  the  muscle  at  its 
geometrical  centre  (Se/izvalbe);  hence  the  point  of  entrance  in  muscles  with  long,  parallel,  or  spindle- 
shaped  fibres  lies  near  its  middle.  If  the  muscle  with  parallel  fibres  is  more  than  2  to  3  centimetres 
[i  inch]  in  length,  several  branches  enter  its  middle.  In  triangular  muscles,  the  point  of  entrance  of 
the  nerve  is  displaced  more  toward  the  strong  tendinous  point  of  convergence  of  the  muscular 
fibres. .  A  nerve  fibre  usually  enters  a  muscle  at  the  point  where  there  is  the  least  displacement  of 
the  muscular  substance  during  contraction. 

Motor  Nerve. — Every  muscular  fibre  receives  a  motor  nerve  fibre  (Fig.  281, 
I,  N).  K:ich  nerve  does  not  contain  originally  as  many  motor  nerve  fibres  as  there 
are  muscular  fibres  in  the  muscle  it  enters ;  in  the  human  eye  muscles,  there  are 
only  3  nerve  fibres  to  7  muscular  fibres ;  in  other  muscles  (dog),  i  nerve  fibre  to 
40  or  80  {Tergast ).  Hence,  when  a  nerve  enters  a  muscle  it  must  divide,  which 
occurs  dichotomously  [at  Ranvier's  nodes],  the  structure  undergoing  no  change 
until  there  are  exactly  as  many  nerve  fibres  as  muscular  fibres.  In  warm-blooded 
animals  each  muscular  fibre  has  only  one,  while  cold-blooded  animals  have  seve- 
ral points  of  insertion  of  the  nerve  fibre  {SanJmann).  A  nerve  fibre  enters  each 
32 


498 


RED    AND    PALE    MUSCLES. 


muscular  fibre,  and  where  it  enters  it  forms  an  eminence  {Doycre,  1846),  the 
"  motorial  end  plate  "  (Fig.  281,  1,  c).  The  neurilemma  unites  directly  with 
the  sarcolemma,  the  white  substarxe  of  Schwann  ceases,  while  the  axis  cylinder 
passes  in  and  divides  within  the  sarcolemma.  There  is  an  elevation  of  a  proto- 
plasmic nature  containing  nuclei  immediately  under  the  sarcolemma  at  the  entrance 
of  the  nerve  (Kiihne's  end  plate,  Fig.  285).  The  branches  of  the  axis  cylinder 
traverse  this  mass,  where  they  subdivide  into  fine  fibrils  recognizable  only  after 
the  action  of  gold  chloride  (Fig.  286).  These  fibrils  penetrate  between  the  fibril- 
l:e  along  the  whole  extent  of  the  fibre,  and,  perhaps,  they  terminate  in  the  aniso- 
tropous  substance  (  Gcrlacli). 

Sensory  fibres  also  occur  in  muscles,  and  they  are  the  channels  for  muscular 
sensibility.  They  seem  to  be  distributed  on  the  outer  surface  of  the  sarcolemma, 
where  they  form  a  branched  plexus  and  wind  round  the  muscular  fibres  {Artiiit, 
Sachs)  ;  but,  according  to  Tschirjew,  the  sensory  nerves  traverse  the  substance  of 
the  muscle,  and  after  dividing  dichotomously,  end  on/y  in  the  aponeurosis,  either 
suddenly  or  by  means  of  a  small  swelling — a  view  confirmed  by  Rauber.  The 
existence  of  sensory  nerves  in  muscles  is  also  proved  by  the  fact  that,  stimulation 
of  the  central  end  of  a  motor  nerve,  e.  g.,  the  phrenic,  causes  increase  of  the 
blood  pressure  and  dilatation  of  the  pupil  {Asp,  Kowak^osky,  Nmarofki),  as  well 
as  by  the  fact  that  when  they  are  inflamed  they  are  painful.  They,  of  course,  do 
not  degenerate  after  section  of  the  anterior  root  of  tlie  spinal  nerves. 

Red  and  Pale  Muscles. — In  many  fishes  (skate,  pKiice,  herring,  mackerel)  {IV.  Stirlini;),h\xi\s, 


le  stained  with  gold  chloride 


and  mammals  (rabbits),  there  are  two  kinds  of  striped  muscle  {Kyaase,),  differing  in  color,  hislo- 
loeical  structure  (Kanvu-r)  and  physiological  properties  [Jironecker  and  Slirhng).  borne  are 
"red  "  e  "  the  soleus  and  semitendinosus  of  the  rabbit,  and  others  "pale,  e.^.,  the  adductor 
macnus.  In  the  falc  muscles  the  transverse  striation  is  less  regular,  and  their  nuclei  fewer  than  in 
the  red  muscles  (Kanvier) ;  they  comain  less  glycogen  and  mytjsin.  [W.  .Stirling  finds  that  the  red 
muscles  in  many  fishes,  e.  g.,  the  mackerel,  contain  granules  of  oil,  and  present  all  the  appearances  of 
muscle  in  a  stale  of  fatty  degeneration,  while  the  pale  muscles,  lying  side  by  side,  contain  no  fatty 

^'Tspectrum  —The  red  color  of  the  ordinary  skeletal  muscle  is  due  to  haemoglobin  in  the  sarcous 
substance  iKiihne).  This  is  proved  by  the  fact  that  the  color  is  retained  when  all  the  blood  is 
washed  out  of  the  vessels,  when  a  thin  muscle  still  shows  the  absorption  bands  of  hemoglobin  when 
examined  with  the  spectroscope.]  .    ■       1      . 

rMyo-h^matin.— MacMunn  points  out  that,  although  most  voluntary  muscles  owe  their  color  to 
haemoglobin,  it  is  accompanied  by  myoh.emalhi  in  most  cases,  and  sometimes  entirely  replaced  by 
it.  Myo-ha-matin  is  found  in  the  hea,-t  of  vertebrates,  and  in  some  muscles  of  vertebrates  and  inver- 

"^  Muscular  Fibres  of  the  Heart.— The  mammalian  cardiac  muscle  has  certain  peculiarities 
already  mentioned  (3  43):  (I )  It  is  striped,  but  it  is  involuntary ;  (2)  it  has  no  sarcolemma;  (3)  its 
fibres  branch  and  anastomose;  (4)  the  transverse  striation  is  not  so  distinct,  and  it  is  sometimes 
striated  longitudinally;  (5)  the  nucleus  is  placed  in  the  centre  of  each  cell  (see  I  43)-  [The  cardiac 
muscle  viewed  from  a  physiologiial  point  of  view,  stands  midway  between  striped  and  unstnped 
muscle.  Its  contraction  occurs  slowly  and  lasts  for  a  long  time  (p.  104),  while,  although  it  is  trans- 
versely striped,  it  is  involuntary.]  

rPurkinie's  Fibres.— These  fibres,  which  form  a  plexus  of  grayi.sh  fibres  under  the  endocardium 
of  the  heart  of  ruminants,  have  been  described  already  (Fig.  2S) ;  the  cells  have,  as  it  were,  advanced 
only  to  a  certain  stage  of  development  {\  46).] 


NON-STRIPED    MUSCLE. 


499 


Development. —  Each  muscular  fibre  is  developed  from  a  uninucleated  cell  of  ihe  niesoblast, 
which  elongates  into  the  form  of  a  spindle.  As  the  cell  elongates,  the  nuclei  multiply.  The  super- 
ficial or  parietal  part  of  the  cell  substance  shows  transverse  markings  (Fig.  281,  7),  while  the  nuclei 
with  a  small  amount  of  protoplasm  are  continuous  along  the  axis  ot  the  fibre,  where  they  remain  in 
some  animals.  Young  muscles  have  fewer  fibres  than  those  of  adults,  and  the  former  are  also 
smaller  {Biitige). 

In  developing  muscles,  the  number  of  fibres  is  increased  by  the  proliferation  of  the  muscle 
corpuscles,  which  form  new  fibres.  Striped  muscle,  besides  occurring  in  the  corresponding  organs 
of  veitebrata,  occurs  in  the  iiis  and  choroid  of  birds.  The  arlhropoda  have  only  striped  muscle, 
the  molluscs,  worms,  and  echinoderms  chiefly  smooth  muscles;  in  the  latter,  there  are  muscles  with 
double  oblique  striation  \Sc/iwa!he). 

2.  Non-Striped  Muscle. —  [Distribution. — It  occurs  very  widely  distributed  in  the  body,  in 
the  muscular  coat  of  the  lower  half  of  the  human  cesophagus,  stomach,  small  and  large  intestine, 
muscularis  mucosae  of  the  intestinal  tract,  in  the  arteries,  veins  and  lymphatics,  posterior  part  of 
the  trachea,  bronchi,  infundibula  of  the  lung,  muscular  coat  of  the  ureter,  bladder,  urethra,  vas 
deferens,  ves'culas  seminalis,  and  prostate  ;  corpora  cavernosa  and  spongiosa  penis,  ovary,  P^allopian 
tube,  uterus,  skin,  ciliary  muscle,  iris,  upper  eyelid,  spleen  and  capsule  of  lymphatic  glands,  tunica 
dartos  of  the  scrotum,  gall  bladder,  in  ducts  of  glands,  and  in  some  other  situations.] 

Structure Smooth  muscular  fibres  consist  of  fusiform  or  spindle  shaped  elongated  cells,  with 

their  ends  either  tapering  to  fine  points  or  divided  (Fig.  281,  10).     These  contractile  fibre  cells  may 


Fir..  287. 


Fig.  288. 


Smooth  muscular  fibre  from  the  mcsen-  Termi 

tery  of  a  newt  (ammonium  chro- 
mate).  N,  nucleus:  F,  fibrils;  S, 
markings  in  the  sheath. 

be  isolated  by  steeping  a  piece  of  the  tissue  in  a  30  per  cent,  solution  of  caustic  potash,  or  a  strong 
solution  of  nitric  acid.  They  are  45  to  230  fi  [ji^  to  ji^  in.]  in  length,  and  4  to  10  fi  [jjj'jj  to 
uVl  '"•]  '"  breadth.  Each  cell  contains  a  solid,  oval,  elongated  nucleus,  which  may  contain  one 
or  more  nucleoli.  It  is  brought  into  view  by  the  action  of  dilute  acetic  acid,  or  by  staining  reagents. 
The  mass  of  the  cell  appears  more  or  less  homogeneous  [and  is  surrounded  by  a  thin  elastic  envel- 
ope]. In  some  places  it  shows  longitudinal  fibrillation.  [Method. — This  fibrillation  is  revealed 
mote  distinctly  thus:  Place  the  mesentery  of  a  newt  (A'/ehi)  or  the  bladder  of  the  salamandra 
musculata  (/■lemming)  in  a  5  per  cent,  solution  of  ammonium  chromate,  and  afterward  stain  it  with 
picrocarmine.  Each  cell  consists  of  a  thin  elastic  sheath  (sarcolemma  of  Krause)  enclosing  a 
bundle  of  fibrils  (F),  which  run  in  a  longitudinal  direction  within  the  fibre  (Fig.  287).  They  are 
continuous  at  the  poles  of  the  nucleus  with  the  plexus  of  fibrils  which  lies  within  the  nucleus,  and, 
according  to  Klein,  they  are  the  contractile  part,  and  when  they  contract,  the  sheath  becomes 
shriveled  transversely  and  exhibits  what  looks  like  thickenings  (S).  These  fibrils  have  been  observed 
by  Flemming  in  the  cells  while  ik'ing.  Sometimes  the  cells  are  branched,  while  in  the  frog's  bladder 
they  are  triradiate.] 

[Arrangement. — Sometimes  the  fibres  occur  singly,  but  usually  they  are  arranged  in  groups, 
forming  lamella:,  sheets,  or  bundles,  or  in  a  plexiform  manner,  the  bundles  being  surrounded  by 
connective  tissue.]  A  very  delicate  elastic  cement  substance  unites  the  individual  cells  to  each 
other.     [This  cement  may  be  demonstrated  by  the  action  of  nitrate  of  silver.     In  transverse  section 


500  PHYSICAL   AND    CHEMICAL    PROPERTIES   OF    MUSCLE. 

( Fig.  281 , 1 1 )  they  appear  oval  or  polygonal,  with  the  delicate  homogeneous  cement  between  them ; 
but,  as  the  fibres  are  cut  at  various  levels,  the  areas  are  unequal  in  size,  and  all  of  them,  of  course, 
are  not  divided  at  the  position  of  the  nucleus.] 

They  vary  in  length  from  yj^  to  ,^5  of  an  inch ;  those  in  the  blood  vessels  are  short,  while  they 
are  long  in  the  intestinal  tract,  and  especially  in  the  pregnant  uterus.  According  to  Engelmann, 
the  separation  of  the  smooth  muscular  substance  into  its  individual  spindle-like  elements  is  a  post- 
mortem change  of  the  tissue.  Sometimes  transverse  thiclienings  are  seen,  which  are  not  due  to 
transverse  striation  {/i'rause),  but  to  a  partial  contraction  {Meissiier). 

Blood  Vessels. — Occasionally  they  have  a  tendinous  insertion.  Non-striped  muscle  is  richly 
supplied  with  tlood  vessels,  and  the  capillaries  form  elongated  meshes  between  the  fibres  [although 
it  is  not  so  vascular  as  striped  muscles].     Lymphatics  also  occur  between  the  fibres. 

Motor  Nerves. — According  to  J-  Arnold,  they  consist  of  medullated  and  non-meduUated  fibres 
[derived  from  the  sympathetic  system]  which  form  a  ple.xus — ground  plexus — partly  provided 
with  ganglionic  cells,  and  lying  in  the  connective  tissue  of  the  perimysium.  [The  fibres  are  sur- 
rounded  with  an  endothelial  sheath.]  Small  branches  [composed  of  bundles  of  fibrils]  are  given 
off  from  this  plexus,  forming  the  intermediary  plexus  with  angular  nuclei  at  the  nodal  points.  It 
lies  either  immediately  upon  the  musculature  or  in  the  connective  tissue  between  the  individual 
bundles.  From  the  intermediary  plexus,  the  finest  fibriliae  (0.3  to  0.5  /')  pass  off  either  singly  or  in 
groups,  and  reunite  to  form  the  intermuscular  plexus  (Fig.  28S,  d),  which  lies  in  the  cement 
suljstance  between  the  muscle  cells,  to  end,  according  to  Franltenhauser,  in  the  nucleoli  of  the 
nucleus,  or  in  the  neighborhood  of  the  nucleus  (Lustig).  According  to  J.  Arnold,  the  fibrils  traverse 
the  fibre  and  the  nucleus,  so  that  the  fibres  appear  to  be  strung  upon  a  fibril  passing  through  their 
nuclei.  According  to  Lowil,  the  fibrils  reach  only  the  interstitial  substance,  while  Gscheidlen  also 
observed  that  the  finest  terminal  fibrils,  one  of  which  goes  to  each  muscular  fibre,  ran  along  the 
margins  of  the  latter  (Fig.  2S8).  The  course  of  these  fibrils  can  only  be  traced  after  the  action  of 
gold  chloride.     [Ranvier  has  traced  their  terminations  in  the  stomach  of  the  leech.] 

Nerves  of  Tendon. — Within  the  tendons  of  the  frog  there  is  a  plexus  of  medullated  nerve 
fibres,  from  which  brush-like  divided  fibres  proceed,  which  ultimately  end  with  a  point  in  nucleated 
plates,  the  nerve  flakes  of  Rollett.  According  to  Sachs,  bodies  like  end  bulbs  occur  in  tendons, 
while  Rauber  found  Vater's  corpuscles  in  their  sheaths;  Golgi  found,  in  a.Ai\{\on,  sjiinJie-s/iaped 
terminal  corptiscles,  which  he  regards  as  a  specific  apparatus  for  estimating  tension. 

293.  PHYSICAL  AND  CHEMICAL  PROPERTIES  OF  MUS- 
CLE.—  I.  The  consistence  of  the  sarcous  siib.stance  is  the  same  as  that  of  living 
protoplasm,  e.  g.,  of  lymph  cells;  it  is  semi-solid,  /.  e.,  it  is  not  fluid  to  such  a 
degree  as  to  flow  like  a  fluid,  nor  is  it  so  solid  that,  when  its  parts  are  separated, 
these  parts  are  unable  to  cotne  together  to  form  a  continuous  whole.  The  consis- 
tence may  be  compared  to  a  jelly  at  the  moment  when  it  is  dissolved  (^.  g.,  by 
heat).     The  power  of  imbibition  is  increased  in  a  contracted  muscle  {Ranke). 

Proofs. — The  following  facts  corroborate  the  view  expressed  above  :  {a)  The  analogy  between 
the  function  of  the  sarcous  substance  and  the  contractile  protoplasm  of  cells  (|  9).  (/;)  The  so- 
called  Porret's  phenomenon  ( IV.  Kiihne)  which  consists  in  this,  that  when  a  galvanic  current  is 
conducted  through  the  living,  fresh,  sarcous  substance,  the  contents  of  the  muscular  fibre  exhibit  a 
streaming  movement  from  the  positive  to  the  negative  pole  (as  in  all  other  fluids),  so  that  the  fibre 
swells  at  the  negative  pole,  (f)  By  the  fact  that  wave  movements  have  been  observed  to  pass  along  the 
muscular  fibre.  (</)  Direct  observation  has  shown  that  a  .small  parasitic  round  worm  (Myoryctes 
Weismanni)  moved  freely  in  the  sarcous  substance  within  the  sarcolemma,  while  the  semi-solid  mass 
closed  up  in  the  track  behind  it  (  W.  Kiihne,  Eberth). 

2.  Polarized  Light. — The  contractile  substance  doubly  refracts  light,  and  is  said  to  be  aniso- 
tropous,  while  the  ground  substance  causes  single  refraction,  and  is  isotropous.  According  to 
Briicke,  muscle  behaves  like  a  doubly-refractive,  positively  uniaxial  body,  whose  optical  axis  lies  in 
the  long  axis  of  the  fibre.  When  a  muscular  fibre  is  examined  under  the  polarization  microscope, 
the  doubly-refractive  substance  is  recognized  by  its  appearing  l>rig/it  in  the  dark  field  of  the  micro- 
scope when  the  Nicols  are  crossed  (J  297).  During  contraction  of  the  muscular  fibre,  the  contrac- 
tile part  of  the  fibre  becomes  narrow-er,  and  at  the  same  time  broader,  whilst  the  optical  constants 
do  not  thereby  undergo  any  change.  Hence,  Briicke  concludes  that  the  contractile  disks  are  not 
simple  bodies  like  crystals,  but  must  consist  of  a  whole  series  of  small,  doubly-refractive  elements 
arranged  in  groups,  which  change  their  position  during  contraction  and  relaxation.  These  small 
elements  Briicke  called  disdiaclasts.  According  to  Schipiloft',  Danielewsky,  and  O.  Nasse,  the 
contractile  anisotropous  substance  consists  of  myosin,  which  occurs  in  a  crystalline  condition,  and 
represents  the  disdiaclasts.  According  to  Engelmann,  however,  all  contractile  elements  are  doubly 
refractive,  and  the  direction  of  contraction  always  coincides  with  the  optical  axis. 

The  investigations  of  v.  Ebner  have  shown  that  during  the  process  of  growth  of  the  tissue,  ten- 
sion is  produced — the  tension  of  bodies  subjected  to  imbiliition — which  results  in  double  refraction, 
and  so  gives  rise  to  the  condition  called  anisotropous. 


CHEMICAL   COMPOSITION    OF    MUSCLE    SERUM.  501 

The  chemical  composition  of  muscle  undergoes  a  great  change  after  death, 
owing  to  the  spontaneous  coagulation  of  a  proteid  within  the  muscular  fibres.  As 
frog's  muscles  may  be  frozen  and  thawed,  and  still  remain  contractile,  they  cannot, 
therefore,  be  greatly  changed  by  the  process  of  freezing.  W.  Kiihne  bled  frogs, 
cooled  their  muscles  to  io°  or  7°  C,  pounded  them  in  an  iced  mortar,  and  ex- 
pressed their  juice  through  linen.  The  juice  so  expressed,  when  filtered  in  the 
cold,  forms  a  neutral,  or  alkaline,  slightly  yellowish,  opalescent  fluid,  the  so-called 
"muscle  plasma."  Like  blood  plasma,  it  coagulates  spontaneously;  at  first 
it  is  like  a  uniform  soft  jelly,  but  soon  becomes  opaque  ;  doubly-refractive  fibres 
and  specks,  similar  to  the  fibrin  of  blood,  appear  in  the  jelly,  and  as  these  begin 
to  contract,  they  squeeze  out  of  the  jelly  an  acid  "muscle  serum."  Cold 
prevents  or  delays  the  coagulation  of  the  muscle  plasma  ;  above  0°,  coagulation 
occurs  very  slowly,  and  the  rapidity  of  coagulation  increases  rapidly  as  the  tem- 
perature rises,  while  coagulation  takes  place  very  rapidly  at  40°  C.  in  cold-blooded 
animals,  or  at  48°  to  50°  C.  in  warm-blooded  muscles.  The  addition  of  distilled 
water  or  an  acid  to  muscle  plasma  causes  coagulation  at  once.  The  coagulated 
proteid,  most  abundant  in  muscle,  and  which  arises  from  the  doubly-refractive 
substance,  is  called  "myosin  "   (JF.  Kuhne). 

Myosin. — It  is  a  globulin  (^  245),  and  is  soluble  in  strong  fio  per  cent.)  solutions  of  common 
salt,  and  is  again  precipitated  from  such  a  solution  by  dilution  with  water,  or  by  the  addition  of  very 
small  quantities  of  acids  (o. i  to  0.2  percent,  lactic  or  hydrochloric  acid).  It  is  soluble  in  dilute 
alkalies  or  slightly  stronger  acids  (0.5  percent,  lactic  or  hydrochloric  acid),  and  also  in  13  per  cent, 
ammonium  chloride  solution.  Like  fibrin,  myosin  rapidly  decomposes  hydric  peroxide.  When 
treated  with  dilute  hydrochloric  acid  and  heat,  it  is  changed  into  syntonin  {\  245).  Myosin  may 
be  extracted  fioni  muscle  by  a  10  to  15  per  cent,  solution  of  NH^Cl,  and  if  it  be  hca'ed  to  65°  it  is 
precipitated  again  yDatiit'Uiuskv).  Danielevvsky  succeeded  in  partly  changing  syntonin  into  myosin 
by  the  action  of  milk  of  lime  and  ammonium  chloride.  Myosin  occurs  in  other  animal  structures 
(cornea),  nay,  even  in  some  vegetables  (O.  Nasse). 

Muscle  serum  still  contains  three  proteids  (2.3  to  3  per  cent.),  viz.:  i. 
Alkali  albuminate,  which  is  precipitated  on  adding  an  acid,  even  at  20°  to  24° 
C.  2.  Ordinary  serum  albumin,  1.4  to  1.7  per  cent.  (§  32,  a),  which  coagu- 
lates at  73°  C.     3.  An  albuminate  which  coagulates  at  47°  C. 

The  other  chemical  constituents  of  muscle  have  been  referred  to  in  treating  of 
fiesh  (§  233).  I.  Briicke  found  traces  of  pepsin  and  peptone  in  muscle  juice; 
Piotrowsky,  a  trace  of  a  diastatic  ferment.  2.  In  addition  to  volatile  fatty  acids 
(formic,  acetic,  butyric),  there  are  two  isomeric  forms  q>{  lactic  acid  (CsHsOa)  pre- 
sent in  muscle  with  an  acid  reaction  :  (a)  Ethylidene-lactic  acid,  in  the  inodifica- 
tion  known  as  right  rotatory  sarcolaciic  or  paralactic  acid,  which  occurs  only  in 
muscles,  and  some  other  animal  structures,  {b)  Ethylene-lactic  acid  in  small 
amount  (§  251,  3  c).  It  was  formerly  assumed  that  lactic  acid  is  formed  by  fer- 
mentation from  the  carbohydrates  of  the  muscle  (glycogen,  dextrin,  sugar),  and 
Maly  has  observed  that  paralactic  acid  is  occasionally  formed  when  these  bodies 
undergo  fermentation.  According  to  Bohm,  however,  the  glycogen  of  muscle 
does  not  pass  into  lactic  acid,  as  during  rigor  mortis,  if  putrefaction  be  prevented, 
the  amount  of  glycogen  does  not  diminish.  If  muscle  be  suddenly  boiled  or 
treated  with  strong  alcohol,  the  ferment  is  destroyed,  and  hence  the  acidification 
of  the  muscular  tissue  is  prevented  {Du  Bois-jRtymond).  Acid  potassium  phospkate 
also  contributes  to  the  acid  reaction.  3.  Caniin  (CjHgNjOa),  which  is  changed  by 
bromine  or  nitric  acid  into  sarkin,  occurs  to  the  extent  of  i  per  cent,  in  Liebig's 
extract  of  meat  {IVeidcl).  4.  Only  o.oi  per  cent,  of  urea  {Haycrafi).  5.  Gly- 
cogen occurs  to  the  amount  of  over  \  per  cent,  after  copious  flesh  feeding,  and  to 
0.5  per  cent,  during  fasting.  It  is  stored  up  in  the  muscles,  as  well  as  in  the  liver, 
during  digestion,  but  it  disappears  during  hunger.  It  is  perhaps  formed  in  the 
muscles  from  proteids  (§  174,  2).  6.  Lccitliin,  derived  in  part  from  the  motor 
nerve  endings  (§  23  and  §  251 ).  7.  The  gases  are  CO.,  (15  to  18  vol.  per  cent.), 
partly  absorbed,  partly  chemically  uniteil ;  some  absorbed  N,  but  no  O,  although 


502  METABOLISM    IN    MUSCLE. 

muscle  continually  absorbs  O  from  the  blood  passing  through  it  (Z.  Hermann). 
The  muscles  contain  a  substance  whose  decomposition  yields  CO,.  When  muscles 
are  exercised,  this  substance  is  used  up,  so  that  severely  fatigued  muscles  yield  less 
CO.,  {Stinzing).  [It  is  to  be  remembered  that  all  muscles  have  not  the  same 
chemical  composition.] 

294.  METABOLISM  IN  MUSCLE.— I.  A  passive  muscle  continu- 
ally absorbs  a  certain  amount  of  U  from  the  blood  flowing  through  its  capillaries, 
and  returns  a  certain  amount  of  CO,  to  the  blood  stream.  The  amount  of  CO2 
given  off  is  less  than  corresponds  to  the  amount  of  O  absorbed.  Excised  muscles 
freed  from  blood  exhibit  an  analogous  but  diminished  gaseous  exchange  {Du 
Bois-Reymond,  G.  Liebig).  As  an  excised  muscle  remains  longer  excitable  in  O 
or  in  air  than  in  an  atmosphere  free  from  O,  or  in  indifferent  gases  {Al.  v.  Hum- 
boldf),  we  must  conclude  that  the  above-named  gaseous  exchange  is  connected 
with  the  normal  metabolism,  and  is  a  condition  on  which  the  life  and  activity  of 
the  muscle  depends. 

If  a  living  muscle  be  exciserl,  and  if  blood  be  perfused  through  its  blood  vessels,  the  amount  of 
O  used  up  is,  within  pretty  wide  limit*,  almost  independent  of  temperature ;  if  the  variations  of 
temperature  be  great,  it  rises  and  falls  with  the  temperature.  The  CO2  given  off  by  muscular  tissue 
falls  when  the  muscle  is  cooled  (less  than  the  O  used  up),  but  it  is  not  increased  when  the  muscle 
is  subsequently  warmed  {Rubner). 

This  exchange  of  gases  must  be  distinguished  from  the  putrefactive  phenomena  due  to  the  devel- 
opment of  living  organisms  in  the  muscle.  These  putrefactive  phenomena  are  also  connected  with 
the  consumption  of  O  and  the  excretion  of  CO,,  and  occurs  soon  after  death  (Z.  Hermann). 

II.  In  an  active  muscle  the  blood  vessels  are  always  dilated  {Litdwig 
and  Sczelkoio,  Gaskell) — a  condition  pointing  to  a  more  lively  material  exchange 
in  the  organ.  Hence,  the  active  muscle  is  distinguished  from  the  passive  one  by 
a  series  of  chemical  transformations. 

1.  Reaction. — The  neutral  or  feebly  alkaline  reaction  of  a  passive  muscle 
(also  of  the  non-striped  variety)  passes  into  an  acid  reaction  during  the  activity 
of  the  muscle,  owing  to  the  formation  of  paralactic  acid  {^Dii  Bois-Rcymond, 
iS^g) ;  the  degree  of  acidity  increases  up  to  a  certain  extent,  according  to  the 
amount  of  work  performed  by  the  muscle  {R.  Heidenhain).  The  acidification  is 
due,  according  to  Weyl  and  Zeitler,  to  the  phosphoric  acid  produced  by  the 
decomposition  of  lecithin  and  (?  nuclein). 

It  is  doubtful  if  the  acidity  is  due  to  lactic-acid,  as  Warren  and  Astaschewsky  find  that  there  is 
less  lactic  acid  in  the  active  than  in  the  passive  muscle. 

2.  Production  of  CO,. — An  active  muscle  excretes  considerably  more  COj 
than  a  passive  one :  (a)  active  muscular  exertion  on  the  part  of  a  man  or  of  ani- 
mals increases  the  amount  of  CO,  given  off  by  the  lungs  (§127);  {b)  venous 
blood  flowing  from  a  tetanized  muscle  of  a  limb  contains  more  CO..,,  more  CO2 
being  formed  than  corresponds  to  the  O,  which  has  simultaneously  been  absorbed 
(Ludwig  and Sczelko7(.i).  The  same  result  is  obtained  when  blood  is  passed  through 
an  excised  muscle  artificially ;  {c)  an  excised  muscle  caused  to  contract  excretes 
more  CO,  {Mattcucci,  Valentin). 

3.  Consumption  of  Oxygen. — An  active  muscle  uses  up  more  O — {a)  when 
we  do  muscular  work,  the  bod)  absorbs  much  more  O  (p.  366) — even  4  to  5  times  as 
much  (^Regnauli  and  Reisef  )  :  (b)  venous  blood  flowing  from  an  active  muscle  of 
a  limb  contains  less  O  (Liidwig.  Sczclkmo  and  Al.  Sclimidt).  Nevertheless,  the 
increase  of  O  used  up  by  the  active  muscle  is  not  so  great  as  the  amount  of  CO, 
given  off  {y.  Pettenkofer  and  v.  Voit).  The  increase  of  O  used  up  may  be  ascer- 
tained even  during  the  period  of  rest  directly  following  the  period  of  activity, 
and  the  same  is  the  case  with  the  CO,  excreted  (?■.  Frey). 

As  yet,  it  is  not  possilile  to  prove,  by  gasometric  methods,  that  O  is  used 
up  in  an  excised  muscle  free  from  blood.     Indeed,  the  presence  of  O  does  not 


METABOLISM    IN    MUSCLE. 


503 


seem  to  be  absolutely  necessary  for  the  activity  of  muscle  during  short  periods,  as 
an  excised  muscle  may  continue  to  contract  in  a  vacuum,  or  in  a  mixture  of  gases 
free  from  O,  and  no  O  can  be  obtained  from  muscular  tissue  (Z.  Hermann).  A 
frog's  muscles  rob  easily  reducible  substances  of  their  O  ;  they  discharge  the  color 
of  a  solution  of  indigo  ;  muscles  which  have  rested  for  a  time,  acting  less  ener- 
getically than  those  which  have  been  kept  in  a  state  of  continued  activity  (  Griitz- 
7ier,  Gscheidlen). 

4.  Glycogen. — The  amount  of  glycogen  (0.43  per  cent,  in  the  muscles  of  a 
frog  or  rabbit )  and  grape  sugar  is  diminished  in  an  active  muscle  (  O.  Nassc,  JVass), 
but  muscles  devoid  of  glycogen  do  not  lose  their  excitability  and  contractility. 
Hence,  glycogen  is  certainly  not  the  direct  source  of  the  energy  in  an  active 
muscle.  Perhaps  it  is  to  be  sought  for  in  an  as  yet  unknown  decomposition 
product  of  glycogen  (^Luchsinger).  [There  is  more  glycogen  in  the  red  than  in 
the  pale  muscles  of  a  rabbit.] 

5.  Extractives. — An  active  muscle  contains  less  extractive  substances  soluble 
in  water,  but  more  extractives  soluble  in  alcohol  {v.  Hebnholtz,  1843")  >  •'  ^'so 
contains  less  of  the  substances  which  form  CO.j  {Hanke)  ;  less  fatty  acids  (Sczelkow)  ; 
less  kreatin  and  kreatinin  (v.  Voif). 

6.  During  contraction,  the  amount  of  water  in  the  muscular  tissue  increases, 
while  that  of  the  blood  is  correspondingly  diminished  (J.  Ranke).  The  solid 
substances  of  the  blood  are  increased,  while  they  (albumin)  are  diminished  in 
the  lymph  ( Fano). 

7.  Urea. — The  amount  of  urea  excreted  from  the  body  is  not  materially 
increased  during  muscular  exertion  (v.  Voif,  Fick  and  IVis/iceniis).  According  to 
Parkes,  however,  although  the  excretion  of  urea  is  not  increased  immediately,  yet 
after  i  to  i}i  days  there  is  a  slight  increase.  The  amount  of  work  done  cannot 
be  determined  from  the  amount  of  albumin  which  is  changed  mto  urea. 

[Relation  of  Muscular  Work  to  Urea  — Ed.  Smith,  Parkes  and  others  have  made  numerous 
investigations  on  this  subject.  Fick  and  Wislicenus  (1S66)  ascended  the  Faulhorn,  and  for  seven- 
teen hours  before  the  ascent  and  for  si.\  hours  after  the  ascent  no  proteid  food  was  taken — tlie  diet, 
consisting  of  cakes  made  of  fat,  sugar  and  .starch.  The  urine  was  collected  in  three  periods,  as 
follows  : — 


Fick. 

Wislicenus. 

1.  Urea  of  11  hours  before  the  ascent  .  . 

2.  "            8      "      during        "           .  . 

3.  "            6      "      after            "           .  . 

238  55  grs. 

221.05  gr^- 

79.S9 "  j  ^^^ 

A  hearty  meal  was  taken  after  this  period,  and  the  urine  of  the  next  eleven  hours  after  the  period 
of  rest  coiitamed  159.15  grains  of  urea  f/iV/'),  and  176  71  (  IVisiitenus).  All  the  e.xperimciits  go 
to  show  that  the  amount  of  urea  excreted  in  the  urine  is  far  more  dependent  upon  the  nitrogen 
ingested,  i.e.,  the  nature  of  the  food,  than  upon  the  decomposition  of  the  muscular  substance.  A 
vegetable  diet  diminishes,  while  an  animal  diet  greatly  increases,  the  amount  of  urea  in  the  urine. 
North's  researches  confirm  those  of  Parkes,  Ijut  he  finds  that  the  disturbance  produced  by  severe 
muscular  labor  is  considerable.  The  elimination  of  phosphates  is  not  affected,  while  the  sulphates 
in  the  urine  are  increased.] 

During  the  activity  of  a  muscle,  a!/  the  groups  of  the  chemical  substances 
present  in  muscle  undergo  more  rapid  transformations  (_/.  Ranke).  It  is  still  a 
matter  of  doubt,  therefore,  whether  we  may  assume  that  the  kinetic  energy  of  a 
muscle  is  chiefly  due  to  the  transformation  of  the  chemical  energy  of  the  carbo- 
hydrates which  are  decomposed  or  used  up  in  the  process  of  contraction.  As  yet 
we  do  not  know  whether  the  glycogen  is  supplied  by  the  blood  stream  to  the 
muscles,  perhaps  from  the  liver,  or  whether  it  is  formed  within  the  muscles  them- 
selves from  some  unknown  derivative  of  the  proteids.  The  normal  circulation  is 
certainly  one  of  the  conditions  for  the  formation  of  glycogen  in  muscle,  as  gly- 
cogen diminishes  after  ligature  of  the   blood  vessels  (JOhandehm).     A  muscle  in 


504  STAGES   OF   CADAVERIC    RIGIDITY. 

which  the  blood  circulates  freely  is  capable  of  doing  more  work  than  one  devoid 
of  blood  {Hanke),  and  even  in  the  intact  body  more  blood  is  always  supplied  to 
the  contracted  muscles. 

295.  RIGOR  MORTIS. — Cause. — Excised  striped,  or  smooth  muscles,  and 
also  the  muscles  of  an  intact  body,  at  a  certain  time  after  death,  pass  into  a  con- 
dition of  rigidit) — cadaveric  rigidity  or  rigor  mortis.  When  all  the  muscles 
of  a  corpse  are  thus  affected,  the  whole  cadaver  becomes  completely  stiff  or  rigid. 
The  cause  of  this  phenomenon  depends  upon  the  spontaneous  coagulation  of  a 
proteid,  viz.,  the  myosin  of  the  muscular  fibre  {Kiihiie),  in  consequence  of  the 
formation  of  a  small  amount  of  an  acid.  Under  certain  circumstances,  the 
coagulation  of  the  other  proteids  of  the  muscle  may  increase  the  rigidity. 
During  the  process  of  coagulation,  heat  is  set  free  {v.  Walthcr,  Fick — §  223), 
owing  to  the  passage  of  the  fluid  myosin  into  the  solid  condition,  and  also  to  the 
simultaneous  and  subsequently  increased  density  of  the  tissue. 

Properties  of  a  Muscle  in  Rigor  Mortis. — It  is  shorter,  thicker  and  some- 
what denser  (Schiiiiileioitsili,  U\illt-r) ;  stiff,  compact  and  solid;  turbid  and 
opaque  (owing  to  the  coagulation  of  the  myosin)  ;  incompletely  elastic,  less 
extensible,  and  more  easily  torn  or  ruptured  ;  it  is  completely  inexcitable  to 
stimuli ;  the  muscular  electrical  current  is  abolished  (or  there  is  a  slight  current  in 
the  opposite  direction)  ;  its  reaction  is  acid,  owing  to  the  formation  of  both  forms 
of  lactic  acid  (§  293)  glycero-i)hosphoric  acid  (Diakanow)  ;  while  it  also  develops 
free  COj.  When  an  incision  is  made  into  a  rigid  muscle,  fluid  (^muscle  serum, 
p.  501)  appears  spontaneously  in  the  wound. 

The  first  formed  lactic  acid  converts  the  salts  of  the  muscle  into  acid  salts ;  thus  potassium  lactate 
and  acid  potassium  phosphate  are  fonned  from  potassium  phosphate.  The  lactic  acid,  which  is 
formed  thereafter,  remains  fiee  and  ununited  in  the  muscle. 

Amount  of  Glycogen. — The  newest  observations  of  Bohm  are  against  the  view  that,  during 
rigor  mortis,  a  partial  or  complete  transformation  of  the  glycogen  into  sugar  and  then  into  lactic 
acid  takes  place.  During  digestion,  a  temporary  storage  of  glycogen  occurs  in  the  muscles  as  well 
as  in  the  liver,  so  that  about  as  much  is  found  iu  the  muscles  as  in  the  liver.  There  is  no  diminu- 
tion of  the  glycogen  when  rigidity  takes  place,  provided  putrefaction  be  prevented  ;  so  thai  the 
lactic  acid  of  rigid  muscles  cannot  be  formed  from  glycogen,  but  more  probably  it  is  formed  from  the 
decomposition  of  the  albuminates  [Demant^  Bohm). 

The  amount  of  acid  does  not  vary,  whether  the  rigidity  occurs  rapidly  or  .slowly  (J.  Xanie) ; 
when  acidification  begins,  the  rigidity  becomes  more  marked,  owing  to  the  coagulation  of  the  alkali 
albuminate  of  the  muscle.  Less  CO,  is  formed  from  a  rigid  muscle,  the  more  CO2  it  has  given  off 
previously,  during  muscular  exertion.  A  rigid  muscle  gives  off  N  and  absorbs  O.  In  a  cadaveric 
rigid  muscle,  fibrin  ferment  is  present  (.41.  SchmiJt  anJ  others).  It  seems  to  be  a  product  of  pro- 
toplasm, and  is  never  absent  where  this  occurs  [Rauschenbach'). 

[Rigor  Mortis  and  Coagulation  of  Blood. — Thus  there  is  a  marked 
analogy  between  the  coagulation  of  the  blood  and  that  of  muscle.  In  both  cases, 
a  fluid  body  yields  a  solid  body,  fibrin  from  blood,  and  myosin  from  muscle,  and 
there  are  many  other  points  of  analogy  (p.  506).] 

Stages  of  Rigidity. ^ — Two  stages  are  recognizable  in  cadaveric  muscles:  In 
the  first  stage,  the  muscle  is  rigid,  but  still  excitable;  in  this  stage  the  myosin 
seems  to  be  in  a  jelly-like  condition.  Restitution  is  still  possible  during  this 
stage.  In  the  second  stage,  the  rigidity  is  well  pronounced,  with  all  the  phe- 
nomena above  mentioned. 

The  onset  of  the  rigidity  varies  in  man  from  ten  minutes  to  seven  hours  [and  it 
is  complete,  as  a  rule,  within  four  to  six  hours  after  death.  The  muscles  of  the 
jaws  are  first  affected,  then  those  of  the  neck  and  trunk,  afterward  (as  a  rule)  the 
lower  limbs,  and  finally  the  upper  limbs].  Its  duration  is  equally  variable — one 
to  six  days.  After  the  cadaveric  rigidity  has  disappeared,  the  muscles,  owing  to 
further  decotnpositions  and  an  alkaline  reaction,  become  soft  and  the  rigidity  dis- 
appears (Nysten,  Sommer).  The  onset  of  the  rigidity  is  always  preceded  by  a  loss 
of  nervous  activity.  Hence,  the  muscles  of  the  head  and  neck  are  first  affected, 
and  the  other  muscles  in  a  descending  series  (§  325).     Disappearance  of  the  rigid- 


EFFECTS  OF  HEAT  AND  WATER  ON  MUSCLE.         505 

ity  occurs  first  in  the  muscles  first  affected  (A^ysteit).  Great  muscular  activity  be- 
fore death  (e.g.,  spasms  of  tetanus,  cholera,  strychnin,  or  opium  poisoning)  causes 
rapid  and  intense  rigidity  ;  hence  the  heart  becomes  rigid  relatively  rapidly 
and  strongly.  Hunted  animals  may  become  affected  within  a  few  minutes 
after  death.  [This  is  often  seen  in  the  fox.]  Usually  the  rigidity  lasts  longer  the 
later  it  occurs.  Rigidity  does  not  occur  in  a  foetus  before  the  seventh  month.  A 
frog's  muscle  cooled  to  o°  C.  does  not  begin  to  exhibit  cadaveric  rigidity  for  four 
to  seven  days. 

Stenson's  Experiment. — The  amount  of  blood  in  a  muscle  has  a  marked 
effect  upon  the  onset  of  the  rigidity.  Ligature  of  the  muscular  arteries  causes  at 
first  in  all  mammals  an  increase  of  the  muscular  excitability  and  then  a  rapid  fall  of 
the  excitability  {Schmiiletvitsch ) ;  thereafter  stiffness  occurs,  the  one  stage  following 
closely  upon  the  other  (Swammerdam,  Nic.  Sfenson,  i66j).  [If  the  ligature  be 
removed  in  the  first  stage,  the  muscle  recovers,  but  in  the  later  stages  the  rigidity 
is  permanent.]  If  the  artery  going  to  a  muscle  be  ligatured,  Stannius  observed 
that  the  excitability  of  the  motor  nerves  disappeared  after  an  hour,  that  of  the  mus- 
cular substance  after  four  to  five  hours,  and  then  cadaveric  rigidity  set  in. 

Pathological. — When  the  blood  vessels  of  a  muscle  are  occluded,  by  coagulation  taking  place 
within  them  \  Lmidois),  rigidity  of  the  muscles  is  produced  (^  102).  True  cadaveric  rigidity  may 
be  produced  by  too  tight  bandaging ;  the  muscles  are  paralyzed,  rigid,  and  break  up  into  flakes, 
while  the  contents  of  the  fibre  are  afterward  absorbed  (R.  Volkmann).  Occlusion  of  the  blood 
vessels  of  muscles  by  infarcts,  especially  in  persons  with  atheromatous  arteries,  roay  even  cause 
necrosis  of  the  muscles  implicated  (Finc/t,  Girandcaii). 

If  the  circulation  be  reestablished  during  the  first  stage  of  the  rigidity,  the 
muscle  soon  recovers  its  excitability  {Stannius).  When  the  second  stage  has  set 
in,  restitution  is  impossible  (Kiihne).  In  cold-blooded  animals,  cadaveric  rigidity 
does  not  occur  for  several  days  after  ligaturing  the  blood  vessels.  Brown-Sequard, 
by  injecting  fresh  oxygenated  blood  into  the  blood  vessels,  succeeded  in  restoring 
the  excitability  of  the  muscles  of  a  human  cadaver  four  hours  after  death,  /.  e., 
during  the  first  stage  of  cadaveric  rigidity.  Ludwig  and  Al.  Schmidt  found  that 
the  onset  of  cadaveric  rigidity  was  greatly  retarded  in  excised  muscles,  when  arte- 
rial blood  was  passed  through  their  blood  vessels.  Blood  deprived  of  its  O  did 
not  produce  this  effect.  Cadaveric  rigidity  occurs  relatively  early  after  severe 
hemorrhage.  If  a  weak  alkaline  fluid  be  conducted  through  the  dead  muscles  of 
a  frog,  cadaveric  rigidity  is  prevented  [Schipi/off). 

Section  of  Nerves. — Preliminary  section  of  the  motor  nerves  causes  a 
later  onset  of  the  rigidity  in  the  corresponding  muscles  {Brown-Scqiiard,  Heineke). 
Perhaps  this  is  caused  by  the  greater  accumulation  of  blood  in  the  paralyzed  parts 
(due  to  section  of  the  vasomotor  nerves).  In  fishes,  whose  medulla  oblongata  is 
suddenly  destroyed,  cadaveric  rigidity  occurs  much  more  slowly  than  in  those  ani- 
mals that  die  slowly  {Blane). 

Rigidity  may  be  produced  artificially  by  various  reagents  : — 

1.  Heat  ["  Heat  stiffening  "  (Fickfonf)']  causes  the  myosin  to  coagulate  at 
40°  C.  in  cold-blooded  animals,  in  birds  about  53^  C,  and  in  mammals  at  48°  to 
50°  C.  The  protoplasm  of  plants  and  animals,  e.  g.,  of  the  amoeba,  is  coagulated 
by  heat,  giving  rise  to  heat  rigor. 

Schmulewitsch  found  that  the  longer  a  muscle  had  been  excised  from  the  bo(ly,  the  greater  was 
the  heat  required  to  produce  stiffening.  Heat  stiffening  differs  from  cadaveric  rigidity  thus:  a  13 
per  cent,  solution  of  ammonium  chloride  dissolves  out  the  myosin  from  a  cadaveric  rigid  muscle,  but 
not  from  one  rendered  rigid  by  heat  (S<-/i!/>iloff).  If  the  rigid  cadaveric  muscles  of  a  frog  be  heated, 
another  proteid  coagulates  at  45°,  and  Lastly  at  75°  the  serum  albumin  itself.  Hence,  both  processes 
together  make  the  muscle  more  rigid  (J  295). 

2.  When  a  muscle  is  saturated  with  distilled  water,  it  produces  "  water 
stiffening  " — an  acid  reaction  being  developed  at  the  same  time. 

Muscles  rendered  stiff  by  water  still  exhibit  electro-motive  phenomena,  while  muscles  rendered 
rigid  by  ether  means  do  not  (BicJermann).     If  the  upper  limb  of  a  frog  be  ligatured,  deprived  of 


506  MUSCULAR   EXCITABILITY. 

its  skin,  and  dipped  in  warm  water,  it  becomes  rigid.  If  the  ligature  he  removed  and  the  circulation 
reestablished,  the  rigidity  may  be  partially  set  aside.  If  there  be  well-marked  rigidity,  it  can  only 
be  set  aside  by  placing  the  limb  in  a  lo  per  cent,  solution  of  common  salt,  wliich  dissolves  the  coag- 
ulum  of  myosin  (Pieyer). 

3.  Acids,  even  CO.,,  rapidly  produce  "acid  stiffening,"  which  is  probably 
different  from  ordinary  stiffening,  as  such  muscles  do  not  evolve  any  free  COj  (Z. 
Hennanii).  The  injection  of  o.i  to  0.2  per  cent,  solutions  of  lactic  or  hydro- 
chloric acid  into  the  muscles  of  a  frog  produces  stiffening  at  once,  which  may  be 
set  aside  by  injecting  0.5  per  cent,  solution  of  an  acid,  or  by  a  solution  of  soda,  or 
by  15  per  cent,  solution  of  ammonium  chloride.  The  acids  form  a  compound 
with  the  myosin  {Sihipi/off). 

4.  Freezing  and  thawing  a  part  alternately,  rapidly  produces  stiffening ;  and 
it  is  aided  by  mechanical  injuries. 

Poisons. — Rigor  mortis  is  favored  by  quinine,  caffein,  digitalin,  [a  concentrated  solution  of 
caffein  or  digitalin,  applied  to  the  muscle  of  a  frog,  produces  rigor  mortis,]  veratrin,  hydrocyanic 
acid,  ether,  chloroform,  the  oils  of  mustard,  fennel,  and  aniseed  ;  direct  contact  of  muscular  tissue 
with  potassium  sulphocyanide  (Bernard,  Setulu'now),zxmaom?i,  alcohol,  and  metallic  salts. 

Position  of  the  Body. — The  attitude  of  the  body  during  cadaveric  rigidity  is  generally  that 
occupied  at  death  ;  the  position  of  the  limbs  is  the  result  of  the  varying  tensions  of  the  different 
muscles.  During  the  occurrence  of  rigor  mortis,  a  limb,  or  more  frequently  the  arm  and  fingers, 
may  move  {Sojiimer).  Thus,  if  stiffening  occurs  rapidly  and  firmly  in  certain  groups  of  muscles, 
this  may  produce  movements,  as  is  sometimes  seen  in  cholera.  If  cadaveric  rigidity  occurs  very 
rapidly,  the  body  may  occupy  the  same  position  which  it  did  at  the  moment  of  death,  as  sometimes 
happens  on  the  battle-field.  In  these  cases  it  does  not  seem  that  a  contracted  condition  of  the  muscle 
passes  at  once  into  rigor  mortis;  but  between  these  two  conditions,  according  to  Briicke,  there  is 
always  a  very  short  relaxation. 

Muscles  which  have  been  plunged  into  boiling  water  do  not  undergo  rigor  mortis,  neither  do 
they  become  acid  (Dii  Bnis- KayiiiniiJ),  nor  evolve  free  CO,  {L.  Hermann). 

Analogy  between  Contraction  and  Rigidity.  —  L.  Hermann  has  drawn  attention  to  the 
analogy  which  exists  between  a  muscle  in  a  state  of  contraction  and  one  in  a  state  of  cadaveric 
rigidity — both  evolve  CO2  and  the  other  acids  from  the  same  source.  The  form  of  the  contracted 
and  the  stiffened  muscle  is  shorter  and  thicker;  both  are  denser,  less  elastic,  and  evolve  heat ;  in 
both  cases,  the  muscular  contents  behave  negatively  as  regards  their  electro-motive  force,  in  refer- 
ence to  the  unaltered,  living,  resting  sulxstance.  Hence  he  is  inclined  to  regard  a  muscular  contrac- 
tion as  a  temporary,  physiological,  rapidly  disappearing  rigor,  whilst  other  observers  regard  stiffen- 
ing as  in  a  certain  sense  the  last  flickering  act  of  a  living  muscle. 

Work  done  during  Rigidity. — .\  muscle  in  the  act  of  becoming  stiff  will  lift  a  weight,  but  the 
height  to  which  it  is  lifted  is  greater  with  small  weights,  but  less  with  heavier  weights,  than  when  a 
living  muscle  is  stimulated  with  a  maximal  stimulus. 

Disappearance  of  Rigidity. — When  rigor  mortis  passes  off,  there  is  a  con- 
siderable amount  of  acid  formed  in  the  muscle,  which  dissolves  the  coagulated 
myosin.  After  a  time  putrefaction  sets  in,  accompanied  by  the  presence  of 
micro-organisms  and  the  evolution  of  ammonia  and  putrefactive  gases  (H„S,  N, 
C0,-§  184). 

According  to  Onimus,  the  loss  of  excitability  which  precedes  the  onset  of  rigor  mortis  occurs 
in  the  following  order  in  man:  Left  ventricle,  stomach,  intestine  (55  minutes) ;  urinary  bladder, 
right  ventricle  (60  minutes) ;  iris  (105  minutes);  muscles  of  face  and  tongue  (iSo  minutes)  ;  the 
extensors  of  the  extremities  (about  one  hour  before  the  flexors) ;  the  muscles  of  the  trunk  (five  to 
six  hours).     The  oesophagus  reinains  excitable  for  a  long  time  (^  325). 

296.  MUSCULAR  EXCITABILITY.— By  the  term  excitability  or 
irritability  of  a  muscle,  is  meant  that  property  in  virtue  of  which  a  muscle 
shortens  when  it  is  stimulated.  The  condition  of  excitement  is  the  active  condi- 
tion of  a  muscle  produced  by  the  application  of  stimuli,  and  is  usually  indicated 
by  the  act  of  contraction.  Stimuli  are  simply  various  forms  of  energy,  and  they 
throw  the  muscle  into  a  state  of  excitement,  while  at  the  moment  of  activity  the 
chemical  energy  of  the  muscle  is  transformed  into  work  and  heat,  so  that  stimuli 
act  as  liberating  or  "  discharging  forces."  The  normal  temperature  of  the 
body  is  most  favorable  for  maintaining  the  normal  muscular  excitability  ;  the  ex- 
citability varies  as  the  temperature  rises  or  falls. 


ACTION    OF   CURARA.  507 

As  long  as  the  blood  stream  within  a  muscle  is  uninterrupted,  the  first  effect 
of  stimulation  of  a  muscle  is  to  increase  its  energizing  power,  partly  because  the 
circulation  is  more  lively  and  the  blood  vessels  are  dilated,  but  after  a  time  the 
energizing  power  is  diminished.  Even  in  excised  muscles,  especially  when  the 
large  nerve  trunks  have  already  lost  their  excitability,  the  excitability  is  increased 
after  a  stimulus,  so  that  the  application  of  a  series  of  stimuli  of  the  same  strength 
causes  a  series  of  contractions  which  are  greater  than  at  first  {J Fund/).  Hence, 
we  account  for  the  fact  that,  although  the  first  feeble  stimulus  may  be  unable  to 
discharge  a  contraction,  the  second  may,  because  the  first  one  has  increased  the 
muscular  excitability  (Fick). 

Effect  of  Cold. — If  the  muscles  of  a  frog  or  tortoise  be  kept  in  a  cool  place,  they  may  remain 
excitable  for  ten  days,  while  the  muscles  of  warm-blooded  animals  cease  to  be  excitable  after  one 
and  a  half  to  two  and  a  half  hours.  (For  the  heart,  see  ^  55.)  .\  muscle,  when  stimulated  direclly, 
always  remains  excitable  for  a  longer  time  when  its  motor  nerve  is  already  dead. 

[Independent  Muscular  Excitability. — .Since  the  time  of  .Albrecht  v.  Haller  and  R.  Whytt, 
physiologists  have  ascribed  to  muscle  a  condition  of  excitability  which  is  entirely  independent  of 
the  existence  of  motor  nerves,  and  which  depends  on  certain  constituents  of  the  sarcous  substance. 
Excitability,  or  the  property  of  responding  to  a  stimulus,  is  a  widely  distributed  function  of  proto- 
plasm or  its  modifications.  A  colorless  blood  corpuscle  or  an  amieba  is  excitable,  and  so  are  secre- 
tory and  nerve  cells.  In  the  first  cases,  the  application  of  a  stimulus  results  in  motion  in  an  indefi- 
nite direction,  in  the  second  in  a  formation  of  the  secretion,  and  in  the  third  in  the  discharge  of 
nerve  energy.  In  the  case  of  muscle,  a  stimulus  causes  movement  in  a  definite  direction,  called  a 
contraction,  and  depending  on  the  contractility  of  the  sarcous  sulistance.  There  are  many  considera- 
tions which  show  that  excitability  is  independent  of  the  nervous  system,  although  in  the  higher 
animals  nerves  are  the  usual  medium  through  which  the  excitability  is  brought  into  action.  Thus 
plants  are  excitable,  and  they  contain  no  nerves.] 

Numerous  experiments  attest  the  "  independent  excitability  "  of  muscle  : 
I.  There  are  chemical  stimuli,  which  do  not  cause  movement  when  applied  to 
motor  nerves,  but  do  so  when  they  are  applied  directly  to  muscle  ;  ammonia,  lime 
water,  carbolic  acid.  2.  The  ends  of  the  sartorius  of  the  frog,  in  which  no  nerve 
terminations  are  observable  by  means  of  the  microscope,  contract  when  they  are 
stimulated  directly  (Kiiline).  3.  Curara  paralyzes  the  extremities  of  the  motor 
nerves,  wliile  the  muscles  themselves  remain  excitable  (C/.  Bernard,  Kolliker). 
The  action  of  cold,  or  arrest  of  the  blood  supply  in  an  animal,  abolishes  the  excita- 
bility of  the  nerves,  but  not  of  the  muscles  at  the  same  time.  4.  After  section  of 
its  nerve,  a  muscle  still  remains  excitable,  even  after  the  nerves  have  undergone 
fatty  degeneration  { B rown- Si'quard ,  Bidder).  5.  Sometimes  electrical  stimuli  act 
only  upon  the  nerves  and  not  upon  the  muscle  \\.%t\{  (BrUcke).  [6.  The  fcetal 
heart  contracts  rhythmically  before  any  nervous  structures  are  discoverable  in  it.] 

[The  Action  of  Curara. — Curara,  woorali,  urari,  or  Indian  arrow  poison  of  South  America,  is 
the  inspissated  juice  of  the  Strychnos  crevauxi.  A  watery  extract  of  the  drug,  when  injected  under 
the  skin  or  into  the  blood  of  an  animal,  acts  chiefly  upon  the  motor  nerve  endings,  and  does  not 
aft'ect  the  muscular  contractility.  An  active  substance,  ciirarin,  has  been  isolated  from  it  fp.  510). 
I'oison  a  frog  by  injecting  a  few  milligrammes  into  the  dorsal  lymph  sac.  In  a  few  minutes  after 
the  poison  is  absorbed,  the  animal  ceases  to  support  itself  on  its  fore  limbs;  it  lies  flat  on  the  table, 
its  limbs  are  paralyzed,  and  so  are  the  respiratory  movements  in  the  throat.  When  completely  under 
the  action  of  the  poison,  the  frog  lies  in  any  position,  limp  and  motionless,  neither  exhibiting  vol- 
untary nor  reflex  movements.  If  the  brain  be  destroyed  and  the  skin  removed,  on  faradizing  the 
sciatic  ner\'e  no  contraction  of  the  muscles  of  the  hind  limb  occurs;  but  if  the  electrical  stimulus 
be  applied  directly  to  the  muscles,  they  contract,  thus  proving  that  curara  poisons  the  motor 
connections  and  not  the  muscles.  If  the  dose  be  not  too  large,  the  heart  still  continues  to  beat, 
and  the  vasomotor  nerves  remain  active.] 

[Methods. — fi)  This  may  be  shown  also  by  applying  the  drug  locally. 
Bernard  took  two  nerve-muscle  preparations,  put  some  solution  of  curara  into 
two  watch  glasses,  and  dipped  the  nerve  into  one  glass  and  the  muscle  into  the 
other.  The  curara  penetrated  into  both  preparations,  and  he  found,  on  stimu- 
lating the  nerve  which  had  been  steeped  in  curara,  that  its  muscle  still  contracted, 
so  that  the  curara  had  not  acted  on   the  motor  fibres ;  while  stimulation  of  the 


508 


ACTION    OF    CURARA. 


02  with  sciatic  artery  liga- 
tured. S  P,  spinal  cord  ; 
P,  poisoned,  N  P,  non- 
poisoned  leg;  M,  gastroc- 
nemius muscles,  afferent, 
efferent,  nerve  (after 
.■^utlter/ord  and  Brun- 
ton). 


Fig.  289.  nerve  of  the  other  preparation  produced  no  contraction, 

s.R      _  although   the  corresponding   muscle  contracted.     In  this 

case,    the    curara    had    penetrated    into    the    muscle    and 
affected  the  intra-muscular  nerve  endings.] 

[(2)  But  it  is  the  terminal  or  intra-muscular  portions 
of  the  nerves,  not  the  nerve  trunk,  which  are  paralyzed. 
Ligature  the  sciatic  artery,  or,  better  still,  tie  all  the  parts 
of  the  hind  limb  of  a  frog  at  the  upper  part  of  a  thigh, 
except  the  sciatic  nerve  (Fig.  2S9).  Inject  curara  into  the 
dorsal  lymph  sac.  The  poisoned  blood  will,  of  course,  cir- 
culate in  every  part  of  the  body  except  the  ligatured  limb. 
[The  shaded  parts  are  traversed  by  the  poison.]  The  animal 
can  still,  at  a  certain  stage  of  the  poisoning,  pull  up  the 
non-poisoned  limb,  while  it  cannot  move  the  poisoned  one. 
At  this  time,  although  poisoned  blood  has  circulated  in  the 
sacral  and  intra-abdominal  parts  of  the  nerves,  yet  they  are 
not  paralyzed,  so  that  the  poison  does  not  act  on  this  part 
of  the  trunk  of  the  nerve.  But  we  can  show  that  it  does 
not  act  on  any  part  of  the  extra-muscular  trunk  of  the 
nerve.  This  is  done  by  ligaturing  the  arteries  going  to 
the  gastrocnemius  muscle,  and  then  poisoning  the  animal. 
On  stimulating  the  nerve  on  the  ligatured  side,  the  gas- 
trocnemius of  that  side  contracts,  although  the  whole 
length  of  the  nerve  trunk  has  been  supplied  by  poisoned 
blood.  Therefore,  it  is  ihe  infra-muscular  terminations  oi 
the  nerves  which  are  acted  on.] 
[By  means  of  the  following  arrangement,  we  may  prove  that  the  actual  termina- 
tions or  end  plates  are  paralyzed.  Ligature  the  sciatic  artery  of  one  leg  of  a  frog, 
and  then  inject  curara  into  a  lymph  sac.  After  the  animal  is  fuUv  poisoned,  dissect 
out  the  whole  length  of  the  sciatic  nerve  in  both  legs,  leaving  all  the  muscles  below 
the  knee  joint,  then  clean  and  divide  the  femur  at  its  middle.  Pin  a  straw  flag  to 
each  limb,  and  fix  both  femora  in  a  clamp,  or  muscle  forceps,  with  the  gastroc- 
nemii  uppermost,  as  in  Fig.  290.  Place  the  two  nerves,  N,  on  Du  Bois-Reymond's 
electrodes  (Fig.  291),  attached  to  two  wires  coming  from  a  commutator,  C  (Fig. 
290).  From  two  other  binding  screws  of  the  commutator,  two  wires  pass  and  are 
made  to  pierce  the  gastrocnemii.  The  other  two  binding  screws  of  the  commu- 
tator are  connected  with  the  secondary  coil  of  a  Du  Bois-Reymond's  induction 
machine  (§  330).  The  bridge  of  the  commutator  can  be  turned  so  as  to  pass  the 
current  either  through  both  muscles  or  both  nerves — the  latter  is  the  case  in  the 
diagram  (^H).  When  both  nerves  are  stimulated,  only  the  non-poisoned  leg  (N  P) 
contracts.  Reverse  the  commutator,  and  pass  the  current  through  both  muscles, 
when  both  contract.'] 

[Rosenthal's  Modification. — Pull  the  secondary  coil  far  away  from  the  primary,  and  pass  the 
current  through  both  muscles.  Gradually  approximate  the  secondary  to  the  primary  coil,  and  in 
doing  so  it  will  be  found  that  the  non-poisoned  leg  contracts  first,  and  on  continuing  to  push  up  the 
secondary  coil  botii  limbs  contract.  Thus  the  poisoned  limb  does  not  respond  to  so  feeble  a  faradic 
stimulus  as  the  non  poisoned  one,  a  result  which  is  not  due  to  the  action  of  the  curara  on  the 
excitability  of  the  muscle.  The  non-poisoned  limb  responds  to  a  feebler  stimulus  because  its  motor 
nerve  terminations  are  not  paralyzed,  while  the  poisoned  leg  does  not  do  so,  because  the  motor  ter- 
minations are  paralyzed.  A  feebler  induced  shock  suffices  to  cause  a  muscle  to  contract  when  it  is 
applied  to  the  nerve  than  when  it  is  applied  to  the  muscle  itself  directly.  In  large  doses,  curara 
also  affects  the  spinal  cord.] 

The  whole  question  of  "  specific  muscular  excitability  "  has  entered  upon  a  new  phase, 
owing  to  the  researches  of  Gerlach  on  the  terminations  of  motor  nerves  in  muscle.  Since  it  has 
been  shown  that  a  nerve  fibre,  after  penetrating  the  sarcolemma,  breaks  up  into  inter- fibrillar 
threads,  which  come  into  direct  relation  with  the  sarcous  substance,  we  can  scarcely  speak  of  an 
isolated  stimulation  of  a  muscle,  for  all  stimuli  which  are  applied  to  a  muscle  must  at  the  same  time 
act  on  the  iTerve,  for  the  muscle  is  the  proper  end  organ  of  a  motor  nerve. 


MUSCULAR   AND    CHEMICAL   STIMULI    OF    MUSCLE. 


509 


Neuro- Muscular  Cells. — Even  in  the  lower  animals,  e.^..  Hydra  [Alemenlieig),  and  Medusa 
(Eimer)  there  are  uni-cellular  structures  caWeA"  nc!iro-mi(sciiiar  cel/s"  in  which  the  nervous  and 
muscular  substances  are  represented  in  the  same  cell.  [The  outer  part  of  these  cells  is  adapted  for 
the  action  of  stimuli,  and  corresponds  to  the  nervous  receptive  organ,  while  the  inner  deeper  part  is 
contractile,  and  is  the  representative  of  the  muscular  part.] 

Muscular  Stimuli. — Various  stimuli  cause  a  muscle  to  contract,  either  by  act- 
ing upon  its  motor  nerve  (indirect),  or  upon  the  muscular  substance  itself 
(direct)  (j;  324). 

1.  Under  ordinary  circumstances,  the  normal  stimulus  causing  a  muscle  to 
contract  is  the  nerve  impulse  which  passes  along  a  curve,  but  its  exact  nature  is 
unknown,  e.g.,  in  vokmtary  movements,  automatic  motor  movements,  and  reflex 
acts. 

2.  Chemical  Stimuli. — \\\  chemical  substances,  which  alter  the  chemical 
composition  of  a  muscle  with  sufficient  rapidity,  act  as  muscular  stimuli.  Accord- 
ing to  Kiihne,  mineral  acids  (HCl  o.i)  per  cent.,  acetic  and  oxalic  acids,  the 


Fig.  290. 


Scheme  of  the  curara  experiment.  B,batler>' : 
I,  primary;  II.  secondary  spiral;  N, 
nerves;  F,  clamp;  N  P,  ncn-poisoned 
leg;  P.  poisoned  leg  ;  C, commutator;  K, 
key  (after  Rutlu-r/ord). 


Du  Bois-Reymond's  platinum  electrode 
over  the  two  pieces  of  platinum,  P, 
B,  universal  joint;  V,  support. 


salts  of  iron,  zinc,  copper,  silver  and  lead,  bile  (Budge),  all  act  in  weak  solutions 
as  muscular  stimuli ;  while  they  act  upon  the  motor  nerve  only  when  they  are  more 
concentrated.  Lactic  acid  and  glycerin,  when  concentrated,  excite  only  (?)  the 
nerve ;  when  dilute,  only  the  muscle.  Neutral  alkaline  salts  act  equally  upon 
nerve  and  muscle  ;  alcohol  and  ether  act  on  both  very  feebly.  When  water  is 
injected  into  the  blood  vessels,  it  causes  fibrillar  muscular  contractions  {v.  Wittich'), 
while  a  0.6  per  cent,  solution  of  NaCl  may  be  passed  through  a  muscle  for  da}s 
without  causing  contraction  i^Kolliker,  O.  Nasse).  .4cids,  alkalies  and  extract  of 
flesh  diminish  the  muscular  excitability,  while  the  muscular  stimuli,  in  small  doses, 
increase  it  (Ranke^.  Gases  and  vapors  stimulate  muscle ;  they  cause  either  a 
simple  contraction  (e.g.,  HCl),  or  at  once  permanent  contraction  or  con- 
tracture (e.g.,  CI).  Long  exposure  to  the  gas  causes  rigidity.  The  vapor  of 
bisulphide  of  carbon  stimulates  only  the  nei-oes,  while  most  vapors  (e.g.,  HCl) 
kill  without  exciting  them  {Kiihne  ami Jani). 


510    THERMAL,   MECHANICAL   AND   ELECTRICAL   STIMULI    OF    MUSCLE. 

Method. — In  making  experiments  upon  the  chemical  stimulation  of  muscle,  it  is  inadvisable  to 
dip  the  transverse  section  of  the  muscle  into  the  solution  of  the  chemical  reagent  {/iering).  The 
chemical  stimulus  ought  to  be  applied  in  solution  to  a  limited  portion  of  the  uninjured  surface  of 
the  muscle ;  after  a  few  seconds,  we  obtain  a  contraction  or  fibrillar  twitchings  of  the  superficial 
muscular  layers  \hering). 

[Rhythmical  Contraction. — While  rhythmical  contractions  are  very  marked  in  smooth  muscle 
(especially  if  it  is  stretched  or  subjected  to  considerable  internal  pressure,  as  in  the  hollow  viscera), 
eg.,  the  intestine,  uterus,  ureter,  blood  vessels,  and  also  in  the  striped  but  involuntary  cardiac  mus- 
culature (j,  58),  they  are  not,  as  a  rule,  very  common  in  striped  voluntary  muscle.  Chemical 
stimuli  are  particularly  effective  in  producing  them,]  If  the  sartoriusof  a  curarized  frog  be  dipped 
into  a  solution  composed  of  5  grms.  NaCl,  2  grms.  alkaline  sodium  phosphate,  and  0.5  grm.  sodium 
carbonate  in  i  litre  of  water,  at  io°  C,  the  muscle  contracts  rhythmically,  and  may  do  so  for 
several  days  [especially  with  a  low  temperature]  (Bieihrmann).  This  recalls  the  rhythmical  con- 
traction of  the  heart.  [KUhne  found  a  similar  result.  The  rhythm  is  arrested  by  lactic  acid  and 
restored  by  an  alkalme  solution  of  NaCl.]  Rhythmical  movements  may  also  be  induced  in  the 
sartorius  (frog),  by  the  combined  action  of  a  dilute  solution  of  sodic  carbonate  and  an  ascending 
constant  electrical  current.     Compare  also  the  action  of  a  constant  current  on  the  heart  (J  58). 

3.  Thermal  Stimuli. — If  an  excised  frog's  muscle  be  rapidly  heated  toward 
28"'  C,  a  gradually  increasing  contraction  occurs,  which,  at  30°  C,  is  more  pro- 
nounced, reaching  its  rnaximum  at  45°  C.  (^EckharJ,  Schiimlcwitsch).  If  the 
temperature  be  raised,  "heat  stiffening"  rapidly  ensues.  The  smooth  muscles 
of  warm-blooded  animals  also  contract  when  they  are  warmed,  but  those  of  cold- 
blooded animals  are  elongated  by  heat  (Griinhagen,  Samkowy).  If  a  frog's 
muscle  be  cooled  to  0°,  it  is  very  excitable  to  mechanical  stimuli  (^Griinhagen)  ; 
it  is  even  excited  by  a  temperature  under  0°  {Eckhard). 

CI.  Bernard  observed  that  the  muscles  of  animals,  artificially  cooled  (|  225),  remained  excitable 
many  hours  after  death.  Heat  causes  the  excitability  to  disappear  rapidly,  but  increases  it  tempo- 
rarily. 

4.  Mechanical  Stimuli. — Every  kind  of  sudden  mechanical  stimulus,  pro- 
vided it  be  applied  with  sufficient  rapidity  to  a  muscle  (and  also  to  a  nerve), 
causes  a  contraction.  If  stimuli  of  sufficient  intensity  be  repeated  with  sufficient 
rapidity,  tetanus  is  produced.  Strong  local  stimulation  causes  a  weal-like,  long- 
continued  contraction  at  the  part  stimulated  (§  297,  3,  a).  Moderate  tension  of 
a  muscle  increases  its  excitability. 

5.  Electrical  Stimuli  will  be  referred  to  when  treating  of  the  stimulation  of 
nerve  (§  324). 

Other  Actions  of  Curara. — When  injected  into  the  blood  or  subcutaneously,  it  causes  at  first 
paralysis  of  the  intra-muscular  enJs  of  tlie  motor  nerves  (p.  507),  while  the  muscles  themselves  re- 
main excitable  ;  the  sensory  nerves,  the  central  nervous  system,  viscera,  heart,  intestine,  and  the 
blood  vessels  are  not  affected  at  first  [CI.  Bernard,  A'Slliier).  [If  the  skin  be  stimulated,  the  frog 
will  still  pull  up  the  ligatured  leg  reflexly,  although  the  other  leg  will  remain  quiescent;  this  shows 
that  the  sensory  nerve  and  nerve  centres  are  still  intact ;  but  when  the  action  of  the  drug  is  fully 
developed,  no  amount  of  stimulation  of  the  skin  or  the  posterior  roots  of  the  nerves  will  give  rise 
to  a  reflex  act.  although  the  motor  nerve  of  the  ligatured  limb  is  known  to  be  excitable,  hence  it  is 
probable  that  the  nerve  centres  in  the  cord  themselves  are  uliimatcly  affected.  If  the  dose  be  very 
large,  the  he.art  and  blood  vessels  may  be  affected.]  In  warm-blooded  animals,  death  takes 
place  by  asphyxia,  owing  to  paralysis  of  the  diaphragm,  but  of  course  there  are  no  spasms.  In 
frogs,  where  the  skin  is  the  most  important  respiratory  organ,  if  a  suitable  dose  be  injected  under 
the  skin,  the  animal  may  remain  motionless  for  days  and  yet  recover,  the  poison  being  eliminated  by 
the  urine  [JCii/ine,  Bidder').  If  the  dose  be  larger,  the  inhibitory  fibres  of  the  vagus  may  be  para- 
lyzed. In  electrical  fishes,  the  sensory  nerves  concerned  with  the  electrical  discharge  are  paralyzed 
{^Alarey).  In  frogs,  the  lymph  hearts  are  paralyzed.  A  dose  sufficient  to  kill  a  frog,  when  injected 
under  its  skin,  will  do  so  if  administered  by  the  mouth,  because  the  poison  seems  to  be  eliminated  as 
rapidly  by  the  kidneys  as  it  is  absorbed  from  the  gastric  mucous  membrane.  For  the  same  reason 
the  flesh  of  an  animal  killed  by  curara  is  not  poisonous  when  eaten.  If,  however,  the  ureters 
be  tied,  the  poison  collects  in  the  blood,  and  poisoning  takes  place  (  L.  Hermann).  [In  this  case 
the  mammal  may  exhibit  convulsions.  Why  ?  The  action  of  curara  is  to  paralyze,  and  it  para- 
lyzes the  respiratory  nerves,  so  that  asphyxia  is  produced  from  the  venosity  of  the  blood.  It  affects 
the  respiratory  nerve  endings  before  those  in  the  muscles  generally,  so  that  w^hen  the  venous  blood 
stimulates  the  nerve  centres  the  partially  affected  muscles  respond  by  convulsions.  In  this  way, 
other  narcotics  may  excite  convulsions  indirectly  by  inducing  a  venous  condition  of  the  blood,  while 
the  motor  centres,  nerves,  and  muscles  are  still  unaffected.]     Large  doses,  however,  poison  unin- 


TOTAL   AND    PARTIAL    MUSCULAR   CONTRACTION.  511 

jured  animals  even  when  given  by  the  mouth.  The  nerves  [Funke)  and  muscles  ( I'a/eittin)  of 
poisoned  animals  exhibit  considerable  electro  motive  force.  [For  the  effect  of  curaia  on  lymph 
formation  (|  igg,  6).] 

Atropin  appears  to  be  a  specific  poison  for  smooth  muscular  tissue,  but  different  muscles  are 
differently  atlecttd  [Szpi/niann,  Luchsin^er).  [This  is  oouUful.  A  small  quantity  of  atropin 
seems  to  aft'ect  the  motor  nerves  of  smooth  muscle  in  the  same  way  that  curara  does  those  of  striped 
muscle;  we  must  remember,  however,  that  there  are  no  end  plates  proper  in  the  former,  so  that  the 
link  between  the  nerve  tibrils  and  the  contractile  substance  is  probably  difterent  in  the  two  ca^es.  It 
is  well  known  that  the  amount  of  striped  and  smooth  muscle  varies  in  the  resophagus  in  different 
animals.  Szpilmann  and  Luchs.nger  find  that  after  the  action  of  atropin,  stimulation  of  the  periph- 
eral end  of  the  vagus  will  stdl  cause  contraction  of  the  striped  muscular  fibres  in  the  oes.,phagus, 
but  not  of  the  smooth  fibres,  although  1  oth  forms  of  muscular  tissue  respond  to  direct  stimulation.] 

Excitability  after  Section  of  the  Motor  Nerves. — After  section  of  the  motor  nerve  of  a 
muscle,  the  cxcitabihtv  undergoes  remarkable  changes  ;  after  three  to  four  days  the  excitability  of 
the  paralyzed  muscle  is  diminished,  both  for  direct  and  indirect  (/.  e.,  through  the  nerve)  stimuli ; 
this  condition  is  followed  by  a  stage,  during  which  a  constant  current  is  more  active  than  normal, 
while  induction  currents  are  scarcely  or  not  at  all  effective  (|  339,  I).  The  excitability  for  mechan- 
ical stimuli  is  also  increased.  The  increased  excitability  occurs  until  about  the  seventh  week;  it 
gradually  diminishes  until  it  is  abolished  toward  the  sixth  to  the  seventh  month.  Fatty  degenera- 
tion begins  in  the  second  week  after  section  of  the  motor  nerve,  and  goes  on  until  there  is  complete 
muscular  atrophy.  Immediately  after  section  of  the  sciatic  nerve,  bchmulewitsch  found  that  the 
excitability  of  the  muscles  supplied  by  it  was  increased. 

297.  CHANGES  IN  A  MUSCLE  DURING  CONTRACTION.— 
I.  Macroscopic  Phenomena. — i.  When  a  muscle  contracts,  it  becoiiies 
shorter  and  at  the  same  time  thicker. 

The  degree  of  contraction,  which  in  very  excitable  frogs  may  be  65  lo  85  per  cent.  (72  per 
cent,  mean)  of  the  total  length  of  the  muscle,  depends  upon  various  conditions:  (a)  Up  to  a  cer- 
tain point,  increasing  the  strength  of  the  stimulus  causes  a  greater  degree  of  contraction ;  (b) 
as  the  muscular  fatigue  increases,  i.  c. ,  after  continued  vigorous  exertion,  ihe  stimulus  remaining 
the  same,  the  extent  ol  contraction  is  diminished  ;  (c;  the  temperature  of  the  surroundings  has  a 
certain  effect.  The  extent  of  the  contraction  is  increased  in  a  irog's  muscle — the  strength  of  stim- 
ulus and  degree  of  fatigue  remaining  the  same — when  it  is  heated  to  33°  C.  If  the  temperature  be 
increased  al)ove  this  point,  the  degree  of  contraction  is  diminished  [Sc/imiilc-witsch). 

2.  The  volume  of  a  contracted  inuscle  is  slightly  diminished  (Swammeniam, 
f  1680).  Hence,  the  specific  gravity  of  a  contracted  muscle  is  slightly  in- 
creased, the  ratio  to  the  non-contracted  muscle  being  1062  :  1061  {^Valentiii)  ; 
the  diminution  in  volume  is,  however,  only  y^y^. 

Methods. — («)  Ernian  placed  portions  of  the  body  of  a  live  eel  in  a  glass  vessel  filled  with  an 
indifferent  fluid.  A  narrow  lube  communicated  with  the  glass  ves.sel,  and  the  fluid  rose  in  the  tube 
to  a  certain  level.  As  soon  as  the  muscles  of  the  eel  were  caused  to  contr,act,  the  fluid  in  the  index 
tube  sank,  [b)  Laudois  demonstrates  the  decrease  in  volume  by  means  of  a  manometric  flame. 
The  cylindrical  vessel  containing  the  muscle  is  provided  with  two  electrodes  fi.xed  into  it  in  an  air- 
tight manner.  The  interior  of  the  vessel  communicates  with  the  gas  supply,  while  there  is  a  small 
narrow  exit  tube  for  the  gas,  which  is  lighted.  Every  time  the  muscle  contracts  the  flame  dimin- 
ishes.    The  same  experiment  may  be  performed  with  a  contracting  heart. 

3.  Total  and  Partial  Contraction. — Xormally,  all  stimuli  applied  to  a  muscle 
or  Its  motor  nerve  cause  contraction  in  all  its  muscular  fibres.  Thus,  the  muscle 
conducts  the  state  of  e.xcitement  to  all  its  parts.  Under  certain  circumstances, 
however,  this  is  not  the  case,  viz.:  (a)  when  the  muscle  is  greatly  fatigued,  or 
when  it  is  about  to  die,  a  violent  mechanical  stimulus,  as  a  vigorous  tap  with  the 
finger  or  a  percussion  hammer  (and  also  chemical  or  electrical  stimuli !,  cause  a 
localized  contraction  of  the  muscular  fibres.  This  is  Schiff's  "  idio-muscular 
contraction."  The  same  phenomenon  is  e.xhibited  by  the  muscles  of  a  healthy 
man,  when  the  blunt  edge  of  an  instrument  is  drawn  transversely  over  the  direc- 
tion of  the  muscular  fibres  (J//V/;//;(7//jv/-,  Auerbach).  {I/')  Under  certain  as  yet  but 
imperfectly  unknown  conditions,  a  muscle  exhibits  so-called  fibrillar  contrac- 
tions, i.e.,  short  contractions  occur  alternately  in  different  bundles  of  muscular 
fibres.  This  is  the  case  in  the  muscles  of  the  tongue,  after  section  of  the  hypo- 
glossal nerve  {Schiff) ;  and  in  the  muscles  of  the  face,  after  section  of  the  facial 
nerve. 


512 


MICROSCOPIC    PHENOMENA    OF    MUSCULAR    CONTRACTION. 


[In  some  phthisical  patients  there  is  marked  muscular  excitabilty,  so  that  if  the  pectoral  muscle 
be  percussed,  a  local  contraction  — idio-niuscular — occurs,  either  confined  to  the  spot,  or  two  waves 
may  proceed  outward  and  return  to  the  spot  struck.] 

Cause  of  Fibrillar  Contraction. — According  to  Bleuler  and  Lehmann,  section  of  the  hypo- 
glossal nerve  in  rabbits  is  followed  by  fibrillar  contractions  after  sixty  to  eighty  hours ;  these  con- 
tractions may  continue  for  six  m  jnths,  even  when  the  divided  nerve  has  healed  and  is  stimulated  above 
the  cicatrix  so  as  to  produce  movements  in  the  corresponding  half  of  the  tongue.  Stimulation  of 
the  lingual  ner\'e  increases  the  fibrillar  contractions  or  arrests  them.  This  nerve  contains  vaso- 
dilator fibres  derived  from  the  chorda  tympani.  .Schiff  is  of  opinion  that  the  increased  blood 
stream  through  the  organ  is  the  cause  of  the  contractions.  Sig.  Mayer  found  that,  by  compressing 
the  carotids  and  subclavian,  and  again  removing  the  pressure,  so  as  to  permit  free  circulation,  the 
muscles  of  the  face  contracted.  Section  of  the  motor  nerves  of  the  face  did  not  abolish  the  phe- 
nomenon, but  compression  of  the  arteries  did.  The  cause  of  the  phenomenon,  therefore,  seems  to 
lie  within  the  muscles  themselves.  This  phenomenon  may  be  compared  to  the  paralytic  secretion 
of  saliva,  and  pancreatic  juice  which  follows  section  of  the  nerves  going  to  these  glands  (pp.  239, 
284).  Similar  fibrillar  contractions  occur  in  man  under  pathological  conditions,  but  they  may  also 
occur  without  any  signs  of  pathological  disturbance.  [Fibrillar  contractions,  due  to  a  central  cause, 
occur  in  monkeys  after  excision  of  the  thyroid  gland  (  K  jYcri/cv,  ?  103,  III).]  [Some  drugs 
cause  fibrillar  muscular  contractions,  e.  g.,  aconitin,  guanidin,  nicotin,  pilocarpin,  but  physostigmin 
produces  them  in  warm-blooded  animals  (not  in  frogs).  According  to  Brunton,  these  drugs  prob- 
ably act  by  irritating  the  motor  nerve  endings,  as  the  contractions  are  gradually  abolished  by 
curara.] 

Fig.  292. 


licroscopic  appearances  during  a  muscular  contraction  in  the  individual  elements  of  the  librillae. 
Engelmann) ;  4, 5  (after  Mcrkel). 


II.  Microscopic  Phenomena. — i.  Single  muscular yf/w/fe  exhibit  the  same 
phenomena  as  an  entire  muscle,  in  that  they  contract  and  become  thicker.  2. 
There  is  great  difficulty  in  observing  the  changes  that  occur  in  the  individual 
parts  of  a  muscular  fibre  during  the  act  of  contraction.  This  much  is  certain, 
that  the  muscular  elements  become  shorter  and  broader  during  contraction.  Thus, 
it  is  evident  that  the  transverse  stride  must  appear  to  approach  nearer  to  each  other 
{Bowman,  1840).  3.  There  is  great  difference  of  opinion  as  to  the  behavior  of 
the  doubly-refractive  (anisotropous)  and  the  singly-refractive  media. 

Fig.  292,  I,  on  the  left,  represents,  according  to  Engelmann,  a  passive  muscular  element — from 
£■  to  (?is  the  doubly-refractive  contractile  substance,  with  the  median  disk,  <?,  b,  in  it;  /;  and  g  are 
the  lateral  disks.  Besides  these,  in  each  of  the  singly-refractive  disks  there  is  a  clear  disk — "  sec- 
ondary disk  " — -f  and  c,  which  is  only  slightly  doubly  refractive.  This  occurs  only  in  the  muscles 
of  insects.  Fig.  I,  on  the  right,  shows  the  same  element  in  polarized  light,  whereby  the  middle 
area  of  the  element,  as  far  as  the  contractile  substance  proper  extends,  is,  owing  to  its  double  refrac- 
tion, bright ;  while  the  other  part  of  the  muscular  element,  owing  to  its  being  singly  refractive,  is 
black.  Fig.  292,  2,  is  the  transition  stage,  and  3  the  proper  stage  of  contraction  of  the  muscular 
element.  In  both  cases  the  figures  on  the  left  are  viewed  in  ordinary  light,  and  on  the  right,  in 
polarized  light. 

Engelmann's  View. — .According  to  Engelmann,  during  contraction  (Fig.  292,  3),  the  singly- 
refractive  disk  becomes,  as  a  whole,  more  refractive,  the  doubly  refractive  less  so.     Consequently, 


MUSCULAR    CONTRACTION. 


513 


a  fibre  at  a  certain  degree  of  contraction  (2),  when  viewed  in  ordinary  light,  may  appear  homoge- 
neous and  but  slightly  striped  transversely  =  //le  homogeneous  and  transition  stage.  During  a  greater 
degree  of  contraction  (3),  very  dark  transverse  stripes  reappear,  corresponding  to  the  singly-refrac- 
tive disks.  At  every  stage  of  the  contraction,  as  well  as  in  the  transition  stage,  the  singly-  and 
doubly-refractive  disks  are  sharply  defined,  and  are  recognized  by  the  polariscope  as  regular  alter- 
nating layers  (in  1,2  and  3  on  the  right).  These  do  not  change  places  (luring  the  contraction.  The 
height  of  both  di^ks  is  diminished  during  contraction,  but  the  singly-refractive  do  so  more  rapidly  than 
the  doubly-refractive  disks.  The  total  volume  of  each  element  does  not  undergo  any  appreciable 
alteration  in  volume  during  the  contraction.  Hence,  the  doubly-refractive  disks  increase  in  volume 
at  the  expense  of  the  singly  refractive.  From  this  it  is  concluded  that,  during  the  contraction,  fluid 
passes  from  the  singly-refractive  into  the  doubly-refractive  disks;  the  former  shrink,  the  latter  swell. 

Merkel's  view  is  partially  different.  In  Fig.  292,  4,  are  two  muscular  elements  at  rest;  in  (5), 
two  in  a  state  of  contraction,  after  Merkel.  The  gray  punctuated  areas  are  the  doubly-refractive 
substance,  (■,  the  median  disk.  According  to  Merkel,  during  contraction  the  dark  substance  lying 
in  the  middle  of  the  element  changes  its  position — either  in  part  or  as  a  whole ;  it  leaves  the  middle 
of  the  element  (the  two  surfaces  of  Hensen's  median  disks,  4,  c),  and  places  itself  at  the  lateral 
disks,  5,  at  e  and  </,  while  the  clear  substance  leaves  the  lateral  disks,  4,  e  and  </,  and  applies  itself 
to  both  surfaces  of  the  median  disk,  5,  c.  The  clear  substance  of  the  isotropous  disks  is  fluid,  and 
plays  a  more  passive  role ;  during  contraction,  it  is  in  part  absorbed  by  the  dark  substance  which 
thus  swells  up.  This  mutual  e.'ichange  of  place  of  the  substances  is  accompanied  by  an  interme- 
diate "stage  of  dissolution,"  in  which  the  whole  contents  of  the  element  appear  equally  homoge- 
neous [Montgomery);  in  which,  therefore,  the  fluid,  singly-refractive  substance  has  uniformly  pene- 
trated the  doubly-refractive  substance.     M  this  moment  only  the  lateral  disks  are  still  visible. 

[If  a  living  portion  of  an  insect's  muscle  be  examined  in  its  own  juice,  contraction  waves  may  be 
seen  to  pass  over  the  fibres.  When  a  contraction  wave  passes  over  part  of  the  fibres,  the  disks 
become  s/iorler  iinA  broader;  at  the  same  time,  in  the  fully-contracted  part,  the  dim  disk  appears 
lighter  than  the  centre  of  the  light  disk.  There  is  said  to  be  a  "  reversal  of  the  stripes  "  from 
what  obtains  in  a  passive  muscle.  Before  this  stage  is  reached  there  is  an  intermediate  stage,  where 
the  two  bands  are  almost  uniform  in  appearance.] 

Methods. — These  phenomena  are  best  observed  by  "  fixing"  the  difierent  stages  of  rest  or  con- 
traction, by  suddenly  plunging  the  muscular  fibrill^  of  insect's  muscles  into  alcohol  or  osmic  acid, 
which  coagulates  the  muscle  substance.  The  actual  contraction  may  be  observed  under  the  micro- 
scope in  the  transparent  parts  of  the  larvne  of  insects. 

Spectrum. — A  thin  muscle,  eg  ,  the  sartorius  of  the  frog,  when  placed  directly  behind  a  narrow 
slit  running  at  right  angles  to  the  course  of  the  fibres,  yields  a  diffraction  spectrum.  When  the 
muscle  contracts,  as  by  mechanical  stimulation,  the  spectrum  broadens — a  proof  that  the  interspaces 
of  the  transverse  stripes  become  narrower  [Ranvier). 

298.    MUSCULAR    CONTRACTION.— Myography— Simple  Con- 
traction— Tetanus. — Methods. — In  order  to  determine  the  duration  of  each 
phase  of  a  muscular  contraction,  myo- 
graphs of  various  forms  are  used. 

V.  Helmholtz's  Myograph. — Helniholtz 
constructed  a  myograph  of  the  form  shown  in 
Fig.  293.  A  muscle,  M — say  the  gastroc- 
nemius of  a  frog  attached  to  the  femur — is 
fixed  by  the  femur  in  a  clamp,  K,  the  lower 
free  end  of  the  muscle  being  attached  to  a 
movable  lever  carrying  a  scale  pan  and 
weight,  W,  the  weight  being  varied  at 
pleasure.  When  the  muscle  contracts,  neces- 
sarily it  must  raise  the  lever.  To  the  free 
end  of  the  lever  is  attached  a  movable  style, 
F,  capable  of  adjustment,  and  which,  when 
properly  adjusted,  inscribes  its  movements 
on  a  revolving  cylinder  caused  to  rotate  at 
a  uniform  rate  by  means  of  clockwork  (Fig. 
98).  The  cylinder  is  covered  with  enameled 
paper  smoked  in  the  flame  of  a  turpentine 
lamp.  When  the  muscle  contracts,  it  inscribes 
a  curve — the  "  muscle  curve,"  or  "myo- 
gram." The  abscissa  indicates  the  dura- 
tion of  the  contraction,  but  of  course  the  rate  at 
which  the  cylinder  is  moving  must  be  known.  Sch 
The  ordinates  rejiresent  the  height  of  con-  for"the  \. 
traction  at  any  particular  part  of  the  curve.  for  the  le 


of  V.  Helmholtz's  myogr; 
IP,   K;   F.  writing  style: 
W,  scale  pan 


514 


PENDULUM    MYOGRAPH. 


The  muscle  curve  may  be  mscribed  upon  a  smoked  glass  plate  attached  to  one  limb  of  a  vibrating 
tuning  fork  (Fig.  91).  Such  a  curve  registers  the  lime  units  in  all  its  parts.  Suppose  each 
vibration  of  the  tuning  fork  =  0.01613  second,  then  the  duration  of  any  part  of  such  a  curve  is 
obtained  by  counting  the  number  of  \'ibralions  and  multiplying  by  0.01613  second. 

[Pendulum  Myograph. — A.  Kick  invented  this  instrument.  In  its  improved  form  by  v.  Helm, 
holtz  (Fig.  294),  it  is  shown  both  from  the  front  and  the  side.  A  board  fixed  to  the  wall  carries  a 
heavy  iron  pendulum,  P,  whose  axis,  A,  A,  moves  on  friction  rollers.  At  the  lower  swinging  end 
are  two  glass  plates,  G  and  G',  fixed  to  a  bearer,  T.  The  plates  can  be  adjusted  by  means  of  the 
screw,  s,  so  that  several  curves  can  be  written  one  above  the  other.     The  plate  G',  on  the  posterior 


surface,  is  merely  a  compensator,  so  that  when  G  is  elevated  G'  is  lowered,  and  thus  the  duration 
of  the  oscillation  is  not  altered.  The  spring  catches,  H,  H,  which  can  be  turned  inward  or  out- 
ward, are  used  to  fix  the  pendulum  by  the  teeth,  a,  a,  when  it  is  drawn  to  one  side.  The  pendu- 
lum is  drawn  to  one  side  and  fixed,  11,  in  H,  so  that  when  H  is  pulled  down,  it  is  liberated  and 
swings  to  the  other  side,  where  it  is  caught  by  H  at  the  opposite  side.  In  the  improved  form,  the 
catches,  H,  are  made  to  slide  along  a  rod  like  the  arc  of  a  circle,  so  that  the  length  of  the  swing  can 
be  varied.  .'\s  the  pendulum  swings  from  the  one  side  to  the  other,  the  projecting  points,  a,  a,  knock 
over  the  contact  key,  /',  and  the  current  is  opened  and  a  shock  transmitted  to  the  muscle.  The 
writing  lever  to  which  the  muscle  is  attached  is  usually  a  heavy  one,  and  a  style  writes  upon  the 


CONTRACTION    CURVE    OF    HUMAN    MUSCLE. 


515 


Fig, 


smoked  surface  of  the  glass.     Of  course,  when  the  pendulum  swings,  it  moves  with  unequal  velo- 
cities at  different  parts  of  its  course.] 

[When  using  the  pendulum  myograph  to  study  a  muscular  contraction,  arrange  it  as  in  Fig.  295. 
The  frog's  muscle  is  attached  to  a  writing  lever,  which  is  very  like  the  lever  in  Fig.  293,  while  the 
style  inscribes  its  movements  on  the  blackened  plate.] 

[The  pendulum  is  fixed  in  the  catch,  C,  as  shown  in  the  figure  ;  the  key,  K',  is  closed  and  placed 
in  the  primary  circuit,  while  two  wires  from  the  secondary  coil  of  an  induction  machine  are  attached 
to  the  muscle.  When  the  pendulum  swings,  the  projecting  tooth,  S,  knocks  over  the  contact  at  K', 
and  breaks  the  primary  circuit,  when  a  shock  is  instantly  transmitted  through  the  muscle.  Before 
stimulating,  allow  the  pendulum  to  swing  to  obtain  an  abscissa.  The  time  is  recorded  by  a  vibrating 
tuning  fork,  of  known  rate  of  vibration,  connected  with  a  Depr^'s  electric  chronograph.  Depri's 
chronograph  is  merely  a  small  electro-magnet  with  a  fine  writing  style  attached  to  the  magnet,  which 
vibrates  when  it  is  introduced  in  an  electrical  circuit,  in  which  is  placed  a  vibrating  tuning  fork. 
The  signal  vibrates  just  as  often  as  the  tuning  fork.] 

[Spring  Myograph. — This  is  used  by  Du  Bois-Reymond  chiefly  for  demonstrations  (Fig.  296). 
It  consists  of  a  glass  plate  fixed  in  a  frame,  and 
moving  on  two  polished  steel  wires,  stretched 
between  the  supports  A  and  B.  At  ii  is  a  spring, 
which, when  it  is  compressed  between  the  upright, 
B,  and  the  knot,  b,  drives  the  glass  plate  from  B 
to  A.  As  the  plate  moves  from  one  side  to  the 
other,  a  small  tooth,  </,  on  its  under  surface, 
opens  the  key.  A,  and  thus  a  shock  is  transmitted 
to  the  muscle.  The  arrangement  otherwise  is 
the  same  as  for  the  pendulum  myograph.  The 
smoked  glass  plate  is  liberated  by  the  projecting 
finger  plate  attached  to  the  upright.  A.] 

[Simple  Myograph  of  Marey. — The  gas- 
trocnemius is  attached  to  a  horizontal  lever, 
which  inscribes  its  movements  on  a  revolving 
cylinder.  This  form  of  myograph,  when  pro- 
vided with  two  levers,  is  very  useful  for  compar- 
ing the  action  of  a  poison  on  one  limb,  the  other 
being  unpoisoned.] 

[Pfliiger's  stationary  form,  which  is  simply 
a  Helmholtz's  myograph  (Fig.  293)  arranged  to 
record  its  movements  on  a  stationary  glass  plate, 
so  that  the  muscle  merely  makes  a  vertical  line 
or  ordinate  instead  of  a  curve ;  it  thus  merely 
indicates  the  height  or  e.xtent  of  the  contraction, 
not  its  duration.] 

A  rapidly  rotating  disk  was  used  by  Valentin 
and  Rosenthal  for  registering  the  muscle  curve, 
while  Harless  used  a  plate  which  was  allowed  to 
fall  rapidly,  the  so  called  "Fall  myograph." 
In  all  these  experiments  it  is  necessary  to  indicate  at  the  same  time  the  moment  of  stimulation. 

Contraction  Curve  of  Human  Muscle.— In  man,  another  principle  is 
adopted,  viz.,  to  measure  the  increase  in  thickness  during  the  contraction,  either 
by  means  of  a  lever  or  a  compressible  tambour  {Mcirey),  such  as  is  used  in  Brond- 
geest's  pansphygmograph  (Fig.  72).  \T\\^  ihickening  oi  the  adductor  muscles  of 
the  thumb  may  be  registered  by  means  of  Marey's  pince  myographique.] 

I.  Simple  Contraction. — If  a  stn^^/e  shock  or  stimulus  of  tnoincutarv  duration 
be  applied  to  a  muscle,  a  "  simple  muscular  contraction  "  [or  shortly,  a  con- 
traction, a  twitch  {BurdoH  Sanderson)]  \?,  the  result, /.«".,  the  muscle  rapidly 
shortens  and  quickly  returns  again  to  its  original  relaxed  condition. 

Myogram  or  Muscle  Curve. — Suppose  a  single  stimulus  be  applied  to  a 
muscle  attached  to  a  light  writing  lever,  which  is  not  "  overweighted  "  with  any 
weight  attached  to  it,  then,  when  the  muscle  contracts,  the  following  events  take 
place  :  — 

[(i)  A  period  or  stage  of  latent  stimulation  (Fig.  29S). 

(2)  A  period  of  increasing  energy  or  contraction. 

(3)  A  period  of  decreasing  energy  or  more  rapid  relaxation. 

(4)  A  period  of  slow  relaxation,  or  the  elastic  after-vibration.] 


Scheme  of  the  arrangement  of  the  pendulum  r 
B,  battery:  1,  primary,  11,  secondary  spi 
induction  machine  :  S,  tooth  ;  K'.  kej 
catches  ;  K'  in  the  corner,  scheme  of  K' 


516 


LATENT    PERIOD    OF    A    MUSCLE    CURVE. 


The  muscle  curve  proper  is  composed  of  2,  3,  and  4,  and  its  characters  are 
shown  in  Figs.  297,  298. 

I.  The  latent  period  (Fig.  297,  i?,  b)  consists  in  this,  that  the  muscle  does 
not  begin  to  contract  precisely  at  the  moment  the  stimulus  is  applied  to  it,  but  the 
contraction  occurs  somewhat  /ater,  i.  ,-.,  a  short  but  measurable  interval  elapses 
between  the  application  of  a  momentary  stimulus  and  the  contraction  (v.  Helm- 
holtz).     If  the  entire  muscle  be  stimulated  by  a  momentary  stimulus,  e.g.,  a  single 


opening  induction  shock,  the  duration  of  the  latent  period  is  about  o.oi   second. 
In  smooth  muscle,  the  latent  period  may  last  for  several  seconds. 

[Although  no  change  be  visible  in  a  muscle  during  the  latent  period,  neverthe- 
less we  have  proof  that  some  change  does  take  place  within  the  muscle  substance, 
for  we  know  that  the  electrical  current  of  the  muscle  is  diminished  during  this 

Fig.  297. 


Muscle  curve  produced  by  the  application  ot  a  single  induction  shock  to  a  muscle,  a-f.  abscij 
a  b,  period  of  latent  stimulation ;  b  d,  period  of  increasing  energy  ;  d  c,  period  of  decre: 
elastic  after-vibrations. 


period,  or  we  have  what  is  known  as  the  negative  variation  of  the   muscle  cur- 
rent {Benis/ein—i;  2,2,1,)-'] 

In  man  the  latent  period  varies  between  0.004  and  o.oi  second.  If  the  experiment  be  so  arranged 
that  the  muscle  can  contract  as  soon  as  the  stimulus  is  applied  to  it,  i.  e.,  before  time  is  lost  in  mak- 
ing the  muscle  tense;  or,  to  put  it  otherwise,  if  the  muscle  has  not  "to  tal;e  in  slack,"  as  it  were, 
the  latent  period  may  fall  to  0.004  second  [Gad).  If  the  muscle  be  still  attached  to  the  body,  pro- 
tected as  much  as  possible  from  external  influences  and  properly  supplied  with  blood,  the  latent 
period  may  be  reduced  to  0.003. 


PENDULUM    MYOGRAPH    CURVE. 


517 


Modifying  Influence. — Tlie  latent  period  is  shortened  by  an  increased  strength  of  the  stimulus 
and  by  heat ;  while  fatigue,  cooling  and  increasing  weight  lengthen  \i  [Lauterbach,  Mendehohn, 
Yeo,Cash).  The  latent  period  of  an  opening  contraction  may  he  even  as  much  as  o. 04  second 
longer  than  that  of  a  closing  contraction.  The  red  muscles  have  a  longer  latent  period  than  the 
white  (p.  523).  Before  the  muscle  contracts  as  a  whole,  the  individual  fibres  within  it  must  have 
contracted.  We  must,  therefore,  conclude  that  the  latency  of  the  individual  muscular  elements 
is  shorter  than  that  of  the  entire  muscle  (GaJ,  Ti^ersledl). 

2.  The  Contraction  or  Stage  of  Increasing  Energy,  i.e.,  from  the 
moment  the  muscle  begins  to  shorten  until  it  reaches  its  greatest  degree  of  con- 
traction {b  d ).  At  first  the  muscle  contracts  slowly,  then  more  rapidly,  and 
again  more  slowly,,  so  that  the  ascending  limb  of  the  curve  has  somewhat  the 
form  of  an/.  This  stage  lasts  0.03  to  0.4  second.  It  is  shorter  when  the  con- 
traction is  shorter  (weak  stimulus)  and  the  less  the  weight  the  muscle  has  to  lift. 
It  also  varies  with  the  excitability  of  the  muscle,  being  shorter  in  a  fresh,  non- 
fatigued  muscle. 

3.  Elongation  or  Stage  of  Decreasing  Energy. — After  the  muscle  has 
contracted  up  to  its  maximum  for  an)-  particular  stimulus,  it  begins  to  relax — at 
first  slowly,  then  rapidly — and  lastly  more  slowly,  so  that  an  inverse  of  an/  is 
obtained  {d  e).  This  stage  is  usually  of  shorter  duration  than  2.  The  duration 
varies  with  the  strength  of  the  stimulus,  being  shorter  than  2  with  a  weak  stimulus, 
and  longer  with  a  strong  stimulus.  It  also  depends  upon  the  extent  to  which  the 
muscle  is  loaded  during  contraction. 

4.  The  fourth  stage  has   received   various   names — stage  of  elastic  after- 

FiG.  298. 


Muscle  curve  tji  a  frog's  gastrocnemius  attached  tu  a  heavy  lever  tracing  on  a  pendulum  myograph.  'lime  tracing 
of  chronograph  120  double  vibrations  per  sec.  Stimulus  applied  at  a  ;  a  6  {\)  latent  period,  d  c  (2)  shortening, 
cd  ii)  elongation,  {<:)  height  of  contraction;  ^(4)  slow  relaxation  (after  Ritther/ord). 

vibration   [residual   contraction   or  contraction   remainder  (Hermann). 

The  after-vibrations  {e f),  which  disappear  gradually,  depend  upon  the  elasticity 
of  the  muscle.  The  duration  of  this  stage  is  longest  with  a  powerful  contraction, 
and  when  the  weight  attached  to  the  muscle  is  small.] 

[In  studying  a  Muscle  Curve,  the  more  or  less  vertical  character  of  the 
ascent  will  indicate  the  rapidity  of  the  contraction,  the  height  above  the  base 
line,  the  extent  and  power  of  contraction,  the  length  of  the  curve  the  duration, 
and  the  line  of  descent  the  rate  of  its  extensibility.] 

If  the  stimulus  be  applied  to  the  motor  nerve  instead  of  to  the  muscle  itself, 
the  contraction  is  greater  {Ffliii^er),  and  lasts  longer  (^IViindt)  the  nearer  to  the 
spinal  cord  the  stimulus  is  applied  to  the  nerve. 

[Pendulum  Myograph  Curve. — The  form  of  the  muscle  curve  will  vary 
with  the  kind  of  myograph  used  ;  if  it  be  stationary,  then  the  muscle  will  merely 
record  a  vertical  line  ;  if  the  recording  surface  move  quickly,  the  two  parts  of 
the  curve  will  form  an  acute  angle  ;  and  if  it  move  with  great  rapidity,  they  will 
have  the  form  of  Fig.  298,  which  is  that  obtained  with  a  pendulum  myograph.  A 
vibrating  tuning  fork  records  time  directly  under  the  tracing,  whereby  the  dura- 
tion of  each  part  of  the  curve  is  readily  determined.  The  parts  marked  i,  2,  3 
and  4  correspond  to  those  so  numbered  on  p.  515.] 

[In  measuring  the  myogram,  all  that  is  required  is  to  know  the  moment  at  which  the  stimulus 
was  applied,  and  to  note  when  the  curve  begins  to  leave  the  base  line  or  abscissa.     Raise  a  vertical 


518 


OVERWEIGHTED    MUSCLES. 


Fig.  299. 


line  from  each  of  these  points,  and  the  interval  between  tliese  lines,  as  measured  by  the  chronograph, 
indicates  the  time  (Fig.  298).] 

[Method — Faradic  Shocks. — The  time  relations  of  a  muscular  contrac- 
tion may  be  studied  by  means  of  the  following  arrangement :  Attach  a  frog's 
gastrocnemius  to  a  lever,  as  in  Fig.  299,  and 
through  the  frog's  muscle  place  two  wires  from 
the  secondary  coil  of  an  induction  machine. 
A  scale  pan,  into  which  weights  may  be  placed, 
may  be  attached  to  the  lever,  especially  if  it  is 
one  of  the  light  levers  used  by  Marey.  On  the 
same  support  adjust  an  electro-magnet  with  a 
writing  style  in  the  primary  circuit,  and  in  this 
circuit  also  place  a  key  (K)  to  make  and  break 
the  current.  Fix  also  a  Depre's  chronograph 
to  the  same  sujjport,  and  make  it  vibrate  by 
connecting  it  in  circuit  with  a  tuning  fork  of 
known  rate  of  vibration,  and  driven  by  a  gal- 
vanic battery.  See  that  the  points  of  all  three 
levers  write  exactly  over  each  other  on  the 
revolving  cylinder.  The  upper  lever  registers 
the  contraction,  the  electro-magnet  the  moment 
the  stimulus  is  applied  to  the  muscle,  and  the 
electrical  chronograph  the  time.] 


rangement  lor  estini. 
during  contraction 
by  a  faradic  shock 


ting  the  time  rclal 
of  a  muscle  prod 

B,  battery  ;  K,  ke; 
[,  primary,  II,  secor 
ary  spiral ;  /,  muscle  lever ;  e,  electri 
magnet  in  primary  circuit;  /.electric  sij 
nal :  Si,  support :  R  C,  revolving  cylind' 
(after  Ruther/ard). 


7- 


muscle  contracts  it  has  to  lift  these 


Overweighted  Muscles. — The  foregoing  remarks 
apply  to  curves  obtained  l>y  a  light  lever  connected  with 
the  muscle.  If  the  muscle  lever  be  "  over%veighteii!'  or 
overloaded,  i.e.,  if  the  lever  be  loaded,  so  that  when  the 
lights,  the  course  of  the  curve  is  varied  according  to  the 
weight  to  be  lifted.  It  is  necessary,  however,  to  support  the  lever  in  the  intervals  when  the  muscle 
is  at  rest.  As  the  weights  are  increased,  the  occurrence  of  the  contraction  is  delayed.  This  is  due 
to  the  fact  that  the  muscle,  at  the  moment  of  stimulation,  must  accumulate  as  much  energy  as  is 
necessary  to  lift  the  weight.  The  greater  the  weight  the  longer  is  the  time  before  it  is  raised. 
Lastly,  the  muscle  may  be  so  "  loaded,"  or  "  overloaded,"  that  it  cannot  contract  at  all :  this  is  the 
limit  of  the  muscular  or  mechanical  energy  of  the  muscle  (7'.  Helmholtz). 

Fatigue. — If  a  muscle  be  caused  to  contract  so  frequently  that  it  becomes 
"fati^i^ued,"  the  latent  period  is  longer,  the  curve  is  not  so  high,  because  the  mus- 
cular contraction  is  less,  and  the  abscissa  is  longer,  /.  e.,  the  contraction  is  s/otver 
and  lasts  longer  (Figs.  300,  I,  312).  Cooling  a  muscle  has  the  same  effect  {v. 
Hehnholtz  and  others).  Soltmann  finds  that  the  fresh  muscles  oi  jinv-born  animals 
behave  in  a  similar  manner.  The  myogram  has  a  flat  apex  and  considerable  elon- 
gation in  the  descending  limb  of  the  curve. 

Constant  Current. — If  the  motor  nerve  of  a  muscle  be  stimulated  by  a  closing 
or  opening  shock  of  a  constant  earrent,  the  resulting  muscular  contraction  cor- 
responds exactly  to  that  already  described.  If,  however,  the  current  be  closed  or 
opened,  with  the  muscle  itself  directly  in  the  circuit,  during  the  closing  shock, 
there  is  a  certain  degree  of  contraction  which  lasts  for  a  time,  so  that  the  curve 
assumes  the  form  of  Fig.  301,  where  S  represents  the  moment  of  closing  or 
making  the  current,  and  O  the  moment  of  opening  or  breaking  it  {Witndt — com- 
pare §336,  D). 

The  investigations  of  Cash  and  Kronecker  show  that  individual  muscles  have  a  special  form  of 
muscle  curve;  the  omohyoid  of  the  tortoise  contracts  more  rapidly  than  the  pectoralis.  Similar 
differences  occur  in  the  muscles  of  frogs  and  mammals.  Tlie  flexors  of  the  frog  contract  more 
rapidly  than  the  extensors  (  Grii/zner).  .Sometimes  within  one  and  the  same  muscle  there  are  "  red  " 
(rich  in  glycogen)  and  "pale  "  fibres  (^  292).  The  red  fibres  contract  more  slowly, are  less  excitable 
and  less  easily  fatigued  (Grlilzner).  The  muscles  of  flying  insects  contract  very  rapidly,  even  more 
han  100  times  per  second. 


EFFECT   OF   VERATRIN   AND   OTHER    POISONS   ON    MUSCLE. 


519 


Poisons. — Ver)'  small  doses  of  curara  or  quinine  [ScktsL'ht'potiew)  increase  the  height  of  the 
contraction  (excited  by  stimulation  of  the  motor  nerve),  while  larger  doses  diminish  it,  and  finally 
abolish  it  altogether.  Guanidin  has  a  similar  action  in  large  doses,  but  the  maximum  of  contrac- 
tion lasts  for  a  longer  time.  Suitable  doses  of  veratrin  also  increase  the  contractions,  but  the  stage 
of  relaxation  is  greatly  lengthened  [Kosslnich  anj  Closterincytr).  Veratrin,  antiarin  and  digitalin, 
in  large  doses,  act  upon  the  sarcous  substance  in  such  a  way  that  the  contractions  become  very  pro- 
longed, not  unlike  a  condition  of  prolonged  tetanus  (I/ar/ess,  /S6s).  The  latent  period  of  muscles 
poisoned  with  veratrin  and  strychnin  is  shortened  at  first,  and  afterward  lengthened.  The  gastroc- 
nemius of  a  frog  supplied  by  blood  containing  soda  contracts  more  rapidly  [Griitziier).  Kunkel  is 
of  opinion  that  muscular  poisons  act  by  controlling  the  imbibition  of  water  by  the  sarcous  substance. 
As  muscular  contr.action  depends  on  imbibition  (j  297,  II),  the  fonn  of  the  contraction  of  the  poi- 
soned^muscle  will  depend  upon  the  altered  condition  of  imbibition  produced  by  the  drug. 

Fig.  ^oo. 


I,  Contraction  of  ayatignei/  irog's  muscle  writing  its 

vibration  =  o.oiert  second  ;  a  />  =  latent  period  ;  &  c 
The  most  rapid  writing  movements  of  the  right  hand 
bling  tetanic  movements  of  the  right  forearm  inscribe 


ion  on  a  vibrating  plate  attached  to  a  tuning  fork.  Each 
ge  of  increasing  energy  :  c d,ai  decreasing  energy.  II, 
:ribed  on  a  vibrating  plate.  Ill,  The  most  rapid  trem- 
I  the  same  plate. 


dl[Veratrin. — If  a  frog  be  poisoned  with  veratrin,  and  then  be  made  to  spring,  it  does  so  rapidly, 
but  when  it  alights  again  the  hind  legs  are  extended,  and  they  are  only  drawn  up  after  a  time. 
Thus,  rapid  and  powerful  contraction,  with  slow  and  prolonged  relaxation,  are  the  char.icter  of  the 
movements.  In  a  muscle  poisoned  with  veratrin  the  ascent  is  quick  enough,  but  it  remains  con- 
tracted for  a  long  time,  so  that  this  condition  has  been  called  "  contracture."  A  single  stimulation 
may  cause  a  contraction  lasting  five  to  fifteen  seconds,  according  to  circumstances.  Brunton  and 
Cash  find  that  cold  has  a  marked  effect  on  the  action  of  veratrin ;  in  fact,  its  effect  may  be  perma- 
nently destroyed  by  exposure   to   extremes  of  heat  or  cold.     The   muscle   curve  of  a  brainless  frog 

Fig.  ^01. 


and  u,.. 


S,  clnsing  ;  O,  opening  shock  {Wundt). 


cooled  artificially,  and  then  poisoned  by  veratrin,  occasionally  gives  no  indications  of  the  action  of 
the  poison  until  its  temperature  is  raised,  and  this  is  not  due  to  non-absoqition  of  the  poison.  Cold, 
therefore,  abolishes  or  lessens  the  contracture  peculiar  to  the  veratrin  curve.  Similar  results  are 
obtained  with  salts  of  barium,  and  to  a  less  degree  by  those  of  strontium  and  calcium  (Bruiilon 
,uulC<uh\.-\ 

Smooth  Muscles. — The  muscle  curve  of  smooth  or  non-striped  muscles  is 
similar  to  that  of  the  striped  muscles,  but  tlie  duration  of  the  contraction  is  visibly 
much  longer,  and  there  are  other  points  of  difference.  Some  muscles  stand  mid- 
way between  these  two — at  least,  so  far  as  the  duration  of  their  contractions  are 
concerned. 


520  ACTION    OF   TWO    SUCCESSIVE    STIMULI. 

The  "  red  "  muscles  of  rabbits,  the  muscles  of  the  tortoise,  the  adductors  of  the  common  mussel, 
and  the  heart,  all  react  in  a  similar  manner.  ■  The  muscles  of  flying  insects  contract  extremely 
rapidly,  more  than  loo  times  per  second  (//.  Landois). 

Contraction  Remainder. — A  contracted  muscle  assumes  its  original  length 
only  when  it  is  extended  by  sufficient  traction,  c.^.,  by  means  of  a  weight  (A'a/iw). 
Otherwise,  the  inuscle  may  remain  partially  shortened  for  a  long  time  {v.  Helm- 
holtz,  Schiff").  This  condition  has  been  called  "contracture"  {Tiegel),  or, 
better,  contraction  remainder  {Hermann).  This  condition  is  most  marked  in 
muscles  that  have  been  previously  subjected  to  strong,  direct  stimulation,  and  are 
greatly  fatigued  {Ticgfl),  which  are  distinctly  acid,  and  ready  to  pass  into  rigor 
mortis,  or  in  muscles  excised  from  animals  poisoned  with  veratrin  {v.  Bezold). 

Rapidity  of  Muscular  Contraction. — In  man,  smgle  muscular  movements 
can  be  executed  with  great  rapidity.  The  time  relations  of  such  movements  are 
most  readily  ascertained  by  inscribing  the  movements  upon  a  smoked  glass  plate 
attached  to  a  tuning  fork.  Fig.  300,  II,  represents  the  most  rapid  voluntary 
movements  that  Landois  could  execute,  as,  1?.^.,  in  writing  letters,  n,  n,  and  every 
contraction  is  equal  to  about  3.5  vibrations  (i  vibration  ^  0.01613  second)  = 
0.0564  second.  In  III,  the  right  arm  was  tetanized,  in  which  case  2  to  2.5  vibra- 
tions occur  :=  0.0323  to  0.0403  second. 

Pathological. — In  secondary  degeneration  of  the  spinal  cord  after  apoplexy,  atrophic  muscular 
anchylosis  of  the  limbs  {Edinger),  muscular  atrophy,  progressive  ataxia,  and  paralysis  agitans  of  long 
standing,  the  latent  ^e.x\aiX\%  lengthened ;  wMXt'W-'M  shortened  m  the  contracture  of  senile  chorea 
and  spastic  tabes  (Mendelsohn).  The  whole  curve  is  lengthened  in  jaundice  and  diabetes  (Edin- 
ger).  In  cerebal  hemiplegia,  during  the  stage  of  contracture,  the  muscle  curve  resembles  the  curve 
of  a  muscle  poisoned  with  veratrin,  and  the  same  is  the  case  in  spastic  spinal  paralysis  and  amyo- 
trophic lateral  sclerosis;  in  pseudo-hypertrophy  of  the  muscles  the  ascent  is  short  .and  the  descent 
very  elongated.  In  muscular  atrophy,  after  cerebral  hemiplegia,  and  in  tabes,  the  latent  period  in- 
creases, while  the  height  of  the  curve  diminishes.  In  chorea  the  curve  is  short  (For  the  /Bene- 
tton 0/ Degeneration,  see  ^  339.)  In  rare  cases  in  man  it  has  been  observed  that  the  execution  of 
spontaneous  movements  results  in  a  very  prolonged  contraction  (Thomson's  disease).  In  such 
cases  the  muscular  fibres  are  very  broad,  and  the  nuclei  increased  (£ri). 

II.  Action  of  Two  Successive  Stimuli. — Let  two  momentary  stimuli  be 
applied  successively  to  a  muscle  :  (A)  U  cac/t  stimulus  or  shock  be  of  itself  suffi- 
cient to  cause  a  maximal  contraction,  /.  e,  the  greatest  possible  contraction 
which  the  muscle  can  accomplish,  then  the  effect  will  vary  according  to  the  time 
which  elapses  between  the  application  of  the  two  stimuli,  {a)  If  the  second  stim- 
ulus is  applied  to  the  muscle  after  the  relaxation  of  the  muscle  following  upon  the 
first  stimulus,  we  obtain  merely  two  maximal  contractions.  (/')  If,  however,  the 
second  stimulus  be  applied  to  the  muscle  during  the  time  tliat  the  effect  of  the  first 
is  present,  /.  e.,  while  the  muscle  is  in  the  phase  of  contraction  or  of  relaxation  ; 
in  this  case  the  second  stimulus  causes  a  new  maximal  contraction,  according  to 
the  time  of  the  particular  phase  of  the  contraction,  (c)  When,  lastly,  the  second 
stimulus  follows  the  first  so  rapidly  that  both  occur  during  the  latent  period,  we 
obtain  only  one  maximal  contraction  (<■.  Helmholtz).  It  is  to  be  specially  noted 
that  a  single  maximal  stimulus  never  excites  the  same  degree  of  shortening  as 
tetanic  stimulation  (III),  but  only  about  yi  of  the  height  of  the  contraction  in 
tetanus. 

(B)  If  the  stimuli  be  not  maximal,  but  only  such  as  cause  a  medium  or  sub- 
maximal  contraction,  the  effects  of  both  stimuli  are  superposed,  or  there  is  a 
summation  of  the  contractions  (Fig.  302).  It  is  of  no  consequence  at  what 
particular  phase  of  the  primary  contraction  the  second  shock  is  applied.  In  all 
cases,  the  second  stimulus  causes  a  contraction,  just  as  if  the  phase  of  contraction 
caused  by  the  first  shock  was  the  natural  passive  form  of  the  muscle,  /.  e.,  the  new 
contraction  (/',  c)  starts  from  that  point  as  fro  in  an  abscissa  (Fig.  302,  I,  b).  Thus, 
under  favorable  conditions  the  contraction  may  be  twice  as  great  as  that  caused  by 
the  first  stimulus.  The  most  favorable  time  for  the  application  of  the  second 
stimulus  is  -^^  second  after   the  application  of  the  first  iSeioall).     The  effects  of 


TETANUS   OF    MUSCLE. 


521 


both  stimuli  are  obtained  even  when  the  second  stimulus  is  applied  during  the 
latent  period  ( ?■.  Hflinholtz). 

III.  Tetanus — Summation  of  Stimuli. — If  stimuli,  each  capable  of  causing 
a  contraction  following  each  other  with  medium  rapidity,  be  applied  to  a  muscle,  the 
muscle  has  not  sufficient  time  to  elongate  or  relax  in  the  intervals  of  stimulation. 
Therefore,  according  to  the  rapidity  of  the  successive  stimuli,  it  remains  in  a  con- 
dition of  continued  vibratory  contraction,  or  in  a  state  of  tetanus.  Tetanus  is, 
however,  not  a  continuous  uniform  condition  of  contraction,  but  it  is  a  discontinu- 
ous condition  or  form  of  the  muscle,  depending  upon  the  summation  or  accu- 
mulation of  contractions.  If  the  stimuli  are  applied  with  moderate  rapidity,  the 
individual  contractions  appear  in  the  curve  (Fig.  302,  11)  ;  if  they  occur  rapidly, 
and  thus  become  superposed  and  fused,  the  curve  appears  continuous  and  unbroken 
by  elevations  and  depressions  (Fig.  302,  III).  As  a  fatigued  muscle  contracts 
slowly,  it  is  evident  that  such  a  muscle  will  become  tetanic  by  a  smaller  number  of 
stimuli  per  second  than  will  suffice  for  a  fresh  muscle  {Marey,  Fick,  Minot. )  All 
muscular  movements  of  long  duration  occurring  in  our  bodies  are  probably  tetanic 
in  their  nature  (Ed.  Wc-bt-r). 

[Summation  of  Stimuli. — If  a  stimulus,  insufficient  in  itself  to  cause  con- 
traction of  a  muscle,  be  repeatedly  applied   to  a  muscle  in  proper  tempo   and  of 


Fig.  302. 


induction  shocks  pe: 


contractions  produced  by  stimulating ; 
:  produced  with  very  rapid  induction  shocks  (complet( 


sufficient  strength,  at  first  a  slight  and  then  a  stronger  or  maximal  contraction  may 
be  produced.      This  process  of  summation  occurs  also  in  nervous  ti.ssue  (§  360).] 

A  continued  voluntary  contraction  in  man  consists  of  a  series  of  single  con- 
tractions rapidly  following  each  other.  Every  such  movement,  on  being  carefully 
analyzed,  consists  of  intermittent  vibrations,  which  reach  their  maximum  when  a 
person  shivers  {Ed.  Weber).  [Baxt  found  that  the  simplest  possible  voluntary 
contraction,  e.  g.,  striking  with  the  index  finger,  occupies  on  an  average  nearly 
twice  as  long  time  as  a  similar  movement  discharged  by  a  single  induction  shock.] 

The  requisite  degree  of  shortening  is  obtained  by  the  summation  of  single  stimuli  applied  to  the 
slowly  contracting  muscle  until  the  desired  degree  of  shortening  is  obtained.  In  estimating  exactly 
the  amount  of  movement  we  generally  oppose  some  resistance  by  contracting  antagonistic  muscles, 
as  is  shown  by  observations  on  spare  individuals  [Briicki). 

The  tetanic  contractions,  which  occur  normally  in  an  intact  body,  are  proved  to  consist  of  a 
series  of  successive  contractions, because  they  can  give  rise  to  secondary  tetnntis  {\  332),  which  may 
also  be  caused  by  muscles  thrown  into  tetanus  by  strychnin  poisoning  (Loi'eii).  The  muscle  sound 
cannot  be  regarded  as  a  certain  proof  of  the  oscillatory  movement  in  tetanus  [as  Ilelmlioltz  has 
shown  that  this  sound  coincides  with  the  resonance  sound  of  the  ear  (Neriitg  and  /■'liiu/rit/i). 

If  a  muscle  be  connected  with  a  telephone,  whose  wires  are  brought  mto  connection  with  two 
needles,  one  placed  in  the  tendon,  and  the  other  in  the  substance  of  the  muscle,  we  hear  a  sound 
when  the  muscle  is  thrown  into  tetanus,  which  proves  that  periodic  vibratory  processes,  /.  e,  succes- 
sive contractions,  occur  in  the  muscle  {Btriis/cin  and  Sc/tSn/fin).    The  sound  is  most  distinct  when 


522 


TETANUS   OF    MUSCLE. 


the  tetanizing  Neefs  hammer  of  an  induction  machine  vibrates  about  50  times  per  sound  (  Wedensii 
and  Krotn-iker). 

The  number  of  stimuli  requisite  to  produce  tetanus  varies  in  different  animals,  and  in  different 
muscles  of  the  same  animal.     About  15  stimuli  per  second  are  required  to  produce  tetanus  in  the 

Fig.  303. 


Fig.  304. 


Opening  and  closing  induction  shocks  of  300  units,  applied  at  intervals  of  \/^  second  to  the  pale  (lower)  and  red 
(upper)  muscles  of  a  rabbit.     The  lowest  line,  '1',  marks  \i  second  (KromcUer  and  Stirling). 


1  by  wheels,  /:. 


muscles  of  X\it  frog  (hyoglossus  only  10,  gastrocnemius  27)  ;  very  feeble  stimuli  (more  than  20  per 
second)  cause  tetanus  (Kronecker)  ;  the  muscles  of  the  tortoise  become  tetanic  with  two  to  three 
shocks  per  second  ;  the  red  muscles  of  the  rabbit  by  10,  the  pale  by  over  20  (Kroiiecker  and  Stir- 
ling); muscles  of  birds   not  even  with  70   (Marey);   muscles  of  insects  330  to  340  per  second 


RAPIDITY   OF   TRANSMISSION    OF    A    CONTRACTION.  523 

(Marev,  Lniiiiois).  Tetanic  stimulation  of  the  muscles  of  the  crayfish  ( Astacus)  and  also  in  hydroph- 
ilus,  may  cause  rhythmical  contractions  (7?/c/;c/),  or  rhythmically  interrupted  tetanus  (.SV/;<v«/t/«). 

[The  red  and  pale  muscles  of  a  rabbit,  as  already  shown,  differ  structurally,  and  also  in  re- 
gard to  their  blood  supply  (p.  496).  They  also  differ  physiologically.  When  both  muscles  are 
caused  to  contract,  by  stimulating  the  sciatic  nerve  with  a  single  induction  shock,  the  curves  obtained 
are  shown  in  Fig.  303 ;  the  lower  one  from  the  pale,  and  the  upper  from  the  red  muscle.  The 
latent  period  is  longer,  while  the  duration  of  a  simple  contraction  of  a  red  muscle  is  three  times 
longer  than  that  of  a  pale  muscle.  Four  stimuli  per  second  cause  an  incomplete  tetanus,  and  10 
per  second  a  nearly  complete  tetanus  in  the  red  muscles  of  a  rabbit,  while  the  pale  muscles  require 
20  to  30  stimuli  per  second  to  be  completely  tetanized.  Fig.  304  shows  the  results  produced  by  in- 
duction shocks  applied  to  both  muscles  at  intervals  of  ](  second.] 

The  extent  of  shortening  in  a  tetanically  contracted  muscle,  within  certain  limits,  is  dependent 
upon  the  strength  of  the  individual  stimuli — but  not  upon  their  frequency.  The  contraction  re- 
mainder after  tetanus  is  greater  the  stronger  the  stimuli,  the  longer  they  are  applied,  and  the  feebler 
the  muscle  used  [Bohr).  Sometimes  a  stimulus  applied  to  a  muscle  immediately  after  tetanus  pro- 
duces a  greater  effect  than  it  did  before  the  tetanus  (Rossbach,  Bohr). 

Duration  of  Tetanus. — A  tetanized  muscle  cannot  remain  contracted  to  the  same  extent  for  an 
indefinite  period,  even  if  the  stimuli  are  kept  constant.  It  gradually  begins  to  elongate,  at  first  some- 
what rapidly,  and  then  more  slowly,  owing  to  the  occurrence  of  fatigue.  If  the  tetanic  stimulation 
is  arrested,  the  muscle  does  not  regain  its  original  position  and  shape  at  once,  but  a  contraction  re- 
mainder exists  for  a  certain  time,  this  being  more  evident  after  stimulation  with  induction  shocks. 

O.  Saltmann  found  that  the  /a/f  muscles  of  new-born  rabbits  were  rendered  tetanic  with  16 
stimuli  per  second,  so  that  tetanus  was  produced  in  them  with  the  same  number  of  shocks  as  in 
fatigued  adult  muscles.  This  may  serve  partly  to  explain  the  facility  with  which  spasms  occur  in 
new-born  animals. 

Curarized  muscles  sometimes  pass  into  tetanus  on  the  application  of  a  momentary  stimulus 
{Kiihne,  Hiring). 

IV.  If  very  rapid  (224  to  360  per  second)  induction  shoiks  be  applied  to  a 
muscle,  the  tetanus,  after  a  so-called  "  initial  contraction  "  {Bernsifin),  may 
cease  {Har/ess,  Hcidenliain").  This  occurs  most  readily  when  the  nerves  are  cooled 
(  V.  Kries).  Kronecker  and  Stirling,  however,  found  that  stimuli  following 
each  other  at  greater  rapidity  than  24,000  per  second  produced  tetanus. 

[Tone  inductorium  of  Kronecker  and  Sterling. — This  apparatus  (Fig.  305),  consists  of  a  rod 
of  iron,  J,  fixed  in  an  iron  upright  at  a.  The  primary,  s' ,  and  secondary  spiral,  s" ,  rest  on  wooden 
supports,  which  can  be  pushed  over  both  ends  of  the  rod.  One  end  of  the  rod  lies  between  leather 
rollers, y  and  ■,'■,  which  can  be  made  to  rub  on  the  rod  by  moving  the  toothed  wheels,  /;.  In  this 
way  a  tone  is  produced  by  the  longitudinal  vibrations  of  the  rod,  the  number  of  vibrations  being 
proportional  to  the  length  of  the  rod,  so  that  by  means  of  this  instrument  we  can  produce  from 
1000  to  24,000  alternating  induction  shocks  per  second.] 

299.  RAPIDITY  OF  TRANSMISSION  OF  A  CONTRACTION. 

■ — I.  If  a  long  muscle  be  stimulated  at  one  end,  a  contraction  occurs  at  that 
point,  and  is  rapidly  proj^agated  in  a  wave-like  manner  through  the  whole  length 
of  the  muscle,  until  it  reaches  the  other  end.  The  condition  of  excitement  or 
molecular  disturbance  is  communicated  to  each  successive  part  of  the  muscle,  in 
virtue  of  a  special  conductive  capacity  of  the  muscle.  The  mean  velocity  of 
the  contraction  wave  is  3  to  4  metres  per  second  in  the  frog  {Bernstein,  3.S69 
metres);  rabbit,  4  to  5  metres  {Bernstein  and  Steiner)  ;  lobster,  i  metre  {Fri- 
deritij  and  van  de  J'c/de)  ;  in  smooth  muscle  and  in  the  heart,  only  10  to  15 
millimetres  per  second  (Engelmann,  Marchland — pages  97,  98).  These  results 
have  reference  only  to  excised  muscles,  the  velocity  of  transmission  being  much 
greater  in  the  voluntary  muscles  of  a  living  man,  viz.,  10  to  13  metres  {Her- 
mann, §  334,  II). 

Methods. — Aeby  placed  writing  levers  upon  both  ends  of  a  muscle,  the  levers  resting  trans- 
versely to  the  direction  of  the  muscular  fibres.  The  muscle  was  stimulated,  and  both  levers  regis- 
tered their  movements,  the  one  directly  over  the  other,  on  a  revolving  cylinder.  On  stimulating  one 
end  of  the  muscle,  the  lever  nearest  to  this  point  is  raised  by  the  contraction  wave,  and  a  little 
later  the  other  lever.  When  we  know  the  rate  at  which  the  cylinder  is  moving,  and  the  distance 
between  the  two  elevations,  it  is  easy  to  calculate  the  rapidity  of  transmission  of  the  contraction  wave. 

Duration  and  Wave  Length. — The  time,  corresponding  to  the  length  of 
the  abscissa  of  the  muscle  curve  inscribed  by  each  writing  lever,  is  equal   to  the 


524 


MUSCULAR    WORK. 


duration  of  the  contraction  of  this  part  of  the  muscle  (according  to  Bernstein, 
0.053  to  0.098  second).  If  this  vahie  be  multiplied  by  the  rapidity  of  transmis- 
sion of  the  muscular  contraction  wave,  we  obtain  the  wave  length  of  the  contraction 
wave  {==  206  to  3S0  millimetres). 

Modifying  Influences. — Cold  (Fig.  306),  fatigue,  approaching  death,  and 
many  poisons  [Veratrin,  KCy]  diminishes  the  velocity  and  the  height  of  the  con- 
traction wave,  while  the  strength  of  the  stimulus  and  the  e.xtent  to  which  the 
muscle  is  loaded  are  without  any  effect  upon  the  velocity  of  the  wave  (Aefiv). 
In  excised  muscles,  the  size  of  the  wave  diminishes  as  it  passes  along  the  muscle 
{Bernstein),  but  this  is  not  the  case  in  the  muscles  of  living  men  and  animals. 
The  contraction  wave  never  passes  from  one  muscular  fibre  to  a  neighboring  fibre. 

[Fig.  306  shows  the  effect  of  cold  on  the  muscles  of  a  rabbit,  in  delaying  the  contraction  wave. 
There  is  a  longer  distance  between  i  and  2  in  the  lower  than  in  the  upper  curves.] 

2.  If  a  long  muscle  be  stimulated  locally  near  its  middle,  a  contraction  wave 
is  propagated  toward  both  ends  of  the  muscle.  If  several  points  be  stimulated 
simultaneously,  a  wave  movement  sets  out  from  each,  the  waves  passing  over  each 
other  in  their  course  {Sciiiff ). 

3.  If  a  stimulus  be  applied  to  the  motor  nerve  of  a  muscle,  an  impulse  is 
communicated  to  every  muscular  fibre ;  a  contraction  wave  begins  at  the  end  organ 

Fig.  306. 


z  and  I,  obtainedfri 


nuscle  by  the  above  an 
vhcn  It  was  cooled  by  i 


[motorial  end  plate],  and  must  be  propagated  in  both  directions  along  the  mus- 
cular fibres,  whose  length  is  only  3  to  4  centimetres.  .\s  the  length  of  the  motor 
fibres  from  the  nerve  trunk  to  where  they  terminate  in  the  motorial  end  plates  is 
unequal,  contraction  of  all  the  muscular  fibres  cannot  take  place  absolutely  at  the 
same  moment,  as  the  nerve  impulse  takes  a  certain  time  to  travel  along  a  nerve. 
Nevertheless,  the  difference  is  so  small  that,  when  a  muscle  is  caused  to  contract 
by  stimulation  of  its  motor  nerve,  practically  the  whole  muscle  appears  to  contract 
smiultaneously  and  at  once. 

4.  A  complete,  uniform,  momentary  contraction  of  all  the  fibres  of  a  muscle  can 
only  take  place  when  all  the  fibres  are  excited  at  the  same  moment.  This  occurs 
when  the  electrodes  are  placed  at  both  ends  of  the  muscle,  and  an  electrical 
stitnulus  of  momentary  duration  passes  through  the  whole  length  of  the  muscle. 

300.  MUSCULAR  WORK. — Muscles  are  most  perfect  machines,  not  only 
because  they  make  the  most  thorough  use  of  the  substances  on  which  their  activity 
depends  (§  217),  but  they  are  distinguished  from  all  machines  of  human  manu- 
facture by  the  fact  that  by  frequent  exercise  they  become  stronger,  and  are  thereby 
capable  of  accomplishing  more  work  {Du  Bois-Reymond). 

The  amount  of  work  (W)  which  a  muscle  can  perform  (see  introduction)  is 
equal  to  the  product  of  the  weight  lifted  (/)  and  the  height  to  which  it  is  lifted 


LAWS   OF    MUSCULAR   WORK. 


525 


(/i),  i.e.,  W  ^^ ph.  Hence,  it  follows  that  when  a  muscle  is  not  loaded  (where 
^=  o),  then  w  must  be  =  o,  i.e.,  no  work  is  performed.  If,  again,  it  be 
overloaded  with  too  great  a  load,  so  that  it  is  unable  to  contract  (//  ^=^  o),  here 
also  the  work  is  nil.  Between  these  two  extremes  an  active  muscle  is  capalsle  of 
doing  a  certain  amount  of  "  work." 

I.  Work  with  Maximal  Stimulation. — ^^'hen  the  strongest  possible,  or 
maximal  stimulus  is  applied,  i.e.,  when  the  strength  of  the  stimulus  is  such  as 
to  cause  a  muscle  to  contract  to  the  greatest  possible  extent  of  which  it  is  capable, 
the  amount  of  work  done  increases  more  and  more  as  the  weight  is  increased, 
but  only  up  to  a  certain  maximum.  If  the  weight  be  gradually  increased,  so  that 
it  is  lifted  to  a  less  height,  the  amount  of  work  diminishes  more  and  more,  and 
gradually  falls  to  be  =  o,  when  the  weight  is  not  lifted  at  all. 


Example  of  the  work  done  by 

a  frog's  muscle  {Ed.  Webei-)  :— 

- 

Weight  Lifted  In  Grammes. 

Height  in  Millimetres. 

Work  done  in  Gramme-Millimetres. 

5 
30 

27.6 
25.1 
11.45 

7-3 

376 
286 
220 

[Suppose  a  muscle  be  loaded  with  a  certain  number  of  grammes,  and  then  caused  to  contract, 
we  get  a  certain  height  of  contraction.  Fig.  307  shows  the  result  of  an  experiment  of  this  kind. 
The  vertical  lines  represent  the  height  to  which  the  weights  (in  grammes)  noted  under  them  were 
raised,  so  that,  as  a  rule,  as  the  weight  increases  the  height  to  which  it  is  raised  decreases.] 

Laws  of  Muscular  Work. — i.  A  muscle  can 
lift  a  greater  load,  the  larger  its  transverse  section,  ^^^-  307- 

/.('.,  the  more  fibres  it  contains  arranged  parallel  to 
each  other  (Ediiard  Weber,  1846). 

2.  The  longer  the  muscle,  the  higher  it  can  lift 
a  weight. 

3.  When  a  muscle  begins  to  contract,  it  can  lift 
the  largest  load  ;  as  the  contraction  proceeds  it  can 
only  lift  less  and  less  loads,  and  when  it  is  at  its 
maximum  of  shortening  only  relatively  very  light 
loads  {  Th.  Si/ncnitii,  18 jf).  250 

4.  By  the  term  "  absolute  muscular  force,"  grammes, 
is  meant,  according  to  Ed.  Weber,  just  the  weight  "='8*"  '°  "''''raite?  "'  ""  ''■''®'"'  *' 
which   a  muscle  undergoing   maximal  stimulation 

is  no  longer  able  to   lift   (the  muscle  being  in   its  normal  resting  phase),  and 
without  the  muscle  at  the  moment  of  stimulation  being  elongated  by  the  weight. 

Comparative. — Comparing  the  absolute  muscular  force  of  different  muscles,  even  in  different 
animals,  it  is  usual  to  calculate  it  with  reference  to  that  of  a  square  centimetre.  The  mean 
transverse  section  of  a  muscle  is  obtained  by  dividing  its  volume  by  its  length.  The  volume  is 
equal  to  the  absolute  weight  of  the  muscles  divided  by  its  specific  gravity  =  1058.  The  absolute 
muscular  force  for  i  Q  centimetre  of  a  frog's  muscle  =  28  to  3  kilos.  [6.6  llis.]  (J.  Rosenlliat)  ; 
for  I  □  centimetre  of  human  muscle  7  to  8  [Hetike  ami  Knorz),  or  even  9  to  10  kilos.  [20  to  23 
fijs.]  [Korsler,  Hatighton).  Insects  can  perform  an  extraordinary  amount  of  work — an  insect  can 
drag  along  sixty-seven  times  its  body  weight ;  a  horse  scarcely  three  times  its  own  weight. 

5.  During  tetanus,  when  a  weight  is  kept  suspended,  no  work  is  done  as  long 
as  the  weight  is  suspended,  but  of  course  work  is  done  in  the  act  of  lifting  the 
load.  To  produce  tetanus,  successive  stimuli  are  required,  the  muscular  meta- 
bolism is  increased,  and  fatigue  rapidly  occurs.  The  potential  energy  in  this  case 
is  converted  into  heat  (§  302).  When  a  muscle  is  stimulated  with  a  ma.ximal 
stimulus,  it  cannot  lift  so  great  a  weight  with  one  contraction  as  when  it  is  stimu- 
lated    tetanically  {Hermann').       Tiie    energy  evolved,   even    during    tetanus,   is 


526 


THE    ELASTICITY    OF    MUSCLE. 


greater  the  more  frequent  the  stimulation,  at   least  up  to  loo  stimuli  per  second 
(^Berns/i'in). 

II.  Medium  Stimuli. — If  a  muscle  be  caused  to  contract  by  stimuli  of 
moderate  strength,  i.e.,  such  as  do  not  cause  a  maximal  contraction,  there  are  two 
possibilities:  Either  the  feeble  stimulus  is  kept  constant  while  the  load  is  varied, 
in  which  case  the  amount  of  work  done  follows  the  same  law  as  obtains  for  maxi- 
mal stimulation  ;  or,  the  load  may  be  kept  the  same,  while  the  strength  of  the 
stimulus  is  varied.  In  the  latter  case,  Fick  observed  that  the  height  to  which  the 
load  was  lifted  increased  in  a  direct  ratio  with  the  strength  of  the  stimulus. 

The  stimulus  which  causes  a  muscle  to  contract  must  reach  a  certain  strength  or  intensity  before 
it  becomes  elTective,  i.  c,  the  "  liminal  intensity  "  of  the  stimulus,  but  this  is  independent  of  the 
weight  applied  to  the  muscle.  With  minimal  stimuli  a  small  weight  is  raised  higher  than  a  large 
one,  but  as  the  stimulus  is  increased,  the  contractions  also  increase  in  a  larger  ratio  with  an  increased 
load  (v.  Kries). 

The  blood  stream  within  the  muscles  of  an  intact  body  is  increased  during 
muscular  activity.  The  blood  vessels  of  the  muscle  dilate,  so  that  the  amount  of 
blood  flowing  through  them  is  increased  {Ludioig  and  Seze/hmi).  At  the  time  that 
the  motor  fibres  are  excited,  so  also  are  the  vaso-dilator  fibres,  which  lie  in  the 
same  nervous  channels  (^  294,  II).  [Gaskell  found  that  faradization  of  the  nerve 
of  the  mylo-hyoid  muscle  of  the  frog  not  only  caused  tetanus  of  the  muscle,  but 
also  dilatation  of  its  blood  vessel.] 

Testing  Individual  Muscles. — In  estimating  the  absolute  force  of  the  inJk'idiint  musdes  or 
groups  of  muscles  in  man,  we  must  always  pay  particular  attention  to  the  physical  relations,  /.  e.,  to 

the  arrangement  of  the  levers,  direction  of  the 
traction,  degree  of  shortening,  etc  ((!  306).  Dy- 
namometer.— The  absolute  force  of  certain  groups 
of  muscles  is  very  conveniently  and  practically 
ascertained  by  means  of  a  dynamometer  (Fig. 308). 
This  instrument  is  very  useful  for  testing  the  differ- 
ence between  the  power  of  the  two  arms  in  cases 
of  paralysis.  The  patient  grasps  the  instrument  in 
his  hand  and  an  inde.x  registers  the  force  exerted, 
(^uetelet  has  estimated  the  force  of  certain  muscles 
— the  pressure  of  both  hands  of  a  man  to  be  =  70 
kilos.;  while  by  pulling  he  can  move  double  this 
weight.  The  force  of  the  female  hand  is  one- 
third  less.  .\  man  can  carry  more  than  double 
his  own  weight ;  a  woman  about  the  half  Boys  can  carry  about  one-third  more  than  girls.  [Very 
convenient  dynamometers  are  made  by  Salter,  of  Birmingham,  both  for  testing  the  strength  of  pull 
and  squeeze ;  in  testing  the  former,  the  instrument  is  held  as  an  archer  holds  his  bow  when  in  the 
act  of  drawing  it,  and  the  strength  of  pull  is  given  by  an  index ;  in  the  latter,  another  form  of  the 
instrument  is  used.  Large  numbers  of  observations  were  made  by  means  of  these  instruments  by 
Francis  Galton,  at  the  Health  Exhibition,  1S85.] 

Amount  of  Work  Daily .^In  estimating  the  work  done  by  a  man,  we  have  to  consider,  not 
only  the  amount  of  work  done  at  any  one  moment,  but  how  often,  time  after  time,  he  can  succeed 
in  doing  work.  The  mean  value  of  the  daily  work  of  a  man  working  eight  hours  a  day  is  lo 
(10.5  to  II  at  most)  kilogramme  metres  per  second,  i.  e.,  a  daily  amount  of  work  =  288,000 
(300,000)  kilogramme  metres. 

Modifying  Conditions. — Many  substances  after  being  introduced  into  the  body  diminish,  and 
ultimately  paralyze  the  production  of  work — mercury,  digitalin,helleborin,  potash  salts,  etc.  Others 
increase  the  muscular  activity — veratrin  (Rossbai/i),  glycogen  [caffein,  and  allied  alkaloids],  mus- 
carin  (King  and  Fr.  Hogyes),  kreatin  and  hypoxanthin;  extract  of  meat  rapidly  restores  the  muscles 
after  fatigue  (Kohert).  [Those  drugs  which  excite  muscular  tissue  restore  it  after  fatigue.  Now 
kreatin  is  a  waste  product  of  muscle,  and  beef  tea  and  Liebig's  extract  of  meat,  perhaps,  owe  their 
restorative  qualities  partly  to  these  extractives.] 

301.  THE  ELASTICITY  OF  MUSCLE.— Physical.— Every  elastic  body  has  its  "natural 
shape,"  /.  (". ,  its  sh.ijie  when  no  external  force  (tension  or  pressure)  acts  upon  it  so  as  to  distort  it. 
Thus,  the  passive  muscle  has  a  "  natural  form."  If,  however,  a  muscle  be  extended  in  the  course 
of  its  fibres,  the  parts  of  the  muscle  are  evidently  pulled  asunder.  If  the  stretching  be  carried  only 
to  a  certain  degree,  the  muscle,  in  virtue  of  its  elasticity,  will  regain  its  natural  form.  Such  a  body 
is  said  to  possess  "complete  elasticity,"  i.e.,  after  being  stretched  it  regains  exactly  its  original 


Dyn., 


ELASTIC    AFTER-EFFECT. 


52? 


shape.  By  the  term  "amount  of  elasticity"  {modulus)  is  meant  the  weight  (expressed  in  kilo- 
grammes) necessary  to  extend  an  elastic  body  i  Q  millimetre  in  diameter,  its  own  length,  without 
the  body  breaking.  Of  course,  many  bodies  are  ruptured  before  this  occurs.  For  a  passive  muscle 
it  is  ^=  0.2734  [ll'iintil)  [that  of  bone  =  2264  ( ll'drf/uim),  tendon  =r  1.6693,  nerve  ^  1.0905, 
the  arterial  walls  ^  0.0726  ( IViind/]'].  Thus  the  amount  of  elasticity  of  a  passive  muscle  is  small, 
as  it  requires  only  a  slight  stretching  force  to  extend  it  to  its  own  length.  It  has, therefore,  no  <Teat 
amount  of  elasticity.  The  term  "coefficient  of  elasticity  "  is  applied  to  the  fraction  of  the  length 
of  an  elastic  body,  to  which  it  is  elongated  by  the  unit  of  weight  applied  lo  stretch  it.  It  is  large 
in  a  passive  muscle.  If  the  tension  be  sufficiently  great,  the  elastic  body  ruptures  at  last.  The 
■^carrying  capacity^'  of  muscular  tissue,  until  it  ruptures,  is  in  the  follow-ing  ratios  for  youth,  middle, 
and  old  age,  nearly  7:3:2.  [Instead  of  the  word  "elasticity,"  Brunton  suggests  the  use  of 
extensibility  and  retractibility,  terms  suggested  by  Marey,  the  one  referable  to  the  elongation  on 
the  application  of  a  weight,  and  the  other  to  the  shortening  after  its  removal.] 

Curve  of  Elasticity. — In  inorganic  elastic  bodies,  the  line  of  elongation,  or 
the  extension,  is  directly  proportional  to  the  extending  jaeight ;  in  organic  bodies, 
and  therefore  in  muscle,  this  is  not  the  case,  as  the  weight  is  continually  increased 
by  equal  increments — the  muscle  is  less  extended  than  at  the  beginning,  so  that 
the  extension  is  not  proportional  to  the  H'eight.  If  equal  weights  be  added  to  a 
scale  pan  attached  to  a  piece  of  India-rubber,  with  a  writing  lever  connected  with 
it,  and  writing  its  movements  on  a  plate  of  glass  that  can  be  moved  with  the  hand, 
we  get  such  a  curve  as  in  Fig.  309,  while,  if  the  same  be  done  with  the  sartorius 
of  a  frog,  we  get  a  result  similar  to  Fig.  310.     A  straight  line  joins  the  apices 


Fig.  309. 


Fig.  310. 


Fig.  309.— Curve  of  elasticity  Irom  an  inorg.inic  body  (India-rubber).  Fig.  310.— Curve  of  elasticity  trom  the  sartorius 
of  a  frog,  obtained  by  adding  equal  increments  of  weight  at  A,  B,  C,  etc.  Fig.  311. — Curve  of  elasticity  produced 
by  continuous  extension  and  recoil  of  a  frog's  muscle ;  a  .r,  abscissa  before,  .v',  after  e.xtension. 


of  the  former,  while  the  curve  of  elasticity  is  a  hyperbola,  or  something  near  it, 
in  the  latter  case. 

Elastic  After-effect. — .\t  the  same  time,  after  the  first  elongation,  corres- 
ponding to  the  extending  weight,  is  reached,  the  muscle  may  remain  for  days,  and 
even  weeks,  somewhat  elongated.  This  is  called  the  "  e/astie  after-effeet"  (^  65). 
[Marey  attached  a  lever  to  a  frog's  muscle,  and  allowed  to  latter  to  record  its 
movements  on  a  slowly  revolving  cylinder.  To  the  lever  was  fi.ved  a  vessel  into 
which  mercury  slowly  flowed.  This  extended  the  muscle,  and  when  it  had  ceased 
to  elongate,  the  mercury  was  allowed  slowly  to  run  out  again.  The  curve  ob- 
tained is  shown  in  Fig.  311.  The  abscissae,  o  x  and  .v',  indicate  the  position  of 
the  writing  style  before  and  after  the  experiment,  and  we  observe  that  x  is  lower 
than  0  X,  so  that  the  recoil  is  imperfect.  There  has  been  an  actual  elongation  of 
the  muscle,  so  that  the  limit  of  its  elasticity  is  exceeded.  Although  a  frog's  gas- 
trocnemius may  be  loaded  with  1500  grammes  without  rupturing  it,  100  grammes 
will  prevent  it  regaining  its  original  length.] 

Method. — In  order  to  test  the  elasticity  of  a  muscle,  fix  it  to  a  support  provided  with  a  gradu- 
ated scale,  and  to  the  lower  end  of  the  muscle  attach  a  scale  pan,  into  which  are  placed  various 
weights,  measuring  on  each  occasion  the  corresponding  elongation  of  the  muscle  thereby  obtained 
(Ed.  Webir).  In  order  to  obtain  the  curve  of  elongation  or  extensibility,  take  as  abscissa*  the 
successive  units  of  weight  added  and  the  elongation  corresponding  to  each  weight  as  ordinates. 
Example  from  the  hyoglossus  of  the  frog: — 


528 


ELASTICITY    OF    ACTIVE    AND    INTACT    MUSCLES. 


Weight  in  Grammes. 

Length  of  the  Muscle  in 
Millimetres. 

Extension. 

In  Millimetres. 

Percentage. 

°-3 
1-3 
2-3 

3-3 
4-3 
5-3 

24.9 
30.0 

32-3 
33-4 
34-2 
34-6 

2-3 

I.I 

0.8 
04 

20 

7 
3 
2 

I 

The  elasticity  of  passive  muscle  is  small,  but  very  compktt-,  and  is  com- 
parable to  th.Tt  of  a  caoutchouc  fibre.  Small  weights  greatly  elongate  the  muscle. 
If  the  weights  be  uniforml)- increased  there  is  not  a  uniform  elongation;  with 
equal  increments  of  weight,  the  greater  the  load,  the  increase  in  elongation  always 
becomes  less  ;  or,  to  express  it  in  another  way,  the  amount  of  elasticity  of  the 
passive  muscle  increases  with  its  increased  extension  (F.il.   Weber). 

In  inorganic  bodies  the  curve  of  extension  is  a  straight  line,  but  in 
organic  bodies  it  more  closely  resembles  a  hyperbola  (  Wertheim).  The  elas- 
ticity of  a  passive, yi/Z/^gv^fv/ muscle  does  not  differ  essentially  from  that  of  a  non- 
fatigued  muscle. 

Muscles  in  the  living  body,  and  still  in  connection  willi  their  nerves  and  blood  vessels,  are  more 
extensible  than  excised  ones.  Muscles,  when  quite  fresh,  are  elongated  (within  certain  small  limits 
as  regards  the  weight)  at  first  with  a  uniformly  increasing  weight,  to  an  extent  proportional  to  the 
latter,  just  as  with  an  inorganic  body.  When  heavy  weights  are  used,  we  must  be  careful  to  take 
into  consideration  the  ^^  elastic  after-effect^^  {\  65). 

The  volume  of  a  stretched  muscle  is  slightly  less  than  an  unstretched  one,  similar  to  the  con- 
tracted (J  297,  2)  and  stiffened  muscle  {\  295). 

Dead  muscles  and  muscles  in  rigor  mortis  have  greater  elasticity,  i.  e.y  they  require  a  heavier 
weight  to  stretch  them  than  fresh  muscles;  but,  on  the  other  hand,  the  elasticity  of  dead  muscles 
is  less  complete,  /.  e.,  after  they  are  stretched  they  only  recover  their  original  form  within  certain 
limits. 

Elasticity  of  Intact  Muscles. — Normally,  within  the  body,  the  muscles  are 
stretched  to  a  very  slight  extent,  as  can  be  shown  by  the  slight  degree  of  retrac- 
tion which  occurs  when  the  insertion  of  a  muscle  is  divided.  This  slight  degree 
of  extension,  or  stretching,  is  important.  If  this  were  not  so,  when  a  muscle  is 
about  to  contract,  and  before  it  could  act  upon  a  bone  as  a  lever,  it  would  have 
to  take  in  so  much  slack.  The  elasticity  of  muscles  is  manifested  during  the  con 
traction  of  antagonistic  muscles.  The  position  of  a  passive  limb  depends  upon 
the  resultant  of  the  elastic  tension  of  the  different  muscle  groups. 

The  elasticity  of  an  active  muscle  is  less  than  that  of  a  passive  muscle, 
/.  e.,  it  is  elongated  by  the  same  weight  to  a  greater  extent  than  a  passive  muscle. 
For  this  reason,  the  active  muscle,  as  can  be  shown  in  an  excised  contracted  mus- 
cle, is  J(y?c/' ;  the  apparently  great  hardness  manifested  by  stretched,  contracted 
muscles  depends  upon  their  tension.  When  the  active  muscle  becomes  faligued 
its  elasticity  is  diminished  (§  304). 

Method. — Ed.  Weber  took  the  hyoglossus  muscle  of  a  frog  and  suspended  it  vertically,  noticing 
its  length  when  it  was  passive.  It  was  then  tetanized  with  induction  shocks  and  its  height  again 
noted.  One  after  the  other  heavier  weights  were  attached  to  it,  and  the  length  of  the  passive  and 
tetanized  muscle  observed  for  each  weight.  The  extent  to  which  the  active  loaded  muscle  shortened 
from  the  position  of  the  passive  loaded  muscle  he  called  the  "height  of  the  lift  "  (or"  Hubhohe  "). 
The  latter  becomes  less  as  the  weight  increases,  and  lastly,  the  tetanized  muscle  may  be  so  loaded  that 
it  cannot  contract,  /.  <•.,  the  height  of  the  lift  is  ^  O. 

Weber's  Paradox. — The  case  may  occur  where,  when  a  muscle  is  so  loaded  that  it  cannot  con- 
tract when  it  is  stimulated,  it  may  even  elongate.  According  to  Wundt,  even  in  this  condition  the 
elasticity  is  not  changed.  [The  usual  explanation  given  is  that,  as  the  elasticity  of  a  muscle  is  dimin- 
ished during  contraction,  it  is  more  extended  with  the  same  weight  iii  the  contracted  as  compared 


FORMATION    OF    HEAT    IN    AN    ACTIVE    MUSCLE.  529 

with  the  passive  or  uncontracted  state,  so  that  a  heavily-weighted  muscle,  when  stimulated,  may 
elongate  instead  of  shorten.]  According  to  Wundt,  however,  there  is  no  change  in  the  elas  icity 
of  the  muscle.  In  these  experiments,  the  length  of  the  active  loaded  muscle  is  equal  to  the  length 
of  the  passive  muscle  when  similarly  loaded,  minus  the  "  height  of  the  lift." 

Poisons. — Potash  causes  shortening  of  a  muscle  with  simultaneous  increase  of  its  elasticity. 
Digitalin  produces  other  changes  with  increased  elasticity.  Physostigmin  increases  it,  while  vera- 
trin  diminishes  it,  and  interferes  with  its  completeness  (Jiossbach  and  v.  Anrep),  and  tannin  makes 
a  muscle  less  extensible,  but  more  elastic  [Le-Min).  Ligature  of  the  blood  vessels  produces  at  first 
a  decrease,  and  then  an  increase,  of  the  elasticity  ;  section  of  the  motor  nerve  diminishes  the  elas- 
ticity (v.  Aiirc/i) ;  heat  increases  it. 

Eduard  Weber  concluded  from  his  experiments  that  a  muscle  assumes  two  forms,  the  active  and  the 
passive  form.  Each  of  these  corresponds  to  a  special  natural  form.  The  passive  muscle  is  longer 
and  thinner — the  active  is  shorter  and  thicker  in  form.  The  passive  as  well  as  the  active  muscle 
strives  to  retain  its  form.  If  the  passive  muscle  be  set  into  activity,  the  passive  rapidly  changes  into 
the  active  form,  in  virtue  of  its  elastic  force.  The  latter  is  the  energy  which  causes  muscular  work. 
Schwann  compared  the  force  of  an  active  muscle  to  a  long,  elastic,  tense,  spiral  spring.  Both  can 
lift  the  greatest  weight  only  from  that  form  in  which  they  are  most  stretched.  The  more  they 
shorten,  the  less  the  weight  which  they  can  lift. 

[Tonicity  of  Muscle  (§  362) — Sensibility  of  Muscle. — That  muscles  contain  sensory  fibres 
is  certain  (J  430).  Strction  of  inflamed  muscles  is  painful,  and  during  muscular  cramp  intense  pain 
is  felt.  Sachs  discharged  a  reflex  action  by  stimulating  the  central  end  of  an  intra-muscular  nerve 
filament  in  a  frog,  while  stimulation  of  the  central  end  of  the  phrenic  nerve  raises  the  blood 
pressure  (Muscular  Sense,  J  430).] 

[Uses  of  Elasticity. — .\s  already  pointed  out,  all  muscles  are  slightly  on  the 
stretch,  so  that  no  time  is  lost  nor  energy  wasted  in  "  taking  in  slack,"  as  it  were  ; 
but  the  elasticity  also  lessens  the  shock  of  the  contraction,  so  that  it  is  developed 
gradually,  and  muscles  are  not  liable  to  be  torn  from  their  attachments.  The 
muscular  energy  is  transmitted  to  the  mass  to  be  moved  through  an  elastic  and 
easily  extensible  body  (muscle),  whereby  the  shock  due  to  the  contraction  is 
lessened,  but,  as  Marey  has  shown,  the  amount  of  work  is  thereby  considerably 
increased.] 

302.  FORMATION    OF    HEAT    IN    AN  ACTIVE    MUSCLE.— 

After  Bunzen.  m  1805  (§  209,  i,  /'),  showed  that  during  muscular  activity  heat  is 
evolved,  v.  Helmholtz  proved  that  an  excise/  frog's  muscle,  when  ietanized  iox 
two  to  three  minutes,  e.xhibited  an  increase  of  its  temperature  of  0.14°  to 
0.18°  C.  R.  Heidenhain  succeeded  in  showing  an  increase  of  0.001°  to  0.005° 
C.  for  each  single  contraction.     The  heart  is  warmer  during  every  systole  i^Marey). 

[Method. — The  rise  in  temperature  of  a  frog's  muscle  may  be  estimated  by  placing  the  two 
gastrocnemii  of  a  frog's  muscle  on  the  two  junctions  of  a  thermo  electric  pile,  connected  with  a  heat 
galvanometer.  Of  course,  when  the  two  muscles  are  at  the  same  temperature,  the  needle  of  the 
galvanometer  is  stationary  ;  but,  if  one  muscle  be  made  to  contract,  or  is  tetanized,  then  an  elec- 
trical current  is  set  up  which  deflects  the  needle  (g  208,  B).] 

The  following  facts  have  been  ascertained  with  regard  to  the  development  of 
heat : — 

I.  Relation  to  Work. — It  bears  a  relation  to  the  amount  of  work,  (a)  If 
a  muscle  during  contraction  carries  a  weight  which  extends  it  again  during  rest, 
no  work  is  transferred  beyond  the  muscle  (§  300).  In  this  case  all  the  chemi- 
cal potential  energy  during  this  movement  is  converted  into  heat.  Under 
these  circumstances  the  amount  of  heat  evolved  runs  parallel  with  the  amount  of 
work  done,  i.e.,  it  increases  as  the  load  and  the  height  increase  up  to  a  maximum 
point,  and  afterward  diminishes  as  the  load  is  increased.  The  heat  maximum  is 
reached  with  a  less  load  sooner  than  the  work  maximum  (^Heidenhain). 

(b)  If,  when  the  muscle  is  at  the  height  of  its  contraction,  the  load  be  removed, 
then  the  muscle  has  produced  work  referable  to  something  outside  itself;  in  this 
case  the  amount  of  heat  produced  is  less  {A.  Ficli).  The  amount  of  work  pro- 
duced, and  the  diminished  amount  of  heat  formed,  when  taken  together,  repre- 
sent the  same  amount  of  energy,  corresponding  to  the  law  of  the  conservation  of 
energy. 

34 


530  THE    MUSCLE    SOUND. 

(c)  If  the  same  amount  of  work  is  performed  in  one  case  by  many  but  small 
contractions,  and  in  another  by  fewer  but  larger  contractions,  then  in  the  latter 
case  the  amount  of  heat  is  greater  {^Heidenhain  and  Ninvalichiii).  This  shows 
that  larger  contractions  are  accompanied  by  a  relatively  greater  metabolism  of  the 
muscular  substance  than  small  contractions,  which  is  in  harmony  with  practical 
experience  ;  thus  the  ascent  of  a  tower  with  steei)  high  steps  causes  fatigue  more 
rapidly  (metabolism  greater)  than  the  ascent  of  a  more  gentle  slope  with  lower 
steps. 

(d)  If  the  weighted  muscle  executes  a  series  of  contractions  one  after  the  other, 
and  at  the  same  time  does  work,  then  the  amount  of  heat  it  produces  is  greater 
than  when  it  is  tetanic,  and  keeps  a  weight  suspended.  Thus  the  transition  of 
the  muscle  into  a  shortened  form  causes  a  greater  production  of  heat  than  the 
maintenance  of  this  form. 

2.  Relation  to  Tension. — The  amount  of  heat  evolved  depends  upon  the 
tension  of  the  muscle ;  it  also  increases  as  the  muscular  tension  increases  [Heiden- 
hain).  If  the  ends  of  a  muscle  be  so  fixed  that  it  cannot  contract,  the  maximum 
of  heat  is  obtained  (i?(V/rt/v/).  Such  a  condition  occurs  during  tetanus,  in  which 
condition  the  violently  contracted  muscles  oppose  each  other,  and  very  high  tem- 
peratures have  been  registered  by  Wunderlich  (§  213,  7),  while  the  same  is  true 
of  animals  that  are  tetanized  {Leyden).  Dogs  kept  m  a  state  of  tetanus  by  elec- 
trical stimulation  die,  because  their  temperature  rises  so  high  (44°  to  45°  C), 
that  life  no  longer  can  be  maintained  {Riehet).  In  addition  to  the  formation  of 
heat,  there  is  a  considerable  amount  oi  acid  ax\A.  of  alcoholic  extractives  produced 
in  the  muscular  tissue. 

3.  Relation  to  Stretching. — Heat  is  also  evolved  during  the  elongation  or 
relaxation  of  a  contracted  muscle,  e.g.,  by  causing  a  muscle  to  contract  without 
the  addition  of  any  weight,  and  loading  it  when  it  begins  to  relax,  whereby  heat 
is  produced  {Steiner,  Schmulewitsch  anil  Westerman^. 

4.  The  formation  of  heat  diminishes  as  the  muscular  fatigue  increases. 

5.  In  a  muscle  duly  supplied  with  blood,  the  production  of  heat  (as  well  as  the 
mechanical  work)  is  far  more  active  than  in  a  muscle  whose  blood  vessels  are 
ligatured  or  its  blood  stream  cut  off.  Recovery  takes  place  more  rapidly  and 
completely  after  fatigue,  while  at  the  same  time  there  is  a  new  increase  in  the 
production  of  heat  {Meade  Smith). 

The  amount  of  work  and  heat  in  a  muscle  must  always  correspond  to  the  transformation  of  an 
equivalent  amount  of  chrmical  energy.  A  greater  part  of  this  energy  is  manifested  as  work,  the 
greater  the  resistance  that  is  offered  to  the  muscular  contraction.  When  the  resistance  is  great,  \  of 
the  chemical  energy  may  be  manifested  as  work,  but  when  it  is  small,  only  a  small  part  of  it  is  so 
converted. 

It  was  stated  that  a  nerve  in  action  is  ^ij°  C.  warmer  (  Valentin),  but  this  is  denied  by  v.  Helm- 
holtz  and  Heidenhain. 

In  man,  if  the  muscles  be  stimulated  with  electricity  or  contracted  voluntarily,  the  production  of 
heat  may  be  detected  through  the  skin  [v.  Ziemssen).  The  venous  blood  flowing  from  an  actively- 
contracting  muscle  is  0.6°  C.  warmer  than  the  arterial  blood  [Mendc  Smith). 

303.  THE  MUSCLE  SOUND.— Muscle  Sound.— When  a  muscle  con- 
tracts, and  is  at  the  same  time  kept  in  a  state  of  tension  by  the  application  of 
sufficient  resistance,  it  emits  a  distinct  sound  or  tone,  depending  upon  the  inter- 
mittent variations  of  tension  occurring  within  it  (  VVollaston). 

Methods. — The  muscle  sound  may  be  heard  by  placing  the  ear  over  the  tetanically  contracted 
and  tense  biceps  of  another  person;  or  we  may  insert  the  tips  of  our  index  fingers  into  our  ears, 
and  forcibly  contract  the  muscles  of  our  arm ;  or  the  sound  of  the  muscles  that  close  the  jaw  may 
be  heard  by  forcibly  contracting  them^  especially  at  night  when  all  is  still,  and  when  the  outer  ears 
are  closed.  V.  Helmholtz  found  that  this  tone  coincides  with  the  resonance  tone  of  the  ear,  and  he 
thought  that  the  vibrations  of  the  muscles  caused  this  resonance  tone.  The  sound  of  an  isolated 
frog's  muscle  may  be  heard  by  placing  one  end  of  a  rod  in  the  ear,  the  other  ear  being  closed.  To 
the  other  end  of  the  rod  is  attached  a  loaded  frog's  muscle  kept  in  a  tetanic  condition.  The  pitch 
of  the  note,  ;'.  e.,  the  number  of  vibrations,  may  be  estimated  by  comparing  the  muscle  sound  with 
that  produced  by  elastic  springs  vibrating  at  a  known  rate. 


FATIGUE    AND    RECOVERY    OF    MUSCLE.  531 

When  a  muscle  contracts  voluntarily,  /.  e.,  through  the  will,  it  makes  19.5 
vibrations  per  second.  We  do  not  hear  this  very  low  tone,  owing  to  the  number 
of  vibrations  per  second  being  too  few ;  but  what  we  actually  hear  is  the  first 
overtone,  with  double  the  number  of  vibrations.  The  muscle  sound  has  19.5 
vibrations,  when  the  muscles  of  an  animal  are  caused  to  contract,  by  stimulating 
its  spinal  cord  (v.  Helmholtz),  and  also  when  the  motor  nei-re  trunk  is  excited  by 
chemical  means  (Bernstein).  If,  however,  tetanizing  induction  shocks  be  applied 
to  a  muscle,  then  the  number  of  vibrations  of  the  muscle  sound  corresponds  exactly 
with  the  number  of  vibrations  of  the  vibrating  spring  or  hammer  of  the  induction 
apparatus.  Thus  the  tone  may  be  raised  or  lowered  by  altering  the  tension  of  the 
spring. 

Lov^n  found  that  the  muscle  sound  was  loudest  when  the  weakest  currents  capable  of  producing 
tetanus  were  employed.  The  sound  corresponded  to  the  number  of  vibrations  of  the  octave  just 
below  it  in  the  scale.  With  stronger  currents  the  muscle  sound  disappears,  but  it  reappears  with  the 
same  number  of  vibrations  as  that  of  the  interrupter  of  the  induction  apparatus,  if  sill  stronger 
currents  are  used. 

If  the  induction  shocks  be  ajiplied  to  the  nerve,  the  sound  is  not  so  loud,  but 
it  has  the  same  number  of  vibrations  as  the  interrupter.  With  rapid  induction 
shocks,  tones  caused  by  704  (Lovhi)  and  1000  vibrations  per  second  have  been 
produced  (Bernstein). 

The  first  heart  sound  is  partly  muscular  (§  53). 

The  muscle  sound  is  regarded  as  a  sign  that  tetanus  is  due  to  a  series  of  single  variations  of  the 
density  of  the  muscle  {\  298,  III). 

304.  FATIGUE  AND  RECOVERY  OF  MUSCLE.— Fatigue.— By 

the  term  fatigue  is  meant  that  condition  of  diminished  capacity  for  work  which  is 
produced  in  a  muscle  by  prolonged  activity.  This  condition  is  accompanied  in 
the  living  person  with  a  peculiar  feeling  of  lassitude,  which  is  referred  to  the 
inuscles.  A  fatigued  muscle  rapidly  recovers  in  a  living  animal,  but  an  excised 
muscle  recovers  only  to  a  slight  extent  (Ed.  Weber,  Valentin'). 

[Waller  recognizes  a  certain  resemblance  between  experimental  fatigue  and  the  natural  decline 
of  excitability  at  death,  in  disease,  and  in  poisoning.] 

The  cause  of  fatigue  is,  probably,  piartly  due  to  the  accumulation  of  decomposi- 
tion products — "fatigue  stuffs" — in  the  muscular  tissue,  these  products  being 
formed  within  the  muscle  itself  during  its  activity.  They  are  phosphoric  acid, 
either  free  or  in  the  form  of  acid  phosphates,  acid  potassium  phosphate  (§  294), 
glycerin-phosphoric  acid  (?),  and  CO2.  If  these  substances  be  removed  from  a 
muscle,  by  passing  through  its  blood  vessels  an  indifferent  solution  of  common 
salt  (0.6  per  cent.),  or  a  weak  solution  of  sodium  carbonate  [or  a  dilute  solution 
of  permanganate  of  potash  (Kroneckery],  the  mu.scle  again  becomes  capable  of 
energizing  (J.  Ranke,  J86j).  The  using  up  of  O  by  an  active  muscle  favors 
fatigue  (v.  Fettenkofer  and  v.  Voit).  The  transfusion  of  arterial  blood  (not  of 
vtXiov&—Bichat )  removes  the  fatigue  (Ranke,  Kronecker),  probably  by  replacing 
the  substances  that  have  been  used  up  in  the  muscle.  Conversely,  an  actively- 
energizing  muscle  may  be  rapidly  fatigued  by  injecting  into  its  blood  vessels  a 
dilute  solution  of  phosphoric  acid,  of  acid  potassium  phosphate,  or  dissolved 
extract  of  meat  (Kcmmericli).  A  muscle  fatigued  in  this  way  absorbs  less  O,  and 
when  so  fatigued  it  evolves  only  a  small  amount  of  acids  and  CO^.  The  condi- 
tions which  lead  up  to  fatigue  are  connected  with  considerable  metabolism  in  the 
muscular  tissue. 

[Zabludowski  found  that  if  a  frog's  muscles  be  systematically  stimulated  by  maximum  induction 
shocks  until  they  cease  to  contract,  massage,  or  kneading  them  rapidly,  restored  their  excitability, 
while  simple  rest  had  little  effect.  Massage  acts  on  the  nerves,  but  chiefly  by  favoring  the  blood 
and  lymph  streams  which  wash  out  the  waste  products  from  the  muscle.  K  simdar  result  obtains 
in  man,  so  that  the  ancient  Roman  practice  of  "  rubbing  "  after  a  bath  and  after  exercise  was  one 
conducive  to  restoration  of  the  power  of  the  muscles.] 


532  MODIFYING    CONDITIONS. 

Modifying  Conditions. — In  order  to  obtain  the  same  amount  of  work  from 
a  fatigued  muscle,  a  much  more  powerful  stimulus  must  be  applied  to  it  than  to  a 
fresh  one.  A  fatigued  muscle  is  incapable  of  lifting  a  considerable  load,  so  that 
its  absolute  muscular  force  is  diminished.  If,  during  the  course  of  an  experiment, 
an  excised  muscle  be  loaded  with  the  same  weight,  and  if  the  muscle  be  stimulated 
at  regular  intervals  with  maximal  stimuli  (strong  induction  shocks),  contraction 
after  contraction,  gradually  and  regularly  diminishes  in  height,  the  decrease  being 
a  constant  fraction  of  the  total  shortening.  Thus  the  fatigue  curve  is  represented 
by  a  straight  tine  [/.  e.,  a  straight  line  will  touch  the  apices  of  all  the  contractions]. 
The  more  rapidly  the  contractions  succeed  each  other,  the  greater  is  the  fall  in  the 
height  of  the  contraction  [/.  e.,  if  the  ////(Vtv?/ between  the  contractions  be  short, 
the  fatigue  curve  falls  rapidly  toward  the  abscissa],  and  conversely.  After  a  cer- 
tain number  of  contractions,  an  excised  muscle  becomes  exhausted. 

This  result  occurs  whether  the  stimuli  are  applied  at  short  or  long  intervals 
(AV^//d7-/(Y/-),  and  a  similar  result  is  obtained  with  submaximal  stimuli  (/"/fo-f/). 
A  fatigued  muscle  contracts  more  slowly  than  a  fresh  one,  while  the  latent  period 
is  also  longer  during  fatigue  (p.  518).  The  fatigued  muscle  is  said  to  be  more 
extensible  {Dont/i'/s  a/tit  7'a/!  Afa/isve/t).  If  a  muscle  be  so  loaded  that  when  it 
contracts  it  cannot  lift  the  load,  fatigue  occurs  even  to  a  greater  extent  than  when 
the  load  is  such  that  the  muscle  can  lift  it  (ZiVw).  The  metabolism  and  the  forma- 
tion of  acid  are  greater  in  a  contracted  muscle  kept  on  the  stretch,  than  in  a  contracted 
muscle  allowed  to  shorten  (^Hclitenhain).  If  a  muscle  contract,  but  is  not  required 
to  lift  any  load,  it  becomes  fitigued  only  very  gradually.  If  a  muscle  be  loaded 
only  during  contraction,  and  not  during  relaxation,  it  is  fatigued  more  slowly  than 
when  it  is  loaded  during  both  phases ;  and  the  same  is  true  when  a  muscle  has  to 
lift  its  load  only  during  the  course  of  its  contraction,  instead  of  at  the  beginning 
of  the  contraction.  Loads  may  be  suspended  to  perfectly  passive  muscles  without 
fatiguing  them  {Jdarlcss,  Leber). 

[Signs  of  Fatigue. — In  the  record  of  the  series  of  contractions  (i)  the  con- 
tractions become  more  prolonged,  (2)  they  decrease  in  extent,  (3)  but  Waller 
finds  that  a  skeletal  muscle  exhibits  after  a  period  of  rest  a  "  staircase  "  character 
of  its  contractions  just  like  the  heart  (§  57J.] 

[While  an  excised  frog's  muscle  is  fairly  rapidly  exhausted  by  single  opening  induction  shocks 
at  intervals  of  one  second,  human  muscle  in  its  normal  relations  may  be  almost  indefinitely  so 
treated,  and  there  is  no  change  in  the  record  or  any  sensation  of  fatigue,  and  Waller  regards  this  as 
favoring  the  view  that  the  "  fatigue  consequent  upon  prolonged  muscular  exertion  is  normally  cen- 
tral rather  than  peripheral."  Such  results,  however,  do  not  harmonize  with  those  of  Zabludowski 
on  the  kneading  of  muscles  or  massage.  Probably  there  are  two  factors,  one  central  the  other  periph- 
eral.] 

Blood  Supply. — If  the  arteries  of  a  mammal  be  ligatured,  stimulation  of  the  motor  ner\'es  pro- 
duces complete  fatigue  after  120  to  240  contractions  (in  two  to  four  minutes),  but  direct  muscular 
stimulation  still  causes  the  muscles  to  contract.  In  both  cases  the  fatigue  cun'e  is  in  the  form  of 
a  straight  line.  If  the  blood  supply  to  a  mammalian  muscle  be  normal,  on  stimulating  the  motor 
nerve  the  muscular  contractions  at  first  increase  in  height  and  then  fall,  their  apices  forming  a  straight 
line  [Rossbach  and  Harleneck).  In  persons  who  have  used  their  muscles  untd  fatigue  sets  in,  it  is 
found  that  at  the  beginning  the  nerves  and  muscles  react  better  to  galvanic  and  faradic  stimulation, 
but  afterward  always  to  a  less  degree  {Orsckanski).  According  to  v.  Kries,  a  muscle  tetanized  and 
fatigued  with  maximal  stimuli  behaves  like  a  fresh  muscle  tetanized  with  submaximal  stimuli ;  both 
show  an  incomplete  transition  from  the  passive  to  the  active  condition. 

[Relation  of  End  Plates. — Muscle  is  fatigued  far  more  rapidly  than  nerve,  and  the  fatigue  begins 
in  the  muscle  and  not  in  the  nerve,  and  it  seems  to  be  the  weakest  link  in  the  chain  between  nerve 
and  muscle  which  is  affected  during  excessive  action,  viz.,  the  motor  end  plate  ( IValler).  In  a 
nerve  its  conductivity  is  sooner  affected  by  fatigue  than  its  direct  excitability.  Waller  finds  that 
after  death  "  the  excitability  of  a  nerve  persists  when  its  action  upon  muscle  has  ceased,  such  muscle 
being  still  excitable  by  direct  stimulation."  Some  link  in  the  chain  is  obviously  affected,  and  it  is 
perhaps  the  end  plates.] 

[Action  of  Drugs  on  Fatigue. — Waller  finds,  in  a  frog  poisoned  with  veratrin,  that  if  the  mus- 
cles be  stimulated  electrically  the  characteristic  elongation  of  the  descent  (J  298)  gradually  disap- 
pears, but  reappears  after  a  period  of  rest.  In  this  respect  strychnin  in  its  action  on  the  spinal  cord 
behaves    precisely  the  same  as  veratrin  on   muscle,  viz.,  its   effect  is  dissipated   by  action   and 


MECHANISM    OF   THE    BONES   AND   JOINTS. 


533 


restored  by  rest.]  Curara  and  the  ptomaines  cause  an  irregular  course  of  the  fatigue  curve  ( Cuaresc/ii 
and  Mosso). 

[If  strychnin  be  injected  into  a  frog,  and  the  sciatic  nerve  on  one  side  divided  after  the  strychnin 
tetanus  has  lasted  for  a  time,  the  leg  muscles  of  the  side  with  the  nerve  undivided  exhibit  signs  of 
fatigue,  as  shown  by  direct  stmiulation  of  the  muscles  of  both  legs  when  a  curve  similar  to  Fig.  312 
is  obtained.  The  higher  one  is  the  non-fatigued,  the  lower  that  of  the  side  with  the  nerve  undi- 
vided (;(•«//«•)-] 

Recovery  from  the  condition  of  fatigue  is  promoted  by  passing  a  constant  elec- 
trical current  through  the  entire  length  of  the  muscle  {Heitlenhain),  also  by  inject- 
ing fresh  arterial  blood  into  its  blood  vessels,  or  by  very  small  doses  of  veratrin 
[or  permanganate  of  potash]  and  by  rest. 

If  the  muscle  of  an  intact  animal  be  stimulated  continuously  (fourteen  days  or  thereby),  until 
complete  fatigue  occurs,  the  muscular  fibres  become  granular  and  exhibit  a  wax-like  degeneration. 
The  transverse  striation  is  still  visible  as  long  as  the  sa'cous  substance  is  in  large  masses, but  as  soon 
as  it  breaks  up  into  small  pieces  the  transverse  striation  disappears  completely  (O.  Roth). 

305.    MECHANISM    OF   THE    BONES   AND  JOINTS.— Bones 

exhibit  in  the  inner  architecture  of  their  ^[longiosa  an  arrangement  of  their 
lamellffi  and  spicules  which  represents  the  static  result  of  those  forces — pressure 
and  traction — which  act  on   the  developing  bone.     They  are  so  arranged  that, 

Fi.;.  ^12. 


»n  of  the  gastrocnemius  o(  a  frog  poisoned  with  5tr>'chnin  { IVtt/ler),  the 
side  tupper  curve)  and  not  on  the  other  (lower  or  fatigue  curve). 

with  the  minimum  of  material,  they  afford  the  greatest  resistance  as  a  supporting 
structure  or  framework  {H.  v.  Meyer,  Culmann,  Jul.   Wolff). 

I.  The  joints  permit  the  freest  movements  of  one  bone  upon  another  [such  as  exist  between  the 
extremities  of  the  bones  of  the  limbs.  In  other  cases,  sutures  are  formed,  which,  while  permitting 
no  movement,  allow  the  contents  of  the  cavity  which  they  surround  to  enlarge,  as  in  the  case  of  the 
cranium.]  The  articular  end  of  a  fresh  bone  is  covered  with  a  thin  layer  or  plate  of  hyaline  car- 
tilage, which  in  virtue  of  its  elasticity  moderates  any  shocks  or  impulses  coinmunicated  to  the  bones. 
The  surface  of  the  articular  cartilage  is  perfectly  smooth,  and  facilitates  an  easy  gliding  movement 
of  the  one  surface  upon  the  other.  At  the  outer  boundary  line  of  the  cartilage,  there  is  fixed  the  cap- 
sule of  the  joint,  which  encloses  the  articular  ends  of  the  bones  like  a  sac.  The  inner  surface  of 
the  capsule  is  lined  by  a  synovial  membrane,  which  secretes  the  sticky,  seini-fluid,  synovia,  moisten- 
ing the  joint.  The  outer  surface  of  the  capsule  is  provided  at  various  pans  with  bands  of  fibrous 
tissue,  some  of  which  strengthen  it,  while  others  restrain  or  limit  the  movements  of  the  joint.  Some 
osseous  processes  limit  the  movements  of  particular  joints,  e.  g.,  the  coronoid  process  of  the  ulna, 
which  permits  the  forearm  to  be  flexed  on  the  upper  arm  only  to  a  certain  extent ;  the  olecranon, 
which  prevents  over-extension  at  the  elbow  joint.  The  joint  surfaces  are  kept  in  apposition— ( i ) 
by  the  adhesion  of  the  synovia-covered  smooth  articular  surfaces;  (2)  by  the  capsule  and  its  fibrous 
bands;  and  (3)  by  the  elastic  tension  and  contraction  of  the  muscles. 

[Structure  of  Articular  Cartilage.— The  thin  layer  of  hyaline  encrusting  cartilage  is  fixed  by 
an  irregular  surface  upon  the  corres^ionding  surface  of  the  head  of  the  bone.  In  a  vertical  section 
through  the  articular  cartilage  of  a  bone,  which  has  been  softened  in  chromic  or  other  suitable  acid, 
we  observe  that  the  cartilage  cells  are  flattened  near  the  free  surface  of  the  cartilage,  and  their  long 
axes  are  parallel  to  the  surface  of  the  joint ;  lower  down,  the  cells  are  arranged  in  irregular  groups, 


534  HINGE    AND    SCREW-HINGE   JOINTS. 

and  further  down  still,  nearer  the  bone,  in  columns  or  rows,  whose  long  axis  is  in  the  long  axis  of 
the  bone.  These  rows  are  produced  by  transverse  cleavage  of  pre  existing  cells.  In  the  upper 
two-thirds  or  thereby  the  matrix  of  the  cartilage  is  hyaline,  but  in  the  lower  third,  near  the  bone, 
the  matrix  is  granular  and  sometimes  tibrillaled.  This  is  the  calcified  zone,  which  is  impregnated 
with  lime  salts,  and  shaqjly  defined  by  a  nearly  straight  line  from  the  hyaline  zone  al)0ve  it,  and  by 
a  bold  wavy  line  from  the  osseous  head  of  the  bone.] 

Synovial  Membrane. — Synovi.^l  membrane  consists  of  bundles  of  delicate  connective  tissue 
mixed  with  elastic  tissue,  while  on  its  inner  surface  it  is  provided  with  folds,  some  cf  which  contain 
fat,  and  others  blood  vessels  (synovial  villi).  The  inner  surface  is  lined  with  endoth<  hum.  The 
intra-capsular  ligaments  and  cartilages  are  not  covered  by  the  synovial  membrane,  nor  are  they 
covered  by  endothelium.  The  synovia  is  a  colorless,  stringy,  alkaline  fluid,  with  a  chemical  com- 
position closely  allied  to  that  of  transud.itions,  with  this  difference,  that  it  contains  much  mucin, 
together  with  albumin  and  traces  of  fat.  Excessive  movement  diminishes  its  amount,  makes  it  more 
inspissated,  and  increases  the  mucin,  but  diminishes  the  salts. 

Joints  may  be  divided  in'to  several  classes,  according  to  the  kind  of  movement 
which  they  permit : — 

1.  Joints  with  movement  around  one  axis  :  (a)  The  Ginglymus,  or  Hinge  Joint. — The  one 
articular  surface  represents  a  portion  of  a  cylinder  or  sphere,  to  which  the  other  surface  is  adapted 
by  a  corresponding  depression,  so  that,  when  flexion  or  extension  of  the  joint  takes  place,  it  moves 
only  on  one  axis  of  the  cylinder  or  sphere.  The  joints  of  the  fingers  and  toes  are  hinge  joints  of 
this  description.  Lateral  ligaments,  which  prevent  a  lateral  displacement  of  the  articular  surfaces, 
are  always  present. 

The  Screw-hinge  Joint  is  a  modification  of  the  simple  hinge  form  (Longer,  Henke),  e.g.,  the 
humcro-uinar  articulation.  Strictly  speaking,  simple  flexion  and  extension  do  nut  take  place  at  the 
elbow  joint,  but  the  ulna  moves  on  the  capitellum  of  the  humerus  like  a  nut  on  a  bolt ;  in  the 
right  humerus  the  screw  is  a  right  spiral,  in  the  left,  a  left  spiral.  The  ankle  joint  is  another  ex- 
ample ;  the  nut  or  female  screw  is  the  tibial  surface,  the  right  joint  is  like  a  left-handed  screw,  the 
left  the  reverse,  (b)  The  pivot  joint  (rotatoria),  with  a  cylindrical  surface,  e.g.,  the  joint  between 
the  atlas  and  the  axis,  the  axrs  of  rotation  being  around  the  odontoid  process  of  the  axis.  In  the 
acts  of  pronation  and  supination  of  the  forearm  at  the  elbow  joint,  the  axis  of  rotation  is  from 
the  middle  of  the  cotyloid  cavity  of  the  head  of  the  radius' to  the  styloid  process  of  the  ulna.  The 
other  joints  which  assist  in  these  movements  are  above  the  joint  between  the  circumferential  part  of 
the  head  of  the  radius  and  the  sigmoid  cavity  of  the  ulna,  and  below  the  joint  between  the  sigmoid 
cavity  of  the  radius  which  moves  over  the  rounded  lower  end  of  the  ulna. 

2.  Joints  with  movements  arotinJ  two  axes. — (a)  Such  joints  have  two  unequally  curved  surfaces 
which  intersect  each  other,  but  which  lie  in  the  same  direction,  e.  g.,  the  atlanto  occipital  joint,  or 
the  wrist  joint,  at  which  lateral  movements,  as  well  as  flexion  and  extension,  take  place,  (b)  Joints 
with  curved  surfaces,  which  intersect  each  other,  but  which  do  not  lie  in  the  same  direction.  To 
this  group  belong  the  saddle-shaped  articulations,  whose  surface  is  concave  in  one  direction,  but 
convex  in  the  other,  e.  g.,  the  joint  between  the  metacarpal  bone  of  the  thumb  and  the  trapezium. 
The  chief  movements  are — (l)  flexion  and  extension,  (2)  abduction  and  adduction.  Further,  to  a 
limited  degree,  movement  is  po.ssible  in  all  other  directions;  and,  lastly,  a  pyramidal  movement  can 
be  described  by  the  thumb. 

3.  Joints  with  movement  on  a  spiral  articular  surface  [spiral joints),  e.  g.,  the  knee  joint  [Good- 
sir).  The  condyl  of  the  femur,  curved  from  before  backward,  in  the  antero-posterior  section  of  its 
articular  surface,  represents  a  spiral  (Ed.  Weber'),  whose  centre  lies  nearer  the  posterior  part  of  the 
condyle,  and  whose  radius  vector  increases  from  behind,  downward  and  forward.  Flexion  and 
extension  are  the  chief  movements.  The  strong  lateral  ligaments  arise  from  the  condyles  of  the 
femur  corresponding  to  the  centre  of  the  spiral,  and  are  inserted  into  the  head  of  the  fibula  and  in- 
ternal condyle  of  the  tibia.  When  the  knee  joint  is  strongly  flexed,  the  lateral  ligaments  are  relaxed 
— they  become  tense  as  the  extension  increases;  and  when  the  knee  joint  is  fully  extended,  they  act 
quite  like  tense  bands  which  secure  the  lateral  fixation  of  the  joint.  Corresponding  to  the  sj^iral 
form  of  the  articular  surface,  fiexion  and  extension  do  not  take  place  around  one  axis,  but  the  axis 
moves  continually  with  the  p')int  of  contact;  the  axis  moves  also  in  a  spiral  direction.  The  greatest 
flexion  and  extension  covers  an  angle  of  about  145°.  The  anterior  crucial  ligament  is  more  tense 
during  extension,  and  acts  as  a  check  ligament  for  too  great  extension,  while  the  posterior  is  more 
tense  during  flexion  and  is  a  check  ligament  for  too  great  flexion.  The  movements  of  extension 
and  flexion  at  the  knee  are  further  complicated  by  the  fact  that  the  joint  has  a  screw-like  move- 
ment, in  that  during  the  greater  extension  the  leg  moves  outward.  Hence,  the  thigh,  when  the  leg 
is  fixed,  must  be  rotated  outward  during  fiexion.  Pronation  and  supination  take  place  during  the 
greatest  flexion  to  the  extent  of  41°  (Albert)  at  the  knee  joint,  while  with  the  greatest  extension  it 
IS  nil.  It  occurs  because  the  external  condyle  of  tjie  tibia  rotates  on  the  internal.  In  all  positions 
during  flexion  the  crucial  ligaments  are  fairly  and  uniformly  tense,  whereby  the  articular  surfaces  are 
pressed  against  each  other.  Owing  to  their  arrangement,  during  increasing  tension  of  the  anterior 
ligament  (extension),  the  condyles  of  the  femur  must  roll  more  on  to  the  anterior  part  of  the  articular 


ARRANGEMENT   AND    USES    OF   THE    MUSCLES.  535 

surface  of  the  tibia,  while  by  increasing  tension  of  the  posterior  ligament  (flexion)  they  must  pass 
more  backward. 

4.  Joints  with  the  axis  of  rotation  round  one  fixed  point. — These  are  the  freely  movable 
arthrodial  joints.  The  movements  can  take  place  around  innumerable  axes,  which  all  intersect 
each  other  in  the  centre  of  rotation.  One  articular  surface  is  nearly  spherical,  the  other  is  cup- 
shaped.  The  shoulder  and  hip  joints  are  typical  "ball  and  socket  joints."  We  may  represent 
the  movements  as  taking  place  around  three  axes,  intersecting  each  other  at  right  angles.  The 
movements  which  can  be  performed  at  these  joints  may  be  grouped  as:  (l)  pendulum  like  move- 
ments in  any  plane;  (2)  rotation  round  the  long  axis  of  the  limb;  and  (3)  circumscribing  movements 
[circumduction],  such  as  are  made  round  the  circumference  of  a  sphere;  the  Centre  is  in  the  point 
of  rotation  of  the  joint,  while  the  circumference  is  described  by  the  limb  itself. 

Limited  arthrodial  joints  are  ball  joints  with  limited  movements,  and  where  rotation  on  the 
long  axis  is  wanting,  e.g.,  the  metacarpo-phalangeal  joints. 

5.  Rigid  joints  or  amphiarthroses  are  characterized  by  the  fact  that  movement  may  occur  in 
all  directions,  but  only  to  a  very  limited  extent,  in  consequence  of  the  very  tough  and  unyielding 
external  ligaments.  Both  articular  surfaces  are  usually  about  the  same  size,  and  are  nearly  plane 
surfaces,  e.g.,  the  articulations  of  the  cirpal  and  the  tarsal  bones. 

II.  Symphyses,  synchondroses,  and  syndesmoses  unite  bones  without  the  formation  of  a 
proper  articular  cavity,  are  mov.able  in  all  directions,  but  only  to  the  very  slightest  extent.  Physio- 
logically, they  are  closely  related  to  amphiarthrodial  joints. 

III.  Sutures  unite  bones  without  permitting  any  movement.  The  physiological  importance  of 
the  suture  is  that  the  bones  can  still  grow  at  their  edges,  which  thus  renders  possible  the  distention 
of  the  cavity  enclosed  by  the  bones  (Herm.  v.  Jileyer). 

306.  ARRANGEMENT  AND  USES  OF  THE  MUSCLES.— The 

muscles  form  45  per  cent,  of  the  total  mass  of  the  body,  those  of  the  right  side 
being  heavier  than  those  on  the  left  (Ed.  U'c/'er).  Muscles  may  be  arranged  in 
the  following  groups,  as  far  as  their  mechanical  actions  are  concerned  : — 

A.  Muscles  without  a  definite  origin  and  insertion  : — 

1.  The  hollow  muscles  surrounding  globular,  oval,  or  irregular  cavities,  such 
as  the  urinary  bladder,  gall  bladder,  uterus,  and  heart  ;  or  the  walls  of  more  or 
less  cylindrical  canals  (intestinal  tract,  muscular  gland  ducts,  ureters,  Fallopian 
tubes,  vasa  deferentia,  blood  vessels,  and  lymphatics).  In  all  these  cases  the 
muscular  fibres  are  arranged  in  several  layers,  e.g.,  in  a  longitudinal  and  a  circular 
layer,  and  sometimes  also  in  an  oblique  layer.  All  these  layers  act  together,  and 
thus  diminish  the  cavity.  It  is  inadmissible  to  ascribe  different  mechanical  effects 
to  the  different  layers,  e.g.,  that  the  circular  fibres  of  the  intestine  narrow  it,  while 
the  longitudinal  dilate  it.  Both  sets  of  fibres  rather  seem  to  act  simultaneously, 
and  diminish  the  cavity  by  making  it  narrower  and  shorter  at  the  same  time. 
The  only  case  where  muscular  fibres  may  act  in  partially  dilating  the  cavity  is 
when,  owing  to  pressure  from  without  or  from  partial  contraction  of  some  fibres, 
a  fold,  projecting  into  the  lumen,  has  been  formed.  When  the  fibres,  necessarily 
stretching  across  the  depression  thereby  produced,  contract,  they  must  tend  to 
undo  it,  /.  c\,  enlarge  the  cavity.  The  various  layers  are  all  innervated  from  the 
same  motor  source,  which  supports  the  view  of  their  conjoint  action. 

2.  The  sphincters  surround  an  opening  or  a  short  canal,  and  by  their  action 
they  either  constrict  or  close  it,  e.g.,  sphincter  papilla;,  palpebrarum,  oris,  pylori, 
ani,  cunni,  urethrae. 

B.  Muscles  with  a  definite  origin  and  insertion  : — 

1.  The  origin  is  completely  fixed  when  the  muscle  is  in  action.  The 
course  of  the  muscular  fibres,  as  they  pass  to  where  they  are  inserted,  permits  of 
the  insertion  being  appro.\imated  in  a  straight  line  toward  their  origin  during 
contraction,  e.g.,  the  attolens,  attrahens,  and  retrahentes  of  the  outer  ear,  and 
the  rhomboidei.  Some  of  these  muscles  are  inserted  into  soft  parts  which  neces- 
sarily must  follow  the  line  of  traction,  e.g.,  the  azygos  uvulae,  levator  palati  mollis, 
and  most  of  the  muscles  which  arise  from  bone  and  are  inserted  into  the  skin,  such 
as  the  muscles  of  the  face,  styloglossus,  stylopharyngeus,  etc. 

2.  Both  Origin  and  Insertion  Movable. — In  this  case  the  movements  of 
both  points  are  inversely  as  the  resistance  to  be  overcome.  The  resistance  is  often 
voluntary,  which  may  be  increased  either  at  the  origin  or  insertion  of  the  muscle. 


536  VARIOUS   KINDS   OF    LEVERS   ACTED    ON    BY    MUSCLES. 

Thus,  the  sternocleidomastoid  may  act  either  as  a  depressor  of  the  head  or  as  an 
elevator  of  the  cliest ;  the  pectoralis  minor  may  act  as  an  adductor  and  depressor 
of  the  shoulder,  or  as  an  elevator  of  the  3d  to  5th  ribs  (when  the  shoulder  girdle 
is  fixed). 

3.  Angular  Course. — Many  muscles  having  a  fixed  origin  are  diverted  from 
their  straight  course  ;  either  their  fibres  or  their  tendons  may  be  hcnt  out  of  the 
straight  course.  Sometimes  the  curving  is  slight,  as  in  the  occipito-frontalis  and 
levator  palpebrae  superioris,  or  the  tendon  may  form  an  angle  round  some  bony 
process,  whereby  the  muscular  traction  acts  in  quite  a  different  direction,  /.  e.,  as 
if  the  muscle  acted  directly  from  this  process  upon  its  point  of  insertion,  e.g.,  the 
obliquus  oculi  superior,  tensor  tympani,  tensor  veli  palatini,  obturator  internus. 

4.  Many  of  the  muscles  of  the  extremities  act  upon  the  long  bones  as  upon 
levers:  (<z)  Some  act  upon  a  lever  with  one  arm,  in  which  case  the  insertion 
of  the  muscle  (power)  and  the  weight  lie  upon  one  side  of  the  fulcrum  or  point  of 
support,  e.g.,  biceps,  deltoid.  The  insertion  of  (or  power)  often  lies  very  close 
to  the  fulcrum.  In  such  a  case,  the  rapidity  of  the  movement  at  the  end  of  the 
lever  is  greatly  increased,  but  force  is  lost  [/.  e.,  what  is  gained  in  rapidity  is  lost 
in  power].  This  arrangement  has  this  advantage,  that,  owing  to  the  slight  con- 
traction of  the  muscle,  little  energy  is  evolved,  which  would  be  the  case  had  the 
muscular  contraction  been  more  considerable  {§  300,  I,  3).  (/')  The  muscles  act 
upon  the  bones  as  upon  a  lever  with  two  arms,  in  which  case  the  power  (insertion 
of  the  muscle)  lies  on  the  other  side  of  the  fulcrum  opposite  to  the  weight,  e.  g., 
the  triceps  and  muscles  of  the  calf.  In  both  cases,  the  muscular  force  necessary 
to  overcome  the  resistance  is  estimated  by  the  principles  of  the  lever:  equilibrium 
is  established  when  the  static  moments  (=  product  of  the  power  in  its  vertical 
distance  from  the  fulcrum)  are  equal;  or  when  the  power  and  weight  are  inversely 
proportional,  as  their  vertical  distance  from  the  fulcrum. 

[The  Bony  Levers. — All  the  three  orders  of  levers  are  met  with  in  the  body.     Indeed,  in  the 

elbow  joint  all  the  three  orders  are  represented.     The  annexed  scheme  shows  the  relative  positions 

of  P,  W  and  F  (Fig.  313).     The  ist  order  is  represented  by  such 

jTjQ   -,j^  a  movement  as  nodding  the  head,  the  2d  by  raising  the  body  on 

the  tiptoes  by  the  muscles  of  the  calf,  and  the  3d  by  the  action 

of  the  biceps  in  raising  the  forearm.      At  the  elbow  joint  the  first 

(1)  order  is  illustrated  by  extending  the  flexed  forearm  on  the  upper 
arm,  as  in  striking  a  blow  on  the  table,  where  the  triceps  attached 
to  the  olecranon  is  the  power,  the  trochlea  the  fulcrum,  and  the 
hand  the  weight.     If  the  hand  rest  on  the  table  and  the  body  be 

(2)  rised  on  it,  then  the  hand  is  the  fulcrum,  while  the  triceps  is  the 
power  raising  the  humerus  and  the  parts  resting  on  it  (W).  The 
third  order  has  already  been  referred  to  in  flexing  the  forearm.] 

Direction  of  Action. — It  is  most  important  to  observe  the 

'3/     direction  in    which  the  muscular  force  and  weight  act  upon  the 

'  '  lever  arm.     Thus,  the  direction  may  be  vertical  to  the  lever  in  one 

1  he  three  orders  of  levers.  position,  while  after  flexion  it  may  act  obliquely  upon  the  lever. 

The  static  moment  of  a  power  acting  obliquety  on  the  lever  arm  is 

obtained  by  multiplying  the  power  with  the  power  acting  in  a  direction  vertical  to  the  pomt  of 

rotation. 

Examples. — In  Fig.  314,  I,  B  jr  presents  the  humerus,  and  .r  Z  the  radius;  A_)',  the  direction 
of  the  traction  of  the  biceps.  If  the  biceps  acts  at  a  right  angle  only,  as  by  lifting  horizontally  a 
weight  (P)  lying  on  the  forearm  or  in  the  hand,  then  the  power  of  tlie  biceps  {^=^  A)  is  obtained 
from  the  formula,  A  y  .v  =  P  jr  Z,  i.e.,  K  =  (V  x  T.)  :  y  x.  It  is  evident  that,  when  the  radius  is 
depressed  to  the  position  x  C,  the  result  is  different ;  then  the  force  of  the  biceps  =  A,  =  (P,  v  x); 
0  X.  In  Fig.  314,  II,  TF  is  the  tibia,  F,  the  ankle  joint,  MC,  the  foot  in  a  horizontal  position. 
The  power  of  the  muscles  of  the  calf  (=  a)  necessary  to  equalize  a  force,/,  directed  frcm  below 
against  the  anterior  part  of  the  foot,  would  be  «  ^  (/  M  F) :  F  C.  If  the  foot  be  altered  to  the 
position,  R  S,  the  force  of  the  muscles  of  the  calf  would  then  be  a^  =  (/j  MF)  :  F  C. 

In  muscles  also,  which,  like  the  coraco-brachialis,  are  stretched  over  the  angle 
of  a  hinge,  the  same  result  obtains. 

In   Fig.  314,  III,  H   E  is  the  humerus,  E,  the  elbow  joint,  E  R,  the  radius,  B  R,  the  coraco- 


• 

F 

% 

w 

A 

p 

F 

• 

A 

w 

p 

• 

F 

w 

i> 

A 

VARIOUS    KINDS   OF    LEVER    ACTION    OF   MUSCLES. 


537 


brachialis.  Its  moment  in  this  position  is  =  A,  //  E.  When  the  radius  is  raised  to  E  R,,then  it  is 
^  A,  a  E.  We  must  notice,  however,  that  B  Rj  <  B  R.  Hence,  the  absolute  muscular  force 
must  be  less  in  the  flexed  position,  because  every  muscle,  as  it  becomes  shorter,  lifts  less  weight. 
What  is  lost  in  power  is  gained  by  the  elongation  of  the  lever  arm. 

5.  Many  muscles  have  a  double  action  ;  when  contracted  in  the  ordinary 
way  they  execute  a  combined  movement,  e.g.,  the  biceps  is  a  flexor  and  supinator 
of  the  forearm.  If  one  of  these  movements  be  prevented  by  the  action  of  other 
muscles,  the  muscle  takes  no  part  in  the  execution  of  the  other  movement. 

If  the  forearm  be  strongly  pronated  and  flexed  in  this  position,  the  biceps  takes  no  part  therein  ; 
or,  when  the  elbow  joint  is  rigidly  supinated,  only  the  supinator  brevis  acts,  not  the  biceps.  Tl  e 
muscles  of  mastication  are  another  example.  The  masseter  elevates  the  lower  jaw,  and  at  the 
same  time  pulls  it  forward.  If  the  depressed  jaw,  however,  be  strongly  pulled  backward  when  the 
jaw  is  raised,  the  masseter  is  not  concerned.  The  temporal  muscle  raises  the  jaw,  and  at  the  same 
time  pulls  it  backward.  If  the  depressed  jaw  be  raised  after  being  pushed  forward,  then  the  ttm- 
poral  is  not  concerned  in  its  elevation. 

6.  Muscles  acting  on  two  or  more  joints  are  those  which  in  their  course 
from  their  origin    to  their   insertion  pass  over  two  or  more  joints.      Either  the 


Scheme  of  the  action  of 


tendons  may  deviate  from  a  straight  course,  if.^--. ,  the  extensors  and  flexors  of  the 
fingers  and  toes,  as  when  the  latter  are  flexed  ;  or  the  direction  is  always  straight, 
e.g.,  the  gastrocnemius.  The  muscles  of  this  group  present  the  following  points 
of  interest:  (a)  The  phenomenon  of  so-called  "  active  insufficiency"  (Hueter, 
Henke).  If  the  position  of  the  joints  over  which  those  muscles  pass  be  so  altered 
that  their  origin  and  insertion  come  too  near  each  other,  the  muscle  may  require 
to  contract  so  much  before  it  can  act  on  the  bones  attached  to  it,  that  it  cannot 
contract  actively  any  further  than  to  the  extent  of  the  shortening  from  which  it 
begins  to  be  active,  e.g.,  when  the  knee  joint  is  bent  the  gastrocnemius  can  no 
longer  produce  plantar  flexion  of  the  foot,  but  the  traction  on  the  tendo  Achilles 
is  produced  by  the  soleus.  (/')  "  Passive  insufficiency"  is  shown  by  many- 
jointed  muscles  under  the  following  circumstances  :  In  certain  positions  of  the 
joint,  a  muscle  may  be  so  stretched  that  it  may  act  like  a  rigid  strap,  and  thus 
limit  or  prevent  the  action  of  other  muscles,  e.g.,  the  gastrocnemius  is  too  short 
to  permit  complete  dorsal  flexion  of  the  foot  when  the  knee  is  extended.  The 
long  flexors  of  the  leg,  arising. from  the  tuber  ischii,  are  too  short  to  permit  com- 
plete extension  of  the   knee  joint  when  the  hip  joint  is  flexed  at  an  acute  angle. 


538  GYMNASTICS,   MASSAGE    AND    CHANGES    IN    MUSCLE. 

The  extensor  tendons  of  the  fingers  are  too  short  to  permit  of  complete  flexion 
of  the  joints  of  the  fingers  when  the  hand  is  completely  flexed. 

7.  Synergetic  muscles  are  those  which  together  subserve  a  certain  kind  of 
movement,  c.  .t,'-.,  the  flexors  of  the  leg,  the  muscles  of  the  calf,  and  others.  The 
abdominal  muscles  act  along  with  the  diaphragm  in  diminishing  the  abdomen 
during  straining,  while  the  muscles  of  inspiration  or  expiration,  even  the  different 
origins  of  one  muscle,  or  the  two  bellies  of  a  biventral  muscle,  may  be  regarded 
from  the  same  point  of  view. 

Antagonistic  muscles  (  Galen)  are  those  which,  during  their  action,  have  ex- 
actly the  opposite  effect  of  other  muscles,  e.g.,  flexors  and  extensors — pronators 
and  supinators — adductors  and  abductors — elevators  and  depressors — sphincters 
and  dilators — inspiratory  and  expiratory. 

When  it  is  necessary  to  bring  the  full  power  of  our  muscles  into  action,  we 
quite  involuntarily  bring  them  beforehand  into  a  condition  of  the  greatest  tension, 
as  a  muscle  in  this  condition  is  in  the  most  favorable  position  for  doing  work 
(§300,  I,  3 — Schwanti).  Conversely,  when  we  execute  delicate  movements  requir- 
ing little  energy,  we  select  a  position  in  which  the  corresponding  muscle  is  already 
shortened. 

All  the  fascia;  of  the  body  are  connected  with  muscles,  which,  when  they  contract,  alter  the  ten- 
sion of  the  former,  so  that  they  are,  in  a  certain  sen.se,  aponeuroses  or  tendons  of  the  latter  (A' 
Bariieleben).  [For  the  importance  of  muscular  movements  and  those  of  the  fascist  in  connection 
with  the  movements  of  the  lymph,  see  §  201.] 

307.  GYMNASTICS  ;  MOTOR  PATHOLOGICAL  VARIATIONS.— Gymnastic 
exercise  is  most  important  for  the  proper  development  of  the  muscles  and  motor  power,  and  it 
ought  to  be  commenced  in  both  sexes  at  an  early  age.  .Systematic  muscular  activity  increases  the 
volume  of  the  muscles,  and  enables  them  to  do  more  work.  The  amount  of  blood  is  increased 
with  increase  in  the  muscular  development,  while  at  the  same  time  the  bones  and  ligaments  become 
more  resistant.  As  the  circulation  is  more  lively  in  an  active  muscle,  gymnastics  favor  the  circula- 
tion, and  ought  to  be  practice!,  especially  by  persons  of  sedentary  habits,  who  are  apt  to  suffer 
from  congestion  of  the  blood  in  the  abdominal  organs  (f  i'.,  hiemorrhoids),  as  it  favors  the  move- 
ment of  the  tissue  juices  [^  201].  An  active  muscle  also  uses  more  O  and  produces  more  CO,,  so 
th.at  respiration  is  also  excited.  The  total  increase  of  the  metabolism  gives  rise  to  the  feeling  of 
well-being  and  vigor,  diminishes  abnormal  irritability,  and  dispels  the  tendency  to  fatigue.  The 
whole  body  becomes  firmer  and  specifically  heavier  [jaifer). 

By  Ling's,  or  the  Swedish  system,  a  systematic  attempt  is  made  to  strengthen  certain  weak 
muscles,  or  groups  of  muscles,  whose  weakness  might  lead  to  the  production  of  deformities  These 
muscles  are  exercised  systematically  by  opposing  to  them  resistances,  which  must  either  be  over- 
come, or  against  which  the  patient  must  strive  by  muscular  action. 

Massage,  which  consists  in  kneading,  pressing,  or  rubbing  the  muscles,  favors  the  blood  stream; 
hence,  this  system  may  be  advantageously  used  for  such  muscles  as  are  so  weakened  by  disease  that  an 
independent  treatment  by  means  of  gymnastics  cannot  be  adopted.  [The  importance  of  massage 
as  a  restorative  practice  in  getting  rid  of  the  waste  products  of  muscular  activity  has  been  already 
referred  to  (J  304).     It  is  much  practiced  on  the  Continent.] 

Disturbances  of  the  normal  movements  may  partly  afi'ect  the  passive  motor  organs  (e.g.,  the 
bones,  joints,  ligaments,  and  aponeuroses),  or  the  active  organs  (muscles  with  their  tendons,  and 
motor  nerves). 

Passive  Organs  — Fractures,  caries  and  necrosis,  and  inflammation  of  the  bones,  which  make 
movements  painful,  influence  or  even  make  movement  impossible.  Similarly,  dislocations,  relaxa- 
tion of  the  ligaments,  arthritis,  or  anchylosis  interfere  with  movement.  Also  cunature  of  bones, 
hyperostosis  or  exostosis;  lateral  curvature  of  the  vertebral  column  (Scoliosis),  backward  angular 
curvature  (Kyphosis),  or  forward  curvature  (Lordosis).  The  latter  interfere  with  respiration. 
In  the  lower  extremities,  which  have  to  carry  the  weight  of  the  body,  genu  valgum  may  occur  in 
flabby,  tall,  rapidly-growing  individuals,  especially  in  some  trades,  e.g.,  bakers.  The  opposite 
form,  genu  varum,  is  generally  a  result  of  rickets.  Flat  foot  depends  upon  a  depression  of  the 
arch  of  the  foot,  which  then  no  longer  rests  upon  its  three  points  of  support.  Its  causes  seem  to  be 
similar  to  those  of  genu  valgum.  The  ligaments  of  the  small  tarsal  joints  are  stretched,  and  the  long 
a.xis  of  the  foot  is  usually  directed  outward;  the  inner  margin  of  the  foot  is  more  turned  to  the  ground, 
while  pain  in  the  fool  and  malleoli  make  walking  and  standing  impossible.  Club  foot  (Talipes 
varus)  m  which  the  inner  margin  of  the  foot  is  raised,  and  the  point  of  the  toes  is  directed  inward 
and  downward,  depends  upon  imperfect  development  during  fretal  life.  All  children  are  born 
with  a  certain  very  slight  degree  of  bending  of  the  foot  in  this  direction.  Talipes  equinus,  in 
which  the  toes,  and  T.  calcaneus,  in  which  the  heel  touches  the  ground,  usually  depend  upon 


STANDING.  539 

contracture  of  the  muscles  causing  these  positions  of  the  foot,  or  upon  paralysis  of  the  antago- 
nistic muscles. 

Rickets  and  Osteomalacia. — If  the  earthy  salts  be  withheld  from  the  food,  the  bones  gradually 
undergo  a  change  ;  they  become  thin,  translucent,  and  may  even  bend  under  pressure.  In  certain 
persistent  defecfs  of  nutrition,  the  lime  sails  of  the  food  are  not  absorbed,  giving  rise  to  rachitis, 
or  rickets,  in  children.  If  fully-formed  bones  lose  their  lime  salts  to  the  extent  of  yi  to  ',^  (halis- 
terisis),  they  become  brittle  and  soft  (osteomalacia).     This  occurs  to  a  limited  extent  in  old  age. 

Muscles.  —  The  normal  nutrition  of  muscle  is  intimately  dependent  on  a  proper  supply  of  sodium 
chloride  and  potash  salts  in  the  food,  as  these  foim  integral  parts  of  the  muscular  tissue  {Kenimerich, 
Forster].  Besides  the  atrophic  changes  which  occur  in  the  muscles  when  these  substances  are 
withheld,  there  are  disturbances  of  the  central  nervous  system  and  digestive  apparatus,  and  the 
animals  ultimately  die.  The  condition  of  the  muscles  during  inanition  is  given  in  §  237.  If  mus- 
cles and  bones  be  kept  inactive  they  tend  to  atrophy  (^  244).  In  atrophic  muscles,  and  in  cases  of 
anchylosis,  there  is  an  enormous  increase,  or  "  atrophic  proliferation,"  of  the  muscle  corpuscles, 
which  takes  place  at  the  e,xpense  of  the  contractile  contents  {Cohnheim).  .\  certain  degree  of  mus- 
cular atrophy  takes  place  in  old  age.  The  uterus,  after  delivery,  undergoes  a  great  decrease  in 
size  and  weight — from  1000  to  350  grammes — due  chiefly  to  the  diminished  blood  supply  to  the 
organ.  In  chronic  lead  poisoning,  the  extensors  and  interossei  chiefly  undergo  atrophy.  Atrophy 
and  degeneration  of  the  muscles  are  followed  by  shortening  and  thinning  of  the  bones  to  which  the 
muscles  are  attached. 

Section  and  paralysis  of  the  motor  nerves  cause  palsy  of  the  muscle,  thus  rendering  them 
inactive,  and  they  ultimately  degenerate.  .Atrophy  also  occurs  after  inflammation  or  softening  of 
the  multipolar  nerve  cells  in  the  anterior  horn  of  the  gray  matter  of  the  spinal  cord,  or  the  motor 
nuclei  (facial,  spinal  accessory,  and  hypoglossal  of  Stilling  in  the  medulla  oblongata),  in  the  muscles 
connected  with  these  parts.  Rapid  atrophy  takes  place  in  certain  forms  of  spinal  paralysis  and  in 
acute  bulbar  paralysis  (paralysis  of  the  medulla  oblongata),  and  in  a  chronic  form  in  progressive 
muscular  atrophy  and  progressive  bulbar  par,alysis.  The  muscles  and  their  nerves  become  small 
and  soft.  The  muscles  show  many  nuclei,  the  sarcous  substance  becomes  fatty  and  ultimately  dis- 
appears. According  to  Charcot,  these  areas  are  at  the  same  time  the  trophic  centres  for  the  nerves 
proceeding  from  them  as  well  as  for  the  muscles  belonging  to  them.  According  to  Friedreich,  the 
primary  lesion  in  progressive  muscular  atrophy  is  in  the  muscles,  and  is  due  to  a  primary  interstitial 
inflammation  of  the  muscle,  resulting  in  atrophy  and  degenerative  changes,  while  the  nerve  centres 
are  afl'ected  secondarily,  just  as  after  amputation  of  a  limb  the  corresponding  part  of  the  spinal  cord 
degenerates. 

In  pseudo-hypertrophic  muscular  atrophy  the  muscular  fibres  atrophy  completely,  with 
copious  development  of  fat  and  connective  tissue  between  the  fibres,  without  the  nerves  or  spinal 
cord  undergoing  degeneration.  The  muscular  substance  may  also  undergo  amyloid  or  wax  like 
degeneration,  whereby  the  amyloid  substance  infiltrates  the  tissue  {\  249,  VI).  Sometimes  atrophic 
muscles  have  a  deep-brown  color,  dca^  to  a  change  of  the  ha;moglobin  of  the  muscle.  When  muscles 
are  much  used,  they  hypertrophy,  as  the  heart  in  certain  cases  of  valvular  lesion  or  obstruction 
(I  49),  the  bladder  and  intestine.  [In  true  hypertrophy  there  is  an  increased  number  or  increase 
in  the  size  of  its  tissue  elements,  throughout  the  entire  tissue  or  organ,  without  any  deposit  of  a 
foreign  body.  Perhaps,  in  hypertrophy  of  the  bladder,  the  thickened  muscular  coat  not  only  serves 
to  overcome  resistance,  but  it  oflfers  greater  resistance  to  bursting  under  the  increased  intra-vesical 
pressure.  Mere  enlargement  is  not  hypertrophy,  for  this  may  be  brought  about  by  foreign  ele- 
ments. In  atrophy  there  is  a  diminution  in  size  or  bulk,  even  when  the  blood  stream  is  kept  up, 
the  decrease  being  due  to  pressure.  An  atrophied  organ  may  be  even  enlarged,  as  seen  in  pseudo- 
hypertrophic paralysis,  where  the  muscles  are  larger,  owing  to  the  interstitial  growth  of  fatty  and 
connective  tissue,  while  the  true  muscular  tissue  is  diminished  and  truly  atrophied.] 

308.  STANDING. — The  act  of  standing  is  accomplished  by  muscular  action, 
and  is  the  vertical  position  of  ecjuilibrium  of  the  body,  in  which  a  line  drawn  from 
the  centre  of  gravity  of  the  body  falls  within  the  area  of  both  feet  placed  upon 
the  ground.  In  the  military  attitude  the  muscles  act  in  two  directions — (ij  to 
fix  the  jointed  body,  as  it  were,  into  one  unbending  column  ;  and  (2)  in  case  of 
a  variation  of  the  equilibrium,  to  compensate,  by  muscular  action,  for  the  dis- 
turbance of  the  equilibrium. 

The  following  individual  motor  acts  occur  in  standing  : — 

I.  The  fixation  of  the  head  upon  the  vertebral  column.  The  occiput  maybe  moved  in  various 
directions  upon  the  atlas,  as  in  the  acts  of  nodding.  As  the  long  arm  of  the  lever  lies  in  front  of 
the  atlas,  necessarily  when  the  muscles  of  the  back  of  the  neck  relax,  as  in  sleep  or  death,  the  chin 
falls  upon  the  breast.  The  strong  neck  muscles,  which  pull  from  the  vertebral  column  upon  the 
occiput,  fix  the  head  in  a  firm  position  on  the  vertebral  column.  The  chief  rotatory  movement  of 
the  head  on  a  vertical  axis  occurs  round  the  odontoid  process  of  the  axis.  The  articular  surfaces  on 
the  pedicles,  ar.d  part  of  the  bodies  of  the  1st  and  2d  vertebne,  are  conve.x  toward  each  other  in  the 


540  SITTING. 

middle,  becoming  somewhat  lower  in  front  and  behind,  so  that  the  head  is  highest  in  the  erect 
posture.  Hence,  when  the  head  is  greatly  rotated,  compression  of  the  medulla  oblongata  is  pre- 
vented {I/enki).  In  standing,  these  muscles  do  not  require  to  be  fixed  by  muscular  action,  as  no 
rotation  can  take  place  when  the  neck  muscles  are  at  rest. 

2.  Fix  Vertebral  Column The  vertebral  column  itself  must  be  fixed,  especially  where  it  is 

most  mobile,  /.  t'.,  in  the  cervical  and  lumbar  regions.  This  is  brought  about  by  the  strong  muscles 
situate  in  these  regions,  e.  g.,  the  cervical  spinal  muscles,  Extensor  dorsi  communis  and  Quat/ratus 
Itimboruni. 

Mobility  of  the  Vertebrae. — The  least  movable  vertebrae  are  the  3d  to  the  6th  dorsal ;  the 
sacrum  is  quite  immovable.  For  a  certain  length  of  the  column,  the  mobility  depends  on  [a)  the 
number  and  height  of  the  interarticular  fibro-cartilages.  They  are  most  numerous  in  the  neck, 
thickest  in  the  lumbar  region,  and  relatively  also  in  the  lower  cervical  region.  They  permit  move, 
ment  to  take  place  in  every  direction.  Collectively,  the  interarticular  disks  form  one-fourth  of  the 
height  of  the  whole  vertebral  column.  They  are  compressed  somewhat  by  the  pressure  of  the  body  ; 
hence  the  body  is  longest  in  the  morning  and  after  lying  in  the  horizontal  position.  The  smaller 
periphery  of  the  bodies  of  the  cervical  vertebras  favors  the  mobility  of  these  vertebr.'E  compared  with 
the  larger  lower  ones.  (/')  The  position  of  the  processes  also  influences  greatly  the  mobility.  The 
strongly-depressed  spines  of  the  dorsal  region  hinder  hyperextension.  The  articular  processes  on 
the  cervical  vertebra;  are  so  placed  that  their  surfaces  look  obliquely  from  before  and  upward,  back- 
ward and  downward ;  this  permits  relatively  free  movement,  rotation,  lateral  and  nodding  move- 
ments. In  the  dorsal  region  the  articular  surfaces  are  directed  vertically  and  directly  to  the  front, 
the  lower  directly  back\^'ard  ;  in  the  lumbar  region  the  jiosiiion  of  the  articular  processes  is  almost 
completely  vertical  and  antero-posterior.  In  bending  backward  as  far  as  possible,  the  most  mobile 
parts  of  the  colimin  are  the  lower  cervical  vertebra,  the  iilh  dorsal  to  the  2d  lumbar  and  the  lower 
two  lumbar  vertebme  (E.  H.  Weber). 

3.  The  centre  of  gravity  of  the  head,  trunk  and  arms,  when  fixed  as  above,  lies  in  front  of  the 
loth  dorsal  vertebra.  It  lies  further-  forward,  in  a  horizontal  plane,  passing  through  the  xiphoid 
process  (  ll'eber),  the  greater  the  distention  of  the  abdomen  by  food,  fat  or  pregnancy.  A  line 
drawn  vertically  downward  from  the  centre  of  gravity  passes  behind  the  line  uniting  both  hip  joints. 
Hence,  the  trunk  would  fall  backward  on  the  hip  joint,  were  it  not  prevented  partly  by  ligaments 
and  partly  by  muscles.  The  former  are  represented  by  the  ileo-femoral  band  and  the  anterior  tense 
layer  of  the  fascia  lata.  As  ligaments  alone,  however,  never  resist  permanent  traction,  they  are 
aided,  especially  by  the  ileo-psoas  muscle  inserted  into  the  small  trochanter,  and  in  part,  al.so,  by  the 
rectus  femoris.  Lateral  movement  at  the  hip  joint,  whereby  the  one  limb  must  be  abducted  and  the 
other  adducted,  is  prevented  especially  by  the  large  mass  of  the  glutei.  When  the  leg  is  extended, 
the  ileo-femoral  ligament,  aided  by  the  fascia  lata,  prevents  adduction. 

4.  The  rigid  part  of  the  body,  head  and  trunk,  with  the  arms  and  the  legs,  whose  centre  of 
gravity  lies  lower  and  only  a  little  in  front,  so  that  the  vertical  line  drawn  downward  inter.sects  a 
line  connecting  the  posterior  surfaces  of  the  knee  joints,  must  now  be  fixed  at  the  knee  joint.  Falling 
backward  is  prevented  by  a  slight  action  of  the  quadriceps  femoris.  aided  by  the  tension  of  the  fascia 
lata.  Indirectly  it  is  aided  also  by  the  ileo-femoral  ligament.  Lateral  moven  ent  of  the  knee  is 
prevented  by  the  disposition  of  the  strong  lateral  ligaments.  Rotation  cannot  take  place  at  the  knee 
joint  in  the  extended  position  [\  305,  I,  3). 

5.  A  line  drawn  downward  from  the  centre  of  gravity  of  the  whole  body,  which  lies  in  the  pro- 
monotory,  falls  slightly  in  front  of  a  line  between  the  two  ankle  joints.  Hence,  the  body  would 
{&\\  forward  on  the  latter  joint.  This  is  prevented  especially  by  the  muscles  of  the  calf,  aided  by 
the  muscles  of  the  deep  layer  of  the  leg  (tibialis  posticus,  flexors  of  the  toes,  peroneus  longus  et 
brevis). 

Other  Factors. — (a)  As  the  long  axis  of  the  foot  forms  with  the  leg  an  angle  of  50°,  falling 
forward  can  only  occur  after  the  feet  are  in  a  positii>n  more  nearly  parallel  with  their  long  axis.  (/') 
The  form  of  the  articular  surfaces  helps,  as  the  anterior  broad  part  of  the  astragalus  must  be  pressed 
between  the  two  malleoli.     The  latter  mechanism  cannot  be  of  much  importance. 

6.  The  metatarsus  and  phalanges  are  united  by  tense  ligaments  to  form  the  arch  of  the  foot, 
which  touches  the  ground  at  three  points— tuber  calcanei  (heel),  the  head  of  the  first  metatarsal 
bone  (ball  of  the  great  toe),  and  of  the  fifth  toe.  Between  the  latter  two  points  the  heads  of  the 
metatarsal  bones  also  form  points  of  supports.  The  weight  of  the  body  is  transmitted  to  the  highest 
part  of  the  arch  of  the  foot,  the  caput  tali.  The  arching  of  the  foot  is  fixed  only  by  ligaments.  The 
toes  play  no  part  in  standing,  although,  when  moved  by  their  muscles,  they  greatly  aid  the  balancing 
of  the  body.     The  maintenance  of  the  erect  attitude  fatigues  one  more  rapidly  than  walking. 

309.  SITTING. — Sitting  is  that  position  of  equilibrium  whereby  the  body  is  supported  on  the 
tubera  ischii,  on  which  a  too-and-fro  movement  may  take  place  (//.  v.  Meyer),  The  head  and 
trunk  together  are  made  rigid  to  form  an  immovable  column,  as  in  standing.  We  may  distinguish 
— ( I )  the  forward  posture,  in  which  the  line  of  gravity  passes  in  front  of  the  tubera  ischii ;  the 
body  being  supported  either  against  a  fixed  object,  e,  g.^  by  means  of  the  arm  on  a  table,  or  against 
the  upper  surface  of  the  thigh.  (2)  The  backward  posture,  in  which  the  line  of  gravity  falls 
behind  the  tubera.     A  person  is  prevented  from  falling  backward  either  by  leaning  on  a  support,  or 


WALKING,   RUNNING    AND    SPRINGING. 


541 


by  the  counter  weight  of  the  legs  kept  extended  by  muscular  action,  whereby  the  sacrum  forms  an 
additional  point  of  support,  while  the  trunk  is  fixed  on  the  thigh  by  the  ileopsoas  and  rectus  femoris, 
the  leg  being  kept  extended  by  the  extensor  quadriceps.  Usually  the  centre  of  gravity  is  so  placed 
that  the  heel  also  acts  as  a  point  of  support.  The  latter  sitting  posture  is,  of  course,  not  suited  for 
resting  the  muscles  of  the  low-er  limbs.  (3)  When  "  sitting  erect  "  the  line  of  gravity  falls 
between  the  tubera  themselves.  The  muscles  of  the  legs  are  relaxed,  the  rigid  trunk  only  requires 
to  be  balanced  by  slight  muscular  action.  Usually  the  balancing  of  the  head  is  sufficient  to  main- 
tain the  equilibrium. 

310.  WALKING,  RUNNING,  AND  SPRINGING.— By  the  term 
walking  is  understood  progression  in  a  forward  horizontal  direction  with  the 
least  possible  muscular  exertion,  due  to  the  alternate  activity  of  the  two  legs. 

Methods.— The  Brothers  Weber  were  the  first  to  analyze  the  various  positions  of  the  body  in 
walking,  running,  and  springing,  and  they  represented  them  in  a  continuous  series,  which  represents 
the  successive  phases  of  locomotion.  These  phases  may  be  examined  with  the  zoetrope  (J  398,  3). 
Marey  estimated  the  lime  relations  of  the  individual  acts,  by  transferring  the  movements  by  means 
ol  his  air  tambours  to  a  recording  surface.  Recently,  by  means  of  a  revolving  camera,  he  has  suc- 
ceeiled  in  photographing,  in  instantaneous  pictures  (x^'ijj  second),  the  whole  series  of  acts.  Of 
course  this  series,  when  placed  in  the  zoetrope,  represents  the  natural  movements.  Figs.  316,  317, 
318  represent  these  acts. 

In  walking,  the  legs  are  active  alternately;  while  one — the  "supporting"  or 
"active"  leg — carries  the  trunk,  the  other  is  "inactive"   or  "passive."     Each 


Ptiases  of  walking.     The  thick  lines  represent  the  active,  the  thin  the  passive  leg  ;  h,  the  hip  joint  ;  k,  a,  knee  ;  /,l\ 
ankle  :  c,  it,  heel ;  /h,  e,  ball  ot  the  tarso-metatarsal  joints  ;   js,  g,  point  of  great  toe. 

leg  is  alternately  in  an  active  and  a  passive  j)hase.     Walking  may  be  divided  into 
the  following  movements  : — 

I.  Act  (Fig.  315,  2). — The  active  \tg  is  vertical,  slightly  flexed  at  the  knee,  and  it  alone  supports 
the  centre  of  gravity  of  the  body.  The  passive  leg  is  completely  extended,  and  touches  the  ground 
only  with  the  tip  of  the  great  toe  (s).  This  position  of  the  leg  corresponds  to  a  right-angled  tri- 
angle, in  which  the  active  leg  and  the  ground  form  two  sides,  while  the  passive  leg  is  the  hypo- 
tenuse. 

II.  Act. — For  the  forward  movement  of  the  trunk,  the  active  leg  is  inclined  slightly  from  its 
vertical  position  (cathetus)  to  an  oblique  and  more  forward  (hypotenuse)  position  (3).  In  order 
that  the  trunk  may  remain  at  the  same  height,  it  is  necessary  that  the  active  leg  be  lengthened.  This 
is  accomplished  by  completely  extending  the  knee  (3,  4,  5),  as  well  as  by  lifting  the  heel  from  the 
ground  (4,  5),  so  that  the  foot  rests  on  the  balls  or  the  heads  of  the  metatarsal  bones,  and  lastly,  by 
elevating  it  on  the  point  of  the  great  toe  (2,  thin  line).  During  (he  extension  and  forward  move- 
ment of  the  active  leg,  the  tips  of  the  toes  of  the  passive  leg  have  left  the  ground  (3).  It  is  slightly 
flexed  at  the  knee  joint  (owing  to  the  shortening),  it  performs  a  "  pendulum-like  movement  "  (4,5), 
whereby  its  foot  is  moved  as  far  in  front  of  the  active  leg  as  it  was  formerly  behind  it.  The  foot  is 
then  placed  flat  upon  the  ground  (I,  2,  thick  lines) ;  the  centre  of  gravity  is  now  transferred  to  this 
active  leg,  which,  at  the  same  lime,  is  slightly  flexed  at  the  knee,  and  placed  vertically.  The  first 
act  is  then  repeated. 

Simultaneous  Movements  of  the  Trunk. — During  walking  the  trunk  performs  certain  char- 
acteristic movements,     ^i)   It  leans  every  time  toward  the  active  leg,  owing  to  the  traction  of  the 


542 


WALKING,   RUNNING    AND    SPRINGING. 


glutei  and  the  tensor  fascice  lata;,  so  that  the  centre  of  gravity  is  moved,  which,  in  short,  heavy  per- 
sons with  a  broad  pelvis,  leads  to  their  "  waddling  "  gait.  (2)  The  trunk,  especially  during  ra|<id 
walking,  is  inclined  slightly  forward  to  overcome  the  resistance  of  the  air.  (3)  During  the  "  pen- 
dulum-like action,"  the  trunk  rotates  slightly  on  the  head  of  the  active  femor.  This  rotation  is 
compensated,  especially  in  rapid  walking,  by  the  arm  of  the  same  side  as  the  oscillating  leg  swinging 
in  the  opposite  direction,  while  that  on  the  other  side  at  the  same  time  swings  in  the  same  direction 
as  the  oscillating  limb. 

Modifying  Conditions  :  i.  The  Duration  of  the  Step. — As  the  rapidity  of  the  vibration  of  a 
pendulum  (leg)  depends  upon  its  length,  it  is  evident  that  each  individual,  according  to  the  length 
of  his  legs,  must  have  a  certain  natural  rate  of  walking  The  "  duration  of  a  step  "  depends  also 
upon  the  time  during  which  both  feet  touch  the  ground  simultaneously,  which,  of  course,  can  be 
altered  voluntarily.  When  "walking  rapidly  "  the  time  =  O,  i.e.,  at  the  same  moment  in  which 
the  active  leg  reaches  the  ground,  the  passive  leg  is  raised.  2.  The  Length  of  the  Step. — Usually 
about  6  to  7  decimetres  [23  to  27  inches]  (  Vleronit)  must  be  greater,  the  more  the  length  of  the 
hypotenuse  of  the  passive  leg  exceeds  the  catherus  of  the  active  one.  Hence,  during  a  long  step, 
the  active  leg  is  greatly  shortened  (by  flexion  of  the  knee),  so  that  the  trunk  is  pulled  downward. 
Similarly,  long  legs  can  make  longer  steps. 

According  to  Marey  and  others,  the  pendulum  movement  of  the  passive  leg  is  not  a  true  pen- 
dulum movement,  because  its  movement,  owing  to  muscular  action,  is  of  more  uniform  lapidity. 
During  the  pendulum  movement  of  the  whole  limb,  the  leg  vibrates  by  itself  at  the  knee  joint 
(luce.  H.   Vieronil). 

Fixation  of  the   Femur. — According  to   Ed.  and   W.   Weber,  the  head  of  the  femur  of  the 

Fic.  316. 


Phases  ot  slow  walking.  Instam.ineous  photograph  {.Uarty),  only  the  side  directed  to  the  observer  is  shown.  From 
the  vertical  position  of  the  right,  active  leg;  (1).  all  the  phases  of  this  leg  are  represented  in  six  pictures  |I  to 
VI).  while  after  VI  the  vertical  position  is  regained.  The  Arabic  numerals  indicate  the  simultaneous  position 
of  the  corresponding  left  leg  ;  thus  i  =  I,  2=  II,  etc.,  so  that  during  the  position  IV  of  the  right  leg,  at  the 
same  time  the  left  leg  has  the  position  as  1. 


passive  leg  is  fixed  in  its  socket  chiefly  by  the  atmospheric  pressure,  so  that  no  muscular  action  is 
necessary  for  carrying  the  whole  limb.  If  all  the  muscles  and  the  capsule  be  divided,  the  head  of 
the  femur  still  remains  in  the  cotyloid  cavity.  Rose  refers  this  condition  not  to  the  action  of  the 
atmospheric  pressure,  but  to  two  adhesion  .surfaces  united  by  means  of  synovia.  The  experiments  of 
Aeby  show  that  not  only  the  weight  of  the  limb  is  supported  by  the  atmospheric  pressure,  but 
that  the  latter  can  support  several  times  its  weight.  When  traction  is  exerted  on  ihe  limb,  the 
margins  of  the  cotyloid  ligament  of  the  cotyloid  cavity  are  applied  like  a  valve  tightly  to  the 
margin  of  the  cartilage  of  the  head  of  the  femur.  According  to  the  Broihers  Weber,  the  leg  falls 
from  its  socket  as  soon  as  air  is  admitted  by  making  a  perforation  into  the  articular  cavity. 

Work  done  during  Walking. — Marey  and  Demery  estimate  the  amount  done  by  a  man 
weighing  64  kilos,  [  10  stones],  wlien  walking  slowly,  as  =  6  kilogrammetres  per  second;  rapiil 
running  =  56  kilogrammetres.  The  work  done  is  due  to  the  raising  of  the  entire  body  and 
extremities,  to  the  velocity  communicated  to  the  body,  as  well  as  to  the  maintenance  of  the  centre 
of  gravity. 

In  springing  or  leaping  the  body  is  rapidly  projected  upward  by  the  greatest  possible  and  most 
rapid  contraction  of  the  leg  muscles,  while  at  the  same  time  the  centre  of  gravity  is  maintained  by 
other  muscular  acts  (Fig.  31S). 

The  pressure  upon  the  sole  of  the  foot  in  walking  is  distributed  in  the  following  manner:  The 
supporting  leg  always  presses  more  strongly  on  the  ground  than  the  other;  the  longer  the  step  the 
greater  the  pressure.  The  heel  receives  the  maximum  amount  of  pressure  sooner  than  the  poii.t 
of  the  foot  (Cnr/et). 


WALKING,  RUNNING    AND    SPRINGING. 


543 


Running  is  distinguished  from  rapid  walking  by  the  fact  that,  at  a  particular 
moment,  both  legs  do  not  touch  the  ground,  so  that  the  body  is  raised  in  the  air. 
The  active  leg,  as  it  is  forcibly  extended  from  a  flexed  position,  gives  the  body 
the  necessary  impetus  (Fig.  317). 

Fig. 


Instantaneous  photograph  of 


Ten  pictures  per  second.     The  abscij 
step  in  metres. 


the  length  of  the 


Pathological. — Variations  of  the  walking  movements  depend  primarily  upon  diseases  of  bones, 
ligaments,  muscles,  and  tendons,  and  also  upon  affections  of  the  motor  nerves.  The  effect  of  sen- 
sory nerves  and  the  reflex  mechanism  of  the  spinal  cord,  and  also  of  the  muscular  sense  on  walk 
ing,  are  stated  in  J;^  351;,  360,  430. 

311.  COMPARATIVE. — The  absolute  muscular  force  in  animals  is  not,  as  a  rule,  much 

Fig.  siS. 


High  leap. 

the  forward  mov( 
radius  of  which  i 


i  photograph  {Mi 


:tures  partly  overlap  each  other 
It  diminisncs  alter  springing.  In  the  left-hand  co 
in  ^  second.    The  abscissa  indicates  the  dis'ance 


Mten 


the  dial  plate,  the 


different  from  man.  The  great  motor  power  exerted  by  animals  results  from  the  thickness  and 
number  of  the  muscles,  as  well  as  from  the  different  arrangement  of  the  levers  and  the  action  of 
muscles  on  them.  Insects  particularly  exert  a  large  amount  of  force;  some  insects  can  drag  a  body 
sixty-seven  times  their  own  weight ;  a  horse  scarcely  its  own  weight.  A  man  pressing  upon  a 
dynamometer  with  one  hand  exerts  pressure  =  o  70  times  his  own  weight,  while  a  dog  in  lifting 


544  ACT   OF    SWIMMING. 

its  lower  jaw  exerts  8.3  times.  A  crab  by  closing  its  pincers  28.5  times.  A  mussel  on  closing  its 
shell  3S2  times  its  bofly  weight  (Plateau). 

In  mammals  stanfling  is  much  more  easy,  as  they  have  four  supporting  surfaces.  The  spring- 
ing animals  have  a  sitting  attitude,  while  the  tail  is  often  used  as  a  support  (kangaroo,  squirrel). 
In  birds  there-is  a  mechanical  arrangement  by  which,  while  perching,  the  tendons  are  flexed  ; 
hence,  a  bird  while  sleeping  can  still  retain  its  hold  [Cuvier).  In  the  stork  and  crane,  which  stand 
for  a  long  time  on  one  leg,  this  act  is  unaccompanied  by  muscular  action,  as  the  tibia  is  fixed  by 
means  of  a  process  which  fits  into  a  depression  of  the  articular  surface  of  the  femur. 

In  walking  we  distinguish  in  mammals  the  step  (le  pas) — the  four  feet  are  generally  moved  in 
four  tempo,  and  usually  diagonally,  ^.^.,  in  the  horse  right  fore,  left  hind;  left  fore,  right  hind. 
[The  camel  is  an  exception — it  moves  the  fore  and  hind  limbs  simultaneously  on  each  side.]  In 
trotting  this  movement  is  accelerated  ;  the  two  limbs  in  a  diagonal  direction  lift  together,  so  that 
only  two  hoof  sounds  are  heard,  while,  at  the  same  time,  the  body  is  raised  more  in  the  air.  Dur- 
ing the  interval  between  two  hoof  beats  the  body  is  free  in  the  air,  all  the  limbs  having  left  the 
ground.  Strictly  speaking,  the  fore  limb  leaves  the  ground  slightly  sooner  than  the  hind  one.  The 
gallop. — When  a  (right)  galloping  horse  moves  in  the  air,  the  upper  part  of  its  body  is  fairly  hori- 
zontal; when  it  touches  the  ground,  the  left  hind  foot  is  the  first  to  touch  the  ground.  Shortly 
thereafter,  the  left  fore  leg  and  right  hind  foot  touch  the  ground,  while  the  right  fore  leg  has  not  yet 
reached  the  ground  and  is  directed  forward.  The  upper  part  of  the  body  still  retains  its  horizontal 
direction.  When,  however,  a  few  moments  thereafter,  the  left  hind  leg  again  leaves  the  ground,  it 
is  higher  than  the  fore  leg — simultaneously  the  right  fore  leg  is  thrown  forward  and  lower,  while  the 
right  hind  and  left  fore  leg  are  stretched  to  the  extreme.  Immediately  thereafter,  these  limlis  leave 
the  ground,  while  the  hind  limb  so  far  overtakes  the  fore  limb  that  it  comes  to  lie  higher  than  the 
latter.  The  body,  therefore,  is  projected  forward  and  downward  un  il  the  right  fore  limb,  which 
alone  touches  the  ground,  actively  contracts  and  again  raises  the  body  from  the  ground.  When 
this  happens,  the  horse  again  tloats  in  the  air,  its  body  being  directed  horizontally.  The  long  axis 
of  the  horse's  body  in  galloping  is  placed  obliquely  to  the  direction  of  the  movement,  and  forming 
a  right  angle.  In  forced  galloping  (la  carriere),  which  is  really  a  springing  movement,  the  right 
hind  leg  and  left  fore  leg  do  not  touch  the  ground  at  the  same  time,  but  the  former  does  so  sooner. 
The  amble  is  a  modification  of  the  step,  which  consists  in  this,  that  both  feet  on  the  same  side 
move  at  the  same  time  or  shortly  after  each  other  (camel,  girafl'e,  elephant).  Marey  attached  com- 
pressible ampulh^  under  the  hoof  of  a  horse,  connecting  them  with  registering  apparatus,  and  thus 
accurately  registered  the  time  relations  of  each  act.  Muybridge  photographed  the  actions  of  a 
horse  and  the  dilTerent  phases  of  the  movement. 

In  snakes  the  rudder-like  elevation  and  depression  of  the  ribs  causes  the  progression  of  the 
body. 

Swimming  is  an  acquired  art  in  man.  The  specific  gravity  of  the  body  is  slightly  greater  than 
that  of  ordinary  water,  but  slightly  lighter  than  that  of  sea  water.  When  lying  quietly  on  the 
back,  so  that  only  the  mouth  and  nose  are  at  last  above  the  water,  very  slight  movements  of  the 
hands  are  necessary  to  keep  a  person  from  sinking.  In  this  position,  progression  can  be  accom- 
plished by  extending  and  adducting  the  legs,  while  the  movement  is  accelerated  by  rudder  like 
movements  of  the  arms.  Swimming  belly  downward  is  more  difficult,  because  the  head,  being 
held  above  the  water,  makes  the  body  specifically  heavier.  The  forward  movement  and  the  act  of 
supporting  the  body  in  the  water  consist  of  three  acts:  Firsts  horizontal,  rudder-like  movements  of 
the  extended  arms  from  before  backward,  until  they  reach  the  horizontal  position  (forward  move- 
ment) ;  second,  pressure  of  the  arms  downward,  and  subsequent  adduction  of  the  elbow  joint  to 
the  body  (elevation  of  the  body),  together  with  retraction  of  the  extended  legs;  third,  projection  of 
the  arms,  now  brought  together,  and  at  the  same  time  extension  and  adduction  of  the  legs  obliquely 
backward  and  downward,  thus  causing  elevation  of  the  body  as  well  as  a  forward  movement.  Too 
rapid  movements  cause  fatigue,  while  the  respirations  must  be  carefully  regulated.  Many  land 
mammals,  whose  body  is  specifically  lighter  than  water,  can  swim,  especially  with  the  aid  of  their 
hind  limbs,  while  at  the  same  time  all  the  legs  being  directed  downward,  and  being  specifically  the 
heaviest  part  of  the  body,  keep  the  trunk  in  the  normal  position.  Fishes  chiefly  use  their  tail  fin 
as  a  motor  organ,  which  is  moved  by  powerful  lateral  muscles.  When  the  tail  is  suddenly  extended, 
it  presses  upon  the  water  and  displaces  it.  Some  fish,  as  the  salmon,  can  lift  their  body  out  of  the 
water  by  a  blow  of  their  tail  fin.  The  dorsal  and  anal  fins  enable  the  animal  to  preserve  the  erect 
position.  The  pectoral  and  abdominal  fins  corresponding  to  the  extremities  execute  slight  move- 
ments, especially  upward  and  downward,  which  are  greater  during  sleep.  The  swimming 
bladder  is  the  homologue  of  the  lung,  and  is  used  for  hydrostatic  purposes  in  some  fishes,  and  as 
an  auxiliary  respiratory  organ  in  others,  e.g.,  the  dipnoi  (^  140).  It  is  absent  or  rudimentary  in  the 
cyclostomata.  In  swimming  birds,  the  body  is  specifically  very  much  lighter  than  the  water, 
while  their  feathers  are  lubricated  by  the  oily  secretion  of  the  coccygeal  glands  (J  291).  Their 
feet  are  usually  webbed. 

Flight. — Bats  and  their  allies  are  the  only  flying  mammals.  The  bones  of  the  upper  limb  and 
phalanges  are  greatly  elongated,  and  between  these  and  the  elongated  hind  limb  (except  the  foot) 
there  is  stretched  a  thin  membrane.  The  membrane  is  moved  by  the  powerful  pectoral  muscles. 
The  flying  squirrel  has  only  a  duplicature  of  the  skin  stretched  between  the  large  bones  of  the  ex- 


ARRANGEMENT  OF  THE  LARYNX.  545 

tremities,  ■nhicli  serves  as  a  parachute  when  the  animals  spring.  In  birds  the  body  is  specifically 
very  light ;  numerous  air  sacs  in  the  chest  and  belly  communicate  with  the  lungs,  and  with  the 
cavities  of  most  of  the  bones  (5  140).  The  modified  upper  extremities  are  supported  by  the  cora- 
coid  bone  and  the  united  clavicles  or  furculum,  and  are  moved  by  the  powerful  pectoral  muscles 
attached  to  the  keeled  sternum.  Marey,  by  means  of  his  revolving  photographic  camera,  has 
analyzed  all  the  phases  of  flight  in  a  bird. 

[Warner  has  studied  the  movements  of  the  fingers,  and  correlated  these  movements  with 
changes  in  the  nerve  centres  in  certain  diseased  conditions,  <•.,?•.,  chorea.  An  India-rubber  tube  is 
attached  to  each  finger,  and  this  "  motor  "  part  of  the  apparatus  is  connected  with  a  Marey's  tam- 
bour. The  several  finger  tubes  are  fixed  to  an  arrangement  not  unlike  a  cricketer's  glove,  so  that 
voluntary  or  involuntary  movements  of  the  fingers  can  be  registered  and  studied.] 

312.  VOICE  AND   SPEECH,  PHYSICAL  CONSIDERATIONS. 

— The  blast  of  expired  air — and  under  certain  circumstances  the  inspiratory 
blast  also — is  employed  to  throw  the  tense  vocal  cords  into  a  state  of  regular 
vibration,  whereby  a  sound  is  produced.  The  sound  so  produced  is  the  human 
voice. 

The  true  vocal  cords  are  really  elastic  membranous  reeds.  If  a  blast  of  air  be  forcibly  driven 
upward  through  the  partially  closed  glottis,  the  vocal  cords  are  pushed  asunder,  as  the  elastic  tension 
of  the  air  overcomes  the  resistance  of  the  cords.  After  the  escape  of  air  from  below,  the  cords  rapidly 
return  to  their  former  position,  and  are  again  pushed  asunder,  and  caused  to  vibrate. 

1.  Thus,  when  a  membrane  vibrates,  the  air  must  be  alternately  condensed  and  rarefied.  The 
condensation  and  rarefaction  are  the  chief  cause  of  the  tone  or  note  (as  in  the  siren),  not  so  much 
the  membranes  themselves  {v.  Helmhollz). 

2.  The  "air  tube"  or  porte  vente,  conducting  the  air  to  the  membranes  in  man,  is  the  lower 
portion  of  the  larynx,  the  trachea,  and  the  whole  bronchial  system ;  the  bellows  is  represented  by 
the  chest  and  lungs,  which  are  forcibly  diminished  in  size  by  the  expiratory  muscles. 

3.  The  cavities  which  lie  above  the  membranes  constitute  "  resonators,"  and  consist  of  the  upper 
part  of  the  larynx,  pharynx,  and  also  of  the  cavities  of  the  nose  and  mouth,  arranged,  as  it  were,  in 
two  stories,  the  one  over  the  other,' which  can  be  closed  alternately. 

The  pitch  of  the  tone  produced  by  a  membranous  apparatus  depends  upon  the  following 
factors  : — 

(a)  On  the  length  of  the  elastic  membranes  or  plates.  The  pitch  is  inversely  proportional  to  the 
length  of  the  elastic  membrane,  i.  e.,  the  shorter  the  membrane  the  higher  the  pitch,  or  the  greater  the 
number  of  vibrations  per  second.  Hence,  the  pitch  of  a  child's  vocal  cords  (shorter)  is  higher  than 
that  of  an  adult. 

(b)  The  pitch  of  the  tone  is  directly  proportional  to  the  square  root  of  the  amount  of  the  elas- 
ticity of  the  elastic  membrane.  In  membranous  reeds,  and  also  with  silk,  it  is  directly  proportional 
to  the  square  root  of  the  extending  weight,  which  in  the  case  of  the  larynx  is  the  force  of  the  mus- 
cles rendering  the  cords  tense. 

(c)  The  tone  of  membranous  reeds  is  not  only  strengthened  hy  a  viore  poiuerfitl  blasts  as  the 
amplitude  of  the  vibrations  is  increased,  but  the  pitch  of  the  tone  may  also  be  raised  at  the  same 
time,  because,  owing  to  the  great  amplitude  of  the  vibration,  the  mean  tension  of  the  ela-'tic  mem- 
brane is  increased. 

((/)  The  supra-laryngeal  cavities,  which  act  as  resonators,  are  inflated  when  the  larynx  is  in 
action,  so  that  the  tone  produced  by  these  cavities  is  added  to  and  blended  with  the  sound  of  the 
elastic  membranes,  whereby  certain  partial  tones  of  the  latter  are  strengthened  (^  415).  The  char- 
acteristic timbre  of  the  voice  largely  depends  upon  the  form  of  the  resonators. 

(1?)  'When  vocalizing,  the  strongest  resonance  takes  place  in  the  air  tubes,  as  they  contain  com- 
pressed air.     It  causes  the  vocal  fremitus  which  is  audible  on  placing  the  ear  over  the  chest  [\  117, 

(/)  Narrowing  or  dilating  (he  glottis  has  no  effect  on  the  pitch  of  the  tone,  only  with  a  wide 
glottis  much  more  air  must  be  driven  through  it,  which,  of  course,  greatly  increases  the  work  of  the 
thorax. 

313.  ARRANGEMENT  OF    THE   LARYNX.— I.  The  Cartilages 

and  Ligaments  of  the  Larynx. — The  fundamental  part  of  the  larynx  consists 
of  the  cricoid  cartilage,  whose  small,  narrow  portion  is  directed  forward  and  the 
broad  plate  backward.  The  thyroid  cartilage  articulates  by  its  inferior  cornu 
with  the  posterior  lateral  portion  of  the  cricoid.  This  permits  of  the  thyroid  car- 
tilage rotating  upon  a  horizontal  axis  directed  through  both  of  the  articular  sur- 
faces, so  that  the  upper  margin  of  the  thyroid  passes  forward  and  downward,  while 
the  joint  is  so  constructed  as  to  permit  also  of  a  slight  upward,  downward,  for- 
ward, and  backward  movement  of  the  thyroid  upon  the  cricoid  cartilage.  The 
35 


546 


STRUCTURE  OF  THE  LARYNX  AND  VOCAL  CORDS. 


triangular  arytenoid  cartilages  articulate  at  some  distance  from  the  middle  line, 
with  oval,  saddle-like,  articular  surfaces  placed  upon  the  upper  margin  of  the  plate 
of  the  cricoid  cartilage.  The  articular  surfaces  permit  two  kinds  of  movements  on 
the  part  of  the  arytenoid  cartilages ;  first,  rotation  on  their  base  around  their  ver- 
tical long  axis,  whereby  either  the  anterior  angle  or  processus  vocalis,  which  is 
directed  forward,  is  rotated  outward  ;  while  the  processus  muscularis,  which  is 
directed  outward  and  projects  over  the  margin  of  the  cricoid  cartilage,  is  rotated 
backward  and  inward,  or  conversely.  Further,  the  arytenoids  may  be  slightly  dis- 
placed upon  their  bases  either  outward  or  inward. 

The  true   vocal   cords,  or  thyro-arytenoid  ligaments,  are  in  man  about  15 
millimetres,  and   in   women   11  millimetres   in   length,  and   consist   of  numerous 


Fig.  319. 


Fig.  320. 


Fig.  JI9. — Larynx  from  the  front,  with  the  lig-ime 
Cart,  thyreoidea;  Corp.  i fit.,  Corpus  triti 
hyoid.  med.,  Ligamentum  thyreo-hyoitieun 
eric.  ihyr.  nted.,  Ligam.  crico-thyreoideui 
Muse,  sterno-hyoideus  ;  M.  th.-hyoid.,  Mu 


s  and  the  insertions  of  the  muscles.  L 
um  :  C  c.  Cart  cricoitlea  ;  C.  Ir.,  Cai 
nedium  :  Li(.  th.-h.  Int.,  Ligara.  thyre 
medium  ;  J.i^.  cric.-trach.,  Ligam.  i 
,  thyreo-hyoideus  ;  M.  st.-th..  Muse,  si 


)-thyreoideus.  Fig.  320. —  Laryn 
eushion  (W.)  :  L.  ar.-ep.,  Lig.  ary-epiglotticum  ; 
Cart.  Santorini;  Caryt.,  Cart,  arytanoidea  ;  C.  c.  Cart,  erieoidea:  P.  1 
arytaen.  ;  L.  cr.-nr.,  Ligam  crieo-arytaean. :  C.  s.,  Cornu  superius ;  C.i.  C 
ce.-cr.  p.  i.,  Lig.  Icerato-ericoideum.  post.  inf.  ;  C.  tr..  Cart,  tracheale 
traehea. 


/,.,  oshyoidcum:  C.  th., 
:.  irache.iles  :  Lif.  t/iyr.. 
)-hyoideum  laterale  :  /./f . 
rico-traeheale :  M.  St.-h., 
;rno-thyreoideus  :  M.  cr.~ 

muscles.     E.,   Epiglottis 

Cart.  Wrisbergii;  C.  S., 
:ssus  muscularis  of  Cart, 
rius  Cart,  thyreoidea  :  L. 

tr.,   Pars  m. 


elastic  fibres.  They  arise  close  to  each  other  from  near  the  middle  of  the  inner 
angle  of  the  thyroid  cartilage,  and  are  inserted  each  into  the  anterior  angle  or 
processus  vocalis  of  the  arytenoid  cartilages.  The  ventricles  of  Morgagni 
permit  free  vibration  of  the  true  vocal  cords,  and  separate  them  from  the  upper  or 
false  cords,  which  consist  of  folds  of  mucous  membrane.  The  false  vocal  cords 
are  not  concerned  in  phonation,  but  the  secretion  of  their  numerous  mucous  glands 
moistens  the  true  vocal  cords. 

The  obliquely  directed  under  surface  of  the  vocal  cords  causes  the  cords  to  come  together  very 
easily  when  the  glottis  is  narrow  during  respiration  (e.g.,  in  sobbing),  while  the  closure  may  be 
made  more  secure  by  respiration.     The  opposite  is  the  condition  of  the  false  vocal  cords,  which. 


ACTION    OF   THE    LARYNGEAL    MUSCLES. 


547 


when  they  touch,  are  easily  separated  during  inspiration;  while  during  expiration,  owing  to  the 
dilatation  of  the  ventricles  of  Morgagni,  they  easily  come  together  and  close  ( Wyllie,  L.  Brunton, 
and  Cash). 

II.  Action  of  the  Laryngeal  Muscles. — -These  muscles  have  a  double 
function  :  i.  One  connected  with  respiration,  in  as  far  as  the  glottis  is  widened 
and  narrowed  alternately  during  respiration  ;  further,  when  the  glottis  is  firmly 
closed  by  these  muscles,  the  entrance  of  foreign  substances  into  the  larynx  is 
prevented.  The  glottis  is  closed  immediately  before  the  act  of  coughing  (§  120). 
2.  The  laryngeal  muscles  give  the  vocal  cords  the  proper  tension  and  other 
conditions  for  phonation. 

I.  The  glottis  is  dilated  by  the  action  of  the  posterior  crico-arytenoid 


Fig.  321. 


Fig.  322. 


Fig  321 —Larynx  from  behind  wilh  IK  muscles.     £•.,  Epiglottis,  with  the  cushion  (W  )      C  H-     Cirt   Wnsbergii;    C. 
5    Cart   bantonni      C  c     Cart  cricoidea.  Curnu  sup. — Cornu  inf  Cart   th>reoidea;      1/  ar   ir     Muse,  arytae- 
;  transversus  ;   .!//«,  rtr.  f^/.,  MusculiarytECnoidei  obliqui     M  cr   aryt  post  ^  Mubculuscnco  ajytae; 


;  posticus;  /*«r.v  car/. ,  Pars  cartilaEinea:  /"rtrj  we??//*..  Pars  membran 
the  laryn.\.  O.  h.,  Oshyoideum  ;  C.  th  ,  Cart,  thyreoidea  :  C.  c  ,  Cart  cric( 
M.  thyreo-arytaenoideiis :  M.  cr.-ar.  p  ,  M.  crico-arytaenoideus  posticus  M 
alls:  Al.cr.-ih.,  M.  crico-thyreoideus  :  N.  lar.  sitfi.  v.,'ii.  laryngeus  sup 
Ramus  ext.  :  N.  Inr.  rec.  v.,  N.  laryngeus  recurrens ;  R.  I.  N  L  R  Rat 
ext.  nervi  laryngei  recurrcntis  vagi. 


of 


achese  Fig  ^2 
idei  TV  Trachea  1/  th  -ar., 
:r  ar  I  M  cnco  arytaen.  later- 
R  I ,  Ramus  internus  ;  R.  E., 
lus  int      R   E   N  L   R  ,  Ramus 


muscles.  When  they  contract,  they  pull  both  processus  musculares  of  the  aryte- 
noid cartilages  backward,  downward,  and  toward  the  middle  line  (Fig.  323),  so 
that  the  processus  vocales  (I,  I)  must  go  apart  and  upward  (II,  II).  Thus,  between 
tiie  vocal  cords  (glottis  vocalis ),  as  well  as  between  the  inner  margins  of  the 
arytenoid  cartilages,  a  large  triangular  space  is  formed  (glottis  respiratoria), 
and  these  spaces  are  so  arranged  that  their  bases  come  together,  so  that  the  aperture 
between  the  cords  and  the  arytenoid  cartilages  has  a  rhomboidal  form.  Fig.  323 
shows  the  action  of  the  muscles.  The  vocal  cords,  represented  by  lines  converging 
in  front,  arise  from   the  anterior  angle  of  the  arytenoid  cartilages  (I,  I).     When 


548 


ACTION    OF   THE    LARYNGEAL    MUSCLES. 


these  cartilages  are  rotated  into  the  position  (II,  II),  the  cords  take  the  position 
indicated  by  the  dotted  lines.  The  widening  of  the  respiratory  portion  of  the 
glottis  between  the  arytenoid  cartilages  is  also  indicated  in  the  diagram. 

PathologicaL — When  these  muscles  are  paralyzed,  the  widening  of  the  glottis  does  not  take 
place,  and  there  may  be  severe  dyspncea  during  inspiration,  although  the  voice  is  unaffected  (Jiiegel, 
L.  Weber). 

2.  The  entrance  to  the  glottis  is  constricted  by  the  arytenoid  muscle 

(transverse),  which  extends  transversely  between  both  outer  surfaces  of  the  aryte- 
noids along  their  whole  length  (Fig.  324).  On  the  posterior  surface  of  this  muscle 
is  placed  the  cross  bundles  (Fig.  321)  of  the  thyro-aryepiglotticus  (or  arytaenoidei 
obliqui)  ;  they  act  like  the  foregoing.  The  action  of  these  muscles  is  indicated 
in  Fig.  324;  the  arrows  point  to  the  line  of  traction. 

Pathological. — Paralysis  of  this  muscle  enfeeliles  the  voice  and  makes  it  hoarse,  as  much  air 
escapes  between  the  arytenoid  cartilages  during  phonation. 

3.  In  order  that  the  vocal   cords  be   approximated  to  each  other,  which 


Fig.  323. 


Fig.  324. 


Fig.  323, — Schematic  horizontal  section  of  the  larynx.  I.  Position  of  the  horizont.illy  divided  arytenoid  cartilages 
during  respiration  ;  from  their  anterior  processes  run  the  converging  vocal  cords.  The  arrows  show  the  line  of 
traction  o(  the  fiosti'rior  crico-arytenoid  m\i%c\e%  ;  II,  II,  the  position  of  the  arytenoid  muscles  as  a  result  of  this 
action.  Fig.  324. — Schematic  horizontal  section  of  the  larynx,  to  illustrate  theaction  of  the  arytenoid  muscle. 
I,  I,  position  of  the  arytenoid  cartilages  during  quiet  respiration.  The  arrows  indicate  the  direction  of  the  con- 
traction of  the  muscle ;  II,  II,  the  position  of  the  arytenoid  cartilages  after  the  arytenoideus  contracts. 

occurs  during  phonation,  the  processus  vocales  of  the  arytenoid  cartilages  must 
be  closely  apposed,  whereby  they  must  be  rotated  inward  and  downward.  This 
result  is  brought  about  by  the  processus  musculares  being  inoved  in  a  forward  and 
upward  direction  by  the  thyro-arytenoid  muscles.  These  muscles  are  applied 
to,  and,  in  fact,  are  imbedded  in,  the  substance  of  the  elastic  vocal  cords,  and 
their  fibres  reach  to  the  external  surface  of  the  arytenoid  cartilages.  When 
they  contract,  they  rotate  these  cartilages,  so  that  the  processus  vocales  must 
rotate  inward.  The  glottis  vocalis  is  thereby  narrowed  to  a  mere  slit  (Fig. 
326),  whilst  the  glottis  respiratoria  remains  as  a  broad  triangular  opening.  The 
action  of  these  muscles  is  indicated  in  Fig.  325. 

The  lateral  crico-arytenoid  muscle  is  inserted  into  the  anterior  margin  of 
the  articular  surface  of  the  arytenoid  cartilage ;  hence,  it  can  only  pull  the  car- 
tilage forward  ;  but  some  have  supposed  it  can  also  rotate  the  arytenoid  cartilage 
in  a  manner  similar  to  the  thyro-arytenoid  (?),  with  this  difference,  that  the  pro- 
cessus vocales  do  not  come  so  close  to  each  other. 


POSITION    DURING    PRONATION. 


549 


Scheme  of  the  closure  of  the  glottis  by  the  ihyro-arytenoid 
muscles,  II,  II,  position  of  the  aiytenoid  cartilages  during 
quiet  respiration.  The  arrows  indicate  the  direction  of  the 
muscular  traction. — I,  I,  position  of  the  arytenoid  carti- 
lages after  the  muscles  contract. 


Pathological  — Paralysis  of  both  thyro-  Fig.  325. 

arytenoid  muscles  causes  loss  of  voice. 

4.  The  vocal  cords  are  ren- 
dered tense  by  their  points  of 
attachment  being  removed  from 
each  other  by  the  action  of  muscles. 
The  chief  agents  in  this  action  are 
the  crico-thyroid  muscles,  which 
pull  the  thyroid  cartilage  forward 
and  downward.  At  the  same  time, 
however,  the  posterior  crico-aryte- 
noids  must  pull  the  arytenoid  carti- 
lages slightly  backward,  and  at  the 
same  time  keep  them  fixed. 

The  genio-hyoid  and  thyro-hyoid,  when 
they  contract,  pull  the  thyro'd  upward  and 
forward  toward  the  chin,  and  also  tend  to 
increase  the  tension  of  the  vocal  cords  (C. 
Mayer,  Griitzner). 

Pathological. — Paralysis  of  the  crico- 
thyroid causes  the  voice  to  become  harsh 
and  deep,  owing  to  the  vocal  cords  not  being  sufficiently  tense. 

Position  during  Phonation. — The  tension  of  the  vocal  cords  brought  about 
in  this  way  is  not  of  itself  sufficient  for  phonation.  The  triangular  aperture  of 
the  glottis  respiratoria  between  the  arytenoid  cartilages,  produced  by  the  unaided 
action  of  the  internal  thyro-arytenoid  muscles  (see  3)  must  be  closed  by  the  action 
of  the  transverse  and  oblique  arytenoid  muscles.  The  vocal  cords  themselves 
must  have  a  concave  margin,  which  is  obtained  through  the  action  of  the  crico- 
thyroids and  posterior  crico-arytenoids,  so  that  the  glottis  vocalis  presents  the 
appearance  of  a  myrtle  leaf  {Henle),  while  the  rima  glottidis  has  the  form  of  a 
linear  slit  (Fig.  329).  The  contraction  of  the  internal  thyro-arytenoid  converts 
the  concave  margin  of  the  vocal  cords  into  a  straight  margin.  This  muscle  adjusts 
the  delicate  variations  of  tension  of  the  vocal  cords  themselves,  causing,  more 
especially,  such  variations  as  are  necessary  for  the  production  of  tones  of  slightly 
different  pitch.  -\s  these  muscles  come  close  to  the  margin  of  the  cords,  and  are 
securely  woven,  as  it  were,  among  the  elastic  fibres  of  which  the  cords  consist, 
they  are  specially  adapted  for  the  above-mentioned  purpose.  When  the  muscles 
contract,  they  give  the  necessary  resistance  to  the  cords,  thus  favoring  their  vibra- 
tion. As  some  of  the  muscular  fibres  end  in  the  elastic  fibres  of  the  cords,  these 
fibres,  when  they  contract,  can  render  certain  parts  of  the  cords  more  tense  than 
others,  and  thus  favor  the  modifications  in  the  formation  of  the  tones.  The 
coarser  variations  in  the  tension  of  the  vocal  cords  are  produced  by  the  separa- 
tion of  the  thyroid  from  the  arytenoid  cartilages,  while  the  finer  variations  of 
tension  are  produced  by  the  thyro-arytenoid  muscles.  The  value  of  the  elastic 
tissue  of  the  cords  does  not  depend  so  much  upon  its  extensibility  as  upon  its 
property  of  shortening  without  forming  folds  and  creases. 

Pathological. — In  paralysis  of  these  muscles,  the  voice  can  only  be  produced  by  forcible  expira- 
tion,  as  much  air  escapes  through  the  glottis ;  the  tones  are  at  the  same  time  deep  and  impure. 
Paralysis  of  the  muscle  of  one  side  causes  flapping  of  the  vocal  cord  on  that  side  [Gerkuriit). 

5.  The  relaxation  of  the  vocal  cords  occurs  spontaneously  when  the 
stretching  forces  cease  to  act  ;  the  elasticity  of  the  displaced  thyroid  and  arytenoid 
cartilages  comes  into  play,  and  restores  thein  to  their  original  position.  The 
vocal  cords  are  also  relaxed  by  the  action  of  the  thyro-arytenoid  and  lateral  crico- 
arytenoid muscles. 

It  is  evident  from  the  above  statements  that  tension  of  the  vocal  cords  and 


550 


RELAXATION  OF  THE  VOCAL  CORDS. 


narrowing  of  the  glottis  are  necessary  for  phonation.  The  tension  is  pro- 
duced by  the  crico-thyroids  and  posterior  crico-arytenoids  ;  the  narrowing  of  the 
glottis  respiratoria  by  the  arytenoids,  transverse  and  oblique,  the  glottis  vocalis 
being  narrowed  by  the  thyro-arytenoids  and  (?  lateral  crico-arytenoids),  the  former 
muscles  causing  the  cords  themselves  to  become  tense. 

Nerves  (§  352,  5). — The  crico-thyroid  is  supplied  by  the  superior  laryngeal 
branch  of  the  vagus,  which  at  the  same  time  is  the  sensory  nerve  of  the  mucous 
membrane  of  the  larynx.  All  the  other  intrinsic  muscles  of  the  larynx  are  sup- 
plied by  the  inferior  laryngeal. 


Fig.  326. 


A  vertical  section  through  the  head  and  neck,  to  the  first  dorsal  vertebra,  a.  the  position  of  the  laryngoscope  on 
observing  the  posterior  part  of  the  glottis,  arytenoid  cartilages,  the  upper  surface  of  the  posterior  wall  of  the 
larynx ;  ^,  its   position   on  observing  the  anterior  angle  of  the  glottis.     Large,  a,  and  6,  small  laryngoscopic 


The  mucous  membrane  of  the  larynx  is  richly  supplied  with  el.istic  fibres,  .ind  so  is  the  sub- 
mucosa.  The  sub-mucosa  is  more  lax  near  the  entrance  to  the  glottis  and  in  the  ventricles  of  Mor- 
gagni,  which  explains  the  enormous  swelling  that  sometimes  occurs  in  these  parts  in  cedema 
glottidis.  A  thin,  clear  limiting  membrane  lies  under  the  epithelium.  The  epithelium  is  stratified, 
cylindrical,  and  ciliated  with  intervening  goblet  cells.  On  the  true  vocal  cords  and  the  anterior 
surface  of  the  epiglottis,  however,  this  is  replaced  by  stratified  squamous  epithelium,  which  covers 
the  small  papilhe  of  the  mucous  membrane.  Numerous  branched  miicoiis  glands  occur  over  the 
cartilages  of  Wrisberg,  the  cushion  of  the  epiglottis,  and  in  the  ventricles  of  Morgagni ;  in  other 
situations,  as  on  the  posterior  surface  of  the  larynx,  the  glands  are  more  scattered.  The  blood 
vessels  form  a  dense  capillaiy  plexus   under  the   membrana  propria  of  the  mucous  membrane; 


THE    LARYNGOSCOPE. 


551 


under  this,  however,  there  are  other  two  strata  of  blood  vessels.  The  lymphatics  form  a  superficial 
narrow  mesh-work  under  the  blood  capillaries,  with  a  deeper,  coarser  plexus.  The  medullated 
nerves  have  ganglia  in  their  branches,  but  their  mode  of  termination  is  unknown.  [W.  Stirling 
has  described  a  rich  sub- epithelial  ple.xus  of  medullated  nerve  fibres  on  the  anterior  surface  of  the 
epiglottis,  while  he  finds  that  there  are  ganglionic  cells  in  the  course  of  the  superior  laryngeal 
nerve.] 

Cartilages. — The  thyroid,  cricoid,  and  nearly  the  whole  of  the  arytenoid  cartilages  consist  of 
hyaline  cartilage.  The  two  former  are  prone  to  ossify.  The  apex  and  processus  vocalis  of  the 
arytenoid  cartilages  consist  of  yellow  Jibro  cartilage,  and  so  do  all  the  other  cartilages  of  the 
larynx. 

The  larynx  grows  until  about  the  sixth  year,  when  it  rests  for  a  time,  but  it  becomes  again  much 
larger  at  puberty  (J  434). 

314.  LARYNGOSCOPY. — Historical.— After  Bozzini  (1807)  gave  the  first  impulse  toward 
the  investigation  of  the  internal  cavities  of  the  body,  by  illuminating  them  with  the  aid  of  mirrors, 
Babington  (1S29)  actually  observed  the  glottis  in  this  way.  The  famous  singer  Manuel  Garcia 
(1854)  made  investigations  both  on  himself  and  other  singers,  regarding  the  movements  of  the  vocal 
cords,  during  respiration  and  phonation.  The  examination  of  the  larynx  by  means  of  the  laryngo- 
scope was  rendered  practicable  chiefly  by  Tiirck  (1857)  and  Czermak,  the  latter  observer  being  the 
first  to  use  the  light  of  a  lamp  for  the  illumination  of  the  larynx.  Rhinoscopy  was  actually  first 
practised  by  Baumis  (1838),  but  Czermak  was  the  first  person  who  investigated  this  subject  system- 
atically. 

Fic.  327. 


The  Laryngoscope  consists  of  a  small  mirror  fixed  to  a  long  handle,  at  an  angle  of  125°  to 
130°  ( Fig.  326,  </,  /').  When  the  mouth  is  opened,  and  the  tongue  drawn  forward,  the  mirror  is  in- 
troduced, as  is  shown  in  Fig.  327.  The  position  of  the  mirror  must  be  varied,  according  to  the 
portion  of  the  larynx  we  wish  to  examine  ;  in  some  cases,  the  soft  palate  has  to  be  raised  by  the 
back  of  the  mirror,  as  in  the  position  b.  A  picture  of  the  part  of  the  larynx  examinfed  is  formed 
in  the  small  mirror,  the  rays  of  light  passing  in  the  direction  indicated  by  the  dotted  lines  from  the 
mirror  ;  they  are  reflected  at  the  same  angle  through  the  mouth  into  the  eye  of  the  observer,  who 
must  place  himself  in  the  direction  of  the  reflected  rays. 

The  illumination  of  the  larynx  is  accomplished  either  by  means  of  direct  sunlight  or  by  light 
from  an  artificial  source,  e.  g.,  an  ordinary  lamp,  an  oxyhydrogen  lime  light  or  the  electric  light. 
The  beam  of  light  impinges  upon  a  cotiiave  mirror  of  15  to  20  centimetres  focus,  and  lo  centi- 
metres  in  width,  and  from  its  surface  the  concentrated  beam  of  light  is  reflected  through  the  mouth 
of  the  patient,  and  directed  upon  the  small  mirror  held  in  the  back  part  of  the  throat.  The  beam 
of  light  is  reflected  at  the  same  angle  toward  the  larynx  by  the  small  throat  mirror,  so  that  the 
larynx  is  brightly  illuminated.  The  observer  has  now  to  direct  his  eye  in  the  same  direction  as  the 
illuminating  rays,  which  can  be  accomplished  by  having  a  hole  in  the  centre  of  the  concave  mirror 
through  which  the  observer  looks.  Practically,  however,  this  is  unnecessary ;  all  that  is  necessary 
is  to  fix  the  concave  mirror  to  the  forehead  by  means  of  a  broad  elastic  band,  so  that  the  observer, 
by  looking  just  under  the  margin  of  the  concave  mirror,  can  see  the  picture  of  the  larynx  in  the 
small  throat  muTor  (Fig.  327). 


552 


RHINOSCOPY. 


Fig.  32S. 


In  order  to  examine  the  larynx,  place  the  patient  immediately  in  front  of  you,  and  cause  him  to 
open  his  mouth  and  protrude  his  tongue.  A  lamp  is  placed  at  the  side  of  the  head  of  the  patient, 
and  light  from  this  source  is  reflected  from  the  concave  mirror  on  the  obsen'er's  forehead,  and  con- 
centrated upon  the  laryngoscopic  mirror  introduced  into  the  back  part  of  the  throat  of  tlie  patient 
(Fig.  327). 

Oertel  was  able  by  means  of  a  rapid  intermittent  illumination  of  the  larynx  through  a  stroboscopic 
disk  to  study  the  movements  of  the  vocal  cords  directly  with  the  eye.  Ssimanowsky  put  a  pho- 
tographic camera  in  the  position  of  the  eye,  and  photographed  the  movements  of  the  vocal  cords  of 
an  artificial  larynx.     [Brown  and  Behnke  have  photographed  the  human  vocal  cords.] 

Laryngeal  Electrodes. — V.  Ziemssen  showed  that  long,  narrow  electrodes  can  be  introduced 
into  the  larynx,  so  that  the  muscles  can  be  stimulated  and  their  actions  studied ;  while  Rossbach 
finds  that  the  muscles  and  nerves  of  the  interior  of  the  larynx  may  be  stimulated  by  stimulating 
the  skin,  i.e.,  percutaneously.  These  methods  are  used  both  for  physiological  and  therapeutical 
purposes. 

The  Picture  of  the  Larynx. — Fig.  328  shows  the  following  structures:  Z., 
the  root  of  the  tongue,  with  the  ligamentum  glosso-epiglotticum  continued  from 
its  middle;  on  each  side  of  the  latter  are  /'./',  the  so-called  vallecullie.  The 
epiglottis  (E.)  appears  like  an  arched  upper  lip  ;  under  it,  during  normal  respira- 
tion, the  lancet-shaped  ^/c/z'/.f  (-^0'  ^"d  on  each  sideof  it  the  true  vocal  cords  (Z.  v.). 
The  length  of  the  vocal  cord  in  a  child  is  6  to  8  mm.,  in  the  female  10  to  15  mm. 
when  they  are  relaxed,  and  15  to  20  mm. 
when  tense.  In  man,  the  length  under  the 
same  conditions  is  15  to  20  mm.  and  20  to 
25  mtn.  The  breadth  varies  from  2  to  5  mrn. 
On  the  external  side  of  each  vocal  cord  is 
the  entrance  to  the  sinus  of  Alorgagni  (S.Af.), 
represented  as  a  dark  line.  Further  upward 
and  more  external  are  (L.v.s.)  the  upper  or 
false  vocal  cords.  [The  upper  or  false  vocal 
cords  are  red,  the  lower  or  true,  white.]  On 
each  side  of  F.  are  {S.S.),  the  apices  of  the 
cartilages  of  Saiitoriiii,  placed  upon  the  apices 
of  the  arytenoid  cartilages,  while  immediately 
behind  is  the  wall  of  the  pharynx,  F.  In  the 
aryteno-epiglottidean  fold  are  {JJ'.JV.)  the 
cartilages  of  U'risberg,  while  outside  these  are 
the  depressions  {S.p.)  constituting  the  Sinus 
piriforincs. 

During  normal  respiration  the  glottis 
(Fig.  329)  has  the  form  of  a  lancet-shaped 
slit  between  the  bright,  yellowish-white  vocal  cords.  If  a  deep  inspiration  be 
taken,  the  glottis  is  considerably  widened  (Fig.  330),  and  if  the  mirror  be  favor- 
ably adjusted  we  may  see  the  rings  of  the  trachea,  and  even  the  bifurcation  of  the 
trachea  (Fig.  330). 

If  a  high  note  be  uttered,  the  glottis  is  contracted  to  a  very  narrow  slit  (Fig. 
33°)- 

Rhinoscopy. — If  a  small  mirror,  fixed  to  a  handle  at  an  angle  of  100°  to  110°,  be  introduced 
into  the  pharynx,  as  shown  in  Fig.  331,  and  if  the  mirror  be  directed  iip-wnrd,  certain  structures  are 
with  difficulty  rendered  visible  (Fig.  332).  In  the  middle  is  the  septum  narium  (^S.n.),  and  on 
each  side  of  it  the  long,  oval,  large  posterior  nares  (T//.),  below  this  \.\\e  soft  palate  (P.m.),  with  the 
pendant  uvula  {U.).  In  the  posterior  nares  are  the  posterior  extremities  of  the  lower  (C/.),  middle 
(Cm.),  and  upper  turbinated  bones  (C.s.).  At  the  upper  part,  a  portion  of  the  roof  of  the  pharynx 
(O.R.)  is  seen,  with  the  arched  masses  of  adenoid  tissue  lying  between  the  openings  of  the 
Eustachian  tubes  (T.T.),  and  called  by  Luschka  \.)x&  pharyngeal  tonsils.  External  to  the  opening 
of  the  Eustachian  tube  is  the  tubular  eminence  {IV.),  and  outside  this  is  the  groove  of  Rosen- 
miiller  (A'.). 

Experiments  on  the  Larynx. — Ferrein  (J  741),  and,  above  all,  Joh.  MUUermade  experiments 
upon  the  excised  larynx.  A  tracheal  tube  was  tied  into  the  excised  human  larynx,  and  air  was 
blown  through  it,  the  pressure  being  measured  by  means  of  a  mercurial  manometer,  while  various 


The  larynx,  as  seen  with  the  laryngoscope, 
tongue;  j5'.,  epiglottis  ;  K,  valleculla  :  . 
glottis  :  L.V.,  true  vocal  cortis  ;  S.M.,  sii 
Morgagni ;  L.v.s. ,  false  vocal  cords  ;  . 
position  of  pharynx;  S.,  cartilage  of  S; 
torini;  IV.,  of  Wrisberg;  i"./>.,  sinus  p 
formes. 


CONDITIONS   AFFECTING   THE    LARYNGEAL   SOUNDS. 


553 


arrangements  were  adopted  for  putting  the  vocal  cords  on  the  stretch  and  for  opening  or  closing 
the  glottis. 

315.     CONDITIONS     INFLUENCING     THE     LARYNGEAL 
SOUNDS.— The  pitch  of  the  note  emitted  by  the  larynx  depends  upon  :  — 


Fig.  329. 


Fig.  330. 


Position  of  the  vocal  cords  on  uttering  a  high  note. 


'  of  the  rings  and  bifurcation  of  trachea. 


1.  The  Tension  of  the  Vocal  Cords,  i.e.,  upon  the  degree  of  contraction 
of  the  crito-thyroid  and  posterior  crico-arytenoid  muscles,  and  also  of  the  internal 
thyro-arytenoids  (§  313,  II,  4). 

2.  The  Length  of  the  Vocal  Cord. — {a)  Children  and  females  with  short 


I  of  the  lar>-ngoscopic 


view.     S.n.,  Septum  ra- 
C.S.,  lower,  middle  and 

upper  turbinated  bones  ;  7'.,  Eustachian  tube  ; 

//'. ,  tubuiar  eminence;  A'.,  groove  of  Rosen- 

mUUer:    F.m.,    soft    palite;     O.R.,    roof    of 

pharynx;   £/.,  uvula. 


vocal  cords  produce  high  notes.  (/^)  If  the  arytenoid  cartilages  are  pressed 
together  by  the  action  of  the  arytenoid  muscles  (transverse  and  oblique),  so  that 
the  vocal  cords  alone  can  vibrate,  while  their  intercartilaginous  portions  lying 
between   the  processus   vocales   do   not,  the   tone    thereby  produced    is    higher 


554  RANGE   OF   THE   VOICE. 

{Garcia).  In  the  production  of  low  notes,  the  vocal  cords,  as  well  as 
margins  of  the  arytenoid  cartilages,  vibrate.  At  the  same  time  the  space 
above  the  entrance  to  the  glottis  is  enlarged  and  the  larynx  becomes  more 
prominent.  (c)  Every  individual  has  a  certain  medium  pitch  of  his  voice, 
which  corresponds  to  the  smallest  possible  tension  of  the  intrinsic  muscles 
of  the  larynx. 

3.  The  Strength  of  the  Blast. — That  the  strength  of  the  blast  from  below 
raises  the  pitch  of  the  tones  of  the  human  larynx  is  shown  by  the  fact  that  tones 
of  the  highest  pitch  can  only  be  uttered  by  powerful  expiratory  efforts.  With 
tones  of  medium  pitch,  the  pressure  of  the  air  in  the  trachea  is  160  mm.,  with 
iiig/i  pitch  200  mm.,  and  with  veiy  high  notes  945  mm.,  and  in  whispering  30  mm., 
of  water  ( Cagniard-Laiour,  Griitzner).  These  results  were  obtained  from  a  tra- 
cheal fistula. 

Accessory  Phenomena. — The  following  as  yet  but  partially  explained  phenomena  are  observed 
in  connection  with  the  production  of  high  notes:  («)  As  the  pitch  of  the  note  rises,  the  larynx  is 
elevated,  partly  because  the  muscles  raising  it  are  active,  partly  because  the  increased  intra-tracheal 
pressure  so  lengthens  the  trachea  that  the  larynx  is  thereby  raised;  the  uvula  is  raised  more  and 
more  (Lalins).  (b)  The  upper  vocal  cords  approximate  to  each  other  more  and  more,  without, 
however,  coming  into  contact,  or  participating  in  the  vibrations,  [c)  The  epiglottis  inclines  more 
and  more  backward  over  the  glottis. 

4.  The  falsetto  voice  with  its  soft  timbre  and  the  absence  of  resonance  in 
the  air  tubes  (pectoral  fremitus)  is  particularly  interesting.  Oertel  observed 
that  during  the  falsetto  voice  the  vocal  cords  vibrated  so  as  to  form  nodes  across 
them,  but  sometimes  there  was  only  one  node,  so  that  the  free  margin  of  the  cord 
and  the  basal  margin  vibrated,  being  separated  from  each  other  by  a  nodal  line 
(parallel  to  the  margins  of  the  vocal  cord).  During  a  high  falsetto  note,  there 
may  be  three  such  nodal  lines  parallel  to  each  other.  The  nodal  lines  are  pro- 
duced probably  by  a  partial  contraction  of  the  fibres  of  the  thyro-arytenoid  muscle 
(p.  54S),  while  at  the  same  titne  the  vocal  cords  must  be  reduced  to  as  thin  plates 
as  possible  by  the  action  of  the  crico-thyroid,  posterior  arytenoid,  thyro-  and 
genio-hyoid  muscles  (Oertet).  The  fortn  of  the  glottis  is  elliptical,  while  with 
the  chestvoice  the  vocal  cords  are  limited  by  straight  surfaces  (yif/f/y^)',  Oertel); 
the  air  also  passes  more  freely  through  the  larynx. 

Oertel  also  found  that  during  the  falsetto  voice  the  epiglottis  is  erect.  The  apices  of  the  aryte- 
noid cartil.iges  are  slightly  inclined  backward,  the  whole  larynx  is  larger  from  before  backward,  and 
narrower  from  side  to  side,  the  aryepiglottidean  folds  are  tense,  with  sharp  margins,  and  the  entrance 
to  the  ventricles  of  Morgagni  is  narrowed.  The  vocal  cords  are  narrower,  the  processus  vocales 
touch  each  other.  The  rotation  of  the  arytenoid  cartilages  necessary  for  this  is  brought  about  by 
the  action  of  the  crico-arytenoid  alone,  while  the  thyroarytenoid  is  to  be  regarded  only  as  an  acces- 
sory aid.  The  pitch  of  the  note  is  increased  solely  by  increased  tension  of  the  vocal  cords.  In 
addition,  there  are  a  number  of  transverse  and  longitudinal  partial  vihralions.  During  the  chest 
voice,  a  smaller  part  of  the  margin  vibrates  than  in  the  faUetto  voice,  so  that  in  the  production  of 
the  latter  we  are  conscious  of  less  muscular  exertion  in  the  larynx.  The  uvula  is  raised  to  the  hori- 
zontal position  [Labus). 

Production  of  Voice. — In  order  that  voice  be  produced,  the  following  con- 
ditions are  necessary  :  (i)  The  necessary  amount  of  air  is  collected  in  the  chest ; 
(2)  the  larynx  and  its  parts  are  fixed  in  the  proper  position;  (3)  air  is  then  forced 
by  an  expiratory  effort  either  through  the  linear  chink  of  the  closed  glottis,  so 
that  the  latter  is  forced  open,  or  at  first  some  air  is  allowed  to  pass  through  the 
glottis  without  producing  a  sound,  but  as  the  blast  of  air  is  strengthened,  the  vocal 
cords  are  thrown  into  vibration. 

316.  RANGE  OF  THE  VOICE.— The  range  of  the  human  voice  for 
chest  notes  is  given  in  the  following  schema  :  — 


SPEECH    AND    THE    FORMATION    OF    VOWELS.  555 


128  Tenor.  512 

The  accompanying  figures  indicate  the  number  of  vibrations  per  second  in  the  corresponding  tone. 
It  is  evident  from  c'  to/'  is  common  to  all  voices ;  nevertheless,  they  have  a  different  timbre.  The 
lowest  note  or  tone,  which,  however,  is  only  occasionally  sung  by  bass  singers,  is  the  contra-F,  with 
42  vibrations :  ihe  highest  note  of  the  soprano  voice  is  a'",  with  1708  vibrations. 

Timbre. — The  voice  of  every  individual  has  a  peculiar  quality,  clang  or  timbre, 
which  depends  u]jon  the  shape  of  all  the  cavities  connected  with  the  larynx.  In 
the  production  of  nasal  tones,  the  air  in  the  nose  is  caused  to  vibrate  strongly,  so 
that  the  entrance  to  the  nares  must  necessarily  be  open. 

317.  SPEECH— THE  VOWELS.— The  motor  processes  connected  with 
the  production  of  speech  occur  in  the  resonating  cavities,  the  pharynx, 
mouth  and  nose,  and  are  directed  toward  the  production  of  musical  tones  and 
noises. 

Whispering  and  Audible  Speech. — When  sounds  or  noises  are  produced 
in  the  resonating  chambers,  the  larynx  being  passive,  the  vox  clandestina,  or 
whispering,  is  produced  ;  when  the  vocal  cords,  however,  vibrate  at  the  same 
time,  "audible  speech"  is  produced.  [Whispering,  therefore,  is  speech 
without  voice.]  Whispering  may  be  fairly  loud,  but  it  requires  great  exertion, 
/'.  e.,  a  great  expiratory  blast,  for  its  production  ;  hence  it  is  very  fatiguing.  It 
may  be  performed  both  with  inspiration  and  expiration,  while  audible  speech  is 
but  temporary  and  indistinct  if  it  is  produced  during  inspiration.  Whispering  is 
caused  by  the  sound  produced  by  the  air  passing  through  the  moderately-contracted 
rima  glottidis,  and  passing  over  the  obtuse  margin  of  the  cord.  During  the  pro- 
duction of  audible  sounds,  however,  the  sharp  margins  of  the  vocal  cords  are 
directed  toward  the  air  by  the  position  of  the  processus  vocales. 

During  speech,  the  soft  palate  is  in  action ;  at  each  word  it  is  raised,  while,  at  the  same  time, 
Passavant's  transverse  band  is  formed  in  the  pharynx  (J  156).  The  soft  palate  is  raised  highest 
when  u  and  i  are  sounded,  then  with  0  and  c,  and  least  with  a.  When  sounding  m  and  n  it  does 
not  move;  it  is  high  (like  n)  during  the  utterance  of  the  explosives.  With  1,  s,  and  especially  with 
the  gutteral  r,  it  exhibits  a  trembling  movement  (Gentzen,  Falksoit). 

Speech  is  composed  of  vowels  and  consonants. 

A.  Vowels  (analysis  and  artificial  formation,  55415). — A.  During  whisper- 
ing, a  vowel  is  the  musical  tone  produced,  either  during  expiration  or  inspiration, 
by  the  inflated  characteristic  form  of  the  mouth  {^Danders'),  which  not  only  has  a 
definite  pitch,  but  also  a  particular  and  characteristic  timbre.  The  characteristic 
form  of  the  mouth  may  be  called  "  t'owel  cavity." 

I.  The  pitch  of  the  vowels  may  be  estimated  musically.  It  is  remarkable  that  the  fundamental 
tone  of  the  "vowel  cavity  "  is  nearly  constant  at  different  ages  and  in  the  sexes.  The  different 
capacities  of  the  mouth  can  be  compensated  by  dift'erent  sizes  of  the  oral  aperture.  The  pitch  of 
the  vowel  cavity  may  be  estimated  by  placing  a  number  of  vibrating  tuning  forks  of  different  pitch 
in  front  of  the  moutli,  and  testing  them  until  we  find  the  one  which  corresponds  with  the  funda- 
mental tone  of  the  vowel  cavity.  This  is  known  by  the  fact  that  the  tone  of  the  tuning  fork  is 
intensified  by  the  resonance  of  the  air  in  the  mouth  {v.  I/elnt/toltz),  or  the  vibrations  may  be  trans- 


556 


THE    FORMATION    OF    VOWELS. 


ferred  to  a  vibrating  membrane  and  recorded  on  a  smoked  surface,  as  in  the   phonautograph  of 
Bonders. 

According  to  Konig,  the  fundamental  tones  of  the  vowel  cavity  are  for 
U  =  b,  O  =  b',  A  =  b",  E  =  b'",  I  =  b"". 

If  the  vowels  be  whispered  in  this  series,  we  find  at  once  that  their  pitch  rises. 
The  fundamental  tone  in  the  production  of  a  vowel  may  vary  within  certain 
limits.  This  may  be  shown  by  giving  the  mouth  the  characteristic  position  and 
then  percussing  the  cheeks  {^Auerbach)  ;  the  sound  emitted  is  that  of  the  vowel, 
whose  pitch  will  vary  according  to  the  position  of  the  mouth. 

When  sounding  A,  the  mouth  has  the  form  of  a  funnel  widening  in  front  (Fig.  333,  A).  The 
tongue  lies  in  the  floor  of  the  mouth,  and  the  lips  are  wide  open.  The  soft  palate  is  moderately 
raised  (Czermai).  It  is  more  elevated  successively  with  O,  E,  U,  I.  The  hyoid  lione  appears  as  if 
at  rest,  but  the  larynx  is  slightly  raised.     It  is  higher  than  with  U  but  lower  than  with  I. 

If  we  sound  A  to  I,  the  larynx  and  the  hyoid  bone  retam  their  relative  position,  but  both  are 
raised.  In  passing  from  A.  to  U,  the  larynx  is  depressed  as  far  as  possible.  The  hyoid  bone  passes 
slightly  forward  [Briiiie).  When  sounding  A,  the  space  between  the  larynx,  posterior  wall  of  the 
pharynx,  soft  palate,  and  the  root  of  the  tongue,  is  only  moderately  wide  ;  it  becomes  wider  with  E, 
and  especially  with  I  yPurkirtje),  but  it  is  smallest  with  U. 

When  sounding  U  (Fig.  333),  the  form  of  the  cavity  of  the  mouth  is  like  that  of  a  capacious 

Fig.  333. 


'-V^  n 


Section  of  the  parts 


thyroid 


I,     Z.  tongue  :  /,  soft  palate  ;  e,  epiglottis  ;   g,  glottis  ;  h,  hyoid  bone  ; 
,,  2,  3,  cricoid,  4,  arytenoid  cartilage. 


flask  with  a  short,  narrow  neck.  The  whole  resonance  apparatus  is  then  longest.  The  lips  are 
protruded  as  far  as  posssible,  are  arranged  in  folds  and  closed,  leaving  only  a  small  opening.  The 
larynx  is  depressed  as  far  as  possible,  while  the  root  of  the  tongue  is  approximated  to  the  posterior 
margin  of  the  palating  arch. 

When  sounding  O,  the  mouth,  as  in  U,  is  like  a  wide-bellied  flask  with  a  short  neck,  but  the 
latter  is  shorter  and  wider  as  the  lips  are  nearer  to  the  teeth.  The  larynx  is  slightly  higher  than 
with  U,  while  the  resonance  chambers  also  are  shorter  (Fig.  333). 

When  sounding  I,  the  cavity  of  the  mouth,  at  the  posterior  part,  is  in  the  form  of  a  small-beUied 
flask  with  a  long,  narrow  neck,  of  which  the  belly  has  the  fundamental  tone,  f,  the  neck  that  of 
d"''.  The  resonating  chambers  are  shortest,  as  the  larynx  is  raised  as  much  as  possible,  while  the 
mouth,  owing  to  the  retraction  of  the  lips,  is  bounded  in  front  by  the  teeth.  The  cavity  between 
the  hard  palate  and  the  back  of  the  tongue  is  exceedingly  narrow,  there  being  only  a  median  nar- 
row slit.  Hence,  the  air  can  only  enter  with  a  clear,  piping  noise,  which  sets  even  the  vertex  of 
the  skull  in  vibration,  and  when  tlie  ears  are  stopped  the  sounds  seem  very  shrill.  When  the  lar- 
ynx is  depressed  and  the  lips  protruded,  as  for  sounding  U,  I  cannot  be  sounded. 

When  sounding  E,  which  stands  next  to  I,  the  cavity  has  also  the  form  of  a  flask  with  a  small 
belly  (fundamental  tone,  f)  and  with  a  long,  narrow  neck  (fundamental  tone,  h"')  [v.  HelmhoUz). 
The  neck  is  wider,  so  that  it  does  not  give  rising  to  a  piping  noise.  The  larynx  is  slightly  lower 
than  for  I,  but  not  so  high  as  for  A. 

Fundamentally  there  are  only  three  primary  vowels — I,  A,  U,  the  others  and  the  so-called  diph- 
thongs standing  between  them  [Briicke). 


CLASSIFICATION   OF   CONSONANTS.  557 

Diphthongs  occur  when,  during  vocalization,  we  pass  from  the  position  of  one 
vowel  into  that  of  another.  Distinct  diphthongs  are  sounded  only  on  passing 
from  one  vowel  with  the  mouth  wide  open  to  one  with  the  mouth  narrow  ;  dur- 
ing the  converse  process  the  vowels  appear  to  our  ear  to  be  separate  {Briicke). 

II.  Timbre  or  Clang  Tint. — Besides  its  pitch,  every  vowel  has  a  special 
timbre,  quality,  or  clang  tint. 

The  vocal  timbre  of  U  (whispering)  has,  in  addition  to  its  fundamental  tone,  b,  a  deep,  piping 
timbre.  The  timbre  depends  upon  the  number  and  pilch  of  \.\ie  parliah  or  overtones  of  the  vowel 
sound  I  J  415). 

Nasal  Timbre. — The  timbre  is  modified  in  a  special  manner  when  the  vowels  are  spoken  with  a 
"  nasal  "  twang,  which  is  largely  the  case  in  the  French  language.  The  nasal  timbre  is  produced 
by  the  soft  palate  not  cutting  off  the  nasal  cavity  completely,  which  happens  every  time  when  a  pure 
vowel  is  sounded,  so  that  the  air  in  the  nasal  cavity  is  thrown  into  sympathetic  vibration.  When  a 
vowel  is  spoken  with  a  nasal  timbre,  air  passes  out  of  the  nose  and  mouth  simultaneously,  while 
with  a  pure  vowel  sound  it  passes  out  only  through  the  mouth. 

WTien  sounding  a  pure  vowel  (non-nasal),  the  shutting  off  of  the  nasal  cavity  from  the  mouth  is 
so  complete,  that  it  requires  an  artificial  pressure  of  30  to  100  mm.  of  mercury  to  overcome  it 
(Hartmaitn). 

The  vowels,  a,  a  (se),  6  (oe),  o,  e,  are  used  with  a  nasal  timbre — a  nasal  i  does  not  occur  in  any 
language.  Certainly  it  is  very  difficult  to  sound  it  thus,  because,  when  sounding  i,  the  mouth  is  so 
narrow  that,  when  the  passage  to  the  nose  is  open,  the  air  passes  almost  completely  through  the  lat- 
ter, while  the  small  amount  passing  through  the  mouth  scarcely  suffices  to  produce  a  sound. 

In  sounding  vowels,  we  must  obser\'e  if  they  are  sounded  through  a  previously  closed  glottis,  as  is 
done  in  the  German  language  in  all  words  beginning  with  a  vowel  (spiritus  lenis).  The  glottis, 
however,  may  be  previously  opened  with  a  preliminary  breath,  followed  by  the  vowel  sound ;  we  ob- 
tain the  aspirate  vowel  (spiritus  asper  of  the  Greeks). 

B.  If  the  vowels  are  sounded  in  an  audible  tone,  /.  e.,  along  with  the  sound 
from  the  larynx,  the  fundamental  tone  of  the  vocal  cavity  strengthens  in  a  char- 
acteristic manner  the  corresponding  partial  tones  present  in  the  laryngeal  sound 

{IV/ieatsione,  v.  Helmholtz). 

318.  CONSONANTS. — The  consonants  are  noises  which  are  produced  at 
certain  parts  of  the  resonance  chambers.  [As  their  name  denotes,  they  can  only 
be  sounded  in  conjunction  with  a  vowel.] 

Classification. — The  most  obvious  classification  is  according  to — (I.)  Their  acoustic  properties, 
so  that  they  are  divided  into — ( I )  liquid  consonants,  i.  e.,  such  as  are  appreciable  without  a  vowel 
(m,  n,  1,  r,  s)  ;  (2)  mutes,  including  all  the  others,  which  cannot  be  distinctly  heard  without  an 
accompanying  vowel.  (II.)  According  to  their  mechanism  of  formation,  as  well  as  the  type  of  the 
organ  of  speech,  by  which  they  are  produced.     They  are  divided  into — 

1.  Explosives  — Their  enunciation  is  accompanied  by  a  kind  of  bursting  open  of  an  obstacle,  or 
an  explosion,  occasioned  by  the  confined  and  compressed  air  which  causes  a  stronger  or  weaker 
noise ;  or,  conversely,  the  current  of  air  is  suddenly  interrupted,  while,  at  the  same  time,  the  nasal 
cavities  are  cut  off  by  the  soft  palate. 

2.  Aspirates,  in  which  one  part  of  the  canal  is  constricted  or  stopped,  so  that  the  air  rushes  out 
through  the  constriction,  causing  a  faint  whistling  noise.  (The  nasal  cavity  is  cut  off.)  In  uttering 
L,  which  is  closely  related  to  the  aspirates,  but  differs  from  them  in  that  the  narrow  passage  for  the 
rush  of  air  is  not  in  the  middle  but  at  both  sides  of  the  middle  of  the  closed  part.  (The  nasal 
cavity  is  shut  off.) 

3.  Vibratives,  which  are  produced  by  air  being  forced  through  a  narrow  portion  of  the  canal, 
so  that  the  margins  of  the  narrow  tube  are  set  in  vibration.      (The  nasal  cavity  is  shut  off.) 

4.  Resonants  (also  called  nasals  or  semi-vowels;.  The  nasal  cavity  is  completely  free,  while 
the  vocal  canal  is  completely  closed  in  the  front  part  of  the  oral  channel.  According  to  the  posi- 
tion of  the  obstruction  in  the  oral  cavity,  the  air  in  a  larger  or  smaller  portion  of  the  mouth  is  thrown 
into  sympathetic  vibration. 

We  may  also  classify  them  according  to  the  position  in  which  they  are  produced 
— the  "articulation  positions"  of  Briicke.     These  are  : — 

A.  Between  both  lips  ;  B,  between  the  tongue  and  the  hard  palate  ;  C,  between 
the  tongue  and  the  soft  palate ;  D,  between  the  true  vocal  cords. 

A.  Consonants  of  the  First  Articulation  Position. — I.  Explosive  Labials. — b,  the  voice  is 
sounded  before  the  slight  explosion  occurs ;  p,  the  voice  is  sounded  after  the  much  stronger  explo- 
sion has  taken  place  [A'empelen).  [The  former  is  spoken  of  as  "  voiced  "  and  the  latter  as 
"  breathed."] 


558  PATHOLOGICAL    VARIATIONS    OF   VOICE    AND    SPEECH. 

2.  Aspirate  Labials. — f,  between  the  upper  incisor  teeth  and  the  lower  lip  (labiodental).  It 
is  absent  in  all  true  Slavic  words  (Piiriine) ;  v,  between  both  lips  (labial) ;  w  is  formed  when  the 
mouth  is  in  the  position  for  f,  but  instead  of  merely  forcing  in  the  air,  the  voice  is  sounded  at  the 
same  time.  Really  there  are  two  different  w — one  corresponding  to  the  labial  f,  as  in  wiirde,  and 
the  labiodental,  e.  g.,  quelle  {Briicke). 

3.  Vibrative  Labials. — The  burring  sound,  emitted  by  grooms,  but  which  is  not  used  in  civilized 
language. 

4.  Resonant  Labials. — m  is  formed  essentially  by  sounding  the  voice  whereby  the  air,  in  the 
mouth  and  nose,  is  thrown  into  sympathetic  vibration  ["  voiced  "]. 

B.  Consonants  of  the  Second  Articulation  Position. — I,  The  explosives,  when  enunciated 
sharply  and  without  the  voice,  are  T  hard  (also  dt  and  th)  ;  when  they  are  feeble  and  produced 
along  with  simultaneous  laryngeal  sounds  (voice),  we  have  D  soft. 

2.  The  aspirates  embrace  S,  including  s  sharp,  written  s  s  or  s  z,  which  is  produced  without 
any  audible  laryngeal  vibration  ;  or  soft,  which  requires  the  voice.  Then,  also,  there  are  modifica- 
tions according  to  the  position  where  the  noises  are  produced.  The  sharp  aspirates  include  Sch, 
and  the  hard  English  Th  ;  to  the  soft  belong  the  French  J  soft,  and  the  English  Th  soft.  L,  which 
occurs  in  many  modifications,  belongs  here,  e.  g.,  the  L  soft  of  the  French.  L  may  be  sounded 
soft  with  the  voice,  or  sharp  without  it. 

3.  The  vibratives,  or  R,  which  is  generally  voiced,  but  it  can  be  formed  without  the  larynx. 
The  resonants  are  N  sounds,  which  also  occurs  in  several  modifications. 

C.  Consonants  of  the  Third  Articulation  Positiott. — I.  The  explosives  are  the  K  sounds,  which 
are  hard  and  breathed  and  not  voiced ;  G  sounds,  which  are  voiced. 

2.  The  aspirates,  when  hard  and  breathed  but  not  voiced,  the  Ch,  and  when  sounded  softly  and 
not  voiced,  J  is  formed. 

3.  The  vibrative  is  the  palatal  R,  which  is  produced  by  vibration  of  the  uvula  (Briicke). 

4.  The  resonant  is  the  palatal  N. 

D.  Consonants  of  the  Fourth  Articulation  Position. — I.  An  explosive  sound  does  not  occur 
when  the  glottis  is  forced  open,  if  a  vowel  is  loudly  sounded  with  the  glottis  previously  closed.  If 
this  occurs  during  whispering,  a  feeble,  short  noise,  due  to  the  sudden  opening  of  the  glottis,  may  be 
heard. 

2.  The  aspirates  of  the  glottis  are  the  H  sounds,  which  are  produced  when  the  glottis  is  moder- 
ately wide. 

3.  A  glottis-vibrative  occurs  in  the  so-called  laryngeal  R  of  lower  Saxon  (Briicke). 

4.  A  laryngeal  resonant  cannot  exist. 

The  combination  of  different  consonants  is  accomplished  by  the  successive  movements  necessary 
for  each  being  rapidly  executed.  Compound  consonants,  however,  or  such  as  are  formed  when  the 
oral  parts  are  adjusted  simultaneously  for  two  different  consonants,  so  that  a  mixed  sound  is  formed 
from  the  two.     Examples:  Sch — tsch,  tz,  ts — Ps  (^'0 — Ks  (X£'). 

319.   PATHOLOGICAL  VARIATIONS  OF  VOICE  AND  SPEECH.— Aphonia.— 

Paralysis  of  the  motor  nerves  (vagus)  of  the  larynx  by  injury,  or  the  pressure  of  tumors,  causes 
aphonia  or  loss  of  voice  (  Galen).  In  aneurism  of  the  aortic  arch,  the  left  recurrent  nerve  may 
be  paralyzed  from  pressure.  The  laryngeal  nerves  may  be  temporarily  paralyzed  by  rheumatism, 
over-exertion,  and  hysteria,  or  by  serous  eftusions  into  the  laryngeal  muscles.  If  the  tensors  are 
paralyzed,  monotonia  is  the  chief  result ;  the  disturbances  of  respiration  in  paralysis  of  the  larynx 
are  important.  As  long  as  the  respiration  is  tranquil,  there  may  be  no  di.^turbance,  but  as  soon  as 
increased  respiration  occurs,  great  dyspncea  sets  in,  owing  to  the  inability  of  the  glottis  to  dilate. 

If  only  one  vocal  cord  is  paralyzed,  the  voice  becomes  impure  and  falsetto-like,  while  we  may 
feel  from  without  that  there  is  less  vibration  on  the  paralyzed  s\At  [Gerhardt).  Sometimes  the 
vocal  cords  are  only  so  far  paralyzed  that  they  do  not  move  during  phonation,  but  do  so  during 
forced  respiration  and  during  coughing  (phonetic  paralysis). 

Diphthongia. — Incomplete  unilateral  paralysis  of  the  recurrent  nerve  is  sometimes  followed  by 
a  double  tone,  owing  to  the  unequal  tension  of  the  two  vocal  cords.     According  to  Tiirck  and 
Schnitzler,   however,   the    double    tone   occurs  when    the   two 
Fig.  334.  vocal   cords  touch   at    some    part    of  their    course    {e.g.^  from 

the  presence  of  a  tumor.  Fig.  334),  so  that  the  glottis  is 
divided  into  two  unequal  portions,  each  of  which  produces 
its  own  sound. 

Hoarseness  is  caused  by  mucus  upon  the  vocal  cords,  by 
roughness,  swelling  or  looseness  of  the  cords.  If,  while  speak- 
ing, the  cords  are  approximated,  and  suddenly  touch  each 
other,  the  **  speech  is  broken,"  owing  to  the  formation  of  nodal 
points  (^  352).  Disease  of  the  pharynx,  nasopharyngeal 
cavity,  and  uvula  may  produce  a  change  in  the  voice  reflexly. 

Paralysis  of  the  soft   palate    (as  well  as  congenital  per. 

foration  or  cleft  palate)  causes  a  nasal  timbre  of  all  vowels ; 

1  the  larynx.       "     the  former  renders  difficult  the  normal  formation  of  consonants 


COMPARATIVE   AND    HISTORICAL.  559 

of  the  third  articulation  position;  resonance  is  imperfect,  while  the  explosives  are  weak,  owing  to 
the  escape  of  the  air  through  the  nose. 

Paralysis  of  the  tongue  weakens  I ;  E  and  A  (JE)  are  less  easily  pronounced,  while  the  for- 
mation of  consonants  of  the  second  and  third  articulation  position  is  affected.  The  term  aph- 
thongia  is  applied  to  a  condition  in  which  every  attempt  to  speak  is  followed  by  spasmodic 
movements  of  the  tongue  (Floury). 

In  paralysis  of  the  lips  (facial  nerve),  and  in  hare-lip,  regard  must  be  had  to  the  formation  of 
consonants  of  the  first  articulation  position.  When  the  nose  is  closed,  the  speech  has  a  character- 
istic sound.  The  normal  formation  of  resonants  is,  of  course,  at  an  end.  After  excision  of  the 
larynx,  a  metal  reed  enclosed  in  a  tube,  and  acting  like  an  artificial  larynx,  is  introduced  between 
the  trachea  and  the  cavity  of  the  mauth  [(^erny). 

Stammering  is  a  disturbance  of  the  formation  of  sounds.  [Stammering  is  due  to  long-con- 
tinued spasmodic  contraction  of  the  diaphragm,  just  as  hiccough  is  (?  120),  and,  therefore,  it  is 
essentially  a  spasmodic  inspiration.  As  speech  depends  upon  the  expiratory  blast,  the  spasm  pre- 
vents expiration.  It  may  be  brought  about  by  mental  excitement  or  emotional  conditions.  Hence, 
the  treatment  of  stammering  is  to  regulate  the  respirations.  In  stuttering,  which  is  defective 
speech  due  to  inability  to  form  the  proper  sounds,  the  breathing  is  normal.] 

320.  COMPARATIVE— HISTORICAL.— Speech  may  be  classified  with  the  "  expres- 
sion of  the  emotions"  (Darioin).  Psychical  excitement  causes  in  man  characteristic  movements, 
in  which  certain  groups  of  muscles  are  always  concerned,  t'.f^., laughing,  weeping,  the  facial  expres- 
sion in  anger,  pain,  shame,  etc.  These  movements  afford  a  means  whereby  one  creature  can  com- 
municate with  another.  Primarily  in  their  origin,  the  movements  of  expression  are  rejiex  motor 
phenomena;  when  they  are  produced  for  purposes  of  explanation,  they  are  voluntary  imitations  of 
this  reflex.  Besides  the  emotional  movements,  impressions  upon  the  sense  organs  produce  char- 
acteristic reflex  movements,  which  may  be  used  for  purposes  of  expression  (Geiger),  e.g.,  stroking 
or  painful  stimulation  of  the  skin,  movements  after  smelling  pleasant  or  unpleasant  or  disagreeable 
odors,  the  action  of  sound  and  light,  and  the  perception  of  all  kinrls  of  objects. 

The  expression  of  the  emotions  occurs  in  its  simplest  form  in  what  is  known  as  expression  by 
means  of  signs  or  pantomime  or  mimicry.  Another  means  is  the  imitation  of  sounds  by  the 
organ  of  speech,  constituting  onamatofocsy,  e.g.,  the  hissing  of  a  stream,  the  roll  of  thunder,  the 
tumult  of  a  storm,  whistling,  etc.  The  expression  of  speech  is,  of  course,  dependent  upon  the 
process  of  ideation  and  perception. 

The  occurrence  of  different  sounds  in  different  languages  is  very  interesting.  Some  languages 
(e.g.,  of  the  Hurons)  have  no  labials;  in  some  South  Sea  Islands,  no  laryngeal  sounds  are  spoken; 
f  is  absent  in  Sanskrit  and  Finnish  ;  the  .short  e,  0,  and  the  soft  sibilants  in  Sanskrit ;  d,  in  Chinese 
and  Mexican,  s,  in  many  Polynesian  languages;   r,  in  Chinese,  etc. 

Voice  in  Animals. — .\nimals,  more  especially  the  higher  forms,  can  express  their  emotions  by 
facial  and  other  gestures.  The  vocal  organs  of  mammals  are  essentially  the  same  as  those  of 
man.  Special  resonance  organs  occur  in  the  orang-outang, mandril,  macacus  and  mycetes  monkeys 
in  the  form  of  large  cheek  pouches,  which  can  be  inflated  with  air,  and  open  between  the  larynx 
and  the  hyoid  bone. 

Birds  have  an  upper  (larynx)  and  a  lower  larynx  (syrinx)  the  latter  being  placed  at  the  bifur- 
cation of  the  trachea,  and  is  the  true  vocal  organ.  Two  folds  of  mucous  membrane  (three  in  singing 
birds)  project  into  each  bronchus,  and  are  rendered  tense  by  muscles,  and  are  thus  adapted  to  serve 
for  the  production  of  voice. 

Among  reptiles  the  tortoises  produce  merely  a  sniffling  sound,  which  in  the  Emys  has  a  peculiar 
piping  character.  The  blind  snakes  are  voiceless,  the  chameleon  and  the  lizards  have  a  very  feeble 
voice ;  the  cayman  and  crocodile  emit  a  feeble  roaring  sound,  which  is  lost  in  some  adults  owing 
to  changes  in  the  larynx.  The  snakes  have  no  special  vocal  organs,  but  by  forcing  out  air  from 
their  capacious  lung  they  make  a  peculiar  hissing  sound,  which  in  some  species  is  loud,  .-^mong 
amphibians  the  frog  has  a  larynx  provided  with  muscles.  The  sound  emitted  without  any  muscu- 
lar action  is  a  deep  intermittent  tone,  while  more  forcible  expiration,  with  contraction  of  the  laryn- 
geal constrictors,  causes  a  clearer  continuous  sound.  The  male,  in  Rana  esculenta,  has  at  each  side 
of  the  angle  of  the  mouth  a  sound  bag,  which  can  be  inflated  with  air  and  acts  as  a  resonance 
chamber.  The  "  croaking  "  of  the  male  frog  is  quite  characteristic.  In  Pipa,  the  larynx  is  pro- 
vided with  two  cartilaginous  rods,  which  are  thrown  into  vibration  by  the  blast  of  air,  and  act  like 
vibrating  rods  or  the  limbs  of  a  tuning  fork.  Some  fishes  emit  sounds,  either  by  rubbing  together 
the  upper  and  lower  pharyngeal  bones,  or  by  the  expulsion  of  air  from  the  swimming  bladder, 
mouth  or  anus. 

Some  insects  cause  sounds  partly  by  forcing  the  expired  air  through  their  stigmata  provided  with 
muscular  reeds,  which  are  thus  thrown  into  vibration  (bees  and  many  diptera).  The  wings,  owing 
to  the  rapid  contraction  of  their  muscles,  may  also  cause  sounds  (flies,  cockroach,  bees).  The 
Sphinx  atropos  (death-heap  moth)  forces  air  from  its  sucking  stomach.  In  others,  sounds  are  pro- 
duced by  rubbing  their  legs  on  the  wing  cases  (.'^cridiuml,  or  the  wing  cases  on  each  other  (Gryl- 
lus,  locust),  or  on  the  thorax  (Cerambyx),  on  the  leg  (C.eotrupesl,  on  the  abdomen  or  the  margin  of 
the  wing   (Nekrophorus).     In  Cicadacia;,  membranes  are   pulled  upon  by  muscles,  and  are  thus 


660  HISTORICAL. 

caused  to  vibrate.  Friction  sounds  are  produced  between  the  cephalothorax  and  the  abdomen  in 
some  spiders  (Theridium),  and  in  some  crabs  (Palinurus).  Some  mollusca  (Pecten)  emit  a  sound 
on  separating  their  shells. 

Historical. — The  Hippocratic  School  was  aware  of  the  fact  that  division  of  the  trachea  abolished 
the  voice,  and  that  the  epiglottis  prevented  the  entrance  of  food  into  the  larynx.  Aristotle  made 
numerous  observations  on  the  voice  of  animals.  The  true  cause  of  the  voice  escaped  him  as  well 
as  Galen.  Galen  observed  complete  loss  of  voice  after  double  pneumothorax,  after  section  of  the 
intercostal  muscles  or  their  nerves,  as  well  as  after  destruction  of  part  of  the  spinal  cord,  even 
although  the  diaphragm  still  contracted.  He  gave  the  cartilages  of  the  larynx  the  names  that  still 
distinguish  them ;  he  knew  some  of  the  laryngeal  muscles,  and  asserted  that  voice  was  produced 
only  when  the  glottis  was  narrowed.  He  compared  the  larynx  to  a  flute.  The  weakening  of  the 
voice,  in  feeble  conditions,  especially  after  loss  of  blood,  was  known  to  the  ancients.  Dodart  (1700) 
was  the  first  to  explain  voice  as  due  to  the  vibration  of  the  vocal  cords  by  the  air  passing  between 
them. 

The  production  of  vocal  sounds  attracted  much  attention  among  the  ancient  Asiatics  and  Ara- 
bians— less  among  the  Greeks.  Pietro  Ponce  (f  1584)  was  the  first  to  advocate  instruction  in  the 
art  of  speaking  incases  of  dumbness.  Bacon  (1638)  studied  the  shape  of  the  mouth  for  the  pro- 
nunciation of  the  various  sounds.  Kratzenstein  (1781)  made  an  artificial  apparatus  for  the  pro- 
duction of  vowel  sounds,  by  placing  resonators  of  various  forms  over  vibrating  reeds.  Von  Kem- 
pelen  (1769  to  1791)  constructed  the  first  speaking  machine.  Rob.  Willis  (1828)  found  that  an  elastic 
vibrating  spring  gives  the  vowels  in  the  series — U,  O,  A,  E,  I — according  to  the  depth  or  height 
of  its  tone;  further,  that  by  lengthening  or  shortening  an  artificial  resonator  on  an  artificial  vocal 
apparatus  the  vowels  may  be  obtained  in  the  same  series.  The  newest  and  most  important  inves- 
tigations on  speech  are  by  Wheatstone,  v.  Helmholtz,  Donders,  Briicke,  etc.,  and  are  mentioned  in 
the  context.  Hensen  succeeded  in  showing  exactly  the  pitch  of  vocal  tone,  thus :  The  tone  is  sung 
against  a  Konig's  capsule  with  a  gas  flame.  Opposite  the  flame  is  placed  a  tuning  fork  vibrating 
horizontally,  and  in  front  of  one  of  its  limbs  is  a  mirror,  in  which  the  image  of  the  flame  is  reflected. 
When  the  vocal  tone  is  of  the  same  number  of  vibrations  as  the  tuning  fork,  the  flame  in  the  mirror 
shows  one  elevation,  if  double,  i.  e.,  the  octave,  two,  and  with  the  double  octave,  four  elevations. 


General  Physiology  of  the 
Nerves  and  electro-physiology. 


321.  STRUCTURE  OF  THE  NERVE  ELEMENTS.— The  ner- 
vous elements  present  two  distinct  forms:  — 

I.    Nerve     f  Non-medullated.  2.    Nerve  |  Various  forms  and 

Fibres.  \  Medullated.  Cells.   \         functions. 

An  aggregation  of  nerve  cells  constitutes  a  nerve  ganglion.  The  fibres  rep- 
resent a  cotiihicting  apparatus,  and  serve  to  place  the  central  nervous  organs  in 
connection  with  peripheral  end  organs.  The  nei-ce  cells,  however,  besides  trans- 
mitting impulses,  act  as  physiological  centres  for  automatic  or  reflex  movements, 
and  also  for  the  sensory,  perceptive,  trophic,  and  secretory  functions. 

I.   Nerve  Fibres  occur  in  several  forms  : — 

1.  Primitive  Fibrils. — The  simplest  form  of  ner\e  fibril,  which  is  visible  with  a  magnifying 
power  of  500  to  Soo  diameters  linear,  consists  of  primitive  nerve  fibrils.  They  are  very  delicate 
fibres  (Fig.  335,  i),  often  with  small  varicose  swellings  here  and  there  in  their  course,  which, 
however,  are  due  to  changes /(?.?/- w^jr/tvw.  They  are  stained  of  a  brown  or  purplish  color  by  the 
gold  chloride  method,  and  they  occur  when  a  nerve  fibre  is  near  its  termination,  being  formed  by 
the  splitting  up  of  the  axis  cylinder  of  the  nerve  fibre,  e.g.,  in  the  terminations  of  the  corneal 
nerves,  the  optic  nerve  layer  in  the  retina,  the  terminations  of  the  olfactory  fibres,  and  in  a  plexi- 
form  arrangement  in  non-striped  muscle  ip.  500).  .Similar  fine  fibrils  occur  in  the  gray  matter  of 
the  brain  and  spinal  cord,  and  the  finely-divided  processes  of  nerve  cells. 

2.  Naked  or  simple  axial  cylinders  (Fig.  335,  2),  which  represent  bundles  of  primitive  fibrils 
held  together  by  a  slightly  granular  cement,  so  that  they  exhibit  very  delicate  longitudinal  striation 
with  fine  granules  scattered  in  their  course.  The  best  example  is  the  axial  cylinder  process  of 
nerve  cells  (Fig.  335,  I,  ;).  [The  thickness  of  the  axis  cylinder  depends  upon  the  number  of 
fibrils  entering  into  its  composition.] 

3.  Axis  cylinders  surrounded  writh  Schwann's  sheath  or  Remak's  fibres  (3.8  to  6.8  ;>. 
broad),  the  latter  name  being  given  to  them  from  their  discoverer  (Fig.  335,  3).  [These  fibres  are 
also  called /<;/(■  or  non-meduUated,  and  from  their  abundance  in  the  sympathetic  nervous  system, 
sympathetic]  They  consist  of  a  sheaih,  corresponding  to  Schwann's  sheath  [neurilemma,  or 
primitive  sheath,  which  incloses  an  axial  cylinder,  while  lying  here  and  there  under  the  sheath,  and 
between  it  and  the  axial  cylinder,  are  nerve  corpuscles.  These  fibres  are  always  fibrillated  longitudi- 
nally]. The  sheath  is  delicate,  structureless,  and  elastic.  Dilute  acids  clear  up  the  fibres  without 
causing  them  to  swell  up,  while  gold  chloride  makes  them  brownish-red.  They  are  widely  distributed 
in  the  sympathetic  nerves  \e.g.,  splenic]  and  in  the  branches  of  the  olfactory  nerves.  All  nerves 
in  the  embryo,  as  well  as  the  nerves  of  many  invertebrata,  are  of  this  kind.  [According  to  Ran- 
vier,  these  fibres  do  not  possess  a  sheath,  but  the  nuclei  are  merely  applied  to  the  surface,  or  slightly 
embedded  in  the  superficial  parts  of  the  fibre,  so  that  they  belong  to  the  fibre  itself  These  fibres 
also  branch  and  form  an  anastomosing  network  (Fig.  336).  This  the  medullated  fibres  never  do. 
These  fibres,  when  acted  on  by  silver  nitrate,  never  show  any  crosses.  The  branched  form  occurs 
in  the  ordinary  nerves  of  distribution,  and  they  are  numerous  in  the  vagus,  but  the  olfactory  nerves 
have  a  distinct  sheath  which  is  nucleated.] 

4.  Axis  cylinders,  or  nerve  fibrils,  covered  only  by  a  medullary  sheath,  or  white  substance 
of  Schwann,  are  met  with  in  the  white  and  gray  matter  of  the  central  ner\'ous  system,  in  the  optic 
and  auditory  nerves.  These  medtillatt\i  ner-je  fibres,  witliout  any  neurilemma,  often  show  after 
death  varicose  swellings  in  their  course  [due  to  the  accumulation  of  fluid  between  the  medulla  or 
myelin  and  the  axis  cylinder].  Hence,  they  are  called  varicose  fibres.  [The  varicose  appearance 
is  easily  produced  by  squeezing  a  small  piece  of  the  white  matter  of  the  spinal  cord  between  a  slide 
and  a  cover  glass.  Nitrate  of  silver  does  not  reveal  any  crosses,  and  there  are  no  nodes  of  Ranvier, 
while  osmic  acid  reveals  no  incisures.     When  acted  upon  by  coagulating  reagents,  e.^.,  chromic 

36  561 


562 


STRUCTURE    OF   NERVE    FIBRES. 


acid,  the  metiullary  sheath  appears  laminated,  so  that  on  transverse  section,  when  the  axis  cylinder 
is  stained,  it  is  surrounded  by  concentric  circles  (Fig.  337)-] 

5.  MeduUated  Nerve  Fibres,  with  Schwann's  Sheath  (Fig.  335,  5,  6). — These  are  the 
most  complex  nerve  fibres,  and  are  10  to  22.6  'i  [jjbjj  to  .j^'^^  inch]  broad.  They  are  most 
numerous  in,  and,  in  fact,  they  make  up  the  great  mass  of,  the  cerebrospinal  nerves,  although  they 


Fig.  335. 


Primitive  fibrilte  ;  2,  axis 
Schwann's  she  ith  ;  c.  ne 
neurium  ;  a,  axis  cylinder; 
silver  nitrate.     I.  multipolai 
)  the  right  of  it  a  bipol; 


cell  with, 


■linder:  3,  Remak's  fibres:  4,  medullated  varicose  fibre:  5, 
lemijia:  t,  t,  Ranvier's  nodes  :  b,  white  substance  of  Schwa 
.r,  myelin  drops  ;  7,  transverse  section  of  nerve  fibres  ;  8,  nerve  fibre 
lerve  cell  from  the  spinal  cord  ;  2,  axial  cylinder  process  ;  y,  protopla: 
ell.     II,  peripheral  ganglionic  cell,  with  a  connective-tissue  capsule 


piral,  and,  «,  straight  process  ;  m,  sheath. 


are  also  present  in  the  sympathetic  nerves.  [When  examined  in  the  fresh  and  living  condition  in 
situ,  they  appear  refractive  and  homogeneous  [Ranvier,  Stirling) ;  but  if  acted  upon  by  reagents, 
they  are  not  only  refractive,  but  exhibit  a  double  contour,  the  margins  being  dark  and  well  defined.] 
Each  fibre  consists  of — [l.  Schwann's  sheath,  neurilemma,  or  primitive  sheath;  2.  White  substance  of 
Schwann,  medullary  sheath,  or  myelin;  3.  Axis  cylinder  composed  of  fibrils;  4.  Nerve  corpuscles.]. 


STRUCTURE    OF    NERVE    FIBRES. 


563 


A.  The  axis  cylinder,  which  occupies  ^  to  ^  of  the  breadth  of  the  fibre,  is  the  essential  part  of  the 
nerve,  and  lies  in  the  centre  of  the  fibre  (Fig.  335,6,  </)  lil<e  the  wick  in  the  centre  of  a  candle.  Its  usual 
shape  is  cylindrical,  but  sometimes  it  is  flattened  or  placed  eccentrically  [most  probably  due  to  the 
hardening  process  employed].  It  is  composed  o{  fibrils  [united  by  cement;  they  become  more 
obvious  near  the  terminations  of  the  nerve,  or  after  the  action  of  reagents,  which  sometimes  cause 
the  fibrils  to  appear  beaded.  It  is  quite  transparent,  and  stains  deeply  with  carmine  or  logwood], 
while  during  life  its  consistence  is  semi-fluid.  According  lo  Kupffer,  a  fluid — nerve  serum — lies 
between  the  fibrils  [while,  according  to  other  observers,  the  whole  cylinder  is  enclosed  in  an  elastic 
sheath  peculiar  to  itself  and  composed  of  neuro-keratin]. 


Fig.  336. 


Fig.  337- 


■wn-  ■  , 

■:^'§~ 

•  }^ 

W:-' 

W^ 

-m.,  ■ 

,  ';>f 

.,.:/-'-\ 

'.  section  of  the  nerve  fibre? 
of  the  spinal  cord,  the  axis  cylinder; 
like  dots  surrounded  by  a  cleai 
space  (myelin). 

Fig.  338. 


Remak's  fibre  from  vagus  of 
dog.  6,  fibrils  ;  «,  nucleus  ; 
/,  protoplasm  surrounding 


^IG.  339. 


(single 
res)  stained 
Endothelial 
sheath  stained,  and  some  nodes  ot 
Kanvier  indicated  by  < 


fibres  blackened  by 


Fromann's  Lines. — Chloroform  and  collodion  render  it  visible,  while  it  is  most  easily  isolated 
as  a  solid  rod,  by  the  action  of  nitric  acid  with  excess  of  potassium  chlorate.  When  acted  on  by 
silver  nitrate,  Fromann  observed  transverse  markings  on  it,  but  their  significance  is  unknown  (Fig. 
335.  8). 

B.  White  substance  of  Schwann,  medullary  sheath  or  myelin,  surrounds  the  axis  cylinder, 
like  an  insulating  medium  around  an  electric  wire.  In  the  perfectly  fresh  condition  it  is  quite  homo- 
geneous, highly  glistening,  bright  and  refractive ;  its  consistence  is  fluid,  so  that  it  oozes  out  of  the 


564  STRUCTURE    OF   NERVE    FIBRES. 

cut  ends  of  the  fibres  in  spherical  drops  (Fig.  335,  Jr),  [myelin  drops,  which  are  always  marked 
by  concentric  lines,  are  highly  refractive,  and  best  seen  when  a  fresh  nerve  is  teased  in  salt  solution.] 
After  death,  or  after  the  action  of  reagents,  it  shrinks  slightly  from  tlie  sheatii,  so  that  the  fibres 
have  a  double  contour,  while  the  substance  itself  breaks  up  into  smaller  or  larger  droplets,  due  not 
to  coagulation  [P^rfik],  but,  according  to  Toldt,  to  a  process  like  emulsification,  the  drops  pressing 
against  each  other.  Thus  the  fibre  it  broken  up  into  masses,  so  that  it  has  a  characteristic  appear- 
ance (Fig.  335,  6).  It  contains  a  large  amount  of  cereln-in,  which  swells  up  to  form  myelin-like 
forms  in  warm  water.  It  also  contains  fatty  matter,  so  that  these  fibres  are  blackened  by  osmic 
acid  [while  boiling  ether  extracts  cholesterin  from  them].  Chloroform,  ether,  and  benzin,  l>y  dissolv- 
ing the  fatty  and  some  other  constituents  of  the  fibres,  make  them  very  transparent.  [Some  ob- 
servers describe  a  fluid  lying  between  the  medulla  and  the  axis  cylinder.] 

C.  The  Sheath  of  Schwann,  or  the  neurilemma,  lies  immediately  outside  of  and  invests  the 
white  sheath  (Fig.  335,  6,  r),  and  is  a  delicate,  structureless  membrane,  comparable  to  the  sarco- 
lemma  of  a  muscular  fibre. 

D.  Nerve  Corpuscles. — At  fairly  wide  intervals  under  the  neurilemma,  and  lying  in  depressions 
between  it  and  the  medullary  sheath,  are  the  nucleated  nerve  covpuscleSy  which  are  readily  stained 
by  pigments.  [They  may  be  compared  to  the  muscle  corpuscles,  the  nuclei  being  surrounded  by  a 
small  amount  of  protoplasm  which  sometimes  contains  pigment.  They  are  not  so  numerous  as  in 
muscle.] 

[Adamkiewicz  describes  nerve  corpuscles,  or  "demilunes'*  under  the  neurilemma,  quite  dis- 
tinct from  the  ordinary  nerve  corpuscles.  They  are  stained  yellow  by  safranin,  while  the  ordinary 
nerve  corpuscles  are  stained  by  methylanilin]. 

Ranvier's  Nodes  or  Constrictions. — The  neurilemma  forms  in  broad  fibres  at  longer  and  in 
narrower  ones  at  shorter  intervals,  the  nodes  at  constrictions  of  Ranvier  (Fig.  335,  (i,t,t\  Fig.  338, 
f,  s).  They  are  constrictions  which  occur  at  regular  intervals  along  a  nerve  fibre  ;  at  them  the  white 
substance  of  Schwann  is  interrupted,  so  that  the  sheath  of  Schwann  lies  upon  the  axis  cylinder  [or 
its  elastic  sheath]  at  the  nodes.  The  part  of  the  nerve  lying  between  any  two  nodes  [is  called  an 
interannidar  or  internodal  segment"],  and  each  such  segment  contains  one  or  more  nuclei,  so  that 
some  observers  look  upon  the  whole  segment  as  equivalent  to  one  cell. 

The  function  of  the  Nodes  seems  to  be  to  permit  the  diffusion  of  plasma  through  the  outer 
sheath  into  the  axis  cylinder,  while  the  decomposition  products  are  similarly  given  off.  [A  coloring 
matter  like  picrocarmine  diffuses  into  the  fibre  only  at  the  nodes,  and  stains  the  axis  cylinder  red, 
although  it  does  not  diffuse  through  the  white  substance  of  .Schwann.] 

[Incisures  (of  Schmidt  and  Lantermann). — Each  interannular  segment  in  a  stretched  nerve  shows 
a  number  of  oblique  lines  running  across  the  white  substance,  which  are  called  incisures.  They 
indicate  that  the  segment  is  built  up  of  a  series  of  conical  sections,  each  of  which  is  bevelled  at  its 
ends,  and  the  bevels  are  arranged  in  an  imbricate  manner,  the  one  over  the  other  (Fig.  33S),  while 
the  slight  interval  between  them  appears  as  an  incisure.  Each  such  section  of  the  white  matter  is 
called  a  cylinder  cone  (ICiihnt).\ 

Neuro- Keratin  Sheath. — ."According  to  Ewald  and  Kiihne,  the  axis  cylinder,  as  well  as  the 
white  substance  of  Schwann,  is  covered  with  an  excessively  delicate  sheath,  consisting  of  neuro- 
keratin, and  the  two  sheaths  are  connected  by  numerous  transverse  and  oblique  fibrils,  which  per- 
meate the  white  substance.     [The  myelin  seems  to  lie  in  the  interstices  of  this  mesh-work.] 

[Rod-like  Structures  in  Myelin. — If  a  nerve  be  hardened  in  ammonium  chroniate  (ox picric 
acid),  M'Carthy  has  shown  that  the  myelin  exhibits  rod-like  structures,  radiating  from  the  axis  cyl- 
inder outward,  and  which  are  stained  with  logwood  and  carmine.  The  rods  are  probably  not  dis- 
tinct from  each  other,  but  are,  perhaps,  part  of  the  neuro-keratin  network  already  described.] 

[Action  of  Nitrate  of  Silver. — When  a  small  nerve,  e.g.,  the  intercostal  nerve  of  a  mouse,  is 
acted  on  by  silver  nitrate,  it  is  seen  to  be  covered  by  an  endothelial  sheath  composed  of  flattened 
endothelial  cells  (Fig.  339'),  while  the  nerve  fibres  themselves  exhibit  crosses  along  their  course. 
These  crosses  are  due  to  the  penetration  of  the  silver  solution  at  the  nodes,  where  it  stains  the  cement 
substance  and  also  part  of  the  axis  cylinder,  so  that  the  latter  sometimes  exhibits  transverse  mark- 
ings called  Fromann's  lines  (Fig.  335,  8).] 

[New  Methods. — Much  progress  has  recently  been  made  in  tracing  the  course  of  meduUated 
nerve  fibres  by  the  action  of  new  staining  reagents  ;  thus,  acid  fuchsin  stains  the  myelin  deeply,  leav- 
ing the  other  parts  unstained,  at  least  it  can  be  so  manipulated  as  to  yield  this  result.  Weigert  finds 
that  the  myelin  is  al.so  stained  by  logwood  after  a  tissue  has  been  hardened  in  cupric  sulphate  (or 
acetate)  and  a  chromium  salt.  By  these  methods  medullated  fibres  have  been  traced  where  their 
existence  was  previously  not  surmised.] 

In  the  spinal  nerves  those  fibres  are  thickest  which  have  the  longest  course  before  they  reach 
their  end  organ  (Schwalbe),  while  those  ganglion  cells  are  largest  which  send  out  the  longest  nerve 
fibres  (Pierret).  [Gaskell  finds  that  the  longest  nerves  are  not,  necessarily,  the  thickest,  for  the 
visceral  nerves  in  the  vagus  are  small  nerves,  and  yet  run  a  very  long  course.] 

Division  of  Nerves. — Nerve  fibres  run  in  the  nerve  trunks  without  dividing;  but  when  they 
approach  their  termination  they  often  divide  dichotomously  [at  a  node],  giving  rise  to  two  similar 
fibres,  but  there  m.ay  be  several  branches  at  a  node  (Fig.  341,  /■). 


STRUCTURE    OF   THE    NERVE   SHEATHS. 


565 


[The  divisions  are  numerous  in  motor  nerves  to  striped  muscles.]  In  the  electrical  nerve?  of  the 
malapterurus  and  gymnotus,  there  is  a  great  accumulation  of  Schwann's  sheaths  round  a  nerve,  so 
that  a  nerve  fibre  is  as  thick  as  a  sewing  needle.  Such  a  fibre,  when  it  divides,  breaks  up  inio  a 
bundle  of  smaller  fibres. 

Nerve  Sheaths. — [An  anatomical  nerve  trunk  consists  of  bundles  of  nerve  fibres.  The  bundles 
are  held  together  by  a  common  connective-tissue  sheath  (Fig.  340,  c/),  the  epineurium  (A.xe! Key 
and  Jietzius),  which  con\.3.\ns  the  larger  blood  vessels,  lymphatics,  and  sometimes  fat  and  plasma 
cells  ]  Each  bundle  is  surrounded  with  its  own  sheath  or  perineurium  (/<•)  [which  consists  of 
lamellated  connective  tissue  disposed  circularly,  and  between  the  lamella?  are  lymph  spaces  hned 
by  flattened  endothelial  plates].  These  lymph  spaces  may  be  injected  from  and  communicate  with 
the  lymphatics. 

[The  nerve  fibres  within  any  bundle  are  held  together  by  delicate  connective  tissue,  which  pene- 
trates between  the  adjoining  fibres,  constituting  the  endoneurium  {ed).  It  consists  of  delicate 
fibres  with  branched  connective-tissue  corpuscles  (Fig.  335,  6,  d),  and  in  it  lie  the  capillaries,  which 
are  not  very  numerous,  and  are  arranged  to  form  elongated  open  meshes.] 

[Henle's  Sheath. — When  a  nerve  is  traced  to  its  distribution,  it  branches  and  becomes  smaller, 
until  it  may  consist  only  of  a  few  bundles  or  even  a  single  bundle  of  nerve  fibres.  As  the  bundle 
branches,  it  has  to  give  oft'  part  of  its  lamellated  sheath  or  perineurium  to  each  branch,  sn  that,  as 
we  pass  to  the  periphery,  the  smaller  buntlles  are  surrounded  by  few  lamellae.     In  a  bundle  con- 

FiG.  340. 


:  (median),     c/,  epineurium;  pe,  perineurium  ;  ed,  endoneuriun 


taining  only  a  few  fibres,  this  sheath  may  be  much  reduced,  or  consist  only  of  thin,  flattened  connective- 
tissue  corpuscles  with  a  few  fibres.  A  sheath  surrounding  a  few  nerve  fibres  is  called  Henle's  Shealh 
[Ranvier).'] 

[Nervi  Nervorum. — Marshall  and  v.  Hor.iley  have  shown  that  the  nerve  sheaths  are  provided 
with  special  nerve  fibres,  in  virtue  of  which  they  are  endowed  with  sensibility.] 

Development. — At  first  nerve  fibres  consist  only  of  fibrils,  which  become  covered  with  connective 
substance,  and  ultimately  the  white  substance  of  Schwann  is  developed  in  some  of  them.  The 
growth  in  length  of  the  fibres  takes  place  by  elongation  of  the  individual  "interannular"  segments, 
and  also  by  the  new  formation  of  these  (  Vignnl). 

II.  Ganglionic  or  Nerve  Cells. — i.  Multipolar  nerve  cells  (Fig.  335,  I)  occur  partly  as 
/i;;jv  cells  (100  ,'/,  and  are,  therefore,  visible  to  the  unaided  eye).  In  the  anterior  horn  of  the 
spinal  cord,  and  in  a  diflerent  form  in  the  cerebellum,  and  partly  in  a  smaller  form  (20  to  10  ,'ji)  in 
the  posterior  horns  of  the  spinal  cord,  many  parts  of  the  cerebrum  and  cerebellum,  and  in  the 
retina.  They  may  be  spherical,  ovoid,  pyramidal  [cerebrum],  pear-  or  flask-shaped  [cerebellum], 
and  are  provided  with  numerous  branched  processes  which  give  the  cells  a  characteristic  appear- 
ance. They  are  devoid  of  a  cell  envelope,  are  of  soft  consistence,  and  exhibit  a  fibrillated  structure, 
which  may  extend  even  into  the  processes.  Fine  granules  lie  scattered  throughout  the  cell  sub- 
stance between  the  fibrils.  Not  unfrequently  yellow  or  brown  granules  of  pigment  are  also  found, 
either  collected  at   certain   parts  in  the  cell   or   scattered   throughout    it.      The    relatively   large 


566 


CHEMISTRY   OF   THE    NERVOUS   SUBSTANCE. 


Fig.  341.  nuc/eus  consists  of  a  clear  envelope  enclosing  a  resistant  substance. 

It  does  not  appear  to  have  a  membrane  in  youth  (Sc/iwa/l/e).  Within 
the  nucleus  lies  the  nucleolus,  which  in  the  recent  condition  is  angu- 
lar, provided  with  processes  and  capable  of  motion,  but  after  death 
is  highly  refractive  and  spherical.  One  of  the  processes  is  always 
until ancheil,  constituting  the  axial  cylinder  process  (1,  z),  which 
remains  unbranched;  but  it  soon  becomes  covered  with  the  white 
substance  of  Schwann  and  the  other  sheaths  of  a  medullated  nerve, 
so  that  it  becomes  the  axial  cylinder  of  a  nerve  fibre.  [Thus  a  nerve 
fibre  is  merely  an  excessively  long,  unbranched  process  of  a  nerve 
cell  pushed  outward  toward  the  periphery.]  It  is  not  definitely  ascer- 
tained that  the  cerebral  cells  have  such  processes.  All  the  other 
processes  divide  very  frequently  until  they  form  a  branched,  root-like, 
complex  arrangement  of  the  finest  primitive  fibrils.  These  are  called 
protoplasmic  processes  (I,j).  By  means  of  these  processes  ad- 
joining cells  are  brought  into  communication  with  each  other,  so  that 
impulses  can  be  conducted  from  one  cell  to  another.  Further,  many 
of  these  fibrils  approximate  to  each  other  and  join  together  to  form 
axis  cylinders  of  other  nerve  fibres. 

2.  Bipolar  cells  are  best  developed  in  fishes,  e.  g.,  in  the  spinal 
ganglia  of  the  skate,  and  in  the  Gasserian  ganglion  of  the  pike. 
They  appear  to  be  nucleated,  fusiform  enlargements  of  the  axis 
cylinder  (Fig.  335,  on  the  right  of  I).  The  white  substance  often 
stops  short  on  each  side  of  the  enlargement,  but  sometimes  the  white 
substance  and  the  sheath  of  .Schwann  pass  over  the  enlargement. 

3.  Nerve  cells  with  connective-tissue  capsules  occur  in  the 
peripheral  ganglia  of  man  (Fig.  335,  II),  e.  g.,  in  the  spinal  gan- 
glia. The  solt  body  of  the  cell,  which  is  provided  with  several 
processes,  is  coveied  by  a  tliick,  tough  capsule  composed  of  sev- 
eral layers  of  connective-tissue  corpuscles;  while  the  inner  surface 
of  the  composite  capsule  is  lined  by  a  layer  of  delicate  endothelial 
cells  (Fig.  341).  The  body  of  the  cells  in  the  spinal  ganglia  is 
traversed  by  a  network  of  fine  fibrils  (Flenuning).  The  capsule  is 
continuous  with  the  sheath  of  the  nerve  fibre. 

Rawitz  and  G.  Retzius  find  that  the  cells  of  the  spinal  gangha  are 
unipolar,  the  outgoing  fibre  taking  a  half-turn  within  the  capsule 
before  it  leaves  the  cell  (Fig.  341).  Retzius  [and  Ranvier]  observed 
the  process  to  divide  like  a  T.  Perhaps  this  division  corresponds  to 
the  two  processes  of  a  bipolar  cell.  The  jugular  ganglion  and  plexus 
gangliiformis  vagi  in  man  contain  only  unipolar  cells,  so  that,  in  this  re- 
spect, they  may  be  compared  to  spinal  ganglia.  The  same  is  the  case  in 
the  Gasserian  ganglion;  while  the  ciliary,  sphenopalatine,  otic  and  sub- 
maxillary ganglia  structurally  resemble  the  ganglia  of  the  sympathetic. 
4.  Ganglionic  cells  with  spiral  fibres  (Baile,  J.  AniolJ)  occur  chiefly  in  the  abdominal 
.sympathetic  of  the  frog.  The  body  of  the  cell  is  u>u.illy  pyriform  in  shape,  and  from  it  proceeds 
a  straight  unbranched  process  (Fig.  335,  III,  «),  which  ultimately  becomes  the  axis  cylinder  of  a 
nerve.  A  spiral  fibre  springs  from  the  cell  (?  a  network),  emerges  from  it,  and  curves  in  a  spiral 
direction  round  the  former  {0).  The  whole  cell  is  surrounded  by  a  nucleated  capsule  («/).  We 
know  nothing  of  the  significance  of  the  different  fibres. 


322.  CHEMISTRY  OF  THE  NERVOUS  SUBSTANCE.— Me- 
chanical Properties  of  Nerves. —  i.  Proteids. — .-Mbiimin  occurs  chiefly  in 
the  axis  cylinder  and  in  the  substance  of  the  ganglionic  cells.  Some  of  this  pro- 
teid  substance  presents  characters  not  unlike  those  of  myosin  (§  293).  Dilute 
solution  of  comtnon  salt  extracts  a  proteid  from  nervous  matter,  which  is  precipi- 
tated by  the  addition  of  much  water  and  also  by  a  concentrated  solution  of 
common  salt  ( Petrozosky).  Potash  a/bu»iin  &nA  a  glohulin-like  substance  &xt  also 
present.  Albuminoids. — Nuclein  occurs  especially  in  the  gray  matter  (§  250, 
2),  while  neuro-keratin,  a  body  containing  much  sulphur  and  closely  related  to 
keratin,  occurs  in  the  corneous  sheath  of  nerve  fibres  (p.  564).  If  gray  nervous 
matter  be  subjected  to  artificial  digestion  with  trypsin,  both  of  these  substances 
remain  undigested  {Kiihnc  and  EivaM).  Pure  neuro-keratin  is  obtained  by  treat- 
ing the  residue  with  caustic  potash.  The  sheath  of  Schzcanii  does  not  yield 
gelatin,  but  a  substance  closely  related  to  elastin  (§  250,  6),  from  which  it  differs, 


REACTION    AND    CHEMICAL   COMPOSITION    OF   NERVES. 


567 


however,  in   being  more  soluble   in   alkalies.     The  connective   tissue  of  nerves 
yields  gelatin. 

2.  Fats  and  otlwr  allied  substances  soluble  in  ether,  more  especially  in  the  white 
matter :  (a)  Cerebrin,  free  from  phosphorus  (§  250,  3). 

It  is  a  white  powder  composed  of  spherical  granules  soluble  in  hot  alcohol  and  ether,  but 
insoluble  in  cold  water.  It  is  decomposed  at  So°  C,  and  its  solutions  are  neutral.  When  boiled 
for  a  long  time  with  acids  it  .splits  up  into  a  left  rotatory  body  like  sugar,  and  another  unknown  pro- 
duct. Preparation. —  Rub  up  the  brain  into  a  thin  fluid  with  baryta  water.  Extract  the  separated 
cuagulum  with  boiling  alcohol.  The  extract  is  frequently  treated  with  cold  ether  to  remove  the 
cholcsterin  (  W.  Miiller).  I'arkus  separated  from  cerebrin  its  homologue,  homocerebrin,  which  is 
slightly  more  soluble  in  alcohol,  and  the  clyster-like  body,  encephalin,  which  is  soluble  in  hot 
water. 

{b)  Lecithin  (§  251)  and  its  decomposition  products — glycero-phosphoric  acid 
and  oleo-phosphoric  acid. 

Neurin  (or  Cholin  =  C.IIjsNO,)  is  a  strongly  alkaline,  colorless  fluid,  forming  crystalline 
salts  with  acids.  It  is  soluble  in  water  and  alcohol,  and  has  been  formed  synthetically  from  glycol 
and  trimethylamin.     Lecithin  is  a  salt  of  the  base  neurin. 

(^)  Protagon,  which  contains  N  and  P,  is  similar  to  cerebrin,  and  is,  accord- 
ing to  its  discoverer  i^Liebreich),  the  chief  constituent  of  the  brain. 

According  to  Hoppe-Seyler  [and  Diaconow],  it  is  a  mixture  of  lecithin  and  cerebrin.  [The 
investigations  of  Gamgee  and  Blankenhorn  have  shown,  however,  that  protagon  is  a  definite 
chemical  body.  They  lind  that,  instead  of  being  unstable,  it  is  a  very  stable  body.]  It  is  a  glyco- 
side, and  crystalline,  and  can  be  extracted  from  the  brain  by  warm  alcohol,  and  when  boiled  with 
baryta  yields  the  decomposition  products  of  lecithin. 

3.  The  following  substances  are  extracted  by  water :  Xanthin  and  hypoxanthin  {Scherer)  kreatin 
(Lerch),  inosit  ( /F.  Midler^,  ordinary  lactic  acid  (Gscheidkn),  and  volatile  fatty  acids;  leucin  (in 
disease),  urea  (in  urremia).  All  these  substances  are  for  the  most  part  products  of  the  regressive 
metabolism  of  the  tissues. 

Reaction. — Nervous  substance,  when  passive,  is  neutral  or  feebly  alkaline  in 
reaction,  while  active  (?  and  dead)  it  is  acid  {Punkc).  The  gray  matter  of  the 
brain,  when  quite  fresh,  is  alkaline  {Liebreicli),  but  death  rapidly  causes  it  to 
becoine  acid  (^Gscheidlen). 

The  reaction  of  nerve  fibres  varies  during  life.  After  introducing  methyl-blue  into  the  body  of 
a  living  animal,  Ehrlich  found  that  the  axis  cylinder  became  blue,  i.e.,  in  those  nerves  which  have 
an  alkaline  reaction  (cortex  cerebri,  cardiac,  sensory,  motor  (non-striped),  gustatory  and  olfactory 
fibres),  while  the  termination  of  motor  (voluntary)  nerves  remain  uncolored.  The  latter  he  regards 
as  acid. 

The  nerves  after  death  have  a  more  solid  consistence,  so  that  in  all  probability 
some  coagulation  or  change,  comparable  to  the  stiffening  of  muscle  (§  295), 
occurs  in  them  after  death,  while  at  the  same  time  a  free  acid  is  liberated.  It  a 
fresh  brain  be  rapidly  "  broiled"  at  100^  C,  it,  like  a  muscle  similarly  treated, 
remains  alkaline  (^§  295.) 


Chemical  Composition. 

Gray  Matter. 

White  Matter. 

The  sohds  consist  of — 

81.6  per  cent. 
1S.4      " 

6S.4  per  cent. 
31.6      •• 

Albumins  and  glutin 

55-4      " 
17.2      " 
1S.7      " 

24,7      " 

99       " 
52.1       " 

Lecithin 

Cholesteria  and  fats 

Cerebrin 

0.5       " 
6.7      " 

9.5       " 

Substances  insoluble  in  ether 

Salts 

1-5      " 

0.5       " 

1000 

100  0 

568  MECHANICAL   STIMULI. 

In  loo  parts  of  Ash,  Breed  found  potash  32,  soda  II,  magnesia  2,  lime  0.7,  XaCl  5,  iron  phos- 
phate 1.2,  fixed  phosphoric  acid  39,  sulphuric  acid  o.i,  silicic  acid  0.4. 

[Ptomaines  (p.  275)  are  obtained  from  putrefied  lirain.  They  have  an  eflfect  on  the  motor  nerves 
like  curara,  but  in  a  much  less  degree,  while  the  phenomena  last  for  a  much  shorter  time  [Guaresc/ii 
and  Mosio).^ 

Mechanical  Properties. — One  of  the  most  remarkable  mechanical  proper- 
ties of  nerve  fibres  is  the  absence  of  elastic  tension  according  to  the  varying  posi- 
tions of  the  body.  Divided  nerves  do  not  retract  ;  such  nerves  exhibit  delicate, 
microscopic,  transverse  folds  (Fontana's  transverse  markings)  [like  watered  silk]. 

The  cohesion  of  a  nerve  is  very  considerable.  When  a  limb  is  forcibly  torn 
from  the  body,  as  sometiines  happens  from  its  becoming  entangled  in  machinery, 
the  nerve  not  unfrequently  remains  unsevered,  while  the  other  soft  parts  are  rup- 
tured. [TiUaux  found  that  a  weight  of  no  to  120  lbs.  was  required  to  rupture 
the  sciatic  nerve  at  the  popliteal  space,  while  to  break  the  median  or  ulnar  nerve 
of  a  fresh  body,  a  force  equal  to  40  to  50  lbs.  was  required.  The  toughness  and 
elasticity  of  nerves  are  often  well  shown  in  cases  of  injury  or  gun-shot  wounds. 
The  median  or  ulnar  nerve  will  gain  15  to  20  centimetres  (6  to  8  inches)  before 
breaking.  Weir  Mitchell  has  shown  that  a  healthy  nerve  will  bear  a  very  con- 
siderable amount  of  pressure  and  handling,  and,  in  fact,  the  method  of  nerve 
stretching  depends  upon  this  property  of  a  nerve  trunk.] 

323.  METABOLISM  OF  NERVES.— Influence  of  Blood  Supply. 

—  We  know  very  little  regarding  the  metabolic  processes  that  occur  in  nerve  tissue. 
Some  extractives  are  obtained  from  nerve  tissue,  and  they  may,  perhaps,  be  re- 
garded as  decomposition  products  (p.  567).  It  has  not  been  proved  satisfactorily 
that  during  the  activity  of  nerves  there  is  an  exchange  of  O  and  CO.j.  That  there 
is  an  exchange  of  materials  within  the  nerves  is  proved  by  the  fact  that  after  com- 
pression of  the  blood  vessels  of  the  nerves,  the  excitability  of  the  nerves 
falls,  and  is  restored  again  when  the  circulation  is  re-established.  Compression  of 
the  abdominal  aorta  causes  paralysis  and  numbness  of  the  lower  half  of  the  body, 
while  occlusion  of  the  cerebral  vessels  causes  almost  instantaneously  cessation  of 
the  cerebral  functions.  The  metabolism  of  the  central  nervous  organs  is  much 
more  active  than  that  of  the  nerves  themselves.  [If  the  abdominal  aorta  of  a 
rabbit  be  compressed  for  a  few  minutes  the  hind  limbs  are  quickly  paralyzed,  the 
animal  crawls  forward  on  its  fore  legs,  drawing  the  hind  limbs  in  an  extended 
position  after  it.]     The  ganglia  form  much  lymph. 

324.  EXCITABILITY    OF    THE    NERVES— STIMULI.— Nerves 

possess  the  property  of  being  thrown  into  a  state  of  excitement  by  stimuli,  and 
are,  therefore,  said  to  be  excitable  or  irritable.  The  stimuli  may  be  applied  to, 
and  may  act  upon,  any  part  of  the  nerve.  [The  following  are  the  various  kinds 
of  stimuli,  /.  c,  modes  of  motion,  which  act  upon  nerves]  :  — 

1.  Mechanical  stimuli  act  upon  nerves  when  they  are  applied  with  sufficient 
rapidity  to  produce  a  change  in  the  form  of  the  nerve  particles,  e:g.,  a  blow, 
pressure,  pinching,  tension,  puncture,  section.  In  the  case  of  sensory  nerves, 
when  they  are  stimulated,  pain  is  produced,  as  is  felt  when  a  limb  "sleeps,"  or 
when  ])ressure  is  exerted  upon  the  ulnar  nerve  at  the  bend  of  the  elbow.  When  a 
motor  nerve  is  stimulated,  motion  results  in  the  muscle  attached  to  the  nerve.  If 
the  continuity  of  the  nerve  fibres  be  destroyed,  or,  what  is  the  same  thing,  if  the 
continuity  of  the  axial  cylinder  be  interrupted  by  the  mechanical  stimulus,  the 
conduction  of  the  impulse  across  the  injured  part  is  interrupted.  If  the  molecular 
arrangements  of  the  nerves  be  permanently  deranged,  e.  g.,  by  a  violent  shock, 
the  excitability  of  the  nerves  may  be  thereby  extinguished. 

A  slight  blow  applied  to  the  radial  nerve  in  the  fore  arm,  or  to  the  axillary  nerves  in  the  supra- 
clavicular groove,  is  followed  by  a  contraction  of  the  muscles  supplied  by  these  nerves.  Under 
pathological  conditions  the  e.scitability  of  a  nerve  for  mechanical  stimuli  may  be  increased  enor- 
mously. 


THERMAL    AND    CHEMICAL    STLMULI.  5G9 

Tigerstedt  ascertained  that  the  minimal  mechanical  stimulus  is  represented  by  900  milligram- 
millimetres,  and  the  maximum  by  7000  to  8000.  Strong  stimuli  cause  fatigue,  but  the  fatigue  does 
not  extend  beyond  the  part  stimulated.  A  nerve  when  stimulated  mechanically  does  not  become 
acid.  Slight  pressure  without  tension  increases  the  excitability,  which  diminishes  afier  a  short  time. 
The  mechanical  work  produced  by  an  excited  muscle  in  consequence  of  a  stimulus  was  100  times 
greater  than  the  mechanical  energy  of  the  mechanical  nerve  stimulus. 

Continued  pressure  upon  a  mixed  nerve  paralyzes  the  motor  sooner  than 
the  sensory  fibres.  If  the  stimultis  be  applied  very  gradually,  the  nerve  may  be 
rendered  inexcitable  without  manifesting  any  signs  of  its  being  stimulated  (Fon- 
iana,  iJjS).  Paralysis,  due  to  continuous  pressure  gradually  applied,  may  occur 
in  the  region  supplied  by  the  brachial  nerves  ;  the  left  recurrent  laryngeal  nerve 
also  may  be  similarly  paralyzed  from  the  pressure  of  an  aneurism  of  the  arch  of 
the  aorta. 

By  increasing  the  pressure  on  a  nerve  by  using  a  gradually  increasing  weight,  there  is  at  first  an 
increase  and  then  a  decrease  of  the  excitability.  Pressure  on  a  mixed  nerve  abohshes  reflex  con- 
duction sooner  than  motor  conduction  {Kionccker  and  Zederbauni). 

Nerve  stretching  is  one  of  the  methods  that  has  recently  been  employed  for  therapeutical  pur- 
poses. If  a  nerve  be  exposed  and  stretched,  or  if  a  certain  tension  be  exerted  upon  it,  this  acts  as 
a  stimulus.  Slight  extension  increases  the  reflex  excitability  (Schleich),  while  violent  extension  pro- 
duces a  temporary  diminution  or  abolition  of  the  excitability  (I'alenlin).  The  centripetal  fibres 
(sensory)  of  the  sciatic  nerve  are  sooner  paralyzed  thereby  than  the  centrifugal  motor  (Conrad). 
During  the  process  of  extension  mechanical  changes  are  produced,  either  in  the  nerve  itself  or  in 
its  end  organs,  causing  an  alteration  of  the  excitability,  but  it  may  also  afiect  the  central  organs. 
The  paralysis  which  sometimes  occurs  after  forcible  stretching  usually  rapidly  disappears.  There- 
fore, when  a  nerve  is  in  an  excessively  excitable  condition,  or  when  this  is  due  to  an  inflammatory 
fixation  or  constriction  of  the  nerve  at  some  part  of  its  course,  then  nerve  stretching  may  be  useful, 
partly  by  diminishing  the  excitability,  partly  by  breaking  up  the  inflammatory  adhesions.  In  cases 
where  stimulation  of  an  afferent  nerve  gives  rise  to  epileptic  or  tetanic  spasms,  nerve  stretching  miy 
be  useful  by  diminishing  the  excitability  at  the  periphery,  in  addition  to  the  other  efi'ects  already 
described.  It  has  also  been  employed  in  some  spinal  affections,  which  may  not  as  yet  have  resulted 
in  marked  degenerative  changes. 

Tetanomotor. — For  physical  purposes,  a  nerve  may  be  stimulated  mechanically  by  means  of 
Heidenhain's  tetanomotor,  which  is  simply  an  ivory  hammer  attac'.ted  to  the  prolonged  spring  of 
a  Neefs  hammer  of  an  induction  machine.  The  rapid  vibration  of  the  hammer  communicates  a 
series  of  mechanical  shocks  to  the  nerve  upon  which  it  is  caused  to  beat.  Rhythmic  extension  of 
a  nerve  causes  contractions  and  even  tetanus. 

2.  Thermal  Stimuli. — If  a  frog's  nerve  be  heated  to  45°  C,  its  excitability 
is  first  increased  and  then  diminished.  The  higher  the  temperature,  the  greater 
is  the  excitability,  and  the  shorter  its  duration  {  Afanasieff).  If  a  nerve  be  heated 
to  50'  C.  for  a  short  time,  its  excitability  and  conductivity  are  abolished.  The 
frog's  nerve  alone  regains  its  excitability  on  being  cooled  {Pickford,  J.  Rosenthal). 
If  the  temperature  be  raised  to  65°  C,  the  excitability  is  abolished  without  the 
occurrence  of  a  contraction,  while  its  medulla  is  broken  up  (^Eckhard).  Sudden 
cooling  of  a  nerve  to  5°  C.  acts  as  a  stimulus,  causing  contraction  in  a  muscle, 
while  sudden  heating  to  40°  to  45°  C.  produces  the  same  result.  If  the  temper- 
ature be  increased  still  more,  instead  of  a  single  contraction  a  tetanic  condition 
is  produced.  All  such  rapid  variations  of  temperature  quickly  exhaust  the  nerve 
and  kill  it.  If  a  nerve  be  frozen  gradually,  it  retains  its  excitability  on  being 
thawed.  The  excitability  lasts  long  in  a  C(wfo/ nerve  ;  in  fact,  it  is  increased  in 
a  motor  nerve,  but  the  contractions  are  not  so  high  and  more  extended,  while  the 
conduction  in  the  nerve  takes  place  more  slowly.  Among  mammalian  nerves,  the 
afferent  and  vaso-dilator  nerves  at  45°  to  50°  C.  exhibit  the  results  of  stimulation, 
while  the  others  only  show  a  change  in  their  excitability.  When  cooled  to  +  5° 
C.,  the  excitability  of  all  the  fibres  is  diminished  (^Griitzner). 

3.  Chemical  Stimuli  excite  nerves  when  they  act  so  as  to  change  their  co.i- 
stitution  with  a  certain  rapidity  (p.  509).  Most  chemical  stimuli  act  by  first  in- 
creasing the  nervous  excitability,  and  then  diminishing  or  paralyzing  it.  Chem- 
ical stimuli,  as  a  rule,  have  less  effect  upon  sensory  than  upon  motor  fibres  (Eck- 
hard,  Setschenow).     According  to  Griitzner,  the  inactivity  of  chemical  stimuli. 


570  PHYSIOLOGICAL   AND    ELECTRICAL    STIMULI. 

so  often  observed  when  they  are  applied  to  sensory  nerves,  depends  in  great  part 
upon  the  non-simultaneous  stimulation  of  all  the  nerve  fibres.  Among  chemical 
stimuli  are — (a)  rapid  abstraction  of  7vatcr  by  dry  air,  blotting  paper,  exposure 
in  a  chamber  containing  sulphuric  acid,  or  by  the  action  of  solutions  which  ab- 
sorb fluids,  e.g.,  concentrated  solutions  of  neutral  alkaline  salts  (NaCl.  excites 
only  motor  fibres  in  mammals — Giiifz/icr),  sugar,  urea,  concentrated  glycerin  (and 
?  some  metallic  salts).  The  subsequent  addition  of  water  may  abolish  the  contrac- 
tions, while  the  nerve  may  still  remain  excitable.  The  abstraction  of  water  first 
increases  and  afterward  diminishes  the  excitability.  The  imbibition  of  rvater 
diminishes  the  excitability,  {b)  Free  alkalies,  mideral  acids  (not  phosphoric), 
many  organic  acids  (acetic,  oxalic,  tartaric,  lactic),  and  most  salts  of  the  heavy 
metals.  While  the  acids  act  as  stimuli,  only  when  they  are  somewhat  concen- 
trated, the  caustic  alkalies  act  in  solutions  of  0.8  to  o.i  per  cent.  {Kiihne). 
Neutral  potash  salts  in  a  concentrated  form  rapidly  kill  a  nerve,  but  they  do  not  ex- 
cite it  nearly  so  strongly  as  the  soda  compounds.  Dilute  solutions  of  the  neutral 
potash  salts  first  increase  and  afterward  diminish  it  {Ranke).  (r)  Various  sub- 
stances, e.g.,  dilute  alcohol,  ether,  chloroform,  bile,  bile  salts,  and  sugar.  These 
substances  usually  excite  contractions,  and  afterward  rapidly  kill  the  nerve.  Am- 
monia {£ckhai-J),  lime  water  {Kiihne),  some  metallic  salts,  carbon  bisulphide 
and  ethereal  oils  kill  the  nerve  without  exciting  it — at  least  without  producing 
any  contraction  in  a  frog's  nerve-muscle  preparation.  Carbolic  acid  does  the 
same,  although  when  applied  directly  to  the  spinal  cord  it  produces  spasms. 
These  substances  excite  the  muscles  when  they  are  directly  applied  to  them. 
Tannic  acid  does  not  act  as  a  stimulus  either  to  nerve  or  muscle.  As  a  general 
rule,  the  stimulating  solutions  must  be  more  concentrated  when  applied  to  a  nerve 
than  to  a  muscle,  in  order  that  a  contraction  may  be  prjduced. 

[Methods. —  If  a  nerve-muscle  preparation  of  a  frog's  limb  be  made,  and  a  straw  flag  (p.  508) 
attached  to  the  toes  while  the  femur  is  fixed  in  a  clamp,  and  its  nerve  be  then  dipped  in  a  saturated 
solulioii  of  common  salt,  the  toes  soon  begin  to  twitch,  and  by  and  by  the  whole  limb  becomes 
tetanic,  and  thus  keeps  the  straw  flag  extended.  The  eflect  of  fluid  on  a  muscle  or  nerve  is  easily 
tested  by  fixing  the  muscle  in  a  clamp,  while  a  drop  of  the  fluid  is  placed  on  a  greased  surface, 
which  gives  it  a  convex  form  [Kiihne).  The  end  of  the  muscle  or  nerve  is  then  brought  into  con- 
tact with  the  cupola  of  the  drop.] 

4.  The  Physiological  or  normal  stimulus  excites  the  nerves  in  the  normal 
intact  body.  Its  nature  is  entirely  unknown.  The  "  nerve  motion  "  thereby  set 
up  travels  either  in  a  "  centrifugal "  or  outgoing  direction  from  the  central 
nervous  system,  giving  rise  to  motion,  inhibition  of  motion,  or  secretion;  or  in 
a  "  centripetal  "  or  ingoing  direction  from  the  specific  end  organs  of  the  nerves 
of  the  special  senses  or  the  sensory  nerves.  In  the  latter  case  the  impulse  reaches 
the  central  organs,  where  it  may  excite  sensation  or  perception,  or  it  may  be 
transferred  to  the  motor  areas  and  be  conducted  in  a  centrifugal  direction,  con- 
stituting a  "reflex  "  stimulation  (§  360).  A  single  physiological  nerve  impulse 
travels  more  slowly  than  that  excited  by  the  momentary  application  of  an  induc- 
tion shock  {Lovcn,  v.  Kries).  It  is  not  a  uniform  process,  excited  by  varying 
intensity  and  greater  or  less  frequency  of  stimulation,  but  it  is  essentially  a  pro- 
cess varying  considerably  in  duration,  and  it  may  even  last  as  long  as  J  3  second 
(?'.  Kries). 

5.  Electrical  Stimuli. — The  electrical  current  acts  most  powerfully  upon  the 
nerves  at  tlie  moment  when  it  is  applied,  and  at  the  moment  when  it  ceases 
(§  336)  ;  in  a  similar  way,  any  increase  or  decrease  in  the  strength  of  a  constant 
current  acts  as  a  stimulus.  If  an  electrical  current  be  applied  to  a  nerve,  and  its 
strength  be  very  gradually  increased  or  diminished,  then  the  visible  signs  of 
stimulation  of  the  nerve  are  very  slight.  As  a  general  rule,  the  stimulation  is 
more  energetic  the  more  rapid  the  variations  of  the  strength  of  the  current  applied 
to  the  nerve,  /.  e.,  the  more  suddenly  the  intensity  of  the  stimulating  current  is 
increased  or  diminished  {Du  Bois-Rcyniond). 


EFFECT   OF    CONSTANT   CURRENT.  571 

An  electrical  current  must  have  a  certain  strength  [liminal  intensity)  before  it  is 
effective.  By  uniformly  increasing  the  strength  of  the  current,  the  size  of  the 
contraction  increases  rapidly  at  first,  then  more  slowly  {Tigerstedt  and  Willhard). 

An  electrical  current,  in  order  to  stimulate  a  nerve,  must  act  at  least  during 
0.0015  second  {Pick,  i86j,  Kihiig);  even  with  currents  of  slightly  longer  dura- 
tion, the  ojiening  shock  may  have  no  effect.  If  the  duration  of  the  closing  shock 
of  a  constant  current  be  so  arranged  that  it  is  just  too  short  to  be  active,  then  it 
merely  requires  to  last  1.3  to  2  times  longer  to  produce  the  most  complete  effect 
(  G>  tin/iageii) . 

The  electrical  current  is  most  active  when  it  flows  in  the  long  axis  of  the  nerve  ; 
it  is  inactive  when  applied  vertically  to  the  axis  of  the  nerve  {Galvani,/.  Albrecht, 
A.  Meyer).  Similarly,  muscles  are  incomparably  less  excited  by  transverse  than 
by  longitudinal  currents  {Giiifre). 

The  grea/er  the  length  of  nerve  traversed  by  the  current,  the  less  the  stimulus 
that  is  required  (Pfaff,  Marciise,  Tschirjew). 

Constant  Current. — If  the  constant  current  be  used  as  a  nervous  stimulus, 
the  stimulating  effect  on  the  sensory  nerves  is  most  marked  at  the  moment  of 
closing  and  opening  [or  breaking]  the  current ;  during  the  time  the  current  passes 
only  slight  excitement  is  perceived,  but  even  under  these  circumstances  very  strong 
currents  may  cause  very  considerable,  and  even  unbearable,  sensations.  If  a  con- 
stant current  be  applied  to  a  motor  nerve,  the  greatest  effect  is  produced  when 
the  current  is  closed  [closing  contraction]  and  when  it  is  opened  [opening 
contraction].  But  while  the  current  is  passmg,  the  stimulation  does  not  cease 
completely  (  Wundt)  ;  for,  with  a  certain  strength  of  stimulus,  the  muscle  remains 
in  a  state  of  tetanus  (galvanotonus  or  "closing  tetanus")  (Pfliigcr).  For 
the  same  effect  on  muscles,  see  p.  51S.  With  strong  currents,  this  tetanus  does 
not  appear,  chiefly  because  the  current  diminishes  the  excitability  of  the  nerves, 
and  thus  develops  resistance,  which  prevents  the  stimulus  from  reaching  the 
muscle.  According  to  Hermann,  a  descending  current  applied  to  the  nerve, 
at  a  distance  from  the  muscles,  causes  this  tetanus  more  readily,  while  an 
ascending  current  causes  it  more  readily  when  the  current  is  closed  near  the 
muscle.  The  constant  current  is  said  by  Griitzner  to  have  no  effect  on  vaso- 
motor and  secretory  fibres. 

Over-maximal  Contraction. — By  gradually  increasing  the  strength  of  the  electrical  stimulus 
apphed  to  a  motor  nerve,  Fick  observed  that  the  muscular  contractions  (height  of  the  lift)  at  first 
increased  proportionally  lo  the  increase  of  the  stmiulus,  until  a  maximal  contraction  was  obtained. 
If  the  strength  of  the  stimulus  be  increased  still  further,  another  increase  of  the  contraction  above 
the  first-reached  maximum  is  obtained.  This  is  called  an  "  over-maximal  contraction^  Occasion- 
ally between  the  first  maximum  and  the  second  there  is  a  diminution,  or,  indeed,  absence  of  or 
gap  in  the  contractions  (fick).  The  cause  of  this  lies  in  the  positive  pole,  which,  with  a  certain 
strength  of  current,  is  sufficient  to  prevent  the  further  transmission  of  the  excitement  (^  335)-  On 
continuing  to  increase  the  induction  current,  ultimately  a  stage  is  reached  where  the  stimulation  at 
the  negative  pole  again  becomes  stronger  than  the  inhibition  at  the  positive,  and  this  overcomes  the 
latter.  The  contractions  before  the  gap  are  caused  by  the  occurrence  of  the  induction  current 
(their  latent  period  is  short) ;  the  contractions  (long  latent  period,  like  that  after  all  opening  shocks 
—  IValter,  p.  518)  after  the  gap  are  caused  by  the  disappearance  of  the  induction  current,  /.  <•.,  by 
polarization  ;  this  is  added  to  the  stimulation  proceeding  from  the  negative  pole,  which,  after  the 
gap,  overcomes  the  inhibition  at  the  positive  pole,  and  excites  the  over-maximal  contractions  (Tigcr- 
stcJt  and  Willhard). 

Tetanus. — \{  single  shocks  of  short  duration  be  rapidly  applied  after  each  other 
to  a  nerve,  tetanus  in  the  corresponding  muscle  is  produced  (§  298,  III). 

A  motor  nerve  has  a  greater  specific  excitability  for  electrical  stimuli  than  the 
muscle  substance.  This  is  proved  by  the  fact  that  a  feebler  stimulus  suffices  to 
excite  a  muscle  when  applied  to  the  nerve  than  when  it  is  applied  to  the  muscle 
directly,  as  occurs  when  the  terminations  of  the  motor  nerves  are  paralyzed  by 
curara  {Rosenthal). 

Soltmann   found  that  the  excitability  of  the  motor  nerves  of  new-born  ani- 


572  DIMINUTION    OF   THE    EXCITABILITY. 

mals  for  electrical  stimuli  is  less  than  in  adults.  The  excitability  increases  until 
the  5th  to  loth  month. 

Unequal  Excitability. — Under  certain  circumstances,  the  nearer  the  part  of 
the  motor  nerve  stimulated  lies  to  the  central  nervous  system,  the  greater  is  the 
effect  produced  (contraction ) ;  [or,  what  is  the  same  thing,  the  further  the  point 
of  a  nerve  which  is  stimulated  is  from  the  muscle,  the  stimulus  being  the  same, 
the  greater  is  the  contraction].  According  to  Fleischl,  all  parts  of  the  nerve  are 
equally  excitable  for  chemical  stimuli.  P'urther,  it  is  said  that  the  higher-placed 
parts  of  a  nerve  are  more  excitable  only  when  the  stimulating  current  passes  in  a 
descending  direction  ;  the  reverse  is  the  case  when  the  current  s&csnd?,  { Hermann, 
Fleischl).  On  stimulating  a  j-^wci-ij  nerve,  Rutherford  and  Hiillsten  found  that 
the  reflex  contraction  was  greater  the  nearer  the  point  stimulated  was  to  the  cen- 
tral nervous  system. 

Unequal  Excitability  in  the  same  Nerve. — Nerve  fibres,  even  when  func- 
tionally the  same  and  included  in  the  same  nerve  trunk,  are  not  all  equally  excitable. 
Thus  feeble  stimulation  of  the  sciatic  nerve  of  a  frog  causes  contraction  of  the 
flexor  muscles,  while  it  requires  a  stronger  stimulus  to  produce  contraction  of  the 
extensors  {Riftei;  iSoj,  Rolletf).  According  to  Ritter,  the  nerves  for  the  flexors 
die  first. 

Direct  stimuL-ition  of  the  muscles  in  ciirarized  animals  shows  that  the  flexors  contract  with  a 
feebler  stimulus  (but  also  fatigue  sooner)  than  the  extensors;  the  pale  muscles  of  the  rabbit  are 
also  more  excitable  than  the  red.  As  a  rule,  poisons  affect  the  flexors  sooner  than  the  extensors. 
In  some  muscles  some  pale  fibres  are  present,  and  they  are  more  excitable  than  the  red  (Grulsner) 
(I  298). 

Unipolar  Stimulation. — If  one  electrode  of  an  induction  apparatus  be  ap- 
plied to  a  nerve  it  may  act  as  a  stimulus.  Du  Bois-Raymond  has  called  this 
"  unipolar  induction  action."  It  is  due  to  the  movement  of  the  electric  current 
to  and  from  the  free  ends  of  the  open  induction  current  at  the  moment  of  induc- 
tion. [Unipolar  induction  is  more  apt  to  occur  with  the  opening  than  the  closing 
shock,  because  the  former  is  more  intense.] 

Upon  muscle  electrical  stimuli  act  quite  as  they  do  upon  nerves.  Elec- 
trical currents  of  very  short  duration  have  no  effect  iipon  muscles  whose  nerves  are 
paralyzed  by  curara  (Briiche),  and  the  same  is  true  of  greatly  fatigued  muscles,  or 
muscles  about  to  die  or  greatly  weakened  by  diseased  condition  (§  399). 

325.  DIMINUTION  OF  THE  EXCITABILITY— DEGENERA- 
TION AND  REGENERATION  OF  NERVES.— i.  Normal  Nutri- 
tion.— The  continuance  of  the  normal  excitability  in  the  nerves  of  the  body 
depends  upon  the  maintenance  of  the  normal  nutrition  of  the  nerves  themselves 
and  a  due  supply  of  blood.  Insufficient  nutrition  causes  in  the  first  instance  in- 
creased excitability,  and  if  the  condition  be  continued  the  excitability  is  dimin- 
ished (§  339,  I). 

When  the  physician  meets  with  the  signs  of  increased  excitability  of  the  nerves,  under  bad  or 
abnormal  conditions  of  nutrition,  this  is  to  be  regarded  as  the  beginning  of  the  stage  of  decrease  of 
the  nerve  energy.     Invigorating  measures  are  required. 

If  the  terminal  nervous  apparatus  be  subjected  to  a  temporary  disturbance  of  its 
nutrition,  the  return  of  the  normal  nutritive  process  is  heralded  by  a  more  or  less 
marked  stage  of  excitement.  The  more  excitable  the  nervous  apparatus  the 
shorter  must  be  the  duration  of  the  disturbance  of  nutrition,  e.g.,  cutting  off 
the  arterial  blood  supply  or  interfering  with  the  respiration. 

2.  Fatigue. — Continued  excessive  stimulation  of  a  nerve,  without  sufficient 
intervals  ot  repose,  zsecati  fatigue  of  the  nerve,  and  by  exhaustion  rapidly  diinin- 
ishes  the  excitability.  A  nerve  is  more  slowly  fatigued  than  a  muscle  {Bernstein), 
but  it  recovers  inore  slowly  (§  304).  [Nerves  of  cold-blooded  animals  (  Widenskii) 
and  mammals  {Bowditch)  may  be  tetanized  for  hours  without  becoming  fatigued.] 


SEPARATION    FROM    NERVE    CENTRES. 


573 


Recovery. — When  a  nerve  recovers,  at  first  it  does  so  slowly  then  more  rap- 
idly, and  afterward  again  more  slowly.  If  recovery  does  not  occur  within  half 
an  hour  after  a  frog's  nerve  has  been  subjected  to  very  long  and  intense  stimula- 
tion, it  will  not  take  place  at  all. 

3.  Continued  inaction  of  a  nerve  diminishes  and  may  ultimately  abolish 
the  excitability. 

Fiu.  342. 

ABC  D  E 


'it 


^  nd  regeneration  of  nerves.    A,  subdi' 

B.  further  disintegration  thereof  (osmic  acid  staining) ; 
of  the  axial  cylinder,  which  is  surrounded  '  '  *     " 
D,  accumulation  of  nuclei,  with"  the 
spindle-shaped  fibre;   E,  a  new  nerve  f 
through  an  old  nen 
sheath  of  Schwann, 


Thus  the  central  ends  of  divided  sensory  nerves,  after  amputation  of  a  limb,  lose  their  excita- 
hilily,  although  the  nerves  are  still  connected  with  the  central  nervous  system,  because  the  end 
organs  through  which  they  were  normally  excited  have  been  removed. 

4.  Separation  from  their  Nerve  Centres, — The  nerve  fibres  remain  in  a 
condition  of  normal  nutrition  only  when  they  are  directly  connected  with  their 
centre,  which  governs  the  nutritive  processes  within  the  nerve.     If  a  nerve 


574 


TRAUMATIC    AND    FATTV'   DEGENERATION. 


within  the  body  be  separated  from  its  centre — either  by  section  of  the  nerve  or 
compressing  it — within  a  short  time  it  loses  its  excitability,  and  the  peripheral 
end  undergoes  fatty  degeneration,  which  begins  in  four  to  six  days  in  warm-blooded 
animals,  and  after  a  long  time  in  cold-blooded  ones  {Joh.  Miillcr).  See  also  the 
changes  of  the  excitability  during  this  condition,  the  so-called  "  Reaction  of 
degeneration"  (§  339).  If  the  sensory  nerve  fibres  of  the  root  of  a  spinal 
nerve  be  divided  on  the  central  side  of  the  ganglion,  the  fibres  on  the  peripheral 
side  do  not  degenerate,  for  the  ganglion  is  the  trophic  or  nutritive  centre  for  the 
sensory  nerves,  but  the  fibres  still  in  connection  with  the  cord  degenerate  (  Waller, 
Bidder). 

[Wallerian  Law  of  Degeneration. — If  a  spinal  nerve  be  divided,  the 
peripheral  part  of  the  nerve  and  its  branches,  including  the  sensory  and  motor 
fibres,  degenerate  completely  (Fig.  343,  A),  while  the  central  parts  of  the  nerve 
remain  unaltered.  If  the  anterior  root  of  a  spinal  nerve  alone  be  divided  before 
it  joins  the  posterior  root,  all  the  peripheral  nerve  fibres  connected  with  the  an- 
terior root  degenerate  (Fig.  343,  B),  so  that  in  the  nerve  of  distribution  only  the 
motor  fibres  degenerate.  The  portion  of  the  nerve  root  which  remains  attached  to 
the  cord  does  not  regenerate.  If  \.\\t  posterior  root  aXone  be  divided,  between  the 
spinal  cord  and  the  ganglion,  the  effect  is  reversed,  the  part  of  the  nerve  root 
lying  between  the  section  and  the  spinal  cord  degenerates,  while  the  part  of  the 


Fig.  343. 


Diagram  of  the  roots  of  a  spinal  nerve  showing  the  effect  of  section  (the  black  parts  represent  the  degenerated  parts). 
A,  section  of  the  nerve  trunk  beyond  the  ganglion  ;  B,  of  the  anterior  root,  and  C,  of  the  posterior  ;  D,  excision 
of  the  ganglion  ;  a,  anterior,/,  posterior  root ;  g,  ganglion. 

nerve  connected  with  the  ganglion  does  not  degenerate  (Fig.  343,  C).  The  cen- 
tral fibres  degenerate  because  they  are  separated  from  the  ganglion.  If  the  gan- 
glion be  excised,  or  if  separated,  as  in  Fig.  343,  D,  both  the  central  and  peri- 
pheral parts  of  the  posterior  root  degenerate.  These  experiments  of  Waller  show 
that  the  fibres  of  the  anterior  and  posterior  roots  are  governed  by  different  cen- 
tres of  nutrition  or  "  trophic  centres."  As  the  anterior  root  degenerates  when 
it  is  separated  from  the  cord,  and  the  posterior  when  it  is  separated  from  its  own 
ganglion,  it  is  assumed  that  the  trophic  centre  for  the  fibres  of  the  anterior  root 
lies  in  the  multipolar  nerve  cells  of  the  anterior  horn  of  the  gray  matter  of  the 
spinal  cord,  while  that  for  the  fibres  of  the  posterior  root  lies  in  the  cells  of  the 
ganglion  placed  on  it.  The  nature  of  this  supposed  trophic  influence  is  entirely 
unknown.] 

Traumatic  and  Fatty  Degeneration. — Both  ends  of  the  nerve  at  the  point  of  section  imme- 
diately begin  to  undergo  "traumatic  degeneration."  (In  the  frog  on  the  first  and  second  day. )  After 
a  time,  neither  the  myelin  nor  axis  cylinder  are  distinguishable  [Schijf),  According  to  Engelmann, 
this  condition  extends  only  to  the  nearest  node  of  Ranvier,  and  afterward  the  so-called  "fatty  degen- 
eration" begins.  The  process  of  "yiz//)'"  degeneration  begins  simultaneously  in  the  whole  peripheral 
portion  ;  the  white  substance  of  Schwann  breaks  up  into  masses  (Fig.  342,  A),  just  as  it  does  after 
death,  in  microscopic  preparations;  afterward,  the  myelin  forms  globules  and  round  masses  (B), 
the  axial  cylinder  is  compressed  or  constricted,  and  is  ultimately  broken  across  (C)  in  many  places 
(7th  day).     The  nerve  fibre  seems  to  break  up  into  two  substances — one  fatty,  the  other  proteid  in 


TROPHIC    CENTRES    AND    EFFECTS    OF    POISONS   ON    NERVES.       575 

constilulion  f^.  Afayer),  the  fat  being  absorbed.  The  nuclei  of  Schwann's  sheath  swell  up  and 
proliferate  (D— until  the  tenth  day).  According  to  Ranvier,  the  nuclei  of  the  interannular  segments 
and  their  surrounding  protoplasm  proliferate,  and  ultimately  interrupt  the  continuity  of  the  axis 
cylinder  and  the  myelin.  They  then  undergo  considerable  development  with  simuhaneous  disap- 
pearance of  the  medulla  and  axis  cyhnder,  or  at  least  the  fatty  substances  formed  bv  their  degenera- 
tion, so  that  the  nerve  fibres  look  like  fibres  of  connective  tissue,  [.\ccording  to  this  view,  (he  pro- 
cess is  in  part  an  aclive  one,  due  to  the  growth  of  the  nerve  corpuscles  breaking  up  the  contents  of 
the  neurilemma,  which  then  ultimately  undergo  chemical  degenerative  changes.]  According  to 
Ranvier,  Tizzoni,  and  others,  leucocytes  wander  into  the  cut  ends  of  the  nerves,  and  also  at  Ran- 
vier's  nodes,  insinuating  themselves  into  the  nerve  fibres,  where  they  take  myelin  into  their  bodies, 
and  subje:t  it  to  certain  changes.  [These  cells  are  best  revealed  by  the  action  of  osmic  acid,  which 
blackens  any  myelin  particles  in  th-.-ir  interior.]  Degeneration  also  takes  place  in  the  motorial  end 
plates,  beginning  first  in  the  nonmedullateil  branches,  then  in  the  terminal  fibrils,  and  lastly  in  the 
nerve  trunks  [Gessler). 

Regeneration  of  Nerves. — In  order  that  regeneration  of  a  divided  nerve  may  take  place 
{Cruickshank,  /ygs),  the  divided  ends  of  the  nerve  must  be  broupht  into  contact  (?  244).  In  man 
this  is  done  by  means  of  sutures.  AI>out  the  middle  of  the  fourth  week,  small  clear  bands  appear 
within  the  neurilemma,  winding  between  the  nuclei  and  the  remains  of  the  myelin  (E).  They  soon 
become  wider,  and  receive  myelin  with  incisures,  and  nodes,  and  a  sheath  of  Schwann  (second  to 
third  month — F).  The  regeneration  process  takes  place  in  each  interannular  segment,  v\'hile  the  in- 
dividual segmerts  unUe  end  to  end  at  the  nodes  of  Ranvier  (^  321,  I,  5).  On  this  view,  each 
nerve  segment  of  the  fibre  corresponds  to  a  "cell  unit"  {E.  Neumann,  Eichhorst).  The  same 
process  occurs  in  nerves  ligatured  in  their  course.  Several  new  fibres  may  be  formed  within  one 
old  nerve  sheath.  The  divided  axis  cylinders  of  the  central  end  of  the  nerve  begin  to  grow  about 
the  fourteenth  day,  untd  they  meet  the  newly  formed  ones,  with  which  they  unite. 

[Primary  and  Secondary  Nerve  Suture.  —Numerous  experiments  on  animals  and  man  have 
established  the  fact  that  immediate  or  primary  suture  of  a  nerve,  after  it  is  divided,  either  acci- 
dentally or  intentionally,  hastens  reunion  and  regeneration,  and  accelerates  the  restoration  of 
function.  Secondary  suture,  i.e.,  bringing  the  ends  together  long  after  the  nerve  has  been 
divided,  has  been  practiced  with  success.  Surgeons  have  recorded  cases  where  the  function  was 
restored  after  division  had  taken  place  for  3  to  16  months,  and  even  longer,  and  in  most  cases  the 
sensibility  was  restored  first,  the  average  time  being  2  to  4  weeks.  Motion  is  recovered  much 
later.  The  ends  of  the  ner\e  should  be  stitched  to  each  other  with  catgut,  the  muscles  at  the  same 
time  being  kept  from  becoming  atrophied  by  electrical  stimulation  and  the  systematic  use  of 
massage  (J  307).  After  suture  of  a  nerve  conductivity  is  restored  in  the  rabbit  in  40  days,  on  the 
31st  in  dogs,  and  25th  in  fowls,  but  after  simple  division  without  suture  not  till  the  60th  day  in  the 
rabbit.     Transplantation  of  nerve  does  not  succeed  ( Johmon).'] 

Union  of  Nerves.— The  central  end  of  a  divided  motor  nerve  may  unite  with  the  peripheral 
end  of  another  and  still  conduct  impulses  {Rava).  [There  seems  to  be  no  doubt  that  sensory 
fibres  will  reunite  with  sensory  fibres,  and  motor  fibres  with  motor  fibres,  and  the  regenerated  nerve 
will,  in  the  former  case,  conduct  sensory  impulses,  and  the  latter  motor  impulses.  There  is  very 
considerable  diversity  of  opinion,  however,  as  to  the  regeneration  or  union  of  sensory  with  motor 
fibres.  Paul  Bert  made  the  following  experiment :  He  stitched  the  tail  of  a  rat  into  the  animal's 
back,  and  after  union  had  taken  place,  he  cut  the  tail  from  the  body  at  the  root,  so  that  the  tail,  as 
it  were,  grew  out  of  the  animal's  back,  broad  end  uppermost.  On  irritating  the  end  of  the  tail, 
which  was  formerly  the  root,  the  animal  gave  signs  of  pain.  This  experiment  shows  that  nerve 
fibres  can  conduct  impulses  in  both  directions.  C)ne  of  two  things  must  have  occurred.  Either 
the  motor  fibres,  which  normally  carried  impulses  down  the  tail,  now  convey  them  in  the  opposite 
direction,  and  convey  them  to  sensory  fibres  with  which  they  have  united;  or  the  sensory  fibres, 
which  normally  conducted  impulses  from  the  tip  upward,  now  carry  them  in  the  opposite  direction. 
If  the  former  weie  actually  what  happened  it  would  show  that  nerve  fibres  of  different  funciion  <lo 
unite  (^  349)-  Reichert  asserts  that  he  has  succeeded  in  uniting  the  hypoglossal  with  the  vagus  in 
the  dog.     According  to  Gessler,  the  end  plate  is  the  first  to  regenerate.] 

Trophic  Centres. — The  regeneration  of  the  nerve  seems  to  take  place  under 
the  influence  of  the  nerve  centres,  which  act  as  their  nutritive  or  trophic 
centres.     Nerves  permanently  separated  from  these  centres  never  regenerate. 

During  the  regeneration  of  a  mixed  nerve,  sensibility  is  restored  first,  subse- 
quently voluntary  motion,  and  lastly,  the  movements  of  the  muscles,  when  their 
motor  nerves  are  stimulated  directly  {Schiff,  Erb,  v.  Ziemssen,  and  others). 

Wallerian  Method  of  Investigation. —  As  the  peri/i/ieral  end  of  a  nerve  undergoes  degenera- 
tion after  section,  we  use  this  method  for  determining  the  course  of  nerve  fibres  in  a  complex 
arrangement  of  nerves.  The  course  of  special  nerve  fibres  may  be  ascertained  by  tracing  the 
degeneration  tract  (  Waller,  Butti^e).  If,  after  section,  reunion  or  regeneration  of  a  motor  nerve 
does  not  take  place,  the  muscle  supplied  by  this  nerve  ultimately  undergoes  fatty  degeneration. 


576  RITTER-VALLI    LAW. 

5.  Certain  poisons,  such  as  veratrin,  at  first  increase  the  excitability  of  the 
nerves,  and  afterward  abolish  it ;  with  some  other  poisons,  the  abolition  of  the 
excitability  passes  off  very  rapidly,  e.g.,  curara.  Conium,  cynoglossum,  iodide 
of  methyl-strychnin,  and  iodide  of  Kthyl-strychnin  have  a  similar  action. 

If  the  nerve  or  muscle  of  a  frog  be  placed  in  a  solution  of  the  poison,  we  obtain  a  different  eifect 
from  that  which  results  when  the  poison  is  injected  into  the  body  of  the  animal.  Atropin 
diminishes  the  excitability  of  a  nerve-muscle  preparation  of  the  frog  without  causing  any  previous 
increase,  while  alcohol,  ether  and  chloroform  increase  and  then  diminish  the  excitability  [Jilomm- 
sen). 

6.  Modifying  Conditions. — -Under  the  action  of  various  operations,  e.g., 
compressing  a  nerve  [so  as  not  absolutely  to  sever  the  physiological  continuity], 
it  has  been  found  that  voluntary  impulses  or  stimuli  applied  above  the  compressed 
.spot,  give  rise  to  impulses  which  are  conducted  through  the  nerve,  and  in  the 
case  of  a  motor  nerve  cause  contraction  of  the  muscles,  while  the  excitability  of 
the  parts  below  the  injured  spot  is  greatly  diminished  (Schiff).  In  a  similar 
manner  it  is  found  that  the  nerves  of  animals  poisoned  with  COj,  curara  or 
coniin,  sometimes  even  the  nerves  of  paralyzed  limbs  in  man,  are  not  excitable  to 
direct  stimuli,  while  they  are  capable  of  conducting  impressions  coming  from 
the  central  nervous  system  (Ducheiirie,  v.  Ziemsscn,  Erb). 

7.  Ritter-Valli  Law. — If  a  nerve  be  separated  from  its  centre,  or  if  the 
centre  dies,  the  excitability  of  the  nerve  is  increased ;  the  increase  begins  at  the 
central  end,  and  travels  toward  the  peiiphery — the  excitability  then  falls  until  it 
disappears  entirely.  This  process  takes  place  more  rapidly  in  the  central  than 
in  the  peripheral  part  of  the  nerve,  so  that  the  peripheral  end  of  a  nerve  separated 
from  its  centre  remains  excitable  for  a  longer  time  than  the  central  end. 

The  rapidity  of  the  transmission  of  impulses  in  a  nerve  is  increased  when  the  excitability  is 
increased,  but  it  is  lessened  when  the  excitability  is  diminished.  In  the  latter  condition  an  electrical 
stimulus  must  last  longer  in  order  to  be  effective;  hence  rapid  induction  shocks  may  not  produce 
any  effect. 

The  law  of  contraction  also  undergoes  some  modification  in  the  different  stages  of  the  changes 
of  excitability  [\  336,  II). 

S.  Excitable  Points. — M.iny  nerves  are  more  excitable  at  certain  parts  of 
their  course  than  at  others,  and  the  excitability  may  last  longer  at  these  parts. 
One  of  these  parts  is  the  upper  third  of  the  sciatic  nerve  of  a  frog,  just  where  a 
branch  is  given  off  {Budge,  Heidenhain). 

The  motor  and  sensory  fibres  of  the  upper  third  of  the  sciatic  nerve  {Hdllsthi)  of  a  frog  is  more 
excitable  for  all  stimuli  (GriUzner  and  Elpo>i\  than  the  lower  parts.  Whether  this  arises  from 
injury  during  preparation  (a  branch  is  given  off  there),  or  is  due  to  anatomical  conditions,  e.g., 
more  connective  tissue  and  more  nodes  in  the  lower  part  of  the  sciatic,  is  undetermined  {Clara 
Na/person) . 

This  increased  excitability  may  be  due  to  injury  to  the  nerve  in  preparing  it  for  experiment. 
After  section  or  compression  of  a  nerve,  all  electrical  currents  employed  to  stimulate  the  nerve  are 
far  more  active  when  the  direction  of  the  current  passes  away  from  the  point  of  injury  than  when 
it  passes  in  the  opposite  direction.  This  is  due  to  the  fact  that  the  current  produced  in  the  nerve 
after  the  lesion  is  added  to  the  stimulation  current  (§  33  r,  5).  Even  in  intact  nerves — sciatic  of  a 
frog  (-■.  fleischl),  where  the  nen'e  ends  at  the  periphery  or  at  the  centre,  or  where  large  branches 
are  given  off,  there  are  points  wdiich  behave  in  the  same  way  as  those  points  wdiere  a  lesion  has 
taken  place  (  Griitzner  and  Mosckner). 

Death  of  a  Nerve. — In  a  dead  nerve  the  excitability  is  entirely  abolished, 
death  taking  place,  according  to  the  Ritter-Valli  Law,  from  the  centre  toward  the 
periphery.  The  reaction  of  a  dead  nerve  has  been  found  by  some  observers  to 
Ije  acid  (§  322). 

The  functions  of  the  brain  cease  immediately  after  death  takes  place,  while  the  vital  functions  of 
the  spinal  cord,  especially  of  the  white  matter,  last  for  a  short  time  ;  the  large  nerve  trunks  gradually 
die,  then  the  nerves  of  the  extensor  muscles,  those  of  the  flexors  after  three  to  four  hours;  while 
the  sympathetic  fibres  retain  their  excitability  longest,  those  of  the  intestine  even  for  ten  hours 
(Onimus).  Compare  ?  295.  The  nerves  of  a  dead  frog  may  remain  excitable  for  several  days, 
provided  the  animal  lie  kept  in  a  cool  place. 


ELECTRO-PHYSIOLOGY.  577 

ELECTRO-PHYSIOLOGY.— Before  beginning  the  study  of  electro-phys- 
iology, the  student  ought  to  read  and  study  carefully  the  following  short  prelimi- 
nary remarks  on  the  physics  of  this  question  :  — 

326.  PHYSICAL  PRELIMINARY  STATEMENTS— THE  GALVANIC  CUR- 
RENT— RHEOCORD.— I.  Electro-motive  Force.— If  two  of  the  under-mentioned  bodies 
be  brought  in'o  direct  contact,  in  one  of  them  positive  electricity  and  in  the  other  negative  electricity 
can  be  tletccted.  The  cause  of  this  phenomenon  is  the  electro-motive  force.  The  electro-motive 
substances  may  be  arranged  in  a  series  of  the  first  class,  so  that  if  the  first-mentioned  substance 
be  brought  into  cont.act  with  any  of  the  other  bodies,  the  first  substance  is  negatively  the  last  posi- 
tively electrified.     This  series  is — carbon,  platinum,  gold,  silver,  copper,  iron,  tin,  lead,  zinc  -)-  . 

The  amount  of  the  electro-motive  force  produced  by  the  contact  of  two  of  these  bodies  is  greater 
the  wider  the  bodies  are  apart  in  the  series.  The  contact  of  the  bodies  may  lake  place  at  one  or 
more  points.  If  several  01  the  bodies  of  this  series  be  arranged  in  a  pile,  the  electrical  tension 
thereby  produced  is  ju't  as  great  as  if  the  two  extreme  bodies  were  brought  into  contact,  the  inter- 
mediate ones  being  left  out. 

2.  The  nature  of  the  two  electricities  is  readily  determined  by  placing  one  of  the  bodies  of  the 
series  in  contact  with  a  fluid.  If  zinc  be  placed  in  pure  or  acidulated  water,  the  zinc  is  -4-  (posi- 
tive) and  the  water —  (negative).  If  copper  be  taken  instead  of  zinc,  the  copper  is  -|-  but  the 
fluid  —  .  Experiment  shows  that  those  metals,  in  contact  with  fluid,  are  negatively  electrified  most 
strongly  which  are  most  acted  on  chemically  by  the  fluid  in  which  they  are  placed.  Each  such 
combination  affords  a  constant  difterence  of  tension  or  potential.  The  tension  [or  power  of  over- 
coming resistance]  of  the  amount  of  electricity  obtained  from  both  bodies  depends  upon  the  size  of 
the  surfaces  in  contact.  The  fluids,  e.g.,  the  solutions  of  acids,  alkalies,  or  salts  are  called  exciters 
of  electricity  of  the  second  class.  They  do  not  form  among  themselves  a  definite  series  with 
different  tensions.  When  placed  in  these  fluids,  the  metals  lying  next  the  -)-  end  of  the  above  series, 
especially  zinc,  are  most  strongly  electrified  negatively,  and  to  a  less  extent  those  lying  nearer  the 
—  end  of  the  series. 

3.  Galvanic  Battery. — If  two  different  exciters  of  the  first  class  be  placed  in  fluid  without  the 
bodies  coming  into  contact,  e.g.,  zinc  and  copper,  the  projecting  end  of  the  (negative)  zinc  shows 
free  negative  electricity,  while  the  free  end  of  the  (positive)  copper  shows  free  positive  electricity. 
.Such  a  combination  of  two  electromotors  of  the  first  class  with  an  electromotor  of  the  second  class 
is  called  ^galvanic  battery.  As  long  as  the  two  metals  in  this  fluid  are  kept  separate  the  circuit  is 
said  to  be  open,  but  as  soon  as  the  free  projecting  ends  of  the  metals  are  connected  outside  the  fluid, 
e.  g.,  by  a  copper  wire,  the  circuit  or  current  is  closed,  and  a  galvanic  or  constant  current  of  elec 
tricity  is  obtained.  The  galvanic  current  has  resistance  to  encounter  in  its  course,  which  is  called 
"  conduction  resistance'  (Vi).  It  is  directly  proportional — (I)  to  the  length  (/)  of  the  circuit ;  (2), 
and  with  the  same  length  of  circuit,  inversely  as  the  section  (</)  of  the  same  ;  and  (3)  it  also  de- 
pends on  the  molecular  properties  of  the  conducting  material  [specific  conduction  resistance  ^=  s),. 
so  that  the  conduction  resistance,  W  ^  (  .r.  /) :  q.  The  resistance  to  conduction  increases  with  the 
increase  of  the  temperature  of  the  metals,  but  diminishes  under  similar  conditions  with  fluids. 

Ohm's    Law. —  The  strength   of  a  galvanic  current   (S),  or  the   amount  of  electricity  passing 
through  the  closed  circuit,  is  proportional  to  the  electro-motive  force  (E) — or  the  electrical  tension,., 
but  inversely  proportional  to  the  total  resistance  to  conduction  (L) — 
So  that  S  =  E  :   L  (Ohm's  Law,  1827). 

The  total  resistance  to  conduction,  however,  in  a  closed  circuit  is  composed  of — (l)  the  resist- 
ance outside  the  battery  ("  extraordinary  resistance") ;  and  (2)  the  resistance  within  the  battery 
itself  ("  essential  resistance  ").  The  specific  resistance  to  conduction  is  very  variable  in  different 
substances ;  it  is  relatively  small  in  metals  [e.  g.,  for  copper  :=  i,  iron  ^  6.4,  German  silver  ^  12), 
but  very  great  in  fluids  (e.g.,  for  a  concentrated  solution  of  common  salt  6,515,000,  for  a  concen- 
trated solution  of  copper  sulphate  10,963,600).  It  is  also  very  great  in  animal  tissues,  almost  a 
million  times  greater  than  in  metals.  When  a  constant  current  is  applied  to  the  skin  so  as  to  traverse 
the  body,  the  resistance  diminishes  because  of  the  conduction  of  water  in  the  epidermis  under  the 
action  of  the  constant  current  ({j  290),  and  the  congestion  of  the  cutaneous  blood  vessels  in  conse- 
quence of  the  stimulation.  But  the  resistance  varies  in  diflerent  parts  of  the  skin,  the  least  being 
in  the  palm  of  the  hand  and  sole  of  the  foot.  The  chief  seat  of  the  resistance  is  the  epidermis, 
but  after  its  removal,  as  by  a  blister,  it  is  greatly  diminished.  Dead  tissue,  as  a  rule,  is  a  worse 
conductor  than  living  tissues  {Jolly).  When  the  current  is  passed  transversely  to  the  direction  of 
the  fibres  of  a  muscle,  the  resistance  is  nearly  nine  limes  as  great  as  when  the  current  passes  in  the 
direction  of  the  fibres  (Hermann) — a  condition  which  disappears  in  rigor  mollis.  In  nerves  the 
resistance  longilu<iinally  is  two  and  a  half  million  times  greater  than  in  mercury,  transversely  about 
twelve  million  limes  (Hermann).  Tetanus  and  rigor  mortis  (Du  Bois-Reymond)  diminish  the  re- 
sistance in  muscle. 

Deductions. — It  follows  from  Ohm's  law  that — I.  If  there  is  very  great  resistance  to  the  current 
outside  the  battery  \_i.  e.,  between  the  electrodes],  as  in  the  case  when  a  nerve  or  a  muscle  lies  on 
the  electrodes,  the  strength  of  the  current  can  only  be  increased  by  increasing  the  number  of  the 
eleclro-moiive  elements.     II.  When,  however,  the  extraordinary  resistance  is  very  small  compared 

37 


578       ACTION    OF    GALVANIC    CURRENT    ON    A    MAGNETIC    NEEDLE. 


with  that  within  the  battery  itself,  the  strength  of  the  current  cannot  be  increased  by  increasing  the 
number  of  the  elements,  but  only  by  increasing  the  surfaces  of  the  plates  in  the  battery. 

Strength  and  Density. — We  must  carefully  distinguish  the  strength  (intensity)  of  the  current 
from  its  density.  As  the  same  amount  of  electricity  always  flows  through  any  given  transverse  sec- 
tion of  the  circuit,  then,  if  the  size  of  the  transverse  section  of  the  circuit  varies,  the  electricity  must 
be  of  greater  density  in  the  narrower  parts,  and  it  is  evident  that  the  density  will  be  less  where  the 
transverse  section  is  greater.  Let  S  =  the  strength  of  the  current,  and  q  the  transverse  section  of 
the  given  part  of  the  circuit,  then  the  density  (</)  at  the  latter  part  is  (/^  S  :  y. 

If  the  galvanic  current  passing  from  the  positive  pole  of  a  battery  be  divided  into  two  or  more 
streams,  which  are  again  reunited  at  the  other  pole,  then  the  sum  of  the  strength  of  all  the  streams 
is  equal  to  the  strength  of  the  undivided  stream.  If,  however,  the  different  streams  are  different  as 
regards  length,  section  and  material,  then  the  strength  of  the  current  passing  in  each  of  the  streams 
is  inversely  proportional  to  the  resistance  to  the  conduction. 

Du  Bois-Reymond's  Rheocord. — Tliis  instrument,  constructed  on  the  principle  of  the  "  second- 
ary "  or  "  short  circuit,"  enables  us  to  graduate  the  strength  of  a  galvanic  current  to  any  required 
degree,  for  the  stimulation  ot  nerve  and  muscle.  From  the 
two  poles  (Fig.  344,  a,  b)  of  a  constant  battery  there  are  two 
conducting  wires  (a,  e  and  </,  /<),  which  go  to  the  nerve  of  a 
frog's  nerve-muscle  preparation  (F).  The  portion  of  nerve 
((-,  a)  introduced  into  this  circuit  (a,  c,  d,  b)  oilers  very  great 
resistance.  The  second  stream  or  secondary  circuit  (a  A, 
b  B),  conducted  from  a  and  b,  passes  through  a  thick  brass 
plate  (.•\,  B),  consisting  of  seven  pieces  ot  brass  (i  to  7) 
placed  end  to  end,  but  not  in  contact.  They  can  all,  with 
the  exception  of  I  and  2,  be  made  to  form  a  continuous  con- 
ductor by  placing  in  the  spaces  between  them  the  brass 
plugs  (Sj  to  S,).  Evidently,  with  the  arrangement  shown 
in  Fig.  344,  only  a  minimal  part  of  the  current  will  pass 
through  the  nerve  (e,  d)  owing  to  the  very  great  resistance 
in  it,  while  by  far  the  greatest  part  will  pass  through  the 
good  conducting  medium  of  brass  (A,  L,  B).  If  new 
resistance  be  introduced  into  this  circuit,  then  the  a,  c,  d,  b 
stream  will  be  strengthened.  This  resistance  can  be  intro- 
duced into  the  latter  circuit  by  means  of  the  thin  wires 
marked  1  a,  I  b,  I  <-,  II,  V,  X.  Suppo.se  all  the  brass  plugs 
from  bj  to  S5  to  be  removed,  then  the  cuirent  entering  at  A 
must  traver.-e  the  whole  system  of  thin  wires.  Thus,  there 
IS  more  resistance  to  the  passage  of  this  current,  so  that  the 
current  through  the  nerve  must  be  strengthened.  If  only 
one  brass  plug  be  taken  out,  then  the  current  passes  through 
only  the  corresponding  length  of  wire.  The  resistances 
olfered  by  the  different  lengths  of  wire  from  1  rt  to  X  are  so 
arranged  that  I  a^  I  /'and  1  e  each  represent  a  unit  of  resist- 
ance ;  11,  double;  V,  five  times;  and  X,  ten  times  the 
resistance.  The  length  of  wire,  I  a,  can  also  be  shortened 
by  the  movable  bridge  (L)  [composed  of  a  small  tube  filled 
with  mercury,  througti  which  the  wires  pass],  the  scale  [x^y) 
indicating  the  length  ot  the  resistance  wires.  It  is  evident 
that,  by  means  of  the  bridge  and  by  the  method  of  using  the 
brass  plugs,  the  apparatus  can  be  graduated  to  yield  very 
variable  currents  for  stimulating  nerve  or  muscle.  When  the  bridge  (L)  is  pushed  hard  up  to  1,2, 
the  current  passes  directly  from  A  to  B,  and  not  through  the  thin  wires  (I  a). 

The  rheostat  is  another  instrument  used  to  vary  the  resistance  of  a  galvanic  current  (  Whea/stone). 

327.  ACTION  OF  THE  GALVANIC  CURRENT  ON  A  MAGNETIC  NEEDLE 
— THE  GALVANOMETER.— In  1820  Oerstedt,  of  Copenhagen,  found  that  a  magnetic 
needle  suspended  in  the  magnetic  meridian  was  deflected  by  a  constant  current  of  electricity  passed 
along  a  wire  parallel  to  it.  [  I'he  side  to  which  the  north  pole  is  deflected  depends  upon  the 
direction  of  the  current,  and  whether  it  passes  above  or  below  the  needle.] 

Ampi^re's  Rule. — .-Xmpire  has  given  a  simple  rule  for  determining  the  direction.  If  an  observer 
be  placed  parallel  to  and  facing  the  needle,  and  if  the  current  be  passing  from  his  feet  to  his  head, 
then  the  north  pole  of  the  needle  will  always  be  deflected  to  the  left,  and  the  south  pole  in  the 
opposite  direction.  The  effect  exerted  by  the  constant  current  acts  always  in  a  direction  toward 
the  so-called  electro-magnetic  plane.  The  latter  is  the  plane  passing  through  the  north  pole  of  the 
needle,  and  two  points  in  the  straight  wire  running  parallel  with  the  needle.  The  force  of  the  con- 
stant current,  which  causes  the  deflection  of  the  magnetic  needle,  is  proportional  to  the  sine  of  the 
angle  between  the  electro  magnetic  plane  and  the  plane  of  vibration  of  the  needle. 


ELECTROLYSIS,   POLARIZATION,   BATTERIES.  679 

Multiplicator  [or  Multiplier], — The  deflection  of  the  needle  caused  by  the  constant  current 
may  be  increased  by  coiling  the  conducting  wire  many  times  in  the  same  direction  on  a  rectangular 
frame,  or  merely  around  and  in  the  same  direction  as  the  needle  [provided  that  each  turn  of  the 
wire  be  properly  insulated  from  the  other].  An  instrument  constructed  on  this  principle  is  called  a 
niiillipiier.  The  greater  the  number  of  turns  of  the  wire  the  greater  is  the  angle  of  deflection  of  the 
needle,  although  the  deflection  is  not  directly  proportional,  as  the  several  turns  or  coils  are  not  at 
the  same  distance  from,  or  in  the  same  position  as,  the  needle.  By  means  of  the  multiplier  we  may 
detect  the  presence  [and  also  the  amount  and  direction]  o\  feeble  currents  [The  instrument  is 
now  termed  a  Galvanometer].  Experience  has  shown  that,  when  great  resistance  (as  in  animal 
tissues)  is  opposed  to  the  weak  galvanic  currents,  we  must  use  a  very  large  number  of  turns  of  thin 
wire  round  the  needle.  If,  however,  the  resistance  in  the  circuit  is  but  small,  e.s;.,  in  thermo- 
electrical  arrangement-,  a  few  turns  of  a  thiek  wire  round  the  needle  are  sufficient.  I'he  multiplier 
may  be  made  more  sensitive  by  iveakening  ihe  magnetie  direetive  force  of  the  needle^  which  keeps 
it  pointing  to  the  north. 

Galvanometer  and  Astatic  Needles. — In  the  multiplier  of  Schweigger,  used  for  phy.siological 
purposes,  the  tendency  of  the  needle  to  point  to  the  north  is  greatly  weakened  by  using  the  astatic 
needles  of  Nobili.  [A  multiplier  or  galvanometer  with  a  single  magnetic  needle  always  requires 
comparatively  strong  currents  to  deflect  the  needle.  The  needle  is  continually  acted  upon  by 
the  directive  magnetic  influence  of  the  earth,  which  tends  to  keep  it  in  the  magnetic  meridian,  and 
as  soon  as  it  is  moved  out  of  the  magnetic  meridian  the  directive  action  of  the  earth  tends  to  bring 
it  back.  Hence,  such  a  simple  form  of  galvanometer  is  not  sufficiently  sensitive  for  detecting  feeble 
currents.  In  1827  Nobili  devised  an  astatic  combination  of  needles,  whereby  the  action  of  the 
earth's  magnetism  was  diminished.]  Two  similar  magnetic  needles  are  united  by  a  solid  light 
piece  of  horn  [or  tortoise  shell],  and  are  so  arranged  that  the  north  pole  of  the  one  is  placed  over 
or  opposite  to  the  south  pole  of  the  other  (Fig.  345).  [If  both  needles  are  equally  magnetized, 
then  the  earth's  influence  on  the  needle  is  neutralized,  so  that  the  needles  no  longer  adjust  them- 
selves in  the  magnetic  meridian  ;  hence,  such  a  system  is  called  astatic]  As  it  is  impossible  to 
make  both  needles  of  absolutely  equal  magnetic  strength,  one  needle  is  always  stronger  than  the 
other.  The  difference,  however,  must  not  be  so  great  that  the  stronger  needle  poims  to  the  north, 
liut  only  that  the  freely  .suspended  system  of  needles  forms  a  certain  angle  with  the  magnetic  meri- 
dian, into  which  position  the  system  alwajs  swings  after  it  is  deflected  from  this  position.  This 
angular  deviation  of  the  astatic  system  toward  the  magnetic  meridian  is  called  the  "  free  deviation." 
The  more  perfectly  an  astatic  condition  is  reached,  the  nearer  the  angle  formed  by  the  direction  of 
the  free  deviation  with  the  magnetic  meridian  becomes  a  right  angle.  The  greater,  therefore,  the 
astatic  condition,  the  astatic  system  will  make  the  fewer  vibrations  in  a  given  tmie,  after  it  has  been 
deflected  from  its  position.  The  duration  of  each  single  vibration  is  also  very  great.  [Hence, 
when  using  a  galvanometer,  and  adjusting  its  needle  to  zero,  if  the  magnets  dance  about  or  move 
quickly,  then  the  system  is  not  sensitive,  but  a  sensitive  condition  of  the  needles  is  indicated  by  a 
slo-tu  period  of  oscillation.] 

In  making  a  galvanometer,  the  turns  of  the  wire  must  have  the  same  direction  as  the  needles. 
In  Nobih's  galvanometer,  as  improved  by  Du  Bois-Reymond,  the  upper  needle  swings  above  a  card 
divided  into  degrees  (Fig.  345),  on  which  the  extent  of  its  deflection  may  be  read  off.  Even  the 
purest  copper  wire  used  for  the  coils  round  the  needles  always  contains  a  trace  of  iron,  which  exerts 
an  influence  upon  the  needles.  Hence,  a  small  fixed  directive  or  compensatory  magnet  {r)  is 
placed  near  one  of  the  j^oles  of  the  upper  needle  to  compensate  for  the  action  of  the  iron  on  the 
needles. 

328.     ELECTROLYSIS,     POLARIZATION,     BATTERIES.— Electrolysis.— Every 

galvanic  current  which  traverses  a  fluid  conductor  causes  decomposition  or  electrolysis  of  the  fluid. 
The  decomposition  products,  called  ions,  accumulate  at  the  poles  (electrodes)  in  the  fluid,  the 
positive  pole  (  -f-  )  being  called  the  anode  ['■<'■"■<,  up,  'j'W;',  a  way],  the  negative  pole  (  — )  the 
cathode  (x«r«,  down,  "'Tuf,  a  way).  The  anions  accumulate  at  the  anode  and  the  kations  at 
the  cathode. 

Transition  Resistance. — When  the  decomposition  products  accumulate  upon  the  electrodes, 
by  their  presence  they  either  increase  or  diminish  the  resistance  to  the  electrical  current.  This  is 
called  transition  resistance.  If  the  resistance  within  the  battery  is  thereby  increased,  the  transition 
resistance  is  said  to  be  positive  ;  if  d'minished,  negative. 

Galvanic  Polarization. — The  ions  accumulated  on  the  electrodes  may  also  vary  the  strength 
of  the  current,  by  developing  between  the  anions  and  kations  a  new  galvanic  current,  just  as  occurs 
between  two  different  bodies  connected  by  a  fluid  medium.  This  phenomenon  is  called  galvanic 
polarization.  Thus,  when  water  is  decomposed,  the  electrodes  being  of  platinum,  the  o.xygen 
(negative)  accumulates  at  the  -f-  pole,  and  the  hydrogen  (positive)  at  the  —  pole.  Usually,  the 
polarization  current  has  a  direction  opposite  to  the  original  current;  hence  we  speak  of  wc.^'tf/jw 
polarization.  When  the  two  currents  have  the  same  direction,  positive  polarization  obtains.  Of 
course,  transition  resistance  and  polarization  may  occur  together  during  electrolysis. 

Test. —  Polarization,  when  present,  may  be  so  slight  as  not  to  be  visible  to  the  eye,  but  it  may  be 
tletected  tlius :  .\fter  a  time,  exclude  the  primary  source  of  the  current,  especially  the  element  con- 


580 


CONSTANT   BATTERIES,  ELEMENTS,  OR   CELLS. 


nected  with  the  electrodes,  and  place  the  free  projecting  end  of  the  electrodes  in  connection  with 
a  galvanometer,  which  will  at  once  indicate,  by  the  deflection  of  its  needle,  the  presence  of  even 
the  slightest  polarization. 

Secondary  Decompositions. — The  ions  excreted  during  electrolysis  cause,  especially  at  their 
moment  of  fonuation,  secondary  decompositions.  With  platinum  electrodes  in  a  solution  of  common 
salt,  chlorine  accumulates  at  the  anode  and  sodium  at  the  cathode ;  but  the  latter  at  once  decom- 
poses the  water,  and  uses  the  oxygen  of  the  water  to  oxidize  itself,  while  the  hydrogen  is  deposited 
secondarily  upon  the  cathode.  The  amount  of  polarization  increases,  although  only  to  a  slight 
extent,  with  the  strength  of  the  eurrent,  while  it  is  nearly  proportional  to  the  increase  of  the  tem- 
perature. The  attempts  to  get  rid  of  polarization,  which,  obviously,  must  very  soon  alter  the  strength 
of  the  galvanic  current,  have  led  to  the  discovery  of  two  important  arrangements,  viz.,  to  the  con- 
struction of  constant  galvanic  batteries  [Becguerel),  and  the  so-called  non-polarizable  elec- 
trodes (Dii  Bois-Kev'iion,/). 

Constant  Batteries,  Elements,  or  Cells. — A  perfectly  constant  element  produces  a  constant 
current,  i.  e.,  one  remaining  of  equal  strength,  by  the  ions  produced  by  the  electrodes  being  got  rid 
of  the  moment  they  are  formed,  so  that  they  cannot  give  rise  to  polarization.     For  this  purpose  each 


Fig.  345. 


Scheme  of  the  galvanometer.  N.  N.  astatic  needles  sus- 
pended by  the  silk  tibre,  G ;  P,  P,  non-polarizable  elec- 
trodes, containing  zinc-sulphate  solution,  s,  and  pads  of 
blotting  paper,  b,  covered  with  clay,  t,  t,  on  which  the 
muscle,  M,  is  placed  ;  II,  III,  arrangements  of  the  mus- 
cle on  the  electrode ;  IV,  non-polarizable  electrodes  ;  Z, 
zinc  wire  ;  K,  cork  ;  a,  zinc-sulphate  solution  ;  t^  t,  clay 


Fig.  346. 


of  the  substances  from  the  tension  series  used  is  placed  in  a  special  fluid  (J  326),  both  fluids  being 
separated  by  a  porous  septum  (porcelam  cylinder). 

Grove's  Element  has  two  metals  and  two  fluids  (Fig.  346).  The  zinc  is  in  the  form  of  a  roll 
placed  in  dilute  sulphuric  acid  [i  acid  to  7  of  water,  which  is  contained  in  a  glass,  porcelain  or 
ebonite  vessel].  The  platinum  is  in  contact  with  strong  nitric  acid  [which  is  contained  in  a  porous 
cell  placed  inside  the  roll  of  zinc].  The  O,  formed  by  the  electrolysis  and  deposited  on  the  zinc 
plate,  forms  zinc  oxide,  which  is  at  once  dissolved  by  the  sulphuric  acid.  The  hydrogen  on  the 
platinum  unites  at  once  with  the  nitric  acid,  which  gives  up  O  and  forms  nitrous  acid  and  water  thus — 
[H2  +  HNO3  =-  HNO,  +  HjO.] 
[Platinuiu  is  the  -|-  pole,  and  zinc  the  — .] 

[Grove's  battery  is  very  powerful,  but  the  nitrous  fumes  are  very  disagreeable  and  irritating; 
hence  these  elements  should  be  kept  in  a  special,  well-ventilated  recess  in  the  laboratory,  in  an  evap- 
orating chamber,  or  under  glass.     The  fumes  also  attack  instruments.] 

Bunsen's  Element  is  quite  similar  to  Grove's,  only  a  piece  of  compressed  carbon  is  substituted 
for  the  platinum  in  contact  with  the  nitric  acid. 

[The  carbon  is  the  -f-  pole,  the  zinc  the  — .] 


DANIELL,  SMEE,  GRENNET   AND    LECLANCHE  S    ELEMENTS. 


581 


[Daniell's  Element  (1836).— It  consists  of  an  outer  vessel  or  glass  of  earthenware,  and  some- 
times of  metallic  copper,  filled  with  a  saturated  solution  of  cupric  sulphate.  A  roll  of  copper,  per- 
forated with  a  few  holes,  is  placed  in  the  copper  solution,  and  in  order  that  the  latter  be  kept  satu- 
rated, and  to  supply  the  place  of  the  copper  used  up  by  the  battery  when  in  action,  there  is  a  small 
shelf  on  the  copper  roll,  on  which  are  placed  crystals  of  cupric  sulphate.  A  porous  earthenware 
vessel  containing  zinc  in  contact  with  dilute  sulphuric  acid  (i  :  7)  is  placed  within  the  copper 
cylinder.  When  the  circuit  is  completed,  the  zinc  is  acted  on,  zinc  sulphate  being  formed,  and 
hydrogen  liberated.  The  hydrogen  in  statu  nascendi  passes  through  the  porous  cell,  reduces  the 
cupric  sulphate  to  metallic  copper,  which  is  precipitated  on  the  copper  cylinder,  so  that  the  latter  is 
always  kept  bright  and  clean.  The  liberated  sulphuric  acid  replaces  that  in  contact  with  the  zinc. 
Owing  to  the  absence  of  polarization,  the  Daniell  is  one  of  the  most  constant  batteries,  and  is  gen- 
erally taken  as  the  standard  of  comparison.] 

[The  copper  is  the  -]-  pole,  zinc  the  — .] 


Fig.  348. 


yi'.    347. 


Grennet's  element.  A,  the  glass  vessel;  K, 
K,  carbon  ;  Z,  zinc  ;  D,  E,  binding  screw 
for  the  wires ;  B,  rod  to  raise  or  depress 
the  zinc  in  the  fluid  ;  C,  screw  to  fix  B. 


[Smee's  Element. — There  is  only  one  fluid,  viz.,  dilute  sulphuric  acid  (1:7),  in  which  the 
two  metals,  zinc  and  platinum,  or  zinc  and  platinized  silver,  are  placed. 
The  platinum  is  the  +  pole,  and  zinc  the  — .] 

[Grennet's  or  the  Bichromate  Element. — It  consists  of  one  plate  of  zinc  and  two  plates 
of  compressed  carbon  in  a  fluid,  which  consists  of  bichromate  of  potash,  sulphuric  acid,  and 
water.  The  fluid  consists  of  i  part  of  potassium  bichromate  dissolved  in  8  parts  of  water,  to  which 
I  part  of  sulphuric  acid  is  added.  Measure  by  wetg/if.]  [The  cell  consists  of  a  wide-mouthed 
glass  bottle  (Fig.  347)  ;  the  carbons  remain  in  the  fluid,  while  the  zinc  can  be  raised  or  depressed. 
When  not  in  action,  the  zinc,  which  is  attached  to  a  rod  (B),  is  lifted  out  of  the  fluid,  and  hence 
this  battery  is  very  convenient  for  purposes  of  demonstration,  although  it  is  not  a  very  constant 
battery.  When  in  action,  the  zinc  is  acted  on  by  the  sulphuric  acid,  hydrogen  being  liberated, 
which  reduces  the  bichromate  of  potash. 

The  carbon  is  the  +  jiole,  and  the  zinc  the  — .] 

[Leclanche's  Element  (Fig.  348)  consists  of  an  outer  glass  vessel  containing  zinc  in  a  solution 
of  ammonium  chloride,  while  the  porous  cell  contains  compressed  carbon  in  a  fluid  mixture  of  black 


582  REFLECTING    GALVANOMETER    AND    SHUNT. 

oxide  of  manganese  and  carbon.     It  is  most  frequently  used  for  electric  bells,  as  its  feeble  current 
lasts  for  a  long  time. 

The  carbon  is  the  -\-  pole,  and  the  zinc  the  — .] 

Non-polarizable  Electrodes. — If  a  constant  current  be  applied  to  moist  animal  tissues,  ^. .f., 
nerve  or  muscle,  by  means  of  ordinary  electrodes  composed  either  of  copper  or  platinum,  of  course 
electrolysis  must  occur,  and  in  consequence  thereof  polarization  t.akes  place.  In  order  to  avoid 
this,  non-polarizable  electrodes  (Figs.  345  and  349)  are  used.  The  researches  of  Regnault,  Mat- 
leucci  and  Du  Bois-Reymond  have  proved  that  such  electrodes  can  be  made  by  taking  two  pieces 
of  carefully  amalgamated  pure  zinc  wire  (z,  s),and  dipping  these  in  a  saturated  solution  of  zinc 
sulphate  contained  in  tubes  [a,  a],  their  lovi'er  ends  being  closed  by  means  of  modeller's  clay  {/,/), 
moistened  with  0.6  per  cent,  normal  saline  solution.  The  contact  of  the  tissues  with  these  elec- 
trodes does  not  give  rise  to  polarity. 

Arrangement  for  the  Muscle  or  Nerve  Current. — In  order  to  investigate  the  electrical  cur- 
rents of  nerve  or  muscle,  the  tissue  must  be  placed  on  non-polarizable  electrodes,  which  may  either 
have  the  form  described  above,  or  the  original  form  used  by  Du  Bois-Reymond  (Fig.  345 1.  The 
last  consists  of  two  zinc  troughs  (/,/>)  thoroughly  amalgamated  inside,  insulated  on  vulcanite,  and 
filled  with  a  saturated  solution  of  zinc  sulphate  {s,  s).  In  each  trough  is  placed  a  thick  pad  or 
cushion  of  white  blotting  paper  (/',  />)  saturated  with  the  same  fluid  [deriving  cushions].  [The 
cushion  consists  of  many  layers,  almost  suflScient  to  fill  the  trough,  and  they  are  kept  together  by  a 
thread.  To  prevent  the  action  of  the  zinc  sulphate  upon  the  tissue,  each  cushion  is  covered  with  a 
thin  layer  of  modeller's  clay  (/,  /),  moistened  with  c.6  per  cent,  saline  solution,  which  is  a  good 
conductor  [clay  guard].  The  clay  guard  prevents  the  action  of  the  solution  upon  the  tissue. 
Connected  with  the  electrodes  are  a  pair  of  binding  screws,  whereby  the  apparatus  is  connected 
with  the  galvanometer  (Fig.  345).] 

Fig.  349. 


Non-polariz,ible  electrode  of  Du  Bois  Reymond.     Z,  zinc  ;   H.  mov;iblc  support ;  C,  clay  point — ihe 
whole  on  a  universal  joint. 

[Reflecting  Galvanometer. — The  form  of  galvanometer  now  used  in  this  country-  for  physio- 
logical purposes  is  that  of  Sir  William  Thomson  (Fig.  350I.  In  Germany,  Wiedemann's  form  is 
more  commonly  used.  In  Thomson's  instrument  the  astatic  needles  are  very  light,  and  connected 
to  each  other  by  a  piece  of  aluminum,  and  each  set  of  needles  is  suirounded  by  a  separate  coil  of 
wire,  the  lower  coil  (/)  winding  in  a  direction  opposite  to  that  of  the  upper  {»).  A  small,  round, 
light,  slightly  concave  mirror  is  fixed  to  the  upper  set  of  needles.  The  needles  are  suspended  by 
a  delicate  silk  fibril,  and  they  can  be  raised  or  lowered  as  required  by  means  of  a  small  milled  head. 
When  the  milled  head  is  raised  the  .system  of  needles  swings  freely.  The  coils  are  protected  by  a 
glass  shade,  and  the  whole  stands  on  a  vulcanite  base,  which  is  levelled  by  three  screws  (s,  s).  On 
a  brass  rod  (/<)  is  a  feeble  magnet  {m),  which  is  used  to  give  an  artificial  meridian.  The  magnet 
[m)  can  be  raised  or  lowered  by  means  of  a  milled  head.] 

[Lamp  and  Scale. — When  the  instrument  is  to  be  used,  place  it  so  that  the  coils  face  east  and 
west.  At  3  feet  distant  from  the  front  of  the  galvanometer,  facing  west,  is  placed  the  lamp  and 
scale  (Fig.  351).  There  is  a  .small  vertical  slit  in  front  of  the  lamp,  and  the  image  of  this  slit  is 
projected  on  the  mirror  attached  to  the  upper  needles,  and  by  it  is  reflected  on  to  the  paper  scale 
fixed  just  above  the  slit.  The  spot  of  light  is  focused  at  zero  by  means  of  the  magnet  m.  The 
needles  are  most  sensitive  when  the  oscillations  occur  slowly.  The  sensitiveness  of  the  needles 
can  be  regulated  by  means  of  the  magnet.  In  every  case  the  instrument  must  be  quite  level,  and 
for  this  puqMse  there  is  a  small  spirit  level  in  the  base  of  the  galvanometer.] 

[Shunt. — As  the  galvanometer  is  very  delicate,  it  is  convenient  to  have  a  shunt  to  regulate  to  a 
certain  extent  the  amount  of  electricity  transmitted  through  the  galvanometer.  The  shunt  (Fig. 
352)  consists  of  a  brass  box  containing  coils  of  German  silver  wire,  and  is  constructed  on  the  same 
principle  as  resistance  coils  or  the  rheocord  (§  326).     On  the  upper  surface  of  the  box  are  several 


POLARIZATION    AND    SECONDARY    RESISTANCE. 


583 


plates  of  brass  separaled  from  each  other,  like  those  of  the  rheocord,  but  which  can  be  united  liy 
brass  plugs.  The  two  wires  coming  from  the  electrodes  are  connected  with  the  two  binding  screws, 
and  from  the  latter  two  wires  are  led  to  the  outer  two  binding  screws  of  the  galvanometer.  15y 
placing  a  plug  between  the  brass  plates  attached  to  the  two  binding  screws  in  the  figure,  the  current 
is  short  circuited.  On  removing  both  plugs  the  whole  of  the  current  must  pass  through  the  galva- 
nometer. If  one  plug  be  placed  between  the  central  disk  of  brass  and  the  plate  marked  \  (the  other 
being  left  out),  then  yj  of  the  current  goes  through  the  galvanometer  and  /^  to  the  electrodes. 
If  the  plug  be  placed  as  shown  in  the  figure  opposite  j'j,  then  yjj,  part  of  the  current  goes  to  the 
galvanometer,  while  ^'j,',,  are  short  circuited.  If  the  plug  be  placed  opposite  -^\^,  only  t^jj^ 
part  goes  through  the  galvanometer. ]- 

Internal  Polarization  of  Moist  Bodies. — Nerves  and  muscular  fibres,  the  juicy  parts  of 
vegetables  and  anmials,  fibrin  and  other  similar  bodies  possessing  a  porous  structure  filled  with 
fluid,  exhibit  the  phenomena  of  polarization  when  subjected  to  strong  currents — a  condition  termed 
ii.ternal  polarization  of  moist  bodies  by  Du  Bois-Reymond.     It  is  assumed  that  the  solid  paits  in 


Fig.  ^50. 


Fig.  351 


Brothers). 


the  interior  of  these  bodies,  which  are  better  conductors,  produce  electrolys's  of  th»  adjoining  fluid, 
just  like  metals  in  contact  with  fluid.  The  ions  produced  by  the  decompo'^ition  of  the  internal 
fluids  give  rise  to  differences  of  potential,  and  thus  cause  internal  polarization  [\  333). 

Cataphoric  Action. — If  the  two  electrodes  from  a  galvanic  battery  be  placed  in  the  two  com- 
partments of  a  fluid,  separated  from  each  other  by  a  porous  septum,  we  observe  that  the  fluid  par- 
ticles pass  in  the  direction  of  the  galvanic  current,  from  the  +  to  the  —  pole,  so  that  after  some 
time  the  fluid  in  the  one-half  of  the  vessel  increases,  while  it  diminishes  in  the  other.  The  phe- 
nomena of  direct  transference  was  called  by  Du  Bois-Reymond  the  cataplioric  action  of  the  con- 
stant current.  The  introduction  of  dissolved  substances  through  the  skin  by  means  of  a  constant 
current  depends  upon  this  action  (^  290),  and  so  does  the  so-called  Porret's  phenomenon  in 
living  muscle  1  \  293.  I,  h\. 

External  Secondary  Resistance; — This  condition  also  depends  on  cataphoric  action.  If  each 
of  the  copper  electrodes  of  a  constant  battery  be  placed  in  a  vessel  filled  with  a  solution  of  cupric 
sulphate,  and  from  each  of  which  there  projects  a  cushion  saturated  with  this  fluid,  then,  on  placing 


584  INDUCED  OR  FARADIC  ELECTRICITY. 

a  piece  of  muscle,  cartilage,  vegetable  tissue,  or  even  a  prismatic  strip  of  coagulated  albumin  across 
these  cushions,  we  observe  that,  very  soon  after  the  circuit  is  closed,  there  is  a  considerable  varia- 
tion of  the  current.  If  the  direction  of  the  current  be  reversed,  it  lirst  becomes  stronger,  hut  after- 
ward diminishes.  By  constantly  altering  the  direction  of  the  current  we  cause  the  same  changes  in 
the  intensity.  If  a  prismatic  strip  of  coagulated  albumin  is  used  for  the  experiment,  we  oliserve 
that,  simultaneously  with  the  enfeeblement  of  the  current  in  the  neighborhood  of  the  -f-  pole,  the 
albumin  loses  water  and  becomes  more  shrivelled,  while  at  the  —  pole  the  albumin  is  swollen  up 
and  contains  more  water.  If  the  direction  of  the  current  be  altered,  the  phenomena  are  also 
changed.  The  shrivelling  and  removal  of  water  in  the  albumin  at  the  positive  pole  must  he  the 
cause  of  the  resistance  in  the  circuit,  which  explains  the  enfeeblement  of  the  galvanic  cuirent. 
This  phenomenon  is  called  "external  secondary  resistance"  (Dii  Bois-Reymond). 

329.  INDUCTION-EXTRA  CURRENT— UNIPOLAR  INDUCTION  ACTION 
—MAGNETIC  INDUCTION.— Induction  of  the  Extra  Current.— If  a  galvanic  element 
is  closed  by  means  of  a  short  arc  of  wire,  at  the  moment  tlie  circuit  is  again  opened  or  l)roken  a 
sliglil  spark  is  observed.  If,  however,  the  circuit  is  closed  by  means  of  a  very  long  wire  rolled  in  a 
coil,  then  on  breaking  the  circuit  there  is  a  strong  spark.  If  the  wires  be  connected  with  two  elec- 
trodes, so  that  a  person  can  hold  one  in  each  hand,  so  that  the  current  at  the  moment  it  is  opened 
must  pass  through  the  person's  body,  then  there  is  a  violent  shock  communicated  to  the  hand.  This 
phenomenon  is  due  to  a  current  induced  in  the  long  spiral  of  wire,  which  Faraday  called  the  extra 
current.  It  is  caused  thus  :  When  the  circuit  is  closed  by  means  of  the  spiral  wire,  the  galvanic 
current  passing  along  it  excites  an  electric  current  in  the  adjoining  coils  of  the  same  spiral.  At  the 
moment  of  closing  or  making  the  circuit  in  the  spiral,  the  induced  current  is  in  the  opposite  direc- 
tion to  the  galvanic  current  in  the  circuit  ;  hence  its  strength  is  lessened,  and  it  causes  no  shock. 
At  the  moment  of  opening,  however,  the  induced  current  has  the  fame  direction  as  the  galvanic 
stream,  and  hence  its  action  is  strengthened. 

Magnetization  of  Iron — If  a  rod  of  soft  iron  be  placed  in  the  cavity  of  a  spiral  of  copper 
wire,  then  the  soft  iron  remains  magnetic  as  long  as  a  galvanic  current  circulates  in  the  spiral.  If 
one  end  of  the  iron  rod  be  directed  toward  the  observer,  the  other  away  from  him,  and  if,  further, 
the  positive  current  traverses  the  spiral  in  the  same  direction  as  the  hands  of  a  clock,  then  the 
end  of  the  magnet  directed  toward  the  person  is  the  negative  pole  of  the  magnet.  The  power 
of  the  magnet  depends  upon  the  number  of  spiral  windings  and  on  tlie  thickness  of  the  iron  bar. 
.•\s  soon  as  tlie  curreiit  is  opened,  the  magnetism  of  the  iron  rod  disappears. 

Induced  or  Faradic  Current. — If  a  very  long,  insulated  wire  be  coiled  into  the  form  of  a  spiral 
roll,  which  we  may  call  the  secondary  spiral,  and  if  a  similar  spiral,  the  primary  spiral,  be 
placed  near  the  former,  and  the  ends  of  the  wire  of  the  primary  spiral  be  connected  with  the  poles 
of  a  constant  battery,  every  time  the  current  in  the  primary  circuit  is  made  (closed),  or  broken 
(opened),  a  current  takes  place,  or,  as  it  is  said,  is  induced  in  the  secondary  spiral.  If  the  primary 
circuit  be  kept  closed,  and  if  the  secondary  spiral  be  brought  nearer  to,  or  removed  further  from,  the 
primary  spiral,  a  current  is  also  induced  in  the  secondary  spiral  (Faraday,  1832).  The  current  in 
the  secondary  circuit  is  called  the  induced  or  Faradic  current.  When  the  primary  circuit  is  closed, 
or  when  the  two  spirals  are  brought  nearer  to  each  other,  the  current  in  the  secondary  spiral  has  a 
direction  opposite  to  that  in  the  primary  spiral,  while  the  current  produced  by  opening  the  primary 
circuit,  or  by  removing  the  spirals  further  apart,  has  the  same  direction  as  the  primary.  Uurijig  the 
lime  the  primary  circuit  is  closed,  or  when  both  spirals  remain  at  the  same  distance  from  each  other, 
there  is  no  current  in  the  secondary  spiral. 

Difference  between  the  Opening  and  Closing  Shocks. — The  opening  [break!  and  closing 
[make]  shocks  in  the  secondary  spiral  are  distinguished  from  each  other  in  the  following  respects 
(Fig.  353)  ;  The  amount  of  electricity  is  the  same  during  the  opening  as  during  the  closing  shock, 
but  during  the  opening  shock  the  electricity  rapidly  reaches  its  maximum  of  intensity  and  lasts 
but  a  sliort  time,  while  during  the  closing  shock  it  gradually  increases,  but  does  not  reach  the 
same  high  maximum,  and  this  occurs  more  slowly.  [In  Fig.  353,  P,  and  Sq  are  the  abscissas  of 
the  primary  (inducing)  and  induced  currents  respectively.  The  vertical  lines  or  ordinates  represent 
the  intensity  of  the  current,  while  the  length  of  the  abscissa  indicates  its  duration.  The  curve  I 
indicates  the  course  of  the  primary  current,  and  2,  that  in  the  secondary  spiral  (induced)  when  the 
current  is  closed,  while  at  I  the  primary  current  is  suddenly  opened,  when  it  gives  rise  to  the  induced 
current,  4,  in  the  secondary  spiral.]  The  c.iuse  of  this  difference  is  the  following:  When  the  pri- 
mary circuit  is  closed  there  is  developed  in  it  the  extra  current,  which  is  opposite  in  direction  to  the 
primary  current.  Hence,  it  opposes  considerable  resistance  to  the  complete  development  of  the 
strength  of  the  primar)'  current,  so  that  the  cuirent  induced  in  the  secondary  spiral  must  also  develop 
slowly.  But  when  the  primary  spiral  is  opened,  the  extra  current  in  the  latter  has  the  same  direction 
as  the  primary  current,  there  is  no  extra  resistance.  The  rapid  and  intense  action  of  the  opening 
induction  shock  is  of  great  physiological  importance. 

Opening  Shock. — [On  applying  a  single  induction  shock  to  a  nerve  or  a  muscle,  the  effect  is 
greater  w  ith  the  opening  shock.  If  the  secondary  spiral  be  separated  from  the  primary,  so  that  the 
induced  currents  are  not  sufficient  to  cause  contraction  of  a  muscle  when  applied  to  its  motor 
nerve,  then,  on  gradually  approximating  the  secondary  to  the  primary  spiral,  the  opening  shock  will 
cause  a  contraction  before  the  closing  one  does  so.] 


HELMIIOLTZ  S    MODIKICATION. 


585 


Helmholtz's  Modification. — Under  certain  circumstances,  it  is  desirable  to  equalize  the  opening 
and  closing  shocks.  This  may  be  done  by  greatly  weakening  the  extra  current,  which  may  be 
accomplished  by  making  the  primary  spiral  of  only  a  few  coils  of  wire.  v.  Helmholtz  accomplishes 
the  same  result  by  introducing  a  secondary  circuit  into  the  primary  current.  By  this  arrangement 
the  current  in  the  primary  spiral  never  completely  disappears,  but  by  alternately  closing  and  open 
ing  this  secondary  circuit  where  the  resistance  is  much  less,  it  is  alternately  weakened  and  strength- 
ened. 

[In  Fig.  354  a  wire  is  introduced  between  a  and/,  while  the  binding  screw,  f,  is  separated  from 
(he  platinum  contact,  c,  of  Neefs  hammer,  but  at  the  same  time  the  screw,  d,  is  raised  so  that 
it  touches  Neef's  hammer.  The  current  passes  from  the  battery,  K,  through  the  pillar,  a,  to/ in 
the  direction  of  the  arrow,  through  the  primary  spiral,  P,  to  the  coil  of  soft  wire,.?-,  and  back  to  the 
battery,  through  h  and  e.  But  g  is  magnetized  thereby,  and.  when  it  is  so  it  attracts  c  and  makes  it 
touch  the  screw,  d.  Thus  a  secondary  circuit,  or  short  circuit,  is  formed  through  a,  b,  c,  d,  c,  which 
weakens  the  current  passing  through  the  electro-magnet,  .f,  so  that  the  elastic  metallic  spring  flies 
up  again  and  the  current  through  the  primary  spiral  is  long  circuited,  and  thus  the  process  is  repeated. 
In  Fig.  353  the  lines  i  and  7  indicate  the  course  of  the  current  in  the  primary  circuit  of  closing  (a ), 
and  opening  [e).  It  must  be  remembered  that  in  this  arrangement  there  is  always  a  current  passing 
through  the  primary  spiral,  P  (Fig.  354).  The  dotted  lines,  6  and  8  aliove  and  below  S„,  represent 
the  course  of  the  opening  {a)  and  closing  shocks  {e)  in  the  secondary  spiral.  Even  with  this  arrange- 
ment the  opening  is  still  slightly  stronger  than  the  closing  shock.]     The  two  shocks,  however,  may 


Fig.  353. 


Fig.  354. 


Fig.  353. — Scheme  of  the  induced  ( 

iiing,  and  E,  end  of  the  inducing  c 

primary  current  is  opened  ; 


!  and  4, 


height:  /.  A,  the  strength  of  the  constant  inducing  < 
is  'opened  and  closed  during  Helmhohz's  modificatioi 
secondary  circuit.  Fig.  354. — Helmholtz's  modificatio 
with  d,  s  h  remains  magnetic  :  thus  c  is  attracted  to  d, 
springs  back  again,  and  thus  the  process  goes  on.     Ane 


I  of  the  primary,  and  So  "f  the  secondary  ( 

of  the  primary  current  weakened  by  the  e.\lra  current ;  3, 
orresponding  currents  induced  in  the  secondary  spiral :   Pj, 


5  and  7,  the  curve  of  the  inducing  current  when  it 
;  6  and  8,  the  corresponding  currents  induced  in  the 
of  Neefs  hammer,  .^s  long  as  c  is  not  in  contact 
nd  a  secondary  circuit,  a,  h,  c,  d,  e,  is  formed  :  c  then 
.■  wire  is  introduced  to  connect  a  withyl    K,  battery. 


be  completely  equalized  by  placing  a  resistance  coil  or  rheostat  in  the  short  circuit,  which  increases 
the  resistance,  and  thus  increases  the  current  through  the  primary  spiral  when  the  short  circuit  is 
closed. 

Unipolar  induction. — When  there  is  a  very  rapid  current  in  the  primary  spiral,  not  only  is  there 
a  current  induced  in  the  secondary  spiral  when  its  free  ends  are  closed,  e.g.,  by  being  connected 
with  an  animal  tissue,  but  there  is  also  a  current  when  one  wire  is  attached  to  a  binding  screw  con- 
nected with  one  end  of  the  wire  of  the  secondary  sniral  (p.  572).  A  muscle  of  a  frog's  leg,  when 
connected  with  this  wire,  contracts,  and  this  is  called  a  unipolar  induced  contraction.  It  usually 
occurs  when  the  primary  circuit  is  opened.  The  occurrence  of  these  contractions  is  favored  when 
the  other  end  of  the  spiral  is  placed  in  connection  with  the  ground,  and  when  the  frog's  muscle 
preparation  is  not  coTipletely  insulated. 

Magneto  Induction. — If  a  magnet  be  brought  near  to,  or  thrust  into  the  interior  of,  a  coil  or 
wire,  it  excites  a  current,  and  also  when  a  piece  of  soft  iron  is  suddenly  rendered  magnetic  or  sud- 
denly demagnetized.  The  direction  of  the  current  so  induced  in  the  spiral  is  exactly  the  same  as 
that  with  F'aradie  electricity,  ;'.  e.,  the  occurrence  of  the  magnetism  on  approximating  the  spiral  to 
a  magnet,  excites  an  induced  current  in  a  direction  opposite  to  that  supposed  to  circulate  in  the 
magnet.  Conversely,  the  demagnetization,  or  the  removal  of  the  spiral  from  the  magnet,  causes  a 
cu  rent  in  the  same  direction. 

Acoustic  Tetanus. — If  a  magnet  be  rapidly  moved  to  and  fro  near  a  spiral,  which  can  easily 
be  done  by  ti.xing  a  vibrating  magnetic  rod  at  one  end  and  allowing  the  other  end  to  swing  freely 


586 


DU    BOIS-REYMOND  S    INDUCTORIUM. 


near  the  spiral,  then  the  pitch  of  the  note  of  the  vibrating  rod  gives  us  the  rapidity  of  the  induction 
shocks.  If  a  frog's  nerve-muscle  preparation  be  stimulated  we  get  what  Grossmann  called  "  acoustic 
tetanus." 

330.  DU  BOIS-REYMOND'S  INDUCTORIUM— MAGNETO-INDUCTION  AP- 
PARATUS.— Inductorium  of  Du  Bois-Reymond. — The  induction  apparatus  of  Du  ISois- 
Reymond,  which  is  used  for  physiological  purposes,  is  a  modification  of  the  magneto-electro-motor 
apparatus  of  Wagner  and  Neef.  A  scheme  of  the  apparatus  is  given  in  Fig.  355.  D  represents 
the  constant  element,  /.  f.,  the  galvanic  battery.  The  wire  from  the  positive  pole,  a,  passes  to  a 
metallic  column,  S,  which  has  a  horizontal  vibrating  spring,  F.  attached  to  its  upper  end.  To  the 
outer  end  of  the  spring  a  squnre  piece  of  iron,  c,  is  attached.  The  middle  point  of  the  upper  sur- 
face of  the  spring  [covered  with  a  little  pif-ce  of  platinum]  is  in  contact  with  a  movable  screw,  /> 
A  moderately  thick  copper  wire,  r,  passes  from  the  screw,  d,  to  the  primary  spiral  or  coil,  -i",  .r, 
which  contains  in  its  interior  a  number  of  pieces  of  soft  iron  wire,  t,  /,  covered  with  an  insulating 
varnish.  The  copper  wire  w-hich  surrounds  the  primary  spiral  is  covered  with  silk.  The  wire,  (/, 
is  continued  from  the  primary  spiral  to  a  Jiorseshoe  piece  of  soft  iron,  H,  around  which  it  is  coiled 
spirally,  and  from  thence  it  proceeds,  at/j  back  to  the  negative  pole  of  the  battery,^.  When  the 
current  in  this  circuit — called  the  primary  circuit — is  closed,  the  following  effects  are  produced  : 
The  horseshoe,  H,  becomes  magnetic,  in  consequence  of  which  it  attracts  the  movable  spring  or 


1:  of  Du  Bois-Riymonri's  sledge-induction  m.ichine.  D,  constant  element:  a.  wire  from  +  pole.  (^) — 
S,  brass  upright :  F,  elastic  spring  ;  b,  binding  screw  ;  c,  wire  round  primary  spiral  \xr^x),  containing!/,  {) 
-on  wire ;  K,  K,  secondary  spiral,  with  board  (/./)  on  which  it  can  be  moved  ;  H,  soft  iron  magnetized  by 
nt  {d,/\  passing  round  it.  II,  key  for  secondary  circuit,  as  shown  it  is  short  circuited.  Ill,  electrodes  (r,  r), 
a  key  (K)  for  breaking  the  circuit. 


Xeef  s  hammer,  e,  whereby  the  contact  of  the  spring,  F,  with  the  screw,  b,  is  broken.  Thus  the 
current  is  broken,  the  horseshoe  is  demagnetized,  the  spring,  e,  is  liberated,  and,  being  elastic,  it 
springs  upward  again  to  its  original  position  in  contact  with  b,  and  thus  the  current  is  re-established. 
The  new  contact  causes  H  to  be  magnetized,  so  that  it  must  alternately  rapidly  attract  and  liberate 
the  spring,  <■,  whereby  the  primary  current  is  rapidly  mide  and  broken  between  F  and  b. 

A  secondary  spiral  or  coil  (K,  K)  is  placed  in  the  same  direction  as  the  primary  f.v,  x),  but 
having  no  connection  with  it.  It  moves  in  grooves  upon  a  long  piece  of  wood  (p,  p).  The  secondary 
spiral  consists  of  a  hollow  cylinder  of  wood  covered  with  numerous  coils  of  thin  silk-covered  wire. 
The  secondary  spiral  moving  in  slots,  can  be  approximated  to  or  even  pushed  entirely  over  the 
primary  spiral,  or  can  be  removed  from  it  to  any  distance  desired. 

[Fie.  356  shows  the  actual  arranyeinent  of  Du  Bois-Reymond's  inductorium.  The  primary 
coil  (R')  consists  of  about  150  coils  of  thick  insulated  copper  wire,  the  wire  being  thick,  to  offer 
slight  resistance  to  the  galvanic  current.  The  secondary  coil  (  W"\  consists  of  6000  turns  of  thin 
insulated  copper  wire  arranged  on  a  wooden  bobbin ;  the  whole  spiral  can  be  moved  along  the 
board  (B),  to  which  a  millimetre  scale  (I)  is  attached,  so  that  the  distance  of  the  secondary  from  the 
primary  spiral  may  be  ascertained.  At  the  left  end  of  the  apparatus  is  Wagner's  hammer  as 
adapted  by  Neef.  which  is  just  an  automatic  arrangement  for  opening  and  breaking  the  primary 
circuit.     When  Neef  s  hammer  is  used,  the  wires  from  the  battery  are  connected  as  in  the  figure, 


MAGNETO    INDUCTION. 


587 


but  when  single  shocks  are  re:|uired,  the  wires  from  the  battery  are  connected  with  a  key,  and  this 
again  with  the  two  terminals  of  the  primary  spiral  S"  and  S'".] 

According  to  the  law  of  induction  (^329),  when  the  primary  circuit  is  closed,  a  current  is  induced 
in  the  secondary  circuit  in  a  direction  the  reverse  of  that  in  the  primary,  while,  when  it  is  opened. 


J  S" 


Fig.  356. 


Induction  apparatus  of  Du  Bois-Reymond,     R',  primary,  R".  secondary  spiral  ;     B,  board  011  which  R"  moves  ;   T. 

scale:    H .  wires  from  battery;    P'.  P".  pillars;    H,  Neef's  hammer;    B'.  electro-magnet:   S',  binding  screw 

touching  the  steel  spring  (H) ;  S"  and  S"',  binding  screws  to  which  to  attach  wires  when  Neef's  hammer  is  nut 
required  {Elliott  Brothers). 

the  induced  current  has  the  same  direction.  Further,  according  to  the  laws  of  magneto  induction, 
there  is  the  magnetization  of  the  iron  rods  (;',  /)  within  the  primary  spiral  (.r,  x),  that  causes  a 
reverse  current  in  the  secondary  spi'al  (K,  K),  while  the  demagnetization  of  the  iron  rods  on  opening 

Fig.  358. 


Magneto  induction  apparatus,  with  Stohrer': 


Du  Boi.'-Reymond's  friction  key. 


the  primary  circuit  causes  an  induced  current  in  the  same  direction.  Thus  we  explain  the  much 
more  powerful  action  of  the  opening  shock  as  compared  witii  the  closing  shock.  [The  direction  of 
the  inducing  current  remains  the  same,  while  the  induced  currents  are  constantly  reversed.] 


588 


ELECTRICAL   CURRENTS    IN    MUSCLE    AND    NERVE. 


The  magneto-induction  (R)  apparatus  of  Pixii  (1832),  improved  by  Saxton,  and  still  further 
improved  by  Siohrer,  consists  of  a  very  powerful  horseshoe  steel  magnet  (Fig.  357).  Opposite 
its  two  poles  (X  and  S)  is  a  horseshoe  shaped  piece  of  iron  (H),  which  rotates  on  a  horizontal 
axis  («,  ^).  On  the  ends  of  the  horseshoe  are  fixed  wooden  bobbins  (<:,  </),  with  an  insulated  wire 
coiled  round  them.  When  the  horseshje  is  at  rest,  as  in  the  figure,  it  becomes  magnetized  by  the 
steel  magnet,  while  in  the  wires  of  both  bobbins  (i-  and  d)  an  electric  current  is  developed  everv 
time  the  horseshoe  is  demagnetized  and  again  magnetized.  When  the  bobbins  rotate  in  front  of 
the  magnet,  as  each  coil  approaches  one  pole  a  current  1*^  induced,  and  similarly  w'hen  it  is  carried 
past  the  pole  of  the  magnet,  so  that  four  currents  are  induced  in  each  coil  by  a  single  rotation.  By 
means  of  Slohrer's  commutator  (m,  n)  attached  to  the  spindle  (a,  l>),  and  the  divided  metal  plates 
(y,  z)  which  pass  to  the  electrodes,  the  two  currents  induced  in  the  bobbins  are  obtained  in  the  same 
direction. 

Keys,  or  arrangements  for  opening  or  breaking  a  circuit,  are  of  great  use.  Fig.  355.  II,  shows 
a  scheme  of  a  friction  key  of  Du  Bois-Reymond,  introduced  into  the  secondary  circuit.  It  con- 
sists of  two  brass  bars  (:  and  r)  fixed  to  a  plate  of  ebonite,  and  as  long  as  the  key  is  down  on  the 
metal  bridge  (y,  r,  z)  it  is  "  short  circuiieii,"  i.  t".,  the  conduction  is  so  good  through  the  thick  bra^s 
bars,  that  none  of  the  current  goes  through  the  wires  leading  from  the  left  of  the  key.  When  the 
bridge  (r)  is  lifted  the  current  is  opened.  [The  term  accessory  circuit  is  also  used  for  short  circuit  ] 
[Fig.  358  shows  the  actual  form  of  the  key,  v  being  a  screw  wherewith  to  clamp  it  to  the  table.] 
Similarly,  the  key  electrodes  (111)  may  be  used,  the  current  being  made  as  soon  as  the  spring  con- 
necting plate  (<•)  is  raised  by  pressing  upon  k.  This  instrument  is  opened  by  the  hand  ;  a,  />  are  the 
wires  from  the  battery  or  induction  machine ;  r,  r,  those  going  to  the  tissue;  G,  the  handle  of  the 
instrument. 

[Plug  Key. — Other  forms  of  keys  are  in  use,  e.g..  Fig.  359,  the  plug  key,  the  two  brass  plates  to 
which  the  wires  are  attached  being  fixed  on  a  plate  of  ebonite.     The  brass  plug  is  used  to  connect 


Fig.  359. 


Fig.  359. — Plug  key.     Fig.  360. — Capillary  cont.ict.     t, 
into  mercury  at  a :  ^,  bent  tube  filled  with  mercurj* 


the  two  brass  plates.  All  these  are  dry  contacts,  but  sometimes  &fiuid  contact  is  used,  as  in  the 
mercury  key,  which  merely  consists  of  a  block  of  wood,  with  a  cup  of  mercury  in  its  centre.  The 
ends  of  the  wires  from  the  battery  dip  into  the  mercury;  when  both  wires  dip  into  the  mercury,  the 
circuit  is  made,  and  when  one  is  out  it  is  broken.] 

[Capillary  Contact  Key. — When  an  ordinary  mercury  key  is  used  to  open  and  close  the  primary 
circuit,  the  layer  of  oxide  formed  on  the  surface  by  the  opening  spark  disturbs  the  conduction  after 
a  short  time;  hence,  it  is  advisable  to  wash  the  surface  of  the  mercury  with  a  dilute  solution  of 
alcohol  and  water  ( IV.  Stirling).  A  handy  form  of  "  capillary  contact "  is  shown  in  Fig.  360,  such 
as  was  used  by  Kronecker  and  Stirling  in  their  experiments  on  the  heart.  "  A  glass  T  tube  is  pro- 
vided at  the  crossing  point  with  a  small  opening  (a).  The  vertical  tube  (b)  is  bent  in  the  form  of  a  U, 
and  filled  so  full  with  mercury  that  the  convex  surface  of  the  latter  projects  within  the  lumen  of  the 
transverse  tube  (<).  One  end  of  c  is  connected  with  a  Mariolte's  flask  containing  diluted  alcohol, 
and  the  supply  of  the  latter  can  be  regulated  by  means  of  a  stop-cock.  The  fluid  flows  over  the 
apex  of  the  mercury  and  keeps  it  clean.  The  vibrating  platinum  style  {e]  is  attached  to  the  end  of 
a  rod,  which,  in  turn,  is  connected  with  the  positive  pole  of  the  battery,  while  the  platinum  wire  (r/) 
is  connected  with  the  negative  pole  of  the  battery."] 

331.  ELECTRICAL  CURRENTS  IN  PASSIVE  MUSCLE  AND  NERVE- 
SKIN  CURRENTS. — Methods.— In  order  to  investigate  the  laws  of  the  muscle  current,  we 
must  use  a  muscle  composed  of  |jarallel  (ibres,  and  with  a  simple  arrangement  of  its  fibres  in  the 
form  of  a  pri'-m  or  cylinder  (Fig.  361,  I  and  II).  The  sartorius  muscle  of  the  frog  supplies  the^e 
conditions.  In  such  a  muscle  we  distinguish  the  surface  or  the  natural  longitudinal  section, 
its  tendinous  ends  or  the  natural  transverse  section;  further,  when  the  latter  is  divided  trans- 
versely ti  the  long  axis,  the  artificial  transverse  section  (Fig.  361,  I,  c,  ./) ;  lastly,  the  term 
equator  (a,  b~m,  v)  is  applied  to  a  line  so  drawn  as  exactly  to  divide  the  length  of  the  muscle  into 


ELECTRICAL    CURRENTS    IN    MUSCLE    AND    NERVE. 


589 


halves.  As  the  currents  are  very  feeble,  it  is  necessary  to  use  a  galvanometer  with  a  periodic  damped 
magnet  (Figs.  345,  I,  and  350),  or  a  tangent  mirror  boussole  similar  to  that  u.^ed  for  thermo-electric 
purposes  (Fig.  216).  The  wires  leading  from  the  tissue  are  connected  with  non-polarizable  elec- 
trodes (F'ig.  345,  P,  P). 

The  capillary  electrometer  of  Lippmann  may  be  used  for  detecting  the  current  (Fig.  362).  A 
thread  of  mercury  enclosed  in  a  capillary  tube  and  touching  a  conducting  fluid,  e.  g.,  dilute  sulphuric 
acid,  is  displaced  by  the  constant  current  in  consequence  of  the  polarization  taking  place  at  the  point 
of  contact  altering  the  constancy  of  the  capillarity  of  the  mercury.  The  displacement  of  the  mer- 
cury which  the  observer  (B)  detects  by  the  aid  of  the  microscope  (M)  is  in  the  direction  of  the 
positive  current.  In  Fig.  362,  R  is  a  capillary  glass  tube,  filled  from  above  with  mercury,  and  from 
below  with  dilute  sulphuric  acid.  Its  lower  narrow  end  opens  into  a  wide  glass  tube,  provided 
below  with  a  platinum  wire  fused  into  it  and  filled  with  Hg  (q),  and  this  again  is  covered  with 
dilute  sulphuric  acid  (s).  The  wires  are  connected  with  non-polarizable  electrodes  applied  to  the 
^  and  —  surfaces  of  the  muscle.  On  closing  the  circuit,  the  thread  of  mercury  passes  downw  ard 
from  c  in  the  direction  of  the  arrow.  [A  very  simple  and  convenient  modification  of  this  instru- 
ment for  studying  the  muscle  current  has  recently  been  invented  by  M'Kendrick.] 

Compensation. — The  strength  of  the  current  in  animal  tissues  is  best  measured  by  the   com- 


FlG.   361. 


Fig.  362. 


Capillary  electrometer  (after 

mercury  in  tube  ;  c.  capillary 
phuric    acid:     q,    Hg :     B,   ol 


pensation  method  of  Poggendorf  and  l)u  Bois  Reymond.  A  current  of  known  strength,  or  which 
can  be  accurately  graduated,  is  passed  in  an  opposite  direction  through  the  same  galvanometer  or 
boussole,  until  the  current  from  the  animal  tissue  is  just  neutralized  or  compensated.  [When  this 
occurs,  the  needle  deflected  by  the  tissue  current  returns  to  zero.  The  principle  is  exactly  the  same 
as  that  of  weighing  a  body  in  terms  of  some  standard  weights  placed  in  the  opposite  scale  pan  of 
the  balance.] 

1.  Perfectly  fresh,  uninjured  muscles  yield  no  current,  and  the  same  is 
true  of  dead  muscle  (Z.  Hermann,  1867). 

2.  Strong  electrical  currents  are  observed  when  the  transverse  section  of  a 
muscle  is  placed  on  one  of  the  cushions  of  the  non-polarizable  electrodes  (Fig. 
345,  I,  M),  while  the  surface  is  in  connection  with  the  other  (Nohili,  Matteticci, 
Dii  Bois-Rcymomi).  The  direction  of  the  current  is  from  the  (positive)  longi- 
tudinal section  to  the  (negative)  transverse  section  in  the  conducting  wires  (/.  e., 
within  the  muscle  itself  from  the  transverse  to  the  longitudinal  section  (Figs.  345, 


590  ELECTRICAL   CURRENTS    IN    MUSCLE   AND    NERVE. 

I,  and  361,)  I).  This  current  is  stronger  the  nearer  one  electrode  is  to  the 
equator,  and  the  other  to  the. centre  of  the  transverse  section  ;  while  the  strength 
diminishes  the  nearer  the  one  electrode  is  to  the  end  of  the  surface,  and  the  other 
to  the  margin  of  the  transverse  section. 

Smooth  muscles  also  yield  similar  currents  between  their  transverse  and  longitudinal  surfaces 
(?334.  II). 

3.  Weak  electrical  currents  are  obtained  when — (a)  two  points  at  unequal  dis- 
tances from  the  equator  are  connected  ;  the  current  then  passes  from  the  point 
nearer  the  equator  (-f)  to  the  point  lying  further  from  it  ( — ),  but  of  course  this 
direction  is  reversed  within  the  muscle  itself  (Fig.  361,  II,  /v  and  /(•).  (/')  Simi- 
larly weak  currents  are  obtained  by  connecting  points  of  the  transverse  section  at 
unequal  distances  from  the  centre,  in  which  case  the  current  outside  the  muscle 
passes  from  the  point  lying  nearer  the  edge  of  tlie  muscle  to  that  nearer  the  centre 
of  the  transverse  section  (Fig.  361,  II,  /,  <'). 

4.  When  two  points  on  the  surface  are  equidistant  from  the  equator  (Fig.  361, 
I,  X,  y,  V,  z, — II,  r,  e),  or  two  equidistant  trom  tlie  centre  of  the  transverse  sec- 
tion {II,  c)  are  connected,  no  current  is  obtained. 

5.  If  the  transverse  section  of  a  muscle  be  oblique  (Fig.  361,  III),  so  that  the 
muscle  forms  a  rhomb,  the  conditions  obtaining  under  III  are  disturbed.  The 
point  lying  nearer  to  the  obtuse  angle  of  the  transverse  section  or  surface  is  posi- 
tive to  the  one  lying  near  to  the  acute  angle.  The  equator  is  oblique  {a,  c).  These 
currents  are  called  "  deviation  currents  "  by  Du  Bois-Reymond,  and  their  course 
is  indicated  by  the  lines  i,  2,  and  3. 

Strength  of  Electro-motive  Force. — The  electro. motive  force  of  a  strong  muscle  airrciil 
(frog)  is  equal  to  0.05  to  o.oS  of  a  DanielPs  element ;  while  the  strongest  deviation  current  may  be 
O.I  Daniell.  The  muscles  of  a  curarized  animal  at  lirst  yield  stronger  currents  ; /ij/^'"""  ol  ''^^ 
muscle  diminishes  the  strength  of  the  current  (Roeber),  while  it  is  completely  abolished  when  the 
muscle  dies.  Heating  a  muscle  increases  the  current ;  but  above  40°  C.  it  is  diminished  (Steiner). 
tooting  diminishes  the  electro-motive  force.  The  warmed  living  muscular  and  nervous  substance 
(Hermann,  IVorm  Miiller,  Griilzner)  is  positive  to  the  cooler  portions;  while,  if  the  dead  ti-sues 
be  heated,  they  behave  practically  as  indifferent  bodies  as  regards  the  tissues  that  are  not  heated. 

6.  The  passive  nerve  behaves  like  muscle,  as  far  as  2,  3,  and  4  are  concerned. 

The  electro-motive  force  of  the  strongest  nerve  current,  according  to  Du  Bois-Reymond,  is  0.02 
of  a  Daniell.  Heating  a  nerve  to  i5°-25°  C.  increases  the  nerve  current,  while  high  temperatures 
diminish  it  (Steiner). 

7.  If  the  two  transversely  divided  ends  of  an  excised  nerve,  or  two  points  on 
the  surface  equidistant  from  the  equator  be  tested,  a  current — the  axial  current 
— flows  in  the  nerve  fibre  in  the  opposite  direction  to  the  direction  of  the  normal 
impulse  in  the  nerve  ;  so  that  in  centrifugal  nerves  it  flows  in  a  centripetal  direc- 
tion, and  in  centripetal  nerves  in  a  centrifugal  direction  (^Mendelsohn  and  Cliris- 
tiani). 

Rheoscopic  Limb. — The  existence  of  a  muscle  current  may  be  proved  with- 
out the  aid  of  a  galvanometer  :  i.  By  means  of  a  sensitive  nerve-muscle  prepara- 
tion of  a  frog,  or  the  so-called  " physiological  rheoscope."  Place  a  moist  conductor 
on  the  transverse  and  longitudinal  surface  of  the  gastrocnemius  of  a  frog.  On 
placing  the  sciatic  nerve  of  a  nerve-muscle  preparation  of  a  frog  on  this  conductor, 
so  as  to  bridge  over  or  connect  these  two  surfaces,  contraction  of  the  muscle  con- 
nected with  the  nerve  occurs  at  once  ;  and  the  same  occurs  when  the  nerve  is 
removed. 

[Use  a  nerve-muscle  preparation,  or,  as  it  is  called,  a  physiological  limb.  Hold  the  preparation 
by  the  femur,  and  allow  its  own  nerve  to  fall  upon  the  gastrocnemius,  and  the  muscle  will  contract, 
but  it  is  better  to  allow  the  nerve  to  fall  suddenly  upon  the  cross  section  of  the  muscle.  The  nerve 
then  completes  the  circuit  Vjetween  the  longitudinal  and  transverse  section  of  the  muscle,  so  that  it 
is  stimulated  by  the  current  from  the  latter,  the  nerve  is  stimulated,  and  through  it  the  muscle. 
That  it  is  so,  is  proved  by  tying  a  thread  round  the  nerve  near  the  muscle,  when  the  latter  no  longer 
contracts.] 


ELECTRICAL   CURRENTS    OF   ACTIVE    MUSCLE.  591 

Contraction  without  Metals. — Make  a  transverse  section  of  a  gastrocnemius 
muscle  of  a  frog's  nerve-muscle  preparation,  and  allow  the  sciatic  nerve  to  fall 
upon  this  transverse  section,  when  the  limb  contracts,  as  the  muscle  current  from 
the  longitudinal  to  the  transverse  surface  now  traverses  the  nerve  (^Galvani,  Al.  v. 
Hiimhohh). 

2.  Self-Stimulation  of  the  Muscle. — We  may  use  the  muscle  current  of  an 
isolated  muscle  to  stimulate  the  latter  directly  and  cause  it  to  contract.  If  the 
transverse  and  longitudinal  surfaces  of  a  curarized  frog's  nerve-muscle  preparation 
be  placed  on  non-polarizable  electrodes,  and  the  circuit  be  closed  by  dipping  the 
wires  coming  from  the  electrodes  in  mercury,  then  the  muscle  contracts.  Simi- 
larly a  nerve  may  be  stimulated  with  its  own  current  (Z>«  Bois-Reymond  and 
others).  If  the  lower  end  of  a  muscle  with  its  transverse  section  be  dipped  into 
normal  saline  solution  (0.6  per  cent.  NaCl),  which  is  quite  an  indifferent  fluid, 
this  fluid  forms  an  accessory  circuit  between  the  transverse  and  adjoining  longi- 
tudinal surface  of  the  muscle,  so  that  the  muscle  contracts.  Other  indifferent 
fluids  used  in  tlie  same  way  produce  a  similar  result. 

3.  Electrolysis. — If  the  muscle  current  be  conducted  through  starch  mixed 
with  potassic  iiniide,  then  the  iodide  is  deposited  at  the  -f  pole,  where  it  makes 
the  starch  blue. 

Frog  Current. — It  is  asserted  that  the  total  current  in  the  body  is  the  sum  of  the  electrical  cur- 
rents of  the  several  muscles  and  nerves  which,  in  a  frog  deprived  of  its  skin,  passes  from  the  lip  of 
the  toes  toward  the  trunli,  and  in  the  trunk  from  tlie  anus  to  the  head.  This  is  the  "  corrente  pro- 
pria ddla  rena"  of  Leopoldo  Nobih  ( 1827),  or  the  "frog  lurrent"  of  Du  Bois-Reymond.  In 
mammals  ihe  corresponding  current  passes  in  the  opposite  direclion. 

After  death  the  currents  disappear  sooner  than  the  excitability  (  Valentin) ;  they  remain  longer 
in  the  muscle  than  the  nerves,  and  in  the  latter  they  disappear  sooner  in  the  central  portions.  If 
the  nerve  current  after  a  time  becomes  feeble,  it  may  be  strengthened  by  making  a  new  transverse 
section  of  the  nerve.  A  motor  nerve  completely  paralyzed  by  curara  gives  a  current  {/•'unit),  and 
so  does  a  nerve  beginning  to  undergo  degeneration,  even  two  weeks  alter  it  has  lost  its  excitability. 
Muscles  in  a  state  of  rigor  mortis  give  currents  in  the  opposite  direction,  owing  to  inequalities  m 
the  decomposition  which  takes  place.  The  nerve  current  is  reversed  by  the  action  of  boiling  water 
or  drying. 

Currents  from  Skin  and  Mucous  Membranes. — In  the  skin  of  the  frog 
the  outer  surface  is  -j-  ,  the  inner  is  —  ,  (Z>«  Bois-Reymond,  Budge),  and  the  same 
is  true  of  the  mucous  membrane  of  the  intestinal  tract  {Rosenthal),  the  cornea 
{Griinhagen),  as  well  as  the  non-glandular  skin  of  fishes  {Hermann)  and  molluscs 
{Oehler). 

Stimulation  of  the  Secretory  Nerves  of  the  g/andiilar  membranes,  besides  causing  secretion, 
affects  the  current  of  rest  (/ioeber).  This  secretion  current  passes  in  the  same  direction  in  the 
skin  of  the  frog  and  warm  blooded  animals  as  the  current  of  rest,  although  in  the  frog  it  is  occa- 
sionally in  the  opposite  direction  (i/ermaim).  If  the  current  be  conducted  uniformly  from  both 
the  hind  feet  of  a  cat,  on  stimulating  the  sciatic  nerve  of  one  side,  not  only  is  there  a  secretion  of 
sweat  (§  2S8),  but  a  secretion  current  is  developed  {Luchsinger  attd  Nermann).  If  two  symmet- 
rical parts  of  the  skin  in  the  leg  or  arm  of  a  man  be  similany  tested,  and  the  muscle  of  one  side 
be  contracted,  a  similar  current  is  developed.  Destruction  or  atrophy  of  the  glands  abolishes  both 
the  power  of  secretion  and  the  secretion  current.  There  is  no  secretion  current  from  skin  covered 
with  hairs,  but  devoid  of  glands  (Btibnoff).  [The  secretion  current  from  the  submaxillary  gland 
is  referred  to  in  ^  145  {Sayliss  and  Bradfoi  J ).'\ 

332.  CURRENTS  OF  STIMULATED  MUSCLE  AND  NERVE. 

—  I.  Negative  Variation  of  the  Muscle  Current. — If  a  muscle,  which 
yields  a  strong  electrical  <;urrent,  be  thrown  into  a  state  of  tetanic  contraction  by 
stimulating  its  motor  nerve,  then,  when  the  muscle  contracts,  there  is  a  diminu- 
tion of  the  muscle  current,  and  occasionally  the  needle  of  the  galvanometer  may 
swing  almost  to  zero.  This  is  the  negative  variation  of  the  muscle  current  (L)u 
Bois-Reymond).  It  is  larger  the  greater  the  primary  deflection  of  the  galva- 
nomfcter  needle  and  the  more  energetic  the  contraction. 

After  tetanus  the  muscle  current  is  weaker  than  it  was  before.  If  the  muscle  was  so  placed  upon 
the   electrodes  that  the  current  was  •'  feeble,"  e  jually  during  tetanus,  there   is  a  diminution  of  this 


592 


SECONDARY    CONTRACTION. 


current.  In  the  inactive  arrangement,  the  contraction  of  the  muscle  has  no  effect  on  the  needle. 
If  the  muscle  be  prevented  from  shortening,  as  by  keeping  it  tense,  the  negative  variation  still 
takes  place. 

2.  Current  during  Tetanus. — An  exa'sei^  frog's  muscle  Maniset/  through  its 
Nr/Te  shows  electro-motor  force — the  so-called  "action  current."  In  a  tetan- 
ized  frog's  gastrocnemius  there  is  a  t/escemfi/zg-  current.  In  completely  uninjured 
human  muscles,  however,  thrown  into  tetanus  by  acting  on  their  nerves,  there  is 
no  such  current  (Z.  Hermanii)  ;  similarly,  in  quite  uninjured  frog's  muscles,  as 
well  as  when  these  muscles  are  directly  and  completely  fetanized,  there  is  no  cur- 
rent. 

3.  Current  during  the  Contraction  Wave. — If  one  end  of  a  muscle  be 
directly  excited  with  a  momentary  stimulus,  so  that  the  contraction  wave  (§  299) 
rapidly  passes  along  the  whole  length  of  the  muscular  fibres,  then  each  part  of 
the  muscle,  successively  and  immediately  before  it  contracts,  shows  the  negative 
variation.  Thus  the  "  contraction  wave"  is  preceded  by  a  "  negative  7vave  "  of 
the  muscle  current,  the  latter  occurring  during  the  latent  period.  Both  waves  have 
the  same  velocity,  about  3  metres  per  second.  The  negative  wave,  which  first 
increases  and  then  diminishes,  lasts  at  each  point  only  0.003  second  {Bernstein). 

4.  During  a  Single  Contraction. — A  single  contraction  also  shows  a  muscle 


FiG.  364. 


Fig.  363. 


.Secondary  contraction.     The  s 
£,  electrodes  applied  to  the  e 


current.  The  best  object  to  use  for  this  purpose  is  a  contracting  heart,  which  is 
placed  upon  the  non-polarizable  electrodes  connected  with  a  sensitive  galva- 
nometer. Each  beat  of  the  heart  causes  a  deflection  of  the  needle,  which  occurs 
before  the  contraction  of  the  cardiac  muscle  {Kollikcr  and  H.  Mitller).  The 
electrical  disturbance  in  the  muscle  causing  the  negative  variation  always  precedes 
the  actual  contraction  {v.  Hclmholtz,  1834).  When  the  completely  uninjured 
frog's  gastrocnemius  contracts  by  stitnulating  the  nerve,  there  is  at  first  a  descend- 
ing and  then  an  ascending  current  {Sig.  Meyer,  §  344,  II). 

Secondary  Contraction. — A  nerve-muscle  preparation  may  be  used  to 
demonstrate  the  electrical  changes  that  occur  during  a  single  contraction.  If  the 
sciatic  nerve,  .\,  of  such  a  preparation  be  placed  upon  another  muscle,  B,  as  in 
Fig.  363,  then  every  time  the  latter,  B,  contracts,  the  frog's  muscle,  A,  connected 
with  the  nerve  also  contracts. 

If  the  nerve  of  a  frog's  nerve-muscle  preparation  be  placed  on  a  contracting 
mammalian  heart,  then  a  contraction  of  the  muscle  occurs  with  every  beat  of  the 
heart  {Matteucci,  1842).  The  diaphragm,  even  after  section  of  the  phrenic  nerve, 
especially  the  left,  also  contracts  during  the  heart  beat  {Schiff).  This  is  the 
"  secondary  contraction  "  of  Galvani. 


NEGATIVE    VARIATION    OF   THE    NERVE   CURRENT. 


593 


Secondary  Tetanus. — Similarly,  if  a  nerve  of  a  nerve-muscle  preparation  be 
placed  on  a  muscle  which  is  tetanized,  then  the  former  also  contracts,  showing 
"  seconda.Ty  tetanus"  (Du  £t)is-J?e)'moni^).  The  latter  experiment  is  regarded 
as  a  proof  that,  during  the  process  of  negative  variation  in  the  muscle,  many 
successive  variations  of  the  current  must  take  place,  as  only  rapid  variations  of 
this  kind  can  produce  tetanus  by  acting  on  a  nerve — continuous  variations  being 
unable  to  do  so. 

Usually  there  is  no  secondary  tetanus  in  a  frog's  nerve  muscle  preparation  when  it  is  laid  upon  a 
muscle  which  is  tetanized  voluntarily,  or  by  chemical  stimuli,  or  by  poisoning  with  strychnin  (^Her- 
ing  and  Friedreich,  Kiikiie) ;  still,  LovSn  has  observed  secondary  strychnin  tetanus  composed  of 
six  to  nine  shocks  per  second.  Observations  with  a  sensitive  galvanometer,  or  Lippmann's  capil- 
lary electrometer  (Eig.  362),  show  that  the  spasms  of  strychnin  poisoning,  as  well  as  a  voluntary 
contraction,  are  discontinuous  processes  (Loven,  p.  521). 

[Nerve-muscle  Preparation. — This  term  has  been  used  on  several  occasions. 
It  is  simply  the  sciatic  nerve  with  the  gastrocnemius  of  the  frog  attached   to   it 


Fig.  365. 


Scheme  of  Bernstein's  differential  rheotome;  N«,  nerve;  J,  inductio 
of  needle  ;  E,  battery  and  primary  circuit  with  C  for  opening  it  ; 
electrodes  in  galvanometer  circuit ;  S,  motor. 


chine;  G,  galvanometer;  jr.jj',  deflectic 
f,  for  closing  galvanometer  circuit ;  z, 


(Fig.  364).  The  sciatic  nerve  is  dissected  out  entire  from  the  vertebral  column 
to  the  knee ;  the  muscles  of  the  thigh  separated  from  the  femur,  and  the  latter 
divided  about  its  middle,  so  that  the  preparation  can  be  fixed  in  a  clamp  by  the 
remaining  portion  of  the  femur  ;  while  the  tendon  of  the  gastrocnemius  is  divided 
near  to  the  foot.  If  a  straw  flag  is  to  be  attached  to  the  foot,  do  not  divide  the 
tendo  Achilles.] 

5.  Negative  Variation  in  Nerve. — If  a  nerve  be  placed  with  its  transverse 
section  on  one  non-polarizable  electrode,  and  its  longitudinal  surface  on  the  other, 
and  if  it  be  stimulated  electrically,  chemically  or  mechanically,  the  nerve  current 
is  also  diminished  (Du  Bois-Reyinoiid).  This  negative  variation  can  be  prop- 
agated toward  Iwth  ends  of  a  nerve,  and  is  composed  of  very  rapid,  successive, 
periodic  interru])tions  of  the  original  current,  just  as  in  a  contracted  muscle  {Bern- 
stein) ;  while  Hering  succeeded  in  obtaining  from  a  nerve,  as  from  a  muscle,  a 
secondary  contraction  or  secondary  tetanus.  The  amount  of  the  negative  varia- 
tion depends  upon  the  extent  of  the  primary  deflection,  also  upon  the  degree  of 
38 


594  ELECTRICAL   CURRENTS   DURLN'G    ELECTROTUNUS. 

nervous  excitability,  and  on  the  strength  of  the  stimulus  employed.  The  negative 
variation  occurs  on  stimulating  with  tetanic  as  well  as  with  single  shocks.  The 
negative  variation  is  not  observed  in  completely  uninjured  nerves. 

Hering  found  that  the  negative  variation  of  the  nerve  current  caused  by  tetanic  stimulation  is 
followed  by  a  positive  variation,  which  occurs  immediately  after  the  former.  It  increases  to  a 
certain  degree  with  the  duration  of  the  stimulation,  as  well  as  with  the  strength  of  the  stimulus 
{Effect  of  Electrotonus,  ?  335,  I). 

Negative  Variation  of  the  Spinal  Cord. — This  is  the  same  as  in  nerves  generally.  If  a  cur- 
rent be  conducted  from  the  transverse  and  longitudinal  surfaces  of  the  upper  part  of  the  medulla 
oblongata,  we  observe  spontaneous  intermittent  ne^^ative  variations^  perhaps  due  to  the  intermittent 
excitement  of  the  nerve  centres,  more  es|)ecially  of  the  respiratory  centre.  Similar  variations  are 
obtained  refle.xly  by  single  stimuli  applied  to  the  sciatic  nerve,  while  strong  stimulation  by  common 
salt  or  induction  shocks  inhibits  them. 

Velocity. — The  process  of  negative  variation  is  propagated  at  a  measureable  velocity  along  the 
nerve,  most  rapidly  at  15°  to  25°  C.  [Steiner),  and  at  the  same  rate  as  the  velocity  of  the  nervous 
impulse  itself,  about  27  to  28  metres  per  second.  The  duration  of  a  single  variation  (of  which  the 
process  of  negative  variation  is  composed)  is  only  0.0005  '°  0.0008  second,  while  the  wave  length 
in  the  nerve  is  calculated  by  Bernstein  at  18  mm. 

Differential  Rheotome.^J.  Bernstein  estimated  the  velocity  of  the  negative  variation  in  a 
nerve  by  means  of  a  difterential  rheotome  (Fig.  365)  thus:  A  long  stretch  of  a  nerve  (Nn)  is  so 
arranged  that  at  one  end  of  it  (N)  its  transverse  and  longitudinal  surfaces  are  connected  with  a 
galvanometer  (Gj,  while  at  the  other  txvX  («)  are  placed  the  electrodes  of  an  induction  machine 
(J).  A  disk  (B),  rapidly  rotating  on  its  vertical  a.xis  (A),  has  an  arrangement  (C)  at  one  point  of 
its  circumference,  by  means  of  which  the  current  of  the  primary  circuit  (E)  is  rapidly  opened  and 
closed  during  each  revolution.  This  causes,  with  each  rotation  of  the  disk,  an  opening  and  a 
closing  shock  to  be  applied  to  the  end  of  the  nerve,  ."^t  the  diametrically  opposite  part  of  the  cir- 
cumference is  an  arrangement  (c)  by  which  the  galvanometer  circuit  is  closed  and  opened  during 
each  revolution.  Thus,  the  stimulation  and  the  closing  of  the  galvanometer  circuit  occur  at  the 
same  moment.  On  rapidly  rotating  the  disk,  the  galvanometer  indicates  a  strong  nerve  current, 
an  excursion  of  the  magnetic  needle  to  y-  At  the  moment  of  stimulation  the  negative  variation 
has  not  yet  reached  the  other  end  of  the  nerve.  If,  however,  the  arrangement  which  closes  the 
galvanometer  circuit  be  so  displaced  (to  0)  along  the  circumference  that  the  galvanometer  circuit  is 
closed  somewhat  later  than  the  nerve  is  stimulated,  then  the  current  is  weakened  by  the  negative 
variation  (the  needle  passing  backward  to  x).  When  we  know  the  velocity  of  rotation  of  the  disk, 
it  is  easy  to  calculate  the  rate  at  which  the  impulse  causing  the  negative  variation  passes  along  a 
given  distance  of  nerve  from  N  to  «. 

The  negative  variation  is  absent  in  degenerated  nerves  as  soon  as  they  lose  their  excitability. 

Eye  Currents. — If  a  freshly-excised  eyeball  be  placed  on  the  non-polarizable  electrodes  con- 
nected with  a  galvanometer,  and  if  light  fall  upon  the  eye,  then  the  normal  eye  current  from  the 
cornea  (  -)-  )  to  the  transverse  section  of  the  optic  nerve  (  —  )  is  at  first  increased.  Yellow  light  is 
most  powerful,  and  less  so  the  other  colors  [Holmgren,  M' Kendrick  and Dezvar).  The  iiiuer  surface 
of  the  passive  retina  is  positive  to  the  posterior.  When  the  retina  is  illuminated  there  is  a  double 
variation,  a  negative  variation  with  a  preliminary  positive  increase;  while,  when  the  light  ceases, 
there  is  a  simple  positive  variation.  Retin;i;  in  which  the  visual  purple  has  disappeared,  owing  to 
the  action  of  light,  show  no  variations  [Kiikne  and  Steiner'). 

333.  ELECTROTONIC  CURRENTS  IN  NERVE  AND  MUS- 
CLE.— I.  Positive  Phase  of  Electrotonus. — If  a  nerve  be  so  arranged  upon 
the  electrodes  (,Fig.  366,  I)  that  its  transverse  section  lies  on  one,  and  its  longi- 
tudinal on  the  other,  electrode,  then  the  galvanometer  indicates  a  strong  current. 
If  now  a  constant  current  be  transmitted  through  the  end  of  the  nerve  pro- 
jecting beyond  the  electrodes  (the  so-called  "■polarizing''^  end  of  the  nerve);  and 
if  the  direction  of  this  current  coincides  with  that  in  the  nerve,  then  the  magnetic 
needle  gives  a  greater  deflection,  indicating  an  increase  of  the  nerve  current — "the 
positive  phase  of  electrotonus."  The  increase  is  greater  the  longer  the  stretch 
of  nerve  traversed  by  the  current,  the  stronger  the  galvanic  current,  and  the  less 
the  distance  between  the  part  of  the  nerve  traversed  by  the  constant  current  and 
that  on  the  electrodes. 

2.  Negative  Phase  of  Electrotonus. — If  in  the  same  length  of  nerve  the 
constant  current  passes  in  the  opposite  direction  to  the  nerve  current  (Fig, 
366,  II),  there  is  a  diminution  of  the  electro-motive  force  of  the  latter — 
"  negative  phase  of  electrotonus." 


THEORIES   OF    MUSCLE    AND    NERVE    CURRENTS. 


595 


3.  Equator. — If  two  points  of  the  nerve  equi- 
distant trom  the  equator  be  placed  on  the  electrodes 
(III),  there  is  no  deflection  of  the  galvanometer 
needle  (p.  590,  4).  If  a  constant  current  be 
passed  through  one  free  projecting  end  of  the 
nerve,  then  the  galvanometer  indicates  an  electro- 
motive effect  in  the  same  direction  as  the  constant 
current. 

Electrotonus. — These  experiments  show  that 
a  constant  current  causes  a  change  of  the  electro- 
motive force  of  the  part  of  the  nerve  directly 
traversed  by  the  constant  current,  and  also  in  the 
part  of  the  nerve  outside  the  electrodes.  This 
condition  is  called  electrotonus  {Du  Bois-IicvmonJ, 
1843)- 

The  electrotonic  current  is  strongest  not  far  from  the  elec- 
trodes, and  it  may  be  twenty-five  times  as  strong  as  the  nerve 
current  of  rest  (^  33^^  5)  i  it  is  greater  on  the  anode  than  on 
the  cathode  side;  it  undergoes  a  negative  variation  like  the 
resting  nerve  current  during  tetanus;  it  occurs  at  once  on 
closing  the  constant  current,  although  it  diminishes  uninter- 
ruptedly at  the  cathode  (Du  Boii-Keymond).  These  phe- 
nomena take  place  only  as  long  as  the  nerve  is  excitable. 

If  the  nerve  be  ligatured  in  the  projecting  part  in  the  galvanometer  circuit,  the  phenomena  cease 
in  the  ligatured  part.  The  negative  variation  [\  332)  occurs  more  rapidly  than  the  electrotonic 
increase  of  the  current,  so  that  the  former  is  over  before  the  electro-motive  increase  occurs.  The 
velocity  of  the  electrotonic  change  in  the  current  is  less  than  the  rapidity  of  propagation  of  the 
excitement  in  the  nerves — being  only  8  to  10  metres  per  second  ( Tschiijew,  Bernstein). 

"  The  secondary  contraction  from  a  nerve  "  depends  upon  the  electrotonic  state.  If  the 
sciatic  nerve  of  a  frog's  nerve-muscle  preparation  be  placed  on  an  excised  nerve,  and  if  a  constant 
current  be  passed  through  the  free  end  of  the  latter — non-electrical  stimuli  being  inactive — the 
muscles  contract.  This  occurs  because  the  electrotonizing  current  in  the  excised  nerve  stimulates 
the  nerve  lying  on  it.  By  rapidly  closing  and  opening  the  current,  we  obtain  "  secondary  tetanus 
from  a  nerve"  (p.  593). 

Paradoxical  Contraction. — Exactly  the  same  occurs  when  the  current  is  applied  to  one  of  the 
two  branches  into  which  the  sciatic  nerve  (cut  through  above)  of  the  frog  divides,  i.e.,  the  muscles 
attached  to  both  branches  of  the  nerve  contract. 

Polarizing  After-Currents. — When  the  constant  current  is  opened,  there  are  after-currents 
depending  upon  internal  polarization  [\  32S).  In  //:•/«;•  nerves,  muscle  and  electrical  organs  this 
internal  polarization  current,  when  a  strong  primary  current  of  very  short  duration  is  used,  is  always 
positive,  i.e.,  has  the  same  direction  as  the  primary  current.  Prolonged  duration  of  the  primary 
current  ultimately  causes  negative  polarization.  Between  these  two  is  a  stage  when  there  is  no 
polarization.  Positive  polarization  is  especially  strong  in  nerves  when  the  primary  current  has  the 
direction  of  the  impulse  in  the  nerve  ;  in  muscle,  when  the  primary  current  is  directed  from  the 
point  of  entrance  of  the  nerve  into  the  muscle  toward  the  end  of  the  muscle  (\  334,  II}. 

4.  Muscle  Current  during  Electrotonus. — The  constant  current  also  pro- 
duces an  electrotonic  condition  in  muscle  ;  a  constant  current  in  the  same 
direction  increases  the  mu.scle  current,  while  one  in  an  opposite  direction  weakens 
it,  but  the  action  is  relatively  feeble. 

334.  THEORIES  OF  MUSCLE  AND  NERVE  CURRENTS.— 
I.  Molecular  Theory. — To  explain  the  currents  in  muscle  and  nerve,  Du  Bois- 
Reymond  proposes  the  so-called  molecular  theory.  According  to  this  theory,  a 
nerve  or  muscle  fibre  is  composed  of  a  series  of  small  electro-motive  molecules 
arranged  one  behind  the  other,  and  surrounded  by  a  conducting  indifferent  fluid. 
The  molecules  are  supposed  to  have  a  positive  equatorial  zone  directed  toward  the 
surface,  and  two  negative  polar  surfaces  directed  toward  the  transverse  section. 
Every  fresh  transverse  section  exposes  new  negative  surfaces,  and  every  artificial 
longitudinal  section  new  positive  areas. 

This  scheme  explains  the  strong  currents — when  the  -j-  longitudinal  surface  is  connected  with 


596  Hermann's  difference  theory. 

the  —  transverse  surface,  a  current  is  obtained  from  the  former  to  the  latter — hut  it  does  not  explain 
l\ie  feeble  currents.  To  explain  their  occurrence,  we  must  assume  that,  on  the  one  hand,  the  electro- 
motive force  of  the  molecules  is  weakened  with  varying  rapidity  at  unequal  distances  from  the 
equator;  on  the  other,  at  unequal  distances  from  the  transverse  sectii  n.  Then,  of  course,  differences 
of  electrical  tension  obtain  between  the  stronger  and  the  feebler  molecules. 

Parelectronomy. —  But  the  Ha/;//!?/ transverse  section  of  a  muscle,  i.e.,  the  end  of  the  tendon,  is 
not  negative,  but  more  or  less  positive  electrically.  To  explain  this  condition,  Du  BoisReymond 
assumes  that  on  the  end  of  the  tendon  there  is  a  layer  of  electro- positive  muscle  substance.  He 
supposes  that  each  of  the  peripolar  elements  of  muscle  consists  of  two  bipolar  elements,  and  that  a 
layer  of  this  /lalf  element  lies  at  the  end  of  the  tendon,  so  that  its  positive  side  is  turned  toward 
the  free  surface  of  the  tendon.  This  layer  he  calls  the  "  parelectronomic  layer."  It  is  never  com- 
pletely absent.  Sometimes  it  is  so  marked  as  to  make  the  end  of  the  tendon  -|-  in  relation  to  the 
surface.     Cauterization  destroys  it. 

The  negative  variation  is  explained  by  supposing  that,  during  the  action  of  a  muscle  and  nerve, 
the  electro-motive  force  of  all  the  molecules  is  diminished.  During  partial  contraction  of  a  muscle 
the  contracted  part  assumes  more  the  characters  of  an  indifferent  conductor,  which  now  becomes 
connected  with  the  negative  zone  of  the  passive  contents  of  the  muscular  fibres. 

The  electrotonic  currents  beyond  the  electrodes  in  nerves  must  be  explained.  To  explain  the 
electrotonic  condition  it  is  assumed  that  the  bipolar  molecules  are  capable  of  rotation.  The  polar- 
izing current  acts  upon  the  direction  of  the  molecules,  so  that  they  turn  their  negative  surfaces 
toward  the  anode,  and  their  positive  surfaces  to  the  cathode,  whereby  the  molecules  of  the  intra- 
polar  region  have  the  arrangement  of  a  Volta's  pile.  In  the  part  of  the  nerve  outside  the  elec- 
trodes, the  further  removed  it  is  the  less  precisely  are  the  molecules  arranged.  Hence,  the  swing 
of  the  needle  is  less  the  further  the  e.\trapolar  portion  is  from  the  electrodes. 

II.  Difference  Theory. — The  difference  theory  was  proposed  by  L.  Her- 
mann, and,  according  to  hini,  the  four  following  considerations  are  sufficient  to 
explain  the  occurrence  of  the  galvanic  phenomena  in  living  tissues:  (i)  Proto- 
plasm, by  undergoing  partial  deafh  in  its  continuity,  whether  by  injury  or  by 
(horny  or  mucous)  metamorphosis,  becomes  negative  toward  the  uninjured  part. 
(2)  Protoplasm,  by  being  partially  excited  m  its  continuity,  becomes  negative  to 
the  uninjured  part.  (3)  Protoplasm,  when  partially  heated  in  its  continuity,  be- 
comes positive,  and  by  cooling  negative,  to  the  unchanged  part.  (4)  Protoplasm 
is  strongly J'o/dnzat'/e  on  its  surface  (muscle,  nerve),  the  polarization  constants 
diminishing  with  excitement  and  in  the  process  of  dying. 

Streamless  Fresh  Muscles. — It  seems  that  passive,  uninjured,  and  abso- 
lutely fresh  muscles  are  completely  devoid  of  a  current,  e.g.,  the  heart  {£?!ge/- 
mann),  also  the  musculature  of  fishes  while  still  covered  by  the  skin. 

As  the  skin  of  the  frog  has  currents  peculiar  to  itself,  it  is  possible  with  certain  precautions,  after 
destroying  the  skin  with  alkalies,  to  show  the  streamless  character  of  frogs'  muscles.  L.  Hermann 
also  finds  that  the  muscle  current  is  always  developed  after  a  time,  which  is  very  short,  when  a  new 
transverse  section  is  made. 

Demarcation  Current. — Every  injury  of  a  muscle  or  nerve  causes  at  the  point  of  injury  (de- 
marcation surface)  a  dying  substance  wiiich  behaves  negatively  to  the  positive  intact  substance. 
The  current  thus  produced  is  called  by  Hermann  the  ^^  Jeinarcation  ctirient.^''  If  individual  parts 
of  a  muscle  be  moistened  with  potash  salts  or  muscle  juice  they  become  negatively  electrical;  if 
these  substances  be  removed,  these  parts  cease  to  be  negative  (Biedermann). 

It  appears  that  all  living  protoplasmic  substance  has  a  special  property,  whereby  injury  of  a  part 
of  it  makes  it,  when  dying,  negative,  while  the  intact  parts  remain  positively  electrical.  Thus 
all  transverse  sections  of  living  parts  of  plants  are  negative  to  their  surface  {Bii/f):  and  the  same 
occurs  in  animal  parts,  e.g  ,  glands  and  bones.  Engelniann  made  the  remarkable  observation  that 
the  heart  and  smooth  muscle  again  lose  the  negative  condition  of  their  transverse  section,  when  the 
muscle  cells  are  completely  dead,  as  far  as  the  cement  substance  of  the  nearest  cells;  in  nerves, 
when  the  divided  portion  dies,  as  far  as  the  first  node  of  Ranvier.  When  all  these  organs  are 
again  completely  streamless,  then  the  absolutely  dead  substance  behaves  essentially  as  an  indifferent 
moist  conductor.  Muscles  divided  subcutaneously  and  healed  do  not  exhibit  a  negative  reaction  of 
the  surface  of  their  section. 

All  these  considerations  go  to  show  that  the  pre-existence  of  a  current  in  living 
uninjured  tissues  is  very  doubtful,  and,  perhaps,  can  no  longer  be  maintained. 

Theoretical. — Griinhagen  and  L.  Hermann  explain  the  electrotonic  currents  as  being  due  to 
internal  polarization  in  the  nerve  fibres  between  the  conducting  nucleus  of  the  nerve  and  the  en- 
closing sheaths.  Matteucci  found  that  when  a  wire  is  surrounded  with  a  moist  conductor,  and  the 
covering  placed  in  connection  with  the  electrodes  of  a  constant  current,  currents  similar  to  the 


VARIATIONS   OF   THE    EXCITABILITi'    DURING    ELECTROTONUS.     597 

electrotonic  currents  in  nerves,  and  due  to  polarization,  are  developed.  If  either  the  wire  or  the 
moist  covering  be  interrupted  at  any  part,  then  the  polarization  current  does  not  extend  beyond  the 
rupture.  The  polarization  developed  on  the  surface  of  the  wire  causes  the  conducted  current  to 
extend  beyond  the  electrodes.  Muscles  and  nerves  consist  of  fibres  surrounded  by  indifferent  con- 
ductors. As  soon  as  a  constant  current  is  closed,  on  their  surface,  internal  polarization  is  developed, 
which  produces  the  electrotonic  variation  ;  it  disappears  again  on  opening  or  breaking  the  current. 
Polarization  is  detected  by  the  fact  that  in  a  living  nerve  the  galvanic  resistance  to  conduction  across 
a  fibre  is  about  five  times,  and  in  muscles  about  seven  times  greater  than  in  the  longitudinal 
direction. 

Action  Currents  — The  term  "  action  current "  is  applied  by  L.  Hermann  to  the  currents  obtained 
during  the  activity  of  a  muscle.  When  a  single  stimulation  wave  (contraction)  passes  along 
muscular  fibres,  which  are  connected  at  two  points  with  a  galvanometer,  then  that  point  through 
which  the  wave  is  just  passing  is  negative  to  the  other.  Occasionally,  in  excised  muscles,  local 
contractions  occur,  and  these  points  are  negative  to  the  <  tber  ]^a-sive  parts  of  the  muscle  [Bieder- 
mnnn).  In  order,  therefore,  to  explain  the  currents  obtained  from  a  frog's  leg  during  tetanus,  we 
must  assume  that  the  end  of  the  fibre  which  is  negative  partici  ates  less  in  the  excitement  than  the 
middle  of  the  fibre.     But  this  is  the  case  only  in  dying  or  fatigued  muscles  (p.  591,  2). 

According  to  J  336,  D,  the  direct  application  of  a  constant  current  to  a  muscle  causes  contraction 
first  at  the  cathode,  when  the  current  is  closed,  and  when  it  is  opened,  at  the  anode.  This  is  ex- 
plained by  assuming  that,  during  the  closing  contraction,  the  muscle  is  negative  at  the  cathode, 
while  with  the  opening  contraction  the  negative  condition  is  at  the  anode. 

If  a  muscle  be  thrown  into  contraction  by  stimulating  its  nerve,  then  the  wave  of  excitement 
travels  from  the  entrance  of  the  nerve  to  both  ends  of  the  muscle,  which  also  behave  negatively 
to  the  passive  parts  of  the  muscle.  According  to  the  point  at  which  the  nerve  enters  the  muscle, 
the  ascending  or  descending  wave  of  excitement  will  reach  the  end  (origin  or  insertion)  of  the 
muscle  sooner  than  the  other.  On  placing  such  a  muscle  in  the  galvanometer  circuit,  then  at  first 
that  end  of  the  muscle  will  be  negative  which  lies  nearest  to  the  point  of  entrance  of  the  nerve 
(t".^.,  the  upper  end  of  the  gastrocnemius),  and  afterward  the  lower  end.  Thus  there  appears  rap- 
idly after  each  other,  at  first  a  descending  and  then  an  ascending  current  in  the  galvanometer  circuit 
(of  course,  reversed  within  the  muscle  itself)  {Six'.  Meyer)  (\  332,4). 

The  same  occurs  in  the  muscles  of  the  human  forearm.  When  these  were  caused  to  contract 
through  their  nerves,  at  first  the  point  of  entrance  of  the  nerve  (10  cm.  above  the  elbow  joint)  was 
negative,  and  then  followed  the  ends  of  the  muscles  when  the  contraction  wave,  with  a  velocity  of 
10  to  13  metres  per  second,  reached  them  (L,  Hermann)  (\  399,  l). 

If  a  completely  uninjured,  streamless  muscle  be  made  to  contract  directly  and  in  toto.  then 
neither  during  a  single  contraction  nor  in  tetanus  is  there  a  current,  because  the  whole  of  the  muscle 
passes  at  the  same  moment  into  a  condition  of  contraction. 

Nerve  Currents. — Hermann  also  supposes  that  the  contents  of  dying  or  active  nerves  behave 
negatively  to  the  passive  normal  portions. 

Imbibition  Currents — When  water  flows  through  capillary  spaces,  this  is  accompanied  by  an 
electrical  movement  in  the  same  direction  ( Quincke,  Zollner).  Similarly,  the  forward  movement  of 
water  in  the  capillar)^  interspaces  of  non-living  parts  (pores  of  a  porcelain  platej  is  also  connected 
with  electrical  movements,  which  have  the  same  direction  as  the  current  of  water.  1  he  same  effect 
occurs  in  the  movement  of  water,  which  results  in  that  condition  known  as  imbibition  of  a  body. 
We  must  remember  that  at  the  demarcation  surface  of  an  injured  nerve  or  muscle  imbibition  takes 
place;  that  also  at  the  contracted  parts  of  a  muscle  imbibition  of  fluid  occurs  (^  227,  II);  and 
that  during  secrttion  there  is  a  movement  of  the  fluid  particles. 

In  Plants,  electrical  phenomena  have  been  observed  during  the  passive  bending  of  vegetable 
parts  (leaves  or  stalks),  as  well  as  during  the  active  movements  which  are  associated  with  the  bend- 
ing of  certiin  parts,  e.g.,  as  in  the  mimosa  and  dioncea  (p.  317)  (Burdon  Sanderson).  These  phe- 
ncmieiia  are  perhaps  explicable  by  the  moveinent  of  water  which  must  take  place  in  the  interior  of 
the  vegetable  parts  (A.  G.  Kunkel).  The  root  cap  of  a  sprouting  plant  is  negative  to  the  seed 
coverings  (j%/v«rtH«) ;  the  cotyledons  positive  to  the  other  parts  of  the  seedling  (MiiUer-Hctt- 
lingen).     In  the  incubated  hen's  egg  the  embryo  is  -f-  ,  the  yelk  —  {Hermann  and -v.  Gendre). 

335.  ELECTRONIC  ALTERATION  OF  THE  EXCITABIL- 
ITY.— Cause  of  Electrotonus. — If  a  certain  stretch  of  a  living  nerve  be  trav- 
ersed by  a  constant  electrical  ( '■'polarizing'' )  current, ^it  pas.ses  into  a  condition 
of  altered  excitability  {Ritter,  1S02,  and  others),  which  Du  Bois-Reyniond 
called  the  electrotonic  condition,  or  i\m\AY  eiectrofoniis.  This  condition  of  altered 
e.vcitability  extends  not  only  over  the  ])art  actually  traversed  by  the  current,  iiilra- 
polar  portion,  but  it  is  communicated  to  tlie  entire  nerve.  Pfliiger  (1859)  dis- 
covered the  following  laws  of  electrotonus  :  — 

At  the  positive  iiole  anode  (Fig.  367,  A)  the  excitability  is  diminished — this  is 
the  region  of  anelectrotonus  ;  at  the  negative  pole  {cathode — K)  it  is  increased 


598 


PROOF   OK    ELECTROTONUS    IN    MOTOR   NERVES. 


— this  is  the  region  of  cathelectrotonus.  The  changes  of  excitability  are  most 
marked  in  the  region  of  the  poles  themselves. 

Indifferent  Point. — In  the  intrapolar  region  a  point  must  exist  where  the 
anelectrotonic  and  cathelectrotonic  regions  meet,  where  therefore  the  excitability 
is  unchanged  ;  this  is  called  the  indifferent  or  neutral  point.  This  point  lies 
nearer  the  anode  (/)  with  a  weak  current,  but  with  a  strong  current  nearer  the 
cathode  (i\'^) ;  hence,  in  the  first  case,  almost  the  whole  intrapolar  portion  is  more 
excitable  ;  in  the  latter,  less  excitable.  [Expressed  otherwise,  a  weak  current  in- 
creases the  area  over  which  the  negative  pole  prevails,  while  the  reverse  is  the  case 
w'ith  a  strong  current.]  Very  strong  currents  greatly  diminish  the  conductivity 
at  the  anode,  and  indeed  may  make  the  nerve  completely  incapable  of  conduction 
at  this  part. 

Extrapolar  Region. — The  extrapolar  area,  or  that  lying  outside  the  electrodes, 
is  greater  the  stronger  the  current.  Further,  with  the  weakest  currents,  the  extra- 
polar  anelectrotonic  area  is  greater  than  the  extrapolar  cathelectrotonic.  With 
strong  currents  this  relation  is  reversed. 

Fig.  367  shows  the  excitability  of  a  nerve  (A',  n)  traversed  by  a  constant  current  in  the  direction 
of  the  arrow.  The  curve  shows  the  degree  of  increased  excitabihty  in  the  neighborhood  of  the 
cathode  [/C]  as  an  elevation  above  the  nerve,  diminution  at  the  anode  [A)  as  a  depression.  •  The 

Fig.  367. 


Scheme  of  the  electrotonic  excitability. 


curve  m,  0,  i,,,p,  r,  shows  the   degree  of  excitability  with  a  strong  current ;  e,f,  i^,  h,  k,  with  a 
medium  current ;  lastly,  a,  h,  i,  c,  tij  with  a  weak  cui  rent. 

The  electrotonic  effect  increases  with  the  length  of  the  nerve  traversed  by  the  current.  The 
changes  of  the  excitability  in  eleclrotonus  occur  instantly  when  the  circuit  is  closed,  while  anelec- 
trotonus  develops  and  extends  more  slowly.  Cold  diminishes  electrolonus  [Hermann  ajid  v. 
Genitre). 

When  the  polarizing  current  is  opened,  at  first  there  is  a  reversal  of  the  rela- 
tions of  the  excitability,  and  then  there  follows  a  transition  to  the  normal  condi- 
tion of  excitability  of  the  passive  nerve  iyPfliiger).  At  the  very  first  moment  of 
closing,  Wundt  observed  that  the  excitability  of  the  whole  nerve  was  increased. 

I.  Proof  of  Electrolonus  in  Motor  Nerves. — To  test  the  laws  of  electrolonus,  take  a  frog's 
nerve-muscle  preparation  (Fig.  364).  A  constant  current  (p.  577)  is  applied  to  a  limited  part  of 
the  nerve  by  means  of  non-polarizable  electrodes  A  stimulus,  electrical,  chemical  (saturated  solu- 
tion of  common  salt),  or  mechanical  is  applied  either  in  the  region  of  the  anode  or  cathode;  and 
we  observe  whether  the  contraction  which  results  is  greater  when  the  polarizing  current  is  opened 
or  closed.     We  will  consider  the  following  cases  (Fig.  36S): — 

(a)  Descending  extrapolar  anelectrotonus,  i.  e.,  with  a  descending  current  we  have  to  test 
the  excitability  of  the  extrapolar  region  at  the  anode.  If  the  stimulus  (common  salt)  applied  at  R 
(while  the  circuit  was  open)  causes  in  this  case  (A)  moderately  strong  contractions  in  the  limb,  then 
these  at  once  become  weaker,  ox  disappear  as  soon  as  the  constant  current  is  transmitted  through  the 
nerve.  After  the  circuit  is  opened,  the  contractions  produced  by  the  salt  again  occur  of  the  original 
strength. 


PROOF   OF    ELECTROTONUS    IN    INHIBITORY    NERVES. 


599 


(b)  Descending  extrapolar  cathelectrotonus  (A).  The  stimulus  (salt)  is  at  R,  and  the  con- 
tractions thereliy  produced  are  at  once  increased  after  closing  the  polarizing  current.  On  opening 
it  they  are  again  weakened. 

(c)  Ascending  extrapolar  anelectrotonus  (B).  The  salt  lies  at  r.  In  this  case  we  must 
distinguish  the  strenglh  of  the  polarizing  current :  (i)  When  the  current  is  very  weak,  which  can 
b.'  obtained  with  the  aid  of  the  rheocord  (Fig.  344),  on  closing  the 
polarizing  current,  there  is  an  increase  of  the  contraction  produced  by 
the  salt.  (2)  If,  however,  the  current  is  stronger,  the  contractions 
become  either  smaller  or  cease.  This  is  due  to  the  fact  that  with 
strong  currents  the  conductivity  of  the  anode  is  diminished  or  even 
abolished  (p.  597).  Although  the  salt  acts  on  the  excitable  nerve, 
there  is  no  contraction  of  the  muscle,  as  the  conduction  of  an  impulse 
is  prevented  by  the  resistance  in  the  nerve. 

The  law  of  electrotonus  may  also  be  demonstrated  on  a  completely 
isolated  nerve.  The  end  of  the  ner\'e  is  properly  disposed  upon 
electrodes  connected  with  a  galvanometer,  so  as  to  obtain  a  strong 
current.  If  the  nerve,  when  the  constant  current  is  closed,  is  stimu- 
lated in  the  anelectrotonic  area,  e.  f.,  by  an  induction  shock,  then  the 
negative  variation  is  weaker  than  when  the  polarizing  circuit  was 
open.  Conver>ely,  it  is  stronger  when  it  is  stimulated  in  the  cathelec- 
trotonic  area  (Bernstein).  The  currents  from  the  extrapolar  areas  of 
a  nerve  in  a  condition  of  electrotonus  exhibit  the  negative  variation 
when  the  nerve  is  stimulated. 

Proof  in  Man. — In  performing  this  experiment  it  is  important  to 
remember  the  distribution  of  the  current  in  the  body.  If  both  elec- 
trodes, for  example,  be  placed  over  the  course  of  the  ulnar  nerve 
(Fig.  369),  the  currents  entering  the  nerve  at  the  anode  (-(-  a  a)  must 
diminish  the  excitability;  only  aliove  and  below  the  anode  (at  <-  r)  the 
positive  current  emerges  from  the  nerve  and  excites  cathelectrotonus 
at  these  points.  Similarly,  where  the  cathode  is  applied  (—  c  c)  there 
is  increased  excitability;  but  in  higher  and  lower  parts  of  the  nerve, 
where  (at  a  a)  the  positive  current  (coming  from  +)  enters  the  nerve,  the  excitability  is  diminished 
(anelectrotonus)  {v.  Hehnholtz,  Erb).  If  we  desire  to  stimulate  in  the  neighborhood  of  an  elec- 
trode, then  we  cannot  act  upon  that  part  of  the  nerve  whose  excitability  is  influenced  by  the  electrode. 


Method  of  testing  the  e.xcil 
bility  in  electrotonus.  R, 
R,,  r,,  where  the  comm. 
salt  (stimulus)  is  applied. 


Fig.  369. 


Scheme  of  the  distribution  of  an  electrical 


In  order,  therefore,  to  stimulate  directly  the  same  point  on  which  the  electrode  acts,  it  is  necessary 
I'l  apply  the  stimulus  at  the  same  time  by  the  electrode  itself,  e.  g.,  either  mechanically  or  by  con- 
ducting the  stimulating  current  through  the  polarizing  circuit  (  IVa/ier  and de  IVattevilte). 

II.  Proof  of  Electrotonus  in  Sensory  Nerves. — Is  ilate  the  sciatic  nerve  of  a  decapitated 
frog.  When  this  nerve  is  stimulated  in  its  course  with  a  saturated  solution  of  common  salt,  reflex 
movements  are  excited  in  the  other  leg,  the  spinal  cord  being  still  intact.  These  disappear  as  soon 
as  a  constant  current  is  applied  to  the  ner\e,  provided  the  salt  lies  in  the  anelectrotonic  3xt3.(Pfliiger, 
and  Zurhelle,  Hdllsten). 

III.  Proof  of  Electrotonus  in  Inhibitory  Nerves. — To  show  this,  proceed  thus  :  On  causing 
dyspnoea  in  a  rabbit,  the  number  of  heart  heats  is  diminished,  owing  to  the  action  of  the  dyspnoeic 
blood  on  the  cardio. inhibitory  centre  in  the  medulla  oblongata.  If,  after  dividing  the  vagus  on  one 
side,  a  constant  descending  current  be  passed  through  the  other  intact  vagus,  the  number  of  pulse 
beats  is  again  increased  (descending  extrapolar  anelectrotonus).     If,  however,  the  current  through 


600 


THE    LAW   OF   CONTRACTION. 


the  nerve  be  an  ascending  one,  then  with  weak  currents  the  number  of  heart  beats  increases  still 
more  (ascending  extrapolar  calhelectrotonus).  Hence,  the  action  of  inhibitory  nerves  in  eleclrotonus 
is  the  opposite  of  that  in  motor  nerves. 

During  the  electrotonus  of  muscle,  the  excitability  of  the  intrapolar  portion 
is  altered.  The  delay  in  the  conduction  is  confined  to  this  area  alone  {v.  Bezold) 
—compare  §337,  i. 

336.  ELECTROTONUS— LAW  OF  CONTRACTION.— Opening 

and  Closing  Shocks. — A  nerve  is  stimulated  both  at  the  moment  of  the  occur- 
rence and  that  of  disappearance  of  electrotonus  (/.  c,  by  closing  and  opening  the 
current — Ritter):  (i)  When  the  current  is  closed,  the  stimulation  occurs  only 
at  the  cathode,  /.  e.,  at  the  moment  when  the  electrotonus  takes  place.  (2) 
When  the  current  is  opened,  stimulation  occurs  only  at  the  anode,  /.  e.,  at  the 
moment  when  the  electrotonus  disappears.  (3)  The  stimulation  at  the  occurrence 
of  cathelectrotonus  is  stronger  than  at  the  disappearance  of  anelectrotonus 
{Pfliigc-)- 

Ritter's  Opening  Tetanus. — That  stimulation  occurs  only  at  the  anode,  when  the  current  is 
opened,  was  proved  by  PflUger  by  means  of  "  Ritter's  opening  tetanus."  Ritter's  tetanus  consists 
in  this,  that  when  a  constant  current  is  passed  for  a  long  time  through  a  long  stretch  of  nerve,  on 
opening  the  current,  tetanus  lasting  for  a  considerable  time  results.  If  the  current  was  a  descending 
one,  then  this  tetanus  ceases  at  once  after  section  of  the  intrapolar  area,  a  proof  that  the  tetanus 
resulted  from  the  now  separated  anode.  If  the  current  was  an  ascending  one,  section  of  the  nerve 
has  no  effect  on  the  tetanus. 

Pfliiger  and  v.  Bezold  also  proved  that  the  closing  contraction  at  the  cathode  precedes  that  at  the 
anode.  Thus,  they  observed  that  with  a  descending  current  the  closing  contraction  in  the  muscle 
at  the  moment  of  closing  occurred  earlier  than  the  opening  contraction  at  the  moment  of  opening; 
and,  conversely,  with  an  ascending  current,  the  closing  contraction  occurred  later,  and  the  opening 
contraction  sooner.  The  difterence  in  time  corresponds  to  the  time  required  for  the  propagation  of 
the  impulse  in  the  intrapolar  region  (|  337).  If  a  large  part  of  the  intrapolar  region  in  a  frog's 
nerve  be  rendered  inexcitable  by  applying  ammonia  to  it,  then  only  the  electrode  next  the  mus- 
cle stimulates,  i.  e.,  always  on  closing  a  descending  current  and  on  opening  an  ascending  one 
[Biedermann). 

A.  The  law  of  contraction  is  valid  for  all  kinds  of  nerves. — I.  The  contrac- 
tion occurring  at  the  closing  or  opening  of  a  constant  current  varies  with  {a)  the 
direction  (Pfaff),  and  (/')  the  strength  of  the  current  (Heidenhairi). 

(i)  Very  feeble  currents,  in  conformity  with  the  third  of  the  above  state- 
ments, cause  only  a  closing  contraction,  both  with  an  ascending  and  a  descend- 
ing current.  The  disappearance  of  electrotonus  is  so  feeble  a  stimulus  as  not  to 
excite  the  nerve. 

(2)  Medium  currents  cause  opening  or  closing  contractions  both  with  an 
ascending  and  a  descending  current. 

(3)  Very  strong  currents  cause  only  a  closing  contraction  with  a.dcsceniiing  cur- 
rent ;  the  opening  shock  does  not  occur,  because,  with  very  strong  currents,  al- 
most the  whole  of  the  intrapolar  portion  of  the  electrotonic  nerve  is  incapable  of 
conducting  an  impulse  (p.  598).  Ascending  currents  cause  only  an  opening  con- 
traction for  the  same  reason.  With  a  certain  strength  of  current,  the  muscle  re- 
mains tetanic  while  the  current  is  closed  ("  closing  tetanus^'). 

[The  law  of  contraction  is  formulated  : — R  =  rest ;  C  =  contraction.] 


Strength 

of  Current. 

Ascending. 

Descending. 

On  Closing. 

On 

Open 

ing. 

On  Closing. 

On  Open 

ng.      1 

Weak 

C 
C 
R 

R 

c 
c 

C 
C 
C 

R 

C 
R 

Medium, . 
Strong,    . 

THE    LAW   OF   CONTRACTION.  601 

II.  In  a  dying  nerve,  losing  its  excitability,  according  to  the  Ritter-Valli  law 
(§  325,  7),  the  law  of  contraction  is  modified.  In  the  stage  of  increased  excita- 
bility weak  currents  cause  only  closing  contractions  with  both  directions  of  the 
current.  In  the  following  stage,  when  the  excitability  begins  to  diminish,  weak 
currents  cause  opening  and  closing  contractions  with  both  currents.  Lastly,  when 
the  excitability  is  very  greatly  diminished,  the  descending  current  is  followed  only 
by  a  closing  contraction,  and  the  ascending  by  an  opening  contraction  {Ri/ter, 

III.  As  the  various  changes  in  excitability  occur  in  a  centrifugal  direction 
along  the  nerve,  we  may  detect  the  various  stages  simultaneously  at  different  parts 
along  the  course  of  the  nerve.  According  to  Valentin,  Fick,  CI.  Bernard,  and 
Schiff,  the  living  intact  nerve  shows  only  a  closing  contraction  with  both  direc- 
tions of  the  current,  and  opening  contractions  only  with  very  strong  currents. 

Fleischl's  Law  of  Contraction. — v.  FleischI  and  Strieker  have  stated  a  different  law  in  re- 
spect to  the  fact  that  the  excitability  varies  at  certain  points  in  the  course  of  a  nerve.  The  sciatic 
nerve  is  divided  into  three  areas:  (l)  Stretches  from  the  muscle  to  the  place  where  the  branches 
for  the  thigh  muscles  are  given  off ;  (2)  from  here  to  the  intervertebral  ganglion;  (3)  from  here 
into  the  spinal  cord.  Each  of  these  three  areas  consists'of  two  parts  ("  upper  and  lower  pole  "), 
which  adjoin  each  other  at  an  equator.  In  each  upper  pole  the  excitability  of  the  nerve  is  greater 
for  descending  currents,  and  in  each  lower  pole  for  ascending  ones.  At  each  equator  the  excitabil- 
ity of  the  nerve  is  the  same  for  ascending  and  descending  currents.  The  difference  in  the  activity, 
due  to  the  direction  of  the  current,  is  greater  for  each  stretch  of  nerve  the  greater  this  stretch  is  dis- 
tant from  the  equator.  The  excitability  is  less  at  those  points  of  the  nerve  where  the  three  areas 
join  each  other. 

Eckhard  observed  that,  on  opening  an  ascending  medium  current  applied  to  the  hypoglossal  nerve 
of  a  rabbit,  one-half  of  the  tongue  exhibited  a  trembling  movement  instead  of  a  contraction,  while 
on  closing  a  descending  current  the  same  result  occurred  (^  297,  3).  According  to  Pfliiger,  the 
molecules  of  the  passive  nerve  are  in  a  certain  state  of  medium  mobility.  In  cathelectrotonus  the 
mobility  of  the  molecules  is  increased,  in  anelectrotonus,  diminished. 

B.  The  law  for  inhibitory  nerves  is  similar.  Moleschott,  v.  Bezold,  and 
Bonders  have  found  similar  results  for  the  vagus,  with  this  difference,  that,  instead 
of  the  contraction  of  a  muscle,  there  is  inhibition  of  the  heart. 

C.  For  sensory  nerves,  also,  the  result  is  the  same,  but  we  must  remember 
that  the  perceptive  organ  lies  at  the  central  end  of  the  nerve,  while  in  a  motor 
nerve  it  (muscle )  is  at  the  periphery.  Pfliiger  studied  the  effect  of  closing  and  open- 
ing a  current  on  sensory  nerves  by  observing  the  reflex  movement  which 
resulted.  Weak  currents  cause  only  closing  contractions  ;  medium  currents  both 
opening  and  closing  contractions  :  descending  strong  currents  only  opening  con- 
tractions ;  and  ascending  only  closing  contractions.  fFca/' currents  applied  to 
the  human  skin  cause  a  sensation  with  both  directions  of  the  current  only  at  closing  ; 
strong  descetuiing  cwxxtwVs,  S-itVi-izXiow  only  at  opening;  strong  ascending  cwxxtwXi  a 
sensation  only  at  closing  {Marianini,  Matteucei).  When  the  current  is  closed  there 
is  prickly  feeling,  which  increases  with  the  strength  or  the  current  {Volta').  Analo- 
gous phenomena  have  been  observed  in  the  sense  organs  (sensations  of  light 
and  sound)  by  Volta  and  Ritter. 

D.  In  muscle,  the  law  of  contraction  is  proved  thus — by  fixing  one  end  of  the 
muscle,  keeping  it  tense,  so  that  it  cannot  shorten,  and  opening  and  closing  the 
current  at  this  end.  The  end  of  the  muscle,  which  is  free  to  move,  shows  the 
same  law  of  contraction  as  if  the  motor  nerve  was  stimulated  {v.Bezo/d).  On 
closing  the  current,  the  contraction  begins  at  the  cathode  ;  on  opening,  at  the 
anode  {Engelmann).  E.  Hering  and  Biedermann  showed  more  clearly  that  both 
the  closing  and  opening  contractions  are  purely  polar  effects  ;  when  a  weak  cur- 
rent applied  to  a  muscle  is  closed,  the  first  effect  is  a  small  contraction  limited  to 
the  cathodic  surface  of  the  muscle.  Increase  of  the  current  causes  increased  con- 
traction which  extends  to  the  anode,  but  which  is  weaker  there  than  at  the 
cathode  ;  at  the  same  time,  the  muscle  remains  contracted  dunng  the  time  the  cur- 
rent is  closed.    On  opening,  the  contraction  begins  at  the  anode;  even  after  open- 


602  TRANSMISSION    OF    NERVOUS    IMPULSES. 

ing,  the  muscle   for  a  time  may  remain  contracted,  which  ceases  on   closing  the 
current  in  the  same  direction. 

By  killing  the  end  of  a  muscle  in  various  ways,  the  excitability  is  diminished  near  this  part. 
Hence,  at  such  a  place  the  polar  action  is  feeble  (van  Loon  and  Engelmann,  Biedermann). 
Touching  a  part  with  extract  of  flesh,  potash,  or  alcohol  diminishes  locally  the  polar  action,  while 
soda  salts  and  veratrin  increase  it  [Biedermann'). 

Closing  Continued  Contraction. — The  moderate  continued  contraction,  which  is  sometimes 
observed  in  a  muscle  while  the  current  is  closed  (Fig.  301,  O),  depends  upon  the  abnormal  pro- 
longation of  the  closing  contraction  at  the  cathode  when  a  strong  stimulus  is  used,  or  during  the 
stage  of  dying,  or  in  cooled  winter  frogs ;  sometimes  the  opening  of  the  current  is  accompanied  by 
a  similar  contraction  proceeding  from  the  anode  (Biedermann').  This  tetanus  is  also  due  to  the 
summ.ation  of  a  series  of  simple  contractions  (\  298,  III).  By  acting  on  a  muscle  with  a  two  per 
cent,  saline  solution  containing  sodic  carbonate,  the  duration  of  the  contraction  is  increased  consid- 
erably, and  occasionally  the  muscle  shortens  rhythmically  (|  296)  (Biedermann). 

If  the  whole  muscle  is  placed  in  the  circuit,  the  closing  contraction  is  strongest 
with  both  directions  of  the  current ;  during  the  time  the  current  is  closed  a  con- 
tinued contraction  is  strongest  when  the  current  is  ascending  (  Wuuiit). 

Inhibitory  Action. — The  constant  current,  when  applied  to  a  muscle  in  a 
condition  of  continued  and  sustained  contraction,  has  exactly  the  opposite  effect 
to  that  on  a  relaxed  muscle.  If  a  constant  current  be  applied  by  means  of  non- 
polarizable  electrodes  to  a  muscle  in  a  state  of  continued  contraction,  e.g.,  after 
poisoning  with  veratrin  or  through  the  contracted  ventricle,  when  the  current  is 
closed  there  is  a  relaxation  beginning  at  the  anode  and  extending  to  the  other 
parts;  on  opening  the  current  applied  to  muscle  in  continued  contraction,  the 
relaxation  proceeds  from  the  cathode.  Pawlow  found  nerve  fibres  in  the  adductor 
muscle  of  the  mussel,  whose  stimulation  caused  relaxation  of  the  muscular  con- 
traction. 

Ritter's  Opening  Tetanus.^ — If  a  nerve  or  muscle  be  traversed  by  a  constant 
current  for  some  time,  we  often  obtain  a  prolonged  tetanus,  after  opening  the 
current  (Ritter's  opening  tetanus,  1798).  It  is  set  aside  by  closing  the  original 
current,  while  closing  a  current  in  the  opposite  direction  increases  it  ("Vo/ta's 
alternative''''^.  The  continued  passage  of  the  current  increases  the  excitability 
for  the  opening  of  the  current  in  the  same  direction,  and  for  the  closing  of  the 
reverse  current ;  conversely,  it  diminishes  it  for  the  closing  of  the  current  in  the 
same  direction,  and  for  the  opening  of  the  reverse  current  {Volta,  Rosenthal, 
Wundt). 

In  a  nerve-muscle  preparation  used  to  prove  the  law  of  contraction,  of  course  a  demarcation  cur- 
rent is  developed  in  the  nerve  (\  334,  II).  If  an  artificial,  weak  stimulating  current  be  applied  to 
such  a  nerve,  we  obtain  an  interference  effect  due  to  these  two  currents;  closing  a  weak  current 
causes  a  contraction,  which,  however,  is  not  properly  a  closing  contraction,  but  depends  upon  the 
opening  of  a  branch  of  the  demarcation  current ;  conversely,  the  opening  of  a  weak  current  may 
excite  a  contraction,  which  is  really  due  tn  the  closing  of  a  side  branch  of  the  nerve  current  in  a 
secondary  circuit  through  the  electrodes  (Herintr,  Biedertnann,  Gri'itzner).  According  to  Griitzner 
and  Tiegerstedt,  the  cause  of  the  opening  contraction  is  partly  due  to  the  occurrence  of  polarizing 
after-currents  (\  333). 

Engelmann  and  Griinhagen  explain  the  occurrence  of  opening  and  closing  tetanus,  thus,  as  due 
to  'atent  stimulations,  drying,  variations  of  the  temperature  of  the  prepared  nerve,  which  of  them- 
selves are  too  feeble  to  cause  tetanus,  but  which  become  effective  if  an  increased  excitability  obtains 
at  the  cathode  after  closure,  and  at  the  anode  after  opening  the  current. 

Biedermann  showed  that,  under  certain  conditions,  two  successive  opening  contractions  can  be  ob- 
tained in  a  frog's  nerve-muscle  preparation,  the  second  and  later  one  corresponding  to  Ritter's 
tetanus.  The  first  of  these  contractions  is  due  to  the  disappearance  of  anelectrotonus  in  PflUger's 
sense;  the  second  is  explained,  like  Ritter's  opening  tetanus,  in  Engelmann's  and  Griinhagen's 
sense. 

337.  TRANSMISSION  OF  NERVOUS  IMPULSES.— i.  If  a 
motor  nerve  be  stimulated  at  its  central  end  ( i )  a  condition  of  excitation  is 
set  up,  and  (2)  an  impulse  is  transmitted  along  the  nerve  to  the  muscle  with  a 
certain  velocitv.  The  latter  depends  on  the  former  and  represents  the  function 
of  conductivity.     The  velocity  is  about  2iY^  metres  [about  90  feet]  per  second 


METHOD    OF    ESTIMATING    RAPIDITY   OF    A    NERVE    IMPULSE.       603 


(7'.  Hehnholtz)  and  for  the  human  motor  nerves  33.9  [100  to  120  feet  per  second] 
(v.  Helmholtz  and  Baxt).     The  second  depends  on  the  first. 

The  velocity  is  less  in  the  visceral  nerves,  e.g.,  in  the  pharyngeal  branches  of  the  vagus  8.2 
metres  [26  feet]  [C/iauveau)  ;  in  the  motor  nerves  of  the  lobster  6  metres  [18  feet]  (Fredericq  and 

van  de  Velde). 

Modifying  Conditions. — The  velocity  is  influenced  by  various  conditions  : 
Temperature. — It  is  lessened  considerably  by  cold  {v.  Helmholtz),  but  both  high 
and  low  temperatures  of  the  nerve  (above  or  below  15°  to  25°  C.)  lessen  it 
(Steiner  and  Trojtzkf)  ;  also  eiirara,  the  electrotonic  condition  {v.  Bezold) ;  or  only 
anelectrotonus,  while  cathelectrotonus  increases  it  {Rutherford,  JFnndt).  It 
varies  also  with  the  length  of  the  conducting  nerve,  but  it  increases  with  the 
strength  of  the  stimulus  {v.  Helmholtz  and  Baxt ),  although  not  at  first  (r'.  Vint- 
schgait). 

Methods. — (i)  V.  Helmholtz  (1850)  estimated  the  velocity  of  the  nerve  impulse  in  a  frog's 
motor  nerve,  after  the  method  of  Pouillet.  The  method  depends  upon  the  fact  that  the  needle  of 
a  galvanometer  is  deflected  by  a  current  of  very  short  duration;  the  extent  of  the  deflection  being 

Fig.  370. 


w     k 

V.  HelmhoUz'i  method  of  estimating  the  velocity  of  a  nerve  impulse. 

proportional  to  the  duration  and  strength  of  the  current.  The  aoparatus  is  so  arranged  that  the 
"  time-marking  current "  is  closed  at  the  moment  the  nerve  is  stimulated,  and  opened  again  when 
the  muscle  contracts.  If  the  nerve  attached  to  a  muscle  be  now  stimulated  at  the  further  point 
from  the  muscle,  and  a  second  time  near  its  entrance  to  the  muscle,  then  in  the  latter  case  the  time 
between  the  application  of  the  stimulus  and  the  beginning  of  the  contraction  of  the  muscle,  i.  <■., 
the  deflection  of  the  galvanometer,  will  be  less  than  in  the  former  case,  as  the  impulse  has  to  trav- 
erse the  whole  length  of  the  nerve  to  reach  the  muscle.  The  diff^erence  between  the  two  times  is 
the  time  required  by  the  impulse  to  traverse  a  given  distance  of  nerve.  Fig.  370  shows  in  a 
diagrammatic  manner  the  arrangement  of  the  experiment.  The  galvanometer,  G,  is  placed  in  the 
lime-marking  circuit  (open  at  first),  a,  b  (element),  c  (piece  of  platinum  on  a  key,  W),  introduced 
into  the  time-marking  circuit,  d,  e,f,  h.  The  circuit  is  made  by  closing  the  key,  S,  when  d  de- 
presses the  platinum  plate  of  the  key,  W.  At  once,  when  the  current  is  closed,  the  magnetic 
needle  is  deflected,  and  its  extent  noted.  At  the  same  moment  in  which  the  current  between  c  and 
d  is  closed  the  primary  circuit  of  the  induction  machine  is  opened,  the  circuit  being  i,  k,  I  (element), 
m,  O  (primary  spiral),/.  Thereby  an  opening  shock  is  induced  in  the  secondary  spiral,  R.  which 
stimulates  the  nerve  of  the  frog's  leg  at  n.  Thus,  the  closing  of  the  galvanometer  circuit  exactly 
coincides  with  the  stimulation  of  the  nerve.  The  impulse  is  propagated  through  the  nerve  to  the 
muscle,  M,  and  the  latter  contracts  when  the  impulse  reaches  it,  at  the  same  time  opening  the  time- 


604    METHOD    OF   ESTIMATING    RAPIDITY   OF    A    NERVE    IMPULSE. 

measuring  circuit  at  the  double  contact,  e  and  f,  by  raising  the  lever,  H,  which  rotates  on  x.  At 
the  moment  of  opening,  the  fuither  deflection  of  the  magnetic  needle  ceases.  The  contact  at  /  is 
made  by  a  pointed  cupola  of  mercury.  Wlien  the  lever,  H,  falls  after  the  contact  of  the  muscle, 
so  that  the  point,  e,  comes  into  contact  with  the  underlying  solid  plate,  y,  the  contact  at  f  still  re- 
mains open,  ;'.  e.,  through  the  galvanometer  circuit.  If  the  nerve  be  stimulated  with  the  opening 
shock,  first  <it  «,  and  then  at  N,  the  deflection  of  the  needle  is  greater  in  the  former  than  in  the 
latter  case.  From  the  difference,  we  calculate  the  time  for  the  conduction  of  the  impulse  in  the 
stretch  of  the  nerve  between  n  and  N. 

[2.  A  simpler  method  is  that  shown  in  the  scheme,  Fig.  371.     Use  a  pendulum 


Scheme  for  measuring  the  velocity  of  nerve  energy.  /,  clamp  for  ferr 
from,  C,  commutator  :  II,  secondary  ;  I,  primary  spiral  of  indu 
on  the  smoked  plate  P. 


or  spring  myograph  (Fig.  294),  and  suspend  a  frog's  gastrocnemius  (w),  with  a 
long  portion  of  the  sciatic  nerve  (N)  dissected  out,  by  fixing  the  femur  in  a  clamp 
(y"),  while  the  tendo  Achilles  is  fixed  to  a  lever,  which  inscribes  its  movements  on 
the  smoked  glass  plate  (P)  of  the  myograph  ;  place  the  key  of  the  myograph  (2 ) 
in  the  circuit  with  the  battery  (B),  and  the  primary  circuit  of  the  induction 
machine  (I).  To  the  secondary  coil  (II)  attach  two  wires,  and  connect  them 
with  a  commutator  Ttv'/Z/c/// (vvj-j--^;rj- (C).  Connect  the  other  binding  screws 
of  the  commutator  with  two  pairs  of  wires,  arranged  so  that  one  pair  can  stimu- 

Fio.  372. 


1  the  muscle  ;   D,  vibralic 


late  the  nerve  near  the  muscle  (<?).  and  the  other  at  a  distance  from  it  {li).  When 
the  glass  plate  swings  from  one  side  to  the  other,  the  tooth  (3)  on  its  framework 
opens  the  key  (2)  in  the  primary  circuit,  and  if  the  commutator  be  in  the  position 
indicated,  then  the  induced  current  will  stimulate  the  nerve  at  «,  and  a  curve  will 
be  obtained  on  the  glass  plate.  Rearrange  the  pendulum  as  before,  but  turn  the 
handle  of  the  commutator,  and  allow  the  pendulum  to  swing  again.  This  time 
the  induced  current  will  stimulate  the   nerve  at  /',  and  a  second  contraction,  a 


DOUBLE  CONDUCTION  IN  NERVES.  605 

little  later  than  the  first  one,  will  be  obtained.  Register  the  velocity  of  the  swing 
by  means  of  a  tuning  fork,  and  the  curve  obtained  will  be  something  like  Fig. 
372,  although  this  curve  was  obtained  on  a  cylinder  traveling  at  a  uniform  rate. 
The  difference  between  the  beginning  of  the  a  and  b  curves  indicates  the  time 
that  the  nerve  impulse  took  to  travel  from  b  to  a.  This  time  is  measured  by  the 
tuning  fork,  and  if  the  distance  between  the  points  a  and  b  is  known,  then  the 
calculation  is  a  simple  one.  Suppose  the  stretch  of  nerve  between  a  and  b  to  be 
2  inches,  and  the  time  required  by  the  impulse  to  travel  from  b  to  a  to  be  ■^\-^ 
second,  then  we  have  the  simple  calculation — 2  inches  :  12  inches:  :  ■^\-^'  :  ^y, 
or  80  feet  per  second.  In  Fig.  372  the  experiment  was  made  on  man  ;  the  curve 
I  was  obtained  by  stimulating  the  nerve  near  the  muscle,  and  2  when  the  nerve 
was  stimulated  at  a  distance  of  30  centimetres.  The  interval  between  the  ver- 
tical lines  corresponds  to  y^  second,  i.e.,  the  time  required  by  the  nerve  impulse 
to  pass  along  30  centiinetres  of  nerve,  which  is  equal  to  a  velocity  of  30  metres 
(90  feet)  per  second.] 

In  man  v.  Helmholtz  and  Baxt  estimated  the  velocity  of  the  impulse  in  the  median  nerve  by 
causing  the  muscles  of  the  ball  of  the  thumb  to  write  off  their  contractions  on  a  rapidly  revolving 
cylinder.  [In  this  case  the  pince  myographique  of  Marey  (J  708)  may  be  used.  The  ends  of  the 
pince  are  applied  so  as  to  embrace  tlie  ball  of  the  thumb,  so  that  when  the  muscles  contract  the 
increase  in  llticlmess  of  the  muscles  expands  the  pince,  which  acts  on  a  Marey's  tambour,  by  which 
the  movement  is  transmitted  to  another  tambour  provided  with  a  writing  style,  and  inscribing  us 
movements  upon  a  rapidly  moving  surface,  either  rotary  or  swinging.]  'the  nerve  is  siimulated  at 
one  time  in  tlie  axilla  and  again  at  the  wrist.  Two  curves  are  obtained,  which,  of  course,  do  not 
begin  at  the  same  time.  The  difference  in  lime  between  the  beginning  of  the  two  curves  is  the 
lime  taken  by  the  impulse  to  traverse  the  above-mentioned  length  of  nerve.  [The  time  is  easily 
ascertained  by  causing  a  tuning  fork  of  a  known  rate  of  vibration  to  write  its  movements  under  the 
curves.] 

3.  In  the  sensory  nerves  of  man  the  velocity  of  the  impulse  is  probably 
about  the  same  as  in  motor  nerves.  The  rates  given  vary  between  94-30  metres 
[280-90  feet]  per  second  (v.  Helmholtz,  Kohlrausch,  v.  Wittich,  Schelske  and 
others). 

Method. — Two  points  are  chosen  as  far  apart  as  possible,  and  at  unequal  distances  from  the 
brain,  and  they  are  successively  excited  by  a  momentary  stimulus,  e.g.,  an  opening  induction  shock 
applied  successively  to  the  tip  of  the  ear  and  the  great  toe.  The  moment  the  stimulus  is  applied, 
it  is  indicated  on  the  registering  surface.  The  person  experimented  on  is  provided  with  a  key 
attached  to  an  electric  arrangement,  by  which  he  can  mark  on  the  registering  surface  the  moment  he 
feels  the  sensation  in  each  case. 

Reaction  Time. — .The  lime  which  elapses  between  the  application  of  the  stimulus  and  the 
reaction  is  called  the  "  reaction  time."  It  is  made  up  of  the  time  necessary  for  conduction  in  the 
sensory  nerve,  that  for  the  process  of  perception  m  the  brain,  the  conduction  in  the  motor  nerves  to 
the  muscles,  by  which  the  signs  on  the  registering  surface  were  made,  and  las'.ly  by  the  latent 
period  (p.  516).     The  reaction  time  is  usually  about  0.125  to  0.2  second. 

Pathological. — The  conduction  in  the  cutaneous  nerves  is  sometimes  greatly  delayed  in  altera- 
tions of  the  cutaneous  sensibility  in  certain  diseases  of  the  spinal  cord  (§  364).  The  sensation  itself 
may  be  unchanged  Sometimes  only  the  conduction  for  painful  impressions  is  retarded,  so  that  a 
painful  impression  on  the  skin  is  first  perceived  as  a  tactile  sensation,  and  afterward  as  pain,  or  con- 
versely. When  the  interval  of  time  between  these  two  sensations  is  long,  then  there  is  a  distinctly 
double  sensation  (A^aitnyn,  Rcmak,  Eu/enliui%').  It  is  rarely  that  voluntary  movements  are  exe- 
cuted much  more  slowiy  from  causes  dept  nding  on  the  motor  nerves,  but  occasionally  the  time 
between  the  voluntary  impulse  and  the  contraction  is  lengthened,  but  there  may  be  in  addition 
slower  or  longer  continued  contraction  of  the  muscle.  In  tabes  dorsalis  or  locomotor  ataxia,  the 
discharge  of  reflex  movements  is  delayed  ;  it  is  slower  with  thermal  stimuli  (60°)  than  with  cold 
ones  (5°  C,  Ewald). 

338.  DOUBLE  CONDUCTION    IN    NERVES.— Conductivity   is 

that  property  of  a  living  nerve  in  virtue  of  which,  on  the  application  of  a 
stimulus,  it  transmits  an  impulse.  [The  nature  of  a  nerve  impulse  is  entirely 
unknown  ;  we  may  conveniently  term  the  process  nerve  motion,  but  there  is 
some  reason  to  believe  that  ner\e  energy  is  transmitted  by  some  sort  of  molec- 
ular vibration.]     The  conductivity  is  destroyed  by  all  influences  or  conditions 


606  THERAPEUTICAL   USES   OF    ELECTRICITY RHEOPHORES. 

which  injure  the  nerve  in  its  continuity  (section,  ligature,  compression,  destruction 
by  chemical  agents) ;  or  which  abolish  the  excitability  at  any  part  of  its  course 
(absolute  deprival  of  blood;  certain  poisons,  e.g.,  cnrara  for  motor  nerves;  also 
strong  anelectrotonus,  §  335). 

Law  of  Isolated  Conduction. — Conduction  always  takes  place  only  in  the 
continuity  of  fibres,  the  impulse  never  being  transferred  to  adjoining  nerve  fibres. 

Double  Conduction. — Although  apparently  conduction  in  motor  nerves 
takes  place  only  in  a  centrifugal  direction  toward  the  muscles,  and  in  sensory 
nerves  in  a  centripetal  A\x^cX\o\-\,  i.e.,  toward  the  centre  ;  nevertheless,  experiment 
has  proved  that  a  nerve  conducts  an  impulse  in  both  directions.  If  a  pure  motor 
or  sensory  nerve  be  stimulated  in  its  course,  an  impulse  is  propagated  at  the  same 
time  in  a  centrifugal  and  in  a  centripetal  direction.  This  is  the  phenomenon  of 
' '  double  conduction. ' ' 

Proofs. — I.  If  a  nerve  be  stimulated,  its  electro-motive  properties  are  affected 
both  above  and  below  the  point  of  stimulation  (see  Negative  Variation  in  Nen>es, 

§  a^^- 

2.  Union  of  Motor  and  Sensory  Nerves. — If  the  hypoglossal  and  lingual 
nerves  be  divided  in  a  dog,  and  if  the  peripheral  end  of  the  hypoglossal  be 
stitched,  so  as  to  unite  with  the  central  end  of  the  lingual  (Bidder),  then,  several 
months  after  the  union  and  restitution  of  the  nerves,  stimulation  of  the  central 
end  of  the  lingual  causes  contraction  in  the  corresponding  half  of  the  tongue. 
Hence,  it  has  been  assumed  that  the  lingual,  which  is  the  sensory  nerve  of  the 
tongue,  must  conduct  the  impulse  in  a  peripheral  direction  to  the  end  of  the 
hypoglossal. 

This  experiment  is  not  conclusive,  as  tlie  trunk  of  the  lingual  receives  high  up  the  centrifugal 
fibres  from  the  seventh,  viz.,  the  chorda  tympani,  which  may  unite  w  itn  those  of  the  hypoglossal. 
Further,  if  the  chorda  be  divided  and  allosved  to  degenerate  before  the  above  described  experiment 
is  made,  then  no  contractions  occur  on  stimulating  the  lingual  above  the  point  of  union  (§  349). 

3,  Bert's  Experiment. — Paul  Bert  removed  the  skin  from  the  tip  of  the  tail  of  a  rat,  and 
stitched  it  into  the  skin  of  the  back  of  the  animal,  where  it  united  with  the  tissues.  After  the 
first  union  had  taken  place,  the  tail  was  then  divided  at  its  base,  so  that  the  tail,  as  it  were,  grew 
out  of  the  skin  on  the  back  of  the  animal.  On  stimulating  the  tail,  the  animal  exhibited  signs  of 
sensation,  so  that  the  impuLes  in  the  sensory  nerves  must  have  traversed  the  nerves  from  the  base 
to  the  tip  of  the  tail  (\  325). 

4.  Electrical  Nerves. — If  the  free  end  of  the  electrical  centrifugal  nerves 
of  the  nialapterurus  be  stimulated,  the  branches  given  off  above  the  point  of 
stimulation  are  also  excited,  so  that  the  whole  electrical  organ  may  discharge  its 
electricity  (^Babuchin,  Mantey). 

339.  ELECTRO-THERAPEUTICS— REACTION  OF  DEGENERATION.— Elec- 
tricity is  frequently  employed  for  therapeutical  purposes,  the  rapidly  interrupted  current  of  the  in- 
duction machine,  or  Faradic  current,  being  frequently  used  (especially  since  Duchenne,  1847),  the 
magiieto-eleclrical  apparatus,  and  the  extra-currtnt  apparatus.  The  constant  or  galvanic  current 
is  also  used,  especially  since  Remak's  time,  1855  (J  330). 

I.  In  paralysis,  /'araa'/f  currents  are  applied  either  to  the  muscles  themselves  {^Duchenne),  or 
the  points  of  entrance  01  the  motor  nerves  \v.  Ziemssen),  by  means  of  suitable  electrodes,  or  rheo- 
phores  covered  with  spjnge,  etc.,  and  moistened. 

[Rheophores. — Many  different  forms  are  used,  according  to  the  organ  or  part  to  be  stimulated, 
or  the  effect  desired.  When  electricity  is  applied  to  the  skin  to  remove  anesthesia,  hyperaesthesia, 
or  altered  sensibility,  and  we  desire  to  limit  the  effect  to  the  skin  alone,  then  the  rheophores  are 
applied  dry,  and  are  usually  made  of  metal.  If,  however,  deeper-seated  structures,  as  muscles  or 
nerve  trunks,  are  to  be  affected,  the  skin  must  be  well  moistened  and  soitened  by  sponging  with 
warm  water,  while  the  rJieophores  are  fitted  with  sponges  moistened  with  common  salt  and  water 
which  diminishes  the  resistance  of  the  skin  to  the  passage  of  electricity  (Figs.  373-375)-]  > 

In  faradizing  the  paralyzed  muscle,  the  object  is  to  cause  artificial  movements  in  it,  and  thus  pre- 
vent the  degeneration  which  it  would  otherwise  undergo,  merely  from  inaction.  If,  in  addition  to 
the  motor  nerves,  its  trophic  nerves  are  also  paralyzed,  then  a  muscle  atrophies,  notwithstanding  the 
faradization  (J  325,  4).  The  use  of  the  induced  current  also  improves  a  paralyzed  muscle,  as  it  in- 
creases  the  blood  stream  through  it,  while  it  affects  the  metabolism  of  the  muscle  reflexly.  In 
addition,  weak  currents  may  restore  the  excitability  of  enfeebled  ner\-es  {v.  Bczold,  Eiigelinann). 


THERAPEUTICAL   ACTIONS   OF   THE    CONSTANT   CURRENT. 


607 


The  Figs.  376,  377,  378,  and  379  indicate  the  positions  of  the  motor  points  of  the  extremities, 
where,  bv  stimulating  at  the  entrance  of  the  nerve,  each  muscle  may  be  caused  to  contract  singly. 
In  I  349  the  motor  points  of  the  face,  and  in  J  347  those  oi  the  neck,  are  indicated. 

The  constant  current  may  be  employed  as  a  stimulus  when  it  is  closed  and  opened  in  the  form 
of  an  iitterriipled  current,  by  altering  its  direction  and  increasing  or  diminishing  its  intensity,  but  it 
also  causes  a  polai  aclion.  On  closing  the  current,  the  nerve  at  the  cathode  is  stimulated  ;  similarly, 
on  opening  the  current,  at  the  anode  (J  336).  Thus,  when  the  current  is  closed,  the  excitability  of 
the  nerve  is  increased  at  the  cathode  (^.  335),  which  may  act  favorably  upon  the  nerve.  Increased 
excitability  in  electrotonus  at  the  anode,  although  feebler,  has  been  observed  during  percutaneous 
galvanization  in  man.  This  is  especially  the  case  by  repeatedly  reversing  the  current,  sometimes 
also  by  opening  and  closing,  or  even  with  a  uniform  current.  If  the  increase  of  the  excitability  is 
obtained,  then  the  direction  of  the  current  increases  the  excitability  on  closing  the  reverse  cuirent, 
and  on  opening  the  one  in  the  same  direction. 

Restorative  Effect. — Further,  in  using  the  constant  current,  we  have  to  consider  its  restorative 
effects,  especially  when  it  is  ascending.  R.  Heidenhain  found  that  feeble  and  fatigued  muscles  re- 
cover after  the  passage  of  a  constant  current  through  them. 


Fig.  375. 


Fig.  373. 


Fig.  374 


T 


Double  sponge  rheophi 


Disk  rheopho 


Lastly,  the  constant  current  may  be  useful  from  its  catalytic  or  cataphoric  action  {\  328).  The 
effect  is  directly  upon  the  tissue  elements.  It  may  also  act  directly  or  reflexly  upon  the  blood  and 
lymph  vessels. 

Faradization  in  Paralysis.— If  the  primary  cause  of  the  paralysis  is  in  the  muscles  themselves, 
then  the  induced  current  is  generally  applied  directly  to  the  muscles  themselves  by  means  of  sponge 
electrodes  (Fig.  373) ;  while,  if  the  motor  nerves  are  the  primary  seat,  then  the  electrodes  are 
apjilied  over  them.  The  current  used  must  be  only  of  very  moderate  strength;  strong  tetanic  con- 
tractions are  injurious,  and  so  is  too  prolonged  application  (Alb.  Eulenbitrg). 

The  galvanic  current  may  also  be  applied  to  the  muscles  or  to  their  motor  nerves,  or  to  the  cen- 
tres of  the  latter,  or  to  both  muscle  and  nerve  simultaneously.  As  a  rule,  the  cathode  is  placed  «i'a/cr 
the  centre,  as  it  increases  the  excitability.  When  the  electrode  is  moved  along  the  course  of  the  nerve, 
or  when  the  strength  of  the  current  is  varied,  the  action  is  favored.  If  the  seat  of  the  lesion  is  in 
the  central  nervous  system,  then  the  electrodes  are  applied  along  the  vertebral  column,  or  on  the 
vertebral  column,  and  the  course  of  the  nerves  at  the  same  time,  or  one  on  the  head  and  the  other 
on  a  point  as  near  as  possible  to  the  supposed  seat  of  the  lesion.  The  current  must  not  be  too  strong 
nor  applied  too  long. 

Induced  f.  Constant  Current :  Reaction  of  Degeneration. — Paralyzed  nerves  and  muscles 
behave  quite  differently  as  regards  the  induced  (rapidly  interrupted)  and  the  constant  oiiitrA.  This 
is  called  the  "  reaction  of  degeneration."  We  must  remember  the  physiological  fact  that  a  dying 


608  REACTION    OF   DEGENERATION. 

nerve  attached  to  a  muscle  (^  325),  and  also  the  muscles  of  a  curarized  animal,  react  much  less 
strongly  to  rapidly  interrupted  currents  than  fresh  non-curarized  muscles.  Baierlach,  in  1S59,  found 
that  in  a  case  of  facial  paralysis  the  facial  muscles  contracted  but  feebly  to  the  induced  current,  but 
very  energetically  on  the  constant  current  being  used.     The  excitability  for  the  constant  current  may 


Fig.  376. 


N.  radlalia. 
M,  brachiiL  intera  / 
M.  surSaatorlong. 
liial  pxi.  long. 


M,  eitt^iiB,  digit,  communis. 
M.  extens.  digit,  min. 


M.  trifops  faput  "Xf.l 
M.  triceps 
('■aput  long) 
M.  deltnideus 
\  (post.  half). 

tN.  axillaris). 


M.  ttbdnct  pollic.  long. 
M.  extens.  pollic.  brev 
M.  estens.  poll,  long 


(N 


M.  abdact.  digif.  mIn.  (N.  olnarU.) 
dorsal.  I.  11,  III,  et  IV. 
Motor  points  of  the  radial  nerve  and  the  muscle 


upplied  by  it ;  dorsal  surface. 


Fig.  377. 


M.  deltoideufi  lant.  half)  N.  axillaris. 
N.  muaculo-cuianeus, 
M.  biceps  brachiL 

H.  bracb.  anticus. 

"V    __| _^    I        [  I  N.  medianu3 


M  abductor  potHo.  lireT. 
Al  opponeuB  [xiUicia. 
I     M.  flex. 

M.  abductor  polllc>  brer. 
Miu   liimbriua  63 


^  Mm   lumbrl 
cat^IiletlV. 
M   oppoDeDs  dii.lt.  I 
M   flexor  dUIt  mm. 
M.  abiuctor  dijit  uiia. 
M.  t&lo' 

ulnarifl.  M.  flexor  carpi  nlnariB.  N.  ulnaris. 

r  points  of  the  median  and  ulnar  nerves,  with  the  muscles  supplied  by  them. 

be  abnormally  increased,  but  may  disappear  on  recovery  taking  place.  According  to  Neumann,  it 
is  the  longer  duration  of  the  constant  current  as  opposed  to  the  momentary  closing  and  openmg  of 
the  induced  current  which  makes  the  contraction  of  the  muscle  possible.     If  the  constant  current  be 


REACTION    OF    DEGENERATION. 


609 


broken  as  rapidly  as  the  Faradic  current  is  broken,  thfen  the  constant  current  does  not  cause  contrac- 
tion. Conversely,  the  induced  current  may  be  rendered  effective  by  causing  it  tn  last  longer.  We 
may  also  keep  the  primary  circuit  of  the  iiuluclion  machine  closed,  and  move  the  secondary  spiral 
to  and  fro  along  the  slots.  Thus  we  obtain  slow  gradations  of  the  induced  current  which  act  ener- 
getically upon  curarized  muscles  (Brih/cf).  Hence,  in  stimulating  a  muscle  or  ner\'e,  we  have  to 
consider  not  only  the  strength,  but  also  the  duration,  of  the  current,  just  as  the  deflection  of  the 
magnetic  needle  depends  upon  these  two  factors. 

[Galvanic  excitability  is  the  term  applied  to  the  condition  of  a  nerve  or  muscle,  whereby  it  re- 
sponds to  the  opening  or  closing  of  a  continuous  current.  The  effects  differ  according  as  the  current 
is  opened  or  closed,  and  according  to  its  strength.     As  a  rule,  the  cathode  causes  a  contraction 


Fig.  378. 


I  r 


N.  obturator. 
M.  pect: 
M.  adductor  magni 
M    adduct.  longi 


U     J 


:  points  of  the  peroneal  and  tibial  nerves  on  the  front  of  the  leg  ;  the  peroneal  c 
tibial  on  the  right  (after  Eichhorst). 


chiefly  at  closure,  the  anode  at  opening  the  current,  while  the  cathode  is  the  stronger  stimulus.. 
With  a  weak  current  the  cathode  produces  a  simple  contraction  on  closing  the  current,  but  no  con- 
traction from  the  anode.  With  a  medium  current  we  get  with  the  cathode  a  strong  closing  contrac- 
tion but  no  opening  contraction,  while  the  anode  excites  feeble  opening  and  closing  contractions. 
With  a  strong  current  we  get  with  the  cathode  a  tetanic  contraction  at  closure,  and  a  perceptible 
contraction  at  opening,  while  with  the  anode  there  is  contraction  both  at  opening  and  closing.] 

[The  law  of  contraction  is  usually  expressed  by  the  following  formula  (lioss,  after  Erb) :  An  = 
anode,  Ca  =  cathode,  C  =  contraction,  c  =  feeble  contraction,  C  ^=  strong  contraction,  S  = 
closure  of  current,  O  ^  opening  of  current,  Te  =  tetanic  contraction  ;  so  that,  expressing  the 
above  statements  briefly,  we  have — 

39 


610 


REACTION    OF    DEGENERATION. 


Weak  currents  produce  Ca  S  C ; 

Medium    "  "        Ca  S  C,  An  S  c.  An  O  c; 

Strong       •'  "        Ca  S  Te,  An  S  C,  An  O  C,  Ca  Or.] 

[Typical  Reaction  of  Degeneration. — When  the  reaction  of  the  nerve  and 
muscle  to  electrical  stimulation  is  altered  both  qualitatively  and  quantitatively, 
we  have  the  reaction  of  degeneration,  which  is  characterized  essentially  by  the 
following  conditions]  :  The  excitability  of  the  muscles  is  diminished  or  abolished 
for  the  Faradic  current,  while  it  is  increased  for  the  galvanic  current  from  the 
3d-58th  day  ;  it  again  diminishes,  however,  with  variations,  from  the  72d-8oth 
day  ;  the  anode  closing  contraction  is  stronger  than  the  cathode  closing  contrac- 
tion.   The  contractions  in  the  affected  muscles  occur  slowly  in  a  peristaltic  manner, 


Fig.  379. 


/M.   biceps,   fern.   (cap.   long.) 
\  {grt.  sciat.). 


\M.   biceps,   fern.    (cap.   brev.) 


ischiadit 

adduct.  magnus  (n.  obt.), 
tendinosus  (grt.  sciat.) 
ibranosus  (grt. 

)■ 


(cap.  e 
(cap. 


W.  flex.  dig.  conim.  long. 
M.  flexor  hallucis  longus. 


ches  ;  the  peroneal  a 


and  are  local,  in  contrast  with  the  rapid  contraction  of  a  normal  muscle.  The 
diminution  of  the  excitability  of  the  nerves  is  similar  for  the  galvanic  and  Faradic 
currents.  If  the  reaction  of  the  nerves  be  normal,  while  the  muscle  during  direct 
stimulation  with  the  constant  current  exhibits  the  reaction  of  degeneration,  we 
speak  of  "partial  reaction  of  degeneration"  {Erb),  which  is  constantly 
present  in  progressive  muscular  atrophy  {Erb,  Giinthcr). 

[The  "  reaction  of  degeneration  "  may  occur  before  there  is  actual  paralysis,  as  in  lead  poison. 
ing.  When  it  occurs,  we  have  to  deal  with  some  affection  of  the  nerve  fibres  or  of  the  trophic 
nerve  cells.  When  it  is  established,  (i)  stimulation  of  the  nerve  with  Faradic  and  galvanic  elec- 
tricity does  not  cause  contraction  of  the  muscle ;  (2)  direct  Faradic  stimulation  of  the  muscles  does 
not  cause  contraction;  (3)  the  galvanic  current  usually  excites  contraction  more  readily  than  in  a 
normal  muscle,  so  that  the  muscle  responds  to  much  feebler  currents  than  act  on  healthy  muscles; 


ELECTRICAL   CHARGING    OF   THE    BODY.  611 

but  the  contraction  is  longer  and  more  of  a  tonic  character,  and  shows  a  tendency  to  become  tetanic] 
[The  electrical  excitability  is  generally  unaffected  in  paralysis  of  cerebral  origin,  and  in  some  forms 
of  spinal  paralysis,  as  primary  lateral  sclerosis  and  transverse  myelitis  (fiossi ;  but  the  "reaction  of 
degeneration  "  occurs  in  traumatic  paralysis  due  to  injury  of  the  nerve  trunks,  neuritis,  rheumatic 
facial  paralysis,  lead  palsy,  and  in  affections  of  the  nerve  cells  in  the  anterior  cornu  of  the  gray 
matter  of  the  spinal  cord.]  In  rare  cases  the  contraction  of  the  muscles,  caused  by  applying  a 
Faradic  current  to  the  nerve,  follows  a  slow  peristaltic-like  course — "Faradic  reaction  of  degenera- 
tion "  (A.  Remak,  A'ast,  Erh). 

II.  In  Various  Forms  of  Spasm  (spasms,  contracture,  muscular  tremor)  the  constant  current 
is  most  effective  (Remak).  By  the  action  of  anelectrutunus,  a  pathological  increase  of  the  excita- 
bility is  subdued.  Hence,  the  anode  ought  to  be  applied  to  the  part  with  increased  excitability,  and 
if  it  be  a  case  of  reflex  spasm,  to  the  points  which  are  the  origin  or  seat  of  the  increased  excitability. 
Weak  currents  of  uniform  intensity  are  most  effective.  The  constant  current  may  also  be  useful 
from  its  cataphoric  action,  whereby  it  favors  the  removal  of  stimuli  from  the  seat  of  the  irritation. 
Further,  the  constant  current  increases  the  voluntary  control  over  the  affected  muscles.  In  spasms 
of  central  origin  the  constant  current  may  be  applied  to  the  central  organ  itself  (Fig.  387).  Fara- 
dization is  used  in  spasmodic  affections  to  increase  the  vigor  of  enfeebled  antagonistic  muscles. 
Muscles  in  a  condition  of  contracture  are  said  to  become  more  extensible  under  the  influence  of 
the  Faradic  current   (Remak),  as  a  normal  muscle  is  more  excitable   during  active  contraction 

(i30i)- 

In  cutaneous  anaesthesia,  the  Faradtc  current  applied  to  the  -skin  by  means  of  hair-brush 
electrodes  (Fig.  375)  is  frequently  used.  When  using  the  constant  current,  the  cathode  must  be 
applied  to  the  parts  with  diminished  sensibility.  The  con.stant  current  alone  is  applied  to  the  central 
seat  of  the  lesion,  and  care  must  be  taken  to  what  extent  the  occurrence  of  cathelectroionus  in  the 
centre  affects  the  occurrence  of  sensation. 

III.  In  Hyperassthesia  and  Neuralgias,  Faradic  currents  are  applied  with  the  object  of  over- 
stimulating  the  hypersensitive  parts,  and  thus  to  benumb  them.  Besides  these  powerful  currents, 
loeak  currents  act  reflexty  and  accelerate  the  lilood  stream,  increase  the  heart's  action,  and  constrict 
the  blood  vessels,  while  stron.;  currents  cause  the  opposite  effects  (O.  Naiimann).  Both  may  be 
useful.  In  employing  the  constant  current  in  neuralgia  (Remak),  ore  object  is  by  exciting  anelec- 
trotonus  in  the  hypersensitive  nerves,  to  cause  a  diminution  of  the  excitability.  According  to  the 
nature  of  the  case,  the  anode  is  placed  either  on  the  nerve  trunk  or  even  on  the  centre  itself,  and 
thi  cathode  on  an  indifferent  part' of  the  body.  The  catalytic  and  cataphoric  effects  also  are  most 
important,  for  by  means  of  them,  especially  in  recent  rheumatic  neuralgias,  the  irritating  inflamma- 
tory products  are  distributed  and  conducted  away  from  the  part.  A  descending  current  is  trans- 
mitted continuously  for  a  time  through  the  nerve  trunk,  and  in  recent  cases  its  effects  are  sometimes 
very  striking.  Lastly,  of  course  the  constant  current  may  be  used  as  a  cutaneous  stimulus,  while 
the  Faradic  current  also  acts  reflexly  on  the  cardiac  and  vascular  activity. 

Recently,  Charcot  and  Bailet  have  used  the  electric  spark  from  an  electrical  machine  in  cases  of 
anxbthesia,  facial  paralysis  and  paralysis  agitans.  In  some  cases  of  spinal  paralysis,  muscles  can 
be  made  to  contract  with  the  electric  spark,  which  do  not  contract  to  a  Faradic  current.  [Elec- 
tricity is  sometimes  used  to  distinguish  real  from  feigned  disease,  or  to  distinguish  death  from  a  con- 
dition of  trance.] 

Galvano  Cautery. — The  electrical  current  is  used  for  thermal  purposes,  as  in  the  galvano 
cautery. 

Galvano  Puncture. — The  electrolytic  properties  of  electrical  currents  are  employed  to  cause 
coagulation  in  aneurisms  or  varix.  [If  the  electrodes  from  a  constant  battery  in  action  be  inserted 
in  an  aneurismal  sac,  after  a  time  the  fibrin  of  the  blood  is  deposited  in  the  sac,  whereby  the  caviiy 
of  the  aneurism  is  gradually  filled  up.  A  galvanic  current  passed  through  defibrinated  blood  causes 
the  formation  of  a  coagulum  of  proteid  matter  at  the  positive  pole  and  bubbles  of  gas  at  the 
negative.] 

340.  ELECTRICAL  CHARGING  OF  THE  BODY.— Saussure  investigated  by  means 
of  the  electroscope  the  "charge"  of  a  person  standing  on  an  insulated  stool.  The  phenomena 
observed  by  him,  which  were  always  inconstant,  were  due  to  the /riction  of  the  clothes  upon  the 
skin.  Gardini,  Hemmer,  Ahrens  (1S17),  and  Nasse  regarded  the  body  as  normally  charged  with 
positive  electricity,  while  Sjosten  and  others  regarded  it  as  negatively  charged.  Most  probably  all 
these  phenomena  are  due  to  friction,  and  are  modified  effects  of  the  air  in  contact  with  the  hetero- 
geneous clothing  (Hankel).  A  strong  charge  resulting  in  an  actual  spark  has  frequently  been 
described.  Cardanus  (1553)  obtained  sparks  from  the  tips  of  the  hair  of  the  head.  According  to 
Horsford  (1837),  long  sparks  were  obtained  from  the  tips  of  the  fingers  of  a  nervous  woman  in 
Oxford,  when  she  stood  upon  an  insulated  carpet.  Sparks  have  often  been  observed  on  combing 
the  hair  or  stroking  the  back  of  a  cat  in  the  dark.  Freshly-voided  urine  is  negatively  electrical 
(  Vasalli- Eandi,  I'olta) ;  so  is  the  freshly-formed  web  of  a  spider,  while  the  blood  is  positive. 

341.  COMPARATIVE— HISTORICAL.— Electrical  Fishes.— Some  of  the  most  inter- 
esting phenomena  connected  with  animal  electricity  are  obtained  in  electrical  fishes,  of  which  there 
are  about  fifty  species,  including  the  electrical  eel,  oxGymnotus  electricus,  of  the  lagoons  of  the  region 


612  COMPARATIVE HISTORICAL. 

of  the  Orinoco  in  Soutli  America ;  it  may  measure  over  7  feet  in  length.  The  Torpedo  tnartnorala 
and  some  allied  species,  30  to  70  centimetres  [i  to  zy'^  feet],  in  the  Adriatic  and  Mediterranean, 
the  Malapteriiriis  ehclriciis  of  the  Nile,  and  the  Marmyrus,  also  of  the  same  river.  By  means  of 
special  electrical  organs  (Rt\ii,  /6(^6), these  animals  can  in  part  voluntarily  (gymnotus  and  malap- 
terurus),  and  in  part  retlexly  (torpedo)  give  a  very  powerful  electrical  shock.  The  electrical  organ 
consists  of  •'  compartments  "  of  various  lorms,  separated  from  each  other  by  connective  tissue,  and 
filled  with  a  jelly-like  substance,  which  the  nerves  enter  on  one  surface  and  ramify  to  produce  a 
plexus.  From  this  plexus  there  proceed  branches  of  the  axial  cylinder,  which  end  in  a  nucleated 
plate,  the  "  electrical  plate  "  (Billharz,  M.  Scliiihe).  When  the  "  electrical  nerves  "  proceeding  to 
the  organ  are  stimulated,  an  electrical  discharge  is  the  result. 

In  Gymnotus  the  electrical  organ  consists  of  several  rows  of  columns  arranged  along  both  sides 
of  the  spinal  column  of  the  animal,  under  the  skin  as  far  as  the  tail.  It  receives  on  the  anterior 
surface  several  branches  from  the  intercostal  nerves.  Besides  this  large  organ  there  is  a  smaller  one 
lying  on  both  sides  above  the  anal  fins.  Here  the  plates  are  vertical,  and  the  direction  of  the  elec- 
trical current  in  the  fish  is  ascending,  so  that,  of  course,  it  is  descending  in  the  surrounding  water 
{^Faratiay,  Dti  Bois-Rcymond). 

In  Malapterurus  the  organ  surrounds  the  body  like  a  mantle,  and  receives  only  one  nerve  fibre 
(p.  521),  whose  axis  cylmder  arises  near  the  medulla  oblongata  from  one  gigantic  ganglionic  cell 
{BiUharz),  and  is  composed  of  protoplasmic  processes  (I-n/sc/i).  The  plates  are  also  vertical,  and 
receive  their  nerves  from  the  posterior  surface.  The  direction  of  the  current  is  descending  in  the 
tish  during  the  discharge  {Vit  Bois-Reymotid"). 

In  the  Torpedo  the  organ  lies  immediately  under  the  skin  laterally  on  each  side  of  the  head, 
reaching  as  far  as  the  pectoral  fins.  It  receives  several  nerves  which  arise  from  the  lobus  electricus, 
between  the  corpora  quadrigemina  and  the  medulla  oblongata.  The  plates,  which  do  not  increase 
in  number  with  the  growth  of  the  animal  (Del/e  Chiaje,  Bti/>uchin),\\e  horizontally,  while  the  nerve 
fibres  enter  them  on  their  dorsal  surfaces,  the  current  in  the  fish  being  from  the  abdominal  to  the  dorsal 
surface  ( Oalvani).  It  is  extremely  probable  that  the  electric  organs  are  modified  muscles,  in  which 
the  nerve  terminations  are  highly  developed,  the  electrical  plates  corresponding  to  the  motorial  end 
plates  of  the  muscular  fibres,  the  contractile  substance  havmg  disappeared,  so  that  during  physiological 
activity  the  chemical  energy  is  changed  into  electricity  alone,  while  there  is  no  "  work  "  done. 
This  view  is  supported  by  the  observation  of  Babuchin,  that  during  development  the  organs  are 
originally  formed  like  muscles ;  further,  that  the  organs  when  at  rest  are  neutral,  but  when  active  or 
dead,  acid ;  and  lastly,  they  contain  a  substance  related  to  myo'sin  which  coagulates  after  death 
(§295 —  ll'nyl).  The  organs  manifest  fatigue  ;  they  have  a  "  latent  period  "  of  0.016  second,  while 
one  shock  of  the  organ  (comparable  to  the  current  in  an  active  muscle)  lasts  0.07  second.  About 
twenty-five  of  these  shocks  go  to  make  a  discharge,  which  lasts  about  0.23  second.  The  discharge, 
like  tetanus,  is  a  discontinuous  process  [Matey).  Mechanical,  chemical,  thermal  and  electrical 
stimuli  cause  a  discharge;  a  single  induction  sliock  is  not  effective  [Sachs).  During  the  electrical 
discharge  the  current  traverses  the  muscles  of  the  animal  itself;  the  latter  contract  in  the  torpedo, 
while  they  do  not  do  so  in  the  gymnotus  and  malapterurus  during  the  discharge  [Stehier).  A  tor- 
pedo can  give  about  fifty  shocks  per  minute ;  it  then  becomes  fatigued,  and  requires  some  time  to 
recover  itself.  It  may  only  partially  discharge  its  organ  (Al.  v.  Humboldt,  Sachs).  Cooling  makes 
the  organ  less  active,  whUe  lieating  it  to  22°  C.  makes  it  more  so.  The  organ  becomes  tetanic  with 
strychnin  [^Beajuercl),  while  curara  paralyzes  it  (^Sachs).  Stimulation  of  the  electrical  organ  of  the 
torpedo  causes  a  discharge  {Maiteucci) ;  cold  retards  it,  while  section  of  the  electrical  nerves 
paralyzes  the  organ.  The  electrical  fishes  themselves  are  but  slightly  affected  by  very  strong  induc- 
tion shocks  transmitted  through  the  water  in  which  they  are  swimming  [Dti  Bois-Keymond).  The 
substance  of  the  electrical  organs  is  singly  refractive;  excised  portions  give  a  current  during  rest, 
which  has  the  same  direction  as  the  shock  ;  tetanus  of  the  or^^an  weakens  the  current  [Sachs,  Du 
Bois-Rcymoiid ) . 

Historical. — Richer  (1672)  made  the  first  communication  about  the  gymnotus.  Walsh  (1772) 
made  investigations  on  the  torpedo,  on  its  discharge,  and  its  power  of  communicating  a  shock.  J. 
Davy  magnetized  particles  of  steel,  caused  a  defieciion  of  the  magnetic  needle,  and  obtained  elec 
trolysis  with  the  electrical  discharge.  Becquerel,  Brechet  and  Matteucci  studied  the  direction  of 
the  discharge.  Al.  v.  Humboldt  described  the  habits  and  actions  of  the  gymnotus  of  South  America. 
Hausen  (1743)  and  de  Sauvages  (1744)  supposed  that  electricity  was  the  active  force  in  nerves. 
The  actual  investigations  into  animal  electricity  began  with  G.  Aloisio  Ualvani  (1791),  who 
observed  that  frogs'  legs  connected  with  an  electrical  machine  contracted,  and  also  when  they  were 
touched  with  two  difterent  metals.  He  believed  that  nerves  and  muscles  generated  electricity. 
Alessandro  \'olta  ascribed  the  second  experiment  to  the  electrical  current  produced  by  the  contact 
of  dissimilar  metals,  and  therefore  outside  the  tissues  of  the  Irog.  The  contraction  without  metals 
described  by  Galvani  was  confirmed  by  Alex.  v.  Humboldt  (1798).  Pfaft'(i793)  first  observed  the 
effect  of  the  direction  of  the  current  upon  the  contraction  of  a  frog's  leg  obtained  by  stimulating  its 
nerve.  Bunzen  made  a  galvanic  pile  of  Irogs'  legs.  The  whole  subject  entered  on  a  new  phase 
with  the  construction  of  the  galvanometer  and  since  the  introduction  of  the  classical  methods 
devised  by  Du  Bois-Reymond,  i.e.,  from  1S43  onwards. 


Physiology  ™e  peripheral  Nerves. 


342.    FUNCTIONAL  CLASSIFICATION  OF  NERVE  FIBRES. 

— As  nerve  fibres,  on  being  stimulated,  are  capable  of  conducting  impulses  in  both 
directions  (§  338),  it  is  obvious  that  the  physiological  position  of  a  nerve  fibre 
must  depend  essentially  upon  its  relations  to  the  peripheral  end  organ  on  the 
one  hand,  and  its  central  connection  on  the  other.  Tf.us,  each  nerve  is  dis- 
tributed to  a  special  area  within  which,  under  normal  circumstances,  in  the  intact 
body,  it  performs  its  functions. 

I.  Centrifugal  or  Efferent  Nerves. — 'a)  Motor. — Those  nerve  fibres 
whose  peripheral  end  organ  consists  of  a  muscle,  the  central  ends  of  the  fibres 
being  connected  with  nerve  cells  : — 

1.  Motor  fibres  of  striped  muscle  (^  292  to  320). 

2.  Motor  nerves  of  the  heart  (|  57). 

3.  Motor  nerves  of  smooth  muscle,  e.  g.,  the  intestine  (\  171).  The  vasomotor  nerves  are 
specially  treated  of  in  J  371. 

(b  I  Secretory. — Those  nerve  fibres  whose  peripheral  end  organ  consists  of  a 
secretory  cell,  the  central  ends  of  the  fibres  being  connected  with  nerve  cells. 

Examples  of  secretory  nerves  are  the  secretory  nerves  for  saliva  (^  145)  and  those  for  sweating 
(^  289,  II).  It  is  to  be  remembered,  however,  that  these  fibres  not  unfrequently  lie  in  the  same 
sheath  with  other  nerve  fibres,  so  that  stimulation  of  a  nerve  may  give  rise  to  several  results,  accord- 
ing to  the  kind  of  nerve  fibres  present  in  the  nerve.  Thus,  the  secretory  and  vasomotor  nerves  of 
glands  may  be  excited  simultaneously. 

(c)  Trophic. — The  end  organs  of  these  nerve  fibres  lie  in  the  tissues  them- 
selves, and  are  as  yet  unknown.  These  nerves  are  called  trophic,  because  they 
are  supposed  to  govern  or  control  the  normal  metabolism  of  the  tissues. 

Trophic  Influence  of  Nerves. — The  trophic  functions  of  certain  nerves  are  referred  to  as 
under :  On  the  influence  of  the  trigeminus  on  the  eye ;  the  mucous  membrane  of  the  mouth  and 
nose  ;  the  face  (^  347);  the  influence  of  the  vagus  on  the  lungs  (^  352)  ;  motor  nerves  on  muscle 
(^  307) ;  certain  central  organs  upon  certain  viscera  (^  379). 

Section  of  certain  nerves  influences  the  growth  of  the  bones.  H.  Nasse  found  that,  after  section 
of  their  nerves,  the  bones  showed  an  absolute  diminution  of  all  their  individual  constituents,  while 
there  was  an  increase  of  fat.  Section  of  the  spermatic  nerve  is  followed  by  degeneration  of  the 
testicle  (A'i-liiton,  Oholensky).  After  extirpation  of  their  secretory  nerves,  there  is  degeneration  of 
the  submaxillary  glands  (p.  237).  .Section  of  the  nerves  of  the  cock's  comb  interferes  with  the 
nutrition  of  that  organ  [L^gros,  Schiff^.  Section  of  the  cervical  sympathetic  ner\'e  \xi  yoting gron'ing 
animals  is  followed  by  a  more  rapid  growth  of  the  ear  upon  that  side  {Bidder,  Stirling,  Stricter), 
also  of  the  hair  on  that  side  (Schiff,  Stirling,  Sig.  Meyer) ;  while  it  is  said  that  the  corresponding 
half  of  the  brain  is  smaller,  which,  perhaps,  is  due  to  the  pressure  from  the  dilated  blood  vessels 
( Bro-'wn-  Scquard) . 

Blood  Vessels. — Lewaschew  found  that  continued  uninterrupted  stimulation  of  the  sciatic  nerve 
of  dogs,  by  means  of  chemical  stimuli  [threads  dipped  in  sulphuric  acid],  caused  hypertrophy  of 
the  lower  limb  and  foot,  together  with  the  formation  of  aneurismal  dilatations  upon  the  blood 
vessels. 

Skin  and  Cutaneous  Appendages. — In  man,  stimulation  or  paralysis  of  nerves,  or  degenera- 
tion of  the  gray  matter  of  the  spinal  cord  {Jarisch),  is  not  unfrequently  followed  by  changes  in  the 
pigmentation  of  the  skin,  in  the  nails,  in  the  hair  and  its  mode  of  growth  and  color.  [Injury  to  the 
brain,  as  by  a  fall,  sometimes  results  in  paralysis  of  the  hair  follicles,  so  that,  after  such  an  injury, 
the  hair  is  lost  over  nearly  the  whole  of  the  body.]  Sometimes  there  may  be  eruptions  upon  the  skin 
apparently  traumatic  in  their  origin  [v.  Biirensprung,  Leloir).  Sometimes  there  is  a  tendency  to 
decubitus  (J  379),  and  in  some  rare  cases  of  tabes  there  is  a  peculiar  degeneration  of  the  joints 

613 


614  INHIBITORY    NERVES. 

(Charcot's  disease).  The  changes  which  take  place  in  a  nerve  separated  from  its  centre  are  de- 
scribed in  §  325. 

[Trophoneuroses. — Some  of  the  chief  data  on  which  the  existence  of  trophic  nerves  is  assumed 
are  indicated  above.  There  are  many  pathological  conditions  referable  to  diseases  or  injuries  of 
nerves.] 

[Muscles. — As  is  well  known,  paralysis  of  a  motor  nerve  leads  to  simple  atrophy  of  the  corres- 
ponding muscle,  provided  it  be  not  exercised ;  but  when  the  motor  ganglionic  cells  of  the  anterior 
horn  of  the  gray  matter,  or  the  corresponding  cells  in  the  crus,  pons,  and  medulla,  are  paralyzed, 
there  is  an  active  condition  of  atrophy  with  proliferation  of  the  muscular  nuclei  Progressive 
muscular  atrophy,  or  wasting  palsy,  is  another  trophic  change  in  muscle,  whereby  either  individual 
muscles  or  groups  of  muscles  are  one  after  the  other  paralyzed  and  become  atrophied.  In  pseudo- 
hypertrophic paralysis  there  is  cirrhosis  or  increased  development  of  the  connective  tissue,  with 
a  diminution  of  the  tnie  muscular  elements,  so  that  although  the  muscles  increase  in  hulk  their 
power  is  diminished.] 

[Cutaneous  Trophic  Affections. — .\mong  these  may  be  mentioned  the  occurrence  of  red 
patches  or  erythema,  urticaria  or  nettle  rash,  some  forms  of  lichen,  eczema,  the  bullae  or  blebs  of 
pemphigus,  and  some  forms  of  ichthyosis,  e.ach  of  which  may  occur  in  limited  areas  after  injury  to 
a  nerve  or  its  spinal  or  cerebral  centre.  The  relation  between  the  eruption  and  the  distribution  of 
a  nerve  is  sometimes  very  marked  in  herpes  zoster,  which  frei]uently  follows  the  distribution  of 
the  intercostal  and  supraorbital  nerves.  Glossy  skin  (/'(ii.v/,  ]\\ir  Mitchell)  is  a  condition  de- 
pending upon  ittipaired  nutrition  and  circulation,  and  due  to  injuries  of  nerves.  The  skin  is  smooth 
and  glossy  in  the  area  of  distribution  of  certain  nerves,  while  the  wrinkles  and  folds  have  disap- 
peared. In  myxcedema,  the  subcutaneous  tissue  and  other  organs  are  infiltrated  with,  while  the 
blood  contains  mucin.  The  subcutaneous  tissue  is  swollen  and  the  patient  (adult  woman)  looks  as 
if  suffering  from  renal  dropsy.  There  is  marked  alteration  of  the  cerebral  faculties,  and  a  condi- 
tion resembling  a  "  cretinoid  state,"  occurs  after  the  excision  of  the  thyroid  gland.  Victor  Horsley 
has  shown  that  a  similar  condition  occurs  in  monkeys  after  excision  of  the  thyroid  gland  (§  lO'?, 

[Laycock  described  a  condition  of  nervous  oedema  which  occurs  in  some  cases  of  hemiplegia, 
and  apparently  it  is  independent  of  renal  or  cardiac  disease.] 

[There  are  alterations  in  the  color  of  the  skin  depending  on  nervous  affections,  including  local- 
ized leucoderma,  where  circumscribed  p.itches  of  the  skin  are  devoid  of  pigment.  The  pigmenta- 
tion of  the  skin  in  Addison's  disease  or  bronzed  skin,  which  occurs  in  some  cases  of  disease  ol 
the  suprarenal  capsules,  may  be  partly  nervous  in  its  origin,  more  especially  when  we  consider  the 
remarkable  pigmentation  that  occurs  around  the  nipple  and  some  other  parts  of  the  body  during 
pregnancy,  and  in  some  uterine  and  ovarian  affections  {Laycock).'\ 

[In  anaesthetic  leprosy,  the  anesthesia  is  due  to  the  disease  of  the  nervous  structure,  which 
results  in  disturbances  of  motion  and  nutrition.  Among  other  remarkable  changes  in  the  skin, 
perhaps  due  to  trophic  conditions,  are  those  of  symmetrical  and  local  gangrene,  and  acute  decu- 
bitus or  bed  sores.] 

[Bed  sores.— Besides  the  simple  chronic  form,  which  results  from  over- pressure,  bad  nursing, 
and  inattention  to  cleanliness,  combined  with  some  defect  of  the  nervous  conditions,  there  is 
another  form,  acute  decubitus,  which  is  due  directly  to  nerve  influence  (C//<7?yo/).  The  latter 
usually  appears  within  a  few  hours  or  days  of  the  cerebral  or  spinal  lesion,  and  the  whole  cycle  of 
changes — from  the  appearance  of  erythematous  dusky  patch  to  inflammation,  ulceration,  and  gan- 
grene of  the  buttock — are  completed  in  a  few  days.  An  acute  bed  sore  may  form  when  every  at- 
tention is  paid  to  the  avoidance  of  pressure  and  other  unfavorable  conditions.  When  it  depends  on 
cerebral  affections  it  begins  and  develops  rapidly  in  the  centre  of  the  gluteal  region  on  the  paralyzed 
side,  but  when  it  is  due  to  disease  of  the  spinal  cord,  it  forms  more  in  the  middle  line  in  the  sacral 
region;  while  in  unilateral  spinal  lesions  it  occurs  not  on  the  paralyzed,  but  on  the  anaesthetic  side, 
a  fact  which  seems  to  show  that  the  trophic,  like  the  sensory  fibres,  decussate  in  the  cord  {Ross).'\ 

[There  are  other  forms  due  to  nervous  disease,  including  symmetrical  gangrene  and  local 
asphyxia  of  the  terminal  parts  of  the  body,  such  as  the  toes,  nose,  and  external  ear,  caused,  perhaps, 
by  spasm  of  the  small  arterbiles  (Raynaud's  disease)  ;  and  the  still  more  curious  condition  of 
perforating  ulcer  of  the  foot.] 

[Hemorrhage  of  nervous  origin  sometimes  occurs  in  the  skin,  including  those  that  occur  in  loco- 
motor ataxia  after  severe  attacks  of  pain,  and  hematoma  aurium,  or  the  insane  ear,  which  is 
specially  common  in  general  paralytics.] 

(d)  Inhibitory  nerves  are  those  nerves  which  modify,  inhibit,  or  suppress  a 
motor  or  secretory  act  already  in  progress. 

Take  as  an  example  the  effect  of  the  vagus  upon  the  action  of  the  heart.  Stimulation  of  the 
peripheral  end  of  the  vagus  causes  the  heart  to  stand  still  in  diastole  (§  85);  the  efl'ect  of  the 
splanchnic  upon  the  intestinal  movements  (\  161).  The  vasodilator  nerves,  or  those  whose  stimu- 
lation is  followed  by  dilatation  of  the  blood  vessels  of  the  area  which  they  supply,  are  referred  to 
specially  in  \  237. 

[There  is  the  greatest  uncertainty  as  to  the  nature  and  mode  of  action  of  inhibitory  nerves, 


THE    CRANIAL    NERVES.  615 

but  take  the  vagus  as  a  type,  which  depresses  the  function  of  the  heart,  as  shown  by  the  slower 
rhythin,  diminution  of  the  contractions,  relaxation  of  the  muscular  tissue,  lowering  of  the  excitability 
and  conduction.  These  phenomena  are  not  due  to  exhaustion.  Gaskell  points  out  that  the  action 
is  beneficial  in  its  after  effects,  so  that  this  nerve,  although  it  causes  diminished  activity,  is  followed 
by  repair  of  function,  so  that  he  groups  it  as  an  anabolic  nerve,  the  outward  symptoms  of  cessation 
of  function  indicating  that  constructive  chemical  changes  are  going  on  in  the  tissue.] 

(e)  Thermic  and  electrical  nerves  have  also  been  surmised  to  exist. 

[Gaskell  classifies  the  efferent  nerves  differently.  Besides  motor  nerves  to  striped  muscle,  he 
groups  them  as  follows : — 

1.  Nerves  to  vascular  muscles. 

(a)    Vaso-motitr,  i.  e..  vasoconstrictor,  accelerators  and  augmentors  of  the  heart. 
(d)    Vaso-inltibitory,  i.  e.,  vaso-dilators  and  inhibitors  of  the  heart. 

2.  Nerves  of  the  visceral  muscles. 

[a)    Viscero  motor, 
ib)    Viscero  inhibitory. 

3.  Glandular  nerves.] 

[Other  terms  are  applied  to  nerves  with  reference  to  the  chemical  changes  they  excite  in  a  tis- 
sue in  which  they  terminate.  The  ordinary  metabolism  is  the  resultant  of  two  processes,  one  con- 
structive the  other  destructive,  or  of  assimilation  and  dissimilation  respectively.  The  former  process 
is  anabohsm,  the  latter  katabolism.  .\  motor  nerve  excites  chemical  destructive  changes  in  a  mus- 
cle, and  is  so  far  the  katabolic  nerve  of  that  tissue ;  in  the  same  way  the  sympathetic  to  the  heart, 
by  causing  more  rapid  contraction,  is  also  a  katabolic  nerve,  while  the  vagus,  as  it  arrests  the  heart's 
action,  brings  about  a  constructive  metabolism  of  the  cardiac  tissue,  is  an  anabolic  nerve 
[Gas/till ).'[ 

II.  Centripetal  or  Afferent  Nerves. — (a.^  Sensory  Nerves  (sensory  in 
the  narrower  sense),  which  by  means  of  special  end  organs  conduct  sensory 
impulses  to  the  central  nervous  system. 

(b)  Nerves  of  Special  Sense.  Fig.  3S0. 

(c)  Reflex  or  Excito-motor  Nerves. — 
When  the  periphery  of  one  of  these  nerves  is  stim- 
ulated, an  impulse  is  set  up  which  is  conducted 
by  them  to  a  nerve  centre,  from  whence  it  is  trans- 
ferred to  a  centrifugal  or  efferent  fibre,  and  the 
mechanism  (I,  a,  b,  c,  d)  in  connection  with  the 
peripheral  end  of  this  efferent  fibre  is  set  in  action  ; 
thus  there  are — Reflex  motor,  Reflex  secre- 
tory, and  Reflex  inhibitory  fibres.  [Fig.  380 
shows  the  simplest  mechanism  necessary  for  a  reflex 
motor  act.  The  impulse  starts  from  the  skin,  S, 
travels  up  the  nerve  a,f,  to  the  nerve  centre  or 
nerve  cell,  N,  situate  in  the  spinal  cord,  where  it 
is  modified  and  transferred  to  the  outgoing  fibre,  e,f,  and  conveyed  by  it  to  the 
muscle,  M.] 

III.  Intercentral  Nerves. — These  fibres  serve  to  connect  ganglionic  centres 
with  each  other,  as,  for  example,  in  coordinated  movements,  and  in  extensive 
reflex  acts. 

THE  CRANIAL  NERVES.— 343.  I.  NERVUS  OLFACTORIUS.— Anatomical.— 

The  three-sided,  prismatic,  tractus  olfactorius  lying  in  a  groove  on  the  under  surface  of  the  frontal 
lobe,  arises  by  means  of  an  inner,  outer,  and  upper  root,  from  the  tuber  olfactorium  (Fig.  3S5,  I). 
The  tractus  swells  out  upon  the  cribriform  plate  of  the  ethmoid  bone,  and  becomes  the  bulbus 
olfactorius,  which  is  the  analigue  of  the  special  portion  of  the  brain,  existing  in  different  mammals 
with  a  well-developed  sense  of  smell  (Gratio/et).  From  twelve  to  fifteen  olfactory  filaments  pass 
through  the  foramina  in  the  cribriform  plate  of  the  ethmoid  bone.  At  first  they  lie  between  the  peri- 
osteum and  the  mucous  membrane,  but  in  the  lower  third  of  their  course  they  enter  the  mucous 
membrane  of  the  regio  olfactoria.  The  bulb  consists  of  white  maUer  below,  and  above  of  gray 
matter  mixed  with  small  spindle-shaped  ganglionic  cells.  Henle  describes  six,  and  Meynert  eight 
layers  of  nervous  matter  seen  on  tran'^verse  section.  [The  centre  for  smell  lies  in  the  tip  of  the 
uncinate  gyrus  on  the  inner  surface  of  the  cerebral  hemisphere  [Furrier).  According  to  Hill,  the 
three  roots  of  the  olfactory  bulb  stream  backward,  the  inner  one  is  small,  the  middle  one  is  a  thick 
bundle,  which  grooves  the  head  of  the  caudate  nucleus,  curves  inward  to  the  anterior  commissure. 


616  CONNECTIONS   OF   OPTIC   TRACT. 

and  crosses  via  this  commissure  where  it  decussates,  and  passes  to  the  extremity  of  the  temporo- 
sphenoida!  lobe.  The  outer  roots  pass  transversely  into  the  pyriform  lobe,  thence  via  the  fornix, 
corpora  albicantia,  the  bundle  of  Vicq  d'Azyr  into  the  anterior  end  of  the  cptic  thalamus.  Hill 
also  points  out  that  the  elements  contained  in  the  olfactory  bulb  are  identical  with  those  contained 
in  the  four  outer  layers  of  the  retina.] 

Function. — It  is  the  only  nerve  of  smell.  Physiologically,  it  is  excited  only 
by  gaseous  odorous  bodies — {Sense  of  Sme//,  §  420).  Stimulation  of  the  nerve, 
by  any  other  form  of  stimulus,  in  any  part  of  its  course,  causes  a  sensation  of 
smell.  [It  also  conveys  those  impressions  which  we  call  flavors,  but  in  this  case 
the  sensation  is  combined  with  impressions  from  the  organs  of  taste.  In  this  case 
the  stimulus  reaches  the  nerve  by  the  posterior  nares.]  Congenital  absence  or 
section  of  both  olfactory  nerves  abolishes  the  sense  of  smell  (easily  performed 
on  young  animals. — Biffi). 

Pathological. — The  term  Hyperosmia  is  applied  to  cases  where  the  sense  of  smell  is  exces- 
sively and  abnormally  acute,  as  in  some  hysterical  persons,  and  in  cases  where  there  is  a  purely  sub- 
jective sense  of  smell,  as  in  some  insane  persons.  The  latter  is,  perhaps,  due  to  an  abnormal  stim- 
ulation of  the  cortical  centre  (^  378,  IV).  Hyposmia  and  Anosmia  {;'.  <■.,  diminution  and  abo- 
lition of  the  sense  of  smell)  may  be  due  to  mechanical  causes,  or  to  over-stimulation.  Strychnin 
sometimes  increases,  while  morphia  diminishes,  the  sense  of  smell.    [Method  of  Testing,  §  421.] 

344.  II.  NERVUS  OPTICUS.— Anatomical.— The  tractus  opticus  (Fig.  385,  IT)  arises 
by  a  number  of  fibres  from  the  inner  gray  substance  of  the  thalamus  opticus,  anfl  the  anterior  cor- 
pora quadrigemina ;  other  fibres  cover  these  structures  in  the  form  of  a  thin  plate  of  nervous  matter. 
The  corpora  geniculata  (Fig.  385,  i,  e),  form  ganglia,  intercalated,  as  it  were,  in  the  course  of  cer- 
tain of  the  fibres.  Another  set  of  fibres,  quite  distinct  from  the  foregoing,  passes  between  the  bun- 
dles of  the  eras  cerebri,  and  reaches  the  multicellular  nucleus  within  the  tegmentum  of  the  crus 
(corpus  subthalamicum).  Other  fibres  are  said  to  pass  to  the  spinal  cord,  directly  through  the  med- 
ulla oblongata,  without  the  intervention  of  any  gray  matter.  They  are  said  by  Stilling  to  reach  as 
far  as  the  decussation  of  the  pyramids.  According  to  this  view,  the  optic  nerve  has  a  spinal  root, 
which  explains  the  relation  of  stimulation  of  the  retina  to  the  dilator  of  the  iris.  A  broad  bundle 
of  fibres  passes  from  the  origin  of  the  optic  tract  to  the  cortical  psycho-optic  centre,  at  the  apex 
of  the  occipital  lobe  (  Wernii:ke~\  379,  IV). 

The  Optic  Tract  bends  round  the  pedunculus  cerebri,  where  it  unites  with  its  fellow  of  the  oppo- 
site side  to  form  the  chiasma. 

[Connections  of  Optic  Tract. — There  is  very  considerable  difficulty  in  ascertaining  the  exact 
origin  of  all  tlie  fibres  of  the  optic  tract.  Although  as  yet  the  statement  of  Gratiolet  is  not  proved, 
that  the  optic  tract  is  directly  connected  with  every  part  of  the  cerebral  hemisphere  in  man,  from 
the  frontal  to  the  occipital  lobe>  still,  the  researches  of  D.  J.  Hamilton  have  shown  that  its  connec- 
tions are  very  extensive.  It  is  certain  that  some  of  them  are  ganglionic,  i.e.,  connected  with  the 
ganglia  at  the  base  of  the  brain,  while  others  are  cortical,  and  form  connections  with  the  cortex 
cerebri.  The  ganglionic  fibres  arise  from  the  corpora  geniculata,  pulvinar  and  anterior  corpora 
quadrigemina,  and  probably,  also,  from  the  substance  of  the  thalamus.  The  cortical  fibres  join 
the  ganglionic  to  form  the  optic  tract.  According  to  D.  J.  Hamilton,  the  connection  with  the  cortex 
in  the  y>-(!K/a/ region  is  brought  about  by  '•  .VIeynert's  commissure."  The  latter  arises  directly  from 
the  lenticular-nucleus  loop,  decussates  in  the  lamina  cinerea,  and  passes  into  the  optic  nerve  of  the 
opposite  side.  The  lenticular-nucleus  loop  is  formed  below  the  lenticular  nucleus  by  the  junction 
of  the  strife  meduUares ;  the  stria?  medullares  form  part  of  the  fibres  of  the  internal  capsule,  and  the 
inner  capsule  is  largely  composed  of  fibres  descending  from  the  cortex.  Hamilton  also  asserts  that 
other  cortical  connections  join  the  tract  as  it  winds  round  the  pedunculus  cerebri,  and  they  include 
(rt)  a  large  mass  of  fibres  coming  from  the  motor  areas  of  the  opposite  cerebral  hemisphere,  crossing 
in  the  corpus  callosum,  entering  the  outer  capsule,  and  joining  the  tract  directly  ;  (/')  fibres  uniting 
it  to  the  temporo-sphenoidal  lobe  of  the  same  side,  especially  the  first  and  second  temporo-sphenoidal 
convolutions;  (c^  fibres  to  the  gyrus  hippocampi  of  the  same  side;  (r/)  a  large  leash  of  fibres 
forming  the  "optic  radiation"  of  Gratiolet,  which  connect  it  directly  with  the  tip  of  the  occipital 
lobe.  There  are  probably  also  indirect  connections  with  the  occipital  region  through  some  of 
the  basal  ganglia.  Although  some  observers  do  not  admit  the  connections  with  the  frontal 
and  sphenoidal  lobes,  all  are  agreed  as  to  its  connection  with  the  occipital  by  means  of  the 
"  optic  radiation."] 

[The  Optic  Radiation  of  Gratiolet  is  a  wide  strand  of  fibres  expanding  and  terminating  in  the 
occipital  lobes.  It  is  composed  of,  or,  stated  otherwise,  gives  branches  to  (a)  the  optic  tract  directly, 
[b)  the  corpus  geniculatum  internum  and  externum,  (c)  to  the  pulvinar  and  substance  of  the  thal- 
amus, (d")  a  direct  sensitive  band  (Meynert's  "  sensitive  band  ")  to  the  posterior  third  of  the  poste- 
rior limb  of  the  inner  capsule,  \e)  fibres  which  run  between  the  island  of  Reil  and  the  tip  of  the 
occipital  lobe  {D.  J.  Hamilton).'] 


HEMIOPIA    AND    HEMIANOPSIA  617 

Chiasma. — The  extent  of  the  decussation  of  the  optic  fibres  in  the  chia?ma 
is  subject  to  variations.     As  a  rule,  rather  more 
than  half  of  the  fibres  of  one  tract  cross  to  the  Fig.  381. 

optic  nerve  of  the  opposite  side  (Fig.  381),  so 
that  the  left  optic  tract  sends  fibres  to  the  left 
half  of  both  eyes,  while  the  right  tract  supplies 
the  right  half  of  both  eyes  (§378,  IV).  [Thus, 
the  corresponding  regions  of  each  retina  are 
brought  into  relation  with  one  hemisphere.  The 
fibres  which  cross  are  from  the  nasal  half  of  each 
retina.] 

Hence,  in  man,  the  destruction  of  one  optic  tract  (and 
its  central  continuation  in  the  occipital  lobe  of  the  cere- 
brum) produces  "  equilateral   or  homonymous  hemi-     Scheme  of  the  semidecussation  of  the  optic 
opia."     In  the  dog  and  cat  there  is  a  semi-decussalinn;  nerves.  L  /i.,  left  eye;  .«.  ^.,  right  eye. 

hence,  in  these  animals  extirpation  of  one  eyel)aU  causes 

atrophy  and  degeneration  of  half  of  the  nerve  fibres  in  both  optic  tracts  (Cudiien).  Baumgarten 
and  Mohr  have  observed  a  similar  result  in  mm.  A  sagittal  section  of  the  chiasma  in  the  cat  pro- 
duces partial  blindness  of  both  eyes  (A'/ra// 1.  According  to  Gudden.  the  fibres  which  decussate 
are  more  numerous  than  those  which  do  not,  although  J.  Stilling  maintains  that  they  are  only  slightly 
more  numerous.  According  to  J.  Schilling,  the  decussating  fibres  lie  in  the  central  axis  of  the 
nerve,  while  those  which  do  not  decussate  form  a  layer  around  the  former. 

Other  observers  maintain  that  there  is  complete  d -cussation  of  all  the  fibres  in  the  chiasma. 
Htnce,  section  of  one  optic  nei-'e  causes  dilatation  of  the  pupil  and  blindness  on  the  same  side,  while 
section  of  one  optic  tract  causes  dilatation  of  tlie  pupil  and  blindness  of  the  opposite  eye  (Knoll, 
Brown-Scqiiard,  Mamlelstamm).  In  o-seous  fishes,  both  optic  nerves  are  isolated  and  merely  cross 
over  each  other,  while  in  the  cyclostomata  they  do  not  cross  at  all.  [Total  decus-ation  occurs  in 
those  animals  where  the  eyes  do  not  act  together.] 

Injury  of  the  external  geniculate  body  and  section  of  the  anterior  brachium  have  the  same  effect 
as  section  of  the  optic  tract  of  the  same  side  (?  359 — Bechternu). 

In  very  rare  cases  the  decussation  is  absent  in  man,  so  that  the  right  tract  passes  directly  into  the 
right  eyeball,  and  the  left  into  the  left  eyeball  (  Vesalius,  CalUani,  Losel),  the  sight  not  being  inter- 
fered with  (  Vesalius). 

It  is  quite  certain  that  the  individual  fibres  do  not  divide  in  the  chiasma.  Two  commissures,  the 
inferior  commissure  (  Giidden)  and  Meynert's  commissure,  unite  both  optic  tracts  further  back. 

[A  special  commissure  (C.  inferior)  extends  in  a  curved  form  across  the  posterior  angle  of  the 
chiasma  (  Giidden).  It  does  not  degenerate  after  enucleation  of  the  eyeballs,  so  that  it  i>  regarded 
as  an  intercentral  connection.  After  excision  of  an  eye,  there  is  central  degeneration  of  the  fibres 
of  the  optic  nerve  entering  the  eyeball  [Giidden),  and  in  man  about  the  half  of  the  fibres  in  the 
corresponding  optic  tract  (Baumgarten,  Mohr).  After  section  of  both  optic  nerves,  or  enucleation 
of  both  eyeballs,  there  is  a  degeneration,  proceeding  centrally,  of  the  whole  optic  tract.  The 
degeneration  extends  to  the  origins  in  the  corpora  quadrigeniina,  corpora  geniculata,  and  pulvinar, 
but  not  into  the  conducting  paths  leading  to  the  cortical  visual  centre  (v.  Monakow)  (J  378, 
IV.  I).] 

Hemiopia  and  Hemianopsia. — When  one  optic  tract  is  interfered  with  or  divided,  there  is 
interference  with  or  loss  of  sight  in  the  lateral  halves  of  both  retinae,  the  blind  part  being  separated 
from  the  other  half  of  the  field  of  vision  by  a  vertical  line.  When  it  is  spoken  of  as  paralysis  of 
one  half  of  the  retina,  the  term  heviiopia  is  applied  to  it ;  when  with  reference  to  the  field  of  vision, 
the  term  hemianopsia  is  used  (see  Eye).  Suppose  the  left  optic  tract  to  be  divided  or  pressed  upon 
by  a  tumor  at  K  (Fig.  382),  then  the  outer  half  of  the  left  and  the  inner  half  of  the  right  eye  are 
blind,  causing  right  lateral  hemianopsia,  i.  e.,  the  two  halves  are  affected  which  correspond  in  ordi- 
nary vision,  so  that  the  condition  is  spoken  of  as  homonymous  hemianopsia.  Suppose  the  lesion 
to  be  at  T  (Fig.  3S2),  then  there  is  paralysis  of  tlie  inner  halves  of  both  eyes,  causing  double  tem- 
poral hemianopsia.  WTien  there  are  two  lesions  at  N  M,  which  is  very  rare,  the  outer  halves  of 
both  retinie  are  paralyzed,  so  that  there  is  double  nasal  hemianopsia.  In  order  to  explain  some  of 
the  eye  symptoms  that  occasionally  occur  in  cerebral  disease,  Charcot  has  supposed  that  some  of  the 
fibres  which  pass  from  the  external  geniculate  body  to  the  visual  centres  in  the  occipital  lobe  cross 
behind  the  corpora  quadrigemina,  and  this  is  represented  in  the  diagram  as  occurring  at  T  Q,  in 
the  corpora  quadrigemina.  On  this  view,  all  the  occipital  cortical  fibres  from  one  eye  would  ulti- 
mately pass  to  the  cortex  of  the  occipital  lobe  of  the  opposite  hemisphere.  This  view,  however,  by 
no  means  explains  all  the  facts,  for  in  cases  of  homonymous  hemianopsia  the  point  of  central  vision 
on  both  sides,  i.  e.,  both  maculoe  lutes  are  always  unaffected;  so  that  it  is  assumed  that  each  macula 
lutea  is  connected  with  both  hemispheres.  The  second  crossing  suggested  by  Charcot  probably  does 
not  occur.     [Affections  of  the  optic  nerve,  ;'.  e.,  between  tlie  eyeball  and  the  chiasma,  i.  e.,  in  the 


618 


NERVUS   OCULOMOTORIUS. 


orbit,  optic  foramen,  or  within  the  skull,  aflfect  one  eye  only;  of  the  middle  of  the  chiasma,  cause 
temporal  hemiopia;  of  the  optic  tract,  between  the  chiasma  and  occipital  cortex,  hemiopia,  which 
is  always  symmetrical  (  Go7uers).^ 

Munk  supposes  that  there  are  three  areas  in  the  retina  corresponding  to  three  cortical  visual  spheres, 
or  parts  of  the  visual  centre  in  the  occipital  lobe  (dog)  (|  376). 

Function. — The  optic  nerve  is  the  nerve  of  sight;    physiologically,   it   is 

excited  only  by  the  transference  of  the 
vibrations  of  the  ether  to  the  rods  and 
cones  of  the  retina  (§  383).  Every  other 
form  of  stimulus,  when  applied  to  the 
nerve  in  its  course  or  at  its  centre,  causes 
the  sensation  of  light.  Section  or  degen- 
eration of  the  nerve  is  followed  by  blind- 
ness. Stimulation  of  the  ojitic  nerve 
causes  a  refle.x  contraction  of  the  pupils, 
the  efferent  nerve  being  the  oculomotorius 
or  third  cranial  nerve.  If  the  stimulus  be 
very  strong,  the  eyelids  are  closed  and 
there  is  a  secretion  of  tears.  The  influ- 
ence of  light  upon  the  general  metabolism 
is  stated  at  §  127,  9. 

As  the  optic  nerve  has  special  and 
independent  connections  with  the  so-called 
psycho-optic  centre  (§  378,  IV),  as  well  as 
with  the  centre  for  narrowing  the  pupil 
(§  345),  it  is  evident  that,  under  patho- 
logical circumstances,  there  may  be, 
on  the  one  hand,  blindness  with  retention 
of  the  action  of  the  iris,  and  on  the  other 
loss  of  the  movements  of  the  iris,  the 
sense  of  vision  being  retained  (  Wernicke). 

Pathological. — Stimulation  of  almost  the  whole 
of  the  nervous  apparatus  may  cause  excessive  sen- 
sibility of  the  visual  apjiaratus  (JiypeiiCstliesia 
optica),  or  even  visual  impressions  of  the  most  varied  kinds  (photopsia,  chromatopsia),  which 
in  cases  of  stimulation  of  the  psycho-optic  centre  may  become  actual  visual  hallucinations  (§  37^' 
IV).  Material  change  in,  and  inflammation  of,  the  nervous  apparatus  are  often  followed  by  a 
nervous  weakness  of  vision  (amblyopia),  or  even  by  blindness  (amaurosis).  IJoth  conditions, 
however,  may  be  the  sign^  of  disturbances  of  other  organs,  i.e.,  they  are  "  sympathetic  "  signs,  due, 
it  may  be  to  changes  in  the  movement  of  the  blood  stream,  depending  upon  stimulation  of  the  vaso- 
motor nerves.  The  discovery  of  the  partial  origin  of  the  optic  nerve  from  the  spinal  cord  explains 
the  occurrence  of  amblyopia  (with  partial  atrophy  of  the  optic  nerve)  in  disease  of  the  spinal  cord, 
especially  in  tabes.  Many  poisons,  such  as  lead  and  alcoliol,  disturb  vision.  Hemeralopia  and 
Nyctalopia. — There  are  remarkable  intermittent  forms  of  amaurosis  known  as  day  blindness 
(hemeralopia),  which  occurs  in  some  diseases  of  the  liver  [and  is  sometimes  associated  with 
incipient  cataract.  The  person  can  see  better  in  a  dim  light  than  during  the  day  or  in  a  bright 
light.  In  night  bindne«s  (nyctalopia),  the  person  cannot  see  at  night  or  in  a  dim  light,  while 
vision  is  good  during  the  day  or  in  a  bright  light.  It  depends  upon  disorder  of  the  eye  itself,  and 
is  usually  associated  with  imperfect  conditions  of  nutrition. 

345.  III.  NERVUS  OCULOMOTORIUS.— Anatomical.— It  springs  from  the  oculo- 
motorius nucleus  (united  with  that  of  the  trochlearis),  which  is  a  direct  continuation  of  the  anterior 
horn  of  the  spinal  cord,  and  Hes  under  the  aqueduct  of  .Sylvius  (Fig.  385).  [The  motor  nucleus 
(Fig.  384)  gives  origin  to  three  sets  of  fibres,  for  (i)  the  most  of  the  muscles  of  the  eyeballs,  (2) 
the  sphincter  papilla;,  (3)  ciliary  muscle.  The  nucleus  of  the  3d  and  4th  nerves  is  also  connected 
with  that  of  the  6th  under  the  iter,  so  that  alf  the  nerves  to  the  ocular  muscles  are  thus  corelated  at 
their  centres.] 

The  origin  is  connected  with  the  corpora  quadrigemina,  to  which  the  intraocular  fibres  may  be 
traced,  and  also  with  the  lenticular  nucleus  through  the  pedunculus  cerebri.  Beyond  the  pons  it 
appears  on  the  inner  side  of  the  cerebral  peduncle  between  the  superior  cerebellar  and  posterior 
cerebral  arteries  (Fig.  3S5,  III). 


Diagram  of  the  decussation  of  the  optic  tracts.  T 
semi-decussation  in  the  chiasma;  TQ,  deciissa 
tion  of  fibres  behind  the  ext.  geniculate  Ijodie: 
(CQ) :  a'b,  fibres  which  do  not  decussate  in  th< 
chiasma ;  b'  a',  fibres  proceeding  from  the  righ 
eye,  and  coming  together  in  the  left  hemisphert 
(LOG):  LOG,  K,  lesion  of  the  left  optic  trac 
producing  right  lateral  hemianopsia  :  .4,  lesion  ii 
the  left  hemisphere  producing  crossed  amblyopi; 
(right  eye)  ;  T,  lesion  producing  temporal  he 
mianopsia  ;  NN,  lesion  producing  nasal  hemian 
opsia. 


FUNCTIONS   OF   THE   THIRD    CRANIAL   NERVE. 


619 


Function. — It  contains — (i)  the  voluntary  motor  fibres  for  all  the  external 
muscles  of  the  eyeballs — except  the  external  rectus  and  superior  oblique — and  for 
the  levator  palpebrre  superioris.  The  coordination  of  the  movements  of  both 
eyeballs,  however,  is  independent  of  the  will.  (2)  The  fibres  for  the  sphincter 
pupilhe,  which  are  excited  reflexly  from  the  retina.  (3)  The  voluntary  fibres  for 
the  muscle  of  accommodation,  the  tensor  choroidcEe  or  ciliary  muscle.  The  intra- 
bulbar  fibres  of  2  and  3  proceed  from  the  branch  for  the  inferior  oblique  muscle, 
as  the  short  root  of  the  ciliary  ganglion  (Fig.  386).  They  reach  the  eyeball 
through  the  short  ciliary  nerves  of  the  ganglion.  V.  Trautvetter,  Adamiik,  Hen- 
sen  and  Volckers  observed  that  stimulation  of  the  nerve  caused  changes  in  the 
eye  similar  to  those  which  accompany  near  vision.  The  three  centres  for  the 
muscle  of  accommodation,  the  sphincter  pupiUse  and  the  internal  rectus  muscle, 
lie  directly  in  relation  with  each  other,  in  the  most  posterior  part  of  the  floor  of 
the  third  ventricle  {Henscn  and  Viilckers). 

The  centre  for  the  reflex  stimulation  of  the  sphincter  fibres  by  light  is  said  to 
be  in  the  corpora  quadrigemina,  but  newer  researches  locate  it  in  the  medulla 
oblongata  (§§  379,  392).  The  narrowing  of  the  pupil,  which  accompanies  the 
act  of  accommodation  for  a  near  object,  is  to  be  regarded  as  an  associated  move- 
ment (§  392,  5).  . 

Anastomoses. — In  man  the  nerve  anastomoses  on  the  sinus  cavernosus  with  the  ophthalmic 
branch  of  the  trigeminus,  whereby  it  receives  sensory  fibres  for  the  musites  to  which  it  is  distributed 
(  ValcnliK,  Atiiimiil;),  with  the  sympathetic  through  the  carotid  plexus,  and  (?)  indirectly  through 
the  abducens,  whcrel>y  it  receives  vasomotor  fibres  (?J. 


Varieties. — In  some  rare  cases  the  papillary  fibres  for  the  sphincter  run  in  the  abducens 
(Aititmiik),  or  even  m  the  trigeminus  [Sc/tiff,  v.  Grd/e). 

Atropin  paral  zcs  the  intrabulbar  fibres  of  the  oculomotorius,  while  Calabar 
bean  stimulates  them  (or  paralyzes  the  sympathetic,  or  both — compare  §  392J. 

Stimulation  of  the  nerve  which  causes  contraction  of  the  pupil,  is  best  demonstrated  on  the  decapi- 
tated and  opened  head  of  a  bird.  The  pupil  is  dilated  in  paralysis  of  the  oculomotorius,  in  asphyxia, 
sudden  cerebral  ancemia  (,■.  g.,  by  ligature  of  the  carotids,  or  beheading),  sudden  venous  conges- 
tion, and  at  death. 

Pathological. — Complete  paralysis  of  the  oculomotorius  is  followed  by — (i)  drooping  of  the 
upper  eyelid  (Ptosis  paralytica);  (2)  immobility  of  the  eyeball;  (3)  squinting  (strabismus)  out- 
ward and  downward,  and  consequently  there  is  double  vision  (diplopia);  (4)  slight  protrusion  of 
the  eyeball,  because  the  action  of  the  superior  oblique  muscle  in  pulling  the  eyeball  forward  is  no 
longer  compensated  by  the  action  of  three  paralyzed  recti  muscles.  In  animals  provided  with  a  re- 
tractor bulbi  muscle,  the  protrusion  of  the  eyeliall  is  more  pronounced  ;  (1;)  moderate  dilatation  of 
the  pupil  (mydriasis  paralytica) ;  (6)  the  pupil  does  not  contract  to  light;  (7)  inability  to  ac- 
commod.ite  for  a  near  object.  It  is  to  be  noted,  however,  that  the  paralysis  may  be  confined  to 
indivitlual  branches  of  the  nerve,  i.  e.,  there  may  be  incomplete  paralysis. 

[Squinting. — In  paralysis  of  the  Superior  Rectus  the  eye  cannot  be  moved  upward,  and 
especially  upward  and  outward.  There  is  diplopia  on  looking  upward,  the  false  image  being  above 

the  true,  and  turned  to  the  right  when  the  left  eye  is  affected  (Fig.  383,  3).     Inferior  Rectus 

Defect  of  downward,  and  especially  downward  and  outward  movement,  the  eye  being  directed  up- 
ward and  outward.  Diplopia  with  crossed  im.ages,  the  false  one  is  below  the  true  image  and  placed 
obliquely,  being  turned  to  the  left  when  the  left  eye  is  affected.  Diplopia  is  most  troublesome  when 
the  object  is  below  the  line  of  vision  (Fig.  383,  5).  Internal  Rectus. — Defective  inward  move- 
ment, divergent  squint,  and  diplopia,  the  images  being  on  the  same  plane,  the  false  one  to  the 
patient's  right  wlien  the  left  eye  is  affected.     The  head  is  turned  to  the  healthy  side  when   looking 


620 


FUNCTIONS  OF  THE  FOURTH  CRANIAL  NERVE. 


at  an  object,  while  there  is  secondary  devialion  of  the  healthy  eye  outward  (Fig.  383,  i).  Inferior 
oblique  is  rare,  the  eye  is  turned  slightly  downward  and  inward,  and  defective  movement  upward. 
Diplopia  with  the  false  image  above  the  true  one,  especially  on  looking  upward  ;  the  false  image  is 
oblique,  and  directed  to  the  patient's  left  when  the  left  eye  is  affected  (Fig.  3S3,  4).] 

The  black  cross  represents  the  true  image,  the  thin  cross  the  false  image.  The  left  eye  is  affected 
in  all  cases  (Brislcnv). 

Stimulation  of  the  branch  supplying  the  levator  palpebroe  in  man  causes  lagophthalmus  spas- 
ticus,  while  stimulation  of  the  other  motor  fibres  causes  a  corresponding  strabismus  spasticus. 
This  latter  form  of  squinting  may  be  caused  also  reflexly— f.  g.,  in  teething,  or  in  cases  of  diarrha-a 

Fig.  384. 


Drachiuin  conjuncti\-um  anticum. 


TpU3  geoicul&ta 


Podunculua  cerebri. 


rporfiqimtlri.-i 

_J_ od  roeduUam  oljlon-  j  ««'et«ni 

pamni.  or  HilVrigr    j 
.  ^f  cerpbellar  I 

tjl  pedunck-.         J 


Medulla  oblongata,  with  the  corpora  quadrigemina.     The  numbers  JV. — XII.  indicate  the  superficial  origins  of  the 
cranial  nerves,  while  those  (3-12)  indicate  their  deep  origin,  i".  ^.,  the  position  of  their  central  nuclei :  t^  funiculus 


in  children ;  [the  presence  of  worms  or  other  source  of  irritation  in  the  intestines  of  children  is  a 
frequent  cause  of  squinting.]  Clonic  spasms  occur  in  both  eyes,  and  also  as  involuntary  movements 
of  the  eyeballs  constituting  nystagmus,  which  may  be  produced  by  stimulation  of  the  corpora 
quadrigemina,  as  well  as  by  other  means.  Tonic  contraction  of  the  sphincter  pupilla;  is  called 
myosis  spastica,  and  clonic  contraction,  hippus.  Spasm  of  the  muscle  of  accommodation  (ciliary 
muscle)  is  sometimes  observed  ;  owing  to  the  imperfect  judgment  of  distance,  this  condition  is  not 
unlrequently  associated  with  macropia. 

[Conjugate  Deviation. — Some  movements  are  produced  by  non  corresponding  muscles ;  thus, 
on  looking  to  the  right,  we  use  the  right  external  rectus  and  left  internal  rectus,  and  the  same  is  the 


THE    OPHTHALMIC    BRANCH    OF    THE    FIFTH.  621 

case  in  turning  the  head  to  the  right  £■.,;.'.,  the  inferior  oblique,  some  muscles  of  the  right  side  act 
aljng  with  the  left  sternomastoid.  In  hemiplegia  the  muscles  on  one  side  are  paralyzed,  so  that 
the  head  and  often  the  eyes  are  turned  away  from  the  paralyzed  side,  i.  <■,,  to  the  side  of  the  brain 
on  which  the  lesion  occurs.  This  is  called  "  conjugate  deviation  "  of  the  eyes,  with  rotation  of  the 
head  and  neck.  If  the  right  external  rectus  be  paralyzed  from  an  affection  of  the  sixth  nerve,  on 
telling  the  patient  to  look  to  the  right  it  will  be  found  that  the  left  eye  will  squint  more  inward  even 
than  the  right  eye,  ;.  e.,  owing  to  the  strong  voluntary  effort  of  the  muscle,  the  left  internal  rectus 
which  usually  acts  along  with  the  right  external  rectus,  contracts  vigorously,  and  so  we  get  second- 
ary deviation  of  the  sound  eye.  Similar  results  occur  in  connection  with  paralysis  of  other 
ocular  muscles.] 

346.  IV.  NERVUSTROCHLEARIS.— Anatomical.— It  arises  [from  the  valve  of  Vieus- 
sens,  i.  e.,  behind  the  fourth  ventricle],  but  its  tibres  pas^  to  the  oculomotorius  from  the  tmc/i/eaiis 
nucleus  (Fig.  3S4),  which  is  to  a  certain  extent  a  continuation  of  the  anterior  horn  of  the  spinal 
cord.  It  passes  to  the  lower  margin  of  the  corpora  quadrigemina,  pierces  the  root  of  the  aqueduct 
of  Sylvius,  then  into  the  velum  nieduUare  superius,  and  after  decussating  with  the  root  of  the 
opposite  side  behind  the  iter,  it  pierces  the  crus  at  the  superior  and  external  border  (Fig.  385,  IV). 
Its  fibres  cross  between  its  nucleus  and  its  distribution.  It  has  also  an  origin  from  the  locus  cceru- 
leus.  The  root  of  the  nerve  receives  some  fibres  from  the  nucleus  of  the  abducens  of  the  opposite 
side.  Physiologically,  there  is  a  necessity  for  a  conjunction  between  the  centre  and  the  cortical 
motor  centre  for  the  eye  muscles. 

Function. — It  is  the  voluntary  motor  nerve  of  the  superior  oblique  muscle. 
(In  coordinated  movements,  however,  it  is  involuntary.) 

Anastomoses. — Its  connections  with  the  plexus  caroticus  sympathici,  and  with  the  first  branch 
of  the  trigeminus,  have  the  same  significance  as  similar  branches  of  the  oculomotorius. 

Pathological. — Paralysis  of  the  trochlearis  nerve  causes  a  very  slight  loss  of  the  mobility  of  the 
eyeball  outward  and  downward.  There  is  slight  squinting  inward  and  upward,  with  diplopia  or 
double  vision.  The  images  are  placed  obliquely  over  each  other  [the  false  image  being  the  lower,  and 
directed  to  the  patient's  right  when  the  left  eye  is  affected  (Fig.  383,  6)]  ;  they  approach  each  other 
when  the  head  is  turned  toward  the  sound  side,  and  are  separated  when  the  head  is  turned  toward 
the  other  side.  The  patient  at  first  directs  his  head  forward,  later  he  rotates  it  round  a  vertical  axis 
toward  the  sound  side.  In  rotating  his  head  (whereby  the  sound  eye  may  retain  the  primary  posi- 
tion), the  eye  rotates  with  it.     Spasm  of  the  trochlearis  causes  squinting  outward  and  downward. 

347.  V.  NERVUS  TRIGEMINUS.— Anatomical.— The  trigeminus  (Fig.  3S6,  5),  arises 
like  a  spinal  nerve  by  two  roots  (Fig.  385,  V).  The  smaller,  anterior,  motor  root  proceeds  from 
the  "  motor  trigeminal  nucleus  "  ^5),  which  is  provided  with  many  multipolar  nerve  cells,  and 
lies  in  the  fioor  ol  the  medulla  oblongata,  not  far  from  the  middle  line.  Fibres  connect  this  nucleus 
with  the  cortical  motor  centres  on  the  opposite  side  of  the  cerebrum.  Besides  this  the  "descend 
ing  root  "  also  supplies  motor  fibres,  it  extends  laterally  from  the  corpora  quadrigemina  along 
the  aqueduct  of  Sylvius  downward  to  the  exit  of  the  neT\e  (Henle,  Forel).  The  large  posterior 
sensory  root  receives  fibres :  (ij  From  the  small  cells  of  the  "  sensory  trigeminal  nucleus" 
which  lies  at  the  level  of  the  pons,  and  is  the  analogue  of  the  posterior  horn  of  the  gray  matter  of 
the  spinal  cord.  (2)  From  the  gray  matter  of  the  posterior  horn  of  the  spinal  coid  downward  as 
far  as  the  cervical  vertebra.  These  fibres  run  into  the  posterior  column  of  the  cord  and  then  appear 
as  the  "  ascending  root  "  in  the  trigeminus.  (3)  Some  fibres  come  from  the  cerebellum,  through 
the  crura  cerebelli.  The  origins  of  the  sensory  root  anastomose  with  the  motor  nuclei  of  all  the 
nerves  arising  from  the  medulla  oblongata,  with  the  exception  of  the  abducens.  This  explains  the 
vast  number  of  reflex  relations  of  the  fifth  nerve.  The  thick  trunk  appears  on  each  side  of  the 
pons  (Fig.  385),  when  its  posterior  root  (perhaps  in  conjunction  with  some  fibres  from  the  anterior) 
forms  the  Gasserian  ganglion,  upon  the  tip  of  the  petrous  part  of  the  temporal  bone  (Fig.  386). 
Fibres  from  the  sympathetic  proceed  from  the  plexus  cavernosus  to  the  ganglion.  The  nerve 
divides  into  three  large  branches. 

I.  The  ophthalmic  division  (Fig.  386,  d)  receives  sympathetic  fibres  {vaso- 
motor niTves)  from  the  plexus  cavernosus  ;  it  passes  through  the  superior  orbital 
fissure  [sphenoidal]  into  the  orbit.     Its  branches  are  :— 

1.  Ine  small  recurrent  nerve  which  gives  sensory  branches  to  the  tentorium 
cerebelli.  Fibres  proceed  along  with  it  trom  the  carotid  plexus  of  the  sympathetic, 
which  are  the  vasomotor  nerves  for  the  dura  mater. 

2.  The  lachrymal  nerve  gives  off — {a)  Sensory  branches  to  the  conjunctiva, 
the  upper  eyelid,  and  the  neighboring  part  of  the  skin  over  the  temple  (Fig.  3S6, 
a);  {b)  true  sensory  fibres  to  the  lachrymal  gland  (^?j.  Stimulation  of  this 
nerve  is  said  to  cause  a  secretion  of  tears,  while  its  section  prevents  the  reflex 
secretion  excited  through  the  sensory  nerves  of  the  eye.     After  a  time,  section  of 


622 


THE    OPHTHALMIC    BRANCH    OF    THE    FIFTH. 


the  nerve  is  followed  by  a  paralytic  secretion  of  tears  {Hcrzemtein  and  Wolferz, 
Demtschenko),  although  the  statement  is  contested  by  Reich.  The  secretion  of 
tears  may  be  excited  reflexly  by  strong  stimulation  of  the  retina  by  light  by 
stimulation  of  the  first  and  second  branches  of  the  trigeminus,  and  through  all 
the  sensory  cranial  nerves  (^Demtschenko)  (§  356,  A,  6). 

3.  The  frontal  (/)  gives  off  the  supratrochlear,  which  supplies  sensory 


d  ja 


Part  of  the  base  of  the  brain,  with  the  origins  of  the  cranial  nervfs  :  the  convolutions  of  the  island  of  Reil  on  the 
right  side  but  removed  on  the  left.  I',  olfactory  tract  cut  short  :  II,  left  oplic  nerve  ;  II',  right  optic  tract  ; 
■J,  A,  cut  surface  of  the  left  optic  thalamus;  C,  central  lobe,  or  island  of  Reil ;  .S,  j.,  fissure  of  Sylvius  ;  X,  X, 
the  locus  perforalus  anticus  :  c,  the  external,  and  z,  the  internal,  corpus  geniculatum  ;  /(,  hypophysis  cerebri ; 
/,  c,  tuber  cinereum,  with  the  infundibulum  ;  rf,  points  to  one  of  the  corpora  albicantia;  P,  the  cerebral  pe- 
duncle ;  y,  the  fillet:  in.  left  oculo-motor  nerve;  X,  the  locus  perforatus  posticus;  P,  V,  pons  Varolii  :  V, 
the  greater  part  of  the  fifth  nerve  ;  +,  the  lesser  root  (on  the  right  side  this  mark  is  placed  on  the  Gasserian 
ganglion  and  points  to  the  lesser  root);  i,  ophthalmic  division  of  the  fifth;  VII,  <i,  facial ;  VII,  ^,  auditory  ; 
VIII,  vagus;  VIII,  a,  glosso-pharyngeal  ;  VIII,  i,  spinal  accessory;  IX,  hypoglossal ;  /?,  flocculus;/,  i, 
horizontal  fissure  of  the  cerebellum  (t'f)  ;  a,  m,  amygdala;  /,  a,  anterior  pyramid;  a,  olivary  body;  e,  resti- 
form  body  <^  anterior  median  fissure  ;  c, /,  the  lateral  column  of  the  spinal  cord;  C,  I,  the  sub-occipital  or 
-'l  nerve. 


first 

fibres  to  the  upper  eyelids,  brow,  glabelli,  and  those  which  excite  the  secretion 
of  tears  reflexly ;  and  by  its  supraorbital  branch  (/;),  analogous  branches  to 
the  upper  eyelid,  skin  of  the  forehead,  and  the  adjoining  skin  over  the  temple  as 
far  as  the  vertex. 

4.   The  nasociliary  nerve  (//,  e),  by  its  infratrochlear  branch  supplies  fibres. 


CILIARY    NERVES.  623 

similar  to  those  of  3,  to  the  conjunctiva,  caruncula  and  saccus  lacrymalis,  the 
upper  eyelid,  brow  and  root  of  the  nose.  Its  ethmoidal  branch  supplies  the 
tip  and  ate  of  the  nose,  outside  and  inside,  with  sensory  branches,  as  well  as  the 
upper  part  of  the  septum  and  the  turbinated  bones  with  sensory  fibres,  which 
can  act  as  afferent  nerves  in  the  reflex  secretion  of  tears ;  while  it  is  probable  that 
vasomotor  fibres  are  supplied  to  these  parts  through  the  same  channel.  (These 
fibres  may  be  derived  from  the  anastomosis  with  the  sympathetic  (?).)  The  naso- 
ciliary nerve  gives  off  the  long  root  U)  of  the  ciliary  ganglion  {c),  and  i  to  3 
long  ciliary  nerves. 

The  ciliary  ganglion  (Fig.  386,  c),  which,  according  to  Schwalbe,  perhaps 
belongs  rather  to  the  third  than  the  fifth  nerve,  has  three  roots — [a)  the  short 
or  oculomotorius  (3 — see  §  345)  ;  (b)  the  long  (/),  from  the  nasociliary;  and  (c) 
the  sympathetic  (s),  sometimes  united  with  b,  from  the  carotid  plexus.  The 
short  ciliary  nerves  (/),  6  to  10  in  number,  proceed  from  the  ganglion,  along 
with  the  long  ciliary  nerves,  to  near  the  entrance  of  the  optic  nerve,  where  they 
perforate  the  sclerotic  coat  and  run  forward  between  it  and  the  choroid. 
Ciliary  Nerves. — Physiologically,  these  nerves  contain  : — 
I  The  motor  fibres  for  the  sphincter  pupillfe  and  tensor  choroidege  from 
the  root  of  the  oculomotorius  (§  345,  2,  3). 

2.  Sensory  fibres  for  the  cornea  which  are  distributed  as  excessively  fine 
fibrils  between  the  epithelium  of  the  conjunctiva  iulbi ;  they  perforate  the  sclerotic 
{Gi/-al(ics).  These  fibres  cause  a  reflex  secretion  of  tears  (N.  lacrymalis)  and 
closure  of  the  eyelids  (N.  facialis).  Sensory  fibres  are  supplied  to  the  iris  (pain 
in  iritis  and  in  operations  on  the  iris),  the  choroid  (painful  tension  when  the 
ciliary  muscle  is  strained),  and  the  sclerotic. 

3.  Vasomotor  nerves  for  the  blood  vessels  of  the  iris,  choroid  and  retina. 
They  arise  in  part  from  the  sympathetic  root,  and  the  anastomosis  of  the  sym- 
pathetic with  the  ophthalmic  division  of  the  trigeminus  ( IVegner).  The  iris  and 
retina  receive  most  of  their  vasomotor  nerves  from  the  trigeminus  itself  (Rogow), 
and  few  from  the  sympathetic ;  according  to  Klein  and  Svetlin  the  retinal  vessels 
are  not  influenced  either  by  stimulation  or  division  of  the  sympathetic. 

4.  Motor  fibres  for  the  dilator  pupill;e,  which,  for  the  most  part,  are  derived 
from  the  sympathetic  (Petit,  172J),  through  the  sympathetic  root  of  the  ganglion, 
and  the  anastomosis  of  the  sympathetic  with  the  trigeminus  {Balogh,  Oehl).  The 
ophthalmic  division  contains  independent  fibres  for  the  dilatation  of  the  pupil 
(jSchiff),  which  arise  in  the  medulla  oblongata  and  proceed  directly  into  the 
ophthalmic  (?  or  arise  from  the  Gasserian  ganglion — Oehl). 

It  is  not  conclusively  determined  whether  in  man  dilator  fibres  also  proceed  through  the  sympa- 
thetic root  of  the  ciliary  ganglion,  and  reach  the  iris  through  the  ciliary  nerves.  In  the  dog  these 
fibres  do  not  pass  through  the  ciliary  ganglion,  but  go  directly  along  the  optic  nerve  to  the  eye 
{^Hensen  and  Volckers).  In  birds,  the  dilator  fibres  run  only  in  the  fifth  (Z,glinski).  For  the 
centre  (J  367,  8). 

After  section  of  the  trigeminus,  the  pupil  becomes  contracted  after  a  short 
period  of  dilatation  (rabbit,  frog),  but  this  effect  is  not  permanent.  After 
excision  of  the  superior  cervical  ganglion  of  the  sympathetic,  the  power  of  dila- 
tation of  the  pupil  is  not  completely  abolished.  The  narrowing  of  the  pupil 
which  follows  section  of  the  trigeminus  in  the  rabbit,  and  which  rarely  lasts  more 
than  half  an  hour,  may  be  regarded  as  due  to  a  reflex  stimulation  of  the  oculo- 
motorius fibres  of  the  sphincter,  in  consequence  of  the  painful  stimulation  caused 
by  section  of  the  trigeminus. 

Stimulation  of  the  Sympathetic. — Either  in  the  neck,  or  in  its  course  to  the  eye,  when  the 
peripheral  end  of  the  cervical  sympathetic  is  stimulated,  besides  other  effects  on  the  blood  vessels, 
there  is  dilntnlion  of  the  ftipil,  as  well  as  contraction  of  the  smooth  muscular  fibres  in  the  orbit  and 
eyelids.  The  membrana  orbitalis,  which  separates  the  orbit  from  the  temporal  fossa  in  animals, 
contains  numerous  smooth  muscular  fibres  (iiiiiscuhis  orbi/alis).  The  corresponding  membrane  of 
the  inferior  orbital   fissure    [spheno-maxillary  fissure]   in  man   has  a  layer  of  smooth  muscle,  one 


624  TROPHIC    NERVES    IN    THE   TRIGEMINUS. 

millimetre  thick,  and  arranged  for  the  most  part  longitudinally.  Both  eyelids  contain  smooth  mus- 
cular fibres  which  serve  to  close  them;  in  the  upper  lid  they  lie  as  a  continuation  of  the  levator 
palpebrne  superioris,  in  the  lower  lid  close  under  the  conjunctiva.  Tenon' s  capsu/e  aXso  contains 
smooth  muscular  fibres.  The  sympathetic  nerve  supplies  all  these  muscles  {Heinr.  Miillcr) — i^the 
orbital  muscle  is  partly  supplied  from  the  spheno-palatine  ganglion);  in  animals  the  retractor  of 
the  third  eyelid  at  the  inner  angle  of  the  eye  is  similarly  supplied.  Hence,  stinmlalion  of  the  sym- 
pathetie  causes  dilatation  of  the  pupil  and  of  the  palbebral  fissure,  with  protrusion  of  the  eyeball. 
This  result  may  be  caused  reflexly  by  strong  stimulation  of  sensory  nerves.  Strong  stimulation  of 
the  nerves  of  the  sexual  organs  is  followed  by  similar  phenomena  in  the  eye.  The  dilatation  of  the 
pupil,  which  occurs  in  children  affected  with  intestinal  worms,  is  perhaps  an  analogous  phe- 
nomenon. The  pupil  is  dilated  when  the  spinal  cord  is  stimulated  (at  the  origin  of  the  sympa- 
thetic), as  in  tetanus. 

Section  of  the  Sympathetic,  besides  other  effects,  causes  narrowing  of  the  fissure  between  the 
eyelids,  the  eyeball  sinks  in  its  socket  (and  in  animals,  the  third  eyelid  is  relaxed  and  protruded). 
In  dogs,  section  causes  internal  squint,  as  the  external  rectus  receives  some  motor  fibres  from  the 
sympathetic  (p.  631).     (Origin  of  these  fibres  from  the  cilio-spinal  region.     Spinal  cord,  \  362,  I.) 

4.  It  is  probable  that  trophic  fibres  occur  in  the  trigeminus,  and  pass  through 
the  ciliary  nerves  to  reach  the  eye.  If  the  trigeminus  be  divided  within  the  cra- 
nium, after  six  to  eight  days,  inflammation,  necrosis  of  the  cornea,  and  ultimately 
complete  destruction  of  the  eyeball  take  place,   constituting   Panophthalmia 

{Foiii'ra,  1S2J  ;  Magendie). 

Trophic  Fibres. — In  weighing  the  evidence  for  and  against  the  existence  of  trophic  fibres,  we 
must  bear  in  mind  the  following  considerations:  i.  Section  of  the  trigeminus  makes  the  whole 
eye  insensible  ;  the  animal  is  therefore  unconscious  of  direct  injury  to  its  eye,  and  cannot  there- 
fore remove  any  offending  body.  Dust  or  mucus,  which  may  adhere  to  the  eye,  is  no  longer  re- 
moved by  the  reflex  closing  of  the  eyelids;  while,  owing  to  the  absence  of  the  reflex,  the  eye  is 
more  open  and  is  therefore  subject  to  more  injuries ;  the  reflex  secretion  of  tears  is  also  arrested. 
Snellen  (1S57)  fixed  the  ear  of  a  rabbit  in  front  of  its  eye  so  as  to  protect  the  latter  and  shield  it 
from  injuries,  and  he  found  that  the  inflammation  and  other  events  occurred  at  a  later  date,  while, 
according  to  Meissner  and  Bultner,  if  the  eye  be  protected  by  means  of  a  complete  capsule,  the  in- 
flammation does  not  occur  at  all.  There  can  be  no  doubt  that  the  loss  of  the  sensibility  of  the  eye 
favors  the  occurrence  of  inflammation.  But  Meissner,  Biittner,  and  Schiff  observed  that  inflam- 
mation of  the  eye  occurred  when  the  trophic  (most  internal)  fibres  alone  were  divided,  the  eye  at 
the  same  lime  retaining  its  sensibility;  this  would  seem  to  indicate  the  existence  of  trophic  fibres, 
but  Cohnheim  and  Senltleben  dispute  the  statement.  Conversely,  the  sensibility  of  the  eye  may  be 
abohshed  by  partial  section  of  the  nerve,  yet  the  eye  does  not  become  inflamed  [Schiff).  Ranvier, 
who  denies  the  existence  of  trophic  nerves,  made  a  circular  incision  round  the  margin  of  the  cornea 
through  its  superficial  layers  so  as  to  divide  all  the  corneal  nerves.  Insensibility  of  the  cornea  was 
thereby  produced,  but  never  keratitis.  Further,  in  man  and  animals  who  cannot  close  their  eyelids, 
there  is  redness  with  secretion  of  tears,  or  slight  dryness  and  opacity  of  the  surface  of  the  eyeball 
(Xerosis),  but  never  the  inflammation  already  described  [Samuel).  2.  We  must  also  take  into 
consideration  the  following :  Section  of  the  trigeminus  paralyzes  the  vasomotor  nerves  in  the  in- 
terior of  the  eyeball,  which  must  undoubtedly  cause  a  disturbance  in  the  intraocular  circulation. 
According  to  Jesner  and  Griinhagen,  the  trigeminus  also  contains  vaso-dilator  fibres,  whose  stimu- 
lation is  followed  by  increased  flow  of  blood  to  the  eye,  with  consecutive  excretion  of  the  fibrin 
factors  and  increase  in  the  amount  of  albumin  of  the  aqueous  humor.  3.  After  section  of  the 
nerve,  the  intraocular  tension  is  diminished  (while  stimulation  of  the  nerve  is  followed  by  in- 
crease of  the  intraocular  pressure)  [Hippell,  Griinhagen,  Adamiii).  This  diminution  of  the  normal 
tension  necessarily  must  alter  the  normal  relation  of  the  filling  ol  the  blood  and  lymph  vessels, 
and  also  the  movement  of  the  fluids,  upon  which  the  normal  nutrition  is  largely  dependent.  4. 
W.  Kiihne  observed  that  stimulation  of  the  corneal  nerves  was  followed  by  contraction  of  the  so- 
called  corneal  corpuscles.  Very  probably  the  movements  of  these  corpuscles  may  influence  the 
normal  movement  of  the  lymph  in  the  canalicular  system  of  the  cornea  (J  384) ;  these  movements, 
however,  would  seem  to  depend  upon  the  nervous  system,  so  that  its  destruction  is  likely  to  produce 
disturbance  of  nutrition. 

[There  are  three  conditions  on  which  the  changes  may  depend — (i)  mere  loss  of  sensibility, 
which  alone  is  not  sufticient  to  explain  the  phenomena;  (2)  on  vasomotor  disturbance,  which  is 
excluded  by  the  above  facts,  and  also  by  the  other  consideration  that,  if  the  fifth  nerve  be  divided 
and  the  superior  cervical  ganglion  excised  simultaneously,  ophthalmia  does  not  occur,  and,  in  fact, 
excision  of  this  sympathetic  ganglion  may  modify  the  results  of  section  of  the  fifth  (Sinilzin).  Thus, 
we  are  forced  to  (3)  the  theory  of  trophic  fibres,  whose  centre  is  the  Gasserian  ganglion.] 

Pathological. — In  cases  of  anresthesia  of  the  trigeminus  in  man,  and,  more  rarely,  in  severe 
irritation  of  this  nerve,  inflammation  of  the  conjunctiva,  ulceration  and  perforation  of  the  cornea, 
and,  finally,  panophthalmia,  have  been  observed  (Charles  Bell).  This  condition  has  been  called 
ophthalmia  neuroparalytica.     Samuel   found   that  a  similar  result  was  produced   by  electrical 


BRANCHES   AND    CONNECTIONS    OF   THE    TRIGEMINUS. 
Fig.  386. 


626 


ni-diagrammatic  representation  of  the  nerves  of  the  eyeball,  the  connections  of  the  trigeminus  and  its  ganglia, 
together  with  the  facial  and  glosso-pharyngeal  nerves.  3.  Branch  to  the  inferior  oblique  muscle  from  the  oculo- 
motorius,  with  the  thick,  short  root,  to  the  ciliary  ganglion  (r) ;  t,  ciliary  nerves  ;  I,  long  root  to  the  ganglion  from 
the  naso-ciliary  (n  c) ;  s,  sympathetic  root  from  sympathetic  plexus  {S  y)  surrounding  the  internal  carotid  (G) ;  d, 
first  or  ophthalmic  division  of  the  trigeminus  (5),  with  the  naso-ciliary  («  c),  and  the  terminal  branches  of  the  lach- 
rymal (a),  supraorbital  (*),  and  frontal  (y") ;  e,  second  or  superior  maxillary  division  of  the  trigeminus  ;  R,  infraor- 
bital ;  w.spheno-palatine  (Meckel's)  ganglion  with  its  roots  ;  j,  from  the  facial,  and;',  from  the  sympathetic  ;  N,  the 
nasal  branches,  and  //,,  the  palatine  branches  of  the  ganglion,  g,  third  or  inferior  maxillary  division  of  the  tri- 
geminus ;  k,  lingual ;  i  /,  chorda  tympani ;  «/»  otic  ganglion,  with  the  roots  from  the  tympanic  plexus,  the  carotid 
plexus,  and  from  the  3d  branch,  and  with  its  branches  to  the  auriculo-temporal  (A),  and  to  the  chorda  {ii)\  L, 
in  with  its  roots  from  the  tympanico-Hngual,  and  the  sympathetic  plexus  on  the  external 
7.  Facial  nerve—:/',  '^^  great  superficial  petrosal  branch  ;  a.  gang,  geniculatum  ;  /J^  branch 
IS  ;  V  branch  to  the  stapedius  ;  ^  anastomatic  twig  to  the  auricular  branch  of  the  vagus  : 
S,  stylo-mastoid  foramen.  9.  Glosso-pharyngeal — A,  its  tympanic  bmnch  ;  Tt  and  £^ 
connections  with  the  facial :  U,  terminations  of  the  gustatory  fibres  of  9  in  the  circumvallate  papillae :  S.y,  sym- 
pathetic with  G  g,  s,  the  superior  cervical  ganglion  ;  /,  II,  III,  IV,  the  four  upper  cervical  nerves ;  P,  parotid, 
M,  sub-maxillary  gland. 

40 


■maxillary  ganglit 
laxillary  artery  {(f). 
1  the  tympanic  plcxi 
I,  chorda  tympani  ; 


626  Meckel's  ganglion  and  its  connections. 

stimulation  of  the  Ga<serian  ganglion  in  animals.  There  are  other  affections  of  the  eye  depending 
upon  disease  of  the  vaso-motor  nerves,  which  are  quite  different  from  the  foregoing,  as  they  never 
lead  to  degenerative  changes.  Such  is  ophthalmia  intermittens  (due  to  malaria),  a  unilateral, 
intermittent,  excessive  filling  of  the  blood  vessels  of  the  eye,  accomjianied  by  the  secretion  of  tears, 
photophobia,  often  accompanied  by  iritis  and  effusion  of  pus  into  the  chambers  of  the  eye.  This 
condition  was  regarded  as  a  vaso-neurotic  affection  of  the  ocular  blood  vessels  by  Eulenburg  and 
Landois.  Pathological  observations,  as  well  as  experiments  upon  animals  (Mooi-en  and  Riimpf), 
have  .shown  that  there  is  an  intimate  physiological  connection  lietween  the  vascular  areas  of  both 
eyes,  so  that  affections  of  the  vascular  area  of  one  eye  are  apt  to  induce  similar  disturl)ances  of  the 
opposite  eye.  This  serves  to  explain  the  fact  that  inflammatory  processes  in  the  interior  of  one  eye- 
ball are  apt  to  produce  a  similar  condition  in  the  other  eye.  This  is  the  so-called  "  sympathetic 
ophthalmia."  Thus,  stimulation  of  the  ciliary  ner.  es,  or  the  fifth  on  one  side,  causes  dilatation  of 
the  blood  vessels  not  only  on  its  own  side,  but  also  on  the  other  side  as  well  [Jesner  and  Grihi- 
hiii;fn).  The  pathological  condition  of  glaucoma  simplex,  where  the  intraocular  tension  is  greatly 
increased,  is  ascribed  by  Donders  to  irritation  of  the  trigeminus.  [Increased  intraocular  tension 
may  be  produced  by  irritation  of  the  secretory  fibres  contained  in  the  fifth  nerve  (Donders),  by 
stimulating  the  nucleus  of  the  trigeminus  in  the  medulla  oblongata  [Ilipl^ell  and  Griinhagen),  and 
also  reflexly  by  irritation  of  the  peripheral  branches  of  the  fifth,  as  by  nicotin  placed  in  the  eye.  It 
is  possible,  however,  that  some  forms  of  glaucoma  .are  produced  by  diminished  reinoval  of  the 
aqueous  humor  from  the  eye.] 

II.  Superior  Maxillary  Division  (E). — It  gives  off — 

1.  The  delicate  recurrent  nerve,  a  sensory  branch  to  the  dura  mater,  which 
acconnpanies  the  vasomotor  nerves,  derived  froin  the  superior  cervical  ganglion 
of  the  sympathetic,  and  is  distributed  to  the  area  of  the  middle  meningeal 
artery. 

2.  The  subcutaneous  malar  (o)  (or  orbital)  supplies  by  its  temporal  and 
orbital  branches  sensibility  to  the  lateral  angle  of  the  eye  and  the  adjoining  area 
of  skin  of  the  teinple  and  the  cheek.  Certain  fibres  of  the  nerve  are  said  to  be 
the  true  secretory  nerves  for  tears.  Coinpare  N.  lacrymalis,  p.  621  {Herzenstetn 
and  IVo/fcrz). 

3.  The  dental,  anterior,  posterior,  and  inedius,  and  with  thein  the  anterior 
fibres  from  the  infraorbital  nerve,  supply  sensory  fibres  to  the  teeth  in  the  upper 
jaw,  the  gum,  periosteum,  and  the  cavities  of  the  jaw  (p.  624).  The  vasomotor 
nerves  of  all  these  parts  are  supplied  from  the  upper  cervical  ganglion  of  the  sym- 
pathetic. 

4.  The  infraorbital  (R),  after  its  exit  from  the  infraorbital  foramen,  supplies 
sensory  nerves  to  the  lower  eyelid,  the  bridge  and  sides  of  the  nose,  and  the 
upper  lip  as  far  as  the  angle  of  the  mouth.  The  accompanying  artery  receives  its 
vasomotor  fibres  from  the  superior  cervical  ganglion  of  the  sympathetic.  With 
regard  to  the  fibres  for  the  secretion  of  sweat  which  occur  in  it  (pig),  see  §  288. 

The  spheno-palatine  ganglion  (  Meckel's — n)  forms  connections  with  the 
II  division.  To  it  pass  two  short  sensory  root  fibres  from  the  II  division  itself, 
which  are  called  sphciio-palatine.  Motor  fibres  enter  the  ganglion  from  behind, 
through  the  large  superficial  petrosal  branch  of  the  facial  { j — Bidder,  Nuhri)  ; 
and,  lastly,  gray  vasomotor  fibres  (?')  from  the  sympathetic  ple.xus  on  the 
carotid  (the  deep,  large  i)etrosal  nerve).  The  motor  and  vasomotor  fibres  from 
the  Vidian  nerve,  which  reaches  the  ganglion  through  the  canal  of  the  same 
name. 

Branches  of  the  Ganglion. — The  branches  proceeding  from  the  ganglion 
are:  (i)  The  sensory  fibres  (N)  which  supply  the  roof,  lateral  walls,  and  septum 
of  the  nose  (posterior  and  superior  nasal)  ;  the  terminal  fibres  of  the  }iaso-pala- 
tine  pass  through  the  canalis  incisivus  to  the  hard  palate,  behind  the  incisor  teeth. 
The  sensory  inferior  and  posterior  nasals  for  the  lower  and  middle  turbinated 
bones,  and  both  lower  nasal  ducts,  are  derived  from  the  anterior  palatine  branch 
of  the  ganglion,  which  descends  in  the  palato-maxillary  canal.  Lastly,  the  sensory 
branches  for  the  hard  (/)  and  soft  palate  (/,)  and  the  tonsils  arise  from  the/w- 
terior  palatine  nerve.  All  the  sensory  fibres  of  the  nose  (see  also  the  Ethmoidal 
nenie),  when  stimulated,  cause  the  reflex  act  of  sneezing  (§  120).     Preparatory 


INFERIOR    MAXILLARY    DIVISION.  627 

to  the  act  of  sneezing  there  is  always  a  peculiar  feeling  of  tickling  in  the  nose, 
which  is  perhaps  due  to  dilatation  of  the  nasal  blood  vessels.  This  dilatation  is 
rapidly  caused  by  cold,  more  especially  when  it  is  applied  directly  to  the  skin. 
The  dilatation  of  the  vessels  is  followed  by  an  increased  secretion  of  watery  fluid 
from  the  nasal  mucous  membrane.  Stimulation  of  the  nasal  nerves  also  causes  a 
reflex  secretion  of  tears,  and  it  may  also  cause  stand-still  of  the  respiratory  move- 
ments in  the  expiratory  phase  (//if/7>g-  and  Kratschmer) — (c<yci\\)Z.\t  Respiratory 
centre,  §  368).  (2)  The  motor  branches  descend  in  the  posterior  palatine  nerve 
through  the  small  palatine  canal,  and  give  off  (//)  motor  branches  to  the  elevator 
of  the  soft  palate  and  azygos  uvulag  {Nuhn,  Friihwald).  The  sensory  fibres  for 
these  muscles  are  supplied  by  the  trigeminus.  According  to  Politzer,  spasmodic 
contraction  of  these  muscles  occasionally  causes  crackling  noises  in  the  ears.  (3) 
The  vasomotor  nerves  of  this  entire  area  arise  from  the  sympathetic  root,  /.  e., 
from  the  upjier  cervical  ganglion.  (4)  The  root  of  the  trigeminus  supplies  the 
secretory  nerves  of  the  mucous  glands  of  the  nasal  mucous  membrane.  Stimu- 
lation excites  secretion,  while  section  of  the  trigeminus  diminishes  it  with  simul- 
taneous atrophic  degeneration  of  the  mucous  membrane.  Thus  trophic  functions 
for  the  mucosa  have  been  ascribed  to  the  trigeminus  (^Aschenbrandt). 

Stimulation  of  the  Ganglion.  — Feeble  electricil  stimulation  of  the  exposed  ganglion  causes  a 
copious  secretion  of  mucus  and  an  increase  of  the  temperature  in  the  nose  (Prevost),  with  dilation 
of  the  ve.ssels  {Aschenhrandl).  [Meckel's  ganglion  has  been  excised  in  certain  cases  of  neuralgia 
{Walskam).'\ 

III.  Inferior  Maxillary  (G). — It  contains  all  the  motor  fibres  of  the  fifth, 
along  with  a  number  of  sensory  fibres  ;   it  gives  off — 

1.  The  recurrent,  which  springs  by  itself  from  the  sensory  root,  enters  the 
skull  through  the  foramen  spinosum,  and,  along  with  the  nerve  of  the  same  name 
from  the  II  division,  it  supplies  sensory  fibres  to  the  dura  mater.  Fibres  ])roceed 
from  it  through  the  petroso-squamosal  fissure  to  the  mucous  membrane  of  the  cells 
of  the  mastoid  process. 

2.  Motor  fibres  for  the  muscles  of  mastication,  viz.,  the  masseteric,  the  two 
deep  temporal  nerves,  and  the  internal  and  external  pterygoid  nerves.  The  sen- 
sory fibres  for  the  muscles  are  supplied  by  the  sensory  fibres. 

3.  The  buccinator  is  a  sensory  nerve  for  the  mucous  membrane  of  the  cheek, 
and  the  angle  of  the  inouth  as  far  as  the  lips. 

According  to  Jolyet  and  LafFont,  it  contains,  in  addition,  vasomotor  fibres  for  the  mucous  mem- 
brane of  the  cheek,  lower  lip,  and  their  mucous  glands;  but  these  fibres  are  probably  derived  from 
the  sympathetic. 

Trophic  Fibres. — As  this  region  of  the  mucous  membrane  of  the  mouth  ulcerates  after  section 
of  the  trigeminus,  some  have  supposed  that  the  buccinator  nerve  contains  trophic  fibres.  But,  as 
Rollett  pointed  out,  section  of  the  inferior  maxillary  nerve  paralyzes  the  muscles  of  mastication  on 
the  same  side,  and  hence  the  teeth  do  not  act  vertically  upon  each  other,  but  press  against  the  cheek. 
Owing  to  the  loss  of  the  sensibility  of  the  mouth,  food  passes  between  the  gum  and  the  cheek, 
where  it  may  remain  attached,  undergo  decomposition,  and  perhaps  chemically  irritate  the  mucous 
membrane.  .'\t  a  later  stage,  owing  10  the  wearing  away  of  the  teeth  in  an  oblique  manner,  ulcers 
begin  to  form  on  the  soiimi  side.  Hence,  there  is  no  necessity  for  assuming  the  existence  of  trophic 
filires  in  this  nerve.  After  section  of  the  trigeminus,  the  nasal  mucous  membrane  on  the  same  side 
becomes  red  and  congested.  This  is  due  to  the  fact  that  dust  or  mucus,  not  being  removed  from 
the  nose  by  the  usual  reflex  acts,  remains  there,  irritates,  and  ultimately  causes  inflammation. 

4.  The  lingual  (k)  receives  at  an  acute  angle  the  chorda  tympani  (//),  a  branch 
of  the  facial  coming  from  the  tympanic  cavity.  The  lingual  does  not  contain 
any  motor  fibres  ;  it  is  the  sensory  and  tactile  nerve  of  the  anterior  two-thirds 
of  the  tongue,  of  the  anterior  palatine  arch,  the  tonsil,  and  the  floor  of  the  mouth. 
These,  as  well  as  all  the  other  sensory  fibres  of  the  mouth,  when  stimulated,  cause 
a  reflex  secretion  of  saliva  (comjtare  §  145).  The  lingual  is  accompanied  by 
the  nerve  of  taste  (chorda)  for  the  tip  and  margins  of  the  tongue  (/.  e.,  the  parts 
not  supplied  by  the  glosso-pharyngeal).  After  section  of  the  lingual  nerve  in 
man,  Busch,  Inzani  and  Lusanna  found  that  the  tactile  sensibility  was  lost  in  the 


628  SUB-MAXILLARY    GANGLION    AND    ITS   CONNECTIONS. 

half  of  the  tongue,  and  there  was  loss  of  taste  in  the  anterior  part  [two-thirds]  of 
the  tongue.  The  fibres  which  administer  to  the  sense  of  taste  do  not,  as  a  rule, 
belong  to  the  lingual  itself,  but  are  derived  from  ihs  c/wnia  tympani  {^.  631). 
According  to  Schiff,  the  lingual  nerve  is  the  gustatory  nerve,  and  some  cases  of 
Erb  and  Senator  support  this  view.  Such  cases,  however,  seem  to  be  e.vceptions 
to  the  general  rule.  The  lingual  nerve  in  the  substance  of  the  tongue  is  provided 
with  small  ganglia  {Remak,  StirHng).  Schiff  observed  that  section  of  the  lingual 
(and  also  of  the  hypoglossal)  caused  redness  of  the  tongue,  so  that  vasomotor  fibres 
are  present  in  its  course.  It  is  unknown  whether  these  are  derived  from  the  anas- 
tomoses of  the  Gasserian  ganglion  with  the  sympathetic.  The  lingual  appears  to 
receive  vaso-dilator  fibres  from  the  chorda  for  the  tongue  and  gum  (§  349). 

.After  section  of  the  trigeminus,  animals  frequently  bite  their  tongue,  as  they  cannot  feel  the  posi- 
tion and  movements  of  this  organ  in  the  mouth. 

5.  The  inferior  dental  is  the  sensory  branch  to  the  teeth  and  gum;  the 
vasomotor  fibres  reach  it  from  the  superior  cervical  ganglion.  Before  it  passes 
into  the  canal  in  the  lower  jaw  it  gives  off  the  mylo-hyoid  nerve,  which  supplies 
motor  fibres  to  the  mylo-hvoid  and  the  anterior  belly  of  the  digastric,  and  also 
some  fibres  to  the  triangularis  menti  and  the  platysma ;  the  muscular  sensory 
nerves  also  lie  in  these  branches.  The  mental  nerve,  which  issues  from  the 
mental  foramen,  is  the  sensory  nerve  for  the  chin,  lower  lip,  and  the  skin  at  the 
margin  of  the  jaw. 

6.  The  auriculo  temporal  gives  sensory  branches  to  the  anterior  wall  of 
the  external  auditory  meatus,  the  tympanic  membrane,  the  anterior  part  of  the 
ear,  the  adjoining  region  of  the  temple,  and  to  the  maxillary  articulation. 

Fig.  387  shows  the  distribution  of  the  branches  of  the  trigeminus  on  the  head,  and  the  cervical 
nerves,  so  that  the  distribution  of  ancesthetic  and  hypersslhetic  areas  may  easily  be  made  out. 

The  otic  ganglion  (jn)  lies  beneath  the  foramen  ovale  on  the  inner  side  of  the 
third  division.  Its  roots  are — (i)  short  motor  fibres  from  the  third  division  ; 
(2)  vasomotor  from  the  plexus  around  the  middle  meningeal  artery  (ultimately 
derived  from  the  cervical  ganglion  of  the  sympathetic)  ;  (3)  fibres  (/J  run  from 
the  tympanic  branch  of  the  glosso-pharyngeal  to  the  tympanic  plexus,  and  from 
thence  through  the  canaliculus  petrosus  in  the  small  superficial  petrosal  in  the 
cranium,  then  through  a  small  canal  between  the  apex  of  the  petrous  bone 
and  the  sphenoid,  to  reach  the  otic  ganglion.  Through  the  chorda  tympani  the 
facial  nerve  is  constantly  connected  with  the  ganglion  (Fig.  3S7). 

The  branches  of  the  otic  ganglion  are — (i)  the  motor  twigs  for  the  tensor 
tympani  and  tensor  of  the  soft  palate  (these  fibres  are  mixed  with  muscular  sen- 
sory fibres — Ludwig  and  Politzer')  ;  (2)  one  or  more  branches  connecting  the 
ganglion  with  the  auriculo-temporal  are  carried  by  the  roots  2  and  3  from  the 
sympathetic  and  glosso-pharyngeal,  which  the  auriculo-temporal  nerve  (A),  as  it 
passes  through  the  parotid  gland  (P),  gives  off  to  the  gland.  These  are  the 
secretory  fibres  for  the  parotid  ;  their  functions  are  stated  in  §  145. 

Section  of  the  trigeminus  is  followed  by  inflammatory  changes  in  the  (raljbit)  tympanic  cavity; 
the  degree  of  inflammation  varies  much  (BerthoU  and  Griinhagen,  Kirchnei).  Section  of  the 
sympathetic  or  glosso-pharyngeal  has  no  effect. 

The  sub-maxillary  ganglion  (Z  )  lies  close  to  the  convex  archof  thetympanico- 
lingual  nerve  and  the  excretory  duct  of  the  sub-maxillary  gland  (J/).  Its  roots 
are — (1)  branches  of  the  chorda  tympani,  /,  /  (which  undergo  fatty  degenera- 
tion after  section  of  facial  nerve — Vtilpian).  This  root  supplies  secretory  fibres 
to  the  sub-maxillary  and  sublingual  glands,  but  it  also  supplies  vaso-dilator  fibres 
for  the  blood  vessels  of  the  same  glands  (§  145).  In  addition,  fibres  are  supplied 
to  the  smooth  muscular  fibres  in  Wharton's  duct.  All  the  fibres  of  the  chorda  do 
not  pass  into  the  gland  ;  some  pass  along  with  the  lingual  nerve  into  the  tongue 
(see  Chorda,  under  Facial  Nerve).     {2)  The  sympathetic  root  of  the  ganglion 


SUB-MAXILLARY    GANGLION    AND    ITS    CONNECTIONS. 


629 


arises  from  the  plexus  around  the  submental  branch  of  the  external  maxillary 
artery  (g),  i.e.,  ultimately  from  the  superior  cervical  ganglion  ;  it  passes  to  the 
gland,  and  contains  secretory  fibres,  whose  stimulation  is  followed  by  the  secre- 
tion of  thick  concentrated  saliva  (trophic  nerve  of  the  gland).  It  also  carries 
the  vaso-constrictor  nerves  to  the  gland  (p.  238).  (3)  The  sensory  root  springs 
from  the  lingual.  Some  of  the  fibres,  after  passing  through  the  ganglion,  supply 
the  gland  and  its  excretory  ducts,  while  a  few  issue  from  the  ganglion,  and  again 
join  the  tympanico-lingual  nerve  to  reach  the  tongue. 

Pathological. — Trismus,  or  spasm  of  the  muscles  of  mastication,  supplied  by  the  third  divi- 

FlG.  387. 


Muse  temporalis. 


Muse  mosseti 


MtiBc.  splentas. 


Muse.  stenioclei<lomB,ito  Ideas. 

N,  accesHoritu 

WuBo.  levator  nii[:uU  scapulae. 

Muse  cnicull.-irls  or  trape^iti 
N.  dorsalU  Bcaptila«. 


K.  axillaris. 

N.  thoracicu  1  ^ngn*. 


stribution  of  tlie  sensory  nerves  on  the  head  as  well  as  the  position  of  the  motor  points 
distribution  of  the  supraorbital  nerve;  ST,  supratrochlear;  IT,  infratrochlear  ;  L,  lachrymal;  N,  ethmoidal; 
yt?,  infraorbital :  .5,  buccinator  ;  i".!/,  subcutaneous  malae;  ^  T',  auricula-temporal;  ,-J  J/,  great  auricular ;  OMj, 
great  occipital  ;  OMi,  lesser  occipital  :  C,,  three  cervical  nerves  ;  CS,  cutaneous  branches  of  the  cervical  nerves  ; 
CW,  region  of  the  central  convolutions  oi  the  brain  ;  iC,  region  of  the  speech  centre  (third  left  frontal  convolution). 


sion,  is  usually  bilateral ;  it  may  be  clonic  in  its  nature  (chattering  of  the  teeth),  or  tonic,  when  it 
constitutes  the  condition  of  lockjaw  or  trismus.  The  spasms  are  usually  individual  symptoms  of 
more  extensive  convulsions,  more  rarely  when  they  occur  alone  they  are  symptomatic  of  disease  of 
the  cerebrum,  medulla,  pons  and  cortex  of  the  frontal  convolutions  {Eiilenbttrg).  The  spasms  may 
be  caused  reflexly,  e.g.^  by  stimulation  of  the  sensory  nerves  of  the  head. 

Paralysis  — Degeneration  of  the  motor  nuclei,  or  afifections  of  the  intracranial  root  of  the 
nerve,  causes  paralysis  of  the  muscles  of  mastication,  which  is  very  rarely  bilateral.  Paralysis  of 
the  tensor  tympani  is  said  to  cause  difficulty  of  hearing  {Romber^')^  or  buzzing  in  the  ears  [Bene- 
dict), We  require  funher  observations  upon  this  point,  as  well  as  upon  paralysis  of  the  tensor  of 
the  soft  palate. 

Neuralgia  may  occur  in   all  the  branches  of  the  fifth.     It  consists  of  severe  attacks  of  pain 


630  NERVUS    ABDUCENS. 

shooting  into  the  expansions  of  the  nerves.  It  is  usually  unilateral,  and  in  fact  is  often  confined  to 
one  branch,  or  even  to  a  few  twigs  of  one  branch.  The  point  from  which  the  pain  proceeds  is  fre- 
quently the  bony  canal  through  which  the  branch  issues.  The  ear,  dura  mater  and  tongue  are 
rarely  attacked.  The  attack  is  not  unfrequently  accompanied  by  contractions  or  t7oi/cAings  of  the 
corresponding  group  of  the  facial  muscles.  The  twitchings  are  either  reflex,  or  are  due  to  direct 
peripheral  irritation  of  the  fibres  of  the  facial  nerve,  which  are  mixed  with  the  terminal  branches  of 
the  trigeminus.  The  reflex  twitchings  mjy  be  extensively  distributed,  involving  even  the  muscles 
of  the  arm  and  trunk. 

Redness  or  congestion  of  the  afi'ected  part  of  the  face  is  not  an  unfrequent  symptom  in  neu- 
ralgia, and  it  may  be  accompanied  by  increased  or  diminished  secretion  from  the  nasal  and  buccal 
mucous  membranes.  This  is  a  reflex  phenomenon,  the  sympathetic  being  affected.  Reflex  stimu- 
lation of  the  vasomotor  nerves  frequently  gives  rise  to  liisinrbance  of  the  cerebral  aetn'tties,  owing 
to  changes  in  the  di^tribution  of  the  blood  in  the  head.  Ludwig  and  Ditlmar  found  that  stimula- 
tion of  sensory  nerves  caused  a  reflex  contraction  of  the  arterial  blood  vessels,  and  increase  of  the 
blood  pressure  in  the  cerebral  vessels.  Sometimes  there  is  melancholy  or  hypochondriasis,  and  in 
one  case  of  violent  pain  in  the  inferior  maxillary  nerve  the  attack  was  accompanied  by  hallucina- 
tions of  vision. 

The  trophic  disturbances  which  sometimes  accompany  aflections  of  the  trigeminus  are  partic- 
ularly interesting.  They  are  :  a  brittle  character  of  the  hair,  which  frequently  becomes  gray,  or 
may  fall  out ;  circumscribed  areas  of  inflammation  of  the  skin,  and  the  appearance  of  a  vesic- 
ular eruption  upon  the  face  [often  following  the  distribution  of  certain  nerves],  and  constituting 
herpes,  which  may  also  occur  on  the  cornea,  constituting  the  neuralgic  herpes  corneae  of  Schmidt- 
Rimpler. 

Lastly,  there  is  the  progressive  atrophy  of  the  face  which  is  usually  confined  to  one  side,  but 
may  occur  on  both  sides  (Etilenburg,  flasher).  It  is  caused  very  probably  by  a  trophic  affection 
of  the  trigeminus,  although  the  vasomotor  nerves  may  also  be  affected  reflexly.  Landois  found 
that  in  the  famous  case  o(  Romberg,  a  man  named  Schwahn,  the  sphygmographic  tracing  of  the 
carotid  pulse  of  the  atrophied  side  was  distinctly  smaller  than  on  the  sound  side. 

Urbamschitsch  made  the  remarkable  observation  that  stimulation  of  the  branches  of  the  trigemi- 
nus, especially  those  going  to  the  ear,  caused  an  increase  of  the  sensation  of  light  in  the  person 
so  stimulated.  Blowing  upon  the  cheeks  or  nasal  mucous  membrane,  electrical  stimulation,  the  use 
of  snuff,  smelling  strong  perfumes — all  temporarily  increase  the  sensation  of  light.  The  senses  of 
taste  an(.l  smell,  as  well  as  the  sensibility  of  certain  areas  of  the  skin,  can  all  be  exalted  rejlexly  by 
gentle  stimulation  of  the  trigeminus.  In  intense  affections  of  the  ear,  whereby  the  fibres  of  the 
trigeminus  are  often  affected  sympathetically,  these  sensory  functions  may  be  diminished.  As  the 
ear  malady  begins  to  improve,  the  excitability  of  these  sense  organs  also  again  begins  to  improve. 

[Complete  section  of  the  trigeminus  results  in  loss  of  sensibility  in  all  the 
parts  siipplied  by  it  (^Fig.  3S7),  including  one  side  of  the  face,  temple,  part  of 
the  ear,  the  fore  part  of  the  head,  conjunctiva,  cornea,  mouth,  gums,  Schneiderian 
mucous  membrane,  anterior  two-thirds  of  the  tongue,  and  part  of  pharynx.  In 
drinking  from  a  vessel,  the  patient  feels  as  if  one  side  of  it  were  cut  away.  The 
muscles  of  mastication  are  paralyzed  on  that  side,  food  is  not  chewed  on  one  side, 
and  fur  accumulates  on  the  tongue  on  that  side.  The  mucous  membranes  tend  to 
ulcerate,  that  of  the  mouth  being  chafed  by  the  teeth,  the  gums  get  spongy,  the 
nasal  mucous  membrane  tends  to  ulcerate,  so  that  the  smell  is  interfered  with,  and 
ammonia  excites  no  reflex  acts,  while  the  eye  undergoes  panophthalmia.] 

[Gowers  is  of  opinion  that  the  sensation  of  taste  on  the  posterior  part  of  the  tongue,  soft  palate, 
and  palatine  arch  depends  on  the  fifth  nerve  and  not  on  the  glosso  pharyngeal  nerve.] 

348.  VI.  NERVUS  ABDUCENS.— Anatomical.— It  rises  slightly  in  front  of  and  partly 
from  the  nucleus  ot  i\\e  fadal  nerve  (which  corresponds  to  the  anterior  horn  of  the  spina!  cordi, 
from  large-celled  ganglia  in  the  deeper  part  of  the  anterior  region  of  the  fourth  ventricle,  (emenentia 
teres,  Fig.  384).  [Its  nucleus  is  connected  with  the  nucleus  of  the  third  nerve  of  the  opposite  side. 
It  appears  at  the  posterior  margin  of  the  pons  (Kig.  385,  VI).  This  nerve  has  a  very  long  course 
before  it  enters  the  orbit,  and  as  it  bends  over  the  posterior  margin  of  the  pons,  it  is  liable  to  be  com- 
pressed there  or  from  pressure  upon  the  tentorium  cerebelli,  so  that  both  ner\es  aie  very  liable  to 
paralysis.] 

Function. — It  is  the  voluntary  nerve  of  the  external  rectus  muscle.  In  co- 
ordinate movements  of  the  eyeballs,  however,  it  is  involuntary. 

Anastomoses. — Branches  reach  it  from  the  sympathetic  upon  the  cavernous  sinus  (Fig.  386).  A 
few  come  from  the  trigeminus,  and  their  function  is  analogous  to  similar  fibres  supplied  to  the 
trochlearis  and  oculomotorius. 


THE    CHORDA   TYMPANI    AND    TASTE.  631 

Pathological. — Complete  paralysis  causes  squinting  inward  [or  convergent  squint']  and  conse- 
quent diplopia.  [The  eye  cannot  be  rotated  outward  beyond  the  middle  line,  the  double  images 
are  in  the  same  horizontal  plane  and  vertical,  the  false  one  is  to  the  left  of  the  patient's  eye  when 
the  left  eye  is  alTected  (Fig.  3S3,  2).  The  feeling  of  giddiness  is  often  severe.  There  is  secondary 
deviation  to  the  inner  side,  and  the  head  is  turned  toward  the  affected  side.]  In  dogs,  section  of 
the  cervical  sympathetic  causes  a  slight  deviation  of  the  eyeball  inward  (Petit).  This  is  explamed 
by  the  fact  that  the  al>ducens  receives  a  few  motor  fibres  from  the  cervical  sympathetic.  Spasm 
of  the  abducens  causes  external  squint. 

Squint  — In  addition  to  paralysis  or  stimulation  of  certain  nerves  producing  squint,  it  is  to  be 
remembered  that  it  may  also  be  caused  by  a  primary  affection  of  the  muscles  themselves,  if. ^.,  con- 
genital shortness,  contracture,  or  injuries  of  these  muscles.  It  may  also  be  brought  about  owing  to 
opacities  of  the  transparent  media  of  the  eye  ;  a  person  with,  say  an  opacity  of  the  cornea,  rotates 
the  affected  eye  involuntarily,  so  that  the  rays  of  light  may  enter  the  eye  through  the  clear  part  of 
the  media. 

349.  VII.  NERVUS  FACIALIS.— Anatomical.— This  nerve  consists  entirely  of  etferent 
fibres,  and  arises  from  the  floor  of  the  fourth  ventricle  from  the  "  facial  nucleus  "  (Fig.  384,  7), 
which  lies  behind  the  orgin  of  the  abducens,  and  also  by  some  fibres  from  the  nucleus  of  the  ab- 
ducens [although  Gower's  observations  do  not  confirm  this  (\  3^6).]  Other  fibres  arise  from  the 
cerebrum  of  the  opposite  side  (|  378,  I).  It  consists  of  two  roots,  the  smaller — portio  intermedia 
of  Wrisberg — forms  a  connection  with  the  auditory  nerve  (see  \  350).  The  original  fibres  ol  the 
portio  intermedia  are  developed  from  the  glosso-pharyngeal  nucleus  ySapolini).  It  would  thus 
appear  that  the  sensory  and  gustatory  fibres  w  hich  are  present  in  the  chorda  tympani  enter  it  through 
these  fibres  (Duval,  Schultze,  I'ltlpian),  so  that  the  portio  intermedia  is  a  special  part  of  the  nerve 
of  taste,  H  hich  becomes  conjoined  witli  the  facial,  and  runs  to  the  tongue  in  the  chorda.  Along 
with  the  auditory  nerve,  it  traverses  the  porus  acusticus  internus,  where  it  passes  into  the  facial  or 
Fallopian  canal.  At  first  it  has  a  transverse  direction  as  far  as  the  hiatus  of  this  canal ;  it  then 
bends  at  an  acute  angle  at  the  "  knee  "  (a)  above  the  tympanic  cavity,  to  descend  in  an  osseous 
canal  in  the  posterior  wall  of  this  space  (Fig.  386).  It  emerges  from  the  stylo-mastoid  foramen, 
pierces  the  parotid  gland,  and  is  distributed  in  a  fan-shaped  manner  (pes  anserinus  major).  [The 
superficial  origin  is  at  the  lower  margin  of  the  pons,  in  the  depression  between  the  olivary  body 
and  the  restiform  body,  as  indicated  in  Fig.  385,  VII  a.] 

Its  branches  (Fig.  386)  are  :  i.  The  motor,  large  superficial  petrosal  (/). 
It  arises  from  the  "  knee  "  or  geniculate  ganghon  within  the  Fallopian  canal,  in 
the  cavity  of  the  skull,  runs  upon  the  anterior  surface  of  the  temporal  bone, 
traverses  the  foramen  lacerum  medium  on  the  under  surface  of  the  base  of  the 
skull,  and  passes  through  the  Vidian  canal  to  reach  the  spheno-palatine  ganglion 
(p.  626).  It  is  uncertain  whether  this  nerve  conveys  sensory  branches  from  the 
second  division  of  the  trigeminus  to  the  facial. 

2.  Connecting  branches  (,?)  pass  from  the  geniculate  ganglion  to  the  otic  gan- 
glion.    For  the  course  and  function  of  these  fibres,  see  Otic  ganglion  (p.  628). 

3.  The  motor  branch  to  the  stapedius  muscle  (y). 

4.  The  chorda  tympani  (/,  /),  arises  from  the  facial  before  it  emerges  at  the 
stylo-mastoid  foramen  (j-),  runs  through  the  tympanic  cavity  (above  the  tendon  of 
the  tensor  tympani,  between  the  handle  of  the  malleus  and  the  long  process  of  the 
incus),  passes  out  of  the  skull  through  the  petro-tympanic  fissure,  and  then  joins 
the  lingual  nerve  at  an  acute  angle  (p.  627,  4).  Before  it  unites  with  this  nerve, 
it  exchanges  fibres  with  the  otic  ganglion  (m).  Thus,  sensory  fibres  can  enter 
the  chorda  from  the  third  division  of  the  trigeminus  (E.  Bischoff),  which  may  run 
centripetally  to  the  facial  to  be  distributed  along  with  it.  In  the  same  way,  sen- 
sory fibres  may  pass  from  the  lingual  nerve  through  the  chorda  into  the  facial 
(Longet).  Stimulation  of  the  chorda — which  even  in  man  may  be  done  in  cases 
where  the  tympanic  membrane  is  destroyed — causes  a  prickling  feeling  in  the  an- 
terior margins  and  tip  of  the  tongue  (Troltsch).  O.  Wolfe  found  that  the  section 
of  the  chorda  in  man  abolished  the  sensibility  for  tactile  and  thermal  stimuli 
upon  the  tip  of  the  tongue  ;  and  the  same  was  true  of  the  sense  of  taste  in  this 
region.  It  is  supposed  by  Calori  that  these  fibres  enter  the  facial  nerve  at  its  per- 
iphery (especially  through  the  auriculo-temporal  into  the  branches  of  the  facial), 
that  they  run  in  a  centripetal  direction  in  the  facial,  and  afterward  pursue  a  cen- 
trifugal course  in  the  chorda.  [It  is  possible  that  sensory  fibres  pass  from  the 
spheno-palatine  ganglion  of  the  fifth  through   the  Vidian  nerve  and  large  superfi- 


632  BUANCHES   OF   THE    FACIAL. 

cial  petrosal  to  enter  the  facial.  These  fibres  may  be  those  that  appear  in  the 
seventh  as  the  chorda  fibres  which  administer  to  taste.  .Bigelow  asserts  that  the 
chorda  tympani  is  not  a  branch  of  the  facial,  but  the  continuation  of  the  nervus 
intermedins  of  Wrisberg.]  The  chorda  also  contains  secretory  and  vaso-dilator 
fibres  for  the  sub-maxillary  and  sublingual  glands  (§  145). 

Gustatory  Fibres. — The  chorda  also  contains  fibres  administering  to  the  sense 
of  taste,  for  the  margin  and  tip  of  the  tongue  (anterior  two-thirds),  which  are 
conveyed  to  the  tongue  along  the  course  of  the  lingual.  Urbantschitsch  made 
observations  upon  a  man  whose  chorda  was  freely  exposed,  and  in  whom  its  stim- 
ulation in  the  tympanic  cavity  caused  a  sensation  of  taste  (and  also  of  touch)  in  the 
margins  and  tip  of  the  tongue. 

It  would  seem,  therefore,  that  the  gustatory  fibres  of  the  chorda  have  their 
origin  in  the  glosso-pharyngeal  nerve.  They  may  reach  the  chorda:  i.  Through 
the  portio  intermedia  of  Wrisberg,  as  already  mentioned. 

2.  There  is  a  channel  beyond  the  stylomastoid  foramen,  viz.,  through  the  ramus  communicans 
cum  glosso-pharyngeo  (Fig.  386,  e),  which  passes  from  the  last-mentioned  nerve  in  that  branch  of 
the  facial  which  contains  the  motor  fibres  for  the  stylohyoid  and  posterior  belly  of  the  digastric 
(Henle'sN.  styloideus).  This  nerve  also  supplies  muscular  sensibility  to  the  stylohyoid  and  pos- 
terior lielly  of  the  digastric  muscles.  It  is  also  assumed  that,  by  means  of  these  anastomoses,  motor 
fibres  are  supplied  by  the  facial  to  the  glosso-pharyngeal  nerve.  3.  A  union  of  the  glosso-pharyngeal 
and  facial  nerves  occurs  in  the  tympanic  cavity.  The  tympanic  branch  of  the  glosso-pharyngeal  (A) 
passes  into  this  cavity,  where  it  unites  in  the  tympanic  plexus  with  the  small  superficial  petrosal  nerve 
(,5),  which  springs  from  the  knee  on  the  facial.  The  gustatory  fibres  may  first  pass  into  the  otic 
ganglion, which  is  always  connected  with  the  chorda  (Otic  ganglion,  p.  628,  6).  Lastly,  a  connec- 
tion is  described  through  a  twig  (tt)  from  the  petrous  ganglion  of  the  glosso-pharyngeal,  direct  to 
the  facial  trunk  within  the  Fallopian  canal  {Garibaldi). 

Vaso-dilator  Fibres. — According  to  some  observers,  the  chorda  contains 
vaso-iiilator  fibres  for  the  tongue,  but  no  motor  fibres  {^Heidenhain). 

Pseudo-motor  Action. — From  one  to  three  weeks  after  the  section  of  the  hypoglossal  nerve, 
stimulation  of  the  chorda  causes  movements  in  the  tongue  [PJiili/'peau.x  and  I'li/fiaii,  /i.  Hciden- 
hain).  These  movements  are  not  so  energetic,  and  occur  more  slowly  than  those  caused  by  stimu- 
lation of  the  hypoglossal.  A'icotin  first  excites,  then  paralyzes,  the  motor  etiect  of  the  chorda.  Even 
after  cessation  of  the  circulation,  stimulation  of  the  chorda  causes  movements.  Heidenhain  supposes 
that,  owing  to  the  stimulation  of  the  chorda,  there  is  an  increased  secretion  of  lymph  within  the 
musculature,  which  acts  as  the  cause  of  the  muscular  contraction.  He  called  this  action  "  psetido 
fnotory 

[If,  after  the  union  of  the  central  end  of  the  lingualis  and  the  peripheral  end  of"  the  hypoglossal 
nerve,  the  lingualis  be  stimulated,  there  is  a  genuine  contraction  of  the  musculature  of  the  tongue  on 
that  side.  If,  .after  the  union  of  the  central  end  of  the  hypoglossal  with  the  peripheral  end  of  the 
lingual,  there  is  no  effect.  A  pseudo-motor  contraction  is  easily  distinguished  from  a  true  contrac- 
tion, for  when  a  telephone  be  connected  with  the  tongue,  on  stimulating  the  hypoglossal  the  tone  of 
the  tetanus  thereby  produced  is  heard,  but  on  stimulating  the  lingual,  although  the  pseudo-motor 
contractions  occur,  no  sound  is  heard  \Ki^go~oiczY~\ 

5.  Connection  with  Vagus. — Before  the  chorda  is  given  off,  the  trunk  of  the  facial  comes  into 
direct  relation  with  the  auricular  branch  of  the  vagus  ('5),  which  crosses  it  in  the  mastoid  canal  (see 

Vagus),  and  supplies  it  with  sensory  nerves. 

6.  Peripheral  Branches. — After  the  facial  issues  from  its  canal,  it  supplies 
motor  fibres  to  the  stylohyoid  and  posterior  belly  of  the  digastric,  the  occipitalis, 
and  also  to  all  the  muscles  of  the  external  ear  and  the  muscles  of  expression,  to 
the  buccinator  and  platysma.  The  facial  also  contains  secretory  fibres  for  the 
face  (compare  §  288). 

Although  most  of  the  branches  of  the  facial  are  under  the  influence  of  the  will,  yet  most  men 
cannot  voluntarily  move  the  muscles  of  the  nose  and  ear. 

Anastomoses. — The  branches  of  the  seventh  nerve  on  the  face  anastomose 
with  those  of  the  trigeminus.  Thus,  sensory  fibres  are  conveyed  to  the  muscles  of 
expression.  The  sensory  branches  of  the  auricular  branch  of  the  vagus  and  the 
great  auricular  enter  the  peripheral  ends  of  the  facial  and  supply  sensibility  to  the 


UNILATERAL   AND    DOUBLE    PARALYSIS   OF   THE    FACIAL. 


633 


muscles  of  the  ear,  while  the  sensory  fibres  of  the  third  cervical  nerve  sirnilarly 
supply  the  platysma  with  sensibility.  Section  of  the  facial  at  the  stylomastoid  for- 
amen is  painful,  but  it  is  still  more  so  if  the  peripheral  branches  on  the  face  are 
divided  [Mageniiie)  (compare  Recurrent  sensibility,  §  355). 

Pathological. — In  all  cases  of  paralysis  of  the  facial,  the  most  important  point  to  determine 
is  whether  the  seat  of  the  aftection  is  in  the  periphery,  in  the  region  of  the  stylomastoid  foramen, 
or  in  the  course  of  the  long  Fallopian  canal,  or  is  central  (cerebral)  in  its  origin.  This  point  must 
be  determined  by  an  analysis  of  the  symptoms.  Paralysis  at  the  stylomastoid  foramen  is  very  fre- 
quently rheuinatic,  and  probably  depends  upon  an  exudation  compressing  the  nerve  ;  the  exuda- 
tion probably  occupying  the  lymph  space  described  by  Riidinger  on  the  inner  side  of  the  Fallopian 
canal,  between  the  periosteum  and  the  nerve,  and  which  is  a  continuation  of  the  arachnoid  space. 
Other  causes  are— inflammation  of  the  parotid  gland,  direct  injury,  and  pressure  from  the  forceps 
during  delivery.  In  the  course  of  the  canal,  the  causes  are — fracture  of  the  temporal  bone,  effu- 
sion of  the  blood  into  the  canal,  syphilitic  eflusions,  and  caries  of  the  temporal  bone;  the  last  some- 


FlG.  388. 


Uppc 


r  branches  of  the  Facial. 
Trunk  of  the  Facial. 
Mm.  retrahens 

et  atlolens  auricul. 

Muse,  occipitalis. 

Middle  branches  of  the  Facial. 

M.  stylohyoideus, 

M.  digastricus. 


Lower  branches  of  the  Facial — 


M    corrugator  superciin. 
M.  orbicular  palpebr. 


M  compressor  nasi  et  pyram  r 

M  levator  lab.  sup,  alaque  n; 

M  levator  lab.  sup,  propr. 

M  zygomatic,  minor. 

\I  dilatat.narium, 

M  zygomatic  major. 


M .  levator  menti. 
M .  quadratus  men 
M.  triangularis  mt 


r  points  of  the  facial 


d  the  facial  muscles  supplied  by  it. 


times  occurs  in  inflammation  of  the  ear.  Among  intracranial  causes  are — affections  of  the  mem- 
branes of  the  brain,  and  of  the  base  of  the  skull  in  the  region  of  the  nerve,  disease  of  the  "  facial 
nucleus  ;"  lastly,  affection  of  the  cortical  centre  of  the  nerve  and  its  connections  with  the  nucleus. 
[No  nerve  is  so  liable  as  the  seventh  to  be  paralyzed  independently.] 

Symptonns  of  Unilateral  Paralysis  of  the  Facial  or  [Bell's  Paralysis]. — i.  Paralysis  of 
the  muscles  of  expression  :  ihe  for-head  is  smooth,  without  folds,  the  eyelids  remain  open 
(Lagophthalmus  paralyticus),  the  outer  angle  being  slightly  lower.  The  anterior  surface  of  the 
eye  rapidly  becomes  dry,  the  cornea  is  dull,  as,  owing  to  the  paralysis  of  the  orbicularis,  the  tears 
are  not  properly  distributed  over  the  conjunctiva,  and,  in  fact,  in  consequence  of  the  dryness  of  the 
eyeball,  there  may  be  temporary  inflammation  (Keratitis  xeroticai.  In  order  to  protect  the  eye- 
ball from  the  light,  the  patient  turns  it  upward  under  the  upper  eyelid  [Bell),  relaxes  the  levator 
palpebral,  which  allows  the  lid  to  fall  somevvht  {Hasse).  The  nose  is  immovable,  while  the  naso- 
labial fold  is  obliterated.  As  the  nostrils  cannot  be  dilated,  the  sense  of  smell  is  interfered  with. 
The  impairment  of  the  sense  of  smell  depends  more,  however,  upon  the  imperfect  conduction  of 


634  NERVUS    ACUSTICUS. 

the  tears,  owing  to  paralysis  of  the  orbicularis  palpebrarum  and  Horner's  muscle,  and  thus  causing 
dryness  of  the  corresponding  side  of  the  nasal  cavity.  Horses,  which  distend  the  nostrils  widely 
during  respiration,  after  section  of  both  facial  nerves,  are  said  by  CI.  Bernard  to  die  from  interfer- 
ence with  the  respiration,  or  at  least  they  suffer  from  severe  dyspncea  [E/lenberger).  The  face  is 
drawn  toward  the  sound  side,  so  that  the  nose,  mouth,  and  chin  are  oblique.  Paralysis  of  the  buc- 
cinator interferes  with  the  proper  formatioti  of  the  bolus  of  food;  the  food  collects  between  the 
cheek  and  the  gum,  from  which  it  is  usually  removed  by  the  patient  with  his  fingers;  saliva  and 
fluids  escape  from  the  angle  of  the  mouth.  During  vigorous  expiration  the  cheeks  are  puffed  out- 
ward like  a  sail.  The  speech  may  be  affected,  owing  to  the  difficulty  of  sounding  the  labial  con- 
sonants (especially  in  double  paralysis),  and  the  vowels,  u,  ii  (ue),  ii  (oe)  ;  while  the  s-peech,  in 
paralysis  of  the  branches  to  both  sides  of  the  palate,  becomes  nasal  (^  62S).  The  acts  of  whistling, 
sucking,  blowing,  and  spitting  are  interfered  with.  In  double  paralysis  many  of  these  symptoms 
are  greatly  intensified,  while  others,  such  as  the  oblique  position  of  the  features,  disappear.  The 
features  are  completely  rela.\ed ;  there  is  no  mimetic  play  of  the  features,  the  patients  weep  an<l 
laugh, "as  it  were,  behind  a  mask  "  [Jiomlierg).  2.  In  paralysis  of  the  palate,  when  the  uvula 
is  directed  toward  the  sound  side,  and  the  paralyzed  half  of  the  palate  hangs  down  and  cannot  be 
raised  (large  superficial  petrosal  nerve),  it  is  not  delei mined  to  what  extent  this  condition  influences 
the  act  of  diglutition  and  the  fortnation  of  the  consonants.  3.  Taste  is  interfered  with;  either  it 
is  absent  on  the  anterior  two-thirds  of  the  tongue,  or  the  sensation  is  delayed  and  altered.  This  is 
due  to  an  atfeclion  of  the  chorda.  4.  Diminution  of  saliva  on  the  affected  side  was  first  described 
by  Arnold;  still,  we  must  determine  to  what  extent  a  simultaneous  affection  of  the  sense  of  taste 
m.ay  cause  a  reflex  interference  with  the  secretion  of  saliva,  or  whether  rapid  removal  of  the  saliva 
through  the  opened  lips  and  angle  of  the  mouth  may  cause  the  dryness  on  the  affected  side  of  the 
mouth.  5.  Roux  pointed  out  that  hearing  is  affected,  the  sensibility  to  sounds  being  increased 
(Oxyakoia,  Hyperakusis  Willisiana).  The  paralysis  of  the  stapedius  muscle  makes  the  stapes 
loose  in  the  fenestra  ovalis,  so  that  all  impulses  from  the  tympanum  act  vigorously  upon  the  stapes, 
which  consequently  excites  considerable  vibrations  in  the  fluid  of  the  inner  ear.  More  rarely,  in 
paralysis  of  the  stapedius,  it  has  been  observed  that  low  notes  are  heard  at  a  greater  distance  than 
on  the  sound  side  (Lucae,  Moss). 

As  the  facial  in  man  appears  to  contain  fibres  for  the  secretion  of  sweat,  this  explains  the  loss 
of  the  power  of  sweating  in  the  face  when  the  nerve  begins  to  atrophy  [Strauss,  Block). 

Section  of  the  facial  in  young  animals  causes  atrophy  of  the  corresponding  muscles.  The 
facial  hones  are  also  imperfectly  developed  ;  they  remain  smaller,  and  hence  the  bones  of  the  sound 
side  of  the  face  grow  toward,  and  ultimately  across,  the  middle  line  toward  the  affected  side  [Brcwn- 
Sci/uanl,  Briicke.,  Schauta,  Gttdden).     The  salivary  glands  also  remain  smaller  [Bnicke). 

Stimulation — or  irritation  in  the  area  of  ihc  facial — -causes  partial  or  extensive,  either  direct  or 
reflex,  tonic  or  clonic  spasms.  The  extensive  forms  are  known  as  "  mimetic  facial  spasm." 
Among  the  partial  forms,  are  tonic  contraction  of  the  eyelid  (Blepharospasm)  which  is  most 
common;  and  is  caused  reflexly  by  stimulation  of  the  sensory  nerves  of  the  eye,  e.g.,  in  scrofulous 
ophthalmia,  or  from  excessive  sensibility  of  the  retina  (photophobia).  More  rarely  the  excitement 
proceeds  from  some  more  distant  part,  e.g.,  in  one  cause  recorded  by  v.  Grafe,  from  inflammatory 
stimulation  of  the  anterior  palatine  arch.  The  centre  for  the  reflex  is  the  facial  nucleus.  The 
clonic  form  of  spasm — spasmodic  winking  (Spasmus  nictitans) — is  usually  of  reflex  origin,  due 
to  irritation  of  the  eye,  the  dental  nerves,  or  even  of  more  distant  nerves.  In  severe  cases  the 
afl'ection  may  be  bilateral,  and  the  spasms  may  extend  to  the  muscles  of  the  neck,  trunk  and  upper 
extremities.  Contraction  of  the  muscles  of  the  lip  may  be  excited  by  emotions  (rage,  grief),  or 
reflexly.  Fibrillar  contractions  occur  after  section  of  the  facial  as  a  •'  degeneration  phenomenon  " 
(p.  512).  [If  the  facial  be  torn  out  at  the  stylo-masloid  foramen,  there  is  paralytic  oscillation  of 
the  lip  muscles  [Schiff).  If.in  such  an  animal  the  posterior  root  of  the  annulus  of  Vieussens  be 
stimulated  electrically,  as  it  contains  vaso-dilator  fibres  (Vastre  and  Moral),  not  only  do  the  blood 
vessels  of  the  cheek  and  lips  dilate,  but  the  veins  pulsate  and  florid  blood  escapes  from  the  veins, 
just  as  occurs  in  the  sub-maxillary  gland  when  the  chorda  is  stimulated.  On  stimulating  the  ansa 
after  section  of  the  seventh,  there  is  a  pseudomotor  effect  on  the  muscles  of  the  cheek  and  lips, 
so  that  there  is  an  analogy  between  the  chorda  and  the  ansa  {Rogowicz).'\  Intracranial  stimu\aUon 
of  the  most  varied  description  may  cause  spasms.  Lastly,  facial  spasm  may  be  part  of  a  general 
spasmodic  condition,  as  in  epilepsy,  chorea,  hysteria,  tetanus.  Aretaeus  (81  a.d.)  made  the  inter- 
esting observation  that  the  muscles  of  the  ear  contracted  during  tetanus.  Very  rarely  have  spas- 
modic elevation  of  the  palate  and  increa.sed  salivation  been  described  as  the  result  of  irritation  of 
the  facial  (Leul'c).  Moos  observed  a  profuse  secretion  of  saliva  on  stimulating  the  chorda  during 
an  operation  on  the  tympanic  cavity. 

350.  VIII.  NERVUS  ACUSTICUS.— Anatomical.— This  nerve  arises  from  two  nuclei 
(Stieda),  whose  ganglionic  cells  anastomose  (Fig.  3S4,  S,  8',  8").  The  nuclei  lie  in  the  broadest 
part  of  the  calamus  scriptorius  ;  a  process  from  a  spinal  centre  reaches  them  (Roller).  The  an/e- 
r«)/-nucleus,  which  is  connected  with  the  portio  intermedia  Wrisbergii,  appears  to  contain  z'asomotor 
fibres.  Part  of  its  fibres  run  through  the  pedunculus  cerebelli  to  the  dentate  body  of  the  cerebellum  ; 
very  probably  they  are  connected  with  the  regulation  of  the  equilibrium   (J  380).     The  white  .striae 


Brenner's  formula — the  semicircular  canals.  635 

meduUares,  which  run  transversely  across  the  floor  of  the  fourth  ventricle,  are  said  to  pass  into  the 
pedunculus  cerebelli  of  the  opposite  side.  According  to  Meynert,  fibres  of  the  auditor)'  nerve  pass 
in  channels  as  yet  undetermined  from  the  cerebellum  to  the  pedunculus  cerebri,  and  ultimately  to 
the  cortex  of  the  brain,  where  their  cortical  centre  lies  in  the  temporo-sphenoidal  lobes  (§  378,  IV  1. 
In  the  sheep  and  horse  the  two  chief  branches  of  the  auditory  nerve — the  cochlear  and  vestibular 
nerves — arise  separateK-,  which  points  to  the  independence  of  their  {xu\<i\\on%  {Horbaczewski) — 
(Fig.  385,  VII  b\.  In  the  course  of  the  internal  auditory  meatus,  the  auditory  and  portio  inter- 
media of  the  facial  exchange  fibres,  but  the  physiological  significance  of  this  is  unknown. 

Function. — The  acusticus  or  auditory  nerve  has  a  double  function  :  i.  It  is 
the  nerve  of  hearing  ;  when  stimulated,  either  at  its  origin,  in  its  course,  or  at 
its  peripheral  terminations,  it  gives  rise  to  sensations  of  sound.  Every  injury, 
according  to  its  intensity  and  e.xtent,  causes  hardness  of  hearing  or  even  deafness. 

2.  Quite  distinct  from  the  foregoing  is  the  other  function,  which  depends  upon 
the  semicircular  canals,  viz.,  that  stimulation  of  the  peripheral  expansions  in 
the  ampuliifi  influences  the  movements  necessary  for  maintaining  the  equilibrium 
of  the  body. 

Brenner's  Formula. — The  relation  of  the  auditory  nerN'e  to  the  galvanic  current  is  very 
important.  In  healthy  persons,  when  there  is  closure  at  the  cathode,  there  is  the  sensation  of  a 
clang  (or  tone)  in  the  ear,  which  continues  svith  variations  while  the  current  is  closed.  When  the 
anode  is  opened,  there  is  a  feebler  tone  {Brenner  s  Normal  Acoustic  Formula).  This  clang  coin- 
cides exactly  with  the  resonance  fundamental  tone  of  the  sound-conducting  apparatus  of  the  ear 
itself. 

Pathological. — Increased  sensibility  of  the  auditory  nerve  in  any  part  of  its  course,  its  centre, 
or  peripheral  expansions  causes  the  condition  known  as  hyperakusis,  which  usually  is  a  sign  of 
extensive  increased  nervous  excitability,  as  in  hysteria.  When  excessive,  it  may  give  rise  to  dis- 
tinctly painful  impressions,  which  condition  is  known  as  acoustic  hyperalgia  [Eulenburg). 
Stimulation  of  the  parts  above  named  causes  sensations  of  sound,  the  most  common  being  the 
sensation  of  singing  in  the  ears,  or  tinnitus.  This  c  mdition  is  often  due  to  changes  in  the  amount 
of  blood  in  the  blood  vessels  of  the  ear — either  anaemic  or  hyper.-emic  stimulation.  There  is  well- 
marked  tinnitus  after  large  doses  of  quinine  or  salicin,  due  to  the  vasomotor  effect  of  these  drugs  upon 
the  vessels  of  the  labyrinth  (Kirchner).  Not  unfrequently,  in  cases  of  tinnitus,  the  reaction  due  to 
the  galvanic  current  is  often  increased.  More  rarely  there  is  the  so-called  " parado.xical  reaction  " 
— i.e.,  on  applying  the  galvanic  current  to  one  ear,  in  addition  to  the  reaction  in  this  ear,  there  is 
the  opposite  result  in  the  non-stimulated  ear.  In  other  cases  of  disease  of  the  auditory  nerve,  noises 
rather  than  musical  notes  are  produced  by  the  current ;  stimulation,  especially  of  the  cortical 
centre  of  the  auditory  nerve,  chiefly  in  lunatics,  may  cause  auditory  delusions  (\  378,  IV). 
According  as  the  excitability  of  the  auditory  nerve  is  diminished  or  abolished,  there  is  the  condition 
of  nervous  hardness  of  hearing  (Hypakusis),  or  nervous  deafness  (Anakusis). 

The  Semicircular  Canals  of  the  Labyrinth. — Section  or  injury  to  these 
canals  does  not  interfere  with  hearing,  but  otherimportant  symptoms  follow  their 
injury,  such  as  disturbances  of  equilibrium  due  to  a  feeling  of  giddiness,  espe- 
cially when  the  injury  is  bilateral  ( Floureiis).  This  does  not  occur  in  fishes 
{Kieselbach).  The  pendulum-like  movement  of  the  head  in  the  direction 
of  the  plane  of  the  injured  canal  is  very  characteristic.  If  the  horizontal  canal 
is  divided,  the  head  (of  the  pigeon)  is  turned  alternately  to  the  right  and  left. 
The  rotation  takes  place,  especially  when  the  animal  is  about  to  execute  a  move- 
ment :  when  it  is  at  rest,  the  movement  is  less  pronounced.  The  phenomenon 
may  last  for  months,  and  injury  to  the  posterior  vertical  canal  causes  a  well- 
marked  up  and  down  movement  or  nodding  of  the  head,  the  animal  itself  not 
unfrequently  falling  forward  or  backward.  Injtiry  to  the  superior  vertical  canals 
also  causes  pendulum-like  vertical  movements  of  the  head,  while  the  animal  often 
falls  forward.  When  all  the  canals  arc  destroyed,  various  pendulum-like  move- 
ments are  performed,  while  standing  is  often  impossible.  Breur  found  that  elec- 
trical stimulation  of  the  canals  caused  rotation  of  the  head,  while  Landois,  on 
applying  a  solution  of  salt  to  the  canals,  observed  pendulum-like  movements, 
which,  however,  disappeared  after  a  time.  A  25  per  cent,  solution  of  chloral 
dropped  into  the  ear  of  a  rabbit  causes,  after  fifteen  minutes,  a  similar  destruction 
of  the  canals  {Vulpian).  Section  of  the  acoustic  nerves  within  the  cranium  has 
the  same  result  {Bechterew). 


636  GIDDINESS,   NYSTAGMUS. 

Explanation. — GoUz  regards  the  canals  as  organs  of  sense  for  ascertaining  the  equilibrium  or 
position  of  the  head  in  space  ;  Mach,  as  an  organ  for  ascertaining  the  movements  of  the  head. 
According  to  Goltz's  statical  theory,  every  position  of  the  head  causes  the  endolymph  to  exert 
the  greatest  pressure  upon  a  certain  part  of  the  canals,  and  thus  excites  in  a  varying  degree  the 
nerve  terminations  in  the  ampulla;,  .\ccording  to  Breuer,  when  the  head  is  rotated,  currents  are 
produced  in  the  endolymph  of  the  ctnals,  which  must  have  a  fixed  relation  to  the  direction  and 
extent  of  the  movements  of  the  head ;  and  these  currents,  therefore,  when  they  are  perceived, 
afford  a  means  of  determining  the  movement  of  the  head.  The  nervous  end  organs  of  the  ampullae 
are  arranged  for  ascertaining  this  perce|)tion.  If  the  semicircular  canals  are  an  apparatus — in  fact, 
"sense  organs"  [Go/tz) — for  the  sensation  of  the  equilibrium,  and  whose  function  is  to  determine 
the  position  or  movements  of  the  head,  necessarily  their  destruction  or  stimulation  must  alter  the>e 
perceptions,  and  so  give  rise  to  abnormal  movements  of  the  head.  Vulpian  regards  the  rotation  of 
the  head  as  due  to  strong  auditory  perceptions  (?)  in  consequence  of  aftections  of  the  canals. 
Bottcher,  Tomaszewicz  and  Baginsky  regard  the  injury  to  the  cerebellum  as  the  cause  of  the  phe- 
nomena. The  pendulum-like  movements,  1  owever,  are  so  characteristic  that  they  cannot  be  con- 
founded with  disturbances  of  the  equilibrium  which  result  from  injury  to  the  cerebellum. 

[Kinetic   Theory. — In  1875  Crum  Brown  pointed  out  that  if  a  person  be  rotated  passively,  his 
eyes  being  bandaged,  he  can,  up  to  a  certain  point,  indicate  pretty  accurately  the  amount  of  move- 
ment, but  after  a  time  this  cannot  be  done,  and  if  the  rotation, 
as  on   a  potter's  wheel,  be   stopped,  the  sense  of  rotation  con- 
rlG.  309.  tinues.     Crum  Brown  suggested  that  currents  were  produced  in 

the  endolymph,  while  the  terminal  hair  cells  lagged  behind,  and 
were,  in  fact,  dragged  through  the  fluid.  He  pointed  out  that 
the  right  posterior  canal  is  in  line  with  the  left  superior,  and  the 
left  posterior  with  the  right  superior,  a  fact  which  is  readily  ob- 
served by  looking  from  behind  at  a  skull,  with  the  semicircular 
canals  exposed  (Fig.  3S9).  He  assumes  th.it  the  canals  are 
paired  organs,  and  that  each  pair  is  connected  with  rbtalion  or 
movement  of  the  head  in  a  particular  direction.] 

Giddiness. — This  feeling  of  false  impressions  as 

.  RP    to  the  relations  of  the  surroundings  and  consequent 

1  of  the  disposition  of  the  semi-    movements   of  the   body  occurs   especially   during 

:ircuiar  canals.   Rs  and  Ls,  right    aL(7uiri;d  chs.iM'ts  in  the  normal  movements  of  the 

and   left  superior;     LP    and    KV ,  ,        ,  ,  ■  , 

right  and  left  posterior;  LF.  and    eycs,  whether  duc  to  in  voluntary  to  and  fro  move- 

RE,  right  and  left  external.  ments  of  the  cyeballs  (nystagmus)  or  to  paralysis 

of  some  eye  muscle. 

Active  or  passive  movements  of  the  head  or  of  the  body  are  normally  accom- 
panied by  simultaneous  movements  of  both  eyeballs,  which  are  characteristic  for 
every  position  of  the  body.  The  general  character  of  these  "compensatory" 
bilateral  movements  of  the  eyes  consists  in  this,  that  during  the  various  changes  in 
the  position  of  the  head  and  body  the  eyes  strive  to  maintain  their  primary  passive 
position.  Section  of  the  aqueduct  of  Sylvius  at  the  level  of  the  corpora  quadri- 
gemina,  of  the  floor  of  the  fourth  ventricle,  of  the  auditory  nucleus,  both  acustici, 
as  well  as  destruction  of  both  membranous  labyrinths,  causes  disappearance  of 
these  movements  ;  while,  conversely,  stimulation  of  these  parts  is  followed  by 
bilateral  associated  movements  of  the  eyeballs. 

Compensatory  movements  of  the  eyeballs,  under  normal  circumstances,  may  be 
caused  refle.xly  from  the  membranous  labyrinth.  Nerve  channels,  capable  of  ex- 
citing reflex  movements  of  both  eyes,  proceed  from  both  labyrinths,  and,  indeed, 
both  eyes  are  affected  from  both  labyrinths.  These  channels  pass  through  the 
auditory  nerve  to  the  centre  (^nuclei  of  the  3d,  4th,  6th  and  8th  cranial  nerves), 
and  from  the  latter  efferent  fibres  pass  to  the  muscles  of  the  eye  {Hogyes). 

Cyon  found  that  stimulation  of  the  horizontal  semicircular  canal  was  followed  by  horizontal  nys- 
tagmus; of  the  posterior,  by  vertical,  and  of  the  anterior  canal,  by  diagonal  nystagmus.  Stimula- 
tion of  one  auditory  nerve  is  followed  by  rotating  nystagmus,  and  rotation  of  the  body  of  the  animal 
on  its  axis  toward  the  stimulated  side. 

Poisons. — Chloroform  and  other  poisons  enfeeble  the  compensatory  movements  of  the  eyeballs, 
while  nicotin  and  asphyxia  suppress  them,  owing  to  their  action  on  their  nerve  centre. 

It  is  probable  that  the  disturbances  of  equilibrium  and  the  feeling  of  giddiness 
which  follow  the  passage  of  a  galvanic  current  through  the  head  between  the  mas- 


THE    GLOSSO-PHARYNGEAL   NERVE.  637 

toid  processes,  are  also  due  to  an  action  upon  the  semicircular  canals  of  the  laby- 
rinth (§300).  Deviation  of  the  eyeballs  is  produced  by  such  a  galvanic  current 
(Hitzii;).  The  same  result  is  produced  when  the  two  electrodes  are  placed  in  the 
external  auditory  meatuses. 

Pathological. — Meniere's  Disease. — The  feeling  of  giddiness,  not  unfrequently  accompanied 
by  tinnitus,  which  occurs  in  Meniere's  disease,  must  be  referred  to  an  affection  of  the  nerves  of  the 
arnpull.i;  or  their  central  organs,  or  of  the  semicircular  canals  themselves.  By  injecting  fluid  vio- 
lently into  the  ear  of  a  rabbit,  giddiness,  with  nystagmus  and  rotation  of  the  head  toward  ihe  side 
operated  on,  are  produced  {BagiKsiv).  In  cases  in  man,  where  the  tympanic  membrane  was 
defective,  Lucx,  when  employing  the  so-called  ear-air  douche  at  o.i  atmosphere,  observed  abduction 
of  the  eyeball  with  diplopia,  giddiness,  darkness  in  front  of  the  eyes,  while  the  respiration  was 
deeper  and  accelerated.  These  phenomena  must  be  due  to  stimulation  or  exhaustion  of  the  ves- 
tibular branch  of  the  auditory  nerve  (Hdgvt-s).  In  chronic  gastric  catarrh  a  tendency  to  giddiness 
is  an  occasional  symptom  (Trousseau's  gastric  giddiness).  This  may,  perhaps,  be  caused  by  stimu- 
lation of  the  gastric  nerves  exciting  the  vasomotor  nerves  of  the  labyrinth,  which  must  affect  the 
pressure  of  the  endolymph.  Analogous  giddiness  is  excited  from  the  larynx  {^Charcot)  and  from 
the  urethra  (Eyh-nmeyer). 

[Vertigo,  or  giddiness,  is  a  very  common  symptom  in  disease,  and  may  be  produced  by  a  great 
many  diflerent  conditions.  It  literally  means  "a  turning."  As  Cowers  points  out,  the  most  common 
symptom  is  that  the  patient  himself  has  a  sense  of  movement  in  one  or  other  direction;  or  objects 
may  appear  to  move  before  him ;  and  more  rarely  there  is  actual  movement  "  commonly  in  the 
same  direction  as  the  subjective  sense  of  movement."  It  is  sometimes  due  to  a  want  of  harmony 
between  the  impressions  derived  from  different  sense  organs  or  "contradictoriness  of  sensory  impres- 
sions" (Grainger  Sle-wart),s&  is  sometimes  felt  on  ascending  or  descending  a  stair,  or  by  some 
persons  while  standing  on  a  high  tower,  constituting  tower  or  cliff  giddiness.  One  of  the  most 
remarkable  conditions  is  that  called  "Agoraphobia  "  {Benedikt.  H'estphal).  The  person  can  walk 
quite  well  in  a  narrow  lane  or  street,  but  when  he  attempts  to  cross  a  wide  square  he  experiences  a 
feeling  closely  allied  to  giddiness.  The  giddiness  of  seasickness  is  proverbial,  while  some  persons 
get  giddy  with  waltzing  or  swinging.  Besides  occurring  in  Meniere's  disease,  it  sometimes  occurs 
in  locomotor  alaxis  and  some  cerebral  and  cerebellar  a'ffections.  including  cerebral  anx-mia.  Very 
distressing  giddiness  and  headache  are  often  produced  by  paralysis  of  some  of  the.  ocular  muscles, 
c.  g.,  the  external  rectus.  Defective  or  perverted  ocular  impressions,  as  well  as  similar  auditory 
impressions,  may  give  rise  to  vertigo;  in  the  latter  or  labyrinthine  form  the  vertigo  may  be  very 
severe.  Severe  vertigo  is  often  accompanied  by  vomiting.  A  hard  plug  of  ear  wax  may  press  on 
the  membrana  tympani,  and  cause  severe  giddiness.  The  forms  of  dyspeptic  giddiness  and  the 
toxic  forms  due  to  the  abuse  of  alcohol,  tobacco,  and  some  other  drugs  are  familiar  examples  of  this 
condition.] 

[Tinnitus  Aurium,  or  subjective  noises  in  the  ear,  is  a  very  common  symptom  in  disease  of  the 
ear;  the  noise  may  be  continuous  or  discontinuous,  be  buzzing,  singing,  or  rumbling  in  character.] 

351.  IX.  NERVUS  GLOSSO-PHARYNGEUS.— Anatomical.— This  nerve  (Fig.  386, 
g)  arises  from  the  nucleus  of  the  same  name,  which  consists  partly  of  large  cells  (motor)  and  partly 
of  small  cells  (belonging  to  the  gustatory  fibres).  The  nucleus  lies  in  the  lower  half  of  the  fourth 
ventricle,  deep  in  the  medulla  oblongata,  near  the  olive  (Fig.  384).  The  nucleus  is  connected  w-ith 
that  of  the  vagus.  A  special  root  ascending  from  the  spinal  cord  applies  itself  to  the  fibres,  and 
perhaps  (like  the  spinal  roots  of  the  second  and  eighth  nerves)  serves  for  the  production  of  spinal 
reflexes  (Roller).  The  fibres  collect  into  two  trunlis,  which  afterward  unite  and  leave  the  medulla 
oblongata  in  front  of  the  vagus.  In  the  fossula  petrosa  it  has  on  it  the  petrous  ganglion,  from 
which,  occasionally,  a  special  part  on  the  posterior  twig  is  separated  within  the  skull  as  the  ganglion 
of  Ehrenrilter.  Commutticaling  branches  are  sent  from  the  petrous  ganglion  to  the  trigeminus, 
facial  (i  and  -),  v.agus  and  carotid  plexus.  From  this  ganglion  also  the  tympanic  nerve  (/.)  ascends 
vertically  in  the  tympanic  cavity,  where  it  unites  with  the  tympanic  plexus  This  branch  {\  349,  4) 
gives  sensory  fibres  to  the  tympanic  cavity  and  the  Eustachian  tube  ;  while,  in  the  dog,  it  also  carries 
secretory  fibres  for  the  parotid  into  the  small  superficial  petrosal  nerve  (Heidenhain — \  145). 

Function. — i.  It  is  the  nerve  of  taste  for  the  posterior  third  of  the  tongue, 
the  lateral  part  of  the  soft  palate,  and  the  glosso-palatine  arch  (^compare  §  422). 
[This  is  denied  by  Gowers  (p.  630).] 

The  nerve  of  taste  for  the  anterior  two-thirds  of  the  tongue  is  referred  to  under  the  lingual  1  \  347, 
III,  4).  and  chorda  tympani  n-rves  (?  349,  4).  The  glossal  branches  are  provided  with  ganglia, 
especially  where  the  nerve  divides  at  the  base  of  the  circumvallate  papilli"e  (Remak,  Kolliker, 
Schwalbe,  Stirling).  The  nerve  ends  in  the  circumvallate  papillce  (Fig.  320,  U),  and  the  end  organs 
are  represented  by  the  taste  bulbs  (J  422). 

2.   It  is  the  sensory  nerve  for  the  posterior  third  of  the  tongue,  the  anterior 


638       THE    CONNECTING    AND    OTHER    BRANCHES    OF   THE    VAGUS. 

surface  of  the  epiglottis,  the  tonsils,  the  anterior  palatine  arch,  the  soft  palate,  and 
a  part  of  the  pharynx.  From  this  nerve  there  may  be  discharged  reflexly,  move- 
ments of  deglutition,  of  the  palate  and  pharynx  ( I'olkmanii),  which  may  pass  into 
those  of  vomiting  (§  158).  These  fibres,  like  the  gustatory  fibres,  can  excite  a 
reflex  secretion  of  saliva  (§  145). 

3.  It  is  motor  for  the  stylo-pharyngeus  and  middle  constrictor  of  the  pharynx 
(Vo/kmann)  ;  and,  according  to  other  observers,  to  the  (?)  glosso-palatinus  {Heiii) 
and  the  (??)  levator  veli  palatini  and  azygos  uvulse  (compare  Spheno-palatine  gang- 
lion, §  347,  II).  It  is  doubtful  whether  the  glosso-pharyngeal  nerve  is  really  a 
motor  nerve  at  its  origin — although  Meynert,  Huguenin,  W.  Krause,  and  Duval 
have  described  a  motor  nucleus — or  whether  the  motor  fibres  reach  the  nerve  at 
the  petrous  ganglion,  through  the  communicating  branch  from  the  facial. 

4.  A  twig  accompanies  the  lingual  artery  ;  this  nerve,  perhaps,  is  vaso-dilator  for  the  lingual 
blood  vessels. 

Pathological. — There  are  no  satisfactory  observations  on  man  of  uncomplicated  affections  of  the 
glosso-pharyngeal  nerve. 

352.  X.  NERVUS  VAGUS. — Anatomical. — The  nucleus  from  which  the  vagus  arises 
along  with  the  ninth  and  eleventh  nerve  is  in  the  ala  cinerea  in  the  lower  half  of  the  calamus  scrip- 
torius  (Fig.  384,  10)  [and  it  is  very  probably  the  representative  of  the  cells  of  the  vesicular  column 
of  Clarke  (J  366).]  It  leaves  the  medulla  oblongata  by  10  to  15  threads  behind  the  ninth  nerve, 
between  the  divisions  of  the  lateral  column,  and  has  a  ganglion  (jugular)  upon  it  in  the  jugular 
foramen  (Fig.  385,  VHI).     Its  branches  contain  fibres  which  subserve  dift'erent  functions. 

1.  The  sensory  meningeal  branch  from  the  jugular  ganglion  accompanies  the 
vasoinotor  fibres  of  the  sympathetic  on  the  middle  meningeal  artery,  and  sends 
fibres  to  the  occipital  and  transverse  sinus. 

When  it  is  irritated,  as  in  congestion  of  the  head  and  inflammation  of  the  dura  mater,  it  gives  rise 
to  vomiting. 

2.  The  auricular  branch  (from  the  jugular  ganglion)  receives  a  communicat- 
ing branch  from  the  petrous  ganglion  of  the  ninth  nerve,  traverses  the  canaliculus 
mastoideus,  crossing  the  course  of  the  facial,  with  which  it  exchanges  fibres  whose 
function  is  unknown.  On  its  course  it  gives  sensory  branches  to  the  posterior 
part  of  the  auditory  meatus  and  the  adjoining  part  of  the  outer  ear.  A  branch 
runs  along  with  posterior  auricular  branch  of  the  facial,  and  confers  muscular 
sensibility  on  the  muscles. 

When  this  nerve  is  irritated,  either  through  inflammation  or  by  the  presence  of  foreign  bodies  in 
the  outer  ear  passage,  it  may  give  rise  to  I'omitittg.  Stimulation  of  tlie  deep  part  of  the  external 
auditory  meatus  in  the  region  supplied  by  the  auricular  branch  causes  coughing  reflexly  [c.  g.,  from 
tile  presence  of  a  pea  in  the  ear].  Similarly,  contraction  of  the  blood  vessels  of  the  ear  may  be 
caused  reflexly  {Snellen^  Lovhi']. 

The  nerve  is  the  remainder  of  a  considerable  branch  of  the  vagus  which  exists  in  fishes  and  the 
larvK  of  frogs,  and  runs  under  the  skin  along  the  side  of  the  body. 

3.  The  connecting  branches  of  the  vagus  are:  (i)  A  branch  which  directly 
connects  the  petrous  ganglion  of  the  9th  with  the  jugular  ganglion  of  the  loth  ;  its 
function  is  unknown.  (2)  Directly  above  the  plexus  gangliiformis  vagi,  the  vagus 
is  joined  by  the  whole  inner  half  of  the  spinal  accessory.  This  nerve  conveys  to 
the  vagus  the  motor  fibres  for  the  larynx  {Bischoff,  i8j2),  and  the  cervical  part 
of  the  cesophagiis  (which,  according  to  Steiner,  lie  in  the  inner  part  of  the  nerve 
trunk),  as  well  as  the  inhibitory  y?/vrj- for  \\\t  heart  {CI.  Bernard').  (3)  The 
plexus  gangliiformis  fibres,  whose  function  is  unknown,  join  the  trunk  of  the  vagus 
from  the  hypoglossal,  superior  cervical  ganglion  of  the  sympathetic,  and  the  cer- 
vical plexus. 

4.  Pharyngeal  Plexus. — The  vagus  sends  one  or  two  branches  from  the  upper 
part  of  the  plexus  gangliiformis  to  \.\\e  pharyngeal  plexus,  where  at  the  level  of  the 
iniddle  constrictor  of  the  pharynx  it  is  joined  by  the  pharyngeal  branches  of  the 
9th  nerve  and  those  of  the  upper  cervical  sym|)athetic  ganglion,  near  the  ascending 
pharyngeal  artery,  to  form  the  ^haiyngcal plexus.     The  vagal  fibres  in  this  plexus 


SUPERIOR   AND    INFEUIOR    LARYN'GEAL    NERVES.  639 

supply  the  three  constrictors  of  the  pharynx  with  motor  fibres,  while  the  tensor 
palati  {Otic ganglion,  §  347,  III)  and  levator  of  the  soft  palate  (compare  Spheno- 
palatine ganglion,  §  347,  II)  also  receive  motor  (?  sensory)  fibres.  Sensory 
fibres  of  the  vagus  from  the  pharyngeal  ple.xus  supply  the  pharynx  from  the  part 
beneath  the  soft  palate  downward.  These  fibres  excite  the  pharyngeal  constric- 
tors reflexly  during  the  act  of  swallowing  (§  156).  If  stimulated  very  strongly 
they  may  cause  vomiting.  (The  sympathetic  fibres  of  the  oesophageal  plexus  give 
vasomotor  nerves  to  the  oesophageal  vessels;  for  the  oesophageal  branches  of  the 
9th  nerve,  see  above.) 

5.  The  vagus  supplies  two  branches  to  the  larynx,  the  superior  and  inferior 
laryngeal. 

((7)  The  superior  laryngeal  receives  vasomotor  fibres  from  the  superior 
cervical  ganglion  of  the  sympathetic.  It  divides  into  two  branches,  external  and 
internal:  (1)  The  external  branch  receives  vasomotor  fibres  from  the  same 
source  (they  accompany  the  superior  thyroid  artervi,  and  supplv  the  cricothyroid 
muscle  with  motor  fibres  and  sensory  fibres  to  the  lower  lateral  portion  of  the 
laryngeal  mucous  membrane.  (2)  The  internal  branch  gives  oH  sensory  branches 
only  to  the  glosso-epiglottidean  fold  and  the  adjoining  lateral  region  of  the  root 
of  the  tongue,  the  aryepiglottidean  fold,  and  to  the  whole  anterior  part  of  the  lar- 
ynx, except  the  part  supplied  by  the  external  branch  (Longet).  Stimulation  of 
any  of  these  sensory  fibres  causes  coughing  reflexly.  Coughing  is  produced  by 
stimulation  of  the  sensory  branches  of  the  vagus  to  the  tracheal  mucous  membrane, 
especially  at  the  bifurcation,  and  also  from  the  bronchial  mucous  membrane. 
Coughing  is  also  caused  by  stimulation  of  the  auricular  branch  of  the  vagus,  espe- 
cially in  the  deep  part  of  the  external  auditory  meatus,  of  the  pulmonary  tissue, 
especially  when  altered  pathologically;  in  pathological  conditions  (inflammation) 
of  the  pleura  ( ?  certain  changes  in  the  stomach  [stomach  cough]),  of  the  liver  and 
spleen  (Nai/nyn).  The  coughing  centre  is  said  to  lie  on  each  side  of  the  raphe, 
in  the  neighborhood  of  the  ala  cinerea  {Kohts).  Cases  of  violent  coughing  may, 
owing  to  stimulation  of  the  pharynx,  be  accompanied  by  vomiting  as  an  associ- 
ated movement  (§  120). 

The  cough  (dog,  cat)  caused  by  stimulation  of  the  trachea  and  bronchi  occurs  at  once,  and  lasts 
as  long  as  the  stimulus  lasts ;  in  stimulation  of  the  larnyx  the  first  effect  is  inhibition  of  the  respira- 
tion accompanied  by  nioi-ements  of  deglutition,  while  the  cough  occurs  after  the  cessation  of  the 
stimulation   [Kandarazky). 

The  superior  laryngeal  contains  afferent  fibres  which,  when  stimulated,  cause  arrest  of  the  res- 
piration and  closure  of  the  rima  glottidis  (Rosentluil) — (see  Respiratory  centre,  \  368).  Lastly, 
fibres  which  are  efi'erent  and  serve  to  excite  the  vasomotor  centre,  and  are  in  fact,  "pressorfibres" — 
(see  Vasomotor  centre,  ^  371,  II). 

{b)  The  inferior  laryngeal  (recurrent)  bends  on  the  left  side  around  the  arch 
of  the  aorta,  and  on  the  right  around  the  subclavian,  and  ascends  in  the  groove 
between  the  trachea  and  oesophagus,  giving  motor  fibres  to  these  organs,  and  the 
lower  constrictors  of  the  pharynx,  and  passes  to  the  larynx,  to  supply  motor 
fibres  to  all  its  muscles,  except  the  cricothyroid.  It  also  has  an  inhibitory  action 
upon  the  respiratory  centre  (see  §  368). 

A  connecting  branch  runs  from  the  superior  laryngeal  to  the  inferior  (the  anastomosis  of  Galen), 
which  occasionally  gives  off  sensory  branches  to  the  upper  half  of  the  trachea  (sometimes  to  the 
larynx  ?) ;  perhaps,  also,  to  the  cesophagus  (Loni;e/),  and  sensory  fibres  (?)  for  the  muscles  of  the 
larynx  supplied  by  the  recurrent  laryngeal.  According  to  Frangois  Franck,  sensory  fibres  pass  by 
this  anastomosis  from  the  recurrent  into  the  superior  laryngeal.  .According  to  Waller  and  Burck- 
hard,  the  motor  fibres  of  both  laryngeal  nerves  are  all  derived  from  the  accessorius ;  while  Chau- 
veau  maintains  that  the  cricothyroid  is  an  exception. 

Stimulation  of  the  superior  laryngeal  is  painful,  and  causes  contraction  of 
the  cricothyroid  muscle  (while  the  other  laryngeal  muscles  contract  reflexly). 
Section  of  both  nerves,  owing  to  paralysis  of  the  cricothyroids,  causes  slight  slow- 
ing of  the  respirations  (Sklarek).     In  dogs  the  voice  becomes  deeper  and  coarser. 


640 


CARDIAC  BRANCHES  OF  THE  VAGUS. 


owing  to  diminished  tension  of  the  vocal  cords  {Longef).  The  larynx  becomes 
insensible,  so  that  saliva  and  particles  of  food  pass  into  the  trachea  and  lungs, 
without  causing  reflex  contraction  of  the  glottis  or  coughing,  This  excites  "  trau- 
matic pneumonia,"  which  results  in  death  (Friedlander). 

Stimulation  of  the  recurrent  nerves  causes  spasm  of  the  glottis.  Section 
of  these  nerves  paralyzes  the  laryngeal  muscles  supplied  by  them,  the  voice  be- 
comes husky  and  hoarse  (in  the  pig — Galen,  Riolan,  1618)  in  marv,  dog,  and  cat  ; 
while  rabbits  retain  their  shrill  cry.  The  glottis  is  small,  with  every  inspiration 
of  the  vocal  cords  approximate  considerably  at  their  anterior  parts,  while  during 
expiration  they  are  relaxed  and  are  separated  from  each  other.  Hence,  the  inspi- 
ration, especially  in  young  individuals  whose  glottis  respiratoria  is  narrow,  is  dif- 
ficult and  noisy  {Legallois) ;  while  the  expiration  takes  place  easily.  After  a  few 
days,  the  animal  (carnivore)  becomes  more  quiet,  it  respires  with  less  effort,  and 
the  passive  vibratory  movements  of  the  vocal  cords  become  less.  Even  after  a 
considerable  interval,  if  the  animal  be  excited,  it  is  attacked  with  severe  dyspncea, 
which  disappears  only  when  the  animal  has  become  quiet  again.  Owing  to  paralysis 
of  the  laryngeal  muscles,  foreign  bodies  are  apt  to  enter  the  trachea,  while  the 
paralysis  renders  difficult  the  first  part  of  the  process  of  swallowing  in  the  tesoph- 
ageal  region.     Broncho-pneumonia  may  be  produced  {Arnspergcr). 

6.  The  depressor  nerve,  which  in  the  rabbit  arises  by  one  branch  from  the 
superior  laryngeal,  and  usually,  also,  by  a  second  root  from 
Fig.  iqo.  ^'^^  trunk  of  the  vagus  itself  [runs  down  the  neck  in  close 

relation  with  the  vagus,  sympathetic,  and  carotid  artery, 
enters  the  thorax],  and  joins  the  cardiac  plexus  (Fig.  390,  s(). 
It  is  an  afferent  nerve,  and  when  its  central  end  is  stimu- 
lated [provided  both  vagi  be  divided],  it  diminishes  the 
energy  of  the  vasomotor  centre,  and  thus  causes  a  fall  of  the 
blood  pressure  (hence  the  name  given  to  it  by  Cyon  and 
Ludwig,  §  371,  11).  At  the  same  time  [if  the  vagus  on  the 
opposite  side  be  intact],  its  stimulation  affects  the  cardio- 
inhihitory  centre,  and  thus  reflexly  diminishes  the  number  of 
heart  beats.  [Its  stimulation  also  gives  rise  to  pain,  so  that 
it  is  the  sensory  nerve  of  the  heart.  If  in  a  rabbit  the  vagi 
be  divided  in  the  middle  of  the  neck,  and  the  central  end 
of  the  depressor  nerve,  which  is  the  smallest  of  the  three 
nerves  near  the  carotid,  be  stimulated,  after  a  short  time 
there  is  no  alteration  of  tlie  heart  beats,  but  there  is  a  steady 
fall  of  the  blood  pressure  (Fig.  103),  which  is  due  to  a  reflex 
inhibition  of  the  vasomotor  centre,  resulting  in  a  dilatation 
of  the  blood  vessels  of  the  abdomen.  Of  course,  if  the  vagi 
be  intact,  there  is  a  reflex  inhibitory  effect  on  the  heart.  It 
is  doubtful  if  the  depressor  comes  into  action  when  the  heart 
is  over-distended.  If  it  did,  of  course  the  blood  pressure 
would  be  reduced  by  the  reflex  dilatation  of  the  abdominal 
blood  vessels.] 

The  depressor  nerve  is  present  in  the  cat  [Bernhardt^,  hedgehog 
Scheme  of  the  cardiac  n  rv  s  {Aubert,  Rover),  rat  and  mouse;  in  the  horse  and  in  the  man,  fibres 
in  the  rabbit.  P,  pons:  analogous  to  the  depressor  re-enter  the  trunk  of  the  vagus  (^^'mAffra'/, 
M,  medulla  oblongata:  Kreidmanti).  Depressor  fibres  are  also  found  in  the  rabbit  in  the  trunk 
HortrL^TnierlVur^n:  °f  '^e  vagUS  [DrcshfdJ,,  StMng). 
geal ;  s  c,  superior  car- 
diac or  depressor;  ic,  «    'Y\\e.  cardiac  branches,  as  well  as  the  cardiac  plexus, 

inferior  cardiac  or  car-    ,      '        ,  ,  -i       i     ■         [>  rr^i  •  , 

dio-inhibitory;H, heart,   havc  been   described   in   s   57.      1  hese  nerves  contain   the 

inhibitory  fibres  for  the  heart  (Fig.  390,  ic — cardio-in- 

hibitory — Eihvard  Weber,  November,   1845;    Budge,  independently  in   May, 

1846),  also  sensory  fibres  for  the  heart  [in   the  frog  {Budge),  and   partly   in 


PNEUMONIA   AFTER    SECTION    OF   THE    VAGI.  G41 

mammals  (Goltz)\.  Lastly,  in  some  animals  the  heart  receives  some  of  the 
accelerating  fibres  through  the  trunk  of  the  vagus.  Feeble  stimulation  of  the 
vagus  occasionally  causes  acceleration  of  the  beats  of  the  heart  {Schiff,  Molescholt, 
Gianuzzi).  [This  occurs  when  the  vagus  contains  accelerator  fibres.]  In  an 
animal  poisoned  with  nicotin  or  atropin,  which  paralyzes  the  inhibitory  fibres  of 
the  vagus,  stimulation  of  the  vagus  is  followed  by  acceleration  of  the  heart  beats 
{Schiff,  Schmiedeberg)  [owing  to  the  unopposed  action  of  any  accelerated  fibres 
that  may  be  present  in  the  nerve,  e.g.,  of  the  frog]. 

8.  The  pulmonary  branches  of  the  vagus  join  the  anterior  and  posterior 
pulmonary  plexuses.  The  aw/evv'c/- pulmonary  plexus  gives  sensory  and  motor 
fibres  to  the  trachea,  and  runs  on  the  anterior  surface  of  the  branches  of  the 
bronchi  into  the  lungs.  The  posterior  plexus  is  formed  by  three  to  five  large 
branches  from  the  vagus,  near  the  bifurcation  of  the  trachea,  together  with 
branches  from  the  lowest  cervical  ganglion  of  the  sympathetic  and  fibres  from  the 
cardiac  plexus.  The  plexuses  of  opposite  sides  exchange  fibres,  and  branches  are 
given  off  which  accompany  the  bronchi  in  the  lungs.  Ganglia  occur  in  the 
course  of  the  pulmonary  branches  in  the  frog  (Arnold,  W.  Stirling)  [newt — ■  W. 
Stirling;  and  in  mammals  {Remak,  Egerow,  W.  Stirling)^,  in  the  larynx  l^Cock, 
IF.  Stirling'],  in  the  trachea  and  bronchi  [/?'.  Stirling,  Kanda?azki'\.  Branches 
proceed  from  the  pulmonary  plexus  to  the  pericardium  and  the  superior  vena  cava 
(Luschka,  Zuckerkandl). 

The  functions  of  the  pulmonary  branches  of  the  vagus  are — (i)  they  supply 
motor  branches  to  the  smooth  muscles  of  the  whole  bronchial  system  (§  io6 — 
Roy  and  Graham  Broiun) ;  (2)  they  supply  a  small  part  of  tiie  vasomotor  nerves 
of  the  pulmonary  vessels  (Schiff),  but  by  far  the  largest  number  of  these  nerves 
(?  all)  is  supplied  from  the  connection  with  the  sympathetic  (in  animals  from  the 
first  dorsal  ganglion) — (^Bro^on-Sequard,  A.  Fick,  Badoud,  Lichlheim) ;  (3)  they 
supply  sensory  (cough-exciting)  fibres  to  the  whole  bronchial  system,  and  to  the 
lungs ;  (  4J  they  give  afferent  fibres,  which,  when  stimulated,  diminish  the  activity 
of  the  vasomotor  centre,  and  thus  cause  a  fall  of  the  blood  pressure  during  forced 
expiration  ;  (5  )  and  similar  fibres  which  act  upon  the  inhibitory  centre  of  the 
heart,  and  so  influence  it  as  to  accelerate  the  pulse  beats  (§  369,  II).  Simultaneous 
stimulation  of  4  and  5  alters  the  pulse  rhythm  (Sornmerbrodt)  ;  (6)  they  also  con- 
tain afferent  fibres  from  the  pulmonary  parenchyma  to  the  medulla  oblongata, 
which  stimulate  the  respiratory  centre.  [These  fibres  are  continually  in  action], 
and  consequently  section  of  both  vagi  is  followed  by  diminution  of  the  number 
of  respirations ;  the  respirations  become  deeper  at  the  same  time,  while  the  same 
volume  of  air  is  changed  {Valentin).  Stimulation  of  the  central  end  of  the  vagus 
again  accelerates  the  respirations  (  Traube,  J.  Rosenthal).  Thus  labored  and  diffi- 
cult respiration  is  explained  by  the  fact  that  the  influences  conveyed  by  these  fibres 
which  excite  the  respiratory  centre  reflexly  are  cut  off;  so  it  is  evident  that  cen- 
tripetal or  afferent  impulses  proceeding  upward  in  the  vagus  are  intimately  con- 
cerned in  maintaining  normal  reflex  respiration  ;  after  these  nerves  are  divided, 
conditions  exciting  the  respiratory  movements  must  originate  directly,  especially 
in  the  medulla  oblongata  itself  (§  368). 

Pneumonia  after  Section  of  both  Vagi. — The  inflammation  which  follows  section  of  both 
vagi  has  attracted  the  attention  of  many  observers  since  the  time  of  Valsalva,  Morgagni  (1740), 
and  Legallois  (i8i2).  In  offering  an  explanation  of  this  phenomenon,  we  must  bear  in  mind  the 
following  considerations:  (a)  Section  of  both  vagi  is  lollowed  by  loss  of  motor  power  in  the 
muscles  of  the  larynx,  as  well  as  the  sensibiHty  of  the  larynx,  trachea,  bronchi,  and  the  lungs,  pro- 
vided the  section  be  made  above  the  origin  of  the  superior  laryngeal  nerves.  Hence,  the  glottis  is 
not  closed  during  swallowing,  nor  is  it  closed  reflexly  when  foreign  bodies  (saliva,  particles  of  food, 
irrespirable  gases)  enter  the  respiratory  passages.  Even  the  reflex  act  of  coughing,  which,  under 
ordinary  circumstances,  would  get  rid  of  the  offending  bodies,  is  abolished.  Thus,  foreign  bodies 
may  readily  enter  the  lungs,  and  this  is  favored  by  the  fact  that,  owing  to  the  simultaneous  paralysis 
of  the  tesophagus,  the  food  remains  in  the  latter  for  a  time,  and  may  therefore  easily  enter  the 
larjnx.  That  this  constitutes  one  important  factor  was  proved  by  Traube,  who  found  that  the  pneu- 
41 


642  CESOPHAGEAL   AND    GASTRIC    PLEXUSES. 

monia  was  prevented  when  he  caused  the  animals  to  respire  by  means  of  a  tube  inserted  into  the 
trachea  through  an  aperture  in  the  neck.  If,  on  the  contrary,  only  the  motor  recurrent  nerves 
were  divided  and  the  tesophagus  ligatured,  so  that  in  the  process  of  attempting  to  swallow  food 
must  necessarily  enter  the  respiratory  passages,  "  traumatic  pneumonia  "  was  the  invariable  re- 
sult {Tratihe,  O.  Frey).  (b)  A  second  factor  depends  on  the  circumstance  that,  owing  to  the 
labored  and  dithcult  respiration,  the  lungs  become  surcharged  with  blood,  because  during  the  long 
time  that  the  thorax  is  distended,  the  pressure  of  the  air  within  the  lungs  is  abnormally  low.  This 
condition  of  congestion,  or  abnormal  filling  of  the  pulmonary  vessels  with  blood,  is  followed  by 
serous  exudation  (pulmonary  cedema),  and  even  by  exudation  of  blood  and  the  fonnation  of  pus  in 
the  air  vesicles  (/><t)-  This  same  circumstance  favors  the  entrance  of  fluids  through  the  glottis 
(§  35^'  ^)-  The  introduction  of  a  tracheal  cannula  will  prevent  the  entrance  of  fluids  and  the 
occurrence  of  inflammation.  It  is  probable  that  a  partial  paralysis  of  the  pulmonary  vasomotor 
nerves  may  be  concerned  in  the  inflammation,  as  this  conduces  to  an  engorgement  of  the  pulmonary 
capillaries,  (c)  Lastly,  it  is  of  consequence  to  determine  whether  trophic  fibres  are  present  in  the 
vagus,  and  which  may  influence  the  normal  condition  of  the  pulmonary  tissues.  According  to 
Michaelson,  the  pneumonia  which  takes  place  immediately  after  section  of  the  vagi  occurs  especially 
in  the  lower  and  middle  lobes;  the  pneumonia  which  follows  section  of  the  recurrents  occurs otot-; 
slowly,  and  causes  catarrhal  inflammation,  especially  in  the  upper  lobes.  Rabbits,  as  a  rule,  die 
within  twenty-four  hours,  with  all  the  symptoms  of  pneumonia  ;  when  the  above  mentioned  pre- 
cautions are  taken  they  may  live  for  several  days.  Dogs  may  Hve  for  a  long  time.  If  the  9th, 
loth,  and  1 2th  nerves  be  torn  out  on  one  side  in  a  rabbit,  death  takes  place  from  pneumonia  (  Griin- 
hagen).  In  birds,  bilateral  section  of  the  vagi  is  not  followed  by  pneumonia  (Blainville,  Bill- 
roth], because  the  upper  larynx  remains  capable  of  closing  firmly — death  takes  place  in  eight  to 
ten  days  with  the  symptoms  of  inanition  [Einbrodt,  Zander,  v.  Anrep),  while  the  heart  under- 
goes fatty  degeneration  (Eichhorst),  and  so  do  the  liver,  stomach,  and  muscles  (v.  Anrep). 
According  to  Wassilieff,  the  heart  shows  cloudy  swelling  and  slight  wax-like  degeneration.  Frogs, 
which  at  every  respiration  open  the  glottis,  and  close  it  during  the  pause,  die  of  asphyxia.  Section 
of  the  pulmonary  branches  has  no  injurious  effect  {Bidder). 

9.  The  cesophageal  plexus  is  formed  principally  by  branches  from  the  vagus 
above  the  inferior  laryngeal,  from  the  pulmonary  plexus  and  below  from  the  trunk 
itself.  This  plexus  supplies  the  oesophagus  with  motor  power  (§  156),  the  sen- 
sibility which  is  present  only  in  the  upper  part,  and  it  also  supplies  fibres  capable 
of  exciting  feflex  actions. 

10.  The  gastric  plexus  consists  of  {a)  the  anterior  (left)  termination  of 
the  vagus,  which  supplies  fibres  to  the  oesophagus  and  courses  along  the  small 
curvature,  and  sends  a  few  fibres  through  the  portal  fissure  into  the  liver; 
(J))  the  posterior  (right)  vagus,  after  giving  off  a  few  fibres  to  the  oesophagus, 
takes  part  in  the  formation  of  the  gastric  plexus  to  which  (c)  sympathetic  fibres 
are  added  at  the  pylorus.  Section  of  the  vagi  is  followed  by  hyperemia  of 
the  gastric  mucous  membrane  (Faniim,  Finci/s),  but  it  does  not  interfere 
with  digestion  (Bidder  and  Schmidt),  even  when  it  is  performed  at  the  cardia 
{Kritzler,  Schiff). 

11.  About  two-thirds  of  the  right  vagus  on  the  stomach  joins  the  coeliac 
plexus,  and  from  it  branches  accompany  the  arteries  to  the  liver,  spleen,  pan- 
creas, duodenum,  kidney,  and  suprarenal  capsules.  The  vagus  supplies  motor 
fibres  to  the  stomach,  which  belong  to  the  root  of  the  vagus  itself  and  not  to  the 
accessorius  {Slil/ing,  Bischoff,  Chauvcau).  The  gastric  branches  also  contain 
afferent  fibres,  which,  when  stimulated,  cause  rcflexly  a  secretion  of  saliva  (§  145). 
It  is  undetermined  whether  they  also  cause  vomiting.  For  the  effect  of  the  vagus 
upon  the  movements  of  the  intestine  (see  §  161).  According  to  some  ob- 
servers, stimulatton  of  the  vagus  is  followed  by  movements  of  the  large  as  well  as 
of  the  small  intestine  {Stilling,  Kiipffer,  C.  Ludwig,  Remak).  Stimulation  of  the 
peripheral  end  of  the  vagus  causes  contraction  of  the  smooth  muscular  fibres  in 
the  capsule  and  trabecular  of  the  spleen  (in  the  rabbit  and  dog,  §  103).  Stimula- 
tion of  the  vagus  at  the  cardia  causes  increase  in  the  secretion  of  urine  with 
dilatation  of  the  retial  vessels,  while  the  blood  of  the  renal  vein  becomes  more 
arterial  {CI.  Bernard).  According  to  Rossbach  and  Quellhorst,  a  few  vasomotor 
fibres  are  supplied  by  the  vagus  to  the  abdominal  organs,  while  the  greatest  num- 
ber comes  from  the  splanchnic.  According  to  CEhl,  efferent  (centrifugal)  motor 
fibres  run  in  the  vagus  (dog)  direct  to  bladder,  as  well  as  afferent  fibres  whose 


REFLEX   EFFECTS   OF   STIMULATION   OF   THE    VAGUS.  643 

stimulation  causes  reflex  contraction  of  the  bladder.     So  far,  this  observation  has 
not  been  confirmed. 

12.  Reflex  Effects. — The  vagus  and  its  branches  contain  fibres,  some  of 
which  have  been  referred  to  already,  which  act  rtflexly  (afferent)  upon  certain 
nervous  mechanisms. 

(rt)  On  the  vasomotor  centre  there  act  (.;)  prtssor  fibres  (especially  in  both  laryngeal  nerves), 
whose  stimulation  is  followed  by  a  reflex  contraction  of  the  anerial  blood  channels,  and  thus  cause 
a  rise  of  the  blood  pressure  ;  (b)  depressor  fibres  (in  the  depressor  or  the  vagus  itself),  which  have 
exactly  an  opposite  effect.  (This  subject  is  specially  referred  to  under  the  head  of  the  Vasomotor 
nerve  centre,  \  37 1.) 

[b)  On  the  respiratory  centre  there  act  (a]  fibres  (pulmonary  branches)  whose  stimulation  is 
followed  yyj  acceleration  of  the  respiration  ;  zxvi.  [b)  inhibitory  fihxes  (in  both  laryngeals),  whose 
stimulation  is  followed  by  slowing  or  arrest  of  the  respiration.     (S=e  Respi- atory  centre,  \  368.) 

(f )  On  the  Cardio- inhibitory  System. — [When  the  central  end  of  one  vagus  is  stimulated, 
provided  the  other  vagus  is  intact,  the  heart  may  be  arrested  r/Jlexly  in  the  diastolic  phase. 1  Mayer 
and  Pribram  observed  that  sudden  distention  of  the  stomach  caused  slowing  and  even  arrest  of  the 
heart,  while  at  the  same  time  there  was  contraction  of  the  arteries  of  the  medulla  oblongata  and 
increase  of  the  l)lood  pressure. 

{d)  On  the  Vomiting  Centre. — This  centre  may  be  affected  by  stimulation  of  the  central  end 
of  the  vagus,  and,  as  already  mentioned,  by  stimulation  of  many  afferent  fibres  in  the  vagus  (\  158). 

{e)  On  the  Pancreatic  Secretion. — Stimulation  of  the  central  end  of  the  vagus  is  followed  by 
arrest  of  this  secretion  (\  171). 

(/)  According  to  CI.  Bernard,  there  are  fibres  present  in  the  pulmonary  nerves,  which,  when 
they  are  stimulated,  increase  reflexly  the  formation  of  sugar  in  the  liver,  perhaps  through  the 
hepatic  branches  of  the  vagus. 

Unequal  Excitability. — The  various  branches  of  the  vagus  are  not  all  endowed  with  the  same 
degree  of  excitability.  If  ihe  periplieral  end  of  the  vagus  be  stimulated  first  of  all  with  a  weak 
stimulus,  the  laryngeal  muscles  are  first  affected,  and  afterward  the  heart  is  slowed  {^Rutherford). 
If  the  central  euA  be  stimulated  with  feeble  stimuli,  the  "  excito-respiratory  "  fibres  are  exhausted 
before  the  " inhibito-respiratory "  (Burkart).  According  to  Steiner,  the  various  fibres  are  so 
arranged  in  the  vagus  that  the  afferent  fibres  lie  in  the  outer,  and  the  efferent  in  the  inner,  half  of 
the  trunk,  in  the  cervical  region. 

Pathological. — Stimulation  or  paralysis  in  the  area  of  the  vagus  must  necessarily  present  a  very 
ditTererit  picture  according  as  the  affection  is  referred  to  the  whole  trunk  or  only  to  some  of  its 
branches,  or  whether  the  affection  is  unilateral  or  bilateral.  Paralysis  of  the  pharynx  and 
oesophagus,  which  is  usually  of  central  or  intracranial  origin,  interferes  with  or  abolishes  deglu- 
tition, so  that  when  the  oesophagus  becomes  filled  with  food  there  is  difticulty  of  breathing,  and  the 
food  may  even  pass  into  the  nasal  cavities.  A  peculiar  sonorous  gurgling  is  occasionally  heard  in 
the  relaxed  canal  (deglutatio  sonora).  In  incomplete  paralysis  the  act  of  deglutition  is  delayed 
and  rendered  more  difficult,  while  large  masses  are  swallowed  more  easily  than  small  ones. 
Increased  contraction  and  spasmodic  stricture  of  the  oesophagus  are  referred  to  under  the  phe- 
nomena of  general  nervous  excitability  {\  186). 

Spasm  of  the  laryngeal  muscles  causes  spasmodic  closure  of  the  glottis  (Spasmus  glollidis). 
This  condition  is  most  apt  to  occur  in  children,  and  takes  place  in  paroxysms,  with  symptoms  of 
dyspnoea  and  crowing  inspiration  ;  if  the  case  be  very  severe,  there  may  be  muscular  contractions 
(of  the  eye,  jaw,  digits,  etc.).  The  symptoms  are  ver>'  probably  due  to  the  reflex  spasms  which 
may  be  discharged  from  the  sensory  nerves  of  several  areas  (teeth,  intestine,  skin).  The  impulse 
is  conducted  along  the  sensory  nerves  proceeding  from  these  areas  to  the  medulla  oblongata,  where 
it  causes  the  discharge  of  the  reflex  mechanism  which  produces  the  above-mentioned  results. 
1  here  may  be  spasm  of  the  dilators  of  the  glottis  (Frdnt:el  1  and  other  laryngeal  muscles. 

Stimulation  of  the  sensory  ner\'es  of  the  larynx,  as  is  well  known,  produces  coughing.  If  the 
stimulation  be  very  intense,  as  in  whooping-cough,  the  fibres  lying  in  the  laryngeal  nerves,  which 
inhibit  the  respiratory  centre,  may  also  be  stimulated;  the  number  of  respirations  is  diminished, 
and  uhimately  the  respiration  ceases,  the  diaphragm  being  relaxed :  while,  with  the  most  intense 
stimulation,  there  may  be  spasmodic  expiratory  arrest  of  the  respiration  with  closure  of  the  glottis, 
which  may  last  for  filteen  seconds.  Paralysis  of  the  laryngeal  nerves,  which  causes  disturbances 
of  speech,  has  been  referred  to  in  \  313.  In  bilateral  paralysis  of  the  recurrent  nerz'es,  in  conse- 
quence of  tension  upon  them  due  to  dilatation  of  the  aorta  and  the  subclavian  artery,  a  consider- 
able amount  of  air  is  breathed  out,  owing  to  the  futile  efforts  which  the  patient  makes  in  trying  to 
speak ;  expectoration  is  more  difiicult,  while  violent  coughing  is  impossible  {v.  Ziemssen).  Attacks 
of  dyspnoea  occur  just  as  in  animals,  if  the  person  make  violent  efforts.  Some  observers  [Salter, 
Bergson)  have  referred  the  asthma  nervosum  paroxysms,  which  last  for  a  quarter  of  an  hour  or 
more,  and  constitute  asthma  bronchiole,  to  stimulation  of  the  pulmonary  plexus,  causing  spasmodic 
contraction  of  the  bronchial  muscle  (^  io6|.  Physical  investigation  during  the  paroxysms  reveals 
nothing  but  the  existence  of  some  rhonchi   (|  117).     If  this  condition  is  really  spasmodic  in  its 


644  THE    SPINAL   ACCESSORY    NERVE. 

nature  (?  of  the  vessels),  it  must  be  usually  of  a  reflex  character ;  the  afferent  nerves  may  be  those 
of  the  lung,  skin  or  genitals  (in  hysreria).  Perhaps,  however,  it  is  clue  to  a  temporary  paralysis  of 
the  pulmonary  nerves  (afferent),  which  excite  the  respiratory,  centre  (excito-respiratory). 

Stimulation  of  the  cardiac  branches  of  the  vagus  may  cause  attacks  of  temporary  suspension  of 
the  cardiac  contractions,  which  are  accompanied  by  a  feeling  of  great  depression  and  of  impending 
dissolution,  with  occasionally  pain  in  the  region  of  the  heart.  Attacks  of  this  sort  may  be  pro- 
duced reflcxly,  €.g.^  by  stimulation  or  irritation  of  the  abdominal  organs  (as  in  the  experiment  of 
Goltz  of  tapping  the  intestines).  Hennoch  and  Silbermann  observed  slowing  of  the  action  of  the 
heart  in  children  suffering  from  gastric  irritation.  Similarly,  the  respiration  may  be  affected  reflexly 
through  the  vagus,  a  condition  described  by  Hennoch  as  asthma  dyspepticum.  In  cases  of 
intermittent  paralysis  of  the  cardiac  branches  of  the  vagus  we  rarely  find  acccleralion  of  the  pulse 
above  l6o  [Riegel),  200  (  Ttuzek,  L.  Langer^  Weil)  ;  even  240  pulse  beats  per  minute  have  been 
recorded  i^Kufpert),  and  in  such  cases  the  beats  vary  much  in  rhythm  and  force,  and  they  are  very 
irregular.  These  cases  require  to  be  more  minutely  analyzed,  as  it  is  not  clear  how  much  is  due  to 
paralysis  of  the  vagus  and  how  much  to  the  action  of  the  accelerating  mechani.sm  of  the  heart. 
Little  is  known  of  affections  of  the  ififra-nln/ominal  ^hyts  of  the  vagus.  It  seems  that  the  sensory 
branches  of  the  stomach  do  not  come  from  the  vagus.  If  the  trunk  of  the  vagus  or  its  centre  be 
paralyzed,  there  are  labored,  deep,  slow  respirations,  such  as  follow  section  of  both  vagi  ( Gttttmann). 

353.  XI.  NERVUS  ACCESSORIUS  WILLISII— Anatomical.— This  nerve  arises 
by  two  completely  separate  roots;  otie  from  the  accessorius  nucleus  of  the  medulla  oblongata 
( Fig.  384,  II),  which  is  connected  with  the  vagus  nucleus ;  while  the  o/ht'r  root  arises  between  the 
anterior  and  posterior  nerve  roots  from  the  spinal  cord,  usually  between  the  5th  and  6th  cervical 
vertebrae.  In  the  interior  of  the  spinal  cord  Us  fibres  c^n  be  traced  to  an  elongated  nucleus  lying 
on  the  outer  side  of  the  anterior  cornu,  as  far  downward  as  the  5th  cervical  vertebra.  Near  the 
jugular  foramen  both  portions  come  together,  but  do  not  exchange  fibres  (Hoi/);  both  roots  after- 
ward separate  from  each  other  to  form  two  distinct  l^ranches,  the  anterior  [inner],  which  arises 
from  the  medulla  oblongata,  passing  en  masse  into  the  plexus  gangliiformis  vagi.  This  branch  sup- 
plies the  vagus  with  most  of  its  7notor  fibres  (compare  \  352,  3),  and  also  its  cardio-inhibitory 
fibres.  If  the  accessorius  be  pulled  out  by  the  root  m  animals,  these  heart  fibres  undergo  degenera- 
tion. If  the  trunk  of  the  vagus  be  stimulated  in  the  neck  four  to  five  days  after  the  operation,  the 
action  of  the  heart  is  no  longer  arrested  thereby  [owing  to  the  degeneration  of  the  cardio-inhibitory 
fibres]  [Waller,  Schiff,  Daszkieiuiez,  Heidenhain);  according  to  Heidenhain,  the  heart- beats  are 
accelerated  immediately  after  pulling  out  the  nerve.  [The  upper  cervical  metameres  or  segments 
give  origin  not  only  to  the  anterior  and  posterior  roots  of  the  corresponding  nerve  roots,  but  between 
these  roots  arise  the  roots  of  the  spinal  accessory  nerve.  This  nerve  contains  /iz)ycmedullated  nerve 
fibres  andyfKf  meduUated  fibres  such  as  characterize  the  visceral  branches  of  the  thoracic  and  sacral 
regions  (\  356).  The  nerve  passes  by  the  jugular  ganglion  of  the  vagus,  then  divides  into  the 
external  and  internal  branch.  All  the  large  fibres  pass  into  the  external  branch,  which,  along  with 
branches  from  the  cer\'ical  plexus,  supply  the  sterno-mastoid  and  trapezius.  The  internal  branch, 
composed  of  small  fibres,  passes  Into  the  ganglion  of  the  trunk  of  the  vagus.  Gaskell  therefore 
regards  the  Internal  branch  "  as  formed  by  the  rami  viscerales  of  the  upper  cervical  and  vagus 
nerves."  These  fine  medullated  nerve  fibres  probably  arise  from  the  cells  of  the  posterior  vesicular 
column  of  Clarke.  The  motor  fibres  to  the  trapezius  and  sterno-mastoid  arise  from  the  cells  of  the 
lateral  horn  of  gray  matter.] 

The  external  branch  arises  from  the  spinal  roots.  This  nerve  communicates 
with  the  sensory  branches  of  the  posterior  root  of  the  ist,  more  rarely  of  the 
2d  cervical  nerve,  and  these  fibres  supply  sensibility  to  the  muscles;  it  then  turns 
backward  above  the  transverse  process  of  the  atlas,  and  terminates  as  a  motor 
nerve  in  the  sterno-mastoid  and  trapezius  [Galen,  Valentin,  Volkmann).  The  latter 
muscle  usually  receives  motor  fibres  also  from  the  cervical  plexus  (Fig.  386). 

The  external  branch  communicates  with  several  cervical  nerves.  These  fibres  either  participate 
in  the  innervation  of  the  above-named  muscles  or  the  accessorius  returns  part  of  the  sensory  fibres 
supplied  by  the  posterior  roots  of  the  two  upper  cervical  nerves. 

Pathological. — Stimulation  of  the  outer  branch  causes  tonic  or  clonic  spasm  of  the  above-named 
muscles,  usually  on  one  side.  If  the  branch  to  the  sterno-mastoid  be  aftected  alone,  the  head  is 
moved  with  each  clonic  spasm.  If  the  affection  be  bilateral,  the  spasm  usually  takes  place  on  oppo- 
site sides  alternately,  while  It  is  rare  to  have  it  on  both  sides  simultaneously.  In  spasm  of  the 
trapezius  the  head  is  drawn  backward  and  to  the  side.  Toiiie  contraction  of  the  flexors  of  the 
head  causes  the  characteristic  position  of  the  head  known  as  caput  obstipum  (spastlcum)  or  wry- 
neck. In  />aral}'sis  of  one  of  these  muscles  the  head  is  drawn  toward  the  sound  side  (torticollis 
paralyticus).     Paralysis  of  the  trapezius  is  usually  only  partial. 

Paralysis  of  the  whole  trunk  of  the  spinal  accessory  (usually  caused  by  central  conditions), 
besides  causing  paralysis  of  the  sterno-mastoid  and  trapezius,  also  paralyzes  the  motor  branches  of 
the  vagus  already  referred  to  [Erb,  Frdnkel,  Holz). 


THE    SPINAL   NERVES.  645 

354.  XII.  NERVUS  HYPOGLOSSUS.— Anatomical.— It  arises  from  two  large-celled 
nuclei  witliin  the  lowest  part  of  the  calamus  scriptorius,  and  one  adjoining  small-celled  nucleus 
(Roller),  while  addiiional  filires  come  from  the  brain  (^  37S),  and  also  perhaps  from  the  olive  (Fig. 
384,12).  It  springs  by  10  to  15  twigs  in  a  line  with  the  anterior  roots  of  the  spinal  neive  (Fig.  385, 
IX).     In  its  development  part  of  the  hypoglossal  behaves  as  a  spinal  nerve  (Froriep). 

Function. — It  is  motor  to  all  the  muscles  of  the  tongue,  including  the  genio- 
hyoid and  thyro-hyoid. 

Connections. — The  trunk  of  the  hypoglbssal  is  connected  with — ( 1 1  the  superior  cervical  ganglion 
of  the  svmpathelic,  which  supplies  it  with  -Hisomotor  fibres  for  the  blood  vessels  of  the  tongue.  After 
section  of  the  hypoglossal  and  lingual  nerves,  the  corresponding  half  of  the  tongue  becomes  red 
and  congested  [Scliiff).  (2)  There  is  also  a  branch  from  the  plexus  gangliiformis  vagi,  its  small 
lingual  branch  to  the  commencement  of  the  hypoglossal  arch.  These  filires  supply  the  hypoglossal 
with  sensory  filires  for  the  muscles  of  the  tongue,  for  even  after  section  of  the  lingual  the  tongue  still 
possesses  dull  sensibility.  It  is  uncertain  whether  fibres  with  a  similar  function  are  partly  derived 
from  the  cervical  nerves  or  from  the  anastomosis  which  takes  place  with  the  lingual.  {3)  It  is 
united  with  the  np/'er  cervical  nerves  by  means  of  the  loops  known  as  the  ansa  hypoglossi.  These 
connecting  fibres  run  in  the  de^cendens  noni  to  the  sterno-hyoid,  omo-hyoid  and  sterno-thyroid.  Cer- 
vical fibres  do  not,  as  a  rule,  enter  the  tongue;  stimulation  of  the  root  of  the  hypoglossal  acts  upon 
the  above-named  muscles  only  very  rarely  and  to  a  very  slight  extent  [Volkmann).  (Compare 
§297,  3,  and  ^^336,  III.) 

Bilateral  section  of  the  nerve  causes  complete  motor  paralysis  of  the  tongue. 
Dogs  can  no  longer  lap ;  they  bite  the  flaccid  tongue.  Frogs,  which  seize  their 
prey  with  the  tongue,  must  starve ;  when  the  tongue  hangs  from  the  mouth,  it 
must  prevent  the  closure  of  the  mouth,  so  that  these  animals  must  die  from 
asphyxia,  as  air  is  pumped  into  the  lungs  only  when  the  mouth  is  closed. 

Pathological. — Paralysis  of  the  hypoglossal  (glossoplegia),  which  is  usually  central  in  its 
origin,  causes  disturbance  of  .i/ct-iV;  (§  319).  [In  unilateral  palsy  the  tongue  lies  in  the  mouth  in 
its  normal  position,  but  the  base  is  more  prominent  on  the  paralyzed  side.  When  the  tongue  is 
protruded  it  passes  to  the  sound  side  by  the  genio  hyoglossus  (J  155)-]  Paralysis  of  the  tongue 
also  interferes  with  mastication,  the  formation  of  the  bolus  in  the  mouth,  and  deglutition  in  the 
mouth.  Owing  to  the  imperfect  movements  of  the  tongue,  taste  is  imperfect,  and  the  singing  of 
high  notes  and  the  falsetto  voice,  which  require  certain  positions  of  the  tongue,  appear  to  be  impos- 
sible {Bennati). 

Spasm  of  the  tongue,  which  causes  aphthongia  (|  318),  is  usually  reflex  in  its  origin,  and  is 
extremely  rare.  Idiopathic  cases  of  spasm  of  the  tongue  have  been  described;  the  seat  of  the  irri- 
tation lay  either  in  the  cortex  cerebri  or  in  the  oblongata  (Berger,  E.  JHemai).  For  Pseudo-motor 
Action,  p.  632. 

355.  THE  SPINAL  NERVES. — Anatomical. — The  thirty-one  pairs  of  spinal  nerves  arise 
by  means  of  a  posterior  root  (consisting  of  a  few  large  rounded  Imndles)  from  the  sulcus  between 
the  posterior  and  lateral  columns  of  the  spinal  cord,  and  by  means  of  an  anterior  root  (consisting 
of  numerous  fine  flat  strands),  from  the  furrow  between  the  anterior  and  lateral  columns.  The 
posterior  roots,  with  the  exception  of  the  1st  cervical  nerve,  are  the  larger.  Occasionally  the  roots 
on  opposite  sides  are  not  symmetrical ;  one  or  other  mot,  or  even  a  whole  nerve,  may  be  absent 
from  the  dorsal  region  (Adamiicwicz].  On  the  posterior  root  is  ihe  spindle  shaped  spinal  gan- 
glion (^  321,  II,  3),  which  is  occasionally  double  on  the  lumbar  and  sacral  nerves  Beyond  the 
ganglion  the  two  roots  unite  to  form  within  the  spinal  canal  the  mixed  trunk  of  a  spinal  nerve. 
The  branches  of  the  nerve  trunk  invariably  contain  fibres  coming  from  both  roots.  The  number  of 
fibres  in  the  nerve  trunk  is  exactly  the  same  as  in  the  two  roots;  hence,  we  must  conclude  that  the 
nerve  cells  in  the  spinal  ganglion  are  intercalated  in  the  course  of  the  fibres  {Gaule  and  Birge). 

[Structure  of  a  Spinal  Ganglion. — The  ganglion  is  invested  by  a  thin,  firmly  adherent  sheath 
of  connective  tissue,  which  sends  processes  into  the  swelling,  and  is  continuous  with  the  sheaths  of 
the  nerve  entering  and  leaving  the  ganglion  (Fig.  39:,  e).  A  longitudinal  section  of  such  a  gan- 
glion exhibits  the  cells  arranged  in  groups,  with  strands  of  nerve  fibres  coursing  longitudinally 
between  them  (Fig.  T^<)i,a,h).  The  nerve  cells  are  usually  globular  in  form,  with  a  distinct  capsule 
lined  with  epithelium,  and  the  cell  substance  itself  contains  a  well-defined  nucleus  with  a  nuclear 
envelope  and  a  nucleolus.  The  capsule  of  the  cell  is  c  mtiniious  with  the  sheath  of  Schwann  of  a 
nerve  fibre.  The  exact  relation  between  the  nerve  fibres  and  the  nerve  cells  is  difficult  to  establish, 
but  it  is  probable  that  each  nerve  cell  is  connected  with  a  nerve  fibre.  In  the  spinal  ganglia  of  the 
vertebrates  above  fishes,  and  also  in  the  Gas=erian  ganglion,  cells  are  f.jund  with  a  single  process  or 
fibre  attached  to  them,  the  nerve-fibre  process  not  unfrequently  coiling  a  few  times  within  the  cap- 
sule. This  process,  after  emerging  from  the  capsule,  becomes  coa'ed  with  myrlin,  and  usually 
soon  divides  at  a  node  of  Ranvier  (Fig.  341,  /).  Ranvier,  who  first  observed  this  arrangement, 
described  it  as  a  T'^haped  fibre.    These  nerve  cells  with  "T'^'i^P^'J  fibres  have  been  observed  in  the 


646 


RECURRENT   SENSIBILITY. 


spinal  ganglia  of  all  vertebrates  above  fishes,  in  the  Gasserian  and  geniculate  ganglia,  as  well  as  in 
the  jugular  and  ceniical  ganglia  of  the  vagus.  In  fishes  the  nerve  cells  of  the  spinal  ganglia  are 
bipolar  (Fig.  335,4).] 

Bell's  Law.- — Sir  Charles  Bell  discovered  (181 1)  that  the  anterior  roots  of 
the  spinal  nerves  are  motor,  the  posterior  are  sensory. 

Recurrent  Sensibility. — Magendie  discovered  (1S22)  the  remarkable  fact 
X\\-3X  sensory  fibres  zxt  also  present  \n  the  anterior  roots,  so  that  their  stimulation 
causes  pain.  This  is  due  to  the  fact  that  sensory  fibres  pass  into  the  anterior  root 
after  the  two  roots  have  joined,  and  these  fibres  run  in  the  anterior  root  in  a 
centripetal  direction  {Sehiff,  CI.  Bernard^.  The  sensibility  of  the  anterior  root 
is  abolished  at  once  by  section  of  the  posterior  root.  This  condition  is  called 
"recurrent  sensibility"  of  the  anterior  root.  When  the  sensibility  of  the 
anterior  root  is  abolished,  so  is  the  sensibility  of  the  surface  of  the  spinal  cord 
in  the  neighborhood  of  the  root.  A  long  time  after  section  of  the  anterior,  and 
when  the  degeneration  phenomena  have  had  time  to  develop  (§  325),  a  few  non- 
degenerated  sensory  fibres  are  always  to  be  found  in  the  central  stump  (Sehiff, 
Vulpiiih).  Sehiff  found  that,  in  cases  where  the  motor  fibres  had  undergone 
degeneration,  there  were  always  non -degenerated  fibres  to  be  found  in  the 
anterior  root,  which  passed  into  the  membranes  of  the  spinal  cord.  The  sensory 
fibres  pass  into  the  motor  root,  either  at  the  angle  of  union  of  the  roots,  or  in 


1  of  a  spin.il  g.ingl 


lis,  c,  c.ipsule 


the  plexus,  or  in  the  region  of  the  peripheral  terminations.  Sensory  fibres  enter 
many  of  the  branches  of  the  motor  cranial  nerves  at  their  periphery,  and  after- 
ward run  in  a  centripetal  direction  (p.  632).  Even  into  the  trunks  of  sensory 
nerves,  sensory  branches  of  other  sensory  nerves  may  enter.  This  explains  the 
remarkable  observation,  that  after  section  of  a  nerve  trunk  {e.g.,  the  median), 
its  peripheral  terminations  still  retain  their  sensibility  (Arloing  and  Tripier). 
The  tissue  of  the  motor  and  sensory  nerves,  like  most  other  tissues  of  the  body, 
is  provided  with  sensory  nerves  (yVtvz'/  nervorum,  p.  565). 

[It  does  not  follow  that  section  of  a  peripheral  cutaneou'!  nerve  will  cause  ana'sthesia  in  the  part 
to  which  it  is  distributed;  in  fact,  one  of  the  principal  nerve  trunks  of  the  brachial  plexus  may  be 
divided  without  giving  rise  to  complete  anceslhesia  in  any  part  of  the  area  of  distribution  of  the 
sensory  branches  of  the  nerve,  and  even  if  there  be  partial  or  complete  cutaneous  an.-esthesia  it  is 
much  less  in  extent  than  corresponds  to  the  anatomical  area  of  distribution.  The  an;vsthetic  area 
tends  to  become  smaller  in  extent  (Ross).  Thus  there  is  not  complete  independence  in  the  distri- 
bution of  these  nerves.  These  results  are  explained  by  the  anastomosis  between  branches  of  nerves, 
the  exchange  of  fibres  in  the  terminal  networks,  while  some  sensory  fibres  enter  the  peripheral 
parts  of  a  nerve  and  run  centripetally,  perhaps  being  distributed  to  the  skin  and  conferring  recurrent 
sensibility  on  the  peripheral  part  of  the  nerve.] 

Relative  Position  of  Motor  and  Sensory  Fibres. — In  embryos  (rabbit)  the  motor  fibres  stain 
more  deeply  with  carmine  than  the  sensory  fibres,  so  that  their  position  in  the  peripheral  nerves  of 


DEDUCTION    FROM    BELL  S   LAW. 


647 


distribution  may  thereby  be  made  out.  In  the  anterior  branch  of  a  spinal  nerve,  the  sensory  fibres 
he  in  the  outer  part  of  the  branch,  the  motor  in  the  inner  part ;  while  this  relation  is  reversed  in  the 
posterior  root  (Z.  Lowe). 

Deduction  from  Bell's  Law. — Careful  observation  of  the  effects  of  section 
of  the  roots  of  the  spinal  nerves  {Magendie,  1822),  as  well  as  the  discovery  of  the 
reflex  relation  of  the  stimulation  of  the  sensory  roots  to  the  anterior,  constituting 

Fig.  393. 


Fig.  392. 


siiibution  of  ihe  cutaneous 
A,  dorsal  surface;/  sc,  supra-clavit 
axillary  ;  3cps,  superior  posterior 
4  c*nd,  median  cutaneous;  5cpi,  i: 
terior  cutaneous;  b  cm _ 
cl,  lateral  cutaneous  ;  8  «,  ulnar ;  q  ra,  radial'; 
JO  me,  median  ;  B,  volar  surface  ;  /  sc,  supra- 
clavicular; 2  ajtr,  axillary;  ^  cmd,  internal 
cutaneous;  4  cl,  lateral  cutaneous  ;  j"  cm,  cu- 
taneous medius;  6  we,  median;  7  u,  ulnar. 


Vpcismjl  hmj 


cutaneous  nerves  of  the  leg 
A.  Anterior  surface— I,  crural 
.  -,  — jrnal  lateral  cutaneous;  3,  ilio- 
inguinal; 4,  iumbo-inguinal ;  5,  external  sper- 
matic ;  6,  posterior  cutaneous  ;  7,  obturator ; 
8,  great  saphenous  ;  9,  communicating  pero- 
neal;  10,  superficial  peroneal ;  ri.deep  pero- 
;al  ;  12,  communicating  tibial.     B.  Posteri 


surface — i,  posterior  cutaneous; 
femoral  cutaneous;  3,  obturator 
posterior  femoral  cutaneous  ;  5,  1 
ing  peroneal;  6,  great  saphenous 
nicating  tibial;  8,  plantar  cutant 
dian  plantar  ;  lo,  lateral  plantar. 


reflex  movements  {Marshall  Hall,  Johafities  Muller,  i8j2),  enable  us  to  deduce 
the  following  conclusions  from  Bell's  law  :  i.  At  the  moment  of  section  of  the 
anterior  root,  there  is  a  contraction  in  the  muscles  supplied  by  this  root.  2. 
There  is  at  the  same  time  a  sensation  of  pain  due  to  the  '*  recurrent  sensibility," 
3.  After  the  section,  the  corresponding  muscles  ztq  paralyzed.     4.   Stimulation  of 


648  FUNCTIONS   OF   THE   ANTERIOR    SPINAL   ROOTS. 

the  peripheral  trunk  of  the  anterior  root  (immediately  after  the  operation)  causes 
contraction  of  the  muscles,  and  eventually  pain,  owing  to  the  recurrent  sensibility. 
5.  Stimulation  of  the  central  end  is  uiithout  effect.  6.  The  peripheral  end  of  the 
motor  nerves  degenerates  within  a  short  time  (§  325,  4).  7.  The  central  end 
degenerates  somewhat  later  (§  325,  3).  8.  The  sensibility  of  the  paralyzed  parts 
is  retained  completely.  9.  At  the  moment  of  section  of  the  posterior  root 
there  is  severe /(?/>/.  10.  At  the  same  time  movements  are  discharged  refiexly. 
II.  After  the  section  all  parts  supplied  by  the  divided  roots  are  devoid  of  sensi- 
bility. 12.  Stimulation  of  the  peripheral  trunk  of  the  divided  nerve  is  without 
effect.  13.  Stimulation  of  the  central  end  causes  pain  and  reflex  movements. 
14.  With  reference  to  the  degeneration  of  the  peripheral  end  of  the  sensory  fibres, 
see  §  325,  4.  15.  The  central  end  ultimately  degenerates.  16.  Movement  is  re- 
tained completely  in  the  paralyzed  parts,  e.  g.,  in  the  extremities. 

Incoordinated  Movements  of  Insensible  Limbs. — After  section  of  the  posterior  roots,  e.g., 
of  the  nerves  for  the  posterior  extremities,  the  muscles  retain  their  movements,  nevertheless  there 
are  characteristic  disturb.ances  of  their  motor  power.  This  is  expressed  in  the  awkward  manner  in 
which  the  animal  executes  its  movements — it  has  lost  to  a  large  extent  its  harmony  and  elegance  of 
motion.  This  is  due  to  the  fact  that,  owing  to  the  absence  of  the  sensibility  of  the  muscles  and 
skin,  the  animal  is  no  longer  conscious  of  the  resistance  which  is  opposed  to  its  movements. 
Hence  the  degree  of  muscular  energy  necessary  for  any  particular  efibrt  cannot  be  accurately 
graduated.  Animals  which  have  lost  the  sensibility  of  their  extremities  often  allow  their  limbs 
to  lie  in  abnormal  positions,  such  as  a  healthy  animal  would  not  tolerate.  In  man  also,  when  the 
peripheral  ends  of  the  cutaneous  nerves  are  degenerated,  there  are  ataxic  phenomena  (^  364,  3). 

Increased  Excitability. — Harless  (185S),  Ludwig,  and  Cyon  (controverted  by  v.  Bezold, 
Uspensky,  Griinhagen,  and  G.  Heidenhain)  observed  that  the  anterior  root  is  more  excitable  as 
long  as  the  posterior  roots  remain  intact  and  are  sensitive,  and  that  their  excitability  is  diminished 
as  soon  as  the  posterior  roots  are  divided.  In  order  to  explain  this  phenomenon,  we  must  assume 
that  in  the  intact  body  a  series  of  gentle  impulses  (impressions  of  touch,  temperature,  position  of 
limbs,  etc.)  are  continuously  streaming  through  the  posterior  roots  to  the  spinal  cord,  where  they 
are  transferred  to  the  motor  roots,  so  that  a  less  .stimulus  is  required  to  excite  the  anterior  roots 
than  when  these  reflex  impulses  of  the  posterior  root,  which  increase  the  excitability,  are  absent. 
Clearly,  a  less  stimulus  will  be  required  to  excite  a  nerve  already  in  a  gentle  state  of  excitement 
than  in  the  case  of  a  fibre  which  is  not  so  excited.  In  the  former  case,  the  discharging  stimulus 
becomes,  as  it  were,  superposed  on  the  excitement  already  present.      (Compare  §  362.) 

The  anterior  roots  of  the  spinal  nerves  supply  efferent  fibres  to — 

1.  All  the  voluntary  muscles  of  the  trunk  and  extremities. 

Every  muscle  always  receives  its  motor  fibres  from  5^7'^;'^/ anterior  roots  (not  from  a  single  nerve 
root).  Hence,  n'ery  root  supplies  branches  to  a  particular  group  of  muscles  {Preyer,  P.  Bert, 
Gad).  The  experiments  of  Ferrier  and  Yeo  show  that  stimulation  of  each  of  the  anterior  roots  in 
apes  (brachial  and  lumbosacral  plexuses)  caused  a  complex  coordinated  movement.  Section  of 
one  root  did  not  cause  complete  paralysis  of  these  muscles  concerned  in  the  coordinated  move- 
ments, although  the  force  of  the  movement  was  impaired.  These  experiments  confirm  the  results 
of  clinical  observation  on  man.  The  fibres  for  groups  of  muscles  of  different  functions  {e.g..  for 
flexors,  extensors)  arise  from  special  limited  areas  of  the  spinal  cord.  The  cervical  and  lumbar 
enlargements  of  the  spinal  cord  are  great  centres  for  highly  coordinated  muscular  movements. 

2.  The  anterior  roots  also  supply  motor  fibres  for  a  number  of  organs  pro- 
vided with  smooth  muscular  fibres,  e.  g.,  the  bladder  (§  280),  ureter,  uterus. 
[These  are  the  viscero-motor  nerves  of  Gaskell,  and  from  them  come  also  viscero- 
inhibitory  nerves.] 

3.  Motor  fibres  for  the  smooth  muscular  fibres  of  the  blood  vessels,  the  vaso- 
motor, vaso-constrictor,  or  vaso-hypertonic  nerves  [also  accelerator  or  aug- 
mentor  nerves  of  the  heart].  They  run  in  the  sympathetic  for  a  part  of  their 
course  (§  371). 

4.  Inhibitory  fibres  for  the  lilood  vessels.  These  are  but  imperfectly  known. 
They  are  also  called  vaso-dilator  or  vaso-hypotonic  nerves  (§  372).  [Also 
inhibitory  nerves  for  the  heart,  which  leave  the  spinal  axis  in  the  vagus.] 

5.  Secretory  fibres  for  the  sweat  glands  of  the  skin  (§  289).  For  a  part  of 
their  course  they  run  in  the  sympathetic. 

6.  The  trophic  fibres  of  the  tissues  (§  342,  I,  c). 


THE    SYMPATHETIC    NERVE.  649 

The  posterior  roots  contain  all  the  sensory  nerves  of  the  whole  of  the  skin 
and  the  internal  tissues,  except  the  front  part  of  the  head,  face,  and  the  internal 
part  of  the  head.  They  also  contain  the  tactile  nerves  for  the  areas  of  the  skin 
already  mentioned.  Stimuli  which  discharge  reflex  movements  are  conducted  to 
the  spinal  cord  through  the  posterior  roots.  The  sensory  fibres  of  a  mixed  nerve 
trunk  supply  the  cutaneous  area,  which  is  moved  by  those  muscles  (or  which  covers 
those  muscles — Preyef)  to  which  the  same  branch  supplies  the  motor  fibres 
{Schroder  van  der  Kolk).  The  special  distribution  of  the  motor  and  sensory 
nerves  of  the  body  belongs  to  anatomy  (Figs.  387,  388,  392,  393). 

356.  THE  SYMPATHETIC  NERVE.— [Anatomical.— The  sympathetic  nervous  system 
contains  a  large  number  of  non-medullated  or  Remak's  fibres,  and  consists  of  a  series  of  ganglia 
lying  on  each  side  of  the  vertebral  column  and  connected  to  each  other  by  interganglionic  fibres. 
The  typical  distribution  obtains  in  the  thoracic  region,  where  the  lateral  or  vertebral  ganglia  lie 
close  on  the  vertebr;e.  In  front  of  this  is  a  second  series  of  ganglia,  which  do  not  form  a  double 
line,  but  are  connected  with  the  former  and  with  each  other.  They  are  the  prevertebne  or  collat- 
eral ganglia,  e.g.,  semilunar,  inferior  mesenteric,  etc.,  the  nerves  connecting  them  with  the  former 
being  called  rami  efiferentes.  From  these  fibres  proceed  to  connect  them  with  ganglia  lying  in  or 
about  tissues  or  organs — the  terminal  ganglia  [Gtiskell).'\ 

[Each  spinal  nerve  in  this  region  is  connected  with  its  corresponding  sympathetic  ganglion  by 
the  ramus  communicans,  which  is  formed  by  fibres  both  from  the  anterior  and  posterior  roots  of 
a  spinal  nerve.  It  corresponds  to  the  viscer.Tl  nerve  of  the  morphologist,  and  is  composed  of  two 
parts — a  white  and  a  gray  ramus.  The  white  ramus  is  composed  entirely  of  meduUated  fibres, 
and  coming  from  the  anterior  and  posterior  roots  of  a  spinal  nerve,  passes  into  the  lateral  and 
collatenl  ganglia.  These  white  rami  occur  in  the  dog  only  from  the  2d  thoracic  to  the  2d  lumbar 
nerve  {Gaskell).  Above  and  below  this  the  rami  are  all  gray  and  composed  of  non-medullated 
nerve  fibres.] 

[In  man  the  four  upper  rami  communicantes  from  the  four  upper  cervical  nerves  all  join  the 
superior  cervical  ganglion  (Fig.  386,  G  g  s),  the  SIh  and  6th  join  the  middle  cervical,  the  7th  and 
8th  the  inferior  cervical  ganglion.  The  lowest  pair  of  ganglia  are  generally  united  by  a  loop  on 
the  front  of  the  first  coccygeal  vertebra,  and  they  lie  in  relation  with  the  coccygeal  ganglion.] 

[Cephalic  Portion. — As  the  sympathetic  ascends  to  the  head  it  forms  connections  with  many 
of  the  cranial  nerves,  and  there  is  a  free  exchange  of  fibres  between  these  nerves.  (The  function 
and  significance  of  these  exchanges  are  referred  to  under  the  physiology  of  the  cranial  nerves.)] 

[Dorsal  and  Abdominal  Portion. — Numerous  fibres  pass  from  these  parts  chiefly  to  the  MoraaV 
and  abdominal  i'avities.,vj\\tit  they  form  large  gangliated  plexuses, from  which  functionally  different 
fibres  proceed  to  the  different  organs.] 

[In  the  dog  the  2d,  3d,  4th,  and  5th  thoracic  pass  upward  into  the  cervical  sympathetic,  those  in 
the  dorsal  region  being  directed  downward  from  the  lateral  ganglia  to  form  the  splanchnics.  The 
gray  non-medullated  nerve  fibres  of  each  gray  ramus  are  connected  with  the  cells  of  its  ganglion 
(lateral);  the  fibres  do  not  go  beyond  the  ganglion, but  really  run  to  the  corresponding  spinal  nerve 
to  ramify  in  the  sheaths  of  the  nerves,  the  connective  tissue  on  the  veitebri-e  and  the  dura  mater, 
and  perhaps  the  other  spinal  membranes;  so  that,  according  to  Gaskell,  no  non-medullated  nerves 
leave  the  central  nervous  system  by  the  spinal  nerve  roots.  Thus  the  white  rami  communicantes 
alone  constitute  the  rami  visceralis  of  the  morphologist,  and  all  the  visceral  nerves  passing  out  from 
the  central  nervous  system  into  the  sympathetic  system  pass  out  by  them  alone.  All  the  nerves  in 
the  white  ramus  are  of  .small  calibre  (1.8  /t  to  2.7  p.)  and  medullated,  while  the  true  motor  fibres 
are  much  larger  (14.4  ,"■  to  19  ,'i).  The  small  while  can  be  traced  upward  as  medullated  fibres  into 
the  superior  cervical  ganglion,  and  in  the  thorax  over  the  lateral  to  form  the  splanchnics  into  the 
collateral  ganglia,  beyond  which  they  cease  to  be  medullated.  By  the  2d  and  3d  sacral  nerves 
some  fibres  of  smallest  calibre  issue  to  form  the  nervi  erigentes,  which  pass  over  and  do  not  com- 
municate with  the  lateral  ganglia,  but  enter  the  hypogastric  plexus,  whence  they  send  branches 
upward  to  the  inferior  mesenteric  plexus  and  downward  to  the  bladder,  rectum,  and  generative 
organs.     Caskell  proposes  to  call  them  the  pelvic  splanchnic  nerves.] 

[In  the  cervical  region  there  is  no  white  ramus,  and  the  nerve  roots  contain  no  nerve  fibres  of 
small  calibre.  But  in  this  region  rises  the  spinal  accessory  nerve,  between  the  anterior  and 
posterior  roots.  It  contains  small  and  large  nerve  fibres  ;  the  former  pass  into  the  internal  division 
of  this  nerve  and  join  the  ganglion  of  the  trunk  of  the  vagus,  while  the  large  motor  fibres  form  its 
external  branch  and  supply  the  sterno-mastoid  and  trapezius  muscles.] 

[All  the  vasomotor  nerves  arise  in  the  central  nervous  system,  and  they  leave  the  spinal  cord 
as  the  finest  medullated  fibres  in  the  anterior  roots  of  all  the  spinal  nerves  between  the  2d  thoracic 
and  2d  lumbar  (dog)  "along  the  corresponding  ramus  visceralis,  enter  the  lateral  or  main  sympa- 
thetic chain  of  ganglia,  where  they  become  non-medullated,  and  are  thence  distributed  either  directly 
or  after  communication  with  other  ganglia"  {Gaskelt).'\ 

["The  vaso-dilator  nerves  leave  the  central  nervous  system  among  the  fine  medullated  fibres, 


650  FUNCTIONS   OF   THE   CERVICAL   SYMPATHETIC. 

which  help  to  form  the  cervico- cranial  and  sacral  rami  viscerales,  and  pass  without  altering  their 
character  into  the  distal  ganglia"  (  Gaskell\.'\ 

["The  viscero- motor  ner\es  upon  which  the  peristaltic  contraction  of  the  thoracic  portion  of 
the  oesophagus,  stomach,  and  intestines  depends,  leave  the  central  nervous  system  in  the  outflow  of 
fine  mednllated  nerves  which  occurs  in  the  upper  part  of  the  cervical  region,  and  pass  by  way  of 
the  rami  viscerales  of  the  accessory  aud  vagus  nerves  to  the  ganglion  trunci  vagi,  where  they  become 
non-medullated  "  {^GaskeU).~\ 

["  The  inhibitory  nerves  of  the  circular  muscles  of  the  alimentary  canal  and  its  appendages  leave 
the  central  nervovis  system  in  the  anterior  roots,  and  pass  out  among  the  fine  medullated  fibres 
of  the  rami  viscerales  into  the  distal  ganglia  without  communication  with  the  proximal  ganglia  " 
(^Gaskell)?^ 

[Structure  of  a  Ganglion. — The  structure  of  the  sympathetic  nerve  fibres  and  nerve  cells  has 
already  been  described  in  \  32  [.  On  making  a  section  of  a  sympathetic  ganglion,  ('.^.,  the 
human  superior  cervical,  we  observe  groups  of  cells  with  bundles  of  nerve  fibres — chiefly  non- 
medullated — running  between  them,  and  the  whole  surrounded  by  a  laminated  capsule  of  connective 
tissue,  which  sends  septa  into  the  ganglion.  The  nerve  cells  have  many  processes,  and  are,  there- 
fore, multipolar,  and  each  cell  is  surrounded  by  a  capsule  with  nuclei  on  its  inner  surface  (Fig.  335, 
II).  The  processes  pierce  the  capsule,  and  one  of  them  certainly — and  perhaps  all  the  processes — 
are  connected  with  a  nerve  fibre.  Not  unfrequenlly  yellowish-brown  pigment  is  found  in  the  cell 
substance.  Similar  cells  have  been  found  in  the  ophthalmic,  sub- maxillary,  otic,  and  sphenopalatine 
ganglia] 

Functions. — The  following  is  merely  a  ^^«ifr«/ summary  : — 
I.  Independent  functions  of  the  sympathetic  are  those  of  certain  nerve 
plexuses  which  remain  after  all  the  nervous  connections  with  the  cerebro-spinal 
branches  have  been  divided.  The  activities  of  these  plexuses  may  be  influenced 
■ — either  in  the  direction  of  inhibition  or  stimulation — -through  fibres  reaching 
them  from  the  cerebro-spinal  nerves. 
To  these  belong  :  — 

1.  The  automatic  ganglia  of  the  heart  (§  58). 

2.  The  mesenteric  plexus  of  the  intestine  (§  161). 

3.  The  plexuses  of  the  uterus,  Fallopian  tubes,  ureters  (also  of  the  blood  and 
lymph  vessels). 

II.  Dependent  Functions. — Fibres  run  in  the  sympathetic,  which  (like  the 
peripheral  nerves)  are  active  only  when  their  connection  with  the  central  nervous 
system  is  maintained,  e.  g.,  the  sensory  fibres  of  the  splanchnic.  Others  again 
convey  impulses  from  the  central  nervous  system  to  the  ga/ig/ia,  while  the  ganglia, 
in  turn,  modify  the  impulses  which  inhibit  or  excite  the  movements  of  the  corre- 
sponding organs. 

The  following  statement  is  a  rhumi  of  the  functions  of  the  sympathetic,  according  to  the  ana- 
tomical arrangement :  — 

A.  Cervical  Part  of  the  Sympathetic. —  i.  Pupil-dilating  fibres  (com- 
pare Ciliary  gang/ion,  §  347,  I,  and  Iris,  §  39^:).  According  to  Budge,  these  fibres 
arise  from  the  spinal  cord  and  run  through  the  upper  two  dorsal  and  lowest  two 
cervical  nerves  into  the  cervical  sympathetic,  which  conveys  them  to  the  head. 
Section  of  the  cervical  sympathetic  or  its  rami  communicantes  causes  contraction 
of  the  pupil.  (The  central  origin  of  these  fibres  is  referred  to  in  §  362,  i,  and 
§367-  8.) 

2.  Motor  fibres  for  Miiller's  smooth  muscle  of  the  orbit,  and  partly  for  the 
external  rectus  muscle  (§  348). 

3.  Vasomotor  branches  for  the  outer  ear  and  the  side  of  the  face  {CI.  Ber- 
nard), tympanum  {Prttssak),  conjunctiva,  iris,  choroid,  retina  {only  in  part — see 
Ciliary  ganglion,  §347,  I),  for  the  vessels  of  the  cesophagus,  larynx,  thyroid  gland 
— fibres  for  the  vessels  of  the  brain  and  its  membranes  (Donders  and  Callcnfels^  ; 
but,  according  to  Nothnagel,  fibres  also  arise  from  the  cranial  nerves  which  form 
connections  with  the  carotid  plexus. 

4.  Secretory  (trophic)  and  vasomotor  fibres  for  the  salivary  glands  (§  145). 

5.  Sweat-secretory  fibres  (see  §  288,  II). 

6.  .\ccording  to  Wolferz  and  Demtschenko,  the  lachrymal  glands  receive  sym- 
pathetic secretory  fibres  (?). 


SECTION   AND    STIMULATION   OF   THE   CERVICAL    SYMPATHETIC.    651 

B.  Thoracic  and  Abdominal  Sympathetic. — First  of  all  there  is — 

1.  The  sympathetic  portion  of  the  cardiac  plexus  (§  57,  2),  which  receives 
accelerating  or  augmentor  fibres  for  the  heart  from  the  lower  cervical  and  ist 
thoracic  ganglion  {CI.  Bernard,  v.  Bezold,  Cyan,  Schmiedeberg).  The  fibres  arise 
partly  from  the  sympathetic  and  partly  from  the  plexus  around  the  vertebral  artery 
\v.  Bezold,  Bever).     (Compare  §370.) 

2.  The  cervical  sympathetic  and  the  splanchnic  contain  fibres  which,  when  their 
central  ends  are  stimulated,  excite  the  cardio-inhibitory  system  in  the  me- 
dulla oblongata  (Berns/ein). 

3.  The  cervical  sympathetic  contains  afferent  fibres  which,  when  stimulated, 
excite  the  vasomotor  centre  in  the  medulla  oblongata  {Auberf). 

4.  The  functions  of  the  splanchnic  are  referred  to  in  §§164,  175,  276  and 

371- 

5.  The  functions  of  the  coeliac  and  mesenteric  plexuses  are  referred  to  m 
§§  183  and  192.  After  extirpation  of  the  cceliac  ganglion,  Lamansky  observed 
temporary  disturbance  of  digestion,  undigested  food  being  passed  per  anum. 

6.  For  the  secretory  fibres  for  sweating,  see  §  289,  II. 

7.  Lastly,  the  abdominal  portion  of  the  sympathetic  contains  motor  and  vaso- 
motor fibres  for  the  spleen,  the  large  intestine  (accompanying  its  arteries),  bladder 
(§  280),  ureters,  uterus  (running  in  the  hypogastric  plexus),  vas  deferens  and  vesic- 
ulse  seminales.  Stimulation  of  all  of  these  nerve  channels  causes  increased  move- 
ment of  the  organs,  but  it  must  be  remembered  that  the  diminished  supply  of 
blood  thereby  produced  also  acts  as  a  stimulus  (§  161).  Section  of  these  nerves 
is  followed  by  dilatation  of  the  blood  vessels,  with  subsequent  derangement  of  the 
circulation,  and  ultimately  of  the  nutrition.  The  relation  of  the  suprarenal 
bodies  to  the  sympathetic  is  referred  to  in  §  103,  IV.  The  renal  plexus  is 
referred  to  in  §  276,  while  the  cavernous  plexus  is  treated  of  in  §436. 

Pathological. — Considering  the  numerous  connections  of  the  sympathetic,  we  would  naturally 
suppose  that  it  ofiers  an  extensive  area  for  pathological  changes.  It  is  to  be  observed  that  all  afifec- 
lions  involvint;  the  vasomotor  system  are  referred  to  in  ^  371. 

The  cervical  sympathetic  is  most  frequently  paralyzed  or  stimulated  'by  traumatic  conditions, 
wounds  by  bullets  or  knives,  tumors,  enlarged  lymph  glands,  aneurisms,  inflammation  of  the  apices 
of  the  lungs  and  the  adjacent  pleurjs,  while  exostoses  of  the  vertebrje  may  stimulate  it  in  part  or 
paralyze  it  in  part.  The  phenomena  so  produced  have  been  partly  analyzed  in  treating  of  the  cili- 
ary ganglion  (^  347,  I).  Stimulation  of  the  cervical  sympathetic  in  man  causes  dilatation  of 
the  pupil  (mydriasis  spastica),  pallor  of  the  face.'and  occasionally  hyperidrosis  or  profuse  sweating 
(I  289,  2,  and  ^  2S8) ;  disturbance  of  vision  for  near  objects,  as  the  pupil  cannot  be  contracted  (see 
Acfommoitafion')^  and  hence  the  spherical  aberration  of  the  lens  (§  39t)  must  also  interfere  with 
vision  ;  protrusion  of  the  eyeball  with  widening  of  the  palpebral  fissure.  Paralysis  or  section  of 
the  cervical  sympathetic  causes  increased  fullness  of  the  blood  vessels  of  the  side  of  the  head 
with  occasional  anidrosis.  Contraction  of  the  pupil  (myosis  paralytica),  which  undergoes  changes 
in  its  diameter  during  accommodation,  but  not  as  the  effect  of  the  stimulation  of  light — atropin 
dilates  it  slightly.  The  slit  between  the  eyelids  is  narrowed,  the  eyeball  retracted  and  sunk  in  the 
orbit,  the  cornea  somewhat  flattened,  and  the  consistence  of  the  eyeball  diminished.  Stimulation  of 
the  sympathetic  is  followed  by  an  increased secrdion  of  saliva  i,\  145).  The  above  described  symp- 
toms have  been  occasionally  accompanied  by  unilateral  atrophy  of  the  face. 

[Section  of  the  Cervical  Sympathetic. — This  experiment  is  easily  done  on 
a  rabbit,  preferably  an  albino  one.  Divide  the  nerve  in  the  neck,  and  immedi- 
ately thereafter  (i)  the  ear  and  adjoining  parts  on  that  side  become  greatly  con- 
gested with  blood,  blood  vessels  appear  that  were  formerly  not  visible,  as  a  result 
of  the  increased  quantity  of  blood  in  the  ear  (hyperaemia),  there  is  (2)  a  rise  of 
the  temperature  amounting  to  even  4°  to  6°  C.  {CI.  Bernard").  These  are  the 
vasomotor  changes.  (3)  The  pupil  is  contracted,  the  cornea  flattened,  and  there 
is  retraction  of  the  eyeball  and  consequent  narrowing  of  the  palpebral  fissure. 
These  are  the  oculo-pupillary  symptoms.  Stimulation  (electrical)  of  the  peri- 
pheral end  produces  the  opposite  results, — pallor  of  the  ears,  owing  to  contraction 
of  the  blood  vessels,  with  consequent  fall  of  temperature  ;  dilatation  of  the  pupil, 
bulging  of  the  cornea,  protrusion  of  the  eyeball  (exophthalmos),  and  widening 


652  COMPARATIVE HISTORICAL. 

of  the  palpebral  fissure.  At  the  same  time,  the  blood  vessels  to  the  salivary  glands 
are  contracted,  and  there  is  a  secretion  of  thick  saliva.  The  last  results  are  due  to 
the  vaso-constrictor  and  secretory  fibres.  The  vasomotor  and  oculo-pupillary  fibres, 
although  they  lie  in  the  same  trunk  in  the  neck,  do  not  issue  from  the  cord  by 
the  same  nerve  roots,  the  latter  come  out  of  the  cord  with  the  anterior  roots  of  the 
ist  and  2d  dorsal  nerves  (dog),  while  section  of  the  cord  between  the  2d  and  4th 
dorsal  vertebrae  produces  the  vasomotor  changes  only.  The  nasal  mucous  mem- 
brane and  lachrymal  gland  are  influenced  by  the  sympathetic] 

[Division  of  the  cervical  sympathetic  in  young  t;rou'ing  animals  results  in  hypertrophy  of  the 
ear,  and  increaseil  growth  of  the  hair  on  that  side  [Biddcry  \V.  S/irlitig).'] 

[The  vagosympathetic  nerve  (dog)  in  the  neck  contains  vaso-dilator  fibres  (really  in  the 
sympathetic  I  for  the  skin  and  mucous  membianes  of  that  side  of  the  head.  Weak  stimulation  of 
the  central  end  of  the  synipatlietic  causes  dilatation  of  the  blood  vessels  of  these  parts.  The  vaso- 
dilator fibres  of  the  superior  ma)cillary  nerve  probably  come  from  the  same  source.  The  centre  for 
these  nerves  is  in  the  dorsal  region  of  the  cord  between  the  Ist  and  5th  dorsal  vertebr.i?,  when  the 
fibres  pass  out  with  the  rami  communicantes  to  enter  the  cervical  sympathetic  (Diis/re  and  Moral). 
The  vaso-dilator  fibres  occur  in  the  posterior  segment  of  the  ring  of  Vieussens,  and  when  they  are 
stimulated  after  section  of  the  7tli  cranial  nei-ve,  there  is  a  '■  pseudomotor  "  elTect  on  the  muscles 
of  the  cheek  and  lip  (§  349I.] 

Irritation  in  the  area  of  the  splanchnic,  as  occurs  occasionally  in  lead  poisoning,  is  characterized 
by  violent  pain  (lead  colic),  inhibition  of  the  intestinal  movements  (hence,  the  persistent  constipa- 
tion), slowing  of  the  heart's  action,  brought  about  reflexly,  just  as  in  Goltz's  "  tapping"  experiment. 
Irritation  in  the  area  of  the  sensory  nerves  of  the  sympathetic  may  give  rise  to  that  condition  which 
is  called  by  Romberg  neuralgia  hypogastrica,  a  painful  affection  of  the  lower  abdominal  and  sacral 
regions,  hysteralgia,  neuralgia  testis,  which  are  localized  in  the  plexuses  of  the  sympathetic.  In 
affections  of  the  abdominal  sympathclic  there  may  be  severe  constipation,  with  diminished  or  in- 
creased secretion  of  the  intestinal  glands  {\  186). 

357.  COMPARATIVE— HISTORICAL.— Comparative.— Some  of  the  cranial  nerves 

maybe  al^sent,  others,  again,  may  be  abortive,  or  exist  as  branches  of  other  nerves.  The  facial 
nerve,  which  supplies  the  muscles  of  expression  in  man,  and  is,  at  the  same  time,  the  nerve  for  facial 
respiratory  movements,  diminishes  more  and  more  in  the  lower  classes  of  the  vertebrata, /(;W /««;<, 
with  the  diminution  of  the  facial  muscles.  In  birds  and  reptiles  it  supplies  the  muscles  of  the 
hyoid  bone,  or  the  superficial  cervical  muscles  of  the  nape  of  the  neck.  In  amphibians  (frog)  the 
facial  no  longer  exists  as  a  separate  nerve,  the  nerve  which  corresponds  to  it  springing  from  the  tri- 
geminus. In  fishes  the  5th  and  7th  nerves  form  a  joint  complex  nerve.  The  part  corresponding 
to  the  facial  (also  calle  1  ramus  opercularis  trigemini )  is  the  chief  motor  nerve  of  the  muscles  of  the 
gill  cover,  and  is,  therefore,  the  respiratory  nerve.  In  the  cyclostomata  (lamprey)  there  is  an  inde- 
pendent facial.  The  vagus  is  present  in  all  vertebrata;  in  fishes  it  gives  off"  a  large  nerve,  the  lat- 
eral nerve  of  the  body  (N.  lateralis),  which  runs  along  each  side  of  the  body  close  to  the  lateral 
canal.  It  is  also  present  ia  the  tadpole.  Its  rudimentary  representative  in  man  is  the  auricular 
branch.  In  the  frog  the  9th,  loth,  and  nth  arise  together  from  one  trunk,  and  the  7th  and  8th  from 
anDthiir.  In  fishes  and  amphibia  the  hypoglossal  is  the  first  cervical  nerve.  In  amphioxus  the  cere- 
bral and  spinal  nerves  are  not  disiinct  from  each  other.  The  spinal  nerves  are  remarkably  similar 
in  all  classes  of  the  vertebrata.  The  sympathetic  is  absent  in  the  cyclostomata,  where  it  is  repre- 
sented  by  the  vagus.  Its  course  is  along  the  vertebral  column,  where  it  receives  the  rami  commu- 
nicantes of  the  spinal  nerves.  In  the  region  of  the  head  its  connections  wdth  the  5th  and  loth  nerves 
are  soecially  developed.  In  frogs,  and  still  more  so  in  birds,  the  number  of  connections  with  the 
cranial  nerves  increases. 

Historical. — The  vagus  and  sympathetic  were  known  to  the  Hippocratic  School.  According  to 
Erasistratus,  all  the  nerves  proceed  from  the  brain  and  spinal  cord.  Herophilus  was  the  first  to 
distinguish  the  nerves  from  the  tendons,  which  Aristotle  confounded  with  each  other.  Marianus 
(So  A.D.)  recognized  seven  pairs  of  cranial  nerves.  Galen  was  in  possession  ot  a  wide  range  of  im- 
portant facts  in  the  physiology  of  the  nervous  system  (§  140) ;  he  observed  that  loss  of  voice  fol- 
lowed ligature  of  the  recurrent  nerves ;  and  he  was  acquainted  with  the  accessorius,  and  the  ganglia 
on  the  abdominal  nerves.  The  Cauda  equina  is  referred  to  in  the  Talmud ;  Goiter  (1573)  prescribed 
exactly  the  anterior  and  posterior  spinal  nerve  roots.  Van  Helmont  (f  1644)  st.ates  that  the  peri- 
pheral motor  nerves  also  give  rise  to  impressions  of  pain,  and  Cesalpinus  (1571)  remarks  that  inter- 
ruption of  the  blood  stream  makes  the  parts  insensible.  Thomas  Willis  described  the  chief  ganglia 
(1664).  In  Des  Cartes  there  is  the  first  indication  of  reflex  movements;  Stephen  Hales  and  Robert 
Whytt  showed  that  the  spinal  cord  was  necessary  for  such  acts.  Prochaska  described  the  reflex 
channels  [while  Marshall  Hall  established  the  doctrine  of  reflex,  or,  as  he  called  them,  "  diastal- 
tic  "  actions].  Duverney  (1761)  discovered  the  ciliary  ganglion.  Gall  traced  more  carefully  the 
course  of  the  3d  and  6th  nerves,  and  also  the  spinal  nerves  into  the  gray  matter.  Hitherto  only 
nine  nerves  of  the  brain  had  been  enumerated  ;  Sommerring  separated  the  facial  from  the  auditory 
nerve,  Andersch  the  9th,  loth,  and  nth  nerves. 


Physiology  of  the  Nerve  Centres. 


358.  GENERAL. — [The  nerve  fibres  and  nerve  cells  constitute  the  elements 
out  of  which  nerve  centres  are  formed,  being  held  together  by  connective  tissue. 
In  the  process  of  evolution  groups  of  nerve  cells  with  connecting  fibres  are  ar- 
ranged to  constitute  nervous  masses,  whereby  there  is  a  corresponding  integration 
of  function.  Thus  with  structural  integration  there  is  a  functional  integration. 
When  the  structure  suffers  so  also  does  the  function,  and  those  parts  which  are 
most  evolved,  as  well  as  those  actions  which  have  to  be  learned  by  practice,  are 
the  first  to  suffer  during  the  dissolution  of  the  nervous  system.] 

General  Functions. — The  central  organs  of  the  nervous  system  are  in  general 
characterized  by  the  following  properties  :  — 

1.  They  contain  nerve  cells,  which  are  either  arranged  in  groups  in  the  in- 
terior of  the  central  organs  of  the  nervous  system,  or  embedded  in  the  peripheral 
branches  of  the  nerves.  [Nerve  cells  are  centres  of  activity,  originate  impulses 
and  conduct  impulses  as  well,  while  nerve  fibres  are  chiefly  conductors.] 

2.  The  nerve  centres  are  capable  of  discharging  reflexes,  e.  g.,  reflex  motor, 
reflex  secretory,  and  reflex  inhibitory  acts. 

3.  The  centres  may  be  the  seat  of  automatic  excitement,  /.  e.,  they  may 
manifest  phenomena,  without  the  application  of  any  apparent  external  stimulus. 
The  energy  so  liberated  may  be  transferred  to  act  upon  other  organs.  This  auto- 
matic state  of  excitement  or  stimulation  may  be  continuous,  i.  e.,  may  be  continued 
without  interruption,  when  it  is  called  tonic  automatic  or  tonus  ;  or  it  may  be 
intermittent,  and  occur  with  a  certain  rhythm  {rhythmical  automatic). 

4.  The  central  organs  are  trophic  centres  for  the  nerves  proceeding  from 
them ;  they  may  also  perform  similar  functions  for  the  tissues  innervated  by 
them. 

5.  The  physical  activities  are  dependent  upon  an  intact  condition  of  the 
ganglionic  central  organs.  These  various  functions  are  distributed  over  different 
centres. 

As  a  single  momentary  stimulus,  e.  g.,  an  opening  induction  shock,  or  a  puncture  of  a  transverse 
section  of  the  spinal  cord,  may  produce  a  longer  tetanus,  whilst  the  same  stimulus,  if  applied  to  the 
motor  nerves,  causes  only  a  single  contraction,  it  seems  as  if  the  central  nervous  system  possessed 
the  property  of  transforming  an  instantaneous  stimulus  into  a  long-continued  state  of  stimulation 
{R.  Marchand).  The  organs  causing  continued  movement  are  the  ganglionic  cells  of  the  anterior 
horn  of  the  spinal  cord  [Bir/,-e). 

[The  term  "  centre  "  is  merely  applied  to  an  aggregation  of  ner\'e  cells  so  related  to  each  other 
as  to  subserve  a  certain  function,  but  inasmuch  as  these  cells  are  connected  to  each  other  and  with 
other  cells  in  many  ways,  various  combinations  of  them  may  result;  again,  we  have  also  to  take  in 
account  the  greater  or  less  resistance  in  some  paths  than  others,  so  that  the  variety  of  combinations 
which  these  cells  may  subserve  is  enormous.  The.-e  cells  give  off  processes  which  branch,  and 
anastomose  with  processes  from  other  cells.  Thus  innumerable  ways  are  opened  up  to  nervous 
impulses  by  these  combinations,  so  that  in  a  certain  way  we  may  regard  a  cell  as  a  junction  of  these 
conducting  fibres,  or  a  "  shunt"  whereby  an  impulse  may  be  shunted  on  to  one  or  other  branch  in 
the  direction  of  least  resistance,  or  in  the  best  beaten  path  as  it  were,  while  there  may  be  a  "  block  " 
in  other  directions.] 


658 


THE  SPINAL  CORD. 


359.  STRUCTURE    OF   THE    SPINAL    CORD.— [The  key  to  the 

study  of  the  central  nervous  system  is  to  remember  that  it  begins  as  an  involution 
of  the  epiblast,  and  is  original  tubular,  with  a  central  canal,  dilated  in  the  brain 
end  into  ventricles.  In  tiie  spinal  cord  there  are  three  concentric  parts:  first, 
the  columnar  ciliated  epithelium,  outside  this  the  central  gray  tube,  and  covering 
in  all  the  outer  white  conducting  fibres  (Hi/l).'] 

Structure.— The  spinal  cord  consists  of  white  matter  eNternally  and  gray  matter  internally.  [It 
is  invested  l)y  membranes,  the  pin  mater,  composed  of  two  layers  and  consisting  of  connective 
tissue  with  blood  vessels,  being  hrmly  adherent  to  the  white  matter  and  sending  septa  into  the 


the  centre  is  the  butterfly  form  of  the  gray  matter  surrounded  by  whil 
matter.    /,  posterior,  and  rt,  anterior,  horns  of  the  """■"-»"-■■  ■   ^ '^    r...=t..ri.^r  m^tc  -   AR    anr^rlnr  rnnts  nf 


of  the  spinal 


spinal  1 


L,  L,  thela 


J  .........  .   P  R,  posterior  . 

al :  P,  P,  the  posterior  colu 


substance  of  the  cord.  Both  layers  dip  into  the  anterior  median  fissure,  and  only  the  inner  one  into 
the  posterior  median  groove.  The  arachnoid  \%  a  more  delicate  memtirane  and  non-vascular,  while 
the  dura  maler  is  a  tough  membrane  lining  the  vertebral  canal,  and  forming  a  theca  or  protective 
coat  for  the  cord  (J  381).]  The  gray  matter  has  the  form  of  two  crescents  )-(  placed  back  to 
back  [or  a  capital  H]> '"  which  we  can  distinguish  an  anterior  (a)  and  a  posterior  horn  (/),  a 
middle  part,  and  gray  commissure  connecting  the  two  crescents.  In  the  centre  of  this  gray  com- 
missure is  a  canal — central  canal  — which  runs  from  the  calamus  scriptorius  downward  ;  it  is  lined 
throughout  by  a  single  layer  of  ciliated  cylindrical  epithelium  [in  the  fcetus,  the  cilia  not  being  visible 
in  the  adult],  and  the  canal  itself  is  the  representative  of  the  embryonal  "medullary  tube."  [The 
part  of  the  gray  commissure  in  front  of  this  canal  is  called  the  anterior,  and  the  part  behind,  the 
posterior  gxa.y  commissure.]  [In  front  of  the  gray  commissure,  and  between  it  and  the  base  of  the 
anterior  median  fissure,  are  bundles  of  white  nerve  fibres  passing  in  a  horizontal  or  oblique  direction 
from  the  anterior  column  of  one  side  to  the  gray  matter  of  the  anterior  cornu  of  the  opposite  side 
(Fig.  394).     These  decussating  fibres  constitute  the  white  commissure.] 

The  white  matter  surrounds  the  gray,  and  is  arranged  in  several  columns  [anterior,  lateial,  ami 
posterior — by  the  passage  of  the  nerve  roots  to  the  cornua].     Along  the  anterior  surface  of  the  cord 

654 


STRUCTURE   OF   THE   WHITE    MATTER. 


655 


there  runs  a  well-marked  fissure,  which  dips  into  the  cord  itself,  but  does  not  reach  the  gray  matter, 
as  a  mass  of  white  matter — the  white  commissure — runs  from  one  side  of  the  cord  to  the  other. 
Between  this  fissure,  known  as  the  anterior  median  fissure,  and  the  line  of  exit  of  the  anterior 
roots  of  the  spinal  nerves,  lies  the  anterior  column  (A);  the  white  matter  lying  laterally  between 
the  origin  of  the  anterior  and  posterior  roots  of  the  spinal  nerves  is  the  lateral  column  (L|,  while 
the  white  matter  lying  between  the  line  of  origin  of  the  posterior  roots  and  the  so-called  posterior 
median  fissure  is  the  posterior  column  (P).     [The  posterior  median  fissure  is  not  a  real  fissure 


Fig.  396. 


""Iti& 


— -^-^-^ 


Fig.  395. — Transverse  section  of  the  whit 
I-IG.  396. — Multipolar  nerve  cells  fro 
cell ;  6,  axis  cylinder ;  c,  gray  matter 


matter  01  the  spinal  cord  with  connective-tissue  septa  between  the  fibn 
the  gray  matter  of  the  anterior  horn  of  the  spinal  cord  (ox),  u,  ncr 
</,  white  matter  of  column  ;  e,  e,  branches  oi  cells. 


but  is  filled  up  with  the  inner  layer  of  the  pia  mater,  which  dips  down  from  the  under  surface  of 
this  membrane  quite  to  the  gray  matter  of  the  posterior  commissure.]  Each  posterior  column,  in 
certain  regions  of  the  cord,  may  be  subdivided  into  an  inner  part  lying  next  the  fissure,  the  postero- 
median or  Gall's  column,  or  the  inner  root  zone  (Charcot,  Fig.  403,  c) ;  and  an  outer  larger  part 
next  the  posterior  root,  known  as  the  postero-extemal  or  Burdock's  column,  or  the  outer  root  zone 
(Charcot,  Fig.  403,  </). 
The  white  matter  consists  chiefly  of  medullated  fibres  without  the  sheath  of  Schwann  and  Ran- 


FiG.  397. 


Diagram  of  the  absolute  and  relative  extent  uf  the  gray  r 
of  the  spinal  cord,  as  well  as  the  sectional  areas  of  th> 
P  C,  anterior,  lateral  and  posterior  columns :  Gr,  gray 


vier's  nodes,  but  provided  with  the  neuro-keratin  sheaths  of  KUhne  and  Ewald  [\  321),  the  fibres 
themselves  being  chiefly  arranged  longilittlinally.  The  nerve  fibres  of  the  nerve  roots,  as  well  as 
those  that  pass  from  the  gray  matter  into  the  columns,  have  a  transverse  or  oblique  course.  There 
are  also  decussating  fibres  in  the  anterior  or  white  commissure.  [In  a  transverse  section  of  the 
white  matter  of  the  spinal  cord  the  nerve  fibres  are  of  diff^erent  sizes,  and  appear  like  small  circles 
with  a  rounded  dot  in  their  centre — the  axis  cylinder;  the  latter  may  be  stained  with  carmine  or 
other  dye  (Fig.  395).     They  are  smallest  in  the  postero-median  or  Goll's  column,  and  largest  in  the 


656 


ARRANGEMENT  OF  NERVE  CELLS. 


crossed  and  direct  pyramidal  tracts,  which  are  motor.  The  white  substance  of  Schwann,  especially 
in  preparations  hardened  in  salts  of  chromium,  often  presents  the  appearance  of  concentric  lines. 
Fine  septa  of  connective  tissue  carrying  blood  vessels  lie  between  groups  of  the  nerve  fibres,  while 
here  and  there  between  the  nerve  fibres  may  be  seen  branched  neuroglia  corpuscles.  Immediately 
beneath  the  pia  mater  there  is  a  pretty  thick  layer  of  neuroglia,  which  invests  the  prolongations  of 
the  pia  into  the  cord.] 

[The  gray  matter  ditfers  in  shape  in  the  different  regions  of  the  cord,  and  so  does  the  gray 
commissure  (Fig.  39S),  The  latter  is  thicker  and  shorter  in  the  cervical  than  in  the  dorsal  region, 
while  it  is  very  narrow  in  the  lumbar  region.  '1  he  amount  of  gray  matter  undergoes  a  great  increase 
opposite  the  origins  of  the  large  nerves,  the  increase  being  most  marked  opposite  the  cervical  and 
lumbar  enlargements.  Ludwig  and  Woroschilotf  constructed  a  series  of  curves  from  measurements 
by  Stilling  of  the  sectional  areas  of  the  gray  and  white  matter  of  the  cord,  as  well  as  of  the  several 
nerve  roots.  These  curves  have  been  arranged  in  the  following  convenient  form  by  Schafer,  after 
Woroschiloff  (Fig.  397) : — 

[In  the  cervical  region  the  lateral  white  columns  are  large,  the  anterior  cornu  of  the  gray  matter 
is  wide  and  large,  while  the  posterior  cornu  is  narrow ;  Goll's  column  is  marked  off  by  a  depression 
and  a  prolongation  of  the  pia  mater;  the  cord  itself  is 
broadest  from  side  to  side.  In  the  dorsal  region  the  gray 
matter  is  small  in  animals,  and  both  cornua  are  narrow 
and  of  nearly  equal  breadth,  while  the  cord  itself  is 
smaller  and  cylindrical.  In  it  the  intermedio  lateral  and 
posterior  vesicular  groups  of  cells  are  distinct.  They  have, 
probably,  relations  to  viscera.  The  commissure  lies  well 
forward  betwten  the  crescents.  In  the  lumbar  region 
the  gray  matter  is  relatively  and  absolutely  greatest,  while 
the  white  lateral  columns  are  small,  the  central  canal  in 
tile  commissure  being  nearly  in  the  middle  of  the  cord. 
In  the  conus  medullans  the  gray  matter  makes  up  the 
great  mass  of  it,  with  a  few  white  fibres  externally  (Kig. 
39S).] 

1  he  anterior  cornu  of  the  gray  matter  is  shorter  and 
broader,  and  does  not  reach  so  near  to  the  surface  as  the 
posterior;  moreover,  each  anterior  nerve  root  arises  from 
it  by  several  bundles;  it  Contains  several  groups  of  large 
multipolar  ganglionic  cells  (Fig.  396);  the  posterior 
cornu  is  more  pointed,  longer  and  narrower,  and  reaches 
nearer  to  the  surface,  the  posterior  root  arising  by  a  single 
bundle  at  the  postero-lateral  fissure  ;  while  the  cornu  itself 
contains  a  few  fusiform  nerve  cells,  and  is  covered  by  the 
substantia  gelatinosa  of  Rolando,  which  is  merely  an 
accumulation  of  neuroglia. 

[The  outer  margin  of  the  gray  matter  near  its  middle 
is  not  so  sharply  defined  from  the  white  matter  as  else- 
where ;  and,  in  fact,  a  kind  of  anastamosis  of  the  gray 
matter  projects  into  the  lateral  column,  especially  in  the 
cervical  region,  constituting  \.\\t  processus  reticttlaris  (Fig 
399,  /)■] 

[Arrangement  of  Nerve  Cells. — The  nerve  cells  are 
arranged  in  four  groups,  forming  columns  more  or  less 
continuous.  There  are  those  of  the  anterior  and  posterior 
pinal  curd  in  dif-  horns,  those  of  the  lateral  column  (intermedio-lateral), 
igfi  t  e  iiiidi  ic  o  ^jjj  ji^g  po^terior  vesicular  column  of  Clarke.  The  ante- 
rior and  posterior  groups  exist  as  continuous  columns  along 
the  entire  cord.  The  cells  of  the  anterior  horn  being  very 
large  (67  to  135  (J-),  while  the  fusifomi  cells  of  the  posterior 
horn  are  iS  !>■  in  diameter.  Those  of  the  lateral  column 
are  distinct,  except  in  the  lumbar  and  cervical  enlarge- 
ments, where  they  blend  with  the  anterior  hom.  The  column  of  Clarke  (cells  40  to  90  p-)  is  dis- 
continued, and  is  limited  to  (l)  the  thoracic  region,  (2)  cervicocranial  region,  (3)  sacral  region, 
being  most  conspicuous  in  ( i )  ( Gaskell),  where  it  corresponds  absolutely  to  the  outflow  of  visceral 
nerves.  In  the  sacral  region  it  corresponds  to  the  "  sacral  nucleus  of  Stilling,"  while  in  the  cervical 
region  it  begins  in  the  dog  at  the  2d  cervical  nerve,  forming  the  cervical  nucleus,  being  continued 
above  into  the  nuclei  of  the  vagus  and  glosso-pharyngeal  nerves.  The  cells  of  this  column  give  rise 
to  small  mcdullated  nerve  fibres  or  the  leucenteric  fibres  of  Gaskell.] 

The  multipolar  ganglion  cells  are  largest,  and  arranged  in  groups  in  the  anterior  horns  of  the 
gray  matter  (Fig.  394 — "  motor  ganglionic  cells") ;  while  smaller  spindled-shaped  ("  sensory  ") 
cells  occur  in  much  smaller  numbers  m  the  gray  mailer  of  the  posterior  horn. 


ferent  regit 

enlargf 
medull 
F,  at  c 


al;  B 


A,  tfiroiigfi 

ttie  dorsal:  C,  tlie  lurab: 
;  D,  upper  part  of  the  cont 
E,  at  ttie  5th  sacral  vertebra 
c:  A,  B,  C,  enlarged  twice 
,  /,  posterit 


NEUROGLIA. 


657 


[In  a  longitudinal  section  of  the  cord  (Fig.  400)  these  cells  are  seen  to  be  arranged  in  columns, 
the  large  multipolar  cells  in  the  anterior  horn  (»;)  ;  at  the  same  time  the  longitudinal  direction  of 
the  nerve  fibres  in  the  anterior  {a)  and  posterior  white  columns  (<"),  the  horizontal  direction  of  the 
fibres  of  the  anterior  and  posterior  nerve  roots  {/>  andy).l 

The  gray  matter  contains  an  exceedingly  delicate  fibrous  network  of  the  finest  nerve  fibrils 
{Gerlach),  which  is  produced  by  the  repeated  division  of  the  protoplasmic  processes  of  the  multi- 
polar ganglionic  cells.  MeduUated  nerve  fibres  traverse  and  divide  in  the  gray  matter  and  become 
non-medullated  ;  some  of  them  merely  pass  through  the  gray  matter  of  the  non-medullated  fibres 
and  terminate  in  Gerlach's  network.  Fibres  pass  from  the  gray  matter  of  one  side  to  that  of  the 
other  through  the  commissures  in  front  of  and  behind  the  central  canal. 

Gerlach's  Theory. — According  to  Gerlach.  the  connection  of  the  fibres  and  cells  is  as  follows  : 
The  fibres  of  the  anterior  root  proceed  directly  to  the  ganglionic  cells  of  the  anterior  horn,  with 
which  they  form  direct  communications  by  means  of  the  unbranched  axial  cylinder  processes  (Fig. 
401,  2;).  The  gray  network  of  protoplasmic  processes,  produced  by  the  repeated  branchings  of  the 
fibres  of  these  cells,  gives  origin  to  broad  f\\>xss.     A  part  of  the  latter  (the  medinn  bundle)  passes 


section  of  the  spinal  cord  (I 
P.,  anterior  and  posterior  media 

;  ;  J,  gray  commissure  :  /,  reticular  format 


lateral,  and  posterior  column 

:11s  of  the  anterior  horn  ;  d,  posterioi 
lOt  bundles  ;  h,  posterior  root  bundle: 


through  the  anterior  white  commissure  to  the  other  side,  and  then  ascends  in  the  anterior  column  of 
the  opposite  side.  Other  fibres  (the  lateral  h\inA\e)  pass  into  the  lateral  column  of  the  same  side, 
and  ascend  in  it  as  far  as  the  decussation  of  the  pyramids,  where  they  cross  in  the  medulla  to  the 
other  side.  The  fibres  of  (ht  postfrior  root  enter  the  posterior  horn,  and,  after  dividing,  terminate 
in  the  nervous  protoplasmic  network  of  the  gray  matter.  By  means  of  this  network  they  are  con- 
nected indirectly  with  the  ganglionic  cells  of  the  posterior  horn,  which  are  said  not  to  have  an  axial 
cylinder  process.  The  gray  network,  which  connects  the  ganglia  of  the  anterior  and  posterior  horns 
with  each  other,  also  sends  fibres,  which  pass  to  the  other  side  of  the  cord  in  front  of  and  behind 
the  central  canal.  They  then  take  a  backward  course,  to  ascend  partly  in  the  posterior  horns  and 
partly  in  the  lateral  columns. 

Neuroglia. — The  connective  tissue  of  the  spinal  cord  arises  in  part  from  the  pia  mater  and 

passes  only  into  the  white  matter,  carrying  with  it  blood  vessels,  and  forming  septa,  which  separate  the 

nerve  fibres  into  bundles.   We  must  distinguish  from  the  ordinary  connective  tissue  that  special  form 

in  the  gray  matter  to  which  Virchow  gave  the  name  of  neuroglia,  which  is  the  proper  sustentacular 

42 


658 


BLOOD    VESSELS    OF    THE    SPINAL    COKD. 


tissue.  It  is  composed  of  a  fine  network,  which  consists  of  round  and  large  branched  cells  embedded 
in  a  completely  homogeneous  transparent  ground  substance.  The  central  canal  is  surrounded  with 
a  denser  layer  of  this  tissue,  known  as  the  "  central  ependyma."  The  neuroglia  is  also  abundant 
on  the  sides  and  apex  of  the  posterior  horns,  where  it  is  called  the  gelatinous  substance  of  Ro- 


Fii;.  400, 


Fig.  40ir 


,  |IWi^i'[^^f^^€ 


;,:ii...,yC— 


'"d" 


m 


Fig.  400. — Longiiudii 


1  of  the  human  soinal  cord,  a,  anterior,  tr,  posterior,  (/,  lateral  white  cohimns  ;  />, 
;/,  horizontal  (pyramidal)  fibres  passing  to  ;«,  cells  of  anterior  cornu  ;  «,  oblique 
fibres  of  posterior  root  FiG.  401. — Multipolar  nerve  cell,  from  the  anterior  horn  of  the  spinal  cord.  2,  axis 
cylinder  process  ;  y,  branched  processes. 

lando.     Similar  neurolgia  also  occurs  in  the  brain.     On  the  surface  of  the  central  nervous  system, 
and  in  the  eelatinous  substance,  is,  in  addition,  a  fine  network  of  neurokeratin  (|  321). 

[Blood  Vessels. — The  anterior  median  artery  gives  off  branches,  which  dip  into  the  fissure  of 
the  same  name,  pass  to  its  base,  and,  after  perforating  the  anterior  commissure,  divide  into  two 
branches,  one  for  each  mass  of  gray  matter,  and  each  branch  in  turn  splits  into  three,  which  supply 


Fig.  402. 


Fig.  403. 


Fig.  402.  — Injected  bl i  vessels  of  the  spi 

tbe  3d  dorsal  nerve.  The  black  pa 
crossed,  pyramidal  tracts  :  ^,  anterio 
e  and/,  mixed  lateral  paths  ;  h,  dire 


cord.  Fig.  403. — Scheme  of  the 
;  the  gray  matter,  z/,  anterior,  t 
tlumn  groimd  bundle;  cr,  GoU's 
erebellar  tracts. 


mducting  paths  in  the  spinal  cord  at 
Tc,  posterior,  root;  a,  direct,  and^, 
olumn ;  d,  postero-external  column  ; 


part  of  the  interior,  median,  and  posterior  gray  matter.  The  posterior  root  artery  enters  the  gray 
m.itter  along  the  course  of  the  posterior  nerve  roots.  Some  branches  also  pass  from  the  pia  mater 
into  the  substance  of  the  cord,  and  are  known  as  the  antero-  and  median-lateral  branches,  while 
others  dip  in  near  GoU's  column,  and  another  in  the  postero-external  column.     The  large  central 


flechsig's  systems  of  conducting  fibres.  659 

artery  supplies  the  gray  matter.  The  general  result  is  that  the  gray  matter  is  much  more  vascular 
than  the  white,  as  is  shown  in  Fig.  402.  Adamkiewicz  has  given  a  most  minute  description  of  the 
blood  vessels  of  the  spinal  cord.  Some  small  vessels  come  from  the  pia  and  send  branches  to  the 
white  matter,  and  unbranched  arteries  to  the  gray  matter,  where  they  form  a  capillary  plexus.  The 
blood  vessels  are  surrounded  by  perivascular  lymph  spaces  (//«).]  [With  regard  to  the  blood 
vessels  supplying  the  cord  as  a  whole,  Moxon  has  pointed  out  that,  owing  to  the  cord  not  being  as 
long  as  the  vertebral  canal,  the  lower  nerves  have  to  run  down  within  the  vertebral  canal  before 
they  emerge  from  the  appropriate  inter-vertebral  foramina.  As  reenforcing  arteries  enter  the 
cord  along  the  course  of  these  nerves,  necessarily  the  branches  entering  along  the  course  of  the 
lumbar  and  lower  dorsal  nerves  are  long,  and  this,  together  with  their  small  size,  offers  considerable 
resistance  to  the  blood  stream.  Hence,  perhaps,  why  the  lower  part  of  the  cord  is  so  apt  to  be 
atfected  by  various  pathological  conditions.] 

[Functions  of  the  Spinal  Cord. — ( i)  It  is  a  great  conducting  medium, 

conducting  impulses  upward  and  downward,  and  within  itself  from  side  to  side, 
(2)  the  great  reflex  centre,  or  rather  series  of  so-called  centres ;  (3)  impulses 
originate  within  it.] 

Conducting  Systems. — The  whole  of  the  longitudinal  fibres  of  the  spinal 
cord  may  be  arranged  systematically  in  special  bundles,  according  to  their  func- 
tion. 

[Methods. — The  course  of  the  fibres  and  their  division  into  so-called  systems  has  been  ascer- 
tained partly  by  anatomical  and  embryological,  partly  by  physiological  and  pathological 
means,  .-\part  from  exjierimental  methods,  such  as  dividing  one  column  of  the  cord  and  observing 
the  result<,  we  have  the  following  methods  of  investigation  :  (l)  Tiirck  found  that  injury  or  disease 
of  certain  parts  of  the  brain  was  followed  by  a  degeneration  downward,  or  secondary  descending 
degeneration  of  certain  of  the  nen'e  fibres  connected  with  the  seat  of  injury, ;  c,  tliey  were  sepa- 
rated from  their  trophic  centres  and  underwent  degeneration.  (2)  P.  Schieferdecker  found  also,  after 
section  of  the  cord,  that  above  and  below  the  level  of  the  section,  certain  definite  tracts  of  white  matter 
underwent  degeneration  [thus  showing  that  certain  tracts  had  their  trophic  centre  below ;  this  constitutes 
secondary  ascending  degeneration].  [(3)  Gudden's  Method. — He  showed,  as  regards  (he 
brain,  that  excision  of  a  sense  organ  in  a  young  growing  animal  was  followed  by  atrophy  of  the 
nerve  fibres  and  some  other  parts  connected  with  it.  Thus  the  optic  nerve  and  anterior  corpora 
quadrigemina  atrophy  after  excision  of  the  eyeball  in  young  rabbits.]  (4)  Embryological. — 
Flechsig  showed  that  the  fibres  of  the  cord  [and  the  brain  also  |  during  development  became  coz'ei-ed 
with  myelin  at  different  periods,  those  fibres  become  medullated  latest  which  had  the  longest 
course.     In  this  way  he  mapped  out  the  following  system  : — 

Flechsig's  System  of  Fibres. — i.  In  the  anterior  column  lie  (a)  the  un- 
crossed, anterior,  or  direct  pyramidal  tract ;  and  external  to  it  is  {b')  the  anterior 
ground  bundle,  or  anterior  radicular  zone  (Fig.  403). 

2.  In  the  posterior  column  he  distinguishes  (r)  Goll's  column,  or  the  pos- 
tero-median  (postero-internal)  column  ;  and  {d )  Burdach's  funiculus  cuneatus,  or 
the  posterior  radicular  zone,  or  the  postero-external  column. 

3.  In  the  lateral  column  are  {e)  the  anterior,  and  (/)  the  lateral  mixed  Y>a.ths, 
(g)  the  lateral  or  crossed  pyramidal  U&ct,  and  (h)  the  direct  cerebellar  ix'xc^..  All 
the  impulses  from  the  central  convolutions  [motor  areas]  of  the  cerebrum,  by 
means  of  which  voluntary  movements  are  executed,  are  conducted  by  the  pyra- 
midal tracts  a  and  ^  (|  365).  The  fibres  in  these  tracts  descend  from  the  cen- 
tral convolutions  [/.  c. ,  the  motor  areas],  pass  through  the  white  matter  of  the 
cerebrum,  converging  like  the  rays  of  a  fan  to  the  internal  capsule,  where  they  lie 
in  the  knee  and  anterior  two-thirds  of  its  posterior  segment  (the  fibres  for  the  face 
at  the  knee,  and  behind  in  order  those  for  the  arm  and  leg),  they  then  enter  the 
middle  third  of  the  crusta,  pass  through  the  pons  into  the  anterior  pyramids  of  the 
medulla  oblongata,  where  the  great  mass  crosses  over  to  the  lateral  column  of  the 
opposite  side  of  the  cord  (crossed  pyramidal  tract),  a  small  part  descending 
in  the  cord  on  the  same  side  as  the  antero-median  tract  (direct  pyramidal  tract, 
a).  In  the  cord  these  fibres  are  probably  connected  with  large  multipolar  nerve 
cells  in  the  anterior  cornu,  and  from  the  latter  the  motor  nerves  proceed  to  the 
muscles].  The  direct  cerebellar  tract,  h,  connects  the  cerebellum  directly  by  as- 
cending fibres,  which  proceed  through  the  restiform  body  from  Clarke's  cohniin 
of  nerve  cells  in  the  gray  matter.     As  fibres  from  the  posterior  roots  also  enter 


660 


SECONDARY    DEGENERATION    AND   TROPHIC   CENTRES. 


the  latter,  it  follows  that  h  connects  the  posterior  nerve  roots  of  the  trunks  (but 
not  of  the  extremities)  with  the  cerebellum ;  /',  ^, /(and  ?  a  small  part  of  d)  rep- 
resents the  channels  which  connect  the  gray  matter  of  the  spinal  cord  and  that  of 
the  medulla  oblongata;  they  represent  the  channels  for  reflex  effects,  and  they  also 
contain  those  fibres  which  are  the  direct  continuation  of  the  anterior  spinal  nerve 
roots,  which  enter  the  cord  at  different  levels  and  penetrate  into  the  gray  matter. 
In  e  and/there  are  some  sensory  paths.  Lastly,  c  unites  the  posterior  roots  with 
the  gray  nuclei  of  the  funiculi  graciles  of  the  medulla  oblongata  ;  d  connects  some 
of  the  posterior  nerve  roots  through  the  restiform  body  with  the  vermiform  pro- 
cess of  the  cerebellum  (^Flechsig).  The  direction  of  conduction  in  the  posterior 
columns,  which  are  continuations  of  some  of  the  fibres  of  the  posterior  roots,  is 
upward,  as  part  of  them  degenerates  upward  after  section  of  the  posterior  root. 
Of  the  fibres  of  each  posterior  root,  some  pass  directly  into  the  posterior  horn, 
another  part  ascends  in  the  posterior  column  of  the  same  side,  and  gradually,  as  it 
ascends,  it  comes  nearer  the  posterior  median  fissure.  Some  of  these  fibres  enter 
the  gray  matter  of  the  posterior  horn  at  a  higher  level.  The  fibres  of  the  posterior 

Fig.  404. 


d     2 


Transverse  section  of  the  spinal  cord  showing  the 
I,  i'  (CPTJ,  region  of  the  crossed  pyramidal  ti 
column  ;  LC,  lateral  column  {B.  Bramivell). 


1  tracts.  AR,  anterior,  TR,  posterior  root : 
:t  pyramidal  tract;   PEC,  pustero-external 


columns  run  upward  only  as  far  as  the  decussation  of  the  pyramids,  where  they 
seem  to  end,  or  at  least  form  connections  with  the  nerve  cells  of  the  funiculi  gra- 
ciles [clava],  and  cuneati  [triangular  nucleus]. 

Further,  the  transverse  sectional  area  of  the  direct  and  crossed  pyramidal  tracts  [a  and^i-),  the 
lateral  cerebellar  tract  (/;),  and  Goll's  column  (r)  gradually  diminish  from  above  downward;  they 
serve  to  connect  intracranial  central  parts  with  the  ganglionic  centres  distributed  along  the  spinal 
cord.  The  anterior  root  bundle  {^b),  the  funiculus  cuneatus  ((/),  and  the  anterior  mixed  lateral  tracts 
(£')  vary  in  diameter  at  different  parts  of  the  cord,  corresponding  to  the  number  of  nerve  roots.  It 
has  been  concluded  from  this  that  these  tracts  serve  to  connect  the  gray  matter  at  different  levels  in 
the  cordwitli  each  other,  and  ultimately  with  the  medulla  oblongata,  so  that  they  do  not  pass  directly 
to  the  higher  parts  of  the  brain  (Fig.  397). 

Nutritive  Centres  of  the  Conducting  Paths. — Tiirck  observed  that  the 
destruction  of  certain  parts  of  the  brain  caused  a  secondary  degeneration  of 
certain  parts  of  the  cord,  corresponding  to  the  parts  called  pyramidal  tracts  hy 
Fleschig  (Fig.  404).  P.  Schieferdecker  found  the  same  effects  heloui  where  he 
divided  the  spinal  cord  in  a  dog.  Hence  it  is  concluded  that  the  nutritive  or 
trophic  centre  of  the  pyramidal  tracts  lies  in  the  cerebrum.  The  trophic  centre  for 


REFLEX   SPASMS. 


661 


the  fibres  of  the  anterior  root  lies  in  the  multipolar  nerve  cells  of  the  anterior 
cornu  of  the  gray  matter  of  the  cord.  After  section  of  the  spinal  cord,  GoU's 
column  and  the  direct  cerebellar  tracts  degenerate  upward.  The  nutritive  centre 
of  the  latter  is  very  probably  in  the  nerve  cells  of  Clarke's  column,  and  that  of 
the  former  perhaps  in  the  spinal  ganglion  of  the  posterior  root.  Those  fibres  of 
the  spinal  cord  which  do  not  degenerate  after  section  of  the  cord,  especially  numer- 
ous in  the  lateral  and  anterior  columns  {Schieferdecker,  Singer),  are  commissural 
in  function,  connecting  ganglionic  cells  with  each  other,  and  are,  therefore,  pro- 
vided with  a  trophic  centre  at  both  ends. 

Time  of  Development. — With  regard  to  the  time  of  development  of  the  individual  systems, 
Flechsig  finds  that  the  first  formed  paths  are  those  between  the  periphery  and  the  central  gray  matter, 
especially  the  nerve  roots,  i.  e.,  they  are  the  first  to  be  covered  with  the  myelin.  Then  fibres  which 
connect  the  gray  matter  at  different  levels  are  formed — the  fibres  which  connect  the  gray  matter  of 
the  cord  with  the  cerel)ellum,  and  also  the  former  with  the  tegmentum  of  the  cerebral  peduncle.  At 
last  the  fibres  which  connect  the  ganglia  of  the  pedunculus  cerebri,  and  perhaps  also  the  gray  matter 
of  the  cortex  cerebri  with  the  gray  matter  of  the  cord  are  formed.  In  cases  of  anencephalousfcetuses, 
/.  e.,  where  the  cerebrum  is  absent,  neither  the  pyramidal  tracts  nor  the  pyramids  are  developed.  In 
the  brain  before  birth,  medullated  nerve  fibres  are  formed  in  the  paracentral,  central  and  occipital 
convolutions,  and  in  the  island  of  Reil,  and  last  of  all  in  the  frontal  convolutions  ( Tiiczek). 

360.  SPINAL  REFLEXES. — By  the  term  reflex  movement  is  meant  a  movement  caused 
by  the  stimulation  of  an  afferent  (sensory)  nerve.     The  stimulus,  on  being  applied  to  an  afferent 


Fig.  405. 


Fig.  406. 


Fig.  405. — Scheme  of  a  ref 
Fig.  406- — Section  of  a  sp 

surface  ;  M,  muscle  ;  S,  sk 


S,  skin  ;  M,  muscle  ;  N,  nerve  cell,  with  of,  afferent,  anii  e/,  efferent  fibres, 
segment,  showing  a  unilateral  and  crossed  reflex  act.     A,  anterior,  and  P,  posterior 
G,  ganglion. 


nerve,  sets  up  a  state  of  excitement  (nervous  impulse)  in  that  nerve,  which  state  of  excitement  is 
transmitted  or  conducted  in  a  i-<'«/>-;)»^/a/ direction  along  the  nerve  to  the  centre  (spinal  cord  in  this 
case),  where  the  nerve  cells  represent  the  nerve  centre  ;  in  the  centre,  the  impulse  is  transferred 
to  the  motor,  efferent  or  centrifugal  c\\3.wnt\.  Three  factors,  therefore,  are  essential  for  a  reflex 
motor  act — a  centripetal  or  afferent  fibre,  a  transferring  centre,  a  centrifugal  or  efl^erent  fibre  ;  these 
together  constitute  a  reflex  arc  (Fig.  405).  In  a  purely  reflex  act,  all  voluntary  activity  is  ex- 
cluded. 

Reflex  movements  may  be  divided  into  the  three  following  groups  : — 

I.  The  simple  or  partial  reflexes,  which  are  characterized  by  the  fact  that  stimulation  of  a 
sensory  area  discharges  movement  in  one  muscle  only,  or,  at  least,  in  one  limited  group  of  muscles. 
Examples  :  A  blow  upon  the  knee  causes  a  contraction  in  the  quadriceps  extensor  cruris ;  contact 
with  the  conjunctiva  causes  closure  of  the  eyelids.  In  the  former  case  the  afferent  channels  arise 
in  the  tendon  of  the  quadriceps,  and  the  efferent  channels  lie  in  the  nerve  which  supplies  the  quad- 
riceps; in  the  latter  case  the  afferent  nerve  is  the  5th  and  the  efferent  the  7th  cranial  nerve.  In 
the  former  case  the  centre  is  in  the  lumbar  region  of  the  cord ;  in  the  latter,  in  the  gray  matter  of 
the  medulla  oblongata. 

II.  The  Extensive  Incoordinate  Reflexes,  or  Reflex  Spasms. — These 
movements  occur  in  the  form  of  clonic  or  tetanic  contractions;  individual  groups 
of  muscles,  or  all  the  muscles  of  the  body,  may  be  implicated.  Causes  :  K  reflex 
spasm  depends  upon  a  double  cause — {a)  Either  the  gray  matter  or  the  spinal  cord  is 
in  a  condition  oi  exalted  excitability ,  so  that  the  nervous  impulse,  after  having  reached 


662 


SUMMATION    OF   STIMULI    AND    PFLUGER  S    LAW. 


Fig,   407. 


the  centre,  is  easily  transferred  to  the  neigh- 
boring centres.  This  excessive  excitability 
is  produced  by  certain  poisons,  more  espe- 
cially by  strychnin,  brucia,  caffein  {Aubert), 
atropin,  nicotin,  carbolic  acid,  etc.  The 
slightest  touch  applied  to  an  animal  poi- 
soned with  strychnin  is  sufficient  to  throw 
the  animal  at  once  into  spasms.  Pathologi- 
cal conditions  may  cause  a  similar  result ; 
thus,  there  is  excessive  excitability  in  hydro- 
phobia and  tetanus.  On  the  other  hand, 
the  central  organ  may  be  in  such  a  condi- 
tion that  extensive  reflexes  cannot  take 
place ;  thus,  in  the  condition  of  apnoea, 
the  spasms  that  occur  in  poisoning  with 
strychnin  do  not  take  place  (_/.  Roserithal 
and  Leiibe,  Uspensky),  and  the  same  result 
is  brought  about  by  passive  artificial  respi- 
ratory movements  {v.  Ebner — §  361,  3). 
The  performance  of  other  passive  periodic 
movements  in  various  parts  of  the  body  also 
produces  a  similar  condition  (Bitchheini). 
If  the  spinal  cord  be  cooled  very  consider- 
ably, reflex  spasms  may  not  occur  {Ktanie). 
(b)  Extensive  reflex  movements  may  also 
take  place  when  the  discharging  stimulus 
is  very  strong.  Examples  of  this  condi- 
tion occur  m  man;  thus,  intense  neuralgia 
may  be  accompanied  by  extensive  spasmodic 
movements. 

[Fig.  407  shows  the  mechanism  of  simple  and  comple-K  reflex  movements.  Suppose  the  skin  to 
be  stimulated  at  P,  an  impulse  is  sent  to  A,  and  from  it  to  a  muscle,  I,  on  the  same  side,  resulting 
in  a  unilateral  simple  reflex  movement.  The  resistance  being  less  m  this  direction  than  in  the 
other  channels.  If  the  impulse  be  stronger,  or  the  transverse  resistance  in  the  cord  diminished,  the 
impulse  may  pass  to  B,  theijce  to  2,  resulting  in  a  symmetrical  reflex  movement  on  both  sides. 
But  if  a  very  strong  impulse  reaches  the  cord,  or  if  the  excitability  of  the  gray  matter  be  increased, 
e.  g.,  by  strychnin,  the  resistance  to  the  dift'usion  of  the  impulse  is  diminished,  and  it  passes  upward 
to  C  and  1),  resulting  in  more  complex  movements;  thus,  there  is  irradiation — or  it  may  even 
affect  the  centres  in  the  medulla  oblongata,  E,  giving  rise  to  general  convulsive  movements.] 

Summation  of  Stimuli. — By  this  term  is  meant  that  a  single  weak  stimulus, 
which  in  itself  is  incapable  of  discharging  a  reflex  act,  may,  if  repeated  sufficiently 
often,  produce  this  act.  The  single  impulses  are  conducted  to  the  spinal  cord, 
in  which  the  process  of  "summation  "  takes  place.  According  to  J.  Rosenthal, 
3  feeble  stimuli  per  second  are  capable  of  producing  this  effect,  although  16 
stimuli  per  second  are  most  effective.  On  increasing  the  number  of  stimuli  per 
second,  no  further  increase  of  the  reflex  act  is  possible.  Other  observers  (^Stir- 
ling, Ward)  have  found  that  stimuli,  such  as  induction  shocks,  are  active  within 
much  wider  limits,  e.g.,  from  0.05  to  0.4  second  interval.  W.  Stirling  has  shown 
that  it  is  extremely  probable  that  all  reflex  acts  are  due  to  the  repetition  of  impulses 
in  the  nerve  centres. 

[Strychnin  interferes  with  the  summation  of  stimuli,  but  the  reflex  excitability  is  so  greatly  exalted 
that  a  minimal  stimulus  is  at  the  same  time  a  maximal  one.] 

Pfliiger's  Law  of  Reflex  Actions. — (i)  The  reflex  movement  occurs  on  the  same  side  on  which 
the  sensory  nerve  is  stimulated,  while  only  those  muscles  contract  whose  nerves  arise  from  the  same 
segment  of  the  spinal  cord.  (2)  If  the  reflex  occurs  on  the  othet-  side,  only  the  corresponding 
muscles  contract.  (3)  If  the  contractions  be  unequal  upon  the  two  sides,  then  the  most  vigorous 
contractions  always  occur  on  the  side  which  is  stimulated.     (4)  If  the  reflex  excitement  extends  to 


GOLTZ'S    CROAKING    EXPERIMENT.  663 

other  motor  nerves,  those  nerves  are  always  affected  which  lie  in  the  direction  of  the  medulla 
oblongata.     Lastly,  all  the  muscles  of  the  body  may  lie  thrown  into  contraction. 

Crossed  Reflexes. — They  are  cvceptions  to  these  rules.  If  the  region  of  the  eye  be  irritated 
in  a  frog  whose  cerebrum  is  removed,  there  is  frequently  a  reflex  contraction  in  the  hind  limb  of  the 
opposite  side  [Liic/isinger,  Langendorffy  In  beheaded  iritons  and  tortoises,  and  in  deeply-narcotized 
dogs  and  cats,  tickling  one  fore  limb  is  frequently  followed  by  a  movement  of  the  hind  limb  of  the 
opposite  side  [Luc/isinger).  This  phenomenon  is  called  a  "crossed  reflex"  (Fig.  406).  If  the 
spinal  cord  be  divided  along  the  middle  line  throughout  its  entire  extent,  then,  of  course,  the  reflexes 
are  confined  to  one  side  only  (Schiff). 

Extensor  Tetanus. —  General  spasms  usually  manifest  themselves  as  "extensor  tetanus,"  because 
the  extensors  overcome  the  flexor  muscles.  Nerves  which  arise  from  the  medulla  oblongata  may 
be  excited  through  the  stimulation  of  distant  afi'erent  nerves,  without  general  spasms  being  produced. 

Strychnin  is  the  most  powerful  reflex-producing  poison  we  possess,  and  it  acts  upon  the  gray 
matter  of  the  spinal  cord.  [An  animal  poisoned  with  strychnin  exhibits  tetanic  spasms  on  the  appli- 
cation of  the  slightest  stimulus.  \\\  the  muscles  become  rigid,  but  the  extensors  overcome  the 
flexors.]  If  the  heart  of  a  frog  be  ligatured,  and  the  poison  alterward  applied  directly  to  the  spinal 
cord,  reflex  spasms  are  produced,  proving  that  strychnin  acts  upon  the  spinal  cord.  During  the 
spasm  the  heart  is  arrested  in  diastole,  owing  to  the  stimulation  of  the  vagus,  while  the  arterial 
blood  pressure  is  greatly  increased,  owing  to  stimulation  of  the  central  vasomotor  centres  of  the 
medulla  oblongata  and  spinal  cord.  Mammals  may  die  from  asphyxia  during  the  attack  ;  still,  after 
large  doses,  death  may  occur,  owing  to  paralysis  of  the  spinal  cord,  due  to  the  frequently-recurring 
spasms.  Fowls  are  unaffected  by  comparatively  large  doses.  [We  can  prove  that  strychnin  docs 
not  produce  spa.-.ms  by  acting  on  the  brain,  muscle  or  nerve.  Destroy  the  brain  of  a  frog,  divide 
one  sciatic  nerve  high  up,  and  inject  a  small  dose  of  strychnin  into  the  dorsal  lymph  sack;  in  a  few 
minutes  all  the  muscles  of  the  body,  except  those  supplied  by  the  divided  nerve,  will  be  in  spasms, 
showing  that,  although  the  poisoned  blood  has  circulated  in  the  nerves  and  muscles  of  the  leg,  it 
does  not  act  on  them.     Destroy  the  spinal  cord,  and  the  spasms  cease  at  once.] 

Other  Poisons. — Chlorojorm  diminishes  the  reflex  excitability  by  acting  upon  the  centre,  and 
a  similar  effect  is  produced  by  picrotoxin,  morphia,  narcotin,  thebain,  aconitin,  quinine,  hydrocyanic 
acid.  [W.  .Stirling  finds  that  chloral,  potassic  bromide  and  chloride,  ammonium  chloride,  but  not 
sodium  chloride,  greatly  diminish  the  reflex  excitability.     Nicotin  increases  it  in  Uog%\fyeusbeig)  ] 

A  constant  current  of  electricity  passed  longitudmally  through  the  cord  diminishes  the  reflexes 
[A'antf),  especially  if  the  direction  of  the  current  is  from  above  downward  (Legros  and  Onimus, 
Uspensky'). 

III.  Extensive  coordinated  reflexes  are  due  to  stimulation  of  a  sensory 
nerve,  causing  the  discharge  of  complicated  reflex  movements  in  whole  groups  of 
different  muscles,  the  movements  being  "purposive"  in  character,  i.  e.,  as  if 
they  were  intended  for  a  particular  purpose. 

Methods. — The  experiments  are  made  upon  cold-blooded  animals  (decapitated  or  pithed  frogs, 
tortoises,  or  eels),  or  upon  mammals.  In  the  latter,  artificial  respiration  is  kept  up,  and  the  lour 
arteries  going  to  the  head  are  ligatured,  in  order  to  eliminate  the  action  of  the  brain  \Sig.  Mayer, 
Luchsinger).  The  reflexes  of  the  lower  part  of  the  spinal  cord  may  be  studied  on  animals  ^or  men), 
in  cases  where  the  spinal  cord  is  divided  transversely  in  the  upper  dorsal  region.  In  such  cases 
some  time  must  elapse  m  order  that  the  primary  effect  of  the  lesion  (the  so-called  shock),  which 
usually  causes  a  diminution  of  the  reflexes,  may  pass  off.  Very  young  mammals  exhibit  reflexes  lor 
a  considerable  time  after  they  are  beheaded. 

Examples. —  i.  The  protective  movements  of  pithed  or  decapitated  frogs. 
[If  a  drop  of  a  dilute  acid  be  applied  to  the  skin  of  such  a  frog,  immediately  it 
strives  to  get  rid  of  the  offending  body,  and  it  generally  succeeds  in  doing  so.] 
Similarly,  it  kicks  against  any  fixed  body  pushed  against  it.  These  movements 
are  so  purposive  in  their  character,  and  the  actions  of  groups  of  muscles  are  so 
adjusted  to  perform  a  particular  act,  that  Pfliiger  regarded  them  as  directed  by 
and  due  to  "consciousness  of  the  spinal  cord."  If  a  flame  be  applied  to  the  side 
or  part  of  the  body  of  an  eel,  the  body  is  moved  away  from  the  flame.  The  tail 
of  a  decapitated  triton,  tortoise,  newt,  eel,  or  snake  is  directed  toward  a  gentle 
stimulus,  but  if  a  violent  stimulus  is  used,  it  is  directed  away  from  it  {Luchsinger). 

2.  Goltz's  Croaking  Experiment. — .\  pithed  (male)  frog,  i.e.,  one  with  its 
cerebral  lobes  alone  removed  (^or  one  with  its  eyes  or  ears  destroyed — Langendorff ), 
croaks  every  time  the  skin  of  its  back  or  flanks  is  gently  stroked.  [Some  male 
frogs,  when  held  up  by  the  finger  and  thumb  immediately  behind  the  fore  legs, 
croak  every  time  gentle  pressure  is  made  on  their  flank.] 


664  REFLEX   TIME    AND    INHIBITION    OF    REFLEXES. 

3.  Goltz's  "  Embrace  Experiment."— During  the  breeding  season,  in 
spring,  the  part  of  the  body  of  the  male  frog,  between  the  skull  and  the  fourth 
vertebra,  embraces  every  rigid  object  which  is  brought  into  contact  with,  and 
gently  stimulates,  the  skin  over  the  sternum. 

4.  In  mammals  (dogs)  the  following  reflex  acts  are  performed  by  the  posterior 
part  of  the  spinal  cord,  even  after  it  is  separated  from  the  rest  of  the  cord  : 
Scratching  with  the  hind  feet  a  part  of  the  skin  which  has  been  tickled  (just  as 
in  intact  animals) ;  the  movements  necessary  for  emptying  the  bladder  and  for 
deffecation,  as  well  as  those  necessary  for  erection  ;  the  movements  necessary  for 
parturition  {Goltz,  Freusberg  and  Gergens).  Coordinated  movements  do  not,  as 
a  rule,  occur  simultaneously  in  portions  of  the  spinal  cord  lying  widely  apart  after 
removal  of  the  medulla  oblongata.  According  to  Ludwig  and  Owsjannikow,  the 
medulla  oblongata,  perhaps,  contains  a  reflex  organ  of  a  higher  order,  which  forms, 
as  it  were,  a  centre  for  combining,  through  the  medium  of  the  nerve  fibres,  the 
various  reflex  provinces  in  the  spinal  cord. 

5.  Coordinated  reflexes  may  occur  in  man  during  sleep,  and  during  patho- 
logical comatose  conditions. 

Most  of  the  movements  which  we  perform  while  we  are  awake,  and  which  we  execute  uncon- 
sciously  or  even  when  our  psychical  activities  are  concentrated  upon  some  other  object — really 

belong  to  the  category  of  coordinated  reflexes.     Many  complicated  motor  acts  must  first  be  learned 

g_  cr,^  dancing,  skating,  riding,  walking — before  unconscious  harmonious  coordinated  reflexes  can 

again   be   discharged.     The   coordinated   reflex   movements  of  coughing,  sneezing,  and   vomiting 
depend  upon  the  spinal  cord,  together  with  the  medulla  oblongata. 

The  following  facts  are  also  important : — 

1.  Reflexes  are  more  easily  and  more  completely  discharged  when  the  specific 
end  organ  of  the  afferent  nerve  is  stimulated  than  when  the  trunk  of  the  nerve 
is  stimulated  in  its  course  {Marshall  Hall,  i8j~). 

2.  A  stronger  stimulus  is  required  to  discharge  a  reflex  movement  than  for  the 
direct  stimulation  of  motor  nerves. 

3.  A  movement  produced  reflexly  is  of  shorter  duration  than  the  corresponding 
movement  executed  voluntarily.  Further,  the  occurrence  of  the  movement  after 
the  moment  of  stimulation  is  distinctly  delayed.  In  the  frog,  a  period  nearly  twelve 
times  as  long  elapses  before  the  occurrence  of  the  contraction  than  is  occupied  in 
the  transmission  of  the  impulse  in  the  sensory  and  motor  nerves  {Helmholtz,  18^4). 
Thus,  the  spinal  cord  offers  resistance  to  the  transmission  of  impulses  through  it. 

The  term  "reflex  time  "  is  applied  lo  the  time  necessary  for  transferring  the  impulse  from  the 
afferent  fibre  to  the  nerve  cells  of  the  cord,  and  from  them  to  the  efferent  fibre.  In  the  frog  it  is 
equal  to  o.ooS  to  0.015  second.  The  time,  however,  is  increased  by  almost  one-third  if  the  impulse 
pass  to  the  other  side  of  the  cord,  or  if  it  pass  along  the  cord,  e.  g.,  from  the  sensory  nerves  of  the 
anterior  extremity  to  the  motor  roots  of  the  posterior  limb.  Heat  diminishes  the  reflex  time  and 
increases  the  reflex  excitability.  Lowering  the  temperature  (winter  frogs),  as  well  as  the  reflex  ex- 
citing poisons  already  mentioned,  lengthen  the  reflex  lime,  while  the  reflex  excitability  is  simulta- 
neously increased.  Conversely,  the  reflex  time  diminishes  as  the  strength  of  the  stimulus  increases, 
and  it  may  even  become  of  minimal  duration  (^J.  Rosenthal).  The  reflex  time  is  determined  by 
ascertaining  the  moment  at  which  the  sensory  nerve  is  stimulated,  and  the  subsequent  contraction 
occurs.  Deduct  from  this  the  time  of  latent  stimulation  (|  298,  1),  and  the  time  necessary  for  the 
conduction  of  the  impulse  (§  298)  in  the  afferent  and  efferent  nerves  {v.  Helmholtz,  J.  Rosenthal, 
E.xner,  1  Fundi). 

[Influence  of  Poisons. — The  latent  period  and  reflex  time  are  influenced  by  a  large  number 
of  conditions.  In  a  research  as  yet  unpubhshed,  W.  Stirling  finds  that  the  latent  period  may  re- 
main nearly  constant  in  a  pithed  frog  for  nearly  two  days,  when  tested  by  Tiirck's  method.  Sodic 
chloride  does  not  influence  the  time,  nor  does  sodic  bromide  or  iodide.  Potassic  chloride,  however, 
lengthens  it  enormously,  or  even  abolishes  reflex  action  after  a  very  short  time,  and  so  do  potassic 
bromide,  ammonium  chloride  and  bromide,  chloral  and  croton-chloral.  The  lithia  salts  also  lengthen 
the  reflex  time,  or  abohsh  the  reflex  act  after  a  time.] 

361.  INHIBITION  OF  THE  REFLEXES.— Within  the  body  there 
are  mechanisms  which  can  suppress  or  iiihihit  the  discharge  of  reflexes,  and  they 
may  therefore  be  termed  mechanisms  inhibiting  the  reflexes.     These  are  :  — 


EXAMPLES    AND    NATURE    OF    INHIBITION.  665 

1.  Voluntary  Inhibition. — Reflexes  may  be  inhibited  voluntarily,  both  in 
the  region  of  the  spinal  cord  and  brain.  Examples  :  Keeping  the  eyelids  open 
when  the  eyeball  is  touched  ;  arrest  of  movement  when  the  skin  is  tickled.  We 
must  observe,  however,  that  the  suppression  of  reflexes  is  possible  only  up  to  a 
certain  point.  If  the  stimulus  be  strong,  and  repeated  with  sufficient  frequency, 
the  reflex  impulse  ultimately  overcomes  the  voluntary  effort.  It  is  impossible  to 
suppress  those  reflex  movements  which  cannot  at  any  time  be  performed  volun- 
tarily. Thus,  erection,  ejaculation,  parturition,  and  the  movements  of  the  iris, 
are  neither  direct  voluntary  acts,  nor  can  they,  when  they  are  excited  refle.xly,  be 
suppressed  by  the  will. 

2.  Setschenow's  inhibitory  centre  is  another  cerebral  apparatus,  which 
in  the  frog  is  placed  in  the  optic  lobes.  If  the  optic  lobes  be  separated  from 
the  rest  of  tlie  brain  and  spinal  cord  by  a  section  made  below  it,  the  reflex 
excitability  is  increased.  If  the  optic  lobes  be  stimulated  with  a  crystal  of 
common  salt  or  blood,  the  reflex  movements  are  suppressed.  The  same  results 
obtain  when  only  one  side  is  operated  on.  Similar  organs  are  supposed  to 
be  present  in  the  corpora  quadrigemina  and  medulla  oblongata  of  the  higher 
vertebrates. 

[Quinine  greatly  diminishes  the  reflex  excitability  in  the  frog,  but  if  the  medulla  oblongata  be 
divided,  ihe  reflex  excitability  of  the  cord  is  restored.  The  depression  is  ascribed  by  Chaperon  to 
the  action  of  the  quinine  on  Setschenow's  centres.] 

3.  Strong  stimulation  of  a  sensory  nerve  inhibits  reflex  movements.  The 
reflex  does  not  take  place  if  an  afferent  nerve  be  stimulated  very  powerfully 
(Goltz,  Lni'isson,A.  Fick,amt  Erknmeyer).  Examples:  Suppressing  a  sneeze 
by  friction  of  the  nose  [compressing  the  skin  of  the  nose  over  the  exit  of  the 
nasal  nerve]  ;  suppression  of  the  movements  produced  by  tickling,  by  biting  the 
tongue.  Very  violent  stimulation  may  even  suppress  the  coordinated  reflex 
movements  usually  controlled  by  voluntary  impulses.  Violent  pain  of  the  abdom- 
inal organs  (intestine,  uterus,  kidneys,  bladder,  or  liver)  may  prevent  a  person 
from  walking  or  even  from  standing.  To  the  same  category  belongs  the  fact  that 
persons  fall  down  when  internal  organs  richly  supplied  with  nerves  are  injured, 
there  being  neither  injury  of  the  motor  nerves  nor  loss  of  blood  to  account  for  the 
phenomenon. 

It  is  important  to  note  that  in  the  suppression  of  reflexes,  antagonistic  muscles  are  often  thrown 
into  action,  whether  voluntarily  or  by  the  stimulaion  of  sensory  nerves, /.^.,  reflexly.  In  some 
cases,  in  order  to  cause  suppression  of  the  reflex,  it  appears  to  be  suflicient  to  direct  our  attention  to 
the  execution  of  such  a  complicated  reflex  act.  'thus,  some  persons  cannot  sneeze  when  they  think 
intently  upon  this  act  itself  (ZJrtrrc/w).  The  voluntary  impulse  rapidly  reaches  the  reflex  centre, 
and  begins  to  influence  it  so  that  the  normal  course  of  the  reflex  stimulation,  due  to  an  impulse  from 
the  peripher\',  is  interfered  with  i^Sihlosser'). 

[Nature  of  Inhibition. — The  foregoing  view  assumes  the  existence  of  inhibitory  centres,  but  it 
is  important  to  point  out  that  it  has  been  attempted  to  explain  this  phenomenon  without  postulating 
the  existence  of  inhibitory  centres.  During  inhibition  the  function  of  an  organ  is  restrained — dur- 
ing paralysis  it  is  abolished,  so  that  there  is  a  sharp  distinction  between  the  two  conditions.  The 
analogy  between  inhibitory  phenomena  and  the  effects  of  interference  of  waves  of  light  or  sound 
has  been  pointed  out  by  Bernard  and  Romanes,  while  Lauder  Brunton  has  shown  good  reason  for 
placing  the  question  on  a  physical  basis,  and  indicating  that  inhibition  is  not  dependent  on  the  ex- 
istence of  special  inhibitory  centres,  but  that  stimulation  and  inhibition  are  different  phases  of 
excitement,  the  two  terms  being  relative  conditions  depending  on  the  length  of  the  path  along  which 
the  impulse  has  to  travel  and  the  rate  of  its  transmission.  Brunton  points  out  that  the  known  facts 
are  more  consistent  with  an  hypothesis  of  the  interference  of  waves,  one  with  another,  than  that 
there  are  inhibitory  centres  for  every  so-called  inhibitory  act  in  the  body  (see  p.  614).] 

[Some  drugs  affect  the  reflex  excitability  directly  by  acting  on  the  spinal  cord,  ^.(.'.,  meihylconine, 
but  other  drugs  may  produce  the  same  result  indirectly  by  affecting  the  heart  and  the  blood  supply 
to  the  cord.  If  the  abdominal  aorta  of  a  rabbit  be  compressed  for  a  few  minutes  to  cut  off  the 
supply  of  blood  to  the  cord  and  lower  limbs,  temporary  paraplegia  is  produced.] 

If  frogs  be  asphyxiated  in  air  deprived  of  all  its  (J,  the  brain  and  spinal  cord  become  completely 
unexcitable,  and  can  no  longer  discharge  reflex  acts.  The  motor  nerves  and  the  muscles,  however, 
suffer  very  little,  and  may  retain  their  excitability  for  many  days  [Auliert). 


666  THE    SUPERFICIAL    KEFLEXES. 

Tiirck's  method  of  testing  the  reflex  excitability  of  a  frog  is  the  following  : 
A  frog  IS  pithed,  and  after  it  has  recovered  from  the  shock  its  foot  is  dipped  into 
dilute  sulphuric  acid  [^2  per  1000].  The  time  which  elapses  between  the  leg  being 
dipped  in  and  the  moment  it  is  withdrawn  is  noted.  [The  time  may  be  estimated 
by  means  of  a  metronome,  or  the  movements  may  be  inscribed  upon  a  recording 
surface  {Baxt).  The  time  which  elapses  is  known  as  the  "  period  of  latent  stim- 
ulation."] 

This  time  is  greatly  prolonged  after  the  optic  lobes  have  been  stimulated  with  a  crystal  of 
common  salt  or  blood,  or  after  the  stimulation  of  a  sensory  nerve. 

Setschenow  distinguished  tactile  reflexes,  which  are  discharged  by  stimulation  of  the  nerves  of 
touch;  and  pathic,  which  are  due  to  stimulation  of  ji-Kiorj' (patn-conducting)  fibres.  He  and 
Paschutin  suppose  that  the  tactile  reflexes  are  suppressed  by  voluntary  impulses,  and  the  pathic  by 
the  centre  in  the  optic  lobes. 

Theory  of  Reflex  Movements. — The  following  theory  has  been  propounded  to  account  for  the 
phenomena  already  described  :  It  is  assumed  that  the  afferent  fibre  witliin  the  gray  matter  of  the 
spinal  cord  joins  one  or  more  nerve  cells,  and  thus  is  placed  in  communication  in  all  directions  with 
the  network  of  fibres  in  the  gray  substance.  Any  impulse  reaching  the  gray  matter  of  the  cord  has 
to  overcome  considerable  resistance.  The  least  resistance  lies  in  the  direction  of  those  efferent 
fibres  which  emerge  in  the  same  plane  and  upon  the  same  side  as  the  entering  fibre.  Thus  the 
feeblest  stimulus  gives  rise  to  a  simple  reflex,  which  generally  is  merely  a  simple  protective  move- 
ment for  the  part  of  the  skin  which  is  stimulated.  Still  greater  resistance  is  opposed  in  the  direction 
of  other  motor  ganglia.  If  the  reflex  impulse  is  to  pass  to  these  ganglia,  either  the  discharging 
stimulus  must  be  considerably  increased,  or  the  resistance  within  the  connections  of  the  ganglia  of 
the  giay  matter  must  be  diminished.  The  latter  condition  is  produced  by  the  action  of  the  above- 
named  poisons,  as  well  as  during  general  increased  nervous  excitability  (hysteria,  nervousness). 
1  bus,  extensive  reflex  spasms  may  be  produced  either  by  increasing  the  stimulus  or  by  diminishing 
the  resistance  to  conduction  in  the  spinal  cord.  Those  conditions  which  render  the  occurrence  of 
reflexes  more  difficult,  or  abolish  them  altogether,  must  be  regarded  as  increasing  the  resistance  in 
the  reflex  arc  in  the  cord.  The  action  of  the  reflex  inhibitory  mechanism  may  be  viewed  in  a 
similar  manner. 

The  fibres  of  the  reflex  arc  must  have  a  connection  with  the  reflex  inhibitory  paths ;  we  must 
assume  that  equally  by  the  reflex  inhibitory  stimulation  resistance  is  introduced  into  the  reflex  arc. 
The  explanation  of  extensive  coordinated  movements  is  accompanied  with  difliculties.  It  is  assumed, 
that  by  use  and  also  by  heredity,  those  ganglionic  cells  which  are  the  first  to  receive  the  impulse, 
are  placed  in  the  path  of  least  resistance  in  connection  with  those  cells  which  transfer  the  impulse 
to  the  groups  of  muscles,  whose  contraction,  resulting  in  a  coordinated  purposive  movement,  pre- 
vents the  body  or  the  limb  from  being  affected  by  any  injurious  influences. 

Pathological. — Anomalies  of  reflex  activity  afford  an  important  field  to  the  physician  in  the 
investigation  of  nervous  diseases.  Enfeeblement,  or  even  complete  abolition  ot  the  reflexes 
may  occur:  (i)  Owing  to  diminished  sensibility  or  complete  insensibility  of  the  afferent  fibres; 
(2)  in  analogous  aflfections  of  the  central  organ  ;  (J)  or,  lastly,  of  the  efferent  fibres.  Where  there 
is  general  depression  of  the  nervous  activity  (as  after  shocks,  compression  or  inflammation  of  the 
central  nervous  organs;  in  asphyxia,  in  deep  coma,  and  in  consequence  of  the  action  of  many 
poisons),  the  reflexes  may  be  greatly  diminished  or  even  abolished. 

[Reflexes. — The  physician,  by  studying  the  condition  of  the  reflexes,  can 
form  an  idea  as  to  the  condition  of  practically  every  inch  of  the  spinal  cord. 
There  are  three  groups  of  reflexes,  {li)  the  superficial,  [Jt)  the  deep  or  tendon, 
((t)  the  organic  reflexes.] 

[The  superficial  or  skin  reflexes  are  excited  by  stimulating  the  skin,  e.g.,  by 
tickling,  pricking,  scratching,  etc.  We  can  obtain  a  series  of  reflexes  from  below 
as  far  up  as  the  lower  part  of  the  cervical  region.  The  plantar  reflex  is  obtained 
by  tickling  the  soles  of  the  feet,  when  the  leg  on  that  side,  or,  it  may  be,  both 
legs  are  drawn  up.  It  is  always  present  in  health,  and  its  centre  is  in  the  lumbar 
enlargement  of  the  cord.  The  cremasteric  reflex  is  well  marked  in  boys,  and  is 
easily  produced  by  exciting  the  skin  on  the  inner  side  of  the  thigh,  when  the 
testicle  on  that  side  is  retracted.  The  gluteal  reflex  consists  in  a  contraction  of 
the  gluteal  muscles,  when  the  skin  over  the  buttock  is  stimulated.  The  abdo- 
minal reflex  consists  in  a  similar  contraction  of  the  abdominal  muscles,  when  the 
skin  over  the  abdomen  in  the  mammary  line  is  stimulated.  Tiie  epigastric 
reflex  is  obtained  by  stimulating  the  skin  in  front  between  the  fourth  and  sixth 
ribs.     The  interscapular  reflex  results  in  a  contraction  of  the  muscles  attached 


TENDON    REFLEXES. 


667 


to  the  scapula,  when  the  skin  between  the  scapulae  is  stimulated, 
responds  to  the  lower  cervical  and  upper  dorsal  region.] 


Its  centre  cor- 


[The   following  table,  aflei 
segments  on  which  it  depends 

'  Cervical 6 


Gowers,  shows  the  relation  of  each  reflex  to  the  spinal  segment  or 


1 

5  V  Interscapular. 

I  J 

5) 

6  V  Epigastric. 

7) 

81 

9l 
lo  ]•  Abdominal. 

"  I 

I2j 


1  umbar I  )  r-  .     • 

,.  I  Cremastenc. 

3  J   I  A'k«  /^e/7ex. 

][        •*  I  Gluteal. 

Sacral ')-5!si 

2  1 1  I   I  Plantar. 

"         sJ'^GI-  Vesical. 

"         4  Rectal. 

"         5  J  Sexual.] 


Tendon  Reflexes. — -Under  pathological  conditions,  special  attention  is 
directed  to  the  so-called  tendon  reflexes,  which  depend  upon  the  fact  that  a  blow 
upon  a  tendon  (e.g.,  the  quadriceps  femoris,  tendo-Achilles,  etc.),  discharges  a 
contraction  of  the  corresponding  muscle  {^Westphal,  Erb  (1875),  Eitlenberg  and 
others)  ;  that  the  patellar  tendon  reflex  (also  called  "  knee  phenomenon  ")  or  simply 
"  knee  reflex,"  or  "knee  jerk,"  is  invariably  absent  in  cases  of  ataxic  tabes 
dorsalis,  while  in  spastic  spinal  paralysis  it  is  abnormally  strong  and  extensive 
{Erb).  [The  "knee  jerk"  is  elicited  by  percussing  the  ligamentum  patella;, 
and  is  due  to  a  sing/c  spasm  of  the  rectus.  The  latent  period  is  .03  to  .04  second, 
and  it  is  argued  by  Waller  and  others  that  it  is  doubtful  if  this  tendon  reflex  is  sub- 
served by  a  spinal  nervous  arc,  while  admitting  the  effect  of  the  spinal  cord  in 
modifying  the  response  of  the  muscle.]  .Section  of  the  motor  nerves  abolishes 
the  patellar  phenomenon  in  rabbits  {Sehultz),  and  so  does  section  of  the  cord 
opposite  the  5th  and  6th  lumbar  vertebra  {Tschirje70,  Senator).  Landois  finds 
that  in  his  own  person  the  contraction  occurs  0.048  second  after  the  blow  upon 
the  ligamentum  patellse.  Accordmg  to  Waller,  the  patellar  reflex  and  the  tendo- 
Achilles  reflex  occurs  0.03  to  0.4  second,  and  according  to  Eulenberg,  0.032 
second  after  the  blow.  According  to  Westphal  these  phenomena  are  not  simple 
reflex  processes,  but  complex  conditions  intimately  dependent  upon  the  muscle 
tonus,  so  that  when  the  tonus  of  the  quadriceps  femoris  is  diminished  the  phe- 
nomenon is  abolished.  In  order  that  the  phenomenon  may  take  place,  it  is  neces- 
sary that  the  outer  part  of  the  ])osterior  column  of  the  spinal  cord  remain  intact 
(^Westphal).  [A  "jaw  jerk  "  is  obtained  by  suddenly  depressing  the  lower  jaw 
{Go7vers,  Beevor  and  Be  JVattez'i7/e),  a.nd  the  last  observer  finds  that  the  latent 
period  is  .02  second,  and  if  this  be  the  case,  it  is  an  argument  against  these  so-called 
"tendon  reflexes"  being  true  reflexes,  and  that  they  are  direct  contractions  of 
the  muscles  due  to  sudden  stimulation  by  extension.] 

.\nother  important  diagnostic  reflex  is  the  "  abdominal  reflex  "  (O.  Eosen- 
bach),  which  consists  in  this,  that  when  the  skin  of  the  abdomen  is  stroked,  e.  g., 
with  the  handle  of  a  percussion  haminer,  the  abdominal  muscles  contract.  When 
this  reflex  is  absent  on  both  sides  in  a  cerebral  affection,  it  indicates  a  diff"use 
disease  of  the  brain  ;  its  absence  on  one  side  indicates  a  local  affection  of  the  op- 
]iosite  half  of  the  brain.  The  cremasteric,  conjunctival,  mammilary, 
pupillary,  and  nasal  reflexes  may  also  be  specially  investigated.  In  hemiplegia 
complicated  with  cerebral  lesions,  the  reflexes  on  the  paralyzed  side  are  diminished, 
whilst  not  unfrequently  the  patellar  reflex  maybe  increased.  In  extensive  cerebral 
aff"ections  accompanied  by  coma  the  reflexes  are  absent  on  both  sides,  including,  of 
course,  those  of  the  anus  and  bladder  (<9.  Rosenbach). 

[Horsley  finds  that  in  the  deepest  narcosis  produced  by  nitrous  oxide  gas  the  superficial  reflexes 
(f./.,  plantar,   conjunctival)   are  abolished,  when  the  deep  (knee  jerk)   remain.     Ana?niia  of  the 


668  CENTRES   IN    THE   Sl'INAL   CORD. 

lumbar  enlargement  (compression  of  the  abdominal  aorta)  causes  disappearances  of  both  reflexes 
(Prh'ost).  Chloroform  and  asphyxia  abolish  the  deep  as  well  as  the  superficial  reflexes.  Horsley 
regards  the  so-called  deep  reflex  or  knee  jerk  not  as  depending  on  a  centre  in  the  cord,  but  the  con- 
traction of  the  rectus  femoris  is  due  to  local  irritation  of  the  muscle  from  sudden  elongation.] 

[Method. — The  knee  jerk  is  easily  elicited  by  striking  the  patellar  tendon 
with  the  edge  of  the  hand  or  a  percussion  hammer  when  the  leg  is  semi-flexed,  as 
when  the  legs  are  hanging  over  the  edge  of  a  table  or  when  one  leg  is  crcssed  over 
the  other.  It  is  almost  invariably  present  in  health,  but  it  becomes  greatly  exag- 
gerated in  descending  degeneration  of  the  lateral  columns  and  lateral  sclerosis.] 

[Ankle  clonus  is  another  tendon  reflex,  and  it  is  never  present  in  health.  If 
the  leg  be  nearly  extended,  and  pressure  made  upon  the  sole  of  the  foot  so  as  sud- 
denly to  flex  the  foot  at  the  ankle,  a  series  of  (5  to  7  per  second)  rhythmical 
contractions  of  the  muscles  of  the  calf  takes  place.  Gowers  describes  a  modifi- 
cation elicited  by  tapping  the  muscles  of  the  front  of  the  leg,  the  "front  tap  con- 
traction." Ankle  clonus  is  excessive  in  sclerosis  of  the  lateral  columns  and  spastic 
paralysis.] 

[The  organic  reflexes  include  a  consideration  of  the  acts  of  micturition,  erec- 
tion, ejaculation,  defajcation,  and  those  connected  with  the  motor  and  secretory 
digestive  processes,  respiration,  and  circiUation.] 

[In  "  ankle  clonus  "  excited  by  sudden  passive  flexion  of  the  foot,  there  is  a  multiple  spasm  of 
the  gastrocnemius.  Here  also  the  latent  period  is  about  0.3  to  0.4  second  and  the  rhythm  8  to  10 
per  second.  This  short  latent  period  has  led  some  observers  to  doubt  the  essentially  reflex  nature 
of  this  act.] 

When  we  are  about  to  sleep  (^  374)  there  is  first  of  all  a  temporary  increase  of  the  reflexes;  in 
the  first  sleep  the  reflexes  are  diminished,  and  the  pupils  are  contracted.  In  deep  sleep  the  abdom- 
inal, cremasteric,  and  patellar  reflexes  are  absent;  while  tickling  the  soles  of  the  feet  and  the  nose 
only  acts  when  the  stimulus  is  of  a  certain  intensity.  In  narcosis,  e.  g.,  chloroform  or  morphia, 
the  abdominal,  then  the  conjunctival  and  patellar  reflexes  disappear;  lastly,  the  pupils  contract  (O. 
Rosenb(2ch). 

Abnormal  increase  of  the  reflex  activity  usually  indicates  an  increase  of  the  excitability  of  the 
reflex  centre,  although  an  abnormal  sensibility  of  the  afferent  nerve  may  be  the  cause.  As  the  har- 
monious equilibrium  of  the  voluntary  movements  is  largely  dependent  upon  and  regulated  by  the  re- 
flexes, it  is  evident  that  in  aftections  of  the  spinal  cord  there  are  frequent  disturbances  of  the  volun- 
tary movements,  e,  g.^  the  characteristic  disturbance  of  motion  in  attempting  to  walk,  and  in  grasp- 
ing movements  exhibited  by  persons  sufi'ering  from  ataxic  tabes  dorsahs  [or,  as  it  is  more  generally 
called,  locomotor  ataxia.~\ 

362.  CENTRES  IN  THE  SPINAL  CORD.— At  various  parts  of  the 
spinal  cord  are  placed  centres  capable  of  being  excited  reflexly,  and  which  can 
bring  about  the  discharge  of  certain  complicated,  yet  well  coordinated,  motor 
acts.  These  centres  .still  retain  their  activity  after  the  spinal  cord  is  separated  from 
the  medulla  oblongata  ;  further,  those  centres  lying  in  the  lower  part  of  the  spinal 
cord  still  retain  their  activity  after  being  separated  from  the  higher  centres,  but  in 
the  normal  intact  body  they  are  subjected  to  the  control  of  higher  reflex  centres 
in  the  medulla  oblongata.  Hence,  we  may  speak  of  them  as  subordinate  spinal 
centres.  The  cerehnim,  also,  partly  by  the  production  of  perceptions,  and  partly 
as  the  organ  of  volition,  can  excite  or  suppress  the  action  of  certain  of  these  sub- 
ordinate spinal  centres.     [For  the  significance  of  term  "  Centre,"  see  p.  653.] 

I.  The  cilio-spinal  centre  (Budge)  connected  with  the  dilatation  of  the 
pupil  lies  in  the  lower  cervical  part  of  the  cord,  and  extends  downward  to  the 
region  of  the  first  to  the  third  dorsal  vertebra.  It  is  excited  by  diminution  of 
light ;  both  pupils  always  react  simultaneously,  when  one  retina  is  shaded.  Uni- 
lateral extirpation  of  this  part  of  the  spinal  cord  causes  contraction  of  the  pupil 
on  the  same  side.  The  motor  fibres  pass  out  by  the  anterior  roots  of  the  two  lower 
cervical  and  two  upper  dorsal  nerves,  into  the  cervical  sympathetic  (§  392).  Even 
the  idea  of  darkness  may  sometimes,  though  rarely,  cause  dilatation  of  the  pupil 
{.Budge\ 

In  goats  and  cats  this  centre,  even  after  being  separated  from  the  medulla  oblongata,  can  be  ex- 
cited directly  by  dyspnceic  blood,  and  also  retlexly  by  the  stimulation  of  sensory  nerves,  e.g.y  the 


MUSCLE   TONUS.  669 

median,  especially  when  the  reflex  excitability  of  the  cord  is  increased  by  the  action  of  strychnin  or 
atropin  [Luc/isinger).     For  the  dilator  centre  in  the  medulla  oblongata  see  §  367,  8. 

2.  The  ano-spinal  centre  {Budget  or  centre  controlling  the  act  of  defaeca- 
tion.  The  afferent  nerves  lie  in  the  hfemorrhoidal  and  inferior  mesenteric 
plexuses,  the  centre  at  the  5th  (dog)  or  6th  to  7th  (rabbit)  lumbar  vertebra;  the 
efferent  fibres  arise  from  the  pudendal  plexus  and  pass  to  the  sphincter  muscles. 
For  the  relation  of  this  centre  to  the  cerebrum  see  §  160.  After  section  of  the 
spinal  cord  [in  dogs],  Goltz  observed  that  the  sphincter  contracted  rhythmically 
upon  the  finger  introduced  into  the  anus;  the  coordinated  activity  of  the  centre 
therefore  would  seem  to  be  possible  only  when  the  centre  remains  in  connection 
with  the  brain. 

3.  The  vesico-spinal  centre  {Budge)  for  regulating  micturition,  or  Budge's 
vesico-spinal  centre.  The  centre  for  the  sphincter  muscle  lies  at  the  5th  (dog)  or 
the  7th  (rabbit)  lumbar  vertebra,  and  that  for  the  muscles  of  the  bladder  some- 
what higher.  The  centre  acts  only  in  a  properly  coSrdinated  way  in  connection 
with  the  brain  (§  280). 

4.  The  erection  centre  (§  436)  also  lies  in  the  lumbar  region.  The  afferent 
nerves  are  the  sensory  nerves  of  the  penis  ;  the  efferent  nerves  for  the  deep  artery 
of  the  penis  are  the  vaso-dilator  nerves,  arising  from  the  ist  to  3d  sacral  nerves, 
or  Eckhard's  nervi  erigentes — while  the  motor  nerves  for  the  ischio-cavernosus 
and  deep  transverse  perineal  muscles  arise  from  the  3d  to  4th  sacral  nerves  (§  356). 
The  latter  may  also  be  excited  voluntarily,  the  former  also  partly  by  the  brain,  by 
directing  the  attention  to  the  sexual  activity.  Eckhard  observed  erection  to  take 
place  after  stimulation  of  the  higher  regions  of  the  spinal  cord,  as  well  as  of  the 
pons  and  crura  cerebri. 

5.  The  ejaculation  centre.  The  afferent  nerve  is  the  dorsal  of  the  penis,  the 
centre  (Budge's  genito-spinal  centre)  lies  at  the  4th  lumbar  vertebra  (rabbit)  ;  the 
motor  fibres  of  the  vas  deferens  arise  from  the  4th  and  5th  lumbar  nerves,  which 
pass  into  the  sympathetic,  and  from  thence  to  the  vas  deferens.  The  motor  fibres 
for  the  bulbo-cavernosus  muscle,  which  ejects  the  semen  from  the  bulb  of  the 
urethra,  lie  in  the  3d  and  4th  sacral  nerves  (perineal). 

6.  The  parturition  centre  (§  453)  lies  at  the  ist  and  2d  lumbar  vertebra 
{Korner) ;  the  afferent  fibres  come  from  the  uterine  plexus,  to  which  also  the 
motor  fibres  proceed.  Goltz  and  Freusberg  observed  that  a  bitch  became  preg- 
nant after  its  spinal  cord  was  divided  at  the  ist  lumbar  vertebra. 

7.  Vasomotor  Centres. — Both  vasomotor  and  vaso-dilator  centres  are  dis- 
tributed throughout  the  whole  spinal  axis.  To  them  belongs  the  centre  for  the 
spleen,  which  in  the  dog  is  opposite  the  ist-4th  cervical  vertebrae  {Bulgak).  They 
can  be  excited  reflexly,  but  they  are  also  controlled  by  the  dominating  centre  in 
the  medulla  oblongata  (§  371).  Psychical  disturbance  (cerebrum)  influences 
them  (§  377). 

[8.  Perhaps  there  are  vaso-dilator  centres.] 

9.  The  sweat  centre  is,  perhaps,  distributed  similarly  to  the  vasomotor  centre 
(§  288). 

The  reflex  movements  disch.Trged  from  these  centres  are  orderly  coordinated  refle.\es,  and  may 
thu<  be  compared  to  the  orderly  reflexes  of  the  trunk  and  extremities. 

Muscle  Tonus. — P'or.nerly  automatic  functions  were  ascribed  to  the  spinal  cord,  one  of  these 
being  that  it  caused  a  moderate  active  tension  of  the  muscles — a  condition  that  was  termed  muscle 
tone,  or  tonus.  The  existence  of  tonus  in  a  striped  muscle  was  thought  to  be  proved  by  the  fact 
that,  when  such  a  muscle  was  divided,  its  ends  retracted.  This  is  due  merely  to  the  fact  that  all 
the  muscles  are  stretched  slightly  beyond  their  normal  length  (|  301).  Even  paralyzed  muscles, 
which  have  lost  their  muscular  tone,  show  the  same  phenomenon.  Formerly,  the  stronger  contrac- 
tion of  certain  muscles,  after  paralysis  of  their  antagonists,  and  the  retraction  of  the  facial  muscles 
to  the  sound  side,  after  paralysis  of  the  facial  nerve,  were  also  regarded  as  due  to  tonus.  This 
result  is  simply  due  to  the  fact  that,  after  the  activity  of  the  intact  muscles,  the  other  ones  have  not 
sufficient  power  to  restore  the  parts  to  their  normal  median  position.  The  followmg  experiment  of 
Auerbach  and  Heidenhain  is  against  the  assumption  of  a  tonic  contraction  ;    If  the  muscles  of  the 


670  EXCITABILITY   OF   THE    SPINAL    CORD. 

leg  of  a  decapitated  frog  be  stretched,  it  is  found   that   they  do  not  elongate  after  section  of  the 
sciatic  nerve,  or  after  it  is  paralyzed  by  touching  it  with  ammonia  or  carbolic  acid. 

Reflex  Tonus. — If,  however,  a  decapitated  frog  be  suspended  in  an  abnormal  position,  we 
observe,  after  section  of  the  sciatic  nerve,  or  the  posterior  nerve  roots  on  one  side,  that  the  leg  on 
that  side  hangs  limp,  while  the  leg  of  the  sound  side  is  slightly  retracted.  The  sensory  nerves  of 
the  latter  are  slightly  and  continually  stimulated  by  the  weight  of  the  limb,  so  that  a  slight  reflex 
retraction  of  the  leg  takes  place,  which  disappears  as  soon  as  the  sensory  ner\'es  of  the  leg  are 
divided.  If  we  choose  to  call  this  slight  retraction  tonus,  then  it  is  a  reflex  tonus  (Brondgiest). 
(See  the  experiments  of  Harless,  C.  Lmhvig,  and  Cyan — \  355.) 

363.  EXCITABILITY  OF  THE  SPINAL  CORD.— Even  at  the  pres- 
ent time  observers  are  by  no  means  agreed  whether  the  spinal  cord,  like  peripheral 
nerves,  is  excitable,  or  whether  it  is  distinguished  by  the  remarkable  peculiarity 
that  most  of  its  conducting  paths  and  ganglia  do  not  react  to  direct  electrical  and 
mechanical  stimuli. 

If  stimuli  be  cautiously  applied  either  to  the  white  or  gray  matter  there  is  neither  movement  nor 
sensation  (  \'an  Deen  [/S41),  Brozun-Sc'qttard^  Schiff^  Huizinga,  Sigm.  Mayer).  In  doing  this  ex- 
periment, we  must  be  careful  not  to  stimulate  the  roots  of  the  spinal  nerves,  as  these  respond  at  once 
to  stimuli,  and  thus  may  give  rise  to  movements  or  sensations,  ."^s  the  spinal  cord  conducts  to  the 
brain  impulses  communicated  to  it  from  the  stimulated  posterior  roots,  but  does  not  itself  respond 
to  stimuli  which  produce  sensations,  Schifi"  has  applied  to  it  the  term  "  aesthesodic."  Further,  as 
the  cord  can  conduct  both  voluntary  and  reflex  motor  impulses,  without,  however,  itself  being 
affected  by  motor  impulses  applied  to  it  directly,  he  calls  it  "kinesodic."  Schiff's  views  are  as 
follows : — 

1.  In  the  posterior  columns  the  sensory  root  fibres  of  the  posterior  root 
which  traverse  these  columns  give  rise  to  painful  impressions,  but  the  proper  paths 
of  the  posterior  columns  themselves  do  not  do  so.  The  proof  that  stimulation  of 
the  posterior  column  produces  sensory  impressions,  he  finds  in  the  fact  that  dila- 
tation of  the  pupil  occurred  with  every  stimulation  (§  392").  Removal  of  the  pos- 
terior column  produces  anaesthesia  (loss  of  tactile  sensation).  Algesia  [or  the 
sensation  of  pain]  remains  intact,  although  at  first  there  may  even  be  hyperalgesia. 

2.  The  anterior  columns  are  non-excitable,  both  for  striped  and  non-striped 
muscle,  as  long  as  the  stimuli  are  applied  only  to  the  proper  paths  of  this  column. 
But  movements  may  follow,  either  when  the  anterior  nerve  roots  are  stimulated, 
or  when,  by  the  escape  of  the  current,  the  posterior  columns  are  affected,  whereby 
reflex  movements  are  produced. 

According  to  Schiff',  therefore,  all  the  phenomena  of  irritation,  which  occur  when  an  uninjured 
cord  is  stimulated  (spasms,  contracture),  are  caused  either  by  simultaneous  stimulation  of  the  ante- 
rior roots,  or  are  reflexes  from  the  posterior  columns  alone,  or  simultaneously  from  the  posterior 
columns  and  the  posterior  roots.  Diseases  affecting  only  the  anterior  and  lateral  columns  alone 
never  produce  symptoms  of  irritation,  but  always  of  paralysis  In  complete  ancfsthesia  and  apnoea 
every  form  of  stimulus  is  quite  inactive.  According  to  Schiff's  view,  all  centres,  both  spinal  and 
cerebral,  are  inexcitable  by  artificial  means. 

Direct  Excitability. — Many  observers,  however,  oppose  these  views,  and  contend  that  the 
spinal  cord  is  excitable  to  direct  stimulation.  Fick  observed  movements  to  take  place  when  he 
stimulated  the  while  columns  of  the  cord  of  a  frog,  isolated  for  a  long  distance  so  as  to  avoid  the 
escape  of  the  stimulating  currents.  Biedermann  comes  to  the  following  conclusions:  the  transverse 
section  of  a  motor  nerve  is  most  excitable.  Weak  stimuli  (descending  opening  shocks)  excite  the 
cut  surface  of  the  transversely  divided  spinal  cord,  but  do  not  act  when  applied  further  down. 
.  Luchsinger  asserts  that,  after  dipping  the  anterior  part  of  a  beheaded  snake  into  warm  water,  the 
reflex  movements  of  the  upper  part  of  the  cord  are  abolished,  while  the  direct  excitability  remains. 

3.  Excitability  of  the  Vasomotors. — The  vaso-constrictor  nerves, 
which  proceed  from  the  vasomotor  centre  and  run  downward  in  the  [lateral 
columns  of  the]  cord,  are  excitable  by  all  stimuli  along  their  whole  course  ;  direct 
stimulation  of  any  transverse  section  of  the  cord  constricts  all  the  blood  vessels 
below  the  point  of  section  {C.Liidwig  and  Thiry).  In  the  same  way,  the  fibres 
which  ascend  in  the  cord,  and  increase  the  action  of  the  vasomotor  centre — 
pressor  fibres,  2txs  aX'io  e\c\\.a.h\e  {C.Liidwig  and  Dittinar — §  364,  10).  Stimulation 
of  these  fibres,  although  it  affects  the  vasomotor  centre  reflexly,  does  not  cause 


CONDUCTING   PATHS    IN   SPINAL   CORD.  671 

sensation.     Schiff  maintains,  however,   that  these  are  not  the  direct  results  of 
stimulation. 

4.  Chemical  Stimuli,  such  as  the  application  of  common  salt,  or  wetting 
the  cut  surface  with  blood,  appear  to  excite  the  spinal  cord. 

5.  The  motor  centres  are  directly  excited  by  blood  heated  above  40°  C, 
or  by  asphyxiated  blood,  or  by  sudden  and  complete  anaemia  of  the  cord  pro- 
duced by  ligature  of  the  aorta  {Sigm.  Mayer)  ;  and  also  by  certain  poisons — 
picrotoxin,  nicotin  and  compounds  of  barium  {Luchsinger). 

Action  of  Blood  and  Poisons. — In  experiments  of  this  kind  tlie  spinal  cord  ought  to  be 
divided  at  the  first  lumbar  vertebra  at  least  twenty  hours  before  the  experiment  is  begun.  It  is 
well  to  divide  the  posterior  roots  beforehand  to  avoid  reflex  movements.  If,  in  a  cat  thus  operated 
on,  dyspncea  be  produced,  or  its  blood  07'erheated,  then  spnsms^  contraction  of  the  vessels  and  secre- 
tion of  sweat  occur  in  the  hind  limbs,  together  with  evacuation  of  the  contents  of  the  bladder  and 
rectum,  while  there  are  movements  of  the  uterus  and  the  vas  deferens.  Some  poisons  act  in  a 
similar  manner.  In  animals  with  the  medulla  oblongata  divided,  rhythmical  respiratory  movements 
may  be  prochiced  if  the  spinal  cord  has  been  previously  rendered  very  sensitive  by  strychnin  or 
overheated  blood  (P.  v.  A'okitansir,  v.  Schroff — \  368). 

Hyperaesthesia. — After  unilateral  section  of  the  cord,  or  even  only  of  the 
posterior  or  lateral  columns,  there  is  hypenes/hesia  on  the  same  side  below  the 
point  of  section  {Fodera  {182J),  and  others),  so  that  rabbits  shriek  on  the  slightest 
touch.  The  phenomenon  may  last  for  three  weeks,  and  then  give  place  to  normal 
or  sub-normal  excitability.  On  the  sound  side  the  sensibility  remains  perma- 
nently diminished.  A  similar  result  has  been  observed  in  cases  of  injury  in  man. 
An  analoLi'Dus  phenomenon,  or  a  tendency  to  contraction  in  the  muscles  below  the 
section  (Hyperkinesia),  has  been  observed  by  Brown-Sequard  after  section  of 
the  anterior  columns. 

364.  THE  CONDUCTING  PATHS  IN  THE  SPINAL  CORD.— 
[Posterior  Root. — The  fibres  of  the  posterior  root  enter  the  cord  in  three 
bundles  {a)  the  inner  one,  or  internal  radicular  fasciculus  sweeps  through 
the  postero-external  column  to  enter  the  gray  matter.  It  is  supposed  to  convey 
the  impressions  from  tendons  and  those  for  touch  and  locality.  Hence,  when 
this  column  is  diseased,  as  in  locomotor  ataxia,  the  deep  reflexes,  especially  the 
patellar  tendon  reflex,  are  enfeebled,  or  it  may  be  abolished,  while  the  implica- 
tion of  the  fibres  of  the  internal  fasciculus  gives  rise  to  severe  pain.  {/>)  The 
outer  radicular  fibres  enter  the  gray  matter  of  the  posterior  horn,  and  are  sup- 
posed to  convey  the  impressions  for  cutaneous  reflexes  and  temperature,  {c)  The 
central  fibres  pass  directly  into  the  gray  matter,  and  are  supposed  to  conduct 
painful  imijressious  into  the  gray  matter.] 

1.  Localized  tactile  sensations  (temperature,  pressure  and  the  muscular 
sense  impressions)  are  conducted  upward  through  the  posterior  roots  to  the 
ganglia  of  the  posterior  cornu,  and,  lastly,  into  the  posterior  column  of  the  same 
side. 

In  man  the  conducting  path  from  tiie  legs  runs  in  GoU's  column,  while  those  for  the  arms  run  in 
the  ground  bundle  (Fig.  403)  {Flec/isig\. 

In  rabbits  the  path  of  localized  tactile  impressions  lies  in  the  lower  dorsal  region  in  the  lateral 
columns  (Ludzvigand  Woroschiloff,  Ott  and  Meade-Smith). 

Anaesthesia. — Section  of  individual  parts  of  the  lateral  columns  abolishes  the  sensibility  for  the 
parts  of  the  skin  connected  with  the  part  destroyed,  while  total  section  produces  the  same  result 
for  the  whole  of  the  opposite  side  of  the  body  below  the  section.  The  condition  where  tactile  and 
muscular  sensibility  is  lost  is  known  as  aniisthesia. 

2.  Localized  voluntary  movements  in  man  are  conducted  on  the  satne 
side  through  the  anterior  and  lateral  columns  (§§  358  and  365),  in  the  parts  known 
as  the  pyramidal  tracts.  The  impulses  then  pass  into  the  cells  of  the  anterior 
cornu,  and  thence  to  the  corresponding  anterior  nerve  roots  to  the  muscles.  The 
exact  section  experiments  of  Ludwig  and  Woroschiloff  showed  that,  in  the  lower 
dorsal  region  of  the  rabbit,  these  paths  were  confined   to  the  lateral  columns. 


672  LOCOMOTOR   ATAXIA. 

Every  motor  nerve  fibre  is  connected  with  a  nerve  cell  in  the  anterior  horn  of  the 
frog's  spinal  cord  (GauL-  and  Birge).  Section  of  one  lateral  column  abolishes 
vpluntary  movement  in  the  corresponding  individual  muscles  below  the  point  of 
section.  It  is  obvious,  from  the  conduction  in  i  and  2,  that  the  lateral  columns 
must  increase  in  thickness  and  number  of  fibres  from  below  upward  {Stilling, 
Woroscliiloff")  [see  Fig.  397]. 

3.  Tactile  (extensive  and  coordinated)  Reflexes. — The  fibres  enter  by  the 
posterior  root,  and  proceed  to  the  posterior  cornu.  The  groups  of  ganglionic  cells, 
which  control  the  coordinated  reflexes,  are  connected  together  by  fibres  which  run 
in  the  anterior  tracts,  the  anterior  ground  bundle  and  (?)  the  direct  cerebellar 
tracts  (p.  659).  The  fibres  for  the  muscles  which  are  contracted  pass  from  the 
motor  ganglia  outward  through  the  anterior  roots. 

In  ataxic  tabes  dorsalis,  or  locomotor  ataxia,  there  is  a  degeneration  of  the  posterior  columns, 
characterized  by  a  jieculiar  motor  disturbance.  The  voluntary  movements  can  be  executed  with  full 
and  normal  vigor,  l)ut  the  finer  harmonious  adjustments  are  wanting  or  impaired,  both  in  intensity 
and  extent.  These  depend  in  part  upon  the  normal  existence  of  tactile  and  muscular  impressions, 
whose  channels  lie  in  the  posterior  columns.  After  degeneration  of  the  latter,  there  is  not  only 
anaesthesia,  but  also  a  disturbance  in  the  discharge  of  tactile  reflexes,  for  whicli  the  centripetal  arc  is 
interrupted.  But  a  simultaneous  lesion  of  the  sensory  nerves  alone  may  in  a  similar  matter  materi- 
ally influence  the  harmony  of  the  movements,  owing  to  the  analgesia  and  the  disappearance  of  the 
pathic  reflexes  ( ^  355).  As  the  fibres  of  the  posterior  root  traverse  the  white  posterior  columns, 
we  can  account  for  the  disturbances  of  sensation  which  characterize  the  degenerations  of  these  parts 
[Charcot  and  Pierrei).  But  even  the  posterior  roots  themselves  may  undergo  degeneration,  and 
this  may  also  give  rise  to  disturbances  of  sensation  (p.  648).  The  sensory  disturbances  usu.ally  con- 
sist  in  an  abnormal  increase  of  the  tactile  or  painful  sensations,  with  lightning  pains  shooting  down 
the  limbs,  and  this  condition  may  lead  on  to  one  where  the  tactile  and  painful  sensations  are  abol- 
ished. At  the  same  time,  owing  to  stimulation  of  the  posterior  columns,  the  tactile  sensibility  is 
altered,  giving  rise  to  the  sensation  of  formication,  or  a  feehng  of  constriction  ["girdle  sensa- 
tion"]. The  conduction  of  sensory  impressions  is  often  slowed  (^  337)-  The  sensibility  of  the 
muscles,  joints,  and  internal  parts  is  altered. 

The  maintenance  of  the  equilibrium  is  largely  guided  by  the  impulses  which  travel  inward 
to  the  coordinating  centres  through  the  sensory  nerves,  special  and  general,  deep  and  superficial. 
In  many  cases  of  locomotor  ataxia,  if  the  patient  place  his  feet  close  together  and  close  his  eyes,  he 
sways  from  side  to  side  and  may  fall  over,  because  by  cutting  off  the  guiding  sensations  obtained 
through  the  optic  nerve,  the  other  enfeebled  impulses  obtained  from  the  skin  and  the  deeper  struct- 
ures are  too  feeble  to  excite  proper  coordination. 

4.  The  inhibition  of  tactile  reflexes  occurs  through  the  anterior  columns ; 
the  impulses  pass  from  the  anterior  column  at  the  corresponding  level  into  the 
gray  matter,  where  they  form  connections  with  the  reflex  conducting  apparatus. 

5.  The  conduction  of  painful  impressions  occurs  through  the  posterior  roots, 
and  thence  through  the  whole  of  the  gray  matter.  There  is  a  partial  decussation 
of  these  impulses  in  the  cord,  the  conducting  fibres  passing  from  one  side  to  the 
other.     The  further  course  of  these  fibres  to  the  brain  is  given  in  §  365. 

The  experiments  of  Weiss  on  dogs,  by  dividing  the  lateral  column  at  the  limit  of  the  dorsal  and 
lumbar  regions,  showed  that  each  lateral  column  contains  sensory  fibres  for  both  sides.  The  chief 
mass  of  the  motor  fibres  remains  on  the  same  side.  Section  of  both  lateral  columns  abolishes 
completely  sensibility  and  mobility  on  both  sides.  The  anterior  columns  and  the  gray  matter  are 
not  sufficient  to  maintain  these.  If  all  the  gray  matter  be  divided,  except  a  small  connecting  por- 
tion, this  is  sufficient  to  conduct  painful  impressions.  In  this  case,  however,  the  conduction  is  slower 
(Sehiff).  Only  when  the  gray  matter  is  completely  divided  is  the  conduction  of  painful  impressions 
from  below  completely  interrupted.  This  gives  rise  to  the  condition  of  analgesia,  in  which,  when 
the  posterior  columns  are  still  intact,  tactile  impressions  are  still  conducted.  This  condition  is  some- 
times observed  in  man  during  incomplete  narcosis  from  chloroform  and  morphia  (  Thiersch).  Those 
poisons  act  sooner  on  the  nerves  which  administer  to  painful  sensations  than  on  those  for  tactile  im- 
pressions, so  that  the  person  operated  on  is  conscious  of  the  contact  of  a  knife,  but  not  of  the  pain- 
ful sensations  caused  by  the  knife  dividing  the  parts. 

Irradiation  of  Pain. — As  painful  impressions  are  conducted  by  the  whole  of  the  gray  matter, 
and  as  the  impressions  are  more  pjwerful  the  stronger  the  painful  impression,  we  may  thus  explain 
the  .so  called  irradiation  of  painful  impressions.  During  violent  pain,  the  pain  seems  to  extend  to 
wide  areas  ;  thus,  in  violent  toothache,  proceeding  from  a  particular  tooth,  the  pain  may  be  felt  in 
the  whole  jaw,  or  it  may  be  over  one  side  of  the  head. 


CONDUCTION    IN   THE   SPINAI,   CORD.  673 

6.  The  conduction  of  spasmodic,  involuntary,  incoordinated  movements 
takes  place  through  the  gray  matter,  and  from  the  latter  through  the  anterior 
roots. 

It  occurs  in  epilepsy,  in  poisoning  with  strychnin,  in  ursemic  poisoning,  and  tetanus  {§  360,  II). 
The  anaemic  and  dyspnceic  spasms  are  excited  in  and  conducted  from  the  medulla  oblongata,  and 
are  communicated  through  the  whole  of  the  gray  matter. 

7.  The  conduction  of  extensive  reflex  spasms  takes  place  from  the  posterior 
roots,  perhaps,  to  the  cells  of  the  posterior  cornu  and  then  to  the  cells  of  the 
anterior  cornu,  above  and  below  the  plane  of  the  entering  impulse  (Fig.  407), 
and,  lastly,  into  the  anterior  roots,  under  the  conditions  already  referred  to  in 
§  360,  II. 

8.  The  inhibition  of  pathic  reflexes  occurs  through  the  anterior  columns 
downward,  and  then  into  the  gray  matter  to  the  connecting  channels  of  the  reflex 
organ,  into  which  it  mtroduces  resistance. 

9.  The  vasomotor  fibres  run  in  the  lateral  columns  {Dittmar),  and,  after 
they  have  passed  into  the  ganglia  of  the  gray  matter  at  the  corresponding  level, 
they  leave  the  spinal  cord  by  the  anterior  roots.  They  reach  the  muscles  of 
the  blood  vessels  either  through  the  paths  of  the  spinal  nerves,  or  they  pass 
through  the  rami  communicantes  into  the  sympathetic,  and  thence  into  the 
visceral  plexuses  (§  356). 

Section  of  the  spinal  cord  paralyzes  all  the  vasomotor  nerves  below  the  point  of  section ;  while 
stimulation  of  the  peripheral  end  of  the  spinal  cord  causes  contraction  of  all  these  vessels.  [Ott's 
experiments  on  cats  show  that  the  vasomotor  fibres  run  in  the  lateral  columns,  and  that  they  as  well 
as  the  sudorific  nenes  decussate  in  the  cord.] 

10.  Pressor  fibres  enter  through  the  posterior  roots,  run  upward  to  the  lateral 
columns,  and  undergo  an  incomplete  decussation  (C.  Ludwig  and  Miescher). 

They  ultimately  terminate  in  the  dominating  vasomotor  centre  in  the  medulla  oblongata,  which 
they  excite  reflexly.  Similarly,  depressor  fibres  must  pass  upward  in  the  spinal  cord,  but  we  know 
nothing  as  to  their  course. 

11.  From  the  respiratory  centre  in  the  meAviWa.  ohlongaXa,  respiratory  nerves 
run  downward  in  the  lateral  columns  on  the  same  side,  and  without  forming  any 
connections  with  the  ganglia  of  the  anterior  cornu  (?),  pass  through  the  anterior 
roots  into  the  motor  nerves  of  the  respiratory  muscles  {Schiff ). 

Unilateral,  or  total  destruction  of  the  spinal  cord,  the  higher  up  it  is  done,  accordingly  paralyzes 
more  and  more  of  the  respiratory  nerves,  on  the  same  or  on  both  sides.  Section  of  the  cord  above 
the  origin  of  the  phrenic  nerves  causes  death,  owing  to  the  paralysis  of  these  nerves  of  the  diaphragm 

(?"3)- 

In  pathological  cases,  in  degeneration  of,  or  direct  injury  to,  the  spinal  cord  or  its  individual 
parts,  we  must  be  careful  to  observe  whether  there  may  not  be  present  simultaneously  paralytic  and 
irritative  phenomena,  whereby  the  symptoms  are  obscured. 

[Complete  transverse  section  of  the  cord  results  immediately  in  com- 
plete paralysis  of  motion  and  sensation  in  all  the  parts  supplied  by  nerves  below 
the  seat  of  the  injury,  although  the  muscles  below  the  injury  retain  their  normal 
trophic  and  electrical  conditions.  There  is  a  narrow  hyjierKsthetic  area  at  the 
upper  limit  of  the  paralyzed  area,  and  when  this  occurs  in"  the  dorsal  region,  it 
gives  rise  to  the  feeling  of  a  belt  tightly  drawn  round  the  waist,  or  the  "girdle 
sensation."  There  is,  also,  vasomotor  paralysis  below  the  lesion,  but  the  blood 
vessels  soon  regain  their  tone  owing  to  the  subsidiary  vasomotor  centres  in  the 
cord.  The  remote  effects  come  on  much  later,  and  are  secondary  descending 
degeneration  in  the  crossed  and  direct  pyramidal  tracts  and  ascending  degenera- 
tion in  the  postero-internal  columns  (Fig.  404).  According  to  the  seat  of  the 
lesion,  the  functions  of  the  bladder  and  rectum  may  be  interfered  with.  Injury 
to  the  upper  cervical  region  sometimes  causes  hyperpyrexia.] 
43 


674 


EFFECTS   OF   SECTION    OF   THE    CORD. 


[Unilateral  section  results  in  paralysis  of  voluntary  motion  in  the  muscles 
supplied  by  nerves  given  off  below  the  seat  of  the  injury, 
although  the  muscles  do  not  atrophy,  but  when  secondary 
descending  degeneration  occurs  they  become  rigid,  and  ex- 
hibit the  ordinary  signs  of  contracture.  There  is  vasomotor 
paralysis  on  the  same  side,  although  this  passes  off  below  the 
injury,  while  the  ordinary  and  muscular  sensibility  are  dimin- 
ished on  both  sides  (Fig.  408).  There  is  bilateral  anaesthesia. 
On  the  opposite  side  there  is  total  anssthesia  and  analgesia 
below  the  lesion,  but  on  the  same  side  in  the  dorsal  region 
there  is  a  narrow  circular  anaesthetic  zone  (Fig.  408,  b),  cor- 
responding to  the  sensory  nerve  fibres  destroyed  at  the  level 
of  the  section.  The  sensory  nerves  decussate  shortly  after 
they  enter  the  cord,  hence  the  anesthesia  on  the  opposite 
side,  but  they  do  not  cross  at  once,  but  run  obliquely  upward 
before  they  enter  the  gray  matter  of  the  opposite  side,  so  that 
a  unilateral  section  will  involve  some  fibres  coming  from  the 
same  side,  and  hence  the  slightly  diminished  sensibility  in  a 
circular  area  on  the  same  side.  There  is  a  narrow  hypertes- 
thetic  area  on  the  same  side  as  the  lesion,  at  the  upper  limit 
of  paralyzed  cutaneous  area  (Fig.  408,  c),  due,  perhaps,  to 
stimulation  of  the  cut  ends  of  the  sensory  fibres  on  that  side. 
In  man  there  is  hypersesthesia  (to  touch,  tickling,  pain,  heat 
tiie  if/t  half  of  the  and  cold)  on  the  parts  below  the  lesion  on  the  same  side,  but 
doreai  region!"  \a)  the  cause  of  this  is  not  known.  The  remote  effects  are  due 
to  the  usual  descending  and  ascending  degeneration  which 
set  in.] 

[In  monkeys,  after  hemisection  of  the  cord  in  the  dorsal  region,  there 
is  jiaralysis  of  voluntary  motion  and  retention  of  sensibility  with  vasomotor 
paralysis  of  the  same  side,  antl  retention  of  voluntary  motion  with  anaes- 
thesia and  analgesia  on  the  opposite  side.  The  existence  of  hypera-sthesia  on  the  side  of  the  lesion 
is  not  certain  in  these  animals,  but  there  is  no  doubt  of  it  in  man.  Ferrier  also  finds  (in  opposition 
to  Brown-Sequard)  that  the  muscular  sense  is  paralyzed  as  well  as  all  other  forms  of  sensibility,  on 
the  side  opposite  to  the  lesion,  but  unimpaired  on  the  side  of  the  lesion.  The  muscular  sense,  in 
fact,  is  entirely  separalile  from  the  motor  innervation  of  muscle  {Ferrier).  The  power  of  emptying 
the  bladder  and  rectum  was  not  affected.] 


ralysis;  («.  ,i) 
plete  ansEstheM: 
r)  hyperaesthes 
the  skin  (^■W.). 


THE  BRAIN. 


365.  GENERAL  SCHEMA  OF  THE  BRAIN.— In  an  organ  so  complicated  in  its  struc- 
ture as  the  brain,  it  is  nccessarv  to  have  a  general  view  of  the  chief  arrangements  of  its  individual 
parts.  Meynert  gave  a  plan  of  the  general  arrangement  of  this  organ,  and  although  this  plan  may 
not  be  quite  correct,  still  it  is  useful  in  the  stuly  of  brain  function 

[A  special  layer  of  gray  matter  of  the  cerebium  is  placed  externally  and  spread  as  a  thin 
coating  over  the  white  matter,  or  centrum  ovale,  which  lies  internally,  and  consists  of  nerve  fibres 
or  the  white  matter.  That  part  lying  in  each  hemisphere  is  the  centrum  senii-ovale.  The  gray 
matter  is  folded  into  gyri,  or  convolutions,  separated  from  each  other  by  fissures,  or  sulci. 
Some  of  the  latter  are  very  marked,  and  serve  to  separate  adjacent  lobes,  while  the  lobes  themselves 

Fir..  409. 


isection  of  the  brain  from  above,  showing  the  lateral,  3d,  and  4th  ventricles,  with  the  basal  ganglia  and  < 
ine  parts,  a,  knee  of  the  corpus  callosum  :  6,  anterior  part  of  the  right  corpus  striatum  :  d' ,  gray  matter  dissected 
off  10  show  white  tibres  :  c,  points  to  taenia  semicircularis  ;  (/,  optic  thalamus;  if,  anterior  pillars  of  fornix,  with 
5th  ventricle  in  front  of  them,  between  the  two  laminae  of  the  septum  lucidum  :  /",  middle  or  soft  commissure  :  £-, 
3d  ventricle ;  A, /,  corpora  quadrigemina  ;  ,t,  superior  cerebellar  peduncle;  /.hippocampus  majo 


ride 


collateralis ;  o,  4th  ventricle  ;  /*,  medulla  oblongata  ;  j,  cerebellu 


are  further  subdivided  by  sulci  into  convolutions.  For  a  description  of  the  lobes,  see  ^  375.  Some 
masses  of  gray  matter  are  disposed  at  the  base  of  the  brain,  forming  the  corpus  striatum  (pro- 
jecting into  the  lateral  ventricles),  which,  in  reality,  is  composed  of  two  parts — the  nucleus  caudatus 
and  lenticular  nucleus  ( Fig.  409,  /i);  the  optic  thalamus,  which  lies  behind  the  former  and  bounds 
the  31!  ventricle  ( Kig.  409,  i/) ;  the  corpora  quadrigemina,  lying  on  the  upper  surface  of  the  crura 
cerebri  (Fig.  409,  /;.  i) ;  and  within  the  tegmentum  of  the  crura  cerebri  are  the  red  nucleus  and 
locus  niger.  Lastly,  there  is  the  continuation  of  the  gray  matter  of  the  cord  up  through  the 
medulla,  pons,  and  around  the  iter,  forming  the  central  gray  tube  and  terminating  anteriorly  at 
the  tuber  cinereum.     These  various  parts  are  connected  in  a  variety  of  ways  with  each  other,  some 

675 


676 


PROJECTION    SYSTEMS   OF    MEYNERT. 


by  transverse  fibres  stretching  between  the  two  sides  of  the  brain,  while  other  longitudinal  fibres 
bring  the  hinder  and  lower  parts  in  relation  with  the  fore  parts  ] 

[Under  cover  of  the  occipital  lobes,  but  connected  with  the  cerebrum  in  front  and  the  spinal  cord 
below,  is  the  cerebellum,  which  has  its  gray  matter  externally  and  its  white  core  internally.  Thus, 
we  have  to  consiiicr  cerebrospinal  and  cerebello-spinal  connections.] 

Meynert's  Projection    Systems. — The  cortex  of  the   cerebium   consists  of  convolutions  and 


Scheme  of  ihe  brain  C.  C,  cortex  cerebri  :  C,  J,  corpus  striatum  :  N,  /,  nucleus  lenticularis  ;  T,  o,  optic  thal- 
amus :  7',  corpora  quadrigemina  ;  P,  pedunculus  cerebri  :  H,  tegmentum;  and/,  crusta;  i,  i,  corona  radiata  ot 
the  corpus  striatum  ;  2.2,  of  the  lenticular  nucleus  ;  3,  3,  of  the  optic  thalamus  ;  4,  4,  of  the  corpora  quadrigemina  ; 
5,  direct  fibres  to  the  cortex  cerebri  ^Flechsig) ;  6,  6,  fibres  from  the  corpora  quadrigemina  to  the  tegmentum  ; 
«/,  further  course  of  these  fibres  ;  8,  8,  fibres  from  the  corpus  striatum  and  lenticular  nucleus  to  the  crusta  of  the 
pedunculus  cerebri ;  I\I,  further  course  of  these  ;  S,  S,  course  of  the  sensory  fibres  ;  R,  transverse  section  of  tht 
spinal  cord  :  ?',  W,  anterior,  and  k,  W,  posterior  roots  ;  a,  a,  association  systei 
fibres.  II,  Transverse  section  through  the  posterior  pair  of  the  corpora  quadrige: 
of  man, — f>,  crusta  of  the  peduncle :  j,  substantia  nigra  ■  "',  corpora  quadrigemina, 
III,  The  same  of  the  dog  :    IV,  of  an  ape  ;  V,  of  the  guinea  pig.     [See  p.  675.] 


of  fibres :   c,  c,  commissural 
na  and  the  pedunculi  cerebri 
ot  the  aqueduct. 


(itha 


sulci,  the  "peripheral  gray  matter"  (Fig.  410,  C),  which  is  recognized  as  a  nervous  structure 
from  the  presence  of  numerous  ganglionic  cells  in  it  (?358,  i).  From  it  proceed  all  the  motor 
fibres  which  are  excited  by  the  will  and  to  it  proceed  all  the  fibres  cominsj  from  the  organs  of 
special  sense  and  sensory  organs,  which  give  rise  to  the  psychical  perception  of  external  impressions. 
[In  Fig.  410  the  decussation  of  the  sensory  fibres  is  represented  as  occurring  near  the  medulla 
oblongata.     It  is  more  probable  that  a  large  number  of  the  sensory  fibres  decussate  shortly  after 


CEREBELLO-SPINAL   CONNECTIONS. 


677 


they  enter  the  conl,  as  is  represented  in  Fig.  4t2.  Sonie  observers  assert  that  some  of  the  sensory 
fibres  decussate  in  the  medulla  oblongata.] 

First  Projection  System. — The  channels  lead  to  and  from  the  cortex  cerebri,  some  of  them 
traversing  the  basal  ganglia,  or  ganglia  of  the  cerebrum,  the  corpus  striatum  (C,  s),  composed  of 
the  caudate  nucleus  and  lenticular  nucleus  (A",  /),  optic  thalamus  (  T,  o)  and  corpora  quadrigemina  ; 
some  fibres  form  connections  with  cells  within  this  central  gray  matter.  The  fibres  which  proceed 
from  the  cortex  through  the  corona  radiata  in  a  radiate  direction  constitute  Meynert' s  first  projection 
system.  Besides  these,  the  white  substance  also  contains  two  other  systems  of  fibres  :  {a)  Commis- 
sural fihres^  such  as  the  corpus  caliosum  and  the  anterior  commissure  (r,  r),  which  are  supposed  to 
connect  the  two  hemispheres  with  each  other;  and  (b)  a  connecting  or  association  system,  whereby 
two  different  areas  of  the  same  side  are  connected  together  [a,  a).  The  ganglionic  gray  matter  of 
the  basal  ganglia  forms  the  first  stage  in  the  course  of  a  large  number  of  the  fibres.  When  they 
enter  the  central  gray  matter  they  are  interrupted  in  their  course.  According  to  Meynert,  the 
corona  radiata  contains  bundles  of  fibres  from  the  corpus  striatum,  lenticular  nucleus,  optic  thalamus 
and  corpora  quadrigemina. 

The  second  projection  system  consists  of  longitudinal  bundles  of  fibres,  which  proceed  down- 
ward and  reach  the  so-called  "  central  gray  tube,"  which  is  the  ganglionic  gray  matter  reaching 
from  the  3d  ventricle  through  the  aqueduct  of  Sylvius  and  the  medulla  oblongata  to  the  lowest  part 
of  the  gray  matter  of  the  spinal  cord.     It  lines  the  inner  surface  of  the  medullary  tube.     It  is  the 


Fig.  411 


Floor  of  the  fourth  ventrit 
are  cut  short ;  on  the 
mititile  one  has  been  ( 
of  the  auditory  nerve 
the  calamus  scriptorii 
rigemina. 


of  the  cerebellum.  On  the  left  side  the  three  cerebellar  peduncles 
I  of  the  superior  and  inferior  peduncles  have  been  preserved,  while  the 
It  short.  I,  median  groove  of  the  fourth  ventricle  with  the  fasciculi  teretes  ;  2,  the  striae 
)n  each  side  emerging  from  it ;  3,  inferior  peduncle  :  4,  posterior  pyramid  and  clava,  with 
i  above  it ;  5,  superior  peduncle ;  6,  fillet  to  the  side  of  the  crura  cerebri ;  8,  corpora  quad- 


second  stage  in  the  course  of  the  fibres  extending  from  the  basal  ganglia  to  the  central  tubular  gray 
matter.     The  fibres  of  this  system  must,  obviously,  vary  greatly  in  length. 

[While  there  are  three  concentric  tubes  in  the  spinal  cord  (|  359),  in  the  part  which  forms  the 
brain  an  extra  layer  of  gray  matter  is  added— the  peripheral  gray  tube — constituting  the  cortex  of 
the  cerebral  hemispheres  and  cerebellum  and  the  corpora  quadrigemina.  Thus,  the  white  matter 
lies  between  two  concentric  masses  of  gray  matter  (  //;//).] 

Connections  of  the  Cerebellum.  —The  cerebellum  consists  of  two  somewhat  flattened  hemi- 
spheres connected  across  the  middle  line  by  the  middle  lobe  or  vermiform  process,  which  is  the 
fundamental  portion  of  the  organ,  as  it  is  best  developed  in  lower  animals,  while  as  yet  the  lateral 
lobes  are  but  small  or  absent,  e.  g.,  in  birds.  The  surface  is  furrowed  by  sulci  so  as  to  cause  it  to 
resemble  a  series  of  folia,  leaflets  or  laminae  ;  larger  fissures  divide  it  into  lobes.  Peduncles.— 
The  two  itt/«w/- j(ii'a'««i-/f.r  connect  it  with  the  corpora  quadrigemina  and  the  crura  cerebri.  The 
fibres  come  from  the  lower  part  of  the  cerebellum  and  from  its  dentate  nucleus,  and  the  greater  por- 
tion of  these  fibres  decussate  in  the  upper  part  of  the  pons  and  the  tegmentum,  some  of  them  be- 
coming connected  with  the  red  nucleus  in  the  tegmentum  of  the  opposite  side.  Some  of  the  fibres 
seem  to  connect  the  cerebellum  with  the  frontal  lobes,  constituting  a  fronto-cerebellar  tract,  and  they 
are  also  crossed  ( Go^vers).  When  the  cerebellum  is  congenitally  absent  these  fibres  are  absent 
{Flechsig).     By  the  two  inferior  peduncles  or  restiform  bodies,  it  is  connected  with  all  the  columns 


678  CEREBRO-SPINAL   CONNECTIONS. 

of  the  spinal  cord,  and  it  is  to  be  noted  that  some  of  the  fibres  forming  these  peduncles  are  con- 
nected with  the  olivary  body  of  the  opposite  side,  so  that  they  decussate.  The  miiiJU  peduncle  is 
formed  by  the  transverse  fibres  of  the  pons  (I'ig.  41 1).  It  is  evident  that  there  is  a  cerebello  spinal 
as  well  as  cerebro-spinal  connection  to  be  considered. 

[The  gray  matter  is  external  and  the  while  internal,  and  on  section  the  foliated  branched  ap- 
pearance of  the  cerebellum  constitutes  the  arbor  vit(C.  Within  each  lateral  lobe  is  a  folded  mass  of 
jjray  matter  like  that  in  the  olivary  body,  called  the  corpus  dentatum,  and  from  its  interior  white 
fibres  proceed.  Stilling  describes  roof  nuclei  in  the  front  part  of  the  middle  lobe,  so  called  be- 
cause they  lie  in  the  roof  of  the  fourth  ventricle.  As  is  sh  iwn  in  Fig.  411,  the  white  fibres  of 
the  superior  peduncle  pass  to  the  gray  matter  on  the  inferior  surface  of  tlie  ctrebellum,  whde  the 
inferior  peduncular  fibres  .pass  to  the  superior  surface,  chiefly  of  the  median  part  ;  but  both  are  said 
to  form  connections  with  the  corpus  dentatum  ;  the  middle  peduncle  is  connected  with  the  gray 
matter  of  the  lateral  lobes.     The  minute  structure  is  described  in  \  3S0.] 

The  Third  Projection  System. — Lastly,  from  the  central  tubular  gray  matter  there  proceeds 
the  third  system,  or  the  peripheral  nerves,  motor  and  sensory.  They  are  more  numerous  than  the 
fibres  of  the  second  system. 

Conduction  to    and    from    Cerebrum — Voluntary    Motor    Fibres. — 

The  course  of  the  fibres  which  convey  impulses  for  voluntary  motion — the  pyra- 
midal tracts — proceed  from  the  motor  regions  of  the  cerebrum  (§§  375,  378,  I), 
passing  into  and  through  the  white  matter  of  the  cerebrum,  and  converge 
to  the  internal  capsule,  which  lies  between  the  nucleus  caudatus  and  opticus 
thalamus  internally  and  the  lenticular  nucleus  externally  (Fig.  439).  [The 
motor  fibres  for  the  face  and  tongue  occupy  the  knee  of  the  capsule  (F),  those  for 
the  arm  the  anterior  third  of  the  posterior  segment  or  limb  (Aj,  and  those  for  the 
leg  the  middle  third  (L).  They  enter  the  crus  and  occupy  its  middle  third,  the 
fibres  for  the  face  being  next  the  middle  line,  and  those  for  the  leg  most  external, 
the  fibres  for  the  arm  lying  between  the  two.  They  pass  into  the  pons,  where  the 
fibres  for  the  face  (and  tongue)  cross  to  the  opposite  side,  to  become  connected 
with  the  nuclei  from  which  the  facial  and  hypoglossal  nerves  arise.  The  fibres  for 
the  arm  and  leg  (and  trunk)  continue  their  course  to  the  medulla  oblongata,  where 
they  form  the  anterior  pyramids.]  By  far  the  greater  proportion  of  the  fibres 
cross  at  the  decussation  of  the  pyramids  to  form  the  crossed  pyramidal  tracts 
or  lateral  pyramidal  tracts  of  the  lateral  column  of  the  opposite  side.  The  small 
uncrossed  portion  is  continued  as  the  direct  pyramidal  tract  on  the  same  side. 
The  latter  fibres,  perhaps,  supply  those  muscles  of  the  trunk  (f.  ^f.,  respiratory, 
abdominal,  and  perineal),  which  always  act  together  on  both  sides.  According 
to  other  observers,  however,  they  cross  to  the  other  side  of  the  cord  through  the 
anterior  white  commissure,  and  descend  in  the  crossed  pyramidal  tract  or  pyra- 
midal tract  of  the  lateral  column.  The  fibres  of  the  pyramidal  tracts  form  con- 
nections with  the  inultipolar  ganglionic  cells  of  the  anterior  cornu  of  the  gray 
matter  of  the  spinal  cord  at  successively  lower  levels,  and  from  each  multipolar  cell 
a  single  unbranched  process  is  directed  peripherally,  which  ultimately  becomes  a 
nerve  fibre.  The  j)yramidal  tracts  thus  end  in  the  multipolar  nerve  cells  of  the  gray 
matter  of  the  spinal  cord,  from  which  the  anterior  roots  of  the  spinal  nerves  arise. 
[The  course  of  the  pyramidal  tracts  and  the  decussation  of  these  fibres  in  the 
medulla  oblongata,  explains  why  a  hemorrhage  involving  the  cerebral  motor 
centres,  or  affecting  these  fibres  in  any  part  of  their  course  above  the  decussation, 
results  in  paralysis  of  the  muscles  supplied  by  the  fibres  so  involved  on  the  opposite 
side  of  the  body.] 

In  their  passage  through  the  brain,  the  paths  for  direct  motor  impulses  are  not  interrupted  any- 
where in  their  course  by  ganglion  cells,  not  even  in  the  corpus  striatum  or  pons.  They  pass  in  a 
direct  uninterrupted  course  [so  that  they  have  the  longest  course  of  any  fibres  in  the  central  nervous 
system]. 

Variation  in  Decussation. — There  are  variations  as  to  the  number  of  fibres  which  cross  at  the 
pyramids  (F/echsig).  In  some  cases  the  usual  arrangement  is  reversed,  and  in  some  rare  instances 
there  is  no  decussation,  so  that  the  pyramidal  tracts  from  the  brain  remain  on  the  same  side.  In 
this  way  we  may  explain  the  very  rare  cases  where  paralysis  of  the  voluntarvm  ivenients  lakes  pl.nce 
on  the  same  side  as  the  lesion  of  the  cerebrum  (Morgagni,  J'ierrel).  This  is  direct  paralysis. 
[Usually  about  90  per  cent,  of  the  fibres  decuss.ite.] 


COURSE   OF   THE    SENSORY    NERVES.  679 

The  motor  cranial  nerves  have  the  centres  through  which  they  are  excited 
voluntarily  in  the  cortex  cerebri  (§  378).  The  paths  for  such  voluntary  impulses 
also  pass  through  the  internal  capsule  and  the  crusta  of  the  cerebral  peduncle.  [In 
the  internal  capsule  the  fibres  for  the  face  (and  tongue)  lie  in  the  knee,  while  they 
occupy  the  part  of  the  middle  of  the  crusta  next  the  middle  line.  Their  course 
is  then  directed  across  the  middle  line  to  their  respective  nuclei,  from  which  fibres 
proceed  to  the  muscles  supplied  by  these  nuclei.]  The  exact  course  of  many  of 
the  fibres  is  still  unknown.  The  hypoglossal  nerve  runs  with  the  pyramidal  tracts, 
and  behaves  like  the  anterior  root  of  a  spinal  nerve  (§§  354,  357). 

[Sensory  Paths. — Our  knowledge  is  by  no  means  precise.  Sensory  impulses, 
passing  into  the  cord,  enter  it  by  the  posterior  nerve  roots,  and  may  pass  to  the 
cerebrum  or  cerebellum.  If  to  the  cerebellum,  the  course  probably  is  partly  to 
the  direct  cerebellar  tract  and  posterior  column  to  the  restiform  body,  thence  to 
the  cerebellum.  If  to  the  cerebrum,  they  cross  the  middle  line  in  the  cord  not 
far  above  where  they  enter  and  pass  to  the  lateral  column,  in  front  of  the  pyra- 
midal tract.  Some  enter  the  posterior  column  and  others  ascend  in  the  gray  matter 
to  pass  upward.  In  the  medulla  it  is  probable  that  those  fibres  which  do  not  de- 
cussate there  do  so  in  the  pons,  the  impulses  perhaps  traveling  upward  in  the 
formatio  reticularis,  thence  into  the  posterior  half  of  the  pons,  into  the  tegmentum 
of  the  crus  under  the  corpora  quadrigemina,  to  enter  the  posterior  third  of  the 
posterior  limb  of  the  internal  capsule  (Fig.  439,  S).  But,  of  course,  the  sensory 
fibres  from  the  face  have  to  be  connected  with  the  sensory  centres  in  the  cerebrum, 
so  that  the  sensory  paths  from  the  cord,  /.  e.,  from  the  trunk  and  limbs  are  joined 
by  those  from  the  face  in  the  pons,  and  they  also  occupy  part  of  the  posterior 
third  of  the  posterior  segment  of  the  internal  capsule,  so  that  this  important  part 
of  the  internal  capsule  conducts  sensory  impulses  from  the  opposite  half  of  the 
body.  Some  of  the  fibres  pass  into  the  optic  thalamus,  and  others  enter  the  white 
matter  of  the  cerebrum,  but  their  exact  course  is  very  uncertain.  The  sensory 
fibres  derived  from  the  organs  of  special  sense,  e.  g.,  the  ear,  go  to  the  superior 
temporo-sphenoidal  convolution,  but  whether  directly  or  indirectly  we  do  not 
know  ;  perhaps  some  of  those  for  vision  traverse  the  optic  thalamus.  Some  of  the 
afferent  fibres  perhaps  go  to  the  occipital  region,  and  Gowers  asserts  that  some  of 
them  go  to  the  parietal  and  central  regions,  /.  e.,  to  the  "motor"  regions,  for 
he  holds  "  that  disea.se  of  the  motor  cortex  often  causes  impairment  of  the  tactile 
sensibility."] 

[Charcot  has  called  the  posterior  third  of  the  posterior  segment  of  the  internal 
capsule,  lying  between  the  posterior  part  of  the  lenticular  nucleus  and  the  optic 
thalamus,  the  "  Carrefour  Sensitiv  "  or  "  Sensory  Crossway  "  (Fig.  439,  Sj. 
If  it  be  divided,  there  is  hemianresthesia  of  the  opposite  side.] 

Sensory  Decussation  in  Cord. — As  the  greater  part  of  the  sensory  fibres 
from  the  skin  decussate  in  the  spinal  cord,  and  thus  pass  to  the  opposite  side  of 
the  cord  (Fig.  41 2  j,  unilateral  section  of  the  spinal  cord  in  man  (and  monkey — 
Ferrier)  abolishes  sensibility  on  the  opposite  side  below  the  lesion.  There  is 
hyperesthesia  of  the  parts  below  the  seat  of  the  section  on  the  side  of  the  injury 
(§  363).  From  experiments  on  mammals,  Brown-S6quard  concludes  that  the  de- 
cussating sensory  nerve  fibres  pass  to  the  opposite  side  within  the  cord  at  different 
levels,  the  lowest  being  the  fibres  for  touch,  then  those  for  tickling  and  pain,  and, 
highest  of  all,  those  which  administer  to  sensations  of  temperature. 

All  the  fibres,  therefore,  which  connect  the  s]iinal  cord  with  the  gray  matter  of 
the  brain,  undergo  a  complete  decussation  in  their  course.  Hence,  in  man  a  de- 
structive affection  of  one  hemisphere  usually  causes  complete  motor  paralysis  and 
loss  of  sensibility  on  the  opposite  side  of  the  body.  The  fibres  proceeding  from 
the  nuclei  of  origin  of  the  cranial  nerves  also  cross  within  the  cranium. 

Not  unfrequemly  the  motor  paralysis  and  anaesthesia  occur  on  the  same  side  of  the  head,  in  which 
case  the  lesion  (due  to  pressure  or  inflammationj  involves  the  cranial  nerves  lying  at  the  base  of  the 
brain. 


680 


CONDUCTING    PATHS    IN    THE    SPINAL   CORD. 


The  positions  of  decussation  are  (l)  in  the  spinal   cord,  (2)  in   the  medulla  oblongata,  and, 
lastly  (3),  in  the  pons.     The  decussation  is  complete  in  the  peduncle. 


Fig.  412. 


Diagram  of  a  spinal  segment  as  a  spinal  centre  and  conducting  medium.  B,  right,  B',  left  cerebral  hemisphere  ;  MO, 
lower  end  of  medulla  oblongata  :  i ,  motor  tract  from  the  right  hemisphere,  the  larger  part  decussating  at  MO,  and 
passing  down  the  lateral  column  of  the  cord  on  the  opposite  side  to  the  muscles  M  and  M' ;  2,  motor  tract  from 
the  left  hemisphere  ;  S,  S',  sensitive  areas  on  the  left  side  of  the  body  :  3',  3,  the  main  sensory  tract  from  the  left 
side  of  the  body— it  decussates  shortly  .ifter  entering  the  cord  :  S',  S',  sensitive  areas,  and  4',  4,  tracts  from  the 
right  side  of  the  body.  The  arrows  indicate  the  direction  of  the  impulses  {Braiinue/l)).  [Here  all  the  sensory 
fibres  are  shown  as  crossing  the  cord.] 


THE    MEDULLA   OBLONGATA. 


681 


Alternate  Paralysis. — Gubler  observed  that  unilateral  injury  to  the  pons  caused  paralysis  of  the 
facial  nerve  on  the  same  side,  but  paralysis  of  the  opposite  half  of  the  body.  He  concluded  that 
the  nerves  of  the  trunk  decussate  before  they  reach  the  pons,  while  the  facial  fibres  decussate  within 
the  pons.  To  these  rare  cases  the  name  "  a//ernate  /lemip/ei^ia"  h  given.  [When  hemorrhage 
takes  place  into  the  lo-ver  part  of  the  lateral  half  of  the  pons,  there  may  be  alternate  paralysis,  but 
when  the  upper  part  of  the  lateral  half  is  injured,  the  facial  is  paralyzed  on  the  saine  side  as  the 
body,  I  379.] 

The  olfactory  nerve  is  said  not  to  decussate  (?)  while  the  optic  nerve  undergoes  a  partial  decus- 
sation at  the  chiasma  (§  344).  Some  observers  assert  that  the  fibres  of  the  trochlearis  decussate  at 
their  origin. 

366.  THE  MEDULLA  OBLONGATA.— [Structure.— In  the  medulla  oblongata  the 
fibres  from  the  cord  are  rearranged,  the  gray  matter  is  also  much  changed,  while  new  gray  matter 
is  added.  Each  half  of  the  medulla  oblongata  consists  of  the  following  parts  from  before  back- 
wards :     The   anterior  pyramid,  olivary  body,  restiform   body,  and  posterior  pyramid,  or 

funiculus  gracilis  (Figs.  413,  414,  415)-     By  the  divergence  of  the  posterior  pyramids  and  the  resti- 
form bodies,  the  floor  of  the  4th  ventricle  is  exposed.     As  the  central  canal  of  the  cord  gradually 


fv.- 


ction  of  the  decussation  of  the  pyramids.  yZa,  anterior  median  fissure, 
Md:  F,  anterior  column  ;  C«,  anterior  cornu,  with  its  nerve  cells, 
_/>-,  formatio  reticularis  :  ce,  neck,  and  ff,  head  ot  the  posterior  corn 
nerve  ;  mc,  first  indication  of  the  nucleus  of  the  funiculus  cunealus  ; 
H^,  funiculus  gracilis  ;  H^,  funiculus  cuneatus  ;  sip,  posterior  medi: 
the  base  of  the  posterior  cornu.     X  6. 


splaced  laterally  by  the  fibres  decussating 
,  }>  cc,  central  canal ;  S,  lateral  column  ; 
;  r/CY,  posterior  root  of  the  1st  cervical 
',  nucleus  (clava)  of  the  funiculus  gracilis  ; 
fissure  ;  x,  groups  of  ganglionic  cells  in 


comes  nearer  to  the  posterior  surface  of  the  medulla  it  opens  into  the  4th  ventricle.  At  the  lower 
end  of  the  medulla  oblongata,  on  separating  the  anterior  pyramids,  we  may  see  the  decussation 
of  the  pyramids  where  the  fibres  cross  over  to  the  lateral  columns  of  the  cord.  The  anterior 
pyramid  receives  the  direct  pyramidal  tract  of  the  anterior  column  of  the  cord  from  its  own  side, 
and  the  crossed  pyramidal  tract  from  the  lateral  column  of  the  cord  of  the  opposite  side  (Fig.  413). 
The  decussating  fibres  (crossed  pyramidal  tract)  of  the  lateral  column  pass  across  in  oundles  to 
form  the  decussation  of  the  pyramids.  Most  of  the  pyramidal  fibres  pass  through  the  pons  directly 
to  the  cerebrum,  a  few  fibres  pass  to  the  cerebellum,  while  some  join  fibres  proceeding  from  the 
olivary  body  to  form  the  olivary  fa.sciculus  or  fillet.] 

[Thus  only  a  part  of  the  anterior  column  of  the  cord — direct  pyramidal  tract — is  continued  into 
the  anterior  pyramid,  where  it  Hes  e.\ternal  to  the  fibres  which  pass  to  the  lateral  column  of  the 
opposite  side.  The  remainder  of  the  anterior  column — the  antero-e.\ternaI  fibres — are  continued 
upward,  but  lie  deeper  under  cover  of  the  anterior  pyramid,  where  they  serve  to  form  part  of  the 
formatio  reticularis  (p.  682).] 

[Of  the  fibres  of  the  lateral  column  of  the  cord,  some,  the  direct  cerebellar  tract,  pass  backward 


682  STRUCTURE   OF   THE    MEDULLA    OBLONGATA. 

to  join  the  restiform  body  and  go  to  the  cerebellum.  These  fibres  lie  as  a  thin  layer  on  the  surface 
of  the  restiforni  body.  The  iro^sed  pyramidal  fibres  cross  obliquely  at  the  lower  end  of  the  medulla 
to  the  anterior  pyramid  of  the  opposite  side,  and  in  their  course  they  traverse  the  gray  matter  of 
the  anterior  cornu  (Fig.  413,/^').  These  fibres  form  the  larger  and  mesial  portion  of  the  anterior 
pyramid.  The  remaining  fibres  of  the  lateral  columns  are  continued  upward,  and  pass  beneath 
the  olivary  body,  where  they  are  concealed  by  this  structure  and  also  by  the  arcuate  fibres,  but  they 
appear  in  the  fioor  of  the  medulla  oblongata  and  are  ^z\\^(^  fasciculus  leres^  which  goes  to  the  cere- 
brum.    As  they  pa^s  upward  they  help  to  form  the  lateral  part  of  the  formatio  reticularis.] 

[The  posterior  pyramid  of  the  oblongata  is  merely  the  upward  continuation  of  the  postero- 
median column,  or  funiculus  gracillis  of  the  cord.  As  it  passes  upward  at  the  medulla  it  broadens 
out,  forming  the  clava,  which  tapers  away  above.  The  clava  contains  a  mass  of  gray  matter — the 
clavate  nucleus.] 

[The  restiform  body  consists  chiefly  of  the  upward  continuation  of  the  postero-external  column 
or  funiculus  cuneatus  of  the  curd.  It  contains  a  mass  of  gray  matter,  called  the  cuneate  or  tri- 
angular nucleus.  Above  the  level  of  the  clava  the  funiculus  cuneatus  forms  part  of  the  lateral 
boundary  of  the  4th  ventricle.  Immediately  outside  this,  i.e.,  between  it  and  the  continuation  of 
the  posterior  nerve  roots,  is  a  longitudinal  prominence,  which  Schwalbe  has  called  the  funiculus 
of  Rolando.  It  is  formed  by  the  head  of  the  posterior  cornu  of  gray  matter  C(  niing  nearer  the 
surface.  It  also  forms  part  of  the  restiform  body.  Some  arcuate  fibres  issue  from  the  anterior 
median  fissure,  turn  transversely  outward  over  the  anterior  pyramids  and  olivary  body,  and  pass 
along  with  the  funiculus  cuneatus,  the  funiculus  of  Rolando,  and  the  direct  cerebellar  fibres,  to 
enter  the  correspondmg  lateral  lobe  of  the  cerebellum,  all  these  structures  forming  its  inferior 
peduncle.  Some  observers  suggest  that  the  funiculus  cuneatus  and  funiculus  of  Rolando  do  not  pass 
into  the  cerebellum.] 

[The  olivary  body  forms  a  well-marked  oval  or  olive-shaped  body,  which  does  not  extend  the 
whole  length  of  the  medulla  (Fig.  415,  0).  Above,  it  is  separated  from  the  pons  by  a  groove  from 
which  the  6ih  nerve  emerges.  In  the  groove  between  it  and  the  anterior  pyramid  arise  the  strands 
of  the  hypoglossal  nerve,  while  in  a  corresponding  groove  along  its  outer  surface  is  the  line  of  exit 
of  the  vagus,  glosso- pharyngeal,  and  spinal  accessory  nerves.  It  is  covered  on  its  surface  by  longi- 
tudinal and  arcuate  fibres,  while  in  its  interior  it  contains  the  dentate  nucleus.] 

[The  functions  of  the  olivary  bodies  are  quite  unknown,  but  it  is  important  to  remember  that 
they  are  connected  by  fibres  with  the  dentate  nuclei  of  the  cerebellum.  Fibres  pass  into  the  olivary 
body  from  the  posterior  column  of  the  cord  of  the  opposite  side,  and  it  is  also  connected  with  the 
dentate  body  of  the  opposite  side,  while,  as  we  know,  the  dentate  body  is  connected  with  the  teg- 
mentum, so  that  through  the  left  dentate  body  of  the  opposite  side  the  tegmentum  of  say  the  right 
crus  is  connected  with  the  right  olivary  body  (  Go7vers).'\ 

[Decussation  of  the  Pyramids  is  the  term  given  to  those  fibres  which  cross  obliquely  in 
several  bundles  at  the  lower  part  of  the  medulla  from  the  anterior  pyramid  of  the  medulla  into  the 
lateral  column  of  the  cord  of  the  opposite  side  (Fig.  413,  d)  to  form  its  lateral  pyramid  tracts  or 
crossed  pyramidal  tracts.  The  number  of  fibres  which  decussate  varies,  and  in  some  cases  all  the 
fibres  may  cross.] 

[The  gray  matter  of  the  medulla  is  largely  a  continuation  of  that  of  the  cord,  although  it  is 
arranged  difierently.  As  the  fibres  from  the  lateral  column  of  the  cord  pass  over  to  form  part  of  the 
anterior  pyramid  of  the  medulla  on  the  opposite  side,  they  traverse  the  gray  matier.  and  thus  cut 
oft  the  tip  of  the  anterior  cornu,  which  is  also  pushed  backward  by  t'he  olivary  body,  and  exists  as 
a  distinct  mass,  the  nucleus  lateralis  (Fig.  414,  nl).  Part  of  the  anterior  gray  matter  aUo  appears 
in  the  floor  of  the  4th  ventricle  as  the  eminence  of  ihc  fasciculus  teres,  and  from  part  of  it  s^irings 
the  hypoglossal  nerve  (Fig.  415,  XII).  The  neck  joining  the  modified  anterior  and  posterior 
cornua  is  much  broken  up  by  the  passage  of  longitudinal  and  transverse  fibres  through  ir,  so  that  it 
forms  a  formatio  reticularis  {Fig.  414, _//■),  separating  the  two  cornua.  The  caput  cornu  posterioris 
comes  to  be  covered  higher  up  by  the  ascending  root  of  the  5th  nerve  (Fig.  414,  u  V),  and  arcuate 
fibres  passing  to  the  restiform  body.  The  posterior  cornu  is  also  broken  up  and  is  thrown  outward, 
its  caput  giving  rise  to  part  of  the  elevation  seen  on  the  surface  and  described  as  the  funiculus  of 
Rolando,  while  part  of  the  base  now  greatly  enlarged  forms  the  gray  matter  in  the  funiculus  gracilis 
[clavate  nucleus]  (Fig.  413,  «;')  and  funiculus  cuneatus  [cuneate  or  triangular  nucleus]  (Fig.  413, 
nc).  Nearer  the  middle  line,  the  gray  matter  of  the  posterior  gray  cornu  appears  in  the  floor  of 
the  4th  ventricle,  above  where  the  central  canal  opens  into  it,  as  the  nuclei  of  the  spinal  accessory, 
vagus  and  glosso-pharyngeal  ner\'es.] 

[In  the  floor  of  the  4th  ventricle  near  the  raphe,  and  quite  superficial,  is  a  longitudinal  mass  of 
large  multipolar  nerve  cells,  derived  from  the  base  of  the  anterior  cornu  from  which  the  several 
bundles  forming  the  hypoglossal  nerve  springs,  it  is  the  hypoglossal  nucleus  (Fig.  415,  nXII), 
the  nerve  fibres  passing  obliquely  outward  to  appear  between  the  anterior  pyramid  and  the  olivary 
body.  Internal  to  it  and  next  the  median  groove  is  a  small  mass  of  cells  continuous  with  those  in 
the  raphe,  and  called  the  nucleus  of  the  funiculus  teres  (Fig.  415,  nt).  Around  the  central  canal 
at  the  lower  part  of  the  medulla  is  a  group  of  cells  (Fig.  415,  nXI),  which  becomes  displaced  lat- 
erally as  it  comes  nearer  the  surface  in  the  floor  of  the  medulla  oblongata,  where  it  lies  outside  the 
hypoglossal  nucleus,  and  corresponds   to  the  prominence  of  the  ala  cinerea  (Fig.  415,  «A'),  and 


THE    GRAY    MATTER   OF   THE    MEDULLA   OBLONGATA. 


683 


from  it  and  its  continuation  upward  arise  from  below  upward  part  of  the  spinal  accessory  (nth), 
and  the  vagus  (loth,  corresponding  to  the  position  of  the  eminentia  cinerea— Fig.  415,  .V),  so  that 
this  column  of  cells  forms  the  vago-accessorius  nucleus.  External  to  and  in  front  of  this  is  the 
nucleus  for  the  glossopharyngeal  nerve.  Further  up  in  the  medulla,  on  a  level  with  the  auditory 
stria-  and  outside  the  previous  column,  is  a  tract  of  cells  from  which  the  auditory  nerve  (8th)  in  great 
part  arises ;  it  is  the  principal  auditory  nucleus.  It  lies  just  under  the  commencement  of  the 
inferior  cerebellar  peduncle  (  Fig.  384,  S'  8"  8'").  It  consists  of  an  outer  and  inner  nucleus,  which 
extend  to  the  middle  line.  It  forms  connections  with  the  cerebellum,  and  some  fibres  are  said  to 
enter  the  inferior  cerebellar  peduncle.  This  is  an  important  relationship,  as  we  know  that  the  ves- 
tibular branch  of  the  auditory  nerve  comes  partly  from  the  semicircular  canals,  so  that  in  this  way 
these  organs  may  be  connected  with  the  cerebellum.] 

[Superadded  Gray  Matter. — There  is  a  superadded  mass  of  gray  matter  not  represented  in  the 
cord,  that  of  the  olivary  body,  enclosing  a  nucleus,  the  corpus  dentatum,  with  its  wavy  strip  of 
gray  matter  containing  many  small  multipolar  nerve  cells  embedded  in  neuroglia.  The  gray  matter 
is  covered  on  the  surface  by  longitudinal  and  transverse  fibres.     It  is  open  toward   the  middle  line 


Fig.  414, 


si/,. 


of    the  medui:; 


-Section  of    the  medulla  ublong.11.1   at  the   so-caUa*l  upper 

nd  po-terior  median  tissnre  ;  hXI,  nucleus  of  the  accessorius  vagi  ;  «A7/,  nucleus  of  the  hypoglo 
i-called  superior  or  anterior  decussation  of  the  pyramids  ;  py,  anterior  pyramid  ;  «,  Ar,  nucleus  arciformis  ; 
O^  t  median  parolivary  body  ;  O,  beginning  of  the  nucleus  of  the  olivary  body  ;  «/,  nucleus  of  the  lateral  column  ; 
Fr,  formatio  reticularis  :  (.'.  substantia  gelatinosa,  with  trt  V)  the  ascending  root  of  the  trigeminus ;  nc,  nucleus 
of  the  funiculus  cuneatus :  «t-',  external  nucleus  of  the  funiculus  cuneatus ;  ng^  nucleus  of  the  funiculus  gracilis 
(or  clava) ;  //',  funiculus  gracilis;  //^.funiculus  cuneatus;  cc.  central  <:.z.nA\\ /a,/a^  ./a^^  external  arciform 
fibres  X  4-  Fig.  415. — Section  of  the  medulla  oblongata  through  the  olivary  body.  nXlI,  nucleus  of  the  hypo- 
glossal ;  «,V,  «-V*,  more  or  less  cellular  parts  of  the  nucleus  of  the  vagus  ;  XJI,  hypoglossal  nerve  ;  X,  vagu.i  ; 
«,  fi>«,  nucleus  ambiguus;  ///.nucleus  lateralis;  //,  olivary  nucleus;  t/rt/,  external,  and  /j/i»i,  internal  parolivary 
body  ;  yj,  the  round  bundle,  or  funiculus  solitarius ;  Cr,  restiform  body;/,  anterior  pyramid,  surrounded  by 
arciform  fibres  ;  /ae,  pot,  fibres  proceeding  from  the  olive  to  the  raphe  ^pedunculus  olivas)  ;  r,  raphe,     X  4. 

(hilum)  and  into  it  run  white  fibres  forming  \\.% peduncle  (Fig.  415,/,  0,  /).  These  fibres  diverge 
like  a  fan,  some  of  them  ending  in  connection  with  the  small  multipolar  cells  of  the  dentate  body, 
while  others  traverse  the  lamina  of  gray  matter  and  pass  backward  to  appear  as  arcuate  fibres  which 
join  the  restiform  body  ;  others,  again,  pass  directly  through  to  the  surface  of  the  olivary  body,  which 
they  help  to  cover  as  the  superficial  arcuate  fibres.  The  accessory  olivary  nuclei  (Fig.  414,  o', 
0")  are  two  small  masses  of  gray  matter  similar  to  the  last,  and  looking  as  if  they  were  detached 
from  it,  one  lying  above  and  external,  sometimes  called  the  parolivary  body,  and  the  other  slightly 
below  and  internal  to  the  olivary  nucleus,  the  latter  1  e;ng  separ.rled  fiom  the  dentate  l)ody  by  the 
roots  of  the  hypoglossal  nerve.  The  latter  is  sometimes  called  internal  parolivary  body,  or  nucleus 
of  the  pyramid.] 

[The  formatio  reticularis  occupies  the  greater  part  of  the  central  and  lateral  parts  of  the  me- 
dulla, and  is  produced  by  the  intercrossing  of  bundles  of  fibres  running  longitmlinally  and  mure  or 
less  transversely  in  the  medulla  (Fig.  414,/",  r].  In  the  more  lateral  portions  are  large  multipolar 
nerve  cells,  perhaps  continued  upwar  l  from  part  of  the  anterior  cornu,  while  the  i>art  next  the  raphe 
has  no  such  cells.     The  longitudinal  fibres  consist  of  the  upward  prolongation  of  the  antero-external 


684  FUNCTIONS   OF   THE    MEDULLA   OBLONGATA. 

columns  of  the  cord,  while  some  seem  to  arise  from  the  clavate  nuclei  and  olives  as  arcuate  fibres 
passing  upward.  In  the  lateral  portions,  the  longitudinal  fibres  are  the  direct  continuation  upward 
of  Flechsig's  anterolateral  mixed  tracts  of  the  lateral  columns  (p.  659).  The  horizontal  fibres  are 
formed  by  arcuate  fibres,  some  of  which  run  more  or  less  transversely  outward  from  the  raphe.  The 
siif-erficial  arcuate  fibres  (Fig.  415,/!  a,  e)  appear  in  the  anterior  median  fissure,  and,  perhaps,  come 
through  the  raphe  from  the  opposite  side  of  the  medulla,  curve  round  the  anterior  pyramids,  fonn  a 
kind  of  capsule  for  the  olives,  and  join  the  restiform  body  (p.  682),  but  they  are  reinforced  by  some 
of  the  deep  arcuate  fibres  which  traverse  the  olivary  body  (p.  682).  The  (/eep  arctta/e  fibres  run 
from  the  clavate  and  triangular  nuclei  horizontally  inward  to  the  raphe  and  cross  to  the  other  side, 
others  pass  from  the  raphe  to  the  olivary  body  and  through  it  to  the  restiform  body.  In  the  raphe, 
which  contains  nerve  cells,  some  fibres  run  transver.sely,  others  longitudinally,  and  others  from  before 
backward.] 

[Other  Nerve  Nuclei — Sixth  Nerve. — Under  the  elevation  called  eminentia  teres  (Fig.  384) 
in  front  of  the  auditor)'  striae,  close  to  the  middle  line,  is  a  tract  of  large  multipolar  nerve  cells.  It 
was  once  thought  to  be  the  common  nucleus  of  6th  and  7th  facial  nerves,  but  Cowers  has  shown 
that  "the  facial  ascends  to  this  nucleus,  forms  a  loop  round  it  (some  fibres,  mdeed,  go  through  it), 
and  then  passes  downward,  forward  and  outward  to  a  column  of  cells  more  deeply  placed  in  the 
medulla  than  any  other  nucleus  in  the  lower  part."  But  the  7th  has  no  real  origin  from  this  nucleus. 
Facial  Nerve. — The  nucleus  lies  deep  in  the  formatio  reticularis  of  the  pons  under  the  floor  of 
the  4th  ventricle,  but  outside  the  position  of  ihe  nucleus  of  the  6th  ( Fig.  384,  7).  It  extends  down- 
ward about  as  far  as  the  auditory  stri;ie  or  a  little  lower.  The  fifth  nerve  arises  from  its  motor 
nucleus  (with  large  multipolar  cells),  which  lies  more  superficially  above  and  external  tu  the  6th 
(F'ig.  384,  5).  The  fibres  run  backward,  where  they  are  joined  by  fibres  from  the  upper  sensory 
nucleus,  but  another  sensory  nuc  eus  extends  down  nearly  to  the  lower  end  of  the  medulla  (5"). 
Doubtless,  this  extensive  origin  brings  this  nerve  into  intimate  relation  with  the  other  cranial  nerves, 
and  accounts  for  the  numerous  reflex  acts  which  can  be  discharged  through  the  5th  nerve.  Some 
sensory  fibres  are  said  to  pass  up  beneath  the  corpora  quadrigemina  (  Gowers).  The  fourth  nerve 
arises  from  the  valve  of  Vieussens,  i.  e.^  the  lamina  of  white  and  gray  matter  which  stretches  between 
the  superior  cerebellar  peduncles.  It  arises,  therefore,  behind  the  4th  ventricle,  but  some  of  the 
fibres  spring  from  some  nerve  cells  at  the  low  er  part  of  the  nucleus  of  the  3d  nerve.  Some  fibres 
also  descend  in  the  pons  to  form  a  connection  with  the  nucleus  of  the  6th  nerve.  The  fibres  decus- 
sate behind  the  aqueduct,  so  that  in  it  alone,  of  all  the  cranial  nerves,  decussation  occurs  between  its 
nucleus  and  its  superficial  origin  {^Gowers).  The  third  nerve  arises  from  a  tract  of  cells  beneath 
the  aqueduct  and  near  the  m'ddle  line,  and  the  fibres  descend  through  the  tegmentum  to  appear  at 
the  inner  side  of  the  crus  cerebri.  Gowers  points  out  that,  in  reality,  there  are  three  distinct  func- 
tional centres,  (i)  for  accommodation  (ciliary  muscle),  (2)  for  the  light  reflex  of  the  iris,  and  (3) 
most  of  the  external  muscles  of  the  eyeball.  It  is  important  to  notice  the  connection  between  the 
nuclei  of  the  3<-l,  4th  and  6th  nerves,  in  relation  to  innervation  of  the  ocular  muscles.] 

Functions. — The  medulla  oblongata,  which  connects  the  spinal  cord  with  the 
brain,  has  many  points  of  resemblance  with  the  former.  [Like  the  cord,  it  is 
concerned  in  the  (i)  conduction  of  impulses.]  (2)  In  it  numerous  reflex  cen- 
tres are  present,  e.  g.,  for  simple  reflexes  similar  to  the  nerve  centres  in  the  spinal 
cord,  e.g.,  closure  of  the  eyelids  [so  that  they  subserve  the  transference  of  alTerent 
into  efferent  impulses].  There  are  other  centres  present  which  seem  to  dominate 
or  (T^/z/nV  similar  centres  placed  in  the  cord,  e.  g.,  the  great  vasomotor  centre,  the 
sweat-secreting,  pupil-dilating  centres,  and  the  centre  for  combining  the  reflex 
movements  of  the  body.  Some  of  the  centres  are  capable  of  being  excited  re- 
flexly  (§  358,  2).  (3)  It  is  also  said  to  contain  automatic  centres  (S  358,  3). 
The  normal  functions  of  the  centres  depend  upon  the  exchanges  of  blood 
gases  effected  by  the  circulation  of  the  blood  through  the  medulla.  If  this 
gaseous  exchange  be  interrupted  or  interfered  with,  as  by  asphyxia,  sudden  anaemia 
or  venous  congestion,  these  centres  are  first  excited,  and  exhibit  a  condition  of 
increased  excitability,  and,  if  they  are  over-stimulated,  at  last  they  are  paralyzed. 
An  excessive  temperature  also  acts  as  a  stimulus.  All  the  centres,  however,  are 
not  active  at  the  same  titne,  and  they  do  not  all  exhibit  the  same  degree  of  ex- 
citability. Normally,  the  respiratory  centre  and  the  vasomotor  centre  are  con- 
tinually in  a  state  of  rhythmical  activity.  In  some  animals  the  inhibitory  centre 
of  the  heart  remains  continually  non-excited,  in  others  it  is  stimulated  very  slightly 
under  normal  conditions,  simultaneously  with  the  stimulation  of  the  respiratory 
centre  and  only  during  inspiration.  The  spasm  centre  is  not  stimulated  under 
normal  conditions,  and  during  intra-uterine  life  the  respiratory  centre  remains 
quiescent.     The  medulla  oblongata,   therefore,  contains  a  collocation  of  nerve 


CENTRES    IN    THE    MEDULLA   OBLONGATA.  685 

centres  which  are  essential  for  the  maintenance  of  life,  as  well  as  various  conduct- 
ing paths  of  the  utmost  importance.  We  shall  treat  of  the  reflex,  and  afterward  of 
the  automatic  centres. 

367,  REFLEX  CENTRES  OF  THE  MEDULLA  OBLONGATA. 

— The  medulla  oblongata  contains  a  number  of  retle.x  centres,  which  minister  to 
the  discharge  of  a  large  number  of  coordinated  movements. 

1.  Centre  for  Closure  of  the  Eyelids. — The  sensory  branches  of  the  5th 
cranial  nerve  to  the  cornea,  conjunctiva,  and  the  skin  in  the  region  of  the  eye  are 
the  aflferent  nerves.  They  conduct  impulses  to  the  medulla  oblongata,  where 
they  are  transferred  to,  and  excite  part  of,  the  centre  of  the  facial  nerve,  and 
through  branches  of  the  facial  the  efferent  impulses  are  conveyed  to  the  orbicu- 
laris palpebrarum.     The  centre  lies  close  to  the  calamus  scriptorius  {Exner). 

The  reflex  closure  of  the  eyelids  always  occurs  on  hnlli  sides,  but  closure  may  be  produced  volun- 
tarily on  one  side  (winking).  When  the  stimulation  is  strong,  the  corrugator  and  other  groups  of 
muscles  which  raise  the  cheek  and  nose  toward  the  eye  may  also  contr.nct,  and  so  form  a  more 
perfect  protection  and  closure  of  the  eye.  Intense  stimulation  of  the  retina  causes  closure  of  the 
eyelids  [and  in  this  case  the  shortest  reflex  known,  the  latent  period,  is  0.5  second  (  VValler)'\. 

2.  Sneezing  Centre. — The  afferent  channels  are  the  internal  nasal  branches 
of  the  trigeminus  and  the  olfactory,  the  latter  in  the  case  of  intense  odors.  The 
efferent  or  motor  paths  lie  in  the  nerves  for  the  muscles  of  expiration  (§§  120, 
3,  and  347,  II).  Sneezing  cannot  be  performed  voluntarily  [but  it  maybe  inhib- 
ited by  compressing  the  nasal  nerve  at  its  exit  on  the  nose]. 

3.  Coughing  Centre. — .\ccording  to  Kohts,  it  is  placed  a  little  above  the 
inspiratory  centre  ;  the  afferent  paths  are  the  sensory  branches  of  the  vagus 
(§352,  5,  (?).  The  efferent  paths  lie  in  the  nerves  of  expiration  and  those  that 
close  the  glottis  (§  120,  i). 

4.  Centre  for  the  Movements  of  Sucking  and  Mastication. — The 
afferent  paths  lie  in  the  sensory  branches  of  the  nerves  of  the  mouth  and  lips 
(2d  and  3d  branches  of  the  trigeminus  and  glosso-pharyngeal).  The  efferent 
nerves  for  suction  (§  152)  are:  Facial  for  the  lips,  hypoglossal  for  the  tongue,  the 
inferior  maxillary  division  of  the  trigeminus  for  the  muscles  which  elevate  and 
depress  the  jaw.  For  the  movements  of  mastication  the  same  nerves  are  in  action 
(S  153),  but  when  food  passes  within  the  dental  arch  the  hypoglossal  is  concerned 
in  the  movements  of  the  tongue,  and  the  facial  for  the  buccinator. 

5.  Centre  for  the  Secretion  of  Saliva  (p.  241),  which  lies  in  the  floor  of 
the  4th  ventricle.  Stimulation  of  the  medulla  oblongata  causes  a  profuse  secre- 
tion of  saliva,  when  the  chorda  tympani  and  glosso-pharyngeal  nerves  are  intact, 
a  much  feebler  secretion  when  the  nerves  are  divided,  and  no  secretion  at  all 
when  the  cervical  symjiathetic  is  extirjjated  at  the  same  time  (  Griitzner). 

6.  Swallowing  Centre  in  the  floor  of  the  4th  ventricle  (§  156). — The 
afferent  paths  lie  in  the  sensory  branches  of  the  nerves  of  the  mouth,  palate, 
and  pharynx  (2d  and  3d  branches  of  the  trigeminus,  glosso-pharyngeal,  and 
vagusj  ;  the  efferent  channels  in  the  motor  branches  of  the  pharyngeal  plexus 
(§  352.  4)- 

According  to  .Steiner,  every  time  we  swallow  there  is  a  slight  stimulation  of  the  respiratory  centre, 
resulting  in  a  slight  contraction  of  the  diaphragm.  [Kronecker  has  shown  that  if  a  glass  of  water 
be  sipped  slowly,  the  action  of  the  cardio-inhibitory  centre  is  interfered  with  reflexly,  so  that  the 
heart  tieats  much  more  rapidly,  whereby  the  circulation  is  accelerated,  hence  probably  why  sipping 
an  alcoholic  drink  intoxicates  more  rapidly  than  when  it  is  ijuickly  swallowed.] 

7.  Vomiting  Centre  (§  158). — The  relation  of  certain  brancHtes  of  the  vagus 
to  this  art  are  given  at  §  352,  2,  and  12,  li. 

8.  The  upper  centre  for  the  dilator  pupillae  muscle,  the  smooth  muscles 
of  the  orbit,  and  the  eyelids  lies  in  the  mtdulla  oblongata.  The  fibres  pass  out 
partly  in  the  trigeminus  (§  347^  I,  3),  partly  in  the  lateral  columns  of  the  spinal 
cord  as  fiir  down  as  the  cilio-spinal  region,  and  pass  out  by  the  two  lowest  cervical 


686  POSITION    OF   THE    RESPIRATORY    CENTRE. 

ard  the  two  upper  dorsal  nerves  into  the  cervical  sympathetic  (§  356,  A,  i).  The 
centre  is  normally  excited  reflexly  by  shading  the  retina,  /.  e.,  by  diminishing 
the  amount  of  light  admitted  into  the  eye.  It  is  directly  excited  by  the  circula- 
tion of  dyspnojic  blood  in  the  medulla.  (The  centre  for  contracting  the  pupil  is 
referred  to  at  §§  345  and  392.) 

9.  There  is  a  subordinate  centre  in  the  medulla  oblongata,  which  seems  to  be  concerned  in  bring, 
ing  the  various  reflex  centres  of  the  cord  into  relation  with  each  other.  Owsjannikow  found  that, 
on  dividing  the  medulla  6  mm.  above  the  calamus  scriptorius  (rabbit)  the  fcw^'i?/ reflex  movements 
of  the  body  still  occurred,  and  the  anterior  and  posterior  extremities  participated  in  such  general 
movements.  If,  however,  the  section  was  made  I  mm.  nearer  the  calamus,  only  local  partial  reflex 
actions  occurred  (\  360,  III,  4)  ;  [thus,  on  stimulating  the  hind  leg,  the  fore  legs  did  not  react — 
the  transference  of  the  reflex  was  interfered  with].  The  centre  reaches  upward  to  slightly  above 
the  lowest  third  of  the  oblongata. 

Pathological. — The  medulla  oblongata  is  sometimes  the  seat  of  a  typical  disease,  known  as 
bulbar  paralysis,  or  glosso-pharyngo-labial  paralysis  (Diichenne,  1S60),  in  which  there  is  a  pro- 
gressive invasion  of  the  different  ner\'e  nuclei  (centres),  of  the  cranial  nerves  which  arise  within 
the  medulla,  these  centres  being  the  motor  portions  of  an  important  reflex  apparatus.  Usually  the 
disease  begins  with  paralysis  of  the  tongue,  accompanied  by  fibrillar  contractions,  whereby  speech, 
formation  of  the  food  into  a  bolus,  and  swallowing  are  interfered  with  (^  354).  The  secretion  of 
thick  viscid  saliva  points  to  the  impossibility  of  secreting  a  thin,  watery /i?eia/  saliva  (§  145,  A), 
owing  to  paralysis  of  this  nerve  nucleus.  Swallowing  may  be  imposihle,  owing  to  paralysis 
of  the  pharynx  and  palate.  This  interferes  with  the  formation  of  consonanls  [especially  the 
linguals, /, /,  J,  )-,  by  and  by  the  labial  explosives  b,  p,]  (^318,  C);  the  speech  becomes  nasal, 
while  fluids  and  solid  food  often  pass  into  the  nose.  Then  follows  paralysis  of  the  branches 
of  the  facial  to  the  lips,  and  there  is  a  characteristic  expression  of  the  mouth  "  as  if  it  were 
frozen."  All  the  muscles  of  the  face  may  be  paralyzed;  sometimes  the  laryngeal  mttseles  are 
paralyzed,  leading  to  the  loss  of  voice  and  the  entrance  of  food  into  the  windpipe.  The  heart 
bents  are  often  slo-a>edf  pointing  to  stimulation  of  the  cardio-inhibitory  fibres  (arising  from  the  acces- 
sorius).  Attacks  of  dyspnaa,  like  those  following  paralysis  of  the  recurrent  nerves  \\  313,  II.  I, 
and  J  352,  5,  b),  and  death  may  occur.  Paralysis  of  the  muscles  of  mastication,  contraction  of  the 
pupil,  and  paraWsis  of  the  abducens  are  rare.  [This  disease  is  always  bilateral,  and  it  is  important 
to  note  that  it  affects  the  nuclei  of  those  muscles  that  guard  the  orifices  of  the  mouth,  including  the 
tongue,  the  posterior  nares  including  the  soft  palate,  and  the  rima  glottidis  with  the  vocal  cords.] 

368.  THE  RESPIRATORY  CENTRE  AND  THE  INNERVA- 
TION OF  THE  RESPIRATORY  APPARATUS.— The  respiratory 
centre  lies  in  the  medulla  oblongata  KLcgaUois),  behind  the  point  of  origin  of 
the  vagi,  on  both  sides  of  the  posterior  as])ect  of  the  apex  of  the  calamus  scrip- 
torius, between  the  nuclei  of  the  vagus  and  accessorius  {Flourens),  and  was  named 
by  Flourens  the  vital  point,  or  noeud  vital.  The  centre  is  double,  one  for  each 
side,  and  it  may  be  separated  by  means  of  a  longitudinal  incision  lyLonget),  whereby 
the  respiratory  movements  continue  symmetrically  on  both  sides.  Section  of 
Vagi. — If  one  vagus  be  divided,  respiration  on  that  side  is  slowed.  If  I'oth  vagi 
be  divided,  the  respirations  become  much  shiver  and  deeper,  but  the  respiratory 
movements  are  symmetrical  on  both  sides.  Stimulation  of  the  centra/ end  of  one 
vagus,  both  being  divided,  causes  an  arrest  of  the  respiration  only  on  the  same 
side,  the  other  side  continues  to  breathe.  The  same  result  is  obtained  by  stimula- 
tion of  the  trigetninus  on  one  side  {Langendorff).  When  the  centre  is  divided 
transversely  on  one  side,  the  respiratory  movements  on  the  same  side  cease 
{Schiff).  Most  probably  the  dominating  respiratory  centre  lies  in  the  medulla 
oblongata,  and  upon  it  depends  the  rhythm  and  symmetry  of  the  respiratory 
movements  ;  but,  in  addition,  other  and  subordinate  centres  are  placed  in  the 
spinal  cord,  and  these  are  governed  by  the  oblongata  centre.  If  the  spinal  cord 
be  divided  in  newly-born  animals  (dog,  cat)  below  the  medulla  oblongata,  respi- 
ratory movements  of  the  thorax  are  sometimes  observed  {^Bracket  {i8jj),  Laitten- 
bach,  and  Langendorff'). 

[If  the  cord  be  divided  below  the  medulla,  or  the  cranial  arteries  ligatured  (rabbit),  there  may 
still  be  respiratory  movements,  which  become  more  distinct  if  strychnin  be  previously  administered, 
so  that  Langendorfl"  assumes  the  existence  of  a  spinal  respiratory  centre,  which  he  finds  is  also  in- 
fluenced by  reflex  stimulation  of  sensory  nerves.] 


CEREBRAL    INSPIRATORY   CENTRE. 


<J87 


Fig.  416. 


Anatomical. — According  to  Giercke,  Heidenhain,  and  Langendorff,  those  parts  of  the  medulla 
oblongata  whose  destruction  causes  cessation  of  the  respiratory  movements,  are  not  gray  cellular 
substance,  but  only  single  or  double  strands  of  nervous  matter  running  downward  in  the  substance 
of  the  medulla  oblongata.  These  strands  are  said  to  arise  partly  from  the  roots  of  the  vagus, 
trigeminus,  spinal  accessory,  and  glosso-pharyngeal  (Miynerl),  forming  connections  by  means  of 
fibres  with  the  other  side,  and  descending  as  far  downward  as  the  cervical  enlargement  of  the  spinal 
cord  (Go//).  According  to  this  view,  this  strand  represents  an  inttr-central  band  connecting  the 
spinal  cord  (the  place  of  origin  of  the  motor  respiratory  nerves)  with  the  nuclei  of  the  above-named 
cranial  nerves. 

Cerebral  Inspiratory  Centre. — According  to  Christian!,  there  is  a  cerebral 
inspiratorv  centre  in  the  optic  thalamus  in  the 
floor  of  tiie  3d  ventricle,  which  is  stimulated 
through  the  optic  and  auditory  nerves,  even 
after  e.xtirpation  of  the  cerebrum  and  corpora 
striata ;  when  it  is  stimulated  directly,  it 
deepens  and  accelerates  the  inspiratory  move- 
ments, and  may  even  cause  a  stand-still  of  the 
respiration  in  the  inspiratory  phase.  This 
inspiratory  centre  may  be  extirpated.  After 
this  operation,  an  expiratory  centre  is  active 
in  the  substance  of  the  anterior  pair  of  the 
corpora  quadrigemina,  not  far  from  the  aque- 
duct of  Sylvius.  Lastly,  Martin  and  Booker 
describe  a  second  cerebral  inspiratory  centre 
in  the  posterior  pair  of  the  corpora  quadri- 
gemina. These  three  centres  are  connected 
with  the  centres  in  the  meduHa  oblongata. 

Inspiratory  and  Expiratory  Centres. 
— The  respn-atory  centre  consists  of  iivo  cen- 
tres, which  are  in  a  state  of  activity  alternately 
— an  inspiratory  and  an  expiratory  centre 
(Fig.  416),  each  one  forming  the  motor  cen- 
tral point  for  the  acts  of  inspiration  and  ex- 
piration (§  112).  The  centre  is  automatic, 
for,  after  section  of  all  the  sensory  nerves 
which  can  act  reflexly  upon  the  centre,  it  still 
retains  its  activity.  The  degree  of  excita- 
bility and  the  stimulation  of  the  centre  depend 
upon  the  state  of  the  blood,  and  chiefly 
upon  the  amount  of  the  blood  gases,  the  O 
and  CO^  (y.  Rosentlial). 

According  to  the  condition  of  the  centre,  there  are  several  well-recognized 
respiratory  conditions : — 

I.  Apnoea. — Complete  cessation  of  the  respiration  constituting  apnxa,  i.e., 
cessation  of  the  respiratory  movements,  owing  to  the  absence  of  the  proper  stimu- 
lus, due  to  the  blood  being  saturated  with  O  and  poor  in  COo.  Such  blood  satu- 
rated with  O  fails  to  stimulate  tlie  centre,  and  hence  the  respiratory  muscles  are 
quiescent.  This  seems  to  be  the  condition  in  the  foetus  during  intra-uterine  life. 
If  air  be  vigorously  and  rapidly  forced  into  the  lungs  of  an  animal  by  artificial 
respiration,  the  animal  will  cease  to  breathe  for  a  time  after  cessation  of  the  arti- 
ficial respiration  {Hook,  i66j),  the  blood  being  so  arterialized  that  it  no  longer 
stimulates  the  respiratory  centre.  If  a  person  takes  a  series  of  rapid,  deep  respi- 
rations, his  blood  becomes  surcharged  with  oxygen,  and  long  "  apnceic  pauses  " 
occur. 

Apnceic  Blood. — A.  Ewald  found  that  the  arterial  blood  of  apnoeic  animals  was  completely 
STtur.ited  with  ( ),  while  the  CO,^  was  diminished  ;  the  venous  blood  contained  less  O  than  normal 
— this  latter  condition  tieing  due  to  the  apnceic  blood  causing  a  considerable  fall  of  the  blood  pres?ure 


Scheme  of  the  chief  respiratory'  nerves  {Ruther- 
ford). IKS,  inspiratory,  and  ejrp,  expiratory 
centre — motor  nerves  are  in  smooth  lines. 
Expiratory  motor  nerves  to  abdominal  mus- 
cles, «($;  to  muscles  of  back,  (/i3.  Inspiratory 
motor  nerves,  /•/i,  phrenic  to  diaphragm,  d: 
ill/,  intercostal  nerves  :  ri,  recurrent  laryn- 
geal :  ejr,  pulmonary  fibres  of  vagus  that  ex- 
cite inspiratory  centre  :  e.t',  pulmonary  fibres 
that  excite  expiratory  centre  ;  t^-r",  fibres  of 
sup.  laryngeal  that  excite  expiratory  centre  ; 
I'n/i,  fibres  of  sup.  laryngeal  that  inhibit  the 
inspiratory  centre. 


688  ASPHYXIA. 

and  consequent  slowing  of  the  blood  stream,  so  that  the  O  can  be  more  completely  taken  from  the 
blood  in  the  capillaries  (P/lu^'ey).  The  amount  of  O  used  in  apncea,  on  the  whole,  is  not  increased 
(§  127).  Gad  remarks  that  during  forced  arlificial  rfsfiration,  the  pulmonary  alveoli  contain  a 
very  large  amount  of  atmospheric  air ;  hence  they  are  able  to  arterialize  the  blood  for  a  longer  time, 
thus  diminishing  the  necessity  for  respiration. 

[Drugs. — If  the  excitability  of  the  respiratory  centre  be  diminished  by  chloral,  apncea  is  readily 
induced,  while,  if  the  centre  be  excited,  as  by  apomorphine,  it  is  difficult  to  produce  it.] 

2.  Eupncea.— The  normal  stimulation  of  the  respiratory  centre,  eupmva,  is 
caused  by  the  blood  in  which  the  amount  of  O  and  CO2  does  not  exceed  the 
normal  limits  (§§  35  and  36). 

3.  DyspncEa. — All  conditions  which  diminish  the  O  and  increase  the  COj  in 
the  blood  circulating  through  the  medulla  and  respiratory  centre  cause  accelera- 
tion and  deepening  of  the  respirations,  which  may  ultimately  pass  into  vigorous 
and  labored  activity  of  all  the  respiratory  muscles,  constituting  dyspmva,  when  the 
difficulty  of  breathing  is  very  great  (§  134).     [Changes  in  the  rhythm,  §  iii.] 

4.  Asphyxia. — If  blood,  abnormal  as  regards  the  amount  and  quality  of  its 
gases,  continues  to  circulate  in  the  medulla,  or  if  the  condition  of  the  blood  be- 
come still  more  abnormal,  the  respiratory  centre  is  over-sfimiilaUd,  and  ultimately 
exhausted.  The  respirations  are  diminished  both  in  number  and  depth,  and  they 
become  feeble  and  gasping  in  character  ;  ultimately  the  movements  of  the  respi- 
ratory muscles  cease,  and  the  heart  itself  soon  ceases  to  beat.  This  constitutes  the 
condition  of  asphyxia,  and  if  it  be  continued  death  from  suffocation  takes  place. 
(Langendorff  asserts  that  in  asphyxiated  frogs  the  muscles  and  gray  nervous  sub- 
stance have  an  acid  reaction.)  If  the  conditions  causing  the  abnormal  condition 
of  the  blood  be  removed,  the  asphyxia  may  be  prevented  under  favorable  circum- 
stances, especially  by  using  artificial  respiration  (§  134)  ;  the  respiratory  mus- 
cles begin  to  act  and  the  heart  begins  to  beat,  so  that  the  normal  eupnreic  stage 
is  reached  through  the  condition  of  dyspnoea.  If  the  venous  condition  of  the 
blood  be  produced  slowly  and  very  gradually,  asphyxia  may  take  place  without 
there  being  any  symptoms  of  dyspnoea,  as  occurs  when  death  takes  place  quietly 
and  very  gradually  (§  324,  5). 

Causes  of  Dyspnoea. — ( i )  Direct  Hmilation  of  the  activity  of  the  respiratory  organs ; 
diminution  of  the  respiratory  surface  by  inflammation,  acute  oedema  {\  47),  or  collapse  of  the 
alveoli,  occlusion  of  the  capillaries  of  the  alveoli,  compression  of  the  lungs,  entrance  of  air  into 
the  pleura,  obstruction  or  compression  of  the  windpipe.  (2)  Obstricetion  to  the  entrance  of  the 
normal  amount  of  air  by  strangulation,  or  enclosure  in  an  insufficient  space.  (3)  Enfeeblement  oj 
the  circulation,  so  that  the  medulla  oblongata  does  not  receive  a  sufficient  amount  of  blood  ;  in 
degeneration  of  the  heart,  valvular  cardiac  disease,  and  artificially  by  ligature  of  the  carotid  and 
vertebral  arteries  (A'ussmaul ami  Tenner),  or  by  preventing  the  free  efflux  of  venous  blood  from 
the  skull,  or  by  the  injection  of  a  large  quantity  of  air  or  indifferent  particles  into  the  right  heart. 
(4)  Direct  loss  of  blood,  which  acts  by  arresting  the  exchange  of  gases  in  the  medulla  (J.  A'nscn- 
Uial).  This  is  the  cause  of  the  "biting  or  snapping  at  the  air"  manifested  by  the  decapitated 
heads  of  young  animals,  e.g.,  kittens.  [The  phenomenon  is  well  marked  in  the  head  of  a  tortoise 
separated  from  the  body  {  W.  S/irlin:;).]  AH  these  factors  act  rapidly  upon  the  respiratory  activity, 
and  at  first  the  respirations  are  deeper  and  more  rapid,  and  afterward  the  respiratory  movements 
become  more  violent  and  general  convulsions  occur,  ending  with  expiratory  spasm,  which  is  fol- 
lowed by  a  stage  of  cessation  of  the  respiration  and  c  miplete  relaxation.  Before  death  takes 
place  there  are  usually  a  few  "snapping  "  or  gasping  efforts  at  inspiration  (Hogyes,  Sigm.  Mayer — 
I  III). 

Condition  of  the  Blood  Gases. — As  a  general  rule,  in  the  production  of  dyspnoea  the  want  of 
O  and  the  excess  of  COj  act  simultaneously  [Pfliigcr  and  Dohmen),hv.\.  each  of  these  alone  may 
act  as  an  efficient  cause.  According  to  Bernstein,  blood  containing  a  small  amount  of  O  acts 
chiefly  upon  the  inspiratory  centre,  and  blood  rich  in  COj  on  the  expiratory  centre.  Dyspnrea, 
from  want  of  O,  occurs  during  respiration  in  a  space  of  mo'dirate  size  (|  133),  in  spaces  where  the 
tension  of  the  air  is  diminished,  and  by  breathing  in  indifferent  gases  or  those  containing  no  free  O. 
When  the  blood  is  freely  ventilated  with  N  or  H,  the  amount  of  CO^  in  the  blood  may  even  be 
diminished,  and  death  occurs  with  all  the  signs  of  asphyxia  {J'fliiger).  Dyspncea,  from  the  blood 
being  overcharged  with  CO,,  occurs  by  bieathing  air  conia'nmg  much  CO^  (J  133).  Air  contain- 
ing much  CO  2  may  cause  dyspncea,  even  when  the  amount  of  O  in  the  blood  is  greater  than  that 
in  the  atmosphere  (  Thiry).     The  blood  may  even  contain  more  O  than  normal  (Pfliiger). 

Heat  Dyspncea. — An  increased  temperature  increases  the  activity  of  the  respiratory  centre 


CONDITIONS   ACTING   ON   THE   RESPIRATORY   CENTRE.  689 

(I  214,  I[,  3).  This  occurs  when  blood  warmer  than  natural  flows  through  the  brain,  as  Kick  and 
Goldstein  observed  when  they  placed  the  exposed  carotids  in  warm  tubes,  so  as  to  heat  the  blood 
passing  through  them.  In  this  case  the  heated  blood  acts  directly  upon  the  brain,  the  medulla  and 
the  cerebral  respiratory  centres  {Gad).  Direct  cooling  diminishes  the  excitability  [FrcJi-ricq). 
When  the  temperature  is  increased,  vigorous  artificial  respiration  does  not  produce  apncea,  although 
the  blood  is  highly  arterialized  {Ackermann).  Emetics  art  in  a  similar  manner  [Hermann  and 
Grimm). 

Electrical  stimulation  of  the  medulla  oblongata  separated  from  the  brain  discharges  respiratory 
movements  [Kronecker  and  Mankwa/d ^,  or  increases  those  already  present.  Langemlorff  found 
that  electrical,  mechanical  or  chemical  (salts)  stimulation  usually  caused  an  expiratory  effect,  while 
stimulation  of  the  cervical  spinal  cord  (subordinate  centre)  gave  an  inspiratory  effect.  According 
to  Laborde,  a  superficial  lesion  in,  the  region  of  the  calamus  scriptorius  causes  stand  still  of  the 
respiration  for  a  few  minutes.  If  tne  peripheral  end  of  the  vagus  be  stimulated  so  as  to  arrest  the 
action  of  the  heart,  the  respirations  also  cease  after  a  few  seconds.  Arrest  of  the  heart's  action 
causes  a  temporary  ana;mia  of  the  medulla,  in  consequence  of  which  its  excitability  is  lowered,  so 
that  the  respirations  cea.se  for  a  time  (Langindorff ). 

Action  on  the  Centre. — The  respiratory  centre,  besides  being  capable  of 
being  stimulated  directly,  may  be  influenced  by  the  ■will,  and  also  reflexly  by 
stimulation  of  a  number  of  afferent  nerves. 

1.  By  a  voluntary  impulse  we  may  arrest  the  respiration  for  a  short  time, 
but  only  until  the  blood  Decomes  so  venous  as  to  excite  the  centre  to  increased 
action.  The  number  and  depth  of  the  respirations  may  be  voluntarily  increased 
for  a  long  time,  and  we  may  also  voluntarily  change  the  rhythm  of  respiration. 

2.  The  respiratory  centre  may  be  influenced  reflexly  both  by  fibres  which 
excite  it  to  increased  action  and  by  others  which  inhibit  its  action,  {a)  The 
exciting  fibres  lie  in  the  pulmonary  branches  of  the  vagus,  in  the  optic,  audi- 
tory and  sensory  cutaneous  nerves,  and  normally  their  action  overcomes  the 
action  of  the  inhibitory  fibres.  Thus  a  cold  bath  deepens  the  respirations,  and 
causes  a  moderate  acceleration  of  the  pulmonary  ventilation  (Speck). 

Section  of  both  vagi  causes  slower  and  deeper  respiratory  movements, 
owing  to  the  cutting  off  of  those  impulses  which  under  normal  conditions  pass 
from  the  lungs  to  excite  the  respiratory  centre.  The  amount  of  air  taken  in 
and  CO2  given  off,  however,  is  unchanged.  The  inspiratory  efforts  are  more 
vigorous  and  not  so  purposive  {Gad).  IVeak  tetanizing  currents  applied  to  the 
central  end  of  the  vagus  cause  acceleration  of  the  respirations  {Budge,  Eckhard), 
while  at  the  same  time  the  efforts  of  the  respiratory  muscles  may  be  increased  or 
diminished  or  remain  unchanged  (  Gad).  ^V/w/j,'- tetanizing  currents  cause  stand- 
still of  the  respiration  in  the  inspiratory  phase  {Traube)  or  expiratory  phase 
{Budge,  Burkart).  Single  induction  shocks  have  no  effect  {Marckwald  and  Kro- 
ne cker). 

Wedenski  and  Heidenhain  have  recently  reinvestigated  the  effect  of  stimulation  of  the  vagus 
upon  the  respiration.  They  find  that  a  temporary  weak  electrical  stimulus  applied  to  the  central 
end  of  the  vagus,  at  the  beginning  of  inspiration  (rabbit),  affects  the  depth  of  the  succeeding 
inspirations,  wiiile  a  similar  strong  stimulus  affects  also  the  depth  of  the  following  expirations.  If 
the  stimulus  be  applied  just  at  the  commencement  of  expiration,  stronger  stimuli  being  required  in 
this  case,  there  is  a  diminution  of  the  expiration  and  of  the  following  inspiration.  Continued  tetanic 
stimulation  of  the  vagus  may  cause  decrease  in  the  depth  of  the  expirations,  or  at  the  same  time 
alteration  in  the  depth  of  the  inspirations,  without  affecting  the  respiratory  rhythm ;  when  the  stimu- 
lation is  stronger,  inspiration  and  expiration  are  diminished  witli  or  without  alteration  of  the  fre- 
quency, and  with  the  strongest  stimuli  respirations  cease  either  in  the  inspiratory  or  expiratory 
phase. 

{b)  The  inhibitory  nerves  which  affect  the  respiratory  centre  lie  in  the  superior 
laryngeal  nerve  {Rosenthal),  and  also  in  the  inferior  {Pflilger  and  Burkart,  Her- 
ing,  Breuer)  (Fig.  416,  ink). 

According  to  Langendorff,  direct  electrical,  mechanical,  or  chemical  stimulation  of  the  centre  may 
arrest  respiration,  perhaps  in  consequence  of  the  stimulus  affecting  the  central  ends  of  these  inhibi- 
tory nerves  where  they  enter  the  ganglia  of  the  respiratory  centre. 

Stimulation  of  the  superior  or  inferior  laryngeal  nerves  {b)  or  their  central  ends 
causes  slowing,   and  even  arrest  of  the  respiration   (in   expiration — Rosenthal). 
44 


690  METHODS   OF    PERFORMING    ARTIFICIAL    RESPIRATION. 

Arrest  of  the  respiration  in  expiration  is  also  caused  by  stimulation  of  the  nasal 
{Ho-iag  and  Kratschmer)  and  ophthalmic  branches  of  the  trigeminus  (  Cliristiani) ; 
stimulation  of  the  pulmonary  branches  of  the  vagus  by  breathing  irritating  gases 
{Knoll),  although  other  gases  cause  stand-still  in  inspiration.  Chemical  stimula- 
tion of  the  trunk  of  the  vagus — by  dilute  solutions  of  sodic  carbonate — causes 
expiratory  inhibition  of  the  respiration  ;  and  mechanical  stimulation — rubbing 
with  a  glass  rod — inspiratory  inhibition  {Knoll).  The  stimulation  of  sensory 
cutaneous  nerves,  especially  of  the  chest  and  abdomen,  as  occurs  on  taking  a  cold 
douche,  and  stimulation  of  the  splanchnics,  cause  stand-still  in  expiration  {Schiff, 
Falk),  the  first  cause  often  giving  rise  to  temporary  clonic  contractions  of  the  re- 
spiratory muscles.  The  respirations  are  often  slowed  to  a  very  great  extent  by 
pressure  upon  the  brain  [whether  the  pressure  be  due  to  a  depressed  fracture  or 
effusion  into  the  ventricles  and  subarachnoid  space].  The  respiration  may  be 
greatly  oppressed  and  stertorous. 

The  amount  of  work  done  by  the  respiratory  muscles  is  altered  during  the  reflex  slowing  of  the 
respiratory  muscles,  the  work  being  increased  during  sliw  respiration,  owing  to  the  ineffectual  in- 
spiratory efforts  ( Gad).  The  volume  of  the  gases  which  passes  through  the  lungs  during  a  given 
time  remains  unchanged  (I'alfiitin),  and  the  gaseous  exchanges  are  not  altered  at  first  (  Voil  and 
Rauber). 

Automatic  Regulation  of  the  Respiratory  Centre. — Under  normal  cir- 
cumstances, it  would  seem  that  the  pulmonary  branches  of  the  vagus  act  upon  the 
two  respiratory  centres,  so  as  to  set  in  action  what  has  been  termed  the  self-adjust- 
ing mechanism  ;  thus,  the  inspiratory  dilatation  of  the  lungs  stimulates  mechani- 
cally the  fibres  which  reflexly  excite  the  expiratory  centres,  while  the  diminution 
of  the  lungs  during  expiration  excites  the  nerves  which  proceed  to  the  inspiratory 
centre  ( Hering  and  Breuer). 

Discharge  of  the  First  Respiration. — The  fcetusis  in  an  apnreic  condition 
until  birth,  when  the  umbilical  cord  is  cut.  During  intra-uterine  life  O  is  freely 
supplied  to  it  by  the  activity  of  the  placenta.  All  conditions  which  interfere  with 
this  due  supply  of  O,  as  compression  of  the  umbilical  vessels  and  prolonged  labor 
pains,  cause  a  decrease  of  the  O  and  an  increase  of  the  COj  in  the  blood,  so  that  the 
condition  of  the  foetal  blood  is  so  altered  as  to  stimulate  the  respiratory  centre, 
and  thus  the  impulse  is  given  for  the  discharge  of  the  first  respiratory  movement 
{Schwartz).  A  foetus  still  within  the  unopened  fcetal  membranes  may  make  re- 
spiratory movements  {Vcsalius,  1542).  If  the  exchange  of  gases  be  interrupted 
to  a  sufficient  extent,  dyspncea  and  ultimately  death  of  the  foetus  may  occur.  If, 
however,  the  venous  condition  of  the  mother's  blood  develops  very  slowly,  as  in 
cases  of  quiet,  slow  death  of  the  mother,  the  medulla  oblongata  of  the  fojtus  may 
gradually  die  without  any  respiratory  movement  being  discharged  (§  324,  5). 

According  to  this  view,  the  respiratory  movements  are  due  to  the  direct  action  of  the  dyspnoeic 
blood  upon  the  medulla  oblongata.  Death  of  the  mother  acts  like  compression  of  the  umbilical 
cord.  In  the  former  case,  the  maternal  venous  blood  robs  the  fcetal  blood  of  its  O,  so  that  death  of 
the  fcetus  occurs  more  rapidly  (Ziinlz).  If  the  mother  be  rapidly  poisoned  with  CO  (§  17),  the  foetus 
may  live  longer,  as  the  COhajmoglobin  of  the  maternal  blood  cannot  take  any  O  from  the  foetal 
blood  {\  id^Hogyes).  In  slow  poisoning,  the  CO  passes  into  the  fcetal  blood  (  Grihant  and  Quin- 
quand). 

In  many  cases,  especially  in  cases  of  very  prolonged  labor,  the  excitability  of  the  respiratory  centre 
may  be  so  diminished,  that  after  birth  the  dyspnceic  condition  of  the  blood  alone  is  not  sufficient  to 
excite  respiration  in  a  normal  rhythmical  manner.  In  such  cases  stimulation  of  the  siin  also  acts, 
e.  g.,  partly  by  the  cooling  produced  by  the  evaporation  of  the  amniotic  fluid  from  the  skin.  When 
air  has  entered  the  lungs  by  the  first  respiratory  movements,  the  air  within  the  lungs  also  excites  the 
pulmonary  branches  of  the  vagus  (Pflii^er).  and  thus  the  respiratory  centre  is  stimulated  reflexly  to 
increased  activity.  According  to  v.  Preuschen's  observations,  stimulation  of  the  cutaneous  nerves 
is  more  effective  than  that  of  the  pulmonary  branches  of  the  vagus.  In  animals  which  have  been 
rendered  apnceic  by  free  ventilation  of  their  lungs,  respiratory  movements  may  be  discharged  by 
strong  cutaneous  stimuli,  e.  g.,  dashing  on  of  cold  water.  The  mechanical  stimulation  of  the  skin 
by  friction  or  sh.-irp  blows,  or  the  application  of  a  cold  douche,  excites  the  respiratory  centre  (Arti- 
ficial Respiration,  J  '34). 


DIRECT   STIMULATION    OF   THE    CARDIO-INHIBITORY   CENTRE.      691 

[Action  of  Drugs  on  the  Respiratory  Centre. — -Ammonia,  salts  of  zinc  and  copper,  strychnin, 
atropin,  duboisin,  apomorpliin,  emetin,  the  digitalis  group,  and  heat  increase  the  rapidity  and  depth 
of  the  respirations,  while  they  become  frequent  and  shallower  after  the  use  of  alcohol,  opium, 
chloral,  chloroform,  physostigmin.  The  excitability  of  the  centre  is  first  increased  and  then  di- 
minished by  cafl'ein,  nicotin,  quinine,  and  saponin  (Bntii/on).] 

369.  THE  CENTRE  FOR  THE  INHIBITORY  NERVES  OF 
THE  HEART— (CARDIO-INHIBITORYj.— The  fibres  of  the  vagus 
which  when  moderately  stimulated  diminish  the  action  of  the  heart,  when  strongly 
stimulated,  however,  arrest  its  action  and  cause  it  to  stand  still  in  diastole  (§  352,7), 
are  supplied  to  the  vagus  througii  the  spinal  accessory  nerve  (§  353),  and  have 
their  centre  in  the  medulla  oblongata. 

[Guskell  has  shown  that  stimulation  of  the  vagus  not  only  influences  the  rhythm 
of  the  heart's  action,  but  it  modifies  the  other  functions  of  the  cardiac  muscle. 
Stimulation  of  the  vagus  infiuences — {a)  the  aictomatic  rhythm,  i.  e.,  the  rate 
at  which  the  heart  contracts  automatically ;  (/')  i\\c/o>re  of  the  contractions,  more 
especially  the  auricles,  although  in  some  animals,  e.  g.,  the  tortoise,  the  ventricles 
are  not  affected  ;  (c)  the  power  of  conduction,  i.  e.,  the  capacity  for  conducting 
the  muscular  contractions.  According  to  Gaskell,  the  vagus  acts  upon  the  rhyth- 
mical power  of  the  muscular  fibres  of  tlie  heart.] 

This  centre  may  be  excited  directly  in  the  medulla,  and  also  reflexly,  by 
stimulating  certain  afferent  nerves. 

Many  observers  assume  that  this  centre  is  in  a  state  of  tonic  excitement,  i.  e.,  that  there  is  a 
continuous,  uninterrupted,  regulating  and  inhibitory  action  of  this  centre  upon  the  heart  through  the 
fibres  of  the  vagus.  .According  to  Iiernstein,  this  tonic  excitement  is  caused  reflexly  through  the 
abdominal  and  cervical  sympathetic. 

I.  Direct  Stimulation  of  the  Centre. — This  centre  may  be  stimulated 
directly  by  the  same  stimuli  that  act  upon  the  respiratory  centre,  (i)  Sudden 
ananiia  of  the  oblongata,  by  ligature  of  both  carotids,  both  subclavians,  or  decapi- 
tating a  rabbit,  the  vagi  alone  being  left  undivided,  causes  slowing  and  even 
temporary  arrest  of  the  action  of  the  heart.  (2)  Sudden  venous  hyperemia  acts  in 
a  similar  manner,  and  it  can  be  produced  by  ligaturing  all  the  veins  returning 
from  the  head  (^Landois,  Hermann  and  Escher).  (3)  The  increased  venositx  of 
the  blood,  produced  either  by  direct  cessation  of  the  respirations  (rabbit)  or  by 
forcing  into  the  lungs  a  quantity  of  air  containing  much  COj  {Traube).  As  the 
circulation  in  the  placenta  (the  respiratory  organ  of  the  fcetus)  is  interfered 
with  during  severe  labor,  this  sufficiently  explains  the  constant  enfeeblement  of 
the  action  of  the  heart  during  protracted  labor ;  it  is  due  to  stimulation  of  the 
central  end  of  the  vagus  by  the  dyspnceic  blood  (^B.  S.  Schultze).  (^4)  .\t  the 
moment  the  respiratory  centre  is  excited,  and  an  inspiration  occurs,  there  is  a 
variation  in  the  inhibitory  activity  of  the  cardiac  centre  (^Bonders,  Pfliiger,  Fre- 
dericij — ^  74,  a,  4).  (5)  The  centre  is  excited  by  increased  blood  pressure  within 
the  cerebral  arteries. 

II.  The  cardio-inhibitory  centre  may  be  excited  reflexly — (i)  By  stimulation 
of  sensory  nerves  {Loven,  Kratschmer).  (2)  By  stimulation  of  the  central  end  of 
one  vagus,  provided  the  other  vagus  is  intact  {v.  Bezold,  Donders,  Aubert  and 
Roever).  (3)  By  stimulation  of  the  sensory  nerves  of  the  intestines  by  tapping 
upon  the  belly  (Goltz's  tapping  experiment;,  whereby  the  action  of  the  heart 
is  arrested.  Stimulation  of  the  splanchnic  directly  (^Asp  and  Ludwig),  or  of  the 
abdominal  or  cervical  sympathetic  (^Bernstein),  produces  the  same  result.  Very 
strong  stimulation  of  sensory  nerves,  however,  arrests  the  above-named  reflex 
effects  upon  the  vagus  (§  361,  3). 

Tapping  Experiment. — Goltz's  experiment  succeeds  at  once  by  tapping  the  intestines  of  a  frog 

directly,  say  with  the  handle  of  a  scalpel,  especially  if  the  intestine  has  been  exposed  to  the  air  for 
a  short  time,  so  as  to  become  inflamed  1  Tarchanoff).  Stimulation  of  the  stomach  of  the  dog  causes 
slowing  of  the  heart  \ie.3.\.  [Sii;.  Mayer,  and  Pribram).  [M'William  finds  that  the  action  of  the 
heart  of  the  eel  may  be  arrested  rellexly  with  very  great  facility.     The  reflex  inhibition  is  ob'.ained 


692  STIMULATION    OF   THE   TRUNK   OF   THE   VAGUS. 

by  slight  stimulation  of  the  gills  (through  the  branchial  nerves),  the  skin  of  the  head  and  tail  and 
parietal  peritoneum,  by  severe  injury  of  almost  any  part  of  the  animal  except  the  abdominal 
organs.] 

[Effect  of  Swallowing  Fluids. — Kronecker  has  shown  that  the  act  of  swallowing  interferes 
with  or  abolishes  temporarily  the  cardio-inhibitory  action  of  the  vagus,  so  that  the  pulse  rate  is 
greatly  accelerated.  Merely  sipping  a  wineglassful  of  water  may  raise  the  rate  30  per  cent.  Hence, 
sipping  cold  water  acts  as  a  powerful  cardiac  stimulant.] 

According  to  Hering,  the  excitability  of  the  cardio-inhibitory  centre  is  diminished  by  vigorous 
artificial  ventilation  of  the  lungs  with  atmospheric  air.  At  the  same  time  there  is  a  considerable 
fall  of  the  blood  pressure  (§353,8,4).  In  man,  a  vigorous  expiration,  owing  to  the  increased 
intra-pulmonary  pressure,  causes  an  acceleration  of  the  heart  beat,  which  Sommerbrodt  ascribes  to 
a  diminution  of  the  activity  of  the  vagi.  At  the  same  time  the  activity  of  the  vasomotor  centre  is 
diminished  (§  60,  2). 

Stimulation  of  the  trunk  of  the  vagus  from  the  centre  downward,  along 
its  whole  course,  and  also  of  certain  of  its  cardiac  branches  [inferior  cardiac], 
causes  the  heart  either  to  beat  more  slowly  or  arrests  its  action  in  diastole.  The 
result  depends  upon  the  strength  of  the  stimulus  employed  ;  feeble  stimuli  slow 
the  action  of  the  heart,  while  strong  stimuli  arrest  it  in  diastole.  The  frog's  heart 
may  be  arrested  by  stimulating  the  fibres  of  the  vagus  upon  the  sinus  venosus. 
If  strong  stimuli  be  applied  either  to  the  centre  or  to  the  course  of  the  nerve  for  a 
long  time,  the  part  stimulated  becomes  fatigued,  and  the  heart  beats  more  rapidly 
in  spite  of  the  continued  stimulation.  If  a  part  of  the  nerve  lying  nearer  the 
heart  be  stimulated,  inhibition  of  the  heart's  action  is  brought  about,  as  the 
stimulus  acts  upon  a  fresh  portion  of  nerve. 

The  following  points  have  also  been  ascertained  regarding  the  stimulation  of  the  inhibitory 
fibres : — 

1.  The  experiments  of  Lowit  on  the  frog's  heart,  confirmed  by  Heidenhain,  showed  that  electrical 
and  chemical  stimulation  of  the  vagus  produces  different  results  as  regards  the  extent  of  the  ven- 
tricular systole,  as  well  as  the  number  of  heart  beats ;  the  contractions  either  become  smaller  or 
less  frequent,  or  they  become  smaller  and  less  frequent  simultaneously.  Strong  stimuli  cause,  in 
addition,  well-marked  relaxation  of  heart  muscle  during  diastole. 

2.  In  order  to  cause  inhibition  of  the  heart,  a  continuous  stimulus  is  not  necessary. 

3.  Bonders,  with  Prahl  and  Niiel,  observed  that  arrest  of  the  heart's  action  did  not  take  place 
immediately  the  stimulus  was  applied  to  the  vagus,  but  about  J  of  a  second— period  of  latent 
stimulation — elapsed  before  the  effect  was  produced  on  the  heart. 

A  rhythmically-intcri-itpted  moderate  stimulus  suffices  (?'.  Bezold) ;  18  to  20  stimuli  per  second 
are  required  for  mammals,  and  2  to  3  per  second  for  cold-blooded  animals.  If  the  heart  be  arrested 
by  stimulation  of  the  vagus,  it  can  stiil  contract,  if  it  be  excited  directly,  e.  g.,  by  pricking  it  with 
a  needle,  when  it  executes  a  single  contraction.  [This  holds  good  only  for  some  animals,  c. _^.,frog, 
tortoise,  birds  and  mammals.  In  fishes  only  the  ventiicle  responds  to  stimulation  during  marked 
inhibition;  in  the  newt  only  the  bulbus  arteriosus.  In  the  newt's  heart  the  sinus,  auricles  and  ven- 
tricle are  all  inexcitable  to  direct  stimulation  dunng  strong  inhibition.] 

5.  According  to  A.  B.  Meyer,  inhibitory  fibres  are  present  only  in  the  right  vagus  in  the  turtle. 
It  is  usually  stated  that  the  r/j-/;/ vagus  is  more  effective  than  the  left  in  other  animals,  ;•.  g.,  rabbit, 
[Masoin,  Arloing  and  Tripier);  but  this  is  subject  to  many  exceptions  (Landois  and  Langen- 
dorff).  [In  the  newt  the  right  vagus  acts  more  readily  011  the  ventricle  than  on  the  other  pans  of 
the  heart ;  slight  stimulation  of  the  right  vagus  can  arrest  the  ventricle,  while  the  sinus  and  auricles 
go  on  beating.] 

6.  The  vagus  has  been  compressed  by  the  finger  in  neck  of  man  (Czermak,  Concato) ;  but  this 
experiment  is  accompanied  by  danger,  and  ought  not  to  be  undertaken.  The  electrotonic  condition 
of  the  vagus  is  stated  in  J  335,  III. 

7.  Schitf  found  that  stimulation  of  the  vagus  of  the  frog  caused  acceleration  of  the  heart  beat 
when  he  displaced  the  blood  of  the  heart  with  saline  solution.  If  blood  serum  be  supplied  to  the 
heart  the  vagus  regains  its  inhibitory  action. 

8.  Many  soda  salts  in  a  proper  concentration  arrest  the  inhibitory  action  of  the  vagus,  while  pot- 
ash salts  restore  the  inhibitory  function  of  the  vagi  suspended  by  the  soda  salts.  If,  however,  the 
soda  or  pot.ash  salts  act  too  long  upon  the  heart,  they  produce  a  condition  in  which,  after  the  inhibi- 
tory function  of  the  vagi  is  abolished,  it  is  not  again  restored.  The  heart's  action  in  this  condition 
is  usually  arhythmical  {Lowit). 

9.  If  the  intracardial  pressure  be  greatly  increased,  so  as  to  accelerate  greatly  the  cardiac 
pulsations,  the   activity  of  the  vagus  is  correspondingly  diminished  (y.  M.  Ludwig  and  Luchsin- 

[Differences  in  Animals. — Perhaps  the  most  remarkable  fact  in  the  influence  of  the  vagus  on 
the  eel's  heart  and  that  of  all  other  fishes  examined  is  that  vagus  stimulation  causes  the  sinus  and 


THE    NERVUS   ACCELERANS. 


693 


auricle  to  be  entirely  inexcitable  to  direct  stimulation  during  strong  inliibition.  Nerve  stimulation 
has,  in  this  case,  the  very  peculiar  effect  of  rendering  the  muscular  tissue  temporarily  incapable  of 
responding  to  even  the  strongest  direct  stimuli,  e.g.,  powerful  induction  shocks.  This  would  appear 
to  be  decisive  evidence  that  the  vagus  acts  on  muscle  directly,  and  not  simply  on  automatic  motor 
ganglia,  as  was  held  according  to  the  old  view. 

Poisons. — Muscarin  stimulates  the  terminations  of  the  vagus  in  the  heart,  and  causes  the  heart 
to  stand  still  in  diastole  [SchmieJeberg  atid  Kofpe).  If  alropin  be  applied  in  solution  to  the  heart 
this  action  is  set  aside,  and  the  heart  begins  to  beat  again.  Digilalin  diminishes  the  number  of  heart 
beats  by  stimulating  the  cardio -inhibitory  centre  (vagus)  in  the  medulla.  Large  doses  diminish  the 
excitability  of  the  vagus  centre,  and  increase  at  the  same  time  the  accelerating  cardiac  ganglia,  so 
that  the  heart  beats  are  thereby  increased.  In  small  doses,  digitalin  raises  the  blood  pressure  by 
stimulating  the  vasomotor  centre  and  the  elements  of  the  vascular  wall  [Klug').  Nicotin  first  excites 
the  vagus,  then  rapidly  paralyzes  it.  I/vdrocyanic  acii/h.-ds  the  same  effect  (/"/-y <?;-).  Atropin(v. 
Bezold )  and  curara  (large  dose — CI.  Bernard  and  Kolliker)  paralyze  the  vagi,  and  so  does  a  very 
low  temperature  or  high  fever. 

370.  THE  CENTRE  FOR  THE  ACCELERATING  CARDIAC 
NERVES  AND  THE  ACCELERATING  FIBRES.— Nervus  Ac- 
celerans. — It  is  more  than  probable  that  a  centre  exists  in  the  medulla  oblongata 
which  sends  accelerating  fibres  to  the  heart.  These  fibres  pass  from  the  mcdtilla 
oblongata — but  from  which  part  thereof  has  not  been  exactly  ascertained^through 
the  spinal  cord,  and  leave  the  cord  through  the  rami  communicantes  of  the  lower 
cervical  and  upper  six  dorsal  nerves  {Strieker),  to  pass  into  the  sympathetic  nerve. 
Some  of  these  fibres,  issuing  from  the  spinal  cord,  pass  through  the  first  thoracic 
sympathetic  ganglion  and  the  ring  of  Vieussens,  to  join  the  cardiac  plexus  (Figs. 
417,  418).  [These  fibres,  issuing  from  the  spinal  cord, 
frequently  accompany   the   nerve  running  along  the  f,,;.  417. 

vertebral  artery],  and  they  constitute  the  Nervus  ac- 
celerans  cordis.  [Fig.  418  shows  the  accelerator  fibres 
passing  through  the  ganglion  stellatum  of  the  cat  to 
join  the  cardiac  plexus.]  If  the  vagi  of  an  animal  be 
divided,  stimulation  of  the  rneduUa  oblongata,  of  the 
lower  end  of  the  divided  ceivical  spinal  cord,  even 
the  lower  cervical  ganglion,  or  of  the  upper  dorsal 
ganglion  of  the  sympathetic  {Gang,  stellatum^,  causes 
acceleration  of  the  heart  beats  in  the  dog  and  rabbit 
without  the  blood  pressure  undergoing  any  change 
(Cy.  Bernard,  v.  Bezold,  Cyon). 

On  stimulating  the  medulla  oblongata  or  the  cervical  portion 
of  the  spinal  cord,  the  vasomotor  neriu-s  are,  of  course,  simultane- 
ously excited.  The  consequence  is  that  the  blood  vessels,  sup- 
plied by  vasomotor  nerves  from  the  spot  which  is  stimulated,  con- 
tract, and  the  blood  pressure  is  greatly  increased.  Again,  a  sim- 
ple increase  of  the  blood  pressure  accelerates  the  action  of  the 
heart;  this  experiment  does  not  prove  directly  the  existence  of 
accelerating  fibres  lying  in  the  upper  part  ot  the  spinal  cord.  If, 
however,  the  splanchnic  nerves  be  divided  beforehand,  and,  as 
they  supply  the  largest  vasomotor  area  in  the  body,  the  result  of 
their  division  is  to  cause  a  great  fall  of  the  blood  pressure,  then 
on  stimulating  the  above-named  parts,  after  this  operation,  the 
heart  beats  are  still  increased  in  number,  so  that  its  increase  can- 
not be  due  to  the  increased  blood  pressure.  Indirectly  it  may 
be  shown,  by  dividing  or  extirpating  all  the  nerves  of  the  cardiac 
plexus,  or  at  least  all  the  nerves  going  to  the  heart,  that  stimula- 
tion of  the  medulla  oblongata,  or  cervical  part  of  the  spinal  cord, 
no  longer  causes  an  increased  frequency  of  the  heart's  action  to 
the  same  extent  as  before  division  of  these  nerves.  The  slightly 
increased  frequency  in  this  case  is  due  to  the  increased  blood 
pressure. 

The  accelerating  centre  is  certainly  not  continually 
in  a  state  of  tonic  excitement,  as  section  of  the  actelerans  nerve  does  not  cause 


Scheme  of  thi 


oblongata  ;  C,  spinat  cord  :  V, 
hibitory  centre  for  heart ;  A,  accele- 
rans  centre;  Vac,  vagus;  SL,  su- 
perior, IL,  inferior  laryngeal  ;  SC, 
superior,  IC,  inferior  cardiac;  H, 
heart ;  C,  cerebral  impulse  ;  S,  cer- 
vical sympathetic  ;  a,  a,  acceleraiis 


694 


THE    CARDIAC    PLEXUS. 


slowing  of  the  action  of  the  heart ;  the  same  is  true  of  destruction  of  the  medulla 
oblongata  or  of  the  cervical  spinal  cord.  In  the  latter  case  the  splanchnic  nerves 
must  be  divided  beforehand  to  avoid  the  slowing  effect  on  the  action  of  the  heart 
produced  by  the  great  fall  of  the  blood  pressure  consefjuent  upon  destruction  of 
the  cord,  otherwise  we  might  be  apt  to  ascribe  the  result  to  the  action  of  the  ac- 
celerating centre,  when  it  is  in  reality  due  to  the  diminished  blood  pressure 
lyBrothers  Cyoti). 

According  to  the  results  of  the  older  observers  ii\  Bezold  and  others),  some 
accelerating  fibres  run  in  the  ce?-vical  sympathetic.  \  few  fibres  pass  through  the 
vagus  to  reach  the  heart  (§  352,  7),  and  when  they  are  stimulated  the  heart  beat 
is  accelerated  and  the  cardiac  contractions  strengthened  {Heidenhain  and  Lowit). 
The  inhibitory  fibres  of  the  vagus  lose  their  excitability  more  readily  than  the 


Cardiac  plexus,  and  ganglion  stelbtum  ol  the  cat.  R,  right,  L,l<rft  y  i',4:  i, vagus;  2',  cervical  sympathetic,  and  in 
the  annulus  of  Vieussens  ;  2,  communicating  branches  from  the  middle  cervical  ganglion  and  the  ganglion  stel- 
iatum  ;  2",  thoracic  sympathetic;  3,  recurrent  laryngeal  ;  4,  depressor  nerve  ;  5,  middle  cervical  ganglion ;  5', 
communication  between  5  and  the  vagus;  6,  ganglion  stellatum  {ist  thoracic  ganglion);  7,  communicating 
branches  with  the  vagus ;  8,  nervus  accelerans  ;  8,8',  8",  roots  of  accelerans  ;  g,  branch  of  the  ganglion  stellatum. 

accelerating  fibres,  but   the  vagus  fibres  are  more  excitable  than   those   of  the 
accelerans. 

Modifying  Conditions  — When  the  peripheral  end  of  the  nervus  accelerans  is  Mimulated,  a 
considerable  lime  elapses  before  the  effect  upon  the  frequency  of  the  heart  takes  place,  /.  e.,  it  has 
a  long  latent  period.  Kurthrr  the  accelerulion  thus  produced  di.'appears  gradually.  If  the  vagus 
and  accelerans  fibres  be  stimulated  simultaneously,  only  the  inhibitory  action  of  the  vagus  is 
manifested.  If.  u'hile  the  accelerans  is  being  stimulated,  the  vagus  be  suHdenlv  excited,  there  is  a 
prompt  diminution  in  the  number  of  the  heart  beats;  .and  if  the  stimulation  of  the  vagus  is  stopped, 
the  accelerating  effect  of  the  accelerans  is  again  rapidly  manifested  (  C.  Ludwig  with  SchmieJe/ierg, 
Bo~odilch,  Baxt).  According  to  the  experini.ents  of  Strieker  and  Wagner  on  dogs,  with  both  vagi 
divided,  a  diminution  of  the  number  of  the  heart  beats  occured  when  both  accelerantes  were 
divided.     This  would  indicate  a  tonic  innervation  of  the  latter  nerves. 


POSITION    OF   THE    VASOMOTOR    CENTRE.  695 

[Accelerans  in  the  Frog. — Gaskell  showed  that  stimulation  of  the  vagus 
might  produce  two  opposing  effects  ;  the  one  of  the  nature  of  inhibition,  the  other 
of  augmentation.  In  the  crocodile,  the  accelerans  fibres  leave  the  sympathetic 
chain  at  the  large  ganglion  corresponding  to  the  ganglion  stellatum  of  the  dog, 
and  run  along  the  vertebral  artery  up  to  the  superior  vena  cava,  and  after  an  anas- 
tomosing with  branches  of  the  vagus,  pass  to  the  heart.  "Stimulation  of  these 
fibres  increases  the  rate  of  the  cardiac  rhythm,  and  augments  X\\it  force  of  auricular 
contractions  ;  while  stimulation  of  the  vagus  slows  the  rhythm,  and  diminishes 
the  strength  of  the  auricular  contractions."  The  strength  of  the  ventricular  con- 
traction, both  in  the  tortoise  and  crocodile,  does  not  seem  to  be  influenced  by 
stimulation  of  the  vagus,  and  probably,  also,  it  is  unaffected  by  the  sympathetic. 
The  so-called  vagus  of  the  frog  in  reality  consists  of  pure  vagus  fibres  and  sym- 
pathetic fibres,  and  is,  in  fact,  a  vago-sympathetic.  Gaskell  finds  that  sthnutatton 
of  the  sympathetic,  before  it  joins  the  combined  ganglion  of  the  sympathetic  and 
vagus,  produces  purely  augmenlor  or  accelerating  effects  ;  while  stimulation  of  the 
vagus,  before  it  enters  the  ganglion,  produces  purely  inhil'itoiy  effects.  The  two 
sets  of  fibres  are  quite  distinct,  so  that  in  the  frog  the  sympathetic  is  a  purely 
augmentor  (accelerator),  and  the  vagus  a  purely  inliibitory  nerve.  Acceleration 
is  merely  one  of  the  effects  produced  by  stimulation  of  these  nerves,  so  that  Gas- 
kell suggests  that  they  ought  to  be  called  "augmentor,"  or  simply  cardiac 
sympathetic  nerves.] 

[In  his  more  recent  researches  Gaskell  asserts  that  vagus  stimulation  produces  ^f-rf  an  inhibitory 
or  depressing  effect,  but  that  it  ultimately  improves  the  condition  of  the  heart  as  regards  force,  rate 
or  regularity — one  or  ail  of  these.     He  regards  it  as  a  true  anabolic  nerve  (§  342,  d).] 

371.  VASOMOTOR  CENTRE  AND  VASOMOTOR  NERVES.— 
Vasomotor  Centre. — The  chief  dominating  or  general  centre  which  sup- 
]ilies  all  the  non-striped  muscles  of  the  arterial  system  with  ynotor  nerves 
(vasomotor,  vaso-constrictor,  vaso-hypertonic  nerves)  lies  in  the  medulla  oblon- 
gata, at  a  point  which  contains  many  ganglionic  cells  {LiKhvig  and  Thiry).  Those 
nerves  which  pass  to  the  blood  vessels  are  known  as  vasomotor  nerves.  The 
centre  (which  is  3  millimetres  long  and  i]4  millimetre  broad  in  the  rabbit), 
reaches  from  the  region  of  the  upper  part  of  the  floor  of  the  medulla  oblongata 
to  within  4  to  5  mm.  of  the  calamus  scriptorius.  Each  half  of  the  body  has  its 
own  centre  placed  zyi  milliiiietres  from  the  middle  line  on  its  own  side,  in  that 
part  of  the  medulla  oblongata  which  represents  the  upward  continuation  of  the 
lateral  columns  of  the  spinal  cord  ;  according  to  Ludwig  and  Owsjannikow,  and 
Dittmar.  in  the  lower  part  of  the  superior  olives.  Stimulation  of  this  central 
area  causes  contraction  of  all  the  arteries,  and  in  consequence  there  is  great  in- 
crease of  the  arterial  blood  pressure,  resulting  in  swelling  of  the  veins  and  heart. 
Paralysis  of  this  centre  causes  relaxation  and  dilatation  of  all  the  arteries,  and 
consequently  there  is  an  enormous  fall  of  the  blood  pres.sure.  Under  ordinary 
circumstances  the  vasomotor  centre  is  in  a  condition  of  moderate  tonic  excitement 
(§  366).  Just  as  in  the  case  of  the  cardiac  and  respiratory  centres  the  vasomotor 
centre  may  be  excited  directly  and  reflexly. 

[Position — How  Ascertained. — As  stimulation  of  the  central  end  of  a  sen- 
sory nerve,  e.g.,  the  sciatic,  in  an  animal  under  the  influence  of  curara,  causes  a 
rise  in  the  blood  pressure,  even  after  removal  of  the  cerebrum,  it  is  evident  that 
the  centre  is  not  in  the  cerebrum  itself.  By  making  a  series  of  sections  from  above 
downward,  it  is  found  that  this  reflex  effect  is  not  affected  until  a  short  distance 
above  the  medulla  oblongata  is  reached.  If  more  and  more  of  the  medulla  ob- 
longata be  removed  from  above  downward,  then  the  reflex  rise  of  the  blood  pressure 
becomes  less  and  less,  until,  when  the  section  is  made  4  to  5  mm.  above  the  calamus 
scriptorius,  the  effect  ceases  altogether.  This  is  taken  to  be  the  lower  limit  of  the 
general  vasomotor  centre.  The  bilateral  centre  corresponds  to  some  large  multi- 
polar nerve  cells,  described  by  Clarke  as  the  antero-lateral  nucleus.] 


696  COURSE   OF   THE    VASOMOTOR    FIBRES. 

I.  Direct  Stimulation  of  the  Centre. — The  amount  and  quality  of  the 
gases  contained  in  the  blood  flowing  through  the  medulla  are  of  primary  import- 
ance. In  the  condition  of  apncea  (§  368,  1)  the  centre  seems  to  be  very  slightly 
excited,  as  the  blood  pressure  undergoes  a  considerable  decrease.  When  the 
mixture  of  blood  gases  is  such  as  exists  under  normal  circumstances,  the  centre  is 
in  a  state  of  moderate  excitement,  and  running  parallel  with  the  respiratory  move- 
ments are  variations  in  the  excitement  of  the  centre  (Traube-Hering  curves — §  85), 
these  variations  being  indicated  by  the  rise  of  the  blood  pressure.  When  the 
blood  is  highly  venous,  produced  either  by  asphyxia  or  by  the  inspiration  of  air 
containing  a  large  amount  of  CO2,  the  centre  is  strongly  excited,  so  that  all  the 
arteries  of  the  body  contract,  while  the  venous  system  and  the  heart  become  dis- 
tended with  blood  (  Thiry).  At  the  same  time  the  velocity  of  the  blood  stream  is 
increased  {Heidenhain').  The  same  result  is  produced  by  sudden  ansmia  of  the 
oblongata  by  ligature  of  both  the  carotid  and  subclavian  arteries  {Nawalichin, 
Sigm.  Mayer'),  and  no  doubt,  also,  by  the  sudden  stagnation  of  the  blood  in  venous 
hyperemia. 

Action  of  Poisons. — Strychnin  stimulates  the  centre  directly,  even  in  curarized  dogs,  and  so 
do  nicotin  and  Calabar  bean. 

Emptiness  of  the  Arteries  after  Death. — The  venosity  of  the  blood  which  occurs  after  death 
always  produces  an  energetic  stimulation  of  the  vasomotor  centre,  in  consequence  of  which  the 
arteries  are  firmly  contracted.  The  blood  is  thereby  forced  toward  the  capillaries  and  veins,  and 
thus  is  explained  the  "emptiness  of  the  arteries  after  death." 

Effect  on  Hemorrhage. — Blood  flows  much  more  freely  from  large  wounds  when  the  vaso- 
motor centre  is  intact  than  if  it  be  destroyed  (frog).  As  psychical  excitement  undoubtedly  influences 
the  vasomotor  centre,  we  may  thus  explain  the  influence  of  psychical  excitement  (speaking,  etc.) 
upon  the  cessation  of  hemorrhage.  If  the  hemorrhage  be  severe,  stimulation  of  the  medulla  oblon- 
gata, due  to  the  ancemia,  may  ultimately  cause  constriction  of  the  small  arteries,  and  thus  arrest  the 
bleeding.  Thus,  surgeons  are  acquainted  with  the  fact  that  dangerous  hemorrhage  is  often  arrested 
as  soon  as  unconsciousness,  due  to  cerebral  ana:mia,  occurs.  If  the  heart  be  ligatured  in  a  frog,  all 
the  blood  is  ultimately  forced  into  the  veins,  and  this  result  is  also  due  to  the  anaemic  stimulation  of 
the  oblongata  (  Gollz).  In  matnmals,  when  the  heart  is  ligatured,  the  equilibration  of  the  blood 
pressure  between  the  arterial  and  venous  systems  takes  place  more  slowly  when  the  medulla  oblon- 
gata is  destroyed  than  when  it  is  intact  (-'.  Bezold,  Gsiheidlen). 

[Effect  of  Destruction  of  the  Vasomotor  Centre. — If  two  frogs  be  pithed  and  their  hearts 
exposed,  and  both  be  suspended,  then  the  hearts  of  both  will  be  found  to  beat  rhythmically  and  fill 
with  blood.  Destroy  the  medulla  oblongata  and  spinal  cord  of  one  of  them,  then  immediately  in 
this  case  the  heart,  although  continuing  to  beat  with  an  altered  rhythm,  ceases  to  be  filled  with 
blood ;  it  appears  collapsed,  pale,  and  bloodless.  There  is  a  great  accumulation  of  the  blood  in  the 
abdominal  organs  and  veins,  and  it  is  not  returned  to  the  heart,  so  that  tha  arteries  are  empty.  This 
experiment  of  Goltz  is  held  to  show  the  existence  of  venous  tonus  depending  on  a  cerebro-spinal 
centre.  If  a  limb  of  this  frog  be  amputated,  there  is  little  or  no  hemorrhage,  while  in  the  other  frog 
the  hemorrhage  is  severe.     The  bearing  of  this  experiment  on  conditions  of  "shock  "  is  evident.] 

Direct  Electrical  Stimulation.— On  stimulating  the  centre  directly  in  animals,  it  is  found  that 
single  induction  shocks  only  become  efiective  when  they  succeed  each  other  at  the  rate  of  2  to  3 
shocks  per  second.  Thus  there  is  a  "  summation  "  of  the  single  shocks.  The  maximum  contrac- 
tion of  the  arteries,  as  expressed  by  the  maximum  blood  pressure,  is  reached  when  10-12  strong,  or 
20-25  moderately  strong  shocks  per  second  are  applied  (A'ronecker  and  Nieolaides). 

Course  of  the  Vasomotor  Nerves. — From  the  vasomotor  centre  some  fibres  proceed  directly 
through  some  of  the  cranial  nerves  to  their  area  of  distribution ;  through  the  trigeminus  partly  to  the 
interior  of  the  eye  (i,  347,  I,  2),  through  the  lingual  and  hypoglossal  to  the  tongue  (l  347,  III,  4), 
through  the  vagus  to  a  limited  extent  to  the  lungs  (|  352,  8,  2),  and  to  the  intestines  (|  352,  II ). 
All  the  other  vasomotor  nerves  descend  in  the  lateral  columns  of  the  spinal  cord  (J  364,  9) ;  heiice 
stimulation  of  the  lower  cut  end  of  the  spinal  cord  causes  contraction  of  the  blood  vessels  supplied 
by  the  nerves  below  the  point  of  section  (PJiiiger).  In  their  course  through  the  cord  these  fibres 
form  connections  with  the  subordinate  vasomotor  centres  in  the  gray  matter  of  the  cord  (?  362,  7), 
and  then  leave  the  cord  either  directly  through  the  anterior  roots  of  the  spinal  nerves  to  their  areas 
of  distribution,  or  they  pass  through  the  rami  communicantes  into  the  sympathetic,  and  from  them 
reach  the  blood  vessels  to  which  they  are  distributed  (g  356). 

Cephalic  Vasomotors. — The  following  is  the  arrangement  of  these  nerves  in  the  region  of  the 
head  :  The  cet-ncal  portion  of  the  sympathetic  supplies  the  great  majority  of  the  blood  vessels  of 
the  head  (see  Sympathetic,  \  356,  A,  3 — CI.  Bernard).  In  some  M\\m3\%\ht  great  auricular  nen>e 
supplies  a  few  vasomotor  fibres  to  its  own  area  of  distribution  {Schiff,  Lovin,  Moreau).  The  vaso- 
motor nerves  to  the  upper  extremities  pass  through  the  anterior  roots  of  the  middle  dorsal  nerves 


REFLEX    STIMULATION    OK   THE    VASOMOTOR   CENTRE.  697 

into  the  thoracic  sympathetic,  and  upward  to  the  1st  thoracic  ganglion,  and  from  thence  through  the 
rami  comraunicantes  to  the  brachial  plexus  (Schiff,  Cyon).  The  skin  of  the  trunk  receives  its 
vasomotor  nerves  through  the  dorsal  and  lumbar  nerves.  The  vasomotor  nerves  to  the  lower  ex- 
tremities pass  through  the  nerves  of  the  lumbar  and  sacral  plexuses  into  the  sympathetic,  and 
from  thence  to  the  lower  limbs  (Pflliver,  Schiff,  CI.  Bernard).  The  lungs,  in  addition  to  a  few 
fibres  through  the  vagus,  are  supplied  from  tlie  cervical  spinal  cord  through  the  ist  thoracic  gan- 
glion {Brown- ^iijuard.  Pick  and  BaJoudy  Liclilhsim).  The  splanchnic  is  the  greatest  vasomotor 
nerve  in  the  body,  and  supplies  the  abdominal  viscera  (\  356,  B — Bezold,  Liid-n'g  and  Cyon). 
The  vasomotor  nerves  of  the  liver  (\  173,  6),  kidney  (§  276),  and  spleen  {\  103)  have  been 
referred  to  already.  According  to  .Strieker,  most  of  the  vasomotor  nerves  leave  the  spinal  cord 
between  the  5lh  cervical  and  the  ist  dorsal  vertebra.  [Gaskell  finds  that  in  the  dog  they  begin  to 
leave  the  cord  at  the  2d  dorsal  nerve  ({  366).] 

As  a  general  rule,  the  blood  vessels  of  the  trunk  and  extremities  are  innervated  from  those  nerves 
which  give  other  fibres  (e.g.,  sensory)  to  those  regions.  The  difterent  vascular  areas  behave  differ- 
ently with  regard  to  the  intensity  of  the  action  of  the  vasomotor  nerves.  The  most  powerful  vaso- 
motor nerves  are  those  that  act  upon  the  blood  vessels  of  peripheral  parts,  e.g.,  the  toes,  the  fingers 
and  ears ;  while  those  that  act  upon  central  parts  seem  to  be  less  active  (Lewasehe^u),  e.g.,  on  the 
pulmonic  circulation  [\  88). 

II.  Reflex  Stimulation  of  the  Centre. — There  are  fibres  contained  in  the 
different  afferent  nerves  whose  stimulation  affects  the  vasomotor  centre.  There 
are  nerve  fibres  whose  stimulation  excites  the  vasomotor  centre,  thus  causing  a 
stronger  contraction  of  the  arteries,  and  consequently  an  increase  of  the  arterial 
blood  pressure.  These  are  called  "pressor"  fibres.  Conversely,  there  are 
other  fibres  whose  stimulation  refle.^ly  diminishes  the  excitability  of  the  vasomotor 
centre.  These  act  as  refle.\  inhibitory  nerves  on  the  centre,  and  are  known  as 
"  depressor"  nerves. 

Pressor,  or  e.xcito-vasomotor  nerves,  have  already  been  referred  to  in  connec- 
tion with  the  superior  and  inferior  laryngeal  nerves  (§  352,  12,  a)  \  in  the  trigem- 
inus, which,  when  stimulated  directly  (§  347),  causes  a  pressor  action,  as  well 
as  when  stimulating  vapors  are  blown  into  the  nostrils  {Herutg  and  Kratschmcr). 
[The  rise  of  the  blood  pressure  in  this  case,  however,  is  accompanied  by  a  change 
in  the  character  of  the  heart's  beat  and  in  the  respirations.  Rutherford  has 
shown  that  in  the  rabbit  the  vapor  of  chloroform,  ether,  amylic  nitrite,  acetic 
acid  or  ammonia  held  before  the  nose  of  a  rabbit  greatly  retards  or  even  arrests 
the  heart's  action,  and  the  same  is  true  if  the  nostrils  be  closed  by  the  hand. 
This  arrest  does  not  occur  if  the  trachea  be  opened,  and  Rutherford  regards  the 
result  as  due  not  to  the  stimulation  of  the  sensory  fibres  of  the  trigeminus,  but  to 
the  state  of  the  blood  acting  on  the  cardio-inhibitory  nerve  apparatus.]  Hubert 
and  Roever  found  pressor  fibres  in  the  cervical  sympathetic  ;  S.  Mayer  and  Prib- 
ram found  that  mechanical  stimulation  of  the  stomach,  especially  of  its  serosa, 
caused  pressor  effects  (§  352,  12,  c).  According  to  Lov^n,  \.\\t  first  effect  of 
stimulating  every  sensory  nerve  is  a  pressor  action. 

[If  a  dog  be  poisoned  with  curara,  and  the  central  twA.  of  one  sciatic  nerve  be 
stimulated,  there  is  a  great  and  steady  rise  of  the  blood  pressure,  chiefly  owing  to 
the  contraction  of  the  abdominal  blood  vessels,  and  at  the  same  time  there  is  no 
change  in  the  heart  beat.  If,  however,  the  animal  be  poisoned  with  chloral, 
there  is  a  fall  of  the  blood  pressure  resembling  a  depressor  effect.] 

O.  Naumann  found  that  weak  electrical  stimulation  of  the  skin  caused  at  first  contraction  of  the 
blood  vessels,  especially  of  the  mesentery,  lungs  and  the  web.  with  simultaneous  excitement  of  the 
cardiac  activity  and  acceleration  of  the  circulation  (frog).  Strong  stimuli,  however,  had  an  oppo- 
site effect,  i.e.,  a  depressor  etfect,  with  simultaneous  decrease  of  the  cardiac  activity.  The  applica- 
tion of  heat  and  cold  to  the  skin  produces  refiexly  a  change  in  the  lumen  of  the  blood  vessels  and 
in  the  cardiac  activity  (Kohrig,  Winternitz).  Pinching  the  skin  causes  contraction  of  the  vessels 
of  the  pia  mater  of  the  rabbit  [Schiiller),  and  the  same  result  was  produced  by  a  warm  bath,  while 
cold  dilated  the  vessels.  These  results  are  due  partly  to  pressor  and  partly  to  depressor  effects,  but 
the  chief  cause  of  the  dilatation  of  the  blood  vessels  is  the  increased  blood  pressure  due  to  the  cold 
constricting  the  cutaneous  vessels.     Heat,  of  course,  has  the  opposite  effect. 

Depressor  fibres,  i.e.,  fibres  whose  stimulation  diminishes  the  activity  of  the 
vasomotor  centre,  are  present  in  many  nerves.     They  are  specially  numerous  in 


698        LOCAL   AND    SECONDARY    RESULTS    OF    VASOMOTOR    ACTION. 

the  superior  cardiac  branch  of  the  vagus,  which  is  known  as  the  depressor  nerve 
(§  352,  6).  The  trunk  of  the  vagus  below  the  latter  also  contains  depressor 
fibres  {v.  BezoiJ  an./  Dreschfeld),  as  well  as  the  pulmonary  fibres  (dog)  {Ta/jan- 
zeff).  The  latter  also  act  as  depressors  during  strong  expiratory  efforts  (§  74)  ; 
while  Hering  found  that  inflating  the  lungs  (to  50  mm.  Hg  pressure)  caused  a  fall 
of  the  blood  pressure  (and  also  accelerated  the  heart  beats — §  369,  II).  Stimu- 
lation of  the  central  end  of  sensory  nerves,  especially  when  it  is  intense  and  long- 
continued,  causes  dilatation  of  the  blood  vessels  in  the  area  supplied  them  (Lovcn). 
According  to  Latschenberger  and  Deahna,  all  sensory  nerves  contain  both  pressor 
and  depressor  fibres. 

[If  a  rabbit  be  poisoned  with  curara,  and  the  central  end  of  the  great  auric- 
ular nerve  be  stimulated,  there  is  a  double  effect — one  local  and  the  other 
general;  the  blood  vessels  throughout  the  body,  but  especially  in  the  splanchnic 
area  contract,  so  that  there  is  a  general  rise  of  the  blood  pressure,  while  the  blood 
vessels  of  the  ear  are  dilated.  If  the  central  end  of  the  tibial  nerve  be  stimu- 
lated, there  is  a  rise  of  the  general  blood  pressure,  but  a  local  dilatation  of  the 
saphena  artery  in  the  limb  of  that  side  {Zoven').  Again,  the  temperature  of  one 
hand  and  the  condition  of  its  blood  vessels  influences  that  of  the  other.  If  one 
hand  be  dipped  in  cold  water,  the  temperature  of  the  other  hand  falls.  Thus 
pressor  and  depressor  effects  may  be  obtained  from  the  same  nerve.  The  vaso- 
motor centre,  therefore,  primarily  regulates  the  condition  of  the  blood  vessels, 
but  through  them  it  obtains  its  importance  by  regulating  and  controlling  the 
blood  supply  according  to  the  needs  of  an  organ.] 

The  central  artery  of  a  rabbit's  ear  contracts  regularly  and  rhythmically  3  to  S  times  per  minute. 
Schift  observed  that  stimulation  of  sensory  nerves  caused  a  dilatation  of  the  artery,  which  was  pre- 
ceded by  a  slight  temporary  constriction. 

Depressor  effects  are  produced  in  the  area  of  an  artery  to  which  direct  pressure  is  applied,  as 
occurs,  for  example,  when  the  sphygmograph  is  applied  for  a  long  time — the  pulse  curves  become 
larger,  and  there  are  signs  of  diminished  arterial  tension  {\  75). 

Rhythmical  Contraction  of  Arteries. — In  the  intact  body  slow  alternating  contraction  and 
dilatation,  without  there  being  a  uniform  rhythm,  have  been  observed  in  the  arteries  of  the  ear  of 
the  rabbit,  the  membrane  of  a  bat's  wing,  and  the  web  of  a  frog's  foot.  This  arrangement,  observed 
by  Schiff,  supplies  more  or  less  blood  to  the  parts  according  to  the  action  of  external  conditions.  It 
has  been  called  a  "-periodic  regulatory  muscular  movement.'" 

Direct  local  applications  may  influence  the  lumen  of  the  blood  vessels ;  cold  and  moderate  elec- 
trical stimuli  cause  contraction;  while,  conversely,  heat  and  strong  mechanical  or  electrical  stimuli 
cause  dilatation,  although  with  the  latter  two  there  is  usually  a  preliminary  constriction. 

Effect  on  Temperature. — The  vasomotor  nerves  influence  the  temperature, 
not  only  of  individual  parts,  but  of  the  whole  body. 

I.  Local  Effects. — Section  of  a  peripheral  vasomotor  nerve,  e.  t;.,  the  cer- 
vical sympathetic,  is  followed  by  dilatation  of  the  blooil  vessels  of  the  parts 
supplied  by  it  (^such  as  the  ear  of  the  rabbit),  the  intra-arterial  pressure  dilating 
the  paralyzed  walls  of  the  vessels.  Much  arterial  blood,  therefore,  passes  into  and 
causes  a  congestion  and  redness  of  the  parts,  or  hyperasmia,  while  at  the  same  time 
the  temperature  is  increased.  There  is  also  increased  transudation  through  the 
dilated  capillaries  within  the  dilated  areas  ;  the  velocity  of  the  blood  stream  is  of 
course  diminished,  and  the  blood  pressure  increased.  The  pulse  is  also  felt  more 
easily,  because  the  blood  vessels  are  dilated.  Owing  to  the  increase  of  blood 
stream,  the  blood  may  flow  from  the  veins  alinost  arterial  (bright  red)  in  its  char- 
acters, and  the  pulse  may  even  be  propagated  into  the  veins,  so  that  the  blood 
spouts  from  them  {CI.  Bernard).  Stimulation  of  the  peripheral  end  of  a  vaso- 
motor nerve  causes  the  opposite  results — pallor,  owing  to  contraction  of  the 
vessels,  diminished  transudation,  and  fall  of  the  temperature  on  the  surface.  The 
smaller  arteries  may  contract  so  much  that  their  lumen  is  almost  obliterated.  Con- 
tinued stimulation  ultimately  exhausts  the  nerve,  and  causes  at  the  same  time  the 
phenomena  of  paralysis  of  the  vascular  wall. 

Secondary  Results. — The  immediate  results  of  paralysis  of  the  vasomotor  nerves  lead  to  other 


EFFECT   ON    THE   TEMPERATURE    OF   THE    WHOLE    BODY.  699 

effects ;  the  paralysis  of  the  muscles  of  the  blood  vessels  must  lead  to  congestion  of  the  blood  in  the 
part ;  the  blood  moves  more  slowlv,  so  that  the  parts  in  contact  with  the  air  cool  more  easily,  and 
hence  the  first  stage  of  increase  of  the  temperature  may  be  followed  ^y  a  fall  oi  the  temperature. 
The  ear  of  a  rabbit  with  the  sympathetic  divided,  after  several  weeks  becomes  cooler  than  the  ear 
on  the  sound  one.  If  in  man  the  motor  muscular  nerves,  as  well  as  the  vasomotor  fibres,  are  para- 
lyzed, then  the  paralyzed  limb  becomes  cooler,  because  the  paralyzed  muscles  no  longer  contract 
to  aid  in  the  production  of  heat  {\  33S),  and  also  because  the  dilatation  of  the  muscular  arteries, 
which  accompanies  a  muscular  contraction,  is  absent.  Should  atrophy  of  the  paralyzed  muscles  set 
in  the  blood  vessels  also  become  smaller.  Hence  paralyzed  limbs  in  man  generally  become  cooler 
as  time  goes  on.  The  primary  efl^ect,  however,  in  a  limb,  e.  ^.,  after  section  of  the  sciatic  or  lesion 
of  the  brachial  ple.\us,  is  an  increase  of  the  temperature. 

If,  at  the  same  time,  the  vasomotor  nerves  of  a  large  area  of  the  skin  be  par- 
alyzed, e.  g.,  the  lower  half  of  the  body  after  section  of  the  spiniil  cord,  then  so 
much  heat  is  given  off  from  the  dilated  blood  vessels  that  either  the  warming  of 
the  skin  lasts  for  a  very  short  time  and  to  a  slight  degree,  or  there  may  be  cooling 
at  once.  Some  observers  ( Tsclietschichin,  Naiinyn,  Quincke,  Heidenhain,  Wood ) 
observed  a  rise  of  the  temperature  after  section  of  the  cervical  spinal  cord,  but 
Riegel  did  not  observe  this  increase. 

2.  Effect  on  the  Temperature  of  the  Whole  Body. — Stimulation  or 
paralysis  of  the  vasomotor  nerves  of  a  sma//  urea,  has  practically  no  effect  on  the 
general  temperature  of  the  body.  If,  however,  the  vasomotor  nerves  of  a  consider- 
able area  of  the  skin  be  suddenly  paralyzed,  then  the  temperature  of  the  entire 
body  falls,  because  more  heat  is  given  off  from  the  dilated  vessels  than  under 
normal  circumstances.  This  occurs  when  the  spinal  cord  is  divided  high  up  in 
the  neck.  The  inhalation  of  a  few  drops  of  amyl  nitrite,  which  dilates  the  blood 
vessels  of  the  skin,  causes  a  fall  of  the  temperature  {Sassefzki  and  Manasse'iii). 
Conversely,  stimulation  of  the  vasomotor  nerves  of  a  large  area  increases  the  tem- 
perature, because  the  constricted  vessels  give  off  less  heat.  The  temperature  in 
fever  may  be  partly  explained   in  this  way  (§  220,  4). 

The  activity  of  the  heart,  /.  e.,  the  number  and  energy  of  the  cardiac  con- 
tractions, is  influenced  by  the  condition  of  the  vasomotor  nerves.  When  a  large 
vasomotor  area  is  paralyzed,  the  muscular  blood  channels  are  dilated,  so  that  the 
blood  does  not  flow  to  the  heart  at  the  usual  rate  and  in  the  usual  amount,  as  the 
pressure  is  considerably  diminished.  Hence  the  heart  executes  extremely  small 
and  low  contractions.  Strieker  even  observed  that  the  heart  of  a  dog  ceased  to 
beat  on  extirpating  the  spinal  cord  from  the  first  cervical  to  the  eighth  dorsal 
vertebra.  Conversely,  we  know  that  stimulation  of  a  large  vasomotor  area  by 
constricting  the  blood  vessels  raises  the  arterial  blood  pressure  considerably.  .\s 
the  arterial  pressure  affects  the  pressure  within  the  left  ventricle,  it  may  act  as  a 
mechanical  stimulus  to  the  cardiac  wall,  and  increase  the  cardiac  contractions  both 
in  number  and  strength.  Hence,  the  circulation  is  accelerated  {Heidenhain, 
S/aTjansky). 

Splanchnic. — By  far  the  largest  vasomotor  area  in  the  body  is  that  controlled  by  the  splanchnic 
nerves,  as  they  supply  the  blood  vessels  of  the  abdomen  (|  161)  ;  hence  stimulation  of  their  peri- 
pheral ends  is  followeil  by  a  great  rise  of  the  blood  pressure.  When  they  are  divided,  there  is  such 
a  fall  of  the  blood  pres-ure,  that  other  parts  of  the  body  become  more  or  less  ansmic,  and  the 
animal  may  even  die  from  "  being  bled  into  its  own  belly."  Animals  whose  portal  vein  is  ligatured 
die  for  the  same  rea  on  {C.  Lna'^uii;  and  Thiry),  [see  \  87].  The  capicity  of  the  vascular  system, 
depending  as  it  does  in  part  upon  the  condition  of  the  vasomotor  nerves,  influences  the  body  7veigJit. 
Stimulation  of  certain  vascular  areas  may  cause  the  rapid  excretion  of  water,  and  we  may  thus 
account  in  part  for  the  diminution  of  the  body  weight  which  has  been  sometimes  observed  after  an 
epileptic  attack  terminating  with  polyuria. 

Trophic  Disturbances  sometimes  occur  after  affections  of  the  vasomotor  nerves  (§  342,  I,  c). 
Paralysis  of  the  vasomotor  ner\'es  not  only  causes  dilatation  of  the  blood  vessels  and  local  increase 
of  the  blood  pressure,  but  it  may  also  cause  increased  transudation  through  the  capillaries  [?  203]. 
When  the  active  contraction  of  the  muscles  is  abolished,  at  the  same  time  the  blood  stream  becomes 
slower ;  and  in  some  cases  the  skin  becomes  livid  owing  to  the  venous  congestion.  There  is  a 
diminution  of  the  normal  transpiration,  and  the  epidermis  may  be  dry  and  peel  off  in  scales.  The 
growth  of  the  hair  and  nails  may  be  affected  by  the  congestion  of  blood,  and  other  tissues  may  also 
suffer. 


700  PATHOLOGICAL   VASOMOTOR    PHENOMENA. 

Vasomotor  Centres  in  the  Spinal  Cord. — Besides  the  dominating  centre 
in  tlie  medulla  oblongatiT,  the  blood  vessels  are  acted  upon  by  hca/  or  su/it»;iiiiatc 
vasomotor  centres  in  the  spinal  cord,  as  is  proved  by  the  following  observations  : 
If  the  spinal  cord  of  an  animal  be  divided,  then  all  the  blood  vessels  supplied  by 
vasomotor  nerves  below  the  point  of  section  are  paralyzed,  as  the  vasomotor  fibres 
proceed  from  the  medulla  oblongata.  If  the  animal  lives,  the  blood  vessels  re- 
gain their  tone  and  their  former  calibre,  while  the  rhythmical  movements  of  their 
muscular  walls  are  ascribed  to  the  subordinate  centres  in  the  lower  part  of  the 
spinal  cord  {Lister,  Goltz,  Vulpian — §  362,  7). 

These  subordinate  centres  may  also  be  influenced  rcflcxly;  after  destruction  of  the  medulla  ob- 
longata the  arteries  of  the  frog's  web  still  contract  reflexly  when  the  sensory  nerves  of  the  hind  leg 
are  stimulated  {Putnam,  Nussbauin,  Vulpian'). 

If  now  the  lower  divided  part  of  the  cord  be  crushed,  the  blood  vessels  again 
dilate,  owing  to  the  destruction  of  the  subordinate  centres.  In  animals  which 
survive  this  operation,  the  vessels  of  the  paralyzed  parts  gradually  recover  their 
normal  diameter  and  rhythmical  movements.  This  effect  is  ascribed  to  ganglia 
which  are  supposed  to  exist  along  the  course  of  the  vessels.  These  ganglia  [or 
peripheral  nervous  mechanisms]  might  be  compared  to  the  ganglia  of  the  heart, 
and  seem  by  themselves  capable  of  sustaining  the  movements  of  the  vascular  wall. 
Even  the  blood  vessels  of  an  excised  kidney  exhibit  periodic  variations  of  their 
calibre  (C  Ltuiwig  and  Mosso).  It  is  important  to  observe  that  the  walls  of  the 
blood  vessels  contract  as  soon  as  the  blood  becomes  highly  venous.  Hence  the 
blood  vessels  offer  a  greater  resistance  to  the  passage  of  venous  than  to  the  arte- 
rial blood  (  C.  Li/dwig).  Nevertheless,  the  blood  vessels,  although  they  recover 
part  of  their  tone  and  inobility,  never  do  so  completely. 

The  effects  of  direct  mechanical,  chemical,  and  electrical  stimuli  on  blood  vessels  may  be  due  to 
their  action  on  these  peripheral  nervous  mechanisms.  The  arteries  may  contract  so  much  as  almost 
to  disappear,  but  sometimes  dilatation  follows  the  primary  stimulus. 

Lewasch-w  found  that  limbs  in  which  the  vasomotor  fibres  had  undergone  degeneration  reacted 
like  intact  limbs  to  variations  of  temperature  ;  heat  relaxed  the  vessels,  and  cold  constricted  them. 
It  is,  however,  doubtful  if  the  variations  of  the  vascular  lumen  depend  upon  the  stimulation  of  the 
peripheral  nervims  mechanisms.  Amyl  nitrite  and  digitalis  are  supposed  to  act  on  those  hypothetical 
mechanisms. 

The  puhalUi:.;  veins  in  the  bat's  wing  still  continue  to  beat  after  section  of  all  their  neives,  which 
is  in  favor  of  the  existence  of  local  nervous  mechanisms  (Liu/isin^^er,  Sihiff). 

Influence  of  the  Cerebrum. — The  cerebrum  influences  the  vasomotor  centre, 
as  is  proved  by  the  sudden  pallor  that  accompanies  some  psychical  conditions, 
such  as  fright  or  terror.  There  is  a  centre  in  the  gray  matter  of  the  cerebrum 
where  stimulation  causes  cooling  of  the  opposite  side  of  the  body. 

Although  there  is  one  general  vasomotor  centre  in  the  medulla  oblongata  which 
influences  all  the  blood  vessels  of  the  body,  it  is  really  a  complex  composite  centre, 
consisting  of  a  number  of  closely  aggregated  centres,  each  of  which  presides  over 
a  particular  vascular  area.  We  know  something  of  the  hepatic  (§  175)  and  renal 
centres  (§  276). 

Many  poisons  excite  the  vasomotor  nerves,  such  as  ergotin,  tannic  acid,  copaiba,  and  cubebs ; 
others yf/-.i/  excite,  and  then  paralyze,  e.i;.,  chloral  hydrate,  inorphia,  landinosin,  veratrin,  nicotin. 
Calabar  bean,  alcohol;  others  •i^'^xAX-^  paralyze  them,  c.^.,  amyl  nitrite,  CO  (?  17),  atropin,  mus- 
carin.  The  paralytic  action  of  the  poison  is  proved  by  the  fact  that,  after  section  of  the  vagi  and 
accelerantes,  neither  the  pressor  nor  the  depressor  nerves,  when  stimulated,  produce  any  effect. 
Many  pathological  conditions  affect  the  vasomotor  nerves. 

The  veins  are  also  influenced  by  va.soniotor  nerves  ( 6-'(?/;'s).  and  so  are  the 
lymphatics,  but  we  know  very  little  about  this  condition. 

Pathological. — The  angio-neuroses,  or  nervous  affections  of  blood  vessels,  form  a  most  im- 
portant group  of  diseases.  The  parts  primarily  affected  may  be  either  the  peripheral  nervous 
mechanisms,  the  suliordmate  centres  in  the  cord,  the  dominating  centre  in  the  medulla,  or  the  gray 
matter  of  the  cerebrum.  The  effect  may  be  direct  or  reflex.  The  dilatation  of  the  vessrK  may 
also  be  due  to  stimulation  of  vasodilator  nerves,  and  the  physician  must  be   careful  to  distinguish 


VASO-DILATOR   CENTRE   AND   VASO-DILATOR   NERVES.  701 

whether  the  result  is  due  to  paralysis  of  the  vaso- constrictor  nerves  or  stimulation  of  the  vaso-dilator 
fibres. 

Angio-neuroses  of  the  skin  occur  in  affections  of  the  vasomotor  nerves,  either  as  a  diffuse 
redness  or  pallor ;  or  there  may  be  circumscribed  affections.  Sometimes,  owing  to  the  stimula- 
tion of  individual  vasomotor  nerves,  there  are  local  cutaneous  arierio  spasms  (Nothnagel).  In 
certain  acute  febrile  attacks — after  previous  initial  violent  stimulation  of  the  vasomotor  nerves, 
especially  during  the  cold  stage  of  fever — there  may  be  different  forms  of  paralytic  phenomena  of 
the  cutaneous  vessels.  In  some  cases  of  epilepsy  in  man.  Trousseau  observed  irregular,  red,  angio- 
paralytic  patches  (taches  cerebrales).  Continued  strong  stimulation  may  lead  to  interruption  of 
the  circulation,  which  may  result  in  gangrene  of  the  skin  (  Weiss)  and  deeper-seated  parts. 

Hemicrania,  due  to  unilateral  spasm  of  the  branches  of  the  carotid  on  the  head,  is  accompanied 
by  severe  headache  (Dti  Bois-Reymond).  The  cervical  sympathetic  nerve  is  intensely  stimulated; 
a  pale,  collapsed  and  cool  side  of  the  face,  contraction  of  the  temporal  artery  like  a  firm  whipcord, 
dilatation  of  the  pupil,  secretion  of  thick  saliva  are  sure  signs  of  this  affection.  This  form  may  be 
followed  by  the  opposite  condition  of  paralysis  of  the  cervical  sympathetic,  where  the  effects  are 
reversed.     Sometimes  the  two  conditions  may  alternate. 

Basedow's  disease  is  a  remarkable  condition,  in  which  the  vasomotor  nerves  are  concerned ; 
the  heart  beats  very  rapidly  (90  to  120  to  200  beats  per  minute),  causing  palpitation;  there  is 
swelling  of  the  thyroid  gland  (struma)  and  projection  of  the  eyeballs  (exophthalmos),  with 
imperfectly  coordinated  movements  of  the  upper  eyelid,  whereby  the  plane  of  vision  is  raised  or 
lowered.  Perhaps  in  this  disease  we  have  to  deal  with  a  simultaneous  stimulation  of  the  accelerans 
cordis  (^  370),  the  motor  fibres  of  Miiller's  muscles  of  the  orbit  and  eyelids  (§  347,  I),  as  well  as 
of  the  vaso-dilators  of  the  thyroid  gland.  The  disease  may  be  due  to  direct  stimulation  of  the 
sympathetic  channels  or  their  spinal  origins,  or  it  may  be  referred  to  some  reflex  cause.  It  has 
also  been  explained,  however,  thus,  that  the  exophthalmus  and  struma  are  the  consequence 
of  vasomotor  paralysis,  which  resuUs  in  enlargement  of  the  blood  vessels,  while  the  increased 
cardiac  action  is  a  sign  of  the  diminished  or  arrested  inhibitory  action  of  the  vagus.  All 
these  phenomena  may  be  caused,  according  to  Filehne,  by  injury  to  the  upper  part  of  both 
restiform  bodies  in  rabbits. 

Visceral  Angio-neuroses. — The  occurrence  of  sudden  hyperasmia  with  transudations  and 
ecchymoses  in  some  thoracic  or  abdominal  organs  may  have  a  neurotic  basis.  As  already  men- 
tioned, injury  to  the  pons,  corpus  striatum  and  optic  thalamus  may  give  rise  to  hyperjemia,  and 
ecchymoses  in  the  lungs,  pleura;,  intestmes  and  kidneys.  According  to  Brown-Sequard,  compression 
or  section  of  one-halt  of  the  pons  causes  ecchymoses,  especially  in  the  lung  of  the  opposite  side ; 
he  also  observed  ecchymoses  in  the  renal  capsule  after  injury  of  the  lumbar  portion  of  the  spinal 
cord  (?  379). 

The  dependence  of  diabetes  mellitus  upon  injury  to  the  vasomotor  nerves  is  referred  to  in 
^175;  the  action  of  the  vasomotor  nerves  on  the  secretion  of  urine  in  J  276;  and  fever  in 
?220. 

372.  VASO-DILATOR  CENTRE  AND  VASO-DILATOR 
NERVES. — Although  a  vaso-dilator  centre  has  not  been  definitely  proved 
to  e.xist  in  the  medulla,  still  its  e.xistence  there  has  been  surmised.  Its  action  is 
opposite  to  that  of  the  vasomotor  centre.  The  centre  is  certainly  not  in  a  con- 
tinuous or  tonic  state  of  excitement.  The  vaso-dilator  nerves  behave  in  their 
functions  similarly  to  the  cardiac  branches  of  the  vagus  ;  both,  when  stimulated, 
cause  relaxation  and  rest  {Schiff,  CI.  Bernard).  [They  are  not  paralyzed,  how- 
ever, by  a  large  dose  of  atropin.]  Hence,  these  nerves  have  been  called  vaso- 
inhibitory,  vaso-hypotonic  or  vaso-dilator  nerves. 

The  existence  of  vaso-dilator  nerves  is  assumed  in  accordance  with  such  facts  as 
the  following :  If  the  chorda  tympani  be  divided,  there  is  no  change  in  the 
blood  vessels  of  the  sub-maxillary  gland  ;  but  if  its  peripheral  end  be  stimulated, 
in  addition  to  other  results  (§  145),  there  is  dilatation  of  the  blood  vessels  of  the 
sub-maxillary  glands,  so  that  its  veins  discharge  bright  florid  blood,  while  they 
spout  like  an  artery.  Similarly,  if  the  nervi  erigentes  be  divided,  there  is  no 
effect  on  the  blood  vessels  of  the  penis  (§  362,  4) ;  but  if  their /{■/-///zt-nj'/ ends  be 
stimulated  with  Faradic  electricity,  the  sinuses  of  the  corpora  cavernosa  dilate, 
become  filled  with  blood,  and  erection  takes  place  (§  436J).  [Other  examples  in 
muscle  and  elsewhere  are  referred  to  below.] 

Dyspneeic  blood  stimulates  this  centre  as  well  as  the  vasomotor  centre,  so  that 
the  cutaneous  vessels  are  dilated,  while  simultaneously  the  vessels  of  the  internal 
organs  are  contracted  and  the  organs  anjemic,  owing  to  the  stimulation  of  their 
vasomotor  centre  {^Dastre  and  Morat). 


702  SPASM    AND    SWEAT   CENTRE. 

Course  of  the  Vaso-dilator  Nerves. — To  some  organs  they  pass  as  special  nerves;  to  other 
parts  of  the  body,  however,  they  proceed  along  with  the  vasomotor  and  other  nerves.  According  to 
Dastra  and  Morat,  the  vaso-dilator  nerves  for  the  bucco-labial  region  (dog)  pass  out  from  the 
cord  by  the  1st  to  the  5th  dorsal  nerves,  and  go  through  the  rami  communicantes  into  the  sympa- 
thetic, then  to  the  superior  cervical  ganglion,  and,  lastly,  through  the  carotid  and  inter  carotid  plexus 
into  the  trigeminus.  [The  fibres  occur  in  the  posterior  segment  of  the  ring  of  Vieussens,  and  if  they 
be  stimulated  there  is  dilatation  of  the  vessels  in  the  lip  and  cheek  on  that  side  (p.  652).]  The 
maxillary  branch  of  the  trigeminus,  however,  also  contains  vaso-dilator  filires  proper  to  itself 
[Laffonl].  In  the  gray  matter  of  the  cord  there  is  a  special  subordinate  cenlre  for  the  vasodilator 
hbies  of  the  bucco-labial  region.  This  centre  may  be  acted  on  reflexly  by  stimulation  of  the  vagus, 
especially  its  pulmonary  branches,  and  even  liy  stimulating  the  sciatic  nerve.  The  ear  receives  its 
nerves  from  the  1st  dorsal  and  lowest  cerv.cal  gangli  ju,  the  upper  limb  from  the  thoracic  portion, 
and  the  lower  limb  from  the  abdominal  portion  of  the  sympathetic.  The  vaso-dilator  fibres  run 
to  the  sub-maxillary  and  sub-lingual  glands  in  the  chorda  tympani  (§  349,  4),  while  those  for  the 
posterior  part  of  the  tongue  run  in  the  glosso-pharyngcal  nerve  (§  351,  4 — Viilpian).  Perhaps 
the  vagus  contains  those  for  the  kidneys  (§  276J.  Stimulation  of  the  nervi  erigentes  pro- 
ceeding from  the  sacral  plexus  causes  dilatation  of  the  arteries  of  the  penis,  together  with  con- 
gestion of  the  corpora  cavernosa  (^436)  {Eckkard,  Lovin).  Eckhard  found  that  erection  of  the 
penis  can  be  produced  by  stimulation  of  the  spinal  cord  and  of  the  pons  as  far  as  the  peduncles, 
which  may  explain  the  phenomenon  of  priapism  in  connection  w  ith  pathological  irritations  in  these 
regions. 

The  muscles  receive  their  vaso-dilator  fibres  for  their  vessels  through  the  trunks  of  the  motor 
nerves.  Stimulation  of  a  motor  nerve  or  the  spinal  cord  causes  not  only  contraction  of  the  corre- 
sponding muscles,  but  also  dilatation  of  their  blood  vessels  (J  294,  II  —  C.  Luthoig  and  Sczelkoiv, 
Haftz,  Gaiktil,  Heideithain) — the  dilatation  of  the  vessels  taking  place  even  when  the  muscle  is 
prevented  from  shortening.  [Gaskell  observed  under  the  microscope  the  dilatation  produced  by 
stimulation  of  the  nerve  to  the  mylo-hyoid  muscle  of  the  frog.]  Goltz  showed  that  in  the  nerves 
to  the  limbs,  e.g.,  in  the  sciatic  nerve,  the  vasomotor  and  vaso-dilator  fibres  occur  in  the  same  nerve 
If  the  peripheral  end  of  this  nerve  be  stimulated,  immediately  after  it  is  divided,  the  action  of  the 
vaso-constrictor  fibres  overcomes  that  of  the  dilators.  If  the  peripheral  end  be  stimulated  several 
days  after  the  section,  when  the  vaso-constrictors  have  lost  their  excitability,  the  blood  vessels  dilate 
under  the  action  of  the  vasodilator  fibres.  Stimuli,  which  are  applied  at  long  intervals  to  the  nerve, 
act  especially  on  the  vasodilator  fibres;  while  tetanizing  stimuli  act  on  the  vasomotors.  The  sciatic 
nerve  receives  both  kinds  of  fibres  from  the  sympathetic.  It  is  assumed  that  the  peripheral  nervous 
mechanisms  in  connection  with  the  blood  vessels  are  influenced  by  both  kinds  of  vascular  nerves; 
the  vasomotors  (constrictors)  increase,  while  the  vasodilators  diminish,  the  activity  of  these  mech- 
anisms or  ganglia.  Psychical  con&x'Cxon'i,  act  upon  the  vasodilator  nerves;  the  blush  of  shame, 
which  is  not  confined  to  the  face,  but  may  even  extend  over  the  whole  skin,  is  probably  due  to  stim- 
ulation of  the  vaso  dilator  centre. 

Influence  on  Temperature. — The  vasodilator  nerves  obviously  have  a  considerable  influence 
on  the  tenipeialure  of  the  body  and  on  the  heat  of  the  individual  parts  of  the  body.  Both  vascular 
centres  must  act  as  important  regulatory  mechanisms  for  the  radiation  ol  heat  through  the  cutaneous 
vessels  [\  214,  II).  Probably  they  are  kept  in  activity  reflexly  by  sensory  nerves.  Disturbances  in 
their  function  may  lead  to  an  abnormal  accumulation  of  heat,  as  in  fever  (\  220),  or  to  abnormal 
cooling  {\  213,  7).  Some  observers,  however,  assume  the  existence  of  an  intra  cranial  "heat-regu- 
lating centre  "(  7if/;f/ii/«V/««,  A'izhkjk,  (P«;HC/tc'),  whose  situation  is  unknown.  According  to 
Wood,  separation  of  the  medulla  oblongata  from  the  pons  causes  an  increased  radiation  and  a  di- 
minished production  of  heat,  due  to  the  cutting  off  of  the  influences  from  the  heat-regulating  centre 
(«  377)- 

373.  THE  SPASM  CENTRE— THE  SWEAT  CENTRE.— Spasm 
Centre. — In  the  medulla  oblongata,  just  where  it  joins  the  pons,  there  is  a  cen- 
tre whose  stimulation  causes  general  spasms.  The  centre  may  be  excited  by  sud- 
denly producing  a  highly  venous  condition  of  the  blood  ("asphyxia  spasms,"  in 
cases  of  drowning  in  mammals,  but  not  in  frogs)  by  sudden  ancemia  of  the  riiedulla 
oblongata,  either  in  consequence  of  hemorrhage  or  ligature  of  both  carotids  and 
subclavians(A'««w<z///a«(/  Tenner),  and,  lastly,  by  sudden  venous  stagnation  caused 
by  compressing  the  veins  coming  from  the  head.  In  all  these  cases  the  stimula- 
tion of  the  centre  is  due  to  the  sudden  interruption  of  the  normal  exchange  of 
the  gases.  When  these  factors  act  quite  gradually,  death  may  take  place  without 
convulsions.  Intense  direct  stimulation  of  the  medulla,  as  by  its  sudden  destruc- 
tion, causes  general  convulsions. 

Position. — Nothnagel  attempted  by  direct  stimulation  to  map  out  its  position  in  rabbits ;  it  ex- 
tends from  the  area  above  the  ala  cinerea  upward  to  the  corpora  quadrigemina.     It  is  limited  exter. 


PSYCHICAL    FUNCTIONS   OF   THE    BRAIN.  703 

nally  by  the  locus  cceruleus  and  the  tuberculuin  acusticum.  In  the  frog  it  lies  in  the  lower  half  of 
the  4th  ventricle  (j'/«<(5e'/).  The  centre  is  affected  in  extenbive  reflex  spasms  (§  364,  6),  ^ ^.,  in 
poisoning  with  strychnin  and   in  hydrophobia. 

Poisons. — Many  inorganic  and  organic  poisons,  most  cardiac  poisons,  nicotin,  picrotoxin,  ammo- 
nia (§  277),  and  the  compounds  of  barium,  cause  death  after  producing  convulsions,  by  acting  on 
the  spasm  centre  {A'oder,  Heiihcl,  Bohm). 

If  the  arteries  going  to  the  brain  be  ligatured  so  as  to  paralyze  the  oblongata,  then  on  ligaturing 
the  abdominal  aorta  spasms  of  the  lower  limbs  occur,  owing  to  the  anaemic  stimulation  of  the  motor 
ganglia  of  the  spinal  cord  [Sigvi.  Mayer). 

Pathological — Epilepsy. — Schroder  van  der  Kolk  found  the  blood  vessels  of  the  oblongata  dilated 
and  increased  in  cases  of  epilepsy.  Brown-Sequard  observed  that  injury  to  the  central  ur  peripheral 
nervous  system  (spinal  cord,  oblongata,  peduncle,  corpora  quadrigemina,  sciatic  nerve)  of  guinea 
pigs  produced  ep  lepsy,  and  this  condition  even  became  hereditary.  Stimulation  of  the  cheek  or 
ol  the  face,  "  epileptic  zone,"  on  the  same  side  as  the  injury  (spinal  cord),  caused  at  once  an  at- 
tack of  epilepsy;  but  when  the  peduncle  was  injured  the  opposite  side  must  be  stimulated.  West- 
phal  made  guinea  pigs  epileptic  by  repeated  light  blows  on  the  skull,  and  this  condiiion  also  became 
hereditary.  In  these  cases  there  was  effusion  of  blood  in  the  medulla  oblongata  and  upper  part  of 
the  spinal  cord  (§^,  375  and  378,  1).  Direct  stimulation  of  the  cerebrum  also  produces  epileptic 
convulsions.  Strong  electrical  stimulation  of  the  motor  areas  of  the  cortex  c-erebri  is  often  followeil 
by  an  epileptic  attack  (J  375).  [It  is  no  unfrequent  occurrence  that,  while  one  is  stimulating  the 
motor  areas  of  the  cortex  cerebri  of  a  dog,  to  find  the  animal  exhibiting  symptoms  of  local  or  general 
epilepsy.] 

Sweat  Centre. — k  dominating  centre  for  the  secretion  of  the  sweat  of  the 
entire  surface  of  the  body  (§  289,  \\) — with  subordinate  spinal  centres  (§  362,  8) 
— occurs  in  the  medulla  oblongata  (Adamkiewicz,  Marme,  Nawrocki).  It  is 
double,  and  in  rare  cases  the  e.'ccitability  is  unequal  on  the  two  sides,  as  is  mani- 
fested by  unilateral  perspiration  (§  289,  2). 

Poisons. — Calabar  bean,  nicotin,  picrotoxin.  camphor,  ammonium  acetate,  cause  a  secretion  of 
sweat,  by  acting  directly  on  the  sweat  centre.  Muscarin  causes  local  stimulation  of  the  peripheral 
sweat  filjres — it  causes  sweating  of  the  hind  limbs  after  section  of  the  sciatic  nerves.  Atropin  ar- 
rests the  action  of  muscirin  (Ott,  Wood,  Fields  Naiorocki). 

[Regeneration  of  the  Spinal  Cord  — In  some  animals  true  nervous  matter  is  reproduced  after 
part  of  the  spinal  cord  has  been  destroyed,  at  least  this  is  so  in  tritons  and  lizards  (H.  Miiller).  .\s 
is  well  known,  in  these  animals  when  the  tail  is  removed  it  is  reproduced,  and  Miiller  found  that  a 
part  of  the  spinal  cord  corresponding  to  the  new  part  of  the  tail  is  reproduced.  Morphologically  the 
elements  were  the  same,  but  the  spinal  nerves  were  not  reproduced,  while  physiologically  the  new 
nerve  substance  was  not  functionally  active  ;  it  corresponds,  as  it  were,  to  a  lower  stage  of  develop- 
ment. According  to  Masius  and  Vanlair,  an  excised  portion  of  the  spinal  cord  of  a  frog  is  repro- 
duced after  six  months  ;  while  Brown-S^quard  maintains  that  reunion  of  the  divided  surfaces  of  the 
cord  takes  place  in  pigeons  after  six  to  fifteen  months.  A  partial  reunion  is  asserted  to  occur  in  dogs 
by  Dentan,  Naunyn,  and  Eichhorst,  althou.;h  Schieferdccker  obtained  only  negative  results,  the 
divided  ends  being  united  only  by  connective  tissue  {^Schwatbe).'\ 

374.  PSYCHICAL  FUNCTIONS  OF  THE  BRAIN.— The  hemi- 
spheres of  the  cerebrum  are  usually  said  to  be  the  seat  of  all  the  psychical  activities. 
Only  when  they  are  intact  are  the  processes  of  thinking,  feeling,  and  willing  pos- 
sible. .\f(er  they  are  destroyed,  the  organism  comes  to  be  like  a  complicated 
iTiachine,  and  its  whole  activity  is  only  the  expression  of  the  external  and  internal 
stimuli  which  act  upon  it.  The  psychical  activities  appear  to  be  located  in  both 
hemispheres,  so  that  after  destruction  of  a  considerable  part  of  one  of  them  the 
other  seems  to  act  in  place  of  the  part  destroyed.  [Objection  has  been  taken  to 
the  term  the  "seat  of"  the  will  and  intelligence,  and  undoubtedly  it  is  more 
consistent  with  what  we  know,  or  rather  do  not  know,  to  say  that  the  existence  of 
volition  and  intelligence  is  dependent  on  the  connection  of  the  cerebral  cortex 
with  the  rest  of  the  brain.] 

[That  a  certain  condition  of  the  cerebral  hemispheres  is  necessary  for  the  manifestation  of  the  in. 
tellectual  faculties  is  admitted  on  all  hands,  for  compression  of  the  brain,  e.g.,  by  a  depressed  frac- 
ture of  the  skull,  and  sudden  cessation  of  the  supply  of  blood  to  the  brain  abolish  consciousness.  The 
intellectual  faculties  are  affected  by  inflammation  of  the  meninges  involving  the  surface  of  the  brain, 
the  action  of  drugs  afl^ects  the  intellectual  and  other  faculties,  bu',  while  all  this  is  admitted  we  can- 
not say  precisely  upon  what  parts  of  the  brain  ideation  depends.  The  pre-frontal  area,  or  the  con- 
volutions in  front  of  the  ascending  frontal  supplied  by  the   anterior  cerebral  artery,  are  sometimes 


704  EXTIRPATION    OF   THE    CEREBRUM. 

regarded  a<  the  anatomical  substratum  of  certain  mental  acts.  At  any  rate,  electrical  stimulation  of 
these  parts  is  not  followed  by  muscular  motion,  and,  according  to  Ferrier,  if  this  region  be  extii-pated 
in  the  monkey,  there  is  no  motor  or  sensory  disturbance  in  this  animal ;  the  animal  exhibits  emo- 
tional feeling,  all  its  special  senses  remain,  and  the  power  of  voluntary  motion  is  retained,  but  never- 
theless there  is  a  decided  alteration  in  the  animal's  character  and  behavior,  so  that  it  exhibits  consid- 
erable psychological  alterations,  and,  according  to  Ferrier,  "  it  has  lost  to  all  appearance  the  faculty 
of  attention  and  intelligent  observation."] 

Observations  on  Man.— Cases  in  which  considerable  unilateral  lesions  or  destruction  of  one 
hemisphere  have  talien  place,  without  the  psychical  activities  appearing  to  suffer,  sometimes  occur. 
The  following  is  a  case  communicated  by  Longet :  A  boy,  i6  years  of  age,  had  his  parietal  bone 
fractured  by  a  stone  falling  on  it,  so  that  part  of  the  protrudmg  brain  matter  had  to  be  removed. 
(In  reapplying  the  bandages  more  brain  matter  had  lo  be  removed.  After  i8  days  he  fell  out  of 
bed,  and  more  brain  matter  protruded,  which  was  removed.  On  the  35th  day  he  got  intoxicated, 
tore  off  the  bandages,  and  with  them  a  part  of  the  brain  matter.  After  his  recovery  the  boy  still 
retained  his  intelligence,  but  he  was  hemiplegic.  Even  when  bnth  hemispheres  are  moderately 
destroyed  the  intelligence  appears  to  be  intact;  thus  Trousseau  describes  the  case  of  an  officer 
whose  fore-brain  was  pierced  transversely  by  a  bullet.  There  was  scarcely  any  appearance  of  his 
mental  or  bodily  faculties  being  affected.  In  other  cases,  destruction  of  parts  of  the  brain  pecu- 
liarly ahers  the  character.  We  must  be  extreniely  careful,  however,  in  forming  conclusions  in  all 
such  cases.  [In  the  celebrated  "  American  crowbar  case"  recorded  by  Bigelow,  a  young  man 
was  hit  by  a  bar  of  iron  \)^  inch  in  diameter,  which  traversed  the  anterior  part  of  the  left  hemi- 
sphere, going  clear  out  at  the  top  of  his  head.  This  man  lived  for  thirteen  years  without  any  per- 
manent alterations  of  motor  or  sensory  functions;  but  "the  man's  disposition  and  character  were 
observed  to  have  undergone  a  serious  change."  There  were,  however,  some  changes  which  might 
be  referable  to  injury  to  the  frontal  region.  In  all  cases  it  is  most  important  to  know  both  the 
exact  site  and  the  extent  of  the  lesion.  Ross  points  out  that  the  characteristic  features  of  lesions 
in  the  pre-frontal  cortical  region  are  afforded  by  "  psychical  disturbances,  consisting  of  dementia, 
apathy  and  somnolency."] 

Imperfect  Development  of  the  Cerebrum. — Microcephalia  and  hydrocephalus  yield  every 
result  between  diminution  of  the  psychical  activities  and  idiocy.  Extensive  inflammation,  degen- 
eration, pressure,  anaimia  of  the  blood  vessels,  and  the  actions  of  many  poisons  produce  the  same 
effect. 

Flourens'  Doctrine. — Flourens  assumed  that  the  whole  of  the  cerebrum  is  concerned  in 
every  psychical  process.  From  his  experiments  on  pigeons,  he  concluded  that,  if  a  small  part  of  the 
hemispheres  remained  intact,  it  was  sufficient  for  the  manifestation  of  the  mental  functions;  just  in 
proportion  as  the  gray  matter  of  the  hemispheres  is  removed  all  the  functions  of  the  cerebrum  are 
enieebled,  and  when  all  the  gray  matter  is  removed  all  the  functions  are  abolished.  According  to 
this  view,  neither  the  different  faculties  nor  the  different  perceptions  are  localized  in  special  areas. 
Goltz  holds  a  somewhat  similar  view  to  that  of  Flourens.  He  assumes  that  if  an  uninjured  part  of 
the  cerebrum  remain,  it  can  to  a  certain  extent  perform  the  functions  of  the  parts  that  have  been 
removed.     This  Vulpian  has  called  the  law  of  "  functional  substitution  "  (loi  de  suppleance). 

The  phrenological  doctrine  of  Gall  (-j-  1828)  and  Spurzheim  assumes  that  the  different  mental 
faculties  ate  located  in  different  parts  of  the  brain,  and  it  is  assumed  that  a  large  development  of  a 
particular  organ  may  be  detected  by  examining  the  external  configuration  of  the  head  (Crani- 
oscopy). 

Extirpation  of  the  Cerebrum. — 'After  the  removal  of  botli  cerebral  hemi- 
spheres in  animals,  every  voluntary  movement  and  every  conscious  impression  and 
sensory  perception  entirely  ceases.  On  the  other  hand,  the  whole  mechanical 
movements  and  the  maintenance  of  the  equilibrium  of  the  movements  are  retained. 
The  maintenance  of  the  equilibrium  depends  upon  the  mid-brain,  and  is 
regulated  by  important  reflex  channels  (§  379).  The  mid-brain  (corpora  quadri- 
gemina)  is  connected  not  only  with  the  gray  matter  of  the  spinal  cord  and 
medulla  oblongata,  the  seat  of  e.xtensive  reflex  mechanisms  (§  367),  but  it  also 
receives  fibres  coming  from  the  higher  organs  of  sense,  which  also  excite  move- 
ments reflexly.  The  corpora  quadrigemina  are  also  supposed  to  contain  a  reflex 
inhibitory  apparatus  (§  361,  2).  The  joint  action  of  all  these  parts  makes  the 
corpora  quadrigemina  one  of  the  most  important  organs  for  the  harmonious  exe- 
cution of  movements,  and  this  even  in  a  higher  degree  than  the  medulla  oblongata 
itself  {Goltz).  Animals  with  their  corpora  quadrigemina  intact  retain  the  equi- 
librium of  their  bodies  under  the  most  varied  conditions,  but  they  lose  this  power 
as  soon  as  the  mid-brain  is  destroyed  {Goltz).  Christiani  locates  the  coordinating 
centre  for  the  change  of  place  and  the  maintenance  of  the  equilibrium  in  mam- 
mals in  front  of  the  inspiratory  centre  in  the  3d  ventricle  (§  36S). 


REMOVAL   OF   THE    CEREBRUM    FROM    A   FROG. 


705 


That  impressions  from  the  skin  and  sense  organs  are  concerned  in  the  maintenance  of  the 
equilibrium  is  proved  by  the  following  facts  :  A  frog  without  its  cerebrum  at  once  loses  its  power  of 
balancing  itself  as  soon  as  the  skin  is  removed  from  its  hind  limbs.  The  action  of  impressions 
communicated  through  the  eyes  is  proved  by  the  difficulty  or  impossibility  of  maintaining  the  equi- 
Hbrium  in  nystagmus  ('i  350),  and  by  the  vertigo  which  often  accompanies  paralysis  of  the  external 
ocular  muscles.  In  persons  whose  cutaneous  sensibility  is  diminished,  the  eyes  are  the  chief  organs 
for  the  maintenance  of  the  equilibrium  ;  they  fall  over  when  the  eyes  are  closed.  [This  is  well 
illustrated  in  cases  of  locomotor  ataxia  (p.  672).] 

Frog. — A  frog  with  its  cerebrutn  removed  retains  its  power  of  maintaining  its 
equilibrium.  It  can  sit,  spring  or  execute  complicated  coordinated  movements 
when  appropriate  stimuli  are  applied ;  when  placed  on  its  back,  it  immediately 
turns  into  its  normal  position  on  its  belly;  if  stimulated,  it  gives  one  or  two 
springs  and  then  comes  to  rest  ;  when  thrown  into  water,  it  swims  to  the  margin 
of  the  vessel,  and  it  may  crawl  up  the  side,  and  sit  passive  upon  the  edge  of  the 
vessel.  When  incited  to  move,  it  exhibits  the  most  complete  harmony  and  unity 
in  all  its  movements.  It  sits  on  the  same  place  continually  as  if  in  sleep,  it  takes 
no  food,  it  has  no  feelings  of  hunger  and  thirst,  it  shows  no  symptoms  of  fear, 
and  ultimately,  if  left  alone,  it  becomes  desiccated   like  a  mummy  on  the  spot 

Fig.  419. 


/ 


/* 


Fig.  421. 


Frog  without  its  cerebrum  avoiding  ; 
object  placed  in  its  patli. 


Fig.  420. 


where  it  sits.  [If  the  flanks  of  such  a  frog  be  stroked,  it  croaks  with  the  utmost 
regularity  according  to  the  number  of  times  it  is  stroked.  Langendorff  has 
shown  that  a  frog  croaks  under  the  same  circumstances  when  both  optic  nerves 
are  divided.  It  seems  to  be  influenced  by  light ;  for,  if  an  object  be  placed  in 
front  of  it  so  as  to  throw  a  strong  shadow,  then  on  stimulating  the  frog  it  will 
spring  not  against  the  object,  a,  but  in  the  direction,  i  (Fig.  419).  Steiner  finds 
that  if  a  glass  plate  be  substituted  for  an  opaque  object  like  a  book,  the  frog 
always  jumps  against  this  obstacle.  Its  balancing  movements  on  a  board  are 
quite  remarkable  and  acrobatic  in  character.  If  it  be  placed  on  a  board,  and  the 
board  gently  inclined  (Fig.  420),  it  does  not  fall  off  as  a  frog  merely  with  its 
spinal  cord  will  do,  but  as  the  board  is  inclined  so  as  to  alter  the  animal's  centre 
of  gravity  it  slowly  crawls  up  the  board  until  its  equilibrium  is  restored.  If  the 
board  be  sloped  as  in  Fig.  420  it  will  crawl  up  until  it  sits  on  the  edge,  and  if  the 
board  be  still  further  tilted,  the  frog  will  move  as  indicated  in  the  figure.  It  only 
does  so,  however,  when  the  board  is  inclined,  and  it  rests  as  soon  as  its  centre  of 
gravity  is  restored.  It  responds  to  every  stimulus  just  like  a  complex  machine, 
answering  each  stiinulus  with  an  appropriate  action.] 
45 


706  REMOVAL   OF   THE   CEREBRUM. 

A  pigeon  without  its  cerebral  hemispheres  behaves  in  a  similar  manner  (Fig. 
421).  When  undisturbed  it  sits  continuously,  as  if  in  sh-ep,  but  when  stimulated 
it  shows  complete  harmony  of  all  its  movements  ;  it  can  walk,  fly,  jierch,  and 
balance  its  body.  The  sensory  nerves  and  those  of  special  sensation  conduct 
impulses  to  the  brain  ;  they  only  discharge  reflex  movements,  but  they  do  not 
excite  conscious  impressions.  Hence  the  bird  starts  when  a  pistol  is  fired  close 
to  its  ear;  it  closes  its  eyes  when  it  is  brought  near  a  flame,  and  the  pupils 
contract ;  it  turns  away  its  head  when  the  vapor  of  ammonia  is  applied  to  its 
nostrils.  All  these  impressions  are  not  perceived  as  conscious  perceptions.  The 
perceptive  faculties — the  will  and  memory — are  abolished;  the  animal  never 
takes  food  or  drinks  spontaneously.  But  if  food  be  placed  at  the  back  part  of  its 
throat  it  is  swallowed  [reflex  act],  and  in  this  way  the  animal  may  be  maintained 
alive  for  months  {Fhurens,  Loiiget,  Goltz,  and  others). 

Mammals  (rabbit),  owing  to  the  great  loss  of  blood  consequent  on  removal 
of  the  cerebrum,  are  not  well  suited  for  experiments  of  this  kind.  Immediately 
after  the  operation  they  show  great  signs  of  muscular  weakness.  When  they  recover 
they  present  the  same  general  phenomena;  only  when  they  are  stimulated  they 
run,  as  it  were,  blindfold  against  an  obstacle.  Vulpian  observed  a  peculiar  shriek 
or  cry  which  such  a  rabbit  makes  under  the  circumstances.  Sometimes  even  in 
man  a  peculiar  cry  is  emitted  in  some  cases  of  pressure  or  inflammation  rendering 
the  cerebral  hemispheres  inactive. 

Observations  on  somnambulists  show  that  in  man  also  complete  harmony  of 
all  movements  may  be  retained,  without  the  assistance  of  the  will  or  conscious 
impressions  and  perceptions.  As  a  matter  of  fact,  many  of  our  ordinary  move- 
ments are  accomplished  without  our  being  conscious  of  them.  They  take  place 
under  the  guidance  of  the  basal  ganglia. 

The  degree  of  intelligence  in  the  animal  kingdom  is,  in  relation  to  the  size  of  the  cerebral 
hemispheres,  in  proportion  to  the  mass  of  the  other  parts  of  the  central  nervous  system.  Taking 
the  brain  alone  into  consideration,  we  observe  that  those  animals  have  the  highest  intelligence  in 
which  the  cerebral  hemispheres  greatly  exceed  the  mid-brain  in  weight.  The  mid-brain  is  repre- 
sented by  the  optic  lobes  in  the  lower  vertebrates,  and  by  the  corpora  quadrigemina  in  the  higher 
vertebrates.  In  Fig.  42S,  VT  represents  the  brain  of  a  carp;  V,  frog;  and  IV,  pigeon.  In  all 
these  cases  i  indicates  the  cerebral  hemispheres  ;  2,  the  optic  lobes  ;  3,  the  cerebellum  ;  and  4,  the  ■ 
medulla  oblongata.  In  the  carp  the  cerebral  hemispheres  are  smaller  than  the  optic  lobes,  in  the 
frog  they  exceed  the  latter  in  size.  In  the  pigeon  the  cerebrum  begins  to  project  backward  over  the 
cerebellum.  The  degree  of  intelligence  increases  in  these  animals  in  this  proportion.  In  the  dog's 
brain  (Fig.  428,  II)  the  hemispheres  completely  cover  the  corpora  quadrigemina,  but  the  cerebellum 
still  lies  behind  the  cerebrum.  In  man  tlie  occipital  lobes  of  the  cerebrum  completely  overlap  the 
cerebellum  (Fig.  424).  [The  projection  of  the  occipital  lobes  over  the  cerebellum  is  due  to  the 
development  ol  the  frontal  lobes  pushing  backward  the  convolutions  that  lie  behind  them,  and  not 
entirely  to  increased  development  of  the  occipital  lobes.] 

Meynert's  Theory. — According  to  Meynert,  we  may  represent  this  relation  in  another  way.  As 
is  known,  fibres  proceed  downward  from  the  cerebral  hemispheres  through  the  crusta  or  basis  of  the 
cerebral  peduncle.  These  fibres  are  separated  from  the  upper  fibres  or  tegmentum  of  the  peduncle 
by  the  locus  niger,  the  tegmentum  being  connected  with  the  corpora  quadrigemina  and  tlie  optic 
thalamus.  The  larger,  therefore,  the  cerebral  hemispheres  the  more  numerous  will  be  the  fibres 
proceeding  from  it.  In  Fig.  428,  II,  is  a  transverse  section  of  the  posterior  corpora  quadrigemina, 
with  the  aqueduct  of  Sylvius  and  both  cerebral  peduncles  of  an  adult  man  ;  /,  /,  is  the  crusta  of 
each  peduncle,  and  above  it  lies  the  locus  niger,  s.  Fig.  428,  IV,  shows  the  same  parts  in  a  monkey ; 

III,  in  a  dog;  and  V,  in  a  guinea  pig.  The  crusta  diminishes  in  the  above  series.  There  is  a  cor- 
responding diminution  of  the  cerebral  hemispheres,  and  at  the  same  time  in  the  intelligence  of  the 
corresponding  animals. 

Sulci  and  Gyri. — The  degree  of  inteUigence  also  depends  upon  the  number  and  depth  of  the 
convolutions.      In  the  lowest  vertebrates  (fish,  frog,  bird)  the  furrows  or  sulci  are  absent  (Fig.  428, 

IV,  V,  VI) ;  in  the  rabbit  there  are  two  shallow  furrows  on  each  side  (111).  The  dog  has  a  com. 
plexly  furrowed  cerebrum  (I,  II).  Most  remarkable  is  the  complexity  of  the  sulci  and  convolu- 
tions of  the  cerebrum  of  the  elephant,  one  of  the  most  intelligent  of  animals.  Nevertheless  some 
very  stupid  animals,  as  the  ox,  have  very  complex  convolutions. 

The  absolute  weight  of  the  brain  cannot  be  taken  as  guide  to  the  intelligence.  The  elephant 
has  absoliilely  the  heaviest  brain,  but  man  has  relalively  the  heaviest  brain. 

The  mean  weight  of  the  brain  in   man  is  about  135S  grammes;    of  woman,  1220  grammes 


REACTION    TIME. 


707 


{Bischoff).     [We  ought,  also,  to  take  into  account   the  complexity  of  the  convolutions  and   the 
depth  of  the  gray  matter,  its  vascularity,  and  the  extent  of  anastomoses  between  its  nerve  cells.] 

Time  an  Element  in  all  Psychical  Processes. — Every  psychical  process 
requires  a  certain  time  for  its  occurrence — a  certain  time  always  elapses  between 
the  application  of  the  stimulus  and  the  conscious  reaction. 


Nature  of  Stimulus. 


Name  of  Observer. 


Shock  on  left  hand 

Shock  on  forehead 

Shock  on  toe  of  left  foot   .... 

Sudden  noise 

Visual  impression  of  ele^.tric  spark 
i   Hearing  a  sound 

Current  to  tongue  causing  taste     . 

Saline  taste 

Taste  of  sugar 

"         acids 

"         quinine 


.12 

•13 

•>7 
■'j 
■5 
.16 


ExHT. 

Do. 
Do. 
Do. 
Do. 
Donders. 

V.  Vintschgau  and 
Honigschmied. 
Do. 
Do. 
Do. 
Do. 


Reaction  Time. — This  time  is  known  as  "  rc-aclion  time,"  and  is  distinctly  longer  than  the 
simple  reflex  time  required  for  a  reflex  act.  It  can  be  measured  by  causing  the  person  experimented 
on  to  indicate  by  means  of  an  electrical  signal  the  moment  when  the  stimulus  is  applied.  The 
reaction  time  consists  of  the  following  events:  (i)  The  duration  of perctption,  i:e.,  when  we  become 
conscious  of  the  impression;  (2)  the  duration  of  the  time  required  to  direct  the  attention  to  the 
impression;  and  (3)  the  duration  of  the  voluntary  impulse,  together  with  (4)  the  time  required  for 
conducting  the  impulse  in  the  afl^erent  nen-es  to  the  centre,  ami  (5)  the  time  for  the  impulse  to  travel 
outward  in  the  motor  nerves.  If  the  signal  be  made  with  the  hand,  then  the  reaction  time  for  the 
impression  of  sounds  0.136  to  0.167  second;  for  taste,  0.15  to  0.23;  touch,  o  133  to  0.201  second 
(Nonch,  V.  Vintsiki;au  and  H'dnigschmied,  Auerhacli,  Exner,  and  others)  ;  for  olfactory  impres- 
sions, which,  of  course,  depend  upon  many  conditions  (the  phase  of  respiration,  current  of  air).  0.2 
to  0.5  second.  Intense  stimulation,  increased  attention,  practice,  expectation,  and  knowledge  of  the 
kind  of  stimulus  to  be  applied,  all  diminish  the  time.  Tactile  impressions  are  most  rapidly  perceived 
when  they  are  applied  to  the  most  sensitive  parts  (;-.  Vintse/igau].  I'he  time  is  increased  with  very 
strong  stimuli,  and  when  objects  ditficult  to  be  distinguished  are  applied  {v.  Helmholtz  and  Baxt). 
The  time  required  to  direct  the  attention  to  a  number  consisting  of  I  to  3  figures,  Tigerstedt  and 
Bergquist  found  to  be  0.015  'o  oo35  second.  Alcohol  and  the  anfesthetics  alter  the  time;  according 
to  their  degree  of  action  they  shorten  or  lengthen  it  {Krdplin).  In  order  that  two  shocks  applied 
after  each  other  be  distinguished  as  two  distinct  impressions,  a  certain  interval  must  elapse  between 
the  two  shocks ;  for  the  ear,  0.002  to  0.0075  second ;  for  the  eye,  0.044  'o  0.47  second :  for  the 
finger,  0.277  second. 

[The  Dilemma. — When  a  person  is  experimented  on,  and  is  not  told  whether  the  right  or  lett 
side  is  to  be  stimulated  or  what  colored  disk  may  be  presented  to  the  eye,  then  the  time  to  respond 
correctly  is  longer.] 

[Drugs  and  other  conditions  afl'ect  the  reaction  time.  Ether  and  chlor  iform  lengthen  it,  while 
alcohol  does  the  same,  but  the  person  imagines  he  ready  reacts  quicker.     Noises  also  lengthen  it.] 

In  sleep  and  waking  we  observe  the  periodicity  of  the  active  and  passive  conditions  of  the  brain. 
During  sleep  there  is  diminished  excitability  of  the  whole  nervous  system,  which  is  only  partly  due 
to  the  fatigue  of  aft'erent  nerves,  but  is  largely  due  to  the  condition  of  the  central  nervous  system. 
During  sleep  we  require  to  apply  strong  stimuli  to  produce  reflex  acts.  In  the  deepest  sleep  the 
psychical  or  mental  processes  seem  to  be  completely  in  abeyance,  so  that  a  person  asleep  might  be 
compared  to  an  animal  with  its  cerebral  hemispheres  removed.  Toward  the  approach  of  the  period 
when  a  person  wakens,  psychical  activity  may  manifest  itself  in  the  form  of  dreams,  which  difler, 
however,  from  normal  mental  processes.  They  consist  cither  of  impressions,  where  there  is  no 
objective  cause  (hallucinations), or  of  voluntary  impulses  which  are  not  executed,  or  trains  of  thought 
where  the  reasoning  and  judging  powers  are  disturbed.  Often,  especially  near  the  time  of  waking, 
the  actual  stimuli  may  so  act  as  to  give  rise  to  impressions  which  become  mixed  with  the  thoughts 
of  a  dream.  The  diminished  activity  of  the  heart  {\  70,  3,  c),  the  respiration  (J  127,  4),  the  gastric 
and  intestinal  movements  ((J  213,  4),  the  formation  of  heat  (J  216,  4),  and  the  secretions,  point  to  a 
diminished  excitability  of  the  corresponding  nerve  centres,  and  the  diminished  reflex  excitability  to 
a  corresponding  condition  of  the  spinal  cord.  The  pupils  are  contracted  during  sleep  the  deeper 
the  latter  is,  so  that  in  the  deepest  sleep  they  do  not  become  contracted  on  the  application  of  light. 
The  pupils  dilate  when  seusury  or  auditory  stimuli  are  applied,  and  that  the  more  the  lighter  the 


708  HYPNOTISM. 

sleep;  they  are  widest  at  the  moment  of  awaking  (Plo/ke).  [Hughlings- Jackson  finds  that  the 
retina  is  more  anasmic  than  in  the  waking  state.]  During  sleep  there  s-ems  to  be  a  condition  of 
increased  action  of  certain  sphincter  muscles — those  for  contracting  the  pupil  and  closing  the  eyelids 
(Rosfniinc/i).  The  soundness  of  the  sleep  may  be  determined  by  the  intensity  of  the  sound  required 
to  waken  a  person.  Kohlschiitler  lound  that  at  first  sleep  deepens  very  quickly,  then  more  slowly, 
and  the  maximum  is  reached  after  one  hour  (according  to  Monningholf  and  Priesbergen  after  I3^ 
hours);  it  then  rapidly  lightens,  until  several  hours  before  waking  it  is  very  light.  External  or 
internal  stimuli  may  suddenly  diminish  the  depth  of  the  sleep,  but  this  may  be  followed  again  by 
deep  sleep.  The  deeper  the  sleep,  the  longer  it  lasts.  [Durham  asserts  that  the  brain  is  anaemic; 
the  arteries  and  veins  of  the  pia  mater  are  contracted  during  sleep  and  the  brain  is  smaller,  but  is 
this  cause  or  effect  ?] 

The  cause  of  sleep  is  the  using  up  of  the  potential  energy,  especially  in  the  central  nervous 
system,  which  renders  a  restitution  of  energy  necessary.  Perhaps  the  accumulation  of  the  decom- 
position products  of  the  nervous  activity  may  also  act  (?  lactates — Freyer)  as  producers  of  sleep. 
Sleep  cannot  be  kept  up  for  above  a  certain  time,  nor  can  it  be  inteirupted  voluntarily.  Many 
narcotics  rapidly  produce  sltep.  [The  diastolic  phase  of  cerebral  activity,  as  sleep  has  been  called, 
is  largely  dependent  on  the  absence  of  stimuli.  We  must  suppose  that  there  are  two  factors,  one 
central,  represented  by  the  excitability  of  the  cerebrum,  which  will  vary  under  different  conditions, 
and  the  impulses  reaching  the  cerebrum  through  the  different  sense  organs.  We  know  that  a 
tendency  to  sleep  is  favored  by  removal  of  external  stimuli,  by  shutting  the  eyes,  retiring  to  a  quiet 
place,  etc.  The  external  sensory  impressions,  indeed,  mfluence  the  whole  met.ibolism.  Strumjiell 
describes  the  case  of  a  boy  whose  sensory  inlets  were  all  paralyzed  except  one  eye  and  one  ear,  and 
when  these  inlets  were  closed  the  boy  fell  asleep,  showing  how  intimately  the  waking  condition  is 
bound  up  with  sensory  afferent  impulses  reaching  the  cerebral  centres.] 

[Hypnotics,  such  as  opium,  morphia,  KBr,  chloral,  are  drugs  which  induce  sleep.] 

Hypnotism,  or  Animal  Magnetism. — [Most  important  observations  on  this  subject  were  made 
by  Braid  of  Manchester,  and  many  of  the  recent  re- discoveries  of  Weinhold,  Heidenhain,  and 
others  confirm  Braid's  results.]  Heidenhain  assumes  that  the  cause  of  this  condition  is  due  to  an 
inhibition  of  the  ganglionic  cells  of  the  cerebrum,  produced  by  continuous  feeble  stimulation  of  the 
face  (slightly  stroking  the  skin  or  electrical  applications),  or  of  the  optic  nerve  (as  by  gazing  steadily 
at  a  small,  brilliant  object),  or  of  the  auditory  nerve  (by  uniform  sounds) ;  while  sudden  and  strong 
stimulation  of  the  same  nerves,  especially  blowing  upon  the  face,  abolishes  the  condition.  Berger 
[and  so  did  Carpenter  and  Braid  long  ago]  attributes  great  importance  to  the  psychological  factor, 
whereby  the  attention  was  directed  to  a  particular  part  of  the  body.  The  facility  with  which  differ- 
ent persons  become  hypnotic  varies  very  greatly.  When  the  hypnotic  condition  has  been  produced 
a  number  of  times,  its  subsequent  occurrence  is  facilitated,  e.g..,  by  merely  pressing  upon  the  brow, 
by  placing  the  body  passively  in  a  certain  position,  or  by  slrol<ing  the  skin.  In  some  people  the 
mere  idea  of  the  condition  suffices.  A  hypnotized  person  is  no  longer  able  to  open  his  eyelids 
when  they  are  pressed  together.  This  is  followed  by  spasm  of  the  apparatus  for  accommodation  in 
the  eye,  the  range  of  accommodation  is  diminished,  and  there  may  be  deviation  of  the  position  of 
the  eyeballs ;  then  follow  phenomena  of  stimulation  of  the  sympathetic  in  the  oblongata ;  dilatation 
of  the  fissure  of  the  eyelids  and  the  pupil,  exophthalmos,  and  increase  of  the  respiration  and  pulse. 
At  a  certain  stage  there  may  be  a  great  increase  in  the  sensitiveness  of  the  functions  of  the  sense 
organs,  and  also  of  the  muscular  sensibility.  .Afterward  there  may  be  analgesia  of  the  part  stroked, 
and  loss  of  taste;  the  sense  of  temperature  is  lost  less  readily,  and  still  later  that  of  sight,  smell, 
and  hearing.  Owing  to  the  abolition  or  suspension  of  consciousness,  stimuli  applied  to  the  sense 
organs  do  not  produce  conscious  impressions  or  perceptions.  But  stimuli  applied  to  the  sense  organs 
of  a  hypnotized  person  cause  movements,  which,  however,  are  unconscious,  although  they  stimulate 
voluntary  acts.  In  persons  with  greatly  increased  reflex  excitability,  voluntary  movements  may  ex- 
cite reflex  spasms  ;  the  person  may  be  unable  to  coordinate  his  organs  for  speech. 

Types. — According  to  Griitzner,  there  are  several  forms  of  hypnotism  :  ( I )  Passive  sleep,  where 
words  are  still  understood,  which  occurs  especially  in  girls;  (2)  owing  to  the  increased  reflex  ex- 
citability of  the  striped  muscles  certain  grottps  of  muscles  may  be  contracted — a  condition  which 
may  last  for  days,  especially  in  strong  people ;  at  the  same  time  ataxia  may  occur,  and  the  muscles 
may  fail  to  perform  their  functions  (artificial  catalepsy).  During  the  stage  of  lethargy  in  hyster- 
ical persons  the  tendon  reflexes  are  often  absent  ( Charcot  and  Richer)  ;  (3)  autonomy  at  call,  i.  e., 
the  hypnotized  person — in  most  cases  the  consciousness  is  still  retained — obeys  a  command,  in  his 
condition  of  light  sleep.  When  the  hand  is  grasped  or  the  head  stroked  he  executes  involuntary 
movements — runs  about,  dances,  rides  on  a  stool,  and  the  like  ;  (4)  hallucinations  occur  only  in 
some  individuals  when  they  waken  from  a  deep  sleep,  the  hallucinations  (usually  consisting  of  the 
sensation  of  sparks  of  fire  or  odors)  being  very  strong  and  well  pronounced;  (5)  imitation  is  rare, 
ordinary  movements,  such  as  walking,  are  easily  imitated,  the  finer  movements  occur  rarely.  The 
"echo  speech"  is  produced  by  pressure  upon  the  neck,  speaking  into  the  throat,  or  against  the 
abdomen.  Pressure  over  the  right  eyebrow  often  ushers  in  the  speech.  Color  sensation  is  sus- 
pended by  placing  the  warm  hand  on  the  eye,  or  by  stroking  the  opposite  side  of  the  head  (Cohn). 
Stroking  the  limbs  in  the  reverse  direction  gradually  removes  the  rigidity  of  the  limbs  and 
causes   the   person   to   waken.     Blowing   on    a   part  does   so   at   once.     Insane   persons   can    be 


STRUCTURE  OF  THE  CEREBRUM. 


709 


hypnotized.  Disagreeable  results  follow  only  when 
the  condition  is  induced  too  often  and  too  con- 
tinuously. 

Hypnotism  in  Animals. — A  hen  remains  in  a 
fixed  position  when  an  object  is  suddenly  placed 
before  its  eyes,  or  when  a  straw  is  placed  over  its 
beak,  or  when  the  head  of  the  animal  is  pressed 
on  the  ground  and  a  chalk  line  made  before  its 
beak  (Kircher's  experimentum  mirabile,  1644). 
[Langley  has  hypnotized  a  crocodile.]  Birds, 
rabbits,  and  frogs  remain  passive  for  a  time  after 
they  have  been  gently  stroked  on  the  back  for  a 
time.  Crayfish  stand  on  their  head  and  claws 
[Czermak). 

375.  STRUCTURE  OF  THE  CERE- 
BRUM—MOTOR CORTICAL  CEN- 
TRES.—[Cerebral  Convolution.— .A  vertical 
.section  of  a  cerebral  convolution  consists  of  a  thin 
layer  of  gray  matter  externally  inclosing  a  white  core 
(Fig.  423).  The  cortex  consists  of  cells  embedded 
in  a  matrix,  and  to  these  proceed  nerve  fibres  from 
the  white  matter.  The  cells  of  the  cortex  vary 
in  size,  form,  and  distribution  in  the  different 
layers  and  also  in  different  convolutions.  Taking 
such  a  convolution  as  the  ascending  frontal  we 
get  the  appearances  shown  in  Fig.  422.  It  is  cov- 
ered on  its  surface  by  the  pia  mater.  ( i )  The 
most  superficial  layer  is  narrow,  and  consists  of 
much  neuroglia,  a  network  of  branched  nerve 
fibrils,  and  a  few  scattered  small  muhipolar  nerie 
cells;  (2)  a  layer  of  close-set  small  pyramUal 
net~je  cells  ;  (3)  the  thickest  layer  or  formation  of 
the  cornu  ammonis,  consisting  of  several  layers 
of  large  pyramidal  cells,  which  are  larger  in  the 
deeper  than  in  the  more  superficial  layers.  Each 
cell  is  more  or  less  pyramidal  in  shape,  giving  off 
several  processes — (17)  an  «y>/<-a/ process,  which  is 
often  very  long,  and  runs  toward  the  surface  of 
the  cerebrum,  where  it  is  said  to  terminate  in  an 
ovoid  corpuscle,  closely  resembling  those  in  which 
the  ultimate  branches  of  Purkinje's  cells  of  the  cere- 
bellum end;  ((i)the  unbranched  meUian  basilar 
process,  which  is  an  axial  cylinder  process,  and 
becomes  continuous  with  the  axial  cylinder  of  a 
nerve  fibre  of  the  white  matter.  It  uhimately 
becomes  invested  by  myelin.  (<-)  The  lateral  pro- 
cesses are  given  off  chiefly  near  the  base  of  the 
cell,  and  they  soon  branch  to  form  part  of  the 
ground  plexus  of  fibrils  which  everywhere  per- 
vades the  gray  matter.  At  the  lowest  part  of  this 
layer  the  cells  are  larger  than  eKewhere,  present- 
ing some  resemblance  to  the  cells  of  the  anterior 
cornu  of  the  gray  matter  of  the  spinal  cord.  Bv 
some  it  is  described  as  a  special  layer,  and  termed 
the  ganglion  cell  layer.  This  layer  is  sjiecially 
well  marked  in  those  convolutions  which  are  de- 
scribed as  containing  motor'centres.  Among  the 
large  cells  are  a  few  small  angular-looking  cells, 
which  become  more  numerous  lower  down,  and 
form  (4)  a  narrow  layer  of  numerous  small  branched, 
irregular,  ganglionic  cells — the  "  granular  forma- 
tion'" of  .Meynert.  (5)  A  layer  of  spindle-shaped 
fusiform  branched  cells — the  claustral  formation 
of  Meynert — lyinj  for  the  most  part  parallel  to 
the  surface  of  the  convolution.  No  layer  is  com- 
posed exclusively  of  one  form  of  cell.  The  above 
represents  the  motor  type.     Then  follows  the  -white 


Vertical  section  of  the  3d  cerebral  convolution  fman) 
I .  superficial  layer;  2,  layer  of  small  pyramidal  cells; 
3,  layer  of  large  pyramidal  corpiLscies ;  4.  granule 
layer;  5,  layer  of  fusiform  corpuscles; /«,white  matter. 


710 


BLOOD   VESSELS   OF   THE   CEREBRUM. 


matter  ^>«\  consisting  of  medullated  nerve  fibres,  which  run  in  groups  into  the  gray  matter,  where 
they  lose  their  myelin.  The  fibres  are  somewhat  smaller  than  in  the  other  parts  of  the  nervous 
system  (diameter  ^555  inch),  and  between  them  lie  a  few  nuclear  elements.  Each  cell  is  sur- 
rounded by  a  lymph  space,  as  in  those  of  the  cord.] 

[Recent  Results. — Exner  finds  that  after  prolonged  immersion  of  the  cerebrum  in  i  per  cent, 
osmic  acid  and  subsequent  staining  with  ammoniacal  carmine, that  what  has  hitherto  been  described 
as  "  ground  substance  "  in  the  gray  matter  really  consists  of  well-formed  medullated  fibres. 
The  first  layer  contains  many  medullated  nerve  fibres  differing  in  thickness  and  direction.  In  the 
newborn  child  none  are  medullated.  .Similar  fibres  exist  in  the  second  layer,  while  in  the  third 
they  are  in  groups,  and  very  numerous  in  the  fourth.  The  nerve  fibres  do  not  seem  to  divide  in 
the  cortex,  and  Exner  suggests  that  some  of  them  serve  to  connect  the  different  layers  in  the  cortex. 
Fuchs  finds  that  thi  re  are  no  medullated  fibre*  either  in  the  cortex  or  medulla  until  the  end  of  the  fir.st 
month  of  life.  The  medullated  fibres  ai  pear  in  the  u])permost  layer  at  the  fifth  month,  and  in  the 
second  at  the  end  of  the  first  year,  the  radial  bundles  in  the  deeper  layers  at  the  second  month.  The 
medullated  fibres  increase  until  the  seventh  or  eighth  year,  when  they  have  the  saine  arrangement 
as  in  the  adult.] 

[Variations. — Although  the  above  description  indicates  the  typical  arrangement  in  the  motor  area, 


Fig.  423. 


1 ,  medullary  arteries  and  1  i  in  groupb  between  the  convolutions  ;  2,  2,  a 
meshed  plexus  in  fir^t  layer  i>  closer  plexus  m  middle  layer  ;  c,  opener  pie 
substance,  with  its  vessels  {if). 


ies  ot  the  cortex  cerebri ;  a,  large 
in  the  gray  matter  next  the  white 


.•■till,  the  gray  matter  difi'ers  in  different  parts  of  the  brain.  In  the  gray  matter  of  the  cornu  ; 
the  large  pyramidal  cells  of  (3)  make  up  the  chief  mass;  in  the  claustrum  (4)  is  most  abundant.  In 
the  central  convolutions  (ascending  frontal  and  parietal  1,  according  to  Betz,  Mierzejewski  and 
Bevan  Lewis,  very  large  pyramidal  cells  are  found  in  the  lower  part  of  the  third  layer.  Similar  cells 
have  been  found  in  the  posterior  extremities  of  the  frontal  convolutions  in  some  animals,  the  posterior 
parietal  lobule,  and  paracentral  lobule,  all  of  which  have  motor  functions.  In  those  convolu- 
tions which  are  regarded  as  subserving  sensory  functions,  a  somewhat  different  type  prevails,  e.g., 
the  occipital  gyri  or  annectant  convolutions  (B.  Lewis).  The  very  large  pyramidal  cells  are  absent, 
while  the  granule  layer  exists  as  a  well-marked  layer  between  the  layer  of  large  pyramidal  cells 
and  the  ganglion  cell  layer.] 

Blood  Vessels. — The  gray  matter  is  much  more  vascular  than  the  white,  and  when  injected  a 
section  of  a  convolution  presents  the  appearance  shown  in  Fig.  423.  The  nutritive  arteries  con- 
sist of— (a)  the  long  medullary  arteries  (i),  which  pass  from  the  pia  mater  through  the  gray 
matter  into  the  central  white  matter  or  centrum  ovale.  They  are  terminal  arteries,  and  do  not 
communicate  with  each  other  in  their  course;  they  thus  supply  independent  vascular  areas,  nor  do 
they  anastomose  with  any  of  the  arteries  derived  from  the  ganglionic  system  of  blood  vessels:   12  to 


CONVOLUTIONS   OF   THE    CEREBRUM. 


711 


15  of  them  are  seen  in  a  section  of  a  convolution,  (i)  The  short  cortical  nutritive  arteries  (2)  are 
smaller  and  shorter  than  the  foregoing.  Although  some  of  them  enter  the  white  matter,  they  chiefly 
supply  the  cortex,  where  they  form  an  open  meshed  plexus  in  the  first  layer  (0),  while  in  the  next 
layer  (/>)  the  plexus  of  capillaries  is  dense,  the  plexus  again  being  wider  in  the  inner  layers  (c).] 

[Central  or  Ganglionic  Arteries. — From  the  trunks  constituting  the  circle  of  Willis  (Fig.  in 
I  381),  branches  are  given  off,  which  pass  upward  and  enter  the  brain  to  supply  the  basal  ganglia 
with  blood.  They  are  arranged  in  several  groups,  but  they  are  all  terminal,  each  one  supplying 
its  own  area,  nor  do  they  anastomose  with  the  arteries  of  the  cortex.] 

Cerebral  Arteries. — From  a  practical  point  of  view,  the  distribution  of  the  blood  vessels  of  the 
brain  is  im])ortant.  The  artery  of  the  Sylvian  fissure  supplies  the  ttto/or  areas  of  the  brain  in 
animals;  in  man,  the  precentral  lobule  is  supplied  by  a  branch  of  the  anterior  cerebral  artery 
(Durel).  The  region  of  the  third  left  frontal  convolution,  which  is  connected  with  the  function  of 
speech,  is  supplied   by  a  special   branch  of  the  Sylvian  artery.      Those  areas  of  the  frontal  lobes 

Fig.  424. 


it  side  of  the  human  brain  (diagrammatic).  F,  frontal ;  P,  parietal  ;  O.  occipital ;  T,  temporo-sphenoidal  lobe  ; 
S,  fissure  of  Sylvius :  S',  horiztmtal,  S",  ascending  ramus  of  S  :  c,  sulcus  centralis,  or  fissure  of  Rolando  ;  A, 
ascending  frontal,  and  B,  ascending  parietal  convolution  :  F,,  superior,  F,,  middle,  and  F3,  inferior  frontal  convo- 
lutions; yV,  superior,  and  y^,  inferior  frontal  fissures  : /j,  sulcus  pracenlralis  :  P,  superior  parietal  lobule;  P^, 
inferior  parietal  lobule,  consisting  of  Pj,  supramarginal  gyms,  and  P^',  angular  gj'rus  ;  ;^,  sulcus  interparietalis  ; 
cm,  termination  of  calloso-marginal  fissure;  O^,  first,  U3,  second,  O,,  third  occipital  convolutions;  po,  parieto- 
occipital fissure  ;  (?,  transverse-occipit;il  fissure  ;  o^,  inferior  longitudmal  occipital  fissure;  Ti,  first,  Ta,  second, 
Tj,  temporo-sphenoidal  convolutions  ;  /,,  first,  /a,  second  temporo-sphenoidal  fissures. 


whose  injury  results  in  disturbance  of  the  intelligence  (Ferrier)  are  supplied  by  the  anterior  cerebral 
artery.  Those  regions  of  the  cortex  cerebri  whose  injury,  according  to  Ferrier,  causes  hemianaes- 
thesia  are  supplied  by  the  posterior  cerebral  artery. 

[In  connection  with  the  localization  of  the  centres  in  the  cortex,  it  is  important  to  be  thoroughly 
acquainted  with  the  arrangement  of  the  cerebral  convolutions.  Each  half  of  the  outer  cerebral 
surface  is  divided  by  certain  fissures  into  five  lobes — frontal,  parietal,  occipital,  temporo- 
sphenoidal  and  central,  or  island  of  Rail  (Fig.  424).  Die  frontal  lobe  (Fig.  424)  consists  of 
three  convolutions,  with  numerous  secondary  folds  running  nearly  horizontal,  named  superior  (F,), 
middle  (F^)  and  inferior  (F3)  frontal  convolutions.  Behind  these  is  a  large  convolution,  the  ascending 
frontal  (A),  which  ascends  almost  vertically,  immediately  behind  these,  separated  from  them,  how- 
ever, by  the  precentral  fissure  (/j),  and  mapped  oft"  behind  by  the  fissure  ot  Rolando,  or  the  central 
sulcus  (.).] 


712 


CONVOLUTIONS   OF   THE    CEREBRUM. 


[The  parietal  lobe  (Fig.  424,  P)  is  limited  in  front  by  the  fissure  of  Rolando,  below,  in  part  by 
the  Sylvian  fissure,  and  behind  by  the  parieto-occipital  fissure.  It  consists  of  the  ascending  parietal 
(posterior  central)  convolution  (Fig.  424,  B),  which  ascends  just  behind  the  fissure  of  Rolando,  and 
parallel  to  the  ascending  frontal,  with  which  it  is  continuous  below;  above  it  becomes  continuous 
with  the  superior  parietal  lobule  (Pj ),  while  the  latter  is  separated  from  the  inferior  parietal  lobule 
^pli  courhe)  by  the  interparietal  sulcus.  The  inferior  parietal  lobule  consists  of  («)  a  part  arching 
over  the  upper  end  of  the  Sylvian  fissure,  the  supramarginal  convolution  (P^),  which  is  continuous 
with  the  superior  temporo-sphenoidal  convolution.  Behind  is  i^h)  the  angular  gyrus  (P,^),  which 
arches  round  the  posterior  end  of  the  parallel  fissure,  and  becomes  connected  with  the  middle 
temporo-sphenoidal  con\olution.] 

[The  temporo-sphenoidal  lobe  (Fig.  424,  T)  consists  of  three  horizontal  convolutions — supe- 
rior, middle  and  inferior — the  two  former  being  separated  by  the  parallel  sulcus,  while  the  whole 
lobe  is  mapped  off  from  the  frontal  by  the  Sylvian  fissure  (S).] 

[The  occipital  lobe  (Fig.  424,  O)  is  small,  forms  the  rounded  posterior  end  of  the  cerebrum, 
and  is  separated  from  the  parietal  lobe  by  the  parieto-occipital  fissure,  which  fissure  is  bridged  over 
at  the  lower  part  by  the  four  annectant  gyri  (//«  de passage  of  Gratiolet).  It  has  three  convolu- 
tions— superior  (O,),  middle  (O.,)  and  inferior  (O3) — on  its  outer  surface.] 

[The   central  lobe,  or  island  of  Reil,  consists  of  five  or  six  short,  straight  convolutions  (gyri 

Fig.  425. 


Median  aspect  of  the  right  hemisphere.  CC,  corpus  callosum  divided  longitudinally  :  Gf,  gyrus  fomicafus  :  H, 
gyrus  liippocampi  :  A,  sulcus  hippocampi ;  U,  uncinate  gyrus  :  c»/.  calloso-marginal  fissure  ;  F,  first  frontal  con- 
volution ;  r,  terminal  portion  of  fissure  of  Rolando  ;  A,  ascending  frontal ;  B,  ascending  parietal  convolution  and 
paracentral  lobule  :  Pi',  precuneus  or  quadrate  lobule  ;  Oz.  cuneus  ;  Po.  parieto-occipital  fissure  ;  cj,  ,  transverse 
occipital  fissure  ;  oc,  calcarine  fissure  :  oc',  superior,  oc",  inferior  ramus  of  the  same  ;  D,  gyrus  descendens  ;  T4, 
gyrus  occipito-temporalis  lateralis  {lobulus  fusiformis) ;  Tg,  gyrus  occipito-temporalis  medialis  (lobulus  lingualis). 

operti — Fig.  426)  radiating  outward  and  backward  from  near  the  anterior  perforated  spot,  and  can 
only  be  seen  when  the  inargins  of  the  Sylvian  fissure  are  pulled  asunder.  The  operculum,  con- 
sisting of  the  extremities  of  the  inferior  frontal,  ascending  parietal  and  frontal  convolutions,  lie  out- 
side it,  cover  it,  and  conceal  it  from  view.] 

[On  the  inner  or  mesial  surface  of  the  cerebrum  are — the  gyrus  fornicatus  (Fig.  425,  Gf ),  or 
convolution  of  the  corpus  callosum,  which  runs  parallel  to  and  bends  round  the  anterior  and  poste- 
rior extremities  of  the  corpus  callosum,  terminating  posteriorly  in  the  gyrus  uncinatus  or  gyrus 
hippocampi  (Fig.  421;,  Hi,  and  ending  anteriorly  in  a  crooked  extremity,  the  subiculum  cornu  am- 
monis  (Fig.  425,  U).  Above  it  is  the  calloso  marginal  fissure  (Fig.  425,  cm),  and  running  parallel 
to  it  is  the  marginal  convolution  (Fig.  425),  which  lies  between  the  latter  fissure  and  the  margin 
of  the  longitudinal  fissure;  it  is,  however,  merely  the  mesial  aspect  of  the  frontal  and  parietal  con- 
volutions. The  quadrate  lobule  or  praecuneus  lies  (Fig.  425,  Pi)  between  the  posterior  extrem- 
ity of  the  calloso-marginal  fissure  and  the  parieto-occipital  fissure  ;  it  is  merely  the  mesial  aspect  of 
the  ascending  parietal  convolution.  The  parieto-occipital  fissure  terminates  below  in  the  calcarine 
fissure  (Fig.  425,  oc\,  and  the  latter  runs  backward  in  the  occipital  lobe,  dividing  it  into  two 
branches,  oc',  oc" .  Between  the  parieto-occipital  and  calcarine  fissures  lies  the  wedge-shaped 
lobule  termed  the  cuneus  (Fig.  425,  0:).  The  calcarine  fissure  indicates  on  the  surface  the  position 
of  the  calcar  avis  or  hippocampus   minor,  in  the  posterior  cornu  of  the  lateral  ventricle.     The 


CONDITIONS   AFFECTING   THE    MOTOR   CENTRES. 


713 


dentate  fissure  or  sulcus  hippocampi  (Fig.  425,  h),  marks  the  position  of  the  elevation  of  the 
hippocampus  major,  or  cornu  animonis,  in  the  lateral  ventricle.  The  temporo-sphenoidal  lobe 
terminates  anteriorly  in  the  uncinate  gyrus,  while,  running  along  the  former  and  the  occipital 
lobes  is  the  collateral  fissure  (occipito-temporal  sulcus),  which  marks  the  position  of  the  emenentia 
collateralis  in  the  descending  cornu  of  the  lateral  ventricle,  while  it  also  separates  the  superior  from 
the  inferior  temporo-occipital  convolutions  (T^  and  T,).] 

Motor  Centres. — Fritsch  and  Hitzig  (1870)  discovered  a  series  of  circum- 
scribed regions  on  the  surface  of  the  cerebral 

convolutions,  whose  stimulation  by  means  of  Fig.  426. 

electricity  causes  coordinated  ?nove»ien/s  in 
quite  distinct  groups  of  muscles  of  the  opposite 
side  of  the  body  (Fig.  428,  I,  II). 

Methods — Stimulation. — The  surface  of  the  cere- 
brum is  exposed  in  an  animal  (dog,  monkey)  by  remov- 
ing a  part  of  the  skull  covering  the  so-called  motor  con- 
volutions and  dividing  the  dura  mater.  When  the  con- 
volutions are  fully  exposed,  a  pair  of  blunt,  non-polariz- 
able  (J  328)  needle  electrodes  are  applied  near  each 
other  to  various  parts  of  the  cerebral  surface.  We  may 
employ  the  closing  or  opening  shock  of  a  constant 
current,  or  the  constant  current  may  be  rapidly  inter- 
rupted, the  current  being  of  such  a  strength  as  to  be 
distinctly  perceived  when  it  is  applied  to  the  tip  of  the 
tongue  [Frilsch  and  Hitzig).  Or  the  induced  current 
maybe  used  (Ferrier,  iSjj)  of  such  a  strength  that  it 
is  readily  felt  when  applied  to  the  tip  of  the  tongue. 
The  cerebrum  is  completely  insensible  to  severe  opera- 
tions t/iaile  upon  it. 

The  areas  of  the  cerebral  cortex,  whose 
stimulation  discharges  the  characteristic  move- 
ments, are  regarded  as  actual  centres,  because 
the  reaction  time  after  stimulation  of  the 
centres  and  the  duration  of  the  muscular  con- 
traction are  longer  than  when  the  subcortical  Orbi 
fibres  which  lead  toward  the  deeper  parts  of 
the  brain  are  stimulated.  Another  circum- 
stance favoring  this  view  is  that  the  excitabil- 
ity of  these  areas  is  influenced  by  the  stimu- 
lation of  afferent  nerves  {Bubnoff  and  Hei- 
denhain).  It  may  be  that  these  centres  are 
acted  upon  by  voluntary  impulses  in  the  exe- 
cution of  voluntary  movements.  Hence,  they  have  been  called 
centres."  The  motor  areas  of  the  cerebrum  (dog,  cat,  sheep)  are  characterized 
by  the  presence  of  specially  large  pyramidal  cells  {Betz,  Mersejewsky,  Bcvan, 
Lewis) ;  while  similar  cells  were  found  by  Obersteiner  m  the  areas  marked  4  and 
8  (Fig.  428),  and  Betz  found  them  in  the  ascending  frontal  convolution  of  man, 
in  the  third  frontal  convolution,  and  in  the  island  of  Reil.  O.  Saltmann  found 
that  stimulation  of  the  motor  areas  in  newly-born  animals  is  without  result, 
while  only  the  deeper  fibres  of  the  corona  radiata  are  excitable. 

Modifying  Conditions. — In  the  condition  of  deep  narcosis  produced  by  chloroform,  ether, 
chloral,  morphia,  or  in  apncea,  the  excitability  of  the  centres  is  abolished  {Schiff),  whilst  the  sub- 
cortical conducting  paths  still  retain  Iheir  excitability  [Buhnoff  and  Heidejihain).  Small  doses  of 
these  poisons  and  also  of  atropin  at  first  increase  the  excitability  of  the  cenlres.  Moderate  loss  of 
blood  excites  them,  while  a  great  loss  of  blood  diminishes  and  then  abolishes  the  excitability  (Muni 
and  Orschansky).  Slight  inflammation  increases,  while  cooling  diminishes,  the  excilabilily.  If  the 
cortex  cerebri  be  removed  in  animals,  the  excitability  of  the  fibres  of  the  corona  radiala  is  com- 
pletely abolished  about  the  fourth  day,  just  as  in  the  ca.se  of  a  peripheral  nerve  separated  from  its 
centre  (Alliertoni,  JMichieli,  Dupuy,  Franck,  and  Pitres). 


al  surface  of  the  left  frotital  lobe  and  the 
land  of  Reil,  the  tip  of  the  temporo-sphe- 
noidal lobe  removed  to  show  the  latter.  17, 
convolution  of  the  margin  of  the  longitudinal 
fissure  ;  O,  olfactory-  fissure,  with  the  olfactorj* 
lobe  removed  ;  T  R,  triradiate  fissure  :  \"  and 
I '",  convolutions  on  the  orbital  surface;  i,  i, 
1,  I,  under  surface  of  the  infero-frontal  convo- 
lution ;  4,  under  surface  of  the  ascending 
frontal,  and  5,  of  the  ascending  parietal  con- 
volutions ;  C,  central  lobe  or  island. 


'  psychomotor 


714 


COi\UlTIONS   AFFECTING   THE    MOTOR   CENTRES. 


Stimulation  of  Subcortical  Parts. — As  the  fibres  of  the  corona  radiata  converge  toward  the 
centre  of  the  hemisphere,  it  is  evident  tliat,  after  removal  of  the  cortex,  stimulation  of  these  fibres  in 
the  deeper  parts  of  the  hemisphere  is  followed  by  the  same  motor  resahs  {G/iiy  <ini/  £tiAa:d  ). 
The  stimulus  is  applied  merely  to  a  deeper  part  of  the  motor  path.  If  the  stimulus  be  apphed  to 
pirts  situated  still  more  deeply,  as,  for  example,  to  the  internal  capsule,  general  contraction  of  the 
muscles  on  the  opposite  side  is  the  result. 

Time  Relations  of  the  Stimulation. — According  to  Franck  and  Pitres,  the  time  which  elapses 
between  the  moment  of  stimulation  of  the  cortex  and  the  resulting  movement,  a''ter  deducting  the 
period  of  latent  stimulation  for  the  muscles  and  the  time  necessary  for  the  conduction  of  the  impulse 
through  the  cord  and  nerves  of  the  extremities,  is  0.045  second.  Heidenhain  and  Bubnoff  found 
that,  during  moderate  morphia-narcosis,  when  the  stimulating  current  was  increased  in  strength,  the 
muscular  contraction  and -the  reaction  time  became  shorter.  After  removal  of  the  cortex,  the  occur- 
rence of  the  muscular  contraction  from  the  moment  of  stimulation  of  the  white  matter   is  diminished 

Fig.  427. 


%  to  J/^.  The  form  of  the  muscular  contraction  is  longer  and  more  extended  when  the  cortex, 
than  when  the  subcortical,  paths  are  stimulated.  If  the  animal  (dog)  be  in  a  state  of  liigh  reflex 
excitability  these  differences  disappear;  in  both  cases  the  contraction  follows  very  rapidly  [Bubnoff 
and  Heiilenhain).  If  the  stimulus  be  very  strong,  the  muscles  of  the  same  side  may  contract,  but 
somewhat  laler  than  those  of  the  opposite  side.  If  the  motor  areas  for  the  fore  and  hind  limbs  be 
stimulated  simultaneously,  the  latter  contract  somewhat  after  the  former. 

Number  of  Stimuli. — If  40  stimuli  per  second  be  applied  to  a  motor  area,  then  the  corresponding 
muscles  yield  40  single  contractions ;  while  with  46  single  stimuli  per  second  there  results  a  continued 
complete  contraction  (Franck  ami  Pitres').  In  one  and  the  same  animal  the  same  number  of  stimuli 
is  required  to  produce  a  continuous  contraction,  whether  the  cortical  centre,  the  motor  nerve,  or  even 
the  muscle  itself  be  stimulate!.  With  very  feeble  stimuli  summation  of  stimuli  takes  place,  for 
the  muscular  contraction  only  begins  after  several  ineftective  stimuli  have  been  applied.  [It  is  gen- 
erally held  that  the  rhythm  of  a  contracting  muscle  is  the  same  as  the  rhythm  of  the  stimuli  applied 


EFFECT   OF    STIMULI    ON    THE    MOTOR    FIBRES.  715 

to  its  motor  nerve,  but  Schafer  and  Horsley  contend  that  this  holds  good  for  rates  of  sfiniuH  to 
about  lo  or  12  per  second.  They  find  that  the  same  is  true  for  the  cortex  cerebri,  corona  radiata, 
and  medulla  spinalis,  viz..  that  the  muscular  response  does  not  vary  with  the  rhythm  (i.e.,  number 
of  stimuli  per  sec),  but  that  the  rhythm  is  constant — about  10  per  sec. — and  independent  of  the 
number  of  stimuli  per  sec,  provided  they  are  above  10  per  sec  applied  to  these  parts.  Indeed,  all 
voluntary  contractions  show  a  similar  rate  of  undulation  in  the  muscle  curve.  Perhaps  the  rhythm 
of  the  efferent  impulses  is  modified  in  the  motor  nerve  cells  of  the  spinal  cord.] 

[The  matter,  as  regards  electrical  stimulation  of  the  corte.\  cerebri,  resolves  it- 
self into  this,  that  stimulation  of  certain  cortical  areas  always  causes  contraction 
in  definite  muscles  or  groups  of  muscles,  resulting  in  definite  coordinated  move- 
ments on  the  opposite  side  of  the  body;  the  areas  have  been  called  "motor 
areas."  They  have  been  mapped  out  and  ascertained  in  a  large  number  of 
animals,  and  the  question  comes  to  be,  Are  there  similar  areas  in  man  ?] 

Primary  Fissures  and  Convolutions  of  the  Dog's  Brain. — The /m/Z/ok  of  the  motor  centres 
in  the  dog's  brain  is  indicated  in  Fig.  42S,  I  and  II.  The  dog's  brain  is  marked  by  two  "  primary 
fissures,"  viz.,  the  sulcus  cruciatus  (Leiiret)  (S),  which  intersects  the  longitudinal  fi.ssure  at  a  right 
angle  at  the  junction  of  its  anterior  with  its  middle  third.  This  fissure  has  been  called  the  sulcus 
frontalis  (Owiti),  or  the  fissura  coronalis.  The  second  primary  fissure  is  the  fossa  Sylvii  (F).  Four 
"  primary  convolutions,"  in  addition,  are  arranged  with  reference  to  these  primary  fissures.  The 
first  primary  convolution  (I),  in  the  form  of  a  sharply-curved  knee,  embraces  the  fossa  Sylvii  (F). 
The  second  convolution  (II)  runs  nearly  parallel  to  the  first.  The  fourth  primary  convolution  (IV) 
bounds  the  longitudinal  fissure,  and  is  separated  from  its  fellow  of  the  opposite  side  by  the  falx 
cerebri;  anteriorly  it  embraces  the  sulcus  cruciatus  (S),  so  that  it  is  divided  into  two  parts  by  this 
sulcus,  a  part,  the  gyrus  prscruciatus  or  priefrontalis,  lying  in  front  of  the  sulcus,  and  the  gyrus  postcru- 
ciatus  (postfrontalis)  lying  behind  it.  The  third  primary  convolution  (III)  runs  parallel  to  the 
fourth.  Some  authors  count  the  convolutions  from  the  longitudinal  fissure  outward.  In  Fig.  428,  I 
and  II,  the  motor  areas  or  centres  are  indicated  by  dots  in  the  individual  primary  convolutions.  We 
must  remember,  however,  that  the  centres  are  not  mere  points,  but  that  they  vary  in  size  from  that 
of  a  pea  upward,  according  to  the  size  of  the  animal.  Motor  areas  have  been  mapped  out  in  the 
brain  of  the  monkey,  rabbit,  rat,  bird,  and  frog. 

Position  of  the  Motor  Centres  (Dog). — Fritsch  and  Hitzig,  in  1870,  mapped  out  the  follow- 
ing motor  areas,  who.se  position  may  be  readily  found  on  referring  to  Fig.  428 :  I  is  the  centre  for 
the  muscles  of  the  neck  ;  2,  for  the  extensors  and  adductors  of  the  fore  limb  ;  3,  for  the  flexion  and 
rotation  of  the  fore  leg;  4,  for  the  movements  of  the  hind  limb,  which  Luciani  and  Tamburini  re- 
solved into  two  antagonistic  centres  ;  5,  for  the  muscles  of  the  face,  or  the  facial  centre.  In  1873 
Ferrier  discovered  the  following  additional  centres :  6,  for  the  lateral  switching  movements  of  the 
tail:  7,  for  the  retraction  and  abduction  of  the  fore  limb  ;  8,  for  the  elevation  of  the  shoulder  and 
extension  of  the  fore  hmb,  as  in  walking;  the  area  marked  g,  9,  9,  controls  the  movements  of  the 
orbicularis  palpebrarum,  and  of  the  zygomaticus  (closure  of  the  eyelids),  together  with  the  upward 
movement  of  the  eyeball  and  narrowing  of  the  pupil.  Stimulation  of  the  areas  a,  a  (Fig.  II),  is  fol- 
lowed by  retraction  and  elevation  of  the  angle  of  the  mouth,  with  partial  opening  of  the  mouth  ;  at 
b,  Ferrier  observed  opening  of  the  mouth  with  protrusion  and  retraction  of  the  tongue,  while  the  dog 
not  unfrequently  howled.  He  called  this  centre  the  "oral  centre."  Stimulation  of  c,  c,  causes  re- 
traction of  the  angle  of  the  mouth,  owing  to  the  action  of  the  platysma,  while  c'  causes  elevation  of 
the  angle  of  the  mouth  and  of  one-half  of  the  face,  until  the  eye  may  be  closed,  just  as  in  9.  Stim- 
ulation of  d  is  followed  by  opening  of  the  eye  and  dilatation  of  the  pupil,  while  the  eyes  and  head 
are  turned  toward  the  other  side.  According  to  H.  Munk,  the  prefrontal  region  has  an  influence 
upon  the  attitude  of  the  body.  The  perineal  muscles  contract  when  the  gyrus  postcruciatus  is  stim- 
ulated. Stimulation  of  the  gyrus  prscruciatus  on  its  anterior  and  sloping  aspect  causes  movements 
in  the  pharynx  and  larynx. 

The  position  of  the  individual  motor  areas  may  vary  somewhat,  and  they  may 
be  slightly  different  on  the  two  sides  (Liiciam  and  Famburiiii). 

Strong  Stimuli. — If  the  stimulation  be  very  strong,  not  only  the  muscles  on 
the  opposite  side  contract,  but  those  on  the  same  side  may  also  contract.  These 
latter  movements  belong  to  the  class  of  associated  movetiients,  and  are  due  to  con- 
duction through  commissural  fibres.  Those  muscles,  which  usually  (muscles  of 
mastication)  or  always  (muscle  of  eye,  larynx,  and  face)  act  together,  appear  to 
have  a  centre  not  only  in  the  opposite,  but  also  in  the  hemisphere  of  the  same  side 
{Exner).  [All  observers  have  found  that  stimulation  of  the  facial  centre  causes 
identical  (a.ssociated )  movements  on  both  sides  of  the  face,  so  that  both  sides  of 
the  face  seem  to  be  represented  in  each  hemisphere.  Schafer  and  Horsley's  experi- 
ments make  it  very  probable  that  some  other  muscles,  e.^;.,  some  of  the  trunk  mtis- 


716 


EFFECT   OF    STIMULI    ON   THE    MOTOR    CENTRES. 


cles,  pectorals,  and  recti  abdominis,  are  represented  bilaterally  in  the  hemispheres. 
This  is  an  important  point  in  relation  to  recovery  after  the  supposed  destruction  of 
a  centre,  and  has  an  intimate  bearing  on  the  question  of  **  Substitution/'  in  refer- 
ence to  the  restoration  of  nerve  function.] 

Fig.  428. 


I,  Cerebrum  of  the  dog  from  above  ;  II,  from  the  side  ;  I.  II,  III,  IV,  the  four  pri 
ciatus:  /,  Sylvian  fossa:  o,  olfactory  lobe  ;  /,  optic  nerve  ;  1,  motor  area 
tensors  and  abductors  of  the  fore  limb ;  3,  flexors  and  rotators  of  the  fore  lim 
5,  the  facial  muscles  ;  6.  lateral  switching  movements  of  the  tail ;  7, 
8,  elevation  of  the  shoulder  and  extension  of  the  fore  limb  (movements  as 
brarum,  zygomaticus,  closure  of  the  eyelids.     II,  a,  a,  retraction   and  ele 
opening  of  the  mouth  and  movements  of  the  oral  centre;  c,  c,  platysma ;  _ 

centre,  according  to  Eulenberg  and  Landois.  Ill,  cerebrum  of  the  rabbit  from  above  ;  IV,  cerebrum  of  the  pip- 
eon  from  above  ;  V,  cerebrum  of  the  frog  from  above  ;  VI,  cerebrum  of  the  carp  from  above — (in  all  these  o  is 
the  olfactory  lobe  ;   1,  cerebrum  ;  2,  optic  lobe;  3,  cerebellum  ;  4,  medulla  oblongata). 


mary  convolutions, — S,  sulcus  cru- 
for  the  muscles  of  the  neck  ;  2,  ex- 
) ;  4.  the  muscles  of  the  hind  limb  ; 

nd  abduction  of  the  fore  limb  ; 

Iking);  9,9,  orbicularis  palpe- 
of  the  angle  of  the  mouth  ;  b, 

pening  of  the  eye;  I,/,  thermit 


Mechanical  stimulation  has  no  effect  upon  these  centres.  Landois  and 
Eulenberg  observed  that  chemical  stimulation  of  these  centres  by  means  of 
common  salt  caused  movements  in  the  extremities. 


CEREBRAL   EPILEPSY. 


717 


Cerebral  Epilepsy. — It  is  of  great  practical  diagnostic  importance  to  ascer- 
tain if  stimulation  of  the  motor  areas  in  man,  due  to  local  diseases  (inflammation, 
tumors,  softening,  degenerative  irritation),  causes  movements.  [Hughlings-Jack- 
son  lias  shown  that  local  diseases  of  the  cortex  may  cause  spasmodic  contractions 
in  certain  groups  of  muscles,  a  condition  known  as  "  Jacksonian  Epilepsy,"] 
and  he  explains  in  this  way  the  occurrence  of  unilateral  local  epileptiform  spasms, 
which  were  observed  by  Ferrier  and  Landois  to  occur  after  inflammatory  irrita- 
tion. Luciani  observed  these  spasms  in  dogs,  and  sometimes  they  were  so  violent 
and   general  as  to  constitute  an   attack  of    epilepsy.     This   condition    became 


Fig.  429. 


e  brain  with  the  chief  convolutions  (after  Ecker).  See  also  Figs.  424-427  in  their  relation  to  the  skull.  The  num- 
bers I  to  14,  and  the  letters  a  to  d,  indicate  conical  areas  (p.  718).  S,  Sylvian  fissure  ;  C,  central  sulcus,  or  fis- 
sure of  Rolando;  A.  anterior,  and  B,  posterior,  central  convolutions;  Fj,  upper,  Fo,  middle,  and  F3,  lowest 
frontal  convolution  ;  y,,  superior,  and/a,  inferior  frontal  fissure  ;  /"a,  sulcus  prxcentralis  ;  P,,  superior,  f*2,  infe- 
rior parietal  lobe,  with  Pj,  gyrus  supramarginalis  ;  Pg',  gyrus  angularis  ;  t^,  sulcus  interpanetalis  ;  c;«,  end  of 
calloso-marginal  fissure  ;  O,,  Oo,  Oa,  occipital  convolutions  ;  pOy  parieto-occipital  fissure;  T,,  Tg,  T3,  temporo- 


sphenoidal  convolutions;   Kj,  Kg,  K3,  points  in  the 


in  the  lambdoid. 


hereditary,  and  the  animals  ultimately  died  from  epilepsy  (§  373).  According  to 
Eckhard,  epileptic  attacks  are  never  produced  by  stimulation  of  the  surface  of 
the  posterior  convolutions. 

Strong  stimulation  of  the  motor  regions  may  give  rise  in  dogs  to  a  complete  general  convulsive 
epileptic  attack,  which  usually  begins  with  contractions  of  the  groups  of  muscles  specially  related 
to  the  stimulated  centre  (Ferrier,  EuUiiberg  and  Landois,  Albertoni,  Lticiani  and  Tamhurini), 
then  often  passes  to  the  corresponding  limb  of  the  opposite  side  (associated  movements) ;  and,  lastly, 
all  the  muscles  of  the  body  are  thrown  into  tonic  and  then  into  clonic  spasms.  The  opposite  side 
of  the  body  has  been  observed  to  pass  into  spasm  from  below  upward,  after  the  contractions  were 
developed  in  the  other  side.     1  he   spasmodic  excitement  passes  from  centre  to  cen're,  an  interme- 


718 


MOTOR   CENTRES    IN    THE    MARGINAL   CONVOLUTION. 


(Hate  motor  region  never  being  passed  over,  ijometimes  feeble  stimulation  above  the  internal  cap. 
sule  is  sufficient  to  cause  this  condition.  After  this  condition  has  once  been  produced,  the  slightest 
stimulation  may  suffice  to  bring  on  a  new  epileptic  attack  (^  373).  Stimulation  of  the  subcortical 
white  matter  causes  epdepsy,  which,  however,  begins  in  the  muscles  of  the  same  side  (Bubnoff  and 
Hiitienhiiin),  These  contractions  are  due  to  an  escape  of  the  electrical  current,  which  thus  reaches 
the  medulla  oblongata  {§  373).  If  certain  motor  areas  are  extirpated,  the  epileptic  attack  is  absent 
from  the  muscles  controlled  by  these  areas  {Luciani).  Separation  of  the  motor  cortical  area  by 
means  of  a  horizontal  section  during  an  attack  cuts  short  tue  latter  \Munk).  During  an  epileptic 
attack  it  is  possible  to  excise  the  motor  area  of  one  extremity  and  thus  exclude  this  limb  from  the 
attack  while  the  rest  of  the  body  is  convulsed. 

Effect  of  Drugs. — The  continued  use  o{ potassium  bromide  prevents  the  possibility  of  producing 
epilepsy  on  stimulating  the  cortical  areas.  Atropin  in  small  doses  increases  the  excitability  of  the 
motor  areas,  while  in  large  doses  it  paralyzes  them. 

[Motor  Centres  in  the  Monkey. — Ferrier  has  mapped  out  a  large  number 
of  centres  on  the  outer  surface  of  the  brain  in  the  monkey,  and  to  each  centre  he 
has  given  a  number.  These  numbers  have  been  transferred  to  corresponding  con- 
volutions on  the  human  brain,  and  numbered  accordingly.  These  convolutions 
in  the  monkey  occupy  the  posterior  extremities  of  the  posterior  and  middle 
frontal  convolutions,  the  ascending  frontal,  ascending  parietal,  and  part  of  the 
parietal  lobule.] 

[Fig.  429  represents  these  areas  transferred  to  the  corresponding  areas  in  man.  (i)  On  the 
superior  parietal  lobule  (advance  of  the  opposite  hind  limb,  as  in  walking).  (2),  (3),  (4)  Around 
the  upper  extremity  of  the  fissure  of  Rolando  (complex  movements  of  the  opposite  leg  and  arm, 
and  of  the  trunk,  as  in  swimming),  {a),  (b),  (c),  («'),  On  the  ascending  parietal  or  posterior  cen. 
tral  convolution  (individual  and  combined  movements  of  the  fingers  and  wrist  of  the  opposite  hand 
or  prehensile  movements).  (5)  Posterior  end  of  the  superior  irontal  convolution  (extension  for- 
ward of  the  opposite  arm  and  hand).  (6)  Upper  part  of  the  ascending  frontal  or  anterior  central 
convolution  (supination  and  flexion  of  the  opposite  forearm).  (7)  Middle  of  the  same  convolution 
(retraction  and  elevation  of  the  opposite  angle  of  the  moutli).  (8)  At  the  lower  end  of  the  same 
convolution  (elevation  of  the  ala  nasi  and  upper  lip,  and  depression  of  the  lower  lip  on  the  oppo- 
site side).  (9),  (10),  Broca's  convolution  (opening  of  the  mouth  with  protrusion  and  retraction  of 
the  tongue — aphasic  region).  (ll)  Between  10  and  the  lower  end  of  the  ascending  parietal  con- 
volution (retraction  of  the  opposite  angle  of  the  mouth,  the  head  turns  toward  one  side).  (12) 
Posterior  part  of  the  superior  and  middle  frontal  convolutions  (the  eyes  open  widely,  the  pupils 
dilate,  and  the  head  and  eyes  turn  toward  the  opposite  side).  (13),  (13')  Supramarginal  and 
angular  gyrus  (the  eyes  move  toward  the  opposite  side,  and  upward  or  downward — centre  of 
vision).  (14)  Superior  temporo-sphenoidal  convolution  (pricking  of  the  opposite  ear,  pupils  dilate, 
and  the  head  and  eyes  turn  to  the  opposite  side — hearing  centre).] 

[Schafer  and  Horsley  have  extended  Ferrier's  researches,  and  shown  that  motor 
centres  exist  in  the  marginal   convolution  (Fig.  430),  which  is  excitable  only 

in    that    portion   which    corresponds   in 


Fig.  430. 


extent  (antero-posteriorly)  with  the  ex- 
citable portion  of  the  outer  surface  of 
the  hemisphere.  Anteriorly  it  reaches 
forward  to  a  line  which  is  opposite  the 
junction  of  the  posterior  and  middle 
thirds  of  the  superior  frontal  convolu- 
tion (centre  12),  while  posteriorly  it 
extends  backward  to  opposite  the  pari- 
etal lobule,  including  the  paracentral 
lobule,  which  contains  large  multipolar 
pyramidal  motor  cells.  The  rest  of  the 
mesial  surface  is  excitable.  They  find 
that  the  centres  are  arranged  from  before 
backward  in  the  following  order :  the 
motor  region  of  the  elbow  and  shoulder, 
then  follow  centres  for  the  trunk  muscles, 
such  as  give  rise  to  arching  of  the  trunk 
in   the   dorsal  and  lumbar  regions  ;  also  flexion  (^ilio-psoas  muscle)  and  extension 


:  of  right  hemi; 

ents  of  the  arm  and  ) 
the  trunk  ;  /e^,  those  of  the  leg  : 
catus  :  CC,  corpus  callosum  ;  0', 
O,  occipital  lobe. 


governing 
r:  TV,  of 
''/.  gyrus  forni- 
unciiiate  gyrus; 


DESTRUCTION    OF    MOTOR    CENTRES. 


719 


(glutei)  of  the  hip  ;  hamstring  and   extensors  of  the  knee  ;   movements  of  the 
ankle  and  digits.      The  centre  for  the  thigh  muscles  is  in  the  paracentral  lobule.] 

[Excitation  of  the  Area  AS  produces  movements  of  the  arm.  These  vary  accorrling  to  the  spot 
stimulated,  but  toward  the  anterior  part  of  the  area,  movements  of  the  wrist  and  fore  arm,  toward 
the  posterior  part  movements  of  the  arm  and  shoulder,  are  more  frequently  the  result  of  the  exci- 
tation. Excitation  of  Tr  produces  movements  of  the  trunk,  generally  arching  and  rotation.  Those 
movements  which  are  called  forth  by  stimulating  the  anterior  part  of  the  area  are  u-ually  confined 
to  the  upper  part  of  the  trunk  (thoracic  region),  and  are  often  associated  with  movements  of  the 
shoulder  and  arm  ;  those  called  forth  by  stimulating  the  posterior  part  are  movements  of  the  ab- 
dominal and  pelvic  regions  and  of  the  tail,  and  are  often  associated  with  movements  of  the  hip  and 
leg.  Excitation  of  the  area  L  produces  movements  in  the  lower  limb.  These  vary  according  to 
the  part  stimulated,  extension  of  the  hip  being  especially  associated  with  excitation  of  the  anterior 
part  of  the  area,  and  contraction  of  the  hambtrings  with  excitation  of  the  middle  part.] 

[Do  similar  Centres  exist  in  Man  ? — The  results  of  clinical  and  patholog- 
ical investigations  show  that  similar,  although  not  absolutely  identical,  areas  exist 
in  man.     The   motor   areas,    or  those 

which  have  a  special  relation  to  volun-  F""--  4H. 

tary  motion  in  man,  occupy  the  "cen- 
tral" convolutions,  i.  c,  the  ascending 
frontal  and  ascending  parietal  convo- 
lutions along  with  the  superior  parietal 
lobule,  and  along  the  mesial  surface  of 
the  hemisphere  the  paracentral  lobule 
and  precuneus  (Fig.  431).  In  this 
region  the  upper  third  of  the  ascend- 
ing frontal  and  parietal  convolutions 
along  with  the  superior  parietal  being 
the  leg  area  (Fig.  431,  kg),  the  mid- 
dle third  of  the  ascending  parietal  and 
ascending  parietal  for  the  arm,  and  the  m 
upper  part  of  the  lowest  third  of  these 
convolutions  for  the  face,  while  the 
very  lowest  part  of  the  ascending  frontal  convolution  is  the  area  for  the  move- 
ments of  the  lips  (L)  and  tongue  (T),  (compare  Fig.  433).  The  last  area,  with 
the  posterior  extremity  of  the  third  left  frontal  convolution,  is  the  centre  for 
voluntary  speech.  We  cannot  say  whether  these  "  centres  "  are  sharply  mapped 
off  from  each  other.  In  any  case  a  very  strong  stimulation  of  one  centre  may  in- 
volve an  adjacent  area.  So  far  as  is  yet  known,  centres  Nos.  5  and  12,  as  repre- 
sented on  the  monkey's  brain — those  on  the  posterior  extremity  of  the  superior 
and  middle  frontal  convolutions — (5)  for  extension  forward  of  the  arm  and  hand, 
and  (12)  for  opening  the  eyes  and  turning  the  head  toward  the  opposite  side  (as 
in  surprise)  are  not  represented  in  the  human  brain.] 

[Gowers  maintains  that  this  region  is  not  exclusively  motor,  but  that  destruction  of  these  parts 
also  leads  to  some  loss  of  sensation.  Starr  also  asserts  that  perceptions  occur  in  the  gray  matter  of 
the  cortex  of  the  "  central  "  region  and  parietal  convolutions,  and  that  the  various  sensory  areas  fi  r 
the  various  parts  of  the  body  lie  about  and  coincide  to  sume  extent  with  the  motor  various  areas  for 
similar  parts,  but  the  sensory  area  is  more  extensive  than  the  motor  area,  extending  into  the  parietal 
behind  the  motor  area,  which  is  confined  to  the  ascending  frontal  and  parietal  convolutions.] 

[II.  Method  of  Destruction  of  Parts  of  the  Cortex.— Much  confusion  in  this  mauer  has 
arisen  from  comparing  the  results  obtained  on  animals  of  ditferent  species.  It  seems  quite  certain 
that  the  results  obtained  in  the  dog  are  quite  different  from  those  in  the  monkey.  The  motor  areas 
may  be  simply  excised  with  a  knife,  or  the  surface  of  the  brain  may  be  washed  away  with  a  stream 
of  water,  as  was  done  by  GoUz  in  dogs.] 

[In  the  dog  the  areas  which  are  described  as  motor  may  be  removed  either  by  the  knife  {Her- 
r/iditn),  or  by  means  of  a  stream  of  water  so  directed  as  to  wash  away  the  gray  matter.  In  both 
cases,  although  there  was  some  paralysis  on  the  opposite  side  of  the  body,  this  was  but  temporary, 
for  the  paralysis  disappeared  w  ithin  a  few  days,  the  animals  having  very  decided  control  over  their 
muscles,  although  Goltz  admits  that  certain  acts,  especially  those  which  the  dogs  had  been  trained 
to  execute,  e.  g.,  giving  a  paw,  were  executed  "  clumsily,"  indicating  some  failure  of  complete  con- 


of  the  left  side  of 
region  ^modified 


720  EXTIRPATION    OF   THE    MOTOR    CENTRES. 

trol,  which  Goltz  ascribed  to  loss  of  tactile  sensil)ility.  Goltz  thinks  that  the  extent  of  the  injury  has 
more  to  do  with  the  result  than  the  locality.  The  restoration  of  motion  was  not  due  to  tlie  action 
of  the  corresponding  centre  of  the  opposite  side,  as  destruction  of  this  centre,  although  it  produced 
the  usual  symptoms  on  the  side  which  it  governed,  had  no  effect  on  the  previous  result  {Carvilte 
and  Duret).'] 

[In  the  monkey  there  can  be  no  doubt,  from  the  experiments  of  Ferrier,  that 
destruction  of  a  motor  centre,  e.  g.,  that  for  the  arm,  results  in  peniiatient  Y)3l- 
ralysis  of  the  arm  of  the  opposite  side,  and  if  the  centres  for  the  arm  and  leg  are 
destroyed  there  is  permanent  hemiplegia  of  the  opposite  side.  Indeed,  Schafer 
and  Horsley  have  removed  the  motor  centres  on  the  outer  surface  of  the  hemi- 
spheres and  those  for  the  trunk  muscles  in  the  marginal  convolution,  and  they  find 
that  the  result  is  absolute  hemiplegia.] 

[In  man  records  of  destructive  lesions  of  the  motor  areas  in  whole  or  part  have 
now  accumulated  to  such  an  extent  as  to  leave  no  doubt,  that  if  there  be  say  a  de- 
structive lesion  of  the  middle  third  of  the  cortex  of  the  ascending  frontal  and 
ascending  parietal  convolutions,  there  will  be  paralysis  of  the  arm  of  the  opposite 
side,  and  the  same  is  true  for  the  other  centres.] 

[In  extirpation  of  the  motor  centres  much  confusion  has  arisen  from  com- 
paring the  results  obtained  on  different  animals.  In  the  dog  there  is  no  permanent 
motor  paralysis,  in  the  monkey  and  man  there  is.  The  difference  is  this,  that  in 
the  dog  the  lower  centres,  perhaps  the  basal  ganglia,  are  able  to  subserve  the  exe- 
cution of  those  coordinated  movements  required  for  standing,  progression,  etc. 
As  we  proceed  higher  in  the  animal  scale,  the  motor  cortical  centres  assume  more 
and  more  of  the  functions  subserved  by  the  basal  ganglia  in  lower  animals.  There 
is,  as  it  were,  a  gradual  displacement  of  motor  centres  to  the  cortical  region  as  we 
ascend  in  the  zoological  scale.] 

Differences  in  Animals. — The  higher  the  development  of  the  intelligence  of  the  animals  the 
more  their  movements  have  been  learned,  and  have  gradually  come  to  be  controlled  by  the  will ; 
in  them  the  disturbance  of  the  motor  phenomena  becomes  more  pronounced  and  persistent  after 
destruction  of  the  cortical  psychomotor  centres.  While  in  the  lower  vertebrates,  including  the 
birds,  extirpation  of  the  whole  hemispheres  does  not  materially  interfere  with  the  movements,  the 
coordinated  reflex  movements  being  sufficient ;  in  dogs  occasionally,  but  exceptionally,  extirpation 
of  sexeral  motor  areas  produces  visible  permanent  disturbance  of  motor  acts,  while  in  monkeys 
and  man  (^  378)  the  paralytic  phenomena  may  be  intense  and  persistent. 

Acquired  Movements. — Among  the  movements  performed  by  men  are  many  which  have  been 
acquired  after  much  practice,  and  have  been  subjected  to  voluntary  control,  e.g.^  the  movements  of 
the  hands  for  many  manual  occupations.  After  a  lesion  of  the  psychomotor  centres,  such  move- 
ments are  reacquired  only  very  slowly  and  incompletely,  or  it  may  be  not  at  all.  [The  interference 
with  these  finer  acquired  movements  sometimes  becomes  very  marked  in  lesions  of  the  motor  areas 
produced  by  hemorrhage,  and  in  some  cases  of  hemiplegia.]  Those  movements,  however,  which 
are,  as  it  were,  innate  [or,  as  they  are  sometimes  termed,  fundamental  in  opposition  to  acquired], 
and  are  under  the  control  of  the  will  without  much  practice — such  as  the  associated  movements  of 
the  eyes,  face,  some  of  those  of  the  limbs — are  either  rapidly  restored  after  the  lesion,  or  they  ap- 
pear to  suffer  but  slightly.  After  a  lesion  of  the  cerebral  cortex,  the  facial  muscles  are  never  so 
completely  paralyzed  as  from  a  lesion  of  the  trunk  of  the  facial  nerve  ;  usually  the  eye  can  be 
closed  in  the  former  case.  The  movements  necessary  for  sucking  have  been  performed  by  a  hemi- 
cephalic  infant. 

Theoretical. — Hitzig  ascribes  the  disturbance  of  movement,  after  the  removal  of  the  motor 
centres,  to  the  loss  of  the  "  muscular  sensibility."  Schiff  ascribes  it  to  the  loss  of  tactile  sensibility. 
According  to  Ferrier,  the  tactile  and  sensory  impressions  are  not  appreciably  diminished  or  altered. 
The  descending  degeneration  of  the  pyramidal  tracts  in  the  lateral  columns,  according  to  Schift, 
occurs  after  section  of  the  posterior  half  of  the  cervical  spinal  cord,  or  even  after  section  of  the  pos- 
terior part  of  the  lateral  colu  nns.  After  dividing  the  latter,  and  allowing  secondary  degeneration 
to  take  place,  it  is  not  possible  to  discharge  movements  by  stimulating  the  cortex  cerebri.  [Schifif 
divided  the  posterior  column  of  the  cord,  and  found  that  stimulation  of  the  opposite  motor  cortex 
failed  to  excite  movements  in  the  opposite  fore  limbs.  He  supposed  that  this  result  was  due  to  as- 
cending degeneration.  Horsley  finds,  however,  that  Schiff's  results  are  due  to  transverse  aseptic 
myelitis  at  the  seat  of  operation,  and  causing  a  "  block  "  there  in  the  motor  tract.]  The  posterior 
columns  and  their  continuation  upward  to  the  brain  are  supposed  to  carry  the  impulses  upward  to 
the  cerebrum  (ascending  limb  of  the  reflex  arc),  where,  after  being  modified  in  the  centres,  they  are 
carried  outward  by  the  pyramidal  tracts  (descending  limb  of  the  reflex  arc).  [Some  hold  that  the 
posterior  columns  are  directly  connected  with  the   cortical   motor  area,  while  others  think  that  a 


THE    SENSORY   CORTICAL   CENTRES.  721 

sensory  perceptive  centre  is  interposed  Ijelween  the  afferent  and  efferent  impulses.]  Between,  but 
deeper  in  the  brain,  lie  the  centres  lor  tactile  sensibility.  Landois  and  Eulenberg  observed  in  a 
dog,  from  which  the  motor  centres  for  the  extremities  had  been  removed  on  both  sides,  that  the  move- 
ments became  completely  ataxic,  i.  e.,  the  animal  could  not  execute  such  coordinated  movements 
as  walking,  standing,  etc.  Goltz  regards  the  disturbances  of  movement  after  injury  of  the  cortex 
as  due  to  inhibition.  Schiff  maintains  that  when  the  cortex  cerebri  is  stimulated  we  do  not  stimu- 
late a  cortical  centre,  but  only  the  sensory  channels  of  a  reflex  arc,  the  continuation  of  the  posterior 
columns,  so  that  on  this  supposition  the  movements  resulting  from  stimulation  of  the  motor  points 
would  be  reflex  movements.  The  centres  lie  deeper  in  the  brain.  This  view  is  not  generally  en- 
tertained. 

Modifying  Conditions. — The  excitability  of  the  motor  centres  is  capable  of 
being  considerably  modified.  Stimulation  of  sensory  nerves  diminishes  it  ;  thus 
the  curve  of  contraction  of  the  muscles  becomes  lower  and  longer,  while  the  re- 
action time  is  lengthened  simultaneously.  Only  when,  owing  to  strong  stimula- 
tion, the  reflex  muscular  contractions  are  vigorous,  the  excitability  of  the  cortical 
centres  appears  to  be  increased.  Specially  noteworthy  is  the  fact  that,  in  a  cer- 
tain stage  of  morphia-narcosis,  a  stimulus  which  is  too  feeble  to  discharge  a 
contraction  becomes  effective  at  once,  if  immediately  before  the  stimulus  is  applied 
to  the  cortical  centre  the  skin  of  certain  cutaneous  areas  be  subjected  to  gentle 
tactile  stimulation.  When  strong  pressure  is  applied  to  the  foot  the  contractions 
become  tonic  in  their  nature,  so  that  all  stimuli,  which  under  normal  conditions 
produce  only  temporary  stimulation,  now  stimulate  these  centres  continuously. 
If  during  the  tonic  contraction  one  gently  strokes  the  back  of  the  foot,  blows  on 
the  face,  gently  taps  the  nose  or  stimulates  the  sciatic  nerve,  suddenly  relaxation 
of  the  muscles  again  occurs.  These  phenomena  call  to  mind  the  analogous  ob- 
servations in  hypnotized  animals  (§  374).  Another  very  remarkable  observation 
is  that,  when  either  owing  to  a  reflex  effect,  or  owing  to  strong  electrical  stimula- 
tion of  a  cortical  centre,  contracture  of  the  corresponding  muscles  is  produced, 
then/cc'/'A'  stimulation  of  the  same  centre,  but  also  of  other  centres,  suppresses 
movement.  Thus  we  have  the  remarkable  fact  that,  according  to  the  strength  of 
the  stimulus  applied  to  the  motor  apparatus,  we  can  either  produce  movement  or 
suppress  a  movement  already  in  progress  lyBubnoff  and  Hcidenhain). 

[Excision  of  the  Thyroid  affects  the  nerve  centres.  After  thyroidectomy  (twenty-four  hours) 
the  tetanus  obtained  by  stimulating  the  cortex  is  greatly  changed.  It  ceases  when  the  stimulating 
current  is  shut  off  as  suddenly  as  that  observed  on  stimulating  the  corona  radiata.  In  more  advanced 
cases  the  tetanus  is  soon  exhausted,  and  is  often  followed  by  clonic  epileptoid  spasms.  In  the  latter 
stages,  after  thyroidectomy,  there  may  be  only  a  feeble  tetanus,  or  none  at  all,  on  stimulating  the 
motor  areas,  so  great  is  the  state  of  depression  of  function  ol  these  centres  (Horsley).^ 

[Warner  has  directed  Mtention  to  visible  muscular  movements  apart  from  those  studied  in 
epilepsy,  chorea,  athetois — and  including  attitude,  gait,  movements  of  the  eyeballs,  position  of  the 
hand,  and  posture  in  general,  etc as  expressive  of  states  of  the  brain  and  nerve  centres.] 

376.  THE  SENSORY  CORTICAL  CENTRES.— [There  must  be 
some  connection  between  the  surface  of  the  brain  and  the  afferent  channels  through 
which  sensory  impulses  pass  inward,  and  although  the  channels  for  sensory 
impulses  are,  perhaps,  not  so  definitely  localized  as  those  for  voluntary  motion, 
still,  we  know  that  sensory  impulses  for  the  opposite  half  of  the  body  travel  up- 
ward through  the  posterior  third  of  the  posterior  limb  of  the  internal  cajjsule 
(Fig.  439,  S),  to  radiate,  in  all  probability,  into  the  occipital  and  temporo-sphe- 
noidal  lobes.  Parts  of  these  convolutions  are  sometimes  spoken  of  as  "  sensory 
centres  "  or  "  psycho-sensorial  "  areas.] 

[The  same  methods  have  been  applied  to  the  investigation  of  these  centres,  viz.,  stimulation  and 
extirpation.  Stimulation. — Ferrier  found  that  electrical  stimulation  of  the  angular  gyrus  ( monkey) 
caused  movements  of  the  eyeballs  toward  the  side,  with  sometimes  associated  movements  of  the 
head,  but  he  regarded  these  as  reflex  movements,  so  that  for  this  and  other  reasons  he,  in  his  earliest 
contributions,  regarded  the  angular  gyrus  and  adjacent  parts  as  the  "  centre  for  vision."  On  stimu- 
lating the  flrst  temporo-sphenoidal  convolution, the  monkey  pricked  the  opposite  ear,  the  pupils  dilated, 
while  the  head  and  ears  turned  to  the  opposite  side;  it  exhibited  movements  similar  to  those  caused 
by  a  loud  sound.  These  movements  are  also  reflex  phenomena,  so  that  he  located  the  '■  auditory 
46 


722 


THE    VISUAL   CENTRE. 


centre"  in  this  region,  and  on  somewhat  similar  grounds.  As  the  result  of  inferences  from  the 
stimulation  and  extirpation  of  other  parts,  he  referred  the  centres  for  smell  and  taste  to  the  tip  of 
the  temporosphenoidal  lobe,  and  toucti  to  the  hippocampus  major;  but  all  these  statements  have 
not  been  confirmed.] 

[Goltz  experimented  on  dogs  by  washing  away  the  cortex  cerebri,  and  found  that  when  a 
sufficient  amount  of  the  gray  matter  is  removed,  and  after  recovery  from  the  immediate  effects  of 
the  operation,  there  is  a  peculiar  defect  of  vision  and  other  sensory  defects;  but,  so  far,  Goltz  has  not 
found  that  there  is  any  difference  in  this  respect  between  removal  of  the  anterior  and  posterior  lobes 
of  the  dog's  brain.  The  dog  is  not  blind,  as  it  can  see  and  use  his  eyes  to  avoid  obstacles,  but  it 
seemed  as  if  the  animal  failed  to  recognize,  as  such,  t*.^^.,  food  or  flesh  placed  before  it,  while  exhi- 
bitions which  before  the  operation  greatly  excited  the  dog  cea.sed  to  do  so.  Goltz  caused  his  servant 
to  dress  himself  in  a  mummer's  red-colored  garb,  which  greatly  excited  the  dog,  but  after  the  opera- 
tion the  tiog,  although  it  was  not  blind,  was  no  longer  excited  thereby.  Nor  was  it  afterward  cowed 
by  the  appearance  of  a  whip.  After  a  time  there  was  recovery,  to  a  certain  extent,  if  the  animal 
was  trained,  whether  by  the  deposition  of  new  impressions,  or  by  opening  up  new  channels,  or  by 
the  partial  recovery  of  some  parts  of  the  gray  matter  not  removed,  it  is  impossible  to  say.] 

[Munk  has  mapped  out  the  surface  of  the  brain  into  a  series  of  "sensory"  or  psycho. sensorial 
centres,  but  he  distinguishes  between  complete  and  total  extirpation  of  these  centres  and  the  phe- 
nomena which  follow  these  operations.] 


Fig.  432. 


When  these  centres  are  partially  disorganized,  the  mechanism  of  the  sensory 
activity  may  remain  intact,  but  "  the  conscious  Hnk  is  wanting."  A  dog  with  its 
centres  thus  destroyed  sees,  hears,  or  smells,  but  it  no  longer  knows  what  it  sees, 
hears,  or  smells.  These  centres  are,  in  a  certain  sense,  the  seat  of  experience  that 
has  been  acquired  through  the  organs  of  sense.  Stimulation  of  these  centres 
may  give  rise  to  movements,  such  as  occur  when  sudden  intense  sensory  impres- 
sions are  produced.  These  movements,  therefore,  are  to  be  regarded  as  reflex, 
partly  as  extensive  coordinated  reflex  movements,  and  are  in  no  way  to  be  con- 
founded with  the  movements  which  result  from  direct  stimulation  of  the  motor 
cortical  centres.  To  this  belongs  dilatation  of  the  ptipil  and  the  fissure  of  the 
eyelids,  as  well  as  lateral  movements  of  the  eyeball. 

I.  The  "visual  centre,"  according  to  Munk,  embraces  the  outer  convex 
part  of  the  occipital  lobe  of  the  dog's  brain.  [This 
centre  and  its  connections  are  represented  in  Fig.  432. 
It  is,  therefore,  in  the  area  supplied  by  the  posterior 
cerebral  artery.]  If  this  region  be  completely  destroyed, 
the  dog  remains  jsermanently  blind  ("  cortical  or  ab- 
solute blindness")  in  the  eye  of  the  opposite  side. 
If,  however,  only  the  central  circular  area  be  destroyed, 
there  is  loss  of  the  conscious  visual  sensation  of  the 
opposite  side,  which  may  be  called  "  psychical  blind- 
ness "  {Munk')  [a  condition  of  visual  defect  like  that 
observed  by  Goltz  in  the  dog,  in  which  the  dog  saw  an 
object,  e.g.,  its  food,  but  failed  to  recognize  it  as  such. 
There  is  a  certain  amount  of  recovery  if  the  whole  visual 
area  be  not  removed]. 

[Ferrier  and  Yeo,  however,  find  that  after  operations 
conducted  antiseptically,  removal  of  both  occipital  lobes 
(monkeys)  does  not  cause  any  recognizable  disturbance 
of  vision  or  other  bodily  or  mental  derangement,  pro- 
vided the  lesion  does  not  extend  beyond  the  paiieto- 
occipital  fissure.  Nor  does  destruction  of  both  angular 
gyri  cause  permanent  loss  of  vision  ;  such  loss  of  vision 
lasts  only  three  days,  so  that  in  Ferrier's  original  ex- 
periments the  animals  lived  for  too  short  a  time  after 
the  operation  to  enable  a  just  conclusion  to  be  arrived 
at.  Destruction  of  both  angular  gyri  and  occipital  lobes  causes  total  and  perma- 
nent blindness  in  both  eyes  in  monkeys,  without  any  impairment  of  the  other 
senses  or  motor  power.] 


Course  of  the  phycho-oplic 
(after  Munk). 


THE    AUDITORY    AREA.  723 

Mauthner  denies  the  existence  of  cortical  blindness,  and  believes  that,  after  destruction  of  the 
middle  of  the  visual  centre,  the  reason  why  the  dog  does  not  recognize  the  object  with  the  opposite 
eye  is  because,  owing  to  their  being  only  indirect  vision,  there  is  no  distinct  impression  on  the  retina. 
The  position  of  the  visual  centre  has  been  variously  stated  by  different  observers.  According  to 
Ferrier,  in  the  dog  it  lies  in  the  occipital  part  of  the  III  primary  convolution,  near  the  spot  marked 
e,  <•,  c,  in  Fig.  428;  according  to  his  newer  researches,  in  the  occipital  lobe  and  gyrus  angularis. 

Connection  with  the  Retina. — Munk  asserts  that  in  dogs  /lot/i  retina:  are  connected  with  each 
psycho-optic  cortical  centre,  and  in  such  a  manner  that  the  greatest  part  of  each  retina  is  connected 
with  the  opposite  cortical  centre,  and  only  by  its  most  external  lateral  marginal  |iart  with  the  centre 
of  the  same  side.  If  we  imagine  the  surface  of  one  retina  to  be  projected  upon  the  centres,  then  the 
most  external  margin  of  the  tirst  is  connected  with  the  centre  of  the  same  side,  the  inner  margin  of 
the  retina  with  the  inner  area  of  the  opposite  centre,  the  upper  margin  with  the  anterior  area,  and 
the  lower  marginal  part  of  the  retina  with  the  posterior  area  of  the  opposite  side.  The  (shaded) 
middle  of  the  centre  corresponds  to  the  position  of  direct  vision  of  the  retina  of  the  opposite  side 
(compare  I  344). 

Stimulation  of  the  visual  centre  in  dog.s  causes  movements  of  the  eyes  toward 
the  other  side,  sometimes  with  similar  movements  of  the  heart  and  contraction  of 
the  pupils.  If  one  eye  be  excised  from  new-born  dogs,  the  opposite  psycho-optic 
centre,  after  several  months,  is  less  developed  {Munk).  After  extirpation  of 
the  visual  centre  in  young  dogs,  the  channels  which  connect  it  with  the  optic  nerve 
undergo  degeneration  (p.  Monakow)  (§  344). 

In  monkeys  the  centre  lies  at  the  tip  of  the  occipital  lobe.  Unilateral  destruction  causes  blindness 
of  the  halves  of  both  retinas  lying  on  the  side  of  the  injury.  The  visual  centre  in  pigeons  f  Fig. 
428,  IV,  where  I  is  placed)  lies  somewhat  behind  and  internal  to  the  highest  curvature  of  the  hemi- 
spheres (.I/'A'ivji/riV.^, />/■/-/£■?-,  J/«j<.7/i7/</).  The  visual  centre  in  the  frog  lies  in  the  optic  lube 
{Blaschko). 

[The  visual  path  is  along  the  optic  nerve  to  the  chiasma,  where  the  fibres  from  the  nasal  half 
of  each  retina  cross  to  the  optic  tract,  some  of  the  fibres,  perhaps,  becoming  connected  with  the 
external  corpora  geniculata,  and  some  with  the  pulvinar  of  the  optic  thalamus  and  corpora  quadri- 
gemina,  while  the  great  mass  sweeps  backward  to  the  occipital  lobes  as  the  optic  expansion  of  Gra- 
tiolet.  Destruction  of  this  path  behind  the  chiasma  causes  hemiopia,  and  certain  diseases  of  the 
occipital  cortex  cause  a  similar  result.  Perhaps,  however,  there  is  another  centre  in  the  angular 
gyrus  (and  supramarginal  lobe),  for  in  cases  of  word-blindness  disease  has  been  found  in  these 
regions.  Sometimes  flashes  of  light  or  the  appearance  of  a  ball  of  tire  forms  the  aura  in  epilejisy, 
and  Hughlings-JacUson  thinks  that  discharging  lesions  of  the  right  occipital  lobe  cause  colored 
vision  more  frequently  than  on  the  left.] 

2.  The  centre  for  hearing,  or  "  auditory  area,"  lies  in  the  dog,  according 
to  Ferrier,  in  the  region  of  the  second  primary  convolution  aX.  /,/,/,  (Fig.  428, 
II),  while  in  the  monkey  and  man  it  is  in  the  first  temporo-sphenoidal  convolution 
(Ferrier's  centre.  No.  14).  Munk  locates  it  in  the  same  region.  According  to 
Munk,  destruction  of  the  entire  region  causes  deafness  of  the  opposite  ear,  while 
destruction  of  the  middle  shaded  part  alone  causes  "psychical  deafness" 
{'^  See/entaubha't"').  Stimulation  of  the  centre  is  followed  by  a  reaction  which 
closely  resembles  that  produced  by  a  sudden  fright  or  that  produced  by  a  sudden 
unexpected  noise.  The  ear  muscles  are  moved  in  different  directions  [the  animal 
pricks  its  ears]  {Ferrier).  [Ferrier  locates  the  centre  for  hearing  in  the  monkey 
in  the  superior  temporo-spiienoidal  convolution,  and  he  finds  that  when  the  centres 
on  both  sides  are  extirpated,  the  animal  is  absolutely  deaf;  it  takes  no  cognizance 
of  a  pistol  fired  in  its  neighborhood.  In  man,  injuries  to  the  first  and  second 
temporo-sphenoidal  convolutions  on  one  side  do  not  appear  to  cause  complete 
deafness  of  one  ear,  as  it  seems  that  the  sense  of  hearing  for  each  ear  is  perhaps 
represented  on  both  sides.  Bilateral  lesions  of  these  convolutions  in  man  causes 
complete  deafness.  Disease  of  these  two  convolutions  is  associated  with  "  word- 
deafness"  (p.  732).  Wernicke  cites  a  case  of  a  person  first  affected  with  word- 
deafness,  who  afterward  became  completely  deaf;  and  after  death  a  bilateral  lesion 
was  found  in  the  first  temporo-sphenoidal  convolution.  These  convolutions  are 
supplied  with  blood  from  the  Sylvian  artery,  a  branch  of  the  middle  meningeal.] 

[Auditory  Aurse. ^Equally  important  with  these  effects  of  disease  are  the  sensory  impressions, 
or  '•  aur;e,"  which  sometimes   usher  in  an  attack  of  epilepsy ;   sometimes  these  aura;  consist  of 


724  THE   THERMAL   CORTICAL   CENTRES. 

sounds  or  noises,  and  in  these  cases  the  seat  of  the  disease  is  often  in  the  first  temporo-sphenoidal 
convolution.] 

[The  auditory  paths  are  from  the  auditory  nuclei  in  the  medulla  oblongata 
through  the  pons,  where  they  perhaps  cross  into  the  tegmentum,  thence  into  the 
"sensory  crossway,"  and  onward  to  the  auditory  centre.] 

[3.  The  olfactory  centre  is  placed  by  Ferrier  in  the  subiculum  cornu  am- 
monis,  or  the  inner  surface  of  the  anterior  extremity  of  the  uncinate  gyrus  (Fig. 
430).  M'Lane  Hamilton  has  recorded  a  case  of  epilepsy  ushered  in  by  an  aura  of 
a  disagreeable  odor,  in  which  there  was  atrophy  of  the  gray  matter  of  the  right 
uncinate  gyrus.] 

[Olfactory  Path. — Although  the  outer  root  of  the  olfactory  tract  runs  direct  to  the  uncinate  gyrus, 
in  JiimianiTsthesia  resulting  from  injury  to  the  "sensory  crossway,"  smell  is  lost  on  the  opposite  side, 
while  it  is  lost  on  the  same  side  when  the  uncinate  gyrus  is  involved.  It  may  be  that  the  impulses 
go  first  to  their  own  side  and  then  cross  afterward.] 

[4.  We  do  not  know  the  centre  for  taste,  and  even  the  course  of  the  nerve  of 
taste  is  disputed.     Ferrier  places  it  close  to  that  of  smell.] 

On  stimulating  the  subiculum  in  monkeys,  dogs,  cats  and  rabbits,  he  observed  peculiar  movements 
of  the  lips  and  partial  closure  of  the  nostrils  on  the  same  side  (\  365).  In  man,  subjective  olfactory 
and  gustatory  perceptions  are  regarded  as  irritative  phenomena,  while  loss  of  these  sensory  activities, 
often  complicated  with  other  cerebral  phenomena,  are  regarded  as  symptoms  of  their  paralysis. 

[The  Gustatory  Path  crosses  in  the  posterior  pait  of  the  posterior  .segment  of  the  internal  capsule. 
While  Cowers  admits  that  the  chorda  tympani  is  the  nerve  of  taste  for  the  anterior  two  thirds  of 
the  tongue,  he  thinks  that  it  reaches  the  facial  nerve  from  the  spheno-palatine  ganglion  through  the 
Vidian  nerve.  He  denies  that  the  glossopharyngeal  is  concerned  in  taste,  and  •'  he  believes  that 
taste  impressions  reach  the  brain  solely  by  the  roots  of  the  5th  nerve  "  He  admits  that  the  nerves 
of  taste  to  the  back  part  of  the  tongue  may  be  distributed  with  the  glossopharyngeal,  reaching 
them  through  the  otic  ganglion  by  the  small  superficial  petrosal  and  tympanic  plexus.] 

[5.  Ferrier  places  the  centre  for  tactile  sensation  in  the  hippocampalxtgxow,  close 
to  the  distribution  of  part  of  the  posterior  cerebral  artery  ;  so  far  this  has  not  been 
confirmed.  The  centre  for  the  sensation  of  pain  has  not  been  defined,  probably 
it  is  very  diffuse.] 

6.  Munk  is  of  opinion  that  the  surface  of  the  cerebrum  in  the  region  of  the  motor  centres  acts  at 
the  same  time  as  "sensory  areas"  (Fii/il>p/iare).  i.  <■.,  they  serve  as  centres  for  the  tactile  and 
muscular  sensations  and  those  of  the  innervation  of  the  opposite  side.  He  asserts  that  after  injury 
to  these  regions  the  corresponding  functions  are  affected. 

According  to  Bechterew,  the  centres  for  the  perception  of  tactile  impressions,  those  of  innerva- 
tion, of  the  muscular  sense,  and  painful  impressions  are  placed  in  the  neighborhood  of  the  motor 
areas  (dog)  ;  the  first  immediately  behind  and  external  to  the  motor  areas,  the  others  in  the  region 
close  to  the  origin  of  the  Sylvian  fissure.     [So  far  this  agrees  with  the  views  of  Starr  1  p.  719).] 

Goltz,  who  first  accurately  described  the  disturbances  uf  vision  following  upon  injuries  to  the 
cortex  in  dogs,  is  opposed  to  the  view  of  sensory  locahzation.  He  believes  that  each  eye  is  con- 
nected with  both  hemispheres.  He  asserts  that  the  disturbance  of  vision,  after  injury  to  the  brain, 
consists  merely  in  a  diminished  color  and  space  sense.  The  recovery  of  the  visual  perception  of 
one  eye  after  injury  of  one  side  of  the  cortex  cerebri  he  explains  by  supposing  that  this  injury 
merely  causes  a  temporary  inhibition  of  the  visual  activity  in  the  opposite  eye,  which  disappears  at 
a  later  period.  Instead  of  psychical  blindness  and  deafness  he  speaks  of  a  "  cerebro-optical  "  and 
"  cerebio-acoustical  weakness." 

377.  THE  THERMAL  CORTICAL  CENTRES.— A.  Eulenberg  and  Landois  dis- 
covered an  area  on  the  cortex  cerebri  whose  stimulation  produced  an  undoubted  effect  upon  the 
temperature  and  condition  of  the  blood  vessels  of  the  opposite  extremities.  This  region  (Fig.  428, 
I,  /),  generally  embraces  the  area,  in  which  at  the  same  lime  the  motor  centres  for  the  flexors  and 
rotators  of  the  fore  Umb  (3),  and  for  the  muscles  of  the  hind  hmb  (4)  are  placed.  The  areas  for 
the  anterior  and  posterior  limbs  are  placed  apart,  that  for  the  anterior  limb  lies  somewhat  more  ante- 
riorly, close  to  the  lateral  end  of  the  crucial  salens.  Destruction  of  this  region  causes  increase  of 
the  temperature  of  the  opposite  extremities;  the  temperature  may  vary  considerably  (1.5°  to  2°, 
and  even  to  13  °C.).  This  result  has  been  confirmed  by  Hitzig,  Bechterew,  Wood  and  others. 
This  rise  of  the  temperature  is  usually  present  for  a  considerable  time  after  the  injury,  although  it 
may  then  undergo  variations.  Sometimes  it  may  last  three  months,  in  other  cases  it  gradually 
reaches  the  normal  in  two  or  three  days.  In  well-marked  cases  there  is  a  diminution  of  the  resist- 
ance of  the  wall  of  the  femoral   artery  to  pressure,  and  the  pulse  curve  is  not  so  high  (Jieinke). 


TOPOGRAPHY  OF  THE  CORTEX  CEREBRI.  725 

Local  electrical  stimulation  of  the  area  causes  a  slight  temporary  cooling  of  the  opposite  extremi- 
ties, which  may  be  detected  by  the  thermo-electric  method.  Stimulation  by  means  of  common  salt 
acts  in  the  same  way,  but  in  this  case  the  phenomena  of  destruction  of  the  centre  soon  appear.  As 
yet  it  has  not  been  proved  that  there  is  a  similar  area  for  each  half  of  the  head.  The  cerebro-epileptic 
attacks  (?  37s )  increase  the  bodily  temperature,  partly  owing  to  the  increased  production  of  heat  by 
the  muscles  (^  302),  partly  owing  to  diminished  radiation  of  heat  through  the  cutaneous  vessels,  in 
consequence  of  stimulation  of  the  thermal  cortical  nerves.  The  experiments  led  to  no  definite 
results  when  perfonned  on  rabbits.  .According  to  Wood,  destruction  of  these  centres  occasions  an 
increased  production  of  heat  that  can  be  measured  by  calorimetric  methods,  while  stimulation 
causes  the  opposite  result. 

These  experiments  explain  how  psychical  stimulation  of  the  cerebrum  may  have  an  effect  upon  the 
diameter  of  the  blood  vessels  and  on  the  temperature,  as  evidenced  by  sudden  paleness  and  con- 
gestion (?  -,7S,  III). 

[Heat  Production. — Injury  to  the  fore-brain  has  no  effect  on  the  temperature.  If  the  brain  of 
a  rabbit  be  punctured  through  the  large  fontanelle  and  the  stylette  be  forced  through  the  gray 
matter  on  the  surface,  white  matter,  and  the  median  portion  of  the  corpus  striatum  right  to  the  base 
of  the  brain,  there  is  a  rapid  rise  of  the  temperature  which  may  last  several  days.  Injury  to  the 
gray  cortex  does  not  affect  the  temperature.  After  puncture  of  the  corpus  striatum  the  highest  tem- 
perature is  reached  only  after  twenty-four  to  seventy  hours,  but  when  the  puncture  reaches  the  base 
of  the  brain  this  result  occurs  in  two  to  four  hours.  Electrical  stimulation  of  these  areas  causes  the 
same  effect  on  the  temperature.  Direct  injury  to  certain  parts  of  the  brain  is  followed  by  a  rise  of 
the  temperature — or  fever.  There  is  at  the  same  time  an  increase  of  the  O  taken  in,  the  CO,  given 
off  and  a  decided  increase  of  the  N  given  off,  indicating  an  increase  in  the  proteid  metabolism, 
which  points  to  an  increased  production  of  heat  (Aronsohn  and  Sachs,  Richet,  Wood).'\ 

General  and  Theoretical. — Goltz's  View. — Goltz  uses  a  different  method  to  remove  the  cortex 
cerebri — he  makes  an  opening  in  the  skuil  of  a  dog,  and  by  means  of  a  stream  of  water  washes 
away  the  desired  amount  of  brain  matter.  He  describes,  first  of  all,  inhibitory  phenomena, 
which  are  temporary  and  due  to  a  temporary  suppression  of  the  activity  of  the  ner\ous  apparatus, 
which,  however,  is  not  injured  anatomically,  but  may  be  explained  in  the  same  way  as  the  suppres- 
sion of  reflexes  by  strong  stimulation  of  sensory  nerves  (\  361,  3).  In  addition,  there  are  the  per- 
manent phenomena,  due  to  the  disappearance  of  the  activity  of  the  nervous  apparatus,  which  is 
removed  by  the  operation.  A  dog  witli  a  large  mass  of  its  cerebral  cortex  removed  may  be  com 
pared  to  an  eating  complex  reflex  machine.  It  behaves  like  an  intensely  stupid  dog,  walks  slowly, 
with  its  head  hanging  down  ;  its  cutaneous  sensibility  is  diminished  in  all  its  qualities — it  is  less  sen- 
sitive to  pressure  on  the  skin ;  it  takes  less  cognizance  of  variations  of  temperature,  and  does  not 
comprehend  how  to  feel ;  it  can  with  difficulty  accommodate  itself  to  the  outer  world,  especially 
with  regard  to  seeking  out  and  taking  its  food.  On  the  other  hand,  there  is  no  paralysis  of  its 
muscles.  The  dog  still  sees,  but  it  does  not  understand  what  it  does  see ;  it  looks  like  a  somnam- 
bulist, who  avoids  obstacles  without  obtaining  a  clear  perception  of  their  nature.  It  hears,  as  it 
can  be  wakened  from  sleep  by  a  call,  but  it  hears  like  a  person  just  wakened  from  a  deep  sleep  by 
a  voice — such  a  person  does  not  at  once  obtain  a  distinct  perception  of  the  sound.  The  same  is  the 
case  with  the  other  senses.  It  howls  from  hunger,  and  eats  until  its  stomach  is  filled  ;  it  manifests 
no  symptoms  of  sexual  excitement. 

With  regard  to  the  localization  of  the  different  centres  in  the  cerebrum,  Goltz  obtained  the  fol- 
lowing results  :  He  finds  that  a  dog  with  both  parietal  lobes  destroyed  has  its  sensibility  perma- 
nently blunted,  its  intelligence  diminished,  and  is  vicious ;  while  when  both  occipital  lobes  are 
destroyed  there  is  severe  and  permanent  disturbance  of  vision.  He  supposes  that  every  part  of  the 
brain  is  concerned  in  the  functions  of  willing,  feeling,  perception  and  thinking.  Every  section  is, 
independently  of  the  others,  connected  by  conductions  with  all  the  voluntary  muscles,  and  on  the 
other  hand  with  all  the  sensory  ner^'es  of  the  body.  He  regards  it  as  possible  that  the  individual 
lobes  have  different  functions. 

Inhibitory  Phenomena. — Injury  to  the  brain  also  causes  inhibitor)'  phenomena,  such  as  the  dis- 
turbances of  motion,  the  complete  hemiplegia  which  is  frequently  observed  after  large  unilateral 
injuries  of  the  cortex  cerebri ;  these  are  regarded  by  Goltz  as  inhibitory  phenomena  due  to  the 
injury  acting  on  lower  infra-cortical  centres  whose  action  inhibits  movement,  but  these  movements 
are  recovered  as  soon  as  the  inhibitory  action  ceases. 

378.  PHYSIOLOGICAL  TOPOGRAPHY  OF  THE  HUMAN 
CORTEX  CEREBRI. — We  accept  the  arrangement  of  convolutions  accord- 
ing to  Ecker,  of  which  a  short  resume  is  given  in  §  375. 

I.  The  cortical  motor  regions  for  the  face  and  the  limbs  are  grouped  around 
the  fissure  of  Rolando,  including  the  ascending  frontal,  ascending  parietal,  and 
part  of  the  parietal  lobule  (Fig.  431 ).  The  centre  for  the  face  occupies  the  low- 
est third  of  the  ascending  frontal  convolution  and  reaches  also  on  the  lowest  fifth 
of  the  ascending  parietal.  The  arm  centre  occupies  the  middle  third  of  the 
ascending  frontal  and  middle  three-fifths  of  the  ascending  parietal  convolutions, 


726 


HEMIPLEGIA. 


while  the  leg  centre  lies  at  the  upper  end  of  the  sulcus  and  extends  backward  into 
the  parietal  lobule  (and  perhaps  on  to  the  superior  frontal  convolution")  (Fig.  431). 
This  leg  centre  is  continued  over  on  to  the  paracentral  lobule  opposite  the  upper 
end  of  the  fissure  of  Rolando  in  the  marginal  convolution  on  the  mesial  aspect 
of  the  hemisphere  (Fig.  433)  where  the  centres  for  the  muscles  of  the  trunk  also 
exist  (p.  719).  The  centre  for  speech  is  in  the  posterior  part  of  the  third  left 
frontal  convolution  (Fig.  431). 

Blood  Supply. — These  convolutions  are  supplied  with  blood  from  four  to  five  branches  of  the  Syl- 
vian artery,  which  may  sometimes  be  plugged  with  an  embolon.  When  a  clot  lodges  in  this  artery, 
the  branches  to  the  basal  ganglia  may  remain  pervious,  while  the  cortical  branches  may  be  plugged 
[Dure/,  Heubney)  {\  381). 

[Hemiplegia  consists  of  motor  paralysis  of  one-half  of  the  body,  although,  as 
a  rule,  all  the  muscles  are  not  paralyzed  to  the  same  extent  ;  in  some  there  may  be 


Fio.  433. 


tion  of  the  cerebral  hemisphere.  CC.i.  corpus  callosum  ;  NC,  caudate  nucleus;  NL,  lenticular  nu- 
cleus; IC,  internal  capsule;  CA.  internal  carotid  artery;  rtSL.  lenticular-striate  artery  ("Artery  of  hemor- 
rhaee  ") ;  F.  A,  L,  T,  position  of  motor  areas  governing  the  movements  of  the  face,  arm,  leg,  and  trunk  muscles 
of  the  opposite  side  {Horsley), 

complete  paralysis,  /'.  e.,  they  are  entirely  removed  from  voluntary  control,  while 
in  others  there  is  merely  impaired  voltmtary  control.  It  may  be  caused  by  affec- 
tions of  the  cortical  centres  or  by  lesion  of  the  motor  tracts  above  the  medtilla, 
and  the  ]jaralysis  is  always  on  the  side  opposite  to  the  lesion  owing  to  the  decussa- 
tion of  the  motor  paths  in  the  medulla.  If  the  case  be  a  severe  one,  we  have 
what  Ciiarcot  terms  haniplegie  centrale  vulgaire,  or  "complete  hemiplegia,"  due 
to  lesion  of  the  cortical  centres  for  the  face,  arm,  and  leg.  While  the  arm  and 
leg  are  completely  paralyzed,  tlie  lower  part  of  the  face  is  more  affected  than  the 
upper  half,  which  is  usually  not  much  affected.  All  those  movements  under  vol- 
untary control,  and  especially  those  that  have  been  learned,  are  abolished,  while 
the  associated  and  bilateral  movements,  which  even  animals  can  execute  imme- 
diately after  birth,  remain  more  or  less  unaffected.  Hence  the  hand  is  more  par- 
alyzed than  the  arm  ;   this,  again,  than  the  leg  ;  the  lower   facial  branches  more 


POSITION    OF   THE    MOTOR    CENTRES.  727 

than  the  upper  ;  the  nerves  of  the  trunk  scarcely  at  all  {Ferrier).  When  an  ex- 
traordinary effort  is  made,  it  will  be  found  that  there  is  some  impairment  of  the 
power  of  the  muscles  of  mastication  and  respiration,  although  the  muscles  on 
o|)posite  sides  act  together  { Cowers).  The  trunk  muscles,  as  a  rule,  are  but 
slightly  affected,  or  not  at  all,  as  their  centre  is  elsewhere.  There  may  be  altera- 
tions of  sensibility  and  of  the  reflexes.] 

Conjugate  deviation  of  the  eyes  with  rotation  of  the  head  is  frequently  present  in  tlie  early 
period  of  hemiplegia,  although  it  usually  disappears.  When  a  person  turns  his  head  to  one  side, 
there  is  an  .associated  movement  of  certain  of  the  ocular  muscles  with  those  of  the  neck.  The 
head  and  eyes  are  usually  turned  to  the  side  of  the  lesion  ;  this  is  termed  "  conjugate  deviation," 
so  that  the  power  of  voluntarily  moving  the  eyes  and  head  to  the  paralyzed  side  is  temporarily  lost. 
The  unopposed  muscles  rotate  the  head  and  eyes  to  the  sound  side.  If  the  lesion  be  in  the  pos- 
terior part  of  the  pons,  the  deviation  is  to  the  paralyzed  side  (Pih'ost). 

[Subsequent  Effects, — If  there  be  say  a  hemorrhage  into  these  motor  regions,  or  from  the 
leniiculo-striate  artery,  so  as  to  compress  the  pyramidal  fibres  in  the  knee  and  anterior  two-thirds 
of  posterior  segment  of  the  internal  capsule,  then  there  is  usually  tonic  or  persistent  contraction  of 
the  muscles  affected.  These  tonic  spasms  may  accompany  the  hemorrhage,  or  come  on  a  few  days 
after  it  and  make  up  the  condition  of  early  rigidity.  The  contraction — if  any — accompanying  the 
hemorrhage  is  due  to  direct  irritation  of  the  pyramidal  fibres,  while  that  which  comes  on  a  few  days 
later,  and  usually  lasts  a  few  weeks,  is  also  due  to  irritation  of  these  fibres,  probably  produced  by 
inflammatory  action  in  and  around  the  seat  of  the  lesion.  The  affected  limb  is  stiff  and  resists 
passive  movement.  After  a  few  weeks,  late  rigidity  sets  in  and  is  persistent,  and  it  is  characterized 
by  structural  changes  in  the  pyramidal  paths  which  lead  to  other  results.  There  is  secondary  de- 
scending degeneration  in  the  pyramidal  tracts,  which  cause  "contracture"  {Charcot)  \n  {he 
paial/zed  limbs,  while  at  the  same  time  the  deep  or  tendinous  and  periosteal  reflexes  (ankle  clonus, 
rectus  clonus,  and  the  deep  reflexes  of  the  arm  tendons,  are  exaggerated).  The  spastic  rigidity  is 
usually  more  marked  in  the  arm  than  leg,  and  it  generally  affects  the  flexors  more  than  the  extensors, 
so  tlial  the  upper  arm  is  drawn  close  to  the  trunk,  the  elbow,  arm,  and  fingers  flexed  ;  in  the  leg 
the  extensors  of  the  leg  overcome  the  peronei.  Hitzig  has  pointed  out  that  the  contracture  is  less 
during  sleep  and  after  rest.  The  muscles  at  first  can  be  stretched  by  sustained  pressure,  but  after 
months  or  years  structural  changes  occur  in  the  muscles,  ligaments,  and  tendons,  and  the  limbs 
assume  a  permanent  and  characteristic  attitude.] 

In  hemiplegic  pfersons,  the  power  of  the  unparalyzed  side  is  sometimes  diminished  (Brown- 
Sequard,  Charcot,  Pitrcs],  which  is  not  sufficiently  explained  by  the  fact  that  some  bundles  of  the 
pyramidal  tracts  remain  on  the  snmf  side. 

Acquired  Movements. — Some  movements  performed  by  man  are  learned  only  after  much 
practice,  and  are  only  completely  brought  under  the  influence  of  the  will  after  a  time,  such  as  the 
movements  of  the  hand  in  learning  a  trade.  Such  movements  are  reacquired  only  very  slowly,  or 
not  at  all,  after  injury  to  the  psychomotor  centres.  Those  movements,  however,  which  the  body 
performs  without  previous  training,  such  as  the  associated  movements  of  the  eyeballs,  the  face,  and 
some  of  those  of  the  legs,  are  rapidly  recovered  after  such  an  injury,  or  they  suft'er  but  little,  if  at 
all.  Thus  the  facial  muscles  seem  never  to  be  so  completely  paralyzed  after  a  lesion  of  the  facial 
cortical  centre,  as  in  aff'ections  of  the  trunk  of  the  facial  nerve  the  eye  especially  can  be  closed. 
Sucking  movements  have  been  observed  in  hemicephalous  fcetuses. 

Degeneration  of  the  Pyramidal  Tracts. — After  destruction  of  the  cortical 
motor  areas,  descending  degeneration  of  the  cortico- motor  paths,  or  "pyramidal 
tracts,"  takes  place  (§  365).  Degenerative  changes  have  been  found  to  occur 
within  the  white  matter  under  the  cortex,  in  the  anterior  two-thirds  of  posterior 
segment  of  the  internal  capsule  [in  the  middle  third  of  the  crusta  (Figs.  434.* 
435 1  I']>  pons,  in  the  pyramids  of  the  medulla  oblongata  (Fig.  434),  and  thence 
they  have  been  traced  into  the  pyramidal  paths  (anterior  and  lateral )  of  the  spinal 
cord  {Charcot,  Singer,  M.  Rosenthal).  It  is  evident  that  lesions  of  these  tracts  at 
any  part  of  their  course  must  have  the  same  result,  viz.,  to  produce  hemiplegia. 
(For  the  subsequent  eflTects,  see  p.  660. )  In  a  case  of  congenital  absence  of  the 
left  fore  arm,  Edinger  found  that  the  right  central  convolutions  were  developed. 

Ataxic  motor  conditions  similar  to  those  that  occur  in  animals  (p.  721)  take  place  in  man,  and 
are  known  as  cerebral  ataxia. 

The  Position  of  the  Centres  is  given  at  p.  718. 

[But  we  may  have  localized  lesions  affecting  one  or  more  of  the  cortical 
motor  areas  ;  these  are  called  Monoplegiae.     Cases  in  man  are  now  sufficiently 


728 


POSITION    OF   THE    MOTOR    CENTRES. 


numerous  to  permit  of  accurate  diagnosis.]  Crural  [rare  lesions  recorded  in  the 
convolutions  at  the  upper  end  of  the  fissure  of  Rolando,  and  the  continuation  of 
this  area  on  to  the  paracentral  lobule  of  the  marginal  convolution], — brachio- 
crural,  more  common,  upper  and  middle  thirds  of  the  ascending  frontal  and 
ascending  parietal  convolutions — brachial,  brachio-facial — facial,  the  last  in 
the  lowest  part  of  the  central  convolutions. 

[Convulsions  and  spasms  may  be  discharged  from  motor  cortical  lesions,  and 
these,  whether  they  affect  the  general  or  localized  areas,  give  rise  to  unilateral 
convolutions  and  monospasms  respectively.] 

Paralysis  of  the  muscles  of  the  neck  and  throat  indicates  a  lesion  of  the  central  convolutions,  and 
so  does  paralysis  of  the  muscles  of  the  eye.  Lesions  of  the  cortex  always  cause  simultaneous  move- 
ments of  the  head  and  eyeballs 

Irritation  of  the  Motor  Centres. — If  the  motor  centres  are  irritated  by 
pathological  processes,  such  as  hyperaemia,  or  inflammation,  in  a  syphilitic  dia- 


Fic.  434 


Fig.  434- — Secondary  descending  generation  in  middle  third  of  right  cni-i  and  in  medulla  after  destruction  of  the 
cortical  motor  centres  on  the  right  side.  FiG.  4S5- — Horizontal  section  of  the  cerebral  peduncle  in  secondary 
degenemtion  of  the  pyramidal  tracts,  where  the  lesion  w.a.s  limited  to  the  middle  third  of  the  posterior  segment 
oi  the  internal  capsule.  F,  healthy  cnista  :  L,  locus  niger ;  P.  internal  third  of  the  crusta  on  the  diseased  side  ; 
D,  secondary  degeneration  in  the  middle  third  ol  the  crusta ;  CQ,  corpora  quadrigemina  with  the  iter  below  them. 


thesis — more  rarely  by  tumors,  tubercle,  cysts,  cicatrices,  fragments  of  bone — 
there  arise  spasmodic  movements  in  the  corresponding  muscle  groups.  This  con- 
dition of  a  sudden  discharge  of  the  gray  matter  resulting  in  local  spasms  is  called 
"  Jacksonian  or  cerebral  epilepsy." 

Monospasm. — .A.ccording  to  the  seat  of  the  spasm,  it  is  called  facial,  brachial,  crural,  mono- 
spasm, ere.  C)f  course,  these  spasms  may  afi'ect  several  groups  of  muscles.  Barlholow  and  Scia- 
manna  have  stimulated  the  exposed  human  brain  successfully  with  electricity. 

Cerebral  Epilepsy. — Very  powerful  stimulation  of  one  side  may  give  rise  to 
(^//rt/f-n?/ spasms,  with  loss  of  consciousness.  In  this  case  impulses  are  conducted 
to  the  other  hemisphere  by  commissural  fibres  (§  379). 

Movements  of  the  Eye. — Nothing  definite  is  known  regarding  the  centre  in  the  cortex  for 
voluntary  combined  movements  of  the  eyeballs  in  man.  In  paralytic  affections  of  the  cortex  and  of 
the  paths  proceeding  from  it,  we  occasionally  find  both  eyes  with  a  lateral  deviation.  If  the  par- 
alytic affection  lies  in  one  cerebral  hemisphere,  the  conjugate  deviation  of  the  eyeballs  is  toward 


APHASIA.  729 

the  sound  side  (p.  620).     If  it  is  situated  in  the  conducting  paths,  after  these  have  decussated,  viz., 
in  the  pons,  the  eyes  are  turned  toward  the  paralyzed  side  (Prhwst). 

If  the  part  be  irritated  so  as  to  produce  spasms  in  the  opposite  half  of  the  body,  of  course  the 
eyes  are  turned  in  the  opposite  direction  to  that  in  pure  paralysis  (Landouzy  ami  Grassel).  Instead 
of  the  lateral  deviation  of  the  eyeballs  already  described,  occasionally  in  cerebral  paralysis  there  is 
merely  a  weakenitvj  of  the  lateral  recti  muscles,  so  that  during  rest  the  eyes  are  not  yet  turned 
toward  the  sound  side,  but  they  cannot  be  turned  strongly  toward  the  affected  side  (Leichtenstern, 
Httnnius).  The  centre  for  the  levator  palpebrfe  superioris  appears  to  be  placed  in  the  gyrus  angu- 
laris  {^Grasset,  Londonzy^  Chauffard'). 

II.  The  Centre  for  Speech. — The  investigations  of  Bouilland  [1825],  Dax 
[1836],  Broca  [1861],  Kussmaul,  and  Broadbent  and  others  have  shown  that  the 
third  left  frontal  convolution  of  the  cerebrum  (Figs.  429,  F,  3,  and  431)  is 
of  essential  iinportance  for  speech,  while  probably,  also,  the  insula,  or  island  of 
Reil,  is  concerned.  It  is  seen  to  be  deeply  placed  on  lifting  up  the  overhanging 
part  of  the  brain  called  the  operculum,  lying  between  the  two  branches  of  the 
Sylvian  fissure  (S).  The  motor  centres  for  the  organs  of  speech  (lips,  tongue)  lie 
in  this  region,  and  in  this  region  also  the  psychical  processes  in  the  act  of  speech 
are  com])leted.  In  the  great  majority  of  mankind  the  centre  for  speech  is  located 
in  the  left  hemisphere.  The  fact  that  most  men  are  righf-hmtded  also  points  to  a 
finer  construction  of  the  motor  apparatus  for  the  upper  extremity,  which  must  also 
be  located  in  the  left  hemisphere.  Men,  therefore,  with  pronounced  i-ight-handed- 
;/«.f  (droitiers)  are  evidently /if/Z-Z^ra/^^;/ (gauchers  du  cerveau — Broca).  By  far 
the  greater  number  of  mankind  are  "lift-brained  speakers"  (Kussmaul)  ;  still 
there  are  exceptions.  As  a  matter  of  fact,  cases  of  left-handed  persons  have  been 
observed  who  lost  their  power  of  speech  after  a  lesion  of  the  right  hemisphere 
(  Ogle,  Hahershon).  Investigations  on  the  brains  of  remarkable  men  have  shown 
that  in  them  the  third  frontal  convolution  is  more  extensive  and  more  complex 
than  in  men  of  a  lower  mental  calibre.  In  deaf  mutes  it  is  very  simple  ;  inicro- 
cejjhales  and  monkeys  possess  only  a  rudimentary  third  frontal  (Rudinger). 

The  motor  tracts  for  speech  pass  along  the  upper  edge  of  the  island  of  Reil,  then  into  the  sub- 
stance of  the  hemispheres  internal  to  the  posterior  edge  of  the  knee  of  the  internal  capsule;  from 
thence  through  the  crusta  of  the  left  cerebral  peduncle  into  the  left  half  of  the  pons,  where  it  crosses, 
then  into  the  medulla  oblongata,  which  is  the  place  where  all  the  motor  nerves  (trigeminus,  facial, 
hypoglossal,  vagus,  and  respiratory  nerves)  concerned  in  speech  arise.  Total  destruction  of  these 
paths,  therefore,  causes  total  aphasia;  while  partial  destruction  causes  a  greater  or  less  disturbance 
of  the  mechanism  of  articulation,  which  has  been  called  "  anarthria  "  by  Leyden  and  Wernicke. 

Conditions. — Three  activities  are  required  for  speech — ^(i)  the  normal  move- 
ment of  the  vocal  apparatus  (tongue,  lips,  mouth,  and  respiratory  apparatus)  ;  (2) 
a  knowledge  of  the  signs  for  objects  and  ideas  (oral,  written,  or  imitative  or  mi- 
metic signs)  ;  (3)  the  correct  union  of  both. 

Aphasia. — Injury  of  the  speech  centre  causes  either  a  loss  or  more  or  less  con- 
siderable disturbance  of  the  power  of  speech.  The  less  of  the  ]:)ower  of  speech  is 
called  "aphasia."  [Aphasia,  as  usually  understood,  means  the  partial  or  com- 
plete loss  of  the  power  of  articulate  speech  from  cerebral  causes.] 

The  following  forms  of  aphasia  may  be  distinguished  : — 

1.  Ataxic  aphasia  for  the  oro-lingua!  heniiparesis  of  Ferrier),  i.e.,  the  loss  of  speech,  owing  to 
inability  to  execute  the  various  movements  of  the  mouth  necessary  for  speech.  Whenever  such  a 
person  attempts  to  speak,  he  merely  executes  incoordinated  grimaces  and  utters  inarticulate  sounds. 
[The  muscles  concerned  in  articulation,  however,  are  not  paralyzed,  but  there  is  an  absence  of  co- 
ordination of  these  muscles  due  to  disease  of  the  cortical  centre.]  Hence,  the  patient  cannot  repeat 
what  is  said  to  him.  Nevertheless,  the /jrj/(-/;/<-«/ processes  necessary  for  speech  are  comiiletely  re- 
tained, and  all  words  are  remembered  ;  and  hence  ihese  persons  can  still  give  expression  to  their 
thoughts  graphically  or  by  wnfing.  If,  however,  the  finely  adjusted  movements  necessary  for  writ- 
ing are  lost,  owing  to  an  affection  of  the  centre  of  the  hand,  then  there  arises  at  the  same  lime  the 
condition  of  agraphia,  or  inability  to  execute  those  movements  necessary  for  writing.  Such  a  per- 
son, when  he  desires  to  express  his  ideas  in  writing,  only  succeeds  in  making  a  few  unintelligible 
scrawls  on  the  paper.  Occasionally  such  patients  suffer  from  loss  of  the  power  of  imitation  or 
aminia  ( A'lissmaiil). 

2.  Amnesic  Aphasia,  or  Loss  of  the  Memory  of  Words. — Should  the  patient,  however,  hear  the 


730  APHASIA. 

word,  its  significance  recurs  to  him.  The  movements  necessary  for  speech  remain  intact ;  hence 
such  a  patient  can  at  once  repeat  or  write  down  what  is  said  to  him.  Sometimes  only  certain  kinds 
of  words  are  forgotten,  or  it  may  be  even  only  parts  of  these  words  are  spoken;  [Nouns  and  proper 
names  usually  go  first.]  Cases  of  amnesic  aphasia,  or  the  mixed  ataxic-amncsic  form  of  disturbance 
of  speech,  point  to  a  lesion  of  the  third  frontal  convolution  and  of  the  island  of  Reil  on  the  left  side. 
Another  form  of  amnesic  aphasia  consists  in  this,  that  the  words  remain  in  one's  memory  but  do  not 
come  when  they  are  wanted,  j.e.^  the  association  between  the  idea  and  the  proper  word  to  give  ex- 
pression to  it  is  inhibited  (A'ussmaul).  It  is  common  for  old  people  to  forget  the  names  of  persons 
or  proper  names ;  indeed,  such  a  phenomenon  is  common  within  physiological  limits,  and  it  may 
ultimately  pass  into  the  pathological  condition  of  amnesia  senilis.  Among  the  disturbances  of 
speech  o{  cere/irnl  or\g\n,  Kussmaul  reckons  the  following: — 

3.  Paraphasia,  or  the  inability  to  connect  rightly  the  ideas  with  the  proper  words  to  express 
these  ideas,  so  that,  instead  of  giving  expression  to  the  proper  ideas,  the  sense  may  be  inverted,  or 
the  form  of  words  may  be  unintelligible.  It  is  as  if  the  person  were  continually  making  a  "  slip  of 
the  tongue." 

4.  Agrammatism  and  ataxaphasia,  or  the  inability  to  form  the  words  grammatically  and  to  ar- 
range them  synthetically  into  sentences.      Besides  these,  there  is — 

5.  A  pathological  slow  way  of  speaking  (bradyphasia),  or  a  pathological  and  stuttering  way  of 
reading  (tumultus  sermonis),  both  conditions  being  due  to  derangement  of  the  cortex  {A'liss- 
mail/).  The  disturbance  of  speech  depending  essentially  upon  affections  of  \.ht peripheral  r\er\ei, 
or  of  the  muscles  of  the  organs  of  the  voice  and  speech,  are  already  referred  to  in  J§  319,  349,  and 
354- 

[In  word-blindness  the  person  cannot  name  a  letter  or  a  word,  so  that  he 

Fig.  436.  Fig.  437. 


Figs.  436,  437.— Schemes  of  aph.isi.i.     A,  centre    or  auditory  images:  M,   or  mo 
Oc.  eye  :   E,  reading  centre;  j  to  7  lesions  {Licktfte 

cannot  understand  symbols,  such  as  printed  or  written  words,  or  it  may  be  any 
familiar  object,  although  he  can  see  quite  well,  while  he  can  speak  fluently  and 
write  correctly.] 

[In  word-deafness  the  person  hears  other  sounds  and  is  not  deaf,  but  he  does 
not  hear  words.] 

[The  study  of  aphasia  in  its  various  forms  is  simplified  by  a  study  of  the  mode  of  acquisition  of 
language  by  a  child.  The  child  hears  spoken  words  and  obtains  auditory  memories  or  impressions 
of  these  sounds  (called  by  Lichtheim  "  auditory  word-representations  "),  and  this  must  form 
the  starling-point  of  language,  and  by  and  by  it  begins  to  coordinate  its  muscles  to  produce  sounds 
imitative  of  these.  Thus  we  have  two  centres,  one  for  "  auditory  images  "  (Fig.  436,  A),  and  the 
other  for  "  motor  images  "  (Fig.  436,  M),  and  these  two  must  be  connected,  thus  establishing  a 
reflex  arc.  There  is  a  receptive  and  an  emissive  department  as  represented  in  the  scheme.  We 
must  assume  the  existence  of  a  higher  centre  (B),  "  where  conceps  are  elaborated,"  where  these 
sounds  become  intelligible.  Volitional  language  requires  a  connection  between  B  and  M,  as  well 
as  between  A  and  M.  But  we  have  also  reading  and  writing.  Suppose  O  to  represent  a  centre 
for  visual  impressions  (printed  words  or  writing),  which  we  can  understand  through  the  connection 
between  such  visual  impressions  and  auditory  impressions,  whereby  a  path  is  established  through 
OA  (Fig.  437).  In  reading  aloud,  however,  the  oro-lingual  muscles  must  be  coordinated,  so  we 
have  the  path  OAM  opened  up.  In  writing  or  copying  written  characters,  the  movements  of  the 
hand  are  special,  and  perhaps  require  a  special  centre,  or  at  least  a  special  arrangement  of  the  chan- 
nels for  impulses  in  the  centre ;  the  movements  are  learned  under  the  guidance  of  ocular  impres- 


THERMAL   AND    SENSORY    CORTICAL    CENTRES.  731 

sions,  so  we  connect  O  and  E,  E  being  the  centre  guiding  the  movements  in  writing.  As  to 
volitional  writing  the  impulses  pass  through  M,  but  does  it  pass  directly  to  E,  or  indirectly  through 
A  ?  Lichtheim  assumes  that  it  goes  direct  from  M  to  E.  It  is  evident  that  there  are  seven  chan- 
nels which  may  be  interrupted,  each  one  giving  rise  to  a  dilTcrent  form  of  aphasia  (i  to  7).] 

[Looked  at  from  another  point  of  view,  either  the  ingoing  («)  or  outgoing  («)  channels  or  cen- 
tres, or  the  commissural  fibres  between  both,  may  be  affected.  If  the  motor  centre  is  affected,  we 
have  Wernicke's  "  motor  aphasia  ;  "  if  the  sensory,  his  "  sensorial  aphasia."] 

[In  the  most  common  form,  or  ataxic  aphasia  (A'ussmniil),  which  was  that  described  by  Broca, 
or  the  "  motor  aphasia"  of  Wernicke,  the  lesion  is  in  Fig.  436,  in  M,  i.  <■.,  in  the  motor,  or  what 
Ross  calls  the  emissive  department.  In  such  a  case  it  is  obvious  that  there  will  be  loss  of  (i)  volitional 
speech,  {2)  repetition  of  words,  (3)  reading  aloud,  (4)  volitional  writing,  and  (5)  writing  to  dicta- 
tion;  while  there  will  exist  [a)  understanding  of  spoken  words,  (1^)  also  of  written  words,  (c)  and 
the  faculty  of  copying.  If  the  lesion  be  in  A,  we  have  the  "  sensorial  aphasia"  of  Wernicke,  i.  e., 
in  the  acoustic  word  centre;  we  find  loss  of  (i)  understanding  of  spoken  language,  (2)  also  of 
written  language.  (3)  faculty  of  repeating  words,  (4)  and  of  writing  to  dictation,  (5)  and  of  reading 
aloud  ;  there  will  exist  (a)  the  faculty  of  writing,  (/')  of  copying  words,  and  (c)  of  volitional 
speech,  but  the  volitional  speech  is  imperfect,  the  wrong  word  being  often  used,  so  that  there  is  the 
condition  of  "paraphasia."  If  the  connection  between  A  and  M  be  destroyed,  other  results  will 
follow,  and  such  cases  of  "  commissural  "  aphasia  have  been  described  by  W'ernicke.  If  the  inter- 
ruption be  between  B  and  M  we  have  a  not  uncommon  variety  of  motor  aphasia  (4),  where  there 
is  loss  of  (i)  volitional  speech,  and  (2)  volitional  writing,  and  there  exist  (a)  understanding  of 
spoken  language,  (b)  of  written  language,  (c)  the  faculty  of  copying;  but  it  differs  from  Broca's 
aphasia  in  that  there  also  exists  [li)  the  faculty  of  repeating  words,  (<■)  writing  to  dictation,  (y),and 
reading  aloud.  If  the  lesion  is  in  Mm  (5)  the  symptoms  will  be  those  of  Broca's  aphasia,  but  there 
will  exist  (l)  the  faculty  of  volitional  writing,  and  (2)  of  writing  to  dictation.  Many  examples  of 
this  occur  where  patients  have  lost  the  faculty  of  speaking,  but  can  express  their  thoughts  in  writ- 
ing. In  lesions  of  the  path  AB  (6)  there  will  be  loss  of  (i)  understanding  of  spoken  language, 
and  (2)  of  written  language,  and  there  will  exist  (a)  volitional  speech  (but  it  will  be  paraphasic), 
(/>)  volitional  writing  (but  it  will  have  the  characters  of  paragraphia,  (c)  the  faculty  of  repeating 
words,  (d)  reading  aloud,  (c)  writing  to  dictation,  and  (f )  power  of  copying  words.  The  person 
will  be  quite  unable  to  understand  what  he  repeats,  reads  aloud,  or  copies.] 

III.  The  thermal  centre  of  Eulenberg  and  Landois  for  the  extremities  is  associated  with  the 
motor  areas.  Injury  or  degeneration  of  these  areas  causes  inequality  of  the  temperature  on  both 
sides  {^Bechtereri'Y  In  long-standing  paralysis  the  initially  high  temperature  of  the  affected  limb 
may  fall  lower  than  that  of  the  sound  limb  (§  377).  In  cases  of  insanity,  with  general  progressive 
paralysis,  due  to  inflammation  of  the  cortex  cerebri,  the  temperature  of  the  axilla  on  the  same  side 
is  usually  higher  on  the  side  which  is  the  seat  of  the  paralysis.  In  cases  of  conviihions,  due  to  in- 
flammatory irritation  of  the  cortex  cerebri,  during  the  attack  the  temperature  on  the  same  side  as 
the  centre  is  several  tenths  of  a  degree  higher  than  on  the  other  side  [J\einharJ), 

IV.  The  sensory  regions  are  those  areas  in  which  conscious  perceptions  of 
the  sensory  impressions  are  accomplished.  Perhaps  they  are  the  substratum  of 
sensory  perceptions,  and  of  the  memory  of  sensory  impressions. 

I.  The  psycho-optic  or  visual  centre,  according  to  'Munk,  Meynert,  and 
Huguenin,  includes  the  occipital  lobes  (Fig.  429,  o',  o',  o'j,  while  according  to 
E.vner  the  first  and  second  occipital  convolutions  are  its  chief  seats.  Huguenin 
observed,  in  a  case  of  long-standing  blindness,  consecutive  disappearance  of  the 
occipital  convolutions  on  both  sides  of  the  parieto-occipital  fissure,  while  Giova- 
nardi,  in  a  case  of  congenital  absence  of  the  eyes,  observed  atrophy  of  the  occi- 
pital lobes,  which  were  separated  by  a  deep  furrow  from  the  rest  of  the  brain. 
Stimulation  of  the  centre  gives  rise  to  the  phenomena  of  light  and  color.  Injury 
causes  disturbance  of  vision,  especially  hemiopia  of  the  same  side  (§  344 — 
U'cstphal,  Jastroiiiitz).  When  oz/f  centre  is  the  seat  of  irritation  there  is  pho- 
tojjsia  of  the  same  halves  of  both  eyes  {Charcot,  Pfinainf).  Stimulation  of  both 
centres  causes  the  occurrence  of  the  phenomena  of  light  or  color,  or  visual  hal- 
lucinations in  the  entire  field  of  vision.  Cases  of  injury  to  the  brain,  where  the 
sensations  of  light  and  space  are  quite  intact,  and  where  the  color  sense  alone  is 
abolished,  seem  to  indicate  that  the  color  sense  centre  must  be  specially  localized 
in  the  visual  centre  {Same/sohn,  Steffaii).  After  injury  of  certain  parts,  especially 
of  the  lower  parietal  lobe,  " psvihica/  />/hidn<'ss  "  may  occur.  A  special  form  of 
this  condition  is  known  as  "-word-blindness  "  or  alexia  (Coecitas  verbalis), 
which  consists  in  this,  that  the  jjatient  is  no  longer  able  to  recognize  ordinary 
written  or  printed  characters  (p.  730). 


lOZ 


THE  AUDITORY,  GUSTATORY  AND  OLFACTORY  CENTRES. 


Charcot  records  an  interesting  case  of  psychical  blindnes's.  After  a  violent  paroxysm  of  rage,  an 
intelligent  man  suddenly  lost  the  memory  of  visual  impressions;  all  objects  (persons,  streets,  houses) 
which  were  well  known  to  him  appearel  to  be  quite  strange,  so  that  he  did  not  even  recognize  him- 
self in  a  mirror.     Visual  perceptions  were  entirely  absent  from  his  dreams. 

Clinical  observations  on  hemiopia  (|  344)  show  that  the  field  of  vision  of  each  eye  is  divided 
into  a  larger  outer  and  a  smaller  inner  portion,  separated  from  each  other  by  a  vertical  line  passing 
throuiih  the  macula  lutea.  Each  right  or  left  half  of  both  visual  fields  is  related  to  one  hemisphere ; 
both  left  halves  are  projected  upon  the  left  occipital  lobes,  and  both  right  upon  the  right  occipital 
lobes.  Thus,  in  binocular  vision  every  picture  (when  not  too  small)  must  be  seen  in  two  halves; 
the  left  half  by  the  left,  the  right  half  by  the  right  hemisphere  (  Wernicke). 

As  a  result  of  pathological  stimulation  of  the  visual  centre,  especially  in  the  insane,  visual  spectres 
may  be  produced.     Pick  observed  a  case  where  the  hallucin.itions  were  confined  to  the  right  eye. 

2.  The  psycho-acoustic  or  auditory  centre  lies  on  both  sides  (crossed)  in 
the  temporo-sphenoidal  lobes ;  when  it  is  completely  removed  deafness  results, 
while  partial  (left  side)  injury  causes  psychical  deafness.  Among  the  phenomena 
caused  by  partial  injury  is  suniitas  verhalis  (word-deafness),  which  may  occur 

Fig.  438. 


Relation  of  the  fissures  and  convolutions  to  the  surface  of  the  scalp  +  Most  prominent  part  of  the  parietal  emi- 
nence :  rt,  convex  line  bounding  parietal  lobe  below ;  i,  convex  line  bounding  the  temporo-sphenoidal  lobe  behind 
{R.  W.  Reid). 

alone  or  in  conjunction  with  coecitas  verbalis.  Wernicke  found  in  all  cases  of 
word-deafness  softening  of  the  first  left  temporo-sphenoidal  convolution  (p.  730). 
In  left-handed  persons  the  centre  lies,  perhaps,  in  the  right  temporo-sphenoidal 
lobes  (  Westphal). 

Clinical. — We  may  refer  the  coecitas  and  suriiilns  verbalis  (Kussmaiil)  to  the  aphataxic  group 
of  diseases,  in  so  far  as  they  resemble  the  amnesic  form.  A  person  word-blind  or  word-deaf  resem- 
bles one  who,  in  early  youth,  has  learned  a  foreign  tongue,  which  he  has  completely  forgotten  at  a 
later  period.  He  hears  or  reads  the  words  and  written  characters;  he  can  even  repeat  or  write  the 
words,  but  he  has  completely  lost  the  significance  of  the  signs.  While  an  amnesic  aphasic  person 
has  only  lost  the  key  to  open  his  vocal  treasure,  in  a  person  who  is  word-blind  or  word-deaf  even 
this  is  gone.  From  a  case  of  recovery  it  is  known  that  to  the  patient  the  word  sounds  like  a  con- 
fused noise.     Huguenin  found  atrophy  of  the  temporo-sphenoidal  lobes  after  long-continued  deafness. 

3.  Gustatory  and  Olfactory  Centre. — In  the  uncinate  gyrus,  on  the  inner 
side  of  the  temporo-sphenoidal  lobe  (especially  on  the  inner  side  of  that  marked 


THE    BASAL    GANGLIA.  733 

U  in  Fig.  425),  Ferrier  locates  the  joint  centres  for  smell  and  taste.     These  two 
centres  do  not  seem  to  be  distinct  locally  from  each  other. 

4.  Tactile  Areas. — According  to  Tripier,  Exner,  Petrina,  and  others,  all  the 
tactile  cerebral  fields  from  different  parts  of  the  body  coincide  with  the  motor 
cortical  centres  for  these  parts. 

Occasionally,  in  epileptics,  strong  stimulation  of  the  sen^^ory  centres,  as  expressed  in  the  excessive 
subjective  sensations,  accompanies  the  spasmodic  attacks  (compare  \  393,  12).  .Such  epileptiform 
hallucinations,  however,  occur  without  sp.asms,  and  are  accompanied  only  by  disturbances  of  con- 
sciousness of  very  short  duration  (Bfrger). 

Course  of  the  Psycho-sensory  Paths. — The  nerve  fibres  which  conduct 
impulses  from  the  sensory  organs  to  the  sensory  cortical  centres,  pass  through 
the  posterior  third  of  the  posterior  limb  of  the  intestinal  capsule  between  the  optic 
thalamus  and  the  lenticular  nucleus  (Fig.  439,  S).  Hence  section  of  this  part  of 
the  internal  capsule  causes  hemiansesthesia  of  the  opposite  half  of  the  body 
(Charcot,  I'eyssiere,  Carville,  Duret).  In  such  a  case  sensory  functions  are  abol- 
ished— only  the  viscera  retaining  their  sensibility.  There  may  also  be  loss  of 
hearing  {Veller,  Donkin),  sinell  and  taste,  and  heiniopia  {Bechterew). 

In  cases  where  there  is  more  or  less  injury  or  degeneration  of  these  paths,  there  is  a  corresponding 
greater  or  less  pronounced  loss  of  the  pressure  and  temperature  sense,  of  the  cutaneous  and  muscular 
sensibility,  of  taste,  smell,  and  hearing.  The  eye  is  rarely  quite  blind,  but  the  sharpness  of  vision 
is  interfered  with,  the  field  of  vision  is  narrowed,  while  the  color  sense  may  be  partially  or  completely 
lost.     The  eye  on  the  same  side  may  suffer  to  a  slight  extent. 

V.  Numerous  cases  of  injury  of  the  anterior  frontal  region,  without  inter- 
ference with  motor  or  sensory  functions,  have  been  collected  by  Charcot,  Pitres, 
Ferrier,  and  others.  On  the  other  hand,  enfeeblement  of  the  intelligence  and 
idiocy  are  often  observed  in  acquired  or  congenital  defects  of  the  prefrontal  region. 
In  highly  intellectual  men,  Riidmger  found,  in  addition,  a  considerable  develop- 
ment of  the  temporo-sphenoidal  lobe.  According  to  Flechsig,  there  is  no  doubt 
that  the  frontal  lobes  and  the  temporo-occipital  zone  are  related  to  intellectual 
processes,  more  especially  the  "  higher  "  of  these. 

Topography  of  the  Brain. — The  relations  of  the  chief  fissures  and  convolutions  of  the  brain 
to  the  surface  of  the  skull  are  given  in  Fig.  429,  the  brain  being  represented  after  Ecker.  [Turner 
and  others  have  given  minute  directions  for  finding  the  position  of  the  different  convolutions  by 
reference  to  the  sutures  and  other  prominent  parts  of  the  skull.  The  foregoing  diagram  (Fig.  438), 
by  R.  W.  Reid,  shows  the  relation  of  the  convolutions  to  certain  fixed  lines.] 

379.  THE  BASAL  GANGLIA— THE  MID-BRAIN.— [The  corpus 
striatum  in  reality  consists  of  two  parts,  an  intra-ventricular  portion  projecting 
into  the  lateral  ventricle  and  called  the  caudate  nucleus,  and  an  extra-ven- 
tricular portion  the  lenticular  nucleus.  Between  the  head  of  the  caudate  nu- 
cleus internally  and  the  lenticular  nucleus  externally  lies  the  anterior  division  of 
the  internal  capsule.  The  fibres  which  pass  between  these  ganglia  do  not  seem  to 
form  connections  with  them.  The  expanded  head  of  the  caudate  nucleus  is  in 
front,  and  lies  mside  and  around  the  front  of  the  lenticular  nucleus,  with  which 
and  the  anterior  perforated  space  it  is  continuous  ;  it  sweeps  backward  into  a 
tailed  extremity,  which  nearly  surrounds  the  lenticular  nucleus  like  a  loop.  The 
lenticular  nucleus  is  biconvex  in  a  horizontal  section  (Fig.  439),  but  triangular 
and  subdivided  into  three  divisions  when  seen  in  a  vertical  section  (Fig.  433)-] 

[The  older  observations  on  the  corpora  striata  in  man  may  be  dismissed,  as  a 
distinction  was  not  drawn  between  injury  to  its  two  parts  on  the  one  hand  and  the 
internal  capsule  on  the  other.] 

[The  caudate  nucleus  and  lenticular  nucleus  in  their  development  are 
coordinate  with  the  development  of  the  cortex  cerebri  (Fig.  439).  Electrical 
stimulation  of  these  ganglia  causes  general  muscular  contractions  in  the  oppo- 
site half  of  the  body.  The  same  result  is  obtained  as  if  all  the  motor  cortical 
centres  were  stimulated  simultaneously.] 


734 


THE    BASAL    GANGLIA, 


Gliky  did  not  observe  movements  on  stimulating  the  corpus  striatum  in  rabbits ;  it  would  seem 
that  in  these  animals  the  motor  paths  do  not  traverse  these  ganglia,  but  merely  pass  alongside  of 
them. 

[Lesions  of  the  lenticular  nucleus  or  of  the  cordate  nucleus  do  not  seem  to 
give  rise  to  any  permanent  symptoms,  provided  the  internal  capsule  be  not  injured.] 

Fig.  43q. 


Cornu  jQtlcum. 


S,  sensory  fib 


Destruction  of  the  internal  capsule,  however,  causes  paralysis  of  motion  or 
sensibility,  or  both,  on  the  opposite  side  of  the  body,  according  to  the  part  of 
it  which  is  injured.  The  corpus  striatum  is  quite  insensible  to  painful  stimulation 
{Longet). 


THE    INTERNAL   CAPSULE.  735 

Pathological. — In  man,  a  lesion,  not  too  small,  destroying  the  anterior  part  of  the  corpus  stri- 
atum is  followed  by  permanent  paralysis  of  the  opposite  side  provided  the  internal  capsule  is  in- 
jured, but  the  paralysis  gradually  disappears  if  the  lenticular  and  caudate  nucleus  only  are  affected 
{compare  §  365).  Sometimes  there  is  dilatation  of  the  blood  vessels  in  consequence  of  vasomotor 
paralysis  (|  377)  if  the  posterior  part  is  injured  (A'otlina^el) ;  redness  and  a  slightly  increased  tem- 
perature of  the  paralyzed  extremities,  at  least  for  a  certain  time;  swelling  or  oedema  of  the  ex- 
tremities ;  sweating  ;  anomalies  of  the  pulse  detectable  by  the  sphygmograph  ;  decubitus  acutus  on 
the  paralyzed  side  ;  abnormalities  of  the  nails,  hair,  skin  ;  acute  inflammations  of  joints,  especially 
of  the  shoulder.  Later,  contracture  or  permanent  contraction  of  the  paralyzed  muscles  takes  place 
(Hu:;uenin,  Charcot).  In  some  cases  there  is  cutaneous  anssthesia,  and  occasionally  enfeeblement 
of  the  sense  organs  of  the  paralyzed  side,  and  both  when  the  posterior  third  or  sensory  crossway 
of  the  posterior  section  of  the  internal  capsule  is  affected.  Usually,  however,  hemiplegia  and  hemi- 
auasl/iesia  occur  together. 

Optic  Thalamus. — Ferrier  did  not  observe  art)'  movements  to  occur  on 
stimulating  the  optic  thalami  with  electricity.  As  the  pulvinar  or  posterior  ex- 
tretnity  of  the  optic  thalamus  is  one  of  the  parts  connected  with  the  origin  of  the 
optic  nerve,  and  is  also  connected  by  fibres  with  the  cortex  cerebri,  it  is  probably 
related  to  the  sense  of  sight.  Injury  to  the  posterior  third  in  man  results  in  dis- 
turbance of  vision  {Nolhnagel).  Ferrier  surmises  that  the  sensory  fibres  pass 
through  the  optic  thalami  on  their  way  to  the  cortex,  so  that  when  they  are  de- 
stroyed insensibility  of  the  opposite  half  of  the  body  is  produced.  Removal  of 
the  optic  thalamus,  or  destruction  of  the  part  in  the  neighborhood  of  the  inspira- 
tory centre  in  the  wall  of  th;  third  ventricle,  influences  the  coordinated  move- 
ments in  the  rabbit  {Christiani). 

We  know  very  little  definitely  as  to  the  functions  of  these  organs.  After  injury  to  one  thalamus 
there  has  been  observed  enfeeblement  or  paralysis  of  the  muscles  of  the  opposite  side,  together  with 
mouvements  de  manege,  and  sometimes  hemianesthesia  of  the  opposite  side,  with  or  without  affec- 
tions of  the  motor  spheres,  have  been  recorded.  Extirpation  of  certain  cortical  areas  (rabbit)  is 
followed  by  atrophy  of  certain  parts  of  the  thalamus  (v.  Monakow). 

[Internal  Capsule. — In  connection  with  the  functions  of  the  basal  ganglia,  it  is 
most  important  to  retnember  their  relation  to  the  internal  capsule.  The  corpus  stri- 
atutn  consists  of  an  intra-ventricular  part,  the  caudate  nucleus ;  and  an  extra-ventric- 
ular part,  the  lenticular  nucleus.  The  lenticular  nucleus  consists  of  three  parts,  best 
seen  in  a  vertical  section  (Fig.  440,  i,  2,  3),  with  white  matter  between  them, 
the  stria  mejullares.  The  anterior  limb  of  the  internal  capsule  sweeps  between 
the  caudate  and  lenticular  nucleus,  while  the  posterior  segment  lies  between  the 
optic  thalamus  and  the  lenticular  nucleus  (Fig.  440).  External  to  the  first  divi- 
sion of  the  lenticular  nucleus  is  the  external  capsule  (Figs.  439,  440),  whose 
function  is  unknown.  External  to  this  is  the  claustrum,  whose  function  is  also 
unknown.  It  is  evident  that  hemorrhage  into  or  about  the  basal  ganglia  is  apt  to 
involve  the  fibres  of  the  internal  capsule.  [When  the  lenticulo-striate  artery,  or, 
as  it  is  called,  the  "  artery  of  hemorrhage"  (Fig.  433,  aSL),  ruptures,  it  may 
destroy  not  only  the  lenticular  nucleus,  but  the  internal  capsule  will  be  compressed, 
and  the  same  is  the  case  with  the  lenticulo-optic  artery  ;  the  external  capsule  will 
tend  to  force  the  blood  inward.  We  know  that  in  the  posterior  segment  of 
the  capsule  the  volitional  or  pyramidal  fibres  lie  in  the  following  order  from  before 
backward,  those  for  the  face  (and  tongue)  in  the  knee,  in  the  anterior  third  those 
for  the  arm  and  hand,  and  in  the  middle  third  for  the  leg,  and,  perhaps,  behind 
these  those  for  the  trunk  (Fig.  439,  F,  A,  L)  ;  so  that  a  very  small  lesion  in  this 
region  will  affect  a  large  number  of  these  fibres,  converging  as  they  do,  like  the 
rays  of  a  fan,  from  the  motor  cortical  areas,  where  the  arrangement  of  these  cen- 
tres is  a  supero-inferior  one  (Fig.  433),  to  become  an  antero-posterior  one  in  the 
knee  and  posterior  limb  of  the  internal  capsule  (Fig.  439).  The  posterior  third 
of  this  limb  is  sensory  and  is  the  "  sensory  crossway." 

[Horsley  points  out  that  hemorrhage  from  the  lenticulo-striate  artery  affects  in  order  the  muscles 
of  the  face,  arm,  leg  and  trunk,  while  recovery  is  in  the  inverse  order.] 


736 


PEDUNCLE    AND    PONS. 


Pedunculi  Cerebri. — Injury  to  one  cerebral  peduncle  causes,  in  the  first  place, 
violent  pain  and  spasm  of  the  opposite  side,  while  the  blood  vessels  on  that  side 
contract  and  the  salivary  glands  secrete.  These  phenomena  of  irritation  are  fol- 
lowed by  paralytic  symptoms  of  the  opposite  side,  viz.,  anaesthesia  (§365)  and 
paresis,  or  incomplete  voluntary  control  over  the  muscles,  as  well  as  paralysis  of 


Fig.  440. 


r^ 


Corpus  callosun 

Pillars  0 

f  the  forni;< 

Inte 

nal  capsul 

Op 

ic  thalamu 

Soft 

commissur 

ExK 

rnal  capsul 

ClaustruiT 

Frontal  section  through  the  right  cerebral  hemisphc 


(posterior  surface  of  the  section). 


Fig.  441. 
P.7\f  fIp.T 


the  vasomotor  nerves.  In  affections  of  the  cerebral  peduncle  in  man,  we  must 
remember  the  relation  of  the  oculomotorius  to  it,  as  the  latter  is  often  paralyzed 
on  the  same  side  (^Nothnagel)  [while  the  extremities,  tongue,  and  half  the  face  are 
paralyzed  on  the  opposite  side  from  the  lesion]. 

The  middle  third  of  the  crusta  of  the  cerebral  peduncle  (Fig. 

435)  includes  the  direct  pyramidal  tracts  [\\  365,  378).  The 
fibres  of  the  inner  third  connect  the  frontal  lobes,  through  the 
superior  cerebellar  peduncles,  with  the  cerebellum.  In  the  outer 
third  are  fibres  which  connect  the  pons  with  the  temporal  and 
occipital  cerebral  lobes  (Flechsig).  The  fibres  which  pass  from 
the  tegmentum  into  the  corona  radiata  conduct  sensory  impulses 
(Flechsig). 

Pons  Varolii. — Stimulation  or  section  of  the  pons 
causes  pain  and  spasms ;  after  the  section  there  may 
be  sensory,  motor  and  vasomotor  paralysis,  together 
with  forced  movements.  For  diagnostic  purposes  in 
man,  it  is  important  to  observe  if  alternate  hemiplegia 
be  present  {Nothnagel.') 

[In  lesions  situated  in  the  lower  half  of  one  side  of  the  pons 
there  is  facial  paralysis  on  the  same  side  as  the  lesion  and  paraly- 
sis (motor  and  sensory,  and  more  or  less  complete)  on  the  oppo. 
site  side  of  the  body ;  this  is  called  alternate  paralysis ;  while, 
if  the  lesion  be  in  the  upper  half  of  one  side  of  the  pons,  the 
facial  paralysis  is  on  the  same  side  as  the  paralysis  of  the  body. 
But  the   parts  supplied  by  the  5th  and  6th  nerves  may  also  be 


Scheme  of  the  fib 
pyramidal 
«,   upper, 


STIMULATION    OF   THE    CORPORA    QUADRIGEMINA.  737 

involved.  This  is  explained  by  Fig.  441,  where  the  upper  facial  fibres  cross  in  the  pons.  Sudden 
and  extensive  lesions  of  the  pons  are  often  associated  with  hyperpyrexia,  the  temperature  often 
rising  rapidly  within  an  hour,  perhaps  from  the  gray  matter  in  the  floor  of  the  4th  ventricle  being 
affected ;  but  whether  it  is  due  to  some  effect  on  a  heat-regulating  or  heat-producing  centre  is  un- 
certain. Tumors  of  considerable  size  may  press  on  the  pons  without  producing  very  marked 
symptoms,  as  tumors  tend  to  push  aside  tissues,  unless  they  be  infiltrating  in  their  character. 
Lesions  of  the  transverse  superficial  fibres  (middle  cerebellar  peduncles)  often  give  rise  to 
involuntary  forced  movements,  there  being  a  tendency  to  move  to  one  side  or  the  other.] 

The  Corpora  Quadrigemina. — Destruction  of  these  bodies  on  one  side 
in  mammals,  or  their  homologues,  the  optic  lobes  in  birds,  amphibians  and 
fishes,  causes  actual  blindness,  which  may  be  on  the  same  or  the  opposite  side, 
according  to  the  relation  of  the  fibres  crossing  at  the  optic  chiasma  (§  344). 
Total  destruction  causes  blindness  of  both  eyes.  At  the  same  time,  the  reflex 
contraction  of  the  pupil,  due  to  stimulation  of  the  retina  with  light,  no  longer 
takes  place  i^Flourens),  where  the  optic  is  the  afferent  and  the  oculomotorius  the 
efferent  nerve  (§  345).  If  the  cerebral  hemispheres  alone  be  removed  the  pupil 
still  contracts  to  light,  as  well  as  after  mechanical  stimulation  of  the  optic  nerve 
(yH.  Mayo').  Destruction  of  the  corpora  quadrigemina  interferes  with  the  com- 
plete harmony  of  the  motor  acts ;  disturbance  of  equilibrium  and  incoordination 
of  movements  occur  {Serres').  In  frogs,  CJoltz  observed  not  only  awkward, 
clumsy  movements,  but  at  the  same  time  the  animals  have  to  a  large  extent  lost 
the  power  of  completely  balancing  the  body  (p.  705).  A  similar  result  was 
observed  in  pigeons  {Af  Kendrick)  and  rabbits  (Ferrier).  Extirpation  of  the  eye- 
ball is  followed  by  atrophy  of  the  opposite  anterior  corpus  quadrigeminum 
{Giidden). 

According  to  Bechterew,  the  fibres  of  one  optic  tract  pass  through  the  anterior  brachium  (Fig. 
439)  into  the  anterior  pair  (nates)  of  the  corpora  quadrigemina;  while  those  fibres  which  cross  in 
the  chiasma  (Fig.  381)  pass  into  the  posterior  pair  (testes).  According  to  this  arrangement  we 
have  partial  blindness,  according  as  one  or  other  pair  of  these  bodies  is  destroyed. 

[In  man  very  little  is  known  regarding  the  effects  of  disease  of  the  corpora  quadrigemina,  inter- 
ference with  the  ocular  muscles  being  the  most  marked  symptom,  but  the  incoordination  of  move- 
ment which  has  been  observed  may  be  due  to  pressure  upon  the  superior  cerebellar  peduncle,  while 
it  is  by  no  means  certain  that  the  defects  of  vision  are  directly  due  to  lesions  of  these  bodies.] 

Stimulation  of  the  Corpora  Quadrigemina. — The  corpora  quadrigemina  react  to  electrical, 
chemical  and  mechanical  stimuli.  The  results  of  stimulation  are  very  variously  staled.  Accord- 
ing to  some  observers  there  is  dilatation  of  the  pupil  on  the  same  side ;  according  to  Ferrier,  it  may 
be  the  pupil  on  the  opposite  or  on  the  same  side.  The  stimulation  may  be  conducted  Irom  the  cor- 
pora quadrigemina  to  the  medulla  oblongata,  and  to  the  origin  of  the  sympathetic,  for  after  section 
of  the  sympathetic  nerve  in  the  neck  dilatation  of  the  pupil  no  longer  takes  place  ( Knoll).  Accord- 
ing to  Knoll,  the  contraction  of  the  pupil  observed  by  the  older  experimenters  occurs  only  when 
the  adjoining  optic  tract  is  stimulated.  Stimulation  of  the  tight  anterior  corpus  quadrigeminum 
causes  deviation  of  both  eyes  to  the  left  (and  conversely)  ;  on  continuing  the  stimulation,  the  head 
is  turned  to  this  side.  On  dividing  the  corpora  ([uadrigemina  by  a  vertical  median  incision,  stimu- 
lation of  one  side  causes  the  result  to  take  place  only  on  one  side  (AJamiik).  Ferrier  observed 
signs  of  pain  on  stimulating  these  organs  in  mammals.  Carville  and  Duret  conclude  from  their 
experiments  that  these  organs  are  centres  for  the  extensor  movements  of  the  trunk.  Ferrier  found, 
on  stimulating  one  optic  lobe  in  a  pigeon,  dilatation  of  the  opposite  pupil,  turning  of  the  head 
toward  the  other  side  and  backward,  movement  of  the  opposite  wing  and  leg;  strong  stimulation 
caused  flapping  movements  of  both  wings.  Danilewsky,  Ferrier  and  Lauder  Brunton  observed  a 
ri-e  of  the  blood  pressure  and  slowing  of  the  heart  beat,  together  with  deeper  inspiration  and 
expiration.  According  to  Valentin  and  Budge,  stimulation  also  causes  movement  of  the  intestines 
and  bladder,  perhaps  excited  secondarily  by  the  action  of  the  vasomotor  nerves. 

Bechterew  ascribes  all  the  phenomena,  except  those  of  vision  itself,  which  accompany  injury  or 
stimulation  of  these  bodies,  to  affections  of  deeper-seated  parts.  He  asserts  that  the  corpora  quad- 
rigemina contain  neither  the  centre  for  the  movements  of  the  pupils  nor  that  for  the  combined 
movements  of  the  eyeballs;  not  even  the  centre  for  maintaining  the  equilibrium  of  the  body. 
Stimulation  of  these  bodies  causes  the  animals  10  perform  marked  movements.  Reflex  phenomena, 
nystagmus,  forced  movements  and  unsteadiness  of  the  gait  only  occur,  however,  when  the  deeper 
parts  are  injured. 

Pathological. — Lesions  of  the  anterior  pair  in  man,  according  to  the  extent  of  the  lesion,  cause 
disturbance  of  vision,  failure  of  the  pupil  to  contract  to  light,  and  even  blindness ;  there  may  be 
paralysis  of  the  oculomotorii  on  buih  sides.  Disease  of  the  posterior  pair  may  be  associated  with 
disturbances  of  coordination  (lYolhiia^il). 

47 


738  FORCED    MOVEMENTS STRABISMUS    AND    NYSTAGMUS. 

Forced  Movements. — It  is  evident  from  what  has  been  said  regarding  the 
importance  of  the  corpora  quadrigemina  for  the  harmonious  execution  of  move- 
ments, that  u iiilcUera/  m]ury  of  such  parts  as  are  connected  to  them  by  conduct- 
ing channels  must  give  rise  to  peculiar  unilateral  disturbance  of  the  equilibrium, 
causing  variations  from  the  symmetrical  movements  of  both  sides  of  the  body. 
These  movements  are  caWed  forced mcvemen/s.  To  this  class  belong  the  mouve- 
ment  de  manege,  where  the  animal,  instead  of  moving  in  a  straight  line,  runs 
round  in  a  circle  ;  index  movements,  where  the  anterior  part  of  the  body  is 
moved  round  the  posterior  part,  which  remains  in  its  place,  just  like  the  move- 
ments of  an  index  round  its  axis;  and  rolling  movements,  when  the  animal  rolls 
on  its  long  axis.  All  these  forms  of  movement  may  pass  into  each  other,  and 
they  are,  in  fact,  merely  different  varieties  of  the  same  kind  of  movement.  The 
parts  of  the  nervous  system  whose  injury  produces  these  movements  are  the  corpus 
striatum,  optic  thalamus,  cerebral  peduncle,  pons,  middle  cerebellar  peduncles, 
and  certain  parts  of  the  medulla  oblongata.  Eulenberg  observed  index  move- 
ments in  the  rabbit  after  injury  to  the  surface  of  the  brain,  and  Bechterew 
observed  the  same  in  dogs.  Forced  movements,  together  with  nystagmus  and 
rotation  of  the  eyeballs,  are  caused  by  injury  to  the  olives  {Bechtereiv).  The 
statements  of  observers  vary  as  to  the  direction  and  kind  of  movement  produced 
by  injuring  individual  parts.  The  following  observations  have  been  made  :  Sec- 
tion of  the  anterior  part  of  the  pons  and  of  the  crura  cerebelli  causes  index, 
or,  it  may  be,  rolling  movements  toward  the  other  side  ;  section  of  the  posterior 
part  of  the  same  regions  causes  rolling  movements  toward  the  same  side,  while 
the  same  result  is  caused  by  a  deeper  puncture  into  the  tuberculum  acusticum,  or 
into  the  restiform  body.  Section  of  one  cerebral  peduncle  causes  mouvements 
de  manege,  while  the  body  is  curved  with  the  convexity  toward  the  same  side. 
The  nearer  to  the  pons  the  section  is  made  the  smaller  is  the  circle  described ; 
ultimately  index  movements  occur.  Injury  to  one  optic  thalamus  produces  results 
similar  to  puncture  of  the  anterior  part  of  the  cerebral  peduncle,  because  the 
latter  is  injured  along  with  it  at  the  same  time.  Injury  to  the  anterior  part  of  one 
optic  thalamus  causes  the  opposite  kind  of  forced  movement,  viz.,  with  the  con- 
cavity of  the  body  toward  the  injured  side.  Injury  to  the  spinal  portion  of  the 
medulla  oblongata  is  followed  by  bending  of  the  head  and  vertebral  column,  with 
the  convexity  toward  the  injured  side,  along  with  movements  in  a  circle.  When 
the  anterior  end  of  the  calamus  and  the  part  above  it  are  injured,  the  movements 
are  toward  the  sound  side. 

Strabismus  and  Nystagmus. — Among  the  forced  movements  may  be  reck- 
oned deviation  of  the  eyeballs,  strabismus  or  squinting,  and  involuntary  oscillation 
of  the  eyeballs,  constituting  nystagmus.  The  latter  condition  occurs  after  superfi- 
cial lesions  of  the  restiform  body,  as  well  as  of  the  floor  of  the  4th  ventricle.  A 
unilateral  deep  transverse  injury,  from  the  apex  of  the  calamus  upward  as  far  as 
the  tuberculum  acusticum,  causes  the  eye  of  the  same  side  to  squint  downward  and 
forward,  that  of  the  other  side  backward  and  upward.  Section  of  both  sides  causes 
this  condition  to  disappear  (Sc/twa/ui).  Hence,  Eckhard  assumes  that  the  me- 
dulla oblongata  is  the  seat  of  an  apparatus  controlling  the  movements  of  the  eyes 
(^Ec-Manf). 

In  pathological  degeneration  of  the  olivary  body  of  the  medulla  oblongata  in  man,  Meschede  ob- 
served intense  rotatory  movements  toward  the  scime  side. 

Theory. — In  order  to  explain  the  occurrence  of  forced  movements,  it  is  suggested  that  there  is 
unilateral  incomplete  paralyi-is  [Lnfarqiie),  so  that  the  animal  in  its  efforts  to  move  onward  leaves 
the  paralytic  side  slightly  behind  the  other,  and  hence  there  is  a  variation  from  the  symmetry  of  the 
movements.  Brown-Sequard  regards  the  matter  in  exactly  an  opposite  light,  viz.,  as  due  to  stimu- 
lation from  injury  causing  an  excessive  activity  of  one-half  of  the  body.  Henle  ascribes  the  move- 
ments to  I'tv/^''',  of  a  feeling  of  giddiness  caused  by  the  injury.  In  all  operations  on  the  central 
nervous  system,  where  the  equilibrium  is  deeply  affected,  there  is  a  considerable  incre.ise  in  the 
number  and  depth  of  the  respirations  ( I.nndois). 

Other  Effects. — Some  observers  noticed  v.-iriations  of  the  blood  pressure  and  a  change  in  the 


STRUCTUUE    AND    FUNCTIONS   OF   THE    CEREBELLUM.  739 

number  of  heart  beats  after  stimulation  of  the  cortex  cerebri,  e.g.,  after  electrical  stimulation  of  the 
motor  areas  for  the  extremities  (Boc/ifftnitnine).  Balogh  observed  acceleration  of  the  pulse  on 
stimulating  several  points  on  the  cortex  cerebri  of  the  dog,  and  from  one  point  slowing  of  the  pulse. 
Eckhard  stimulated  the  surface  of  the  brain  in  rabbits,  and  as  a  rule  he  observed  that  as  long  as  sin- 
gle crossed  movements  occurred  in  the  anterior  extremities  there  was  no  effect  upon  the  heart,  but 
that  the  heart  became  affected  as  soon  as  other  movements  occurred.  This  consists  in  slow,  strong 
pulse  beats,  with  occasional  weaker  beats,  while  at  the  same  time  the  blood  pressure  is  slightly  in- 
creased (Boi/ie/onlaine).  If  the  vagi  be  divided  beforehand,  the  effect  upon  the  pulse  disappears, 
while  the  increase  of  the  blood  pressure  remains.  That  psychical  processes  affect  the  action  of  the 
heart  was  known  to  Homer  and  Chrysipp.  Bochefontaine  and  Lepine,  on  stimulating  several  points, 
especially  in  the  neighborhood  of  the  sulcus  cruciatus  in  a  dog,  observed  increased  secretion  of 
saliva,  slowing  of  the  movements  of  the  stomach,  peristalsis  of  the  intestine,  contraction  of  the 
spleen,  of  the  uterus,  of  the  bladder,  and  increased  respirations.  Bufalini,  on  stimulating  those  parts 
of  the  cortex  which  cause  movements  of  the  jaw,  observed  the  secretion  of  gastric  juice  with  in- 
crease of  the  temperature  of  the  stomach.  .Schiff,  Brown-Sequard,  Ebstein,  Klosterhalfen,  and 
others,  have  observed  that  injury  to  the  pons,  corpus  striatum,  thalamus,  cerebral  peduncle,  and 
medulla  oblongata  often  causes  hyperaemia  and  hemorrhage  into  the  lung  (according  to  Brown- 
Sequard,  especially  after  injury  to  one  side  of  the  pons,  which  affects  the  opposite  lung),  under  the 
pleura,  in  the  stomach,  intestine,  and  kidneys.  Gastric  hemorrhage  is  common  after  injury  to  the 
pons  just  where  the  cerebral  peduncles  join  it.  Similar  phenomena  have  been  observed  in  man  after 
apoplexy  or  cerebral  hemorrhage. 

Specially  interesting  is  the  cerebral  unilateral  decubitus  acutus  described  by  Charcot,  which 
always  occurs  on  the  paralyzed  side  of  the  body,  i.e.,  on  the  side  opposite  to  the  cerebral  injury.  It 
begins  on  the  second  or  third  day,  rapidly  causes  enormous  destruction  and  sloughing  of  the  tissues 
on  the  back  and  lower  extremities,  and  death  soon  takes  place.  The  decubitus  which  occurs  after 
spinal  injuries  usually  begins  in  the  middle  line  of  the  buttocks,  and  extends  symmetrically  on  both 
sides.  In  cases  of  unilateral  injury  to  the  spinal  cord  the  decubitus  occurs  on  the  corresponding ^\&^ 
of  the  sacral  region  (p.  614). 

[Corpus  Callosum. — It  is  usually  stated  that  the  corpus  callosum  connects  the  convolutions  of 
one  side  of  the  brain  with  those  of  the  other, /.?.,  it  is  an  inter-hemispherical  commissure.  D.J. 
Hamilton,  however,  states  that  it  is  not  an  inter- hemispheric  commissure,  but  is  due  to  cortical  tibres 
coming  from  the  cortex  cerebri  to  be  connected  with  the  basal  ganglia  of  the  opposite  side.  On  this 
view,  the  "  corona  radiata,"  as  usually  understood,  consists  only  of  the  fibres  which  pass  from  the 
cerebral  peduncle  directly  up  to  the  cortex  on  the  same  side,  and  are  contained  in  the  posterior  di- 
vision and  knee  of  the  internal  capsule.  They  correspond  to  the  motor  pyramidal  tracts.  Hamilton 
maintains  that  all  the  other  fibres  of  the  internal  capsule  pass  into  the  crossed  callosal  tract,  and, 
instead  of  running  directly  up  to  the  cortex  on  the  same  side,  cross  in  the  corpus  callosum  to  the 
cortex  of  the  opposite  side.  Beevor,  relying  on  the  examination  of  the  brain  of  monkeys,  by  Wei- 
gert's  method,  denies  that  any  filjres  of  the  corpus  callosum  pass  into  the  external  or  internal  cap- 
sules, and  he  maintains  the  old  view  that  the  corpus  callosum  is  a  commissure  between  the  two  hemi- 
spheres.] 

380.  STRUCTURE  AND  FUNCTIONS  OF  THE  CEREBELLUM.— [Structure. 
— On  examining  a  vertical  section  of  a  cerebellar  leaflet  we  observe  the  following  microscopic  ap. 
pearances :  Externally  is  the  pia  mater  with  its  blood  ve.ssels  (Fig.  442,  a)  which  penetrate  into  the 
gray  matter,  within  is  the  medulla  composed  of  white  fibres.  The  gray  inatter  consists  of  b,  a 
broad  outer  or  molecular  layer  largely  composed  of  branched  fibrils,  and  internal  to  it  is  </,  the 
"granular,"  nuclear, or  rust-colored  layer.  On  the  boundary  line  between  these  two  is  the  layer  of 
Purkinje's  cells,  c.  The  cells  of  Purkinje  form  a  single  layer  of  large,  multipolar,  flask-shaped  nerve 
cells,  which  have  been  compared  to  the  branched  antlers  of  a  stag.  From  their  outer  surface  is 
given  off  a  process  which  rapidly  divides  and  gives  rise  to  a  large  number  of  smaller  processes  running 
outward  in  the  outer  gray  layer.  Some  of  these  processes  form  part  of  the  ground  plexus  of  fibrils 
in  this  layer.  An  unbranched  axial  cylinder  process  is  sent  inward  to  the  granular  layers,  where  it 
becomes  continuous  with  a  nen-e  fibre.  Every  cell  of  Purkinje  being  continuous  with  a  straight, 
unljranched  meduUated  nerve  fibre.  The  unbranched  fibres  run  straight  from  the  medulla  tlirough 
the  granular  layer,  forming  no  connection  with  its  granules.  A  second  set  of  branched  or  anasto- 
mosing, often  varicose,  nerve  fibres  finer  than  the  foregoing  pass  from  the  medulla  into  the  granular 
layer,  where  they  form  a  network  which  is  continued  into  the  molecular  layer.  The  granular 
layer  is  composed  of  closely-packed  granules  of  two  kinds,  one  is  stained  by  hematoxylin  and  the 
other  with  eosin  [Denissenko).  The  h.\'m.atoxylin-stained  cells  are  most  numerous,  and  consist  of  a 
nucleus  surrounded  by  protoplasm,  and  they  are  what  were  formerly  called  granules.  The  eosin- 
stained  cells  [which  are  also  stained  by  nigrosin  [Becz'or)']  are  interposed  in  the  course  of  medul- 
lated  nerve  fibres.  The  ha^matoxylin  cells,  called  glia  cells  by  Beevor,  have  processes  and  fonn  a 
network  throughout  the  granular  layer,  which  also  extends  into  the  molecular  layer.  This  network 
is  regarded  as  the  continuation  of  the  modified  myelin  of  the  nerve  fibres,  and  it  forms  a  capsule  for 
the  cells  of  Purkinje,  The  molecular  layer  consists  of  a  ground  substance,  composed  of  a  spongy 
network  of  fine  fibrils  which  seem  to  be  of  the  nature  of  neuro-keratin,  strengthened  here  and  there 
by  stronger  fibres.     In  the  meshes  lies  a  homogeneous  substance.     Some  of  this  substance  is  more 


740 


FUNCTIONS   OF   THE   CEREBELLUM. 


condensed  to  form  a  limitans  externa  on  the  surface  of  the  cerebellum,  while  on  the  boundary  line 
next  the  granular  layer  the  branches  of  the  glia  cells  form  a  Hmitaits  interna^  and  between  the  two 
stretches  the  neuro-keralin  network.  Some  small  variocose  ntrve  fibres  exist  in  this  layer  continuous 
with  those  in  the  granular  layer.  The  branched  process  of  the  cells  of  Purkinje  is  fibrillated, 
and  the  finer  processes  are  composed  also  of  fibrils,  which  are  gradually  distributed  until  they  be- 
come isolated.  It  is  suggested  by  Beevor  that  these  fibrils  bend  at  a  right  angle  in  a  plane  parallel 
to  surface,  and  rearrange  themselves  as  fibres  surrounded  by  a  medullated  sheath,  and  that  these 
fibres  run  inward  through  the  molecular  and  granular  layers — as  the  branched  fibres — to  the 
medulla.] 


Fig.  442. 


Fig.  443. 


Plgeuii  wilh  its  cerebellum  reniuved. 

Function. — Injuries  of  the  cerebellum 
cause  disturbances  of  the  equilibrium  of 
the  body.  Most  probably  the  cerebellum 
is  a  great  and  important  central  organ  for 
the  finer  coordination  and  integration  of 
movements.  The  fact  that  it  is  connected 
with  all  the  columns  of  the  spinal  cord, 
with  the  central  ganglia  of  the  corpora 
quadrigemina,  and  cerebrum,  renders  this 
very  probable.  The  direct  cerebellar 
tracts  from  the  lateral  column  of  the  cord 
conduct  sensory  impressions  to  the  cere- 
bellum, and  thus  indicate  the  posture  of 
the  trunk.  The  cerebellum  may  affect 
the  motor  nerves  of  the  cord  through 
fibres  which  pass  downward  in  the  lateral 
columns  of  the  cord  from  the  restiform 
bodies  {Flechsig).  Injury  of  the  cere- 
bellum produces  neither  disturbance  of  the 
psychical  activities,  nor  does  it  interfere 
,f;  with  the  will  or  consciousness.  Injuries  to 
the  cerebellum  itself  do  not  give  rise  to  pain. 

According  to  Schifif,  the  cerebellum  does  not  actually  regulate  the  coordination  of  movements. 
According  to  him  there  is  a  mechanism  on  both  sides  of  the  middle  line,  which  increases  all  the 
complicated  muscular  movements ;  not  only  those  for  powerful  contractions,  but  also  the  peculiar 
fine  movements  which  fix  the  limbs  and  joints.  Luciani  asserts  that  destruction  of  the  cerebellum 
produces  a  condition  of  incomplete  tonus,  there  being  a  want  of  energy  to  control  the  voluntary 
muscles.     Each  half  of  the  organ  acts  on  both  halves  of  the  body. 

Removal  of  Cerebellum. — The  immediate  results  produced  by  injury  to  or 
removal  of  the  cerebellum  have  been  admirably  described  by  Flourens  (Fig.  443). 
On  removing  the  most  superficial  layers  in  a  pigeon,  the  animal  merely  showed 
signs  of  weakness  and  interference  with  the  uniformity  of  its  inovements.     On 


EXTIRPATION    UF   THE    CEREBELLUM.  741 

removing  more  of  cerebellum,  the  animal  became  greatly  excited,  and  made  violent 
irregular  movements,  which  did  not  partake  of  the  character  of  convulsions.  The 
sensorium  was  unaffected,  while  vision  and  hearing  were  intact.  Coordinated 
movements,  such  as  walking,  flying,  springing  and  turning,  could  be  executed  but 
imperfectly.  After  removal  of  the  deepest  layers,  the  power  of  executing  the  above- 
named  movements  was  completely  abolished.  On  placing  the  pigeon  on  its  back,  it 
could  not  get  on  its  legs;  at  the  same  time  it  made  continually  the  greatest  exertions 
in  its  movements,  but  these  were  always  incoordinated,  and  therefore  without  any 
satisfactory  result.  The  will,  intelligence,  and  perception  remained  intact  ;  the 
animal  could  see  and  hear,  sought  to  avoid  obstacles  placed  in  its  way  ;  it  gradu- 
ally exhausted  itself  in  fruitless  efforts  to  get  on  its  legs,  and  ultimately  remained 
in  its  abnormal  position  quite  exhausted.  Flourens  concluded  from  these  experi- 
ments that  the  cerebellum  is  the  centre  for  coordinating  voluntary  movements. 
Lussana  and  Morganti  regard  the  cerebellum  as  the  seat  of  the  muscular  sense. 

[Extirpation  in  Mammals. — The  dangers  attending  Ihis  operation  are  so  great  that  but  few 
animals  survive.  Luciani,  however,  by  using  antiseptic  and  other  precautions,  has  been  able  to  do 
this  so  that  complete  cicatrization  was  obtained,  the  animal  (young  bitch)  being  restored  to  health 
for  a  few  months.  The  cerebellum  alone  was  removed,  but  not  its  peduncles.  As  in  all  other 
similar  operations,  we  must  distinguish  sharply  the  phenomena  manifested  during  recovery  from 
those  after  complete  recovery.  During  the  first  period  of  six  weeks,  from  the  time  of  the  operation 
until  complete  recovery,  the  symptoms  are  those  of  injury  and  irritation  of  the  divided  peduncles, 
along  with  those  resulting  from  the  removal  of  the  organ.  They  are  clonic  contractions  of  the 
muscles  of  the  fore  limb,  neclv  and  back,  passing  into  tonic  contractions  when  the  animal  attemps 
to  move,  and  also  weakness  of  the  hind  legs,  so  that  all  the  normal  voluntary  movements  are  inter- 
fered with,  /.(-..  incoordinated,  although  these  symptoms  may  be  explained  by  the  injury  to  adjoin- 
ing parts.  There  was  no  sensory  disturbance  or  loss  of  the  muscular  sense,  although  closing  the 
eyes  rendered  standing  impossible.  As  recovery  takes  place  these  .symptoms  disappear,  and  the 
animal  enters  on  the  second  period,  where  the  symptoms  depending  on  the  actual  loss  of  the  organ 
are  pronounced.  The  contracture  and  pseudo-paralytic  weakness  disappear,  while  there  are  altera- 
tions in  the  lone  of  the  individual  muscles,  producing  a  sort  of  "  cerebellar  ataxy."  The  dog 
could  swim  in  quite  a  normal  manner,  its  power  of  equilibration  was  not  interfered  with,  but  acts 
requiring  a  greater  development  of  muscular  energy  could  not  be  properly  executed.  This  period 
lasted  four  to  five  months.  After  this  time  its  health  gave  way,  there  was  otitis,  conjunctivitis, 
articular  and  cutaneous  inflammations,  while  a  peculiar  form  of  marasmus  set  in,  the  animal  dying 
after  eight  months.  In  fishes,  also,  the  removal  of  the  cerebellum  does  not  aft'ect  their  power  of 
locomotion  [Bt7nde/ot).'\ 

Duration  of  the  Phenomena. — After  superficial  lesions,  or  after  a  deep 
incision,  the  disturbances  of  coordination  soon  pass  away  {Flourens).  If  the 
injury  affects  the  lowest  third  of  the  cerebellum,  the  motor  disturbances  remain 
permanently.  Symmetrical  lesions  do  not  disturb  coordination  (Schiff).  Xhtr 
removing  the  greater  portion  of  the  cerebellum  in  birds.  Weir  Mitchell  has 
observed  that  the  original  disturbances  gradually  disappear  ;  and  af/er  months 
only  slight  weakness  and  a  condition  of  rapid  fatigue  remain. 

In  the  dog,  superficial  injuries  of  the  vermiform  process,  or  of  one-half  of  the  organ,  produce 
merely  temporary  disturbances;  while  deep  injuries  to  the  vermiform  process,  or  removal  of  one 
hemisphere  and  a  part  of  the  vermiform  process,  cause  permanent  rigidity  of  the  legs  and  shaking 
of  the  head  ;  if  the  worm  and  both  halves  are  destroyed,  there  follows  permanent  pronounced  dis- 
turbance of  coordination  (v.  A/ering).  According  to  Kaginsky,  destruction  of  a  large  part  of  the 
vermiform  process  alone  causes  in  mammals  permanent  disturbance  of  coordination.  Ferrier  found 
that  a  vertical  section  of  the  cerebellum  in  monkeys  produced  only  inconsiderable  disturbances  of 
equilibrium ;  after  injury  of  the  anterior  part  of  the  middle  lobe  the  animal  often  tumbles  forward, 
wiiile,  when  the  posterior  part  is  injured,  it  falls  backward.  After  injury  of  the  lateral  lobe  the 
animal  is  drawn  toward  the  affected  side  (Sckiff,  Vulpian,  Ferrier.  Hilzig).  If  the  middle  com- 
missure be  injured  the  animal  rolls  violently  on  its  long  axis  toward  the  injured  side  (Ufagendie). 
Paralysis  never  occurs  after  injuries  of  the  cerebellum,  nnr  is  there  ever  disturbance  of  sensation  or 
of  the  sense  of  touch.  Luciani  found  that  mirasmus  ultimately  set  in  in  animals  with  the  cere- 
bellum extir|>ated.  In  frogs  an  important  organ  concerned  with  motion  lies  at  the  junction  of  the 
oblongata  with  the  cerebellum  [EckUard).  After  it  is  removed  the  animal  can  no  longer  execute 
coordinated  jumping  movements,  nor. can  it  crawl  [Goitz). 

[In  man  the  cerebellum  is  connected  with  the  maintenance  of  the  equilibrium.  There  may  be 
a  lesion  of  the   hemispheres  without  any  marked  symptoms,  but  if  the  middle  lobe  be  injured  or 


742 


PROTECTIVE    APPARATUS    OF   THE    BRAIN. 


pressed  on  by  a  tumor  there  is  usually  a  reeling  or  staggering  gait  like  that  of  a  drunken  man. 
Ross  points  out  that  if  the  tumor  atfect  the  upper  part  of  this  lobe  the  tendency  is  to  fall  backward, 
and  if  in  the  lower  part,  to  fall  forward  or  to  revolve  round  a  horizontal  axis.  Vomiting  is  fre- 
quently persistent  and  well-marked,  while  there  may  be  nystagmus  and  tonic  retraction  of  the 
head.] 

After  injuries  of  the  cerebellum,  involuntary  oscillations  of  the  eyeballs  or  nystagmus,  as  well  as 
squinting  [iMn^^ndis^  H^rUoi^)^  have  been  observed  ;  while  Ferrier  observed  movements  of  the 
eyeballs  after  electrical  stimulation.  According  to  Curschmann,  Eckhard  and  Schwahn,  this  occurs 
only  when  the  medulla  ol)longala  is  involved  (^  379). 

Effects  of  Electricity  and  Vertigo.—  If  an  electrical  current  be  passed  through  the  head,  by 
placing  the  electrodes  in  the  masioid  fossx  behind  both  ears,  with  the  \-  pole  behind  the  right  and 
the  —  pole  behind  the  left  ear,  then  on  closing  the  current  there  is  severe  vertigo  and  the  head 
and  body  lean  to  the  -\-  pole,  while  the  objects  around  seem  to  be  displaced  to  the  left.  If  the 
eyes  be  closed  while  the  current  is  passing,  the  movements  appear  to  be  transferred  to  the  person 
himself,  so  that  he  has  a  feehng  of  rotation  to  the  left  [Ptirkinje).  At  the  moment  the  head  leans 
toward  the  anode  the  eyes  turn  in  that  direction,  and  often  e.\hibit  nystagmus.  The  electrical  cur- 
rent probably  stimulates  the  nerves  of  the  ampulh^,  as  we  know  that  affections  of  these  bodies 
cause  vertigo  [\  350).  The  cerebellum  has  no  relation  to  the  sexual  activities,  as  was  maintained 
by  Gall.  The  contractions  of  the  uterus  observed  by  Valentin,  Budge  and  Spiegelberg,  after 
stimulation  of  the  cerebellum,  are  as  yet  unexplained. 

Pathological. — Lfsions  of  one  hemisphere  may  give  rise  to  no  symptoms,  but  if  the  middle  lobe  is 
involved  there  is  incc ordination  of  movement,  especially  a  tendency  to  fall,  unsteady  gait  and  pro- 


FlG.  44.1. 


*   -d 


-  SiL 


of  the  cortex  cerebri  and  us  membranes  X  2^  co,  cortex  cerebri :  /,  intima  piae  dipping  into  the 
arachnoid,  connected  with/  by  means  ot  the  loose  subarachnoid  trabecule  in  the  subarachnoid  space, 
blood  vessels ;  d,  dura  ;  and  sd,  subdural  space. 


nounced  vertigo.     Irritative  lesions  of  the  middle  peduncle  cause  complete  gyrating  movements  of 
the  body  around  its  axis,  together  with  rotation  of  the  eyes  (Nonai)  and  head  (Notkimgel). 

381.  PROTECTIVE  APPARATUS  OF  THE  BRAIN.— The  Membranes.— The 
dura  mater  cerebralis  is  intimately  united  to  the  periosteum  of  the  cavity  of  the  skull,  while  the 
.spinal  dura  mater  forms  around  the  spinal  cord  a  freely  suspended  long  sack,  fixed  only  on  its  ante- 
rinr  surface.  It  is  a  fibrous  membrane,  consisting  of  firm  bundles  of  connective  tissue  intermixed 
with  numerous  clastic  fibres,  and  provided  with  flattened  connective- tissue  corpuscles  and  Waldeyer's 
plasma  cells.  The  smooth  inner  surface  is  covered  with  a  layer  of  endothelium.  It  is  but  slightly 
supplied  with  blood  vessels,  although  they  are  more  numerous  in  the  outer  layers;  the  lymphatics 
are  numerous,  while  nerves  whose  terminations  are  unknown  give  to  the  dura  its  exquisite  sensi- 
bility to  painful  operations  on  it.  Pacinian  corpuscles  have  been  found  in  the  dura  over  the  tem- 
poral bone.  The  lymphatic  subdural  space  i  Key  and  Retzhis)  lies  between  the  dura  and  the 
arachnoid,  and  between  the  jiiaand  arachnoid  is  the  subarachnoid  space  (Fig.  444).  These  two 
spaces  do  not  communicate  directly.  The  delicate  arachnoid,  thin  and  partially  perforated,  poor  in 
blood  vessels  and  without  nerves,  is  covered  on  both  surfaces  with  squamous  endothelium.  Only 
on  the  spinal  cord  is  it  separated  from  the  pia,  so  that  between  the  two  lies  the  lymphatic  sub- 
arachnoid space ;  over  the  brain  the  two  membranes  are  for  the  most  part  united  together,  except 
the  parts  bridging  over  the  sulci  between  adjacent  convolutions.  The  arachnoid  passes  from  convo- 
lution to  convolution  without  dipping  into  the  sulci,  while  the  pia  dips  into  each  sulcus  (Fig.  444,  a). 
The  ventricles  of  the  brain  communicate  freely  with  the  lymphatic  subarachnoid  space,  but  not 


THE    MOVEMENTS   OF   THE    BRAIN.  743 

with  the  subdural  space  ( IFa/Jt-yer  ami  Fischer).  The  pia  consists  of  delicate  bundles  of  con- 
nective tissue  without  any  admixture  of  elastic  filires;  it  is  richly  supplied  with  blood  vessels  and 
lymphatics,  and  carries  nerves  which  accompany  the  blood  vessels  into  the  substance  of  the  brain 
{Kolliker).     The  lymphatics  open  into  the  subarachnoid  space  {\  196). 

[Subarachnoid  Fluid,  or  cerebro  spinal  fluid,  lies  in  the  subarachnoid  space,  which  is  traversed 
by  trabecuUe  of  connective  tissue.  Within  the  brain  are  a  series  of  cavities  called  ventricles, 
which  communicate  one  with  another  in  a  definite  way.  The  fourth  ventricle  is  lined  by  a  layer 
of  columnar  epithelium,  and  covered  in  dorsally  by  a  membrane  and  continuation  of  the  pia  mater, 
from  the  middle  of  which  there  hangs  into  the  roof  of  the  fourth  ventricle  two  vascular  processes 
composed  of  capillaries— the  choroid  ple.\uses  of  the  fourth  ventricle,  which  are  comparable  to  the 
larger  plexuses  of  the  lateral  ventricles.  In  this  membrane  is  the  foramen  of  Magendie  and  two 
other  smaller  foramina,  whereby  the  fluid  in  the  subarachnoid  space  communicates  with  that  in  the 
fourth  ventricle  ;  but  the  lymphatics  of  the  nerve  sheaths  can  be  injected  from  the  subarachnoid 
space,  so  that  there  is  direct  continuity  of  the  fluid  in  the  ventricles  of  the  brain  with  that  in  sub- 
arachnoid space,  perivascular  spaces  of  the  cerebral  substance,  and  the  perineural  lymphatics  of 
nerves.  The  average  quantity  is  about  2  ounces,  and  if  it  be  suddenly  withdrawn  epilepsy  or 
convulsions  may  be  produced,  or  if  it  be  rapidly  increased  in  amount  coma  may  be  produced.  The 
middle  and  posterior  parts  of  the  brain  and  the  medulla  oblongata  do  not  rest  directly  on  bone, 
but  are  separated  by  a  di.stinct  interval  from  their  osseous  case,  an  interval  occupied  by  the  cerebro- 
spinal fluid  and  traver-ed  by  trabeculce,  so  that,  as  Hilton  expresses  it,  this  fluid  forms  a  perfect 
water  bed  for  those  parts,  being  sustained  by  the  venous  circulation  and  the  elasticity  of  the  dura. 
It  has  important  mechanical  functions  protecting  delicate  parts  of  the  brain  from  injury;  by  dis- 
tributing vibratory  impulses  it  insulates  the  nerve  roots  and  has  important  relations  to  the  quantity 
of  blood  in  the  brain  and  the  cerebral  circulation  (Chemical  Composition,  \  198).] 

[Spina  Bifida. — Sometimes  the  laminie  of  the  vertebrs  in  the  lumbar  or  other  region  of  the 
spinal  column  are  imperfectly  developed,  in  which  case  the  membranes  project  through  as  a  tumor 
distended  by  cerebro-spinal  fluid  and  covered  by  skin.  The  effects  of  rapid  tapping  or  compressing 
the  sack  are  readily  studied  in  such  cases.] 

The  Pacchionian  bodies,  or  granulations,  are  connective-tissue  villi,  which  serve  for  the  out- 
flow of  lymph  from  the  subdural  and  subarachnoid  spaces  into  the  sinuses  of  the  dura  mater,  espe- 
cially the  longitudinal  sinus.  The  subarachnoid  space  also  communicates  with  the  spaces  in  the 
spongy  bone  of  the  skull,  and  with  the  veins  of  the  skull  and  surface  of  the  face  \Kollmann). 
The  subdural  space  also  communicates  with  the  lymphatic  spaces  in  the  dura,  while  the  latter  com- 
municate directly  with  the  veins  of  the  dura.  Both  the  subdural  and  subarachnoid  lymphatic 
spaces  communicate  with  the  lymphatics  of  the  nasal  mucous  membrane.  The  space  outside  the 
dura  of  the  spinal  cord  is  called  the  epidural  space,  and  may  be  regarded  as  lymphatic  in  its 
nature ;  the  pleural  and  peritoneal  cavities  may  be  filled  from  it ;  but  it  does  not  communicate  with 
the  cavity  of  the  skull  (  Waldeyer  and  Fischer).  The  plexuses  of  blood  vessels  are  surrounded  by 
undeveloped  connective  tissue.  The  teloe  choroideae  in  the  new-born  are  still  covered  with  ciliated 
epithelium. 

The  Movements  of  the  Brain. — The  pulsations  of  the  large  basal  cerebral 
vessels  communicate  their  pulsatile  movements  (§  79,  6)  to  the  brain — the 
respiratory  movements  also  affect  it,  so  that  the  brain  rises  during  expiration 
and  sinks  during  inspiration.  Lastly,  there  are  slight  alternating  vascular  eleva- 
tions and  depressions,  occurring  2  to  6  times  per  ininute,  due  to  the  periodic 
dilatation  and  contraction  of  the  blood  vessels  {%  371)-  Psychical  e.xcitement 
influences  these,  and  they  are  most  regular  during  sleep  {BurckharJt,  Mays). 
The  moveinents  are  best  seen,  especially  where  the  tnembranes  of  the  brain  offer 
little  resistance,  e.g.,  over  the  fontanelles  in  children,  and  where  the  membranes 
have  been  exposed  by  trephining.  The  presence  of  the  cerebro-spinal  fluid  is 
most  important  for  the  occurrence  of  these  movements,  as  it  propagates  the  pres- 
sure uniformly,  so  that  every  systolic  and  expiratory  dilatation  of  the  blood  vessels 
is  concentrated  upon  those  parts  of  the  cerebral  membrane  which  do  not  offer  any 
resistance  {Domfcrs).  When  the  fluid  escapes,  the  movements  may  alinost  dis- 
appear. 

Mental  excitement  increases  the  pulsations  of  the  brain.  At  the  moment  of  awaking,  the  amount 
of  blood  in  the  brain  diminishes ;  sensory  stimuli  applied  durmg  sleep,  so  that  the  sleeper  does  not 
awake,  increase  the  amount  of  blood.  As  the  arteries  within  the  rigid  skull  case  change  their  vol- 
ume with  each  pulse  beat,  the  veins  (sinuses)  exhibit  at  every  beat  a  pulsatile  variation  in  volume, 
the  opposite  of  that  occurring  in  the  arteries  [A/osso). 

The  Cerebral  Blood  Vessels. — The  blood  vessels  of  the  pia,  of  course,  are  regulated  by  the 
vasomotor  nerves  [if^  356,  A,  3),  and  their  calibre  may  also  be  influenced  by  the  stimulation  of  more 
distant  pans  of  the  body  (^  347).     Donders  trephined  the  skull  so  as  to  make  a  round  hole,  and 


744 


THE    GANGLIONIC    CEREBRAL   ARTERIES. 


filled  it  with  a  piece  of  glass,  so  that  with  a  microscope  he  could  observe  changes  in  the  calibre  of 
the  blood  vessels.  Paralysis  of  the  vasomotor  nerves  and  narcotics  dilate  the  blood  vessels ;  they 
become  greatly  contracted  at  death  (J  373,  I).  The  blood  vessels  are  dilated  during  cerebral 
activity  (^  100,  A)  as  well  as  during  sleep.  Increased  pressure  within  the  skull  causes  great  de- 
rangement of  the  cerebral  activity;  labored  respiration  (^  368,  B),  unconsciousness  even  to  coma, 
and  paralytic  phenomena — all  of  which  may,  in  part,  be  referable  to  disturbances  of  the  circulation. 
If  all  the  cranial  arteries  be  ligatured  suddenly,  there  is  immediate  loss  of  consciousness,  together 
with  strong  stimulation  of  the  medulla  oblongata  and  its  centres,  and  death  takes  place  rapidly  with 
convulsions  (compare  ^  373). 

By  the  free  anastomosis  which  takes  place  at  the  base  of  the  brain  forming  the  circle  of 
Willis  (Fig.  445 ),  the  individual  parts  of  the  brain  are  preserved  from  want  of  blood,  when  one  or 
other  blood  vessel  is  compressed  or  ligatured.  Within  the  brain  the  arteries  are  distributed  as 
"terminal  "  arteries,  i.  e.,  the  terminal  branches  of  any  one  artery  end  in  their  own  area,  and  do 
not  anastomose  with  those  of  adjoining  areas  [Cohnheim).     On  the  other  hand,  the  peripheral 


Fig.  445. 


Arteries  of  the  base  of  the  brain,  or  circle  of  Willis.    CC,  internal  carotids  ;  Q  \,  anterior  cerebral :  SS,  Sylvi; 
teries :  V  V,  vertebrals  ;  B,  basilar  ;    C  P,  posterior  cerebrals  ;  1,  2,  3,  4,  4,  4,  groups  of  nutri 
dotted  line  shows  the  limit  of  the  ganglionic  area. 


arteries  (arteries  of  the  corpus  callosum,  Sylvian  fissure,  and  deep  cerebral)  which  run  externally  on 
the  brain  form  free  anastomoses  ( Tichomirom). 

[The  nutrient  or  ganglionic  arteries  for  the  central  ganglia  arise  in  groups  from  the  circle  of 
Willis,  or  from  the  first  two  centimetres  of  its  trunks.  The  antero-median  group  (i)  supplies  the 
anterior  part  of  the  head  of  the  caudate  nucleus.  The  postero-median  (2)  enter  the  posterior 
perforated  space  and  supply  the  internal  surface  of  the  optic  thalami  and  the  walls  of  the  third 
ventricle.  The  antero-lateral  group.s  (3,3)  from  the  middle  cerebral  enter  the  anterior  perforated 
space,  supply  the  corpora  striata,  the  anterior  part  of  the  optic  thalamus,  and  the  internal  capsule. 
These  branches  are  apt  to  rupture.  The  postero-lateral  (4,  4)  supply  a  large  part  of  the  optic 
thalami  {C/iaicol).  A  line  drawn  at  a  distance  of  two  centimetres  outside  the  circle  of  Willis 
encloses  the  ganglionic  area.  The  cerebral  convolutions  are  supplied  by  the  large  branches  of 
the  circle  of  Willis.  The  anterior  cerebral  curves  round  the  corpus  callosum,  and  supplies  the 
gyrus  rectus  and  the  supraorbital,  the  first  and  second  frontal  convolutions,  the  upper  part  of  the 
ascending  frontal,  and  the  inner  surface  of  the  hemisphere  as  far  as  the  quadrate  lobule  (  Fig.  370, 
I).     The  posterior  cerebral  goes  to  the  region  of  the  occipital  lobe  and  the  inferior  aspect  of  the 


THE    VENOUS   CIRCULATION. 


745 


temporal  lobe;  the  middle  cerebral  or  Sylvian  artery  divides  into  four  branches,  which  go  to  the 
posterior  part  of  the  frontal  lobe,  ascending  frontal,  and  to  all  the  parietal  lobes,  i.  e.,  chiefly  to  the 
motor  areas  (III),  the  angular  gyrus,  and  to  the  first  temporo-sphenoidal  lobule.  The  terminal 
branches  of  these  ganglionic  arteries  do  not  anastomose  with  the  cortical  system.  Fig.  446  shows 
the  ganglionic  arteries  piercing  the  basal  ganglia.  Obviously,  when  hemorrhage  of  the  lenticulo- 
striale  artery  or  "  artery  of  hemorrhage  "  (4,  4)  occurs,  it  will  compress  the  lenticular  nucleus,  or 
tear  it  up,  and  may  even  injure  the  parts  outside,  such  as  the  external  capsule,  claustrum  (T),  and 
island  of  Keil  (R),  or  those  inside,  <>.?■.,  the  internal  capsule.] 

[Thus  the  anterior  cerebral  supplies  the  prefrontal  area  and  a  small  part  of  the  motor  area,  that 
for  the  leg  centre  in  the  paracentral  lobule  and  upper  end  of  the  ascending  front  (and  perhaps  for 
the  trunk).  The  posterior  cerebral  supplies  the  centre  for  vision,  and  that  connected  with  the 
course  of  the  posterior  part  of  the  optic  expansion,  and  also  the  sensory  part  of  the  internal  capsule. 
The  middle  cerebral  supplies  the  motor  areas  of  the  cortex  except  part  of  the  leg  centre  and  the 
basal  ganglia,  the  auditory  centre,  and  that  for  speech  [G(yuiers).'\ 

[The  cerebral  circulation  has  many  peculiarities.  The  curves  on  the  arteries  serve  to  modify 
the  effect  of  the  cardiac  shock;  the  circle  of  Willis  permits  within  limits  a  free  circulation,  but  in 
as  far  as  the  skull  is  largely  a  rigid  box,  it  was  at  one  time  taught  that,  as  the  brain  substance  and 
its  fluids  were  practically  incompressible,  it  was  impossible  to  alter  the  amount  of  blood  in  the 
brain.     This  is  a  mistake.     The  amount  of  blood  undergoes  an  alteration  in  this  way,  that  when 


Fig.  446. 


Transverse  section  of  the  cerebrum  behind  the  optic  chiasma.  Arteries  of  the  corpus  striatum.  C  k,  optic  chiasma  : 
B,  section  of  optic  tract ;  L,  lenticular  nucleus  ;  I,  internal  capsule  ;  C.  caudate  nucleus  ;  E,  external  capsule  ; 
T,  claustrum:  R,  convolutions  of  the  island  of  Reil :  V  V,  section  of  the  lateral  ventricles  ;  P  P,  pillars  of  the 
fornix  ;  O.gray  substance  of  the  third  ventricle.  Vascular  areas— I,  anterior  cerebral  artery;  II,  Sylvian  artery; 
III,  posterior  cerebral  artery  ;  i,  internal  carotid  ;  2,  Sylvian,  3,  anterior  cerebral  artery  ;  4,  4,  lenticulo-striate 
s :  5,  5,  lenticular  arteries. 


more  blood  passes  in,  some  cerebro-spinal  fluid  moves  out,  and  -'ice  zvrsa,  so  that  there  is  an  inti- 
mite  relation  between  the<e  fluids.  In  the  developing  skull  the  cerebro-spinal  fluid  may  accumulate 
in  large  amount  within  the  ventricles,  and  greitly  distend  both  them  and  the  yielding  skull  case 
from  internal  pressure,  as  in  acute  hydrocephalus.  The  peculiarities  and  independence  of  the 
cortical  and  ganglionic  arteries  have  already  been  referred  tn.  Plugging  by  means  of  a  clot, 
vegetation  or  wart  carried  from  the  heart  is  common  in  the  left  middle  cerebral  artery.  Why? 
When  the  plug  is  washed  away  by  the  blood  stream,  owing  to  the  left  carotid  springing  from  the 
aorta  nearly  in  line  with  the  blood  current,  the  plug  readily  passes  into  the  carotid,  and  so  into  the 
left  middle  cerebral,  which  is  in  line  with  the  internal  carotid.  In  such  a  case,  the  convolutions 
and  parts  supplied  by  it  are  suddenly  deprived  of  blood  with  immediate  and  serious  results] 

[The  venous  circulation  is  peculiar.  The  sinuses  are  really  spaces  between  the  layers  of  the 
tough  dura  mater,  and  partly  bounded  by  bone.  The  blood  moves  in  the  longitudinal  sinus  from 
before  backward,  but  most  of  the  cortical  veins  open  into  it  in  a  forward  direction,  so  that  their 
stream  Is  opposed  to  that  in  the  sinus.  Thus,  the  blood  which  enters  the  brain  by  ascending  arteries 
reaches  the  sinuses  by  ascending  veins,  the  reverse  of  what  obtains  elsewhere,  where  ascending 
veins  convey  blood  from  descending  arteries,  whereby  the  hydrostatic  pressure  and  gravity  aid  the 
circulation,  but  here  gravitation  is  opposed  to  the  flow  of  blood  in  the  cerebral  veins.  This  will 
help  to  explain  the  occurrence  of  thrombosis  in  these  vessels.  Some  of  the  veins  on  the  surface 
communicate  with  intracranial  veins,  e.  ^.,  those  of  the   nose,  the   facial   through  the   ophthalmic, 


746 


COMPARATIVE HISTORICAL. 


mastoid  veins  and  veins  of  the  diploe.  Hence,  morbid  processes  affecting  the  scalp  (erysipelas), 
ear  (caries),  or  face  (carbuncle)  may  readily  affect  intracranial  structures  (Gimiers).] 

If  a  person  who  has  been  in  bed  for  a  long  time,  and  whose  blood  is  small  in  amount,  be  suddenly 
lifted  up  into  the  erect  position,  cerebral  anitmia  is  not  unfrequently  produced,  owing  to  hydrostatic 
causes.  At  the  same  time  there  may  be  loss  of  consciousness  and  impiirment  of  the  senses.  Lie- 
bermeister  regards  the  thyyoul  gland  as  a  collateral  blood  reservoir  which  empties  its  blood  toward 
the  head  during  such  changes  of  the  position  of  the  body.  Perhaps  this  may  e.Nplain  the  swelling 
of  the  thyroid  as  a  compensatory  act,  when  the  heart  heats  violently  and  the  brain  is  surcharged 
with  lilood  (^J  103,  111,  and  371).  Very  violent  muscular  e.xertion,  as  well  as  marked  activity  of 
other  organs,  cause  a  very  considerable  fall  of  the  blood  pressure  in  the  carotid. 

Pressure  on  the  Brain. — The  brain  and  the  fluid  surrounding  it  are  constantly  subjected  to  a 
certain  mean  pressure,  which  must  ultimately  depend  upon  the  blood  pressure  within  the  vascular 
system.  The  investigations  of  Naunyn  and  -Schreiber  on  the  cerebral  pressure  (01  cerebro-spinal 
pressure)  showed  that  the  pressure  must  be  slightly  less  than  the  pressure  within  the  carotid  before 
the  symptoms  proper  to  pressure  on  the  brain  occur.  Tliese  are  sudden  attacks  of  headache,  with 
vertigo,  or  it  may  be  loss  of  consciousness,  vomiting,  slowing  of  the  pulse,  slow  and  .shallow  respi- 
ration, convulsions — while  the  pressure  of  the  cerebro-spinal  lluid  is  increased.  The  cause  of  these 
phenomena  lies  in  the  anaemia  of  the  l)rain.  If  the  pressure  is  moderate,  the  above-named  symp- 
toms may  remain  latent;  nevertheless,  disturbances  of  the  nutrition  of  the  brain  occur,  with  con- 
secutive phenomena,  such  as  persistent  slight  headache,  feeling  of  vertigo,  muscular  weakness  and 
disturbances  of  visicm  (owing  to  neuro-retinitis  with  choked  disk).  Increase  of  the  blood  pressure 
diminishes  the  symptoms,  while  diminution  of  the  blood  pressure  causes  more  pronounced  phe- 
nomena of  cerebro-spinal  pressure.  In  the  dog.  frain  begins  with  a  pressure  of  70  to  80  mm.  Hg. 
Consciousness  is  abolished  when  the  pressure  is  higher,  and  at  80  to  100  mm.  spasms  take  place.  A 
pressure  of  100  to  120  mm.  causes  slowing  of  the  pulse,  owing  to  stimulation  of  the  vagus  at  its 
origin;  the  respirations  are  temporarily  accelerated  and  then  diminish.  Long  continued  severe 
compression  always,  sooner  or  later,  ends  fatally.  The  blood  pressure  at  first  is  increased,  owing  to 
reflex  stimulation  of  the  vasomotor  centre  from  the  pressure  stimulating  the  sensory  nerves;  ulti- 
mately the  blood  pressure  falls  and  the  pulse  becomes  very  slow.  Irregular  variations  in  the  blood 
pressure  point  to  a  direct  central  stimulation  of  the  vasomotor  centre  by  pressure.  The  application 
of  continued,  slowly-increasing  pressure  compresses  the  brain  {Adamkiewicz). 

382.  COMPARATIVE— HISTORICAL.— Comparative.— Nerves  are  absent  in  the  pro- 
tozoa. Neuro-muscular  cells  (§  296)  occur  in  the  ccslenterata,  in  the  hydroida  and  medusi'e,  and 
they  are  the  first  indications  of  a  nervous  apparatus.  The  umbrella  of  the  medusa  is  covered  with 
a  plexus  of  nerve  fibrils,  which  at  various  parts  along  its  marcin  is  provided  with  small  cellular 
thickenings  corresponding  to  ganglia,  and  from  these  nerve  fibres  proceed  to  the  sense  organs. 
Many  of  the  worms  possess  a  nervous  ring  in  the  cephalic  portion,  and  in  those  provided  with  an 
intestine  a  single  or  double  nervous  cord,  in  the  form  of  a  ring,  surrounds  the  pharynx.  Branches 
(often  two)  ])ass  from  this  into  the  elongated  body,  and  usually  these  carry  ganglia  corresponding  to 
each  ring  of  the  body  of  the  animal.  In  the  leech  only  one  gangliated  cord  is  present.  In  the 
echinodermata  a  large  nerve  ring  surrounds  the  mrath,  and  from  it  large  nerves  proceed,  corre- 
sponding to  the  chief  trunks  of  the  water-vascular  system.  .'\t  the  points  where  the  nerves  are  given 
off,  the  nervous  ring  is  provided  with  the  so-called  "  amhulacral  brains."  The  arthropoda  are 
provided  with  a  large  cephalic  ganglion  placed  above  the  pharynx,  from  which  nerves  pass  to  the 
sense  organs.  Another  ganglion  lies  on  the  under  surface  of  the  pharynx,  and  is  connected  with 
the  former  by  commissures.  The  pharynx  is  thus  embnced  by  a  gangliated  ring,  and  from  it  pro- 
ceed the  abdominal  gangliated  double  chain,  along  the  ventral  surface  of  the  body,  through  the 
thorax  and  abdomen.  Sometimes  several  ganglia  unite  to  form  a  large  compound  ganglion,  while 
in  other  cases  each  segment  of  the  body  contains  its  own  ganglia.  In  the  mollusca  the  (esopha- 
geal nervous  ring  is  present,  although  the  ganglionic  masses  vary  much  in  position  within  it.  A 
number  of  compound  ganglia  lie  scattered  in  different  parts  of  the  body,  and  are  united  by  nerves 
to  the  former.  They  represent  the  sympathetic  system.  In  the  cephalopoda  the  (esophageal  ring 
has  almost  no  commissure,  and  a  part  of  the  ganglionic  matter  is  enclosed  in  a  cartilaginous  capsule, 
and  is  often  spoken  of  as  a  "  brain."  Additional  ganglia  are  found  in  the  mantle,  heart  and  stomach. 
In  vertebrates  the  nervous  system  invariably  lies  on  the  dorsal  aspect  of  the  body.  In  the  amphi- 
oxus  there  is  no  separation  into  brain  and  spinal  cord.      (See  '</'i  374  and  375.) 

Historical. — Alkmaon  (580  B.C.)  placed  the  seat  of  consciousness  in  the  brain;  Galen  (131-203 
A.D.)  regarded  it  as  the  seat  of  the  impulses  for  voluntary  movements.  Aristotle  (3S4  B.c)  ascribed 
the  relatively  largest  brain  to  man;  he  stated  that  it  was  inexcitable  to  stimuli  (insensible).  One  of 
the  functions  he  ascribed  to  the  brain  was  to  cool  the  heat  ascending  from  the  heart.  Herophilus 
(300 B.C.)  gave  the  name  calamus  scriptorms,  and  he  regarded  the  4th  ventricle  as  the  most  important 
organ  for  the  maintenance  of  life.  Even  in  Homer  there  are  repeated  references  to  the  dangers  of 
injuries  of  the  neck.  Aretaeus  and  Cassius  Felix  (97  A.D.)  were  aware  of  the  fact  that  lesion  of 
one  cerebral  hemisphere  caused  paralysis  on  the  opposite  side  of  the  body.  Galen  was  acquainted 
with  the  path  in  the  spinal  cord  connected  with  movement  and  sensation.  Vesalius  (1540)  <le- 
scribed  the  five  ventricles  of  the  brain.     R.  Colombo  (1559)  observed  the  movements  of  the  brain 


HISTORICAL.  747 

isochronous  with  the  action  of  the  heart.  A  more  careful  description  of  these  movements  was 
given  by  Riolan  (1618).  Coiter  (1573)  discovered  that  an  animal  can  live  after  removal  of  its 
cerebrum.  About  the  middle  of  the  17th  century,  Wepfer  discovered  the  hemorrhagic  nature  of 
apoplexy.  Schneider  (1660)  estimated  the  weight  of  the  brain  in  different  animals.  Mistichelli 
(1709)  and  Petit  ( 1710)  described  the  decussation  of  the  fibres  of  the  spinal  cord  below  the  pons. 
Gall  discovered  the  partial  origin  of  the  optic  nerve  from  the  anterior  pair  of  the  corpora  quadri- 
gemina,  and  by  dissecting  the  brain  from  below  he  attempted  to  trace  the  course  of  the  nerve  fibres 
to  the  convolutions  (1810).  Rolando  described  more  accurately  the  form  of  the  gray  matter  of  the 
spinal  cord.  Carus  (1814)  discovered  the  central  canal.  The  most  compendious  work  on  the  brain 
was  written  by  Burdach  (1819-1826).     The  more  recent  observations  are  referred  to  in  the  text. 


Physiology  of  the  Sense  Organs. 


383.  INTRODUCTORY  OBSERVATIONS.— Requisite  Condi- 
tions.— The  sense  organs  have  the  function  of  transferring  to  the  sensorium  im- 
pressions of  the  various  phenomena  of  the  external  world  ;  they  are,  in  fact,  the 
intermediate  instruments  o{  sensory  perceptions.  In  order  that  this  may  occur,  the 
following  conditions  must  be  fulfilled:  (i)  The  sense  organ,  provided  with  its 
specific  end  organ,  must  be  anatomically  perfect,  and  capable  of  acting  physio- 
logically. (2)  A  "  specific  stimulus"  must  be  present,  which,  under  normal 
conditions,  acts  upon  the  end  organ.  (3)  The  sense  organ  must  be  connected 
with  the  cerebrum  by  means  of  a  nerve,  and  the  conduction  through  this  path 
must  be  uninterrupted.  (4)  During  the  act  of  stimulation,  the  psychical  activity 
(attention)  must  be  directed  to  the  process,  and  then  the  sensation  results,  e.g., 
of  light  or  sound,  through  the  sense  organ.  (5)  Lastly,  when  by  a  psychical  act 
the  sensation  is  referred  to  the  external  cause,  then  there  is  a  conscious  sensory 
perception.  Often,  however,  this  relation  is  completed  as  an  unconscious  con- 
clusion, as  it  is  essentially  a  deduction  from  previous  experience. 

Stimuli.— With  regard  to  the  stimuli  which  are  applied  to  the  sensory  apparatus,  we  distinguish  : 
(l)  Adequate  or  homologous  stimuli,  i.e.,  stimuli  for  whose  action  the  sense  organs  are  specially 
adapted,  such  as  the  rods  and  cones  of  the  retina  for  the  vibrations  of  the  ether.  Thus  each  sense 
organ  has  a  specific  form  of  stimulus  best  adapted  to  act  upon  it.  This  is  what  Johannes  Miiller 
called  the  law  of  specific  energy.  (2)  There  are  many  other  forms  of  stimuli  (mechanical,  thermal, 
chemical,  electrical,  interna!  somatic)  which  act  upon  the  sense  organs,  producing  the  Bash  of  light 
belieltl  when  the  eye  is  struck  ;  singing  in  the  ears  when  there  is  congestion  of  the  head.  These 
heterologous  stimuli  act  upon  llie  nervous  elements  of  the  sensory  apparatus  along  their  entire 
course,  from  the  end  organ  to  the  cortex  cerebri.  The  homologous  stimuli,  on  the  other  hand,  act 
only  on  the  end  organ,  i.e.,  light  has  no  effect  whatever  upon  the  trunk  of  the  exposed  optic  nerve. 

Strengfth  and  Liminal  Intensity. — Homologous  stimuli  act  upon  the  sen- 
sory organs  only  within  certain  limits  as  to  strength.  Very  feeble  stimuli  at  first 
produce  no  effect.  That  strength  of  stimulus  which  is  just  sufficient  to  cause  the 
first  trace  of  a  sensation  is  called  by  Fechner  the  "  liminal  intensity  "  of  the 
sensation.  As  the  strength  of  the  stimulus  increases  so  also  do  the  sensations,  but 
the  sensations  increase  equally  when  the  strength  of  the  stimulus  increases  in  rela- 
tive proportions.  Thus  we  have  the  same  sensation  of  equal  increase  of  light 
when,  instead  of  10  candles,  11,  or  instead  of  100  candles,  no  are  lighted — the 
proportion  of  increase  in  both  cases  is  equal  to  one-tenth.  As  the  logarithm  of 
the  numbers  increases  in  an  equal  degree  when  the  numbers  increase  in  the  same 
relative  proportion,  the  law  may  be  expressed  thus:  "  The  sensations  do  not  in- 
crease with  the  absolute  strength  of  the  stimuli,  but  nearly  as  the  logarithm  of  the 
strength  of  the  stimulus."  This  is  Fechner' s  "  psycho-physical  law,"  but  its 
accuracy  has  recently  been  challenged  by  E.  Hering.  [It  holds  good  only  with 
regard  to  stimuli  of  medium  strength.]  If  the  specific  stimulus  be  too  inten,se  it 
gives  rise  to  peculiar  painful  sensations,  e.g.,  a  feeling  of  blindness  or  deafness,  as 
the  case  may  be.  The  sense  organs  respond  to  adequate  stimuli,  but  only  within 
certain  limits  of  the  stimulus,  e.g.,  the  ear  responds  only  to  vibrating  bodies  emit- 
ting a  certain  range  of  vibrations  per  second ;  the  retina  responds  only  to  the 
vibrations  of  the  ether  between  red  and  violet,  but  not  to  the  so-called  heat  vibra- 
tions or  to  the  chemically  active  vibrations. 

748 


fechner's  law.  749 

[Fechner's  Law. — Expressed  in  another  way,  the  result  depends  on  (i)the  strength  of  the 
stimulus,  and  (2)  the  degree  of  excitability.  Supposing  the  latter  to  be  constant  while  the  former  is 
varied,  it  is  found  that  if  the  stimulus  be  doubled,  tripled  or  quadrupled,  the  sensation  increases 
only  as  the  logarithm  of  the  sthnulus.  Suppose  the  stimulus  to  be  increased  10,  100  or  1000 
times,  then  the  sensation  increases  only  as  i,  2  or  3.  Just  as  there  '\%  2,  lower  limit  of  excitation, 
liminal  intensity  (or  threshold),  so  there  is  an  upper  limit  or  maximum  of  excitation,  or  height  of 
sensibility  ( IVundt),  when  any  further  increase  produces  no  appreciable  increase  in  the  sensation. 
Thus  we  do  not  notice  any  difference  between  the  central  and  peripheral  portion  of  the  sun's  disk, 
though  the  difference  of  light  intensity  is  enormous  (Stilly).  Between  these  two  is  the  range  of 
sensibility  ( IVundt).  There  is  always  a  constant  ratio  between  the  strength  of  the  stimulus  and  the 
intensity  of  the  sensation.  The  stronger  the  stimulus  already  applied  the  stronger  must  be  the 
increase  of  the  stimulus  in  order  to  cause  a  perceptible  increase  of  the  sensation  (IVeber's  Law). 
The  necessary  increment  is  proportional  to  the  intensity  of  the  stimulus,  and  it  varies  for  each  sense 
organ.  If  a  weight  of  10  grams  be  placed  in  the  hand,  it  is  found  that  3.3  grams  must  be  added 
or  removed  before  a  difference  in  the  sensation  is  perceptible  ;  if  100  grams  are  held,  ^^.t,  grams 
must  be  added  or  removed  to  obtain  a  perceptible  difference  in  the  sensation.  The  magnitude  of 
the  fraction  indicating  the  increment  of  stimulus  necessary  to  obtain  a  perceptible  difference  of  the 
sensation  is  spoken  of  as  the  constant  proportion  or  the  discriminative  sensibility.  In  the  above 
case  it  is  I  :  3.     The  following  table  gives  approximately  the  constant  proportion  for  each  sense  : — 

Tactile  Sensation 1:3.^     I     Muscular  Sensation    .    .    .  6  :  100. y^;^ 

Thermal I  :  3.   I3  Visual  "  .    .    .  I  :  loo.jl^] 

Auditory '  •  3-    'i     I 

The  term  after  sensation  is  applied  to  the  following  phenomenon,  viz.,  that, 
as  a  rule,  the  sensation  lasts  longer  than  the  stimulus  producing  it ;  thus  there  is 
an  after  sensation  after  pressure  is  applied  to  the  skin.  Subjective  sensations 
occur  when  stimuli  due  to  internal  somatic  causes  excite  the  nervous  apparatus  of 
the  sense  organ.  The  highest  degrees  of  these,  depending  mostly  upon  patho- 
logical stimulation  of  the  psycho-sensorial  cortical  centres,  are  characterized  as 
hallucinations,  e.g.,  when  a  delirious  person  imagines  he  sees  figures  or  hears 
sounds  which  have  no  objective  reality.  In  opposition  to  this  condition  the  term 
illusion  is  applied  to  modifications  by  the  sensorium  of  sensations  actually  caused 
by  external  objects,  e.g.,  when  the  rolling  of  a  wagon  is  mistaken  for  thunder. 

In  a  new-born  child  the  sense  of  touch  is  strongly  developed,  pain  slightly,  muscular  sensations 
are  undoubtedly  present,  while  smell  and  taste  are  frequently  confounded.  Auditory  stimuli  are 
heard  from  the  second  day  onward,  the  stimulus  of  light  immediately  after  birth,  but  a  peripheral  field 
of  vision  does  not  yet  exist  [Cuignet).  Toward  the  fourth  to  fifth  week  the  movements  of  conver- 
gence and  accommodation  are  noticeable,  while  after  four  months  colors  are  distinguished.  The 
various  stimuli  are  not  perceived  simultaneously — a  reflex  inhibitory  centre  is  not  yet  developed 
{Genzmer). 


THE  VISUAL  APPARATUS-THE  EYE. 


384.  ANATOMICO-HISTOLOGICAL  OBSERVATIONS.— In  the 

following  remarks  it  is  assumed   that   the  student  is  familiar  with  the  anatomical 
structure  of  the  eye  :  — 

The  cornea,  for  the  sake  of  simplicity,  is  regarded  as  uniformly  spherical,  although,  properly 
speaking,  it  differs  slightly  from  this  form.  It  is  more  lil<e  a  vertical  section  of  a  somewhat  oblique 
ellipsoid,  which  we  must  suppose  to  be  formed  by  rotating  an  ellipse  around  us  long  axis  (Briicie). 
It  is  nearly  of  uniform  thickness  throughout,  only  in  the  infant  it  is  slightly  thicker  in  the  centre, 
and  in  the  adult  slightly  thinner.     The  cornea  consists  of  the  following  layers  :  — 

[i.  Anterior  stratified  epithelium.  4.   Posterior  elastic  lamina. 

2.  Anterior  elastic  lamina.  5.  Single  layer  of  epithelium.] 

3.  Substantia  propria. 

I.  The  anterior  epithelium,  stratified   and  nucleated  (Fig.  449,  n),  consists  of  many  layers  of 


Fig.  447 


Fig.  447.— Cornea  of  the  frog  treated  with  chloride  of  gold,  showing  the  corneal  corpuscles  ■  ,      .  ,      , 

fibrils.     Fig.  448.— Cornea  of  the  frog  treated   with  silver  nitrate;  the  ground  substance  is  stained,  while  the 
spaces  for  the  corneal  corpuscles  are  left  unstained 

cells.  The  deepest  cells  are  more  or  less  columnar,  are  arranged  side  by  side,  and  are  called  sup- 
porting cells.  The  cells  of  the  middle  layers  are  more  arched,  and  dip  with  finger-shaped  processes 
into  corresponding  spaces  between  their  neighbors.  The  most  superficial  cells  are  flat,  perfectly 
smooth,  hard,  keratin-containing  squamous  epithelium.  2.  The  epithelial  layer  rests  upon  the 
anterior  elastic  membrane  (Bowman's  elastic  lamina),  a  structureless,  clear  basement-like  mem- 
brane (/'),  whose  existence  is  denied  by  Briicke.  3.  The  substantia  propria  of  the  cornea  consists 
of  (choniirin-yielding)  fibres  {Johannes  Miiller,  Kolletl)  composed  of  delicate  fibrils  of  connective 
tissue.  The  fibres  are  arranged  in  mat-like,  thin  lamell.-e  (/),  more  or  less  united  together,  and  are 
placed  in  layers  over  each  other.  Toward  the  anterior  elastic  lamina  the  fibres  bend  round  and  per- 
forate the  superficial  lamella:,  thus  serving  as  supporting  fibres.  [These  perforating  fibres  are  com- 
parable to  Sharpey's  fibres  in  bone.]  Bttween  the  lamella-  are  a  series  of  intercommunicating 
spaces  lined  by  endothelium.  These  spaces  are  really  lymph  spaces,  and  they  communicate  with 
the  lymphatics  of  the  conjunctiva.  The  fi.\ed  corneal  corpuscles  (r)  lie  in  these  spaces,  and  are 
provided  with  numerous  processes,  which  anastomose  w  ith  the  processes  of  corpuscles  lying  between 

750 


THE    CORNEA    AND    BOWMAN  S   TUBES. 


751 


the  lamella  above  and  below  them,  and  on  either  side  of  them.  KUhne  observed  that  stimulation 
of  the  corneal  nerves  was  foUoweii  by  contraction  of  these  cells  (^  2or,  7) ;  while  KUhne  and  Wal- 
deyer  maintain  that  they  are  connected  with  the  corneal  nerve  fibrils. 

[The  corneal  corpuscles  are  looked  upon  as  branched  connective-tissue  corpuscles  lying  in  and 
not  quite  filling  the  branched  spaces  between  the  lamella;.  The  processes  anastomose  freely  with 
similar  cells  in  the  same  plane,  and  to  a  less  extent  with  the  processes  of  cells  in  planes  immediately 
above  and  below  them.  In  a  section  stained  with  gold  chloride  they  present  the  appearance  seen 
in  Fig.  447.  In  a  vertical  section  of  the  cornea  they  appear  fusiform  (Fig.  449)  and  parallel  to  the 
free  surface  of  the  cornea.  If  the  cornea  of  a  frog  be  pencilled  with  silver  nitrate,  the  cement  sub- 
stance between  the  lamellfe  is  blackened, and  the  branched  cell  spaces  remain  clear,  as  in  Fig.  448. 
The  one  figure  represents,  as  it  were,  the  positive,  and  the  other  the  negative  image.] 

Fig.  449. 


<7^--— :-T 


Antero-posterior  section  at  the  junction  of  the  cornea  with  the 
lium ;  ^,  Bowman's  lamina;  c,  corneal  corpuscles  lying 
thickness  lying  between  6  and  d  is  the  substantia  propria  c 
ering  it ;  A  junction  of  cornea  with  the  sclerotic  :  £-,  limbu 
k,  Leber  s  venous  plexus  (is  regarded  by  Leber  as  belong 
pectinatum  ;  m,  attachment  of  the  iris  ;  (j.longitud: 


irneac)  :  rf,  Descemefs 
conjunctiva  ;  //,  conj 
ig  to  i) ;  m,  f/t,  meshc 
-  (divided  tran: 


corneal,  or  conjunctival  epithe- 
f,  corneal  lamellae  (the  whole 
;  membrane  ;  tr,  epithelium  cov- 

va  :  i,  canal  of  Schlemm  ; 

the  tissue  of  the  lig.  iridis 
ly)  bundles  of  fibres  of  the 


-  Jerotic  ;  ^,  perichoroidal  space  ;  s.  meridional  [radiating] ;  /,  equatorial  (circular)  bundles  of  the  ciliary  muscle; 
u,  transverse  section  of  a  ciliary  artery  ;  v,  epithelium  of  the  iris  (a  continuation  of  that  on  the  posterior  surface 
of  the  cornea)  ;  w,  substance  of  the  iris  ;  jr,  pigment  of  the  iris  ;  z^  a  ciliary  process. 

[Bowman's  tubes  are  artificial  productions,  formed  by  forcing  air  or  a  colored  fluid  between 
the  lamella',  when  it  passes  between  the  bundles  of  fibrils,  forming  a  series  of  tubes  with  dilatations 
un  them  and  running  at  right  angles  to  one  another  between  the  lamelhie.] 

.According  to  v.  Recklinghausen,  leucocytes  also  pass  into  these  lymph  spaces  or  juice  canals. 
The  importance  of  these  leucocyles  in  inflammation  is  referred  to  in  ^  200.  4.  The  transparent 
structureless  posterior  elastic  membrane  (</),  the  membrane  of  Descemel  or  Demours,  is  in  many 
animals  fibrillated,  and  shows  evidence  of  stratification,  while  toward  the  margin  of  the  cornea 
there  are  occasionally  slight  conical  elevations.  This  membrane  is  very  tough  and  very  resi^tant  (of 
great  importance  in  inflammation).  If  it  be  removed,  it  rolls  up  toward  the  convex  side  .At  its 
periphery  it  becomes  continuous  with  the  fibro-elastic  reticulated  ligamentum  pectinatum  iridis, 


752 


THE  NERVES  OF  THE  CORNEA. 


whose  trabeculK  are  covered  by  epithelium.  5.  The  posterior  single  layer  of  epithelium  consists 
of  flat,  delicate  nucleated  cells  {/),  which  are  continued  from  the  margin  of  the  cornea  on  to  the 
anterior  surface  of  the  iris  (v).  Fine  juice  canals  exist  in  the  spaces  between  the  individual  cells 
(v.  /{eciling/iausen).  These  spaces  communicate  with  a  system  of  fine  tubes  under  the  epithelium, 
perforate  Descemet's  membrane,  and  thus  communicate  with  the  corneal  spaces  [Preiss), 

Fig.  450. 
A_       ^ 


,  l^-%^V,f^fT7u    '(.'' 


ucleus  ;  /, 


The  nerves  of  the  cornea,  which  are  derived  from  the  long  and  short  ciliary  nerves  (§  347),  are 
partly  sensory  in  function.  They  enter  the  cornea  at  its  margin  as  medullated  fibres,  but  the  myelin 
soon  disappears,  while  the  axial  cylinders  split  up  into  fibrils.  [The  axial  cylinders  branch  and  form 
a  plexus  between  the  lamella:,  especially  near  the  anterior  surface,  the  fundamental  or  ground 
plexus  (Fig.  450,  «).  There  are  triangular  nuclei  at  the  nodal  points,  but  they  probably  belong  to 
the  sheath  of  fl.attened  cells  which  cover  the  larger  branches.     There  is  a  finer  and  denser  plexus 

Fir    }-i 


Nerve  pie 


L  after  gold  chloride,     n. 


: :  a,  fibrils. 


of  fibrils  immediately  under  the  anterior  epithelium,  subepithelial  plexus  (Fig.  451),  which  is 
derived  from  the  former,  the  fibrils  arising  in  pencils  or  groups.  Some  fibrils  perforate  the  anterior 
elastic  lamina,  rami  perforantes,  and  pass  between  the  anterior  epithelial  cells  to  form  the  intra- 
epithelial network  (Fig.  450,  /',/).  Some  observers  suppose  that  they  terminate  in  free,  pointed, 
or  bulbous  ends.     There  is  also  a  fine  plexus  of  fibrils  in  the  posterior  layers  of  the  cornea,  near 


THE   CHOROID    AND    CILIARY    MUSCLE. 


753 


Descemet's  membrane.  It  gives  off  numerous  fine  fibrils,  which  come  into  intimate,  if  not  direct, 
anatomical  relation  with  the  corneal  corpuscles.  The  trophic  fibres  of  the  cornea  {\  347)  are,  per- 
haps, those  deeper  branches  which  are  connected  with  the  corneal  corpuscles.] 

[Method. — These  fibrils  are  best  revealed  by  staining  a  cornea  with  chloride  of  gold,  which  stains 
them  of  a  purplish  tinge  after  exposure  to  light  (Co/in/ieim).'] 

Blood  Vessels  occur  only  in  the  outer  margin  of  the  cornea  (Fig.  452,  -'),  and  extend  2  mm. 
over  the  cornea  above,  1.5  mm.  below,  and  i  mm.  laterally— the  most  external  capillaries  form 
arched  loops,  and  thus  turn  on  themselves.  The  cornea  is  nourished  from  the  blood  vessels  in  its 
margin.     Opacities  of  the  cornea  give  rise  to  many  forms  of  visual  defects. 

The  sclerotic  is  a  thick  fibrous  membrane,  composed  of,/,  circular  (equatorial)  and,  0,  longi- 
tudinal (meridional)  bundles  of  connective  tissue  woven  together.  The  spaces  between  the  bundles 
contain  colorless  and  pigmented  connective-tissue  corpuscles  ( IValiieyer)^  and  also  leucocytes.  It 
is    thickest  posteriorly,  thinner  at   the    equator, 


Fig.  452. 


while  in  frontof  this  it  again  becomes  thicker,  ow- 
ing to  the  insertion  of  the  tendons  of  the  straight 
muscles  of  the  eyeball.  It  contains  few  blood  ves- 
sels, which  form  a  wide-meshed  capillary  plexus 
immediately  under  its  deep  surface.  Other  vessels 
form  an  arterial  ring  around  the  entrance  of  the 
optic  nerve.  It  rarely  is  quite  spherical  ;  it 
rather  resembles  an  ellipsoid,  which  we  might 
imagine  to  be  formed  by  the  rotation  of  an 
ellipse  around  its  short  axis  (short  eyes)  or  around 
its  long  axis  (long  eyes).  Above  and  below  the 
sclerotic  overlaps  like  a  fold  the  clear  margin  of 
the  cornea;  hence,  when  the  cornea  is  viewed 
from  before  it  appears  transversely  elliptical, 
when  seen  from  behind  it  appears  circular.  Fol- 
lowing the  margin  of  the  cornea,  but  lying  still 
within  the  substance  of  the  sclerotic,  is  the  circu- 
lar canal  of  Schlennm,  /,  which  communicates 
with  other  anastomosing  veins,  the  venus  plexus 
of  Leber,  k.  Schwalbe  and  Waldeyer  regarded 
Schlemm's  canal  as  a  lymphatic.  Posteriorly, 
the  sclerotic  becomes  continuous  with  the  fibrous 
covering  of  the  optic  nerve  derived  from  the  dura 
mater.  The  sclerotic  is  provided  with  nerves, 
which  are  said  to  terminate  in  the  cells  of  the 
scleral  substance  [Hclfycich,  Konigstein). 

The  tunica  uvea,  or  the  uveal  tract,  is  com 
posed  of  the  choroid,  the  ciliary  part  of  the  cho- 
roid, and  the  iris. 

The  choroid  is  composed  of  the  following 
layers:  (l)  Most  internally  is  the  transparent 
limiting  membrane,  0.7  //  in  thickness,  but  it 
is    slightly   thicker   anteriorly.       (2)  The   very 

vascular  capillary  network  of  tht  chorio-capil-  e' 

laris,  or    membrane  of  Ruysch,  embedded  in  a 

homogeneous  layer.     Then  follows— (3)  a  layer  Diagram  of  the  blood  ve 
of  a  thick  elastic  network,  covered  on  both  sur-  .... 

faces  by  endothelium  [Sattler).  (4)  The  cho- 
roid proper  consists  of  a  layer  with  pigmented 
connective-tissue  corpuscles,  together  with  a 
thick  elastic  network,  containing  the  numerous 
venous  vessels  as  well  as  the  arteries.  The  pig- 
mented layers,  called  the  supra-choroidea,  or 
lamina  fusca,  which  surrounds  the  large  lym- 
phatic space  lined  with  endothelium,  and  called 
the  perichoroidal  space,  q.  In  new-born  in- 
fants, which,  according  to  Aristotle,  have  the 
iris  dark-blue,  the  uveal  tissue  is  devoid  of  pig- 
ment ;  in  brunettes  it  is  developed  later,  and  in 
blondes  not  at  all. 

In  the  ciliary  part  of  the  choroid  the  pigmented  connective-tissue  corpuscles  are  not  so  numerous. 

The  ciliary  muscle  (tensor  choroide^e,  or  muscle  of  accommodation )  is  placed  in  this  region.     It 

arises,  .t,  by  means  of  a  branched,  reticulated,  connective  tissue  origin,  from  the  inner  side  of  the 

junction  of  the  cornea  and  sclerotic,  near  the  canal  of  Schlemm,  and  passes  backward  to  be  inserted 

48 


els  of  the  eye  {Leber)  (horizon- 
i  black,  arteries  light,  with  a  double  con- 
short  posterior  ciliary;  b,  long  posterior 
ciliary  ;  c,  c",  anterior  ciliary  artery  and  vein  ;  d,  d' , 
artery  and  vein  of  the  conjunctiva  ;  ^,  e'y  central  artery 
and  vein  of  retina  ;/,  blood  vessels  of  the  inner,  and^, 
of  the  outer  optic  sheath  ;  k,  vorticose  vein  ;  i,  posterior 
short  ciliary  vein  confined  to  the  sclerotic  ;  k,  branch  of 
the  posterior  short  ciliary  artery  to  the  optic  nerve;  /, 
anastomosis  of  the  choroidal  vessels  with  those  of  the 
optic;  ;w,  chorio-capillaris  ;  k,  episcleral  branches  ;  o, 
recurrent  choroidal  artery  ;  /,  great  circular  artery  of 
iris  (transverse  section) ;  a,  blood  vessels  of  the  iris  ; 
r,  ciliary  process  ;  s,  branch  of  a  vorticose  vein  from 
the  ciliary  muscle  ;  t,  branch  of  the  anterior  ciliary 
vein  to  the  ciliary  muscle  •  «,  circular  vein  ;  ;-,  margin- 
al loops  of  vessels  on  the  cornea;  tc,  anterior  artery 
and  vein  of  the  conjunctiva. 


754  THE    VEINS. 

into  the  choroid.  This  constitutes  the  radiating  fibres.  Other  filjres  lying  internal  to  these  are 
arranged  circularly, /,  in  bundles  in  tiie  ciliary  margin.  These  circular  tibres  are  sometimes  called 
Heinrich  Midler's  muscle.  The  muscle  consists  of  smooth  muscular  fibres,  and  is  supplied  by  the 
oculomotorius  (§  345,  3). 

The  iris  consists  of  the  following  parts  from  before  backward  :  a  layer  of  epithelial  cells  (v) 
continuous  with  those  covering  the  posterior  surface  of  the  cornea,  a  Layer  of  reticulated  connective 
tissue,  the  layer  of  blood  vessels,  and,  lastly,  a  posterior  limiting  membrane,  which  contains  the 
pigmentary  epithelium  (j),  (Michel].  In  brunettes,  the  texture  of  the  iris  contains  pigmented  con- 
nective-tissue corpuscles.  The  iris  contains  two  muscles  composed  of  smooth  muscular  fibres — one 
set  constituting  the  sphincter  pupillae  (circular.  Fig.  467),  which  surrounds  the  pupil,  and  lies 
nearer  the  posterior  than  the  anterior  surface  of  the  iris  (^  392).  Its  nerve  o'f  supply  is  derived  from 
the  oculomotorius  (^  345,  2).  The  other  fibres  constitute  the  dilator  pupillae  (radiating),  which 
consists  of  a  thinner  layer  of  fibres  arranged  in  a  radiate  manner.  Some  of  the  fibres  reach  to  the 
margin  of  the  pupd,  while  others  bend  into  the  sphincter.  At  the  outer  margin  of  the  iris  the  radial 
bundles  are  arranged  in  anastomosing  arches,  and  form  a  circular  muscular  layer  [A/eykel).  The 
chief  nerve  of  supply  for  the  dilator  fibres  is  the  sympathetic  (^  347,  3).  Ganglia  occur  in  the 
ciHary  nerves  in  the  choroid  [and  they  are  found,  also,  in  the  iris].  Gerlach  has  recently  applied 
the  term  Hgamenlum  annulare  bnlbi  to  that  complex  fibrous  arrangement  which  surrounds  the  iris, 
and  at  the  same  time  forms  the  point  of  union  of  the  ciliary  body,  iris,  ciliary  muscle,  sinus  venosus 
iridis,  and  the  line  of  junction  of  the  cornea  and  sclerotic. 

The  choroidal  vessels  are  of  great  impoitance  in  connection  with  the  nutrition  of  the  eye. 
According  to  Leber,  they  are  arranged  as  lollows:  The  arteries  are — i.  The  short  posterior 
ciliary  (Fig.  452,  a,  a),  which  are  about  twenty  in  number  and  perforate  the  sclerotic  near  the 
optic  nerve.  They  terminate  in  the  vascular  network  of  the  chorio-capillaris  (;«),  which  reaches 
as  far  as  the  ora-serrata.  2.  The  long  posterior  ciliary,  one  lies  on  the  nasal  and  the  other  on 
the  temporal  side,  and  they  run  (/<)  to  the  ciliary  part  of  the  choroid,  where  they  divide  dichoto- 
mously,  and  penetrate  into  the  iris,  where  they  help  to  form  the  circulus  arteriosus  iridis  major  (p). 
3.  The  anterior  ciliary  (c),  which  arise  from  the  muscular  branches,  perforate  the  sclerotic  ante- 
riorly, and  give  branches  to  the  ciliary  part  of  the  choroid  and  to  the  iris.  About  twelve  branches 
run  backward  (c>)  from  them  to  the  chorio-capillaris. 

The  Veins. —  i.  The  anterior  ciliary  veins  (c)  receive  the  blood  from  the  anterior  part  of  the 
uvea  and  carry  it  outward.  These  branches  are  connected  with  Schlemm's  canal  and  Leber's 
venous  plexus.  They  do  not  receive  any  blood  from  the  iris.  2.  The  venous  plexus  of  the 
ciliary  processes  {r)  receives  the  blood  from  the  iris  (^),  and  passes  backward  to  the  choroidal  veins. 
3.  The  large  vasa  vorticosa  Stenonis  \h)  perforate  the  scleroiic  behind  the  equator  of  the  bulb. 

The  inner  margin  of  the  iris  rests  upon  the  anterior  surface  of  the  lens ;  the  posterior  chamber  is 
small  in  adults,  and  in  the  new-born  child  it  may  be  said  scarcely  to  exist,  it  is  so  small.  When 
BerHn  blue  is  injected  into  the  anterior  chamber  of  the  eye,  it  generally  passes  into  the  anterior 
ciliary  veins  [SchwalOe).  Even  in  living  animals  carmin  also  behaves  in  a  similar  manner  (//els- 
rath),  so  that  these  observers  conclude  that  there  is  a  direct  communication  between  the  veins  and 
the  aqueous  chamber,  as  tliese  substances  do  not  diffuse  through  membranes. 

Internal  to  the  choroid  lies  the  single  layer  of  hexagonal  cells  (0.0135  '°  °°2  tava.  in  breadth) 
filled  with  crystalline  pigment.  This  layer  really  belongs  to  the  retina.  It  consists  of  a  single  layer 
of  cells  as  far  as  the  ora-serrata — it  is  continued  on  to  tlie  ciliary  processes  and  the  posterior  surface 
of  the  iris  (Fig.  449,  -v),  where  it  forms  several  layers.  In  albinos  it  is  devoid  of  pigment;  on  the 
other  hand,  the  uppermost  cells,  which  lie  on  the  ridges  of  the  ciliary  processes,  are  always  devoid 
of  pigment.  [The  processes  of  these  cells  vary  in  length  with  the  nature  and  kind  of  light  acting 
on  the  retina  (J  39^).] 

The  retina  externally  is  in  contact  with  the  layer  of  hexagonal  pigment  cells  (Pi),  which  in  its 
development  and  functions  really  belongs  to  the  retina.  The  cells  are  not  flat,  but  they  send  pig- 
mented processes  into  the  spaces  betw-een  the  ends  of  the  rods.  In  some  animals  (rabbit)  the  cells 
contain  fatty  granules  and  other  substances.  The  cells  are  larger  and  darker  at  the  ora-serrata 
(Kiihne).     The  retina  is  composed  of  the  following  layers  proceeding  from  without  inward : — 

6.  Inner  nuclear  layer. 

7.  Inner  molecular  (granular)  layer. 


[i.  Layer  of  pigment  cells. 

2.  Rods  and  cones. 

3.  Extet  nal  limiting  membrane. 

4.  Outer  nuclear  layer. 

5.  Outer  molecular  (granular  or  inter- 

nuclcar)  layer. 


8.  Layer  of  nerve  cells  (ganglionic) 

layer. 

9.  Layer  of  nerve  fibres. 

10.  Internal  limiting  membrane.'\ 


I.  The  hexagonal  pigment  cells  already  described.  2.  The  layer  of  rods  and  cones  (Si) 
or  nenro-epithelium  of  Schwalbe  \_bacillary  layer,  or  the  visual  cells,  or  visual  epithelium  of  Kiihne] 
(Fig.  454).  These  lie  externally  next  tlie  choroid,  but  they  are  absent  at  the  entrance  of  the  optic 
nerve.  Then  follows  the  external  limiting  membrane  (Le),  which  is  perforated  by  the  bases  of 
the  rods  and  cones.  3.  The  external  nuclear  layer  (iiu.K),  which  with  all  the  succeeding  layers 
are  called  "  brain  layers  "  by  Schwallje.  4.  The  external  granular  (augr),  or  internuclear  layer, 
which  is  perforated  by  the  fibres  which  proceed  inwaid  from  the  nuclei  of  3  (Merkel)  to  reach  5, 


THE    RETINA. 


755 


the  nuclei  of  the  internal  nuclear  layer  iiiiA'}.  The  nuclei  of  this  layer,  which  are  connected 
by  fibres  with  the  rods  and  cones,  are  marlied  by  transverse  lines  in  the  macula  lutea  (AVrta^^, 
Denissenko).  6.  The  finely  granular  internal  granular  layer  (in./;r),  through  which  the  fibres 
proceeding  from  the  inner  nuclear  layer  cannot  be  traced.  It  would  seem  as  if  these  fibres  break 
up  into  the  finest  fibrils,  into  which,  also,  the  branched  processes  of  the  ganfjlionic  cells  of  7,  the 
ganglionic  layer,  extend.  According  to  v.  Vintschgau,  the  processes  of  the  ganglionic  cells  are 
connected  with  the  fibres.  S.  The  ne.xt.  or  fibrous  layer,  consists  of  the  fibres  of  the  optic  nerve 
(o),and  most  internally  is  the  internal  limiting  membrane  (Li).  According  to  \V.  Krause, there 
are  400,000  broad,  and  as  many  narrow,  optic  fibres,  so  that  for  every  fibre  there  are  7  cones,  about 
100  rods,  and  7  pigment  cells.  The  optic  filjres  are  absent  from  the  macula  lutea,  where,  however, 
there  are  numerous  ganglionic  cells.  Between  the  two  homogeneous  limiting  membranes  (Le  and 
Li)  lies  the  connective-tissue  substance  of  the  retina.     It  contains  the  perforating  fibres,  or 


Fi.;.  454. 


Fig.  453. 


9.r;ik^r.\L^ror^O.:^'Qck 


y7* 

b,  ext.  andy,  int.  limit. 

?   ex     .J  d^      t   gran   layers     /    blood  vessel  and  nerve  cells  :  i,  nerve 

Ft  hexagonal  p  gment  cells     St   rods  and  cones  ;  Z,^,  ext.  limiting  membrar 

.  granular  layer  :  inK,  int.  nuclear  ;  in.gr,  int.  granular ;  Ggl,  ganglionic  1 

nembrane;  .ffA,  fibres  of  Muller;  .^.nuclei;  .^,  spaces  for  ttle 


ext.  and  f,  int. 
;.  454— Layers 
A-,  ext.  nuclear 
slls  :  o,  fibres  o! 
elements. 


Miiller's  fibres,  which  nin  in  a  radiate  manner  between  the  two  membranes  and  hold  the  various 
layers  of  the  retina  together.  They  begin  by  a  wing-shaped  expansion  at  the  internal  limiting 
membrane  (fii),  and  in  their  course  outward  contain  nuclei  (k).  They  are  absent  at  the  yellow 
spot.  The  supporting  tissue  forms  a  network  in  all  the  layers,  holes  being  left  for  the  nervous 
portions  (Sg).  The  inner  segments  of  the  rods  and  cones  are  also  surrounded  by  a  sustentacular 
substance.  As  the  retina  passes  forward  to  the  ora  serrata  it  becomes  thinner  and  thmner,  gradually 
becoming  richer  in  connective-tissue  elements  and  poorer  in  ner\'e  elements,  until,  in  the  ciliar)' 
part,  only  the  cylindrical  cells  remain  (  Fig.  453). 

[Macula  Lutea  and  Fovea  Centralis. — There  are  no  rods  in  the  fovea,  while  the  cones  are 
longer  and  narrower  than  in  the  other  parts  of  the  retina  (Fig.  455).  The  other  layers,  also,  are 
thinner,  especially  at   the  macula  lutea,  but  they  become  thicker  toward  the  margins  of  the  fovea. 


756 


VISUAL    PURPLE   OR    RHODOPSIN. 


where  the  ganglionic  layer  consifts  of  several  rows  of  bipolar  cells.  The  yellow  tint  is  due  to 
pigment  lying  between  the  layers  composing  the  yellow  spot.] 

The  blood  vessels  of  the  retina  lie  in  the  inner  layers  near  the  inner  granular  layer.  Only  near 
the  entrance  of  the  optic  nerve  are  they  connected  by  tine  brandies  with  the  choroidal  vessels;  they 
are  surrounded  by  perivascular  lymph  spaces.  The  greatest  number  of  capillaries  runs  in  the  layers 
external  to  the  inner  granular  layer  [//esse,  //is).  The  fovea  centralis  is  devoid  of  blood  vessels 
(A^elt/ei/iif,  Becker).  Except  in  mammals,  the  eel  (Deiiissenko),  and  some  tortoises  [//.  A/iiiler), 
the  retina  receives  no  blood  vessels.     Destruction  of  the  retina  is  followed  by  blindness. 

[Retinal  Epithelium. — The  single  layer  of  pigmentary  cells  containing  granules  of  melanin 
sends  processes  downward,  like  the  hairs  of  a  brush,  betvve  n  the  rods  and  cones.  Kiiline  has 
shown  that  the  nature  and  amount  of  light  influences  the  condition  of  these  processes  (Fig.  497). 
The  protoplasm  of  these  cells  in  a  frog  kept  for  several  hours  in  the  dark  is  retracted,  and  the  pig- 
ment granules  lie  chiefly  in  the  body  of  the  cell  and  in  the  processes  near  the  cell.  In  a  frog  kept 
in  bright  daylight,  the  processes  loaded  with  pigment  penetrate  downward  between  the  rods  and 
cones  as  far  as  the  external  limiting  membrane.] 

Each  rod  and  cone  consists  of  an  outer  and  an  inner  segment.  During  life  the  outer  segment 
contains  a  reddish  pigment  or  the  visual  purple  (Boll). 

Visual  purple  [or  rhodopsin]  may  be  preserved  by  keeping  the  eye  in  darkness,  but  it  is  soon 
bleached  by  daylight,  while  it  is  again  restored  when  the  eye  is  placed  in  darkness.  It  can  be 
extracted  from  the  retina  by  means  of  a  2.5  per  cent,  solution  of  the  bile  acids,  especially  from 
eyes  that  have  been  kept  in  10  per  cent,  solution  of  common  salt  (Ayres).  The  rods  are  0.04 
to  0.06  mm.  high   and  0.0016   to   o.ooiS   mm.  broad,  and   exhibit   longitudinal   striation,  pro- 


FlG.  455. 


Section  of  the  fovea 


tear  layer  ;  (/,  fibres 


duced  by  the  presence  of  fine  grooves;  a  fine  fibril  runs  in  their  interior  [Ritler).  The  external 
segment  occasionally  cleaves  transversely  into  a  number  of  fine  transparent  disks.  [It  is  a  very 
resistant  structure,  and  in  this  respect  resembles  neuro-keratin.]  Krause  found  an  ellipsoidal  body, 
the  '*  rod  ellipsoid,"  at  the  junction  of  the  inner  and  outer  segments  of  the  rods.  The  cones  are 
devoid  of  visual  purple,  but  their  outer  segment  is  striated  longitudinally,  and  it  also  readily  breaks 
across  into  thin  disks.  Only  cones  are  present  in  the  macula  lutea.  In  the  neighborhood  of  the 
yellow  spot  each  cone  is  surrounded  by  a  ring  of  rods.  The  cones  become  less  numerous  toward 
the  periphery  of  the  retina.  In  nocturnal  animals,  such  as  the  owl  and  bat,  there  are  either  no 
cones  or  imperfect  ones.  The  retimie  of  birds  contain  many  cones,  that  of  the  tortoise  only  cones. 
The  rods  and  cones  rest  on  the  sieve  like  perforated  external  limiting  membrane  (Le).  Both  send 
processes  through  the  membrane,  the  cones  to  the  larger  and  higher-placed  nuclei,  the  rods  to  the 
nuclei,  with  transverse  markings  in  the  extern.al  nuclear  layer.  [The  cones  are  particularly  large 
in  some  fishes,  f.^'.,  the  cod,  while  the  skate  h.is  no  cones,  but  only  rods.  The  same  is  the  case  in  the 
shark  and  sturgeon,  hedgehog,  bat  and  the  mole.] 

[Distribution  and  Regeneration  of  Rhodopsin. — Keep  a  rabbit  in  the  dark  for  some  time, 
kill  it,  remove  its  eyeball,  and  examine  its  retina  by  the  aid  of  monochromatic  (sodium)  light.  The 
retina  will  be  purple-red  in  color,  all  except  the  macula  lutea  and  a  small  part  at  the  ora  serrata. 
The  pigment  is  confined  to  the  ouler  segments  of  the  rods.  It  is  absent  in  pigeons,  hens  and  one 
bat,  although  the  last  has  only  rods.  It  is  found  both  in  nocturnal  and  diurnal  animals.  Its  color 
is  quickly  bleached  by  light,  and  it  fades  rapidly  at  a  temperature  of  50°  to  76°  C  ,  while  trypsin, 
alum  and  ammonia  do  not  affect  it.  It  is  restored  in  the  retina  by  the  action  of  the  retinal  epithe- 
lium.    If  the  retinal  epithelium   or  choroid  be  lifted  off  from  an  excised  eye  exposed  to  light,  the 


THE    VITREOUS    HUMOR. 


75/ 


Fig.  456. 


purple  is  destroyed,  but  if  the  eye  be  placed  in  darkness  and  the  retinal  epithelium  replaced,  the 
coliir  is  restored.] 

Chemistry  of  the  Retina. — The  reaction  of  the  retina,  when  quite  fresh,  is  acid,  and  becomes 
alkaline  in  darkness.  The  rods  and  cones  contain  albumin,  neuro-keratrin,  nuclein,  and  in  the 
cones  are  the  pigmented  oil  globules,  the  so-called  "  chromophanes."  The  other  layers  contain 
the  constituents  of  the  gray  matter  of  the  brain. 

[Cones. — There  is  no  coloring  matter  in  the  outer  segment  of  the  cones,  but  in  fishes,  reptiles, 
and  birds  the  inner  segment  contains  a  globular  colored  body  often  red  and  yellow,  the  pigment 
being  held  in  solution  by  a  fatty  body.  Kiihne  has  separated  a  green  (chlorophane),  a  yellow 
(xanthophane),  and  a  red  (rhodophane)  pigment.  They  all  give  a  blue  with  iodine  [Sckwalbe], 
and  are  bleached  by  light.] 

The  crystalline  lens  is  enclosed  in  a  transparent  capsule,  thicker  anteriorly  than  posteriorly,  and 
it  is  covered  on  the  inner  surface  of  the  anterior  wall  by  a  layer  of  low  epithelium.  Toward  the 
margin  of  the  lens,  these  cells  elongate  into  nucleated  fibres 
[h'oiiinski),  which  all  bend  round  the  margin  of  the  lens,  and 
on  both  sides  of  the  lens  abut  with  their  ends  against  each  of  the 
triradiate  figures.  The  lens  fibres  contain  globulin  enclosed  in 
a  kind  of  membrane.  Owing  to  mutual  pressure,  they  are  hex- 
agonal when  seen  in  transverse  section  (Fig.  456,  2),  while  in 
many  animals,  especially  fishes,  their  margins  are  serrated  [the 
teeth  dovetail  into  each  other].  For  the  sake  of  simplicity,  we 
may  regard  the  lens  as  a  biconvex  body  with  spherical  surfaces, 
the  posterior  surface  being  more  curved.  As  a  matter  of  fact, 
the  anterior  part  is  part  of  an  ellipsoid  formed  by  rotation  on  its 
short  axis.  The  posterior  surface  resembles  the  section  of  a 
paraboloid,  i.  e.,  we  might  regard  it  as  formed  by  the  rotation  of 
a  parabola  on  its  axis  [BrihX'e).  1  he  outer  layers  of  the  lens 
have  less  refractive  power  than  the  more  internal  layers.  The 
central  part  of  the  lens  or  nucleus  is,  at  the  same  time,  firmer, 
and  more  convex  than  the  entire  lens.  The  margin  of  the  lens 
is  always  separated  from  the  ciliary  processes  by  an  intermediate 
space. 

[Chemistry. — The  lens  contains  about  two-thirds  of  its 
weight  of  water,  while  its  chief  solid  is  a  globulin,  called  by 
Berzelius  crystallin  (24.6  per  cent.),  with  a  little  serum  albu- 
min, salts,  cholesterin,  and  fats.] 

[Cataract.  — Sometimes  the  lens  becomes  more  or  less  opaque, 
the  opacity  beginning  either  in  the  middle  or  outer  parts  of  the 
lens.  This  is  generally  due  to  fatty  degeneration  of  the  fibres, 
cholesterin  being  deposited.     An  opaque  cataractous  condition 

of  the  lens  may  be  produced  in  frogs  by  injecting  a  solution  of  some  salts  or  sugar  into  the  lymph 
sacks ;  the  result  is  that  these  salts  absorb  the  water  from  the  lens,  and  thus  make  it  opaque.  The 
cataract  of  diabetf  s  is  probably  produced  from  the  presence  of  grape  sugar  in  the  blood.] 

The  zonule  of  Zinn,  at  the  ora  serrata,  is  applied  as  a  folded  niemlirane  to  the  ciliary  part  of 
the  uvea,  so  that  the  ciliary  processes  are  pressed  into  its  folds,  and  are  united  to  it.  It  passes  to  the 
margins  of  the  lens,  where  it  is  inserted  by  a  series  of  folds  into  the  anterior  part  of  the  capsule  of 
the  lens.  Behind  the  zonule  of  Zinn,  and  reaching  as  far  as  the  vitreous  humor,  is  the  canal  of 
Petit.  The  zonule  is  a  fibrous,  perforated  membrane  {S<'/ni'{i//'^,  Vlacowitsch).  According  to 
Merkel,  the  canal  of  Petit  is  enclosed  by  very  fine  fibres,  so  that  it  is  really  not  a  canal  but  a  complex 
communicating  system  of  spaces  (Gerluch].  Nevertheless,  the  zonule  represents  a  stretched  mem- 
brane, holding  the  lens  in  position,  and  m.ay,  therefore,  be  regarded  as  the  suspensory  ligament 
of  the  lens. 

Opacity  or  cloudiness  of  the  lens  (gray  cataract)  hinders  the  passage  of  light  into  the  eye.  The 
absence  of  the  lens  (Aphakia),  as  after  operations  for  cataract,  may  be  remedied  by  a  pair  of  strong 
convex  spectacles.     Of  course  such  an  eye  does  not  possess  the  power  of  accommodation. 

The  vitreous  humor,  as  far  as  the  ora  serrata,  is  bounded  by  the  internal  limiting  membrane  of 
the  retina  [f/enle,  hatjnojf).  From  here  forward,  lying  between  both,  are  the  meredional  fibres  of 
the  zonule,  which  are  united  with  the  surface  of  the  vitreous  and  the  ciliary  processes.  A  part  of 
the  fibrous  layer  bends  into  the  saucer-shaped  depression,  and  bounds  it.  .A  canal,  2  mm.  in  diam- 
eter, runs  from  the  optic  papilla  to  the  posterior  surface  of  the  capsule  of  the  lens;  it  is  called  the 
hyaloid  canal,  and  was  formerly  traversed  by  blood  vessels.  The  peripheral  part  of  the  vitreous 
humor  is  laminated  like  an  onion,  the  middle  is  homogeneous  ;  in  the  former,  especially  in  the 
fiLtus,  are  round  fusiform  or  branched  cells  of  the  mucous  tissue  of  the  vitreous,  while  in  the  centre 
there  are  disintegrated  remains  of  these  cells  (Iwanoff).  The  vitreous  contains  a  very  small  per- 
centage of  solids,  and  1.5  per  cent  of  mucin  [and  according  to  Picard  there  is  0.5  per  cent,  of 
urea,  and  about  .75  of  sodic  chloride]. 

[Structure. — The  vitreous  consists  essentially  of  mucous  tissue,  in  whose  meshes  lies  a  very 


758 


INTRAOCULAR   PRESSURE. 


watery  fluid,  containing  the  organic  and  inorganic  bodies  in  solution.  According  to  Younaii,  the 
vitreous  contains  two  types  of  cells — (i)  amoeboid  cells  of  various  shapes  and  sizes.  They  lie  on 
the  inner  surface  of  the  lining  hyaloid  membrane  and  the  other  membranes  in  the  coitex  of  the 
vitreous;  (2)  large  branching  multipolar  cells.  The  vitreous  is  permeated  by  a  large  number  of 
transparent,  clear,  homogeneous  hyaloid  membranes,  which  are  so  disposed  as  to  give  rise  to  a 
concentric  lamination.  The  canal  of  Stilling  represents  in  the  adult  the  situation  of  the  hyaloid 
artery  of  the  fretus.  It  can  readily  be  injected  l)y  a  colored  fluid.  In  preparations  of  the  vitreous, 
Younan  finds  fibres  not  unlike  elastic  fibres,  and  other  fibres  more  especially  after  staining  with 
chloride  of  gold.] 

The  lymphatics  of  the  eye  consist  of  an  anterior  and  a  posterior  set  {Sc/nualbe).  The  anterior 
consist  of  the  anterior  and  posterior  chambers  of  the  eye  (aqueous),  which  communicate  with  the 
lymphatics  of  the  iris,  ciliary  processes,  cornea,  and  conjunctiva.  The  posterior  consist  of  the 
perichoroidal  space  between  the  sclerotic  and  the  choroid  \Schwalbe).  This  space  is  connected  by 
means  of  the  perivascular  lymphatics  around  the  trunks  of  the  vasa  vorticosa,  with  the  large  lymph 
space  of  Tenon,  which  lies  between  the  sclerotic  and  Tenon's  capsule  (Schwalbe).  Posteriorly  this 
is  continued  into  a  lymph  channel,  which  invests  the  surface  of  the  optic  nerve;  while  anteriorly  it 
communicates  directly  with  the  sub  conjunctival  lymph  spaces  of  the  eyeball  (Gerlach).    The  optic 


Fig.  457. 


Tan 


--^j     ^jf'A  P^^'j  -^^    y' 


/  /' 


'IJjMUj 


)rizontaI  section  of  the  entrance  of  the  opii'    n !  ili'j  eye.     rt,  inner, /',  outer  layers  of  the  retin 

r,  choroid  ;  </.  sclerotic  ;  <?,  physiological  cup  ;  /,  <:enir.il  artt;ry  of  retina  in  axial  canal :  ^,  its  point  of  bifurcalio 
A,  lamina  cribrosa  ;  /,  outer  (dural)  sheath  ;  w,  outer  (subdural)  space;  n,  inner  (subarachnoid)  space  ; 
(arachnoid)  sheath ;/,  inner  (pial)  sheath ;  /,  bundles  of  ner\     "*'  »    .        ■      .       . 


;  k,  longitudinal  septa  of 


nerve  has  three  sheaths — (i)  the  dural ;  (2)  the  arachnoid  ;  and  (3)  the  pial  sheath,  derived 
from  the  corresponding  membranes  of  the  brain.  Two  lymph  spaces  lie  between  these  three  sheaths 
— the  subdural  space  between  i  and  2,  and  the  subarachnoid  space  between  2  and  3  (Fig.  547). 
Both  spaces  are  lined  by  endothelium;  and  the  fine  trabecule  passing  from  one  wall  to  the  other 
are  similarly  covered.  According  to  Axel  Key  and  Retzius,  these  lymph  spaces  communicate  an- 
teriorly with  the  perichoroidal  space. 

The  aqueous  humor  closely  resembles  the  cerebrospinal  fluid,  and  contains  albumin  and  sugar ; 
the  former  is  increased,  and  the  la'ter  disappears  after  death.  The  same  occurs  in  the  vitreous.  The 
albumen  increases  when  the  diff'erence  between  the  blood  pressure  and  the  intraocular  pressure  rises. 
.Such  variations  of  pressure,  and  also  intense  stimuli  applied  to  the  eye,  cause  the  production  of 
fibrin  in  the  anterior  chamber  [Jesner  and  Griinhagen'). 

Intraocular  Pressure. — The  cavity  of  the  bulb  is  practically  filled  with  watery  fluids,  which, 
during  life,  are  constantly  subjected  to  a  certain  pressure,  the  "  intraocular  pressure."  Ultimately, 
this  depends  upon  the  blood  pressure  within  the  arteries  of  the  retina  and  uvea,  and  must  rise  and 
fall  with  it.  The  pressure  is  determined  by  pressing  upon  the  eyeball,  and  ascertaining  whether  it 
is  tense,  or  soft  and  compressible.     Just  as  in  the  case  of  the  arterial  pressure,  the  intraocular  pres- 


DIOPTRIC    OBSERVATIONS,  759 

sure  is  influenced  by  many  circumstances  ;  it  is  increased  at  every  pulse  beat  and  at  every  expiration, 
wliile  it  is  decreased  during  inspiration.  The  elastic  tension  of  the  sclerotic  and  cornea  regulates 
the  increase  of  the  arterial  pressure  by  acting  like  the  air  chamber  in  a  fire  engine  ;  thus,  when  more 
arterial  blood  is  pumped  into  the  eyeball,  more  venous  blood  is  also  expelled.  The  constancy  of 
the  intraocular  pressure  is  also  influenced  by  the  fact  that,  just  as  the  aqueous  humor  is  removed,  it 
is  secreted,  or  rather  formed,  as  rapidly  as  it  is  absorbed  (J  392). 

The  secretion  of  the  aqueous  humor  occurs  pretty  rapidly,  as  may  be  surmised  from  the  fact 
that  ha*moglobin  is  found  in  the  aqueous  humor  half  an  hour  after  dissolved  blood  (lamb's)  is  in- 
jected into  the  blood  vessels  o(  a  dog.  It  is  rapidly  reformed,  after  evacuation,  through  a  wound 
in  the  cornea.  According  to  Knies,  the  watery  fluid  within  the  eyeball  is  secreted,  especially  from 
the  chorio-capillaris,  and  reaches  the  suprachoroidal  space,  in  the  lymph  sheaths  of  the  optic  nerve, 
and  partly  through  the  network  of  the  sclerotic.  It  saturates  the  retina,  vitreous,  lens,  and  for  the 
mo!-t  part  passes  through  the  zonula  ciliaris  into  the  posterior  chamber,  and  through  the  pupil  into 
the  anterior  chamber.  The  movements  of  the  fluid  within  the  eyeball  have  been  recently  studied 
by  Ehrlich,  who  used  fiuorescin,  an  indifferent  substance,  which  on  being  introduced  into  the  body 
passes  into  the  fluitls  of  tlie  eyeball,  and  in  a  very  dilute  solution  may  be  recognized  by  its  green  fluor- 
escence  in  reflected  light.  From  observations  on  the  entrance  of  this  substance  into  the  eye  Scholer, 
and  Uhthoff  regard  the  posterior  surface  of  the  iris  and  the  ciliary  body  as  the  secretory  organs  for 
the  aqueous  humor.  It  passes  through  the  pupil  into  the  anterior  chamber  ;  some  passes  into  the 
lens,  and  along  the  canal  of  Petit  into  the  vitreous  humor  (Pfiiiger).  Section  of  the  cervical  sym- 
pathetic, and  still  more  of  the  trigeminus,  accelerates  the  secretion  of  the  aqueous,  but  its  amount  is 
diminished.  If  the  substance  is  dropped  into  the  conjunctival  sack  it  percolates  toward  the  centre 
of  the  cornea,  and  through  the  latter  into  the  anterior  chamber  (P/liiger). 

The  outflow  of  the  aqueous  humor,  according  to  Leber  and  Ileisrath,  takes  place  chiefly  between 
the  meshes  of  the  ligamentum  pectinatum  iridis  (Fig.  449.  w,  rn),  through  which  it  passes  into  the 
channels  of  the  circulus  venosus,  and  the  canal  of  Schlemm  (/,  i).  A  very  small  part  of  the 
a(jueous  passes  through  the  cornea  into  the  sub-conjunctival  connective  tissue,  and  even  into  the 
conjunctival  sack.  After  burning  the  limbus  corncit  with  a  hot  needle  this  outflow  is  arrested,  the 
eyeball  becomes  very  hard,  so  that  the  intrabulbar  vessels  are  subjected  to  high  pressure  [Scholer). 
Perhaps  there  is  a  direct  communication  between  the  anterior  ciliary  veins  and  the  anterior  chamber 
(p.  754).  -  None  of  the  water  is  conducted  from  the  eyeball  by  any  special  efferent  lymphatics 
{Leber).  Under  normal  circumstances  the  pressure  is  nearly  the  same  in  the  vitreous  and  aqueous 
chambers,  but  atropin  seems  to  diminish  the  pressure  in  the  former  and  to  increase  it  in  the  latter, 
whilst  Calabar  bean  has  an  opposite  action  [Ad.  Weber).  Arrest  of  the  outflow  of  the  venous 
blood  often  increases  the  pressure  in  the  vitreous,  and  diminishes  that  in  the  aqueous  chamber. 
Compression  of  the  bulb  from  without  cause-i  more  fluid  to  pass  out  of  the  eye  temporarily  than 
enters  it.  The  diminution  of  the  intraocular  pressure  is  well  marked  after  section  of  the  trigeminus, 
whde  it  rises  when  this  nerve  is  stimulated.  The  statements  vary  regarding  the  eft'ect  of  the  sym- 
pathetic nerve  upon  the  pressure.  Interruption  to  the  venous  outflow  increases  the  pressure,  while 
an  imperfect  supply  of  blood,  the  outflow  being  normal,  diminishes  the  pressure.  The  innervation 
of  the  blood  vessels  of  the  eye  is  referred  to  at  \  347. 

385.  DIOPTRIC  OBSERVATIONS.— The  eye  as  an  optical  instrument  is  comparable  to  a 
cannera  obscura  ;  in  both  an  inverted  diminished  image  of  the  objects  of  the  external  world 
is  formed  upon  a  back4roun(l,  the  field  of  projection.  [In  the  case  of  the  eye  this  is  represented 
by  the  retina.]  Instead  of  the  single  lens  of  the  camera,  the  eye  has  several  refractive  media 
placed  behind  each  other — cornea,  aqueous  humor,  lens  (whose  individual  parts — capsule,  cortical 
layers,  and  nucleus,  all  possess  different  refractive  indices),  and  vitreous  humor.  Every  two  of  these 
adjacent  media  are  bounded  by  a  "  refractive  surface,"  which  may  be  regarded  as  spherical.  The 
field  of  projection  of  the  eye  is  the  retina,  which  is  colored  with  the  visual  purple  (Boll,  Kiihne).  As 
this  substance  is  bleached  chemically  by  the  direct  action  of  light,  so  that  the  pictures  may  be  tem- 
porarily fixed  upon  the  retina,  the  comparison  of  the  eye  with  the  camera  of  the  photographer  be- 
comes more  striking.  In  order  that  the  passage  of  the  rays  of  light  through  the  media  of  the  eye 
may  be  rightly  understood,  we  must  know  the  following  factors:  (l )  the  refractive  indices  of  a'l 
the  media;  (2)  the  form  of  the  refractive  surfaces;  (3)  the  distance  of  the  various  media  from  each 
other,  and  from  the  field  of  projection  or  retina. 

Action  of  a  Converging  Lens. — We  must  know  how  a  convex  lens  acts  upon  light.  In  a 
convex  lens  we  distinguish  the  centre  of  curvature  (Fig.  458,  I,  m,  »«i),  /.  e.,  the  centre  of  both 
spherical  surfaces.  The  line  connecting  both  is  called  the  chief  axis  ;  the  centre  of  this  line  is  the 
optical  centre  of  the  lens  [0).  All  rays  which  pass  through  the  optical  centre  of  the  lens  pass 
through  unbent  or  without  being  refracted  ;  they  are  called  the  chief  or  principal  rays  («,  «;).  The 
following  are  the  laws  re.;ulating  the  action  of  a  convex  lens  upon  rays  of  light  : — 

I.  Rays  which  fall  upon  the  lens,  parallel  with  the  principal  axis  ( 11,/,  a),  are  so  refracted  that 
they  are  collected  on  the  other  side  of  the  lens,  at  a  point  called  the  focus  or  principal  focus  (f). 
The  distance  of  this  point  from  the  central  point  (n)  of  the  lens  is  called  the  focal  di>tance  (/,  0)  of 
the  lens.  The  converse  of  this  condition  is  evident,  viz.,  rays  which  diverge  from  a  focus  and  reach 
the  lens  pass  through  it  to  the  other  side,  parallel  with  the  principal  axis,  without  again  coming 
together. 


760 


ACTION    OF    LENSES    ON    LIGHT. 


2.  Rays  of  light  proceeding  from  a  srurce  of  light  (IV,  /)  in  the  prolonged  principal  axis,  but 
beyond  the  focal  point  (/),  again  converge  to  a  point  on  the  other  side  of  the  lens.  The  following 
cases  may  occur:  {a)  When  the  distance  of  the  light  from  the  lens  is  equal  to  twice  the  focal 
distance,  the  focus,  or  point  of  convergence,  lies  at  the  same  distance  on  the  other  side  of  the  lens, 


1)     s 

Figures  illustrating  the  action  of  lenses  upon  rays  of  light  passing  through  them. 

/'.  ^.,  twice  the  focal  distance.  \b)  If  the  luminous  point  be  moved  nearer  to  the  focus,  then  the 
focal  point  is  moved  further  away,  (c)  If  the  light  is  still  further  from  the  lens  than  twice  the  focal 
distance,  then  the  focal  point  comes  correspondingly  near  to  the  lens. 

3.  Rays  proceeding  from  a  jioint  of  the  chief  axis  (III,  b)  within  the  focal  distance  pass  out  at 

Fig.  459. 

S  IG 


the  other  side  less  divergent,  but  do  not  come  to  a  focus  again.     Conversely,  rays  which  are  con- 
vergent and  pass  through  a  collecting  lens  have  their  focal  point  within  the  focal  distance. 

4.   If  the  luminous  point  (V,  a)  is  placed  in  the  secondary  ray  (a,  b\,  the  same  laws  obtain,  pro- 
vided the  angle  formetl  by  the  secondary  ray  with  the  principal  axis  is  small. 


REFRACTIVE    INDICES.  761 

Formation  of  Images  by  Convex  Lenses. — -After  what  has  been  stated  regarding  the  position 
of  the  point  of  convergence  of  rays  proceeding  from  a  luminous  point,  the  construction  of  the  image 
of  any  object  by  a  convex  lens  is  easily  accomplished.  This  is  done  simply  by  projecting  images 
of  the  various  parts  of  the  object.  Thus,  evidently  in  V,/>  is  the  focal  point  of  the  object  «,  while 
V  is  the  focal  point  of  the  object  /.  The  picture  is  inverted.  Collectinj;  lenses  form  an  inverted 
and  real  image  (z.  ^.,  upon  a  ^crt&n)  only  of  Sitch  objeels  as  are  placed  beyond  the  foeal  point  of 
the  lens. 

With  regard  to  the  size  and  distance  of  the  image  from  the  lens,  there  are  the  following  cases : 
{a)  If  the  object  be  placed  at  t«  ice  the  focal  distance  from  the  lens,  the  image  of  the  same  is  just 
the  same  size  and  at  the  same  distance  from  the  lens  as  the  object  is.  (l>)  If  the  object  be  nearer 
than  the  focus,  the  image  recedes,  and  at  the  same  time  becomes  larger.  (<)  If  the  object  be 
further  removed  from  the  lens  than  twice  the  focal  distance,  then  the  image  is  nearer  to  the  lens, 
and  at  the  same  time  becomes  smaller. 

Position  of  the  Focal  Point. — The  distance  of  the  focal  point  from  the  lens  is  readily  calcu- 
lated according  to  the  following  formula :  Where  /  =:  the  distance  of  the  luminous  point,  b  =  the 

'  +  '^=i,or±=L-i. 

b       f         b       f       I 

Example. — Let  /r=  24  centimetres,  /=  6  cm.     Then  -^= —  =  — ,so  that  ^  ^  8  cm., 

^  ^  '■'  *       6       24       8 

i.  e.,  the  image  is  formed  8  cm.  behind  the  lens.     Further,  let  /  =^  10  cm.,/^  5  cm.  (/.  e.,  I  = 

2  f\.    Then  _  =  —  —  —  =^ —  ;  so  that  b  =  10,  i.  e.,  the  image  is  placed  at  twice  the  focal  distance 
•"  ,5       5       10       10  ^        ' 

of  the  lens.    Lastly,  let  /  =  00.  Then  -■=  ~-  — —  ;  so  that  i  =/,  ;.  e.,  the  image  of  parallel  rays 

b        f       c/^ 
coming  from  infinity  lies  in  the  focal  point  of  the  lens. 

Refractive  Indices. — A  ray  of  light,  which  passes  in  a  perpendicular  direction  from  one  medium 
into  another  medium  of  different  density,  passes  through  the  bitter  without  changing  its  course  or 
being  refracted.  In  Fig.  459,  if  G  D,  is  j_  A  B,  then  so  is  D  D,  J^  A  B;  for  a  plane  surface  A  B 
is  the  horizontal,  and  G  D  the  vertical  line.  If  the  surface  is  spherical,  then  the  vertical  line  is  the 
prolonged  radius  of  this  sphere.  If,  however,  the  ray  of  light  falls  obliquely  upon  the  surface,  it  is 
"refracted,"  i.  e.,  it  is  bent  out  of  its  original  course.  The  incident  and  the  refracted  ray,  never- 
theless, lie  in  otte plane.  When  the  oblique  incident  ray  passes  from  a  less  dense  medium  (e.g.,  air) 
into  one  more  dense  (e.g.,  water),  the  refracted  or  excident  ray  is  bent  toward  \.\ie.  perpendicular. 
If,  conversely,  it  pass  from  a  more  dense  to  a  less  dense  medium,  it  is  bent  away  from  the  perpen- 
dicular. The  angle  (/  G  D  S)  which  the  incident  ray  (S  D)  forms  with  the  perpendicular  (0  D) 
is  called  the  angle  of  incidence,  the  angle  formed  by  the  refracted  ray  (D  S; )  with  the  prolonged 
peqiendicular  (D  D)  is  called  the  angle  of  refraction,  D  D  S,  (>).  The  refractive  power  is 
expressed  as  the  "  refractive  index."  The  term  refractive  index  (h)  means  that  number  which 
shows  for  a  ceitain  substance  how  many  times  the  sine  of  the  angle  of  incidence  is  greater  than  the 
sine  of  the  angle  of  refraction,  when  a  ray  of  light  passes  from  the  air  into  that  substance.  Thus, 
n  =  sin.  i  :  sin.  r  =  ab,  :  cd.  On  comparing  the  refractive  indices  of  two  media,  we  always  assume 
that  the  ray  passes  from  air  into  the  medium.  On  passing  from  the  air  into  water,  the  ray  of  light 
is  so  refracted  that  the  sine  of  the  angle  of  incidence  is  to  the  sine  of  the  angle  of  refraction   as 

4:3;  the  refractive  index  is  =  —  (or  more  exactly  ^=  1.336).    With  glass  the  proportion  is  =  3  :  2 

(=  1.535) — (Snellius,  1620  :  Descartes'). 

The  construction  of  the  refracted  ray,  the  refractive  index  being  given,  is  simple.  Example. 
—Suppose  in  Fig.  460,  L  =  the  air.  f;  =  a  dense  medium  (glass)  with  a  spherical  surface,  x  v,  and 
with  its  centre  at  m  ;  p  0  =:  the  obli<|ue  incident  ray,  then  m  Z  is  the  perpendicular,  <^)  =  i  the 

angle  of  incidence.     The  refractive  index  given  is    —    !  the  object  is  to  find  the  direction  of  the 

refracted  way.  From  o  as  centre  describe  a  circle  with  a  radius  of  any  length  ;  from  a  draw  a  per- 
pendicular, a  b  to  m  Z\  then  a  b  \i  the  sine  of  the  angle  of  incidence,  i.  Divide  the  line  a  b  into 
three  equal  parts,  and  prolong  it  to  the  extent  of  two  of  these  parts,  viz.,  to/.  Draw  the  line/ 
paiallel  to  m  Z.  The  line  joining  0  to  «  is  the  direction  of  the  refracted  ray.  On  making  a  line, 
«,  .r,  perpendicular  to  m  Z,  n  s  ^=  b p.     Further,  n  s  =  sine  <|)  =  r.     So  that  a  b  :  s  n  (or  :  b p) 

=  •?  :  2  or  sin.  i :  sin.  r  =    —  ■ 

Optical  Cardinal  Point  of  a  Simple  Collecting  System. — Two  refractive  media  (Fig.  461, 
L  and  G)  which  are  separated  from  each  other  by  a  spherical  surface  (a,  b\  form  a  simple  collect- 
ing system.  It  is  easy  to  estimate  the  construction  of  an  incident  ray  coming  from  the  first  medium 
(L)  and  falling  obliquely  upon  the  surface  (a,  b)  separating  the  two  media,  as  well  as  to  ascertain 
its  direction  in  the  second  medium,  G,  and  also  from  the  position  of  a  luminous  point  in  the  first 
medium  to  estimate  the  position  of  the  corresponding  focal  point  in  the  second  medium.  The 
factors  required   to  be   known   are  the   following:   L   (Fig.  461)  is  the  first,  and  G  the   second 


762 


CONSTRUCTION   OF   A    REFRACTED    RAY. 


medium,  a,b  ^  the  spherical  surface  whose  centre  is  m.  Of  course,  all  the  radii  drawn  from  m 
to  <7  h  (m  X,  m  n)  are  perpendiculars,  so  that  all  rays  falling  in  the  direction  of  the  radii  must  pass 
unrefracted  through  m.  All  rays  of  this  sort  are  called  rays  or  lines  of  direction ;  /«,  as  the  point 
of  intersection  of  all  these,  is  called  the  nodal  point.  The  line  which  connects  in  with  the  vertex 
of  the  spherical  surface,  .r,  and  which  is  prolonged  in  both  directions,  is  called  the  optic  axis,  O  Q. 
A  plane  (E,  F)  in  x,  perpendicular  to  O  Q,  is  called  the  principal  plane,  and  in  it  x  is  the  prin- 
cipal point.  The  lollowing  facts  have  been  ascertained:  (I)  All  ravs  [a  to  (Z^),  which  in  the  first 
medium  are  parallel  with  each  other  and  with  the  optic  axis,  and  fall  upon  a  b,  are  so  refracted  in 
the  second  medium  that  they  are  all  again  united  in  one  point  (/,)  of  the  second  medium.  This 
is  called  the  second  principal  focus.     A  plane  in  this  point  perpendicular  to  O  Q  is  called  \ht  second 

Fic;.  461. 


focal  plane  (C,  D).  (2)  All  rays  [c  to  Cjl,  which  in  (he  first  medium  are  parallel  to  each  other 
but  not  parallel  to  O  Q,  reunite  in  a  point  of  the  second  f  >cal  plane  (r),  where  the  non-refracted 
directive  ray  (<-j,  m  r)  meets  this.  (In  this  case  the  angle  formed  by  the  rays  c  to  c^  with  C  Q  must 
be  very  small.)  The  propositions  i  and  2  of  course  maybe  reversed;  the  divergent  rays  pro- 
ceeding from/  toward  a  h  pass  into  the  first  medium  parallel  to  each  other,  and  also  with  the  axis 
C  Q  [a  to  a^^ ;  and  the  rays  proceeding  from  r  pass  into  the  first  medium  parallel  to  each  other, 
but  not  parallel  to  the  axisO  Q  (as  c  to  c,).  (3)  AH  rays,  which  in  the  second  medium  are  parallel 
to  each  other  {/>  to  16.)  and  witn  the  axis  O  Q.  reunite  in  a  point  in  the  first  medium  (/),  called  the 
lirsl  fecal  point ;  of  course,  the    converse  of  this   is   true.     A  plane  in  this  point  perpendicular  to 

FiG   462. 


O  Q  is  called  \)a&  first  focal  plane  (A,  B).  The  radius  of  the  refractive  surface  [m,  x)  is  equal  to 
the  difference  of  the  distance  of  both  focal  points  (/  and  /,)  from  the  principal  focus  {x) ;  thus 
m  x  ^/"i  X  — p  X.  Prom  these  comparatively  simple  propositions  it  is  easy  to  determine  the  fol- 
lowing points  : — 

I.  The  Construction  of  the  Refracted  Ray. — Let  A  (Fig.  462)  be  the  first;  B  the  second 
medium;  c,  d,  the  spherical  surface  separating  the  two;  «,  b,  the  optical  axis;  k,  the  nodal  point; 
/  the  first  and/ J  the  second  prmcipal  focus;  C,  D,  the  second  focal  plane.  Suppose  x, y  to  repre- 
sent the  direction  of  the  incident  ray,  what  is  the  construction  of  the  refracted  ray  in  the  second 
medium  ?  Prolong  the  unrefracted  ray,  P,  X-,  Q  p.arallel  to  -i-,  y,  then  y,  Q  is  the  direction  of  the 
refracted  ray  (according  to  2). 


CONSTRUCTION    OF    A    REFRACTED    RAY. 


763 


2.  Construction  of  the  Image  for  a  given  Object. — In  Fig.  463,  B,  <r,  d,  a,b,  k,p,  and/j,  C. 
D  are  as  before.  .Suppose  a  luminous  point  (i>)  in  the  first  medium,  what  is  the  position  of  the  image 
in  the  second  medium  ?  Prolong  the  unrefracted  ray  (0,  k,  P),  and  draw  the  ray  (o,  x)  parallel  to 
the  axis  (n,  b).  The  parallel  rays  (a,  e,  and  o,  x)  reunite  vap  according  to  proposition  l).  Prolong 
J-,/,  until  it  intersects  the  ray  \o,  P),  then  the  image  of  i?  is  at  P,  the  rays  of  light  (o,  x,  and  0  k) 
proceeding  from  the  luminous  point  (o)  reunite  in  P. 

Construction  of  the  Refracted  Ray  and  the  Image  in  several  Refractive  Media. — If 

Fig.  463. 


several  refractive  media  be  placed  behind  each  other,  we  must  proceed  from  medium  to  medium 
with  the  same  methods  as  above  described.  This  would  be  very  tedious,  especially  when  dealing 
with  small  objects.  Gauss  (1840)  calculated  that  in  such  cases  the  method  of  construction  is  very 
simple.  If  the  several  media  are  "  centred,"  i.e.,  if  all  have  the  same  optic  axis,  then  the  refrac- 
tive indices  of  such  a  centred  system  may  be  represented  by  two  equal  strong  refractive  surfaces  at 
a  certain  distance.  The  rays  falling  upon  the  first  surface  are  not  refracted  by  it,  but  are  essentially 
projected  forward  parallel  with  themselves  to  the  second  surface.   Refraction  takes  place  first  at  the 

Fig.  464. 


P  ^-..^ 

i::;:^;;^^^^^  . 

1  \ 

1 

,%.. 

F 

a 

-f^ 

-C^"""\ 

I1 

;  H 

H, 

h 

11 

ic  krr--...,.^^ 

\^                 F 
F. 

•   m 

h 

\ 

n 

F. 

F 

a 

"^^ 

li 

H 

H, 

k  kr~~~~~~-~._ 

^^^^=====^ 

second  surface,  just  as  if  only  one  refractive  surface  was  present.  In  order  to  make  the  calculation, 
we  must  know  the  refractive  indices  of  the  media,  the  radii  of  the  refractive  surfaces,  and  the  dis- 
tance of  the  refractive  surfaces  from  each  other. 

Construction  of  the  refracted  ray  is  accomplished  as  follows  :  Let  «,  i5  (Fig.  464,  I),  represent  the 
optical  axis  ;  H,  the  first  focal  point  determined  by  calculation  ;  h,  h,  the  principal  plane  ;  H,  the 
second  focal  point  ;/;,,;*,,  the  second  principal  plane :  k,  the  first,  and  /(•,,  the  second  nodal  point ; 
F,  the  second  focal  point  ;  and  Fj,  Fj,  the  second  focal  plane.     Make  the  ray  of  direction/,  k^. 


764 


FORMATION    OF    A    RETINAL    IMAGE. 


parallel  to  »»,,  «j.  According  to  proposition  2,  /,  *,,  and  m^,  »,  mu<;t  meet  in  a  point  of  the 
plane  Fj.Fi-  As/,  i,  passes  through  unrefracted,  the  ray  from  n,  must,  therefore,  fall  at  r;  «,  r 
is,  therefore,  the  direction  of  the  refracted  ray. 

Construction  of  the  Focal  Point. — Let  o  (Fig.  464,  II)  be  a  luminous  point,  what  is  the  posi- 
tion of  its  image  in  the  last  medium  ?  Prolong  from  0  the  ray  of  direction  o,  k,  and  make  0,  x  par- 
allel to  a,  b.  Both  rays  are  prolonged  in  a  parallel  direction  to  the  second  focal  plane.  The  ray 
parallel  to  «,  b  goes  through  F;  /«,  k-^  as  the  ray  of  direction  passes  through  unrefracted.  O,  where 
«,  F,  and  w,  k.^  intersect  each  other,  is  the  position  of  the  image  of  o. 

386.  DIOPTRIC  LAWS  AND  THE  EYE— FORMATION  OF 
THE  RETINAL  IMAGE— OPHTHALMOMETER.— Position  of 
the  Cardinal  Points. — The  eye  surrounded  with  .lir  on  the  anterior  surface  of 
the  cornea,  represents  a  concentric  system  of  refractive  media  with  spherical  sepa- 
rating surfaces.  In  order  to  ascertain  the  course  of  the  rays  through  the  various 
media  of  the  eye,  we  must  know  the  position  of  both  principal  points,  both  nodal 
points  as  well  as  the  two  principal  focal  points.  Gauss,  Listing,  and  v.  Helmholtz 
have  calculated  the  position  of  these  points.  In  order  to  make  this  calculation, 
we  require  to  know  the  refractive  indices  of  the  media  of  the  eye,  the  radii  of  the 
refractive  surfaces,  and  the  distance  of  the  latter  from  each  other.  These  will  be 
referred  to  afterward.  The  following  results  were  obtained  :  (i)  T\\t  first  principal 
point  \s  2.1746  mm.  ;  and  (2)  the  second  principal  point  \s  2.5724  mm.  behind  the 
anterior  surface  of  the  cornea.     (3)  The  first  noilal  point,  o.^s^o  mm.;  and  (4) 

Fig.  465. 


\\\e  second  nodal  point,  0.3602  mm.  in  front  of  the  posterior  surface  of  the  lens. 
(5)  The  second  principal  fiocits,  14.6470  mm.  behind  the  posterior  surface  of  the 
lens;  and  (6)  iht  first  principal  focus,  12.8326  in  front  of  the  anterior  surface  of 
the  cornea. 

Listing's  Reduced  Eye. — The  distance  between  the  two  principal  points,  on 
the  two  nodal  points,  is  so  small  (only  0.4  mm.),  that  practically,  without  introduc- 
ing any  great  error  in  the  construction,  we  may  assume  one  mean  nodal  or  principal 
point  lying  between  the  two  nodal  or  principal  points.  By  this  simple  procedure 
we  gain  one  refractive  surface  for  all  the  media  of  the  eye,  and  only  one  nodal 
point,  through  which  all  the  rays  of  direction  from  without  must  pass  without  be- 
ing refracted.  This  schematic  simplified  eye  is  called  "  the  /-educed  eye  "  of  List- 
ing. 

Formation  of  the  Retinal  Image. — The  construction  of  the  image  on  the 
retina  thus  becomes  very  simple.  In  distinct  vision  the  inverted  image  is  formed 
on  the  retina.  Let  A  B  (Fig.  465)  represent  an  object  placed  vertically  in  front 
of  the  eye.  A  pencil  of  rays  passes  from  A  into  the  eye  ;  the  ray  of  direction,  A 
(/,  passes  without  refraction  through  the  nodal  point,  i.  Further,  as  the  focal  point 
for  the  luminous  point.  A,  is  upon  the  retina,  all  the  rays  proceeding  from  A  must 
reunite  in  (/.  The  same  is  true  of  the  rays  proceeding  from  B,  and,  of  course, 
for  rays  sent  out  from  an  intermediate  point  of  the  body.  A,  B.   The  retinal  image 


THE   OPHTHALMOMETER.  765 

is,  as  it  were,  an  endless  mosaic  of  many  foci  of  the  object.  As  all  the  rays  of 
direction  must  pass  through  tlie  combined  nodal  point,  k,  this  is  also  called  the 
"point  of  intersection  of  the  visual  rays." 

The  inverted  image  on  the  retina  is  easily  seen  in  an  excised  eye  of  an  albino  rabbit,  or  in  any 
other  eye,  by  removing  a  portion  of  the  sclerotic  and  choroid,  and  supplying  its  place  with  a  piece 
of  glass. 

The  size  of  the  retinal  image  may  also  be  calculated,  provided  we  know  the  size  of  the  object 
and  its  distance  from  the  cornea.  As  the  two  triangles.  A,  B,  i,  and  c,  i/,  k,  are  similar.  A,  B  ; 
c,  d  ^  f,k  :  k.  g,  so  that  c,  d  =  (A,  B,  i,  g)  : /,  k.  All  these  values  are  known,  viz.,  /■,  g  = 
15.16  mm. ;  further,/,  k  ^  a,  k  Ys  "</>  where  a,/  is  measured  directly,  and  a,  k  ^  7.44  mm. 
The  size  of  A  B  is  measured  directly. 

The  angle,  A  ,4  B,  is  called  the  visual  angle,  and  of  course  it  is  equal  to  the 
angle  c  k  d.  It  is  evident  that  the  nearer  objects,  xy,  and  r  s,  must  have  the 
same  visual  angle.  Hence,  all  the  three  objects,  A  B,  xy,  and  r  s,  give  a  retinal 
image  of  the  same  size.  Such  objects,  whose  ends  when  united  with  the  nodal 
point  form  a  visual  angle  of  the  same  size,  and  consequently  form  retinal  images 
of  the  same  size,  have  the  same  "  apparent  size." 

In  order  to  determine  the  optical  cardinal  points  by  calculation  after  the  method 
of  Gauss,  we  must  know  the  following  factors : — 

I.  The  refractive  indices,  which  are — for  the  cornea,  1.377;  aqueous  humor, 
1.377  ;  lens,  1.454  (as  the  mean  value  of  all  the  layers)  ;  vitreous  humor,  1.336  ; 
air  being  taken  as  i,  and  water  1.335. 


Scheme  of  the  ophthalmometer  of  Helmholtz 


2.  TTie  radii  of  the  spherical  refractive  surfaces,  which  are — of  the  cornea,  7.7 
mm.  ;  of  the  anterior  surface  of  the  lens,  10.3;  of  the  posterior,  6.1  mm. 

3.  The  distance  of  the  refractive  surfaces — from  the  vertex  of  the  cornea  to  the 
anterior  surface  of  the  lens,  3.4  mm.  ;  from  the  latter  to  the  posterior  surface  of 
the  lens  (axis  of  the  lens),  4  mm.  ;  diameter  of  the  vitreous  humor,  14.6  ram. 
The  total  length  of  the  optic  axis  is  22.0  mm. 

[Kiihne's  Artificial  Eye. — The  formation  of  an  inverted  image  and  the  other  points  in  the 
dioptrics  of  the  eye  can  be  studied  most  efTectively  on  Kiihne's  artilicial  eye,  the  course  of  the  rays 
of  light  being  visible  in  water  tinged  with  eosine.] 

The  Ophthalmometer. — This  is  an  instrument  to  enable  us  to  measure  the  radii  of  the  refrac- 
tive media  of  the  eye.  As  the  normal  curvature  cannot  be  accurately  measured  on  the  dead  eje 
(Petit,  J72J),  owing  to  the  rapid  collapse  of  the  ocular  tunics,  we  have  recourse  to  the  process  of 
Kohlrausch  for  calculating  the  radii  of  the  refractive  surfaces  from  the  size  of  the  reflected  images 
in  the  living  eye.  7'he  size  of  a  luminous  body  is  to  the  size  of  its  reflected  image  as  the  distance  of 
both  to  half  the  radius  of  the  convex  mirror.  Hence  it  is  necessary  to  measure  the  size  of  the  re- 
flected image.  This  is  done  by  means  of  the  ophthalmometer  of  Helmholtz  (Fig.  466).  The 
apparatus  is  constructed  on  the  following  principle :  If  we  observe  an  object  through  a  glass  plate 
placed  obliquely,  the  object  appears  to  be  displaced  laterally;  the  displacement  becomes  greater 
the  more  obliquely  the  plate  is  moved.  .Suppose  the  observer.  A,  to  look  through  the  telescope,  F, 
which  has  the  plate,  G,  placed  obliquely  in  front  of  the  upper  half  of  its  objective,  he  sees  the  cor- 
neal reflected  image,  a,  b,  of  the  eye,  B,  and  the  image  appears  to  be  displaced  laterally,  viz.,  to  a', 
b' .  If  a  second  plate,  G,  be  placed  in  front  of  the  lozver  half  of  the  telescope,  but  placed  in  the 
opposite  direction,  so  that  both  plates,  corresponding  to  the  middle  line  of  the  objective,  intersect  at 
an  angle,  then  the  observer  sees  the  reflected  image,  a  b,  displaced  laterally  to  a",  b".  As  both 
glass  plates  rotate  round  their  point  of  intersection,  the  position  of  both  is  so  .selected  that  both  re- 


766  ACCOMMODATION    OF   THE    EYE. 

fleeted  images  just  touch  each  other  with  their  inner  margins  (so  that  b'  abuts  closely  upon  a"). 
The  size  of  the  reflected  image  can  be  determined  from  the  size  of  the  angle  formed  by  both  plates, 
but  we  must  take  into  calculation  the  thickness  of  the  glass  plates  and  their  refractive  indices.  The 
size  of  the  corneal  image,  and  also  that  in  the  lens,  may  be  ascertained  in  the  passive  eye,  and  also 
in  the  eye  accommodated  for  a  near  object,  and  the  length  of  the  radms  of  the  curved  surface  may 
be  calculated  therefrom  {Hebnhollz,  DonJcrs,  Mautkner). 

Fluorescence. — All  the  media  of  the  eye,  even  the  retina,  are  slightly  fluorescent ;  the  lens 
most,  the  vitreous  humor  least  (i'.  Ilelmholtz). 

Erect  Vision. — .\s  the  retinal  image  is  inverted,  we  must  e.xplain  how  we  see 
objects  erect.  By  a  psychical  djz\,  the  impulses  from  any  point  of  the  retina  are 
again  referred  to  the  e.xterior,  in  the  direction  through  the  nodal  point ;  thus  the 
stimulation  of  the  point,  d  iY\g.  465),  is  referred  to  A,  that  of  c  to  B.  The 
reference  of  the  image  to  the  external  world  happens  thus,  that  all  points  appear 
to  lie  in  a  surface  floating  in  front  of  the  eye,  which  is  called  the  field  of  vision. 
The  field  of  vision  is  the  inverted  surface  of  the  retina  projected  externally  ; 
hence  the  field  of  vision  appears  erect  again,  as  the  inverted  retinal  image  is  again 
projected  externally  but  inverted. 

That  the  stimulation  of  any  point  is  again  projected  in  an  inverse  direction  through  the  nodal 
point,  is  proved  by  (he  simple  experiment  that  pressure  upon  the  oii/er  aspect  of  the  eyeball  is 
projected  or  referred  to  the  inner  asj^ecl  of  the  field  of  vision.  The  entoptical  phenomena  of  the 
retina  are  similarly  projected  externally  and  inverted;  so  that,  e.g.,  the  entrance  of  the  optic  nerve 
lies  external  to  the  yellow  spot  (see  jj  393).     All  sensations  from  the  retina  are  projected  externally, 

387.  ACCOMMODATION  OF  THE  EYE.— According  to  No.  2  (p.  760),  the  rays  of 
light  proceeding  from  a  luminous  point,  eg.,  a  flame,  and  acted  upon  by  a  collecting  (convex)  lens, 
are  brought  to  a  focus  or  focal  point,  which  has  always  a  definite  relation  to  the  luminous  object. 
If  a  projection  surface  or  screen  be  placed  at  this  distance  from  the  lens,  a  real  and  inverted  image 
of  the  object  is  obtaine<l  upon  the  screen.  If  the  screen  be  placed  nearer  to  the  lens  (Fig.  760,  IV, 
a,  b),  or  further  away  from  it  (c,  li),  no  distinct  image  of  the  object  is  formed,  but  diffusion  circles 
are  obtained,  because  in  the  former  case  the  rays  have  not  united,  and  in  the  latter  because  the  rays, 
after  uniting,  have  crossed  each  other  and  become  divergent.  If  the  luminous  point  be  brought 
nearer  to,  or  removed  further  from,  the  lens,  in  order  to  obtain  a  distinct  image,  in  every  case  the 
screen  must  be  brought  nearer,  or  removed  from  the  lens,  to  keep  the  same  tiistance  between  the 
lens  and  the  screen.  If,  however,  the  screen  be  fixed  permanently,  while  the  distance  between  the 
luminous  point  and  the  lens  varies,  a  distinct  image  can  only  be  obtained  upon  the  screen,  provided 
the  lens,  as  the  luminous  point  approaches  it,  becomes  more  convex,  i.  e  ,  refracts  the  rays  of  light 
more  strongly — conversely,  when  the  distance  between  the  luminous  point  and  the  lens  becomes 
greater,  the  lens  must  become  less  curved,  i.e.,  refract  less  strongly. 

In  the  eye,  the  projection  surface  or  screen  is  represented  by  the  retina,  which  is  permanently 
fixed  at  a  certain  distance  ;  but  the  eye  has  the  power  of  forming  distinct  images  of  near  and 
distant  objects  upon  the  retina,  so  that  the  refractive  power,  i.e.,  the  form  of  the  crystalline  lens  in 
the  eye,  must  undergo  a  change  in  curvature  corresponding  in  every  case  to  the  distance  of  the 
object.  [It  is  important  to  remember  that  we  cannot  see  a  near  object  and  a  distant  one  with  equal 
distinctness  al  the  same  lime,  and  hence  arises  the  necessity  for  accommodation.] 

Accommodation. — By  the  term  accoinmodation  of  the  eye  is  understood  the 
property  of  the  eye,  whereby  it  forms  distinct  images  of  distant  as  well  as  near 
objects  upon  the  retina.  This  power  depends  upon  the  fact  that  the  crystalline 
lens  alters  its  curvature,  becoming  more  convex  (thicker),  or  less  curved 
(flatter),  according  to  the  distance  of  the  object.  When  the  lens  is  absent  from 
the  eyeball,  accommodation  is  impossible  (  Th.  Young,  Danders — p.  758). 

During  rest  [or  negative  accommodation],  or  when  the  eye  is  passive,  it 
is  accommodated  for  the  greatest  distance,  i.  e.,  images  of  objects  placed  at  an 
infinite  distance  [e.g.,  the  moon)  are  formed  upon  the  retina.  In  this  case,  rays 
coming  from  such  a  distance  are  practically /(7/-(i//t'/,  and  when  they  enter  the  eye 
are,  in  the  passive  /wz-ot^/ (emmetropic)  eye,  brought  to  a  focus  on  the  retina. 
When  looking  at  a  distant  object,  a  distinct  image  is  formed  on  the  retina  without 
the  aid  of  any  muscular  action. 

That  distant  objects  are  seen  without  the  aid  of  any  muscular  action  is  shown  by  the  following 
considerations:  (i)  The  nonnal.  or  emmetropic,  eye  can  see  distant  objects  clearly  and  distinctly 
without  our  experiencing  any  feeling  of  elilbrt.     On  opening  the  eyelids  after  a  long  period  of  rest. 


ACCOM  MODATION . 


767 


the  objects  at  a  distance  are  at  once  distinctly  visible  in  the  field  of  vision.  (2)  If,  in  consequence 
of  paralysis  of  the  mechanism  of  accommodation  [e.g.^  through  paralysis  of  the  oculomotor  nerve — 
?  345,  7),  the  eye  is  unable  to  focus  images  of  objects  placed  at  different  distances,  still  distinct 

Fig.  467. 


Anterior  quadrant  of  a  horizontal  section  of  the  eyeball,  cornea,  and  lens,  a,  substantia  propria  of  the  cornea;  6, 
Bowman's  elastic  membrane  ;  c^  anteri-.r  corneal  cpiihelium  ;  d,  Descemei's  membrane  :  <•,  its  epithelium  ;  /, 
conjunctiva;  ^.sclerotic;  k,  iris  ;  i,  sphincter  iridis  ;  j,  ligamentum  pectinatum  iridis,  with  the  adjoining  vacuo- 
lated tissue  ;  It,  canal  of  Schlcmm  :  /,  longitudinal,  »«.  circular  muscular  fibres  of  the  ciliary  muscle ;  n,  ciliary 
process;  «>,  ciliary  part  of  the  retina  ;  ^,  canal  of  Petit,  with  Z.  zonule  of  Zinn  in  front  of  it ;  and />,  the  posterior 
layer  of  the  hyaloid  membrane  ;  r,  anterior,  s,  posterior  part  of  the  capsule  of  the  lens  ;  t,  choroid  ;  u,  pericho- 
roidal space ;  '1',  pigment  epithelium  of  the  iris  ;  x,  margin  of  the  lens. 

Fig.  468. 


Scheme  of  accommodation  for  near  and  distant  objects.  The  right  side  of  the  figure  represents  the  condition  of  the 
lens  during  accommodation  for  a  near  object,  and  the  left  side  when  the  eye  is  at  rest.  The  letters  indicate  the 
same  parts  on  both  sides  ;  those  on  the  right  side  are  marked  with  a  stroke  ;  A .  left,  B,  right  half  of  the  lens  ;  C, 
cornea;  .S",  sclerotic  ;  C.5.j,  canal  of  Schiemm  ;  K/f.,  anterior  chamber ;  y,  iris  :  /*,  margin  of  the  pupil ;  V, 
anterior  surface  ;  //,  posterior  surface  of  the  lens  ;  V?,  margin  of  the  lens  ;  >*,  margin  of  the  ciliary  processes  :  a 
and  d,  space  between  the  two  former;  the  line  Z,  A,  indicates  the  thickness  oi  the  lens  during  accommodation 
for  a  near  object ;  Z^  V,  the  thickness  of  the  lens  when  the  eye  is  passive. 


images  are  obtained  of  distant  objects.     Thus,  paralysis  of  the  mechanism  of  accommodation  is 
always  accompanied   by  inability  to   focus  a  near  object,  never  a  distant  object.     A  temporary 


768 


paralysis  with  the  same  results  occurs  when  a  solution  of  atropin  or  duboisin  is  dropped  into  the 
eye,  and  also  in  poisoning  with  these  drugs  (J  392). 

When  the  eye  is  accommodated  for  a  near  object  [positive  accommoda- 
tion], the  lens  is  thicker,  its  anterior  surface  is  more  curved  (convex),  and 
projects  further  into  the  anterior  chamber  of  the  tye  {daiiicr,  v.  Hchnholtz). 
The  mechanism  producing  this  result  is  the  following :  During  rest  the  lens  is 
kept  somewhat  flattened  against  the  vitreous  humor  lying  behind  it  by  the  tension 
of  the  stretched  zonule  of  Zinn  (Fig.  467,  Z),  which  is  attached  round  the  margin 
of  the  lens.  When  the  muscle  of  accommodation,  the  ciliary  muscle  (/,  in), 
contracts,  it  pulls  forward  the  margin  of  the  choroid,  so  that  the  zonule  of  Zinn 
in  intimate  relation  with  it  is  relaxed.  [When  we  accommodate  for  a  near 
object  the  ciliary  muscle  contracts,  pulls  forward  the  choroid,  relaxes  the 
zonule  of  Zinn,  and  this  in  turn  diminishes  the  tension  of  the  anterior  part  of 
the  capsule  of  the  lens.]  The  lens  assumes  a  more  curved  form  in  virtue  of  its 
elasticity,  so  that  it  becomes  more  convex  as  soon  as  the  tension  of  the  zonule 
of  Zinn,  which  keeps  it  flattened,  is  diminished  (?'.  Helmlioltz).  As  the  posterior 
surface  of  the  lens  lies  in  the  saucer-shaped,  unyielding  depression  of  the  vitreous 
humor,  the  anterior  surface  of  the  lens  in  becoming  more  convex  must  neces- 
sarily protrude  more  forward. 

Nerves. — According  to  Hensen  and  Volckers,  the  origin  of  the  nerves  of  accom- 
modation lies  in  the  most  anterior  root  bundles  of  the  oculomotorius.  Stimu- 
lation of  the  posterior  part  of  the  floor  of  the  third  ventricle  causes  accommoda- 
tion ;  if  a  part  lying  slightly  posterior  to  this  be  stimulated,  contraction  of  the 
pupil  occurs.  On  stimulating  the  limit  between  the  third  ventricle  and  the  aque- 
duct there  results  contraction  of  the  internal  rectus  muscle,  while  stimulation 
of  the  other  parts  around  the  iter  causes  contraction  of  the  superior  rectus,  levator 
palpebrfe,  rectus  inferior  and  inferior  oblique  muscles. 

Proofs. — That  the  lens  undergoes  an  alteration  in  its  curvature  during  accommodation  is  proved 
by  the  following  facts  : — 

I.  Purkinje-Sanson's  Images. — If  a  lighted  candle  be  held  at  one  side  of  the  eye,  or  if  light 
be  allowed  to  fall  on  the  eye  through  two  triangular  holes,  placed  above  each  other  and  cut  in  a 
piece  of  cardboard,  the  oijserver  will  see  in  the  latter  case  three  pairs  of  reflected  images  [in  the 
lormer,  three  images].     The  brightest  and  most  distinct  image  (or  pair  of  images)  is  erect,  and  is 


Fig.  469. 


Fig.  470. 


Sanson-Purkinje's  images,    a,  h,  c,  during  neg.itive, 
and  rt,,  l>j,  Cf,  positive  accommodation. 

produced  by  the  anterior  surface  of  the  cornea  (Fig. 
469,  a).  The  second  iiuage  (or  pair  of  images)  is  also 
erect.  It  is  ihe  largest,  but  it  is  not  so  bright  {b),  and  it 
is  reflected  by  the  anterior  surface  of  the  lens.  (The 
size  of  a  reflected  image  from  a  convex  mirror  is  greater 
the  longer  the  radius  of  curvature  of  the  reflecting  surface.) 
The  latter  image  lies  8  ram.  behind  \\\t  plane  of  the  pupil 
The  third  image  (or  pair  of  images)  is  of  medium  size  and 
medium  brightness — it  is  inverted  and  lies  nearly  in  the 
plane  of  the  pupil  (c).  The  posterior  capsule  of  the  lens 
which  reflects  the  last  image  acts  like  a  concave  mirror. 
If  a  luminous  object  be  placed  at  a  distance  from  a  con- 
cave mirror,  its  inverted,  diminished,  real  image  lies  close 
to  the  focus  toward  the  side  of  the  object.     If  the  images 


rh.\koscope  of  Helmholi 


CHANGES   DURING   ACCOMMODATION.  769 

be  studied  when  the  observed  eye  is  passive,  ;.f., in  the  phase  of  negative  accommodation  on  asking 
the  person  experimented  upon  to  accommodate  his  eye  for  a  near  object,  at  once  a  change  In  the 
relative  position  and  size  of  some  of  the  images  is  apparent.  The  middle  pair  of  images  reflected 
by  the  anterior  surface  of  the  lens  diminish  in  si/e  and  approach  each  other  (dy),  which  depends 
upon  tlie  fact  that  the  anterior  surface  of  the  lens  has  become  more  convex.  At  the  same  time  the 
image  (or  pair  of  images)  comes  nearer  to  the  image  formed  by  the  cornea  {{jy  and  c^)  as  the 
anterior  surface  of  the  lens  lies  nearer  to  the  cornea.  The  other  images  (or  pairs  of  images) 
neither  change  their  size  nor  position,  v.  Helmholtz,  with  the  aid  of  the  ophthalmometer,  has 
measured  the  diminution  of  the  radius  of  curvature  of  the  anterior  surface  of  the  lens  during  accom- 
modation for  a  near  object. 

[Phakoscope. — These  images  may  be  readily  shown  by  means  of  the  phakoscope  of  v.  Helm- 
holtz (Kig.  470).  It  consists  of  a  triangular  box  blackened  inside  and  with  its  angles  cut  oflT.  The 
observer's  eye  is  placed  at  ti,  while  on  the  opposite  side  of  the  box  are  two  prisms,  /',  6^;  the 
observed  eye  is  placed  at  the  side  of  the  box  opposite  to  C.  When  a  candle  is  held  in  front  of  the 
prisms,  6  and  d^,  three  pairs  of  images  are  seen  in  the  observed  eye.  Ask  the  person  to  accommo- 
date for  a  distant  object,  and  note  the  position  of  the  images.  On  pushing  up  the  slide,  C,  with  a 
pin  attached  to  it,  and  asking  him  to  accommodate  for  the  pin,  i.e.,  for  a  near  object,  the  position 
and  size  of  the  middle  images  chiefly  will  be  seen  to  alter  as  descrilied  above.] 

2.  In  consequence  of  the  increased  curvature  of  the  lens  during  accommodation  for  a  near 
object,  the  refractive  indices  within  the  eye  must  undergo  a  change.  According  to  v.  Helmholtz, 
the  following  measurements  obtain  in  negative  and  positive  accommodation  respectively : — 


Accommodation. 


Radius  of  the  cornea 

Radius  of  anterior  surface  of  lens 

Radius  of  posterior  surface  of  lens 

Position  of  the  vertex  of  the  outer  surface  of  the  lens  behind  ) 

the  vertex  of  the  cornea j 

Position  of  the  posterior  vertex  of  the  lens 

Position  of  the  anterior  focal  point 

Position  of  the  first  principal  point 

Position  of  the  second  principal  point 

Position  of  the  posterior  focal  point  behind  the  anterior  vertex  I 

of  the  cornea j 


Negative— Mm. 

Positive — Mm. 

8 

8 

10 

6 

6 

55 

3-6 

3-2 

7-2 

7-2 

12.9 

11.24 

1.94 

2.03 

6.96 

6.5> 

22.23 

20.25 

3.  Lateral  View  of  the  Pupil. — If  the  passive  eye  be  looked  at  from  the  side,  we  observe  only 
a  small  black  strip  of  the  pupil,  which  becomes  broader  as  soon  as  the  person  experimented  on  ac- 
commodates for  a  near  object,  as  the  whole  pupil  is  pushed  more  forward. 

4.  Focal  Line. — If  light  be  admitted  through  the  cornea  into  the  anterior  chamber,  the  "  focal 
line  "  formed  by  the  concave  surface  of  the  cornea  falls  upon  the  iris.  If  the  experiment  be  made 
upon  a  person  whose  eye  is  accommodated  for  a  distant  object,  so  that  the  line  lies  near  the  margin 
of  the  pupil,  it  gradually  recedes  toward  the  scleral  margin  of  the  iris,  as  soon  as  the  person  ac- 
commodates for  a  near  object,  because  the  iris  becomes  more  oblique  as  its  inner  margin  is  pushed 
forward. 

5.  Change  in  Size  of  Pupil. — On  accommod.ating  for  a  near  object,  the  pupil  contracts, 
while  in  accommodation  for  a  distant  object  it  dilates  (Descartes,  /6j7).  The  contraction  takes 
place  slightly  after  the  accommodation  [Dont/ers).  This  phenomenon  may  be  regarded  as  an 
associated  movement,  as  both  the  ciliary  muscle  and  the  sphincter  pupilla;  are  supplied  by  the 
oculomotorius  (J  345,  2,  3).  A  reference  to  Fig.  467  shows  that  the  latter  also  directly  supports  the 
ciliary  muscle;  as  the  inner  margin  of  the  iris  pa.sses  inward  (toward  r),  its  tension  tends  to  be 
propagated  to  the  ciliary  margin  of  the  choroid,  which  also  must  pass  inward.  The  ciliary  pro- 
cesses are  made  tense,  chiefly  by  the  ciliary  muscle  (tensor  choroids;).  Accommodation  can  still 
be  performed,  even  though  the  iris  be  absent  or  cleft. 

6.  Internal  Rotation  of  the  Eye. — On  rotating  the  eyeball  inward,  accommodation  for  a  near 
object  is  performed  involuntarily.  As  rotation  of  both  eyeballs  inward  takes  place  when  the  axes 
of  vision  are  directed  to  a  near  object,  it  is  evident  that  this  must  be  accompanied  involuntarily  by 
an  accommodation  of  the  eye  for  a  near  object. 

7.  Time  for  Accommodation. — A  person  can  accommodate  from  a  near  to  a  distant  object 
(which  depends  upon  relaxation  of  the  ciliary  muscle)  much  more  rapidly  than  conversely,  from  a 
distant  to  a  near  object  ( /  'ieroriit,  Aeby).  The  process  of  accommodation  requires  a  longer  time  the 
nearer  the  object  is  brought  to  the  eye  (  Vieronll,  Vo/eiers,  and  liensen).  The  time  necessary  for 
the  image  reflected  from  the  anterior  surface  of  the  lens  to  change  its  place  during  accommodation 
is  less  than  that  required  for  subjective  accommodation  [Auiert  and  Angelucci). 

49 


770 


REFRACTIVE    POWER   OF   THE    EVE. 


8.  Line  of  Accommodation. — When  the  eye  is  placed  in  a  certain  position  during  accommo- 
dation, we  may  see  not  one  point  alone  distinctly,  but  a  whole  series  of  points  behind  each  other. 
Czermak  called  the  line  in  which  these  points  lie  the  line  of  accommodalioti.  The  more  the  eye 
is  accommodated  for  a  distant  object  the  longer  this  line  becomes.  All  objects  placed  at  a  greater 
distance  from  the  eye  than  60  to  70  metres  appear  equally  distinct  to  the  eye.  The  line  becomes 
shorter  the  more  we  accommodate  for  a  near  object,  ;.  e.,  when  we  accommodate  as  much  as  pos- 
sible for  a  near  object,  a  second  point  can  only  be  seen  indistinctly  at  a  short  distance  behind  the 
object  looked  at. 

9.  The  nerves  concerned  in  the  mechanism  of  accommodation  are  referred  to  under  Oculomo- 
torius  {I  345,  and  again  in  ?  704). 

Scheiner's  Experiment. — The  experiment  which  bears  the  name  of  Scheiner 
(1619)  serves  to  illustrate  the  refractive  action  of  the  lens  during  accommodation 

for  a  near  object  as  well  as  for  a  distant 
Fig.  471.  object.     Make  two  small  pin  holes  (S,</) 

o  in  a  cardboard  (Fig.  471,  K,  K,),  the  holes 

being  nearer  to  each  other  than  the  diam- 
eter of  the  pupil.  On  looking  through 
these  holes,  S,  d,  at  two  needles  (/  and  r) 
placed  behind  each  other,  then  on  accom- 
modating for  the  near  needle  (/),  the  far 
needle  (/•)  becomes  double  and  inverted. 
On  accommodating  for  the  near  needle 
(/),  of  course  the  rays  proceeding  from  it 
fall  upon  the  retina  at  the  focus  (/,)  ;  while 
the  rays  coming  from  the  far  needle  (r) 
have  (7 //r(7(?)' united  and  crossed  m  the  vit- 
reous htmior,  whence  they  diverge  more  and 
more  and  form  two  pictures  (r^,  7-^,)  on  the 
retina.  If  the  right  hole  in  the  cardboard 
S,       ■  li,  (^/)  be  closed,  the  /.»/?  picture  on  the  retina 

K,  > — ~J  K    (O  of  the  double  images  of  the  far  needle 

disappears.  An  analogous  result  is  obtained 
on  accommodating  for  the  far  needle  (R). 
The  near  needle  (P)  gives  a  double  image 
(P^,  P^^),  because  the  rays  from  it  have  not 
yet  come  to  a  focus.  On  closing  the  right 
hole  (i/,),  the  right  double  image  (PJ  dis- 
appears (yPorterfield).  When  the  eye  of 
Scheiner's  experiment.  the  obscrver  is  accommodatcd  for  the  near 

needle,  on  closing  one  aperture  the  double 
image  of  the  distant  point  disappears  on  that  side  ;  but  if  the  eye  is  accommo- 
dated for  the  distant  needle,  on  closing  one  hole  the  crossed  image  of  the  near 
needle  disappears. 

388.  REFRACTIVE  POWER  OF  THE  EYE— ANOMALIES 
OF  REFRACTION.— Far  Point— Near  Point.— The  limits  of  distinct 
vision  vary  very  greatly  in  different  eyes.  We  distinguish  the  far  point  [p.  r., 
punctum  remotum]  and  the  near  [p.  p.,  punctum  proximum]  ;  the  former 
indicates  the  distance  to  which  an  object  may  be  removed  from  the  eye,  and  may 
still  be  seen  distinctly;  the  latter  the  distance  to  which  any  object  may  be  brought 
to  the  eye,  and  may  still  be  seen  distinctly.  The  distance  between  these  two 
points  is  called  the  range  of  accommodation.  The  types  of  eyeball  are 
characterized  as  follows  : — 

I.  The  normal  or  emmetropic  eye  is  so  arranged  when  at  rest  that  parallel 
rays  (Fig.  472,  r,  r)  coming  from  the  most  distant  objects  can  be  focussed  on  the 
retina  (rj.  The  far  point,  therefore,  is  =  co  (infinity).  When  accommodating 
as  much  as  possible  for  a  near  object,  whereby  the  convexity  of  the  lens  is 


MYOPIC    AND    HYPERMETROPIC    EYES. 


771 


r  eye  and  during 


increased  (Fig.  472,  a),  rays  from  Fig.  472. 

a  luminous  point  placed  at  a  dis- 
tance of  5  inches  are  still  focussed 
on  the  retina,  i.e.,  the  near  point  \% 
=  5  inches  (i  inch  =  27  mm.). 
The  range  of  accommodation,  or 
["///^  range  of  distinct  vision"'^, 
therefore,  is  from  5  inches  (10-12 
cm.)  to  00  . 

2.  The  short-sighted  (myopic 
or  long)  eye  (Fig.  473 )  cannot,  u>/ien 
at  rest,  bring  parallel  rays  from 
infinity  to  a  focus  on  the  retina. 
These  rays  decussate  within  the 
vitreous  humor  (at  O),  and  after 
crossing  form  a  diffusion  circle  upon 
the  retina.  The  object  must  be  re- 
moved  from   the  passive  eye  to  a 

distance  of  60  to  120  inches  (to/),  in  order  that  the  rays  may  be  focussed  on  the 
retina.  The  passive  myopic  eye,  therefore,  can  only  focus  divergent  rays  upon 
the  retina.  The  far  point,  therefore,  lies  abnormally  near.  With  an  intense 
effort  at  accommodation,  objects  at  a  distance  of  4  to  2  inches,  or  even  less,  from 

Fig.  473. 


-./-„ 


Myopic  eye. 

the  eye  may  be  seen  distinctly.     The  near  point,  therefore,  lies  abnormally  near; 
the  range  of  accommodation  is  diminished. 

Short-sightedness,  or  myopia,  usually  depends  upon  congenital,  and  frequently  hereditary, 
elongation  of  the  eyeball.  This  anomaly  of  the  refractive  media  is  easily  corrected  by  using  a 
diverging  lens  (concave),  which  makes  parallel  rays  divergent,  so  that  they  can  then  be  brought 
to  a  focus  on  the  retina.  It  is  remarkable  that  most  children  are  myopic  when  they  are  born.  This 
myopia,  however,  depends  upon  a  two-curved  condition  of  the  cornea  and  lens,  and  on  the  lens 
being  too  near  to  the  cornea.  As  the  eye  grows,  this  short-sightedness  disappears.  The  cause  of 
myopia  in  children  is  ascribed  to  the  continued  activity  of  the  ciliary  muscle  in  reading,  writing, 
etc.,  or  the  continued  convergence  of  the  eyeballs,  whereby  the  external  pressure  upon  the  eyeball 
is  increased. 

3.  The  long-sighted  eye  (Fig.  474),  hypermetropic,  hyperoptic  (flat  eye), 
when  at  rest,  can  only  cause  convergent  rays  to  come  to  a  focus  on  the  retina. 
Distinct  images  can  only  be  formed  when  the  rays  proceeding  from  objects  are 
rendered  convergent  by  means  of  a  convex  lens,  as  parallel  rays  would  come  to  a 
focus  behind  the  retina  (at  /).  All  rays  proceeding  from  natural  objects  are 
either  divergent,  or  at  most  nearly  parallel,  never  convergent.  Hence  it  follows 
that  no  long-sighted  person,  when  the  eye  '\% passive,  i.e.,  is  negatively  z.ccoxwcao- 
dated,  can  see  distinctly  without  a  convex  lens.  When  the  ciliary  muscle  con- 
tracts, slightly  convergent,  parallel,  and  even  slightly  divergent  rays  may  be 
focussed,  according  to  the  increasing  degree  of  the  accommodation.     The/f/r 


772 


THE    POWER   OR    FORCE   OF   ACCOMMODATION. 


Fig.  474. 


Hypermetropic  £ 


point  of  the  eye  is  negative,  the  near 
point  abnormally  distant  (over  8  to  80 
inches),  while  the  }-ajige  of  accommo- 
dation is  infinitely  great. 

The   cause  of  hypermetropia  is  almormal 
shortness   of  the  eye,  which  is  generally  due 
9.\.r--^^fn  to   imperfect   development   in   all  directions. 
It  is  corrected  hy  using  a  convex  lens. 

[Defective  Accommodation. — 
In  the  presbyopic  eye,  or  long- 
sighted eye  of  old  people,  the  near 
point  is  farther  away  than  normal,  but 
the  far  point  is  still  unaffected.  In  such  cases  the  person  cannot  see  a  near  object 
distinctly,  unless  it  be  held  at  a  considerable  distance  from  the  eye.  It  is  due  to 
a  defect  in  the  mechanism  of  accommodation,  the  lens  becoming  somewhat  flatter, 
less  elastic,  and  denser  with  old  age,  while  the  ciliary  muscle  becomes  weaker. 
In  hypermetropia,  on  the  contrary,  the  mechanism  of  accommodation  may  be 
perfect,  yet  from  the  shape  of  the  eye  the  person  cannot  focus  on  his  retina  the 
rays  of  light  from  a  near  object.  In  presbyopia  the  range  of  distinct  vision  is 
diminished.  The  defect  is  remedied  by  weak  convex  glasses.  The  defect 
usually  begins  about  forty-five  years  of  of  age.] 

Estimation  of  the  Far  Point — Snellen's  Types. — In  order  to  determine  ihe  far  point  of  an 
eye,  gradually  bring  nearer  to  the  eye  objects  which  form  a  visual  angle  of  5  minutes  [e.  g.,  Snel- 
len's small  type  letters,  or  the  medium  type,  4  to  8,  of  Jaeger),  until  they  can  be  seen  distinctly. 
The  distance  from  the  eye  indicates  the  far  point.  In  order  to  determine  the  far  point  of  a  myopic 
person,  place  at  20  inches  distant  from  the  eye  the  same  objects  which  give  a  visual  angle  of  5 
minutes,  and  ascertain  the  comave  tens  which  will  enable  the  person  to  see  the  objects  distinctly. 
To  estimate  the  near  point,  bring  small  objects  [e.  g.,  the  finest  print),  nearer  and  nearer  to  the  eye, 
until  it  finally  becomes  indistinct.  The  distance  at  which  one  can  still  see  distinctly  indicates  the 
far  point. 

Optometer. — The  optometer  may  also  be  used  to  determine  the  near  and  far  points.  A  small 
object,  e.  g.,  a  needle,  is  so  arranged  as  to  be  movable  along  a  scale,  along  which  the  eye  to  be  in- 
vestigated can  look  as  a  person  looks  along  the  sight  of  a  rifle.  The  needle  is  moved  as  near  as 
possible,  and  then  removed  as  far  as  possible,  in  each  case  as  long  as  it  is  seen  distinctly.  The  dis- 
tance of  the  near  and  far  point  and  the  range  of  accommodation  can  be  read  off  directly  upon  the 
scale  [Grafe). 

389.  THE  POWER  OR  FORCE  OF  ACCOMMODATION.— Force  of  Accommoda- 
tion.— The  range  of  accommodation,  which  is  easily  determined  experimentally,  does  not  by  itself 
determine  the  proper /o-iitv-  or  force  of  accommodation.  The  measure  of  the  latter  depends  upon  the 
tneehanieal  -work  done  by  the  muscle  of  accommodation,  or  the  ciliary  muscle.  Of  course,  this 
cannot  be  directly  determined  in  the  eye  itself.  Hence  this  force  is  measured  by  the  optical  effect, 
which  results  in  consequence  of  the  change  in  the  shape  of  the  lens,  brought  about  by  the  energy  of 
the  contracting  muscle. 

In  the  normal  eye,  during  the  passive  condition,  the  rays  coming  from  infinity,  and,  therefore, 
parallel  (which  are  dotted  in  Fig.  475),  are  focussed  upon  the  retina  at  /.  If  rays  coming  from  a 
distance  of  5  inches  (p.  773)  are  to  be  focussed,  the  whole  available  energy  of  the  ciliary  muscle 
must  be  brought  into  play  to  allow  the  lens  to  become  more  convex,  so  that  the  rays  may  be  brought 
to  a  focus  at  f.     The  energy  of  accommodation,  therefore,  produces  an  optical  effect  in  as  far  as  it 

increases  the  convexity  of  the  anterior 
Fig.  471;.  surface  of  the  passive  lens  (A),  by  the 

amount  indicated  by  13.  Practically, 
we  may  regard  the  matter  as  if  a  new 
convex  lens  (B)  were  added  to  the  ex- 
isting convex  lens  (.^j.  What,  there- 
fore, must  be  the  focal  distance  of  the 
lens  (B)  in  order  that  rays  coming 
from  the  near  point  (5  inches)  may  be 
focussed  upon  the  retina  at  /'?  Evi- 
dently the  lens  B  must  make  the  diverg- 
ing rays  coming  from  p  parallel,  and 
then  A  can  focus  them  at  /.     Convex 


SPECTACLES.  773 

lenses  cause  those  rays  proceeding  from  their  focal  points  to  pass  out  at  the  other  side  as  parallel 
rays  (^  385,  I).  In  our  case,  therefore,  the  lens  must  have  a  focal  distance  of  5  inches.  The  nor- 
mal eye,  therefore,  with  the  far  point  =  co,  and  the  near  point  =  5  inches,  has  a  power  of  accom- 
modation equal  to  a  lens  of  5  inches  focal  distance.  When  the  lens  by  the  energy  of  accommoda- 
tion is  rendered  more  powerfully  refractive,  the  increase  (B)  can  readily  be  eliminated  by  placing  be- 
fore the  eye  a  concave  lens  which  posses-es  exactly  the  opposite  optical  effect  of  the  increase  of  ac- 
commodation (B).  Hence,  it  follows  that  it  is  possible  to  indicate  the  power  (force)  of  accommo- 
dation of  the  eye  by  a  lens  of  a  definite  focal  distance,  i.e,  by  the  optical  effect  produced  by  the  latter. 
Therefore,  according  to  Donders,  the  measure  of  the  force  of  accommodation  of  the  eye  is  the 
reciprocal  value  of  the  focal  distance  of  a  concave  lens,  which,  when  placed  before  the  accommo- 
dated eye,  so  refracts  the  rays  of  light  coming  from  the  near  point  (/)  as  if  they  came  from  the  far 
point. 

Example. — We  may  calculate  the  force  of  the  accommodation  according  to  the  following  for- 
mula: -  =:  — -— ,  i.e.,  the  force  of  accommodation,  expressed  as  the  dioptric  value  of  a  lens  (of  jr 

inch  focal  distance),  is  equal  to  the  difference  of  the  reciprocal  values  of  the  distances  of  the  near 
point  (/)  and  of  the  far  point  (r)  of  the  eye.     In  the  emmetropic  eye,  as  already  mentioned,/  =  5, 

r  =  00.     Its  force  of  accommodation  is,  therefore,   -  = ,  so  that  jr  =  5i  '■  e.t  it  is  equal  to  a 

X      p     a 

lens  of  5  inches  focal  distance.     In  a  myopic  eye,/  ^  4,  r  =:   12,  so  that  -  = ,  i.e.,  x  = 

6.  In  another  myopic  eye,  with  /  ^  4  and  r  =r  20,  then  jr  =  5,  which  is  a  normal  force  of  accom- 
modation. Hence,  it  is  evident  thaftwo  different  eyes,  possessing  a  very  different  range  of  accom- 
modation, may,  nevertheless,  have  the  same/o/-«of  accommodation.  Example. — The  one  eye  has 

/  =  4,  r  ^  CO  ,  the  other,/  =  2,  r  =  4.     In  both  cases,  -   =  -,  so  that  the  force  of  accommoda- 

X        4 

tion  of  both  eyes  is  equal  to  the  dioptric  value  of  a  lens  of  4  inches  focal  distance.    Conversely,  two 

eyes  may  have  the  same  range  of  accommodation,  and  yet  their  force  of  accommodation  be  very 

unequal.     Example. — The  one  eye  has/  ^  3,  »-  =  6  ;  the  other/  =  6,  r  =  g.     Both,  therefore, 

have  a  range  of  accommodation  of  3  inches.     For  these,  the  force  of  accommodation,  -  ^  -  —  ~, 

X       3      6 

jr  =  6;  and  -  ^ ,  x  ^  l8. 

JT         6       9 

Relation  o/the  range  to  M^' force  »/ accommodation. — The  general  law  is,  that  the  ranges  of 
accommodation  of  two  eyes  being  equally  great,  then  l\it\T  forces  of  accommodation  are  equal,  pro- 
vided that  their  near  points  are  the  same.  If  the  ranges  of  accommodation  for  both  eyes  are  equally 
great,  but  their  near  points  unequal,  then  i\ie  forces  of  accommodation  are  also  unequal — the  latter 
being  greater  in  the  eyes  with  the  smallest  near  point.  This  is  due  to  the  fact  that  every  difference 
of  distance  near  a  lens  has  a  much  greater  effect  upon  the  image  compared  with  differences  in  the 
distance /ar  from  a  lens.  The  emmetropic  eye  can  see  distinctly  objects  at  60  to  70  metres,  and 
even  to  infinity,  without  accommodation. 

While/  and  r  may  be  directly  estimated  in  the  emmetropic  and  myopic  eyes,  this  is  impossible 
with  the  hypermetropic  (long-sighted)  eye.  The  far  point  in  the  latter  is  negative,  indeed  in  every 
pronounced  hypermetropia  even  the  near  point  may  be  negative.  The  far  point  may  be  estimated 
by  making  the  hypermetropic  eye  practically  a  normal  eye  by  using  suitable  convex  lenses.  The 
relative  near  point  may  then  be  determined  by  means  of  the  lens. 

Even  from  the  I5lh  year  onward,  the  power  of  acccmmodalion  is  generally  diminished  for  near 
objects  —perhaps  this  is  due  to  a  diminution  of  the  elasticity  of  the  lens  (Donders). 

390.  SPECTACLES. — The  focal  distance  of  concave  (diverging)  as  well  as  convex  (converg- 
ing) spectacles  depends  upon  the  refractive  index  of  tlie  glass  (usually  3:  2),  and  on  the  length  of 
the  radius  of  curvature.  If  the  curvature  of  both  sides  of  the  lens  is  the  same  (biconcave  or  bicon- 
vex), then  with  the  ordinary  refractive  index  of  glass  the  focal  distance  is  the  same  as  the  radius  of 
curvature.  If  one  surface  of  the  lens  is  plane,  then  the  focal  distance  is  twice  as  great  as  the  radius 
of  the  spherical  surface.  Spectacles  are  arranged  according  to  their  focal  distance  in  inches,  but  a 
lens  of  shorter  focal  distance  than  I  inch  is  generally  not  used.  They  may  also  be  arranged  accord- 
ing to  their  refractive  po-wer.  In  this  case  the  refractive  power  of  a  lens  of  I  inch  focus  is  taken 
as  the  unit.  A  lens  of  2  inches  focus  refracts  light  only  half  as  much  as  the  unit  measure  of  i  inch 
focus ;  a  lens  of  3  inches  focus  refracts  '^  as  strongly,  etc.  This  is  the  case  both  with  convex  and 
concave  lenses,  the  latter,  of  course,  having  a  negative  focal  distance;  thus,  "concave — ],^  "  indi- 
cates that  a  concave  lens  diverges  the  rays  of  light  one-eighth  as  strongly  as  the  concave  lens  of  I  inch 
(negative)  focal  distance. 

Choice  of  Spectacles. — Having  determined  the  near  point  in  a  myopic  eye,  of  course  we  re- 
quire to  render  parallel  the  divergent  rays  coming  from  the  far  point,  just  as  if  they  came  from  infin- 
ity. This  is  dune  by  selecting  a  concave  lens  of  the  focal  distance  of  the  far  point.  The  greatest 
distance  is  the  far  point  of  the  emmetropic  eye.  -Suppose  a  myopic  eye  with  a  far  point  of  6  inches. 


774  CHROMATIC    AND    SPHERICAL    ABERRATION. 

then  such  a  person  requires  a  concavi'  lens  of  6  inches  focus  to  enable  him  to  see  distinctly  at  the 
gre  itest  distance.  Thus,  in  a  myopic  eye,  the  di-tance  of  the  far  point  from  the  eye  is  directly  equal 
to  the  focus  of  the  (weakest)  concave  lens,  which  enables  one  to  see  distinctly  objects  at  the  greatest 
distance.  These  lenses  generally  have  the  same  number  as  the  spectacles  required  to  correct  the 
defect.  Example. — A  myopic  eye  with  a  far  point  of  8  inches  requires  a  concave  lens  of  8  inches 
focus,  i.e.,  the  concave  spectacle.  No.  S.  For  the  hypermetropic  (long-sighted)  eye,  the  focal  dis- 
tance of  the  strongest  convex  lens,  which  enables  the  hypennetropic  eye  to  see  the  most  distant 
objects  distinctly,  is  at  the  same  time  the  distance  of  the  far  point  from  the  eye.  Example. — A 
hypermetropic  eye  which  can  see  the  most  distant  objects  with  the  aid  of  a  convex  lens  of  I2  inches 
focus  has  a  far  point  of  I2  ;  the  proper  spectacles  is  convex,  No.  I2. 

[Dioptric. — The  focal  length  of  a  lens  used  to  be  expressed  in  inches,  and  as  the  unit  was  taken 
as  I  inch,  necessarily  all  weaker  lenses  were  expressed  in  fractions  of  an  inch.  In  the  method 
advocated  by  Bonders,  the  standard  is  a  lens  of  a  focal  distance  of  i  metre  (33.337  English  inches, 
about  40  inches),  and  this  unit  is  called  a  dioptric.  Thus,  the  standard  is  a  weak  lens,  so  that  the 
stronger  lenses  are  multiples  of  this.  Thus,  a  lens  of  2  dioptrics  is  ^  one  of  about  20  inches 
focus;  10  dioptrics  =  4  inches  focus;  and  so  on.  The  lenses  are  numbered  from  No.  1,  /.  e.,  I 
dioptric,  onward.  It  is  convenient  to  use  signs  instead  of  the  words  convex  and  concave.  For 
convex  the  sign  plus  -\-  is  used,  and  for  concave  the  sign  minus  — .  Thus,  a  -\-  4.0  means  a  convex 
lens  of  4  dioptrics,  and  a  —  40  =  a  concave  lens  of  4  dioptrics.] 

In  all  cases  of  myopia  or  hypermetropia  the  person  ought  to  wear  the  proper  spectacles.  In  a 
myopic  eye,  when  the  far  point  is  still  more  than  5  mches,  the  patient  ought  always  to  wear  spec- 
tacles; but  generally  the  working  distance,  e.  g.,  for  reading,  writing,  and  for  handicrafts,  is  about 
12  inches  from  the  eye.  If  the  person  desires  to  do  finer  work  (etching,  drawing),  requiring  the 
object  to  be  brought  nearer  to  the  eye,  so  as  to  obtain  a  larger  image  upon  the  retina,  then  he  should 
either  remove  the  spectacles  altogether  or  use  a  weaker  pair. 

The  hypermetropic  person  ought  to  wear  his  convex  spectacles  when  looking  at  a  near  object, 
and  especially  when  the  illumination  is  feeble,  because  then,  owing  to  the  dilatation  of  the  pupil,  the 
diffusion  circles  of  the  eye  tend  to  become  very  pronounced.  It  is  advisable  to  wear  at  first  convex 
spectacles  which  are  slightly  too  strong.  Cylindrical  lenses  are  referred  to  under  .4stigmatism. 
.Spectacles  provided  with  dull-colored  or  blue  glasses  are  used  to  protect  the  retina  when  the  light 
is  too  intense.  Stenopaic  spectacles  are  narrow  diaphragms  placed  in  front  of  the  eye,  which 
cause  it  to  move  in  a  definite  direction  in  order  to  see  through  the  opening  of  the  diaphragm. 

391.  CHROMATIC  AND  SPHERICAL  ABERRATION,  ASTIG- 
MATISM.—Chromatic  Aberration. — All  the  rays  of  icihite  light,  which 
undergo  refraction,  are  at  the  same  time  broken  up  by  dispersion  mto  a  bundle  of 
rays,  which,  when  they  are  received  on  a  screen,  form  a  spectrum.  This  is  due 
to  the  fact  that  the  different  colors  of  the  spectrum  possess  different  degrees  of 
refrangibility.     The  violet  rays  are  refracted  most  strongly,  the  red  rays  least. 

A  white  point  on  a  black  ground  does  not  form  a  sharp  simple  image  on  the  retina,  but  many 
colored  points  appear  after  each  other.  If  the  eye  is  accommodated  so  strongly  as  to  focus  the 
violet  rays  to  a  sharp  image,  then  all  the  other  colors  must  form  concentric  diffusion  circles,  which 
become  larger  toward  the  red.  In  the  centre  of  all  the  circles,  where  all  the  colors  of  the  spectrum 
are  superposed,  a  white  point  is  produced  by  their  mixture,  while  around  it  are  placed  the  colored 
circles.  The  distance  of  the  focus  of  the  red  rays  from  that  of  the  violet  in  the  eye  ^  0.58  to  0.62 
mm.  The  focal  distance  for  red  is,  according  to  v,  Helmholtz,  for  the  reduced  eye,  20.524  mm. ; 
for  violet,  20.140  mm.  Hence  the  near  and  far  points  for  violet  light  are  nearer  each  other  than  in 
the  case  of  red  light;  white  objects,  therefore,  appear  reddish  when  beyond  the  far  point,  but  when 
nearer  than  the  near  point  they  are  violet.  Hence  the  eye  must  accommodate  more  strongly  for 
red  rays  than  for  violet,  so  that  we  judge  red  objects  to  be  nearer  us  than  violet  objects  placed  at  an 
equal  distance  {Briickc). 

Monochromatic  or  Spherical  Aberration. — Apart  from  the  decomposition  or  dispersion  of 
white  light  into  its  components,  the  rays  of  white  light,  proceeding  from  a  point  if  transmitted 
through  refractive  spherical  surfaces,  we  find  that  before  the  rays  are  again  brought  to  a  focus,  the 
marginal  rays  are  more  strongly  refracted  than  those  pas-.ing  through  the  central  parts  of  the  lens. 
Hence  there  is  not  one  focus,  but  many.  In  the  eye  this  defect  is  naturally  corrected  by  the  iris, 
which,  acting  as  a  diaphragm,  cuts  off  the  marginal  rays  (Fig.  465),  especially  when  the  lens  is 
most  convex,  when  the  pupd  also  is  most  contracted.  In  addition,  the  margin  of  the  lens  has  less 
refractive  power  than  the  central  substance;  lastly,  the  margins  of  the  refractive  spherical  surfaces 
of  the  eye  are  less  curved  toward  their  margins  than  the  parts  lying  nearer  to  the  optical  axis. 
Compare  the  form  of  the  cornea  (p.  750)  and  the  lens  (p.  757). 

Imperfect  Centring  of  the  Refractive  Surfaces. — The  sharp  projection  of  an  image  is  some- 
what interfered  with  by  the  fact  that  the  refractive  surfaces  are  not  exactly  centred  (Briicke).  Thus, 
the  vertex  of  the  cornea  is  not  exactly  in  the  termination  of  the  optic  axis;  the  vertices  of  both 
surfaces  of  the  lens,  and  even  the  different  layers  of  the  lens  itself,  are  not  exactly  in  the  optic  axis. 
The  variations,  however,  and  the  disturbances  produced  thereby,  are  very  small  indeed. 


FUNCTIONS   OF   THE    IRIS. 


775 


Regular  Astigmatism. — When  the  curvature  of  the  refractive  surfaces  of  the  eye  is  unequally 
great  in  its  different  meridians,  of  course  the  rays  of  light  cannot  be  united  or  focussed  in  one  point. 
Generally,  in  such  cases,  the  cornea  is  more  curved  in  its  vertical  meridian  and  least  in  the  hori- 
zontal (as  is  shown  by  ophthalmometric  measurements,  p.  765).  The  rays  passing  through  the 
vertical  meridian  come  to  a  focus,  firsl^  in  a  horizontal  focal  line  ;  while  the  rays  entering  horizon- 
tally unite  afterward  in  a  vertical  line.  There  is  thus  no  common  focus  for  the  light  rays  in  the 
eye ;  hence  the  name  astigmatism.  The  lens,  also,  is  unequally  curved  in  its  meridians,  but  it  is 
the  reverse  of  the  cornea;  consequently,  a  part  of  the  inequality  of  the  curvature  of  the  cornea  is 
thereby  compensated,  and  only  a  part  of  it  affects  the  rays  of  light.  The  emmetropic  eye  has  a  very 
slight  degree  ol  this  ineiiuality  (normal  astigmatism).  If  two  very  fine  hnes  of  equal  thickness  be 
drawn  on  white  paper,  so  as  to  intersect  each  other  at  right  angles,  it  will  be  found  that,  in  order  to  see 
the   horizontal   line  quite  shaiply,  the  paper  must  be  brought  slightly  nearer  to  the  eye  than  when 


Fig.  476. 


of  light  (Frost). 


FlO.  477. 


we  focus  the  vertical  line.  When  the  inequality  of  curvature  of  the  meridians  is  considerable,  of 
course  exact  vision  is  no  longer  possible. 

[Fig.  476  shows  the  effect  of  an  astigmatic  surface  on  the  rays  of  light.  Let  abed  be  such  a 
surface,  and  suppose  diverging  rays  to  proceed  from/!  The  rays  passing  through  r  </ come  to  a 
focus  at/, ,  while  those  passing  through  the  vertical  meridian  are  focussed  at/2.  The  outline  of 
the  cone  of  rays  between  a  b  c  Jand/„  varies,  as  shown  in  the  figure.  At  a  certain  part  it  is  oval, 
with  its  axis  vertical,  at  another  the  long  axis  of  the  oval  is  horizontal,  while  at  other  places  it  is 
circular,  or  the  rays  are  focussed  in  a  horizontal  or  vertical  line.] 

Correction. — This  condition  is  corrected  by  a  cylindrical  lens,  i.e.,  a  lens  so  cut  as  to  be  with- 
out curvature  in  one  direction,  w-hile  in  the  other  direction  (vertical  to  the  former)  it  is  curved. 
The  lens  is  placed  in  front  of  the  eye,  so  that  the  direction  of  its  curvature  coincides  with  the 
direction  of  least  curvature  of  the  eye  (v.  Helmholtz,  Knafp,  Danders). 
The  section  Q  a  b  e  d  of  the  cylindrical  lens  (Fig.  477)  represents  a  plano- 
convex, the  section  C  a  ji  )■  r!,  a  concavo-convex  lens. 

[Test. — Draw  to  lines  of  equ.il  thickness  at  right  angles  to  each  other. 
An  astigmatic  person  cannot  see  both  Hnes  with  equal  distinctness  at  the 
same  time,  one  line  will  appear  thicker  than  the  other.  Or  a  series  of  lines 
radiating  from  a  centre  may  be  used  (astigmatic  clock)  ;  when  that  line 
which  is  parallel  to  the  astigmatic  meridian  will  be  seen  most  distinctly  ; 
while,  with  the  vertical  meridian  most  curved,  it  would  be  the  vertical 
line.] 

Irregular  Astigmatism. — Owing  to  the  radiate  arrangement  of  the 
fibres  in  the  interior  of  the  crystalline  lens,  and  in  consequence  of  the 
unequal  course  of  the  fibres  within  the  different  parts  of  one  and  //le  same 
■f/ieridiati  of  the  lens,  the  rays  of  light  passing  through  one  meridian  of 
the  lens,  cannot  all  be  brought  to  one  focus.  Hence,  we  do  not  obtain  a 
distinct,  sharp  image  of  distant  luminous  points,  such  as  stars  or  street 
lamps,  but  we  see  a  radiate  jagged  figure  provided  with  rays.  The  same 
obtains  on  holding  a  piece  of  cardboard  with  a  small  hole  in  it  toward 
the  light,  at  a  distance  from  the  eye  slightly  greater  than  the  far  point. 
Slight  degrees  of  this  irregular  astigmatism  are  normal,  but  when  it  is 
highly  developed  it  greatly  interferes  with  vision,  by  forming  set'erai  foci 
of  an  object  instead  of  one  Polyopia  monocularis).  Of  course  this  condition  cannot  obtain  in 
an  eye  devoid  of  a  lens. 

392.  THE  IRIS. — Functions. — i.  The  iris  acts  like  a  diaphragm  in  an 

oiJtical  apparatus  by  cutting  off  the  marginal  rays  (Fig.  465),  which,  if  they 
entered  the  eye,  would  cause  spherical  aberration,  and  thus  produce  indistinct 
vision. 


Cylindri 


776  MOVEMENTS   OF   THE    IRIS. 

2.  As  the  pupil  contracts  strongly  in  a  bright  light,  and  dilates  when  the  light 
is  feeble,  it  regulates  the  amount  of  light  entering  the  eye;  thus  fewer  rays 
enter  the  eye  when  the  light  is  strong  than  when  it  is  feeble. 

3.  To  a  certain  extent  it  supports  the  action  of  the  ciliary  muscle. 
Muscles  and  Nerves. — The  iris  is  provided  with  two  sets  of  muscular  fibres 

— the  sphincter,  which  immediately  surrounds  the  pupil  and  is  supplied  by  the 
oculomotorius  (§  345,  2),  and  the  dilator  pupillae  (p.  754),  supplied  chiefly  by 
the  cervical  sympathetic  (§  356,  A,  i),  and  the  trigeminus  (§  347,  3).  I3oth 
muscles  stand  in  an  antagonistic  relation  to  each  other  (§  345),  the  pupil  dilates 
moderately  after  section  or  paralysis  of  the  oculomotorius,  owing  to  the  contrac- 
tion of  the  dilator  fibres  which  are  supplied  by  the  cervical  sympathetic ;  con- 
versely, the  pupil  contracts  when  the  sympathetic  is  divided  or  extirpated  (Petit, 
I72j^.  When  both  nerves  are  stimulated  simultaneously,  the  pupil  contracts,  so 
that  the  excitability  of  the  oculomotorius  overcomes  the  sympathetic. 

[The  existence  of  a  dilator  pupillie  muscle  is  not  universally  recognized,  and  in  fact  some 
observers  doubt  its  existence.  The  muscular  nature  of  the  radial  fibres  in  the  posterior  limiting 
membrane  of  the  iris  is  denied  by  Griinhagen,  while  Koganei  regards  these  as  in  no  case  muscular, 
and  that  the  dilating  fibres  ate  represented  by  fibres  radiating  from  the  iris.  These  fibres  are  well 
developed  in  birds  and  the  otter,  exist  in  traces  in  the  rabbit,  and  are  absent  in  man.  Gaskell 
points  out  that  in  this  case  the  size  of  the  pupil  must  in  part  depend  on  the  elasticity  of  the  radial 
fibres  of  the  iris,  while  the  dilator  nerve  fibres  must  act  on  the  sphincter  fibres,  causing  them  to 
relax.  Gaskell  groups  the  sphincter  of  the  iris  with  those  muscles  "  supplied  by  two  nerves  of  oppo- 
site character,  the  one  motor  the  other  inhibitory."'] 

Nerves. — Arnstein  and  A.  Meyer  have  studied  the  mode  of  termination  of  the  nerve  fibres  in 
the  iris.  All  the  medullated  nerve  fibres  lose  their  white  sheaths  after  a  time ;  most  of  the  fibres 
[motor)  in  the  region  of  the  sphincter  consist  of  naked  bundles  of  fibrils.  A  network  of  very  deli- 
cate sensory  nerves  lies  under  the  anterior  epithelium.  Numerous  fibrils  pass  to  the  capillaries  and 
arteries  as  vasomotor  nerves.     [Many  ganglionic  cells  are  intercalated  in  the  course  of  the  fibres.] 

Movements  of  the  iris  occur  under  the  following  conditions : — 

1.  Action  of  light  on  the  retina  causes  (according  to  its  intensity  and  amount)  a  correspond- 
ing contraction  of  the  pupil ;  the  same  effect  is  produced  by  stimulation  of  the  of  tic  nerve  itself 
[Herbert  Mavo,  f  1852).  This  movement  is  a  reflex  act  [the  afferent  nerve  being  the  optic  and 
the  efferent  the  oculomotorius;  the  impulse  is  transferred  from  the  former  to  the  latter  in  a  centre 
situated  somewhere  below  the  corpora  quadrigemina  (Fig.  478,  C)].  The  older  observers  locate 
the  centre  in  the  corpora  quadrigemina,  the  recent  observers  in  the  medulla  oblongata  (p.  737). 
Both  pupils  always  react,  although  only  one  retina  be  stimulated;  generally,  under  normal  circum- 
stances both  contract  to  the  same  extent  (Donders),  owing  to  the  intercentral  communication 
[coupling]  of  the  two  pupillo-constricting  centres.  [This  is  called  consensual  contraction  of  the 
pupil.]  After  section  of  the  optic  nerve  the  pupil  dilates,  and  subsequent  section  of  the  oculomo- 
torius no  longer  produces  any  further  dilatation  [Knoll ). 

2.  The  centre  for  the  dilator  fibres  of  the  pupil  (pupillodilating  centre)  is  excited  by  dysp- 
na-ic  blood  (§  367,  8).  If  the  dyspnoea  ultimately  passes  into  asphyxia,  the  dilatation  of  the  pupil 
diminishes.  Of  course,  if  the  peripheral  dilating  fibres  (^  247,  3)  \_e.g;.,  the  sympathetic  nerve  in 
the  neck]  be  previously  divided,  this  effect  cannot  take  place,  as  the  dyspnoeic  blood  acts  on  the 
centre  and  not  on  the  nerve  fibres. 

3.  The  centre,  as  well  as  the  subordinate  "  cilio-spinal  region  "  of  the  spinal  cord  (J  362,  i), 
is  also  capable  of  being  excited  reflexly;  painful  stimulation  of  sensory  nerves,  in  addition  to 
causing  protrusion  of  the  eyeballs  (^  347),  a  fact  proved  in  the  case  of  persons  subjected  to  torture, 
produces  dilatation  of  the  pupils  [Arndt,  Bernard,  Westphal,  Litehsinger) ;  while  a  similar  effect 
is  caused  by  labor  pains,  a  loud  call  in  the  ear,  stimulation  of  the  nerves  of  the  sexual  organs,  and 
even  by  slight  tactile  impressions  [Boa  and  Sehif).  According  to  Bechterew,  the  foregoing  results 
are  due  to  inhibition  of  the  light  reflex  in  the  sense  expressed  in  |  361,  3. 

4.  The  condition  of  the  blood  vessels  of  the  iris  influences  the  size  of  the  pupil ;  all  condi- 
tions causing  injection  or  congestion  of  these  vessels  contract  the  pupil,  all  conditions  diminishing 
them  dilate  it.  The  pupil,  therefore,  is  contracted  hy  forced  expiration,  which  prevents  the  return 
of  venous  blood  from  the  head,  momentarily  by  every /'7<A<' ^^c/,  owing  to  the  diastolic  filling  of 
the  arteries;  diminution  of  the  intraocular  pressure,  e.  g.,  after  puncture  of  the  anterior  chamber, 
because,  owing  to  the  diminished  intraocular  pressure,  there  is  less  resistance  to  the  passage  of  blood 
into  the  blood  vessels  of  the  iris  [Nensen  and  I'olchers) ;  paralysis  of  the  vasomotor  fibres  of  the 
iris  (J  347,  2).  Conversely,  the  pupil  is  dilated  by  conditions  the  reverse  of  those  already  men- 
tioned, and  also  by  strong  tnuscular  exertion,  whereby  blood  flows  freely  into  the  dilated  muscular 
blood  vessels;  also  when  death  takes  place.  The  condition  of  the  filling  of  the  blood  vessels  also 
explains  the  fact  that  the  pupil  dilated  with  atropin  becomes  smaller  when  a  part  of  the  sympathetic 
in  the  upper  cervical  ganglion,  carrying  the  vasomotor  fibres  of  the  iris,  is  excised  ;  also,  that  after 


ACTION   OF   DRUGS   ON   THE   PUPIL. 


7/7 


extirpation  of  this  ganglion  atropin  always  causes  a  less  diminution  of  the  pupil  on  this  side.  The 
fact  that  when  the  pupil  is  already  dilated  by  stimulation  of  the  sympathetic,  it  is  further  dilated  by 
atropin,  is  due  to  a  diminished  injection  of  the  blood  vessels  of  the  iris.  If  an  animal  with  its  pupils 
dilated  with  atropin  be  rapidly  bled,  the  pupils  contract,  owing  to  the  anaemic  stimulation  of  the  origin 
of  the  oculomotorius  [Moriggia).  The  dilatation  of  the  pupils  observed  in  cases  of  neuralgia  of 
the  trigeminus  is  partly  due  to  the  stimulation  of  the  dilating  fibres,  partly  to  the  stimulation  of  the 
vasomotor  fibres  of  the  iris  (§  347»  2). 

5.  Contraction  of  the  pupil  occurs  as  an  associated  movement  during  accommodation  for  a 
near  object  (p.  769),  and  when  the  eyeballs  are  rolaled  inward,  which  is  the  case  during  sleep 
(p.  708).  Conversely,  intense  movements  of  the  iris,  caused  by  variations  in  the  brightness  of 
dazzling  illumination,  e.  g.,  of  the  electric  light,  are  followed  by  disturbing  associated  movements 
of  the  ciliary  muscle  (Ljiibinsky).  In  certain  movements  discharged  from  the  medulla  oblongata 
(forced  respiration,  chewing,  swallowing,  vomiting),  dilatation  of  the  pupil  occurs  as  a  kind  oi  asso- 
ciated ifiovement. 

[Argyll  Robertson  Pupil. — In  this  condition  the  pupil  does  not  contract  to  light,  although  it 
contracts  when  the  eye  is  accommodated  for  a  near  object,  vision  usually  being  normal.  The  lesion 
is  situated  on  those  structures  connecting  the  aflerent  and  efierent  fibres  at  their  central  ends  (at  /^ 
in  Fig.  478),  i.  e.,  the  connection  between  the  corpora  quadrigemina  and  the  oculomotorius.  It  is 
most  frequently  found  in  locomotor  ataxia,  although  it  also  occurs  in  progressive  paralysis  of  the 
insane.] 

Direct  stimulation  at  the  margin  of  the  cornea  causes  dilatation  of  the  pupil  (E.  H.  Weber") ;  in 
fact,  direct  stimulation  of  circumscribed  areas  of  the  margin  of  the  iris  causes  partial  contraction  of 
the  dilator  fibres  (Bernstein  and  Dogiel).  Stimulation  near  the  centre  of  the  cornea  contracts  the 
pupil  [E.  H.  Weber).  In  addition,  we  must  assume  that  the  iris  itself  contains  elements  that  in- 
fluence the  diameter  of  the  pupil  {Sig.  Mayer  and  Pribram). 

Our  knowledge  of  the  action  of  poisons  on  the  iris  is  still  very  obscure.  Those  substances 
which  dilate  the  pupil  are  called  mydriatics,  e.  g.,  atropin,  homatropin,  duboisin  (  Tweedy,  -■. 
Hasner),  daturin,  and  hyoscyamin.  They  act  chiefly  by  paralyzing  the  oculomotorius.  But,  in 
addition,  there  must  be  also  an  effect  upon  the  dilating  fibres,  for  after  complete  paralysis  (section) 
of  the  oculomotorius,  the  moderate  A\\sii3.\\on  of  the  pupil  thereby  produced  (^  345,  5)  is  still  further 
increased  by  atropin.  Minimal  doses  of  atropin  contract  the  pupil,  owing  to  stimulation  of  the 
pupillo-constrictor  fibres  ;  enormous  doses  cause  moderate  dilatation  of  the  pupil  in  consequence  of 
paralysis  of  the  dilating  as  well  as  of  the  constricting  nerve  fibres.  Atropin  acts  after  destruction 
of  the  ciliary  [ophthalmic]  ganglion  [Nensen  and  Vblciers)  [and  division  of  all  the  nerves  except 
the  optic],  and  in  the  excised  eye  (De  Ruyter,  Rottmann),  [so  that  atropin  is  a  local  mydriatic. 
In  moderate  doses  it  paralyzes  the  nervous  termina- 
tions of  the  third  nerve  (but  not  in  birds  whose 
iris  contains  striped  muscle),  and  in  larger  doses 
it  also  paralyzes  the  muscular  fibres].  \^Cocaine, 
or  cucaine,  is  obtained  from  the  leaves  of  Ery- 
throxylon  coca.  When  applied  locally  it  acts  as  a 
powerful  local  an.vsthetic,  and  hence  it  is  very 
u.seful  for  operations  about  the  muco-cutaneous  ori- 
fices. A  4  per  cent,  solution  dropped  into  the  e^e 
produces  complete  insensibility  of  the  cornea  in 
a  few  minutes.  It  causes  dilatation  of  the  pupils, 
though  they  react  to  light  and  to  the  movements 
of  accommodation.  It  also  causes  temporary  pa- 
ralysis of  accommodation,  a  sensation  of  heaviness 
and  coldness  of  the  eyeball,  enlargement  of  the 
palpebral  fissure,  constriction  of  the  small  peripheral 
vessels,  and  slight  lachrymation.] 

Myotics  are  those  substances  which  contract 
the  pupil  :  Physostigmin  (=  Eserin,  the  alka- 
loid of  Calabar  bean),  nicotin,  pilocarpin,  muscarin, 
morphia,  according  to  some  observers  (Griin/iagen), 
cause  stimulation  of  the  oculomotorius,  while  others 
[Nirsclimann,  Rosenthal)  say  they  paralyze  the 
sympathetic.  As  these  substances  cause  spasm  of 
the  ciliary  muscle.  It  is  supposed  that  the  first  of  these 
has  an  analogous  action  on  the  sphincter.  It  is 
probable  that  they  paralyze  the  dilator  fibres  and 
stimulate  the  oculomotor  fibres.  [Among  local  my- 
otics, i.  e.,  those  which  act  on  the  eye,  some  act  on 
the  muscular  fibres  of  the  iris,  c.  g.,  physostigmin  or 
eserin,  while  others  act  on  the  peripheral  termina- 
tions of  the  third  nerve,  e.  g.,  pilocarpin,  muscarin. 


Fig.  478. 


;  of  the  I 


0 

lerves  of  the  iris  (after  Erb),  B,  cen- 
:  C,  oculomotor  centre;  D,  dilator 
centre  ("spinal) ;  E,  iris  :  G,  optic  nerve  :  H,  ocu- 
lomotor (sphincter)  roots;  I,  sympathetic  (dila- 
tor): K,  L,  anterior  roots;  M.  N,  O,  posterior 
roots  ;  ^\,seat  of  lesion,  causing  pupillary  immo- 
bility ;  *  probable  seat  of  lesion,  causing  myosis. 


778 


GORHAM  S   PUPIL    PHOTOMETER. 


Muscarin  causes  very  great  contraction  of  the  pupil  from  spasm  of  the  circular  fibres,  due  to  its 
action  on  the  third  nerve;  eserin^on  the  other  hand,  although  contracting  the  pupil,  also  affects 
the  dilator  fibres.     The  contraction  of  the  pupil  due  to  opium  is  central  in  its  cause.] 

If  the  one  pupil  be  contracted  or  dilated  by  these  substances,  the  other  pupil,  conversely,  is 
dilated  or  contracted,  owing  to  the  change  in  the  amount  of  light  admitted  into  the  eye  into  which 
the  poison  has  been  introduced.  The  anaesthetics  (ether,  chloroform,  alcohol,  etc.),  when  they 
begin  to  cause  stupor,  contract  the  pupil,  and  when  their  action  is  intense  they  dilate  it  (Dogiel). 
Chloroform,  during  the  stage  when  it  causes  excitement  (preceding  the  narcosis),  stimulates  the 
centre  for  the  dilatation  of  the  pupil;  after  a  time  this  centre  is  paralyzed,  so  that  the  pupil  no 
longer  dilates  on  the  application  of  external  stimuli.  Thereafter  the  pupillo-constrictor  centre  is 
stimulated,  whereby  the  pupil  may  be  contracted  to  the  size  of  a  pin's  head;  ultimately  this  centre 
is  paralyzed,  and  the  pupil  becomes  dilated. 

Time  for  Movements  of  Iris. — The  reflex  dilatation  of  the  pupil  occurs  slightly  later  than  the 
reflex  contraction,  the  time  in  the  two  cases  being  0.5  and  0.3  second  respectively  after  stimulation 
by  light  (?'.  l^iiilsihffau).  A  certain  time  always  elapses,  until  the  iris,  corresponding  to  the  strength 
of  the  stimulus  of  light  exciting  the  retina,  "adapts"  {Aitbert)  itself  to  produce  a  suitable  size  of 
the  pupil.  Contraction  of  the  pupil  occurs  very  rapidly  after  stimulation  of  the  oculomotorius  in 
birds ;  in  rabbits  0.89  second  elapses  after  stimulation  of  the  sympathetic,  until  the  dilatation  begins 
(Arlt,Jun.). 

Excised  Eye. — Light  causes  contraction  of  the  pupil  in  the  excised  eye  of  amphibians  and  fishes 
{Arnold,  Budge).  Even  the  iris  of  the  eel,  when  cut  out  and  placed  in  normal  saline  solution, 
contracts  to  light  [Arnold,  Gysi,  and  Luchsinger),  the  green  and  blue  rays  being  most  active. 
Increase  of  the  teniperatnre  causes  mydriasis  in  the  excised  eye  of  the  frog  or  eel,  while  cooling 
causes  niyosis  (//.  Miiller,  Biernatli). 


Fig.  479. 


Fig.  480. 


Gorham's  pupil  photometer 
diameter  of  the  pupil  r 


G.  479  shows  the  disk  with  a  slot  and  two  holes.     Fig.  480  % 
ked  on  it.     The  upper  end  is  closed  by  the  disk,  while  the 


r  end  is  open. 


[Size  of  the  Pupil. — Jonathan  Hutchinson  recommends  a  pupilometer,  consisting  of  a  metal 
plate  perforated  with  a  series  of  holes  of  different  sizes.  The  smallest  hole  measures  about  ';^  of  a 
line,  and  the  largest  is  4 j.^  lines.  The  plate  is  placed  just  below  the  patient's  eye,  and  the  hole  is 
selected  which  corresponds  with  the  size  of  the  pupil.] 

[Gorham's  Pupil  Photometer. — This  ingenious  instrument  may  be  used  as  a  pupilometer, 
and  also  as  a  photometer.  It  consists  of  apiece  of  bronzed  tubing  (Figs.  479  and  480),  1.9  in. 
long  and  1.5  in.  diameter.  One  end  is  closed  by  a  disk  or  cap  (Fig.  479),  which  is  pierced  in  its 
radii  by  a  series  of  holes  at  distances  varying  from  .05  in.  to  .28  in.  There  is  a  slot  in  the  cap 
which  allows  one  pair  of  holes  to  be  visible  at  a  time,  while  on  the  cylinder  is  engraved  the  linear 
distance  of  each  pair  of  holes.  In  using  the  instrument  as  a  pupilometer,  look  through  the  open 
end  of  the  tube  (the  bottom  in  Fig.  480),  with  both  eyes  open,  toward  a  sheet  of  white  paper  or  the 
sky,  when  two  disks  of  light  will  be  seen.  Then  revolve  the  lid  or  cap  slowly  until  the  two  white 
disks  just  touch  one  another  at  their  edges.  The  decimal  fraction  opposite  the  two  apertures  seen 
on  the  scale  outside  indicates  the  diameter  of  the  pupil  in  looths  of  an  inch.] 

[When  using  it  as  a  photometer,  it  is  assumed  that  the  size  of  the  pupil  gives  an  index  of  the 
intensity  of  the  amount  of  light  which  influences  the  diameter  of  the  pupil.] 

Intraocular  Pressure. — The  movements  of  the  iris  are  always  accompanied  by  variations  of  the 
intraocular  pressure.  The  muscles  of  the  iris  affect  the  intraocular  pressure,  in  that  the  dilatation 
of  the  pupil  increases  it,  while  contraction  of  the  pupil  diminishes  it.  The  increased  or  diminished 
tension  can  be  felt  when  two  fingers  are  pressed  on  the  eyeball.  Stimulation  of  the  sympathetic 
increases  while  its  section  diminishes  the  pressure.  Action  of  Drugs. — Atropin  dropped  into  the 
eye,  after  producing  a  short  temporary  diminution  of  the  tension,  increa.ses  it;  eserin,  after  a  primary 
increase,  causes  a  diminution  of  the  pressure  (Graser  and  Holzke). 


ENTOPTICAL    PHENOMENA.  779 

393.  ENTOPTICAL  PHENOMENA.— Entoptical  phenomena  de- 
pend upon  the  perception  of  objects  present  within  the  eyeball  itself.  Among 
them  are — 

I.  Shadows  are  formed  upon  the  retina  by  different  opaque  bodies.  In  order  to  see  them  in 
one's  own  eye  proceed  thus  :  By  means  of  a  strong  convex  lens  project  a  small  image  of  a  flame 
upon  a  paper  screen,  prick  a  small  opening  through  the  image  of  the  flame,  and  place  one  eye  at 
the  other  side  of  the  screen,  so  that  the  illuminated  puncture  lies  in  the  anterior  focus  of  the  eye. 
i.e.,  about  13  mm.  in  front  of  the  cornea.  As  the  rays  proceeding  from  this  point  pass  parallel 
through  the  media  of  the  eye,  a  diffuse  bright  field  of  vision,  surrounded  by  the  black  margins  of 
the  iris,  is  obtained.  All  dark  bodies  which  lie  in  the  course  of  the  rays  of  light  throw  a  shadow 
upon  the  retina,  and  appear  as  specks.     There  are  various  forms  of  these  shadows  (Fig.  481). 

(a)  The  spectrum  mucro-Iacrimale,  especially  upon  the  margin  of  the  eyelids,  depending 
upon  particles  of  mucus,  fat  glolmles  from  the  Meibomian  glands,  dust  mixed  with  tears,  causing 
cloudy  or  drop-like  retinal  shadows,  which  are  removed  by  winking. 

(b)  Folds  in  the  Cornea. — If  the  cornea  be  pressed  laterally  with  the  finger,  wrinkled  shadows, 
due  to  temporary  wrinkles  in  the  cornea,  are  produced. 

(c)  Lens'  Shadows. — Head-like  or  dark  specks,  bright  and  star  like  figures,  the  former  due  to 
deposits  on  and  in  the  lens,  the  latter  to  the  radiate  structure  of  the  lens. 

(d)  The  niuscae  volitantes  {Di'ihdlt-s,  i6go),  like  strings  of  beads,  circles,  groups  of  balls  or 
pale  stripes,  depend  upon  opaque  particles  (cells,  disintegrating  cells,  granular  fibres — Danders, 
Duncan)  in  the  vitreous  humor.  They  move  about  when  the  eye  is  moved  rapidly.  Listing 
( 1845)  showed  that  one  may  determine  pretty  accurately  the  position  of  these  objects.  While  making 
the  observation  upon  one's  own  eyes,  raise  or  depress  the  source  of  light;  tho^e  shadows  which  are 
caused  by  bodies  on  a  level  with  the  pupil  retain  their  relative  positions  in  the  bright  fields  of  vision. 

Fig.  48J. 


Entopi 


Shadows,  which  appear  to  move  in  the  same  direction  as  the  source  of  light,  are  caused  by  bodies 
which  lie  \<ci  front  of  the  plane  of  the  pupil — those,  however,  which  appear  to  move  in  the  opposite 
direction  depend  upon  objects  behind  the  plane  of  the  pupil. 

2.  Purkinje's  figure  (1S19)  depends  upon  the  blood  vessels  within  the  retina,  which  cast  a 
shadow  upon  the  most  external  layer  of  the  retina,  viz.,  upon  the  rods  and  cones,  these  being  the 
]  arts  acted  upon  by  light.  In  ordinary  vision  we  do  not  observe  these  shadows.  According  to  v. 
Helmholt/,  this  is  due  to  the  fact  that  the  sensibility  of  the  shaded  parts  of  the  retina  is  greater,  and 
their  excitability  is  less  exhausted,  than  all  the  other  parts  of  the  retina.  As  soon,  however,  as  we 
change  the  position  of  the  shadow  of  the  blood  vessels,  instead  of  being  directly  behind,  so  that  the 
blood  vessels  come  to  lie  more  laterally  and  behind  them,  i.  e.,  upon  places  which  do  not  receive 
shadows  from  the  blood  vessels  when  the  rays  of  light  pass  through  the  eye  in  the  ordinary  way, 
then  the  figure  of  the  blood  vessels  becomes  apparent  at  once.  AU  that  is  necessary  is  to  cause  the 
light  to  enter  the  eyeball  obliquely.  Method. — (i)  This  may  be  done  by  passing  an  intense  light 
through  the  sclerotic,  e.g.,  by  throwing  upon  the  sclerotic  a  small,  bright,  luminous  image  from  a 
source  of  light.  On  moving  the  source  of  light,  the  figure  of  the  blood  vessels  moves  in  the  same 
direction.  (2)  Look  directly  upward  to  the  sky,  wink  with  the  upper  eyelid  drooping,  so  that  for 
a  moment,  corresponding  to  the  act  of  winking,  rays  of  light  enter  obliquely  the  lowest  part  of  the 
pupils.  (3)  Look  through  a  small  aperture  toward  a  bright  sky,  and  move  the  aperture  rapidly  to 
and  fro,  so  that  from  both  sides  of  the  blood  vessels  shadows  fall  rapidly  upon  the  nearest  series  of 
rods  and  cones.  (4)  In  a  darkened  room  look  straight  ahead,  and  move  a  light  to  and  fro  close 
under  the  eyes.  Occasionally,  while  performing  this  experiment,  one  may  see  the  macula  lutea  as 
a  non-vascular  shaded  depre.ssion  (Piiriinje,  Buro-v),  and,  owing  to  the  inversion  of  the  objects,  it 
lies  on  the  inner  side  of  the  entrance  of  the  optic  nerve. 

3.  Observing  the  Movements  of  the  Blood  Corpuscles  in  the  Retinal  Capillaries  (Bois- 
ser). — On  looking,  without  accommodating  the  eye,  toward  a  large  bright  Surface,  or  through  a  dark 


780 


ENTOPTICAL    PHENOMENA. 


blue  glass  toward  the  sun,  we  see  bright  spots,  like  points,  forming  longer  or  shorter  chains,  moving 
in  tortuous  (aths.  The  phenomenon  is  perhaps,  caused  by  the  red  blood  corpuscles  (in  the  capil- 
laries posterior  to  the  external  granular  layer — His)  acting  as  small,  light-collecting  concave  disks, 
concentrating  the  light  falling  upon  them  from  bright  surfaces,  and  throwing  it  upon  the  rods  of  the 
retina.  Each  corpuscle  must  be  in  a  special  position;  should  it  rotate,  the  phenomenon  disappears. 
Vierordt,  who  projected  the  movement  upon  a  screen,  calculated,  from  the  velocity  of  Iheir  motion, 
the  velocity  of  the  blood  stream  in  the  retinal  capillaries  as  equal  to  0.5  to  0.75  mm.  in  a  second, 
which  corresponds  very  closely  with  the  results  obtained  directly  in  other  capillaries  by  E.  H. 
Weber  and  VolUmann  (§  90,  4).  When  the  carotids  are  compressed,  the  movement  is  slower  on 
freeing  them  from  the  compression;  during  short,  forced  expirations  the  movement  is  accelerated 
[Lani/ois). 

4.  The  entoptical  pulse  (?  79,  2 — Landou)  depends  upon  the  pulsating  arteries  irritating 
mechanically  the  rods  lying  outside  them. 

5.  Pressure  Phosphenes. — Pressure  applied  to  the  eye  causes  a  series  of  phenomena :  («) 
Partial  pressure  upon  the  eyeball  causes  the  so-called  illuminated  "pressure  picture"  or  fhosphene, 
which  was  known  to  .\ristotle.  As  the  impression  upon  the  retina  is  referred  to  something  outside 
the  eye,  the  phosphene  is  always  perceived  on  the  side  of  the  field  of  vision  of'positc  to  where  the 
pressure  affects  the  retina,  e.g.,  pressure  upon  the  outer  surface  of  the  eyeball  causes  the  flash  of 
light  to  appear  on  the  inner  side.  If  the  retina  is  not  well  lighted  the  phosphene  appears  luminous; 
if  the  retina  is  well  lighted  it  appears  as  a  dark  speck,  within  which  the  visual  perception  is  momen- 
tarily abolished.  (b\  If  a  uniform  pressure  be  applied  of  the  eyeball  continuously  from  before 
backward,  as  Purkinje  pointed  out,  after  some  time  very  sparkhng,  variable  figures  appear  in  the 
field  of  vision,  which  perform  a  wonderful  fantastic  play,  and  often  resemble  the  sparkling  effects 
obtained  in  a  kaleidoscope  [v.  Helmholtz),  and  are  probably  comparable  to  the  feeling  of  formica- 
tion produced  by  pressure  upon  sensory  nerves  ("  sleeping  of  the  limbs  "  ).  (f)  By  applying  equable 
and  continued  pressure,  Steinbach  and  Purkinje  obser\'ed  a  network  with  moving  contents  of  a 
bluish  silvery  color,  which  seemed  to  correspond  to  the  retinal  veins.  \^ierordt  and  Laiblin  observed 
the  branching  of  the  blood  vessels  of  the  choroid  as  a  red  network  upon  a  black  ground,  (r/)  Ac- 
cording to  Houdin,  we  may  detect  the  position  of  the  yellow  spot  by  pressure  upon  the  eyeball. 

6.  The  entrance  of  the  optic  nerve  may  be  detected  on  moving  the  eyes  rapidly  backward, 
and  especially  inward,  as  a  fiery  ring  or  semicircle  about  the  size  of  a  pea.  Probably,  owing  to  the 
movement  of  the  retina,  the  entrance  of  the  optic  nerve  is  stimulated  mechanically  by  the  rapid 
bending.  Purkinje  and  others  observed  that  the  ring  remained  persistent  on  turning  the  eye 
strongly  inward.  If  the  retina  be  brightly  illuminated,  the  ring  appears  dark,  and  when  the  field 
of  vision  is  colored  the  ring  has  a  different  tint.  If  Purkinje's  figure  be  produced  at  the  same  time, 
one  may  oljserve  that  the  vascular  trunk  proceeds  from  this  ring — a  proof  that  the  ring  corresponds 
to  the  entrance  of  the  optic  nerve  (Landois). 

7.  Accommodation  Spot. — On  accommodating  the  eye  strongly  toward  a  white  surface,  there 
appears  in  the  middle  a  small,  bright,  trembling  shimmer,  and  in  its  centre  a  coarse,  brown  speck, 
about  the  size  of  a  pea,  is  seen  (Purkinje,  v.  lielinhoUz).  If  pressure  be  applied  externally  to  the 
eyeball  this  speck  becomes  more  distinct.  After  having  once  observed  the  phenomenon,  occasion- 
ally on  pressing  laterally  upon  the  opened  eye  we  may  see  it  as  a  bright  speck  in  the  field  of  vision 
— another  proof  that  the  intraocular  pressure  is  increased  during  accommodation  [Landois). 

8.  Mechanical  Optical  Stimulation. — On  dividing  the  optic  nerve  in  man,  as  in  extiipation  of 
the  eyeball,  a  Bash  of  light  is  observed  at  the  moment  of  section  by  the  person  operated  on.  The 
section  of  the  nerve  fibres  themselves  is  painless,  but  section  of  the  sheaths  is  painful. 

9.  The  accommodation  phosphene  \Purkinje,  Czermak)  is  the  occurrence  of  a  fiery  ring  at 
the  periphei7  of  the  field  of  vision,  seen  on  suddenly  bringing  the  eyes  to  rest  after  accommodating 
for  a  long  time  in  the  dark.  The  sudden  tension  of  the  zonule  of  Zinn  resulting  from  the  relaxa- 
tion causes  a  mechanical  stretching  of  the  outermost  part  of  the  margin  of  the  retina,  or  it  may  be 
of  a  part  of  the  retina  behind  this  [Hensen  and  Volckers,  Berlin).  Purkinje  observed  the  phe- 
nomenon after  suddenly  relaxing  the  pressure  on  the  eye. 

10.  Electrical  Phenomena. — Electrical  currents,  when  applied  to  the  eye,  cause  a  strong  flash 
of  light  over  the  whole  field  of  vision.  One  pole  of  the  battery  may  be  placed  on  the  upper  eyelid 
and  the  other  on  the  neck.  The  flash  at  closing  [making]  the  current  is  strongest  with  an  ascend- 
ing current,  that  with  opening  [breaking]  the  current  with  a  descending  current  (i'.  Helmholtz^. 
If  a  uniform  continuous  ascending  current  be  transmitted  through  the  closed  eyes,  the  dark  disk  of 
the  elevation  at  the  entrance  of  the  optic  nerve  appears  in  a  whitish  violet  field  of  vision ;  with  a 
descending  current,  the  field  of  vision  is  reddish  and  dark,  in  which  the  position  of  the  optic  nerve 
appears  light  blue  (i'.  Helmholtz).  If  external  colors  are  looked  at  simultaneously,  these  colors 
blend  to  form  a  violet  or  yellow  with  the  colors  looked  at  (Schelsie).  During  the  passage  of  the 
ascending  current  we  see  external  objects  indistinctly  and  smaller  when  the  eyes  are  open ;  while 
with  the  descending  current  they  are  more  distinct  and  larger  (Ritter).  Sometimes  the  position  of 
the  macula  lutea  appears  dark  on  a  bright  ground,  or  the  reverse,  according  to  the  direction  of  the 
current.  If  the  current  be  opened  [broken]  the  phenomena  are  reversed  (J  335),  and  the  eye  soon 
returns  to  rest  (-'.  Helmholtz). 

11.  The  yellow  spot  appears  sometimes  as  a  dark  circle  when  there  is  a  uniform  blue  illumina- 


ILLUMINATION    OF   THE    EYE. 


781 


tion  In  a  strong  light  the  position  of  the  yellow  spot  is  surrounded  by  a  bright  area,  twice  or 
thrice  as  large,  called  "LS7Vt''s  ring." 

[Clerk-Maxwell's  Experiment. — On  looking  through  a  solution  of  chrome-alum  in  a  bottle  or 
vessel  with  parallel  glass  sides,  we  observe  an  oval,  purplish  spot  in  the  green  color  of  the  alum. 
This  is  due  to  the  pigment  of  the  yellow  spot.] 

Haidinger's  Brushes. — On  directing  the  eye  toward  a  source  of  polarized  light,  "  Haidinger's 
polarized  brushes"  appear  at  the  point  of  fixation.  They  are  seen  on  looking  through  a  Nicol's 
prism  at  a  bright  cloud  (v.  Helmholtz).  They  are  bright  and  bluish  on  a  surface,  bounded  by  two 
neighboring  hyperbola  on  a  white  field;  the  dark  bundle  separating  them  is  smallest  in  the  centre 
and  yellow.  Of  the  various  colors  of  homogeneous  light,  blue  alone  shows  the  brushes  i^Stokes). 
According  to  v.  Helmholtz  the  seat  of  the  phenomenon  is  the  yellow  spot,  and  is  due  to  the  yellow 
colored  elements  of  the  yellow  spot  being  slightly  doubly  refractive,  while  at  one  part  they  absorb 
more,  at  another  less,  of  the  rays  entering  the  eye. 

12.  Lastly,  there  are  the  visual  sensations  depending  on  internal  causes,  e.g.,  increased  bound- 
ing of  the  blood  through  the  retina,  as  during  violent  coughing,  increased  intraocular  pressure. 
Stimulation  of  \\\e  fsycho-optic  centres  (\  378,  IV )  may  produce  spectra,  which  Cardanus  (1550), 
Goethe,  Nicolai  and  Johannes  Miiller  could  produce  voluntarily. 

394.  ILLUMINATION  OF  THE  EYE— OPHTHALMOSCOPE. 

— The  light  which  enters  the  eye  is  partly  absorbed  by  the  black  uveal  pigment, 

Fig.  482. 


ling  the  eye  of  B.     A,  eye  of  observer  ;  x,  source  of  light :  S,  S,  pla 
liquely,  reflecting  light  into  B, 


of  glass  directed  ob- 


and  partly  again  reflected  from  the  eye,  and  always  in  the  same  direction  in  which 
the  rays  entered  the  eye.  By  placing  one's  self  in  front  of  the  eye  of  another 
person,  of  course  the  head,  being  an  opaque  body,  cuts  off  a  large  number  of 
rays.  Owing  to  the  position  of  the  head,  no  rays  of  light  can  enter  the  eye  ;  and 
of  course  none  can  be  reflected  back  to  the  eye  of  the  observer.  Hence,  the  eye 
of  the  person  being  examined  always  appears  black,  because  those  rays  which 
alone  could  be  reflected  in  the  direction  of  the  eye  of  the  observer  are  cut  oflf. 
As  soon,  however,  as  we  succeed  in  causing  rays  of  light  to  enter  the  eye  at  the 
same  time  and  in  the  same  direction  in  which  we  observe  the  eye  of  another 
person,  the  fundus  of  the  eye  appears  brightly  illuminated. 

The  following  simple  arrangement  (Fig.  482)  is  sufficient  for  the  purpose  :  Let  B  he  the  eye  of 
the  patient,  A  that  of  the  observer,  and  let  a  flame  be  placed  at  x.  The  rays  of  light  proceeding 
from  X  impinge  upon  the  obliquely  placed //a/c  of  glass  (S,  S),  and  are  reflected  in  the  direction  of 
the  dotted  lines  into  the  eye  (B).  The  fundus  of  the  eye  appears  in  this  position  to  be  brightly 
illuminated  in  difiusion  circles  around  b.  As  the  observer  (A)  can  see  through  the  obliquely  plated 
glass  plate  (S,  S),  and  in  the  same  direction  as  the  reflected  rays  {x,y)  he  sees  the  retina  around  b 
brightly  illuminated. 


782 


ILLUMINATION    OF   THE    EYE. 


In  order  that  this  method  be  made  available  for  practical  purposes,  we  must,  of  course,  be  able  to 
distinguish  the  details,  such  as  the  blood  vessels  of  the  fundus  of  the  eye,  the  macula  lutea,  the 
entrance  of  the  optic  nerve,  abnormalities  of  the  retina  and  the  choroidal  pigment,  etc.  The  follow- 
ing considerations  show  us  how  to  proceed  in  order  to  accomplish  this.     As  already  mentioned,  and 

Fig.  483. 


as  Fig.  465  shows,  a  small  inverted  image  is  formed  on  the  retina  (c,  d )  when  we  look  at  an  object 
(A,  B);  conversely,  according  to  the  same  dioptric  law,  an  enlarged  inverted  real  image  of  a  small 
distinct  area  of  the  retina  (c,  d — depending  on  the  distance  for  which  the  eye  was  accommodated), 
must  be  formed  outside  the  eye  (A,  B). 

Fig.  4S4. 


If  the  fundus  of  this  eye  be  sufficiently  illuminated,  this  aerial  image  will  be  correspondingly  bright. 

In  order  to  see  the  individual  parts  of  the  retinal  picture  more  distinctly,  the  observer  must 
accommodate  his  own  eye  for  the  position  of  this  image.  In  such  circumstances  the  eye  of  the 
observer  would  be  too  near  to  the  observed  eye. 

Fig.  485. 


His  eye  when  so  accommodated  is  removed  from  the  eye  of  the  patient  by  his  own  visual 
distance,  and  by  the  visual  distance  of  the  patient.  As  this  distance  is  considerable,  the  individual 
small  details  of  the  fundus  cannot  be  seen  distinctly.  Further,  owing  to  the  contraction  of  the  pupil 
of   the  patient,  only  a  small  area  of  the  fundus   can   be  seen,  and  this  only  under  a  small  visual 


THE    OPHTHALMOSCOPE. 


783 


angle,  quite  apart  from  the  fact  that  it  is  often  impossible  to  accommodate  for  the  real  image  of  the 
fundus  of  the  patient. 

Hence,  the  eye  of  the  observer  must  be  brought  nearer  to  the  eye  of  the  patient.  This  may  be 
done  in  two  ways:  (l)  Either  by  placing  in  front  of  the  eye  of  the  patient  a  strong  convex  lens  (of 
1  to  3  inches  focus — Fig.  4S3,  C).  This  causes  the  retinal  image  to  be  nearer  to  the  eye  (at  B), 
owing  to  the  strong  lens  refracting  the  rays  of  light.  The  observer  (M)  can  come  nearer  to  the  eye, 
and  can  still  accommodate  for  the  image  of  the  fundus  of  the  eye.  (2)  Or  a  concave  lens  is  placed 
immediately  in  front  of  the  eye  of  the  patient  (Fig.  484,  0).  The  rays  of  light  emerging  from  the 
eye  of  the  patient  (P)  are  either  made  parallel  by  the  concave  lens  (<?),  and  are  brought  to  a  focus 
on  the  retina  of  the  emmetropic  observer  (A) ;  or,  if  the  lens  causes  the  rays  to  diverge  (Fig.  485), 
an  erect,  virtual  image  is  formed  at  a  distance  behind  the  eye  of  the  patient  (at  R).  In  these  cases, 
also,  the  observer  can  go  much  nearer  to  the  eye  of  the  patient. 

The  ophthalmoscope  invented  by  v.  Helmholtz  enables  us  to  examine  the 
whole  of  the  fundus  of  the  eye. 

[Direct  Method. — Use  a  concave  mirror  of  20  centimetres  focal  distance,  with  a  central  open- 
ing. Reflect  a  beam  of  light  into  the  patient's  eye,  where  they  cross  in  the  vitreous  and  illuminate 
the  fundus  of  the  eye.     These  rays  again  pass  out  of  the  eye  and  reach  the  observer's  eye  through 


Fig.  486. 


Fig.  487. 


he  optic  nerve,  with  the  adjacent  parts  ot  Morton's  ophthalmoscope, 

the  fundus  of  the  normal  eye.  a,  ring  of  connective 
tissue;  /^,  choroidal  ring  ;  c,  arteries;  f/,  veins  ;  ^.divi- 
sion of  the  central  artery  ;  h,  division  of  the  central  vein  ; 
L,  lamina  cribrosa;  /,  temporal  (outer)  side;  m,  nasal 
(inner)  side. 

the  central  hole  in  the  mirror.  If  the  observer  be  emmetropic,  they  come  to  a  focus  on  his 
retina.  In  this  way  all  the  parts  of  the  retina  are  seen  in  their  normal  position,  but  enlarged. 
Hence,  it  is  sometimes  called  the  examination  of  the  upright  image.  The  eye  of  the  patient  and 
observer  must  be  at  rest,  ;.  <•.,  be  negatively  accommodated,  while  the  mirror  must  be  brought  as 
near  as  possible  to  the  eye  of  the  patient.] 

[Indirect  Method,  by  which  a  more  general  view  of  the  fundus  is  obtained.  Throw  the  light 
into  the  patient's  eye  by  an  ophthalmoscopic  mirror,  as  above,  but  held  at  a  distance  of  about  50 
cm.  (10  inches)  from  the  patient's  eye.  Hold  a  biconvex  lens  of  14  dioptrics  focal  length  vertically 
between  the  mirror  and  the  patient's  eye  (Fig.  4831,  the  observer  looking  through  the  hole  of  the 
mirror.  What  he  does  see  is  an  inverted  aerial  image  at  B.  Only  a  small  part  of  the  fundus 
oculi  can  be  seen  at  one  time.] 

[The  ophthalmoscope,  besides  being  used  for  examining  the  interior  of  the  eyeball,  is  of  the 
utmost  use  in  determining  the  existence  and  amount  of  anomalies  of  refraction  in  the  refractive 
media.  For  this  purpose  an  ophthalmoscope  requires  to  be  provided  with  plus  and  minus  lenses, 
which  can  be  readily  brought  before  the  eye  of  the  observer.  This  is  readily  done  by  an  ingenious 
mechanism  devised  by  Couper,  and  which  is  made  use  of  in  the  handy  students'  ophthalmoscope 
of  Morton  (Fig.  4S7).  The  lenses  are  moved  by  a  driving-wheel  on  the  left  figure,  while  at  the 
same  time  is  indicated  at  a  certain  aperture  the  lens  presented  at  the  sight  hole.     The  instrument  is 


784 


THE    ORTHOSCOPE. 


also  provided  with  a  movable  arrangement  carrying  a  concave  mirror  at  either  end.  One  of  these 
mirrori  is  lo  inches  in  focus,  and  is  used  for  indirect  examin.ition  and  retinoscopy,  while  the  other 
is  of  3  inches  focus  for  direct  examination,  and  is  fixed  at  an  angle  of  25°.] 

[Retinoscopy. — The  ophthalmoscope  is  used  also  for  this  purpose.  A  beam  of  light  is  reflected 
into  the  eye  by  the  ophthahnoscopic  mirror,  and  the  play  of  light  and  shade  on  the  fundus  oculi 
observed.  A  study  of  this  is  important  in  determining  anomalies  of  refraction.  For  the  method, 
the  student  is  referred  to  a  text  book  on  "  Diseases  of  the  Eye."] 

[Artificial  Eye. — The  student  may  practice  the  use  of  the  ophthalmoscope  on  an  artificial  eye 
such  as  that  of  Frost  ( Fig.  4SS)  or  Perrin.] 

Illumination. — In  order  to  dluminate  the  interior  of  the  eye,  v  Helmholtz  used  several  plates 
of  glass,  placed  behind  each  other,  in  the  position  of  S,  S,  in  Fig.  482.  Afterward  he  used  a  plane 
or  concave  mirror  of  7  inches  focus  (Fig.  483,  S,,  S,),  with  a  hole  in  the  centre.  Fig.  486  shows 
the  appearance  of  the  fundus  of  the  eye,  as  seen  with  the  ophthalmoscope.  In  albinos  the  fundus 
of  the  eye  appears  red,  because  light  passes  into  the  eye  through  the  sclerotic  and  uvea,  which  are 
devoid  of  pigment.  If  a  diaphragm  be  placed  over  the  eye,  so  that  the  pupil  alone  is  free,  the  eye 
appears  black  [DonJers). 


Fig.  488. 


Fig.  489. 


tificial  eye 


Action  of  the  orthoscope. 


Tapetum. — In  many  animals  the  eyes  have  a  bright  green  lustre.  These  eyes  have  a  special 
layer,  the  tapetum  or  the  membrana  versicolor  of  Fielding  ;  in  carnivora  it  consists  of  cells,  in  her- 
bivora  of  fibres,  placed  between  the  capillaries  of  the  choroid  and  the  stroma  of  the  uvea.  These 
structures  exhibit  interference  colors  and  reflect  much  light,  so  that  the  colored  lustre  appears  in  the 
eye. 

Oblique  illumination  is  used  with  advantage  for  investigating  the  anterior  chamber.  A  bright 
beam  of  light,  condensed  by  a  convex  lens,  is  thrown  laterally  upon  the  cornea  into  the  eye,  and  so 
directed  upon  the  point  to  he  investigated  as  to  illuminate  it.  A  point  so  illuminated,  e.g.,  a  part 
of  the  iris,  may  be  examined  from  a  distance  by  means  of  a  lens,  or  even  by  a  microscope  [Lieb- 
reicli). 

The  Orthoscope. — Czermak  constructed  this  instrument  (Fig.  489),  in  which  the  eye  is  placed 
under  water.  Take  a  small  glass  trough  with  one  of  its  walls  removed.  Press  the  margins  of  the 
open  side  firmly  against  the  region  of  the  eye.  The  eye  and  its  surroundings  form,  as  it  were,  the 
sixth  side  of  the  trough,  which  is  filled  with  water,  so  that  the  cornea  is  bathed  therewith.  As 
the  refractive  mdex  of  water  is  almost  the  same  as  the  refractive  index  of  the  media  of  the  eye,  the 
rays  of  light  pass  into  the  eye  in  a  straight  direction  without  being  refracted.     Hence,  objects  in  the 


EXPERIMENTS    ON    THE    RETINA.  785 

anterior  chamber  can  be  seen  directly,  as  if  they  were  not  within  the  eye  at  all.  Another  advantage 
is  that  the  objects  can  be  brought  nearer  to  the  eye  of  the  observer.  The  rays  of  light  emerging 
from  the  point  {a)  of  the  fundus,  if  the  eye  were  surrounded  by  air,  would  leave  the  eye  as  the 
parallel  lines,  i,  c,  b.  c.  Under  water,  these  rays,  a,  b,  continue  in  the  direction  a,  i,  as  far  as  b,  d, 
where  they  emerge  from  the  water,  and  are  bent  from  the  perpendicular  to  d,  e,  d,  e.  The  eye  of 
the  observer,  looking  in  the  direction  e,  d,  sees  the  point,  a,  nearer,  viz.,  in  the  direction  e,  d,  a', 
lying  at  a. 

395.  ACTIVITY  OF  THE  RETINA  IN  VISION.— I.  Blind  Spot. 
— The  rods  and  cones  alone  are  the  parts  of  the  retina  sensitive  to  light 
{ffenr.  Miiller),  they  alone  are  excited  by  the  vibrations  of  the  ether.  This  is 
confirmed  by  Marriotte's  experiment  (1688),  which  proves  that  the  entrance  of 
the  optic  nerve,  where  rods  and  cones  are  absent,  is  devoid  of  visual  sensibility. 
Hence,  it  is  spoken  of  as  the  "  blind  spot." 

[Marriotte's  Experiment. — Make  two  marks,  about  three  inches  apart,  upon 
paper  (Fig.  490).  Look  at  the  cross  with  the  right  eye,  keeping  the  left  eye 
closed,  and  hold  the  paper  about  a  foot  from  the  eye,  when  both  the  cross  and 
the  circle  will  be  seen.  Gradually  approximate  the  paper  to  the  eye,  keeping  the 
open  eye  steadily  fixed  on  the  cross  ;  at  a  certain  moment  the  circle  will  dis- 
appear, and  on  bringing  the  paper  nearer  to  the  eye  it  will  reappear.  The  moment 
when  the  circle  disappears  is  when  its  image  falls  upon  the  entrance  of  the  optic 
nerve.] 

Position  and  Size. — The  entrance  of  the  optic  nerve  lies  about  3.5  mm.  internal  to  the  visual 
axis  of  the  eyeball,  in  the  retina.  Its  diameter  is  1.8  mm.  (Hclmholtz).  The  apparent  diameter  of 
the  blind  spot  in  the  field  of  vision  is  in  a  horizontal  direction  6°  56' — this  lies  12°  35'  to  18°  55' 


Fig.  490. 


-I- 


horizontally  from  the  fi.\ed  point.     Eleven  full  mcons  placed  side  by  sitie  would  disappear  on  the 
surface,  and  so  would  a  human  face  at  a  distance  of  over  2  metres. 

Proofs. — The  following  facts  prove  that  the  entrance  of  the  optic  nerve  is  insensible  to  light : 
(i)  Donders  projected,  by  means  of  a  mirror,  a  small  image  of  a  flame  upon  the  entrance  of  the 
optic  nerve  of  another  person,  and  the  person  had  no  sensation  of  light.  But  a  sensation  of  light 
was  experienced  when  the  image  of  the  flame  was  projected  upon  the  neightoring  parts  of  the  retina. 
(2)  On  combining  with  Marriotte's  experiment,  the  experiment  which  causes  entoptical  phenomena 
at  the  entrance  of  the  optic  nerve  (\  393,  6  and  7),  this  coincides  with  the  blind  spot  (Landois). 

Form  of  Blind  Spot. — In  order  to  determine  the  form  and  af<parent  size  of  the  blind  spot  m 
one's  own  eye,  fix  the  head  at  about  25  centimetres  from  a  surface  of  white  paper;  select  a  small 
point  on  the  latter  and  keep  the  eye  directed  toward  it,  then  starting  from  the  position  of  the  blind 
spot  move  a  white  feather  in  all  directions  over  the  paper ;  whenever  the  tip  of  the  feather  becomes 
visible,  make  a  mark  at  this  spot.  Thus  the  blind  spot  may  be  mapped  out.  It  is  found  to  have 
an  irregular  elliptical  form  from  which  processes  proceed,  due  to  the  equally  non-sensitive  origins  of 
the  large  blood  vessels  of  the  retina  (Hitcck,  Helmholtz).  (Marriotte  concluded  from  his  experiment 
that  the  choroid,  which  is  perforated  by  the  optic  nerve,  is  the  membrane  sensitive  to  light,  as  the 
nerves  are  nowhere  absent  from  the  retina.) 

The   blind   spot  causes  no  appreciable  gap  in  the  field  of  vision. — As  this  area  is  not 
excited  by  light,  a  black  spot  cannot  appear  in  the  Held  of  vision,  for  the  sensation  of  black  implies 
the  presence  of  retinal  elements,  which,  however,  are  absent  from  the  blind  spot. 
The  circumstance,  however,  that  in  spite  of  the  existence  of  an  inexcitable  spot  , 

during  vision,  no  part  of  the  field  of  vision  appears  to  be  unoccupied,  is  due  to  a      ft         [)         C 
psychical  action.     The  unoccupied   area  of  the   field  of  vision,  corresponding  to 
the  blind  spot,  is  filleil  in  according  to  probability  by  a  psychical  process  {E.  H.       -  „ 

Weber),     Ilence,  when  a  white  point  disappears  from  a  black  surface,  the  whole      Q        (6/        I 
surface  appears  to  us  black  ;  a  white   surface,   from  which  a  black   point   falls 
on  the   blind  spot,  appears  quite  white;  a  page  of  print,  gray  throughout,  etc.  ,  , 

According  to  the  probabilities,  certain  parts  are  supplied — parts  of  a  circle,  the      ff         D  1 

50 


786  IMAGES    FALLING   ON    THE    RODS    AND    CONES. 

middle  parts  of  a  long  line,  the  central  part  of  a  cross.  Such  images,  however,  which  cannot 
be  constructed  according  to  the  probabilities,  are  not  perfected,  c.?-.,  the  end  of  a  line  or  a  human 
face.  In  other  cases  the  condition  known  as  ^^ contra<'tio7i^^  of  the  field  of  vision  tends  to  fill 
up  the  gap.  This  will  be  evident  on  looking  at  the  nine  preceding  letters,  so  that  c  disappears ; 
we  no  longer  see  the  three  letters  on  each  side  of  it  in  straight  lines,  but  b,f,  h,  d,  are  turned  in 
toward  e.  The  adjoining  parts  of  the  field  of  vision  seem  to  extend  over  and  around  the  blind 
spot,  and  thus  help  to  compensate  for  the  blind  spot. 

II.  Optic  Fibres  Inexcitable  to  Light. — The  layer  of  the  fibres  of  the 
optic  nerve  in  the  retina  is  not  sensitive  to  light.     This  is  proved  by  the  fact  that  in 


Horizontal  section  of  the  right  e>e  a  cornea  ^.conjunctiva  c  sclerotic  (/,  anterior  chamber  containing  the 
aqueous  humor :  f,  ins  fj'  pupil  g  posterior  chamber  /  Petit  s  canal  :  y,  ciliary  muscle  ;  ^,  corneo-scleral 
limit;  !,  canal  of  Schlemm  ,  ;«,  choroid  ,  «,  retina,  o,  vitreous  humor  ,  A'o,  optic  nerve  ;  ji.  nerve  sheaths  ; /, 
nerve  fibres:  Ic,  lamina criorosa.  The  line  O  A  indicates  the  optic  axis  ;  Sr,  the  axis  of  vision;  r,  the  position 
of  the  fovea  centralis. 

the  fovea  centralis,  which  is  the  area  of  most  acute  vision,  there  are  no  nerve 
fibres.  Further,  Purkinje's  figure  proves  that,  as  the  arteries  of  the  retina  lie 
behind  the  optic  fibres,  the  latter  cannot  be  concerned  in  the  perception  of  the 
former. 

III.  Rods  and  Cones. — The  outer  segments  of  the  rods  and  cones  have 
rounded  outlines,  and  are  packed  close  together,  but  natural  spaces  must  exist 
between   them,  corresponding   to  the  spaces  that  must  exist  between  groups  of 


THE    FOVEA   CENTRALIS. 


787 


bodies  with  a  circular  outline.  These  parts  are  insensible  to  light,  so  that  a  retinal 
image  is  composed  like  a  mosaic  of  round  stones.  The  diameter  of  a  cone  in  the 
yellow  spot  is  2  to  2.5  ij.  {M.  Sihu/tzc).  If  two  images  of  two  small  points,  placed 
very  near  each  other,  fall  upon  the  retina,  they  will  still  be  distinguished  as  distinct 
images,  provided  that  both  images  fall  upon  two  different  cones.  The  two  images 
on  the  retina  need  only  be  3-4-5.4  //  apart,  in  order  that  each  may  be  seen  sepa- 
rately, for  then  the  images  still  fall  upon  tico  adjoining  cones.  If  the  distance  be 
diminished  so  very  much  that  both  images  fall  upon  one  cone,  or  one  upon  one 
cone  and  the  other  upon  the  intermediate  [cement]  substance,  then  only  one 
image  is  perceived.  The  images  must  be  further  apart  in  the  peripheral  portion 
of  the  retina  in  order  that  they  may  be  separately  distinguished. 

As  the  rounded  end  surfaces  of  the  cones  do  not  lie  exactly  under  each  other,  but  are  so  arranged 
that  one  series  of  circles  is  adapted  to  the  interstices  of  the  following  series,  this  explains  why  fine 

Fig.  492. 


M'Hardy's  perimeter,     i,  porcelain  button  :    M,  bit:  E,  for  fixing  the  head  :  g,  k,  quadrant  ;  o,  fix 


)inter  for  piercing  the  record  chart  held  in  the  frame  (t-)  which  i 
nt  and  the  automatic  arrangement  of  slides  {k  and  /),  which  ; 


D,  upright  supporting  the  quad- 


dark  lines  lying  near  each  other  appear  to  have  alternating  twists  upon  them,  as  the  images  of  these 
must  fall  upon  the  cones,  at  one  time  to  the  right,  at  another  to  the  left. 

IV.  The  fovea  centralis  is  the  region  of  most  acute  vision,  wliere  only 
.cones  are  present,  and  where  they  are  very  numerous  and  closely  packed  (Fig. 
455).  The  cones  are  less  numerous  in  the  peripheral  areas  of  the  retina,  and 
consequently  vision  is  much  less  acute  in  these  regions.  We  may,  therefore,  con- 
clude that  the  cones  are  more  important  for  vision  than  the  rods.  When  we  wish 
to  see  an  object  distinctly,  we  involuntarily  turn  our  eyes  so  that  the  retinal  image 
falls  upon  the  fovea  centralis.  In  doing  this,  we  are  said  to  "Jix"  our  eyes  upon 
an  object.  The  line  drawn  from  the  fovea  to  the  object  is  called  the  axis  of 
vision  (Fig.  491,  Sr).     It  forms  an  angle  of  only  3.5-7°  with  the  "  o/>/ha/  a.xi's" 


788 


PERIMETRY. 


{O  A),  which  unites  the  centres  of  the  spherical  surfaces  of  the  refractive  media 
of  the  eye.  The  point  of  intersection,  of  course,  lies  in  the  nodal  point  (Kti)  of 
the  lens  (p.  786).  The  term  "direct  vision"  is  applied  to  vision  when  the 
direction  of  the  axis  of  vision  is  in  line  with  the  object  [/.  e.,  when  the  image  of 
the  object  falls  directly  on  the  fovea  centralis]. 

"Indirect  vision"  occurs  when  the  rays  of  light  from  an  object  fall  upon 
the  peripheral  parts  of  the  retina.  Indirect  vision  is  much  less  acute  than  the 
direct. 

To  test  the  acuity  of  direct  vision,  draw  two  fine  parallel  lines  close  to  each  other,  and 
gradually  remove  them  more  and  more  from  the  eye,  until  both  appear  almost  to  unite  and  form  one 
line.  The  size  of  the  retinal  image  may  be  ascertained  by  determining  the  distance  of  the  two  lines 
from  each  other, and  the  distance  of  the  lines  from  the  eye;  or,  from  the  corresponding  visual  angle, 
which  is  generally  between  60  to  90  seconds. 

Perimetry. — In  order  to  test  indirect  vision  we  may  use  the  perimeter  of  Auhert  and  Forster. 
The  eye  is  placed  opposite  a  fixed  point,  from  which  a  semicircle  proceeds,  so  that  the  eye  lies  in 
the  centre  of  it.  As  the  semicircle  rotates  round  the  fi.xed  point,  on  rotating  the  former  we  can 
circumscribe  the  surface  of  a  hemisphere,  in  the  centre  of  which  the  eye  is  placed.  Proceeding 
from  the  fixed  point,  objects  are  placed  upon  semicircles,  and  are  gradually  pushed  more  and  more 
toward  the  periphery  of  the  field  of  vision,  until  the  object  becomes  indistinct,  and  finally  disappears. 
The  process  of  testing  is  continued  by  placing  the  arc  successively  in  the  ditferent  meridians  of  the 
field  of  vision. 

[M'Hardy's  perimeter  is  a  very  convenient  form  (Fig.  492).  It  consists  of  two  uprights  (C 
and  D),  which  are  fixed  to  the  opposite  ends  of  a  flat  basal  plate  (A).  C  carries  an  arrangement  for 
supporting  the  patient's  head,  while  D  carries  the  automatic  arrangement  for  the  perimetiic  record. 
Both  of  these  can  be  raised  or  depressed  by  the  screws  (G  and  b).  The  patient's  chin  rests  on  the 
chin-rest  (E^,  while  in  the  mouth  is  placed  Landolt's  biting  fixation  (L),  which  is  detachable.  The 
position  of  the  head  can  be  altered  by  sliding  F  on  L,  which  can  be  fixed  in  any  position  by  the 
screw  (O).  The  porcelain  button  (I)  just  below  the  patient's  eye  (/)  is  connected  with  the  adjust- 
ment of  the  "  fixation  point."  The  automatic  recording  apparatus  consists  of  a  revolving  quadrant 
[h,  h),  which  describes  a  hemisphere  round  a  horizontal  axis  passing  through  the  centre  of  the  hol- 
low male  axle,  turning  in  the  female  end  of  a,  which  is  supported  by  D.  TJie  quadrant  can  be  fixed 
at  any  point  by  g.  On  the  front  concave  surface  of  the  quadrant  is  fixed  a  circular  white  piece  of 
ivory,  which  represents  the  "  fixation  point,"  from  which  a  needle  projects,  and  which  is  the  zero  of 
the  instrument.  A  carriage  (;'),  in  which  the  test  objects  are  placed,  can  be  moved  in  the  concave 
face  of  the  quadrant  by  means  of  the  milled  head  (y),  which  moves  the  carriage  by  means  of  a  tooth 

and  pinion  wheel.] 

[When  the  milled  head  (j)  is  turned,  it  moves 
the  carriage  and  two  slides  [i  and  /),  the  two 
slides  moving  in  the  ratio  of  2  to  i.  The  rate  of 
the  carriage  is  so  adjusted  that  it  travels  ten  times 
faster  than  /,  and  five  times  faster  than  k.  The 
pointer  (/)  is  connected  with  these  slides,  so  that 
it  moves  when  they  move,  and  records  its  move- 
ments by  piercing  the  record  chart,  which  is  fixed 
in  the  double-faced  frame  (<?).  The  frame  for  the 
record  chart  is  hinged  near  c  to  the  upright  (D). 
The  frame  when  upright  comes  so  near  the  pointer 
that  the  latter  can  pierce  a  chart  placed  in  the 
frame.  The  patient  is  directed  to  look  at  the 
"  fixation  point,"  which  is  merely  a  small  ivory 
button  placed  in  the  imaginary  axis  of  the  hemi- 
sphere on  the  front  of  the  centre  of  the  concave 
surface  of  the  quadrant ;  the  projecting  needle 
point  (0)  indicates  its  position.  This  is  the  zero 
of  the  quadrant,  and  on  each  side  of  it  the  quad- 
rant is  divided  into  90°.] 

[In  testing  the  field  of  vision,  place  the  carriage 
so  as  to  cover  zero,  adjust  the  eye  for  the  fixation 
point,  and  look  steadily  at  it,  and  if  all  is  right 
the  pointer  (/)  ought  to  pierce  the  centre  of  the 
chart.  Move  the  carriage  along  the  quadrant  by 
/  until  it  disappears  from  the  field  of  vision,  and 
wlien  it  does  so  the  pointer  is  made  to  pierce  the 
chart.  Make  another  observation  in  another  di- 
stley  Smith's  perimeter.  rection  by   altering  the  position  of  the  quadrant. 


Fig.  493. 


PERIMETRIC    CHARTS. 


789 


and  go  on  doing  so  until  a  complete  record  is  obtained  of  the  field  of  vision.  Test  the  other  eye 
in  the  same  way.     The  color  field  may  be  tested  by  using  colored  papers  in  the  carriage.] 

[Priestley  Smith's  perimeter  (Fig.  493)  is  simpler.  The  wooden  knob  on  the  left  of  the 
figure  is  placed  under  the  eye  of  the  patient,  who  stares  at  the  fixed  point  in  the  axis  of  the  quad- 
rant, which  can  be  moved  in  any  meridian.  The  test  object  is  a  square  piece  of  white  paper  which 
is  moved  along  the  quadrant.  The  chart  is  placed  on  the  posterior  surface  of  the  hand  wheel  and 
moves  with  it,  so  that  the  meridians  of  the  chart  move  with  the  quadrant.  There  is  a  scale  behind 
the  hand  wheel  corresponding  with  the  circles  on  the  chart,  so  that  the  observer  can  prick  off  his 
observations  directly.] 

[Scotoma  is  the  term  applied  to  dimness  or  blindness  in  certain  parts  of  the  field  of  vision, 
which  may  be  central,  marginal,  or  in  patches.] 

The  capacity  for  distinguishing  colors  diminishes  more  rapidly  at  the  periphery  of  the  retina 
than  that  for  distinguishing  diflerences  in  the  brightness  or  intensity  of  hght.  In  fact,  the  periphery 
of  the  retina  is  slightly  red  blind.  The  diminution  is  greater  in  the  vertical  meridian  of  the  eye 
than   in   the  horizontal,  and  it  diminishes  with  the  distance  from  the  fixation  point  {Aubert  and 


:  chart  of  a  healthy  and  a  di< 


ed  eye. 


forster).  These  observers  also  state  that,  during  accommodation  for  a  distant  object,  the  diminu- 
tion of  the  capacity  to  distinguish  brightness  and  color  toward  the  penphery  of  the  lens,  occur 
more  rapidly  than  with  near  vision.  The  excitability  of  the  retina  for  colors  and  brightness  is 
greater  at  a  point  equally  distant  from  the  fovea  centralis  on  the  temporal  than  on  the  nasal  side  of 
the  eye  {Sdion). 

Perimetric  Chart. — If  the  arc  of  the  perimeter  (Fig.  493)  be  divided  into  90  degrees,  beginning 
at  the  fixation  point  (central  point),  and  proceeding  to  L  and  M  (Fig.  494) ;  and  if  a  series  of  con- 
centric circles  be  inscriljed  on  this,  with  the  point  of  fixation  as  their  centre,  we  can  construct  a 
topoi;rat<hica!  chart  of  the  visual  capacity  of  the  normal  or  healthy  eye  from  the  data  obtained  by 
the  examination  of  the  retina. 

Fig.  494  is  an  example;  the  thick  lines  indicate  a  disea'sed  eye,  the  corresponding  thin  lines  a 
healthy  eye.  The  continuous  line  indicates  the  limits  for  the  perception  of  white;  the  interrupted 
line  that  for  blue;  the  punctuated  and  interrupted  line  that  for  red;  m  is  the  blind  spot  [Hirsch- 
icr^).     In  the  normal  eye  the  limits  for  the  perception  of 


790  PERCEPTION    OF   COLORS. 


Externally  . 
Internally  . 
Upward  .  . 
Downward  . 


7o°-88° 
5o°-6o° 

45°-55° 
65°-7o'' 


60° 

45° 
60° 


3o°-35° 
35° 


V.  Specific  Energy. — The  rods  and  cones  alone  are  endowed  with  what 
Johannes  Miiller  called  "specific  energy'^  i.  e.,  they  alone  are  set  into  activity  by 
the  ethereal  vibrations,  to  produce  those  impulses  which  result  in  vision.  Mechan- 
ical and  electrical  stimuli,  however,  when  applied  to  any  part  of  the  course  of 
the  nervous  apparatus,  produce  visual  phenomena.  Mechanical  stimuli  are  more 
intense  stimuli  than  light  rays,  as  shown  by  performing  the  dark  pressure  figure 
with  the  eyes  open  (§393,  5,  a),  whereby  the  circulation  in  the  retina  is  inter- 
fered with  {Donders) ;  in  the  region  of  pressure  we  cannot  see  external  objects 
which  affect  the  retina  uniformly  and  continuously. 

VI.  The  duration  of  the  retinal  stimulation  must  be  exceedingly  short,  as 
the  electrical  spark  lasts  only  0.00000086S  second  ;  still,  as  a  general  rule,  a  shorter 
time  is  required  the  larger  and  brighter  the  object  looked  at.  Alternate  stimula- 
tion with  light,  17  to  18  times  per  minute,  is  perceived  most  intensely  {Briicke). 
Further,  an  increase  or  diminution  of  o.oi  part  of  the  intensity  of  the  light  is 
perceptible  (§  383).  A  shorter  time  is  required  to  perceive  yellow  than  is  re- 
quired for  violet  and  red  (Vieivnlt).  The  retina  becomes  more  sensitive  to  light 
after  a  person  has  been  kept  in  the  dark  for  a  long  time,  and  also  after  repose 
during  the  night.  If  light  be  allowed  to  act  on  the  eyes  for  a  long  time,  and 
especially  if  it  be  intense,  it  causes  fatigue  of  the  retina,  which  begins  sooner  in 
the  centre  than  in  the  periphery  of  the  organ  {Auberf).  At  first  the  fatigue  comes 
on  rapidly  and  afterward  develops  more  slowly  ;  it  is  most  marked  in  the  morning 
(A.  Pick,  C.  F.  Miiller).  The  periphery  of  the  retina  is  specially  characterized 
by  its  capacity  for  distinguishing  movements  {Exner). 

VII.  Visual  Purple. — The  mode  of  the  action  of  light  upon  the  end  organs 
of  the  retina  has  already  been  referred  to  in  connection  with  the  "  visual  purple" 
[or  Rhodopsin]  (Boll,  Kiiline).  Kiihne  showed  that,  by  illuminating  the  retina, 
actual  pictures  (c.  g.,  the  image  of  a  window)  could  be  produced  on  the  retina, 
but  they  gradually  disappeared.  From  this  point  of  view  we  might  regard  the 
retina  as  comparable,  to  a  certain  extent,  to  the  sensitive  plate  of  a  photographic 
apparatus. 

Optogram. — The  visual  purple  is  formed  by  the  pigment  epithelium  of  the  retina.  Perhaps  we 
might  compare  the  process  to  a  kind  of  secretion.  The  visual  purple  may  be  restored  in  a  retina 
by  laying  the  latter  upon  living  choroidal  epithelium.  The  pigment  disappears  from  the  mamma- 
lian retina  by  the  action  of  light  60  times  more  rapidly  than  from  the  retina  of  the  frog.  In  a 
rabbit's  eye.  whose  pupil  was  dilated  with  atropin,  Ewald  and  Kiihne  obtained  a  sharp  picture  or 
optogram  of  a  bright  object  placed  at  a  distance  of  24  cm.  from  the  eye;  the  image  was  "fixed" 
by  a  4  per  cent,  solution  of  alum.  Visual  purple  withstands  all  the  oxidizing  reagents ;  zinc  chloride, 
acetic  acid  and  corrosive  sublimate  change  it  into  a  yellow  substance ;  it  becomes  white  only  through 
the  action  of  light;  the  dark  heat  rays  are  without  effect,  while  it  is  decomposed  above  a  tempera- 
ture of  52°  C.  [.'\s  visual  purple  is  absent  from  the  cones,  and  cones  only  are  present  in  the  fovea 
centralis,  we  cannot  explain  vision  by  optograms  formed  by  the  visual  purple.] 

VIII.  Destruction  of  the  rods  and  cones  of  the  retina  causes  correspond- 
ing dark  spots  in  the  field  of  vision. 

396.  PERCEPTION  OF  COLORS.- Physical.— The  vibrations  of  the  light  ether  are  per- 
ceived  by  the  retina  only  within  distinct  limits.  If  a  beam  of  white  light,  e.  g.,  from  the  sun,  be 
transmitted  through  a  prism,  the  light  rays  are  refracted  and  dispersed,  and  a  "prismatic  spec- 
trum" (Fig.  14)  is  obtained.  White  light  contains  rays  of  very  different  wave  lengths  or  periods 
of  vibration.  The  dark  heat  rays,  whose  wave  length  is  0.00194  mm.  (Fizeau),  are  refracted  least. 
They  do  not  act  upon  the  retina,  and  are  therefore  invisible.  They  act,  however,  upon  sensory 
nerves.     About  90  per  cent,  of  these  rays  is  absorbed  by  the  media  of  the  eye  [Briicke  and  Knob- 


CONTRAST   AND    COMPLEMENTARY   COLORS.  791 

lauch,  Cima,  Janseii).  From  Frauenhofer's  line,  A,  onward,  the  oscillations  of  the  light  ether 
excite  the  retina  in  the  following  order :  j?i'<2' with  4S1  billions  of  vibrations  per  second,  o^aw^? 
with  ^-t,z,yelhna  with  563,  green  with  607,  blue  with  653,  indii;o  with  676,  and  violet  with  764  bil- 
lion vibrations  per  second.  The  sensation  of  color  therefore  depends  on  the  number  of  vibra- 
tions of  the  light  ether,  just  as  the  pitch  of  a  note  depends  on  the  number  of  vibrations  of  the 
sounding  body  [Newton,  ijo^ ;  Hartley,  iTfj).  Beyond  the  violet  lie  the  chemically  active 
[actinic]  rays  of  the  spectrum.  After  cutting  out  all  the  spectrum,  including  the  violet  rays,  v. 
Helmholtz  succeeded  in  seeing  the  ultra-violet  rays,  which  had  a  feeble  grayish-blue  color.  The 
heat  rays  in  the  colored  part  of  the  spectrum  are  transmitted  by  the  media  of  the  eye  in  the  same 
way  as  through  water  (Franz).  The  existence  of  the  ultra-violet  rays  is  best  ascertained  by  the 
phenomenon  of  fluorescence.  Von  Helmholtz,  on  illuminating  a  solution  of  sulphate  of  quinine 
with  the  ultra-violet  rays,  saw  a  bluish-white  light  proceeding  from  all  parts  of  the  solution  which 
were  acted  on  by  the  ultra-violet  rays.  As  the  media  of  the  eye  themselves  exhibit  fluorescence 
[v.  Helmholtz,  SetseAenow),  they  must  increase  the  power  of  the  retina  to  distinguish  these  rays. 
The  ultra-violet  rays  are  not  largely  absorbed  by  the  media  of  the  eye  (Briicke,  Donthrs). 

In  order  that  a  color  be  perceived,  it  is  essential  that  a  certain  quantity  of  light  must  fall  upon  the 
retina.  Blue,  when  at  the  lowest  degree  of  brightness,  gives  a  color  sensation  with  a  quantity  of 
light,  which  is  sixteen  times  less  than  that  required  for  red  (Dobroiulosky). 

Intensity  of  the  Impression  of  Light. — While  light  of  difierent  periods  of  vibration  applied 
to  the  eye  excites  the  different  sensations  of  color,  the  amplitude  of  the  vibrations  (height  of  the 
waves)  determines  the  intensity  of  the  impression  of  light ;  just  as  the  loudness  of  a  note  depends 
on  the  amplitude  of  the  vibrations  of  the  sounding  body.  The  sun's  light  contains  all  the  rays 
which  excite  the  sensation  of  color  in  us,  and  when  all  these  rays  fall  simultaneously  upon  the  retina 
we  experience  the  sensation  of  white.  If  the  colors  of  the  spectrum  obtained  by  means  of  a  prism 
be  reunited,  white  light  is  again  obtained.  If  no  vibrations  of  the  light  ether  reach  the  retina,  every 
sensation  of  light  and  color  is  absent,  but  we  can  scarcely  apply  the  term  black  to  this  condition. 
It  is  rather  the  absence  of  sensation,  such  as,  for  example,  is  the  case  when  a  beam  of  light  falls 
on  the  skin  of  the  back.  This  does  not  give  the  sensation  of  black,  but  rather  that  of  no  sensation 
of  light. 

Simple  and  Mixed  Colors. — We  distinguish  simple  colors,  e.  g.,  those  of 
the  spectrum.  In  order  to  perceive  these,  the  retina  must  be  e.xcited  (set  into 
vibration)  by  a  distinct  number  of  oscillations  (see  above).  Further,  we  distin- 
guish "  mixed  colors,"  whose  sensation  is  produced  when  the  retina  is  excited 
by  two  or  more  simple  colors,  simultaneously  or  rapidly  alternating.  The  most 
complex  mixed  color  is  white,  which  is  composed  of  a  mixture  of  all  the 
simple  colors  of  the  spectrum. 

The  "  complementary  colors  "  are  important.  Any  two  colors  which  to- 
gether give  the  sensation  of  white  are  complementary  to  each  other.  The  "  con- 
trast colors  "  are  mentioned  here  merely  to  complete  the  list.  They  are  closely 
related  to  the  complementary  colors.  Any  two  colors  which,  when  mixed,  sup- 
plement the  generally  prevailing  tone  of  the  light,  are  contrast  colors.  When  the 
sky  is  blue,  the  two  contrast  colors  must  be  bluish  white ;  with  bright  gaslight 
they  must  be  yellowish  white,  and  in  pure  white  light,  of  course,  all  the  comple- 
mentary are  the  same  as  the  contrast  colors  {Brilcke). 

Methods  of  Mixing  Colors. — i.  Two  solar  spectra  are  projected  upon  a  screen,  and  the  spectra 
are  so  arranged  as  to  cause  any  one  part  of  one  spectrum  to  cover  any  part  of  the  other.  2.  Look 
obliquely  through  a  vertically  arranged  glass  plate  at  a  color  placed  behind  it.  Another  color  is 
placed  xn  front  of  the  glass  plate,  so  that  its  image  is  also  reflected  into  the  eye  of  the  observer ; 
thus,  the  light  of  one  color  transmitted  through  the  glass  plate  and  the  reflected  light  from  the  other 
color  reach  the  eye  simultaneously.  [  Lambert's  Method. — This  is  easily  done  by  Lambert's  method. 
Use  colored  wafers  and  a  slip  of  glass ;  place  a  red  wafer  on  a  sheet  of  white  paper,  and  about  three 
inches  behind  it  another  blue  one.  Hold  the  plate  of  glass  midway  and  vertically  between  them, 
and  so  incline  the  glass  that,  while  looking  through  it  at  the  red  wafer,  a  reflected  image  of  the  blue 
one  will  be  projected  into  the  eye  in  the  same  direction  as  that  of  the  red  image,  when  we  have  the 
sensation  of  purple.] 

3.  A  rotatory  disk,  with  sectors  of  various  colors,  is  rapidly  rotated  in  front  of  the  eyes.  On  rapidly 
rotating  the  colored  disk,  the  impressions  produced  by  the  individual  colors  are  united  to  produce  a 
mixed  color.  If  the  rotating  disk,  which  yield<,  let  us  suppo>-e,  white,  on  mixing  the  colors  of  the 
spectrum,  be  reflected  in  a  rapidly  rotating  mirror,  then  the  individual  components  of  the  white  re- 
appear [Lanilois). 

4.  Place  in  front  of  each  of  the  small  holes  in  the  cardboard  used  for  Scheiner's  experiment 
(Fig.  471),  two  differently  colored  pieces  of  glass;  the  colored  rays  of  light  passing  through  the 
holes  unite  on  the  retina,  and  produce  a  mixed  color  (Czermai). 


792 


GEOMETRICAL   COLOR   TABLE. 


Complementary  Colors. — Investigation  shows  that  the  following  colors  of  the  spectrum  are 
complementary,  i.  e.,  every  pair  gives  rise  to  white  : — 

Red  and  greenish-blue,  Orange  and  Cyan  blue, 

Yellow  and  indigo-blue.  Greenish-yellow  and  violet, 

while  green  has  the  compound  complementary  color  purple  (v.  Helniholtz). 

The  mixed  colors  may  be  determined  from  the  following  table.  At  the  top  of  the  vertical  and 
horizontal  columns  are  placed  the  simple  colors;  the  mixed  colors  occur  where  they  intersect  the 
corresponding  vertical  and  horizontal  columns  (Dk.  =  dark;  wh.  =  whitish)  : — 


Violet. 

Indigo. 

Cyan-blue. 

Bluish-green. 

Green. 

Greenish-yellow. 

Yellow. 

Retl 
Orange 

Yellow 

Gr.-yellow 

Green 

Bluish-green 

Cyan-blue 

Purple 
Dk.-rose 

Wh.-rose 

White 

White-blue 

Water-blue 

Indigo 

Dk.-rose 
Wh.-rose 
White 

Wh.-rose 

White 

Wh.-green 

Wh  -tTPPn 

White 
Wh. -yellow 
Wh.-yellow 
Green 

Wh.-yellow 

Yellow 

Gr.-yellow 

Gold-yellow 
Yellow 

Orange. 

Water-blue    iRl  -t.rp,.n 

Water-blue 



The  following  results  have  been  obtained  from  observations  on  the  mixture  of 
colors : — 

1.  If  two  simple,  but  non-complementary,  spectral  colors  be  mi.xed  with  each 
other,  they  give  rise  to  a  color  sensation,  which  may  be  represented  by  a  color 
lying  in  the  spectrum  between  both,  and  mixed  with  a  certain  quantity  of  white. 
Hence  we  may  produce  every  impression  of  mixed  colors  by  a  color  of  the  spec- 
trum -f-  vvhite  {Grass?>iait). 

2.  The  less  white  the  colors  contain  the  more  "  saturated  "  they  are  said  to 
be ;  the  more  white  they  contain  they  appear  more  unsaturated.  The  saturation 
of  a  color  diminishes  with  the  intensity  of  the  illumination. 

Geometrical  Color  Table. — Since  the  time  of  Newton  attempts  have  been  made  to  construct 
a  so-called  "  geometrical  color  table,"  which  will  enable  any  mixed  color  to  be  readily  found.     Fig. 

495  shows  such  a  color  table;  white  is  placed 
Fig.  495.  '"  '''^  middle,  and  from  it  to  every  point  in  the 

curve, — which  is  marked  with  the  names  of 
the  colors, — suppose  each  color  to  be  so  placed 
that,  proceeding  from  white,  the  colors  are  ar- 
ranged, beginning  with  the  brighle^t  tone,  then 
always  follows  the  most  saturated  tone,  until 
the  pure  saturated  spectral  color  lies  in  the 
point  of  the  curve  marked  with  the  name  of 
the  color.  The  mixed  color  purple  is  placed 
between  violet  and  red.  In  order  to  determine 
from  this  table  the  mixed  color  of  any  two 
spectral  colors,  unite  the  points  of  these  colors 
by  a  straight  line.  Suppose  weights  cone- 
sponding  to  the  units  of  intensity  of  these 
colors  be  placed  on  both  points  of  the  curve 
indicating  colors,  then  the  position  of  the 
Red  centre  of  gravity  of  both  in  the  line  connect- 
ing the  colors  indicates  the  position  of  the 
mixed  color  on  the  table.  The  mixed  color 
of  two  spectral  colors  always  lies  on  the  color 
Geometrical  color  cone  or  table.  table  in  the  Straight  line  connecting  the  two 

color  points.  Further,  the  impression  of  the 
mixed  color  corresponds  to  an  intermediate  spectral  color  mixed  with  white.  The  complementary 
color  of  any  spectral  color  is  found  at  once  by  making  a  line  from  the  point  of  this  color  through 
white,  until  it  intersects  the  opposite  margin  of  the  color  table  ;  the  point  of  intersection  indicates 
the  complementary  color.  \i  pure  white  be  produced  by  mixing  two  complementary  colors,  the 
color  lying  nearest  white  on  the  connecting  line  must  be  specially  strong,  as  then  only  would  the 
centre  of  gravity  of  the  lines  uniting  both  colors  he  in  the  point  marked  white. 

By  means  of  the  color  table  we  may  ascertain  the  mixed  color  of  three  or  more  colors.  For 
example,  it  is  required  to  find  the  mixed  color  resulting  from  the  union  of  the  point,  a  (pale  yellow), 
^  (fairly  saturated  bluish-green),  and  6- (fairly  saturated  blue).  On  the  three  points  place  weights 
corresponding  to  their  intensities,  and  ascertain  the  centre  of  gravity  of  the  w  eight,  a,  b,  c  ;  it  « ill 


Cyan  blue 


YeUow 


HEKING  S   THEORY   OF   COLOR    SENSATION. 


793 


lie  at/.  It  is  obvious,  however,  that  the  impression  of  this  mixed  color,  whitish  green-blue,  can 
be  produceil  by  green-blue  -f  white,  so  that  /  may  be  also  the  centre  of  gravity  of  two  weights, 
which  lie  in  the  line  connecting  white  and  green-blue. 

We  may  describe  a  triangle,  V,  Gr,  R,  about  the  color  table  so  as  to  enclose  it  completely.  The 
three  fundamental  or  primary  colors  lie  in  the  angles  of  this  triangle,  red,  green,  violet.  It  is 
evident  that  each  of  the  colored  impressions,  ;.  e.,  any  point  of  the  color  table,  may  be  determined 
by  placing  weights  corresponding  to  the  intensity  of  ihe  primary  colors  at  the  angles  of  the  triangle, 
so  that  the  point  of  the  color  table,  or,  what  is  the  same  thing,  the  desired  mixed  color,  is  the 
centre  of  gravity  of  the  triangle  with  its  angles  weighted  as  above.  The  intensity  of  the  three 
primary  colors,  in  order  to  produce  the  mixed  color,  must  be  represented  in  the  same  proportion  as 
the  weights. 

Theories. — Various  theories  have  been  proposed  to  account  for  color  sensation. 

1.  According  to  one  theory,  color  sensation  is  produced  by  one  kind  of  element  present  in  the 
retina,  being  excited  in  different  ways  by  light  of  different  colors  (oscillations  of  the  light  ether  of 
ditferent  wave  lengths,  number  of  vibrations,  and  refractive  indices). 

2.  Young-Helmholtz  Theory.— The  theory  of  Thomas  Young  fiSoy)  and 
V.  Helmhohz  (1S52)  as.sumes  that  three  different  kinds  of  nerve  elements, 
corresponding  to  the  three  primary  colors,  are  present  in  the  retina.  Stimulation 
of  the  first  kind  causes  the  sensation  of  red,  of  the  second  green,  and  of  the 
third  violet. 

The  elements  sensitive  to  red  are  most  strongly  excited  by  light  with  the  longest  wave  length,  the 
red  rays;  those  for  green  by  medium  wave  lengths,  green  rays;  tho>e  for  violet  by  the  rays  of 
shortest  wave  length,  violet  rays.  Further,  it  is  assumed,  in  order  to  explain  a  number  of  phe- 
nomena, that  e-jery  color  of  the  spectrum  excites  all  the  kinds  of  fibres,  some  of  them  feebly,  others 
strongly.  Suppose  in  Fig.  496  the  colors  of  the  spectrum  are  arranged  in  their  natural  order  from 
red  to  violet  horizontaly,  then  the  three  curves  raised  upon  the  abscissa  might  indicate  the  strength 


Fig.  496. 


Gr 


B 


of  the  stimulation  of  the  three  kinds  of  retinal  elements.  The  continuous  curve  corresponds  to  the 
rays  producing  the  sensation  of  red,  the  dotted  line  that  of  green,  and  the  broken  line  that  of  violet. 
Pure  red  light,  as  indicated  by  the  height  of  the  ordinates  in  R,  strongly  excites  the  elements  sensi- 
tive to  red,  and  feebly  the  other  two  kinds  of  termina'ions,  resulting  in  the  sensation  of  red.  Simple 
yellow  excites  moderately  the  elements  for  red  and  green,  and  feebly  those  for  violet  =  sensation 
oi  yellow.  Simple  green  excites  strongly  the  elements  for  green,  but  much  more  feebly  the  two 
other  kinds  =  sensation  o^ green.  Simple  blue  excites  to  a  moderate  extent  the  elements  for  green 
and  violet ;  more  feebly  those  for  red  =  sensation  of  blue.  Simple  violet  excites  .strongly  the  cor- 
responding elements,  feebly  the  others  =  sensation  of  7'iolet.  Stimulation  of  any  two  elements  ex- 
cites the  impression  of  a  mixed  color ;  while,  if  all  of  them  be  excited  in  a  nearly  equal  degree, 
the  sensation  of  white  is  produced.  As  a  matter  of  fact,  the  Voung-Helmholtz  theory  gives  a  clear 
and  simple  explanation  of  the  phenomena  of  the  physiological  doctrine  of  color.  It  has  been  at- 
tempted to  make  the  results  obtained  by  examination  of  the  structure  of  the  retina  to  accord  with 
this  view.  According  to  Max  Schullze,  the  cones  alone  are  end  organs  connected  with  the  percep- 
tion of  color.  The  presence  of  longitudinal  slrialion  in  their  outer  segments  is  regarded  as  consti- 
tuting them  multiple  terminal  end  organs.  Our  power  of  color  sensation,  so  far  as  it  depends  on 
the  retina,  would,  on  this  view  of  the  ma'ter,  bear  a  relation  to  the  number  of  cones.  The  degree 
of  color  sensation  is  most  developed  in  the  macula  lutea,  which  contains  only  cone^.  and  diminishes 
as  the  distance  from  the  point  increases,  while  it  is  absent  in  the  peripheral  pans  of  the  retina. 

The  rods  of  the  retina  are  said  to  be  concerned  only  with  the  capacity  to  distinguish  between 
quantitative  sensations  of  light. 

3.  Hering's  Theory. — Ew.  Hering,  in  order  to  explain  the  sensation  of  light,  proceeds  from 
the  axiom  stated  under  I,  p.  792.  What  we  are  conscious  of,  and  call  a  visual  sensation,  is  the 
psjchical  expression  for  the  metabolism  in  the  visual  substance  ("  Sehsiibitanz  "),  i.e.,  in  those 
n-Tve  masses  which  are  excited  in  the  process  of  vision.  I-ike  every  other  corporeal  matter,  this 
su  stance  during  the  activity  of  the  metabolic  process  undergoes  decomposition  or  "  disassimila- 
tion  ;"  while  during  rest  it  must  be  again  renewed,  or  "  assimilate  "  new  material.  Hering 
assumes  that  for  the  perception  of  white   (bright)  and  black  (dark),  two  different  qualities  of  the 


794  COLOR    BLINDNESS. 

chemical  processes  take  place  in  the  visual  substance,  so  that  the  sensation  of  white  or  bright  cor- 
responds to  the  disassimilation  (decomposition),  and  that  of  black  (dark)  to  the  assimilation 

(restitution)  of  the  visual  substance.  According  to  this  view,  the  different  degrees  of  distinctness 
or  intensity  with  which  these  two  sensations  appear,  occur  in  the  several  transitions  between  pure 
white  and  deep  black,  or  the  proportions  in  which  they  appear  to  be  mixed  (gray),  correspond  to 
the  intensity  of  these  two  psycho-physical  processes.  Thus  the  consumption  and  restitution  of 
matter  in  the  visual  substance  are  the  primary  processes  in  the  sensation  of  white  and  black.  In 
the  production  of  the  sensation  of  white,  the  consumption  of  the  visual  substance  is  caused  by  the 
vibrating  ethereal  waves  acting  as  the  discharging  force  or  stimulus,  while  the  degree  of  the  sensa- 
tion of  whiteness  (brightness)  is  proportional  to  the  quantity  of  the  matter  consumed.  The  process 
of  restitution  <lischarges  the  sensation  of  black  ;  the  more  rapidly  it  occurs  the  stronger  is  the  sen- 
sation of  black.  The  consumption  of  the  visual  substance  at  one  place  causes  a  greater  restitution 
in  the  adjoining  ]>arts.  Both  processes  influence  each  other  simultaneously  and  conjointly.  This 
explains  physiologically  the  phenomenon  of  contrast  (p.  799),  of  which  the  old  view  could  give 
only  a  psychical  interpretation.  Similarly,  color  sensation  is  regarded  as  a  sensation  of  decom- 
position (disassimilation)  and  one  of  the  restitution  (assimilation)  ;  in  addition  to  -white,  red  and 
yellow  are  the  expression  of  decomposition  ;  while  green  and  blue  represent  the  sensation  of  resti- 
tution. Thus  the  visual  substance  is  subject  to  three  different  ways  of  chemical  change  or  meta- 
bolism. We  may  thus  explain  the  colored  phenomena  of  contrast  and  the  complementary  after 
images.  The  sensation  of  black-white  may  occur  simultaneously  with  all  colors,  so  that  every 
color  sensation  is  accompanied  by  that  of  dark  or  bright,  so  that  we  cannot  have  an  absolutely  pure 
color.  There  are  three  different  constituents  of  the  visual  substance;  that  connectetl  with  the  sen- 
sation of  black-white  (colorless),  that  with  blue-yellow,  and  that  with  redgreen.  All  the  rays  of 
the  visible  spectrum  act  in  disassimilating  the  black-white  substance,  but  the  different  rays  act  in 
different  degrees.  The  blue- yellow  or  red-green  substances,  on  the  other  hand,  are  disassimilated  only 
by  certain  rays,  some  rays  causing  assimilation,  and  others  are  inactive.  Mixed  light  appears  colorless 
when  it  causes  an  equally  strong  disassimilation  and  assimilation  in  the  blue-yellow  and  in  the  red- 
green  substance,  so  that  the  two  processes  mutually  antagonize  e.-ich  other,  and  the  action  on  the 
black- white  substance  appears  pure.  Two  objective  kinds  of  light,  which  together  yield  white, are 
not  to  be  regarded  as  complementary,  but  as  antagonistic  kinds  of  light,  as  they  do  not  supplement 
each  other  to  produce  white,  but  only  allow  this  to  appear  pure,  because,  being  antagonistic,  they 
mutually  prevent  each  other's  action. 

The  imperfection  of  the  Voung-Helmholtz  theory  of  color  sensation  is  that  it  recognizes  only  one 
kind  of  excitability,  excitement  and  fatigue  (corresponding  to  Hering's  disassimilation),  and  that  it 
ignores  the  antagonistic  relation  of  certain  light  rays  to  the  eye.  It  does  not  regard  white  as  con- 
sisting of  complementary  light  rays,  which  neutralize  each  other  by  their  action  on  the  colored 
visual  substance,  but  as  uniting  to  form  white  [Hering). 

In  applying  this  theory  to  color  blindness  (§  397),  we  must  assume  that 
those  who  are  red  blind  want  the  red-green  visual  substance  ;  there  are  but  two 
partial  spectra  in  their  solar  spectrum,  the  black-white  and  the  yellow-blue.  The 
position  of  green  appears  to  such  an  one  to  be  colorless  ;  the  rays  of  the  red  part 
of  the  spectrum  are  so  far  visible,  as  the  sensation  of  yellow  and  white  produced 
by  these  rays  is  strong  enough  to  excite  the  retina.  Hering  divides  his  spectrum 
into  a  yellow  and  a  blue  half.  A  violet-blind  person  wants  the  yellow-bine 
visual  substance ;  in  his  spectrum  there  are  only  two  partial  spectra,  the  black- 
white  and  the  red-green.  In  cases  of  complete  color  blindness,  the  yellow- 
blue  and  red-green  substances  are  absent.  Hence,  such  a  person  has  only  the 
sensation  of  bright  and  dark.  The  sensibility  to  light  and  the  length  of  the 
spectrum  are  retained  ;  the  brightest  part  in  this  case,  as  in  the  normal  eye,  is  in 
the  yellow  (^Hering). 

Von  Kries  devised  the  following  experiment  against  Hering's  theory :  AiTange  two  gray  surfaces, 
one  formed  by  mixing  white  and  black,  the  other  by  yellow  and  blue,  and  let  both  appear  equally 
an  intense  gray.  On  staring  at  a  red  object  on  these  surfaces  until  the  retina  is  fatigued,  and  until 
the  object  disappears,  a  gray  after  image  appears  in  both  cases.  The  mixture  of  yellow  and  blue 
cannot  in  this  case  have  acted  as  to  cause  restitution  of  the  red-gray  substance;  this  is  done  rather 
by  the  mixed  gray  composed  of  white  and  black. 

397.  COLOR  BLINDNESS  AND  ITS  PRACTICAL  IMPORT- 
ANCE.— Causes. — Hy  the  term  color  blindness  ( Dyschromatopsy)  is 
meant  a  pathological  condition  in  which  some  individuals  are  unable  to  distin- 
guish certain  colors.  Huddart  (1777)  was  acquainted  with  the  condition,  but  it 
was  first  accurately  described  by  Dalton  (1794),  who  himself  was  red  blind. 
The  term  color  blindness  was  given  to  it  by  Brewster. 


COLOR   BLINDNESS.  795 

The  supporters  of  the  Young- Heltnholtz  theory  assume  that,  corresponding  to  the  paralysis  of  the 
three  color-perceiving  elements  of  the  retina,  there  are  the  following  kinds  of  color  blindness ; — 

1.  Red  blindness.         2.  Green  blindness.         3.  Violet  blindness. 
The  highest  degree  being  termed  complete  color  blindness. 

The  supporters  of  E.  Hering's  theory  of  color  sensation  distinguish  the  following  kinds: — 

1.  Complete  Color  Blindness  (Achromatopsy). — The  spectrum  appears  achromatic;  the 
position  of  the  greenish-yellow  is  the  brightest,  while  it  is  darker  on  both  sides  of  it.  A  colored 
picture  appears  like  a  photograph  or  an  engraving.  Occasionally  the  different  degrees  of  light 
intensity  are  ]5erceived  in  one  shade  of  color,  t\^.,  yellow,  which  cannot  be  compared  with  any  other 
Ciller.  O.  Becker  and  v.  Hippel  observed  cases  of  «>2!7<j/.fr(7/ congenital  complete  color  blindness, 
while  the  other  eye  was  normal  for  color  perception. 

2.  Blue-yellow  Blindness  (S/i!!i>i^). — The  spectrum  is  dichromatic,  and  consists  only  of  red 
and  green.  The  blue  violet  end  of  the  spectrum  is  usually  greatly  shortened.  In  pure  cases  only 
the  red  and  green  are  correctly  distinguished  (Mauthner's  Erythrochloropy),  but  not  the  other 
colors.     Unilateral  coses  h.ive  been  observed. 

3.  Red-green  Blindness. — The  spectrum  is  also  dichromatic.  Yellow  and  blue  are  correctly 
distinguished;  violet  and  Ijlue  are  both  taken  for  blue.  The  sensations  for  red  and  green  are  absent 
altogether.  There  are  several  forms  of  this — (a)  Green  blindness,  or  the  red-green  blindness, 
with  undiminished  spectrum  (Mauthner's  Xanthokyanopy),  in  which  bright  green  and  dark  red 
are  confounded.  In  the  spectrum  yellow  abuts  directly  on  blue,  or  between  the  two;  at  most,  there 
is  a  strip  of  gray.  The  maximum  of  brightness  is  in  the  yellow.  It  is  often  unilateral  and  often 
hereditary.  (!•)  Red  blindness  (or  the  red-green  blindness  with  undiminished  spectrum,  also 
called  Daltonism),  in  which  bright  red  and  dark  green  are  confounded.  The  spectrum  consists 
of  yellow  and  blue,  but  the  yellow  lies  in  the  orange.  The  red  end  of  the  spectrum  is  uncolored, 
or  even  dark.  The  greatest  brightness,  as  well  as  the  limit  between  yellow  and  blue,  lies  more 
toward  the  right. 

4. -Incomplete  color  blindness,  or  a  diminished  color  sense,  indicates  the  condition  in  which 
the  acuteness  of  color  perception  is  diminished,  so  that  the  colors  can  be  detected  only  in  large 
objects,  or  only  when  they  are  near,  and  when  they  are  mixed  with  white  they  no  longer  appear  as 
such.  .\  certain  degree  of  this  form  is  frequent,  in  as  far  as  many  persons  are  unable  to  distinguish 
greenish-blue  from  bluish-green. 

Acquired  color  blindness  occurs  in  diseases  of  the  retina  and  atrophy  of  the  optic  nerve 
(Benedict),  in  commencing  tabes,  in  some  forms  of  cerebral  disease  (p.  731),  and  intoxications. 
At  first  green  blindness  occurs,  which  is  soon  followed  by  red  blindness.  The  peripheral  zone  of 
the  retina  suffers  sooner  than  the  central  area  (Schirmer).  In  hysterical  persons  there  may  be 
intermittent  attacks  of  color  blindness  {Charcot,  Landolt);  and  the  same  occurs  in  hypnotized 
persons  fp.  708). 

H.  Cohn  found  that,  on  heating  the  eyeball  of  some  color  blind  persons,  the  color  blindness 
disappeared  temporarily.  Occasionally  in  persons  without  a  lens  red  vision  is  present,  and  is  due 
to  unknown  cause>  Percentage. — Holmgren  found  that  2  7  per  cent,  of  persons  were  color  blind, 
most  being  /ev/ and  ;-;v. «  blind,  and  very  few  violet  blind. 

Limits  of  Normal  Color  Blindness. — The  investigations  on  the  power  of  color  perception  in 
the  normal  retina  are  best  carried  out  by  means  of  Aubert-Forster's  perimeter,  or  that  of  M' Hardy, 
\  395.  It  is  found  that  our  color  perception  is  complete  only  in  the  middle  of  the  field  of  vision. 
Around  this  is  a  middle  zone,  in  which  only  blue  and  yellow  are  perceived,  in  which,  therefore, 
there  is  red  blindness.  Outside  this  zone  there  is  a  peripheral  girdle,  where  there  is  complete  color 
blindness  {\  395).  Hence  a  red-blind  person  is  distinguished  from  a  person  with  normal  vision,  in 
that  the  central  area  of  the  normal  field  of  vision  is  absent  in  the  former,  this  being  rather  included 
in  the  middle  zone.  The  field  of  vision  of  a  green  blind  person  differs  from  that  of  a  person  with 
normal  vision,  in  that  his  peripheral  zone  corresponds  to  the  intermediate  and  peripheral  zones  of 
the  normal  eye.  The  violet-blind  person  is  distinguished  by  the  complete  absence  of  the  normal 
peripheral  zone.  The  incomplete  color  blindness  of  these  two  kinds  is  characterized  by  a  uniformly 
diminished  central  field.  [When  very  intense  colors  are  used,  such  as  those  of  the  solar  spectrum, 
the  retina  can  distinguish  them  quite  up  to  its  margin  (Landolt).'] 

In  poisoning  with  santonin,  violet  blindness  (yellow  vision)  occurs  in  consequence  of  the 
paralysis  of  the  violet  perceptive  retinal  elements,  which  not  unfrequently  is  preceded  by  stimulation 
of  these  elements,  re-ulting  in  violet  vision,  i.  e.,  objects  seem  to  be  colored  violet  (Hiifner).  Such 
is  the  explanation  of  this  phenomenon  given  by  Holmgren.  Max  Schultze,  however,  referred  the 
yellow  vision,  i.e.,  seeing  objects  yellow,  to  an  increase  of  the  yellow  pigment  in  the  macula  lutea. 

When  colored  objects  are  ver)-  small,  and  illuminated  only  for  a  short  time,  the  normal  eye  first 
fails  to  ■perceive  red  {.-ttibert,  Lamansky) ;  hence  it  appears  that  a  stronger  stimulus  is  required  to 
excite  the  sensation  of  red.  Brucke  found  that  verj'  rapidly  intermittent  white  light  is  perceived 
as  green,  because  the  short  duration  of  the  stimulation  failed  to  excite  the  elements  of  the  retina 
connected  with  the  sensation  of  red. 

[The  practical  importance  of  color  blindness  was  pointed  out  by  George  Wilson,  and  again 
more  recently  by  Holmgren.]  No  person  should  be  employed  in  the  marine  or  railway  Service 
until  he  has  been  properly  certified  to  be  able  to  distinguish  red  from  green. 


796  AFTER    IMAGES. 

Methods  of  Testing  Color  Blindness. — Following  Seebeck,  Holmgren  used  small  skeins 
of  colored  wools  as  the  simplest  material,  in  red,  orange,  yellow,  greenish-yellow,  green,  greenish- 
blue,  blue,  violet,  purple,  rose,  brown,  gray.  There  are  five  finely  graduated  shades  of  each  of  the 
above  colors.  When  testing  a  person,  select  only  one  skein — ^■,^.,  a  bright  red  or  rose — from  the 
mass  of  colored  wools  placed  in  front  of  him,  and  place  it  aside,  asking  him  to  seek  out  those  skeins 
which  he  supposes  are  nearest  to  it  in  color. 

Mace  and  Nacali  have  measured  the  acuteness  of  vision  by  illuminating  a  small  object  with 
different  parts  of  the  spectrum.  They  compared  the  observations  on  red  and  green-blind  persons 
with  their  own  result.s,  and  found  that  a  red-blind  person  perceives  green  light  much  brighter  than 
a  normal  person.  The  green  blind  had  an  excessive  sensibility  for  red  and  violet.  It  appears  that 
what  the  color  blind  lose  in  perceptive  power  for  one  olor  they  gain  for  another. 

398.  STIMULATION  OF  THE  RETINA.— Positive  and  Nega- 
tive After  Images — Irradiation — Contrast. — .\s  with  every  other  nervous 
apparatus,  a  certain  but  small  amount  of  time  elapses  after  the  rays  of  light  fall 
upon  the  eye  before  the  action  of  the  light  takes  place,  whether  the  light  acts  so 
as  to  produce  a  conscious  impression,  or  produces  merely  a  reflex  effect  upon  the 
pupil.  The  strength  of  the  impression  produced  depends  partly  and  chiefly  upon 
the  excitability  of  the  retina  and  the  other  nervous  structures.  If  the  light  acts 
for  a  long  time  with  equal  intensity,  the  excitation,  after  having  reached  its 
culminating  point,  rapidly  diminishes  again,  at  first  more  rapidly,  and  afterward 
more  and  more  slowly. 

[When  the  retina  is  stimulated  by  light  there  is  (i)  an  effect  on  the  rho- 
dopsin  (p.  756).  (2)  The  electro-motive  force  is  diminished  (§  332).  (3)  The 
processes  of  the  hexagonal  pigment  cells  of  the  retina  dipping  between  the  rods 
and  cones  are  affected  ;  thus  they  are  retracted  in  darkness,  and  protruded  in  the 
light  (Fig.  497).  (4)  Engelmann  has  shown  that  the  length  and  shape  of  the 
cones  vary  with  the  action  of  light.  The  cones  are  retracted  in  darkness  and 
protruded  under  the  influence  of  light  (Fig.  497).  This  alteration  in  the  shape 
of  the  cones  takes  place  even  if  the  light  acts  on  the  skin,  and  not  on  the  eyeball 
at  alf.] 

After  Images. — If  the  light  acts  on  the  eye  for  some  time  so  as  to  excite  the 
retina,  and  if  it  be  suddenly  withheld,  the  retina  still  remains  for  some  time  in  an 
excited  condition,  which  is  more  intense  and  lasts  longer  the  stronger  and  the 
longer  the  light  was  applied  and  the  more  e.\citable  the  condition  of  the  retina. 
Thus,  after  every  visual  perception,  especially  if  it  is  very  distinct  and  bright,  there 
remains  a  so-called  "  after  image.'"  We  distinguish  a  "  positive  after  image," 
which  is  an  image  of  similar  brightness  and  a  similar  color. 

"  That  the  impression  of  any  picture  remains  for  some  time  upon  the  eye  is  a  physiological  phe- 
nomenon ;  when  such  an  impression  can  be  seen  for  a  long  time  it  becomes  pathological.  The 
weaker  the  eye  is  the  longer  the  image  remains  upon  it.  The  retina  does  not  recover  itself  so 
quickly,  and  we  may  regard  the  action  as  a  kind  of  paralysis.  This  is  not  to  be  wondered  at  in 
the  case  of  dazzling  pictures.  After  looking  at  the  sun,  the  image  may  remain  on  the  retina  for 
several  days.  A  similar  result  sometimes  occurs  with  pictures  which  are  not  dazzling.  Busch  records 
that  the  impression  of  an  engraving,  with  all  its  details,  remained  on  his  eye  for  17  minutes." 
(Goc-lke.) 

Experiments  and  Apparatus  for  Positive  After  Images. — i.  When  a  burning  stick  is 
rapidly  rotated  it  appears  as  a  fiery  circle. 

2.  The  thaumatrope  of  Paris. 

3.  The  phanakistoscope  (Plateau']  or  the  stroboscopic  disks  (S/ampfir).  Upon  a  disk  or  a 
cylinder  a  series  of  objects  art-  so  depicted  that  successive  drawings  represent  individual  factors  of 
one  continuous  movement.  On  looking  through  an  opening  at  such  a  disk  rotated  rapidly,  we  see 
pictures  of  the  different  phases  moving  so  quickly  that  the  one  rapidly  follows  the  one  in  front  of 
it.  As  the  impression  of  the  one  picture  remains  until  the  following  one  takes  its  place,  it  has  the 
appearance  as  if  the  successive  phases  of  the  movement  are  continuous,  and  are  one  and  the  same 
figure.  The  apparatus  under  the  name  of  zoetrope,  which  is  extensively  used  as  a  toy,  is  generally 
stated  to  have  been  invented  in  1S32.  It  was  described  by  Cardanus  in  1550.  It  may  be  used  to 
represent  certain  movements,  f.  g.,  of  the  spermatozoa  and  ciliary  motion  (Puriinje  and  Vatentin), 
the  movements  of  the  heart  and  those  of  locomotion. 

[Illusions  of  Motion. — Silvanus  P.  Thompson  points  out  that  if  a  series  of  concentric  circles 
in  b'ack  and  white  be  made  on  paper,  and  the  sheet  on  which  the  circles  are  drawn  be  moved  with 


NEGATIVE    AFTER    IMAGES IRRADIATION. 


797 


a  motion  as  if  one  were  rinsing  out  a  pail,  but  with  a  very  minute  radius,  then  all  the  circles  appear 
to  rotate  with  the  same  angular  velocity  as  that  imparted.  Professor  Thompson  has  contrived  other 
forms  of  this  illusion,  in  the  form  of  Strobic  disks.] 

4.  The  color  top  contains  on  the  sectors  of  its  disk  the  colors  which  are  to  be  mixed.  As  the 
color  of  each  sector  leaves  a  condition  of  excitation  for  the  whole  duration  of  a  revolution,  all  the 
colors  must  be  perceived  simultaneously,  ;.  <?.,  as  a  mixed  color. 

Negative  After  Images. — Occasionally,  when  the  stimulation  of  the  retina 
is  strong  and  very  intense,  a  "  negative,"  instead  of  a  positive,  after  image  appears. 
In  a  negative  after  image,  the  bright  parts  of  the  object  appear  dark,  and  the 
co/ored  parts  in  their  corresponding  contrast  colors  (p.  791). 

Examples  of  Negative  After  Images. — After  looking  for  a  long  time  at  a  dazzlinglyillumi- 
nated  white  window,  on  closing  the  eyes  we  have  the  impression  of  a  bright  cross,  or  crosses,  as  the 
case  may  be,  with  dark  panes. 

Negative  colored  after  images  are  beautifully  shown  by  NSrrenberg's  apparatus.  Look  steadily 
at  a  colored  surface,  e.  g.,  a  yellow  board  with  a  small  blue  square  attached  to  the  centre  of  its 
surface.  A  white  screen  is  allowed  to  fall  suddenly  in  front  of  the  board ;  the  while  surface  now 
has  a  bluish  appearance,  with  a  yellow  square  in  its  centre. 

The  usu.1l  explanation  of  dark  negative  after  images  is,  that  the  retinal  elements  are  fatigued 
by  the  light,  so  that  for  some  time  they  become  less  excitable,  and,  consequently,  light  is  but  ftebly 
perceived  in  the  corresponding  areas  of  the  retina ;  hence  darkness  prevails. 

Fk;.  497. 


Fig.  49S. 


The  cones  of  the  retina  and  pigment  cells  (of  ihe 
frog)  as  affected  by  light  and  darkness  :  i.  After 


:  cones  ol  trie  retina  ana  pigmen 
frog)  as  affected  by  light  and  dark 

two  days  in  darkness  ;   2.  After  t 

daylight. 

Hering  explains  the  dark  after  images  as  due  to  a  process  of  assimilation  in  the  black-white  visual 
substance.  In  explaining  colored  after  images,  the  Voung-Helmholtz  theory  assumes  that,  under 
the  action  of  the  light  waves,  e.  g.,  red,  the  retinal  elements  connected  with  the  perception  of  this 
color  are  paralyzed.  On  now  looking  suddenly  on  a  white  surface,  the  mixture  of  all  the  colors 
appears  as  white  minus  red,  i.e.,  the  white  appears  ^i,')-t'f«.  In  bright  daylight  the  contrast  color  lies 
\ery  near  the  complementary  color.  According  to  Jlering,  the  contrast  after  image  is  explained  by  the 
assimilation  of  the  corresponding  colored  visual  substance,  in  this  case,  of  the  "red-green"  [\  397). 

Not  unfrequently,  after  intense  stimulation  of  the  retina,  positive  and  negative 
after  images  alternate  with  each  other  until  they  gradually  fuse.  After  looking  at 
the  dark-red  setting  sun  we  see  alternate  disks  of  red  and  green. 

The  phenomena  of  contrast  undergo  some  modification  in  the  peripheral  areas 
of  the  retina,  owing  to  the  partial  color  blindness  which  occurs  in  these  areas 
(^Adamiick  and  IVoinow). 

Irradiation  is  the  term  applied  to  certain  phenomena  where  we  form  a  false 
estimate  of  visual  impressions,  owing  to  inexact  accommodation.  If  from  ine.xact 
accommodation  the  margins  of  the  object  are  projected  upon  the  retina  in  diffu- 
sion circles,  the  mind  tends  to  add  the  undefined  margin  to  those  parts  of  the 
visual  image  which  are  most  prominent  in  the  image  itself.    \V  hat  is  bright  appears 


798  EXAMPLES   OF   CONTRAST. 

larger  (Fig.  498)  and  overcomes  what  is  dark,  while  an  object,  without  reference 
to  brightness  or  color,  has  the  same  relation  to  its  background.  When  the  accom- 
modation is  quite  accurate  the  phenomenon  of  irradiation  is  not  present. 

"  A  dark  object  appears  smaller  than  a  bright  one  of  the  same  size.  On  looking  at  the  same  time 
from  a  certain  distance  at  two  circles  of  the  same  size,  a  white  one  on  a  black  background,  and  a 
black  on  a  white  background,  we  estimate  tlie  latter  to  lie  about  one  fifth  less  than  the  former  (Fig. 
49S).  On  making  the  black  circle  onefifth  larger,  they  will  appear  equal.  Tycho  de  Hrahe  re- 
marks that  the  moon,  when  in  conjunction  (dark),  appears  to  be  one-fifth  smaller  than  in  opposition 
(full,  bright).  The  lirst  lunar  crescent  appears  to  belong  to  a  larger  disk  than  the  dark  one  adjoin- 
ing it,  which  can  occasionally  be  distinguished  at  the  time  of  the  new  light.  Black  clothes  make 
persons  appear  to  be  much  smaller  than  light  clothes.  A  light  seen  behind  a  margin  gives  the 
appearance  of  a  cut  in  the  margin.  A  ruler,  behind  which  is  placed  a  lighted  candle,  appears  to  the 
observer  to  have  a  notch  in  it.  The  sun,  when  rising  and  setting,  appears  to  make  a  depression  in 
the  horizon"  ( Goethe). 

Simultaneous  Contrast. — By  this  term  is  meant  a  phenomenon  like  the  fol- 
lowing :  When  bright  and  dark  parts  are  present  in  a  picture  at  the  same  time, 
the  bright  (white)  parts  always  appear  to  be  more  intensely  bright  the  less  white 
there  is  near  them,  or,  what  is  the  same  thing,  the  darker  the  surroundings,  and, 
conversely,  they  appear  less  bright  the  more  white  tints  that  are  present  near  them. 
A  similar  phenomenon  occurs  with  colored  pictures.  A  color  in  a  picture  appears 
to  us  to  be  more  intense  the  less  of  this  color  there  is  in  the  adjoining  parts,  that 
is,  the  more  the  surroundings  resemble  the  tints  of  the  contrast  color.  Simulta- 
neous contrast  arises  from  simultaneous  impressions  occurring  in  two  adjoining  and 
different  parts  of  the  retina. 

Examples  of  Contrast  for  Bright  and  Dark. — i.  Look  at  a  white  network  on  a  black 
ground;  the  parts  where  the  white  lines  intersect  appear  darker,  because  there  is  least  black  near 
them. 

2.  Look  at  a  point  of  a  small  strip  of  dark  gray  paper  in  front  of  a  dark  black  background.  Push 
a  large  piece  of  white  paper  between  the  strip  and  the  background  ;  the  strip  on  the  white  ground 
now  appears  to  be  much  darker  than  before.  On  again  removing  the  white  paper,  the  strip  at  once 
again  appears  bright  [Hering). 

3.  Look  with  both  eyes  toward  a  grayish-white  surface,  e.g.,  the  ceiling  of  a  room.  After  gazing 
for  some,  place  in  front  of  the  eye  a  paper  tube  eight  inches  long,  and  an  inch  to  an  inch  and  a  quar- 
ter in  diameter,  blackened  in  the  inside.  The  part  of  the  ceiling  seen  through  the  tube  appears  as  a 
round  white  spot  (LanJois). 

Examples  for  Colors.  — l.  Place  a  piece  of  gray  paper  on  a  red,  yellow,  or  blue  ground  ;  the 
contra>t  colors  appear  at  once,  viz.,  green,  blue,  or  yellow.  The  phenomenon  is  made  still  more 
distinct  by  covering  the  whole  with  transparent  tracing  paper  [Herm.  Meyer).  Under  similar  cir- 
cumstances, printed  matter  on  a  colored  ground  appears  in  its  complementary  color  ( W.  v.  BezolJ). 

2.  An  air  bubble  in  the  strongly  tinged  field  of  vision  of  a  thick  microscopical  preparation  appears 
with  an  intense  contrast  color  [LanJois). 

3.  Paste  four  green  sectors  upon  a  rotatory  white  disk,  leave  a  ring  round  the  centre  of  the  disk 
uncovered  by  green,  and  cover  it  with  a  black  strip.  On  rotating  such  a  disk  the  black  part  appears 
red  and  not  gray  [Briicke). 

4.  Look  with  both  eyes  toward  a  grayish-whke  surface,  and  place  in  front  of  one  eye  a  tube  about 
the  length  and  breadth  of  a  finger,  composed  of  transparent  oiled  paper,  gummed  together  to  such 
thickness  as  will  permit  light  to  pass  through  its  walls.  The  part  of  the  surface  seen  through  the 
tube  appears  in  its  contrast  color.  The  experiment  also  shows  the  contrast  in  the  intensity  of  the 
illumination  [Landois).  A  white  piece  of  paper,  with  a  round  black  spot  in  its  centre,  when  looked 
at  through  a  blue  glass,  appears  blue  with  a  black  spot.  If  a  white  spot  of  the  same  size  on  a  black 
ground  be  placed  in  front,  so  that  it  is  reflected  in  the  glass  plate  and  just  covers  the  black  spot,  it 
shows  the  contrast  color  yellow  (Ragona  Scina). 

5.  The  colored  shadows  also  belong  to  the  group  of  simultaneous  contrasts.  "  Two  conditions 
are  necessary  for  the  production  of  colored  shadows — firstly,  that  the  light  gives  some  kind  of  a  color 
to  the  white  surface;  second,  that  the  shadow  is  illuminated,  to  a  certain  extent,  by  another  light. 
During  the  twilight,  place  a  short  lighted  candle  on  a  white  surface,  between  it  and  the  fading  day- 
light hold  a  pencil  vertically,  so  that  the  shadow  thrown  by  the  candle  is  illuminated,  but  not  abol- 
ished, by  the  feeble  daylight ;  the  shadow  appears  of  a  beautiful  blue.  The  blue  shadow  is  easily 
seen,  but  it  requires  a  little  attention  to  observe  that  the  white  paper  acts  like  a  reddish-yellow  sur- 
face, whereby  the  blue  color  apparent  to  the  eye  is  improved.  One  of  the  most  beautiful  cases  of 
colored  shadows  is  seen  in  connection  with  the  full  moon.  The  light  of  the  candle  and  that  of  the 
moon  can  be  completely  equalized.  Both  shadows  can  be  obtained  of  equal  strength  and  distinct- 
ness, so   that  both  colors  are  completely  balanced.     Place  the  plate  opposite  the  light  of  the  moon. 


MOVEMENTS   OF    THE    EYEBALLS.  799 

the  lighted  candle  a  little  to  one  side  at  a  suitable  distance.  In  front  of  the  plate  hold  an  opaque 
body,  when  a  doulile  shadow  appears,  the  one  thrown  by  the  moon  and  lighted  by  the  candle  being 
bright  reddish-yellow  ;  and,  conversely,  the  one  thrown  by  the  candle  and  lighted  by  the  moon  ap- 
pears of  a  beautiful  blue.     Where  the  two  shadows  come  together  and  unite  is  black  ( Goethe). 

6.  "  Take  a  plate  of  green  grass  of  considerable  thickness  and  hold  it  so  as  to  get  the  bars  of  a 
window  reflected  in  it,  the  bars  will  be  seen  double.;  the  image  formed  by  the  under  surface  of  the 
glass  being  green,  while  the  image  coming  from  the  under  surface  of  the  glass,  and  which  ought 
really  to  be  colorless,  appears  to  be  purple.  The  experiment  may  be  performed  with  a  vessel  filled 
with  water,  with  a  mirror  at  its  base.  With  pure  water  colorless  images  are  obtained,  while  by  col- 
oring the  water  colored  images  are  produced  "  [GoelJie). 

Explanation  of  Contrast. — Some  ot  these  phenomena  may  be  explained  as  due  to  an  error  of 
judgment.  During  the  simultaneous  action  of  several  impressions,  the  judgment  errs,  so  that  when 
an  effect  occurs  at  one  place,  this  acts  to  the  slightest  extent  in  the  neighboring  parts.  When,  there- 
fore, brightness  acts  upon  a  part  of  the  retina,  the  judgment  ascribes  the  smallest  possible  action  of 
the  brightness  to  the  adjoining  parts  of  the  retina.  It  is  the  same  with  colors.  It  is  far  more  prob- 
able that  the  phenomena  are  to  be  referred  to  actual  physiological  processes  {//e>inf).  Partial  stim- 
ulation with  light  affects  not  only  the  part  so  acted  on,  but  also  the  surrounding  area  of  the  retina; 
the  part  directly  excited  undergoing  increased  i/isassimilalion,  the  (indirectly  stimulated)  adjoining 
area  undergoing  increased  assimilation  ;  the  increase  of  the  latter  is  greatest  in  the  immediate 
neighborhood  of  the  illuminated  portion,  and  rapidly  diminishes  as  the  distance  from  it  increases. 
By  the  increase  of  the  assimilation  in  those  parts  not  acted  on  by  the  image  of  the  object,  this  is 
prevented,  so  that  the  diffused  light  is  perceived.  The  increase  of  the  assimilation  in  the  immediate 
neighborhood  of  the  illuminated  spot  is  greatest,  so  that  the  perception  of  this  relatively  stronger 
different  light  is  largely  rendered  impossible  (Hering). 

Successive  Contrast. — Look  for  a  long  time  at  a  dark  or  bright  object,  or  at  a  colored  {e.g., 
red)  one,  and  then  allow  the  effect  of  the  contrast  to  occur  on  the  retina,  i.e.,  with  reference  to  the 
above,  bright  and  dark,  or  the  contrast  color  green,  then  these  become  very  intense.  This  phe- 
nomenon has  also  been  called  "  successive  contrast."  In  this  case  the  negative  after  image  obviously 
plays  a  part. 

[Some  drugs  cause  subjective  visual  sensations,  but  these  do  so  by  acting  on  the  brain,  e.g., 
alcohol,  as  in  delirium  tremens,  cannabis  indica,  sodic  salicylate  and  large  doses  of  digitalis 
(Brunton).'] 

399.  MOVEMENTS  OF  THE  EYEBALLS— EYE  MUSCLES.— 

The  globular  eyeball  is  capable  of  extensive  and  free  movement  on  the  corre- 
spondingly excavated  fatty  pad  of  the  orbit,  just  like  the  head  of  a  long  bone  in 
the  corresponding  socket  of  a  freely  movable  arthroidal  joint.  The  movements 
of  the  eyeball,  however,  are  limited  by  certain  conditions,  by  the  mode  in  which 
the  eye  muscles  are  attached  to  it.  Thus,  when  one  muscle  contracts,  its  antag- 
onistic muscle  acts  like  a  bridle,  and  so  limits  the  movement;  the  movements  are 
also  limited  by  the  insertion  of  the  optic  nerve.  The  soft  elastic  pad  of  the  orbit 
on  which  the  eyeball  rests  is  itself  subject  to  be  moved  forward  or  backward,  so 
that  the  eyeball  also  must  participate  in  these  movements. 

Protrusion  of  the  eyeball  takes  place — i.  By  congestion  of  the  blood  vessels,  especially  of  the 
veins  in  the  orbit,  such  as  occurs  when  the  outflow  of  the  venous  blood  from  the  head  is  interfered 
with,  as  in  cases  of  hanging.  2.  By  contraction  of  the  smooth  muscular  fibres  in  Tenon's  cap- 
sule, in  the  spheno-maxillary  fissure,  and  in  the  eyelids  (J  404),  which  are  innervated  by  the  cer- 
vical sympathetic  nerve.  3.  By  voluntary  forced  opening  of  the  palpebral  fissure,  whereby  the 
pressure  of  the  eyelids  acting  on  the  eyeball  is  diminished.  4.  By  the  action  of  the  oblique 
muscles,  which  act  by  pulling  the  eyeball  inward  and  forward.  If  the  superior  oblique  be  con- 
tracted when  the  eyelids  are  forcibly  opened,  the  eyeball  may  be  protruded  about  I  mm.  When 
protrusion  of  the  eyeball  occurs  p,-ithologically  (as  in  I  and  2),  the  condition  is  called  exoph- 
thalmos. 

Retraction  of  the  eyeball  is  the  opposite  condition,  and  is  caused — i.  By  closing  the  eyelids 
forcibly.  2.  By  an  empty  condition  of  the  retrobulbar  blood  vessels,  diminished  succulence,  or  dis- 
appearance of  the  tissue  of  the  orbit.  3.  Section  of  the  cervical  sympathetic  in  dogs  causes  the 
eyeball  to  sink  somewhat  in  the  orbit.  The  smooth  muscular  fibres  of  Tenon's  capsule  are  perhaps 
antagonistic  in  their  action  to  the  four  recti  when  acting  together,  and  thus  prevent  the  eyeball  from 
being  drawn  too  far  backward.  Many  animals  have  a  special  retractor  bulbi  muscle,  e.g.  amphi- 
bians, reptiles  and  many  mammals ;  the  ruminants  have  four. 

The  movements  of  the  eyes  are  almost  always  accompanied  by  similar  move- 
ments of  the  head,  chiefly  on  looking  upward,  less  so  on  looking  laterally,  and 
least  of  all  when  looking  downward. 


800  POSITIONS   OF   THE    EYEBALL. 

The  difficult  inve^ti^rations  on  the  movements  of  the  eyelialls  have  been  carried  out,  especially  by 
Listing,  Meissner,  Helmholtz,  Donders,  A.  ?"ick  and  E.  Hering. 

Axis. — All  the  movements  of  the  eyeball  take  place  round  its  point  of  rotation  (Fig.  499,  0), 
which  lies  1.77  mm.  behind  the  centre  of  the  visual  axis,  or  10.957  mm.  from  the  vertex  of  the 
cornea  [Domidrs).  In  order  to  determine  more  carefully  the  movements  of  the  eyeball,  it  is  neces- 
sary to  have  certain  definite  data  :  i.  The  visual  axis  (S,  S^),  or  the  antero-posterior  axis  of  the 
eyeball,  unites  the  point  of  rotation  with  the  fovea  centralis,  and  is  continued  straight  forward  to 
the  vertex  of  the  cornea.  2.  The  transverse,  or  horizontal  axis  (Q,  Q^),  is  the  straight  line  con- 
necting the  points  of  rotation  of  both  eyes  and  its  extension  outward.  Of  course,  it  is  at  right 
angles  to  I.  3.  The  vertical  axis  passes  vertically  through  the  point  of  rotation  at  right  angles  to 
1  and  2.  These  three  axes  form  a  coordinate  system.  We  must  imagine  that  in  the  orbit  there  is 
a  fixed  determinate  axial  system,  whose  point  of  intersection  corresponds  with  the  point  of  rotation 
of  the  eyeball.  When  the  eye  is  at  rest  (primary  position),  the  three  axes  of  the  eyeball  completely 
coincide  with  the  three  axes  of  the  coordinate  .-ystem  in  the  orbit.  When  the  eyeball,  however,  is 
moved,  two  or  more  axes  are  displaced  from  this,  so  that  they  must  form  angles  with  the  fixed 
orbital  system. 

Planes. — In  order  to  be  more  exact,  and  also  partly  for  further  estimations,  let  us  suppose  three 
planes  passing  through  the  eyeball,  and  that  their  position  is  secured  by  any  two  axes.  i.  The 
horizontal  plane  divides  the  eyeball  into  an  upper  and  lower  half;  it  is  determined  by  the  visual 
transverse  axes.  In  its  course  through  the  retina  it  forms  the  horizontal  line  of  separation  of  the 
latter ;  the  coats  of  the  eyeball  itself  cut  it  in  their  horizontal  meridian.  2.  The  vertical  plane 
divides  the  eyeball  into  an  inner  and  outer  half;  it  is  determined  by  the  visual  and  vertical  axes. 
It  cuts  the  retma  in  the  vertical  line  of  separation  of  the  latter  and  the  periphery  of  the  bulb  in  the 
vertical  meridian  of  the  eyeball.  3.  The  equatorial  plane  divides  the  eyeball  into  an  anterior  and 
posterior  half;  its  position  is  determined  by  the  vertical  and  transverse  axes,  and  it  cuts  the 
sclerotic  in  the  equator  of  the  eyeball.  The  horizontal  and  vertical  lines  of  separation  of  the 
retina,  which  intersect  in  the  fovea  centralis,  divide  the  retma  into  four  quadrants. 

In  order  to  define  more  precisely  the  movements  of  the  eyeball,  v.  Helmholtz  has  introduced  the 
following  terms:  He  calls  the  straight  line  which  connects  the  point  of  rotation  of  the  eye  with  the 
fixed  point  in  the  outer  world  the  visual  line  ("Blicklinie"),  while  a  plane  passing  through  these 
lines  in  both  eyes  he  called  the  visual  plane  ;  the  ground  line  of  this  plane  is  the  line  uniting  the 
two  points  of  rotation,  viz.,  the  transverse  axis  of  the  eyeball.  Suppose  a  sagittal  section  to  be  made 
through  the  head,  so  as  to  .divide  the  latter  into  a  right  and  left  half,  then  this  plane  would  halve  the 
ground  line  of  the  visual  plane,  and  ivhen  prolonged  forward  would  intersect  the  visual  plane  in 
the  median  line.  The  visual  point  of  the  eye  can  be  (i)  raised  or  lowered — the  field  which  it 
traverses  being  called  the  visual  held  (•'  Blickfeld  ") ;  it  is  part  of  a  spherical  surface  with  the  point 
of  rotation  of  the  eye  in  its  centre.  Proceeding  from  the  primary  position  of  both  eyes,  which  is 
characterized  by  both  visual  lines  being  parallel  with  each  other  and  horizontal,  then  the  elevation 
of  the  visual  plane  can  be  determined  by  the  angle  which  this  forms  with  the  plane  of  the  primary 
position.  This  angle  is  called  the  angle  of  elevation — it  is  positive  when  the  visual  plane  is  raised 
(to  the  forehead),  and  negative  when  it  is  lowered  (chinwards).  (2)  From  the  primary  position, 
the  visual  line  can  be  turned  laterally  in  the  visual  plane.  The  extent  of  this  lateral  deviation  is 
measured  by  the  angle  of  lateral  rotation,  i.e.,  by  the  angle  which  the  visual  line  forms  with  the 
median  line  of  the  visual  plane  ;  it  is  said  to  be  positive  when  the  posterior  part  of  the  visual  line 
is  turned  to  the  right,  negative  when  to  the  left.     The  following  are  the  positions  of  the  eyeball: — 

1.  Primary  position,  in  which  both  the  lines  of  vision  are  parallel  with  each 
other,  and  the  visual  planes  are  horizontal.  The  three  axes  of  the  eyeball  coin- 
cide with  the  three  fixed  axes  of  the  coordinate  system  in  the  orbit. 

2.  Secondary  positions  are  due  to  movements  of  the  eye  from  the  primary 
position.  There  are  two  different  varieties :  ((7)  where  the  visual  lines  are  par- 
allel, but  are  directed  uptvani  or  downward.  The  transverse  axis  of  both  eyes 
remains  the  same  as  in  the  primary  position  \  the  deviations  of  the  other  two  axes 
expressed  by  the  amount  of  the  angle  of  elevation  of  the  line  of  vision.  (J)) 
The  second  variety  of  the  secondary  position  is  produced  by  the  convergence  or 
divergence  of  the  lines  of  vision.  In  this  variety  the  vertical  axes,  round  which 
the  lateral  rotation  takes  place,  remain  as  in  the  primary  position  ;  the  other  axes 
form  angles;  the  amount  of  the  deviation  is  expressed  by  the  "angle  of  lateral 
rotation."  The  eye,  when  in  the  primary  position,  can  be  rotated  from  this  posi- 
tion 42°  outward,  45°  inward,  34°  upward  and  57°  downward  (Schuunnann'). 

3.  Tertiary  position  is  the  position  brought  about  by  the  movements  of  the 
eye,  in  which  the  lines  of  vision  are  convergent,  and  are  at  the  same  time  inclined 
upward  or  downward. 

All  the  three  axes  of  the  eye  are  no  longer  coincident  with  the  axes  in  the  pri- 


OCULAR    MUSCLES.  801 

mary  position.  The  exact  direction  of  the  visual  lines  is  determined  by  the 
amount  of  the  angle  of  lateral  rotation  and  the  angle  of  elevation.  There  is  still 
another  important  point.  The  eyeball  is  always  rotated  at  the  same  time  round 
the  line  of  vision  and  round  its  axis  (  Volkmann,  Hering,  Danders).  As  the  iris 
rotates  round  the  visual  line  like  a  wheel  round  its  axis,  this  rotation  is  called 
"  circular  rotation  "  {"Raddfehung")  of  the  eye,  which  is  always  connected  with 
the  tertiary  positions.  Even  oblique  movements  may  be  regarded  as  composed 
of — (i)  a  rotation  round  the  vertical  axis,  and  (2)  round  the  transverse  axis  ;  or 
it  may  be  referred  to  rotation  round  a  single  constant  axis  placed  between  the 
above-named  axes,  passing  through  the  point  of  rotation  of  the  eyeball,  and  at 
right  angles  to  the  secondary  and  primary  direction  of  the  visual  axis  (line  of 
vision) — (Listing).  The  amount  of  circular  rotation  is  measured  by  the  angle 
which  the  horizontal  separation  line  of  the  retina  forms  with  the  horizontal  sepa- 
ration line  of  the  retina  of  the  eye  in  the  primary  position.  This  angle  is  said  to 
be  positive,  when  the  eye  itself  rotates  in  the  same  direction  as  the  hand  of  a 
watch  observed  by  the  same  eye,  i.e.,  when  the  upper  end  of  the  vertical  line  of 
separation  of  the  retina  is  turned  to  the  right. 

According  to  Donders,  the  angle  of  rotation  increases  with  the  angle  of  elevation  and  the  angle 
of  lateral  rotation — it  may  exceed  10°.  With  equally  great  elevation  or  depression  of  the  visual 
plane,  the  rotation  is  greater  the  greater  the  elevation  or  depression  of  the  line  of  vision. 

On  looking  upward  in  the  tertiary  position,  the  upper  ends  of  the  vertical  lines  of  separation  of 
the  retina  dh'erge  ;  on  looking  downward  they  converge.  If  the  visual  plane  be  raised,  the  eye, 
when  it  deviates  laterally  to  the  right,  makes  a  circular  rotation  to  the  left.  When  the  visual  plane 
is  depressed,  on  deviating  the  eye  to  the  right  or  left,  there  is  a  corresponding  circular  rotation  to 
the  right  or  left.  Or  we  may  express  the  result  thus  :  When  the  angle  of  elevation  and  the  angle 
of  deviation  have  the  same  sign  (-f-  or — ),  then  the  rotation  of  the  eyeball  is  negative;  when, 
however,  the  signs  are  unequal,  the  rotation  is  positive.  In  order  to  make  the  circular  rotation 
visible  in  one's  own  eye,  accommodate  one  eye  lor  a  surface  divided  by  vertical  and  horizontal  lines 
until  a  positive  after  image  is  produced,  and  then  rapidly  rotate  the  eye  into  the  third  position.  The 
lines  of  the  after  image  then  form  angles  with  the  lines  of  the  background.  As  the  position  of  the 
vertical  meridian  of  the  eye  is  important  from  a  practical  point  of  view,  it  is  necessary  to  note  that, 
in  the  primary  and  secondary  positions  of  the  eyes,  the  vertical  meridian  retains  its  vertical  position. 
On  looking  to  the  left  and  upward,  or  to  the  right  and  downward,  the  vertical  meridians  of  both 
eyes  are  turned  to  the  left ;  conversely,  they  are  turned  to  the  right  on  looking  to  the  left  and  down- 
ward, or  to  the  right  and  upward. 

In  the  secondary  positions  of  the  eye,  rotation  of  the  axis  of  the  eye  never  occurs  iListing). 
Very  slight  rolling  of  the  eyes  occurs,  however,  when  the  head  is  inclined  toward  the  shoulder,  and 
in  the  direction  opposite  to  that  of  the  head  {Jaral  j — it  is  about  1°  for  every  10°  of  inclination  of 
the  head  (Sir^/ii/ziy,  iVagel). 

Ocular  Muscles. — The  movements  of  the  eyeball  are  accomplished  by 
means  of  the  four  straight  and  two  oblique  ocular  muscles.  In  order 
to  understand  the  action  of  each  of  these  muscles,  we  must  know  the  plane 
of  traction  of  the  muscles  and  the  axis  of  rotation  of  the  eyeball.  The 
plane  of  traction  is  found  by  the  plane  lying  in  the  middle  of  the  origin 
and  insertion  of  the  muscle  and  the  point  of  rotation  of  the  eyeball.  The 
axis  of  rotation  is  always  at  right  angles  to  the  plane  of  traction  in  the 
point  of  rotation  of  the  eyeball. 

The  rectus  internus  (I)  and  externus  (E)  rotate  the  eye  almost  exactly 
inward  and  outward  (Fig.  499).  'Ihe  plane  of  traction  lies  in  the  plane  of  the 
paper  ;  Q,  E,  is  the  direction  of  the  traction  of  the  external  rectus,  Qi,  I,  that  of 
the  internal.  The  axis  of  rotation  is  in  the  point  of  rotation,  O,  at  right  angles 
to  the  plane  of  the  paper,  so  that  it  coincides  with  the  vertical  axis  of  the  eyeball. 
2.  The  axis  of  rotation  of  the  R.  superior  and  inferior  (the  dotted  line,  R. 
sup.,  R.  inf.),  lies  in  the  horizontal  plane  of  separation  of  the  eye,  but  it  forms 
an  angle  of  about  20°  with  the  transverse  axis  ( (^,  Q^) ;  the  direction  of  the 
traction  for  both  muscles  is  indicated  by  the  line,  s,  i.  By  the  action  of  these 
muscles,  the  cornea  is  turned  upward  and  slightly  inward,  or  downward  and 
slightly  inward.  3.  The  axis  of  rotation  of  both  obliiiue  muscles  (the  dotted 
51 


802 


OCULAR    MUSCLES. 


lines,  Obi.  sup.  and  Obi.  inf.)  also  lies  in  the  horizontal  plane  of  separation 
of  the  eyeball,  and  it  forms  an  angle  of  60°  with  the  transverse  axis.  The 
direction  of  the  traction  of  the  inferior  oblique  gives  the  line,  a,  b ;  that  of 
the  superior,  the  line,  c,  d.  The  action  of  these  muscles,  therefore,  is  in  the 
one  case  to  rotate  the  cornea  outward  and  upward,  and  in  the  other  outward 
and  downward.  These  actions,  of  course,  only  obtain  when  the  eyes  are 
in  the  primary  position — in  every  other  position  the  axis  of  rotation  of  each 
muscle  changes. 

When  the  eyes  are  at  rest,  the  muscles  are  in  equilibrium.  Owing  to  the  power 
of  the  internal  recti,  the  visual  axes  converge  and  would  meet,  if  prolonged  40 
centimetres  in  front  of  the  eye.     In  the  movements  of  the  eyeball,  one,  two,  or 


^^.v*^^ 


'>? 


three  muscles  may  be  concerned.  One  muscle  acts  only  when  the  eye  is  moved 
directly  outward  or  inward,  especially  the  internal  and  external  rectus.  Two 
muscles  act  when  the  eyeball  is  moved  directly  upward  (superior  rectus  and 
inferior  oblique),  or  downward  (inferior  rectus  and  superior  oblique).  Three 
muscles  are  in  action  when  the  eyeballs  take  a  diagonal  direction,  especially 
for  inward  and  upward,  by  the  internal  and  the  superior  rectus  and  inferior 
oblique ;  for  inward  and  downward,  the  internal  and  inferior  rectus  and 
superior  oblique ;  for  outward  and  downward,  the  external  and  inferior  rectus 
and  superior  oblique ;  for  outward  and  upward,  the  external  and  superior 
rectus  and  inferior  oblique. 


IDENTICAL   POINTS   OF   THE   RETINA.  803 


[The  following  table  shows  the  action  of  the  muscles  of  the  eyeball : — 

Inward. Rectus  internus. 

Outward Rectus  externus. 

„         J  j  Rectus  superior. 

^^  \  Obliquus  inferior. 

Rectus  inferior. 
Obliquus  superior 
(  Rectus  internus. 


Downward I 


{Rectus  internus. 
Rectus  inferior. 
Obliquus  superior. 
Rectus  externus. 
Outward  and  upward  .  X  Rectus  superior. 
Obliquus  inferior. 
I  Rectus  externus. 


■{i 


Inward  and  Upward  .    .  .j  Rectus  superior.        |     Outivard  and  downward.  I  Rectus  inferior. 

( Obliquus  inferior.      [  (Obliquus  superior.] 

Ruete  imitated  the  movements  of  the  eyeballs  by  means  of  a  model,  which  he  called  the  oph- 
thalmotrope 

•  The  size  of  the  eyeball  and  its  length  diminish  with  age.  The  mobility  is  less  in  the  vertical  than 
in  the  lateral  direction,  and  less  upward  than  downward.  The  normal  and  myopic  eye  can  be 
moved  more  outward,  and  the  long-sighted  eye  more  inward,  the  external  and  internal  rectus  act 
most  when  the  eye  is  moved  outward,  the  obliqui  when  it  is  rotated  inward.  An  eye  can  be  turned 
inward  to  a  greater  extent  when  the  other  eye  at  the  same  time  is  turned  outward  than  when  the 
other  is  turned  inward.  During  near  vision,  the  right  eye  can  be  turned  less  to  the  right,  and  the 
left  to  the  left,  than  during  distant  vision  [Ilering). 

Simultaneous  Ocular  Movements.— Both  eyes  are  always  moved  simul- 
taneously. Even  when  one  eye  is  quite  blind,  the  ocular  muscles  move  when  the 
whole  eyeball  is  excited.  When  the  head  is  straight,  the  movements  always  take 
place  so  that  both  visual  planes  (visual  axes)  lie  in  the  same  plane.  In  front  both 
visual  axes  can  diverge  only  to  a  trifling  extent,  while  they  can  converge  consider- 
ably. If  individual  ocular  muscles  are  paralyzed,  the  position  of  the  visual  axis 
in  the  same  place  is  disturbed,  and  s</uinti>ig  results,  so  that  the  patient  no  longer 
can  direct  both  visual  axis  simultaneously  to  the  same  point,  but  he  directs  the 
one  eye  after  the  other.  Even  nystagmus  (p.  738)  occurs  in  both  eyes  simulta- 
neously, and  in  the  same  direction.  The  innate  simultaneous  movement  of  both 
eyes  is  spoken  of  as  an  associated  movement  {Joh.  Aluller).  E.  Hering 
showed  that  in  all  ocular  movements,  there  is  a  uniformity  of  the  innervation  as 
well.  Even  during  such  movements,  in  which  one  eye  apparently  is  at  rest,  there 
is  a  movement,  due  to  the  action  of  two  antagonistic  forces,  the  movements  result- 
ing in  a  slight  to  and  fro  motion  of  the  eyeball. 

The  motor  nerves  of  the  ocular  muscles  are  the  oculomotorius  (§  345),  the  trochlearis  (§  346), 
and  the  abducens  (ji  348).  The  centre  lies  in  the  corpora  quadrigemina,  and  below  it  (|  379),  and 
partly  in  the  medulla  oblongata  (§  379). 

400.  BINOCULAR  VISION.— Advantages.— Vision  with  both  eyes 
affords  the  following  advantages  :  (i)  TVt  field  of  vision  of  both  eyes  is  consider- 
ably larger  than  that  of  one  eye.  {2)  The  perception  o(  depth  is  rendered  easier, 
as  the  retinal  images  are  obtained  from  two  different  points.  (3)  A  more  exact 
estimate  of  the  distance  and  size  of  an  object  can  be  formed,  in  consequence  of 
the  perception  of  the  degree  of  convergence  of  both  eyes.  (4)  The  correction  of 
certain  errors  in  the  one  eye  is  rendered  possible  by  the  other. 

When  the  position  of  the  head  is  fi.xed,  we  can  easily  form  a  conception  as  to  the  form  of  t/if 
entire  field  of  vision  if  we  close  one  eye  and  direct  the  open  eye  inward.  We  observe  that  it  is 
pear-shaped,  broad  above  and  smaller  below,  the  silhouette,  or  profile  of  the  nose,  causes  the  de- 
pression between  the  upper  and  lower  part  of  the  field. 

401.  SINGLE  VISION— IDENTICAL  POINTS— HOROPTER. 
— Identical  Points. — If  we  imagine  the  retin.-e  of  both  eyes  to  be  a  pair  of  hollow 
saucers  placed  one  within  the  other,  so  that  the  yellow  spots  of  both  eyes  coincide, 
and  also  the  similar  qtiadrants  of  the  retince,  then  all  those  points  of  both  retina: 
which  coincide  or  cover  each  other  are  called  "identical"  or  "  correspond- 
ing points  "  of  the  retina.  The  two  meridians  which  separate  the  quadrants 
coinciding  with  each  other  are  called  the  "lines  of  separation."  Ptiysiologi- 
cally,  the  identical  points  are  characterized  by  the  fact  that  when  they  are  both 
simultaneously  excited   by  light,  the  excitement  proceeding   from  them  is,  by  a 


804 


THE    HOROPTER. 


psychical  act,  referred  to  one  and  the  same  point  of  the  field  of  vision,  lying,  of 
course,  in  a  direction  through  the  nodal  point  of  each  eye.  Stimulation  of  both 
identical  points  causes  only  one  image  in  the  field  of  vision.  Hence  all  those 
objects  of  the  external  world,  whose  rays  of  light  pass  through  the  nodal  points 
to  fall  upon  identical  points  of  the  retina,  are  seen  singly,  because  their  images 
from  both  eyes  are  referred  to  the  same  point  of  the  field  of  vision,  so  that 
they  cover  each  other.  All  other  objects  whose  images  do  not  fall  upon  identical 
points  of  the  retina  cause  "  double  vision,"  or  "diplopia." 

Proofs. — If  we  look  at  a  linear  object  with  the  points  1,2,  3,  then  the  corresponding  retinal 
images  are  I,  2,  3  and  I,  2,  3,  which  are,  obviously,  identical  points  of  the  retina;  (Fig.  500).  ]f, 
while  looking  at  this  hne,  there  be  a  point,  A,  nearer  the  eyes,  or  B,  further  from  them,  then,  on 
focussing  for  I,  2,  3,  neither  the  rays  (.\,  a.  A,  a)  coming  from  A,  nor  those  (B,  b,  B,  b)  from  B, 
fall  upon  identical  points ;  hence  A  and  B  appear  double. 

Make  a  point  {e.g.,  2)  with  ink  on  paper;  of  course  the  image  will  fall  upon  both  fovea;  centrales 
of  the  retin.-e  (2,  2),  which,  of  course,  are  identical  points.  Now  press  laterally  upon  one  eye,  so 
as  to  displace  it  slightly;  then  two  points  at  once  appear,  because  the  image  of  the  point  no  longer 
falls  upon  the  fovea  centralis  of  the  displaced  eye,  but  on  an  adjoining  non-identical  jiart  of  the 
retina.     When  we  squint  voluntarily  all  objects  appear  double. 


Fig.  500. 

B 


Fig.  501. 


3   b 

dentical  points  of  the 


Horopter  for  the  secondary  positic 
convergence  of  the  visual  axe 


The  vertical  surfaces  of  separation  of  the  retina  do  not  exactly  coincide  with  the  vertical  meri- 
dians. There  is  a  certain  amount  of  divergence  (o.5°-3°),  less  above,  which  varies  in  different 
individuals,  and  it  may  be  in  the  same  individual  at  different  times  (Heriiig,  Donders).  The  hori- 
zontal Imes  of  separation,  however,  coincide.  Images  which  fall  upon  the  vertical  lines  of  separa- 
tion appear  to  be  vertical  to  those  on  the  horizontal  lines,  although  they  are  not  actually  so.  Hence 
the  vertical  lines  of  separation  are  the  apparent  vertical  meridians.  Some  observers  regard  the 
identical  points  of  the  retina  as  an  acquired  arrangement ;  others  regard  it  as  normally  innate. 
Persons  who  have  had  a  squint  from  their  birth  see  singly;  in  these  cases  the  identical  points  must 
be  differently  disposed. 

The  horopter  represents  all  those  points  of  the  outer  world  from  which  rays 
of  light  passing  into  both  eyes  fall  upon  identical  points  of  the  retina,  the  eyes 
being  in  a  certain  position.     It  varies  with  the  different  positions  of  the  eyes. 

1.  In  the  primary  position  of  both  eyes  with  the  visual  axes  parallel,  the  rays  of  direction  pro- 
ceeding from  two  identical  points  of  the  two  retin.-e  are  parallel  and  intersect  only  at  infinity.  Hence 
for  the  primar)'  position  the  horopter  is  a  plane  in  infinity. 

2.  In  the  secondary  position  of  the  eyes  with  converging  visual  axes,  the  horopter  for  the  trans- 
verse lines  of  separation  is  a  circle  which  passes  through  the  nodal  points  of  both  eyes  (Fig.  501, 


STEREOSCOPIC   VISION.  805 

K,  K)  and  through  the  fixed  points  I,  II,  III  [Joh.  Miiller).     The  horopter  of  the  vertical  lines  of 
separation  is  in  this  position  vertical  to  the  plane  of  vision. 

3.  In  the  symmetrical  tertiary  position,  in  which  the  horizontal  and  vertical  lines  of  separation 
form  an  angle,  the  horopter  of  the  vertical  lines  of  separation  is  a  straight  line  inclined  toward  the 
horizon.  There  is  no  horopter  for  the  identical  points  of  the  horizontal  lines  of  separation,  as  the 
lines  of  direction  prolonged  from  the  identical  points  of  these  points  do  not  intersect. 

4.  In  the  unsymmetrical  tertiary  position  (with  rolling)  of  the  eyes,  in  which  the  fixed  point  lies 
at  unequal  distances  from  both  npdal  points,  the  horopter  is  a  curve  of  a  complex  form. 

All  objects,  the  rays  proceeding  from  which  fall  upon  non-identical  points  of 
the  retinae,  appear  double.  We  can  distinguish  ilirecf  ox  crossed  Aov^At  images, 
according  as  the  rays  prolonged  from  the  non-identical  points  of  the  retina  inter- 
sect in  front  or  behind  the  fixed  point. 

Experiment. — Hold  two  fingers — the  one  behind  the  other — before  both  eyes,  .\ccommodate 
for  the  far  one,  and  then  the  near  one  appears  double ;  and  when  we  accommodate  for  the  near 
one,  the  far  one  appears  double.  If,  when  accommodating  for  the  near  one,  the  right  eye  be  closed, 
the  left  (crossed)  image  of  the  far  finger  disappears.  On  accommodating  for  the  far  finger  and 
closing  the  right  eye,  the  right  (direct)  double  image  of  the  near  finger  disappears. 

Double  images  are  referred  to  the  proper  distance  from  the  eyes,  just  as  single 
images  are. 

Neglect  of  Double  Images. — Notwithstanding  the  very  large  number  of 
double  images  which  inust  be  formed  during  vision,  they  do  not  disturb  vision. 
As  a  general  rule,  they  are  "  neglected,"  so  that  the  attention  must,  as  a  rule,  be 
directed  to  them  before  they  are  perceived.     This  condition  is  favored  thus : — 

1.  The  attention  is  always  directed  to  the  point  of  the  field  of  vision  which  is  accommodated  for 
at  the  time.  The  image  of  this  part  is  projected  on  to  both  yellow  spots,  which  are  identical  points 
of  the  retina. 

2.  The  form  and  color  of  objects  on  the  lateral  parts  of  the  retina  are  not  perceived  so  sharply. 

3.  The  eyes  are  always  accommodated  for  those  points  which  are  looked  at.  Hence,  indistinct 
images  with  diffusion  circles  are  always  formed  by  those  objects  which  yield  double  images,  so  that 
they  can  be  more  readily  neglected. 

4.  Many  double  images  lie  so  close  together  that  the  greater  part  of  them,  when  the  images  are 
large,  covers  the  other. 

5.  By  practice,  images  which  do  not  exactly  coincide  may  be  united. 

402.  STEREOSCOPIC  VISION.— On  looking  at  an  object,  both  eyes 
do  not  yield  exactly  similar  iinages  of  that  object — the  images  are  slightly  differ- 
ent, because  the  two  eyes  look  at  the  object  from  two  different  points  of  view. 
With  the  right  eye  we  can  see  more  of  the  side  of  the  body  directed  toward  it, 
and  the  same  is  the  case  with  the  left  eye.  Notwithstanding  this  inequality,  the 
two  images  are  united.  How  two  different  images  are  combined  is  best  under- 
stood by  analyzing  the  stereoscopic  images. 

Let,  in  Fig.  502,  L  and  R  represent  two  such  images  as  are  obtained  with  the  left  and  right  eyes. 
These  images,  when  seen  with  a  stereoscope,  look  like  a  truncated 
pyramid,  which  projects  toward  the  eye  of  the  observer,  as  the 
points  indicated  by  the  same  signs  cover  each  other.  On  measur- 
ing the  distance  of  the  points,  which  coincide  or  cover  each  other 
in  both  figures,  we  find  that  the  distances  A,  a,  B,  b,  C,  r,  D,  d,  are 
equally  great,  and  at  the  same  time  are  the  widest  of  all  the  points 
of  both  figures ;  the  distances  E,  e,  F,/,  G,  g,  H,  h,  are  also  equal, 
but  are  smaller  than  the  former.  On  looking  at  the  coinciding 
hnes  (A,  E,  a,  <-,  and  B,  F,  b,f)  we  observe  that  all  the  points  of 
this  line  which  lie  near  to  A  (2  and  B  b  are  further  apart  than  those 
lying  nearer  E  e  and  Y  f. 

Comparing  these  results  with  the  stereoscopic  image,  .j.^^  s„reoscopic  drawings, 

we  have  the  following  laws   for  stereoscopic  vi- 
sion :    I.  All  those  points  of  two  stereoscopic  images,  and,  of  course,  of  two  retinal 
images  of  an  object,  which  in  both  images  are  equally  distant  from  each  other,  ap- 
pear on  the  same  plane.   2.  AUpoints  which  are  nearer  to  each  other,  compared  with 
the  distance  of  other  points,  appear  to  be  nearer  to  the  observer.     3.  Conversely, 


806 


THEORY   OF   STEREOSCOPIC   VISION. 


all   points  which  lie  further  apart   from  each  other  appear  perspectively  in  the 
background. 

The  cause  of  this  phenomenon  lies  in  the  fact  that,  "  in  vision  with  both  eyes 
we  constantly  refer  the  position  of  the  individual  images  in  the  direction  of  the 
visual  axis  to  where  they  both  intersect." 

Proofs. — The  following  stereoscopic  experiment  (Fig.  503)  proves  this:  Take  both  images  of 
two  pairs  of  points  {a,  b,  and  a,  ;i),  which  are  at  unequal  distances  from  each  other  on  the  sur- 
face of  the  paper.  By  means  of  small,  stereoscopic  prisms  cause  them  to  coincide,  then  the  com- 
bined point,  A  of  a,  and  a  appears  at  a  distance  on  the  plane  of  the  paper,  while  the  other  point, 
B,  produced  by  the  superposition  of  /'  and  ,5,  floats  in  the  air  before  the  observer.  Fig.  503  shows 
how  this  occurs.  The  following  experiment  shows  the  same  result :  Draw  two  figures,  which  are 
to  be  superposed  similar  to  the  lines  B,  A,  A,  E,  I),  a,  and  a,  e,  in  Fig.  502.  In  the  lines  B,  A, 
and  b,  a,  all  the  points  which  are  to  be  superposed  lie  equally  distant  from  each  other,  while,  on  the 
contrary,  all  the  points  in  A,  E,  and  «,  e",  which  lie  nearer  E  and  e^  are  constantly  nearer  to  each 
o'ther.  When  looked  at  with  a  stereoscope,  the  superposed  verticals,  A,  e,  and  B,  b,  lie  in  the  plane 
of  the  paper,  while  the  superposed  lines,  A,  a,  and  E,  e,  project  obliquely  toward  the  observer  from 
the  plane  of  the  paper.     From  these  two  fundamental  experiments  we  may  analyze  all  pairs  of 


Fig.  503. 


Fig.  504. 
I 


of  Brewster's  stereoscope 


Stereoscopic  pictures.     Thus,  in  Fig.  502,  if  we  exchange  the  two  pictures,  so  that  R  lies  in  the 
place  of  L,  then  we  must  obtain  the  impression  of  a  truncated  hollow  pyramid. 

Two  stereoscopic  pictures,  which  are  so  constructed  that  the  one  contains  the  body  from  the 
front  and  above,  and  the  other,  it  from  the  front  and  below  (suppose  in  Fig.  502  the  lines  A  B  and 
a  b  were  the  ground  lines),  can  never  be  superposed  by  means  of  the  stereoscope. 

This  process  has  been  explained  in  another  way.  Of  the  two  figures,  R  and  L 
(Fig.  502),  only  A  B  C  D  and  abed  fall  upon  identical  points  of  the  retina, 
hence  these  alone  can  be  superposed  ;  or,  when  there  is  a  different  convergence 
of  the  visual  axis,  only  E  F  G  H  and  efgh  can  be  superposed  for  the  same 
reason.  Suppose  the  square  ground  surfaces  of  the  figures  are  first  superposed,  in 
order  to  explain  the  stereoscopic  impression,  it  is  further  assumed  that  both  eyes, 
after  superposition  of  the  ground  squares,  are  rapidly  moved  toward  the  apex  of  the 
pyramid.  As  the  axis  of  the  eyes  must  thereby  converge  more  and  more,  the 
apex  of  the  pyramid  appears  to  project ;  as  iril  points  which  require  the  conver- 
gence of  the  eyes  for  their  vision  appear  to  us  to  be  nearer  (see  below).     Thus,  all 


THE   TELESTEREOSCOPE. 


807 


corresponding  parts  of  both  figures  would  be  brought,  one  after  the  other,  upon 
identical  points  of  the  retina  by  the  movements  of  the  eyes  {Bhicke). 

It  has  been  urged  against  this  view  that  the  duration  of  an  electrical  spark 
suffices  for  stereoscopic  vision  {Dove) — a  time  which  is  quite  insufficient  for  the 
movements  of  the  eyes..  Although  this  may  be  true  for  many  figures,  yet  in  the 
correct  combination  of  complex  or  extraordinary  figures,  these  movements  of  the 
visual  axes  are  not  excluded,  and  in  many  individuals  they  are  distinctly  advan- 
tageous. Not  only  the  actual  movements  necessary  for  this  act,  but  the  sensations 
derived  from  the  muscles  are  also  concerned. 

When  two  figures  are  momentarily  combined  to  form  a  stereoscopic  picture, 
there  being  no  movement  of  the  eyes,  clearly  many  points  in  the  stereoscopic 
pictures  are  superposed  which,  strictly  speaking,  do  not  fall  upon  identical  points 
of  the  retina.  Hence  we  cannot  characterize  the  identical  points  of  the  retina 
as  coinciding  mathematically;  but,  from  a  physiological  point  of  view,  we  must 
regard  such  points  as  identical,  which,  as  a  rule,  by  simultaneous  stimulation, 
give  rise  to  a  single  image.  The  mind  obviously  plays  a  part  in  this  combination 
of  images.  There  is  a  certain  psychical  tendency  to  fuse  the  double  images  on 
the  retinas  into  one  image,  in  accordance  with  the  fact  that  we,  from  experience, 


Fig.  505. 


Fig.  506. 


Telestereoscope  of  v.  Helmhohz 


Wheatstone's  Pseudoscope. 


recognize  the  existence  of  a  single  object.  If  the  differences  between  two  stereo- 
scopic pictures  be  too  great,  so  that  parts  of  the  retina  too  wide  apart  are  excited 
thereby,  or  when  new  lines  are  present  in  a  picture,  and  do  not  admit  of  a  stereo- 
scopic effect,  or  disturb  the  combination,  then  the  stereoscopic  effect  ceases. 

The  stereoscope  is  an  in-trument  by  means  of  which  two  somewhat  similar  pictures  drawn  in 
perspective  may  be  superposed  so  that  they  appear  single.  Wheatstone  (183S)  obtained  this  result 
by  means  of  two  mirrors  placed  at  an  angle  (Fig.  504J;  Brewster  (1843)  by  two  prisms  (Fig. 503). 
The  construction  and  mode  of  action  are  obvious  from  the  illustrations. 

Some  pairs  of  two  such  pictures  may  be  combined,  without  a  stereoscope,  by  directing  the  visual 
axis  of  each  eye  to  the  picture  held  opposite  to  it. 

Two  completely  identical  pictures,  ;.  c,  in  which  all  corresponding  points  have  exactly  the  same 
relation  to  each  other,  as  the  same  sides  of  two  copies  of  a  book,  appear  quite  fiat  under  the  stereo- 
scope; as  soon,  however,  as  in  one  of  them  one  or  more  points  alters  its  relation  to  the  corresponding 
points,  this  point  either  projects  or  recedes  from  the  plane. 

Telestereoscope. — When  objects,  placed  at  a  great  distance,  are  looked  at,  e. g.,  the  most  distant 
part  of  a  landscape,  they  appear  to  us  to  be  flat,  as  in  a  picture,  and  do  not  stand  out,  because  the 
slight  differences  of  position  of  our  eyes  in  the  head  are  not  to  be  compared  with  the  great  distance. 
In  order  to  obtain  a  stereoscopic  view  of  such  objects,  v.  Helmholtz  constructed  the  telestereoscope 
(Fig.  505),  an  apparatus  which,  by  mean%of  two  parallel  mirrors,  places,  as  it  were,  the  point  of 
view  of  both  eyes  wider  apart.     Of  the  mirrors,  L  and  R  each  projects  its  image  of  the  landscape 


808  ESTIMATION   OF   SIZE   AND    DISTANCE. 

upon  /  and  r,  to  which  both  eyes.  O,  o,  are  directed.  According  to  the  distance  between  L  and  R, 
the  eyes,  O,  o,  as  it  were,  are  displai'ed  to  O^,  o,.  The  distant  landscape  appears  hke  a  stereo- 
scopic view.  In  order  to  see  distant  parts  more  clearly  and  nearer,  a  double  telescope  or  opera 
glass  may  be  placed  in  front  of  the  eyes  (p   S09). 

Take  two  corresponding  stereoscopic  pictures,  with  the  surfaces  black  in  one  case  and  light  in 
the  other.  Draw  two  truncated  pyramids  like  Fig.  502,  make  one  figure  exactly  like  L,  i.  e.,  with 
a  white  surface  and  black  lines,  and  the  other  with  white  lines  and  a  black  surface,  then  under  the 
stereoscope  such  objects  glance.  The  causing  of  the  glancing  condition  is  that  the  glancing  body 
at  a  certain  distance  reflects  bright  light  into  one  eye  and  not  into  the  other,  because  a  ray  reflected 
at  an  angle  cannot  enter  both  eyes  simultaneously  {Dm'e). 

Wheatstone's  Pseudoscope  consists  of  two  right-angled  prisms  (Fig.  506,  A  and  B)  enclosed 
in  a  tube,  through  which  we  can  look  in  a  direction  parallel  with  the  surfaces  of  the  hypotenuses. 
If  a  spherical  surface  be  looked  at  with  this  instrument,  the  image  formed  in  each  eye  is  inverted 
laterally.  The  right  eye  sees  the  view  usually  obtained  by  the  left  eye, and  conversely;  the  shadow 
which  the  body  in  the  light  throws  upon  a  light  ground  is  reversed.      Hence  the  ball  appears  hollow. 

Struggle  of  the  Fields  of  Vision The  stereoscope  is  also  useful  for  the  following  purpose : 

In  vision  with  both  eyes,  both  eyes  are  almost  never  active  simultaneously  and  to  the  same  extent  ; 
both  undergo  variations,  so  that  first  the  impression  on  the  one  retina  and  then  that  on  the  other  is 
stronger.  If  two  different  surfaces  be  placed  in  a  stereoscope,  then,  especially  when  they  are 
luminous,  these  two  alternate  in  the  general  field  of  vision,  according  as  one  or  other  eye  is  active 
(Piiitiim).  Take  two  surfaces  with  lines  ruled  on  them,  so  that  when  the  surfaces  are  superposed 
the  lines  will  cross  each  other,  then  either  the  one  or  the  other  system  of  lines  is  more  prominent 
(Ptiiiiim).  The  same  is  true  with  colored  stereoscopic  figures,  so  that  there  is  a  contest  or  struggle 
of  the  colored  fields  of  vision. 

403.  ESTIMATION  OF  SIZE  AND  DISTANCE— FALSE  ES- 
TIMATES OF  SIZE  AND  DIRECTION.— Size.— We  estimate  the 
size  of  an  object — apart  from  all  other  factors — from  the  size  of  the  retinal 
image;  thus  the  moon  is  estimated  to  be  larger  than  the  stars.  If,  while  looking 
at  a  distant  landscape,  a  Hy  should  suddenly  pass  across  our  field  of  vision,  near 
to  our  eye,  then  the  image  of  the  fly,  owing  to  the  relatively  great  size  of  the 
retinal  image,  may  give  one  the  itnpression  of  an  object  as  large  as  a  bird.  If, 
owing  to  defective  accommodation,  the  image  gives  rise  to  diffusion  circles,  the 
size  may  appear  to  be  even  greater.  But  objects  of  very  unequal  size  give  equally 
large  retinal  images,  especially  if  they  are  placed  at  such  a  distance  that  they  form 
the  same  visual  angle  (Fig.  465 )  ;  so  that  in  estimating  the  actual  size  of  an 
object,  as  opposed  to  the  apparent  size  determined  by  the  visual  angle,  the 
estimate  of  distance  is  of  the  greatest  importance. 

As  to  the  distance  of  an  object,  we  obtain  some  information  from  the  feeling 
of  accommodation,  as  a  greater  effort  of  the  muscle  of  accomtnodation  is  re- 
quired for  exact  vision  of  a  near  object  than  for  seeing  a  distant  one.  But,  as 
with  two  objects  at  unequal  distances  giving  retinal  images  of  the  same  size,  we 
know  from  experience  that  that  object  is  smaller  which  is  near,  then  that  object  is 
estimated  to  be  the  smaller  for  which,  during  vision,  we  must  accommodate  more 
strongly. 

In  this  way  we  explain  the  following:  A  person  beginning  to  use  a  microscope  always  observes 
with  the  eyes  accommodated  for  a  near  object,  while  one  used  to  the  microscope  looks  through  it 
without  accommodating.  Hence  beginners  always  estimate  microscopic  objects  as  too  small,  and 
on  making  a  drawing  of  them  it  is  too  small.  If  we  produce  an  after  image  in  one  eye,  it  at  once 
appears  smaller  on  accommodating  for  a  near  object,  and  again  becomes  larger  during  negative  ac- 
commodation. If  we  look  with  one  eye  at  a  small  body  placed  as  near  as  possible  to  the  eye,  then 
a  body  lying  behind  it,  but  seen  only  indirectly,  appears  smaller. 

Angle  of  Convergence  of  Visual  Axes. — In  estitiiating  the  size  of  an 
object,  and  taking  into  account  our  estimate  of  its  distance,  we  also  obtain  much 
more  important  information  from  the  degree  of  eonvergence  of  the  visual  axes. 
We  refer  the  position  of  an  object,  viewed  with  both  eyes,  to  the  point  where  both 
visual  axes  intersect.  The  angle  formed  by  the  two  visual  axes  at  this  point  is 
called  the  "angle  of  convergence  of  the  vistial  axes"  {"  Gesichtswinkel").  The 
larger,  therefore,  the  visual  angle,  the  size  of  the  retinal  image  remaining  the  same 
— we  judge  the  object  to  be  nearer.  The  nearer  the  object  is,  it  may  be  the  smaller 


ESTIMATION   OF   DISTANCE. 


809 


in  order  to  form  a  "visual  angle"  of  the  same  size,  such  as  a  distant  large 
object  would  give.  Hence,  we  conclude,  that  with  the  same  apparent  size  (equally 
large  visual  angle,  or  retinal  images  of  the  same  size)  we  judge  that  object  to  be 
smallest  which  gives  the  greatest  convergence  of  the  visual  axes  during  binocular 
vision.  As  to  the  muscular  exertion  necessary  for  this  purpose,  we  obtain  infor- 
mation from  the  muscular  sense  of  the  ocular  muscles. 

Experiments  and  Proofs. — The  Chessboard  Phenomenon  of  H.  Meyer. — i.  If  we  look  at 

a  uniform  chessboard-like  pattern  (tapestry),  then,  when  the  visual  axes  are  directed  directly  for- 
ward, the  spaces  on  the  pattern  appear  of  a  certain  size.  If,  now,  we  look  at  a  nearer  object,  we 
may  cause  the  visual  axes  to  cross,  when  the  pattern  apparently  moves  toward  the  plane  of  the  fixed 
point,  so  that  the  crossed  double  images  are  superposed,  and  the  pattern  at  once  appears  smaller. 

2.  Rollett  looks  at  an  object  through  two  thick  plates  of  glass  placed  at  an  angle.  The  plates  are 
at  one  time  so  placed  that  the  apex  of  the  angle  is  directed  toward  the  observer  (Fig.  507,  II),  at 
another  in  the  reverse  position  (I).  If  both  eyes,/and  i,  are  to  see  the  object  a,  in  I,  then  as 
the  glass  plates  $0  displace  the  rays,  a,  c,  and  a,  g,  as  to  make  them  parallel  with  the  direction  of 
these  rays,  viz.,  f,y.  and  h,  i,  then  the  eyes  must  converge  more  than  when  they  are  turned  directly 
toward  a.  Hence  the  object  appears  nearer  and  smaller,  as  at  a.  In  II,  the  rays,  /'j  t,  and  *,  0, 
from  the  nearer  object  d^,  fall  upon  the  glass  plates.  In  order  to  see  />^,  the  eyes  (k  and  q)  must 
Jivei-ge  more,  so  that  b  appears  more  distant  and  larger. 

Fig.  507. 


®    Q  6 

1  •         n 


I  E 

RoUett's  glass  plate  apparatus, 


Fig.  50S. 


3.  In  looking  through  IVIualstone' s  reflecting  stereoscope  (Fig.  504,  II),  it  is  obvious  that  the 
more  the  two  images  approach  the  observer,  the  more  must  the  observer  converge  his  visual  axes, 
because  the  angles  of  incidence  and  reflexion  are  greater.  Hence  the  compound  picture  now  ap- 
pears to  him  to  be  smaller.  If  the  centre  of  the  image,  R,  recedes  to  Rj,  then  of  course  the  angle, 
S,,,  rp,  is  equal  to  S,,  'Rj,  and  the  same  on  the  left  side. 

4.  In  using  the  telestereoscope,  ihe  two  e\es  are,  as  it  were,  separated  from  each  other,  then,  of 
course,  in  looking  at  objects  at  a  certain  distance,  the  convergence  of  the  visual  axes  must  be  greater 
than  in  normal  vision.  Hence  objects  in  a  landscape  appear  as  in  a  small  model.  But  as  we  are 
accustomed  to  infer  that  such  small  objects  are  at  a  great  distance,  hence  the  objects  themselves  ap- 
pear to  recede  in  the  distance. 

Estimation  of  Distance. — When  the  retinal  images  are  of  the  same  size,  we 
estimate  the  distance  to  be  greater  the  less  the  effort  of  accommodation,  and 
conversely.  In  binocular  vision,  when  the  retinal  images  are  of  the  same  size,  we 
infer  that  that  object  is  most  distant  for  which  the  optic  axes  are  least  converged, 
and  conversely.  Thus  the  estimation  of  size  and  distance  go  hand  in  hand,  in 
great  part  at  least,  and  the  correct  estimation  of  the  distance  also  gives  us  a  cor- 
rect estimate  of  the  size  of  objects  {Descartes).  A  further  aid  to  the  estimation 
of  distance  is  the  observation  of  the  apparent  displacement  of  objects,  on  moving 


810  THE    LACHRYMAL   APPARATUS. 

our  head  or  body.  In  the  latter,  especially,  lateral  objects  appear  to  change  their 
position  toward  the  background,  the  nearer  they  are  to  us.  Hence,  when  travel- 
ing in  a  train,  in  which  case  the  change  of  position  of  the  objects  occurs  very 
rapidly,  the  objects  themselves  are  regarded  as  nearer  (Sick),  and  also  smaller 
{JDove).  Lastly,  those  objects  appear  to  us  to  be  nearest  which  are  most  distinct 
in  the  field  of  vision. 

Example. — A  light  in  a  dark  landscape,  and  a  dazzling  crown  of  snow  on  a  hill,  appear  to  be 
near  to  us;  looked  at  from  the  top  of  a  high  mountain,  the  silver  glancing  curved  course  of  a  river 
not  unfrequently  appears  as  if  it  were  raised  from  the  plane. 

False  Estimates  of  Size  and  Direction. — i.  A  line  divided  by  intermediate  points  appears 
longer  than  one  not  so  divided.  Hence,  the  heavens  do  not  appear  to  us  as  a  hollow  sphere,  but 
as  curved  like  an  ellipse;  and  for  the  last  reason  the  disk  of  the  setting  sun  is  estimated  to  be 
larger  than  the  sun  when  it  is  in  the  zenith  (Ptolemv,  150  A.D.).  2.  If  we  move  a  circle  slowly  to 
and  fro  behind  a  slit  it  appears  as  a  horizontal  ellipse,  if  we  move  it  rapidly  it  appears  as  a  vertical 
ellipse.  3.  If  a  very  fine  line  be  drawn  obliquely  across  a  vertical  thick  black  line,  then  the 
direction  of  the  fine  line  beyond  the  thick  one  appears  to  be  different  from  its  original  direction. 
4.  Zollner's  Lines. — Draw  three  parallel  horizontal  lines  i  centimetre  apart,  and  through  the 
upper  and  lower  ones  draw  short  oblique  parallel  lines  in  the  direction  from  above  and  the  left  to 
below  and  the  right;  through  the  middle  line  draw  similar  oblique  lines,  but  in  the  opposite 
direction,  then  the  three  horizontal  lines  no  longer  appear  to  be  parallel.  [Fig.  50S  shows  a 
modification  of  this.  The  lines  are  actually  parallel,  although  some  of  them  appear  to  converge 
and  others  to  diverge.]  If  we  look  in  a  dark  mom  at  a  bright  vertical  line,  and  then  bend  the 
head  toward  the  shoulder,  the  line  appears  to  be  bent  in  the  opposite  direction  (Auliert). 

404.  PROTECTIVE  ORGANS  OF  THE  EYE.— I.  The  eyelids  are  represented  in 
section  in  Fig.  509.  The  tarsus  is  in  realitv  not  a  cartilage,  but  merely  a  rigid  plate  of  connective 
tissue,  in  which  the  Meibomian  glands  arc  imbedded  ;  acinous  sebaceous  glands  moisten  the  edges 
of  the  eyelids  with  fatty  matter.  At  the  basal  margin  of  the  tarsus,  especially  of  the  upper  one, 
close  to  the  reflection  of  the  conjunctiva,  there  opens  the  acino-tubular  glands  of  Krause.  The 
conjunctiva  covers  the  anterior  surface  of  the  bulb  as  far  as  the  margin  of  the  cornea,  over  which 
the  epithelium  alone  is  continued.  On  the  posterior  surface  of  the  eyelid  the  conjunctiva  is  partly 
provided  with  papilla".  It  is  covered  by  stratified  prismatic  epitheHum.  Coiled  glands  occur  in 
ruminants  just  outside  the  margin  of  the  cornea  (hfeissner),  while  outside  this,  toward  the  outer 
angle  of  the  eye  in  the  pig,  there  are  simple  glandular  sacks  {Ma>n).  Waldeyer  describes  modified 
sweat  glands  in  the  tarsal  margins  in  man.  .Small  lymphatic  s.acks  in  the  conjunctiva  are  called 
trachoma  glands.  Krause  found  enii  Inilhs  in  the  conjunctiva  bulbi.  The  blood  vessels  in  the  con- 
junctiva communicate  with  the  juice  canals  in  the  cornea  and  sclerotic  (p.  753).  The  secretion  of 
the  conjunctiva,  besides  some  mucus,  consists  of  tears,  which  may  be  as  abundant  as  those  formed 
in  the  lachrymal  gland*. 

The  closure  of  the  eyelids  is  accomplished  by  the  orbicularis  palpebrarum 
(facial  nen'e,  §  349),  whereby  the  upper  lid  falls  in  virtue  of  its  own  weight. 
This  muscle  contracts — (i)  voluntarily;  (2)  involuntarily  (single  contractions)  ; 
(3)  reflexly,  by  stimulation  of  all  the  sensory  fibres  of  the  trigeminus  distributed 
to  the  bulb  and  its  immediate  neighborhood  (§  347),  also  by  intense  stimulation 
of  the  retina  by  light ;  (4)  continued  involuntary  closure  occurs  during  sleep. 

The  opening  of  the  eyelids  is  brought  about  by  the  passive  descent  of  the 
lower  one.  and  the  active  elevation  of  the  upper  eyelid  by  the  levator  palpebrae 
superioris  (§  345).     The  smooth  muscular  fibres  of  the  eyelids  also  aid  (p.  623). 

II.  The  lachrymal  apparatus  consists  of  the  lachrymal  glands,  which  in  structure  closely 
resemble  the  parotid,  their  acini  being  lined  by  low,  cylindrical,  granular  epithelium.  Four  to  five 
larger  and  eight  to  ten  smaller  excretory  ducts  conduct  the  tears  .above  the  outer  angle  of  the  lid 
into  the  forni.x  conjunctiva.  The  tear  ducts,  beginning  at  the  puncta  lachrymalia,  are  composed 
of  connective  and  elastic  tissue,  and  are  lined  by  stratified  squamous  epithelium.  Striped  muscle 
accompanies  the  duct,  and  by  its  contraction  keeps  the  duct  open  (  IVeJl).  Toldt  found  no 
sphincter  surrounding  the  puncta  lachrymalia,  while  Gerlach  found  an  incomplete  circular  muscu- 
lature. The  connective-tissue  covering  of  the  tear  sack  and  canal  is  united  with  the  adjoining 
periosteum.  The  thin  mucous  membrane,  which  contains  much  adenoid  tissue  and  lymph  cells,  is 
lined  by  a  single  layer  of  ciliated  cylindrical  epithelium,  which  below  passes  into  the  stratified  form. 
The  opening  of  the  duct  is  often  provided  with  a  valve-like  fold  (Hasner's  valve). 

The  conduction  of  the  tears  occurs  between  the  lids  and  the  bulb  by  means 
of  capillarity,  the  closure  of  the  eyelids  aiding  the  process.     The  Meibomian 


THE    CONDUCTION    OF   TEARS. 


811 


secretion  prevents  the  overflow  of  the  tears  [just  as  greasing  the  edge  of  a  glass 
vessel  prevents  the  water  in  it  from  overflowing].  The  tears  are  conducted  from 
the  puncta  through  the  duct,  chiefly  by  a  siphon  action  {Ad.  JVebi-r).  Horner's 
muscle  (also  known  to  Duvernoy,  1678)  likewise  aids,  as  every  time  the  eyelids 
are  closed  it  pulls  upon  the  posterior  wall  of  the  sack,  and  thus  dilates  the  latter, 
so  that  it  aspirates  tears  into  it  {Henke). 


Fig.  509. 


Vertical  section  through  the  upper  eyelid  (after  Waldeyct).  .^.culib;  i,  epidermis  ;  2,  chorium  ;  5  and  3,  subcuta- 
neous connective  tissue  :  C and  7,  orbicularis  muscle  and  its  bundles  ;  Z),  loose  sub-muscular  connective  tissue; 
E,  insertion  of  H.  Miiller's  muscle  ;  F,  tarsus ;  G,  conjunctiva  :  J,  inner  edge  of  the  lid  ;  K,  outer  edge  ;  4,  pig- 
ment cells  in  the  cutis  ;  5.  sweat  glands  ;  6,  hair  follicles  with  hairs  :  8  and  23,  sections  of  nerves ;  9,  arteries  :  10, 
veins:  11,  cilia:  I2,  modified  sweat  glands  :  13,  circular  muscle  of  Riolan  ;  14,  opening  of  a  Meibomian  gland  ; 
15,  section  of  an  acinus  of  the  same;  16,  posterior  tarsal  glands  :  18  and  19,  tissue  of  the  tarsus  ;  20,  pretarsa!  or 
sub-muscular  connective  tissue  ;  2t  and  22,  conjunctiva,  with  its  epithelium  ;  24,  fat ;  25,  loosely  woven  posterior 
end  of  the  tarsus :  26,  section  of  a  palpebral  artery. 

E.  H.  Weber  and  Hastier  ascribe  the  aspiration  of  the  tears  to  the  diminution  of  the  amount  of 
air  in  the  nasal  cavities  during  inspiration.  Arlt  asserts  that  the  tear  sack  is  compressed  by  the  con- 
traction of  the  orl)icularis  muscle,  so  that  the  tears  must  l)e  forced  toward  the  nose.  Lastly,  Stell- 
Hag  supposes  that  when  the  eyelids  are  closed,  the  tears  are  simply  pressed  into  the  puncta,  while 
Gad  denies  that  there  is  any  kind  of  pumping  mechanism  in  the  nasal  canal.  I.andois  points  out 
that  the  tear  ducts  are  surrounded  by.  a  plexus  of  veins,  which,  according  to  their  state  of  distention, 
may  influence  the  size  of  these  tubes. 


812  COMPARATIVE HISTORICAL. 

The  secretion  of  tears  takes  place  only  by  direct  stimulation  of  the  lachrymal 
nerve  (§347,  I,  2),  subcutaneous  malar  (§347,  II,  2)  and  cervical  sympathetic 
(§  356,  A,  6),  which  have  been  called  secretory  nerves.  Secretion  may  also  be 
excited  reflexly  (p.  623)  by  stimulation  of  the  nasal  mucous  membrane  only  on 
the  same  side  {Hcrzcnsiein).  The  ordinary  secretion  in  the  waking  condition  is 
really  a  reflex  secretion  produced  by  the  stimulation  of  the  anterior  surface  of  the 
bulb  by  the  air  or  by  the  evaporation  of  tears.  In  sleep  all  these  factors  are 
absent,  and  there  is  no  secretion.  Histological  Changes. — Reichel  found  that 
in  the  active  gland  (after  injection  of  pilocarpin),  the  secretory  cells  became 
granular,  turbid  and  smaller,  while  the  outlines  of  the  cells  became  less  distinct 
and  the  nuclei  spheroidal.  In  the  resting  gland  the  cells  are  bright  and  slightly 
granular,  with  irregular  nuclei.  Intense  stimulation  by  /ight  acting  on  the  optic 
nerve  causes  a  reflex  secretion  of  tears.  The  flow  of  tears  accompanying  certain 
violent  emotions,  and  even  hearty  laughing,  is  still  unexplained.  During  cough- 
ing and  vomiting  the  secretion  of  tears  is  increased,  partly  reflexly  and  partly  by 
the  outflow  being  prevented  by  the  expiratory  pressure. 

Function. — The  tears  moisten  the  bulb,  prevent  it  from  drying,  and  float 
away  small  particles,  being  aided  in  this  by  the  closure  of  the  eyelids.  Atropin 
diminishes  the  tears  (Mogaanf). 

Composition. — The  tears  are  alkaline,  saline  to  taste,  and  represent  a  "serous  " 
secretion.  Water,  98.1  to  99;  1.46  organic  substances  (o.  i  albumin  and  mucin, 
0.1  epithelium)  ;  0.4  to  0.8  salts  (especially  NaCl). 

[Action  of  Drugs. — Essential  volatile  oils  and  eserin  increase  the  secretion  of  tears,  atropin 
arrests  it,  while  eserin  antagonizes  the  effect  of  atropin  and  causes  an  increa>.ed  secretion.] 

405.  COMPARATIVE— HISTORICAL.— Comparative.— The  simplest  form  of  visual 
apparatus  is  represented  by  aggregations  of  pigment  cells  in  the  outer  coverings  of  the  body,  which 
are  in  connection  with  the  termination  of  afferent  nerves.  The  pigment  absorbs  the  rays  of  light, 
and  in  virtue  of  the  light  ether  discharges  kinetic  energy,  which  excites  the  terminations  of  the 
nervous  apparatus.  Collections  of  pigment  cells,  with  nerve  fibres  attached,  and  provided  with  a 
clear  refractive  body,  occur  on  the  margin  of  the  bell  of  the  higher  medusi-e,  while  the  lower  forms 
have  only  aggregations  of  pigment  on  the  bases  of  their  tentacles.  Also,  in  many  lower  worms 
there  are  pigment  spots  near  the  brain.  In  others  the  pigment  lies  as  a  covering  round  the  termi- 
nations of  the  nerves,  which  occur  as  "crystalline  rods"  or  "crystalline  spheres."  In  parasitic 
worms  the  visual  apparatus  is  absent.  In  star  fishes  the  eyes  are  at  the  tips  of  the  arms,  and 
consist  of  a  spherical  crystal  organ  surrounded  with  pigment,  with  a  nerve  going  to  it.  In  all 
other  eehinodermata  there  are  only  accumulations  of  pigment.  Among  the  annulosa  there  are 
several  grades  of  visual  apparatus — (i)  Without  a  cornea  there  may  be  only  one  crystal  sphere 
(nervous  end  organ)  near  the  brain,  as  m  the  young  of  the  crab;  or  there  may  be  several  crystal 
spheres  forming  a  compound  eye,  as  in  the  lower  crabs.  (2)  With  a  cornea,  consisting  of  a  len- 
ticular body  formed  from  the  chitin  of  the  outer  integument,  the  eye  itself  may  be  simple,  merely 
consisting  of  one  crystal  rod,  or  it  may  be  compound.  The  compound  eye  consists  of  only  one 
large  lenticular  cornea,  common  to  all  the  crystal  rods,  as  in  the  spiders;  or  each  crystal  rod  has  a 
.special  lenticular  cornea  for  itself.  The  numerous  rods  surrounded  by  pigment  are  closely  packed 
together,  and  are  arranged  upon  a  curved  surface,  so  that  their  free  ends  also  form  a  part  of  a  sphere. 
The  chitinous  investment  of  the  head  is  faceted,  and  forms  a  small  corneal  lens  on  the  free  end  of 
each  rod.  According  to  one  view,  each  facette,  with  the  lens  and  the  crystal  sphere,  is  a  special 
eye,  and  just  as  man  has  two  eyes,  so  insects  have  several  hundred.  Each  eye  sees  the  picture  of 
the  outer  world  in  toto.  This  view  is  supported  by  the  following  experiment  of  van  Leeuwenhock : 
If  the  cornea  be  sliced  off,  each  facette  thereof  gives  a  special  image  of  an  object.  If  a  cross  be 
made  on  the  mirror  of  a  microscope,  while  a  piece  of  the  faceted  cornea  is  placed  as  an  object  upon 
the  stage,  then  we  see  an  image  of  the  cross  in  each  facette  of  the  cornea.  Thus,  for  each  rod 
(crystal  sphere)  there  would  be  a  special  image.  Each  corneal  facette,  however,  forms  only  a  part 
of  the  image  of  the  outer  world,  so  that  we  must  regard  the  image  as  composed  like  a  mosaic. 
.■Vmong  mollusca  the  fixed  branchipoda  have  two  pigment  spots  near  the  brain,  but  only  in  their 
larval  condition ;  while  the  mussel  has,  under  similar  conditions,  pigment  spots  with  a  refractive 
body.  The  adult  mussel,  however,  has  pigment  spots  (oceli)  only  in  the  margin  of  the  mantel,  but 
some  molluscs  have  stalked  and  highly-developed  eyes.  Some  of  the  lower  snails  have  no  eyes, 
some  have  pigment  spots  on  the  head,  while  the  garden  snail  has  stalked  eyes  provided  with  a  cornea, 
an  optic  nerve  with  retina  and  pigment,  and  even  a  lens  and  vitreous  body.  Among  cephalopoda 
the  nautilus  has  no  cornea  or  lens,  so  that  the  sea  water  flows  freely  into  the  orbits.  Others  have  a 
lens  and  no  cornea,  while  some  have  an  opening  in  the  cornea  (Loligo,  Sepia,  Octopus).     All  the 


COMPARATIVE HISTORICAL.  813 

other  parts  of  the  eye  are  well  developed.  Among  vertebrata  aitiphioxus  has  no  eyes.  They 
exist  in  a  degenerated  condition  in  Proteus  and  the  mammal  Spalax.  In  many  fishes,  amphibians 
and  reptiles  the  eye  is  covered  by  a  piece  of  transparent  skin.  Some  hag-tishes,  the  crocodile,  and 
birds  have  eyelids,  and  a  nictitating  membrane  at  the  inner  angle  of  the  eye.  Connected  with 
it  is  the  Harderian  gland.  In  mammals  the  nictitating  process  is  represented  only  by  the  plica 
semilunaris.  Therj  is  no  lachrymal  apparatus  in  fishes.  The  tears  of  snakes  remain  under  the 
watch-glass-like  cutis  with  which  the  eye  is  covered.  The  sclerotic  often  contains  cartilage  which 
may  ossify.  A  vascular  organ,  the  processus  falciformis,  passes  from  the  middle  of  the  choroid 
into  the  interior  of  the  vitreous  body  in  osseous  fishes,  its  anterior  extremity  being  termed  the  cam- 
panula Halleri.  Similarly,  there  is  the  pecten  in  birds,  but  it  is  provided  with  muscular  fibres.  In 
birds  the  cornea  is  surrounded  by  a  bony  ring.  The  whale  has  an  enormously  thick  sclerotic.  In 
aquatic  animals  the  lens  is  nearly  spherical.  The  muscles  of  the  iris  and  choroid  are  trans- 
versely striped  in  birds  and  reptiles.  The  retinal  rods  in  all  vertebrates  are  directed  from  before 
backward,  while  the  analogous  elements  (crystal  rods  and  spheres)  in  invertebrata  are  directed  from 
behind  forward. 

Historical. — The  Hippocratic  School  were  acquainted  with  the  optic  nerve  and  lens.  Aristotle 
(384  B.C.)  mentions  that  section  of  the  optic  nerve  causes  blindness — he  was  acquainted  with  after 
images,  short  and  long  sight.  Herophilus  (307  B.  c.)  discovered  the  retina,  and  the  ciliary  pro- 
cesses received  their  name  in  his  school.  Galen  (131-203  A.  D.)  described  the  six  muscles  of  the 
eyeball,  the  puncta  lachrymalia,  and  tear  duct.  Aeranger  (1521)  was  aware  of  the  fatty  matter  at 
the  edge  of  the  eyelids.  Stephanus  (1545)  and  Casseri  (1609)  described  the  Meibomian  glands, 
which  were  afterward  redescribed  by  Meibom  (1666).  Fallopius  described  the  vitreous  membrane 
and  the  ciliary  ligament.  Plater  (1 583)  mentions  that  the  posterior  surface  of  the  lens  is  more  curved. 
Aldrovandi  observed  the  remainder  of  the  pupillary  membrane  (1599).  Observations  were  made 
at  the  time  of  Vesalius  (1540)  on  the  refractive  action  of  the  lens.  Leonardo  da  Vinci  compared 
the  eye  to  a  camera  obscura.  Maurolykos  compared  the  action  of  the  lens  to  that  of  a  lens  of  glass, 
but  it  was  Kepler  ( 161 1 )  who  first  showed  the  true  refractive  index  of  the  lens  and  the  formation  of 
the  retinal  image,  but  he  thought  that  during  accommodation  the  retina  moved  forward  and  back- 
ward. The  Jesuit,  Scheiner  (f  1650),  mentions,  however,  that  the  lens  becomes  more  convex  by 
the  ciHary  processes,  and  he  assumed  the  existence  of  muscular  fibres  in  the  uvea.  He  referred 
long  and  short  sight  to  the  curvature  of  the  lens,  and  he  first  showed  the  retinal  image  in  an  excised 
eye.  With  regard  to  the  use  of  spectacles  there  is  a  reference  in  Pliny.  It  is  said  that  at  the 
beginning  of  the  14th  century  the  Florentine,  Salvino  d'.\rmato  degli  Armati  di  Fir  (f  1317),  and 
the  monk,  Alessandro  de  Spina  (f  1313),  invented  spectacles.  Kepler  (1611)  and  Descartes  (1637) 
described  their  action.  Mayo  [f  1S52),  described  the  third  nerve  as  the  constrictor  nerve  of  the 
pupil.  Zinn  contributed  considerably  to  our  knowledge  of  the  structure  of  the  eye.  Ruysch  de- 
scribed muscular  fibres  in  the  iris,  and  Monro  described  the  sphincter  of  the  pupil  (1794).  Jacob 
described  the  bacillary  layer  of  the  retina — Scemmering  (1791)  the  yellow  spot.  Brewster  and 
Chossat  (1819)  tested  the  refractive  indices  of  the  optical  media.  Purkinje  (1819)  studied  subjective 
vision. 


HEARING. 


406.  STRUCTURE  OF  THE  ORGAN  OF  HEARING— Stimu- 
lation of  the  Auditory  Nerve. — The  normal  manner  in  which  the  auditory 
nerve  is  excited  by  means  of  sonorous  vibrations,  which  set  in  motion  the  end 
organs  of  the  acoustic  nerve,  which  lie  in  the  endolymph  of  the  labyrinth  of  the 
inner  ear,  on  membranous  expansions  of  the  cochlea  and  semicircular  canals. 
Hence  the  sonorous  vibrations  are  first  transmitted  to  the  fluid  in  the  labyrinth, 
and  this,  in  turn,  is  thrown  into  waves,  which  set  the  end  organs  into  vibration. 
Thus  the  excitement  of  the  auditory  nerves  is  brought  about  by  the  mechankal 
stimulation  of  the  wave  motion  of  the  lymph  of  the  /abyiiiith. 

The  fluid  or  lymph  of  the  labyrinth  is  surrounded  by  the  exceedingly  hard  osse- 

FiG.  510. 


Scheme  of  the  organ  of  hearing.  A  G,  external  auditory  meatus  ;  T,  tympanic  membrane  ;  K,  malleus  with  its  head 
[k),  short  process  {k/),  and  handle  ('«);  a,  incus  with  its  short  process  (.v)  and  long  process — the  latter  is  united 
to  the  stapes  (5)  by  means  ol  the  Sylvian  ossicle  (s)  ;  P,  middle  ear;  o,  fenestra  ovalis ;  r,  fenestra  rotunda;  x, 
beginning  of  the  lamina  spiralis  of  the  cochlea  ;  pi,  its  scala  t>^mpani,  and  vt,  its  scala  vestibuli  :  V,  vestibule  ; 
S,  saccule  ;  XJ,  utricle;  H,  semicircular  canals,  T  E  ;  Eustachian  tube.  The  long  arrow  indicates  the  line  of 
"    1  of  the  tensor  tympani  ;  the  short  curved  one,  that  of  the  stapedius. 


ous  mass  of  the  temporal  bone  (Fig.  510).  Only  at  one  small  roundish  and  slightly 
triangular  point  {>■),  the  fenestra  rotunda,  the  fluid  is  bounded  by  a  delicate 
yielding  membrane,  which  is  in  contact  with  the  air  in  the  middle  ear  or  tympanum 
(P).  Not  far  from  the  fenestra  rotunda  is  the  fenestra  ovalis  (o),  in  which  the 
base  of  the  stapes  (j)  is  fixed  by  means  of  a  yielding  membranous  ring.  The  outer 
surface  of  this,  also,  is  in  contact  with  the  air  in  the  middle  ear.  As  the  perilymph 
of  the  inner  ear  is  in  contact  at  these  two  places  with  a  yielding  boundary,  it  is 
clear  that  the  lymph  itself  may  exhibit  oscillatory  movements,  as  it  must  follow 
the  movements  of  the  yielding  boundaries. 

814 


PHYSICAL    INTRODUCTION.  815 

The  sonorous  vibrations  may  set  the  perilymph  in  vibration  in  three  different 
ways  :  — 

1.  Conduction  through"  the  Bones  of  the  Head. — This  occurs  especially 
only  when  the  vibrating  solid  body  is  applied  directly  to  some  part  of  the  head, 
e.g.,  a  tuning-fork  placed  on  the  head,  the  sound  being  propagated  most  intensely 
in  the  direction  of  the  prolongation  of  the  handle  of  the  instrument — also  when 
the  sound  is  conducted  to  the  head  by  means  of  fluid,  as  when  the  head  is 
ducked  under  water.  Vibrations  of  the  air,  however,  are  practically  not  transferred 
directly  to  the  bones  of  the  head,  as  is  shown  by  the  fact  that  we  are  deaf  when 
the  ears  are  stopped. 

The  soft  parts  of  the  head  which  he  immediately  upon  bone  conduct  sound  best,  and  of  the  pro- 
jecting part  the  best  conductor  is  the  cartilaginous  portion  of  the  external  ear.  But  even  under  the 
most  favorable  circumstance,  conduction  through  the  bones  of  the  head  is  far  less  effective  than  the 
conduction  of  the  sound  waves  through  the  external  auditory  meatus.  If  a  tuning-fork  be  made  to 
vibrate  between  the  teeth  until  we  no  longer  hear  it,  its  tones  m.iy  still  be  heard  on  bringing  it  near 
the  ear  (Rinne).  The  conduction  through  the  bones  is  favored  when  the  oscillations  are  not  trans- 
ferred from  the  bones  to  the  tympanic  membrane,  and  are  thus  transferred  to  the  air  in  the  outer  ear. 
Hence,  we  hear  the  sound  of  the  tuning-fork  applied  to  the  head  better  when  the  ears  are  stopped, 
as  this  prevents  the  propagation  of  the  sound  waves  through  the  air  in  the  outer  ear.  If,  in  a  deaf 
person,  the  conduction  is  still  normal  through  the  cranial  bones,  then  the  cause  of  the  deafness  is 
not  in  the  nervous  part  of  the  ear,  but  in  the  external  sound-conducting  part  of  the  apparatus. 

2.  Normal   hearing  takes  place  through  the  external  auditory  meatus. 

The  enormous  vibrations  of  the  air  first  set  the  tympanic  membrane  in  vibration 
(Fig.  510,  T)  ;  this  moves  the  malleus  (/i),  whose  long  process  is  inserted  into  it ; 
the  malleus  moves  the  incus  {a),  and  this  the  stapes  (xj,  which  transfers  the  move- 
ments of  its  plate  to  the  perilymph  of  the  labyrinth. 

3.  Direct  Conduction  to  the  Fenestra. — In  man,  in  consequence  of  occasional  disease  of  the 
middle  ear,  whereby  the  tympanic  membrane  and  auditory  ossicles  may  be  destroyed,  the  auditory 
apparatu-i  may  be  excited,  although  only  in  a  very  feeble  manner,  by  the  vibrations  of  the  air  being 
directly  transferred  to  the  membrane  of  the  fenestra  rotunda  (r),  and  the  parts  closing  the  fenestra 
ovalis  (0).  The  membrane  of  the  fenestra  rotunda  may  vibrate  alone,  even  when  the  oval  window 
is  rigidly  closed  (  Weber- Liel). 

407.  PHYSICAL  INTRODUCTION.— Sound.— Sound  is  produced  by  the  vibration  of 
elastic  bodies  capable  of  vibration.  Alternate  condensation  and  rarefaction  of  the  surrounding 
air  are  thus  produced ;  or,  in  other  words,  sound  waves  in  which  the  particles  vibrate  longitudinally 
or  in  the  direction  of  the  propagation  of  the  sound  are  excited.  Around  the  point  of  origin  of  the 
sound  these  condensations  and  rarefactions  occur  in  equal  concentric  circles,  which  conduct  the  sound 
vibrations  to  our  outer  ear.  The  vibrations  of  the  sounding  body  are  so  called  "  stationary  vibra- 
tions" (E.  H.  and  IV.  Weber),  ie.,  all  the  particles  of  the  vibrating  body  are  always  in  the  same 
phase  of  movement,  in  that  they  pass  into  movement  simultaneously,  they  reach  the  maximum  of 
movement  simultaneously,  e.g.,  in  the  particles  of  a  sounding  vibrating  metal  rod.  Sound  is  pro- 
duced by  the  stationary  vibrations  of  elastic  bodies ;  it  is  propagated  by  progressive  wave  motion 
of  elastic  media,  generally  the  air.  The  wave  length  of  a  tone,  i.e.,  the  distance  of  one  maximum 
of  condensation  to  the  next  one  in  the  air,  is  proportional  to  the  duration  of  the  vibration  of  the 
body,  whose  vibrations  produce  the  sound  waves. 

If  /  is  the  wave  length  of  a  tone,  /  in  seconds  the  duration  of  a  vibration  of  the  body  producing 
the  wave,  then  /,  =  «/,  where  «  =340.88  metres,  which  is  ihe  rate  per  second  of  propagation  of 
sound  waves  in  the  air.  The  rapidity  of  the  transmission  of  sound  waves  in  water  =  1435  metres  per 
second,  i.e.,  nearly  four  times  as  rapid  as  in  air;  while  in  solids  capable  of  vibration  it  is  propagated 
from  seven  to  eighteen  times  faster  than  in  the  air.  Sound  waves  are  conducted  best  through  the 
same  medium ;  when  they  have  to  pass  through  several  media  they  are  always  weakened. 

Reflection  of  the  sound  waves  occurs  when  they  impinge  upon  a  solid  obstacle,  in  which  case 
the  angle  of  reHeclion  is  always  equal  to  the  angle  of  incidence. 

Wave  Movements. — We  distinguish — I.  Progressive  wave  movements  which  occur  in  two 
forms — (i)  As  longilttJinal waves  (ChlaUni),  in  which  the  individual  particles  of  the  vibrating  body 
vibrate  around  their  centre  of  gravity  in  the  direction  of  the  propagation  of  the  wave ;  examples  are 
the  waves  in  water  and  air.  This  movement  causes  an  accumulation  of  the  particles  at  certain  places, 
e.g.,  on  the  crests  of  the  waves  in  water  waves,  while  at  other  places  they  are  diminished.  This 
kind  of  wave  is  called  a  wave  of  condensation  and  rarefaction.  (2)  If,  however,  each  particle 
in  the  progressive  wave  moves  vertically  up  and  down,  i.e.,  transversely  to  the  direction  of  the  pro- 
pagation of  the  wave,  then  we  have  the  simple  transverse  waves  (Chladni),  or  progressive  waves,  in 


816 


TYMPANIC    MEMBRANE. 


Fig.  511 


which  there  is  no  condensation  or  rarefaction  in  the  direction  of  propagation,  as  each  particle  is 
merely  displaced  laterally.     An  example  of  this  is  the  progressive  -waves  in  a  rope. 

II.  Stationary  Flexion  Waves. — When  all  the  particles  of  an  elastic  vibrating  body  so  oscil- 
late that  all  of  them  are  always  in  the  same  phase  of  movement  as  the  limbs  of  a  vibrating  tuning, 
fork  or  a  plucked  string,  then  this  kind  of  movement  is  described  as  stationary  flexion  waves.  As 
bodies,  whose  expansion  in  the  direction  of  oscillation  is  very  slight,  vibrate  10  and  fro  in  the  station- 
ary flexion  wave,  so  we  see  that  the  small  parts  of  the  auditory  apparatus  (tympanic  membrane,  os- 
sicles, lymph  of  the  labyrinth)  oscillate  in  stationary  flexion  waves. 

408.  EAR    MUSCLES— EXTERNAL    AUDITORY    MEATUS.— External    Ear.— 

When  the  external  ear  is  ab-ent,  little  or  no  impairment  of  the  hearing  is  observed  ;  hence,  the 
physiological  functions  of  these  organs  are  but  slight.  Boerhaave  thought  that  the  elevations  and 
depressions  of  the  outer  ear  might  be  connected  with  the  reflection  of  the  sound  waves.  Numerous 
sound  waves,  however,  must  be  again  reflected  oulward;  and  those  waves  v^-hich  reach  the  deep 
p4rt  of  the  concha  are  said  to  be  reflected  toward  the  tragus,  to  be  reflected  by  it  into  the  external 
auditory  meatus.  According  to  Schneider,  when  the  depressions  in  the  ear  are  filled  up  with  wax, 
hearing  is  impaired.  Mach  points  out  that  the  dimensions  of  the  external  ear  are  proportionally  too 
small  to  act  as  reflecting  organs  for  the  wave  lengths  of  noises. 

Muscles  of  the  External  Ear. — (I)  The  whole  ear  is  moved  by  the  retrahenter,  attrahens, 
and  attollens.  (2)  The/»;v«  of  the  ear  may  be  altered 
by  the  tragicus,  antitragicus,  helicis  major  and  minor 
internally  ;  and  by  the  transversus  and  obliquus  auriculae 
externally.  Persons  who  can  move  their  ears  do  not 
find  that  the  hearing  is  influenced  during  the  movement. 
The  Mm.  helicis  major  and  minor  are  regarded  as  ele- 
vators of  the  helix,  the  transversus  and  obliquus  auric- 
ulse  as  dilators  of  the  concha ;  the  tragicus  and  anti- 
tragicus as  constrictors  of  the  meatus.  In  animals  the 
external  ear  and  the  action  of  its  muscles  have  a  marked 
efl^ect  upon  hearing.  The  muscles  point  the  ear  in  the 
direction  of  the  sound,  while  other  muscles  contract  or 
dilate  the  space  within  the  external  ear.  In  many  div- 
ing animals  the  meatus  can  be  closed  by  a  kind  of 
valve. 

The  external  meatus  is  3  to  3.25  cm. 
long  [i^  to  i^  inch],  8  to  9  mm.  high,  and 
6  to  8  mm.  broad  at  its  outer  opening  (Fig. 
511).  It  is  the  conductor  of  the  sound  waves 
to  the  tympanic  membrane,  so  that  almost  all 
npanic  the  sound  waves  first  impinge  upon  its  wall, 
lurpart'of'theSu?!  and  are  then  reflected  toward  the  tympanic 
membrane.  To  see  well  down  into  the 
meatus,  we  must  pull  the  auricle  upward  and 
backward.  Occlusion  of  the  meatus,  espe- 
cially by  a  plug  of  inspissated  wax  (§  287),  of  course  interferes  with  the  hearing 
[and  when  it  presses  on  the  membrana  tympani  may  give  rise  to  severe  vertigo]. 

409.  TYMPANIC  MEMBRANE.— The  tympanic  membrane  (Fig. 
513),  which  is  tolerably  laxly  fixed  in  a  special  osseous  cleft,  with  a  thickened 
margin,  is  an  elastic,  unyielding,  and  almost  non-extensible  membrane,  of  about 
0.1  mm.  in  thickness,  and  with  a  superficial  area  of  50  square  millimetres.  It  is 
elliptical  in  form,  its  greatest  diameter  being  9.5  to  10  mm.,  and  its  lesser  8  mm., 
and  it  is  fixed  in  the  floor  of  the  external  meatus  obliquely,  at  an  angle  of  40°, 
being  directed  from  above  and  outward,  downward  and  inward.  Both  tympanic 
membranes  converge  anteriorly,  so  that  if  both  were  prolonged  they  would  meet 
to  form  an  angle  of  130°  to  135".  The  oblique  position  enables  a  larger  surface 
to  be  presented  than  would  be  obtained  if  it  were  stretched  vertically,  so  that 
more  sound  waves  can  fall  vertically  upon  it.  The  membrane  is  not  stretched 
flat,  but  a  little  under  its  centre  (umbilicus)  it  is  drawn  slightly  inward  by  the 
handle  of  the  malleus,  which  is  attached  to  it ;  while  the  short  process  of  the 
malleus  slightly  bulges  out  the  membrane  near  its  upper  margin  (Figs.  510  and 
518). 


between  both  : 
ticular  surface  for  the  condyle  of  the  lowei 
jaw  (after  Urbantschitsch). 


FUNCTIONS   OF   THE    OUTER    EAR. 


817 


Structure. — The  tympanic  membrane  consists  of  three  layers:  (i)  The  membrana  propria  is 
a  fibrous  membrane  with  radial  fibres  on  its  outer  surface,  and  circularly  arranged  fibres  on  its 
inner  aspect.  (2)  The  surface  directed  toward  the  meatus  is  covered  with  a  thin  and  semi. trans- 
parent part  of  the  cutis.  (3)  The  side  toward  the  tympanum  is  covered  with  a  delicate  mucous 
membrane,  with  simple  squamous  epithelium.  Numerous  nerves  and  lymph  vessels  as  well  as 
inner  and  outer  blood  vessels  occur  in  the  membrane. 

[The  middle  layer,  or  substantia  propria,  is  fixed  to  a  ring  of  bone,  which  is 
deficient  above.  It  is  filled  up  by  a  layer  composed  of  the  mucous  and  cutaneous 
layers  called  the  membrana  flaccida,  or  Shrapnell's  membrane.] 

[Examination. — When  examining  the  outer  ear  and  membrana  tympani  pull  the  auricle  upward 
and  backward.  The  membrana  tympani  is  examined  by  means  of  an  ear  speculum  (Fig.  515). 
The  speculum  is  placed  in  the  ear,  and  light  is  reflected  into  it  by  means  of  a  concave  mirror,  per- 
forated in  the  centre,  and  having  a  focal  distance  of  four  or  five  inches.  It  is  convenient  to  have 
the  mirror  fixed  to  a  band  placed  round  the  head,  as  in  the  case  of  the  laryngoscopic  reflector  (Fig. 
327).  It  is  important  to  remember  that  the  membrane  is  placed  obliquely,  so  that  the  posterior  and 
upper  parts  are  nearer  the  surface.     The  membrane  in  health  is  grayish  in  color  and  transparent, 


Fig.  512. 


Fig.  513. 


Fig.  514. 


J.  5:2. — Tympanic  membrane  with  the  auditory  ossicles  (leftl  seen  from  within.  O",  incus ;  0«,  malleus;  CA, 
chorda  tympani  ;  T,  pouch-like  depression  (after  Urbantschitsch).  Kig  51J. — Tympanic  membrane  and  the 
auditory  ossicles  (lelt)  seen  from  within,  z.  (?,,  from  the  tympanic  cavity.  M,  manubrium  or  handle  of  the  mal- 
leus; T,  insertion  of  the  tensor  tympani  :  A, head;  /F,  long  process  of  the  malleus  :  a,  incus,  with  the  short  (K.) 


nd  the  long  (/)  process  ;  S,  plate  of  the  stapes  ;  \x,  A.r,  is  the 
S,  the  pinion-wheel  arrangement  between  the  malleus  and 
born  child  seen  from  without,  with  the  handle  of  the  malleus 
(»)  and  posterior  [h)  ends. 


iible  i 


s  of  rotation  of  the  auditory  ossicles  ; 
14. — Tympanic  membrane  of  a  new- 
A/,  tympanic  ring  with  its  anterior 


so  that  the  handle  of  the  malleus  is  seen  running  from  above  downward  and  backward,  while  at  the 
anterior  and  inferior  part  there  is  a  cone  of  light,  with  its  ape.x  directed  inward.] 

Function. — The  tympanic  membrane  catches  up  the  sound  waves  which  pene- 
trate into  the  external  meatus,  and  is  set  into  vibration  by  them,  the  vibrations 
corresponding  in  number  and  amplitude  to  the  vibrating  movements  of  the  air. 
Politzer  connected  the  auditory  ossicles  fixed  to  the  tympanic  membrane  of  a  duck 
with  a  recording  apparatus,  and  could  thus  register  the  vibrations  produced  by 
sounding  any  particular  tone.  Owing  to  its  small  dimensions,  the  tympanic  mem- 
brane can  vibrate  in  toto  to  and  fro  in  the  direction  of  the  sound  waves  corre- 
sponding to  the  condensations  and  rarefactions  of  the  vibrating  air,  and  therefore 
executes  transverse  vibrations,  for  which  it  is  specially  adapted,  owing  to  the  rela- 
tively slight  resistance. 

Fundamental  Note. — Stretched  strings  and  membranes  are  generally  only 
thrown  into  actual  and  considerable  sympathetic  vibration  when  they  are  affected 
52 


818 


FUNCTIONS   OF   THE   OUTER    EAR. 


by  tones  which  correspond  with  their  own  fundamental  tone,  or  whose  number  of 
vibrations  is  some  multiple  of  the  number  of  vibrations  of  tlie  same,  as  the  octave. 
When  other  tones  act  on  them,  they  exhibit  only  inconsiderable  sympathetic 
vibration.  If  a  membrane  be  stretched  over  a  funnel  or  cylinder,  and  if  a  nodule 
of  sealing  wax  attached  to  a  silk  thread  be  made  just  to  touch  the  centre  of  the 
membrane,  then  the  sealing  wax  remains  nearly  at  rest  when  tones  or  sounds  are 
made  in  the  neighborhood ;  as  soon,  however,  as  the  fundamental  or  proper  tone 
of  this  arrangement  is  sounded,  the  nodule  is  propelled  by  the  strong  vibrations 
of  the  membrane. 

If  we  apply  this  to  the  tympanic  membrane,  then  it  also  should  exhibit  very 
great  vibrations  when  its  own  fundamental  note  is  sounded,  but  only  slight  vibra- 
tions when  other  tones  are  produced.  This,  however,  would  produce  great  ine- 
quality in  the  audible  sounds.  There  is  an  arrangement  of  the  membrane  whereby 
this  IS  prevented,  (i)  Great  resistance  is  offered  to  the  vibrations  of  the  tympanic 
membrane,  owing  to  its  union  with  the  auditory  ossicles.  These  act  as  a  damping 
apparatus,  which  provides,  as  in  damped  membranes  generally,  that  the  tympanic 
membrane  shall  not  exhibit  excessive  sympathetic  vibrations  for  its  own  funda- 
mental note.     But  the  damping  also  makes  the  sympathetic  vibrations  less  for  all 


Fig.  516. 


Fig.  517. 


;.  515.— Ear  specula  of  various  sizes.  Fig.  516.— Toynbee's  artifici.il  membrana  tympani.  FlG.  517.— The  audi- 
tory ossicles  (right).  C.w,  head;  C,  neck ;  /Yr,  short  process  :  /"W,  long  process ;  A/,  handle  of  the  malleus; 
O',  body  :  G,  articular  surface  ;  //,  short,  and  v,  long  process  of  the  incus  ;  0,S.,  so-called  lenticular  ossicle  ; 
C,s.,  head  ;  a,  anterior,  and/,  posterior  limb  ;  P,  plate  of  the  stapes. 


the  other  tones.  In  this  way,  aH  vibrations  of  the  tympanic  membrane  are  modi- 
fied ;  especially,  however,  is  the  excessive  vibration  diminished  during  the  sounding 
of  its  fundamental  tone.  The  membrane  is  at  the  same  time  rendered  more  capable 
of  responding  to  the  vibrations  of  different  wave  lengths.  The  damping  also 
prevents  after  vibrations.  (2)  Corresponding  to  the  small  mass  of  the  tympanic 
membrane,  its  sympathetic  vibrations  must  also  be  small.  Nevertheless,  these 
slight  elongations  are  quite  sufficient  to  convey  the  sonorous  movements  to  the 
most  delicate  end  organs  of  the  auditory  nerve ;  in  fact,  there  are  arrangements 
in  the  tympanum  which  still  further  diminish  the  vibrations  of  the  tympanic 
membrane. 

As  V.  Helmholtz  has  shown,  the  strong  sympathetic  vibrations  of  the  tympanic  membrane  are  not 
completely  set  aside  by  this  damping  arrangement.  The  painful  sensations  produced  by  some  tones 
are,  perhaps,  due  to  the  sj-mpathetic  vibration  of  the  membrana  tympani.  According  to  Kessel, 
certain  parts  of  the  membrane  vibrate  to  certain  tones. 

Pathological.— Thickenings  or  inequalities  of  the  tympanic  membrane  interfere  with  the  acute- 
ness  of  hearing,  owing  to  the  diminished  capacity  for  vibration  thereby  produced.  Holes  in  and 
loss  of  its  substance  act  similarly.  In  extensive  destruction,  an  artificial  tympanum  is  placed  in  the 
external  meatus,  and  its  vibrations,  to  a  certain  extent,  replace  those  of  the  lost  membrane  {^Toyn- 
hte).     [Fig.  516  shows  an  -.rtificial  tympanic  membrane.] 


MECHANISM    OF   THE   AUDITORY   OSSICLES. 


819 


410.  THE    AUDITORY   OSSICLES   AND  THEIR   MUSCLES. 

— Function. — The  auditory  ossicles  have  a  double  function — [^i)  By  means  of 
the  "  chain  "  which  they  form,  they  transfer  the  vibrations  of  the  tympanic  mem- 
brane to  the  perilymph  of  the  labyrinth.  (2)  They  also  afford  points  of  attach- 
ment for  the  muscles  of  the  middle  ear,  which  can  alter  the  tension  of  the  mem- 
brana  tympani  and  \.\\'i pressure  on  the  lymph  of  the  labyrinth. 

Mechanism. — T\\^  form  and  position  of  the  ossicles  are  given  in  Figures  517 
and  518.  They  form  a  jointed  chain  which  connects  the  tympanic  membrane,  M, 
by  means  of  the  malleus,  h,  incus,  a,  and  stapes,  S,  with  the  perilymph  of  the 
labyrinth.  The  mode  of  movement  of  the  ossicles  is  of  special  importance. 
The  handle  of  the  malleus  (Fig.  518,  //)  is  firmly  united  to  the  fibres  of  the  tym- 
panic membrane.  Besides  this,  the  malleus  is  fixed  by  ligaments  which  prescribe 
the  direction  of  its  movements.  Two  ligaments — the  lig.  mallei  anticum  (passing 
from  the  processus  Folianus),  and  the  posticum  (from  a  small  crest  on  the  neck) — 


Fig.  518. 


Tympanum  and  auditory  ossicles  (left)  magnified.  A.G,  e.\ternal  meatus  :  M.membrana  tympani,  which  is  attached 
to  the  handle  of  the  malleus,  «,  and  near  it  the  short  process,/  ;  It,  head  of  the  malleus  ;  a,  incus  ;  k,  its  short 
process  with  its  ligament :  /,  long  process  ;  s.  Sylvian  ossicle  ;  S,  stapes ;  A_r,  Ajr,  is  tlie  axis  of  rotation  of  the 
ossicles,  it  is  shown  in  perspective,  and  must  be  imagined  to  penetrate  the  plane  of  the  paper ;  /,  line  of  traction 
of  the  tensor  tympani.     The  other  arrows  indicate  the  movement  of  the  ossicles  when  the  tensor  contracts. 


together  form  a  common  axial  band  {v.  Helmholtz),  which  acts  in  the  direction 
from  behind  forward,  i.e.,  parallel  to  the  surface  of  the  tympanic  membrane. 
The  neck  of  the  malleus  lies  between  the  insertions  of  both  ligaments.  The  united 
ligament  determines  the  "  axis  of  rotation  "  of  the  movement  of  the  malleus. 

When  the  handle  of  the  malleus  is  drawn  inward,  of  course  its  head  moves  in 
the  opposite  direction,  or  outward.  The  i?iius,  a,  is  only  partially  fi.xed  by  a 
ligament,  which  attaches  its  short  process  to  the  wall  of  the  tympanic  cavity,  in 
front  of  the  entrance  to  the  mastoid  cells,  k.  The  not  very  tense  articulation 
joining  it  to  the  head  of  the  malleus,  //,  which  lies  with  its  saddle-shaped  articular 
surface  in  the  hollow  of  the  incus,  is  important.  The  lower  margin  of  the  incus 
(Fig.  517,  S)  acts  like  a  tooth  of  a  cog-wheel.  Thus,  when  the  handle  of  the 
malleus  moves  inward  to  the  tympanic  cavity,  the  incus,  and  its  long  process,  b. 
which  is  parallel  to  the  handle  of  the  malleus,  also  pass  inward.  The  incus  forms 
almost  a  right  angle  with  the  stapes,  S,  through  the  intervention  of  the  Sylvian 


820  MODE   OF    VIBRATION    OF   THE   OSSICLES. 

ossicle,  s.  If,  however,  as  by  condensation  of  the  air  in  the  tympanum,  the 
membrana  tympani  and  the  handle  of  the  malleus  move  outward,  the  long  pro- 
cess of  the  incus  does  not  make  a  similar  movement,  as  the  malleus  moves  away 
from  this  margin  of  the  incus.  Hence  the  stapes  is  not  liable  to  be  torn  from  its 
socket.  The  malleus  and  incus  form  an  angular  lever,  which  moves  round  a 
common  axis  (Fig.  513  and  Fig.  518,  h.x,  Ajc).  In  the  inwani  movement  the 
malleus  follows  the  incus,  as  if  both  formed  one  piece.  The  common  axis  (Fig. 
513)  is  not,  however,  the  axial  ligament  of  the  malleus,  but  it  is  formed  anteriorly 
by  the  processus  Folianus,  IF,  directed  forward,  and  posteriorly  by  the  short  pro- 
cess of  the  incus  directed  backward.  The  rotation  of  both  ossicles  around  this 
axis  occurs  in  a  plane  vertical  to  the  plane  of  the  membrana  tympani.  During 
the  rotation,  of  course  the  parts  above  this  axis  (head  of  the  malleus  and  upper 
part  of  the  body  of  the  incus)  take  a  direction  opposite  to  the  parts  lying  below 
it  (the  handle  of  the  malleus  and  the  long  process  of  the  incus),  as  is  indicated 
in  Fig.  518  by  the  direction  of  the  arrows.  The  movement  of  the  handle  of  the 
malleus  must  follow  that  of  the  membrana  tympani,  and  vice  versa,  while  the 
movement  of  the  stapes  is  connected  with  the  movement  of  the  long  process  of 
the  incus.  As  the  long  process  of  the  incus  is  only  two-thirds  of  the  length  of 
the  handle  of  the  malleus  (Figs.  510,  513,  518),  of  course  the  excursion  of  the 
tip  of  the  former,  and  with  it  of  the  stapes,  must  be  correspondingly  less  than  the 
movement  of  the  tip  of  the  handle  of  the  malleus  ;  while,  on  the  other  hand,  the 
force  of  the  movement  of  the  tip  of  the  handle  of  the  malleus,  corresponding  to 
the  diminution  of  the  excursion,  will  be  increased. 

Mode  of  Vibration. — Thus,  the  movement  of  the  membrana  tympani  inward 
causes  a  less  extensive  but  a  more  poiverful  movement  of  the  foot  of  the  stapes 
against  the  perilymph  of  the  labyrinth.  V.  Helmholtz  and  Politzer  calculated 
the  extent  of  the  movement  to  be  0.07  mm.  The  mode  in  which  the  vibrations 
of  the  membrana  tympani  are  conveyed  to  the  Ijmph  of  the  labyrinth,  through 
the  chain  of  ossicles,  is  quite  analogous  to  the  mechanism  of  these  parts  already 
described.  Long  delicate  glass  threads  have  been  fixed  to  these  ossicles,  and  their 
movements  were  thus  graphically  recorded  on  a  smoked  surface  {Folitzer,  Nen- 
sen).  Or  strongly  refractive  particles  are  fixed  to  the  ossicles,  while  the  beam  of 
light  reflected  from  them  can  be  examined  by  means  of  a  microscoi)e  {Buck,  v. 
Helmholtz,  Mach  and  Kessel).  All  the  experiments  showed  that  ilie  transference 
of  the  sound  waves  is  accomplished  by  means  of  the  mechanism  of  the  angular 
lever,  composed  of  the  auditory  ossicles  already  described.  As  the  vibrations 
of  the  membrana  tympani  are  conveyed  to  the  handle  of  the  malleus,  they  are 
weakened  to  about  one-fourth  of  their  original  strength  {Politzer,  Buck).  [The 
membrana  tympani  is  many  times  (30)  larger  than  the  fenestra  ovalis,  and  the 
relation  in  size  might  be  represented  by  a  funnel.  The  arm  of  the  malleal  end 
of  the  lever  where  the  power  acts  is  9^  mm.  long,  while  the  short  or  stapedial 
arm  is  6i4  mm.,  so  that  the  latter  moves  less  than  the  former,  but  what  is  lost  in 
extent  is  gained  in  force.] 

[Methods. — Politzer  attached  small,  very  liglit  levers  to  each  of  the  ossicles,  and  inscribed  their 
movements  on  a  revolving  cylinder.  An  organ  pipe  was  sounded,  and  when  the  levers  were  of  the 
same  length,  the  malleus  made  the  greatest  excursion  and  the  stapes  the  least.  Buck  attached  starch 
grains  to  the  ossicles,  illuminated  them,  and  observed  the  movements  of  the  refractive  starch 
granules  by  means  of  a  microscope  provided  with  a  micrometer.] 

[The  ossicles  move  en  masse,  and  not  in  the  way  of  propagating  molecular 
vibrations.]  As  the  excursions  of  the  ossicles  during  sonorous  vibrations  are,  how- 
ever, only  nominal,  there  is  practically  no  change  in  the  position  of  the  joints 
with  each  vibration.  The  latter  will  only  occur  when  extensive  movements  take 
place  by  means  of  the  muscles. 

The  muscles  of  the  auditory  ossicles  alter  the  position  and  tension  of  the 
membrana  tympani,  as  well  as  the  pressure  of  the  lymjih  of  the  labyrinth.     The 


CONTRACTION    OF   THE    TENSOR.  821 

tensor  tympani,  which  lies  in  an  osseous  groove  Fig.  519. 

above  the  Eustachian  tube,  has  its  tendon  deflected 
round  an  osseous  projection  [processus  cochleari- 
formis],  which  lies  external  to  it,  almost  at  right 
angles  to  the  groove  above  it,  and  is  inserted  im- 
mediately above  the  axes  of  the  malleus  (Fig.  519, 
M).  When  the  muscle  contracts  in  the  direction 
of  the  arrow,  /  (Fig.  518),  then  the  handle  of  the 
malleus  (//)  pulls  the  membrana  tympani  (M)  in- 
ward and  tightens  it.  This  also  causes  a  move- 
ment of  the  incus  and  stapes  (S)  which  must  be 
pressed  more  deeply  into  the  fenestra  ovalis,  as  al- 
ready described.     When  the  muscle  relaxes,  then, 

owing  to  the  c/aJ-Z/ir//)' of  the  rotated  axial  ligament    Tensor  tympani— the  Eustachian  tube  (left). 

and  the  tense  membrana  tympani  itself,  the  posi- 
tion of  equilibrium  is  again  restored.     The  motor  nerve  of  this  muscle  arises 
from  the  trigeminus,  and  passes  through  the  otic  ganglion  (p.  628).      C.  Ludwig 
and  Politzer  observed  that  stimulation  of  the  fifth  nerve  within  the  cranium  [dog] 
caused  the  above-mentioned  movement. 

Use  of  the  Tension. — The  tension  of  the  membrana  tympani  caused  by  the 
tensor  tympani  has  a  double  function  {/oh.  Miiller). — i.  The  tense  membrane 
offers  very  great  resistance  to  sympathetic  vibrations  when  the  sound  waves  are 
very  intense,  as  it  is  a  physical  fact  {Savart)  that  stretched  membranes  are  more 
difficult  to  throw  into  sym[)athetic  vibration  the  tenser  they  are.  Thus,  the  tension 
so  far  protects  the  auditory  organ,  as  it  prevents  too  intense  vibrations  applied  to 
the  membrana  tympani  from  reaching  the  terminations  of  the  nerves.  2.  The  tension 
of  the  membrana  tympani  must  vary  according  to  the  degree  of  contraction  of  the 
tensor.  Hereby  the  membrana  for  the  time  being  has  a  different  fundamental 
tone,  and  is  thus  capable  of  vibrating  to  the  correspondingly  higher  tone,  it,  as  it 
were,  being  in  a  certain  sense  accommodated. 

Comparison  with  Iris. — The  membrana  tympani  has  been  compared  with  the  iris.  Both  mem- 
branes prevent  by  contraction — narrowing  of  the  pujiil  and  tension  of  the  membrana  tympani — the 
too  intense  action  of  the  specific  stimulus  from  causing  too  great  stimulation,  and  both  adapt  the 
sensory  app.iratus  for  the  action  of  moderate  or  we.ik  stimuH.  This  movement  in  both  membranes 
is  brought  aliout  reflexly  in  the  ear  through  the  N.  acusticus,  which  causes  a  reflex  stimulation  of 
the  motor  fibres  for  the  tensor  tympani. 

Effect  of  Tension. — That  increased  tension  of  the  membrana  tympani  renders  it  less 
sensitive  to  sound  waves  is  easily  proved,  thus:  Close  the  mouth  and  nose,  and  make  either  a 
forced  expiration,  so  that  the  air  is  forced  into  the  Eustachian  tube,  which  bulges  out  the 
membrana  tympani,  or  inspire  forcibly,  whereby  the  air  in  the  tympanum  is  diminished,  so 
that  the  membrai.a  bulges  inward.  In  both  cases  hearing  is  interfered  with  as  long  as  the 
increased  tension  lasts.  If  a  funnel  with  a  small  lateral  opening,  and  whose  wide  end  is 
covered  by  a  membrane,  be  placed  in  the  external  meatus,  hearing  becomes  less  distinct  when 
the  membrane  is  stretched  (Joh.  Miiller). 

Normally,  the  tensor  tympani  is  excited  reflexly.  The  muscle  is  not  directly  and  by  itself  subject 
to  the  control  of  the  will.  According  to  L.  Fick,  the  following  phenomenon  is  due  to  an  "associ- 
ated movement "  of  the  tensor  :  When  he  pressed  his  jaws  firmly  against  each  other  he  heard  in 
his  ear  a  piping,  singing  tone,  while  a  capillary  tube,  which  was  fixed  air  tight  into  the  meatus,  had 
a  drop  of  water  which  was  in  it  rapidly  drawn  inward.  During  this  experiment,  a  person  with 
normal  hearing  hears  all  musical  tones  as  if  they  were  louder,  while  all  the  highest  non-musical 
tones  are  enfeebled  (Z«c«f).  When  ji;a//n«n,  v.  Helmholtz  and  Politzer  found  that  hearing  was 
enfeebled  for  certain  tones. 

Contraction  of  the  Tensor. — Hensen  showed  that  the  contraction  of  the 
tensor  tympani  during  hearing  is  not  a  continued  contraction,  but  what  might  be 
termed  a  "  twitch."  A  twitch  takes  place  at  the  beginning  of  the  act  of  hearing, 
which  favors  the  perception  of  the  sound,  as  the  membrana  tympani  thus  set  m 
motion  vibrates  more  readily  to  higher  tones  than  when  it  is  at  rest.  On  expos- 
ing the  tympanum  in  cats  and  dogs,  it  was  found  that  this  contraction  or  twitch 


822  THE    EUSTACHIAN    TUBE. 

occurs  only  at  the  beginning  of  the  sound,  and  that  it  soon  ceases,  although  the 

sound  may  continue. 

Action  of  the  Stapedius. — This  muscle  arises  within  the 
Fig.  520.  eminentia  pyramidalis,   and   is  inserted    into   the  head   of  the 

stapes  and  Sylvian  ossicle  (Fig.  520)  ;  when  it  draws  upon  the 
head  of  the  stapes,  as  indicated  in  Fig.  510,  by  the  small  curved 
arrow,  it  must  place  the  bone  obliquely,  whereby  the  posterior 
end  of  the  plate  of  the  stapes  is  pressed  somewhat  deeper  in- 
ward into  the  fenestra  ovalis,  while  the  anterior  is,  as  it  were, 
displaced  somewhat  cmizvard.  The  stapes  is  thereby  more  fi.xed, 
as  the  fibrous  mass  [annular  ligament]  which  surrounds  the  fe- 
nestra ovalis  and  keeps  the  stapes  in  its  place  becomes  more  tense. 

Right  stapedius  muscle.  The  activity  of   this    muscle,   therefore,   prevents  too  intense 
shocks,  which  may  be  communicated  from  the  incus  to  the  stapes, 

from  being  conveyed  to  the  perilymph  (§  808,  5).     It  is  supplied  by  the  facial 

nerve  (§  349,  3). 

The  stapedius  in  many  persons  executes  an  associated  movement  when  the  eyelids  are  forcibly 
closed  (^  349).  Some  persons  can  cause  it  to  contract  refle.xly  by  scratching  the  skin  in  front  of  the 
meatus,  or  by  gently  stroking  the  outer  margin  of  the  orbit  (  Hen/e). 

Other  Views. — According  to  Lucae,  when  the  stapes  is  displaced  obliquely,  its  head  forces  the 
long  process  of  the  incus,  and  also  the  membrana  tynipani,  oulward,  so  tliat  it  is  regarded  as  an 
antagonisl  of  the  tensor  tympani.  Politzer  observed  that  the  pressure  within  the  labyrinth  fell 
when  he  stimulated  the  muscle.  According  to  Toynbee,  the  stapedius  acts  as  a  lever  and  moves 
the  stapes  slightly  out  of  the  fenestra  ovalis,  thus  making  it  more  free  to  move,  so  that  it  is  more 
capable  of  vibrating.  Henle  supposes  that  the  stapedius  is  more  concerned  in  /f.r/«^'than  in  moving 
the  stapes,  and  that  it  comes  into  action  when  there  is  danger  of  too  great  movement  being  commu- 
nicated to  the  stapes  from  the  incus.  Landois  agrees  with  this  opinion,  and  compares  the  stapedius 
with  the  orbicularis  palpel>rarum,  both  being  protective  muscles. 

Pathological. — Immobility  of  the  auditory  ossicles,  either  by  adhesions  or  anchyloses,  causing 
diminished  vibrations,  interferes  with  hearing;  while  the  same  result  occurs  when  the  stapes  is 
firmly  anchylosed  into  the  fenestra  ovalis.  The  tendon  of  the  tensor  tympani  has  been  divided  in 
cases  of  contracture  of  the  muscles.  For  paralysis  of  the  tensor,  see  p.  629,  and  for  the  stapedius, 
p.  .634- 

411.  EUSTACHIANTUBE— TYMPANUM.— The  Eustachian  tube 

[4  centimetres  in  length,  iS/g  in.]  is  the  ventilating  tube  of  the  tympanic  cavity. 
It  keeps  the  tension  of  the  air  within  the  tympanum  the  same  as  that  within  the 
pharynx  and  outer  air  (Figs.  510,  519).  Only  when  the  tension  of  the  air  is  the 
same  outside  and  inside  the  tympanum  is  the  normal  vibration  of  the  membrana 
tympani  possible.  The  tube  is  generally  closed,  as  the  surfaces  of  the  mucous 
membrane  lining  it  come  into  apposition.  During  swallowing,  however,  the 
tube  is  opened,  owing  to  the  traction  of  the  fibres  of  the  tensor  veli  palatini 
[spheno-salpingo-staphylinus  sive  abductor  tubae  {v.  Trd/tsik'',  sive  dilator  tubae 
{Riidi>iger)]  inserted  into  the  membrano-cartilaginous  part  of  the  tube  (^Toynbee, 
Politzer,  Moos).  (Compare  §  139,  2.)  When  the  tube  is  closed  the  vibrations  of 
the  membrana  tympani  are  transferred  in  a  more  undiminished  condition  to 
the  auditory  ossicles  than  when  it  is  open,  whereby  part  of  the  vibrating  air  is 
forced  through  the  tube  (^Mach  and  Kessel).  If,  however,  the  tympanic  cavity  is 
closed  perma7icntly,  the  air  within  it  becomes  so  rarefied  (§  139)  that  the  mem- 
brana tympani,  owing  to  the  abnormally  low  tension,  becomes  drawn  inward, 
thus  causing  difficulty  of  hearing.  As  the  tube  is  lined  by  ciliated  epithelium 
(p.  491),  it  carries  outward  to  the  pharynx  the  secretions  of  the  tympanum. 

Noise  in  the  Tube. — A  sharp  hissing  noise  is  heard  in  the  tube  during  swallowing,  when  we 
swallow  slowly  and  at  the  same  time  contract  the  tensor  tympani,  due  to  the  separation  of  the 
adhesive  surfaces  of  its  lining  membrane.  Another  person  may  hear  this  noise  by  using  a  stetho- 
scope or  his  ear. 

In  Valsalva's  experiment  (\  60),  as  soon  as  the  pressure  of  the  air  reaches  10  to  40  mm.  Hg 
air  enters  the  tube.  T  he  sound  is  heard  first,  and  then  we  feel  the  increased  tension  of  the  tympanic 
membrane,  owing  to  the  entrance  of  air  into  the  tympanum.  During  forced  inspiration,  when  the 
nose  and  mouth  are  closed,  air  is  sucked  out,  while  the  tympanum  is  ultimately  drawn  inward. 


RELATIONS   OF   THE   T\-MPANUM. 


823 


The  M.  levator  veli  palatini,  as  it  passes  under  the  base  of  the  opening  of  the  tube  into  the 
pharynx,  forms  the  levator  eminence  or  cushion  (Fig.  332,  W).  Hence,  when  this  muscle  contracts 
and  its  belly  thickens,  as  at  the  commencement  of  the  act  of  deglutilion  and  during  phonation,  the 
lower  wall  of  the  pharyngeal  opening  is  raised,  and  the  opening  thereby  narrowed  { Lucae).  The 
contrnction  of  the  tensor,  occurring  during  the  latter  part  of  the  act  of  deglutition,  dilates  the  tube. 

Other  Views. — According  to  Rudinger,  the  tube  is  always  open,  although  only  by  a  very  narrow 
passage  in  the  upper  part  of  the  canal,  while  the  canal  is  dilated  during  swallowing.  According  to 
Cleland,  the  tube  is  generally  open,  and  is  closed  during  swallowing. 

[Practical  Importance. — The  tympanic  cavity  forms  an  osseous  box,  and, 
therefore,  a  protective  organ  for  the  auditory  ossicles  and  their  muscles,  while  the 
increased  air  space,  obtained  by  its  communication  with  the  mastoid  cells,  permits 
free  vibration  of  the  membrana  tympani.  The  six  sides  of  the  tympanum  have 
important  practical  relations.  It  is  about  half  an  inch  in  height,  and  one  or  two 
lines  in  breadth,  /.  e.,  from  without  inward.  Its  roof  is  separated  from  the  cavity 
of  the  brain  by  a  very  thin  piece  of  bone,  which  is  sometimes  defective,  so  that 
encephalitis  may  follow  an  abscess  of  the  middle  ear.  The  outer  wall  is  formed 
by  the  membrana  tympani,  while  on  the  inner  ^sW.  are  the  fenestra  ovalis  and 
rotunda,  the  ridge  of  the  aqueductus  Fallopii,  the  promontory  and  the  pyramid. 

Fig.  521. 


Fig.  522. 


The  floor  consists  of  a  thin  plate  of  bone,  which  roofs  in  the  jugular  fossa  and 
separates  it  from  the  jugular  vein.  Fractures  of  the  base  of  the  skull  may  rupture 
the  carotid  artery  or  internal  jugular  vein  ;  hence  hemorrhage  from  the  ears  is  a 
bad  symptom  in  these  cases.  Caries  of  the  ear  may  extend  to  other  organs.  The 
anterior  wall  is  in  close  relation  with  the  carotid  artery,  while  the  posterior  com- 
municates with  the  mastoid  cells,  so  that  fluids  from  the  middle  ear  sometimes 
escape  through  the  mastoid  cells.] 

That  the  air  in  the  tympanum  can  communicate  its  vibrations  to  the  membrane  of  the  fenestra 
rotunda  is  true  (p.  814),  but  normally  \\\\s  is  so  slight,  when  compared  with  the  conduction  through 
the  auditory  ossicles,  that  it  scarcely  need  be  taken  into  account. 

Structure. — The  tube  and  tympanum  are  lined  by  a  common  mucous  membrane,  covered  by 
ciliated  epithelium,  while  the  membrana  is  lined  by  a  layer  of  squamous  epithelium.  Mucous 
glands  were  found  by  Troltsch  and  Wendt  in  the  mucous  membrane.  [The  epithelium  covering  the 
ossicles  and  tensor  tympani  is  not  ciliated.] 

Pathological. — The  tube  is  often  occluded,  owing  to  chronic  catarrh  and  narrowing  from  cica- 
trices, hypertrophy  of  the  mucous  membrane,  or  the  presence  of  tumors.  The  deafness  thereby 
produced  may  often  be  cured  by  catheterizing  the  tube  from  the  nose  (Fig.  521 ).  Effusions  into  or 
suppuration  within  the  tympanum,  of  course,  paralyze  the  sound-conducting  mechanism,  while  in- 
flammation often  causes  subseciuent  affections  of  the  plexus  tympanicus.     If  the  temporal  bone  be 


824  METHOD    OF   TESTING   SOUND   CONDUCTION. 

destroyed  by  progressive  caries  within  the  tympanum,  inflammation  of  the   neighboring  cerebral 
structures  may  occur  and  cause  death. 

[Methods. — Not  unfrequently  the  aurist  is  called  upon  to  dilate  the  Eustachian  tube,  which,  in 
certain  cases,  requires  the  use  of  a  Eustachian  catheter  introduced  into  the  tube  along  the  floor 
of  the  nose  (Fig.  521).  At  other  times  he  requires  to  fill  the  tympanic  cavity  with  air,  which  is 
easily  done  by  means  of  a  Politzer's  bag  (Fig.  522).  The  nozzle  is  introduced  into  one  nostril, 
while  the  other  nostril  is  closed,  and  the  patient  is  directed  to  swallow,  while  at  the  same  moment 
liie  surgeon  compresses  the  bag,  and  the  patient's  mouth  being  closed,  air  is  forced  through  tlie  open 
Eustachian  tube  into  the  middle  ear.  Sometimes  a  small,  curved,  narrow  manometer,  containing  a 
drop  of  colored  water,  is  placed  in  the  outer  ear  [Poli/zer).  Normally,  when  the  patient  swallows, 
the  fluid  ought  to  move  in  the  tube.] 

412.  CONDUCTION  OF  SOUND  IN  THE   LABYRINTH.— The 

vibrations  of  the  foot  of  the  stapes  in  the  fenestra  ovalis  give  rise  to  waves  in  the 
perilymph  within  the  inner  ear  or  labyrinth.  These  waves 
are  so-called  "flexion  waves,'^  i.  e.,  the  perilymph  moves  in 
mass  before  the  impulse  of  the  base  of  the  stapes.  This  is 
only  possible  from  the  existence  of  a  yielding  membrane — 
that  filling  the  fenestra  rotunda,  and  sometimes  called  the 
membrana  secundaria,  which  during  rest  bulges  inward  to  the 
scala  tympani,  and  can  be  bulged  outward  toward  the  tym- 
panic cavity  by  the  impulse  communicated  to  it  by  the  move- 
ment of  the  perilymph  (Fig.  510,  r).  The  flexion  waves 
the"'raby*rmtir,"f"n1str°a  niust  Correspond  in  number  and  intensity  to  the  vibrations  of 
ovalis,  cochlea  to  the    {he  auditory  ossicles,  and  must  also  excite  the  free  termina- 

lett,  and  ( f)  the  upper,         .  r     ^  ^■  i-in  r  •         ^  ^     ^  1 

(h)  horizontal,  and  (s)    tious  01  the  auditory  nerve,  which  float  tree  in  the  endolymph. 

canluicft)  ^''""^"■'^"'^''  As  the  endolymph  of  the  saccule  and  utricle  lying  in  the 
vestibule  receive  the  first  impulse,  and  as  they  communicate 
anteriorly  with  the  cochlea,  and  posteriorly  with  the  semicircular  canals,  conse- 
quently the  motion  of  the  perilymph  must  be  propagated  through  these  canals. 
To  reach  the  cochlea  the  movement  passes  from  x\\^  saccule  (lying  in  the  fovea 
hemispherica)  along  the  scala  vestibuli  to  the  helicotrema,  where  it  passes  into  the 
scala  tympani,  where  it  reaches  the  membrane  of  the  fenestra  rotunda,  and  causes 
it  to  bulge  outward.  From  the  utricle  (lying  in  the  fovea  hemielliptica),  in  a 
similar  manner,  the  movement  is  propagated  through  the  semicircular  canals. 
Politzer  observed  that  the  endolymph  in  the  superior  semicircular  canal  rose  when 
he  caused  contraction  of  the  tensor  tympani  by  stimulating  the  trigeminus,  just  as 
the  base  of  the  stapes  must  be  forced  against  the  perilymph  with  every  vibration 
of  the  membrani  tympani. 

[Practical. — It  is  well  to  view  the  organ  of  hearing  as  consisting  of  two  mech- 
anisms :  — 

1.  The  sound-conducting  apparatus. 

2.  The  sound-perceiving  apparatus. 

The  former  includes  the  outer  ear,  with  its  auricle  and  external  meatus  ;  the 
middle  ear  and  the  parts  which  bound  it,  or  open  into  it.  The  latter  consists  of 
the  in7ter  ear  with  the  expansion  of  the  auditory  nerve  in  the  labyrinth,  the  nerve 
itself,  and  the  sound-perceiving  and  interpreting  centre  or  centres  in  the  brain 

(P-  723)-] 

[Testing  the  Sound  Conduction. — In  any  case  of  deafness  it  is  essential  to 
estimate  the  degree  of  deafness  by  the  methods  stated  at  p.  815,  and  it  is  well  to 
do  so  both  for  such  sounds  as  those  of  a  watch  and  conversation.  We  have  next 
to  determine  whether  the  sound-conducting  or  the  sound-perceiving  apparatus  is 
affected.  If  a  person  is  deaf  to  sounds  transmitted  through  the  air,  on  applying 
a  sounding  tuning-fork  to  the  middle  line  of  the  head  or  teeth,  and  if  it  be  heard 
distinctly,  then  the  sound-perceiving  apparatus  is  intact,  and  we  have  to  look  for 
the  cause  of  deafness  in  the  outer  or  middle  ear.  In  a  healthy  person,  the  sound 
of  the  tuning-fork  is  heard  of  ecjual  intensity  in  both  ears.  In  this  case  the  sound 
is  conducted  directly  to  the  labyrinth  by  the  cranial  bones.     In  cases  of  disease 


STRUCTURE   OF   THE    LABYRINTH.  82o 

of  the  sound-conducting  mechanism,  the  sound  of  the  tuning-fork  is  heard  loudest 
in  the  deafer  ear.  Ed.  Weber  pointed  out  that,  if  one  ear  be  stopped  and  a 
vibrating  tuning-fork  placed  on  the  head,  the  sound  is  referred  to  the  plugged 
ear,  where  it  is  heard  loudest.  It  is  assumed  that  when  the  ear  is  plugged,  the 
sound  waves  transmitted  by  the  cranial  bones  are  prevented  from  escaping  (Mach). 
If,  on  the  contrary,  the  sound  be  heard  loudest  in  the  good  ear,  then  in  all  proba- 
bility there  is  some  affection  of  the  sound-perceiving  apparatus  or  labyrinth, 
although  there  are  exceptions  to  this  statement,  especially  in  elderly  people. 
Another  plan  is  to  connect  two  telephones  with  an  induction  machine,  provided 
with  a  vibrating  Neef 's  hammer.  The  sounds  of  the  vibrations  of  the  latter  are 
reproduced  in  the  telephones,  and  if  they  be  placed  to  the  ears,  then  the  healthy 
ears  hear  only  one  sound,  which  is  referred  to  the  middle  line,  and  usually  to  the 
back  of  the  head.  In  diseased  conditions  this  is  altered — it  is  referred  to  one 
side  or  the  other.] 

413.  STRUCTURE  pF  THE  LABYRINTH,  AND  TERMINATION  OF  THE 
AUDITORY  NERVE.— Scheme.— The  vestibule  (Fig.  524,  III)  contains  two  separate  sacks, 
one  of  them   the  saccule,  j   (round  sack  or  S.  hemispha;ricus),  communicates  with   the  ductus 

Fig.  524. 


..^  ^^^ 1  of  a  tum  of  the  cochlea;  II,  A,  ampulla  of  a  semicircular  canal  with  the  crista  acustica  ;  a, p. 

aiiaitory  cells  ;  f,  provided  with  a  fine  hair;  T,  otoliths  ;  III,  scheme  of  the  human  labyrinth  ;  IV,  scheme  of 
a  bird's  labyrinth ;  V,  scheme  of  a  fish's  labyrinth. 

cochlearis,  C  c,  of  the  cochlea,  the  other  the  utricle,  U  (elliptical  sack,  or  sacculus  hemiellipticus), 
communicates  with  the  semicircular  canals,  C  s,Q.  s. 

The  cochlea  consists  of  2|^  turns  of  a  tube  dispo^e<3  round  a  central  column  or  modiolus.  The 
tube  is  divided  into  two  compartments  (Fig.  527,  Fig.  524,  I )  by  a  horizontal  septum,  partly  osse- 
ous and  partly  membranous,  the  lamina  spiralis  ossea  and  membranacea.  The  lowei  compart- 
ment is  the  scala  tympani,  and  is  separated  from  the  cavity  of  the  tympanum  by  the  membrane  of 
the  fenestra  rotunda. 

The  upper  compartment  is  the  scala  vestibuli,  which  communicates  with  the  vestibule  of  the 
labyrinth  (Fig.  524,  I).  These  two  compartments  communicate  directly  by  a  small  opening  at  the 
apex  of  the  cochlea,  a  sickle-shaped  edge  ["  hamulus  "]  of  the  lamina  spiralis  bounding  the  heli- 
cotrema  (Fig.  510).  The  scala  vestibuli  is  divided  by  Reissner's  membrane  (Fig.  524, 1), 
which  arises  near  the  outer  part  of  the  lamina  spiralis  ossea,  and  runs  obliquely  outward  to  the  wall 
of  the  cochlea  so  as  to  cut  off  a  small  triangular  canal,  the  ductus  or  canalis  cochlearis,  or  scala 
media,  C  c,  whose  floor  is  formed  for  the  most  part  by  the  lamina  spiralis  membranacea,  and  on 
which  the  end  organ  of  the  auditory  nerve — Corti's  organ— is  placed.  The  lower  end  of  the  can- 
alls  cochlearis  Is  blind,  III,  and  divided  toward  the  saccule,  with  which  it  communicates  by  means 
of  the  small  canalis  reuniens,  C  r  (/fensen).  The  utricle  (Fig.  524,  III,  U)  communicates  with 
the  three  semicircular  canals,  C  s,  C  s — each  by  means  of  an  ampulla,  within  which  lies  the  termi- 
nations of  the  ampullary  nerves,  but  as  the  posterior  and  the  superior  canals  unite  there  is  only  one 


826 


MACUL.^    ACUSTIC^   AND    COCHLEA. 


common  ampulla  for  them.  The  membranous  semicircular  canals  lie  within  the  osseous  canals, 
perilymph  lying  between  the  two.  Perilyinph  also  fills  the  scala  vestibuli  and  tympani,  so  that  all 
the  spaces  within  the  labyrinth  are  filled  by  fluid,  while  the  spaces  themselves  are  lined  by  short 
cylindrical  epithelium. 

The  system  of  spaces,  filled  by  endolymph,  is  the  only  part  containing  the  nervous  end  organs 
for  hearing.  .All  these  spaces  communicate  with  each  other  ;  the  semicircular  canals  directly  with 
the  utricle,  the  ductus  cochlearis  with  the  saccule  through  the  canalis  reuniens;  and,  lastly,  the  sac- 
cule and  utricle  through  the  "  saccus  endolymphaticus,"  which  springs  by  an  isolated  limb  from 
each  sack  ;  the  limbs  then  unite,  as  in  the  letter  Y.  and  pass  through  the  osseous  aqueductus  vestibuli 
to  end  blindly  in  the  dura  mater  of  the  brain  (t'ig.  Ill,  R — Bollcher,  Retzhis).  The  aqueductus 
cochleae  is  another  narrow  passage,  which  begins  in  the  scala  tympani,  immediately  in  front  of  the 
fenestra  rotunda,  and  opens  close  to  the  fossa  jugularis.  It  forms  a  direct  means  of  communication 
between  the  perilymph  of  the  cochlea  and  the  subarachnoid  space. 

Semicircular  Canals  and  Vestibular  Sacks  — The  membranous  semicircular  canals  do  not  fill 
the  corresponding  osseous  canals  completely,  but  are  separated  from  them  bv  a  pretty  wide  space, 
which  is  filled  with  perilymph  (Fig.  525).  At  the  concave  margin  they  are  fixed  by  connective  tis. 
sue  to  the  osseous  walls.  The  ampulla',  however,  completely  fill  the  corresponding  osseous  dilata- 
tions. The  canals  and  ampullae  consist  externally  of  an  outer,  vascular,  connective-tissue  layer,  on 
which  there  rests  a  well-marked  hyaline  layer,  bearing  a  single  layer  of  flattened  epithelium. 

Crista  Acustica. — The  vestibular  branch  of  the  auditory  nerve  sends  a  branch  to  each  ampulla 
and  to  the  saccule  and  utricle  (Fig.  526).     In  the  ampullae  (Fig.  524,  II,  A),  the  nerve  (<)  termi- 


FlG.  525. 


Fig.  526. 


interior  of  the  right  labyrinth  with  its  membranous  canals  and  nerves.  In  Fig.  525.  A,  the  outer  wall  of  the  bony 
labyrinth  is  removed  to  show  the  membranous  parts  within — i,  commencement  of  the  spiral  tubeof  the  cochlea  ; 
2,  posterior  semicircular  canal,  partly  opened ;  3,  horizontal :  4,  superior  canal :  5,  utricle  ;  6,  saccule  ;  7,  lamina 
spiralis;  /.scala  tympani;  8,  ampulla  of  the  superior  membranous  canal;  9.  of  the  horizontal;  10,  of  the 
posterior  canal.  FlG  526  shows  the  membranous  labyrinthand  nerves  detached — i,  facial  nerve  in  the  internal 
auditory  meatus  ;  2,  anterior  division  of  the  auditory  nerve  giving  branches  to  5,  8,  and  g,  the  utricle  and  the 
ampullse  of  the  superior  and  horizontal  canals  ;  ^,  posterior  division  of  the  auditory  nerve,  giving  branches  to 
the  saccule,  6,  and  posterior  ampulla,  10,  and  cochlea,  4  ;  7,  united  part  of  the  posterior  and  superior  canals; 
II,  posterior  extremity  of  the  horizontal  canal. 


nates  in  connection  with  the  crista  acustica.  which  is  a  yellow  elevation  projecting  into  the  equa- 
tor of  the  ampulla.  The  medullated  nerve  fibres,  «,  form  a  plexus  in  the  connective-tissue  layer, 
lose  their  myelin  as  they  pass  to  the  hyaline  basement  membrane,  and  each  ends  in  a  cell  provided 
with  a  rigid  hair  (o,p)  90  u  in  length,  so  that  the  crista  is  largely  covered  with  these  hair  cells 
(Hatimann),  but  between  them  are  supporting  cells  like  cylindrical  epithelium  (i?!,  and  not  unfre- 
quently  containing  granules  of  yellow  pigment.  The  hairs  or  "auditory  hairs  "  (.)/.  Schulfze)  are 
com[X>sed  of  many  fine  fibres  (Ki-tzius).  An  excessively  fine  membrane  (membrana  tectoria) 
covers  the  hairs  (PritcharJ,  Latisr). 

Maculae  Acusticae. — The  nerve  terminations  in  the  maculje  acustic;E  of  the  saccule  .and 
utricle  are  exactly  the  same  as  in  the  ampullar,  only  the  free  surface  of  their  membrana  tectoria  is 
sprinkled  with  small,  white,  chalk-hke  crystals  or  otoliths  (II,  T),  composed  of  calcic  carbonate, 
which  are  sometimes  amorphous  and  partly  in  the  form  of  arragonite,  lying  fixed  in  the  viscid  endo- 
lymph. The  non-medullated  axis  cylinders  of  the  saccular  nerves  enter  directly  into  the  substance 
of  the  hair  cells.  The  terminations  of  the  nerves  have  been  investigated,  chiefly  in  fishes,  in  the 
rays. 

Cochlea. — The  terminations  of  the  cochlear  branch  of  the  auditory  nerve  lie  in  connection  with 
Corti's  organ,  which  is  placed  in  the  canalis  or  ductus  cochlearis  (Fig.  524,  I,  C  c,  and  III,  C  c, 
and  Fig.  527),  the  small  triangular  chamber  or  [scala  media],  cut  off  from  the  scala  vestibuli  by 
the  membrane  of  Reissner.  Corti's  organ  is  placed  on  the  lamina  spiralis  membranacea.  and  con- 
sists of  a  sufipprlini:^  apparatus  composed  of  the  so-called  Corti's  arches,  each  of  which  consi.sts 
of  two  Corti's  rods  (:,}'),  which  lie  upon  each  other  like  the  beams  of  a  house.     But  every  two 


INTRA-LABYRINTHINE    PRESSURE. 


827 


rods  do  not  form  an  arch,  as  there  are  always  three  inner  to  two  outer  rods  [Clauiiius).     There  are 
about  4500  uuter  rods  (  IVii/i/^yer}. 

The  ductus  cochlearis  becomes  larger  toward  the  apex  of  the  cochlea,  and  the  rods  also  become 
longer;  the  inner  ones  are  30  //  long  in  the  first  turn,  and  34  /i  in  the  upper,  the  outer  rods  47  11 
and  69  «  respectively.  The  span  of  the  arches  a'so  increases  [Heii^en),  [The  arches  leave  a 
Iri.ingular  tunnel  beneath  them.]  The  proper  end  organs  of  the  cochlear  nerve  are  the  cylindrical 
"  hair  cells  "  {Kolliker]  previously  observed  by  Corti.  which  are  from  16,400  to  20,000  in  number 
(Nt-nsfit.  IVa/tleyer).  There  is  one  row  of  inner  cells  (/)  which  rests  on  a  layer  of  small  granular 
cells  (K)  [Bottcher,  Waiiieyer);  the  outer  cells  (a,  a)  number  12,000  in  man  (Ketzius\,  and  rest 
upon  the  basement  membrane,  being  disposed  in  three  or  even  four  rows.  Between  the  outer  hair 
cells  there  are  other  cellular  structures,  which  are  either  regarded  as  special  cells  (Deiter's  cells), 
or  are  regarded  merely  as  processes  of  the  hair  cells  i^Lavdou'sky),  [The  cochlear  branch  of  the 
auditory  nerve  enters  the  modiolus,  and  runs  upward  in  the  osseous  channels  there  provided  for  it, 
and  as  it  does  so  gives  branches  to  the  lamina  spiralis,  where  they  run  between  the  osseous  plates 
which  form  the  lamina.]  The  fibres  (N)  come  out  of  the  lamina  spiralis  after  traversing  the  gan- 
glionic cells  in  their  course  (Figs.  524,  527,  I,  G),  and  end  by  fine  varicose  fibrils  in  the  hair 
cells  (Fig.  527)  (  Waldeyer,  Got/stein,  Lavdowsky,  Ketzius). 


Fig.  527. 


lerae  of  the  ductus  cochlearis  and  the  organ  of  Corti.  N,  cochlear  nerve:  K,  inner,  and  P,  outer  hair  cells;  «, 
nerve  fibrils  terminating  in  P  ;  a,  a,  supporting  cells :  d,  cells  in  the  sulcus  spiralis  :  z,  inner  rod  of  Corti ;  ^I  b. 
Corti,  membrane  of  Corti,  or  the  membrana  tectoria  ;  o,  the  membrana  reticularis;  H,  G.  cells  filling  up  the 
space  near  the  outer  wall. 


Membrana  Reticularis. — Corti's  rods  and  the  hair  cells  are  covered  by  a  special  membrane 
(<>),  the  membrana  reticularis  of  Kolliker.  The  upper  ends  of  the  hair  cells,  however,  project 
through  holes  in  this  membrane,  which  consists  of  a  kind  of  a  cement  substance  holding  these 
parts  together  [Lavdoiusky'\.  [Springing  from  the  outer  end  of  the  lamina  spiralis,  or  crista  spiralis, 
is  the  membrana  tinctoria,  sometimes  called  the  membrane  of  Corti.  It  is  a  well-defined  struc- 
ture, often  fibrillated  in  appearance,  and  extends  outward  over  the  organ  of  Corti.]  Waldeyer 
regards  it  as  a  damping  apparatus  for  this  organ  (Fig.  527,  Mb.  Corti). 

[Basilar  Membrane. — Its  breadth  increases  from  the  base  to  the  apex  of  the  cochlea.  This 
fact  is  important  in  connection  with  the  theory  of  the  perception  of  tone.  It  is  supposed  that  high 
notes  are  appreciated  by  structures  in  connection  with  the  former,  and  low  notes  by  the  upper  parts 
of  the  basilar  membrane.  In  one  case,  recorded  by  Moss  and  Steinbrugge,  a  patient  heard  low 
notes  only  in  the  right  ear,  and  after  death  it  was  found  that  the  auditory  nerve  in  the  first  turn  of 
tile  cochlea  was  atrophied.] 

Intra- Labyrinthine  Pressure. — The  lymph  within  the  labyrinth  is  under  a  certain  pressure. 
Every  diminution  of  the  pressure  of  the  air  in  the  tym])anum  is  accompanied  by  a  corresponding 
diminution  of  the  intra-labyrinthine  pressure,  while  conversely  every  increase  of  pressure  is  accom- 
panied by  an  increase  of  the  lymph  pressure  (/'.  Bezotd). 


828  THE    QUALITY   OF   A   TONE. 

The  perilymph  of  the  inner  ear  flows  away  chiefly  through  the  aqueductus 
cochleffi,  in  the  circumference  of  the  foramen  jugulare,  into  the  peripheral  lym- 
phatic system,  which  also  takes  up  the  cerebro-spinal  fluid  of  the  subarachnoid 
space,  while  a  small  part  drains  away  to  the  subdural  space  through  the  internal 
auditory  meatus.  The  endolymph  flows  through  the  arachnoid  sheath  of  the 
N.  acusticus  into  the  subarachnoid  space  (C  Hasse). 

414.  QUALITY  OF  AUDITORY  PERCEPTIONS-PERCEP- 
TION OF  THE  PITCH  AND  STRENGTH  OF  TONES.— Tones 
and  Noises. — Every  normal  ear  is  able  to  distinguish  musical  tones  and  lunscs. 
Physical  experiments  prove  that  tones  are  produced  when  a  vibrating  elastic  body 
executes  periodic  movements,  i.e.,  when  the  sounding  body  executes  the  same 
movement  in  equal  intervals  of  time,  as  the  vibrations  of  a  string  which  has  been 
plucked.  A  noise  is  produced  by  non-periodic  movements,  i.e.,  when  the 
sounding  body  executes  unequal  movements  in  equal  intervals  of  time.  [The 
non-periodic  movements  clash  together  on  the  ear,  and  produce  dissonance,  as 
when  we  strike  the  keyboard  of  a  piano  at  random.]  This  is  readily  proved  by 
means  of  the  siren.  Suppose  that  there  are  forty  holes  in  the  rotatory  disk  of  this 
instrument,  placed  at  exactly  the  same  distance  from  each  other — on  rotating  the 
disk  and  directing  a  current  of  air  against  it,  obviously  with  every  rotation  the 
air  will  be  rarefied  and  condensed  exactly  forty  times.  Every  two  condensations 
and  rarefactions  are  separated  from  each  other  by  an  equal  \x\\.tx\2\  of  time.  This 
arrangement  yields  a  characteristic  musical  tone  or  note.  If  a  similar  disk  with 
holes  perforated  in  it  at  unequal  distances  be  used,  on  air  being  forced  against  it, 
a  whirring,  non-musical  nnise  is  produced,  because  the  movements  of  the  sounding 
body  (the  condensations  and  rarefactions  of  the  air)  are  non-periodic .  [The 
double  siren  of  v.  Helmholtz  is  an  improved  instrument  for  showing  the  same 
facts.] 

The  normal  ear  also  distinguishes  in  every  tone  three  distinct  factors  : — 
[(i)  Intensity  or  force  ;  (2)  Pitch  ;   (3)  Quality,  timbre  or  "  klang."'\ 

1.  The  intensity  of  a  tone  depends  upon  the  greater  or  lesser  amplitude  of 
the  vibrations  of  the  sounding  body.  Every  one  knows  that  a  vibrating  string 
emits  a  feebler  sound  when  its  excursions  are  smaller.  (The  intensity  of  a  sound 
corresponds  to  the  degree  of  illumination  or  brightness  in  the  case  of  the  eye.) 

2.  The  pitch  depends  upon  the  number  of  vibrations  which  occur  in  a  given 
time  {Mersenne,  i6j6)  [or  the  length  of  time  occupied  by  a  single  vibration]. 
This  is  proved  by  means  of  the  siren.  If  the  rotating  disk  have  a  series  of  forty 
holes  at  equal  intervals,  and  another  series  of  eighty  equidistant  from  each  other, 
on  blowing  a  stream  of  air  against  the  rotating  disk  we  hear  two  sounds  of  unequal 
pitch,  one  being  the  octave  of  the  other.  (The  perception  of  pitch  corresponds 
to  the  sensation  of  color  in  the  case  of  the  eye.) 

3.  The  quality  or  timbre  {"Klangfar-be"^  is  peculiar  to  different  sonorous 
bodies.  [It  is  the  peculiarity  of  a  musical  tone  by  which  we  are  enabled  to  distin- 
guish it  as  coming  from  a  particular  instrument,  or  from  the  human  voice.  Thus, 
the  same  note  struck  on  a  piano  and  sounded  on  a  violin  differs  in  quality  or 
timbre.~\  It  depends  upon  the  peculiar  form  of  the  vibration,  or  the  form  of  the 
wave  of  the  sonorous  body.  (There  is  no  analogous  sensation  in  the  case  of 
light.) 

I.  Perception  of  Pitch. — By  means  of  the  organ  of  hearing  we  can  determine  that  dift'erent 
tones  have  a  different  pilch.  In  the  so  called  musical  scale,  or  gamut,  this  difference  is  very  marked 
to  a  normal  ear.  But  in  the  scale  there  are  again  four  tones,  which,  when  they  are  sounded  together, 
cause  in  a  normal  ear  the  sensation  of  an  agreeable  sound,  which  once  heard  can  readily  be  repro- 
duced. This  is  the  tone  of  the  so-called  Accord,  Triad,  or  Common  Chord,  consisting  of  the  ist, 
3d,  and  5th  tones  of  the  scale,  to  which  the  8th  tone  or  octave  is  added.  We  have  next  to  determine 
the  pitch  of  the  tones  of  the  chord,  and  then  that  of  the  other  tones  of  the  scale.  The  siren  is  used 
for  the  fundamental  experiment,  from  which  the  others  can  easily  be  calculated.  Four  concentric 
circles  are  drawn  upon  the  rotatory  disk  of  the  siren ;  the  inner  circle  contains  40  holes,  the  second 


PERCEPTION    OF    PITCH.  829 

50,  the  third  60,  and  the  outer  So — all  the  holes  being  at  equal  distances  from  each  other.  If  the 
disk  be  rotated,  and  air  forced  against  each  series  of  holes  in  /urn,  we  distinguish  successively  the 
four  tones  of  the  accord  (major  chord  with  its  octave) ;  when  all  the  four  series  are  blown  upon 
simullaneously,  we  hear  in  complete  purity  the  major  chord  itself.  The  relative  number  of  the 
holes  in  the  four  series  indicates  in  the  simplest  manner  the  relative  pitch  of  the  tones  of  the  major 
chord.  While  one  revolution  of  the  disk  is  necessary  to  produce  the  fundamental  ground  tone 
(key-note  or  tonic)  with  40  condensations  and  rarefactions  of  the  air — in  order  to  produce  the 
octave,  we  must  have  double  the  number  of  condensations  and  rarefactions  during  one  revolution 
in  the  same  time.  Thus,  the  relation  of  the  number  of  vibrations  of  the  Ground  tone  or  Tonic  to 
the  Octave  ne.\t  above  it,  is  I  :  2.  In  the  second  series  we  have  50  holes,  which  cause  the  pitch  o( 
the  Third  ;  hence,  the  relation  of  the  Ground  tone  to  the  Third  in  this  case  is  40 :  50,  or  i  :  i ^  =  |, 
i.  e.,  for  every  vibration  of  the  Ground  tone  there  are  J  vibrations  in  the  Third.  In  the  third  series 
are  60  holes,  which,  when  blown  upon,  yield  the  Fifth  ;  hence,  the  ratio  of  the  Ground  tone  to  the 
Fifth  in  our  disk  is  40  :  60,  or  i  :  i^  =  |.  In  the  same  way  we  can  estimate  the  pitch  of  the  Fourth 
tone,  and  we  tind  that  the  number  of  vibrations  of  the  First,  Third,  Fifth,  and  Octave  are  to  each 
other  as  I  :  1 :  3  :  2. 

The  Minor  chord  is  quite  as  characteristic  to  a  normal  ear  as  the  Major.  It  is  distinguished 
essentially  from  the  latter  by  its  Third  being  half  a  tone  lower.  We  can  easily  imitate  it  by  the 
siren,  as  the  Minor  Third  consists  of  a  number  of  vibrations  which  stand  to  the  Ground  tone  as 
6  :  5,  i.  e.,  if  5  vibrations  occur  in  a  given  time  in  the  Ground  tone,  then  6  occur  in  the  Minor  Third; 
its  vibration  number,  therefore,  is  f . 

From  these  relations  of  the  Major  and  Minor  common  chords  we  may  calculate  the  relative  tones 
in  the  scale,  and  we  must  remember  that  the  Octave  of  a  tone  always  yields  the  fullest  and  most 
complete  harmony.  It  is  evident  that  as  the  Major  Third,  the  Minor  Third,  and  the  Fifth  harmonize 
with  the  fundamental  Ground  tone  or  key-note,  they  must  also  harmonize  with  the  Octave  of  the 
key-note.  We  obtain  from  the  Major  Third  with  the  number  of  vibrations  J,  the  Minor  Sixth  with 
|,  from  the  Minor  Third  with  |,  the  Major  Sixth  =  (^^  =)  |;  from  the  Fifth  with  |,  the  Fourth 
=  |.  These  relations  are  known  as  the  ■'  Inversions  ot  the  intervals."  These  relations  of  the  tones 
are,  collectively,  the  consonant  intervals  of  the  scale.  The  dissonant  stages,  or  discords,  of  the  scale 
can  be  obtained  as  follows:  Suppose  that  we  have  the  Ground  tone  or  key-note  C,  with  the  number 
of  vibrations  =  I,  the  Third  E  ^  J,  the  Fifth  G  =  |,  and  the  Octave  ^=  2,  we  then  derive  from  the 
Fifth  or  Dommant  G  a  Major  chord — this  is  G,  B,  L)i.  The  relative  number  of  vibrations  of  these 
3  tones  is  the  same  as  in  the  Major  chord  of  C,,  C,  E,  G.  Hence,  the  number  of  vibraSons  of  G :  B 
is  as  C  :  E.  When  we  substitute  the  values  we  obtain  |  :  B  :=  i  :  J — i.  e.,  B  =  '/ .  But  D' :  B  = 
G  :  E ;  so  that  D  :  '/'  —  3  •  t>  '■  '^■>  '-''  =  ¥'  °''  ^"  octave  lower,  we  have  D  =  |.  Deduce  from  F 
(subdominant)  a  Major  chord,  F,  A,  CI.  The  relation  of  A  :  Cl=  E  :  G,  or  A  :  2  ^  | :  ?,  !.  e-.,  A 
=  f .  Lastly,  F  :  A  =  C  :  E,  or  F  :  f  =  I  :  ^,  !.  ir.,  F  =  |.  So  that  all  the  tones  of  the  scale  have 
the  following  number  of  vibrations:  I,  C  =  i ;  II,  D  =  | ;  HI,  E  =  f;  IV,  F  =  f  ;  V,  G  =  | ; 
VI,  A  =  5 ;   VII,  B  =  V  ;  VIII,  C  =  2. 

Conventional  Estimate  of  Pitch. — Conventionally,  the  pitch  or  concert  pitch  of  the  note,  a, 
is  taken  at  440  vibrations  in  the  second  [Scheiblcr,  18^4),  although  in  France  it  is  taken  at  435 
vibrations  per  second.  From  this  we  can  estimate  the  absolute  number  of  vibrations  for  the  tjncs 
of  the  scale:  C  =  33,  D  =  37.125,  E  =  41.25,  F  =  44,  G  =  49.5,  A  =  55,  B  =  61.875  vibrations. 
The  number  of  vibrations  of  the  next  highest  octave  is  found  at  once  by  multiplying  these  numbers 
by  2. 

Musical  Notes. — The  lowest  notes  used  in  mu»ic  are  the  double  bass,  E,  with  41.25  vibrations, 
piano-forte  C  with  33,  grand  piano  A'  with  27.5,  and  organ  C  with  16.5.  The  highest  notes  in 
music  are  the  piano-forte  C  with  4224,  and  d''  on  the  piccolo  flute,  with  4752  vibrations  per  .second. 

Limits  of  Auditory  Perception. — According  to  Preyer,  the  limit  of  the 
perception  of  the  lowest  audible  tone  lies  between  sixteen  and  twenty-three  vibra- 
tions per  second,  and  e""  with  40,960  vibrations  as  the  highest 
audible  tone;  so  that  this  embraces  about  11 1^  octaves.  ^^^' 

[Audibility  of  Shrill  Notes. — This  varies  very  greatly  in  different  persons 
(ll'ollaston).  There  is  a  remarkable  falling  off'  of  the  power  as  age  advances 
[Galton).  For  testing  this,  Gallon  uses  a  small  whistle  (Fig.  528)  made  of  a 
brass  tube,  with  a  diameter  of  le-s  than  j'^th  of  an  inch.  A  plug  is  fitted  at  the 
lower  end  to  lengthen  or  shorten  the  lube,  whereby  the  pitch  of  the  note  is 
ahered.  Among  animals  Galton  finds  none  superior  to  cats  in  the  power  of  hear- 
ing  shrill  sounds,  and  he  attributes  this  "to  differentiation  by  natural  selection 
among  these  animals  until  they  have  the  power  of  hearing  all  the  high  notes 
made  by  mice  and  other  little  creatures  they  have  to  catch."] 

Variations  in  Auditory  Perception. — It  is  rare  to  find  that  tones  produced  by 
more  than  35,000  vibrations  per  second  are  heard.  When  the  tensor  tympani  is 
contracted,  the  perception  may  be  increased  for  tones  3000  to  5000  vibrations 
higher,  but  rarely  more.     Pathologically,  the  perception  for  high  notes  may  be    Galton': 


830  PERCEPTION    OF   QUALI'n\ 

abnormally  acute — (i)  When  the  tension  of  the  sound-conducting  apparatus  generally  is  increased. 
(2)  By  elimination  of  the  sound-conducting  apparatus  of  the  middle  ear,  which  offers  greater  or 
less  resistance  to  the  propagation  of  very  high  notes,  as  perforation  of  the  membrana  tympani,  or 
loss  of  the  incus  and  malleus.  In  these  cases  the  stapes  is  directly  set  in  vibration  by  the  sound 
waves,  when  tones  up  to  So.ooo  vibrations  have  been  perceived.  Diminished  tension  of  the  sound- 
conducting  apparatus  causes  diminution  of  the  perception  foi  high  tones  (Bluie). 

A  smaller  number  of  vibrations  than  16  per  second  (as  in  the  organ)  are  no  longer  heard  as  a 
tone,  but  as  single,  dull  impulses.  The  tones  thai  are  produced  b.yond  the  highest  audible  note, 
as  by  stroking  small  tuning-forUs  with  a  violin  bow,  are  also  no  longer  heard  as  tones,  but  they 
cause  a  painful  cutting  kind  of  impression  in  the  ear.  In  the  musical  scale  the  range  is,  approxi- 
mately, from  C  of  the  first  octave  with  16.5  vibrations  to  e,  the  eighth  octave. 

Comparison  of  Ear  and  Eye. — In  comparing  the  perception  of  the  eye  with  that  of  the  ear, 
we  see  at  once  that  the  \ange  of  accommodation  of  the  ear  is  much  greater.  Red  has  456  billions 
of  vibrations  per  second,  while  the  visible  violet  has  but  667,  so  that  the  eye  only  takes  cognizance 
of  vibrations  which  do  not  form  even  one  octave. 

Lowest  Audible  Tone. — As  to  the  smallest  number  of  successive  vibrations 
which  the  ear  can  perceive  as  a  sensation  of  tone,  Savart  and  Pfaundler  considered 
that  two  would  suffice.  If,  however,  we  exclude  in  our  experiments  the  possibility 
of  the  occurrence  of  over- tones  (4  to  8)  {Afach),  or  even  16  to  20  vibrations  {F. 
Aiterbach,  Kohlrausch)  are  necessary  to  produce  a  characteristic  tone. 

When  tones  succeed  each  other  rapidly,  they  are  still  perceived  as  distinct, 
when  at  least  o.i  second  intervenes  between  two  successive  tones  {11.  Helmholtz)  ; 
if  they  follow  each  other  more  rapidly  they  fuse  with  each  other,  although  a  short- 
time  interval  is  sufficient  for  many  musical  tones. 

By  the  term,  "fineness  of  the  ear,"  or,  as  we  say,  a  "  good  ear,"  is  meant  the 
capacity  of  distinguishing  from  each  other,  as  different,  two  tones  of  nearly  the 
same  number  of  vibrations.  This  power  can  be  greatly  increased  by  practice,  so 
that  musicians  can  distinguish  tones  that  differ  in  pitch  by  only  -5-^,  or  even  j-jVif 
of  their  vibrations. 

With  regard  to  the  time  sense,  it  is  found  that  beats  are  more  precisely  per- 
ceived by  the  ear  than  by  the  other  sense  organs  {Horing,  Mach,  Vierordt). 

Pathological. — According  to  Lucae,  there  are  some  ears  that  are  better  adapted  for  hearing  low 
notes  ami  others  for  high  notes.  Both  conditions  are  disadvantageous  for  hearing  speech.  Those 
who  hear  low  notes  best  hear  the  highest  consona'its  imperlectiy.  The  low  notes  are  heard  abnor- 
mally loud  in  rheumatic  facial  paral)sis,  while  the  high  tones  are  heard  abnormally  loud  in  cases  of 
loss  of  the  membrana  tympani,  incus,  and  malleus.  The  stapedius  is  in  full  action,  whereby  the 
highest  tones  are  heard  louder  at  the  expense  of  the  lower  notes.  Many  persons  with  normal  liear- 
ing  hear  a  tone  higher  with  one  ear  than  with  the  otner.  This  condition  is  called  diplacusis  bin- 
auralis.  In  rare  cases  sudden  loss  of  the  perception  of  certain  tones  has  been  observed,  e.  g.,  the 
base-deafness  of  Moos.  In  a  case  described  by  Magnus,  the  tones  dl,bl,were  not  heard 
(S316). 

II.  Perception  of  the  Intensity  of  Tone. — The  intensity  of  a  tone  depends  upon  the  ampli- 
tttdc  of  the  vihrations  ol  the  sounding  body.  The  intensity  of  the  tone  is  proportional  to  the  square 
of  the  amplitude  of  vibration  of  the  sounding  body,  /.  e.,  with  2,  3,  or  4  times  the  amplitude  the 
intensity  of  the  tone  is  4,  9,  16  times  as  strong.  As  sonorous  vibrations  are  communicated  to  our 
ears  by  the  wave  movements  of  the  air,  it  is  evident  that  the  tones  must  become  less  and  less  intense 
the  further  we  are  from  the  source  of  the  sound.  The  intensity  of  the  sound  is  inversely  propor- 
tional to  the  square  of  the  distance  of  the  source  of  the  sound  from  the  ear. 

Tests. — I.  Place  a  watch  horizontally  near  the  ear,  and  test  how  close  it  may  be  brought  to  the 
ear,  and  also  how  far  it  may  be  removed,  and  still  its  sounds  be  heard.  Measure  the  distance.  2. 
Itard  uses  a  small  hammer  suspended  like  a  pendulum,  and  allowed  to  fall  upon  a  hard  surface.  3. 
Balls  of  different  weights  are  allowed  to  fall  from  varying  heights  upon  a  plate.  In  this  case  the 
intensity  of  the  sound  is  proportional  to  the  product  of  the  weight  of  the  ball  into  the  height  it 
falls. 

As  to  the  limits  of  the  perception  of  the  intensity  of  a  tone,  it  is  found  that  a  spherule  weighing 
I  milligram,  and  falling  from  a  height  of  i  mm,  upon  a  glass  plate,  is  heard  at  a  distance  of  5  cen- 
timetres (Sc/iaf/uiiilt). 

415.  PERCEPTION  OF  QUALITY— ANALYSIS  OF  VOWELS.- By  the  term 
quality  ("  Klangfarbe  "J,  musical  color  or  timbre,  is  understood  a  peculiar  character  of  the  tone, 
by  \\'hich  it  can  be  distinguished  apart  from  its  pitch  and  intensity.  Thus,  a  flute,  horn,  violin,  and 
the  human  voice  may  all  sound  the  same  note  with  equal  intensity,  and  yet  all  the  four  are  distin- 
guished at  once  by  tlieir  specific  quality.  Wherein  lies  the  essence  ("  Wesen  "')  of  tone  color?    The 


ANALYSIS   OF   VOWELS. 


831 


investigations  of  v.  Helmholtz  have  proved  that,  among  mechanisms  which  produce  tones,  only 
those  that  produce  pendulum-like  vibrations,  /.  i.,  the  to-andfro  viljrations  of  a  metallic  rod  with 
one  end  fixed,  and  tuning-forks,  execute  simple  pendulum  like  vibrations.  This  can  be  shown  by 
making  a  tuning-fork  write  off' its  vibrations  on  a  recording  surface,  when  a  completely  uniform 
wave  line,  with  equal  elevations  and  depressions,  is  noted.  The  term  "  tone  "  is  restricted  to  those 
sounds,  hardly  ever  occurring  in  nature,  which  are  due  to  simple  pentlulum  like  vibrations.  Other 
investigations  have  shown  that  the  tones  of  musical  instruments  and  of  the  human  voice,  all  of 
which  have  a  characteristic  quality  of  their  own,  are  composed  of  many  single  simple  tones.  Among 
these  one  is  characterized  by  its  intensity,  and  at  the  same  time  it  determines  the  pitch  of  the  whole 
compound  musical  "tone-picture."  This  is  called  the  fundamental  tone  or  key-note.  The  other 
weaker  tones  which,  as  it  were,  spring  from  and  are  mingled  with  this,  vary  in  dilTerent  instruments 
both  in  intensity  and  number.  They  are  "  upper  tones,"  and  their  vibrations  are  always  some 
multiple — 2,  3,  4,  5  ... .  times — of  the  fundamental  tone  or  key-note.  In  general,  we  say  that  all 
those  outbursts  of  sound  which  embrace  numerous  strong  upper  tones,  especially  of  high  pitch,  in 
addition  lo  the  fundamental  tone,  are  characterized  by  a  sharp,  piercing,  and  rough  quality,  such  as 
emanates  from  a  trumpet  or  clarionet,  and  that  conversely  the  quality  is  characterized  by  mildness 
and  softness  when  the  over-tones  are  few,  leeble,  and  low,  e.  g.,  such  as  are  produced  by  the  flute. 
It  requires  a  well-trained  musical  ear  to  distinguish,  in  an  instrumental  burst,  the  over-tones  apart 
from  the  fundamental  tone.  But  this  is  very  easily  done  with  the  aid  of  resonators  (Fig.  532). 
These  consist  of  spherical  or  funnel-shaped  hollow  bodies,  made  of  brass  or  some  other  substance, 
which,  by  means  of  a  short  tube,  can  be  placed  in  the  outer  ear.  If  a  resonator  be  placed  in  the 
ear,  we  can  hear  the  feeblest  over-tone  of  the  same  number  of  vibrations  as  the  fundamental  tone. 
Thus,  musical  instruments  are  distinguished  by  the  number,  intensity,  and  pitch  of  the  over-tones 
which  they  produce.  A  vibrating  metallic  rod  and  a  tunmg  fork  have  no  over. tones ;  they  only  give 
the  fundamental  tone.  As  already  mentioned,  the  term  simple  tone  is  appUed  to  sounds  due  to 
simple  pendulum-like  vibrations,  while  a  sound  composed  of  a  fundamental  tone  and  over-tones  is 
called  a  "  klang  "  or  compound  musical  tone. 

Vibration  Curve  of  a  Musical  Tone. — When  we  remember  that  a  musical  tone  or  clang  con- 
sists of  a  fundamental  tone  and  a  number  of  over- 
tones of  a  certain  intensity,  which  determine  its 
quality,  then  we  ought  to  be  able  to  construct 
geometrically  the  vibration  curve  of  the  musical 
tone.  Let  A  represent  the  vibration  curve  of  the 
fundamental  tone,  and  B  that  of  the  first  moder- 
ately weak  over-tone  (Fig.  529).  The  combina- 
tion of  these  two  curves  is  obtained  simply  by 
computing  the  height  of  the  ordinates,  whereby 
the  ordinates  of  the  over-tone  curve,  lying  above 
the  abscissa  or  horizontal  line,  are  added  to  the 
fundamental  tone  curve,  while  those  of  the  ordi- 
nates below  the  line  are  subtracted  from  it.  Thus 
we  obtain  the  curve  C,  which  is  not  a  simple  pen- 
dulum-like curve,  but  one  which  corresponds  to 
an  unsteady  movement.  A  new  curve  of  the 
second  over  tone  may  be  added  to  C,  and  so  on. 
The  result  of  all  these  combinations  is  that  the 
vibration  curves  correspondm^  to  the  compound 
musical  tones  are  unsteady  periodic  curves.  All 
these  curves  must,  of  course,  vary  with  the  number 
and  pitch  of  the  compounded  over -tone  curves. 

Displacement  of  the  Phases. — The  form  of  ^^ 
the  vibration  of  one  and  the  same  musical  tone 
may  vary  greatly,  if,  in  compounding  the  curves 

A  and  B,  the  curve  B  is  only  slightly  displaced  laterally.  If  B  is  displaced  so  that  the  hollow  of 
the  wave  r  falls  under  A,  the  addition  ol  both  curves  yields  the  curve  r,  r,  r,  with  small  elevations 
and  broad  valleys.  If  B  be  displaced  still  further,  until  the  elevation  of  the  wave,  //,  coincides 
with  A,  we  obtain  still  another  form,  so  that  by  displacement  of  i\ie  phases  of  the  wave  motions  of 
the  compounded  pendulum-like  vibrations,  we  obtain  numerous  different  forms  of  the  same  musical 
tone.     The  displacement  of  the  phases,  however,  h<is  no  effect  on  the  ear. 

The  general  result  of  these  observations,  and  those  of  Fourier,  is  that  the  quality  of  a  musical 
tone  depends  upon  the  characteristic  form  of  the  vibratory  movement. 

Analysis  of  Vowels. — The  human  voice  represents  a  reed  instrument  with  vibrating  elastic 
membranes,  the  vocal  cords  (^  3'2).  In  uttering  the  various  vowels  the  mouth  assumes  a  charac- 
teristic form,  so  that  its  cavity  has  a  certain  fundamental  tone  peculiar  to  itself.  Thus,  to  the  funda- 
mental tone  of  a  certain  pitch  produced  within  the  larynx,  there  are  added  certain  over-tones,  which 
communicate  to  the  larnygeal  tone  the  vocal  or  vowel  quality.  Hence,  a  vowel  is  the  timbre  or 
quality  of  a  musical  tone  which  is  produced  in  the  larynx.     The  quality  depends  upon  the  number, 


832 


ARTIFICIAL   VOWELS. 


intensity,  and  pitch  of  the  over-tones,  and  the  latter,  again,  depend  on  the  configuration  of  the 
"  vocal  cavity"  (^  317)  in  uttering  the  different  vowels. 

Suppose  a  person  to  sing  the  vowels  one  after  the  other  on  a  special  note,  e.  g.,  b  2,  we  can,  with 
the  aid  of  resonators,  determine  the  overtones,  and  in  what  intensity  they  are  mixed  with  the  fun- 
damental tone,  b  7,  to  give  the  characteristic  quality.  According  to  v.  Helmholtz,  when  we  sound 
the  vowels  on  b  [2,  for  each  of  the  three  vowels,  one  over-tone  is  specially  characteristic  for  A-b"  [2  ; 
for  O-b'l?;  for  U-f.  The  other  vowels  and  the  diphthongs  have  each  t-wo  specially  characteristic 
over-tones,  because  in  these  cases  the  mouth  is  so  shaped  that  the  posterior  larger  cavity,  and  also 
the  anterior  narrower  part,  each  yields  a  special  tone  (^  316,  I  and  E).  These  two  over-tones  are 
for  E-B'"  t  and  f ' ;  for  I-d'"  and  f ;  for  A-g'"  and  d";  for  O-c'"  ft  and  f  1 ;  for  U-g'''  and  f.  These, 
however,  are  only  the  special  upper  tones.  There  are  many  more  upper  tones,  but  they  are  not  so 
prominent. 

Artificial  Vowels. — Just  as  it  is  possible  to  analyze  a  vowel  into  its  fundamental  tone  and  its 
upper  tones,  it  is  possible  to  compound  tones  to  produce  the  vowels  by  simultaneously  sounding  the 
fundamental  tone  and  the  corresponding  upper  tones,  (i)  A  vowel  is  produced  simply  by  singing 
loudly  a  vowel,  e.  ^.,  A,  upon  a  certain  note  against  the  free  strings  of  an  open  piano,  while  by  the 
pedal  the  damper  is  kept  raised.  As  soon  as  we  stop  singing,  the  characteristic  vowel  is  sounded 
by  the  strings  of  the  piano.     The  voice  sets  into  sympathetic  vibration  all  those  strings  whose  over- 


FlG.  530. 


apsiile  I  A)  and  i 


r(.M)-(AV^«,i-J- 


tones  (in  addition  to  the  fundamental  tone)  occur  in  the  vocal  compound  tone,  so  that  they  vibrate 
for  a  time  after  the  voice  ceases  {v. //e/mAo//z}.  (2)  The  vowel  apparatus  devised  by  v.  Helm- 
holtz consists  of  numerous  tuning-forks,  which  are  kept  vibrating  by  means  of  electro-magnets. 
The  lowest  tuning-fork  gives  the  fundamental  tone,  B  2  and  the  others  the  over-tones.  A  resonator 
is  placed  in  front  of  each  tuning-fork,  and  the  distance  between  the  two  can  be  varied  at  pleasure. 
The  resonators  can  be  opened  and  closed  by  a  lid  passing  in  front  of  their  openings.  When  the 
resonator  is  closed,  we  cannot  hear  the  tone  emitted  by  the  tuning-fork  placed  in  front  of  it ;  but 
when  one  or  more  resonators  are  opened  the  tone  is  heard  distinctly,  and  it  is  louder  the  more  the 
resonator  is  opened.  By  means  of  a  series  of  keys,  like  the  keys  of  a  piano-forte,  we  can  rapidly 
open  and  close  the  resonators  at  will,  and  thus  combine  various  over  tones  with  the  fundamental 
tone  so  as  to  produce  vowels  with  different  qualities.  V.  Helmholtz  makes  the  following  composi. 
tions : — U  =  B  1?  with  b  ^  weak  and  f ' ;  O  =  damped  B  |2  with  b'  k  strong  and  weaker  b  ^,  f ' , 
d" ;  A  =  b  I2  (fundamental  tone)  with  moderately  strong  b'  g  and  f ",  and  strong  b''  i?  and  d'"  ; 
A  :^  b  [2  (fundamental  tone)  with  b'  [?  and  f  ".somewhat  stronger  than  for  A,d'  strong,  b"  [?  weaker, 
d"'and  f '"  as  strong  as  possible;  E  =  b  2  (as  fundamental  tone)  moderately  strong,  with  b'  \i 
and  f '  moderate  also,  and  f '"  ,  a"'  [?,  and  b'"  I?,  as  strong  as  possible ;  I  could  not  be  produced. 


ACTION    OF   THE    LABYRINTH    DURING    HEARING. 


833 


In  Appunn's  apparatus,  the  fundam'ental  tone  and  the  over-tones  are  produced  by  means  of 
organ  pipes,  whose  notes  can  be  combined  to  produce  the  vowels,  but  it  is  not  so  good  as  the  tuning- 
forks,  since  the  organ  pipes  do  not  yield  simple  tones;  but,  nevertheles-;,  some  of  the  vowels  can 
be  admirably  reproduced  with  this  apparatus. 

Edison's  Phonograph. — If  we  utter  the  vowels  against  a  delicate  membrane  stretched  over  the 
end  of  a  hollow  cylinder,  and  if  a  writing  style  be  fixed  to  the  centre  of  the  membrane,  and  the 
style  be  so  arranged  that  it  can  write  or  record  its  movements  on  a  piece  of  soft  tinfoil  arrange<l  on 
a  revolving  apparatus,  then  the  vowel  curve  is  stamped,  as  it  were,  upon  the  tinfoil.  If  the  style 
now  be  made  to  touch  the  tinfoil  while  the  latter  is  moved,  then  the  style  is  moved;  it  moves  the 
membrane,  anfl  we  hear  distinctly,  by  resonance,  the  vowel  sound  reproduced. 

[Koenig's  Manometric  Flames. — This  is  a  most  ingenious  apparatus,  and  by  means  of  it  the 
quality  of  the  vowel  sounds  is  easily  shown.  It  consists  of  a  small  wooden  capsule.  A,  divided 
into  two  comi">artments  by  a  piece  of  thin  sheet  India-rubber.  Ordinary  gas  passes  into  the  chamber 
on  one  side  of  the  membrane,  through  the  stop-cock,  and  it  is  lighted  at  a  small  burner.  To  the 
other  compartment  is  attached  a  wider  tube,  with  a  mouth  piece.  The  whole  is  fixed  on  a  stand 
(Fig.  530),  and  near  it  is  placed  a  four-sided  rotating  mirror,  M,  as  suggested  by  Wheatstone.  On 
speaking  or  singing  a  vowel  into  the  mouth  piece,  and  rotating  the  mirror,  a  toothed  or  zigzag  flame 


picture  is  obtained  in  the  mirror.  The  lorm  of  the  flame  picture  is  characteristic  for  each  vowel, 
and  varies,  of  course,  with  the  pitch.]  [Fig.  531  shows  the  form  of  the  flame  picture  obtained  in 
the  rotating  mirror  when  the  vowels  ou,  o.  A,  a.e  sung  at  the  pilch  of  «/,,  sol^  and  ut^.  This 
series  shows  how  they  difter  in  quality.] 

[Koenig  has  also  invented  the  apparatus  (Fig.  532)  for  analyzing  any  compound  tone  whose 
fundamental  tone  is  UTj.  It  consists  of  a  series  of  resonators,  from  UT,  to  UT-,  fixed  in  an  iron 
frame.  Each  resonator  is  connected  with  its  special  flame,  which  is  pictured  in  a  long,  narrow, 
square,  rotating  mirror.  If  a  tuning-fork  UT,  be  sounded,  only  the  flame  ur,  is  aflfected,  and  so 
on  with  each  tuning-fork  of  the  harmonic  series.  Suppose  a  compound  note  containing  the  funda- 
mental tone  UT,,  and  its  harmonics  be  sounded,  then  the  flame  of  UTj,  and  those  of  the  other  har- 
monics in  the  note  are  also  affected,  so  that  the  tone  can  be  analyzed  optically.  The  same  may  be 
done  with  the  vowels.] 

416.  ACTION  OF  THE  LABYRINTH  DURING  HEARING.— 

If  we  ask  what  role  the  ear  plays  in  the  perception  of  the  qiitiliiv  of  sounds,  then 
we   must  assume   that,  just  as  with  the  help  of  resonators  a  musical   note  can  be 
S3 


834 


ACTION    OF   THE    LABYRINTH    DURING    HEARING. 


resolved  into  its  fundamental  tone  and  over-tones,  so  the  ear  is  capable  of  per- 
fornaing  such  an  analysis.  The  ear  resolves  the  complicated  wave  forms  of  mu- 
sical tones  into  their  components.  These  components  it  perceives  as  tones  harmo- 
nious with  each  other  ;  with  marked  attention  each  is  perceived  singly,  so  that 
the  ear  distinguishes  as  different  tone  colors  only  different  combinations  of  these 
simple  tone  sensations.  The  resolution  of  complex  vibrations,  due  to  quality,  into 
simple  pendulum-like  vibrations  is  a  characteristic  function  of  the  ear.  What 
apparatus  in  the  ear  is  capable  of  doing  this?  If  we  sing  vigorously — e.g.,  the 
musical  vowel  A  on  a  definite  note,  say  b  b — against  the  strings  of  an  open  piano- 
forte while  the  damper  is  raised,  then  we  cause  all  those  strings,  and  only  those,  to 
vibrate  sympathetically,  which  are  contained  in  the  vowel  so  sung.     We  must, 


Fig.  532. 


Koenig's  apparatus  for  aiialy 


therefore,  assume  that  an  analogous  sympathetic  apparatus  occurs  in  the  ear,  which 
is  tuned,  as  it  were,  for  different  pitches,  and  which  will  vibrate  sympathetically 
like  the  strings  of  a  piano-forte.  "  If  we  could  so  connect  every  string  of  a  piano 
with  a  nerve  fibre  that  the  nerve  fibre  would  be  excited  and  perceived  as  often  as 
the  string  vibrated,  then,  as  is  actually  the  case  in  the  ear,  every  musical  tone 
which  affected  the  instrument  would  excite  a  series  of  sensations  exactly  corre- 
sponding to  the  pendulum-like  vibrations  into  which  the  original  movements  of 
the  air  can  be  resolved  ;  and  thus  the  existence  of  each  individual  over-tone 
would  be  exactly  perceived,  as  is  actually  the  case  with  the  ear.  The  perception 
of  tones  of  different  pitch  would,  under  these  circumstances,  depend  upon  dif- 
ferent nerve  fibres,  and  hence  would  occur  quite  independently  of  each  other. 


SIMULTANEOUS   ACTION   OF   TWO   TONES.  835 

Microscopic  investigation  shows  that  there  are  somewhat  similar  structures  in  the 
ear.  The  free  ends  of  all  the  nerve  fibres  are  connected  with  small  elastic  par- 
ticles, which  we  must  assume  are  set  into  sympathetic  vibration  by  the  sound 
waves"  (<■.  Helmholtz). 

Resolution  by  the  Cochlea.— Formerly,  v.  Helmholtz  considered  the  rods 
of  Corti  to  be  the  apparatus  that  vibrated  and  stmiulated  the  terminations  of 
the  nerves.  But,  as  birds  and  amphibians,  which  certainly  can  distinguish 
musical  tones,  have  no  rods  {Hasse),  the  stretched  radial  fibres  of  the  membrana 
basilaris,  on  which  the  organ  of  Corti  is  placed,  and  which  are  shortest  in  the  first 
turn  of  the  cochlea,  becoming  longer  toward  the  apex  of  the  cochlea,  are  now 
regarded  as  the  vibrating  threads  {Hensen).  Thus,  a  string-like  fibre  of  the  mem- 
brana basilaris,  which  is  capable  of  vibrating,  corresponds  to  every  possible 
simple  tone.  According  to  Hensen,  the  hairs  of  the  labyrinth,  which  are  of 
unequal  length,  may  serve  this  purpose.  Destruction  of  the  apex  of  the  cochlea 
causes  deafness  to  deeper  tones  (^JSaginsky). 

[Hensen' s  Experiments. — That  the  hairs  in  connection  with  the  hair  cells 
vibrate  to  a  particular  note  is  also  rendered  probable  by  the  experiments  of  Hensen 
on  the  crustacean  Mysi's.  He  found  that  certain  of  the  minute  hairs  (auditory 
hairs)  in  the  auditory  organ  of  this  animal,  situate  at  the  base  of  the  antennce, 
vibrated  when  certain  tones  were  sounded  on  a  keyed  horn.  The  movements  of 
the  hairs  were  observed  by  a  low-power  microscope.  In  mammals,  however,  there 
is  a  difficulty,  as  the  hairs  attached  to  the  cells  appear  to  be  all  about  the  same 
length.     We  must  not  forget  that  the  perception  of  sound  is  a  mental  act.] 

This  assumption  also  explains  the  perception  of  muses. 

Of  noises  in  the  strictly  physical  sense,  it  is  assumed  that  they,  like  single 
impulses,  are  perceived  by  the  aid  of  the  saccules  and  the  ampullae. 

It  is  assumed  that  the  saccules  and  the  ampullae  are  concerned  in  the  general 
perception  of  hearing,  ;>.,  of  shocks  communicated  to  the  auditory  nerve  (by 
impulses  and  noises)  ;  while  by  the  cochlea  we  estimate  the  pitch  and  depth  of 
the  vibrations,  and  musical  character  of  the  vibrations  produced  by  tones. 

The  relation  of  the  semicircular  canals  to  the  equilibrium  of  the  body  is 
referred  to  in  §  350. 

417.  SIMULTANEOUS  ACTION  OF  TWO  TONES— HAR- 
MONY  — BEATS-  DISCORDS  — DIFFERENTIAL    TONES.  — 

When  l7o<>  tones  of  different  pitch  fall  upon  the  ear  simultaneously,  they  cause 
different  sensations,  according  to  the  difference  in  pitch. 

1.  Consonance.— -If  the  number  of  vibrations  of  the  two  tones  is  in  the  ratio 
of  simple  multiples,  as  i  :  2  :  3  :  4,  so  that  when  the  low  note  makes  one  vibra- 
tion the  higher  one  makes  2  :  3  or  4  ...  .  then  we  experience  a  sensation  of  com- 
plete harmony  or  concord. 

2.  Interference. — If,  however,  the  two  tones  do  not  stand  to  each  other  in 
the  relation  of  simple  multiples,  then  when  both  tones  are  sounded  simultaneously 
interference  takes  place.  The  hollows  of  the  one  sound  wave  can  no  longer  coin- 
cide with  the  hollows  of  the  other,  and  the  crests  with  the  crests,  but,  corre- 
sponding to  the  difference  of  number  of  vibrations  of  both  curves,  sometimes  a 
wave  crest  must  coincide  with  a  wave  hollow.  Hence,  when  wave  crest  meets 
wave  crest,  there  must  be  an  increase  in  the  strength  of  the  tone,  and  when  a 
hollow  coincides  with  a  crest,  the  sound  must  be  weakened.  Thus  we  obtain 
the  impression  of  those  variations  in  tone  intensity  which  have  been  called 
"  beats." 

The  number  of  vibrations  is,  of  course,  always  equal  to  the  difference  of  the  number  of  vibrations 
of  both  tones.  The  beats  are  perceived  most  distinctly  when  two  organ  tones  of  low  pitch  are 
sounded  together  in  unison,  but  slightly  out  of  tune.  Suppo.se  we  take  two  organ  pipes  with  ^t, 
vibrations  per  second,  and  so  alter  one  pipe  that  it  gives  34  vibrations  per  second,  then  one  distinct 
beat  will  be  heard  every  second.  The  beats  are  heard  more  frequently  the  greater  the  difl'erence 
between  the  number  of  vibrations  of  the  two  tones. 


836  PERCEPTION    OF   THE    DIRECTION    OF   SOUNDS. 

Successive  Beats.— The  beats,  however,  produce  very  different  impressions 
upon  the  ear,  according  to  the  rapidity  with  which  they  succeed  each  other. 

1.  Isolated  Beats. — When  they  occur  at  long  intervals,  we  may  perceive  them 
as  completely  isolated,  but  single  intensifications  of  the  sound  with  subsequent 
enfeeblement,  so  that  they  give  rise  to  the  impression  of  isolated  heats. 

2.  Dissonance. — When  the  beats  occur  more  rapidly  they  cause  a  continuous 
disagreeable  whirring  impression,  which  is  spoken  of  as  dissonance,  or  an  unhar- 
monious  sensation.  The  greatest  degree  of  unpleasant  painful  dissonance  occurs 
when  there  are  33  beats  per  second. 

3.  Harmony. — If  the  beats  take  place  more  rapidly  than  33  times  per  second, 
the  sensation  of  dissonance  gradually  diminishes,  and  it  does  so  the  more  rapidly 
the  beats  occur.  The  sensation  passes  gradually  from  moderately  inharmonious 
relations  (which  in  music  have  to  be  resolved  by  certain  laws)  toward  consonance 
or  harmony.  The  tone  relations  are  successively  the  Second,  Seventh,  Minor 
Third,  Minor  Sixth,  Major  Third,  Major  Sixth,  Fourth,  and  Fifth. 

4.  Action  of  the  Musical  Tones  ("A7(ir;/^f  "). — Two  musical  "klangs," 
or  compound  tones,  falling  on  the  ear  simultaneously,  produce  a  result  similar  to 
that  of  two  simple  tones;  but  in  this  case  we  have  to  deal  not  only  with  the  two 
fundamental  tones,  but  also  with  the  over-tones.  Hence  the  degree  of  dissonance 
of  two  musical  tones  is  the  more  pronounced  the  more  the  fundamental  tones  and 
the  over-tones  (and  the  "  differential  "  tones)  produce  beats  which  number  about 
33  per  second. 

5.  Differential  Tones. — Lastly,  two  "klangs,"  or  two  simple  musical  tones 
sounding  simultaneously,  may  give  rise  to  new  tones  when  they  are  uniformly  and 
simultaneously  sounding  in  corresponding  intensity.  VVe  can  hear,  if  we  listen 
attentively,  a  third  new  tone,  whose  number  of  vibrations  corresponds  to  the  dif- 
ference between  the  two  primary  tones,  and  hence  it  is  called  a  '■^differential 
tone. ' ' 

Summational  Tones. — It  was  formerly  supposed  that  new  tones  cculd  arise  from  the  summation 
or  addilion  of  their  number  of  vibralions,  but  it  has  been  shown  that  tliese  tones  are,  in  reality, 
differential  tones  of  a  high  order  [A/'pimn,  Preyer). 

418.  PERCEPTION  OF  SOUND— FATIGUE  OF  THE  EAR- 
OBJECTIVE  AND  SUBJECTIVE  AUDITION— AFTER  SEN- 
SATION.— Objective  Auditory  Perceptions. — When  the  stimulation  of 
the  terminations  of  the  nerves  of  the  labyrinth  is  referred  to  the  _  outer  world, 
then  we  have  objective  auditory  perceptions.  Such  stimulations  are  only  referred 
to  the  outer  world  as  are  conveyed  to  the  membrana  tympani  by  vibrations  of  the 
air,  as  is  shown  by  the  fact  that  if  the  head  be  immersed  in  water,  and  the  audi- 
tory meatuses  be  filled  thereby,  we  hear  all  the  vibrations  as  if  they  occurred 
within  our  head  itself  {Ed.  JFelier),  and  the  same  is  the  case  with  our  own  voice, 
as  well  as  with  the  sound  waves  conducted  through  the  bones  of  the  head,  when 
both  ears  are  firmly  plugged. 

Perception  of  Direction. — As  to  the  perception  of  the  direction  whence 
sound  comes,  we  obtain  some  information  from  the  relation  of  both  meatuses  to 
the  source  of  the  sound,  especially  if  we  turn  the  head  in  the  supposed  direction  of 
the  sound.  We  distinguish  more  easily  the  direction  from  which  noises  mixed 
with  musical  tones  come  than  that  of  tones  {Raylcigh).  When  both  ears  are 
stimulated  equally,  we  refer  the  source  of  the  sound  to  the  middle  line  anteriorly, 
but  when  one  ear  is  stimulated  more  strongly  than  the  other,  we  refer  the  source 
of  the  sound  more  to  one  side  (Kessel).  The  position  of  the  ear  muscles,  which, 
perhaps,  act  like  an  ear  funnel,  is  important.  According  to  Ed.  Weber,  it  is 
more  difficult  to  determine  the  direction  of  sound  when  the  ears  are  firmly  fixed 
to  the  side  of  the  head.  Further,  if  we  place  the  hollow  of  both  hands  in  front 
of  the  ear,  as  to  form  an  open  cavity  behuid  them,  we  are  apt  to  suppose  that  a 
sounding  body  placed  in  front  is  behind  us. 


COMPARATIVE HISTORICAL.  837 

The  distance  of  a  sound  is  judged  of  partly  by  the  intensity  or  loudness  of  the 
sound,  such  as  we  have  learned  to  estimate  from  sound  at  a  known  distance.  But 
still  we  are  subject  to  many  misconceptions  in  this  respect. 

Among  subjective  auditory  sensations  are  the  a/Ur  vibrations,  especially  of  intense  and 
continued  musical  tones ;  the  tinnitus  aurium  (p  637),  which  often  accompanies  abnormal  move- 
ments of  the  blood  in  the  ear,  may  be  due  to  a  mechanical  stimulation  of  the  auditory  fibres,  perhaps 
by  the  blood  stream  [Brenner). 

[Drugs. — Cannabis  indica  seems  to  act  on  the  hearing  centre,  giving  rise  to  subjective  sounds; 
the  hearing  is  rendered  more  acute  by  strychnin;  while  quinine  and  sodic  salicylate  in  large  doses 
cause  ringing  in  the  ears  (BrtiMton).'\ 

Entotical  perceptions,  which  are  due  to  causes  within  the  ear  itself,  are  such  as  hearing  the 
f'ulse  beats  in  the  surrounding  arteries,  and  the  rushing  sound  of  the  blood,  which  is  especially  strong 
when  there  is  increased  resonance  of  the  ear  (as  when  the  meatus  or  tympanum  is  closed,  or  when 
fluid  accumulates  in  the  latter),  during  increased  cardiac  action,  or  in  hypersesthesia  of  the  auditory 
nerve  (Brenner).  Sometimes  there  is  a  cracking  noise  in  the  maxillary  articulation,  the  noise  pro- 
duced by  traction  of  the  muscles  on  the  Eustachian  tube  (J  411),  and  when  air  is  forced  into  the 
latter,  or  when  the  membrana  tympani  is  forced  outward  or  inward  (§  350). 

Fatigue. — The  ear  after  a  time  becomes  fatigued,  either  for  one  tone  or  for  a  series  of  tones 
which  have  acted  on  it,  while  the  perceptive  activity  is  not  affected  for  other  tones.  Complete  re- 
covery, however,  takes  place  in  a  few  seconds  ( G'rbantscJiilseii). 

Auditory  After  Sensations. — (l)  Tho^e  that  correspond  to  positive  after  sensations,  where  the 
after  sensation  is  so  closely  connected  with  the  original  tone  that  both  appear  to  be  continuous.  (2) 
There  are  some  after  sensations,  where  a  pause  intervenes  between  the  end  of  the  objective  and  the 
beginning  of  the  subjective  tone  ( Urbantschitsch).  (3)  There  seems  to  be  a  form  corresponding  to 
negative  after  images. 

In  some  persons  the  perception  of  a  tone  is  accompanied  by  the  subjective  colors,  or  the  sensation 
of  light,  e.g.,  the  sound  of  a  trumpet,  accompanied  by  the  sensation  of  yellow.  More  seldom  are 
visual  sensations  of  this  kind  observed  when  the  nerves  of  taste,  smell,  or  touch  are  excited  [Xiiss- 
baiimer,  Lehmann  and  Bleuler).  It  is  more  common  to  find  that  an  intense  sharp  sound  is  accom- 
panied by  an  associated  sensation  of  the  sensory  nerves.  Thus  many  people  experience  a  cold  shud- 
der when  a  slate  pencil  is  drawn  in  a  peculiar  manner  across  a  slate. 

[Color  Associations. — Color  is  in  some  persons  instantaneously  associated  with  sound,  and  Gal- 
ton  remarks  that  it  is  rather  common  in  children,  although  in  an  ill-developed  degree,  and  the  ten- 
dency seems  to  be  very  hereditary.  Sometimes  a  particular  color  is  associated  with  a  particular 
letter,  vowel  sounds  particularly  evoking  colors.  Galton  has  given  colored  representations  of  these 
color  associations,  and  he  points  out  their  relation  to  what  he  calls  number  forms,  or  the  associa- 
tion of  certain  forms  with  certain  numbers.] 

An  auditory  impulse  communicated  to  one  ear  at  the  same  time  often  causes  an  increase  in  the 
auditory  function  of  the  other  ear,  in  consequence  of  the  stimulation  of  the  auditory  centres  of  both 
sides  [C'rbantschitseh,  Eitelberg). 

Other  Stimuli. — The  auditory  apparatus,  besides  being  excited  by  sound  waves,  is  also  affected 
by  heterologous  stimuli.  It  is  stimulated  meehanical/yhy  a  sudden  blow  on  the  ear.  The  effects 
of  eleetrieity  and  pathological  conditions  are  referred  to  in  §  350. 

419.  COMPARATIVE— HISTORICAL.— The  lowest  fishes,  the  cyclostoniata  (Petromy- 
zon),  have  a  saccule  provided  with  auditory  hairs  containing  otoliths,  and  communicating  with  two 
semicircular  canals,  while  the  myxinoids  have  only  one  semicircular  canal.  Most  of  the  other  fishes, 
however,  have  a  utricle  communicating  with  three  semicircular  canals.  In  the  carp,  prolongations 
of  the  labyrinth  communicate  with  the  swimming  bladder.  In  amphibia,  the  structure  of  the  laby- 
rinth is  somewhat  like  that  in  fishes,  but  the  cochlea  is  not  typically  developed.  Most  amphibia, 
except  the  frog,  are  devoid  of  a  membrani  tympani.  Only  the  fenestra  ovalis  (not  the  rotunda)  ex- 
ists, and  it  is  connected  in  the  frog  by  three  ossicles  with  the  freely  exposed  membrana  tympani. 
Among  reptiles  the  appendix  to  the  saccule,  corresponding  to  the  cochlea,  begins  to  be  prominent. 
In  the  tortoise  it  is  saccular,  but  in  the  crocodiles  it  is  longer,  and  somewhat  curved  and  dilated  at 
the  end.  In  all  reptiles  the  fenestra  rotunda  is  developed,  whereby  the  cochlea  is  connected  with 
the  labyrinth.  In  crocodiles  and  birds  the  cochlea  is  divided  into  a  scala  vestibuli  and  S.  tympani. 
Snakes  are  devoid  of  a  tympanic  cavity.  In  birds  both  saccules  (Fig.  524,  IV,  U  S')  are  united 
{//asse),  the  canal  of  the  cochlea  (U  C),  which  is  connected  by  means  of  a  fine  tube  (C).  with  the 
saccule,  is  larger,  and  .shows  indications  of  a  spiral  arrangement,  and  has  a  flask-like  blind  end,  the 
lagena  (L).  The  auditory  ossicles  in  reptiles  and  birds  are  reduced  to  one  column-like  rod,  corre- 
sponding to  the  stapes,  and  called  the  columella.  The  lowest  mammals  (Echidna)  have  struc- 
tures very  like  those  of  birds,  while  the  higher  mammals  have  the  same  type  as  in  man  (Fig.  524, 
HI).     The  Eustachian  tube  is  always  open  in  the  whale. 

Among  invertebrata  the  auditory  organ  is  very  simple  in  medusa;  and  mollusca.  It  is  merely  a 
bladder  filled  with  fluid,  with  the  auditory  nerves  provided  with  ganglia  in  its  walls.  Hair  cells 
occur  in  the  interior,  provided  with  one  or  more  otoliths.     Hensen  observed  that  in  some  of  the 


838  COMPARATIVE HISTORICAL. 

annulosa,  when  sound  was  conducted  into  the  water,  some  of  the  auditory  bristles  vibrated,  being 
adapted  for  special  tones.  In  cephalopoda  we  distinguish  the  first  ditTerentiation  into  a  membran- 
ous and  cartilaginous  labyrinth. 

Historical.— Empedocles  (473  B.c)  referred  auditory  impressions  to  the  cochlea.  The  Hippo 
cratic  School  was  acquainted  with  the  tympanum,  and  Aristotle  (384  B.c)  with  the  Eustachian  tube. 
Vesalius  (1561)  described  the  tensor  tympani;  Cardanus  (1560)  the  conduction  through  the  boms 
of  the  head;  while  Fallopius  (1561)  described  the  vestibule,  the  semicircular  canals,  chorda  tym- 
pani, the  two  fenestrse,  the  cochlea,  and  the  aqueduct.  Eustachius  (f  1570)  described  the  modio- 
lus, the  lamina  spiralis  of  the  cochlea,  the  Eustachian  lube,  as  well  as  the  muscles  of  tlie  ear;  Plater 
the  ampulla;  (1583);  Casseri  (1600)  the  lamina  spiralis  membranacea.  Sylvius  (1667)  discovered 
the  ossicle  called  by  his  name ;  Vesling  (1641)  the  s'apedius.  Mersenne  (1618)  was  acquainted 
with  over-tones ;  Gassendus  (1658)  experimented  on  the  conduction  of  sound.  Acoustics  was  greatly 
advanced  by  the  work  of  Chladni  (1802).  The  most  recent  and  largest  work  on  the  ear  in  verte- 
brates is  by  G.  Retzius  (1881-84). 


THE  ORGAN  OF  SMELL. 


420.  STRUCTURE  OF  THE  ORGAN  OF  SMELL.— Regio  Olfactoria.— The  area 
of  the  distribution  of  the  olfactory  nerve  is  the  regio  olfactoria,  which  embraces  the  upper  part  of 
the  septum,  the  upper  (Fig.  534,  Cs),  and  part  of  the  middle  (Cm)  turbinated  bone.  All  the  re- 
mainder of  the  nasal  cavity  is  called  the  regio  respiratoria.  These  two  regions  are  distinguished 
as  follows:  (i)  The  regio  olfactoria  has  a  thicker  mucous  membrane.  (2)  It  is  covered  by  a  sin- 
gle layer  of  cylindrical  epithelium  (Fig.  533,  E),  the  cells  being  often  branched  at  their  lower  ends, 
and  contain  a  yellow  or  brownish-red  pigment.  (3)  It  is  colored  by  this  pigment,  and  is  thereby 
distinguished  from  the  uncolored  regio  respiratoria,  which  is  covered  by  cilated  epithelium.  (4) 
It  contains  peculiar  tubular  glands  (Bowman's  glands),  while  the  rest  of  the  mucous  membrane 
contains  numerous  acinous  serous  glands  ( Heidenhain).  (5)  Lastly,  the  regio  olfactoria  embraces 
the  end  organs  of  the  olfactory  nerve  (/I/.  Schul/ze).  The  long,  narrow  olfactory  cells  (N)  are 
distributed  between  the  ordinary  cylindrical  epithelium  (E)  covering  the  regia  olfactoria.  The  body 
of  the  cell  is  spindle  shaped,  with  a  large  nucleus  containing  nucleoli,  and  it  sends  upward  between 
the  cylindrical  cells  a  narrow  (0.9  to  1.8  /i),  smooth  rod,  quite  up  to  the  free  surface  of  the  mucous 
membrane.    In  the  frog  («),  the  free  end  carries  delicate  projecting  hairs  or  bristles.    In  the  deeper 


F'G-  533- 


Fig.  534. 


333. — N,  olfactory  celh  (human) ;  «,  from  the  frog  ; 
pnaryngo-nasal  cavities.  L,  levator  elevation  ;  \ 
nated  bones  {UriuntS'Jiitsch). 


;,  epitheln 
i/».,  plica 


1  of  the  regio  olfactoria.     Fig.  534  — Nasal  and 
lalpingo-palatina ;    Ls,  Cut,  Ci,  the  three  liirbi- 


part  of  the  mucous  membrane  the  olfactory  cells  pass  into,  and  become  continuous  with,  varicose  tine 
nerve  fibres,  which  pass  into  the  olfactory  nerve  (^  321,  I,  I).  According  lo  C.  K.  Hoffmann  and 
Exner,  after  section  of  the  olfactory  nerve  the  specific  olfactory  end  organs  become  changed  into 
cylindrical  epithelium  (frog),  and  in  warm  blooded  animals  they  undergo  fatty  degeneration,  even 
on  the  15th  day.  V.  Brunn  found  a  homogeneous  limiting  membrane,  which  had  holes  in  it  for 
transmitting  the  processes  of  the  olfactory  cells  only. 

[The  respiratory  part  of  the  nasal  mucous  membrane  is  lined  by  ciliated  epithelium  stratified 
like  that  in  the  trachea  and  resting  on  a  basement  membrane.  Below  this  there  are  many  lymph 
corpuscles  and  aggregations  of  adenoid  tissue.] 

[The  organ  of  Jacobson  is  present  in  all  mammals,  and  consists  of  two  narrow  tubes  protected 
by  cartilage,  and  placed  in  the  lower  and  anterior  part  of  the  nasal  septum.  Each  tube  terminates 
blindly  behind,  but  anteriorly  it  opens  into  the  nasal  furrow  or  into  the  nasopalatine  canal  (dog). 
The  wall  next  the  middle  line  is  covered  by  olfactory  epithelium,  and  receives  olfactory  nerves 
(rabbit,  guinea  pig),  and  it  contains  glands  similar  to  those  of  the  olfactory  region;  the  outer  wall 
IS  covered  by  columnar  epithelium  ciliated  in  some  animals  (A7«'«).] 

839 


840  OLFACTORY    SENSATIONS. 

421.  OLFACTORY  SENSATIONS.— Olfactory  sensations  are  produced 
by  the  action  of  gaseous  odorous  substances  being  brought  into  direct  contact 
with  the  olfactory  cells,  during  the  act  of  inspiration.  The  current  of  air  is 
divided  by  the  anterior  projection  of  the  lowest  turbinated  bone,  so  that  a  part 
above  the  latter  is  conducted  to  the  regio  olfactoria.  Odorous  bodies  taken  into 
the  mouth  and  then  expired  through  the  posterior  nares  are  said  not  to  be  smelled 
{BiMer). 

During  inspiration  the  air  streams  along  close  to  the  septum,  while  little  of  it  passes  through  the 
nasal  passages,  especially  the  superior  [Paulsen  and  Exner). 

T\\t  first  moment  of  contact  between  the  odorous  body  and  the  olfactory  mucous 
membrane  appears  to  be  the  time  when  the  sensation  takes  place,  as,  when  we 
wish  to  obtain  a  more  exact  perception,  we  j///^ several  times,  /.  e,,  a  series  of 
rapid  inspirations  are  taken,  the  mouth  being  kept  closed.  During  sniffing,  the 
air  within  the  nasal  cavities  is  rarefied,  and  as  air  rushes  in  to  equilibrate  the 
pressure,  the  air  laden  with  odorous  particles,  streams  over  the  olfactory  region. 
Odorous  fluids  are  said  not  to  give  rise  to  the  sensation  of  smell  when  they  are 
brought  into  direct  contact  with  the  olfactory  mucous  membrane,  as  by  pouring 
eau  de  Cologne  into  the  nostrils  [Tourtiial,  182/  ;  E.  H.  Weher,  1841).  This  is, 
perhaps,  due  to  the  action  of  the  fluid  on  the  olfactory  cells  paralyzing  them,  per- 
haps, owing  to  imbibition,  shriveling,  or  chemical  action.  Even  water  alone 
temporarily  affects  the  cells.  We  know  practically  nothing  about  the  nature  of 
the  action  of  odorous  bodies,  but  many  odorous  vapors  have  a  considerable  power 
of  absorbing  heat  {Tyndall  ). 

The  intensity  of  the  sensation  depends  on — i.  The  size  of  the  olfactory 
surface,  as  animals  with  a  very  keen  sense  of  smell  are  found  to  have  complex 
turbinated  bones  covered  by  the  olfactory  mucous  membrane.  2.  The  concen- 
tration of  the  odorous  mixture  of  the  air.  Still,  some  substances  may  be  attenu- 
ated enormously  {e.g.,  musk  to  the  two-millionth  of  a  milligram),  and  still  be 
smelled.  3.  The  frequency  of  the  conduction  of  the  vapor  to  the  olfactory  cells 
(sniffing). 

[The  acuteness  of  the  sense  of  smelt  is  greatly  improved  by  practice.  A  boy 
named  James  Mitchell,  who  was  deaf,  dumb,  and  blind,  used  his  sense  of  smell, 
like  a  dog,  to  distinguish  persons  and  things.] 

Elfctrical,  chemical,  or  thermal  stimuli  do  not  give  rise  to  olfactory  sensations.  [Althaus  found 
that  electrical  stimulation  of  the  olfactory  mucous  membrane  gave  rise  to  the  sensation  of  the  smell 
of  phosphorus.] 

The  variations  are  referred  to  in  §  343.  If  the  two  nostrils  are  filled  with  different  odorous 
substances  there  is  no  mixture  of  the  odors,  but  we  smell  sometimes  the  one  and  sometimes  the 
other  (  Valentin').  The  sense  of  smell,  however,  is  very  soon  blunted,  or  even  paralyzed.  Mor- 
phia, when  mixed  with  a  little  sugar  and  taken  as  .snuff,  paralyzes  the  olfactory  apparatus,  while 
strychnin  makes  it  more  sensitive  [Lichtenfels  and  frohlich). 

The  sensory  nerves  of  the  na^al  mucous  membrane  (\  347,  II)  [/.  i-.,  those  supplied  from  the 
fifth  cranial  nerve]  are  stimulated  by  irritating  vapors,  and  may  even  cause  pain,  e.g.,  ammonia  and 
acetic  acid.  In  a  very  diluted  condition,  they  may  c  en  act  on  the  olfactory  nerves.  The  nose  is 
useful  as  a  sentinel  for  guarding  against  the  introduction  of  di.sagreeable  odors  and  foods.  The 
sense  of  smell  is  aided  by  the  sense  of  taste,  and  conversely. 

[Flavor  depends  on  the  sense  of  smell,  and,  to  test  it,  use  substances,  solid  or  fluid,  with  an 
aroma  or  boiupict,  such  as  wine  or  roast  beef.  J 

[Method  of  Testing. — In  doing  so,  avoid  the  use  of  pungent  substances  like  ammonia,  whicli 
excite  the  fifth  nerve.  Use  some  of  the  essential  volatile  oils,  such  as  cloves,  berganiot,  and  the  fetid 
gum  resins,  or  musk  and  camphor.    Electrical  stimuli  are  not  available.     Action  of  Drugs,  J  343] 

Comparative. — In  the  lowest  vertebrata,  pits,  or  depressions  provided  with  an  olfactory  nerve, 
represent  the  simplest  olfactory  organ,  .^mphioxus  and  the  cyclistomata  have  only  one  olfactory 
pit;  all  other  vertebrates  have  two.  In  some  animals  (frog), the  nose  communicates  with  the  mouth 
by  ducts.     The  olfactory  nerve  is  absent  in  the  whale. 

Historical. — Rufus  Ephesius  (97  a.d.  )  described  the  passage  of  the  olfactory  nerve  through  the 
ethmoid  bone.  Rudius  (1600)  dissected  the  body  of  a  man  with  congenital  anosmia,  in  whom  the 
olfactory  nerves  were  absent.  Magendie  orii;inally  supposed  that  the  nasal  branch  of  the  fifth  was 
the  nerve  of  smell,  a  view  successfully  combated  by  Eschricht. 


THE  ORGAN  OF  TASTE. 


422.  STRUCTURE  OF  THE  GUSTATORY  ORGANS.— Gusta- 
tory Region. — There  is  considerable  difference  of  opinion  as  to  what  regions  of 
the  mouth  are  endowed  with  taste  :  (i)  The  root  of  the  tongue  in  the  neighbor- 
hood of  the  circumvallate  papillae,  the  area  of  distribution  of  the  glosso-pharyngeal 
nerve,  is  undoubtedly  endowed  with  taste  (§  351).  (2)  The  tip  and  margins  of 
the  tongue  are  gustatory,  but  there  are  very  considerable  variations  (  Urhantschitsck). 
(3)  The  lateral  part  of  the  soft  palate  and  the  glosso-palatine  arch  are  endowed 
with  taste  from  the  glosso-pharyngeal  nerve.  (4)  It  is  uncertain  whether  the  hard 
])alate  and  the  entrance  to  the  larynx  are  endowed  with  taste  {Drielsma).  The 
middle  of  the  tongue  is  not  gustatory. 

Taste  Bulbs. — The  end  organs  of  the  gustatory  nerves  are  the  taste  bulbs  discovered  by 
Schwalbe  and  Loven  (1867).  They  occur  on  the  literal  surfaces  of  the  circumvallate  papilla;  (Fig. 
535,  I),  also  upon  the  opposite  side,  K,  of  the  fossa  or   capillary  slit,  R  R,  which  surrounds  the 


I,  Transverse  section  of 


allate  pap 


W,  the  papilla  ;  t/j,  t-j,  the  wall  in  sectic 
bulbs  in  position  ;  N.  N,  the  nerves.  11,  isolated  taste  bulbs 
lis  ;  K,  under  end  ;  E,  free  end,  open,  with  the  projecting  apices  of  the  taste  c 
11  (d)  with  a  UTSte  cell  (<■). 


R,  R.the  circular  slit 
D,  supporting  or  pro- 
Is.     Ill,  Isolated  pro- 


central  eminence  or  papilla;  they  occur  more  rarely  on  the  surface.  They  also  occur  on  the  fungi- 
form papillse,  in  the  papilla  of  the  soft  palate  and  uvula  {A.  Hoffman\,  on  the  under  surface  of  the 
epiglottis,  the  upper  part  o(  the  posterior  surface  of  the  epiglottis,  and  the  inner  side  of  the  arytenoid 
cartilages  (  Versott,  Davis),  and  on  the  vocal  cords  (Siniancrwsky).  Many  buds  or  bulbs  disappear 
in  old  age. 

Structure. — The  taste  bulbs  are  Si  fi  high  and  33  //  thick,  are  barrel  shaped  and  embedded  in 
the  thick  stratified  squamous  epithelium  of  the  tongue.  Each  bulb  consists  of  a  seritsof  lancet- 
shaped,  bent,  nucleated,  outtr,  supporting  or  protective  cells,  arranged  like  the  staves  of  a  barrel 
(Fig.  535,  II,  D.  isolated  in  III.  n).  They  are  so  arranged  as  to  leave  a  small  opening,  or  the 
"  gustatory  pore  "  at  the  free  eml  of  the  liulb.  Surrounded  by  tliee  cells  and  lying  in  the  axis  of 
the  bud  are  i  to  10  gustatory  cells  1 II,  E),  some  of  which  are  provided  with  a  delicate  process 
(III,  e)  at  their  free  ends,  while  their  lower  fixed  ends  send  out  basal  processes,  which  become 
continuous  with  the  terminations  of  the  nerves  of  taste,  which  have  become  non  mf^dullated.  .After 
section  of  the  glosso  pharyngeal,  the  taste  buds  degenerate,  while  the  protective  cells  become  changed 
into  ordinary  epithelial  cells  within  four  months  (v.  V'intschgau  and  Honigschmied).     Very  similar 

841 


842  GUSTATORY    SENSATIONS. 

structures  were  found  by  Leydig  in  the  skin  of  fresh-water  fishes.  The  glands  of  tlie  tongue  and 
their  secretory  fibres  from  the  9th  cranial  nerve  are  referred  to  in  §  141  (Drasch). 

423.  GUSTATORY  SENSATIONS.— Varieties.— There  are  >;//- dif- 
ferent gustatory  iiualities,  the  sensations  of 

1.  Sweet.  3.  Acid. 

2.  Bitter.  4.  Saline. 

Acid  and  saline  substances  at  the  same  time  also  stimulate  the  sensory  nerves  of 
the  tongue,  but  when  greatly  diluted  they  only  excite  the  end  organs  of  the 
specific  nerves  of  taste.  Perhaps  there  are  special  nerve  fibres  for  each  different 
gustatory  quality  (i>.  Vintschgau). 

Conditions. — Sapid  substances,  in  order  that  they  may  be  tasted,  require  the 
following  conditions :  They  must  be  dissolved  in  the  fluid  of  the  mouth,  espe- 
cially substances  that  are  solid  or  gaseous.  The  intensity  of  the  gustatory  sen- 
sation depends  on  :  i.  The  size  of  the  surface  acted  on.  Sensation  is  favored  by 
rubbing  in  the  substance  between  the  papillce,  in  fact,  this  is  illustrated  in  the 
rubbing  movements  of  the  tongue  during  mastication  (§  354).  2.  The  concen- 
tration of  the  sapid  substance  is  of  great  importance.  Valentin  found  that  the 
following  series  of  substances  ceased  to  be  tasted  in  the  order  here  stated,  as  they 
were  gradually  diluted — syrup,  sugar,  common  salt,  aloes,  quinine,  sulphuric  acid. 
Quinine  can  be  diluted  20  times  more  than  common  salt  and  still  be  tasted  (  C<z;«- 
erer').  3.  The  time  which  elapses  between  the  application  of  the  sapid  substance 
and  the  production  of  the  sensation  varies  with  different  substances.  Saline  sub- 
stances are  tasted  most  rapidly  (after  0.17  second,  according  to  v.  Vintschgau), 
then  sweet,  acid  and  bitter  (quinine  after  0.25S  second,  v.  Vintschgau).  This  even 
occurs  with  a  mixture  of  these  substances  (Schirmer).  The  last-named  substances 
produce  the  longest  "  after  taste."  4.  The  delicacy  of  the  sense  of  taste  is  partly 
congenital,  but  it  can  be  greatly  improved  by  practice.  If  a  person  uses  the  same 
sapid  substance,  or  a  nearly  related  one,  or  even  any  very  intensely  sapid  substance, 
the  sense  of  taste  is  soon  affected,  and  it  becomes  impossible  to  give  a  correct 
judgment  as  to  the  taste  of  the  sapid  body.  5.  Taste  is  greatly  aided  by  the  sense 
of  sme//,  and  in  fact  we  often  confound  taste  with  smell ;  thus  vanilla,  garlic,  and 
asafoetida  only  affect  the  organ  of  smell,  while  chloroform  only  excites  taste.  [The 
combined  action  of  taste  and  smell  in  some  cases  gives  rise  to  flavor  (p.  840). 
The  eye  even  may  aid  the  determination,  as  in  the  experiment  where  in  rapidly 
tasting  red  and  white  wine  one  after  the  other,  when  the  eyes  are  covered,  we 
soon  become  unable  to  distinguish  between  the  one  and  the  other.  6.  The  most 
advantageous  temperature  for  taste  is  between  io°-35°  C.  ;  hot  and  cold  water 
temporarily  paralyze  taste. 

Action  of  the  Electrical  Current. — The  constant  current,  when  applied  to  the  tongue, 
excites,  both  during  its  passage  and  when  it  is  opened  or  closeii,  a  sensation  of  acidity  at  the  -\- 
pole,  and  at  the  —  pole  an  alkaline  taste,  or,  more  correctly,  a  harsh,  burning  sensation  (Suher, 
1752).  This  is  not  due  to  the  action  of  the  electrolytes  of  the  fluid  in  the  mouth,  for  even  when 
the  tongue  is  moistened  with  an  acid  fluid  the  alkaline  sensation  is  experienced  at  the  —  pole 
(  Volla).  We  cannot,  however,  set  aside  the  supposition  that  perhaps  electrolytes,  or  decomposi- 
tion products,  may  be  formed  in  the  deeper  parts  and  excite  the  gustatory  fibres.  Rapidly  inter- 
rupted currents  do  not  excite  taste  {Griinhagen\.  V.  Vintschgau,  who  lias  only  incomplete  taste 
on  the  tip  of  the  tongue,  finds  that  when  the  ///  of  the  tongue  is  traversed  by  an  electrical  current, 
there  is  never  a  gustatory  sensation,  but  always  a  distinct  tactile  one.  In  experiments  on  Honig. 
schmeid,  who  is  possessed  of  normal  taste  in  the  tip  of  the  tongue,  there  was  often  a  metallic  or 
acid  taste  at  the  +  pole  o"  'he  tip  of  the  tongue,  while  at  the  —  pole  ta^te  was  often  absent,  and 
when  it  was  present  it  was  almost  always  alkaline,  and  acid  only  exceptionally.  After  interrupting 
the  current  there  was  a  metallic  after  taste  with  both  directions  of  the  current. 

[Testing  Taste. — Direct  the  person  to  put  out  his  tongue  and  close  his  eyes, 
and  after  drying  the  tongue  apply  the  sapid  substance  by  means  of  a  glass  rod  or 
a  small  brush.  Try  to  confine  the  stimulus  as  much  as  possible  to  one  place,  and 
after  each  experiment  rinse  the  mouth  with  water.     A  wine  taster  chews  an  olive 


PATHOLOGICAL COMPARATIVE HISTORICAL.  843 

to  "clean  the  palate,"  as  he  says.  For  testing  hitter  taste  use  a  solution  of 
quinine  or  quassia  ;  for  sweet  %\x%sx  [or  the  intensely  sweet  substance  "saccharine  " 
obtained  from  coal  tar]  ;  saline,  common  salt ;  and  acid,  dilute  citric  or  acetic 
acid.     The  galvanic  current  may  also  be  used.] 

Pathological. — Diseases  of  the  tongue,  as  well  as  dryness  of  the  mouth  caused  by  interference 
with  the  salivary  secretion,  interfere  with  the  sense  of  taste.  Subjective  gustatory  impressions 
are  common  among  the  insane,  and  are  due  to  some  central  cause,  perhaps  to  irritation  of  the 
psychogeusic  centre  (J  378,  IV,  3),  After  poisoning  with  santonin  a  Ijitter  taste  is  experienced, 
while  after  the  subcutaneous  injection  of  morphia  there  is  a  bitter  and  acid  taste.  The  terms 
hypergeusia,  hypogeusia  and  ageusia  are  applied  to  the  increase,  diminution  and  abolition  of 
the  sense  of  taste.  Many  tactile  impressions  on  the  tongue  are  frequently  confounded  with  gusta- 
tory sensations,  e.g.,  the  so-called  biting,  cooling,  prickling,  sandy,  mealy,  astringent  and  harsh 
tastes. 

Comparative. — About  1760  taste  bulbs  occur  on  the  circumvallate  papilla;  of  the  ox.  The 
term  papilla  foliata  is  applied  to  a  large  folded  gustatory  organ  placed  laterally  on  the  side  of  the 
tongue,  especially  of  the  rabbit  (A'<;//,  /<?j'2),  and  which  in  man  is  represented  by  analogous 
organs,  composed  of  longitudinal  folds,  lying  in  the  fimbria;  lingua;  on  each  side  of  the  posterior 
part  of  the  tongue  [Krause,  v.  IVyss).  Taste  bulbs  are  absent  in  reptiles  and  birds.  They  are 
numerous  in  the  mouth  of  the  tadpole  (F.  E.  Schtiltze),  while  the  tongue  of  the  frog  is  covered 
with  epithelium  resembling  gustatory  cells  { Billrotli,  A.xel  Key).  The  goblet-shaped  organs  in  the 
skin  of  fishes  and  tadpoles  have  a  structure  similar  to  the  taste  bulbs,  and  may  perhaps  have  the 
same  function.     There  are  taste  bulbs  in  the  mouth  of  the  carp  and  ray. 

Historical. — Bellini  regarded  the  papillre  as  the  organs  of  taste  (171 1).  Richerand,  Mayo  and 
Fodera  thought  that  the  lingua!  was  the  only  nerve  of  taste,  but  Magendie  proved  that,  after  it  was 
divided,  the  posterior  part  of  the  tongue  was  still  endowed  with  taste.  Panizza  {1834)  described 
the  glosso-pharyngeal  as  the  nerve  of  taste,  the  gustatory  as  the  nerve  of  touch,  and  the  hypoglossal 
as  the  motor  nerve  of  the  tongue. 


THE  SENSE  OF  TOUCH. 


424  TERMINATIONS  OF  SENSORY  NERVES.— i.  The  touch  corpuscles  of 
Wagner  and  Meissner  lie  in  tlie  papillse  of  the  cutis  vera  (§  2S3),  and  are  most  numerous  in 
the  palm  of  the  hand  and  the  sole  of  the  foot,  especially  in  the  fingers  and  toes,  there  being  about 
21  to  every  square  millimetre  of  skin,  or  108  to  400  of  the  papilla;  containing  blood  vessels.  They 
are  less  abundant  on  the  back  of  the  hand  and  foot,  mamma,  lips  and  tip  of  the  tongue,  rare  on 
the  glans  clitoridis,  and  occur  singly  and  scattered  on  the  volar  side  of  the  fore  arm,  even  in  the 
anthropoid  apes.  They  are  oval  or  elliptical  bodies,  40-200  fi  long  [jj,,  in.],  and  60-70  n  broad 
[.j^jj  (o  ^^j  in],  and  are  covered  externally  by  layers  of  connective  tissue  arranged  transversely  in 
layers,  and  withm  is  a  granular  mass  with  elongated  striped  nuclei  (Figs.  536,  537,  e).  One  to  three 
medullated  nerve  fibres  pass  to  the  lower  end  of  each  corpuscle,  and  surround  it  in  a  spiral  manner 


Fig.  537- 


Fig.  536, 


Fig.  536. — Wagni 
gl  .meruli      F 


touch  corpuscle   from  the  palm,  treated  with  gold  chloride, 
flG.  537. — Vertical  section  of  the  skin  of  the  palm  of  the  hand. 
c,  capillary;   d,  nerve  fibre   passing   to   a   touch   corpuscle;  /,  ne 
touch  corpuscle  ;  g,  cells  of  the  Malpighian  layer  of  the  skin. 


res,  a,  a.  groups  ot 
el  ;  i,  papilla  of  the 
^-ided    transversely ; 


two  or  three  times;  the  fibres  then  lose  their  myelin,  and  after  dividing  into  4  to  6  fibrils,  divide 
within  the  corpuscle.  The  exact  mode  of  termination  of  the  fibrils  is  not  known.  Some  observers 
suppose  that  the  transverse  fibrillation  is  due  to  the  coils  or  windings  of  the  nerve  fibrils;  while, 
according  to  others,  the  inner  part  consists  of  numerous  flattened  cells  lying  one  over  the  other, 
between  which  the  pale  terminal  fibres  end  either  in  swellings  or  with  disk-like  expansions,  such  as 
occur  in  Merkel's  corpuscles. 

[These  corpuscles  do  not  contain  a  soft  core  such  as  exists  in  Pacini's  corpuscles.  The  corpuscles 
appear  to  consist  of  connective  tissue  with  imperfect  septa  passing  into  the  interior  from  the  fibrous 
capsule.  After  the  nerve  fibre  enters  it  loses  its  myelin,  and  then  branches,  while  the  branches 
anastomose   and   follow  a  spiral   course  within  the  corpuscle,  finally  to  terminate  in  slight  cnlarge- 

844 


TERMINATIONS   OF   SENSORY    NERVES. 


845 


ments.      According  to  Thin,  there  are  simple  and  compound  corpuscles,  depending  on  the  number 
of  nerve  fibres  entering  them.] 

KoUmann  describes  three  special  tactile  areas  in  the  hand:  (l)  The  tips  of  the  fingers  with 
24  touch  corpuscles  in  a  length  of  10  mm. ;  (2)  the  three  eminences  lying  on  the  palm 
behind  the  slits  between  the  fingers,  with  5.4-2.7  touch  corpuscles  in  the  same  length  ;  and 
(3)  the  ball  of  the  thumb  and  little  finger  with  3.1-3  5  touch  corpuscles.  The  first  two  aieas 
also  contain  many  of  the  corpuscles  of  Vater  or  Pacini,  whi'e  in  the  latter  these  corpuscles 
are  fewer  and  scattered.  In  the  other  parts  of  the  hand  the  nervous  end  organs  are  much 
le.-s  developed. 

2.  Vater's  (1741)  or  Pacini's  corpuscles  are  oval  bodies  (Fig.  538),  1-2  mm.  long,  lyin;;  in 
the  subcutaneous  tissue  on  the  nerves  of  the  fingers  and  toes  (600-1400),  in  the  neighliorhood  of 
joints  and  muscles,  the  sympathetic  abdominal  plexuses,  near  the  aorta  and  coccygeal  gland,  on  il  e 
dorsum  of  the  penis  and  clitoris,  and  in  the  mesocolon  [and  mesentery]  uf  the  cat.  [They  also 
occur  in  the  course  of  the  intercostal  and  perio.^teal  nerves,  and 
Stirling  has  seen  them  in  the  capsule  of  lymphatic  glands. 
They  are  attached  to  the  nerves  of  the  hand  and  feet,  and  are 
so  Urge  as  10  be  visible  to  the  naked  eye,  both  in  these  regions 
ar.d  between  the  layers  of  the  mesentery  of  the  cat.  They  are 
whitish  or  somewhat  transparent,  with  a  white  line  in  the 
centre  (cat)  ;  in  man,  they  are  j'.  to  ^'^  inch  long,  and  ^',  to 
y'j  inch  broad,  and  are  attached  by  a  stalk  or  pedicle  (Fig. 
538,  a)  to  the  nerve.]  They  consist  of  numerous  nucleated 
Connective-tissue  capsules  or  lamellse  lined  by  endothelium 
separated  from  each  other  by  fluid,  and  lying  one  within  the 
other  like  the  coats  of  an  onion,  while  in  the  axis  is  a  central 
cere.  A  medullated  nerve  fibre  passes  to  each,  where  its 
sheath  of  Schwann  unites  with  the  capsule.  It  loses  its  myelin, 
and  passes  into  the  interior  as  an  axial  cylinder  (Fig.  538,  <■ ), 
where  it  either  ends  in  a  small  knob  or  may  divide  dichoto- 
mously  (Fig.  538,/), each  branch  terminating  in  asmall  pear- 
shaped  enliii-^'c-meii/.  [Each  large  corpuscle  is  covered  by 
40-50  lamellae,  or  tunics,  which  are  thinner  and  closer  to 
each  other  (Fig.  538,  il)  internally  than  in  the  outer  part, 
where  they  are  thicker  and  wider  apart.  The  lamella  are 
like  the  laminse  in  the  lamellated  sheath  of  a  nerve,  and  are 
composed  of  an  elastic  basis  mixed  with  white  fil)res  of  con. 
neclive  tissue,  while  the  inner  surface  of  each  lamella  is  luied 
by  a  single  continuous  layer  of  endothelium  continuous  with 
that  of  the  perineurium.  It  is  easily  stained  with  silver  nitrate. 
The  efferent  nerve  fibre  is  covered  with  a  thick  sht-alh  of 
lamellated  connective  tissue  (sheath  of  Henle),  which  be- 
comes blended  with  the  outer  lamella;  of  the  corpuscle.  The 
medullated  nerve  is  sometimes  accompanied  by  a  blood  vessel, 
and  pierces  the  various  tunics,  retaining  its  myelin  until  it 
reaches  the  core,  where  it  terminates  as  already  described. 

3.  Krause's  end  bulbs  very  probably  occur  as  a  regular 
mode  of  nerve  termination  in  the  cutis  and  mucous  membrane 
of  all  mammals.  They  are  elongated,  oval,  or  round  bodies, 
0.075  '°  °''4  ■""i-  l°"g'  ^""1  ^Oi^'e  been  found  in  the  deeper 
layers  of  the  conjunctiva  bulbi,  floor  of  the  mouth,  margins  of 
the  lips,  nasal  mucous  membrane,  epiglottis,  fungiform  and  cir- 
cumvallate  papilla;,  glans  penis  and  clitoris,  volar  surface  of 
the  toes  of  the  guinea  pig,  ear  and  body  of  the  mouse,  and  in 
the  wing  of  the  bat.  [In  the  calf,  the  "cylindrical  end 
bulbs  "  are  oval,  with  a  nerve  fibre  terminaling  within  them. 
The  sheath  of  Henle  becomes  continuous  with  the  nucleated 
capsule,  while  the  axial  cylinder,  devoid  of  its  myelin,  is  con- 
tinued into  the  soft  core.  In  man  the  end  bulbs  are  "spheroidal," 
and  consist  of  a  nucleated  connective  tissue  capsule  continuous  with  Henle's  sheath  of  the  nerve, 
anil  enclosing  many  cells,  among  which  the  axis  cylinder  which  enters  the  bulb  branches  and  ter- 
minates.] The  spheroidal  and  end  bulbs  occur  in  man,  in  the  nasal  mucous  membrane,  conjunctiva, 
mouth,  epiglottis,  and  the  mucous  folds  of  the  rectum.  According  to  Waldeyer  and  l.ongworih, 
the  nerve  fibrils  terminate  in  the  cells  within  the  capsule.  These  cells  are  said  to  be  comparable  t  > 
Merkel's  tactile  cells  (  ll^aUeyer). 

The  genital  corpuscles  of  Krause,  which  occur  in  the  skin  and  mucous  membrane  of  the  glans 
penis,  clitoris,  and  vagina,  appear  to  be  end  bulbs  more  or  less  fused  together. 

The  articulation  nerve  corpuscles  occur  in  the  synovial  mucous  membrane  of  the  joints  of  the 


Pacini's  corpuscle,  a,  stalk 
e  fibre  entering  it:  c,ii,cai 
:-tissue  envelope  ;  e  axis  cylii 
ith  its  end  divided  aty". 


846  SENSORY   AND   TACTILE    SENSATIONS. 

fingers.  They  are  larger  than  the  end  bulbs,  and  have  numerous  oval  nuclei  externally,  while  one 
to  four  nerve  tibres  enter  them. 

4.  Tactile  or  touch  corpuscles  of  Merkel,  sometimes  also  called  the  corpuscles  of  Grandry, 
occur  in  the  beak  and  tongue  of  the  duck  and  goose,  in  the  epidermis  of  man  and  mammals,  and 
in  the  outer  root  sheath  of  tactile  hairs  or  feelers.  They  are  small  bodies,  composed  of  a  capsule 
enclosing  two,  three  or  more  large,  granular,  somewhat  flattened  nucleated  and  nucleolated  cells, 
piled  one  on  the  other  in  a  vertical  row,  like  a  row  of  cheeses.  Each  corpuscle  receives  at  one  side 
a  medullated  nerve  fibre,  which  loses  its  myelin,  and  branches,  to  terminate,  according  to  some 
observers  {A/erkel)^'\n  the  cells  themselves,  and  according  to  others  {A'tifiz'ier,  Izqtiierdo,  Hesse)^ 
in  the  protoplasmic  transparent  substance  or  disk  lying  between  the  cells.  [This  intercellular  disk 
is  the  "  disk  tactil "  of  Kanvier,  or  the  "  Tastphitte"  of  Hesse.]  When  there  is  a  great  aggregation 
of  these  cells,  large  structures  are  formed,  which  appear  to  form  a  kind  of  transition  between  these 
and  touch  corpuscles.  [According  to  Klein,  the  terminal  fibrils  end  neither  in  the  touch  cells  nor 
tactile  disk,  but  in  minute  swellings  in  the  interstitial  substance  between  the  touch  cells,  in  a  manner 
very  similar  to  that  occurring  in  the  end  bulbs.] 

[According  to  Merkel,  tactile  cells,  either  isolated  or  in  groups,  but  in  the  latter  case  never  form- 
ing an  independent  end  organ,  occur  in  the  deeper  layers  of  the  epidermis  of  man  and  mammals, 
and  also  in  the  papilla;.  They  consist  of  round  or  flask-shaped  cells,  with  the  lower  pointed  neck 
of  the  flask  continuous  with  the  axis  cylinder  of  a  nerve  fibre.  They  are  regarded  by  Merkel  as 
the  simplest  form  of  a  tactile  end  organ,  but  their  existence  is  doubted  by  some  observers.] 

Among  animals  there  are  many  other  forms  of  sensory  end  organs.  [Herbst's  corpuscles 
occur  in  the  mucous  membrane  of  the  tongue  of  the  duck,  and  resemble  small  Vater's  corpuscles, 
but  their  lamellce  are  thinner  and  nearer  each  other,  while  the  axis  cylinder  within  the  central  core 

Fig.  539. 


Bouchon  epidermique  from  the  groin  of  a  guinea  pig,  after  the  action  of  gold  chloride,    n,  nerve  fibre  ;  rt,  tactile  cells  ; 
;«,  tactile  disks  ;  c,  epithelial  cells. 

is  bordered  on  each  sid-;  by  a- row  of  nuclei.]  In  the  nose  of  the  mole  there  is  a  peculiar  end 
organ  (Eimer),  while  there  are  "end  capsules"  in  the  penis  of  the  hedgehog  and  the  tongue  of 
the  elephant,  and  "  neKZ'e  rings"  in  the  ears  of  the  mouse. 

5.  [Other  Modes  of  Ending  of  Sensory  Nerves. — Some  sensory  ner\'es  terminate  not  by 
means  of  special  end  organs,  but  their  axis  cylinder  splits  up  into  fibrils  to  form  a  nervous  network, 
from  which  fine  fibrils  are  given  off  to  terminate  in  the  tissue  in  which  the  nerve  ends.  The^e  fibrils, 
as  in  the  cornea  (§  384),  terminate  by  means  of  free  ends  between  the  epithelium  on  the  anterior 
surface  of  the  cornea,  and  some  observers  state  that  the  free  ends  are  provided  with  small  enlarge- 
ments ("boutons  terminals  ")  (Fig.  539,  a).  These  enlargements  or  "  tactile  cells  "  occur  in  the 
groin  of  the  guinea  pig  and  mole.  .\  similar  mode  of  termination  occurs  between  the  cells  of  the 
epidermis  in  man  and  mammals  (Fig.  271).] 

6.  Tendons,  especially  at  their  junction  with  muscles,  have  special  end  organs  {Sachs,  RolUtt, 
Golgi),  which  assume  various  forms;  it  may  be  a  network  of  primitive  nerve  fibrils,  or  flattened 
end  flakes  or  plates  in  the  sterno-radial  muscle  of  the  frog,  or  elongated  oval  end  bulbs,  not  unlike 
the  end  bulbs  of  the  conjunctiva,  or  small  simple,  Pacinian  corpuscles.] 

425.  SENSORY  AND  TACTILE  SENSATIONS.— In  the  sensory 
nerve  trunks  there  are  two  functionally  different  kinds  of  nerve  fibres:  (i)  Those 
which  administer  to /a//y9// impressions,  which  are  sensory  nerves  in  the  narrower 
sense  of  the  word  ;  and  (2)  which  administer  to  tactile  impressions,  and  may, 
therefore,  be  called  tactile  nerves.  The  sensations  of  temperature  and  pressure  are 
also  reckoned  as  belonging  to  the  tactile  group.     It  is  extremely  probable  that  the 


THE    SENSE   OF    LOCALITY.  847 

sensory  and  tactile  nerves  have  different  end  organs  and  fibres,  and  that  they  have 
also  special  perceptive  nerve  centres  in  the  brain,  although  this  is  not  definitely 
proved.     This  view,  however,  is  supported  by  the  following  facts: — 

I.  That  sensory  and  tactile  impressions  cannot  be  discharged  at  the  same  time 
from  all  the  parts  which  are  endowed  with  sensibility.  Tactile  sensations,  in- 
cluding pressure  and  temperature,  are  only  discharged  from  the  coverings  of  the 
skin,  the  mouth,  the  entrance  to  and  floor  of  the  nose,  the  pharynx,  the  lower 
end  of  the  rectum  and  genito-urinary  orifices  ;  feeble,  indistinct  sensations  of  tem- 
perature are  felt  in  the  oesophagus.  Tactile  sensations  are  absent  from  all  internal 
viscera,  as  has  been  proved  in  man  in  cases  of  gastric,  intestinal  and  urinary 
fistulas.  Pain  alone  can  be  discharged  from  these  organs.  2.  The  conduction 
channels  of  the  tactile  and  sensory  nerves  lie  in  different  parts  of  the  spinal  cord 
(§364,  I  and  5).  This  renders  probable  the  assumption  that  their  central  and 
peripheral  ends  also  are  different.  3.  Very  probably  the  reflex  acts  discharged 
by  both  kinds  of  nerve  fibres — the  tactile  and  pathic — are  controlled,  or  even 
inhibited,  by  special  central  nerve  organs  (§  361 — ?).  4.  Under  pathological 
conditions,  and  under  the  action  of  narcotics,  the  one  sensation  may  be  suppressed 
while  the  other  is  retained  (§  364,  5). 

Sensory  Stimuli. — In  order  to  discharge  a  painful  impression  from  sensory 
nerves,  relatively  strong  stimuli  are  required.  The  stimuli  may  be  mechanical, 
chemical,  electrical,  thermal,  and  somatic,  the  last  being  due  to  inflammation  or 
anomalies  of  nutrition  and  the  like. 

Peripheral  Reference  of  the  Sensations. — These  nerves  are  excitable 
along  their  entire  course,  and  so  is  their  central  termination,  so  that  pain  may 
be  produced  by  stimulating  them  in  any  part  of  their  course  ;  but  this  pain, 
according  to  the  "law  of  peripheral  perception,"  is  always  referred  to 
the  periphery. 

The  tactile  nerves  can  only  discharge  a  tactile  impression  or  sensation  of  con- 
tact when  moderately  strong  mechanical  pressure  is  exerted,  while  thermal  stimuli 
are  required  to  produce  a  temperature  sensation  ;  and  in  both  cases  the  results  are 
obtained  only  when  the  appropriate  stimuli  are  applied  to  the  end  organs.  If 
pressure  or  cold  be  applied  to  the  course  of  a  nerve  trunk,  e.  g.,  to  the  ulna  at  the 
inner  surface  of  the  elbow  joint,  we  are  conscious  of  painful  sensations,  but  never 
of  those  of  temperature,  referable  to  the  peripheral  terminations  of  the  nerves  in 
the  inner  fingers.  All  strong  stimuli  disturb  normal  tactile  sensations  by  over- 
stimulation, and  hence  cause  pain. 

426.  THE  SENSE  OF  LOCALITY.— We  are  not  only  able  to  distin- 
guish  differences  of  pressure  or  temperature    by  our  sensory 
nerves,  but  we  are  able  to  distinguish  the  part  which  has  been  Fig.  540. 

touched.     This  capacity  is  spoken  of  as  the  sense  of  space  or 
locality. 

Methods  of  Testing. — Place  the  two  blunted  points  of  a  pair  of  com- 
passes (tig.  540)  upon  the  part  of  the  skin  to  be  investigated,  and  determine 
the  smallest  fiistance  at  which  the  two  points  are  felt  only  as  one  impression. 
Sieveking's  eesthesiometer  (Fig.  541)  may  be  used  instead;  one  of  the 
points  is  movable  along  a  graduated  rod,  while  the  other  is  fixed.  2.  The 
distance  between  the  points  of  the  instrument  being  kept  the  same,  touch 
several  parts  of  the  skin,  and  ask  if  the  person  feels  the  impression  of  the 
points  coming  nearer  to  or  going  wider  apart.  3.  Touch  a  part  of  the  skin 
with  a  blunt  instrument,  and  observe  if  the  spot  touched  is  correctly  indicated 
by  the  patient. 

The  investigations  have  led  to  the  following  results :  The 
sense  of  locality  of  a  part  of  the  skin  is  more  acute  under  the 
following  conditions : 

I.  The  greater  the  ««»/^fr^/a^///^«^/-Z'«  in  the  correspond-      '   .;EsthesioniM<:r. 
ing  part  of  the  skin. 


848 


MODIFYING    CONDITIONS. 


2.  The  greater  the  mobility  of  the  part,  so  that  it  increases  in  the  extremities 
toward  the  fingers  and  toes.  The  sense  of  locality  is  always  very  acute  in  parts 
of  the  body  that  are  very  rapidly  moved  (^Vierordt). 

3.  The  sensibility  of  the  limbs  is  finer  in  the  transverse  axis  than  in  the  long 
axis  of  the  limb,  to  the  extent  of  Yz  on  the  flexor  surface  of  the  upper  limb, 
and  Y,  o"  t'^^  extensor  surface. 

4.  The  moiie  of  application  of  the  points  of  the  ssthesiometer  :  {a)  According 
as  they  are  applied  one  after  the  other,  instead  of  simultaneously,  or  as  they  are 
considerably  warmer  or  colder  than  the  skin  {King),  a  person  may  distinguish  a 
less  distance  between  the  points,  {b)  If  we  begin  with  the  points  wide  apart  and 
approximate  them,  then  we  can  distinguish  a  less  distance  than  when  we  proceed 
from  imperceptible  distances  to  larger  ones,  {c)  If  the  one  point  is  warm  and  the 
other  cold,  on  exceeding  the  next  distance  we  feel  two  impressions,  but  we  cannot 
rightly  judge  of  their  relative  positions  {Czennak). 

5.  Exercise  greatly  improves  the  sense  of  locality ;  hence  the  extraordinary 
acuteness  of  this  sense  in  the  blind,  and  the  improvement  always  occurs  on  both 
sides  of  the  body  (  Volkmanii). 

[Fr.  Gallon  finds  that  the  reputed  increased  acuteness  of  the  other  senses  in  the  case  of  the  bUnd 
is  not  so  great  as  is  generally  alleged.  He  tested  a  large  number  of  boys  at  an  educational  blind 
asylum,  with  the  result  that  the  performances  of  the  blind  boys  were  by  no  means  superior  to  those 

Fii;.  541. 


of  other  boys.  He  points  out,  however,  that  "  the  guidance  of  the  blind  depends  mainly  on  the 
multitude  of  collateral  indications,  to  which  they  give  much  heed,  and  not  in  their  superiority  to  any 
one  of  them."] 

6.  Moistening  \\\^  skin  with  indifferent  fluids  increases  the  acuteness.  If,  how- 
ever, the  skin  between  two  points,  which  are  still  felt  as  two  distinct  objects,  be 
slightly  tickled,  or  be  traversed  by  an  imperceptible  electrical  current,  the  im- 
pressions become  fused  {Suslowa).  The  sense  of  locality  is  rendered  more  acute 
at  the  cathode  when  a  constant  current  is  used  (S//slo7va),  and  when  the  skin  is 
congested  by  stimulation  (Klinkenberg),  and  also  by  slight  stretching  of  the  skin 
{Schmey)  ;  further,  by  baths  of  carbonic  acid  {v.  Basch  and  v.  Dietl),  or  warm 
common  salt,  and  temporarily  by  the  use  of  caffein  {Rumff). 

7.  A?ice>nia,  produced  by  elevating  the  limbs,  or  venous  hypenemia  (by  com- 
pressing the  veins),  blunts  the  sense,  and  so  does  too  frequent  testing  of  the  sense 
of  locality,  by  producing  fatigue.  The  sense  is  also  blunted  by  cold  applied  to 
the  skin,  the  influence  of  the  anode,  strong  stretching  of  the  skin,  as  over  the  ab- 
domen during  pregnancy,  previous  exertion  of  the  muscles  under  the  part  of  the 
skin  tested,  and  some  poisons,  ?.  ^.,  atropin,  daturin,  morphin,  strychnin,  alcohol, 
potassium  bromide,  cannabin,  and  chloral  hydrate. 

Smallest  Appreciable  Distance.  —  The  following  statement  gives  the 
smallest  distance,  in  millimetres,  at  which  two  points  of  a  pair  of  compasses  can 


^STHESIOMETRY. 


849 


Millimetres. 

Eyelid 11.3     [9] 

Centre  of  hard  palate 13.5  [113] 

Lower  third  of  the  forearm,  volar 

surface 15. 

In  front  of  the  zygoma 15.8  [11.3] 

Plantar  surface  of  the  great  toe  .    .15.8     [9.] 

Inner  surface  of  the  lip 20.3  [13.5] 

Behind  the  zygoma 22.6  [15.8] 

Forehead 22.6  [18.] 

Occiput 27.1  [22.0] 

Back  of  the  hand 31.6  [22.6] 

Under  the  chin 33.8  [22.6] 

Vertex 33.8  [22.6] 

Knee 36.1  [31.6] 

Sacrum,  gluteal  region 44.6  [33.8] 

Forearm  and  leg 45.1  [33. 8J 

Neck 54.1  [36.1] 

Back   at  the  fifth  dorsal   vertebra, 

lower  dorsal  and  lumbar  region     .  54.1 

Middle  of  the  neck 67.7 

Upper  arm,  thigh  and  centre  of  the 

back 67.7   [31.6-40.6] 


Still  be  distinguished  as  double  by  an  adult.     The  corresponding  numbers  for  a 
boy  twelve  years  of  age  are  given  within  brackets  :  — 

Millimetres. 

Tip  of  tongue i.i     [!•'] 

Third    phalanx  of  finger,    volar 

surface 2.-2.3      [''7] 

Red  part  of  the  Up 4.5     [3.9] 

Second  phalanx  of  finger,  volar 

surface. 4-4-5      [3-9] 

First    phalanx    of   finger,    volar 

surface 5--5-5 

Third  phalanx   of  finger,  dorsal 

surface 6.8      [4.5] 

Tip  of  nose 6.8     [4.5] 

Head  of  metacarpal  bone,  volar  .  5-.6.8     [4.5] 

Ball  of  thumb     ." 6.5-7. 

Ball  of  little  finger 5-5-6- 

Centre  of  palm 8.-g. 

Dorsum  and  side  of  tongue,  white 

of  the  lips,  metacarpal  part  of 

the  thumb. 9.      [6.8] 

Third  phalanx  of  the  great  toe, 

plantar  surface 1 1.3  [6.8] 

Second   phalanx    of  the  fingers, 

dorsal  surface 1 1.3     [9.] 

Back 1 1.3     [9.] 

Illusions  of  the  sense  of  locality  occur  very  frequently  ;  the  most  marked  are:  (i)  A  uni- 
form movement  over  a  cutaneous  surface  appears  to  be  quicker  in  those  places  which  have  the 
finest  sense  of  locality.  (2)  If  we  merely  touch  the  skin  with  the  two  points  of  an  a;sthesiometer, 
then  they  feel  as  if  they  were  wider  apart  than  when  the  two  points  are  moved  along  Vne  skin 
(Fechner).  (3)  A  sphere,  when  touched  with  short  rods,  feels  larger  than  when  long  rods  are 
used  (  Toitrtual).  (4)  When  the  fingers  of  one  hand  are  crossed,  a  small  pebble  or  sphere  placed 
between  them  feels  double  (Aristotle's  experiment).  [When  a  pebble  is  rolled  between  the 
crossed  index  and  middle  finger  (Fig.  542,  B),  it  feels  as  if  two  balls  were  present,  but  with  the 
fingers  uncrossed  single,  (5)  When  pieces  of  skin  are  transplanted,  e.g.,  from  the  forehead,  to  form 
a  nose,  the  person  operated  on  feels,  often  for  a  long  time,  the  new  nasal  part  as  if  it  were  his  fore- 
head.] 

Theoretical. — Numerous  experiments  were  made  by  E.  H.  Weber,  Lotze,  Meissner,  Czermak 
and  others,  to  explain  the  phenomen.i  of  the 

sense   of    space.      Weber's    theory   goes  Fig.  542. 

upon  the  assumption,  that  one  and  the  same 
nerve  fibre  proceeding  from  the  brain  to  the 
skin  can  only  take  up  one  kind  of  impres- 
sion, and  admimsterihereto.  He  calleti  the 
part  of  the  skin  to  which  each  single  nerve 
fibre  is  distributed  a  "  circle  of  sensa- 
tion." When  two  stimuli  act  simultaneously 
upon  the  tactile  end  organ,  then  a  double 
sensation  is  felt,  when  one  or  more  circles  of 
sensation  lie  between  the  two  points  stimu- 
lated. This  explanation,  based  upon  ana- 
tomical considerations,  does  not  explain  how 
it  is  that,  with  practice,  the  circles  of  sensa- 
tion become  smaller,  and  also  how  it  is  that 
only  one  sensation  occurs,  when  both  points 
of  the  instrument  are  so  applied,  that  both 
points,  although  further  apart  than   the  di-  ^• 

ameter  of  a  circle  of  sensation,  at  one  time  Aris 

he  upon  two  adjoining  circles,  at  another 
between  two  others  with  another  circle  intercalated  between  them. 

AWundt's  Theory. — In  accordance  with  the  conclusions  of  Lotze,  Wundt  proceeds  from  a 
psycho-physiological  basis,  that  every  part  of  the  skin  with  tactile  sensibility  always  conveys  to  the 
brain  the  locilily  of  the  sensation.  Every  cutaneous  area,  therefore,  gives  to  the  tactile  sensation  a 
"  lottil  color"  or  quality,  which  is  spoken  of  as  the  "  local  sign."  He  assumes  that  this  local  color 
diminishes  from  point  to  point  of  the  skin.  This  gradation  is  very  sudden  in  those  parts  of  the 
skin  where  the  sense  of  space  is  very  acute,  but  occurs  very  gradually  where  the  sense  of  space  is 
54 


B. 


xpenmcnt. 


850 


THE    PRESSURE    SENSE. 


more  obtuse.  Separate  impressions  unite  into  a  common  one,  as  soon  as  the  gradation  of  the  U)cal 
color  becomes  imperceptible.  By  practice  and  attention  differences  of  sensation  are  experienced, 
which  ordinarily  are  not  observed,  so  that  he  e.xpUins  the  diminution  of  the  circles  of  sensation  by 
practice.  The  circle  of  sensation  is  an  area  of  the  skin,  within  which  the  local  color  of  the  sensa- 
tion changes  so  little  that  two  separate  impressions  fuse  into  one. 

427.  THE  PRESSURE  SENSE.— By  the  sense  of  pressure  we  obtain  a 
knowledge  of  the  amount  of  weight  or  pressure  which  is  being  exercised  at  the 
time  on  the  different  parts  of  the  skin. 

Methods. — i.  Place,  on  the  part  of  the  skin  to  be  investigated,  different  weights,  one  after  the 
other,  and  ascertain  what  perceptions  they  give  rise  to,  and  the  sense  of  the  difterence  of  pressure 
to  which  they  give  rise.  We  must  be  careful  to  exclude  differences  of  temperature  and  prevent  the 
displacement  of  the  weights — the  weights  must  always  be  placed  on  the  same  spot,  and  the  skin 
should  be  covered   beforehand  with  a  plate,  while  the  muscular  sense  must  be  eliminated  (§  430). 


Fig.  543. 


1  balance  for  testing  the  pressun 


[This  is  done  by  supporting  the  hand  or  part  of  the  skin  which  is  being  tested,  so  that  the  action 
of  all  the  muscles  is  excluded.]  2.  A  process  is  attached  to  a  balance  and  made  to  touch  the  skin, 
while  by  placing  weights  in  the  scale  pan  or  removing  them,  we  test  what  differences  in  weight  the 
person  experimented  on  is  able  to  distinguish  (Dohrn).  3.  In  order  to  avoid  the  necessity  of 
changing  the  weights,  A.  Eulenberg  invented  his  bar£esthesiometer,  which  is  constructed  on  the 
same  principle  as  a  spiral  spring  paper  clip  or  balance.  There  is  a  small  button  which  rests  on  the 
skin  and  is  depressed  by  the  spring.  An  index  shows  at  once  the  pressure  in  grammes,  and  the 
instrument  is  so  arranged  that  the  pressure  can  be  very  easily  varied.  4.  Goltz  uses  a  pulsating 
elastic  tube,  in  which  he  can  produce  waves  of  different  height.  He  tested  how  high  the  latter 
must  be  before  they  are  experienced  as  pulse  waves,  when  the  tube  is  placed  upon  the  skin.  5. 
Landois  uses  a  mercurial  balance  (Fig.  543).  The  beam  of  a  balance  (W)  moves  upon  two 
knife  edges  (O,  O),  and  is  carried  on  the  horizontal  arm  |ii)  of  a  heavy  support  (T).  One  arm  of 
the  beam  is  provided  with  a  screw  (/n)  on  which  an  equilibrating  weight  (S)  can  be  moved.     The 


RESULTS   OF   THE    PRESSURE    SENSE.  851 

other  arm  (d)  passes  into  a  vertical  calibrated  tube  (R).  Below  this  is  the  pressure  pad  (Pi,  which 
can  be  loaded  as  desired  by  a  weight  (G).  and  which  can  be  placed  upon  the  part  of  the  skin  to  be 
tested  (H).  From  an  adjoining  burette  (B)  held  in  a  clamp  (A),  mercury  can  pass  through  a  tube 
in  the  direction  of  the  arrows,  to  one  part  of  the  balance  and  into  the  tube  (R).  On  the  stop-cock 
(/;)  being  closed,  whenever  pressure  is  exerted  on  the  tube  |  D,  I)),the  mercury  rises  through  d  into 
R,  and  increases  the  pressure  on  P.  We  measure  the  weight  of  the  mercury  corresponding  to  each 
division  of  the  tube  (R).  This  instrument  enables  rapid  variations  of  the  weight  to  be  made  with- 
out giving  rise  to  any  shock.  In  estimating  both  the  pressure  sense  and  temperature  sense,  it  is  best 
to  proceed  on  the  principle  of  "  the  least  perceptible  difference,"  i.e.,  the  different  pressures  or  tem- 
peratures are  graduated,  either  beginning  with  great  differences,  or  proceeding  from  the  smallest 
difference,  and  determining  the  limit  at  which  the  person  can  distinguish  a  difference  in  the  sensa- 
tion. 

Results. — I.  The  smallest  perceptible  pressure,  when  applied  to  different  parts 
of  the  skin,  varies  very  greatly  according  to  the  locality.  The  greatest  acuteness 
of  sensibility  is  on  the  forehead,  temples,  and  the  back  of  the  hand  and  forearm, 
which  perceive  a  pressure  of  0.002  grm.  ;  the  fingers  first  feel  with  a  weight  of 
0.005  'o  0.015  grm.  ;  the  chin,  abdomen,  and  nose  with  0.04  to  0.05  grm.  ;  the 
finger  nail  i  grm.  {^Kammler  and  Aubert). 

The  greater  the  sensibility  of  the  skin,  the  more  rapidly  can  single  stimuli  succeed  each  other, 
and  still  be  perceived  as  single  impressions;  52  stimuli  per  second  may  be  applied  to  the  volar  side 
of  the  upper  arm,  61  on  the  back  of  the  hand,  70  to  the  tips  of  the  fingers,  and  still  be  felt  singly 
i^Bloch). 

2.  Intermittent  variations  of  pressure,  as  in  Goltz's  tube,  are  felt  more  acutely 
by  the  tips  of  the  fingers  than  with  the  forehead. 

3.  Differences  between  two  weights  are  perceived  by  the  tips  of  the  fingers  when 
the  ratio  is  29  :  30  (in  the  fore  arm  as  18.2  :  20),  provided  the  weights  are  not 
too  light  or  too  heavy,  In  passing  from  the  use  of  very  light  to  heavy  weights, 
the  acuteness  or  fineness  of  the  perception  of  difference  increases  at  once,  but 
with  heavier  weights,  the  power  of  distinguishing  differences  rapidly  diminishes 
again  ( E.  Heriiig,  Ltvwit,  and  Biedei-mann).  This  observation  is  at  variance  with 
the  psycho-physical  law  of  Fechner  (§  383). 

4.  A.  Eulenberg  found  the  following  gradations  in  the  fineness  of  the  pressure 
sense  :  The  forehead,  lips,  dorsum  of  the  cheeks,  and  temples  appreciate  differ- 
ences of  ^jj  to  -^^  (200  :  205  to  300  :  310  grm.).  The  dorsal  surface  of  the  last 
phalanx  of  the  fingers,  the  fore  arm,  hand,  ist  and  2d  phalanx,  the  volar  surface 
of  the  hand,  fore  arm,  and  upper  arm,  distinguishes  differences  of  j'lj  to  -^jj  (200  : 
220  to  220  :  210  grm.).  The  anterior  surface  of  the  leg  and  thigh  are  smiilar  to 
the  fore  arm.  Then  follow  the  dorsum  of  the  foot  and  toes,  the  sole  of  the  foot, 
and  the  posterior  surface  of  tlie  leg  and  thigh.  Dohrn  determined  the  smallest 
additional  weight,  which,  when  added  to  i  grm.  already  resting  on  the  skin,  was 
appreciated  as  a  difference,  and  he  found  that  for  the  3d  phalanx  of  the  finger  it 
was  .499  grm.  ;  back  of  the  foot,  0.5  grm.  ;  2d  phalanx,  0.771  grm.  ;  ist  pha- 
lanx, 0.02  grm.  ;  leg,  i  grm.  ;  back  of  the  hand,  1.156  grm.  ;  palm,  1.018  grm.  ; 
patella,  1.5  grm.;  fore  arm,  1.99  grm.;  umbilicus,  3.5  grms. ;  and  the  back, 
3.8grms. 

5.  Too  long  time  must  not  elapse  between  the  application  of  two  successive 
weights,  but  100  seconds  may  elapse  when  the  difference  between  the  weights  is 
4:  ^  {£.  ff.   Weber). 

6.  The  sensation  of  an  after  pressure  is  very  marked,  especially  if  the  weight 
is  considerable  and  has  been  applied  for  a  length  of  time.  But  even  light  weights, 
when  applied,  must  be  separated  by  an  interval  of  at  least  ^^  to  -^\-^  second,  in 
order  to  be  perceived.  When  they  are  applied  at  shorter  intervals,  the  sensations 
become  fused.  When  Valentin  pressed  the  tips  of  his  fingers  against  a  wheel 
provided  with  blunt  teeth  he  felt  the  impression  of  a  smooth  margin,  when  the 
teeth  were  applied  to  the  skin  at  the  intervals  above  mentioned  ;  when  the  wheel 
was  rotated  more  slowly,  each  tooth  gave  rise  to  a  distinct  impression.     \'ibrations 


852  RESULTS   OF   THE   TEMPERATURE    SENSE. 

of  strings  are  distinguished  as  such  when  the  number  of  vibrations  is  1506  to  1552 
per  second  (r.  JVi'/tiih  and  Griinhageti). 

7.  It  is  remarkable  that  pressure  produced  by  the  uniform  compression  of  a  part 
of  the  body,  e.g.,  by  dipping  a  finger  or  arm  in  mercury,  is  not  felt  as  such  ;  the 
sensation  is  felt  only  at  the  limit  of  the  fluid,  on  the  volar  surface  of  the  finger,  at 
the  limit  of  the  surface  of  the  mercury. 

428.  THE  TEMPERATURE  SENSE.— The  temperature  sense  makes 
us  acquainted  with  the  variations  of  the  lieat  of  the  skin.  The  circumstance  de- 
termining the  sensation  of  temperature  is,  according  to  E.  Hering,  the  tempera- 
ture of  the  thermal  end  organs  themselves.  As  often  as  any  part  of  the  skin  has 
a  temperature  above  its  zero,  /.  e.,  its  neutral  proper  temperature,  we  feel  warm  ; 
in  the  opposite  condition  we  feel  cold.  The  one  or  the  other  sensation  becomes 
stronger  the  more  the  temperature  of  the  thermal  end  organ  differs  from  its  zero 
temperature.  The  zero  temperature,  however,  may  vary  pretty  rapidly  from  ex- 
ternal causes  within  certain  limits. 

Methods. — To  the  surface  of  the  skin  objects  of  the  same  size  and  with  the  same  thermal  con- 
ductivity are  apphed  successively  at  different  temperatures:  i.  Nothnagel  uses  small  wooden  cups 
with  a  metallic  base,  and  filled  with  warm  and  cold  water,  the  temperature  being  regislered  by  a 
thermometer  placed  in  the  cups.  [2.  Clinically,  two  test  tubes  filled  with  cold  and  warm  water, 
or  two  spoons,  the  one  hot  and  the  other  cold,  may  be  used.] 

Results. — I.  As  a  general  rule,  the  feeling  of  cold  is  produced  when  a  body 
applied  to  the  skin  robs  it  of  heat ;  and,  conversely,  we  have  a  sensation  of  warmth 
when  heat  is  communicated  to  the  skin. 

2.  The  greater  the  thermal  conductivity  of  the  substance  touching  the  skin,  the 
more  intense  is  the  feeling  of  heat  or  cold  (§  218). 

3.  At  a  temperature  of  i5S°-35°  C.,  we  distinguish  distinctly  differences  of 
temperature  of  o.2°-o.i6°  R.  with  the  tips  of  the  fingers  {E.  H.  Weber).  Tem- 
peratures just  below  that  of  the  blood  (33°-27°  C. — Nothnagel)  are  distinguished 
most  distmctly  by  the  most  sensitive  parts,  even  to  differences  of  0.05°  C.  {Lin- 
dermann).  Differences  of  temperature  are  less  easily  made  out  when  dealing  with 
temperatures  of  33°-39°  C,  as  well  as  between  i4°-2  7°  C.  A  temperature  of 
55°  C,  and  also  one  a  few  degrees  above  zero,  cause  distinct  pain  in  addition  to 
the  sensation  of  temperature. 

4.  The  different  parts  of  the  skin  also  vary  in  the  acuteness  of  their  thermal 
sense,  and  in  the  following  order ;  Tip  of  the  tongue,  eyelids,  cheeks,  lips,  neck, 
and  body.  The  perceptible  minimum  Nothnagel  found  to  be  0.4°  on  the  breast; 
0.9°  on  the  back ;  0.3°,  back  of  the  hand  ;  0.4°,  palm  ;  0.2°,  arm ;  0.4°  back  of 
the  foot;  0.5°,  thigh;  0.6°  leg;  o.4°-o. 2°,  cheek;  o.4°-o.3°  C,  temple.  The 
thermal  sense  is  less  acute  in  the  middle  line,  e.g.,  the  nose,  than  on  each  side  of 
it  {£.  H.  Weber). 

5.  Differences  of  temperature  are  most  easily  perceived  when  the  same  part  of 
the  skin  is  affected  successively  by  objects  of  different  temperature.  If,  however, 
two  different  temperatures  act  simultaneously  and  side  by  side,  the  impressions  are 
apt  to  become  fused,  especially  when  the  two  areas  are  very  near  each  other. 

[Goldschneider  finds  that  when  two  cold  or  two  warm  cylinders  are  applied  to  the  skin,  the 
sensation  of  heal  and  cold  can  be  appreciated  as  double  at  exceedingly  small  distances  apart,  e.g., 
cold  to  the  forehead,  cheek,  or  chin  at  0.8  mm.  apart,  palm  of  the  little  finger  o. i  mm,] 

6.  Practice  improves  the  temperature  sense;  congestion  of  venous  blood  in  the 
skin  diminishes  it ;  diminution  of  the  amount  of  blood  in  the  skin  improves  it  (J/. 
Alsberg).  When  large  areas  of  the  skin  are  touched,  the  perception  of  differences 
is  more  acute  than  with  small  areas.  Rapid  variations  of  temperature  produce 
more  intense  sensations  than  gradual  changes  of  temperature. 

[Goldschneider  asserts  that  there  are  special  cutaneous  nerves,  some  of  which  administer  only  to 
the  sensation  of  cold,  and  others  for  that  of  heat,  others  for  pressure,  and,  lastly,  those  for  touch.  In 
the  "  cold  points  "  of  the  skin,  when  gently  touched  with  a  cold  conical  metal  cylinder,  only  the 


COMMON    SENSATION PAIN.  853 

sensation  of  cold  is  felt,  and  in  tlie  "  heat  points  "  only  heat,  while  such  points  are  insensible  to  a 
gentle  touch.  The  sensation  of  cold  occurs  at  once,  that  of  heat  gradually  increases,  and  is  more 
diffuse.     Pain  cannot  be  discharged  from  these  "temperature  points." 

Illusions  are  very  common :  i.  The  sensations  of  heat  and  cold  sometimes  alternate  in  a  para- 
doxical manner.  ^Vhen  the  skin  is  dipped  first  into  water  at  io°  C.  we  feel  cold,  and  if  it  be  then 
dipped  at  once  into  water  at  l6°  C.  we  have  at  first  a  feeling  of  warmth,  but  soon  again  of  cold. 
2.  The  same  temperature  applied  to  a  large  surface  of  the  skin  is  estimated  to  be  greater  than  when 
it  is  applied  to  a  small  area,  (■  g.,  the  whole  hand  when  placed  in  water  at  29.5°  C.  feels  warmer 
than  when  a  finger  is  dipped  into  water  at  32°  C.  3.  Cold  weights  are  judged  to  be  heavier  than 
warm  ones. 

Pathological. — Tactile  sensibility  is  only  seldom  increased  (hjrperpselaphesia),  but  great  sen- 
sibility to  differences  of  temperature  is  manifested  by  areas  of  the  skin  whose  epidermis  is  partly 
removed  or  altered  by  vesicants  or  herpes  zoster,  and  the  same  occurs  in  some  cases  of  locomotor 
ataxia ;  while  the  sense  of  locality  is  rendered  more  acute  in  the  two  former  cases  and  in  erysipelas. 
An  abnnrmal  condition  of  the  sense  of  locality  was  described  by  BrownSequard,  where  three  points 
were  felt  when  only  two  were  apjjlied,  and  two  when  one  was  applied  to  the  skin.  Landois  finds 
that  in  himself  pricking  the  skin  of  the  sternum  over  the  angle  of  Ludovicus  is  always  accompanied 
by  a  sensation  in  the  knee.  [.Some  persons,  when  cold  water  is  applied  to  the  scalp,  have  a  sensa- 
tion referable  to  the  skin  of  the  loins  (^StirUng).'\  A  remarkable  variation  of  the  sense  of  locality 
occurs  in  moderate  poisoning  with  morphia,  where  the  person  feels  himself  abnormally  large  or 
greatly  diminished.  In  degeneration  of  the  posterior  columns  of  the  cord,  Obersteiner  observed  that 
the  patient  was  unable  to  say  whether  his  right  or  left  side  was  touched  ('*  AUochiria").  Ferrier 
observed  a  case  where  a  stimulus  applied  to  the  right  side  was  referred  to  the  left,  and  vice  versa. 

Diminution  and  paralysis  of  the  tactile  sense  (Hypopselaphesia  and  Apselaphesia) 
occur  either  in  conjunction  with  simultaneous  injury  to  the  sensory  nerves,  or  alone.  It  is  rare  to 
find  that  one  of  the  qualities  of  the  tactile  sense  is  lost,  e.  g.,  either  the  tactile  sense  or  the  sense  of 
temperature — a  condition  which  has  been  called  '^partial  taclile  paralysis."  Limbs  which  are 
^^  sleeping'^  feel  heat  and  not  cold  \//erzen). 

429.  COMMON  SENSATION— PAIN.— Definition.— By  the  term 
common  sensation  we  understand  pleasant  or  unpleasant  sensations  in  those 
parts  of  our  bodies  which  are  endowed  with  sensibility,  and  which  are  not  refer- 
able to  external  objects,  and  whose  characters  are  difficult  to  describe,  and  cannot 
be  compared  with  other  sensations.  Each  sensation  is,  as  it  were,  a  peculiar  one. 
To  this  belong  pain,  hunger,  thirst,  malaise,  fatigue,  horror,  vertigo,  tickling, 
well-being,  illness,  the  respiratory  feeling  of  free  or  impeded  respiration. 

Pain  inay  occur  wherever  sensory  nerves  are  distributed,  and  it  is  invariably 
caused  by  a  stronger  stimulus  than  normal  being  applied  to  sensory  nerves.  Every 
kind  of  stimulation,  mechanical,  thermal,  chemical,  electrical,  as  well  as  somatic 
(inflammation  or  disturbances  of  nutrition)  may  excite  pain.  The  last  appear  to 
be  especially  active,  as  many  tissues  become  extremely  painful  during  inflamma- 
tion (1".^'.,  muscles  and  bones),  while  they  are  comparatively  insensible  to  cutting. 
Pain  may  be  produced  by  stimulating  a  sensory  nerve  in  any  part  of  its  course, 
from  its  centre  to  the  periphery,  but  the  sensation  is  invariably  referred  to  the 
peripheral  end  of  the  nerve.  This  is  the  law  of  the  peripheral  reference  of 
sensations.  Hence,  stimulation  of  a  nerve,  as  in  the  scar  of  an  amputated 
limb,  may  give  rise  to  a  sensation  of  pain  which  is  referred  to  the  parts  already 
removed.  Too  violent  stimulation  of  a  sensory  nerve  in  its  course  may  render  it 
incapable  of  conducting  impressions,  so  that  peripheral  impressions  are  no  longer 
perceived.  If  a  sufficient  stimulus  to  produce  pain  be  then  applied  to  the  cen- 
tral part  of  the  nerve,  such  an  impression  is  still  leferred  to  the  ])eripheral  end  of 
the  nerve.  Thus  we  explain  the  paradoxical  anaesthesia  dolorosa.  In  con- 
nection with  painful  impressions,  the  patient  is  often  unable  to  localize  them  ex- 
actly. This  is  most  easily  done  when  a  small  injury  ( prick  of  a  needle)  is  made  on 
a  peripheral  part.  When,  however,  the  stimulation  occurs  in  the  course  of  the 
nerve,  or  in  the  centre,  or  in  nerves  whose  peripheral  ends  are  not  accessible,  as 
in  the  intestines,  pain  (as  belly-ache),  which  cannot  easily  be  localized,  is  the  result. 

Irradiation. — During  violent  pain  there  is  not  unfrequently  irradiation  of  the 
pain  (§  364,  5),  whereby  localization  is  impossible.  It  is  rare  for  pain  to  remain 
continuous  and  uniform  ;  more  generally  there  are  exacerbations  and  diminutions 
of  the  intensity,  and  sometimes  periodic  intensification,  as  in  some  neuralgias. 


854  METHODS   OF   TESTING    PAIN THE    MUSCULAR    SENSE. 

The  intensity  of  the  pain  depends  especially  upon  the  excitability  of  the  sen- 
sory nerves.  There  are  considerable  individual  variations  in  this  respect,  some 
nerves,  e.g.,  the  trigeminus  and  splanchnic,  being  very  sensitive.  The  larger  the 
number  of  fibres  affected  the  more  severe  the  pain.  The  duration  is  also  of  im- 
portance, in  as  far  as  the  same  stimulation,  when  long  continued,  may  become 
unbearable.  We  speak  of  piercing,  cutting,  boring,  burning,  throbbing,  press- 
ing, gnawing,  dull,  and  other  kinds  of  pain,  but  we  are  quite  unacquainted  with 
the  conditions  on  which  such  different  sensations  depend.  Painful  impressions  are 
abolished  by  anaesthetics  and  narcotics,  such  as  ether,  chloroform,  morphia, 
etc.  (§  364,  5). 

Methods  of  Testing. — To  test  the  cutaneous  sensibility,  we  usually  employ  the  constant  or  in- 
duced electrical  current.  Determine  first  the  minimum  sensibility,  i.e.,  the  strength  of  the  current 
which  excites  the  first  trace  of  sensation,  and  also  the  minimum  of  pain,  i.e.,  the  feeblest  strength  of 
the  current  which  first  causes  distinct  impressions  of  pain.  The  electrodes  consist  of  thin  metallic 
needles,  and  are  placed  i  to  2  cm.  apart  (I'ig.  375). 

Pathological. — When  the  excitability  of  the  nerves  which  administer  to  painful  sensations  is  in- 
creased, a  slight  touch  of  the  skin,  nay,  even  a  breath  of  cold  air,  may  excite  the  most  violent  pain, 
constituting  cutaneous  hyperalgia,  especially  in  inflammatory  or  exanthematic  conditions  of  the 
skin.  The  term  cutaneous  paralgia  is  applied  to  certain  anomalous,  disagieeable,  or  painful  sen- 
sations which  are  frequently  referred  to  the  skin — itching,  creeping,  formication,  cold,  and  burning. 
In  cerebro-spinal  meningitis,  sometimes  a  prick  in  the  sole  of  the  foot  produces  a  double  sensation  of 
pain  and  a  double  reflex  contraction.  Perhaps  this  condition  may  be  explained  by  supposing  that 
in  a  part  of  the  nerve  the  condition  is  delayed  (|  337,  21.  In  neuralgia  there  is  severe  pain,  oc- 
curring in  paroxysms,  with  violent  exacerbations  and  pain  shooting  into  other  pans  (p.  629).  Very 
frequently  excessive  pain  is  produced  by  pressure  on  the  nerve  where  it  makes  its  exit  from  a  fora- 
men or  traverses  a  fascia. 

Valleix's  Points  Douloureux  (l84i).^The  skin  itself  to  which  the  sensory  nerve  runs,  espe- 
cially at  first,  may  be  very  sensitive;  and  when  the  neuralgia  is  of  long  duration  the  sensibility  may 
be  diminished  even  to  the  condition  of  analgesia  ( /"arc/J) ;  in  the  latter  case  there  may  be  pro- 
nounced ani"esthesia  dolorosa  (p.  S53). 

Diminution  or  paralysis  of  the  sense  of  pain  (hypalgia  and  analgia)  may  be  due  to  afTections 
of  the  ends  of  the  nerves,  or  of  their  course,  or  central  terminations. 

Metalloscopy. — In  hysterical  patients  suffering  from  hemiana'Sthesia,  it  is  found  that  the  feeling 
of  the  paralyzed  side  is  r-stored,  when  small  metallic  plates  or  larger  pieces  of  different  metals  are 
applied  to  the  affected  parts  (Buret/,  Charcot).  At  the  same  time  that  the  affected  part  recovers  its 
sensibility  the  opposite  limb  or  side  becomes  anaesthetic.  This  condition  has  been  spoken  of  as 
transference  of  sensibility.  The  phenomenon  is  not  due  to  galvanic  currents  developed  by  the 
metals.  The  phenomenon  is,  perhaps,  explained  by  the  fact  that,  under  physiological  conditions, 
and  in  a  healthy  person,  every  increase  of  the  sensiljility  on  one  side  of  the  body,  produced  by  the 
application  of  warm  metallic  plates  or  bandages,  is  followed  by  a  diminution  of  the  sensibility  of  the 
opposite  side.  Conversely,  it  is  found  that  when  one  side  of  the  body  is  rendered  less  sensitive  by 
the  application  of  cold  plates,  the  homologous  part  of  the  other  side  becomes  more  sensitive  (Rumpf 
and  M.  Rosenthal). 

430.  THE  MUSCULAR  SENSE.— Muscular  Sensibility.— The  sen- 
sory nerves  of  the  muscles  (§  292)  always  convey  to  us  impressions  as  to  the  activ- 
ity or  non-activity  of  these  organs,  and  in  the  former  case  these  impressions  enable 
us  to  judge  of  the  degree  of  contraction.  It  also  informs  us  of  the  amount  of  the 
contraction  to  be  employed  to  overcome  resistance.  Obviously,  the  muscular 
sense  must  be  largely  supported  and  aided  by  the  sense  of  pressure,  and  conversely. 
E.  H.  Weber  showed,  however,  that  the  muscle  sense  is  finer  than  the  pressure 
sense,  as  by  it  we  can  distinguish  weights  in  the  ratio  of  39  :  40,  while  the  pressure 
sense  only  enables  us  to  distinguish  those  in  the  ratio  of  29  :  30.  In  some  cases 
there  has  been  observed  total  cutaneous  insensibility,  while  the  muscular  sense  was 
retained  completely.  A  frog  deprived  of  its  skin  can  spring  without  any  apparent 
disturbance.  The  muscular  sense  is  also  greatly  aided  by  the  sensibility  of  the 
joints,  bones  arid  fasciae.  Many  muscles,  e.g.,  those  of  respiration,  have  only 
slight  muscular  sensibility,  while  it  seems  to  be  absent  normally  in  the  heart  and 
non-striped  muscle. 

[The  muscular  sense  stands  midway  between  special  and  common  sensations, 
and   by  it  we  obtain  a  knowledge  of  the  condition  of  our  muscles,  and  to  what 


METHODS   OF   TESTING   THE    MUSCULAR    SENSE.  855 

extent  they  are  contracted  ;  also  the  position  of  the  various  parts  of  our  bodies 
and  the  resistance  offered  by  external  objects.  Thus,  sensations  accompanying 
muscular  movement  are  twofold — (n)  the  movements  in  the  unopposed  muscles, 
as  the  movements  of  the  limbs  in  space;  and  (l>)  those  of  resistance  where  there 
is  opposition  to  the  movement,  as  in  lifting  a  weight.  In  the  latter  case  the  sen- 
sations due  to  innervation  are  important,  and,  of  course,  in  such  cases  we  have 
also  to  take  into  account  the  sensations  obtained  from  mere  pressure  upon  the 
skin.  Our  sensations  derived  from  muscular  movements  depend  on  the  direction 
and  duration  of  the  movements.  On  the  sensations  thus  conveyed  to  the  senso- 
rium  we  form  judgments  as  to  the  direction  of  a  point  in  space,  as  well  as  of  the 
distance  between  two  points  in  space.  This  is  very  marked  in  the  case  of  the 
ocular  muscles.  It  is  also  evident  that  the  muscular  sense  is  ultimately  related  to, 
and  often  combined  with,  the  exercise  of  the  sensations  of  touch  and  sight 
iSully\-\ 

Methods  of  Testing. — Weights  are  wrapped  in  a  towtl  and  suspended  to  the  part  to  be  tested. 
The  patient  estimates  the  weight  by  raising  and  lowering  it.  The  electro-muscular  sensibility  also 
may  be  proved  thus :  cause  the  muscles  to  contract  by  means  of  induction  shocks,  and  observe  the 
sensation  thereby  produced.  [Direct  the  patient  to  place  his  feet  together  while  standing,  and  then 
close  his  eyes.  A  healthy  person  can  stand  quite  steady,  but  in  one  with  the  muscular  sense  im- 
paired, as  in  locomotor  ataxia,  the  patient  may  move  to  and  fro,  or  even  fall.  Again,  a  person  with 
his  muscular  sense  impaired  may  not  be  able  to  touch  accurately  and  at  once  some  part  of  his  body 
when  his  eyes  are  closed.] 

Section  of  a  sensory  nerve  causes  disturbance  of  the  fine  gradation  of  movement 
(p.  646).  Meynert  supposes  that  the  cerebral  centre  for  muscular  sensibility  lies 
in  the  motor  cortical  centres,  the  muscles  being  connected  by  motor  and  sensory 
paths  with  the  ganglionic  cells  in  these  centres. 

Too  severe  muscular  exercise  causes  the  sensation  of  fatigue,  oppression  and 
weight,  in  the  limbs  (§  304). 

Pathological. — Abnormal  increase  of  the  muscular  sense  is  rare  [^muscular  hyperlagia  and 
hyperiTsthesia),  as  in  anxietas  tibianim,  a  painful  condition  of  unrest  which  leads  to  a  continual 
change  in  the  position  of  the  limbs.  In  cramp  there  is  intense  pain,  due  to  stimulation  of  the 
sensory  nerves  of  the  muscle,  and  the  same  is  the  case  in  inflammation.  Diminution  of  the  mus- 
cular sensibility  occurs  in  some  choreic  and  ataxic  persons  {\  364,  5).  In  locomotor  ataxia  the 
muscular  sense  of  the  upper  extremities  may  be  normal  or  weakened,  while  it  is  usually  consider- 
ably diminished  in  the  legs.  [The  muscular  sense  is  said  to  be  increased  in  the  hypnotic  condition 
and  in  somnambulists.] 


REPRODUCTION  AND  DEVELOPMENT. 


431.  FORMS  OF  REPRODUCTION.— I.  Abiogenesis  (Generatio  fcquivoca,  sive  spon- 
tanea, spontaneous  generation). — It  was  formerly  assumed  that,  under  certain  circumstances, 
non-living  matter  derived  from  the  decomposition  of  organic  materials  became  changed  sponta- 
neously into  living  beings.  While  Aristotle  ascribed  this  mode  of  origin  to  insects,  the  recent 
observers  who  advocate  this  form  of  generation  restrict  its  action  solely  to  the  lowest  organism. 
Experimental  evidence  is  distinctly  against  spontaneous  generation.  If  organized  matter  be  heated 
to  a  very  high  temperature  in  sealed  tubes,  and  be  thus  deprived  of  all  living  organisms  or  their 
spores,  there  is  no  generation  of  any  organism.  Hence  the  dictum  "  Ornne  vh'itm  ex  ovo  "  {^Harvey^ 
or  ex  viva).  Some  highly-organized  invertebrate  animals  (Gordius,  Anguillula,  Tardigrada,  and 
Rotatoria)  may  be  dried,  and  even  heated  to  140°  C,  and  yet  regain  their  vital  activities  on  being 
moistened  (Anabiosis). 

II.  Division  or  fission  occurs  in  many  protozoa  (amoeba,  infusoria).  The  organism,  just  as  is 
the  case  with  cells,  divides,  the  nucleus,  when  present,  taking  an  active  part  in  the  process,  so  that 
two  nuclei  and  two  masses  of  protoplasm,  forming  two  organisms,  are  produced.  Tlie  Ophidiasters, 
among  the  echinoderms,  divide  spontaneously,  and  they  are  said  to  throw  off  an  arm  which  may 
develop  into  a  complete  animal.  According  to  Trembley  (1744),  the  hydra  may  be  divided  into 
pieces,  and  each  piece  gives  rise  to  a  new  individual  [.althbugh  under  normal  circumstances  the 
hydra  gives  oft"  buds,  and  is  provided  with  generative  organs]. 

[Division  of  Cells. — Although  a  cell  is  defined  as  a  "  nucleated  mass  of  living  protoplasm," 
recent  researches  have  shown  that,  from  a  histological  point  of  view,  a  cell  is  really  a  very  complex 

structure.     The  apparently  homogeneous  cell  substance 
Fig.  544.  is  traversed  by  a  tine  plexus  of  fibrils,  with  a  homoge- 

neous substance  in  its  meshes,  while  a  similar  network  of 
fibrils  exists  within  the  nucleus  itself  (Fig.  544).  A  cell 
may  divide  directly,  as  it  were,  by  simple  cleavage, 
and  in  the  process  the  nucleus  usually  divides  before  the 
cell  protoplasm.  The  nucleus  becomes  constricted  in 
the  centre,  has  an  hourglass  shape,  and  soon  divides 
into  two.  But  recent  observations,  confirmed  by  a  great 
number  of  investigators,  conclusively  prove  that  the  pro- 

cess  of  division   in   cells  is  a  very  complicated  one,  the 

Changes  in  a  cell  nucleus  during  karyokinesis.  changes  in  the  nucleus  being  very  remarkable.  The  term 
karyokinesis,  or  indirect  division,  has  been  applied 
to  this  process.  Fig.  544  shows  the  changes  that  take  place  in  the  nucleus.  The  intranuclear 
network  {a)  passes  into  a  convolution  of  thinner  fibrils,  while  the  nuclear  envelope  becomes  less 
distinct,  the  fibrils  at  the  same  time  becoming  thicker  and  forming  loops,  which  gradually  arrange 
themselves  around  a  centre  {c  and  d)  in  the  form  of  a  wreath  or  rosette.  The  fibres  curve  round 
both  at  the  periphery  and  the  centre;  but  when  their  peripheral  connections  are  severed  or  dis- 
solved, we  obtain  a  star-shaped  form,  or  aster,  composted  of  single  loops  radiating  from  the  centre 
(c).  After  further  subdivision,  the  whole  is  composed  of  fine  radiating  fibrils  (/),  which  gradually 
arrange  themselves  around  two  poles,  or  new  centres,  to  form  a  diaster,  or  double  star  ([,'),  the  two 
groups  being  separated  by  a  substance  called  the  equatorial  plate.  Each  of  the  groups  of  fibrils 
becomes  more  elongated,  and  forms  a  nuclear  spindle,  which  indicates  the  position  of  a  new 
nucleus.  The  separate  groups  of  fibrils  again  become  convoluted ;  each  group  gets  a  nuclear 
membrane,  while  the  cell  protoplasm  divides,  and  two  daughter  nuclei  are  obtained  from  the 
original  cell.] 

III.  Budding  or  gemmation  occurs  in  a  well-marked  form  among  the  polyps  and  in  some  in- 
fusorians  (Vorticella).  A  bud  is  given  oflT  by  the  parent,  and  gradually  comes  more  and  more  to 
resemble  the  latter.  The  bud  either  remains  permanently  attached  to  the  parent,  so  that  a  complex 
organism  is  produced,  in  which  the  digestive  organs  communicate  with  each  other  directly,  or  in 
some  cases  there  may  be  a  "  colony  "  with  a  common  nervous  system,  such  as  the  polyzoa.  In 
.some  composite  animals  (siphonophora)  the  difl'erent  polyps  perform  different  functions.  Some  have 
a  digestive,  others  a  motor,  and  a  third  a  generative  function,  so  that  there  is  a  physiological  division 
of  labor.  Buds  which  are  given  off  from  the  parent  are  formed  internally  in  the  rhizopoda.  In 
some  animals  (polyps,  infusoria),  which  can  reproduce  themselves  by  buds  or  divisions,  there  is  also 

85« 


TESTIS.  857 

the  formation  of  male  and  female  elements  of  generation,  so  that  they  have  a  sexual  and  non  sexual 
mode  of  reproduction. 

IV.  Conjugation  is  a  form  of  reproduction  which  leads  up  to  the  sexual  form.  It  occurs  in  the 
unicellular  Gregarinae.  The  anterior  end  of  one  such  organism  unites  with  the  posterior  end  of 
another ;  both  become  encysted,  and  form  one  passive  spherical  body.  The  conjoined  structures 
form  an  amorphous  mass,  from  which  numerous  globular  bodies  are  formed,  and  in  each  of  which 
numerous  oblong  structures — the  pseudo-navicelli — are  developed.  These  bodies  become,  or  give 
rise  to,  an  amoeboid  structure,  which  forms  a  nucleus  and  an  envelope,  and  becomes  transformed  into 
a  gregarina. 

Sexual  reproduction  requires  the  formation  of  the  embryo  from  the  conjunction  of  the  male 
and  female  reproductive  elements,  the  sperm  cell  and  the  germ  cell.  These  products  may  be 
formed  either  in  one  individual  (hermaphroditism,  as  in  the  flat  worms  and  gasteropods),  or  in  Iwo 
separate  organisms  (male  or  female).     Sexual  reproduction  embraces  the  following  varieties: — 

V.  Metamorphosis  is  that  form  of  sexual  reproduction  in  which  the  embryo  from  an  early 
period  undergoes  a  series  of  marked  changes  of  external  form,  e.  i^.,  the  chrysalis  stage,  and  the 
pupa  stage,  and  in  none  of  these  stages  is  reproduction  possible.  Lastly,  the  final  sexually  developed 
form  (the  imago  stage  in  butterflies)  is  produced,  which  forms  the  sexual  products  whose  union  gives 
rise  to  organisms  which  repeat  the  same  cycle  of  changes.  Metamorphosis  occurs  extensively 
among  the  insects;  some  of  them  have  several  stages  (holo-metabolic),  and  others  have  few  stages 
(hemimetabolic).  It  also  occurs  in  some  arthropoda,  and  woims,  c.^.,  trichina;  the  sexual  form 
of  the  animal  occurs  in  the  intestine,  the  numerous  larzue  wander  into  the  muscles,  where  they 
become  encysted,  and  form  undeveloped  sexual  organs,  constituting  the  pupa  stage  of  the  muscular 
trichina.  When  the  encysted  form  is  eaten  by  another  animal,  the  sexual  organs  come  into  activity, 
a  new  brood  is  formed,  and  the  cycle  is  repeated.  Metamorphosis  also  occurs  in  the  frog  and  in 
petromyzon.  [This  is  really  a  condition  in  which  the  embryo  undergoes  marked  changes  of  form 
before  it  becomes  sexually  mature.] 

VI.  Alternation  of  Generations  (Steensfrup). — In  this  variety  some  of  the  members  of  the 
cycle  can  produce  new  beings  nonsexually,  while  in  the  final  stage  reproduction  is  always  sexual. 
From  a  medical  point  of  view  the  life-history  of  the  tapeworm  or  Taenia  is  most  important.  The 
segments  of  the  tapeworm  are  called  proglottides,  and  each  segment  is  hermaphrodite,  with  testes, 
vas  deferens,  penis,  ovary,  etc.,  and  numerous  ova.  The  segments  are  evacuated  with  the  fieces. 
The  eggs  are  fertilized  after  they  are  shed,  and  from  them  is  developed  an  elliptical  embryo,  pro- 
vided with  six  booklets,  which  is  swallowed  by  another  animal,  the  host.  These  embryos  bore  their 
way  into  the  tissues  of  the  host,  where  they  undergo  development,  forming  the  encysted  stage 
(Cysficercus,  Coenurus,  or  Echinococcus).  The  encysted  capsule  may  contain  one  (cysticercus)  or 
many  (coenurus)  sessile  heads  of  the  t:enia.  In  order  to  undergo  further  development,  the  cysti- 
cercus must  be  eaten  alive  by  another  animal,  when  the  head  or  scolex  fixes  itself  by  its  booklets 
and  suckers  to  the  intestine  of  its  new  host,  where  it  begins  to  bud  and  produce  a  series  of  new 
segments  between  the  head  and  the  last-formed  segment,  and  thus  the  cycle  is  repeated. 

The  most  important  flat  worms  are  :  Taenia  solium,  in  man  ;  the  Cysticercus  cellulose  in  the 
pig,  where  it  constitutes  the  measle  in  pork;  Ttenia  mediocanellala,  the  encysted  stage,  in  the  ox; 
Tcenia  toenurus,  in  the  dog's  intestine  ;  the  encysted  stage,  or  Coenurus  cerebralis,  in  the  brain  of 
the  sheep,  where  it  gives  rise  to  the  condition  of  "staggers;"  Tccnia  echinococcus,  in  the  dog's 
intestine;  the  embryos  or  scolices  occur  in  the  liver  of  man  as  "  hydatids." 

The  medusii!  also  exhibit  alternation  of  generations,  and  so  do  some  insects,  especially  the  plant 
lice  or  aphides. 

VII.  Parthenogenesis  (Owen  v.  Siebolcf). — In  this  variety,  in  addition  to  sexual  reproduction, 
new  individuals  may  be  produced  without  sexual  union.  The  non-sexually  produced  brood  is  always 
of  one  sex,  as  in  the  bees.  A  bee-hive  contains  a  queen,  the  workers,  and  the  drones  or  males. 
During  the  mutual  flight  the  queen  is  impregnated  by  the  males,  and  the  seminal  fluid  is  stored  up 
in  the  receptaculum  seminis  of  the  queen,  and  it  appears  that  the  queen  may  voluntarily  pennit  the 
contact  of  this  fluid  with  the  ova  or  withhold  it.  All  fertilized  eggs  give  rise  to  female,  and  all  un- 
fertilized ones  to  male  bees. 

VIII.  Sexual  reproduction  without  any  intermediate  stages  occurs  in,  besides  man,  mammals, 
birds,  reptiles,  and  most  fishes, 

432.  TESTIS— SEMINAL  FLUID.— [Testis.— In  the  testis  or  male  reproductive  organ, 
the  seminal  fluid  which  contains  the  male  element  or  spermatozoa  is  formed.  The  framework  of 
the  gland  consists  of  a  thick,  strong,  white  fibrous  covering,  the  tunica  albuginea,  composed 
chiefly  of  white  interlacing  fibrous  tissue.  Externally  this  layer  is  covered  by  the  visceral  layer  of 
the  serous  membrane,  or  the  tunica  vaginalis,  which  invests  the  testis  and  epididymis.  The  tunica 
albuginea  is  prolonged  for  some  distance  as  a  vertical  septum  into  the  posterior  part  of  the  testis,  to 
form  the  mediastinum  testis  or  corpus  Highmori.  Septa  or  trabeculte — more  or  less  complete 
— stretch  from  the  under  surface  of  the  T.  albuginea  toward  the  mediastinum,  so  that  the  organ  is 
subdivided  thereby  into  a  number  of  compartments  or  lobules,  with  their  bases  directed  outward 
and  their  apices  toward  the  media-stihum.  From  these,  finer  sustentacular  fibres  pass  into  the  com- 
partments to  support  the  structures  lying  in  these  compartments.  ] 


858 


STRUCTURE  OF  A  SEMINAL  TUBULE. 


[Arrangement  of  Tubules. — Each  compartmenl  contains  several  seminal  tubules,  long  con- 
voluted tubules  (y^5  in.  in  diam.)  which  rarely  branch  except  at  their  outer  end ;  they  are  about 
two  feet  in  length  and  exceed  800  in  number.  These  tubules  run  toward  the  mediastinum,  those  in 
one  compartment  uniting  at  an  acute  angle  with  each  other,  to  form  a  smaller  number  of  narrower, 
straight  tubules— tubuli  recti  (Fig.  546).  These  straight  tubules  open  into  a  network  of  tubules 
in  the  mediastinum  to  form  the  rete  testis,  a  dense  network  of  tubules  of  irregular  diameter  (Fig. 
546).  From  this  network  there  proceed  12  to  15  wider  ducts — the  vasa  efferentia — which  after 
emerging  from  the  testis  are  at  first  straight,  but  soon  become  convoluted — and  form  a  series  of 
conical  eminences — the  coni  vasculosi — which  together  form  the  head  of  the  epididymis.  These 
tubes  gradually  unite  with  each  other  and  form   the   body  and  globus  minor  of  the   epididymis, 


Seminal  tubules  c 


^ 


Transverse  section  of  the  testis  (low-power  view). 

which,  when  unraveled,  is  a  tube  about  20  feet  long  terminating  in  the  vas  deferens  (2  feet  long), 
which  is  the  excretory  duct  of  the  testis]. 

[Structure  of  a  Tubule. — The  seminal  tubules  consist  of  a  thick,  well-marked  basement 
membrane,  composed  of  flattened,  nucleated  cells  arranged  like  membranes  (Fig.  550,  I).  These 
tubes  are  lined  by  several  layers  of  more  or  less  cubical  cells ;  there  is  an  outer  row  of  such  cells 
next  the  basement  membrane,  and  often  showing  a  dividing  large  nucleus.  Internal  to  these  are 
several  layers  of  inner  large  clear  cells  with  nuclei  often  dividing,  so  that  they  form  many  daughter 
cells  which  lie  internal  to  them  and  next  the  lumen.  From  these  daughter  cells  are  formed  the 
spermatozoa,   and    they   constitute  the  spermatoblasts.      These  several  layers  of    cells  leave  a 


CHEMICAL   COMPOSITION    OF   THE    SEMINAL    FLUID. 


859 


distinct  lumen.  The  tubuli  recti  are  narrow  in  diameter,  and  lined  by  a  single  layer  of  squamous 
or  flattened  epithelium  (Fig.  546).  The  rete  testis  consists  merely  of  channels  in  the  fibrous 
stroma  without  a  distinct  membrana  propria,  but  lined  bytlallened  epithelium.  The  vasa  efferentia 
and  cotii  vasculosi  have  circular  smooth  muscular  fibres  in  their  walls,  and  are  lined  by  a  layer 
of  columnar  ciliated  epithelium  with  striated  protoplasm.  At  the  bases  of  these  cells  in  some  parts 
'  is  a  layer  of  smaller  granular  cells.  These  tubules  form  the  epididymis,  whose  tubules  have  the 
same  structure  (Fig.  547).  In  the  sheep  pigment  cells  are  often  found  m  the  basement  mem- 
brane. The  vas  deferens  is  lined  by  several  layers  of  columnar  epithelium  re>ting  on  a  dense 
layer  of  fibrous  tissue — the  mucosa.  Outside  this  is  the  muscular  coat,  a  thick  layer  of  non- 
striped  muscle  composed  of  a  thick  inner  circular,  and  ihick  outer  loni^iliidinal  layer,  a  ihin  sub- 
mucous coat  connecting  the  muscular  and  mucous  coats  together;  outside  all  is  the  fibrous 
adventitia.] 

[The  interstitial  tissue  (Fig.  545),  supporting  the  seminal  tubules,  is  laminated,  and  covered  by 
endothelial  plates,  with  slits  or  spaces  between  the  I  imells,  which  form  the  origin  of  the  lym- 
phatics. These  lymph  spaces  are  easily  injected  by  the  puncture  method.  In  fact,  if  Berlin  blue 
be  forced  into  the  testis  the  lymphatics  of  the  testis  and  spermatic  cord  are  readily  filled  with  the 
injection.  In  some  animals  (boar),  and  a  less  extent  in  man,  dog,  there  are  also  fairly  large  poly- 
hedral interstitial  cells,  often  with  a  large  nucleus  and  sometimes  pigmented.  They  represent 
the  residue  of  the  epithelial  cells  of  the  Wolffian  bodies  (Klein),  or,  according  to  Waldeyer,  they 


Fig.  546. 


Fig.  547. 


Transverse 
section  nf  a  lube 
of  epididymis. 


are  plasma  cells.     The  blood  vessels  are  numerous,  and  form  a  dense  plexus  outside  the  base- 
ment membrane  of  the  seminal  tubules.] 

Chemical  Composition. — The  seminal  fluid,  as  discharged  from  the 
urethra,  is  mixed  with  the  secretion  of  the  glands  of  the  vas  deferens,  Cowper's 
glands,  and  those  of  the  prostate,  and  with  the  fluid  of  the  vesiculse  seminales. 
Its  reaction  is  neutral  or  alkaline,  and  it  contains  82  per  cent,  of  water,  serum- 
albumin,  alkali-albuminate,  nuclein,  lecithin,  cholesterin,  fats  (protamin?),  phos- 
phorized  fat,  salts  (2  per  cent.),  especially  phosphates  of  the  alkalies  and  earths, 
together  with  sulphates,  carbonates,  and  chlorides.  The  odorous  body,  whose 
nature  is  unknown,  was  called  "■  sper matin"  by  Vanquelin. 

Seminal  Fluid. — The  sticky,  whitish-yellow  seminal  fluid,  largely  composed  of  a  mixture  of 
the  secretions  of  the  above-named  glands,  when  exposed  to  the  air,  becomes  more  fluid,  and  on 
adding  water  it  becomes  gelatinous,  and  from  it  separates  whitish,  transparent  flakes.  When  long 
exposed,  it  forms  rhomboidal  crystals,  which,  according  to  Schreiner,  consist  of  phosphatic  sails 
with  an  organic  base  (CjHjN).  '  These  crystals  ^Fig.  548)  are  said  to  be  derived  from  the  pros- 


860 


DEVELOPMENT   OF   SPERMATOZOA. 


permatK 


tatic  fluid,  and  are  identical  with  the  so-called  Charcot's  crystals  (Fig.  144,  c,  and  ^  138).  The 
prostatic  tluid  is  thin,  milky,  amphoteric,  or  of  slightly  acid  reaction,  and  is  possessed  of  the  seminal 
odor.  The  phosphoric  acid  necessary  for  the  formation  of  tlie  crystals  is  obtained  from  the  seminal 
fluid.  A  somewhat  similar  odor  occurs  in  the  albumin  of  eggs  not  quite  fresh.  The  secretion  of 
the  vesiculae  seminales  of  the  guinea  pig  contains  much  fibrinogen  (Hcnsen  and  Landwehr). 

The  spermatozoa  are  50  /z  long,  and  consist  of  a  flattened,  pear-shaped  head 
(Fig.   549,    I   and  2,  k),  which  is  followed   by  a  rod-shaped  middle  piece,  m 

(Schweigger-Seiiiel),  and  a  long  tail-like 
Fig.  548.  prolongation  or  cilium,  /.     The  whole 

spermatozoon  is  propelled  forward  by  the 
to-and-fro  movements  of  the  tail  at  the 
rate  of  0.05  to  0.5  mm.  per  second  ;  the 
movement  is  most  rapid  immediately 
after  the  fluid  is  shed,  but  it  gradually 
becomes  feebler. 

Finer  Structure. — The  observations  of  Jensen 
have  shown  that  the  middle  piece  and  head  are 
still  more  complex,  although  this  is  not  the  case  in 
human  spermatozoa  and  thoseof  tlie  bull  [G.  I\et- 
zius).  These  consist  of  a  flattened,  long,  narrow, 
transparent,  protoplasmic  mass,  with  a  fibre  com- 
posed of  many  delicate  threads  in  both  margins. 
M  the  tip  of  the  tail  both  fibres  unite  into  one. 
The  fibre  of  the  one  margin  is  gentrally  straight ; 
the  other  is  thrown  into  wave-like  folds,  or  winds 
in  a  spiral  manner  round  the  other  (  ]V.  A'raiise, 
Gi/i/'es).  G.  Retzius  describes  a  special  terminal 
filament  (Fig.  549,  <■).  An  axial  thread,  sur- 
rounded by  an  envelope  of  protoplasm,  traverses 
the  middle  piece  and  the  tail  (Eimcr,  v.  Braun). 
[Leydig  showed  that  in  the  salamander  there  is  a  delicate  membrane  attaclied  to  the  tail,  and  Gibbes 
lias  described  a  spiral  thread  attached  to  the  head  (nevvtl  and  connected  with  the  middle  piece  by  a 
hyaline  memlirane.] 

Motion  of  the  Spermatozoa. — [.^fter  the  discharge  of  the  .seminal  fluid,  the  spermatozoa  ex- 
hibit spontaneous  movements  for  many  hours  or  days.]  The  movements  are  due  to  the  lashing 
movements  of  the  tail,  which  moves  in  a  circle  or  rotates  on  its  long  axis,  the  impulse  to  movement 
proceeding  from  the  protoplasm  of  the  middle  piece  and  the  tail,  which  seem  to  be  capable  of  mov- 
ing when  they  are  detached  {Eiiiwr).  These  movements  are  comparable  to  those  that  occur  in 
cilia  (J  292),  and  there  are  transition  forms  between  ciliary  and  amceboid  movements,  as  in  the 
Monera.  Reagents. — Within  the  testis  they  do  not  exhibit  movement,  as  the  fluid  is  not  sufficiently 
dilute  to  permit  them  to  move.  Their  movements  are  specially  lively  in  the  normal  secretion  of 
the  female  sexual  organs  [Bischoff),  and  they  move  pretty  freely,  and  for  a  long  time,  in  all  normal 
animal  secretions  except  saliva.  Their  movements  are  paralyzed  by  water,  alcohol,  ether,  chloro- 
form, creosote,  gum.  dextrin,  vegetable  mucin,  syrup  of  grape  sugar,  or  very  alkaline  or  acid  uterine 
orvaginal  mucus  (Donne),  acids  and  metallic  salts,  and  a  too  high  or  too  low  temperature.  The 
narcotics,  as  long  as  they  are  chemically  indifferent,  behave  as  indifferent  fluids,  and  so  do  medium 
solutions  of  urea,  sugar,  albumin,  common  salt,  glycerin,  amygdalin,  etc. ;  but  if  these  be  too  dilute 
or  too  concentrated,  they  alter  the  amount  of  water  in  the  spermatozoa  and  paralyze  them.  The 
quiescence  produced  by  water  may  be  set  aside  by  dilute  alkalies  (  Virc/ioni),  as  with  cilia  (p.  491 ). 
Engelmann  finds  that  minute  traces  of  acids,  alcohol,  and  ether  excite  movements.  The  sperma- 
tozoa of  the  frog  may  be  frozen  four  times  in  succession  without  killing  them.  They  bear  a  heat  of 
43.75°  C,  and  they  will  live  for  70  days  when  placed  in  the  abdominal  cavity  of  another  frog 
(Aluntegazza). 

Resistance. — Owing  to  the  large  amount  of  earthy  salts  which  they  contain,  when  dried  upon 
a  microscopical  slide  they  still  retain  their  form  ( I'li/entin).  Their  form  is  not  destroyed  by  nitric, 
sulphuric,  hydrochloric,  or  boiling  acetic  acid,  or  by  caustic  alkalies;  solutions  of  NaCl  and  salt- 
petre (10  to  15  per  cent.)  change  them  into  amorphous  masses.  Their  organic  basis  resembles  the 
semi-solid  albumin  of  epithelium. 

.Seminal  fluid,  besides  spermatozoa,  also  contains  seminal  cells,  a  few  epithelial  cells  from  the 
seminal  passages,  numerous  lecithin  granules,  stratified  amyloid  bodies  (inconstant),  granular  yellow 
pigment,  especially  in  old  age,  leucocytes,  and  sperma  crystals  (Fiirhiitgcr). 

Development  of  Spermatozoa. — The  walls  of  the  seminal  tubules,  n,  which 
are  made  up  of  spindle-shaped  cells,  are  lined  by  a  nucleated,  protoplasmic  layer 


DEVELOPMENT   OF   SPERMATOZA. 


861 


(Fig.  550,  I,  b,  and  IV,  h),  from  which  there  project  into  the  lumen  of  the  tube, 
long  (0.053  mni.)  column-like  prolongations,  (I,  c,  and  II,  III,  IV),  which  break 


Fig.  549. 


,  human  (X  600),  the  head  seen  Irom  the  side  ;  2,  on  edge  :  k,  head  ;  ;«,  middle  piece  ;  /,  tail :  e,  ter- 
minal filament ;  3,  from  the  mouse  ;  4,  bothriocephalus  latus ;  5,  deer  :  6,  mole  ;  7,  green  woodpecker ;  8,  black 
swan ;  9,  from  a  cross  between  a  goldfinch  (M)  and  a  canary  (Fj ;  10,  from  cobitis. 

up  at  their  free  end  into  several  round  or  oval  lobules  (II) — the  spermatoblasts 
{v.  Ehner^  ;  these  consist  of  soft,  finely  granular  protoplasm,  and  usually  have  an 
oval  nucleus  in  their  lower  part.      During  development,  each  lobule  of  the  sper- 

FiG.  550. 


Semi-diagrammatic  spermatogenesis:  I,  transverse  section  of  a  seminal  tubule — «,  membrane  ;  <^,  protopla 

lining  ;  c,  spermatoblast ;  s,  seminal  cells.  II,  Unripe  spermatoblast—:/",  rounded  cleavate  lobules  ;  ft,  semn.al 
cells.  IV,  spermatoblast,  with  ripe  spermatozoa  {k)  not  yet  detached ;  tail,  r  ;  «,  wall  of  the  seminal  tubule  ; 
k,  its  protoplasmic  layer.     Ill,  spermatoblast  with  a  spermatozoon  free,  t. 

niatoblast  elongates  into  a  tail  (IV,  r),  while  the  deeper  part  forms  the  head  and 
middle  piece  of  the  future  spermatozoon  (IV,  k).    At  this  stage  the  spermatoblast 


862 


STRUCTURE    OF   THE   OVARY. 


is  like  a  greatly  enlarged,  irregular,  cylindrical,  epithelial  cell.  When  develop- 
ment is  complete,  the  head  and  middle  piece  are  detached  (III,  i),  and  ultimately 
the  remaining  part  of  the  spermatoblast  undergoes  fatty  degeneration.  Not  un- 
frequently  in  spermatozoa  we  may  observe  a  small  mass  of  protoplasm  adhering  to 
the  tail  and  the  middle  piece  (III,  /).  Between  the  spermatoblasts  are  numerous 
round  amoeboid  cells  devoid  of  an  envelope,  and  connected  to  each  other  by  pro- 
cesses. They  seem  to  secrete  the  Jl/a'd  part  of  the  semen,  and  they  may,  therefore, 
be  called  seminal  cells  (I,  s,  II,  III,  IV,  /).  A  spermatozoon,  therefore, 
is  a  detached,  independently  mobile  cilium  of  an  enlarged  epithelial  cell.  Some 
observers  adhere  to  the  view  that  the  spermatozoa  are,  in  part,  at  least,  formed 
within  round  cells,  by  a  process  of  endogenous  development. 

Shape. — The  spermatozoa  of  most  animals  are  like  cilia  with  larger  or  smaller  heads.  The  head 
is  eUiptical  (mammals),  or  pear-shaped  (mammals),  or  cylindrical  (birds,  amphibians, fish),  or  cork- 
screw (singing  birds,  paludina),  or  merely  like  hairs  (insects — Fig.  549).  Immobile  seminal  cells, 
quite  ditTerent  from  the  ordinary  forms,  occur  in  mynapoda  and  the  oyster. 

433.  THE  OVARY— OVUM— UTERUS.— [Structure  of  the  Ovary  (Fig.  551).— The 
ovary  consists  of  a  connective-tissue  framework,  with  blood  vessels,  nerves,  lymphatics,  and  numer- 
ous non-striped  muscular  fibres.  The  ova  are  embedded  in  this  matrix.  The  surface  of  the  ovary 
is  covered  with  a  layer  of  columnar  epithelium  (Fig.  552,  e),  the  remains  of  the  germ  epithelium. 


Fig.  551. 


it's  ovary.    The  pi 


I  corpus  luteum. 


The  most  superficial  layer  is  called  the  albuginea  ;  it  does  not  contain  any  ova.  Below  it  is  the 
cortical  layer  of  Schron,  which  contains  the  smallest  Graafian  follicles  (^^5  inch — Fig.  551),  while 
deeper  down  are  the  larger  follicles  (^'^  to  i-Jj  inch).  There  are  40,000  to  70,000  follicles  in  the 
ovary  of  a  female  infant.     Each  ovum  lies  within  its  follicle  or  Graafian  vesicle.] 

Structure  of  an  Ovum. — The  human  ovum  {C.  E.  v.  Baer,  iS^-j)  is  0.18  to  0.2  mm.  [yjj  in.] 
in  diameter,  and  is  a  spherical,  cellular  body  with  a  thick,  solid,  elastic  envelope,  the  zona  pellu- 
cida,  with  radiating  strise.  The  zona  pellucida  encloses  the  cell  contents,  represented  by  the  pro- 
toplasmic, granular,  contractile  vitellus  or  yelk,  which  in  turn  contains  the  eccentrically-placed 
spherical  nucleus  or  germinal  vesicle  (40-50 /i — Purkinje,  iS^s  :  Coste,  1SJ4).  The  germinal 
vesicle  contains  the  nucleolus  or  germinal  spot  (5-7 /i — H.  Wagner,  /Sjj).  The  chemical  com- 
position is  given  in  |  232. 

[Ovum.  Cell. 

Zona  pellucida  corresponds  to  the  Cell  wall. 

Vitellus  '•  "      Cell  contents. 

Germinal  vesicle        "  "       Nucleus. 

Germinal  spot  "  "       Nucleolus.] 

[This  arrangement  shows  the  corresponding  parts  in  a  cell  and  the  ovum,  snd  in  fact  the  ovum 
represents  a  typical  cell] 

The  zona  pellucida  (Fig.  553,  V,  Z),  to  which  cells  of  the  Graafian  follicle  are  often  adherent, 
is  a  cuticular  membrane  formed  secondarily  by  the  follicle  IPJUiger).  .According  to  van  Beneden, 
it  is  lined  by  a  tliin  membrane  next  the  vitellus,  and  he  regards  the  thin  membrane  as  the  original 
cell  membrane  of  the  ovum.     The  fine  radiating  .stri;e  in  the  zona   are  said  to  be  due  to  the  exist- 


DEVELOPMENT   OF  THE   OVA.  863 

ence  of  numerous  canals  {Kolliker,  v.  Sehleti).     It   is  still  undecided   whether  there   is  a  special 
niicropyle  or  hole  for  the  entrance  of  the  spermatozoa. 

A  micropyle  has  been  observed  in  some  ova  (holothurians,  many  fishes,  mussels).  The  ova  of 
some  animals  (many  insects,  e.g.^  the  flea)  have  porous  canals  in  some  part  of  their  zona,  and  these 
serve  both  for  the  entrance  of  the  spermatozoa  and  for  the  respiratory  exchanges  in  the  ovum. 

The  development  of  the  ova  takes  place  in  the  following  manner :  The 
surface  of  the  ovary  is  covered  with  a  layer  of  cylindrical  epithelium — the  so- 
called  "  germ  epithehum  " — and  between  these  cells  lie,  somewhat  spherical, 
"primordial  ova"  (Fig.  553,  I,  a,  a).  The  epithelium  covering  the  surface 
dips  into  the  ovary  at  various  places  to  form  "  ovarian  tubes"  {  IVa/deyer). 
These  tubes,  from  and  in  which  the  ova  are  developed  (  Wahieyer),  become  deeper 
and  deeper,  and  they  contain,  in  their  interior,  large,  single  spherical  cells  with 
a  nucleus  and  a  nucleolus,  and  other  smaller  and  more  numerous  cells  lining  the 
tube.  The  large  cells  are  the  cells  (primordial  ova)  that  are  to  develop  into 
ova,  while  the  smaller  cells  are  the  epithelium  of  the  tube,  and  are  direct  con- 
tinuations of  the  cyhndrical  epithelium  on  the  surface  of  the  ovary.  The  upper 
extremities  of  the  tubes  become  closed,  while  the  tube  itself  is  divided  into  a 


Section  of  an  ovarj-,     e,  genu  t.\  luicjuuti  .  i,  l.irgc  ^i7cd  f  ■llii.lcb  .  2,  2,  middle-sized,  and  3,  3,  smaller-sized  follicles  ; 
(7,  ovum  withm  a  Graahan  fulliclc ,  v,  v,  blood  vesseU  of  the   stroma ,  ff,  cells  of  the  membrana  granulosa. 

number  of  rounded  compartments — snared  off,  as  it  were,  by  the  ingrowth  of  the 
ovarian  stroma  (I,  c').  Each  compartment  so  snared  off  usually  contains  one,  or, 
at  most,  two,  ova  (IV,  o,  o),  and  becomes  developed  into  a  Graafian  follicle. 
The  embryonic  follicle  enlarges,  and  fluid  appears  within  it ;  while  its  lateral 
small  cells  become  changed  into  the  epithelium  lining  the  Graafian  follicle  itself, 
or  those  of  the  membrana  granulosa.  The  cells  of  the  membrana  granulosa  form 
an  elevation  at  one  part — the  discus  proligerus — by  which  the  ovum  is  attached 
to  the  membrana  granulosa.  The  follicles  are  at  first  only  0.03  mm.  in  diameter, 
but  they  become  larger,  especially  at  puberty.  [The  smaller  ova  are  near  the 
surface  of  the  ovary,  the  larger  ones  deeper  in  its  substance  (Fig.  551).  When  a 
Graafian  follicle  with  its  ovum  is  about  to  ripen  (IV),  it  sinks  or  passes  down- 
ward into  the  substance  of  the  ovary,  and  enlarges  at  the  same  time  by  the  accu- 
mulation of  fluid — the  liquor  foUiculi — between  the  tunica  and  membrana 
granulosa.  It  is  covered  by  a  vascular  outer  membrane — the  theca  foUiculi — 
which  is  lined  by  the  epithelium  constituting  the  membrana  granulosa  (IV, 
g).     When  a  GraaRan  follicle  is  about  to  burst,  it  again  rises  to  the  surface  of 


864 


DEVELOPMENT   OF   THE   OVA. 


the  ovary,  and  attains  a  diameter  of  i.o  to  1.5  mm.,  and  is  now  ready  to  burst 
and  discharge  its  ovum.  [The  tissue  between  the  enlarged  Graafian  follicle  and 
the  surface  of  the  ovary  gradually  becomes  thinner  and  thinner  and  less  vascular, 
and  at  last  gives  way,  when  the  ovum  is  discharged  and  caught  by  the  fimbriated 
extremity  of  the  Fallopian  tube  embracing  the  ovary,  so  that  the  ovum  is  shed 
into  the  Fallopian  tube  itself.]  Only  a  small  number  of  the  Graafian  follicles 
undergo  development  normally,  by  far  the  greatest  number  atrophy  and  never 
ripen.  (The  study  of  the  development  of  the  ova  and  ovary  was  advanced  par- 
ticularly by  Martin  Barry,  Pfliiger,  Billroth,  Schron,  His,  Waldeyer,  Kolliker, 
Koster,  Lindgren,  Schulin,  Foulis,  Balfour  and  others.) 

.According  to  Waldeyer,  the  mammalian  ovum  is  not  a  simple  cell,  but  a  compound  structure. 
The  original  primitive  ovum  is,  according  to  him,  formed  only  of  the  germinal  vesicle  and  ger- 

FiG.  553. 


1  tube  in  process  of  development  (new-born  girl),  a,  a,  young 
surface  of  the  ovary ;  (i,  the  ovarian  tube  with  ova  and  epithelial  cells  ;  c 
an  ovum.  II,  Open  ovarian  tube  from  a  bitch.  Ill,  Isolated  primordial  < 
two  ova  {o,  0)  and  the  tunica  granulosa  (.^)  of  a  bitch.  V,  Part  of  the 
zona  pellucida ;  d^  vitellus  ,  e,  adherent  cells  of  the  membrana  granulosa. 
Formation  of  the  second  polar  globule  {Fol). 


the  epithelial  cells  on  the 
a  small  follicle  cut  off  and  enclosing 
■um  (human).  IV,  Older  follicle  with 
irface  ol  a  ripe  ovum  of  a  rabbit — z, 
VI,  First  polar  globule  formed.    VII, 


minal  spot,  with  the  surrounding  membranous  clear  part  of  the  vitellus  (Fig.  553,  III).  The 
remainder  of  the  vitellus  is  developed  by  the  transformation  of  granulosa  cells,  which  also  form  the 
zona  pellucida. 

Holoblastic  and  Meroblastic  Ova. — The  ova  of  frogs  and  cyclostomata  are  built  on  the  same 
type  as  mammalian  ova;  they  are  called  holoblastic  ova,  because  all  their  contents  go  to  form 
cells  which  take  part  in  the  formation  of  the  embryo.  In  contrast  with  these,  the  birds,  the  mono- 
tremes  alone  among  the  mammals  (CuUwell),  the  reptiles,  and  the  other  fishes  have  meroblastic 
ova  [Jieichert).  The  latter,  in  addition  to  the  white  or  formative  yelk,  which  corresponds  to  the 
yelk  of  the  holoblastic  eggs,  and  gives  rise  to  the  embryonic  cells,  contains  the  food  yelk  (yellow  in 
birds),  and  which  during  development  is  a  reserve  store  of  food  for  the  developing  embryo. 

Hen's  Egg. — The  small,  white,  round,  finely  granular  speck,  the  cicatricula,  blastoderm,  or 
tread,  which  is  2.5-3.5  "i™-  broad  and  0.2S-0.37  thick,  lying  upon  the  surface  of  the  yellow  yelk, 
corresponds  to  the  contents  of  the  mammalian  ovum,  and  is,  therefore,  the  formative  yelk.     [The 


STRUCTURE   OF   A   HEN  S   EGG. 


865 


cicatricula  in  an  unincubated  egg  is  always  uppermost  whatever  the  position  of  the  egg,  provided 
the  contents  can  rotate  freely,  and  this  is  due  to  the  lighter  specific  gravity  of  that  part  of  the  yell< 
in  connection  with  the  cicatricula.  In  a  fecundated  egg  the  cicatricula  has  a  white  margin  (the 
area  opaca),  surrounding  a  clear,  transparent  area,  the  beginning  of  the  area  pellucida,  containing 
an  opaque  spot  in  its  centre.  If  an  egg  be  boiled  very  hard  and  a  section  mad::  of  the  yelk,  it  will 
be  found  to  consist  of  alternating  layers  of  white  and  yellow  yelk.  The  outermost  layer  is  a  thin 
layer  of  white  yelk,  which  is  slightly  thicker  at  the  margin  of  the  cicatricula.  Within  the  centre  of 
the  yelk  is  a  flask-shaped  mass  of  white  yelk,  the  neck  of  the  flask  being  connected  with  the  white 
yelk  outside.  This  flask-shaped  mass  does  not  become  so  hard  on  being  boiled,  and  its  upper, 
expanded  end  is  known  as  the  "  nucleus  of  Pander  "  The  great  mass  of  the  yelk  is  made  up, 
however,  of  yellow  yelk]  Microscopically,  the  yellow  yelk  consists  of  soft,  yellow  spheres,  of 
from  23-100  ft  in  diameter,  and  they  are  often  polyhedral  from  mutual  pressure.  [They  are  very 
delicate  and  non-nucleated,  but  filled  with  fine  granules,  which  are,  perhaps,  proteid  in  their  nature, 
as  they  are  insoluble  in  ether  or  alcohol.  Thev  are  developed  by  the  proliferation  of  the  granulosa 
cells  of  the  Graafian  follicle,  which  also  seem  ultimately  to  form  the  granulo-fibrous  double  envelope 
or  the  vitelline  membrane  (Eimer).     The  whole  yelk  of  the  hen's  egg  is  regarded  by  some  ob- 


FlG.  554. 


Vertical  section  of  the 
ular  glands ; 


membrane  of  the  human  uterus,     e,  columnar  epithelium,  the  cilia  absent;  ffg,  utric- 
i-glandular connective  tissue  ;  v,  v,  blood  vessels ;  mm,  mu^cularis  mucosz. 


servers  as  equivalent  to  the  mammalian  ovum  plus  the  corpus  luteum.  Microscopically,  the  white 
yelk  consists  of  small  vehicles  (5-75  f^)  containing  a  refractive  substance,  and  larger  spheres  con- 
taining several  smaller  spherules.  The  whole  yelk  is  enveloped  by  the  vitelline  membrane,  which 
is  transparent,  but  possesses  a  fine  fibrous  structure,  and  it  seems  to  be  allied  to  elastic  tissue.] 
When  the  yelk  is  fully  developed  within  the  Graafian  follicle  of  the  hen's  ovarium,  the  follicle  bursts 
and  discharges  the  yelk,  which  passes  into  the  oviduct,  where  in  its  passage  it  rotates,  owing  to  the 
direction  of  the  folds  of  the  mucous  membrane  of  the  oviduct.  The  numerous  glands  of  the  oviduct 
secrete  the  albumin,  or  white  of  the  egg,  which  is  deposited  in  layers  around  the  yelk  in  its  passage 
along  the  duct,  and  forms  at  the  anterior  and  posterior  poles  the  chalazae.  [The  chalazae  are 
two  twisted  cords  composed  of  twisted  layers  of  the  outer,  denser  part  of  the  albumin.  They  extend 
from  the  poles  of  the  yelk  not  quite  to  the  outer  part  of  the  albumin.]  [The  albumin  is  invested 
by  the  membrana  testacea,  or  shell  membrane,  which  is  composed  of  two  layers — an  outer 
thicker  and  an  inner  thinner  one.  Over  the  greater  part  of  the  albumin  these  two  layers  are  united, 
but  at  the  broad  end  of  the  hen's  egg  they  tend  to  separate,  and  air  passing  through  the  porous  shell 
separates  them  more  and  more  as  the  fluid  of  the  egg  evaporates.  This  air  space  is  not  found  in 
fresh-laid  eggs.]     The  layers  consist  of  spontaneously  coagulated  keratin-like  fibres  arranged  in  a 

55 


866 


PUBERTV'. 


spiral  manner  around  the  albumin  (Lindvall  and  Haviarsicti).  [External  to  this  is  the  test,  or 
shell,  which  consists  of  an  organic  matrix  impregnated  with  lime  salts.]  The  shell  consists  of 
albumin  impregnated  with  lime  salts,  which  form  a  very  jxirous  mortar.  [The  shell  is  porous,  and 
its  inner  layer  is  perforated  by  vertical  canals,  through  which  the  respiratory  exchange  of  the  gases 
can  lake  place.]  In  the  eggs  of  some  birds  there  is  an  outer  structureless,  porous,  slimy,  or  fatty 
cuticula.  The  shell  is  secreted  in  the  lower  part  of  the  oviduct.  The  shell  is  partly  used  up  for 
the  development  of  the  bones  of  the  chick  ( Front,  Gruwe,  although  this  is  denied  by  Poll  and 
Preyer).  The  pigment  which  often  occurs  in  many  layers  on  the  surface  of  the  eggs  of  some  birds 
appears  to  be  a  derivative  of  hssnioglobin  and  biliverdin. 

Chemical  Composition.— The  yellow  yelk  is  alkaline  and  colored  yellow,  owing  to  the 
presence  of  lutein,  which  contains  iron.  It  contains  several  proteids  [including  a  globulin  body 
called  vitellin  (p.  409)],  a  body  resembling  nuclein,  lecithin,  vitellin,  glycerin-phosphoric  acid, 
cholesterin,  olein,  palmitin,  dextrose,  potassic  chloride,  iron,  earthy  phosphates,  fluoric  and  silicic 
acids.  The  presence  of  cerebrin,  glycogen,  and  starch  is  uncertain.  [Dareste  states  that  starch  is 
present.] 

[The  albumin  of  egg  contains— water,  86  per  cent.;  proteids,  12;  fat  and  extractives,  1. 5; 
saline  matter,  including  sodic  and  potassic  chlorides,  phosphates,  and  sulphates,  .5  per  cent.] 

[The  uterus,  a  thick,  hollow,  muscular  organ,  is  covered  externally  by  a  serous  coat,  and  lined 
internally  by  a  mucous  membrane,  while  between  the  two  is  the  thick  muscular  coat  composed 
of  smooth  muscular  fibres  arranged  in  a  great  number  of  layers  and  in  different  directions.     The 


Fig.  555. 


Left  broad  ligament,  Fallopian  tube,  ovary  and  parovarium,    a,  uterus  ;  A,  isthmus  of  Fallopian  tube  ; 
g,  timbriaied  end  of  the  tube,  with  the  parovarium  to  its  right ;  e,  ovary ;  /,  ovarian  ligament 


npulla  ; 


mucous  membrane  of  the  body  of  the  uterus  in  the  unimpregnated  condition  has  no  folds,  while  the 
muscularis  mucosae  is  very  well  developed  and  forms  a  great  part  of  uterine  muscular  wall.  The 
mucous  membrane  is  lined  by  a  single  layer  ol  columnar  ciliated  epithelium.  A  vertical  section 
shows  the  mucous  membrane  to  contain  numerous  tubular  glands  (Fig.  554) — the  uterine  glands 
— which  branch  toward  their  lower  ends.  They  have  a  membrana  propria,  and  are  lined  by  a  single 
layer  of  ciliated  epithelium,  a  small  lumen  being  left  in  the  centre.  The  utricular  glands  are  not 
formed  during  intra  uterine  life  {Turner),  nor  are  there  any  glands  in  the  human  uterus  at  birth 
[G.  J.  Engelmann).  There  are  numerous  slit-like  lymphatic  spaces  in  the  mucous  membrane 
{Leopold),  which  communicate  with  well-marked  lymphatic  vessels  existing  in  this  and  the  other 
layers  of  the  organ.  In  the  cervix  the  mucous  membrane  is  folded,  presenting  in  the  virgin  the 
appearance  known  as  the  arbor  vita;.  The  external  surface  of  the  vaginal  part  of  the  neck  is  covered 
by  stratified  squamous  epithelium,  like  the  vagina.] 

[The  Fallopian  tubes  are  really  the  ducts  of  the  ovaries  (Fig.  555).  They  consist  of  a  serous, 
muscular  (an  external,  longitudinal  and  an  internal  circular  layer  of  non-striped  muscle),  and  a 
mucous  layer  thrown  into  many  folds  and  lined  by  a  single  layer  of  ciliated  columnar  epithelium, 
but  no  glands  (Fig.  556).] 

434.  PUBERTY. — The  term  puberty  is  applied  to  the  period  at  which  a 
human  being  becomes  capable  of  procreating,  which  occurs  from  the  13th  to  isth 


SIGNS   OF   MENSTRUATION. 


867 


years  in  the  female  and  the  14th  to  i6th  in  the  male.  In  warm  climates,  puberty 
may  occur  in  girls  even  at  8  years  of  age.  Toward  the  40th  to  50th  year  the 
procreative  faculty  ceases  in  the  female  with  the  cessation  of  the  menses ;  this 
constitutes  the  menopause  or  grand  climacteric,  while  in  man  procreation 
has  been  observed  up  to  any  age.  From  the  age  of  puberty  onward,  the  se.vual 
appetite  occurs,  and  the  ripe  ova  are  discharged  from  the  ovary.  [It  seems,  how- 
ever, that  ova  are  discharged  even  before  puberty  or  menstruation  has  occurred.] 
At  puberty  the  internal  and  external  generative  organs  and  their  annexes  become 
more  vascular  and  undergo  development ;  the  pelvis  of  the  female  assumes  the 
characteristic  female  shape.  For  the  changes  in  the  mammae,  see  §  230.  At  the 
same  time  hair  is  developed  on  the  pubes  and  axilla,  and  in  the  male  on  the  face, 
while  the  sebaceous  glands  become  larger  and  more  active. 

Other  changes  occur,  especially  in  the  larynx.  In  the  boy  the  larynx  elongates  in  its  antero- 
posterior diameter,  the  thyroid,  or  .\dam's  apple,  becomes  more  prominent,  while  the  vocal  cords 
lengthen,  so  that  the  voice  is  hoarse,  or  husky,  or  "  breaks,"  the  voice  being  lowered  at  least  an 
octave.  In  the  female  the  larynx  becomes  longer,  while  the  compass  of  the  voice  is  increased. 
The  vital  capacity  (§  108),  corresponding  to  the  increase  in  the  size  of  the  chest,  undergoes  a  con- 


FlG.  556. 


J  Connective  tissue. 

■  Ciliated  epithelium. 
Circular  muscular  tibri 


section  of  the  Fallopian  tube. 


siderable  increase ;  the  whole  form  and  expression  assume  the  characteristic  sexual  appearance, 
while  the  psychical  energies  also  receive  an  impulse. 

435.  MENSTRUATION.— External  Signs.— .\t  regular  intervals- of 
time,  of  27I3-2S  days,  in  a  mature  female,  there  is  a  rupture  of  one  or  more  ripe 
Graafian  follicles,  while  at  the  same  time  there  is  a  discharge  of  blood  from  the 
external  genitals.  This  is  known  as  the  process  oi  menstruation  (or  menses,  cata- 
menia  or  periods).  Most  women  menstruate  durihg  the  first  quarter  of  the  moon, 
and  only  a  few  at  new  and  full  moon  {Stro/iD.  In  mammals,  the  analogous  con- 
dition is  spoken  of  as  the  period  of  heat  [or  the  "  rut  "  in  deer].  There  is  a 
slightly  bloody  discharge  from  the  external  genitals  in  carnivora,  the  mare  and 
cow  (Aristotle),  while  apes  in  their  wild  condition  have  a  well-marked  menstrual 
discharge  {Neubert).  [Observations  on  cases  where  abdominal  section  has  been 
performed  have  shown  that  the  Graafian  follicles  mature  and  burst  at  any  time 
i^Larvson  Tait,  Leopold).^ 

The  onset  of  menstruation  is  usually  heralded  by  constitutional  and  local  phenomena— there  is 
an  increased  feeling  of  congestion  in  the  internal  generative  organs,  pain  in  the  back  and  loins,  ten- 
sion  in  the  region  of  the  uterus  and  ovaries,  which  are  sensitive  to  pressure,  fatigue  in  the  limbs, 


8G8 


OVULATION. 


Fig.  558. 


alternate  feeling  of  heat  and  cold,  and  even  a  slight  increase  of  the  temperature  of  the  skin 
{/CerscA).  There  may  be  retardation  of  the  process  of  digestion  and  variations  in  the  evacuation 
of  the  fcECes  and  urine,  and  in  the  secretion  of  sweat.  The  discharge  is  s/imy  at  first,  and  then 
becomes  bloody,  lasting  three  to  four  days  ;  the  blood  is  venous,  and  shows  Hltle  tendency  to  coagu- 
late, provided  it  is  mixed  with  much  alkaline  mucus  from  the  genital  passages;  but  if  the  hemor- 
rhage be  free,  the  blood  may  be  clotted.  The  quantity  of  blood  is  100  to  200  grms.  [The  blood 
contains  many  white  blood  corpuscles  and  epithelial  cells.]  After  cessation  of  the  discharge  of 
blood  there  is  a  moderate  amount  of  mucus  given  oft. 

The  characteristic  internal  phenomena  which  accompany  menstruation  are  : 
(i)  The  changes  in  the  uterine  mucous  membrane;  and  (2)  the  rupture  of  the 
Graafian  follicle. 

I.  Changes  in  the  Uterine  Mucous  Membrane. — The  uterine  mucous 
membrane  is  the  chief  source  of  the  blood.  The  ciliated  epithelium  of  the  con- 
gested, swollen,  and  folded,  soft,  thick  (3 
to  6  mm.)  mucous  membrane  is  shed.  The 
orifices  of  the  numerous  mucous  glands  of 
the  mucous  membrane  are  distinct,  the 
glands  enlarge,  and  the  cells  undergo  fatty 
degeneration,  and  so  do  the  tissue  and  the 
blood  vessels  lying  between  the  glands.  The 
tissue  contains  more  leucocytes  than  normal. 
This  fatty  degeneration  and  the  excretion  of 
the  degenerated  tissue  occur,  however,  only 
in  the  superficial  layers  of  the  mucosa, 
whose  blood  vessels,  when  torn  across,  yield 
the  blood.  The  deeper  layers  remain  in- 
tact, arid  from  them,  after  menstruation  is 
over,  the  new  mucous  membrane  is  devel- 
oped {Kundrat  and  G.  J.  Engehnann'). 
[Leopold  denies  the  existence  of  this  fatty 
degeneration.  According  to  Williams,  the 
entire  mucous  membrane  is  removed  at  each 
menstrual  period,  and  it  is  regenerated  from 
the  muscular  coat  (Fig.  558).  The  mucous 
membrane  of  the  cervix  remains  free  from 
these  changes.] 

2.  Ovulation. — The  second   important 
_"meIbrant.''''°Fir"5°8"--TCur when '"'^'■"^1  P'i<^"oni«^"on  is  oviilation,  in  which 

menstruationhasjustceased,  showing  the  cavity  process  the    OVary  bcCOmeS    more  Vascular — - 
of  the  body  deprived  of  mucous  membrane  ( /.  -u  r   ii*    1  .         ■  j         ti      a    ■  j  j    ■ 

Williams).  the  ripe  follicle  is  turgid  with  tluid,  and  in 

part  projects  above  the  surface  of  the  ovary. 
The  follicle  ultimately  bursts,  its  membranes  and  the  epithelium  covering  of  the 
ovary  being  torn  or  give  way  under  the  pressure,  the  bursting  being  accompanied 
by  the  discharge  of  a  small  amount  of  blood.  At  the  same  time,  the  congested, 
turgid,  and  erected  fimbriated  extremity  of  the  Fallopian  tube  (Fig.  555)  is  applied 
to  the  ovary,  so  that  the  discharged  ovum,  with  its  adherent  granulosa  cells,  and  the 
liquor  folliculi,  are  caught  by  the  funnel-shaped  extremity  of  the  tube.  The  ovum, 
when  discharged,  is  carried  toward  the  uterus  by  the  ciliated  epithelium  (§  433) 
of  the  tube,  and  perhaps,  also,  partly  by  the  contraction  of  its  muscular  coat. 
Ducalliez  and  Kiiss  found  that,  by  fully  injecting  the  blood  vessels,  they  could 
imitate  the  erection  of  the  Fallopian  tube.  Rouget  points  out  that  the  non-striped 
muscle  of  the  broad  ligaments  may  cause  constriction  of  the  vessels,  and  thus 
secure  the  necessary  injection  of  the  blood  vessels  of  the  Fallopian  tube. 

Pfiiiger's  Theory. — There  are  two  theories  as  to  the  connection  between  ovulation  or  the  dis- 
charge of  an  ovum  and  the  escape  of  blood  from  the  uterine  mucous  membrane.  Pfluger  regards 
the  bloody  discharge  from  the  superficial  layers  of  the  uterine  mucous  membrane  as  a  puysiological 
preparation  or  "  freshening  "  of  the  tissue  (in  the  surgical  sensej,  by  which  it  will  be  prepared  to 


ERECTION    OF   THE    PENIS. 


869 


receive  the  ovum  when  the  latter  reaches  the  uterus,  so  that  union  can  take  place  between  the  ovum 
and  the  freshly-exposed  surface  of  the  mucous  membrane,  and  thus  the  ovum  will  receive  nourish- 
ment from  a  new  surface. 

Reichert's  Theory. — This  view  is  opposed  to  that  of  Reiehert,  Engelmann,  Williams,  and 
others,  .-\ccording  to  Reichert's  theory,  before  an  ovum  is  discharged  at  all  there  is  a  sympathetic 
change  in  the  uterine  mucous  membrane,  whereby  it  becomes  more  vascular,  more  spongy,  and 
swollen  up.  Tire  mucous  membrane  so  altered  is  spoken  of  as  the  tmmhrana  decidua  meitstntaiis, 
and  from  its  nature  it  is  in  a  proper  condition  to  receive,  retain,  and  nourish  a  fertilized  ovum  which 
may  come  into  contact  with  it.  If  the  ovum,  however,  be  not  fertilized,  and  escapes  from  the  gen- 
ital passages,  then  the  uterine  mucous  membrane  degenerates  and  blood  is  shed  as  above  described. 
According  to  this  view,  the  hemorrhage  from  the  uterine  mucous  membrane  is  a  sign  of  the  non- 
occurrence of  pregnancy;  the  mucous  membrane  degenerates  because  it  is  not  required  for  this 
occasion ;  the  menstrual  blood  is  an  external  sign  that  the  ovum  has  not  been  impregnated.  So  that 
pregnancy,  ;'.  c,  the  development  of  the  embryo  in  utero,  is  to  be  calculated,  not  from  the  last  men- 
struation, but  from  some  time  between  the  last  menstruation  and  the  period  which  does  not  occur. 

In  some  cases  the  ovulation  and  the  formation  of  the  decidua  nienstrualis  occur  separately,  so 
that  there  may  lie  menstruation  without  ovulation,  and  ovulation  without  menstruation. 

Corpus  Luteum. — When  a  Graafian  follicle  bursts,  it  discharges  its  contents  and  collapses ;  in 
the  interior  are  the  remains  of  the  membrana  granulosa  and  a  small  effusion  of  blood,  which  soon 
coagulates.     The  small  rupture  soon  heals,  after  the  serum  is  absorbed.     The  vascular  wall  of  the 


Fig.  SS9. 


'V  uo. 


trabeculje  of  connective  t 


'ith  elastic  fibres  and  smooth  muscles  (C) ;  d,  \ 


follicle  swells  up.  Villous  prolongations  or  granulations  of  young  connective  tissue,  rich  in  cipil- 
laries  and  cells,  grow  int )  the  interior  of  the  follicle.  Colorless  blood  corpuscles  also  wander  into 
the  interior.  At  the  same  time  the  cells  of  the  granulosa  proliferate,  and  form  several  layers  of 
cells,  which  ultimately,  after  the  disappearance  of  a  number  of  blood  vessels,  undergo  fatty  degen- 
eration, lutein  and  fatty  matter  being  formed,  and  it  is  this  mass  which  gives  the  corpus  luteuni  its 
yellow  color.  The  capsule  becomes  more  and  more  fused  with  the  ovarian  stroma.  If  pregnancy 
does  not  take  place  after  the  menstruation,  then  the  fatty  matter  is  rapidly  absorbed,  and  the  efiused 
blood  is  changed  into  hojmatoidin  (^  20)  and  other  derivatives  of  ha'mogloliin,  while  there  is  a 
gradual  slirivelling  of  the  whole  mass,  which  is  complete  in  about  four  weeks,  only  a  very  small 
remainder  being  left.  Such  a  corpus  luteum,  /'.  t".,  one  not  accompanied  by  pregnancy,  is  called  a 
false  corpus  luteum.  If,  however,  pregnancy  occurs,  then  the  corpus  luteum,  instead  of  shrivel- 
ling, grows  and  becomes  a  large  body,  especially  at  the  third  and  fourth  month,  the  walls  .ire  thicker, 
the  color  deeper,  so  that  the  corpus  luteum  at  the  period  of  delivery  may  be  6  to  id  mm.  in  diam- 
eter, and  its  remains  may  be  found  in  the  ovary  (or  a  verj'  long  time  thereafter  (Fig  551).  This 
form  is  sometimes  spoken  of  as  a  true  corpus  luteum  [Bischoff).  [We  cannot  draw  too  sharp  a 
distinction  between  these  two  forms.]  Only  a  very  small  number  of  the  ova  in  the  ovary  undergo 
development  and  are  discharged;  by  far  the  greater  number  degenerates  [Slnvjansky). 

436.  PENIS  ERECTION. — Penis. — [The  penis  is  composed  of  two  long  cylindrical  corpora 
cavernosa,  the   corpus   spongiosum,  which   lies  between   and   below  them,  and   surrounds  the 


870  MECHANISM    OF    ERECTION. 

urethra;  these  are  held  together  by  fibrous  and  muscular  sheaths,  and  are  composed  of  erectile 
tissue.]  Our  knowledge  of  the  distribution  of  the  blood  within  the  penis  is  chiefly  due  to  C. 
Langer's  researches.  The  albuginea  of  the  corpus  spongiosum  consists  of  tendinous  connective 
tissue,  containing  thickly-woven  elastic  ti>sue  and  smooth  muscular  fibres,  which  together  form  a 
solid  fibrous  envelope,  from  which  numerous  interlacing  trabecukis  pass  into  the  interior,  so  that  the 
corpus  spongiosum  comes  to  resemble  a  sponge.  The  anastomosing  spaces  bounded  by  these  tra- 
becul?e  fonn  a  series  of  inter-communicating  venous  spaces,  or  sinuses,  filled  with  blood  and  lined 
by  a  layer  of  endothelium  constituting  erectile  tissue  (Fig.  559).  The  largest  sinuses  lie  in  the 
lower  and  external  part  of  the  corpus  caverno.sum,  while  they  are  less  numerous  and  smaller  in  the 
upper  part.  The  small  arteries  arise  from  the  A.  profunda  penis,  which  runs  along  the  septum, 
and  pass  to  the  trabecule  after  following  a  very  sinuous  course.  At  the  outer  part  of  the  corpus 
spongiosum  some  of  the  small  arteries  become  directly  continuous  with  the  larger  venous  sinu«es; 
some  of  them,  however,  terminate  in  capillaries  both  in  the  outer  part  and  within  the  corpus  spongi- 
osum, the  capillaries  ultimately  terminating  in  the  venous  sinuses.  The  helicine  arteries  of  the 
penis  described  by  |oh.  Miiller  are  merely  much  twisted  arteries.  The  deep  veins  of  the  penis  arise 
by  fine  veinlets  within  the  body  of  the  organ,  while  the  veins  proceeding  from  the  cavernous  spaces 
pass  to  the  dorsum  of  the  penis  to  form  the  vena  dorsalis  penis.  As  these  vessels  have  to  traverse 
the  meshes  of  the  vascular  network  in  the  cortex  of  the  corpora  cavernosa  penis,  it  is  evident  that, 
when  the  network  is  congested  by  being  filled  with  blood,  it  must  compress  the  outgoing  venous 
trunks.  The  corpus  cavernosum  urethri-e  consists,  for  the  most  part,  of  an  external  layer  of  closely- 
packed  anastomosing  veins,  which  surround  the  longitudinally-directed  blood  vessels  of  the  urethra. 
In  the  dog  all  the  arteries  of  the  penis  run  at  first  toward  the  surface,  where  they  divide  into 
penicilli.  The  veins  arise  from  the  capillary  loops  in  the  papilla,  and  they  empty  their  blood  into 
the  cavernous  spaces.  Only  a  small  part  of  the  blood  passes  to  the  cavernous  spaces  through  the 
internal  capillaries  and  veins,  but  arterial  blood  never  flows  directly  into  these  spaces  (J/,  v.  Frey). 

Mechanism  of  Erection. — Erection  is  due  to  the  overfilling  of  the  blood 
vessels  of  the  penis  with  blood,  whereby  the  volume  of  the  organ  is  increased  four 
or  five  times,  while  at  the  same  titne  there  are  also  a  higher  temperature,  increased 
blood  pressure  (to  |  of  that  in  the  carotid — Eck/uird),  with  at  first  a  pulsatile 
movement,  increased  consistence,  and  erection  of  the  organ. 

Regner  de  Graaf  obtained  complete  erection  of  the  penis  by  forcibly  injecting  its  blood  vessels 
{1668). 

The  preliminary  phenomena  consist  in  a  considerable  increase  of  the  arte- 
rial blood  supply,  the  arteries  being  dilated  and  pulsating  strongly.  The  arteries 
are  controlled  by  the  nervi  erigentes.  The  nervi  erigentes  [called  by  Gaskell 
the  pelvic  splanchnics  (p.  649)]  arise  chiefly  from  the  second  (more  rarely  the 
third)  sacral  nerves  (dog),  and  have  ganglionic  cells  in  their  course  (Loven, 
Nikolskv).  These  nerves  contain  vaso-dilator  fibres,  which  can  be  e.xcited  in 
part  refiexly  from  the  sensory  nerves  of  the  penis,  the  transference  centre  being 
in  the  centre  for  erection  in  the  spinal  cord  (§  362,  4).  Sensory  impressions  pro- 
duced by  voluntary  movements  of  the  genital  apparatus  (by  the  ischio-  and  bulbo- 
cavernosi  and  cremaster  muscles)  can  also  discharge  this  reflex  ;  while  the  thought 
of  sexual  imptilses,  referable  to  the  penis,  tends  to  induce  erection.  The  nervi 
erigentes  also  supply  the  longitudinal  fibres  of  the  rectum  {Fellner). 

The  centre  for  erection  in  the  spinal  cord  (§362,  2)  is,  however,  controlled 
by  the  dominating  vaso-dilator  centre  in  the  medulla  oblongata  (§372),  and  the 
two  centres  are  connected  by  fibres  within  the  cord  ;  hence  stimulation  of  the 
upper  part  of  the  cord,  as  by  asphyxiated  blood  (§  362,  5)  or  muscarin,  may  also 
be  followed  by  erection  {Nikolsky).  [The  seminal  fluid  is  frequently  found  dis- 
charged in  persons  who  have  been  hanged.] 

The  psychical  activity  of  the  cerehrtim  has  a  decided  influence  on  the  genital 
vaso-dilator  nerves.  Just  as  the  psychical  disturbance  which  accompanies  anger 
or  shame  is  followed  by  dilatation  of  the  blood  vessels  of  the  head,  owing  to 
stimulation  of  the  vaso-dilator  fibres;  so  when  the  attention  is  directed  to  the 
sexual  centres,  there  is  an  action  upon  the  nervi  erigentes.  This  action  of  the 
brain  is  more  comprehensible,  since  we  know  that  the  diameter  of  the  blood 
vessels  is  afi'ected  by  the  cortex  cerebri  (§  377).  The  fibres  probably  pass  from 
the  cerebrum  through  the  peduncles  of  the  cerebrum  and  the  pons  ;  as  a  matter 
of  fact,  if  these  parts  be  stimulated,  erection  may  take  place  (§362,  4)  {Eckhani). 


MECHANISM    OF    ERECTION. 


871 


When  the  impulse  to  erection  is  obtained  by  the  increased  supply  of  arterial 
blood,  \\\t  full  completion  of  the  act  is  brought  about  by  the  activity  of  the  follow- 
ing transversely  striped  muscles:  (i)  The  ischio-cavernosus  (Fig.  164)  arises 
from  the  coccyx,  and  by  its  tendinous  union  surrounds  the  root  of  the  penis. 
When  it  contracts  it  compresses  the  root  of  the  penis  from  above  and  laterally,  so 
that  the  outflow  of  blood  from  the  penis  is  hindered.  It  has  no  action  on  the 
dorsal  vein  of  the  penis,  as  this  vessel  lies  in  a  groove  on  the  dorsum  of  the  penis, 
and  is,  therefore,  protected  from  compression  by  the  tendon.  (2)  The  deep 
transversus  perinei  is  perforated  by  the  vense  profundse  penis,  which  come  from 
the  corpora  cavernosa,  so  that  when  it  contracts  it  must  compress  these  veins  be- 
tween the  tense  horizontal  fibres  (Fig.  560,  6).  The  deep  veins  of  the  penis  join 
the  common  pudendal  vein  and  the  plexus  Santorini.  (3)  Lastly,  the  bulbocav- 
crnosus  is  concerned  in  the  hardening  of  the  urethral  corpus  spongiosum,  as  it  com- 


Anterior  wall  of  the  pelvis  with  the  urogenital  septum  seen  from  the  front.  The  corpus  cavernosum  (4)  with  the  ure- 
thra (3)  is  cut  across  below  its  exit  from  the  pelvis,  i,  symphysis  pubis;  2,  dorsal  vein  of  the  penis;  5,  part 
of  the  bulbo-cavemosus :  /,  deep  transversus  perinei  with  its  fascia  (_/) ;  6,  vena  profunda  penis  ;  7,  artery  and 
vein  of  the  bulbo-cavemosus. 


presses  the  bulb  of  the  urethra  (Figs.  560,  5,  164).  k\\  these  muscles  are  partly 
under  the  control  of  the  will,  whereby  the  erection  mav  be  increased.  Normally, 
however,  their  contraction  is  excited  reflexly  by  stimulation  of  the  sensory  nerves 
of  the  penis  (§  362,  4). 

The  congestion  of  blood  is  not  complete,  else,  in  pathological  cases,  continuous  erection,  as  in 
satyriasis,  would  give  rise  to  gangrene.  The  accumulation  of  the  blood  in  the  penis  is  favored  by 
the  fact  that  the  origins  of  the  veins  of  the  penis  lie  in  the  corpus  cavernosum,  which,  when  it  en- 
larges, must  compress  them.  There  are  also  trabecular,  smooth,  muscular  fibres,  which  compress  the 
large  venous  plexus  of  Santorini. 

That  erection  is  a  complex  motor  act  depending  on  the  nervous  system,  is  proved  by  an  experi- 
ment of  Hausmann,  who  found  that  section  of  the  nerves  of  the  penis  prevented  erection  in  a  stal- 
lion. The  imperfect  erection  which  occurs  in  the  female  is  confined  to  the  corpora  cavernosa  clito- 
ridis  and  the  bulhi  vestibuli.  During  erection,  the  passage  from  the  urethra  to  the  l>ladder  is  closed, 
partly  by  the  swelling  of  the  caput  gallinaginis,  and  partly  by  the  action  of  the  sphincter  urethrje, 
which  is  connected  with  the  deep  transversus  perinei. 


872  FERTILIZATION    OF   THE   OVUM. 

437.  EJACULATION— RECEPTION  OF  THE  SEMEN.— In  con- 
nection with  the  ejaculation  of  the  seminal  fluid,  we  must  distinguish  two  differ- 
ent factors — (i)  its  passage  from  the  testicles  to  the  vesiculae  seminales ;  (2)  the 
act  of  ejaculation  itself.  The  former  is  caused  by  the  newly-secreted  fluid  forcing 
on  that  in  front  of  it,  by  the  action  of  the  ciliated  epithelium  (which  lines  the 
epididymis  to  the  beginning  of  the  vas  deferens),  and  also  by  the  peristaltic 
inovements  of  the  smooth  muscular  fibres  of  the  vas  deferens.  Ejaculation,  how- 
ever, requires  strong  peristaltic  contractions  of  the  vasa  deferentia  and  the  vesiculae 
seminales,  which  are  brought  about  by  the  reflex  stimulation  of  the  ejaculation 
centre  in  the  spinal  cord  (§  362,  5).  As  soon  as  the  seminal  fluid  reaches  the  ure- 
thra, there  is  a  rhythmical  contraction  of  the  bulbo-cavernosus  muscle  (produced 
by  the  mechanical  dilatation  of  the  urethra),  whereby  the  fluid  is  forcibly  ejected 
from  the  urethra.  Both  vasa  deferentia  and  vesiculcc  do  not  always  eject  their 
contents  into  the  urethra  simultaneously.  With  moderate  excitement  the  contents 
of  only  one  may  be  discharged.  The  ischio-cavernosus  and  deep  transversus  per- 
inei  contract  at  the  same  time  as  the  bulbo-cavernosus,  although  the  former  have 
no  effect  on  the  act  of  ejaculation.  In  the  female  also,  undernormal  circum- 
stances, at  the  height  of  the  sexual  excitement  there  is  a  reflex  movement  corre- 
sponding to  ejaculation.  It  consists  of  a  movement  analogous  to  that  in  man.  At 
first  there  is  a  reflex  peristaltic  movement  of  the  Fallopian  tube  and  uterus,  pro- 
ceeding from  the  end  of  the  tube  toward  the  vagina,  and  produced  reflexly  by  the 
stimulation  of  the  genital  nerves.  Derabo  observed  that  stimulation  of  the  ante- 
rior upper  wall  of  the  vagina  in  animals  caused  a  gradual  contraction  of  the  uterus. 
By  this  movement,  corresponding  to  that  of  the  vasa  deferentia  in  man,  a  certain 
amount  of  the  mucus  normally  lining  the  uterus  is  forced  into  the  vagina. 

This  is  followed  by  the  rhythmical  contraction  of  the  sphincter  cunni  (analo- 
gous to  the  bulbo-cavernosus),  also  of  the  ischio-cavernosus,  and  deep  transversus 
perinei.  The  uterus  is  erected  by  the  powerful  contraction  of  its  muscular  fibres 
and  round  ligaments,  while  at  the  same  time  it  descends  toward  the  vagina,  its 
cavity  is  more  and  more  diminished,  and  its  mucous  contents  are  forced  out.  When 
the  uterus  relaxes  after  the  stage  of  excitement,  it  aspirates  into  its  cavity  the  sem- 
inal fluid  injected  into  the  vestibule  {Aristotle,  Bischoff). 

But  the  suction  of  the  greatly  excited  uteras  is  not  necessary  for  the  reception  of  the  semen  (Aris- 
totle). The  spermatozoa  may  wriggle  by  their  own  movements  from  the  vagina  into  the  orifice  of 
the  uterus  (Kristeller').  The  cases  of  pregnancy  where,  from  some  pathological  causes  (partial 
closure  of  the  vagina  or  vulva),  the  penis  has  not  passed  into  the  vagina  during  coition,  prove  that 
the  spermatozoa  can  traverse  the  whole  length  of  the  vagina,  and  pass  into  the  uterus. 

438.  FERTILIZATION  OF  THE  OVUM.— The  ovum  is  fertilized 
by  a  spermatozoon  passing  into  it. 

Swammerdam  (f  16S5)  proved  that  contact  of  tlie  semen  with  the  ovum  was  necessary  for  fer- 
tilization. Spallanzani  ( 1 76S)  proved  that  the  fertilizing  agent  was  the  spermatozoa,  and  not  the 
clear,  filtered  fluid  part  of  the  semen,  and  that  the  spermatozoa,  even  after  being  enormously  diluted, 
were  still  capable  of  action.  Martin  Barry  (1S50)  was  the  first  to  observe  the  entrance  of  a  sperma- 
tozoon into  the  ovum  of  the  rabbit.  This  occurs  pretty  rapidly,  by  a  boring  movement  through  the 
vitelline  membrane  (Leuck/iart).  The  entrance  is  effected  either  through  the  porous  canals  or  the 
micropyle  [Keber,  p.  863). 

Theories. — As  to  the  manner  in  which  the  spermatozoon  affects  the  ovum,  there  are  great  differ- 
ences of  opinion.  Aristotle  compared  it  to  an  action  like  that  of  rennet  on  milk  ;  Bischoff,  to  that 
of  yeast  on  a  fermentable  mass,  i.  e.,  to  a  catalytic  action.  These  theories,  however,  are  quite  un- 
satisfactory, as  we  know  that  the  unfertilized  ova  of  the  hen,  rabbit  (Hensen),  pig  {Bischoff),  salpa 
{Kuppfer),  (but  not  the  frog — Pfiiiger)  can  undergo  the  initial  stages  of  development  as  far  as  the 
stage  of  cleavage,  and  the  star  fishes  even  as  far  as  the  larval  form  (Gieef). 

Place  of  Fertilization. — The  place  where  fertilization  occurs  is  either  the 
ovary,  as  indicated  by  the  occurrence  of  abdominal  pregnancy,  or  the  Fallopian 
tube,  and  the  numerous  recesses  in  the  latter  afford  a  good  temporary  nidus  for  the 
spermatozoa.  This  view  is  supported  by  the  occurrence  of  tubal  pregnancy.  Thus 
the  spermatozoa  must  be  able  to  pass  through  the  Fallopian  tube  to  the  ovary, 


MATURATION    OF   THE   OVUM.  873 

which  is  probably'brought  about  chiefly  by  the  movements  proper  to  the  sperma- 
tozoa themselves.  It  is  uncertain  whether  the  peristaltic  movements  of  the  uterus 
and  Fallopian  tube  are  concerned  in  this  process;  certainly  ciliary  movement  is 
not  concerned,  as  the  cilia  of  the  Fallopian  tube  act  from  above  downward. 
When  once  the  ovum  has  passed  unfertilized  into  the  uterus,  it  is  not  fertilized  in 
the  uterus.  It  is  assumed  that  the  ovum  reaches  the  uterus  within  two  to  three 
weeks  fin  the  bitch,  8  to  14  days). 

Twins  occur  in  i  in  87  pregnancies,  but  oftener  in  warm  climates:  triplets, 
I  :  7600  ;  four  at  a  birth,  i  :  330,000.  More  than  six  at  a  birth  have  not  been 
observed.     The  average  number  of  pregnancies  in  a  woman  is  414. 

Superfecundation.^By  this  term  is  understood  the  fertilization  of  two  ova  at  the  same  men- 
struafioH,  by  two  different  acts  of  coition.  Thus,  a  mare  may  throw  a  foal  and  a  mule,  after  being 
covered  first  by  a  stallion  and  then  by  an  ass.  A  white  and  a  black  child  have  been  born  as  twins 
by  a  woman. 

Superfoetation  is  when  a  second  impregnation  takes  place  at  a  later  period  of  pregnancy,  as  in 
the  second  or  third  month.  This,  however,  is  only  possible  in  a  double  uterus,  or  when  menstrua, 
tion  persists  until  the  time  of  the  second  impregnation.     It  is  said  to  occur  frequently  in  the  hare. 

Hybrids  are  produced  when  there  is  a  cross  between  different  species  (horse,  ass,  zebra — dog, 
jackal,  wolf — goat,  ibe.x — goat,  sheep — species  of  llama — camel,  dromedary — tiger,  lion — species 
of  pheasant — goose,  swan — carp,  crucian — species  of  butterflies).  Most  hybrids  are  sterile,  espe- 
cially as  regards  the  formation  of  properly  formed  spermatozoa  ;  while  the  hybrid  females  are  for 
the  most  part  fertile  with  the  male  of  both  parents,  e.  g.,  the  mule;  but  the  characters  of  the  off- 
spring tend  to  return  to  those  of  the  species  of  the  parents.  Very  few  hybrids  are  fertile  when 
crossed  by  hybrids.  In  many  species  of  frogs  the  absence  of  hybrids  is  accounted  for  by  the  me- 
chanical obstacles  to  fertilization  of  the  ova. 

Tubal  Migration  of  the  Ovum. — Under  exceptional  circumstances,  the 
ovum  discharged  from  a  ruptured  Graafian  follicle  passes  into  the  Fallopian  tube 
of  the  other  side,  as  is  proved  by  the  occurrence  of  tubal  pregnancy  and  preg- 
nancy of  an  abnormal  rudimentary  horn  of  the  uterus,  in  which  case  the  true 
corpus  luteum  is  found  on  the  other  side  of  the  ovary.  This  is  spoken  of  as  "  ex- 
ternal migration  "  (Kussmaul,  Leopold).  This  observation  coincides  with 
experiment,  a-s  granular  fluids,  e.  g.,  China  ink,  when  injected  into  the  peritoneal 
cavity,  pass  into  both  Fallopian  tubes,  and  are  carried  by  the  ciliated  epithelium  to 
the  uterus  {Pinner^.  In  animals,  with  a  double  uterus  with  two  orifices,  the  ova 
may  migrate  through  the  os  of  the  one  into  the  other  uterus,  a  condition  which 
is  spoken  of  as  "  internal  migration." 

439.  IMPREGNATION  OF  THE  OVUM— CLEAVAGE— LAY- 
ERS AND  POSITION  OF  THE  EMBRYO.— Maturation  of  the 
Ovum. — In  birds  and  mammals  important  changes  occur  in  the  ovum  before  im- 
pregnation. The  genninal  vesicle  comes  to  the  surface  and  disappears  from  view, 
while  the  germinal  spot  also  disappears  (^Reiii).  In  place  of  the  germinal  vesicle, 
a  spindle-shaped  body  appears.  The  granular  elements  of  the  protoplasmic  vitellus 
arrange  themselves  around  each  of  the  two  poles  of  the  spindle,  in  the  form  of  a 
star,  the  double  star,  or  diaster  of  Fol — nuclear  spindle.  When  this  takes  place 
\\\&  peripheral  pole  of  the  nucletis  or  altered  germinal  vesicle,  along  with  some  of 
the  cellular  substance  of  the  ovum,  protrudes  upon  the  surface  of  the  vitellus, 
where  they  are  nipped  off  from  the  ovum  in  the  form  of  small  corpuscles  just  like 
an  excretory  product  (Fig.  553).  These  bodies,  which  are  not  made  use  of  in  the 
further  development  and  growth  of  the  ovum,  are  called  polar  or  directing 
globules  (Fol,  Biitsehli,  O.  Hertwig),  although  the  elimination  of  small  bodies 
from  the  yelk  was  known  to  Dumortier  [1837],  Bischoff,  P.  J.  vanBeneden,  Fritz 
Miiller  [1848],  Rathke,  and  others.  The  remaining  part  of  the  germinal  vesicle 
stays  within  tlie  vitellus  and  travels  back  toward  the  centre  of  the  ovum,  to  form 
the  female  pronucleus  {O.  Hertwig,  Fol,  Selenka,  E.  van  Beiieden).  [Before, 
however,  the  altered  germinal  vesicle  travels  downward  again  into  the  substance 
of  the  ovum,  it  divides  again  as  before,  and  from  it  is  given  off  the  second  polar 
globule,  and  then  the  remainder  of  the  germinal  vesicle  forms  the  female  pro- 


874 


BLASTODERM. 


nucleus.     At  the  same  time  the  vitellus  shrinks  somewhat  \v4thin   the  vitelline 
membrane.] 

Impregnation. — As  a  rule,  only  one  spermatozoon  penetrates  the  ovum,  and 
as  it  does  so  it  moves  toward  the  female  pronucleus,  while  its  head  becomes  sur- 
rounded with  a  star;  it  then  loses  its  head  and  cilium  or  tail,  the  latter  only 
serving  as  a  motor  organ,  while  the  remaining  middle  piece  swells  up  to  form  a 
second  new  nucleus,  the  male  pronucleus  ( Fol,  Selenkd).  According  to  Flem- 
niing,  it  is  the  anterior  part  of  the  head,  and  according  to  Rein  and  Eberth,  it  is 
the  head  which  is  so  changed.  Thereafter,  the  male  and  female  ])ronucleus 
unite,  undergoing  amoeboid  movements  at  the  same  time,  to  form  the  new  nu- 
cleus of  \.\\t  fertilized  ovum.  The  female  pronucleus  receives  the  male  pronucleus 
in  a  little  depression  on  its  surface.  Thereafter  the  yelk  assumes  a  radiate  appear- 
ance {Rein).  [The  union  of  the  representatives  of  the  male  and  female  elements 
forms  the  first  embryonic  segmentation  sphere  or  blastosphere.] 

In  Echinoderms,  O.  Hertwig  and  Fol  observed  that  several  embryos  were  formed  when,  under 
abnormal  conditions,  several  spermatozoa  penetrated  an  ovum.  The  male  pronuclei,  formed  from 
the  several  spermatozoa,  then  fused  each  with  a  fragment  of  the  female  pronucleus.  Under 
similar  circumstances,  Born  observed  in  amphibians  abnormal  cleavage,  but  no  further  develop- 
ment. 


Cleavage  of  the  Yelk. 

Fig.  561. 


-In  an  ovum  so  fertilized  the  yelk  contracts  some- 
what around  the  newly-formed  nucleus, 
so  that  it  becomes  slightly  separated 
from  the  vitelline  membrane,  and  for 
the  first  time  the  nucleus  and  the  yelk 
divides  into  two  nucleated  spheres. 
This  process  is  spoken  of  as  complete 
cleavage  or  fission.  Each  of  these 
two  cells  again  divides  into  two,  and 
the  process  is  repeated,  so  that  4,  8,  16, 
32,  and  so  on,  spheres  are  formed  (Fig. 
561).  This  constitutes  the  cleavage  of 
the  yelk,  and  the  process  goes  on  until  the  whole  yelk  is  subdivided  into  numer- 
ous small,  nucleated  spheres,  the  "mulberry  mass"  or  "segmentation 
spheres  "  or  "  morula,"  or  the  protoplasmic  primordial  spheres  (20  to  25  /i) 
which  are  devoid  of  an  envelope. 

Variation  of  Lines  of  Cleavage. — According  to  the  observations  of  Pfliiger,  the  ova  of  the 
frog  can  be  made  to  undergo  cleavage  in  very  different  directions,  according  to  the  angle  between 
the  axis  of  the  egg  and  the  line  of  gravitation.  This,  of  course,  we  can  alter  as  we  please,  by 
placing  the  eggs  at  any  angle  to  the  line  of  gravitation.  By  the  axis  of  the  ovum  is  meant  a  line 
connecting  the  centre  of  the  black  surface  and  the  middle  of  the  white  part,  which,  in  the  fertilized 
ovum,  is  always  vertical.  In  such  cases  of  abnormal  cleavage  the  deposition  of  the  organs  takes 
place  from  other  constituents  of  the  egg  than  those  from  wliich  tliey  are  formed  under  normal  con- 
ditions. Under  normal  circumstances,  according  to  Roux,  the  first  line  of  cleavage  in  the  frog  is  in 
the  same  direction  as  the  central  nervous  system.  The  second  intersects  the  first  at  a  right  angle, 
so  as  to  divide  the  mass  of  the  ovum  into  two  unequal  parts,  the  larger  of  which  forms  the  anteri'.r 
part  of  the  embryo. 

Blastoderm. — During  this  time  the  ovum  is  enlarging  by  absorption  of  fluid 
into  its  interior.  All  the  cells,  from  mutual  pressure  against  each  other,  become 
polyhedral,  and  are  so  arranged  as  to  form  a  cellular  envelope  or  bladder,  the 
blastoderm,  which  lies  on  the  internal  surface  of  the  vitelline  membrane  {De 
Graaf,  v.  Baer,  Bischoff,  Coste).  A  small  part  of  the  cells  not  used  in  the  for- 
mation of  the  blastoderm  is  found  on  some  part  of  the  latter.  [In  the  ovum  of 
the  bird,  where  there  is  only  partial  segmentation,  the  blastoderm  is  a  small 
round  body  resting  on  the  surface  of  the  yelk,  under  the  vitelline  membrane,  so 
that  it  does  not  completely  surround  the  yelk,  or  a  hollow  cavity,  as  in  mammals.] 
The  hollow  sphere,  composed  of  cells,  is  called  the  blastodermic  vesicle  by 
Reichert,  and  in  the  human  embryo  it  is  formed  at  the  loth  to  12th  day,  in  the 


STRUCTURE    OF   THE    BLASTODERM. 


875 


rabbit  at  the   4th,  the  guinea  pig  at  the  3'^,  the  cat  7th,  dog  nth,  fox  i4lh, 
ruminantia  at  the  loth  to  12th  day,  and  the  deer  at  the  60th  day. 

When  the  blastoderm  grows  to  2  mm.  (rabbit),  whereby  the  vitelline  membrane 
is  distended  to  a  very  thin,  delicate  membrane,  then  at  one  part  of  it  there 
appears  the  germinal  area,  the  area  germinativa,  or  the  embryonal  shield  {Coste, 
Kblliker),  as  a  round  white  spot,  in  which  the  blastoderm,  owing  to  proliferation 
of  its  cells,  becomes  double.  The  upper  laj'cr  is  called  the  ectoderm  or  epi- 
blast,  and  in  some  animals  it  consists  of  several  layers  of  cells,  while  tlie  lower 
layer  is  the  endoderm  or  hypoblast.  The  hypoblast  continues  to  grow  at  its 
edges,  so  that  it  ultimately  forms  a  completely  closed  sack,  on  which  the  epiblast 
is  applied  concentrically.  The  embryonal  area  soon  becomes  more  pear-shaped, 
and  afterward  biscuit-shaped.  At  the  same  time  the  surface  of  the  zona  pellu- 
cida  develops  numerous  small,  hollow,  structureless  villi,  and  is  called  the  primi- 
tive chorion. 

At  the  posterior  part  of  the  embryonic  shield,  the  primitive  streak  (Fig. 
562,  I,  Pr)  appears  at  first  as  an  elongated  circular  thickening  (^Hensen),  and 
later  as  a  longer  streak  or  groove,  the  primitive  groove.  This  thickening, 
however,  is  confined  to  the  epiblast,  while  the  hypoblast  is  completely  unchanged 
in  the  region  of  the  streak,  and  the  former  consists  of  three  layers  of  cells.  At 
the  same  time  a  new  layer  of  cells  is  developed  between  the  epiblast  and  hypo- 
blast, the  mesoderm  or  mesoblast  (Fig.  563,  I),  which  soon  extends  over  the 
embryonal  area,  and  into  the  blastoderm.  Blood  vessels  are  formed  within  the 
mesoblast,  and  are  distributed  over  the  blastoderm  to  form  the  area  vasculosa. 

Medullary  Groove. — .\  longitudinal  groove,  the  medullary  groove,  is  formed 
at  the  anterior  part  of  the  embryonal  shield, 

but  it  gradually  extends  posteriorly,  embrac-  Fig.  562. 

ing  the  anterior  part  of  the  primitive  streak 
with  its  divided  posterior  end,  while  the 
primitive  streak  itself  gradually  becomes 
relatively  and  absolutely  smaller  and  less  dis- 
tinct, until  it  disappears  altogether  (Fig. 
562,  I  and  II,  Pr—Kolliker). 

The  position  of  the  embryo  is  indicated 
by  the  central  part  becoming  more  trans- 
parent,— the  area  pellucida, — which  is 
surrounded  by  a  more  opaque  part — the  area 
opaca.   [The  area  opaca  rests  directlv  upon 

.,  U-.  n      •       .1        r        1  J     •»     ..    r  Pr,  primilive  streak  :    ;?.  medullary  groove  ;    U, 

the  white  yelk  in  the  fowl,  and  it   takes  no  first  protovenebra. 

share  in  the  formation  of  the  embryo,  but 

gives  rise  to  structures  which  are  temporary,  and  are  connected  with  the  nutrition 

of  the  embryo.     The  embryo  is  formed  in  the  area  pellucida  alone.] 

From  the  epiblast  \jieuro-epidermal  layer]  are  developed  the  central  nervous 
system  and  epidermal  tissues,  including  the  epithelium  of  the  sense  organs. 

From  the  mesoblast  are  formed  most  of  the  organs  of  the  body  [including 
the  vascular,  muscular,  and  skeletal  systems,  and,  according  to  some,  the  connect- 
ive tissue.     It  also  gives  rise  to  the  generative  glands  and  excretory  organs]. 

From  the  hypoblast,  epithelio-glandular  layer  [which  is  the  secretory  layer], 
arise  the  intestinal  epithelium,  and  that  of  the  glands  which  open  into  the  intestine. 
[The  mouth  and  anus  being  formed  by  an  inpushing  of  the  epiblast,  are  lined  by 
epiblast,  and  are  sometimes  called  the  stomodceum  and  protodceum  respect- 
ively.] 

[Structure  of  the  Blastoderm.— Originally  it  is  composed  of  only  two 
layers,  and  in  a  vertical  section  of  it  the  epiblast  consists  of  a  single  row  of 
nucleated  granular  cells  arranged  side  by  side,  with  their  long  axes  placed  verti- 
cally. The  hypoblast  consists  of  larger  cells  than  the  foregoing,  although  they 
vary  in  size.     They  are  spherical  and  very  granular,  so  that  no  nucleus  is  visible 


«76 


STRUCTURES    FORMED    FROM    THE    EPIBLAST. 

Fig.  563. 


I,  The  three  layers  of  the  blastoderm  of  the  mammalian  ovum — Z,  zona  pellucida  ;  E,  ectoderm,  or  epiblast  ;  m, 
mesoblast ;  f,  endoderm,  or  hypoblast.  II,  Section  of  an  embryo,  with  six  proto vertebrae  at  the  ist  day — M, 
medullary  groove;  A,  somatopleure  ;  U,  protovertebra ;  c,  chorda  dorsalis ;  S,  the  lateral  plates  divided  into 
two  ;  e,  hypoblast.  Ill,  Section  of  an  embryo  chick  at  the  zd  day  in  the  region  behind  the  heart — M,  medullary 
groove  ;  /t,  outer  part  of  somatopleure  ;  u,  protovertebra  ;  c,  chorda  :  ■zu.  Wolffian  duct ;  K,  calom  ;  x,  inner 
part  of  somatopleure  ;  y.  inner  part  of  splanchnopleure  ;  A,  amniotic  fold  :  a,  aorta;  e,  hypoblist.  IV,  Scheme 
of  a  longitudinal  section  of  an  early  embryo.  V,  Scheme  of  the  formation  of  the  head- and  tail-folds — r,  head- 
fnld  ;  T>,  anterior  extremity  of  the  future  intestinal  tract ;  S.  tail-fold,  first  rudiment  of  the  cavity  of  the  reclum. 
VI,  Scheme  of  a  longitudinal  section  through  an  embryo  after  the  formation  of  the  heid-and  tail-folds — A  o,  om- 
phalo-mesenteric  arteries  ;  V  (j,  omphalo-mesenteric  veins  ;  rf,  position  of  the  allantois  ;  A,  amniotic  fold.  VII, 
Scheme  of  a  longitudinal  section  through  a  human  ovum — Z,  zona  pellucida  ;  S,  serous  cavity  ;  r,  union  of  the 
amniotic  folds  ;  A,  cavity  of  the  amnion  ;  a,  allantois  ;  N,  umbilical  vesicle  ;  t/i,  mesoblast ;  A,  heart ;  U,  primitive 
intestine.  VIII.  Schematic  transverse  section  of  the  pregnant  uterus  during  the  formation  of  the  placenta  ;  U, 
muscular  wall  of  the  uterus  ;  /,  uterine  mucous  membrane,  or  decidua  vera ;  ^,  maternal  part  of  the  placenta,  or 
decidua  serontina  ;  r,  decidua  reflexa;  c/t,  chorion  ;  A,  amnion  ;  «,  umbilical  cord;  n,  allantois,  with  the  urachus; 
N,  umbilical  vesicle,  with  D,  the  omphalo-mesenteric  duel  :  /  i,  openings  of  the  Fallopian  tubes  ;  G,  canal  of  the 
cervix  uteri.  IX,  Scheme  of  a  human  embryo,  with  the  visceral  arches  still  persistent — A,  amnion:  V,  fore- 
brain;  M,  mid-brain;  H,  hind-brain  ;  N,  after-brain  ;  U,  primitive  veriebra  ;  a,  eye  ;/,  nasal  pits  ;  S,  frontal 
process;  j*.  internal  nasal  process;  m,  external  nasal  process;  /•,  superior  maxillary  process  of  the  1st  visceral 
arch  ;  1,2.3  ^'^'^  4>  ^^^  f*^"*"  visceral  arches,  with  the  visceral  clefts  between  them  ;  e>,  auditory  vesicle;  /i.  heart, 
with  f,  primitive  aorta,  which  divides  into  five  aortic  arches  ;  X.  descending  aorta  ;  om,  omphalo-mesenteric  ar- 
tery; ^,  the  omphalo-me'senteric  arteries  on  the  umbilical  vesicle;  c,  omphalo-mesenteric  vein;  L,  Liver,  with 
venae  advehentes  and  revehentes  ;  D,  intestine  ;  /,  inferior  cava  ;  T,  coccyx  ;  «//,  allantois,  with  s,  one  umbilical 
artery,  and  x,  an  umbilical  vein. 


STRUCTURES    FORMED    FROM   THE    MESOBLAST.  877 

in  them.  The  cells  form  a  kind  of  network,  and  occur  in  more  than  one  layer, 
especially  at  the  periphery.  It  rests  on  white  yelk,  and  under  it  are  large  spher- 
ical refractive  cells,  spoken  of  as  formative  cells.] 

The  cells  of  the  epiblast,  and  especially  those  of  the  hypoblast,  nourish  themselves  by  the  direct 
absorption  and  incorporation  of  the  constituents  of  the  yelk  into  themselves.  The  amoeboid  move- 
ments of  these  cells  jjlay  a  part  in  the  process  of  absorption.  The  absorbed  particles  are  changed, 
or,  as  it  were,  digested  within  the  cells,  and  the  product  used  in  the  processes  of  growth  and  de- 
velopment (Kollmann). 

440.  STRUCTURES  FORMED  FROM  THE  EPIBLAST.— 
Laminae  Dorsales. — The  medullary  groove  upon  the  epiblast  (also  called 
outer,  serous,  sensorial,  corneal,  or  animal  layer j  becomes  deejjer  (Fig.  563,  II). 
The  two  longitudinal  elevations  or  laiiiime  dorsales  consist  of  a  thickening  of  the 
epiblast,  and  grow  up  over  the  tneduUary  groove,  to  meet  each  other  and  coalesce 
by  their  free  edges  in  the  middle  line  posteriorly.  Thus  the  open  groove  is 
changed  into  a  closed  tube — the  medullary  or  neural  tube  (III).  The  cells 
next  the  lumen  of  the  tube  ultimately  become  the  ciliated  epithelium  lining  the 
central  canal  of  the  spinal  cord,  while  the  other  cells  of  the  nipped-ofif  portion  of 
the  epiblast  form  the  ganglionic  part  of  the  central  nervous  system  and  its  pro- 
cesses. 

Primary  Cerebral  Vesicles. — [The  laminae  dorsales  unite  first  in  the  region 
of  the  neck  of  the  embryo,  and  soon  this  is  followed  by  the  union  of  those  over 
the  future  head.]  The  medullary  tube  is  not  of  uniform  diameter,  for  at  the 
anterior  end  it  becomes  dilated  and  mapped  out  by  constrictions  into  the  primary 
vesicles  of  the  brain,  which  at  first  are  arranged,  one  behind  the  other,  in  the 
following  order:  Each  one  being  smaller  than  the  one  in  front  of  it  ;  the  fore- 
brain  (representing  the  structures  from  which  the  cerebral  hemispheres  are  devel- 
oped);  the  mid-brain  (corpora  quadrigemina) ;  the  hind-brain  (cerebellum); 
and  the  after-brain  (medulla  oblongata),  which  is  gradually  continued  into  the 
spinal  cord  (IV  and  V).  The  posterior  part  of  the  medullary  tube  has  a  dilatation 
at  the  lumbar  enlargement.  In  birds,  the  medullary  groove  remains  open  in  this 
situation  to  form  a  lozenge-shaped  dilatation,  the  sinus  rhomboidalis. 

Cranial  Flexures. — The  anterior  part  of  the  medullary  tube  curves  on  itself, 
especially  at  the  junction  of  the  spinal  cord  and  oblongata,  between  the  mid-brain 
and  hind-brain,  and  again  almost  at  right  angles  between  the  fore-brain  and  mid- 
brain. [Thus  is  produced  a  displacement  of  the  primary  vesicles,  and  the  head 
of  the  future  embryo  is  mapped  off.]  At  first  all  the  cerebral  vesicles  are  devoid 
of  convolutions  and  sulci.  On  each  side  of  the  fore-brain  there  grows  out  a 
stalked,  hollow  vesicle  (VI),  the  primary  optic  vesicle.  The  remainder  of 
the  ejjiblast  forms  the  epidermal  covering  of  the  body.  At  an  early  period  we 
can  distinguish  the  stratum  corneum  and  the  Malpighian  layer  of  the  skin  (ij  283)  ; 
from  the  former  are  developed  the  hairs,  nails,  feathers,  etc. 

Partial  Cleavage. — Only  a  partial  cleavage  takes  place  in  the  eggs  of  birds  and  in  mesoblastic 
ova,  i.  e.,  only  the  white  yctk  in  the  neighborhood  of  the  cicatricula  divides  into  numerous  segmen- 
tation spheres  (Coste,  JS4S).  The  cells  arrange  themselves  in  two  layers,  lying  one  over  the  other. 
The  upper  layer  or  epiblast  is  the  larger,  and  contains  small,  pale  cells ;  the  lower  layer,  or  hype- 
blast,  which  at  iirst  is  not  a  continuous  layer,  ultimately  forms  a  contmuous  layer,  but  its  periphery 
is  smaller  than  the  upper  layer,  while  its  cells  are  larger  and  more  granular. 

Between  the  epiblast  and  hypolilast,  from  the  primitive  streak  outward,  is  formed  the  mesoblast, 
which  is  said  by  Kolliker  to  be  due  to  the  division  of  the  cells  of  the  epiblast.  It  gradually  extends 
in  a  peripheral  direction  between  the  two  other  layers.  All  the  three  layers  grow  at  their  periphery. 
In  the  mesobla.st  blood  vessels  are  developed.  .All  the  three  layers,  as  they  grow,  come  ultimately 
to  enclose  the  yelk,  so  that  their  margins  come  together  at  the  opposite  pole  of  the  )'elk. 

441.  STRUCTURES  FORMED  FROM  THE  MESOBLAST 
AND  HYPOBLAST.— The  mesoblast  (^vascular  layer  or  middle  laycrj 
forms,  immediately  under  the  medullary  groove,  a  cylindrical,  cellular  cord,  the 
chorda  dorsalis,  or  notochord,  which  is  thicker  at  the  tail  than  at  the  cephalic 


878  FORMATION    OF    EMBRYO,    ETC. 

end  (Fig.  563,  II,  III,  c).  It  is  present  in  all  vertebrata,  and  also  in  the  larval 
form  of  the  ascidians,  but  in  the  latter  it  disappears  in  the  adult  form  (Kowa- 
lewsky).  In  man  it  is  relatively  small.  It  forms  the  basis  of  the  bodies  of  the 
vertebrje,  and  around  it,  as  a  central  core,  the  substance  of  the  bodies  of  the 
vertebra  is  deposited,  so  that  they  are  strung  on  it,  as  it  were,  like  beads  on  a 
string.  After  it  is  formed  it  becomes  surrounded  by  a  double  sheath-like  covering 
( Gegenbaiir,  KoUiker). 

The  recent  observations  of  L.  Gerlach  and  Strahl  ascribe  the  origin  of  the  chorda  to  the  hypoblast. 
It  does  not  contain  chondrin  or  glutin,  but  albumin  {Kdzius). 

Protovertebrae. — The  cells  of  the  mesoblast,  on  each  side  of  the  chorda, 
arrange  themselves  into  cubical  masses,  always  disposed  in  pairs  behind  each  other, 
the  protovertebrse  (U  and //).  The  first  pair  correspond  to  the  atlas.  At  a 
later  period  each  protovertebra  shows  a  marginal,  cellular  area  and  a  nuclear  area. 
Only  part  of  it  goes  to  form  a  future  vertebra.  The  part  of  the  mesoblast  lying 
external  to  the  protovertebra,  the  lateral  plates  (II,  s),  splits  into  two  layers 
(^Wolff,  J768),  an  upper  one  and  a  lower  one,  which,  however,  are  united  by  a 
median  plate  at  the  protovertebrae.  The  space  between  the  two  layers  of  the 
mesoblast  is  called  the  pleuro-peritoneal  cavity,  or  the  coelom  (III,  K)  of 
Haeckel.  The  upper  layer  of  the  lateral  jjlate  becomes  united  to  the  epiblast, 
and  forms  the  cutaneo-muscular  plate  of  German  authors,  or  the  somatopleure 
(III,  .v),  while  the  inner  one  unites  with  tjie  hyiJoblast  to  form  the  intestinal  plate 
of  German  authors,  or  the  splanchnopleure  (III,  1).  On  the  surfaces  of  these 
plates,  which  are  directed  toward  each  other,  the  endothelium  lining  the  pleuro- 
peritoneal  cavity  is  developed.  On  the  surface  of  the  median  plate,  directed 
toward  the  coelom,  some  cylindrical  cells,  the  "  germ  epithelium  "  of  Waldeyer, 
remain,  which  form  the  ovarian  tubes  and  the  ova  (Ji  433). 

.According  to  Remak,  the  skin,  the  muscles  of  the  trunk,  and  the  hlood  vessels,  and  according  to 
His,  only  the  musculature  of  the  trunk,  are  derived  from  the  somatopleure.  Both  observers  agree 
that  the  splanchnopleure  furnishes  the  musculature  of  the  initstinal  tract. 

Parablastic  and  Archiblastic  Cells. — According  to  His  the  blood  vessels, 
blood,  and  connective  tissue  are  not  developed  from  true  mesoblastic  cells,  but  he 
asserts  that  for  this  purpose  certain  cells  wander  in  from  the  margins  of  the  blasto- 
derm between  the  epiblast  and  hypoblast,  these  cells  being  derived  from  outside  the 
position  of  tiie  embryo,  from  the  elements  of  the  white  yelk.  His  calls  these 
structures  parablastic,  in  opposition  to  the  arc/i/b/as/ic,  which  belong  to  the  three 
layers  of  the  embryo.  Waldeyer  also  adheres  to  the  parablastic  structure  of  blood 
and  connective  tissue,  but  he  assumes  that  the  material  from  which  the  latter  is 
formed  is  continuous  protoplasm,  and  of  equal  value  with  the  elements  of  the 
blastoderm. 

The  hypoblast  does  not  undergo  any  change  at  this  time ;  it  applies  itself  to 
the  inner  layer  of  the  mesoblast,  as  a  single  layer  of  cells  to  form  the  splanchno- 
pleure. 

442.  FORMATION  OF  EMBRYO,  HEART,  PRIMITIVE  CIR- 
CULATION.—Head-  and  Tail-Folds. — Up  to  this  time  the  embryo  lies 
with  its  three  layers  in  the  plane  of  the  layers  themselves.  The  cephalic  end  of 
the  future  embryo  is  first  raised  above  the  level  of  this  plane  (Fig.  563,  V).  In 
front  of,  and  under  the  head,  there  is  an  inflection  or  tucking  in  of  the  layers, 
which  is  spoken  of  as  the  head-fold  {Y ,  r).  [It  gradually  travels  backward,  so 
that  the  embryo  is  raised  above  the  level  of  its  surroundings.]  The  raised  cephalic 
end  is  hollow,  and  it  communicates  with  the  space  in  the  interior  of  the  umbilical 
vesicle.  The  cavity  in  the  head  is  spoken  of  as  the  head-gut  or  fore-gut  (V, 
D).  The  formation  of  the  fore-gut,  by  the  elevation  of  the  head  from  the  plane 
of  the  three  layers,  occurs  on  the  second  day  in  the  chick,  and  in  the  dog  on  the 
22d  day.  The  tail-fold  is  formed  in  precisely  the  same  way  in  the  chick  on  the 
3d  day,  and  in  the  dog  on  the  22d  day.     The  caudal  elevation,  S,  also  is  hollow, 


FORMATION   OF   THE    HEART.  879 

and  the  space  within  it  is  the  hind-gut,  d.  Thus  the  body  of  tlie  embryo  is  sup- 
ported or  rests  on  a  hollow  stalk,  which  at  first  is  wide,  and  communicates  with  the 
cavity  of  the  umbilical  vesicle.  This  duct  or  communication  is  called  the  om- 
phalo-mesenteric  duct,  or  the  vitello-intestinal  or  vitelline  duct.  The 
saccular  vesicle  attached  to  it  in  mammals  is  called  the  umbilical  vesicle  (VII, 
N),  while  the  analogous  much  larger  sack  in  birds,  which  contains  the  yellow  nutri- 
tive yelk,  is  called  the  yelk-sack.  The  omphalo-mesenteric  or  vitelline  duct  in 
course  of  time  becomes  narrower,  and  is  ultmiately  obliterated  in  the  chick  on  the 
5th  day.  The  point  where  it  is  continuous  with  the  abdominal  wall  is  the  abdom- 
inal umbilicus,  and  where  it  is  inserted  into  the  primitive  intestine,  the  intestinal 
umbilicus. 

[Sometimes  part  of  the  vitelline  duct  remains  attached  to  the  intestine,  and  may  prove  dangerous 
by  becoming  so  displaced  as  to  constrict  a  loop  of  intestine,  and  thus  cause  strangulation  of  the  gut.] 

Heart. — Before  this  process  of  constriction  is  complete,  some  cells  are  mapped 
off  from  that  part  of  the  splanchnopleure  which  lies  immediately  under  the  head- 
gut  ;  this  indicates  \\\&  position  of  the  heart,  which  appears  in  the  chick  at  the  end 
of  the  first  day,  as  a  small,  bright  red,  rhythmically  contracting  point,  the piinetuni 
saliens,  or  the  ariynri  xi-jouiiivri  of  Aristotle.     In  mammals  it  appears  much  later. 

The  heart,  VI,  begins  first  as  a  mass  of  cells,  some  of  which  in  the  centre  dis- 
appear to  form  a  central  cavity,  so  that  the  whole  looks  like  a  pale  hollow  bud 
(originally  a  pair)  of  the  splachnopleure.  The  central  cavity  soon  dilates  ;  it 
grows,  and  becomes  suspended  in  the  coelom  by  a  duplicature  like  a  mesentery 
(meso-cardium),  while  the  space  which  it  occupies  is  spoken  of  as  lh.e  fovea  car- 
dica.  The  heart  now  assumes  an  elongated  tubular  form  with  its  aortic  portion 
directed  forward  and  its  venous  end  backward  ;  it  then  undergoes  a  slighty-shaped 
curve  (Fig.  570,  i).  From  the  middle  of  the  2d  day  the  heart  begins  to  beat  in  the 
chick  at  the  rate  of  about  40  beats  per  minute.  [It  is  very  important  to  note  that 
at  first,  although  the  heart  beats  rhythmically,  it  does  not  contain  any  nerve  cells.] 

From  the  anterior  end  of  the  heart  there  proceeds  from  the  bulbus  aortas  the 
aorta,  which  passes  forward  and  divides  into  two  arches  the  primitive  aortae, 
which  then  curve  and  pass  backward  under  the  cerebral  vesicles,  and  run  in  front 
of  the  protovertebra:.  Opposite  the  omphalo-mesenteric  duct  each  primitive  aorta 
in  the  chick  sends  off  one,  in  mammals  several  (dog  4  to  5),  omphalo-mesenteric 
arteries  (VI,  A,  0),  which  spread  out  to  form  a  vascular  network  within  the  meso- 
blast  of  the  umbilical  vesicle.  From  this  network  there  arise  the  omphalo-mesen- 
teric veins,  which  run  backward  on  the  vitelline  duct,  and  end  by  two  trunks  in 
the  venous  end  of  the  tubular  heart.  In  the  chick  these  veins  arise  from  the  sinus 
terminalis  of  the  subsequent  vena  terminalis  of  the  area  vasculosa.  Thus  the  first 
or  primitive  circulation  is  a  closed  system,  and  functionally  it  is  concerned  in 
carrying  nutriment  and  oxygen  to  the  embryo.  In  the  bird  the  latter  is  supplied 
through  the  porous  shell,  and  the  former  is  supplied  up  to  the  end  of  incubation 
by  the  yelk.  In  mammals  both  are  supplied  by  the  blood  vessels  of  the  uterine 
mucous  membrane  to  the  ovum.  In  birds,  owing  to  the  absorption  of  the  con- 
tents of  the  yelk-sack,  the  vascular  area  steadily  diminishes,  until  ultimately,  to- 
ward the  end  of  the  incubation  time,  the  shriveled  yelk-sack  slips  into  the  abdom- 
inal cavity.  In  mammals,  the , circulation  on  the  umbilical  vesicle,  i.e.,  through 
the  omphalo-mesenteric  vessels,  soon  diminishes,  while  the  umbilical  vesicle  itself 
shrivels  to  a  small  appendix,  and  the  second  circulation  is  formed  to  replace 
the  omphalo-mesenteric  system.  The  first  blood  vessels  are  formed  in  the  chick, 
in  the  area  vasculosa,  outside  the  position  of  the  embryo,  at  the  last  quarter 
of  the  first  day,  before  any  part  of  the  heart  is  visible.  The  blood  vessels  begin 
in  vaso-formative  cells  [constituting  the  "  blood  islands  "  of  Pander].  At  first 
they  are  solid,  but  they  soon  become  hollow  (§  7,  A). 

A  narrow-meshed  plexus  of  lynifhatics  is  formed  in  the  area  vasculosa  of  the  chick  (His),  and 
it  commun  cates  with  the  amniotic  cavity  (A.  Bud^e). 


880  VERTEBRAL  COLUMN. 

443.    FURTHER    FORMATION    OF  THE    BODY.— Body  Wall. 

— (i)  The  coelom,  or  pleuro-peritoneal  cavity,  becomes  larger  and  larger,  while, 
at  the  same  time,  the  difference  between  the  body  wall  and  the  wall  of  the  intes- 
tine becomes  more  pronounced.  The  latter  becomes  more  separated  from  the 
pro  to  vertebra,  as  the  middle  plate  begins  to  be  elongated  to  form  a  mesentery. 
The  body  wall,  or  somatopleure,  composed  of  the  epiblast  and  the  outer  layer  of 
the  cleft  mesoblast,  becomes  thickened  by  the  ingrowth  into  it  of  the  muscular 
layer  from  the  muscle  plate,  and  the  position  of  the  bones  and  the  spinal  nerves 
from  the  protovertebrae.  These  grow  between  the  epiblast  and  the  outer  layer  of 
the  mesoblast  {Jiemak).  [The  somatopleure,  or  parietal  lamina,  from  each  side 
grows  forward  and  toward  the  middle  line,  where  they  meet  to  form  the  body 
wall,  while  at  the  same  time  the  splanchnopleure,  or  visceral  lamina,  on  each  side 
also  grow  and  meet  in  the  middle  line,  and  when  they  do  so  they  enclose  the 
intestine.  Thus,  there  is  one  tube  within  the  other,  and  the  space  between  is  the 
pleuro-peritoneal  cavity.] 

1  2 )  Vertebral  Column. — A  dorsally-placed  structure,  called  the  muscle 
plate  \^Iit»mk'.  is  differentiated  from  each  of  the  protovertebrse ;  the  remainder 
of  the  protovertebra,  the  protovertebra  proper  (Kolliker),  coalesces  with  that  on 
the  other  side,  so  that  both  completely  surround  the  chorda,  to  form  the  mem- 
brana  reuniens  inferior  {Rdchert ),  in  the  chick  on  the  3d,  and  in  the  rabbit 
on  the  loth  day,  while  at  the  same  time  they  close  over  the  medullary  tube  dor- 
sally  in  the  chick  at  the  4th  day,  to  form  the  membrana  reuniens  superior. 
Thus,  there  is  a  union  of  the  masses  of  the  protovertebrs  in  front  of  the  medul- 
lary tube,  which  encloses  the  chorda,  and  represents  the  basis  of  the  bodies  of  all 
the  vertebrae,  whilst  the  membrana  reuniens  superior,  pushed  between  the  muscle 
plates  and  the  epiblast  on  the  one  hand  and  the  medullary  tube  on  the  other, 
represents  the  position  of  the  entire  vertebral  lamintr  as  well  as  the  intervertebral 
ligaments  between  them.  In  some  rare  cases  the  membrana  reuniens  superior  is 
not  developed,  so  that  the  medullary  tube  is  covered  only  by  the  epiblast  (epidermis), 
either  throughout  its  entire  extent  or  at  certain  parts.  This  constitutes  the  condi- 
tion of  spina  bifida,  or,  when  it  occurs  in  the  head,  hemicephalia.  The  vertebral 
column  at  this  membranous  stage  is  in  the  same  condition  as  the  vertebral  column 
of  the  cyclostomata  (Petromyzon).  The  membranes  of  the  spinal  cord,  the  spinal 
ganglia,  and  spinal  ner\-es  are  formed  from  the  membrana  reuniens  superior. 

Lastly,  parts  of  the  somatopleures  also  grow  toward  the  middle  line  of  the  back, 
and  insinuate  themselves  between  the  muscle  plate  and  the  epiblast ;  thus,  the 
dorsal  skin  is  formed  {^Jiemak). 

In  the  membranous  vertical  column  there  are  formed  the  several  cartilaginous 
vertebrae,  the  one  behind  the  other,  in  man  at  the  6th  to  7th  week,  although  at 
first  they  do  not  form  closed  vertebral  arches;  the  latter  are  closed  in  man  about 
the  4th  month.  Each  cartilaginous  vertebra,  however,  is  not  formed  from  a  pair 
of  protovertebrae,  /.  e.,  the  6th  cervical  vertebra  from  the  6th  pair  of  protover- 
tebrte,  but  there  is  a  new  subdivision  of  the  vertebral  column  {Rcmak),  so  that 
the  lower  half  of  the  preceding  protovertebra  and  the  upper  half  of  the  succeeding 
protovertebra  unite  to  form  the  final  vertebra.  While  the  bodies  are  becoming 
cartilaginous  the  chorda  becomes  smaller,  but  it  still  remains  larger  in  the  inter- 
vertebral disks.  The  body  of  the  first  vertebra  or  atlas  unites  with  that  of  the 
axis  to  form  its  odontoid  process  (Rathke),  and,  in  addition,  it  forms  the  arcus 
anterior  atlantis  and  the  transverse  ligament  {Hasse).  The  chorda  can  be  followed 
upward  through  the  ligamentum  suspensorium  dentis  as  far  as  the  posterior  part  of 
the  sphenoid  bone. 

The  histogenetic  formation  of  cartilage  from  the  indifferent  formative  cells  takes  place  by 
division  and  growth  of  the  cells,  until  they  ultimately  form  clear  nucleated  sacks.  The  cement  sub- 
stance is  probably  formed  by  the  outer  parts  of  the  cells  (parietal  substance)  uniting  and  secreting 
the  intercellular  substance.  It  is  supposed  by  some  that  the  latter  contains  fine  canals,  which  connect 
tlie  protoplasm  of  the  adjoining  cells. 


FORMATION    OF   THE   AMNION    AND    ALLANTOIS.  881 

Visceral  Clefts  and  Arches. — Each  side  of  the  cervical  region  contains 
four   slit-like   openings — the    visceral  clefts    or 

branchial  openings  i Rathke)  ;    in  the  chick  the  y\q.  564. 

upper  three  are  formed  at  the  3d,  and  the 
fourth  on  the  4th  day.  Above  the  slits  are 
thickenings  of  the  lateral  wall,  which  constitute 
the  visceral  or  branchial  arches.  The 
clefts  are  formed  by  a  perforation  from  the  fore- 
gut,  but  which,  perhaps,  does  not  always  occur 
in  the  chick,  mammal  and  man  (His),  and  they 
are  lined  by  the  cells  of  the  hypoblast.  On 
each  side  in  each  viscera!  arch,  i.e.,  above  and 
below  each  cleft,  there  runs  an  aortic  arch,  five 
on  each  side  (Fig.  563,  IX).  These  aortic 
arches  persist  in  fishes.  In  man  all  the  slits 
close  except  the  uppermost  one,  from  which  the 
auditory  meatus,  the  tympanic  cavity,  and  the 
Eustachian  tube  are  developed  i^Huschke,  Rathke, 
.  Reichert).  The  four  visceral  arches  are,  for  the 
most  part,  made  use  of  later  for  other  forma-  Embrjo  of  the  mole  (  x  ?)■ 

tions  I  p.  8S9  ). 

Primitive  Mouth  and  Anus. — Immediately  under  the  fore-brain,  in  the 
middle  line,  is  a  thin  spot,  where  there  is  at  first  a  small  depression,  and  ulti- 
mately a  rupture,  forming  the  primitive  oral  aperture,  which  represents  both 
the  mouth  and  the  nose.  Similarly,  there  is  a  depression  at  the  caudal  end,  and 
the  depression  ultimately  deepens,  thus  communicating  with  the  hind-gut  to  form 
the  anus.  When  the  latter  part  of  the  process  is  incomplete  there  is  atresia  ani, 
or  imperforate  anus.  Several  processes  are  given  off  from  the  primitive  intestine, 
including  the  hypoblast  and  its  muscular  layers,  to  form  the  lungs,  the  liver,  the 
pancreas,  the  caecum  (in  birds),  and  the  allantois. 

The  extremities  appear  at  the  sides  of  the  body  as  short,  unjointed  stumps  or 
projections  at  the  3d  or  4th  week  in  the  human  embryo  (Fig.  564). 

444.   FORMATION    OF   THE  AMNION    AND  ALLANTOIS.— 

Amnion. — During  the  elevation  of  the  embryo  from  its  surroundings,  imme- 
diately in  front  of  the  head  (at  the  end  of  the  2d  day  in  the  chick),  there  rises  up 
a  fold  consisting  of  the  epiblast  and  the  outer  layer  of  the  mesoblast,  which 
gradually  extends  to  form  a  sort  of  hood  over  the  cephalic  end  of  the  embryo 
(VI,  A).  In  the  same  way,  but  somewhat  later,  a  fold  rises  at  the  caudal  end, 
and  between  both  along  the  lateral  borders  similar  elevations  occur,  the  lateral 
folds  (Fig.  563,  III,  A).  All  these  folds  grow  over  the  back  of  the  embryo  to 
meet  over  the  middle  line  posteriorly,  where  they  unite  at  the  3d  day  in  the  chick 
to  form  the  amniotic  sack.  Thus,  a  cavity  which  becomes  filled  with  fluid — the 
amniotic  fluid-s— is  developed  around  the  embryo  [so  that  the  embryo  really 
floats  in  the  fluid  of  the  amniotic  sack].  In  mammals,  also,  the  amnion  is  devel- 
oped very  early,  just  as  in  birds  (Fig.  563,  VII,  A).  From  the  middle  of  preg- 
nancy onward  the  amnion  is  applied  directly  to  the  chorion,  and  united  to  it  by 
a  gelatinous  layer  of  tissue,  the  tunica  medica  of  Bischoff. 

Amniotic  Fluid. — The  amnion,  and  the  allantois  as  well,  are  formed  only  in  mammals,  birds 
and  reptiles,  which  have  hence  been  called  amniota,  while  the  lower  vertebrates,  which  are  devoid 
of  an  amnion,  are  called  anamnia.  Composition. — The  amniotic  fiuid\%  a  clear,  serous,  alkaline 
fluid,  specific  gravity  1007  to  ion,  containing,  besides  epithelium,  lanugo  hairs,  )/^  to  2  per  cent, 
of  fixed  solids.  Among  the  latter  are  albumin  (yjto  \i  per  cent.), mucin,  globulin,  a  vitelline  like 
l)ody,  some  grape  sugar,  urea,  ammonium  carbonate,  ver)-  probably  derived  from  the  decomposi- 
tion of  urea,  sometimes  lactic  acid  and  kreatinin,  calcic  sulphate  and  phosjihate,  and  common 
salt.  -About  the  middle  of  pregnancy  it  amounts  to  about  1-1-5  k'lo- [2.2-3.3  ft>s.],  and  at  the 
end  about  0.5  kilo.     The  amniotic  fluid  is  of  fcetal  origin,  as  is  shown  bv  its  occurrence  in  birds, 

S6 


882  ALLANTOIS. 

and  is,  perhaps,  a  transudation  through  the  fatal  membranes.  In  mammals,  the  urine  of  the  foetus 
forms  part  of  it  during  the  second  half  of  pregnancy  (Gtisserow).  In  the  pathological  condition 
of  Hydramnion,  the  blood  vessels  of  the  uterine  mucous  membrane  secrete  a  watery  fluid.  The 
fluid  preserves  the  fa;tus,  and  also  the  vessels  of  the  foetal  membranes,  from  mechanical  injuries;  it 
permits  the  limbs  to  move  freely,  and  protects  them  from  growing  together;  and,  lastly,  it  is  import- 
ant for  dilating  the  os  uteri  during  labor.  The  amnion  is  capable  of  contraction  at  the  7th  day  in 
the  chick ;  and  this  is  due  to  the  smooth  muscular  fibres  which  are  developed  in  the  cutaneous 
plate  in  its  mesoblastic  portion  [/iema/t),  but  nerves  have  not  been  found. 

Allantois. — From  the  anterior  surface  of  the  caudal  end  of  the  embryo  there 
grows  out  a  small  double  projection,  which  becomes  hollowed  out  to  form  a  sack 
projecting  into  the  cavity  of  the  coelom  or  pleuro-peritoneal  cavity  (VI,  a);  it 
constitutes  the  allantois,  and  is  formed  in  the  chick  before  the  5th  day,  and  in 
man  during  the  2d  week.  Being  a  true  projection  from  the  hind-gut,  the  allan- 
tois has  two  layers,  one  from  the  hypoblast  and  the  other  from  the  muscular  layer, 
so  that  it  is  an  offshoot  from  the  si)lanchnopleure.  From  both  sides  there  pass  on 
to  the  allantois  the  umbilical  arteries  from  the  hypogastric  arteries,  and  they 
ramify  on  the  surface  of  the  sack.  The  allantois  grows,  like  a  urinary  bladder 
gradually  being  distended,  in  front  of  the  hind-gut  in  the  pleuro-peritoneal  cavity 
toward  the  umbilicus  ;  and,  lastly,  it  grows  out  of  the  umbilicus,  and  projects 
beyond  \X  alongside  the  omphalo-mesenteric  or  vitelline  duct,  its  vessels  growing 
with  it  (VII,  a)  ;  but  after  this  stage  it  behaves  differently  in  birds  and  mammals. 

In  birds,  after  the  allantois  passes  out  of  the  umbilicus,  it  undergoes  great  development,  so  that 
within  a  short  time  it  lines  the  whole  of  the  interior  of  the  shell  as  a  highly  vascular  and  saccular 
membrane.  Its  arteries  are  at  first  branches  of  the  primitive  aoitse,  but  with  the  development  of  the 
posterior  extremities  they  appear  as  branches  of  the  hypogastric  arteries.  Two  allantoidal,  or  um- 
bilical veins,  proceed  from  the  numerous  capillaries  of  the  allantois.  They  pass  backward  through 
the  umbilicus,  and  at  first  unite  with  the  omphalo-mesenteric  veins  to  joni  the  venous  end  of  the 
heart.  In  birds  this  circulation  on  the  allantois,  or  second  circulation,  is  respiratory  in  function, 
as  its  vessels  serve  for  the  exchange  of  gases  through  the  porous  shell.  This  circulation  gradually 
assumes  the  respiratory  functions  of  the  umbilical  vesicle,  as  the  latter  gradually  becomes  smaller 
and  smaller,  and  ceases  to  be  a  sufficient  respiratory  organ.  Toward  the  end  of  the  period  of  in- 
cubation, the  chick  may  breathe  and  cry  within  the  shell  (Aristotle) — a  proof  that  the  respiratory 
function  of  the  allantois  is  partly  taken  over  by  the  lungs.  The  allantois  is  also  the  excretory  organ 
of  the  urinary  constituents.  Into  its  cavity  in  mammals  the  ducts  of  the  priiiiitiie  kidneys,  or  the 
Wolffian  duets,  open,  but  in  birds  and  reptiles,  which  possess  a  cloaca,  these  open  into  the  posterior 
wall  of  the  cloaca.  The  primitive  kidneys,  or  Wolftian  bodies,  consist  of  many  glomeruli,  and 
empty  their  secretion  through  the  Wolffian  ducts  into  the  allantois  (in  birds  into  the  cloaca),  and 
the  secretion  passes  through  the  allantois,  per  the  umbilicus,  into  the  peripheral  part  of  the  urinary 
sack.  Remak  found  ammonium  and  sodium  urate,  allantoin,  grape  sugar,  and  salts  in  the  contents 
of  the  allantois.  From  the  eighth  day  onward,  the  allantois  of  the  chick  is  contractile  (  Vulpian), 
owing  to  the  presence  of  smooth  fibres  derived  from  the  splanchnopleure.  Lymphatics  accompany 
the  branches  of  the  arteries  (A.  BiiJi^'e). 

Allantois  in  Mammals. — In  mammals  and  man  the  relation  of  the  allantois 
is  somewhat  different.  The  first  part  or  its  origin  forms  the  urinary  bladder, 
and  from  the  vertex  of  the  latter  there  proceeds  through  the  umbilicus  a  tube,  the 
urachus,  which  is  open  at  first  (^VIII,  a).  The  blind  part  of  the  sack  of  the  al- 
lantois outside  the  abdomen  is  in  some  animals  filled  with  a  fluid  like  urine.  In 
man,  however,  this  sack  disappears  during  the  second  month,  so  ttiat  there  remains 
only  the  vessels  which  lie  in  the  muscular  part  of  the  allantois.  In  some  animals, 
however,  the  allantois  grows  larger,  does  not  shrivel,  but  obtains  through  the 
urachus  froin  the  bladder  an  alkaline  turbid  fluid,  which  contains  some  albumin, 
sugar,  urea,  and  allantoin.  The  relations  of  the  umbilical  vessels  will  be  described 
in  connection  with  the  foetal  membranes. 

445.  FCETAL  MEMBRANES,  PLACENTA,  FCETAL  CIRCU- 
LATION.— Decidua. — WHien  a  fecundated  ovum  reaches  the  uterus,  it  then 
becomes  surrounded  by  a  special  covering,  which  William  Hunter  ( 17 75)  described 
as  tiie  membrana  decidua,  because  it  was  shed  at  birth.  We  distinguish  the 
decidua  vera  1  Fig.  563,  \'11I,/),  which  is  merely  the  thickened,  very  vascular, 
softened,  more  spongy,  and   somewhat  altered   mucous  membrane  of  the  uterus. 


STRUCTURE    OF   THE    DECIDUA   VERA.  883 

[Sometimes  in  a  diseased  condition,  as  in  dysmenorrhcea,  the  superficial  layer  of 
the  uterine  mucous  membrane  is  thrown  off  nearly  en  masse  in  a  triangular  form 
(Fig.  565 ).  This  serves  to  show  the  shape  of  the  decidua,  which  is  that  of  the 
uterus.]  When  the  ovum  reaches  the  uterus  it  is  caught  in  a  cryi)t  or  fold  of  the 
decidua,  and  from  the  latter  there  grow  up  elevations  around  the  ovum  ;  but  these 
elevations  are  thin,  and  soon  meet  over  the  back  of  the  ovum  to  form  the  de- 
cidua reflexa  (VIII,  /-).  At  the  second  to  third  month  there  is  still  a  space  in 
the  uterus  outside  the  reflexa  ;  in  the  fourth  month  the  whole  cavity  is  filled  by 
the  ovum.  At  one  part  the  ovum  lies  directly  upon  the  d.  vera  [and  that  part  is 
spoken  of  as  the  decidua  serotina],  but  by  far  the  greatest  part  of  the  surface 
of  the  ovum  is  in  contact  with  the  reflexa.  In  the  region  of  the  d.  serotina  the 
placenta  is  ultimately  formed. 

Structure  of  the  Decidua  Vera. — The  d.  vera  at  the  third  month  is  4  to  7  mm.  thick,  and  at 
the  fourth  only  i  to  3  mm.,  and  it  no  longer  has  any  epithelium  ;  but  it  is  very  vascular,  and  is 
possessed  of  lymphatics  around  the  glands  and  blood  vessels  (Leopold),  and  in  its  loose  substance 
are  large  round  cells  (decidua  cells — A'd/liker),  which  in  the  deeper  parts  become  changed  into 
fibre  cells — there  are  also  lymphoid  cells.     The  uterine  glaiids,  which  become  greatly  developed  at 

Fig.  565. 


A  dysmenorrhceal  membrane  laid  open. 

the  commencement  of  pregnancy,  at  the  third  to  the  fourth  month  form  non-cellular,  wide,  bulging 
lubes,  which  become  indistinct  in  the  later  months,  and  in  which  the  epithelium  disappears  more 
and  more.  The  reflexa,  much  thinner  than  the  vera  from  the  middle  of  pregnancy,  is  devoid  of 
eoithelium,  and  is  without  vessels  and  glands.     Toward  the  end  of  pregnancy  both  deciduxe  unite. 

The  ovum,  covered  at  first  with  small  hollow  villi,  is  surrounded  by  the  decidua. 
From  the  formation  of  the  amnion  it  follows  that,  after  it  is  closed,  a  completely 
closed  sack  passes  away  from  the  embryo  to  lie  next  the  primitive  chorion.  This 
membrane  is  the  "serous  covering"  of  v.  Baer  (Fig.  563,  VII,  .f),  or  the  false 
amnion.  It  becomes  closely  applied  to  the  inner  surface  of  the  chorion,  and 
extends  even  into  its  villi.  The  allantois  proceeding  from  the  umbilicus  comes 
to  lie  directly  in  contact  with  the  ftetal  memb'rane  ;  its  sack  disappears  about  the 
second  month  in  man,  but  its  vascular  layer  grows  rapidly  and  lines  the  whole  of 
the  inner  surface  of  the  chorion,  where  it  is  found  on  the  eighteenth  day  ( Coste). 
From  the  fourth  week  the  blood  vessels,  along  with  a  covering  of  connective 
tissue,  branch  and  penetrate  into  the  hollow  cavities  of  the  villi,  and  completely 
fill  them.     At  this  time  the  primitive  chorion  disappears.     Thus  we  have  a  stage 


884  PLACENTA. 

of  general  vascularization  of  the  chorion.  In  the  place  of  the  derivative  of  the 
zona  pellucida  we  have  the  vascular  villi  of  the  allantois,  which  are  covered  by 
the  epiblastic  cells  derived  from  the  false  amnion.  This  stage  lasts  only  until  the 
third  month  ;  when  the  chorionic  villi  disappear  all  over  the  surface  of  the  ovum 
in  contact  with  the  decidua  reflexa.  On  the  other  hand,  the  villi  of  the  chorion, 
where  they  lie  in  direct  contact  with  the  decidua  serotina,  become  larger  and  more 
branched.     Thus  there  is  distinguished  the  chorion  laeve  and  c.  frondosum. 

The  chorion  laeve,  which  consists  of  a  connective-tissue  matrix  covered  externally  by  several 
layers  of  cells,  has  a  few  isolated  villi  at  wide  intervals.  Between  the  chorion  and  the  amnion  is 
a  gelatinous  substance  (membrana  intermedia)  or  undeveloped  connective  tissue. 

Placenta. — The  large  villi  of  the  chorion  frondosum  penetrate  into  the  tissue 
of  the  decidua  serotina  of  the  uterine  mucous  membrane.  [It  was  formerly  sup- 
posed that  the  chorionic  villi  entered  the  mouths  of  the  uterine  glands,  but  the 
researches  of  Ercolani  and  Turner  have  shown  that,  although  the  uterine  glands 
enlarge  during  the  early  months  of  utero-gestation,  the  villi  do   not   enter  the 

Fig.  566. 


Hum.in  pl.-icent.ll  villi.     Blood 


glands.  The  villi  enter  the  crypts  of  the  uterine  mucous  membrane.  The  glands 
of  the  inner  layer  of  the  decidua  serotina  soon  disappear.]  As  the  villi  grow  into 
the  decidua  serotina  they  push  against  the  walls  of  the  large  blood  vessels,  which 
are  similar  to  capillaries  in  structure,  so  that  the  villi  come  to  be  bathed  by  the 
blood  of  the  mother  in  the  uterine  sinuses,  or  they  float  in  the  colossal  decidual 
capillaries  (VIII,  b).  The  villi  do  not  float  naked  in  the  maternal  blood,  but 
thpy  are  covered  by  a  layer  of  cells  derived  from  the  decidua.  Some  villi,  with 
bulbous  ends,  unite  firmly  with  the  tissue  of  the  uterine  part  of  the  placenta  to 
form  a  firm  bond  of  connection.  [The  placenta  is  formed  by  the  mutual  inter- 
growth  of  the  chorionic  villi  and  the  decidua  serotina.]  Thus,  it  consists  of  a 
foetal  part,  including  all  the  villi,  and  a  maternal  or  uterine  part,  which  is 
the  very  vascular  decidua  serotina.  At  the  time  of  birth,  both  parts  are  so  firmly 
united  that  they  cannot  be  separated.  Around  the  margin  of  the  placenta  is  a 
large  venous  vessel,  the  marginal  sinus  of  the  placenta.  [Friedlander  found  the 
uterine  sinuses  below  the  placental  site  blocked  by  giant  cells  after  the  8th  month 


STRUCTURE   OF   THE    UMBILICAL    CORD.  885 

of  pregnancy.  Leopold  confirms  this,  and  found  the  same  in  the  serotinal  veins.] 
Functions. — The  placenta  is  the  nutritive,  excretory,  and  respiratory  organ  of 
the  fLetus  (§  368) ;  the  latter  receives  its  necessary  pabulum  by  endosmosis  from 
the  maternal  sinuses  through  the  coverings  and  vascular  wall  of  the  villi  in  which 
the  fcetal  blood  circulates.     [The  placenta  also  contains  ^/irc^if//.] 

[Structure. — If  a  piece  of  a  fresh  placenta  be  leased  in  normal  saline  solution,  one  sees  the 
structure  at  once.  The  villi  are  provided  with  lateral  otTshoots,  and  consist  of  a  connective-tissue 
framework,  containing  a  capillary  network  with  arteries  and  veins  (Fig.  566),  while  the  villi  them- 
selves are  covered  by  a  layer  of  somewhat  cubical  epithelium.] 

Uterine  Milk. — Between  the  villi  of  the  placenta  there  is  a  clear  fluid  which 
contains  numerous  small  albuminous  globules,  and  this  fluid,  which  is  abundant 
in  the  cow,  is  spoken  of  as  the  uterine  milk.  It  seems  to  be  formed  by  tiie  break- 
ing up  of  the  decidual  cells.  It  has  been  supposed  to  be  nutritive  in  function. 
[The  maternal  placenta,  therefore,  seems  to  be  a  secreting  structure,  while  the 
fcetal  part  has  an  absorbing  function.  The  uterine  milk  has  been  analyzed  by 
Gamgee,  who  found  that  it  contained  fatty,  albuminous,  and  saline  constituents, 
while  sugar  and  casein  were  absent.] 

The  investigations  of  Walter  show  that  after  poisoning  pregnant  animals  with  strychnin,  morphia, 
veratrin,  curara,  and  ergotin,  these  substances  are  not  found  in  the  foetus,  although  many  other 
chemical  substances  pass  into  it. 

[Savory  fouiid  that  strychnin  injected  into  a  foetus  in  utero  caused  tetanic  convulsions  in  the 
mother  (bitch),  while  syphilis  may  be  communicated  from  the  father  to  the  mother  through  the 
medium  of  the  fcetus  (Hutchinson).  A.  Harvey's  record  of  observations  on  the  crossing  of  breeds 
of  animals— chiefly  of  horses  and  allied  species — show  that  materials  can  pass  from  the  foetus  to 
the  mother.] 

On  looking  at  a  placenta,  it  is  seen  that  its  villi  are  distributed  on  large  areas  separated  from  each 
other  by  depressions.  This  complex  arrangement  might  be  compared  with  the  cotyledons  of  some 
animals. 

The  position  of  the  placenta  is,  as  a  rule,  on  the  anterior  or  posterior  wall  of  the  uterus,  more 
rarely  on  the  fundus  uteri,  or  laterally  from  the  opening  of  the  Fallopian  tube,  or  over  the  internal 
orifice  of  the  cervix,  the  last  constituting  the  condition  of  placenta  praevia,  which  is  a  very  dan- 
gerous form  of  placental  inserti  m,  as  the  placenta  has  to  be  ruptured  before  birth  can  take  place, 
so  that  the  mother  often  dies  from  hemorrhage.  The  umbilical  cord  may  be  inserted  in  the  centre 
of  the  placenta  (insertio  centralis),  or  more  towar<l  the  margin  (ins.  marginalis],  or  the  cord  may 
be  fixed  to  the  chorion  laeve.  .Sometimes,  though  rarely,  there  are  small  subsidiary  placenta  (pi. 
sitccenturiutii),  m  addition  to  the  Urge  one  (Hvrtl).  When  the  placenta  consists  of  two  halves,  it 
is  called  duplex  or  bipartite,  a  condition  said  by  Hyrtl  to  be  constant  in  the  apes  of  the  old  world. 

Structure  of  the  Cord. — The  umbilical  cord  ('48  to  60  cm.  [20  to  24  inches] 
long,  II  to  13  mm.  thick)  is  covered  by  a  sheath  from  the  amnion.  The  blood 
vessels  make  about  forty  spiral  turns,  and  they  begin  to  appear  about  the  2d 
month.  [The  cause  of  the  twisting  is  not  well  understood,  but  Virchow  has 
shown  that  capillaries  pass  from  the  skin  for  a  short  distance  on  the  cord,  and 
they  do  so  unequally,  and  it  may  be  that  this  may  aid  in  the  production  of  the 
torsion.]  It  contains  two  strongly  muscular  and  contractile  arteries,  and  one 
umbilical  vein.  The  two  arteries  anastomose  in  the  placenta  (^Hyrll).  In  addi- 
tion, the  cord  contains  the  continuation  of  the  urachus,  the  hypoblastic  portion 
of  the  allantois  (VIII,  a),  which  remains  until  the  second  month,  but  afterward 
is  much  shrivelled.  The  omphalo-mesenteric  d'lct  of  the  umbilical  vesicle  (N)  is 
reduced  to  a  thread-like  st.ilk  (VIII,  D).  Wharton's  jelly  surrounds  the 
umbilical  blood  vessels.  Wharton's  jelly  is  a  gelatinous-like  connective  tissue, 
consisting  of  branched  corpuscles,  lymphoid  cells,  some  connective-tissue  fibrils, 
and  even  elastic  fibres.  It  yields  mucin.  It  is  traversed  by  numerous  juice 
canals  lined  by  endothelial  cells,  but  other  blood  and  Ivmphatic  vessels  are  absent. 
Nerves  occur  3-8-1 1  cm.  from  the  umbilicus  (Sc/wlf,  Valentiti). 

The  foetal  circulation,  which  is  established  after  the  development  of  the 
allantois,  has  the  following  course  :  The  blood  of  the  foetus  passes  from  the  hypo- 
gastric arteries  through  the  two  umbilical  arteries,  through  the  umbilical  cord  to 
the  placenta,  where  the  arteries  split  up  into  capillaries.     The  blood  is  returned 


886  CHRONOLOGY  OF  HUMAN  DEVELOPMENT. 

from  the  placenta  by  the  umbilical  vein,  although  the  color  of  the  blood  cannot 
be  distinguished  from  the  venous  or  impure  blood  in  the  umbilical  arteries.  The 
umbilical  vein  (Fig.  573,  3,  //),  returns  to  the  umbilicus,  passes  upward  under  the 
margin  of  the  liver,  gives  a  branch  to  the  vena  port.-e  (a),  and  runs  as  the  ductus 
venosus  into  the  inferior  vena  cava,  which  carries  the  blood  into  the  right 
auricle.     Directed  by  the  Eustachian  valve  and  the  tubercle  of  Lower  (Fig.  570, 

6,  /,  L),  the  great  mass  of  the  blood  passes  through  the  foramen  ovale  into  the 
left  auricle,  from  which  it  cannot  pass  backward  into  the  right  auricle,  owing  to 
the  presence  of  the  valve  of  the  foramen  ovale.  From  the  left  auricle  it  passes 
into  the  left  ventricle,  aorta  and  hypogastric  arteries,  to  the  umbilical  arteries. 
The  blood  of  the  superior  vena  cava  of  the  foetus  passes  from  the  right  auricle 
into  the  right  ventricle  (Fig.  570,  6,  Cs).  From  the  right  ventricle  it  passes  into 
the  pulmonary  artery  (Fig.  570,  7,/),  and  through  the  ductus  arteriosus  of 
Botalli  (B)  into  the  aorta.  There  are,  therefore,  two  streams  of  blood  in  the 
right  auricle  which  cross  each  other,  the  descending  one  from  the  head  through 
the  superior  vena  cava,  passing  in  front  of  the  transverse  one  from  the  inferior 
vena  cava  to  the  foramen  ovale.]  Only  a  small  amount  of  the  blood  passes 
through  the  as  yet  small  branches  of  the  pulmonary  artery  to  the  lungs  (Fig.  570, 

7,  7,  2).  The  course  of  the  blood  makes  it  evident  that  the  head  and  upper 
limbs  of  the  foetus  are  nourished  by  purer  blood  than  the  remainder  of  the  trunk, 
which  is  supplied  with  blood  mixed  with  the  blood  of  the  superior  vena  cava. 
After  birth  the  umbilical  arteries  are  obliterated,  and  become  the  lateral  liga- 
ments of  the  bladder,  while  their  lower  parts  remain  as  the  superior  vesical  arte- 
ries. The  umbilical  vein  is  obliterated,  and  remains  as  the  ligamentum  teres,  or 
round  ligament  of  the  liver,  and  so  is  the  ductus  venosus  Arantii.  Lastly,  the 
foramen  ovale  is  closed,  and  the  ductus  arteriosus  is  obliterated,  the  latter  form- 
ing the  lig.  arteriosus. 

The  condition  of  the  membranes  where  there  are  more  foetuses  than  one:  (i)  With  twins 
there  are  two  completely  separated  ova,  with  two  placenta:  and  two  deciduse  reflexx.  (2)  Two 
completely  separate  ova  may  have  only  one  refle.\a,  whereby  the  placenti-e  grow  together,  while 
their  blood  vessels  remain  distinct.  The  chorion  is  actually  double,  but  cannot  be  separated  into 
two  lamelLi;  at  the  point  of  union.  (3)  One  reflexa,  one  chorion,  one  placenta,  two  umbilical 
cords  and  two  amnia.  The  vessels  anastomose  in  the  placenta.  In  this  case  there  is  one  ovum 
with  a  double  yelk,  or  with  two  germinal  vesicles  in  one  yelk.  (4)  As  in  (3),  but  only  one  amnion, 
caused  by  the  formation  of  two  embryos  in  the  same  blastoderm  of  the  same  germinal  vesicle. 

Formation  of  the  foetal  membranes  in  animals. — The  oldest  mammals  have  no  placenta  or 
umbilical  vessels;  these  are  the  Mammalia  implacentalia  ( Ciccw),  including  the  monotremala 
and  marsupials.  The  second  group  includes  the  Mammalia  placentalia.  Among  these  (a)  the 
non-deciduata  possess  only  chorionic  villi  supplied  by  the  umbilical  vessels,  which  project  into  the 
depressions  of  the  uterine  mucous  membrane,  and  from  which  they  are  pulled  out  at  birth  (PI.  dif- 
fusa, e.g.,  pachydermata,  cetacea,  solidungula.  camclid*).  In  the  ruminants  the  villi  are  arranged 
in  groups  or  cotyledons,  which  grow  into  the  uterine  mucous  membrane,  from  which  they  are 
pulled  out  at  birth,  (b)  In  the  deciduata  there  is  such  a  firm  union  between  the  choiionic  villi 
with  the  uterine  mucous  membrane,  that  the  uterine  part  of  the  placenta  comes  away  with  the  fo;tal 
part  at  birth.  In  this  case  the  placenta  is  either  zonary  (carnivora,  pinnipedia,  elephant),  or  dis- 
coid (apes,  insectivora,  edentata,  rodentia). 

446.  CHRONOLOGY  OF  HUMAN  DEVELOPMENT.— Development  during  the 
ist  Month. — At  the  I2th-i3th  day  the  ovum  is  saccular  (5.5  mm.  and  3  mm.  in  diameter) ;  there  is 
simply  the  blastodermic  vesicle,  with  the  blastoderm  at  one  part,  consisting  of  two  layers;  the  zona 
pellucida  beset  with  small  villi  (Reichert).  At  the  I5th-l6(h  day  the  ovum  (5-6  mm.)  is  covered 
with  simple  cylindrical  villi.  The  zona  pellucida  consists  of  embryonic  connective  tissue  covered 
with  a  layer  of  flattened  epithehum.  The  prhnitive  groove  and  the  lamina:  dorsales  appear.  Then 
follows  the  stage  when  the  allantois  is  first  formed.  At  the  I5th-l8th  day  Coste  investigated  an 
ovum.  It  was  1 3.2  mm.  long,  with  small  branched  villi ;  the  embryo  itself  was  2.2  mm.  long,  of  a 
curved  form,  and  with  a  moderately  enlarged  cephalic  end.  The  amnion,  umbilical  vesicle  with  a 
wide  vitelline  duct,  and  the  allantois  were  developed,  the  last  already  united  lo  the  false  amnion. 
The  S-shaped  heart  lies  in  the  cardiac  cavity,  shows  a  cavity  and  a  bulbus  aorta:,  but  neither 
auricles  nor  ventricles.  The  visceral  arches  and  clefts  are  indicated,  but  they  are  not  perforated. 
The  omphalomesenteric  vessels  forming  the  first  circulation  on  the  umbilical  vesicle  are  developed, 
the  duct  (vitelline)  is  still  quite  open,  and  two  primitive  aorts:  run  in  front  of  the  protovertebrce. 
The  allantois  attached  to  the  fcetal  membranes  is  provided  with  blood  vessels.     The  two  omphalo- 


CHRONOLOGY   OF   HUMAN    DEVELOPMENT. 


887 


mesenteric  veins  unite  with  the  two  umbilical  veins,  and  pass  to  the  venous  end  of  the  heart.  The 
mouth  is  in  process  of  formation.  The  limbs  and  sense  organs  absent ;  the  WoltiSan  bodies  pro- 
bably present. 

At  the  20th  day  all  the  visceral  arches  are  formed,  and  the  clefts  are  perforated.  The  mid-brain 
forms  the  highest  part  of  the  brain,  while  the  two  auricles  appear  in  the  heart.  The  connection  with 
the  umbilical  vesicle  is  still  moderately  wide.  The  embryo  is  2.6-3.3-4  mm.  long,  while  the  head 
is  turned  to  one  side  (His).  At  a  slightly  later  period  the  temporal  and  cervical  flexures  take  place, 
and  the  hemispheres  appear  more  prominently ;  the  vitelline  duct  is  narrowed,  the  position  of  the 
liver  is  indicated,  while  the  limbs  are  still  absent  [His). 

At  the  2ist  day  the  ovum  is  13  mm.  long  and  the  embryo  4-4.5  mm. ;  the  umbilical  vesicle  2.2 
mm.,  and  the  intestine  almost  closed.  Three  branchial  clefts.  Wolffian  lx)dies  laid  down,  and  the 
first  appearance  of  the  limbs,  three  cerebral  vesicles,  auditory  capsules  present  [R.  ll'agiur).  Coste 
also  observed,  in  addition,  the  nasal  pits,  eve,  the  opening  for  the  mouth,  with  the  frontal  and  supe- 
rior ma.xillary  processes,  the  heart  with  two  ventricles  and  two  auricles. 

Knd  of  the  ist  Month. — The  embryos  of  25-2S  days  are  characterized  by  the  distinctly  stalked 
condition  of  the  umbilical  vesicle  and  the  distinct  presence  of  limbs.  Size  of  the  ovum,  17.6  mm.; 
embryo,  13  mm.  ;  umbilical  vesicle,  4.5  mm.,  with  blood  vessels. 

2d  Month. — The  embryos  of  28-35  days  are  more  elongated,  and  all  the  branchial  clefts  are 
closed  e.xcept  the  first.  The  allantois  has  now  only  three  vessels,  as  the  right  umbilical  vein  is  ob- 
literated. .\t  the  5th  week  the  nasal  pits  are  united  by  furrows  with  the  angle  of  the  mouth,  which 
close  to  form  canals  at  the  6th  week  { Toldt).  At  35-42  days  the  nasal  and  oral  orifices  are  sepa- 
rated, the  face  is  flat,  the  limbs  show  three  divisions,  the  toes  are  not  so  sharply  defined  as  the  fingers. 
The  outer  ear  appears  as  a  low  projection  at  the  7th  week.  The  Wolfiian  bodies  are  much  reduced 
in  size. 

End  of  the  2d  Month. ^Ovum,  6;^  cm.;  villi,  1.3  mm.  long;  the  circulation  on  the  umbilical 
vesicle  has  disappeared ;  embryo,  26  mm.  long,  and  weighs  4  grammes.  Eyelids  and  nose  present, 
umbilical  cord  8  mm.  long,  ab .Nominal  cavity  closed,  ossification  beginning  in  the  lower  jaw,  clavicle, 
ribs,  bodies  of  the  vertebr.'e  ;  sex  indistinct,  kidneys  laid  down. 

3d  Month. — Ovum  as  large  as  a  goose's  egg,  beginning  of  the  placenta,  embryo  7-9  cm.,  weigh- 
ing 20  grammes,  and  is  now  spoken  of  as  ^  feetus.  External  ear  well  formed,  umbilical  cord  7  cm. 
long.  Beginning  of  the  diflerence  between  the  sexes  in  the  external  genitals,  umbilicus  in  the  lower 
fourth  of  the  linea  alba. 

4th  Month. — Foetus,  17  cm.  long,  weighing  120  grammes,  sex  distinct,  hair  and  nails  beginning 
to  be  formed,  placenta  weighs  So  grammes,  umbilical  cord  19  cm.  long,  umbilicus  above  the  lowest 
fourth  of  the  linea  alba,  contractions  or  movements  of  the  limbs,  meconium  in  the  intestine,  skin 
with  blood  vessels  shining  through  it,  eyelids  closed. 

5th  Month. — Foitus,  18  to  27  cm.,  weighing  284  grammes ;  hair  on  the  head  and  lanugo  dis- 
tinct; skin  still  somewhat  red  and  thin,  and  covered  with  vernix  caseosa  (§  287,  2),  is  less  trans- 
parent; weight  of  placenta,  178  grammes  ;  umbilical  cord,  31  cm.  long. 

6th  Month. — Foetus,  28  to  34  cm.,  weighing  634  grammes:  lanugo  more  abundant;  vernix  more 
abundant;  testicles  in  the  abdomen;  pupillary  membrane  and  eyelashes  present;  meconium  in  the 
large  intestine. 

7th  Month. — Foetus,  28.34  cm.  long,  weighing  1218  grammes,  the  descent  of  the  testicles  begins 
— one  testicle  in  the  inguinal  canal,  the  eyes  open,  the  pupillary  membrane  often  absorbed  at  its 
centre  in  the  28th  week.  In  the  brain  other  fissures  are  formed  besides  the  primary  ones.  The 
fieius  is  capable  of  living  independently.  At  the  beginning  of  this  month  there  is  a  centre  of  ossi- 
fication in  the  os  calcis. 

8th  Month. — Fo;tus,  42  cm.,  weighing  1.5  to  2  kilos,  {i.;^  to  4.4  lbs.),  hair  of  the  head  abun- 
dant, t.3  cm.  long,  nails  with  a  small  margin,  umbilicus  below  the  middle  of  the  linea  alba,  one 
testicle  in  the  scrotum. 

gth  Month. — Fretus,  47  cm.,  weighing  2'/^  kilos.  (5.5  lbs.),  and  is  not  distinguishable  from  the 
child  at  the  full  period. 

Foetus  at  the  Full  Period. — Length  of  body,  51  cm.  [20  inches],  weight  3J{  kilos.  [7  lbs.], 
lanugo  present  only  on  the  slioulders,  skin  white.  The  nails  of  the  fingers  project  beyond  the  tips 
of  the  fingers,  umbilicus  slightly  below  the  middle  of  the  linea  alba.  The  centre  of  ossification  in 
the  lower  epiphysis  of  the  femur  is  4  to  S  mm.  broad. 


Days. 

Coluber 12 

Hen \ 

Duck J  ^' 

Goose 29 

Stork 42 

Cassowary     ....  65 
Mouse 24 


Rabbit 
Hare 


Period  of  Gestation  or  Incubation. 

Days 


Rat  ...  . 
Guinea  pig 
Cat  ...  . 
Marten     ,    . 


Dog  .  . 
Fox  .  . 
Foumart 
Badger  . 
Wolf  . 
Lion  .    . 


14 


Sheep  .  . 
Goat  .  ,  . 
Roe  .  .  . 
Bear  .  .  . 
Small  apes 
Deer    .    .    . 


Pig 17I  Woman 


36-40 
40 


Horse,  Camel,  13  months;   Rhinoceros,  18  months;  and  the  Elephant,  24  months  (Sc/ieitt). 
Limitation  of  the  supply  of  O  to  eggs,  during  inculiation,  leads  to  the  formation  of  dwarf  chicks. 


888  FORMATION    OF   THE    OSSEOUS   SYSTEM. 

447.  FORMATION  OF  THE  OSSEOUS  SYSTEM.— Vertebral  Column.— The  ossi- 
fication of  the  verlehr.i:  begins  at  the  Sth  to  the  9th  week,  and  first  of  all  there  is  a  centre  in  each 
vertebral  aich,  then  a  centre  is  formed  in  the  body  behind  the  chorda  {Robin),  which,  however,  is 
composed  of  two  closely  apposed  centres.  At  the  5th  month  the  osseous  matter  has  reached  the 
surface,  the  chorda  within  the  body  of  the  vertebra  is  compressed  ;  the  three  parts  unite  in  the  1st 
year.  The  atlas  has  one  centre  in  the  anterior  arch  and  two  in  the  posterior  ;  they  unite  at  the  3d 
year.  The  epistropheus  has  a  centre  at  the  1st  year.  The  three  points  of  the  sacral  vertebrns  unite 
or  anchylose  between  the  2d  and  the  6th  year,  and  all  the  vertebra;  (sacral)  become  united  to  form 
one  body  between  the  iSth  and  25th  years.  Each  of  the  four  coccygeal  vertebra;  has  a  centre  from 
the  1st  to  loth  year.  The  vertebrce  in  later  years  produce  I  to  2  centres  in  each  process;  i  to  2 
centres  in  each  transverse  process  ;  i  in  the  mammillary  process  of  the  lumbar  vertebra; ;  and  one 
in  each  articular  process  (8  to  15  years).  Of  the  upper  and  under  surfaces  of  the  body  of  a  vertebra 
each  forms  an  epiphysial,  thin  osseous  plate,  which  may  still  be  visible  at  the  20th  year.  Groups  of 
the  cells  of  the  chorda  are  still  to  be  found  within  the  intervertebral  disks.  As  long  as  the  coccy- 
geal vertebne,  the  odontoid  process,  and  the  base  of  the  skull  are  cartilaginous,  they  still  contain 
the  remains  of  the  chorda  [H.  Midler).  The  coccygeal  vertebra:  form  the  tail,  and  they  originally 
project  in  man  like  a  tail  (Fig.  563,  IX,  T),  which  is  ultimately  covered  over  by  the  growth  of  the 
soft  parts  (His). 

The  ribs  bud  out  from  the  protovertebrre,  and  are  represented  on  each  vertebra.  The  thoracic 
ribs  become  cartilaginous  in  the  2d  month  and  grow  forward  into  the  wall  of  the  chest,  whereby  the 
seven  upper  ones  are  united  by  a  median  portion  (Kathie),  which  represents  the  position  of  one- 
half  of  the  sternum,  and  when  the  two  halves  meet  in  the  middle  line  the  sternum  is  formed.  When 
this  does  not  occur  we  have  the  condition  of  cleft  sternum.  At  the  6th  month  there  is  a  centre 
of  ossification  in  the  manubrium,  then  4  to  13  in  pairs  in  the  body,  and  I  in  the  ensiform  process. 
Each  rib  has  a  centre  of  ossification  in  its  body  at  the  2d  month,  and  at  the  8th  to  14th  one  in  the 
tubercle  and  another  in  the  head.  These  anchylose  at  the  14th  to  25th  year.  Sometimes  cervical 
ribs  are  present  in  man,  and  they  are  largely  developed  in  birds. 

The  skull. — The  chorda  extends  forward  into  the  axial  part  of  the  base  to  the  sphenoid  bone. 
The  skull  at  first  is  membranous,  or  the  primordial  cranium  ;  at  the  second  month  the  basal 
portion  becomes  cartilaginous,  including  the  occipital  bone,  except  the  upper  half,  the  anterior 
and  posterior  part  and  wings  of  the  sphenoid  bone,  the  petrous  part  and  mastoid  process  of  the  tem- 
poral bone,  the  ethnoid  with  the  nasal  septum,  and  the  cartilaginous  part  of  the  nose.  The  other 
parts  of  the  skull  remain  membranous,  so  that  there  is  a  cartilaginous  and  a  membranous  primor- 
dial cranium. 

I.  The  occipital  bone  has  a  centre  of  ossification  in  the  basilar  part  of  the  3d  month,  and  one 
in  the  condyloid  part  and  another  in  the  fossa  cerebelli,  while  there  are  two  centres  in  the  mem- 
branous cerebral  fossfe.  The  four  centres  of  the  body  unite  during  intra-uterine  life.  All  the  other 
parts  unite  at  the  1st  to  2d  year. 

II.  The  post-sphenoid. — From  the  3d  month  it  has  two  centres  in  the  sella  turcica,  two  in  the 
sulcus  caroticus,  two  in  both  great  wings,  which  also  form  the  lamina  externa  of  the  pterygoid  pro- 
cess, while  the  non-cartilaginous  and  previously  formed  inner  lamina  arises  from  the  superior  max- 
illary process  of  the  first  branchial  arch.  During  the  fir»t  half  of  foetal  life  these  centres  unite  as 
far  as  the  great  wings ;  the  dorsum  sella;  and  the  clinoid  process,  as  far  as  the  synchondrosis  spheno- 
occipitalis,  are  still  cartilaginous,  but  they  ossify  at  the  13th  year. 

III.  The  pre-sphenoid  at  the  8th  month  has  two  centres  in  the  small  wings  and  two  in  the 
body.     At  the  6th  month  they  unite,  but  cartilage  is  still  found  within  them  even  at  the  13th  year. 

IV.  The  ethmoid  has  a  centre  in  the  labyrinth  at  the  5th  month,  then  in  the  ist  year  a  centre 
in  the  central  lamina.     They  unite  about  the  5th  or  6th  year. 

V.  Among  the  membranous  bones  are  the  inner  lamina  of  the  pterygoid  process  (one  centre), 
the  upper  half  of  the  tabular  plate  of  the  occipital  (two  points),  the  parietal  bone  (one  centre  in 
the  parietal  eminence),  the  frontal  bone  (one  double  centre  in  the  frontal  eminence),  three  small 
centres  in  the  nasal  spine,  spina  trochlearis  and  zygomatic  process,  nasal  (one  centre),  the  edges  of 
the  parietal  bones  (one  centre),  the  tympanic  ring  (one  centre),  the  lachrymal,  vomer,  and  inter- 
maxillary bone. 

The  facial  bones  are  intimately  related  to  the  transformations  of  the  branchial  archa  and 
branchial  clefts.  The  median  end  of  the  first  branchial  arch  projects  inward  from  each  side 
toward  the  large  oral  aperture.  It  has  two  processes,  the  superior  maxillary  process,  which 
grows  more  laterally  toward  the  side  of  the  mouth,  and  the  inferior  maxillary  process,  which 
surrounds  the  lower  margin  of  the  mouth  (Fig.  563,  IX).  From  above  downward  there  grows  as 
an  elongation  of  the  basis  cranii  the  frontal  process  (.t),  a  broad  process  with  a  point  (r)  at  its 
lower  and  outer  angle,  the  inner  nasal  process.  The  frontal  and  the  superior  maxillary  processes 
(r)  unite  with  each  other  in  such  a  way  that  the  former  projects  between  the  two  latter.  At  the 
same  time  there  is  anchylosed  with  the  superior  maxillary  process  the  small  external  nasal  process 
(«),  a  prolongation  of  the  lateral  part  of  the  skull,  and  lying  above  the  superior  maxillary  process. 
Between  the  latter  and  the  outer  nasal  process  is  a  slit  leading  to  the  eye  (<?).  Thus  the  mouth  is 
cut  off  from  the  nasal  apertures  which  lie  above  it.  But  the  separation  is  continued  also  within  the 
mouth;  the  superior  maxillary  process  produces  the  upper  jaw, the  nasal  process, and  the  intermax- 


BRACHIAL   CLEFTS    AND   THEIR    RELATION   TO    NERVES.  889 

illary  process  {Goethe') — the  latter  is  present  in  man,  but  is  united  to  the  upper  jaw.  The  inter- 
maxillary bone,  which  in  many  animals  remains  as  a  separate  bone  (os  incisivuml,  carries  the 
incisor  teeth.  At  the  gth  week  the  hard  palate  is  closed,  and  on  it  rests  the  septum  of  the  nose, 
descending  vertically  from  the  frontal  process.  The  lower  jaw  is  formed  from  the  inferior  maxil- 
lary process.  At  the  circumference  of  the  oral  aperture  the  lips  and  the  alveolar  walls  are  formed. 
The  tongue  is  formed  behind  the  point  of  the  union  of  the  second  and  third  branchial  arches  {His) ; 
while,  according  to  Born,  it  is  formed  by  an  intermediate  part  between  the  inferior  ma.\illary  pro- 
cesses. 

These  transformations  may  be  interrupted.  If  the  frontal  process  remains  separate  from  the 
superior  maxillary  processes,  then  the  mouth  is  not  separated  from  the  nose.  This  separation  may 
occur  only  in  the  soft  parts,  constituting  hair-lip  (Fig.  567) ;  or  it  may  involve  the  hard  palate,  con- 
stituting cleft  palate.  Both  conditions  may  occur  on  one  or  both  sides.  From  the  po^terior  part 
of  the  first  branchial  arch  are  formed  the  malleus  {ossified  at  the  4th  month),  and  Meckel's  carti- 
lage (Fig.  568),  which  proceeds  from  the  latter  behind  the  tympanic  ring  as  a  long  cartilaginous 
process,  extending  along  the  inner  side  of  the  lower  jaw,  almost  to  its  middle.  It  disappears  after 
the  6th  month  ;  still  its  posterior  pirt  forms  the  inter  lal  lateral  ligament  of  the  maxillary  articula- 
tion. Near  where  it  leaves  the  malleus  is  the  processus  Folii  (Baumuller).  A  part  of  its  median 
end  ossifies,  and  unites  with  the  lower  jaw.  The  lower  jaw  is  laid  down  in  membrane  from  the 
first  branchial  arch,  while  the  angle  and  condyle  are  formed  from  a  cartilaginous  process.  The 
union  of  both  bones  to  form  the  chin  occurs  at  the  1st  year.  From  the  superior  maxillary  process 
are  formed  the  inner  lamella  of  the  pterygoid  process,  the  palatine  process  of  the  upper  jaw,  and 
the  palatine  bone  at  the  end  of  the  2d  month,  and,  lastly,  the  malar  bone. 

The  second  arch  [//v«'(/],  arising  from  the  temporal  bone,  and  running  parallel  with  the  first 
arch,  gives  rise  to  the  stapes  (although,  according  to  Salensky,  this  is  derived  from  the  first  arch), 
the  eminentia  pyramidalis,  with  the  stapedius  muscle,  the  incus,  the  styloid  process  of  the  temporal 

Fig.  567. 

Fig.  568. 


FiG.  567. — Hare-lip  on  the  left  side.  FiG.  568. — Inner  view  of  the  lower  jaw  of  an  embryo  pig  3  inches  long  (X  3^). 
wi,  Meckel's  ci'-tilage  ;  (/,  dent.try  bone;  rr,  coronoid  process;  a/*,  articular  process  (condyle);  a^,  angular 
process;  /«/,  malleus;  m^,  manubrium. 

bone,  the  (formerly  cartilaginous)  stylohyoid  ligament,  the  smaller  cornu  of  the  hyoid  bone,  and, 
lastly,  the  glosso- palatine  arch  (//is). 

The  third  arch  [lAyro/tyot'J]  forms  the  greater  cornu  and  body  of  the  hyoid  bone  and  the 
pharyngopalatine  arch  {//is). 

The  fourth  arch  gives  rise  to  the  thyroid  cartilage  {//is). 

Branchial  Clefts. — The  firsl  branchial  or  visceral  is  represented  by  the  external  auditory  meatus, 
the  tympanic  cavity,  and  the  Eustachian  tube  ;  all  the  other  clefts  close.  .Should  one  or  other  of 
the  clefts  remain  open,  a  c  mdition  that  is  sometimes  hereditary  in  some  families,  a  cervical  fistula 
results,  and  it  may  be  firmed  either  from  without  or  within.  Sometimes  only  a  blind  diverticulum 
remains.     Rranchiogenic  turn  irs  and  cysts  depend  upon  the  branchial  arches  {/!.   I'olkrnann). 

[Relation  of  Branchial  Clefts  to  Nerves. — It  is  important  to  note  that  the  clefts  in  front  of 
the  m^uth  (/>rt'-on;/),  and  those  behind  it  ( post-oral  ),ha.\t  a  relation  to  certain  nerves.  The 
lachrymal  slit  between  the  frontal  and  nasal  processes  is  supplied  by  the  first  division  of  the  tri- 
geminus. The  nasal  slit  between  the  superior  maxillary  process  and  the  nasal  process  is  supplied  by 
the  bifurcation  of  the  thin/  ner-je.  The  oral  cleft,  between  the  superior  maxillary  processes  and  the 
mandibular  arch,  is  supplied  by  the  second  and  third  divisions  of  the  trigeminus.  The  first  post- 
oral  or  tympanic- Eustachian  cleft,  between  the  mandibular  arch  (ist)  and  the  hyoid  arch,  is  sa^- 
plied  by  the /()r//o  r/K/-r7.  The  next  cleft  is  supplied  by  the  ^/oiw-/.inry«^t'rt/,  and  the  succeeding 
clefts  by  branches  of  the  vagus.^ 

The  thymus  and  thyroid  glands  are  formed  as  paired  diverticula  from  the  epithelium  covering 
the  branchial  arches.  The  epithelium  of  the  last  two  clefts  does  not  disappear  (pig),  but  proliferates 
and  pushes  inward  cylindrical  processes,  which  develop  into  two  epithelial  vesicles,  the  paired  com- 
mencement of  the  thyroid  glands.  These  vesicles  have  at  first  a  central  slit,  which  communicates 
with  the  pharynx  ( IVol/ler).     According  to  His,  the  thyroid  gland  appears  as  an   epithelial  vesicle 


890 


DEVELOPMENT   OF   THE    BONES   OF   THE    LIMBS. 


in  the  region  of  the  2d  pair  of  visceral  arches  in  front  of  the  tongue — in  man  at  the  4th  week.  Solid 
buds,  which  ultimately  become  hollow,  are  given  off  from  the  cavity  in  the  centre  of  the  embryonic 
thyroid  gland.  The  two  glands  ultimately  unite  together.  The  only  epithelial  part  of  the  thymus 
which  remains  is  the  so-called  concentric  corpuscles  (p.  178).  According  to  Born,  this  gland  is  a 
diverticulum  from  the  3d  cleft,  while  His  ascribes  its  origin  to  the  4th  and  5th  aortic  arches 
in  man  at  the  4th  week.  The  carotid  gland  is  of  epithelial  origin,  being  a  variety  of  the 
thyroid  {^Stiida). 

The  Extremities. — The  origin  and  course  of  the  nerves  of  the  brachial  plexus  show  that  the 
t4ppcr  exiretnily  was  originally  placed  much  nearer  to  the  cranium,  while  the  position  of  \ht  poste- 
rior pair  corresponds  to  the  last  lumbar  and  the  3d  or  4th  sacral  vertebrre  {His). 

The  clavicle,  according  to  Bruch,  is  not  a  membrane  bone,  but  is  formed  in  cartilage  like  the 
furculum  of  birds  (  Ce^evlHiui).  At  the  2d  month  it  is  four  times  as  large  as  the  upper  limb  ;  it  is 
the  first  bone  to  ossify  at  the  7th  week.  At  puberty  a  sternal  epiphysis  is  formed.  Episternal  bones 
must  be  referred  to  the  clavicles  ( Gotte).  Ruge  regards  pieces  of  cartilages  existing  between  the 
clavicle  and  the  sternum,  as  the  analogues  of  the  episternum  of  animals.  The  clavicle  is  absent  in 
many  mammals  (carnivora) ;  it  is  very  large  in  flying  animals,  and  in  the  rabbit  is  half  membranous. 
The  furculum  of  birds  represents  the  united  clavicles. 

The  scapula  at  first  is  united  with  the  clavicle  {Rathke,  Gotte),  and  at  the  end  of  the  2d  month 

Fig.  569. 


it  has  a  median  centre  of  ossification,  which  rapidly  extends.  Morphologically,  the  accessory  centre 
in  the  coracoid  process  is  interesting ;  the  latter  also  forms  the  upper  part  of  the  articular  surface. 
In  birds  the  corresponding  structure  forms  the  coracoid  bone,  and  is  united  with  the  sternum; 
while  in  man  only  a  membranous  band  stretches  from  the  tip  of  the  coracoid  process  to  the  sternum. 
The  long,  basal,  osseous  strip  corresponds  to  the  sitfrasiapiilar  bone  of  many  animals.  The  other 
centres  of  ossification  are —one  in  the  lower  angle,  two  or  three  in  the  acromion,  one  in  the  articular 
surface,  and  an  inconstant  one  in  the  spine.     Complete  consolidation  occurs  at  puberty. 

The  humerus  ossifies  at  the  8th  to  the  9th  week  in  its  shaft.  The  other  centres  are  —one  in  the 
upper  epiphysis,  and  one  in  the  capitellum  (ist  year) ;  one  in  the  great  tuberosity  and  one  in  the 
small  tuberosity  (2d  year) ;  two  in  the  condyles  (5th  to  loth  year) ;  one  in  the  trochlea  (12th  year). 
The  epiphyses  unite  with  the  shaft  at  the  i5th  to  20th  year. 

The  radius  ossifies  in  the  shaft  at  the  3d  month.  The  other  centres  are — -one  in  the  lower  epi- 
physis (5th  year),  one  in  the  upper  (6th  year),  and  an  inconstant  one  in  the  tuberosity,  and  one  in 
the  styloid  jarocess.     They  unite  at  puberty. 

The  ulna  also  ossifies  in  the  shaft  at  the  3d  month.  There  is  a  centre  in  the  lower  end  (6th  year), 
two  in  the  olecranon  (nth  to  14th  year),  and  an  inconstant  one  in  the  coronoid  process,  and  one  in 
the  styloid. process.     They  consolidate  at  puberty. 


CHEMICAL   COMPOSITION   OF   BONE.  891 

The  carpus  is  arranged  in  mammals  in  two  rows.  The  first  row  contains  three  bones — the 
radial,  intermediate  and  ulnar  bones.  In  man  these  are  represented  by  the  scaphoid,  semilunar 
and  cuneiform  bones;  the  pisii'orm  is  only  a  sesamoid  bone  in  the  tendon  of  the  flexor  carpi  ulnaris. 

The  second  row  really  consists  of  as  many  bones  as  there  are  digits  {eg.,  salamander).  In  man 
the  common  position  of  the  4th  and  5th  fingers  is  represented  by  the  unciform  bone.  Morphologic- 
ally, it  is  interesting  to  observe  that  an  os  centrale,  corresponding  to  the  os  carpale  centrale  of 
reptiles,  amphibians,  and  some  mammals,  is  formed  at  first,  but  disappears  at  the  end  of  the  3d 
month,  or  unites  with  the  scaphoid.  Only  m  very  rare  cases  is  it  persistent.  All  the  carpal  bones  are 
cartilaginous  at  birth.  They  ossify  as  follows :  Os  magnum,  unciform  ( 1st  year),  cuneiform  (3d  year), 
trapezium,  semilunar  (5lh  year),  scaphoid  (6th  year),  trapezoid  (7th  year),  and  pisiform  (12th  year). 

The  metacarpal  bones  have  a  centre  in  their  diaphyses  at  the  end  of  the  3d  month,  and  so 
have  the  phalanges.  All  the  phalanges  and  the  first  bone  of  the  thumb  have  their  cartilaginous 
epiphyses  at  the  central  end,  and  the  other  metacarpal  bones  at  the  peripheral  end,  so  that  the  first 
bone  of  the  thumb  is  to  be  regarded  as  a  phalanx.  The  epiphyses  of  the  metacarpal  bones  ossify  at 
the  2d,  and  those  of  the  phalanges  at  the  3d  year.     They  consolidate  at  puberty. 

The  innominate  bone,  when  cartilaginous,  consists  of  two  parts — the  pubis  and  the  ischium 
{Hosenberg).  Ossification  begins  with  three  centres — one  in  the  dium  (3d  to  4th  month),  one  in  the 
descending  ramus  of  the  ischium  (4th  to  5th  month),  one  in  the  horizontal  ramus  of  the  pubis  (5th 
to  7th  month).  Between  the  6th  to  the  14th  year  three  centres  are  formed  where  the  bodies  of  the 
three  bones  meet  in  the  acetabulum,  another  in  the  superficies  ouricularis,  and  one  in  the  symphysis. 
Other  accessory  centres  are  :  One  in  the  anterior  inferior  spine,  the  crest  of  the  ilium,  the  tuberosity 
and  the  spine  of  the  ischium,  the  tuberculum  pubis,  eminentia  ileopectinea,  and  floor  of  the  ace- 
tabulum. At  first  the  descending  ramus  of  the  pubis  and  the  a.'cending  ramus  of  the  ischium  unite 
at  the  7th  to  8th  year;  the   Y-shaped  suture  in  the  acetabulum  remains  until  puberty  (Fig.  569). 

The  femur  has  its  middle  centre  at  the  end  of  the  2d  month.  At  birth  there  is  a  centre  in  the 
lower  epiphysis  ;  slightly  later  in  the  head.  In  addition,  there  is  one  in  the  great  trochanter  (3d  to 
I  ith  year),  one  in  the  lesser  trochanter  (13th  to  14th  year),  two  in  the  condyles  (4th  to  8th  yearl  ; 
all  unite  about  the  time  of  puberty.  The  pattlla  is  a  sesamoid  bone  in  the  tendon  of  the  quadriceps 
femoris.     It  is  cartilaginous  at  the  2d  month,  and  ossifies  from  the  1st  to  the  3d  year. 

The  tarsus  generally  resembles  the  carpus.  The  os  calcis  ossifies  at  the  beginning  of  the  7th 
month,  the  astragalus  at  the  beginning  of  the  8th  month,  the  cuboid  at  the  end  of  the  loth,  the 
scaphoid  (ist  to  5th  year),  the  I  and  II  cuneiform  (3d  year),  and  the  III  cuneiform  (4th  year). 
An  accessory  centre  is  formed  in  the  heel  of  the  calcaneum  at  the  5lh  to  loth  year,  which  consoli- 
dates at  puberty. 

The  metatarsal  bones  are  formed  like  the  metacarpals,  only  later. 

[Histogenesis  of  Bone. — The  great  majority  of  our  bones  are  laid  down  in  cartilage,  or  are 
preceded  by  a  cartilaginous  stage,  including  the  bones  of  the  limbs,  backbone,  base  of  the  skull, 
sternum  and  ribs.  These  consist  of  solid  masses  of  hyaline  cartilage  covered  by  a  memb/ane, 
which  is  identical  with  and  ultimately  becomes  the  periosteum.  The  formation  of  bone,  when 
preceded  by  cartilage,  is  called  endochondral  bone.  Some  bones,  such  as  the  tabular  bones  of 
the  vault  of  the  cranium,  the  facial  bones,  and  part  of  the  lower  jaw,  are  not  preceded  by  cartilage. 
In  the  latter  there  is  merely  a  membrane  present,  while  from  and  in  it  the  future  bone  is  formed. 
It  becomes  the  future  periosteum  as  well.  This  is  called  the  intra-membranous  or  periosteal 
mode  of  formation.] 

[Endochondral  Formation. — (i)  The  cartilage  has  the  shape  of  the  future  bone,  only  in  minia- 
ture, and  it  is  covered  with  periosteum.  In  the  cartilage  an  opaque  spot  or  centre  of  ossification 
appears,  due  to  the  deposition  of  lime  salts  in  its  matrix.  The  cartilage  cells  proliferate  in  this 
area,  but  the  first  bone  is  formed  under  the  periosteum  in  the  shaft,  so  that  an  o.sseous  case,  like  a 
mufT,  surrounds  the  cartilage.  This  bone  is  formed  by  the  subperiosteal  osteoblasts.  (2)  Blood 
vessels,  accompanied  by  osteoblasts  and  connective  tissue,  grow  into  the  cartilage  from  the  osteogenic 
layer  of  the  periosteum  [periosteal  processes  of  Virchow),  so  that  the  cartilage  becomes  channelled 
and  vascular.  As  these  channels  extend  they  open  into  the  already  enlarged  cartilage  lacuna-, 
absorption  of  the  matrix  taking  place,  while  other  parts  of  the  cartilaginous  matrix  become  calcified. 
Thus,  a  series  of  cavities,  bounded  by  calcified  cartilage — the  primary  medullary  cavities — are 
formed.  They  contain  the  primary  or  cartilage  marrow,  consisting  of  blood  vessels,  osteoblasts, 
and  osteoclasts,  carried  in  from  the  osteogenic  layer  of  the  periosteum,  and,  of  course,  the  cartilage 
cells  that  have  been  liberated  from  their  lacunae.  (3)  The  osteoblasts  are  now  in  the  interior  of  the 
cartilage,  where  they  dispose  themselves  on  the  calcified  cartilage,  and  secrete  or  form  around  them 
an  osseous  matrix,  thus  enclosing  the  calcified  cartilage,  while  the  osteoblasts  themselves  become 
embedded  in  the  products  of  their  own  activity  and  remain  as  bone  corpuscles.  Bone,  therefore, 
is  at  first  spongy  bone,  and  as  the  primary  medullary  spaces  gradually  become  filled  up  by  new 
osseous  matter  it  becomes  denser,  while  the  calcified  cartilage  is  gradually  absorbed.  It  is  to  be 
remembered  that,  pari  passu  with  the  deposition  of  the  new  bone,  bone  and  cartilage  are  being 
absorbed  by  the  osteoclasts.] 

Chemical  Composition  of  Bone. — Dried  bone  contains  \  of  organic  matter  or  ossein,  from 
which  gelatin  can  be  extracted  by  prolonged  boiling;  and  about  5  mineral  matter,  which  consists 
of  neutral  calcic  phosphate,  57  per  cent. ;  calcic  carbonate,  7  per  cent. ;  magnesic  phosphate,  I  to  2 


892 


DEVELOPMENT   OF   THE    HEART. 


per  cent. ;  calcic  fluoride,  I  per  cent.,  with  traces  of  chlorine ;  and  water,  about  23  per  cent.  The 
marrow  contains  fluid,  fat,  albumin,  hypoxanthin,  cholesterin  and  extractives.  Tlie  red  marrow 
contains  more  iron,  corresponding  to  its  larger  proportion  of  haemoglobin  (Nasse). 

[The  medullary  cavity  of  a  long  bone  is  occupied  hy  yel/o~v  marrow,  which  contains  about  96 
per  cent,  of  fat.  The  red  marrow  occurs  in  the  ends  of  long  bones,  in  the  flat  bones  of  the  skull, 
and  in  some  short  bones.  It  contains  very  little  fat,  and  is  really  lymphoid  in  its  characters,  being, 
in  fact,  a  blood-forming  tissue  (p.  28).] 

Growth  of  Bones. — Long  bones  grow  in  thickness  by  the  deposition  of  new  bone  from  the 
periosteum,  the  osteoblasts  becoming  embedded  in  the  osseous  matrix  to  form  the  bone  corpuscles. 
Some  of  the  fibres  of  the  connective  tissue,  which  are  caught  up,  as  it  were,  in  the  process,  remain  as 
Sharpey's  fibres,  which  are  calcified  fibres  of  while  fibrous  tissue,  bolting  together  the  peripheric 
lamelloe.  [Miiller  and  Schafer  have  shown  that  there  are  also  fibres  in  the  peripheric  lamellre  com- 
parable to  yellow  elastic  fibres ;  they  branch,  stain  deeply  with  magenta,  and  are  best  developed  in 
the  bones  of  birds.] 

[At  the  same  time  that  bone  is  being  deposited  on  the  surface  it  is  being  absorbed  in  the  marrow 
cavity  by  the  action  of  the  osteoclasts,  so  that  a  metallic  ring  placed  round  a  hone  in  a  young 
animal  ultimately  comes  lo  lie  in  the  medullary  cavity  [Diihaviel).  The  growth  in  length  takes 
place  by  the  continual  growth  and  ossification  of  the  epiphysial  cartilage.  Tlie  cartilage  is  gradu- 
ally absorbed  from  below,  but  it  proliferates  at  the  same  time,  so  that  what  is  lost  in  one  direction  is 
more  than  made  up  in  the  other  (y.  Hunter).'] 

When  the  growth  of  bone  is  at  an  end,  the  epiphysis  becomes  united  to  the  diaphysis,  the  epi- 
physiai  cartilage  itself  becoming  ossified.  It  is  not  definitely  proved  whether  there  is  an  interstitial 
expansion  or  growth  of  the  true  osseous  substance  itself,  as  maintained  by  WoW  (§  244,  9). 

[Howship's  Lacunae. — The  osteoclasts  or  myeloplaxes  are  large  muUinucIear  giant  cells, 
which  erode  bone.  They  can  be  seen  in  great  numbers  lying  in  small  depressions,  corresponding 
to  them — Howship's  lacunne — on  the  fang  of  a  temporary  tooth,  when  it  is  being  alisorhed.  They 
are  readily  seen  in  a  microscopical  section  of  spongy  bone  with  the  soft  parts  preserved.] 

The  form  of  a  bone  is  influenced  by  external  conditions.  The  bones  are  stronger  the  greater 
the  activity  of  the  muscles  acting  on  them.  If  pressure  acting  normally  upon  a  bone  be  removed, 
the  bone  develops  in  the  direction  of  least  resistance,  and  becomes  thicker  in  that  direction.  Bone 
develops  more  slowly  on  the  side  of  the  greatest  external  pressure,  and  it  is  curved  by  unilateral 
pressure  [Lesshaft). 

448.  DEVELOPMENT  OF  THE  VASCULAR  SYSTEM.— Heart.  — [The  heart  appears 
as  a  solid  mass  of  cells  in  the  splanchnopleure,  at  the  front  end  of  the  embryo,  immediately  under 
the  "fore-gut."  Very  soon  a  cavity  appears  in  this  mass  of  cells;  some  of  the  latter  float  free  in 
the  fluid,  while  the  cellular  wall  begins  to  pulsate  rhythmicallv.  This  hollow  cellular  structure 
elongates  into  a  tube,  which  very  soon  assumes  a  shape  somewhat  like  an  S  (Fig.  570,  I),  and  there 
are  indications  of  its  being  subdivided  into  (a)  an  upper  aortic  part  with  the  bulbus  arteriosus  ; 
[b)  a  middle  or  ventricular  part;  and  (v\  a  lower  venous  or  auricular  part.  The  heart  then 
curves  on  itself  in  the  form  of  a  horseshoe  (2),  so  that  the  venous  end  f.A)  comes  to  lie  above  and 
slightly  behind  the  arterial  end.  On  the  right  and  left  side,  respectively,  of  the  venous  part  is  a 
blind  hollow  outgrowth,  which  forms  the  large  auricle  on  each  side  (3,  0,  Oj).  The  flexure  of  the 
body  of  the  heart  corresponding  to  the  great  curvature  (2,  V)  is  divided  into  two  large  compart- 
ments (3),  the  division  being  indicated  by  a  slight  depression  on  the  surface.  The  large  truncus 
venosus  (4,  V),  which  joins  with  the  middle  of  the  posterior  wall  of  the  auricular  part,  is  composed 
of  the  superior  and  inferior  venae  cava>.  This  common  trunk  is  absorbed  at  a  later  period  into  the 
enlarging  auricle,  and  thus  arise  the  separate  terminations  of  the  superior  and  inferior  venii;  cavEe. 
In  man,  the  heart  soon  comes  to  lie  in  a  special  cavity,  which  in  part  is  bounded  by  a  portion  of 
the  diaphragm  {//is).  At  the  4th-5th  week  the  heart  begins  to  be  divided  into  a  right  and  a  left 
half.  Corresponding  to  the  position  of  the  vertical  ventricular  furrow,  a  septum  grows  upward 
vertically  in  the  interior  of  the  heart,  and  divides  the  ventricular  part  into  a  right  and  lefi  ventricle 
(5,  R,  L).  There  is  a  constriction  in  the  heart  between  the  auricular  and  ventricular  portions, 
forming  the  canalis  auricularis.  It  contains  a  communication  between  the  auricle  and  both 
ventricles,  lying  between  an  anterior  and  posterior  projecting  lip  of  endothelium,  from  which  the 
auriculo-ventricular  valves  are  formed  (F.  Schmidt).  The  ventricular  septum  grows  upward  toward 
the  canalis  auricularis,  and  is  complete  at  the  8th  week.  Thus,  the  large  undivided  auricle  commu- 
nicates by  a  right  and  left  auriculo-ventricular  opening  with  the  corresponding  ventricle  (5).  At 
the  same  time  two  septa  (4, /(?)  appear  in  the  interior  of  the  truncus  arteriosus  (4,  ;>|,  which 
ultimately  meet,  and  thus  divide  this  tube  into  two  tubes  (5,  a  f>),  the  latter  forming  the  aorta  and 
pulmonary  artery,  and  are  disposed  toward  each  other  like  the  tubes  in  a  double-barrelled  gun. 
The  septum  grows  downward  until  it  meets  the  ventricular  septum  (5),  so  that  the  right  ventricle 
comes  to  be  connected  with  the  pulmonary  artery,  and  the  left  with  the  aorta.  The  division  of  the 
truncus  arteriosus,  however,  takes  place  only  in  the  first  part  of  its  course.  The  division  does  not 
take  place  above,  so  that  the  pulmonary  artery  and  aorta  unite  in  one  common  trunk  above.  This 
communication  between  the  pulmonary  artery  and  the  aorta  is  the  ductus  arteriosus  Botalli 
(7,  B). 


DEVELOPMENT   OF   THE   HEART. 


893 


In  the  auricle  a  septum  grows  from  the  front  and  behind,  ending  internally  with  a  concave 
margin.  The  vena  cava  superior  f6,  Cs)  terminates  to  the  right  of  this  fold,  so  that  its  blood  will 
tend  to  go  toward  the  right  ventricle,  in  the  direction  of  the  arrow  in  6,  x.  The  cava  inferior,  on 
the  other  hand  (6,  C7),  opens  directly  opposite  the  fold.     On  the  left  of  its  orifice,  the  valve  of  the 

Fig.  570. 


Development  of  the  heart,  i.  Early  appearance  of  the  heart; — a,  aortic  part,  with  the  bulbus,  d;  v,  venous  end.  2, 
Horseshoe-shaped  curving  of  the  neart — a,  aortic  end,  with  the  bulbus,  1^;  K,  ventricle :  W,  auricular  part.  3, 
Formation  of  the  auricular  appendages,  0,  o^ ,  and  the  external  furrow  in  the  ventricle.  4,  Commencing  division 
of  the  aorta,/,  into  two  tubes,  a.  5.  View  from  the  behind  of  the  opened  auricle,  v,  v,  into  the  L  and  R  ven- 
tricles, and  between  the  two  latter  the  projecting  ventricular  septum,  while  the  aorta  {a)  and  pulmonarj'  artery 
(p)  open  into  their  respective  ventricles.  6.  Relation  of  the  orifices  of  the  superior  {Cs)  and  inferior  vena  cava 
(O")  to  the  auricle  (scnematic  view  from  above) — x,  direction  of  the  blood  of  the  superior  vena  cava  into  the 
right  auricle  ;  y,  that  of  the  inferior  cava  to  the  left  auncle  ;  tL,  tubercle  of  Lower.  7.  Heart  of  the  ripe  fcetus — 
^,  right,  /.,,left  ventricle;  a,  aorta,  with  the  innominate,  c.c,  carotid,  c,  and  left  subclavian  artery,  s;  B,  ductus 
arteriosus  ;  p,  pulmonary  artery,  with  the  small  branches  /  and  ^,  to  the  lungs. 

Fig.  571. 


The  aortic  arches,  i.  The  first  position  of  the  i,  2  and  3  arches  ;  2,  5,  aortic  arches  ;  ta,  common  aortic  trunk  ;  ad. 
descending  aorta.  Disappearance  of  the  upper  two  arches  on  each  side — 5,  subclavian  artery  ;  v,  vertebral 
artery;  rtjr,  axillary  artery.  4.  Transition  to  the  final  stage — ^,  pulmonary  artery  ;  W,  aorta;  rf5,  ductus  arte- 
riosus {Botalli)  ;  S,  right  subclarian,  united  with  the  right  common  carotid,  which  divides  into  the  internal  (Cr) 
and  external  carotid  (CV)  ;  ajc,  axillary  ;  f,  vertebral  artery. 


foramen  ovale  is  formed  by  a  fold  growing  toward  the  auricular  fold,  so  that  the  blood  current  from 
the  inferior  vena  cava  goes  only  to  the  left^  in  the  direction  of  the  arrow,  _>/ :  on  the  right  of  the 
orifice  of  the  cava,  and  opposite  the  fold,  is  the  Eustachian  valve,  which,  in  conjunction  with  the 
tubercle  of  Lower  (/Zj,  directs  the  stream  from  the  inferior  vena  cava  to  the   left  into  the  left 


894 


DEVELOPMENT   OF   THE   VEINS. 


auricle,  through  the  previous  foramen  ovale.  Compare  the  fcetal  circulation  (]).  885).  After 
birth,  tlie  valve  of  the  foramen  ovale  closes  that  aperture,  while  the  ductus  arteriosus  also  becomes 
impervious,  so  that  the  blood  of  the  pulmonary  artery  is  forced  to  go  through  the  pulmonary 
branches  proceefimg  to  the  expanding  lungs.  Sometimes  the  foramen  ovale  remains  pervious, 
giving  rise  to  serious  symptoms  after  a  time,  and  constituting  morbus  ceruleus. 

Arteries. — Witli  the  formation  of  the  branchial  arches  and  clefts,  the  number  of  aortic  arches 
on  each  side  becomes  increased  to  5  (Fig.  571),  which  nm  above  and  below  each  branchial  cleft, 
in  a  branchial  arch,  and  then  all  reunite  behind  in  a  common  descending  trunk  (2,  ad)  [Knthke). 
These  blood  vessels  remain  only  in  animals  that  breathe  by  gills.  In  man,  the  upper  two  arcltes 
disappear  completely  (3).  When  the  truncus  arteriosus  divides  into  tlie  pulmonary  artery  and  the 
aorta  (4,  P,  A),  the  lowest  arch  on  the  left  side,  with  its  origin,  forms  the  pulmonary  artery  (4), 
and  it  springs  from  the  right  side  of  the  heart.  Of  these  the  lefl  lowest  arch  forms  the  ductus 
arteriosus  ((/^l,  and  from  the  commencement  of  the  latter  proceed  the  pulmonary  branches  of 
the  pulmonary  artery.  Of  the  remaining  arches  which  are  united  with  the  aorta,  the  left  middle 
one  {i.e.,  the  fourth  left)  forms  the  permanent  aortic  arch  into  which  the  ductus  arteriosus  opens, 
while  the  right  one  (fourth)  forms  the  subclavian  artery:  the  third  arch  forms  on  each  side  the 
origin  of  the  carotids  (O',  Ce).  The  arteries  of  the  first  and  second  circulations  have  been  referred 
to  already  (p.  879).     When   the  umbilical  vesicle,  with  its  primary   circulation,   diminishes,  only 


I,  First  appearance  of  the  veins  of  the  embryo.     II,  Their  transformations  to  form  the  final  arrangement. 


one  omphalo-inesenteric  artery  is  present,  which  gives  a  branch  to  the  intestine.  At  a  later  period 
the  omphalo-mesenteric  arteries  atrophy,  while  the  artery  to  the  intestine — the  superior  mesenteric 
— becomes  the  largest  of  all,  it  being  originally  derived  from  one  of  the  omphalo-mesenteric 
arteries. 

Veins  of  the  Body. — The  veins  first  formed  in  the  body  of  the  embryo  it'elf  are  the  two 
cardinal  veins  ;  on  each  side  an  anterior  (Fig.  572,  I,  c  s),  and  a  posterior  (</ — Rallike),  which 
proceed  toward  the  heart  and  unite  on  each  side  to  form  a  large  trunk,  the  duct  of  Cuvier  (DC^ 
which  passes  into  the  venous  part  of  the  heart.  The  anterior  cardinal  veins  give  off  the  subclavian 
veins  (bb)  and  the  common  jugular  veins,  which  divide  into  the  external  (1^)  and  internal  (^i) 
jugular  veins.  In  addition,  there  is  a  Irnnsverse  anastomosing  branch  passing  obliquely  from  the 
left  (where  it  divides)  to  the  right,  which  joins  their  trunk  lower  down.  In  the  tinal  arrangement 
(II),  this  anastomosis  (Ks)  becomes  very  large  to  form  the  left  innominate  vein,  while  with  the 
growth  of  the  arms  the  subclavian  veins  increase  [hh) ;  and  lastly,  the  calibre  of  the  jugular  vein 
changes,  the  internal  jugular  (]i)  becoming  very  large,  and  the  external  jugular  (I*")  smaller.  In 
some  animals,  e.i^.,  the  dog  and  rabbit,  the  large  embryonic  size  is  retained.  The  part  of  the  left 
superior  cardinal  vein,  from  the  anastomosis  downward  to  the  left  duct  of  Cuvier,  disappears. 
'X'iii  posterior  cardinal  veins  divide  in  the  pelvis  into  the  hypogastric  (I,//)  and  external  iliac  (//). 
The  inferior  cava  at  first  is  very  small  (I,  Vc),  divides  at  the  entrance  of  the  pelvis,  and  on  each 
side  goes   into  the  point  of  division   of  the  cardinal  veins.     There  is  also  a  transverse  ascending 


FORMATION    OF   THE    INTESTINAL   CANAL. 


895 


anastomosis  between  the  right  and  left  cardinal  veins.  For  the  final  arrangement,  the  cava  inferior 
(II,  Ci)  dilates,  and  with  it  the  hypogastric  and  external  iliac  vein  on  each  side.  The  right  car- 
dinal vein  remains  very  small  (  I'^ftii  azygos,  Ac),  and  also  the  lower  part  from  the  left  one  to  the 
transverse  anastomosis.  The  latter  itself  also  remains  very  small  (  Toia  hemiazygos,  Hz).  On  the 
other  hand,  the  upper  part  above  the  anastomosis  to  the  duct  of  Cuvier  disappears.  Lastly,  the 
common  large  venous  trunk  is  so  absorbed  into  the  wall  of  the  auricle  (V)  that  both  venK  cavoe 
h»ve  each  a  separate  oritice  (p.  892).     The  embryonic  condition  of  the  veins  persists  in  fishes. 

Veins  of  the  First  and  Second  Circulation,  and  Formation  of  the  Portal  System. — The 
two  omphalo-mesenteric  veins  [om,  om ^ )  open  into  the  posterior  or  venous  end  of  the  tubular  heart 
(Fig.  573,  I,  Hi.  The  right  vein,  however,  disappears  very  soon.  As  soon  as  the  allantois  is 
formed,  the  two  umbilical  veins  join  the  truncus  venosus  (I,  u  ii^).  At  first,  the  omphalo-mesen- 
teric  veins  are  larger  than  the  umbilical  veins ;  at  a  later  period  this  is  reversed,  and  the  right 
umbilical  vein  disappears.  As  soon  as  veins  are  formed  within  the  body  proper  of  the  embryo,  the 
inferior  cava  al^o  opens  into  the  truncus  venosus  (2  Ci).  Gradually,  the  umbilical  vein  (2,  «j) 
becomes  the  chief  trunk,  while  the  small  omphalo-mesenteric  (2,  cm,)  carries  little  blood. 

Portal  System. — The  umbilical  and  omplialo-mesenteric  veins  pass  in  part  directly  under  the 
liver  to  reach  the  heart.  They  send  branches— carrying  arterial  blood — to  the  liver,  and  the  latter 
grows  round  these  vessels.  These  branches  are  the  venae  advehentes  (2  and  3,  a).  The  blood 
circulating  through  the  liver  from  the  vence  advehentes  is  returned  by  other  veins,  the  venae  reve- 
hentes  (2  and  3,  /■),  which  reunite  at  the  blunt  margin  of  the  liver  with  the  chief  trunk  of  the 
umbilical  vein.  The  umbilical  vein  (3,  a,)  and  the  omphalo-mesenteric  vein  (3,  i"«,)  anastomose 
in  the  liver.     \Mien  the  intestine  develops  (3,  II),  the  mesenteric  vein  (7/;)  opens  into  the  omphalo- 

Fig.  573. 


Development  of  the  veins  and  porta!  system.  H,  heart;  R  L,  right  and  left  side  of  the  body  ; 
mesenteric  vein ;  ow,,  left,  h.  right  umbilical  vein;  K,.left;  Ct.  vena  cava  inferior;  a,  ve 
vense  revehentes  ;  D,  intestine  ;  in,  mesenteric  vein  ;  4,  /,  splenic  vein;   2,  /,  liver. 


mesenteric  vein,  and  the  splenic  vein  as  well  (4,  I),  when  the  spleen  is  formed.  When  the 
omphalo-mesenteric  vein  (4,  om^)  at  a  later  period  disappears,  the  vein  from  the  intestine  now 
becomes  the  common  trunk  of  the  previously  united  vessels.  It  unites  in  the  liver  with  the  umbili- 
cal vein  to  form  the  trunk  of  the  vena  porta;.  When,  after  birth,  the  umbilical  vein  disappears 
(4,  »<,),  the  mesenteric  alone  remains  as  the  portal  vein.  As  the  ductus  venosus  is  obliterated, 
the  portal  vein  must  send  its  blood  through  the  liver,  and  thus  the  portal  circulation  is  completed. 

449.  FORMATION  OF  THE  INTESTINAL  CANAL.— The  primitive  intestine,  or 

gut,  consists  of  a  straight  tube  ]iroceeding  from  the  head  to  the  tail.  The  vitelline  duct  is  inserted 
at  that  point,  which  at  a  later  period" corresponds  to  the  lower  part  of  the  ileum.  At  the  4th  week 
the  tube  makes  a  slight  bend  toward  the  umbilicus  (Fig.  574,  I).  As  already  mentioned,  the 
vitelline  duct  is  obliterated,  remaining  only  for  a  time  as  a  thread  attached  to  the  intestine,  being 
still  visible  at  the  3d  month.  Sometimes  it  remains  as  a  short  blind  tube  communicating  with  the 
intestine.  Thus  is  the  so-called  ^^  true  intestinal  diverticulum  :^^  occasionally  a  cord — the  obliter- 
ated omphalo  mesenteric  vessels— passes  from  it  to  the  umbilicus.  In  very  rare  cases  the  duct  may 
remain  open  as  far  as  the  umbilicus,  forming  a  congenital  fistula  of  the  ileum,  or  it  may  give  rise  to 
cystic  formations  [M.  Roth).  In  a  human  fnetus  at  the  4th  week.  His  distinguished  the  cavity  of 
the  mouth,  pharynx,  a-sophagus,  stomach,  duodenum,  mesenterial  intestine,  and  the  hind-gut,  with 
the  cloaca.  The  intestine  then  forms  the  first  coil  (Fig.  574,  II)  by  rotating  on  itself  at  the  intes- 
tinal umbilicus,  so  that  the  lower  part  of  the  intestine  lying  next  the  knee-like  bend  comes  to  lie 
above,  while  the  upper  part  lies  below.  From  the  lower  part  of  this  loop  the  coils  of  the  small 
intestine  (III,  /),  which  gradually  grows  longer.     From  the  upper  limb  of  the  loop,  which  also 


896 


SALIVARY    GLANDS,  LUNGS. 


elongates,  the  large  intestine  is  formed ;  first  the  descending  colon,  then  by  elongation  the  trans- 
verse colon,  and  lastly  the  ascending  colon. 

Glands. — By  diverticula,  or  protrusions  from  the  intestine,  the  various  glands  are  formed.  The 
cells  of  the  hypoblast  proliferate  and  take  part  in  the  process  as  they  form  the  secretory  cells  of  the 

Fig.  575. 


Fig.  574. — Development  of  the  intestine,  p,  stomach  ;  o,  insertion  of  the  vitelline  duct :  t,  small  intestine;  c,  colon  ; 
r,  rectum.  Fig.  575. — Formation  of  the  lungs.  A,  Diverticula  of  the  lungs  as  double  sacks — k,  mesoblastic  layerj; 
/,  hypoblastic  layer;  tn,  stomach;  j,  oesophagus.  B,  Further  branching  of  the  lungs — t,  trachea;  i>,  e,  bronchi; 
/,  projecting  vesicles. 

glands,  while  the  mesoblastic  part  of  the  splanchnopleure  forms  the  membranes  of  the  glands,  giv- 
ing them  their  form.     The  diverticula  are  as  follows  : — 

1 .  The  salivary  glands,  which  grow  out  from  the  oral  cavity  at  first  as  simple  solid  buds,  but 
afterward  become  hollow  and  branched.  [The  salivary  glands  are  developed  from  the  epiblast  lin- 
ing the  mouth  (stomodceum),] 

2.  The  lungs,  which  arise  as  two  separate  hollow  buds  (Fig.  575,  A,  1),  and  ultimately  have 
only  one  common  duct,  are  protrusions  from  the  oesophagus.  The  upper  part  of  the  united  tracheal 


of  the  omentum.    I  and  \\.~kg,  gastro-hepatic  ligament;  ///,  great,  «,  lesser  curvature  of  the  stomach  ; 

J,  posterior,  and  i  anterior  fold  or  plate  of  the  omentum  ;  tnc,  mesocolon  ;  c,  colon.    III.— L,  Liver;  t,  small  in- 
testine ;  3,  mesentery ;  /*,  pancreas;  ^,  duodenum  ;  r,  rectum;  N,  great  omentum. 

tube  forms  the  larynx.  The  epiglottis  and  the  thyroid  cartilage  originate  from  the  part  which  forms 
the  tongue  ( Gan^ho/ner).  The  two  hollow  spheres  grow  and  ramify  like  branched  tubular  glands 
with  hollow  processes  (B,/).  In  the  first  period  of  development  there  is  no  essential  difference 
between  the  epithelium  of  the  bronchi  and  that  of  the  primitive  air  vesicles  {Slieda).     The  spleen 


DEVELOPMENT   OF   THE    URINARY   APPARATUS. 


897 


and  suprarenal  capsules,  however,  are  not  developed  in  this  way.     The  former  arises  in  a  fold  of 
the  mesogastrium  (/^is)  at  the  second  month  ;  the  latter  are  originally  larger  than  the  kidneys. 

3.  The  pancreas  arises  in  the  same  way  as  the  salivary  glands,  but  is  not  visible  at  the  fourth 
week  (His). 

4.  The  liver  begins  very  early,  and  appears  as  a  diverticulum,  with  two  \\o\\ovi  primilive  hepatic 
duels,  which  branch  and  form  bile  ducts.  At  their  periphery  they  penetrate  between  the  solid 
massis  of  cells — the  liver  cells — which  are  derived  from  the  hypoblast.  At  the  second  month  the 
liver  is  a  large  organ,  and  secretes  at  the  third  month  (j*  1S2). 

5.  In  birds  two  small  blind  sacks  are  formed  from  the  hind-gut. 

6.  The  fetal  respiratory  organ,  the  allantois,  is  treated  of  specially  {\  444). 

Peritoneum  and  Mesentery. — The  inner  surface  of  the  coeloin,  or  body  cavity,  the  surface  of 
the  intestine,  and  its  mesentery  are  covered  by  a  serous  coat — \.\ie  peri/oneum.  At  first  the  simple 
nitestine  is  contained  in  a  fold,  or  duplicature  of  the  per  toneum  ;  on  the  stomach,  which  is  merely 
at  first  a  spindle-shaped  dilatation  of  the  tube  placed  vertically,  it  is  called  mesogastrium.  After- 
ward, the  stomach  turns  on  its  side,  so  that  the  left  surface  is  directed  forward  and  the  right  back- 
ward. Thus,  the  insertion  of  the  mesogastrium,  which  originally  was  directed  backward  (to  the 
vertebral  column),  is  directed  to  the  left  ;  the  line  of  insertion  forming  the  region  of  the  great  cur- 
vature, which  becomes  still  more  curved.  From  the  great  curvature  the  mesogastrium  becomes 
elongated  like  a  pouch  (Fig.  576,  I  and  II,  s,  i),  constituting  the  omental  sack,  which  extends  so  far 


Development  of  the  internal  generative  organs.     I,  UndifTerential  condition — D,  reproductive  gland,  lying 
tubules  ol  the  Wolffian  body  :  VV,  Wolffian  duct ;  M,  Mullerian  duct :  S,  urogenital  sinus.     ll.Tra     ' 
in  the  female — F,  ftmbria,  with  the  hydatid,  A';  T,  Fallopian  tube;  U,  uterus ;  S,  uro-genital  sinus 
P,  parovarium.     Ill,  Transformations  in  the  male — H,  testis;   E,  epididymis,  with  the  hydatid,  A; 
rans  :    V,  vas  deferens;    S,  uro-genital  sinus;    »,  male  uterus;    4,  ^,  hind-gut ;    a,  allantois  ;    u,  l 
w,  perineum  ;  ^,  position  of  the  bladder ;  S,  uro-genital  sinus. 


downward  as  to  pass  over  the  transverse  colon  and  the  loops  of  the  small  intestine  (III,  N).  As 
the  mesogastrium  originally  consists  of  two  plates,  of  course  the  omentum  must  consist  of  four 
plates.  .-\t  the  fourth  month  the  posterior  surface  of  the  omental  sack  unites  with  the  surface  of  the 
transverse  colon  (yc/i.  Miillcr). 

450.     DEVELOPMENT    OF    THE  URINARY  AND  GENERATIVE  ORGANS. 

— Urinary  Apparatus. — The  first  indication  of  this  apjiaratus  occurs  in  the  chick  at  the  second 
day,  and  in  the  rabbit  at  the  ninth,  as  the  ducts  of  the  primitive  kidneys  or  Wolffian  ducts  (Fig. 
577.  I.  W),  which  are  formed  from  some  cells  mapped  off  from  the  lateral  plate  above  and  to  the 
side  of  the  protovertebra;,  and  extending  from  the  fifth  to  the  last  vertebra.  Tlie  ducts  are  solid  at 
first,  but  soon  become  hollow,  and  from  their  cavities  there  extend  laterally  a  series  of  small  tubes, 
which  in  the  chick  communicate  freely  with  the  peritoneal  cavity  [A'o/IHer).  Into  one  end  of  each 
of  these  tubes  grows  a  tuft  of  blood  vessels  forming  a  structure  resembling  the  glomeruli  of  the 
kidney.  The  tubes  elongate,  form  convolutions,  and  increase  in  number.  The  upper  end  of  the 
Wolffian  duct  is  closed  at  first,  its  lower  end,  which  lies  in  a  projecting  fold — the  plica  urogenitalis 
of  Waldeyer — in  the  peritoneal  cavity,  opens  into  the  urogenital  sinus.  Close  above  the  orifice  of 
the  Wolffian  duct  appears  the  ureter  as  the  duct  of  the  kidney.  The  duct  elongates,  and  branches 
at  its  upper  end.  Each  canal  at  its  end  is  like  a  stalked  c.routchouc  sack  ( ToLil),  and  into  it  there 
grows  the  already  formed  glomerules.  The  duct  of  the  kidney  opens  independently  into  the  uro- 
genital sinus,  and  forms  the  ureter.     The  part  where  the   1  .ranching  of  the  duct   stops   forms  the 

57 


898  DEVELOPMENT   OF   THE    OVARY    AND   TESTICLE. 

pelvis  of  the  kidney,  and  the  branches  themselves  the  renal  tubules.  Toldt  found  Malpighian  cor- 
puscles  in  the  human  kidney  at  the  second  month,  and  Henle's  loops  at  the  fourth.  The  first  ap- 
pearance of  the  urinary  bladder  is  at  the  fourth  week  (//is),  and  is  more  distinct  at  the  second 
month,  as  the  dilated  first  part  of  the  allanlois  (Fig.  577,  4,  a).  The  upper  part  of  the  allantois 
remains  as  the  obliterated  urachus,  in  the  middle  vesical  ligament. 

Internal  Reproductive  Organs. — In  front  of  and  internal  to  the  Wolffian  bodies,  there  arises 
in  the  mesoblast  the  elongated  reproductive  gland  or  mass  of  germ  epithelium  (Fig.  577,  I,  D), 
which  in  both  sexes  is  originally  alike.  In  addition,  there  is  formed  a  canal  or  duct  parallel  to  the 
Wolffian  duct  (W),  which  also  opens  into  the  urogenital  sinus;  this  is  Midler's  duct  (M).  The 
elevation  of  the  future  reproductive  gland  is  covered  originally  by  germ  epithelium  [Wa/devt-r) 
The  upper  end  of  the  Miillerian  duct  opens  free  into  the  abdominal  cavity,  while  the  lower  ends  of 
both  ducts  unite  for  a  distance.  Some  of  the  germinal  cells  covering  the  surface  of  the  future 
ovary  enlarge  to  form  ova,  and  sink  into  the  stroma  to  form  ova  embedded  in  their  Graafian  follicles 
(^  43^).  In  the  female,  the  Miillerian  ducts  form  the  Fallopian  tube  (II,  T),and  the  lower  united 
ends  the  uterus. 

In  the  male  the  germ  epithelum  is  not  so  tall.  According  to  Waldeyer,  there  are  two  kinds  of 
tubes  in  the  Wolffian  bodies  and  some  of  these  penetrate  the  position  of  the  reproductive  gland. 
These  tubes,  which  are  connected  with  the  Wolftian  ducts,  become  the  seminiferous  tubules  (v. 
VVilluh),  and  the  Wolffian  duct  itself  becomes  the  vas  deferens,  with  the  vesicula;  seminales. 
According  to  some  other  observers,  however,  lubes  which  become  the  seminiferous  tubules,  are  de- 
veloped within  the  reproductive  gland  itself,  and  these  tubes  Uned  with  their  germ  epithelium  ulti- 
mately form  a  connection  with  the  Wolffian  ducts. 

The  Miillerian  ducts,  which  are  really  the  ducts  of  the  reproductive  glands,  disappear  in  man, 
all  except  the  lowest  part,  which  becomes  the  male  uterus  or  vtsicula  prostatica  (III,  u) — the  homo- 
logue  of  the  uterus.  The  upper  tubules  of  the  Wolffian  body  unite  at  the  3d  month  with  the 
reproductive  gland  (which  has  now  become  the  body  of  the  testis),  and  become  the  coni  vasculosi 
of  the  epididymis,  which  are  lined  by  ciliated  epithelium  (E);  the  remainder  of  the  Wolffian  body 
disappears.  Some  detached  tubules  form  the  vasa  aberrantia  (a)  of  the  testicle  (A'oliel/).  The 
hydatid  of  Morgagni  [h),  at  the  head  of  the  epididymis,  according  to  Luschka  and  others,  is  a  part 
of  the  epididymis — Fleischl  regards  it  as  the  rudiment  of  the  male  ovary.  The  organ  of  Girald^s 
is  part  of  the  Wolffian  body.  The  Wolffian  duct  itself  becomes  the  vas  deferens  (V)  from  which 
the  vesicula;  seminales  are  developed.  The  two  Wolffian  and  two  Miillerian  ducts,  as  they  enter 
the  pelvis,  unite  to  form  a  common  cord — the  genital  cord. 

In  the  female  the  tubes  of  the  Wolffian  bodies  disappear,  all  except  a  few  tubules,  lined  with 
ciliated  epithelium,  constituting  the  parovarium,  or  organ  of  Rosemiiller  (Fig.  555)  and  a  part 
analogous  to  the  organ  of  Giraldes  in  the  broad  ligament  of  the  uterus  (iraMtycr)  (Fig.  577,  P). 
The  same  is  the  case  with  the  Wolffian  ducts.  In  some  animals  (ruminants,  pig,  cat,  and  fox)  they 
remain  permanently  as  the  ducts  of  Gaertner. 

The  Miillerian  duct  is  frayed  out  at  its  upper  end  to  form  the  fimbrise  of  the  Fallopian  tube,  and 
it  is  often  provided  with  a  hydatid  (/;').  That  part  of  the  uro-genital  sinus  into  which  the  four 
ducts  open  grows  above  into  a  hollow  sphere,  which  forms  the  vagina  (Rathie).  According  to 
Thiersch  and  Leuckart,  however,  the  two  Miillerian  ducts  unite  at  their  lower  ends  to  form  the 
united  uterus  (U)  and  vagina,  while  their  free  upper  ends  form  the  Fallopian  tubes  (T).  The 
Miillerian  ducts  at  first  open  into  the  posterior  part  of  the  urinary  bladder  below  the  ureters  (uro- 
genital sinus,  S),  while  uUimately  this  part  of  the  bladder  becomes  so  elongated  posteriorly  that  the 
vagina  (the  united  Miillerian  ducts)  and  the  urethra  are  united  below  and  deeply  within  the  vesti- 
bule of  the  vagina.  At  the  3d  to  the  4th  month,  the  uterus  and  vagina  are  not  separate  from  each 
other,  but  at  ihe  5th  to  6th  month  the  uterus  is  defined  from  the  vagina. 

The  testicles  lie  originally  in  the  lumbar  region  of  the  abdominal  cavity  (Fig.  578,  V /),  and 
are  carried  by  a  fold  of  the  peritoneum — the  mesorchium  (w).  From  the  hilum  of  the  testicle  a 
cord,  the  gubernaculum  testis,  runs  through  the  inguinal  canal  into  the  base  of  the  scrotum. 
At  the  same  time  a  septum-like  process  is  developed  independently  from  the  peritoneum  to 
the  base  of  the  scrotum  (/.  t').  The  testicle  passes  through  the  inguinal  canal  into  the  scrotum, 
but  the  mechanism  and  cause  of  the  descent  are  not  accurately  ascertained. — [^Descent  of 
testis,  \  446.] 

The  ovaries  also  descend  somewhat.  The  round  ligament  of  the  uterus  corresponds  to  the 
gubernaculum  testis.  A  process  of  the  peritoneum  passes  in  the  female  into  the  inguinal  canal  as 
Nuck's  canal.     It  is  rare  to  find  the  ovaries  descending  into  the  labia  majora. 

[The  origin  of  the  urinary  and  generative  organs  is  undoubtedly  associated  with  the  development 
of  the  Wolffian  bodies.  The  researches  of  Semper  and  Balfour  on  elasmobranch  fishes  show  that 
the  process  is  a  very  complex  one.  There  is  a  mass  of  cells  on  each  side  of  the  vertebral  column, 
which  is  divided  into  three  parts,  the  first  called  the  pronephros,  or  head  kidney  of  Balfuur  and 
Sedgwick,  the  middle  one,  the  mesonephros  or  Wolffian  body,  and  the  posterior  one  or  meta- 
nephros,  which  is  formed  after  the  other  two,  gives  origin  to  the  permanent  kidney  in  the  amniota. 
The  Miillerian  duct  is  connected  with  the  pronephros,  the  Wolffian  duct  with  the  mesonephros,  and 
the  ureter  to  the  metanephros.] 

[The  following  table,  modified  from  Quain,  shows  the  destiny  of  these  structures: — 


DEVELOPMENT   OF   THE    EXTERNAL    GENITALS. 


899 


Femah. 
Fallopian  tubes. 
Hydatid. 
Uterus  and  vairina. 


MuLLERiAN  Ducts  (Ducts  of  the  Pronephros). 
Male. 
Hydatid  of  Morgagni. 
Male  uterus. 


Wolffian  Bodies  (Mesonephros). 

Vasa  efferentia,  Coni  vasculosi. 
Organ  of  Giraldes,  Vasa  aberrantia. 
Gubernaculum  testis. 
Wolffian  Ducts. 

Convoluted  tube  of  epididymis. 
Vas  deferens  and  vesiculje  seminales. 
Metanephros. 

Ureter.] 

The  external  genitals  are  at  first  not  distinguishable  in  the  two  sexes  (Fig.  578,  I).  At  the  4th 
week  there  is  merely  a  hole  at  the  posterior  extremity  of  the  trunk,  representing  both  the  anus  and 
the  opening  of  the  urachus,  and  forming  a  cloaca  (Fig.  577,  4,  K).  In  front  of  this  an  elevation — 
the  genital  eminence — appears  about  the  6th  week,  and  on  each  side  of  the  orifice  a  large  cutane- 
ous elevation  (II,  w).  At  the  end  of  the  2d  month  there  is  a  groove  on  the  under  surface  of  the 
genital  eminence,  leading  back  to  the  cloaca,  and  with  distinct  walls  bounding  it  (II,  r).     At  the 


Parovarium. 
Paroophoron. 
Round  ligament  of  the  uterus. 

Chief  tube  of  parovarium. 
Ducts  of  Gaertner. 

Kidney. 


Development  of  the 


ternal  genitals,     /and//, — Genital 
Penis  :  R^  raphe  penis  :  S, 

V  and  F/— Descent  of  the  testicle  ;  /, 

M,  abdominal  wall;  5,  scrotum. 


:  r,  genital  groo' 
r,  clitoris  ;  /,  labi 

a  :  /  r,  processus  vagi 


,  coccyx  :  tv,  cutaneous  ele- 


alis   of  the  perito- 


middle  of  the  3d  month  the  cloacal  opening  is  divided  by  the  growth  of  the  perineum,  between  the 
urachus  (now  become  the  urinary  bladder)  (Fig.  578,  5,  b)  and  the  rectum  (M). 

In  the  male  the  genital  eminence  enlarges,  its  groove  deepens  from  the  opening  of  the  bladder 
onward  to  the  apex  of  the  elevation  at  the  loth  week.  The  two  edges  unite  to  enclose  the  groove 
which  becomes  the  urethra.  When  this  does  not  take  place,  hypospadias  occurs.  At  the  4th 
month  the  glaus,  and  at  the  6th  the  prepuce,  are  formed.  The  large  cutaneous  folds  meet  in  the 
middle  line  or  raphe  to  form  the  scrotum. 

In  the  female  the  undifferentiated  condition  remains  to  a  certain  extent  permanent.  The  small 
genital  eminence  remains  as  the  clitoris,  the  margins  of  its  furrow  become  the  nymphcr,  the  cutane- 
ous elevations  remain  separate  to  form  the  labia  majora.  The  uro  genital  sinus  remains  short  as  the 
vestibule  of  the  vagina,  while  in  man,  by  the  closing  of  the  genital  groove,  it  has  a  long  additional 
tube,  the  urethra.  [The  following  illustrations,  after  Schroeder,  show  the  changes  of  the  external 
organs  of  generation  in  the  female.  In  the  early  p;riod  (6th  week)  the  hind-gut  (Fig.  579,  R,)  al- 
lantois  {All),  and  the  Miillerian  ducts  (M)  communicate,  but  not  with  the  exterior.  .J^bout  the  loih 
week  a  depression  or  inflection  of  the  skin  takes  place,  genital  cleft,  until  it  meets  the  hindgut  and 
allantois,  whereby  the  cloaca  (Fig.  580,  CI)  is  formed.  The  cloaca  is  then  divided  into  an  anterior 
part,  the  urogenital  sinus,  into  which  the  Miillerian  ducts  open,  and  a  posterior  part  the  anus. 
There  is  a  downward  growth  of  the  tissue  between  the  hind-gut  and  the  allantois  to  form  the  peri- 
neum (Fig.  581).  The  uro. genital  sinus  then  contracts  at  its  upper  part  to  form  the  short  urethra, 
its  lower  part  remaining  as  the  vestibule  (Fig.  582,  Sv),  while  the  vagina  has  been  formed  by  the 
union  of  the  lower  parts  of  the  two  Miillerian  ducts.  The  bladder  (B)  is  the  expanded  lower  end 
of  the  stalk  of  the  allantois.] 

The  causes  of  the  difference  of  sex  are  by  no  means  well  known.  From  a  statistical  analysis 
of  80,000  cases,  the  influence  of  the  age  of  the  parents  has  been  shown  by  Hofacker  and  Sadler. 
If  the  husband  is  younger  than  the  wife,  there  are  as  many  boys  as  girls;  if  Ixith   are  of  the   same 


900 


FORMATION    OF   THE    CENTRAL   NERVOUS   SYSTEM. 


age,  there  are  1029  boys  to  1000  girls;  if  the  husband  is  older,  1057  boys  to  1000  girls.  In  insects, 
food  has  a  most  important  influence.  Pfliiger's  investigations  on  frogs  show  that  all  external  condi- 
tions during  development  are  without  effect  on  the  determination  of  the  se.\,  so  that  the  latter  would 
seem  to  be  determined  before  impregnation. 

451.  FORMATION  OF  THE  CENTRAL  NERVOUS  SYSTEM.— Fore  brain.— At 
each  side  of  the  fore  brain,  or  anterior  cerebral  vesicle,  which  is  covered  externally  by  epiblast  and 
internally  by  the  ependyma,  there  grows  out  a  large  stalked  hollow  vesicle,  the  rudiment  of  the  cere- 
bral hemispheres.  The  relatively  wide  opening  in  the  stalk,  or  communication,  ultimately  be- 
comes very  small,  and  is  the  foramen  of  Monro.  The  middle  part  between  the  two  cerebral  vesi- 
cles remains  small,  and  is  the  'tween  or  inter  brain  with  the  3d  ventricle  in  its  interior.  It  elon- 
gates at  the  second  month  toward  the  base  of  the  brain  as  a  funnel  shaped  projection,  to  form  the 
tuber  cinereum  with  the  infundibulum.  The  thalami  optici,  projecting  and  enlarging  from  the  sides 
of  the  3d  ventricle,  narrow  the  foramen  of  Monro  to  a  semilunar  slit.  At  the  base  of  the  brain  are 
formed,  in  the  2d  month,  the  corpora  albicantia,  at  the  3d  thechiasma;  while  within  the  3d  ventri- 
cle, the  commissures  are  formed.  The  hypophysis,  belonging  to  the  mid-brain,  is  a  diverticulum  of 
the  nasal  mucous  membrane,  extending  through  the  base  of  the  skull  toward  the  hollow  infundibulum, 
which  grows  to  meet  it.  The  choroid  plexus,  which  grows  into  the  ventricles  of  the  hemispheres 
through  the  foramen  of  Monro,  is  a  vascular  development  of  the  tependyma.  At  the  4th  month,  the 
conarium  (pineal  gland)  is  formed,  and  at  this  time  the  corpora  quadrigemina  cover  the  hemi- 
spheres. The  corpora  striata  begin  to  be  developed  in  the  cerebral  (lateral)  ventricle  at  the  2d 
month,  while  the  cornu  ammonis  is  formed  at  the  4th  month.  At  the  3d  month  the  Sylvian  fissure 
is  formed,  and  the  basis  of  the  island  of  Reil.  The  permanent  cerebral  convolutions  are  formed 
from  the  7th  month  onward. 


Fig.  579. 


Fig.  5  So. 


Fig.  581 


Fig.  582. 


^/^vV/ 


with  the  rectum  and  a 
genital  sinus  (Su)  and 
to  form  the  vagina  (V) 


nuous  with  the  allantois  (.■!//— bladder)  ;  M,  duct  of  MUlIer  (v 
e.  growing  inward  to  lorm  the  vulva.  Fig.  580. — I'he  depre) 
llantois,  to  form  the  cloaca  (C  L).     '-         -        —        - 


by  the  downward  gri 
Fig.  582.— Perineum  cot 


•th  of  the  I 
ipletely  forn 


al  septum.     The  du 


:  A,  depressio 
as  become  co 
ling  divided 
,  of  M  tiller  ar 


The  mid  brain,  or  middle  cerebral  vesicle,  is  gradually  covered  over  by  the  backward  growth  of 
the  hemispheres;  its  cavity  forms  the  aqueduct  of  Syh'itis.  Depressions  appear  on  the  surface  of 
the  vesicle  to  divide  it  into  four,  the  corpora  quadrigemina,  the  longitudinal  depression  being 
formed  at  the  3d,  and  the  transverse  one  at  the  7th  month.  The  cerebral  peduncle  is  formed  by  a 
thickening  in  the  base  of  this  vesicle. 

In  the  hind-brain  are  formed  the  cerebellar  hemispheres,  which  grow  backward  to  meet  in  the 
middle  line.  The  vermes  is  formed  at  the  7th  month.  The  cerebellum  covers  in  the  part  of  the 
medullary  tube  lying  below  it,  and  which  is  not  closed,  as  far  as  the  calamus.  The  pons  arises  in 
the  floor  of  the  hind-brain  at  the  3d  month. 

The  spindle-shaped  narrow  after  brain  forms  the  medulla  oblongata,  with  the  opening  of  the 
medullary  tube  in  its  upper  part. 

[The  following  table,  from  Quain,  shows  the  destiny  of  each  cerebral  vesicle: — 

C  Cerebral  hemispheres,  corpora  striata, 

■(     corpus  callosum,  fornix  lateral  ven- 

\    tricles,  olfactory  bulb. 

12.    Thalamencephalon      .    .    f  Thalami  optici,  pineal  gland,  pitttitary 

(inter  or 'tween  brain.)      \    ^"fX'   """"^     «'''='^"'   ^q^^duct    of 

>-       ^  '      y    Sylvius 


I.  Anterior    Primary 
Vesicle    .    .    . 


I.  Prosencephalen    . 
(fore-brain. ] 


,  optic  nerve. 


II.   Middle       Primary 
Vesicle    .    .    . 

III.  Posterior  Primary 
Vesicle    .    .    . 


f  3.  Mesencephalon (  ^°''^°'f  quadrigemina.  crura  , 

\  (mid-brain.)  \    ^q^educt    of    Sylvms,    optic 

l  ^  '  \    (secondarily). 


cerebri, 
nerve 


("4.  Epencephalon f  Cerebellum,  pons,  anterior  part  of  the 

J  (hind-brain.)  \    fourth  ventricle. 

j  5.  Aletencep/ialon |  Medulla    oblongata,  fourth   ventricle, 

[  (after-brain.)  \    auditory  nerve. 

[Spinal  Cord. — The  spinal  cord  is  developed   from  the  medullary  tube  behind  the  medulla 

oblongata,  first  the  gray  matter  around  the  canal,  while  the  white  matter  is  added  afterward  outside 

this.     The  ganglionic  cells  increase  by  division  in  amphibians  [Lominsky).     At  first  the  spinal  cord 

reaches  the  coccyx.     The  first  muscles  are  formed  in  the  back  at  the  2d  month  ;  at  the  4th   month 


DEVELOPMENT   OF   THE    SENSE    ORGANS. 


901 


they  are  red.  The  spinal  ganglia  are  formed  from  a  special  strip  of  cells,  and  they  are  seen  at 
the  4th  week,  and  so  are  the  anterior  spinal  roots  and  some  of  the  trunks  of  the  spinal  nerves, 
while  the  posterior  roots  are  still  absent.  The  peripheral  nerves  grow  out  from  the  ganglia  of  the 
spinal  cord  (first  the  motor  and  afterward  the  sensory  nerves),  and  penetrate  into  the  other  parts  of 
the  body  [His].     At  first  tliey  are  devoid  of  myelin. 

452.  DEVELOPMENT  OF  THE  SENSE  ORGANS.— Eye.— The  primary  optic 
vesicle  grows  out  from  the  fore-brain  toward  the  outer  covering  of  the  head  or  epiblast,  and  soon 
becomes  folded  in  on  itself  (4th  week),  so  that  the  stalked  optic  vesicle  is  shaped  like  an  eggcup 
(Fig.  583,  1).  The  cavity  in  the  anterior  of  this  cup  is  called  the  secondary  optic  vesicle.  The 
inflected  part  becomes  the  retina  (IV,  r),  while  the  posterior  part  becomes  the  choroidal  epithelium 
(IV,  yt).  The  stalk  becomes  the  optic  nerve.  At  the  under  surface  of  the  depression  there  is  a 
slit — the  choroidal  fissure — which  permits  some  of  the  mesoblast  to  gain  access  to  the  interior  of 
the  eye.  This  slit  forms  the  coloboma  (II) ;  it  is  prolonged  backward  on  the  stalk,  and  contains 
the  central  artery  of  the  retina.  The  margins  of  the  colobonia  afterward  unite  completely  with 
each  other,  but  in  some  rare  conditions  this  does  not  take  place,  in  which  case  we  have  to  deal 
with  a  coloboma  of  the  choroid  or  retina,  as  the  case  may  be.  In  the  bird,  the  embryonic  colo- 
boma  slit  does  not  close  up,  but  a  vascular  process  of  the  mesoblast  dips  into  it,  and  passes  into  the 
eye  to  form  the  pecten  (p.  813)  (Lieberku/in).  The  same  is  the  case  in  fishes  where  there  is  a 
large  vascular  process  of  the  meso-  and  epiblasl  forming  \he processus  falciformis  (p.  813). 


Development  of  the  eye.  I. — inflexion  of  the  sack  of  the  lens  (L)  into  the  primary  opti 
///,  mesoblast.  II. — The  inflexion  seen  from  below — »,  optic  nerve;  tf,  the  ouce 
inflected  vesicle  ;  L,  lens.  HI. — Longitudinal  section  of  II.  IV — Further  developl 
f,  cornea  ;  m,  membrana  capsulo-pupiltaris  :  L,  lens  ;  <i,  central  artery  of  the  retina 
/,  pigment  layer  of  the  retina  ;   r,  retina.     V. — Persistent  remains  of  the  pupillary  i 


vesicle  (P)—f,  epidermis; 
;  I,  the  inner  layer  of  the 
lent — €,  corneal  epithelium  ; 
;  s,  sclerotic  ;  ch,  choroid  ; 
lembrane. 


The  depression  or  inflection  of  the  optic  vesicle  is  due  to  the  down  growth  into  it  of  a  thickening 
of  the  epiblast  (I,  L).  It  is  hollow,  and  as  it  grows  inward  ultimately  becomes  spherical  and 
separated  from  the  epiblast  to  form  the  crystalline  lens,  so  that  the  lens  is  epiblastic  in  its  origin, 
while  the  capsule  of  the  lens  is  a  cuticular  structure  formed  from  epiblast.  That  part  of  the  epi- 
blast which  covers  the  vesicle  in  front  of  the  lens  ultimately  becomes  the  stratified  epithelium  of  the 
cornea.  The  cornea  is  formed  at  the  6th  week.  The  substance  of  the  choroid,  sclerotic  and 
cornea  is  formed  around  the  position  of  the  eye  from  the  mesoblast  (w).  The  capsule  of  the 
lens  is  at  first  completely  surrounded  by  a  vascular  membrane — the  membrana  capsulo-pupil- 
laris.  Afterwartl  the  lens  passes  more  posteriorly  into  the  eye — the  anterior  part  of  the  capsulo- 
pupillary  membrane,  however,  remains  in  the  anterior  part  of  the  eye,  while  toward  it  grows  the 
margin  of  the  iris  (7th  week),  so  that  the  pupil  is  closed  by  this  part  of  the  va.scular  capsule  (mem- 
brana  pupillaris).  The  blood  vessels  of  the  iris  are  continuous  with  those  of  the  pupillary  mem- 
brane ;  those  of  the  posterior  capsule  of  the  lens  give  off  the  hyaloid  artery,  a  continuation  of  the 
central  artery  of  the  retina;  its  veins  pass  into  those  of  the  iris  and  choroid.  The  vitreous  humor 
at  the  4th  week  is  represented  by  a  cellular  mass  between  the  lens  and  the  retina  [Kolliker).  The 
pupillary  membrane  disappears  at  the  7th  month.     It  may  remain  throughout  life  (V). 

Organ  of  Smell. — On  the  under  surface  and  lateral  limit  of  the  fore-brain,  the  epiblast  forms  a 
groove  or  pit  with  thickened  epithelium,  which  forms  a  depression  toward  the  brain,  but  always 
remains  as  a  pit  or  depression  ;  this  is  the  olfactory  or  nasal  pit,  to  which  the  olfactory  nerve  after- 
ward sends  its  branches. 

Organ  of  Hearing.— On  both  sides  of  the  after-brain  there  is  a  depression  or  pit  formed  in  the 
epiblast,  which  gradually  extends  deeper  toward  the  brain — this  is  the  labyrinth  pit.  The  pit  is 
ultimately  completely  cut  off'  from  the  epiblast,  just  like  the  lens,  and  is  now  called  the  vtsicle  of 
the  labyrinth.  It  represents  the  utricle,  from  which,  at  the  2d  month,  the  semicircular  canals  and 
the  cochlea  are  developed.  The  union  with  the  brain  occurs  later  along  with  the  developmenV  of 
the  auditory  nerve.  The  first  visceral  cleft  remains  as  an  irregular  passage  from  the  Eustachian 
tube  to  the  external  auditory  meatus.     The  outer  ear  appears  at  the  7th  week. 


902  INFLUENCE  OF  NERVES  ON  THE  UTERUS. 

453.  BIRTH. — With  the  growth  of  the  ovum,  the  uterus  becomes  more  dis- 
tended, its  walls  more  muscular  and  more  vascular,  although  the  uterine  walls  are 
not  thicker  at  the  end  of  pregnancy.  Toward  the  end  of  gestation  the  cervical 
canal  is  intact  until  labor  begins,  or  at  any  rate  it  is  only  slightly  opened  up  at  its 
upper  parts.  After  a  period  of  2S0  days  of  gestation  "labor"  begins,  whereby 
the  contents  of  the  uterus  are  discharged.  The  labor  pains  occur  rhythmically 
and  periodically,  being  separated  from  each  other  by  intervals  free  from  pain. 
Each  pain  begins  gradually,  reaches  a  maximum,  and  then  slowly  declines.  With 
each  pain  the  heat  of  the  uterus  increases  (§  302),  while  the  heart  beat  of  the 
fcetus  becomes  slower  and  feebler,  which  is  due  to  stimulation  of  the  vagus  in  the 
medulla  oblongata  (§  369,  3). 

[.\t  the  full  time  the  membranes  and  placenta  line  the  uterus.  The  membranes 
consist,  from  within  outward,  of  amnion,  chorion,  decidua  reflexa,  and  decidua 
vera.  The  fundi  of  the  uterine  glands  persist  in  the  deep  part  of  the  decidua 
vera  and  thus  form  a  spongy  layer,  the  part  above  this  being  the  compact  layer 
in  the  deep  part  of  the  placenta,  e.  g.,  near  the  uterine  wall,  we  have  also  the 
fundi  of  the  uterine  glands  persisting  in  the  decidua  serotina.  When  the  placenta 
and  membranes  are  expelled  after  birth,  the  line  of  separation  takes  place  in 
the  part  of  the  membranes  and  placenta  where  the  fundi  of  the  glands  persist. 
After  labor  is  completely  iinished  the  uterus  is  lined  by  the  remains  of  the  spongy 
layer  of  the  decidua  vera  and  serotina,  e.  g.,  is  lined  by  a  layer  which  contains 
the  fundi  of  the  uterine  glands.  The  new  mucous  membrane  is  regenerated  by 
the  growth  of  the  epithelium  and  connective  tissue  in  this  part.  The  mem- 
branes expelled  are  made  up  of  amnion,  chorion,  deciduK  reflexje,  and  the 
compact  layer  of  the  decidua  vera.] 

[Po\ver  in  Ordinary  Labors. — Sometimes  the  ovum  is  expelled  whole,  the 
membranes  containing  the  liquor  amnii  remaining  unruptured.  Poppel  has  pointed 
out  that  the  force  which  ruptures  the  bag  of  membranes  is  sufficient  to  complete 
delivery,  so  that,  as  Matthews  Duncan  remarks,  the  strength  of  the  membranes 
gives  us  a  means  of  ascertaining  the  power  of  labor  in  the  easiest  class  of  natural 
labors.  Matthews  Duncan,  from  experiments  on  the  pressure  required  to  rupture 
the  membranes,  concludes  that  the  great  majority  of  labors  are  completed  by  a 
propelling  force  not  exceeding  forty  pounds.] 

Polaillon  estimates  the  pressure  exerted  by  the  uterus  upon  the  foetus  at  each  pain  to  be  154  kilos. 
[33S.8  lbs.],  so  that,  according  to  this  calculation,  the  uterus  at  each  pain  performs  8820  kilogram- 
metres  of  work  (^  301).     [This  estimate  is  certainly  far  too  high.] 

After-birth. — After  the  fcetus  is  expelled,  the  placenta  remains  behind  ;  but  it  is  soon  expelled 
by  the  contractions  of  the  uterus.  During  the  contraction  of  the  uterus  to  expel  the  placenta,  a  not 
inconsiderable  amount  of  the  placental  blood  is  forced  into  the  child  {?/,  40).  [It  is  more  probable 
that  the  child  aspirates  the  blood  from  the  fcetal  portion  of  the  placenta.  This  can  be  seen  in  late 
ligature  of  the  cord.  The  child  may  thus  gain  two  ounces  of  blood.]  After  a  time  the  placenta, 
the  membranes,  and  the  decidua — constituting  the  afler-birth — are  expelled. 

Influence  of  Nerves  on  the  Uterus. — i.  Stimulation  of  the  hypogastric  plexus  causes  con- 
traction of  the  uterus.  The  fibres  arise  from  the  spinal  cord,  from  the  last  dorsal,  and  upper  three 
or  four  lumbar  nerves,  run  into  the  sympathetic,  and  then  reach  the  hypogastric  ])lexus  (Frank^n- 
Jiaiiser).  2.  Stimulation  of  the  nervi  erigentes,  which  are  derived  from  the  sacral  plexus,  causes 
movement  (v.  Basch  and  Hofmanii).  3.  Stimulation  of  the  lumbar  and  sacral  parts  of  the  cord 
causes  powerful  movements  (Spiegelberg,  Schiff).  There  is  a  centre  for  the  act  of  partiiritio7i  in 
the  lumbar  region  of  the  cord  (\  362,  6).  The  uterus,  like  the  intestine,  probably  contains  inde- 
pendent or  pareneliymatous  nei'ue  centres  [A'orner),  which  can  be  excited  by  suspension  of  the 
respiration,  and  by  anajmia  (by  compressing  the  aorta,  or  rapid  hemorrhage).  Decrease  of  the 
bodily  temperature  diminishes  the  movement,  while  an  increase  of  the  temperature  increases  it, 
which,  however,  ceases  during  high  fever  (Fromme).  The  experiments  made  by  Rein  upon  bitches 
show  that,  if  all  the  nerves  going  to  the  uterus  be  divided,  practically  all  the  functions  connected 
with  conception,  pregnancy,  and  parturition  can  take  place,  even  although  the  uterus  is  separated 
from  all  its  cerebrospinal  connections.  Hence  we  must  look  to  the  presence  of  some  automatic 
ganglia  m  the  uterus  itself.  According  to  Dembo,  there  is  a  centre  in  the  anterior  wall  of  the 
vagina  of  the  rabbit.  According  to  Jastreboff,  the  vagina  of  the  rabbit  contracts  rhythmically. 
Sclerotic  acid  greatly  excites  the  uterine  contractions  (v.  S-wiecici-i).  4.  The  uterus  contracts  re- 
flexly  on  stimulating  the  central  end  of  the  scalic  nerve  (v.  Basch  and  Hofmann),  the  central  end 
of  branchial  plexus  (Schlesinger),  and  the  nipple  [Soanzoni).     5.  The  uterus  is  supplied  by  z'aso- 


COMPARATIVE HISTORICAL.  903 

motor  nerves  (hypogastric  plexus),  which  come  from  the  splanchnic  ;  and  also  by  vasodilator  fibres, 
the  latter  through  the  nervi  erigenles.  The  vasomotor  nerves  are  affected  reflexly  by  stimulation  of 
the  sciatic  nerve  (y.  Basch  and  Hnfmann). 

Lochia. — After  birth,  the  whole  mucous  membrane  (decidua)  is  shed  ;  its  inner 
surface,  therefore,  represents  a  Jarge  wounded  surface,  on  which  a  new  mucous 
membrane  is  developed.  The  discharge  given  off  after  birth  constitutes  the 
lochia. 

Involution  of  the  Uterus. — After  birth  the  thick  muscular  mass  decreases 
in  size,  some  of  its  fibres  undergoing  fatty  degeneration.  Within  the  lumen  of 
the  blood  vessels  of  the  uterus  itself,  there  begins  in  the  interna  of  these  vessels  a 
proliferation  of  the  connective-tissue  elements,  whereby  within  a  few  months  the 
blood  vessels  so  affected  become  completely  occluded.  The  smooth  muscular 
fibres  of  the  middle  coat  of  the  arteries  undergo  fatty  degeneration.  The  rela- 
tively large  vascular  spaces  in  the  region  of  the  placenta  are  filled  by  blood  clots, 
which  are  ultimately  traversed  by  outgrowths  of  the  connective  tissue  of  the  vas- 
cular walls. 

Milk  Fever. — .\fter  birth  there  is  a  peculiar  action  on  the  vasomotor  system, 
constituting  milk  fever,  while  at  the  2d  to  3d  day  there  is  a  more  copious  supply 
of  blood  to  the  mammary  gland  for  the  secretion  of  milk  (§  231).  [After  birth 
the  pulse  becomes  slow  and  remains  so  in  a  normal  puerperum.  The  so-called 
milk  fever  is  not  found  in  cases  where  strict  cleanliness  is  observed  during  the 
labor  and  puerperum.]  The  cause  of  the  first  respiration  in  the  child  is  referred 
to  at  p.  692. 

454.  COMPARATIVE— HISTORICAL. — A  sketch  of  the  development  of  man  must 
necessarily  have  some  reference  to  the  general  scheme  of  development  in  the  Animal  Kingdom. 
The  question  as  to  how  the  numerous  forms  of  animal  life  at  present  existing  on  the  globe  have 
arisen  has  been  answered  in  several  ways.  It  has  been  asserted  that  each  species  has  retained  its 
characters  unchanged  from  the  beginning,  so  that  we  speak  of  the  "  constancy  of  species."  This 
view,  developed  by  Linnaeus,  Cuvier,  .\gassiz,  and  others,  is  opposed  by  that  supported  by  Lamarck 
(1809),  or  the  doctrine  of  the  "  Unity  of  the  .Vnimal  Kingdom,"  corresponding  to  the  ancient  view 
of  Empedocles,  that  all  species  of  aninnls  were  derived  by  variations  from  a  few  fundamental 
forms ;  that  at  first  there  were  only  a  few  lower  forms  from  which  the  numerous  species  were  devel- 
oped—  a  view  supported  by  Geoffrey  St.  Hilaire,  and  Goethe.  After  a  long  period  this  view  was 
restated  and  elucidated  in  the  most  brilliant  and  most  fruitful  manner  by  Charles  Darwin  (1S59)  in 
his  "  Origin  of  Species,"  and  other  works.  He  attempted  to  show  how  modifications  may  be 
brought  about  by  uniform  and  varying  conditions  acting  for  a  long  time.  Among  created  beings 
e.ach  one  struggles  with  its  neighbor,  so  that  there  is  a  real  "  struggle  for  existence."  Many 
qualities,  such  as  vigor,  rapidity,  color,  reproductive  activity,  etc.,  are  hereditary,  so  that  in  this  way 
by  "  natural  selection  "  there  may  be  a  gradual  improvement,  and  therewith  a  gradual  change 
of  the  species.  In  adduion,  organisms  can,  within  certain  limits,  accommodate  themselves  to  their 
surroundings  or  environment.  Thus  certain  useful  organs  or  parts  may  undergo  development, 
while  inactive  or  useless  parts  may  undergo  retrogression,  and  form  "  rudimentary  organs." 
This  process  of  "  natural  selection,"  causing  gradual  changes  in  the  form  of  organisms,  finds  its 
counterpart  in  "  artificial  selection,"  among  plants  and  animals.  Breeders  of  animals,  for  ex- 
ample, by  selecting  the  proper  crosses,  can  within  a  relatively  short  time  produce  very  material 
alterations  in  the  form  and  characters  of  the  animals  which  they  breed,  the  changes  being  more 
pronounced  than  many  of  those  that  separate  well-defined  species.  But,  just  as  with  artificial  se- 
lection, there  is  sometimes  a  sudden  **  rei^ersion  "  to  a  former  type,  so  in  the  development  of  species 
by  natural  selection  there  is  sometimes  a  condition  of  atavism.  Obviously,  a  wide  distribution  of 
one  species  in  different  climates  must  increase  the  liability  to  change,  as  very  different  conditions  of 
environment  come  into  play.  Thus,  the  migration  of  organisms  may  gradually  lead  to  a  change  of 
sjjecies. 

Biological  Law. — Without  discussing  the  development  of  different  organisms,  we  may  refer  to 
the  "  Jiiiidamintal  biological  law"  of  H;eckel,  viz.,  "that  the  ontogeny  is  a  short  repetition  of  the 
phylogeny,"  fontogeny  being  the  history  of  the  development  of  single  beings,  or  of  the  individual 
i'rom  the  ovum  onward,  while  phylogeny  is  the  history  of  the  development  of  a  whole  slock  of 
organisms,  from  the  lowest  forms  of  the  series  upward]  (p.  xxxii).  When  applied  to  man,  this  law 
assens  that  the  individual  stages  in  the  course  of  the  development  of  the  human  embryo,  e.g.,  its 
existence  as  a  unicellular  ovum,  as  a  group  of  cells  after  complete  cleavage,  as  a  blastodermic  ves- 
icle, as  an  organism  without  a  body  cavity,  etc. ;  that  these  stages  of  development  indicate  or  rep- 
resent so  many  animal  forms,  through  which  the  human  species  in  the  course  of  untold  ages  has 
been  gradually  evolved.  The  individual  stages  which  the  human  race  has  passed  in  this  process 
of  evolution  are  rapidly  rehearsed  in  its  embryonic  development.     This  conception  has  not  passed 


904  COMPARATIVE HISTORICAL. 

without  challenge.  In  any  case,  the  comparison  of  the  human  development  and  its  individual 
organs  with  the  corresponding  perfect  organs  of  the  lower  vertebrates  is  of  great  importance.  Thus, 
a  mammal  during  the  development  of  its  organs  is  originally  possessed  of  the  tubular  heart,  the 
branchial  clefts,  the  undeveloped  brain,  the  cartilaginous  chorda  dorsalis,  and  many  arrangements 
of  the  vascular  system,  etc  ,  which  are  permanent  throughout  the  life  of  the  lowest  vertebrates. 
These  incomplete  stages  are  perfected  in  the  ascending  classes  of  vertebrates.  Still,  there  are  many 
difticulties  to  contend  with  in  establishing  both  the  evolution  hypothesis  of  Darwin  and  the  biolog- 
ical  law  of  Hxckel. 

Historical. — Although  the  impetus  to  the  study  of  the  history  of  development  has  been  most 
stimulated  in  recent  times,  the  ancient  philosophers  held  distinct  but  varied  views  on  the  question  of 
development.  Passing  over  the  views  of  Pythagoras  (550  B.C.)  and  Anaxagoras  {500  B.C.),  Empe- 
docles  (473  B.C.)  taught  that  the  embryo  was  nourished  through  the  umbilicus;  while  he  named  the 
chorion  and  amnion.  Hippocrates  observed  incubated  eggs  from  day  to  day,  noticed  that  the 
allantois  protruded  through  the  umbilicus,  and  observed  that  the  chick  escaped  from  tlie  egg  on  the 
20th  day.  He  taught  that  a  7  months'  foetus  was  viable,  and  explained  the  possibility  of  superfre- 
tation  from  the  horns  of  the  uterus.  The  writings  of  Aristotle  (born  384  B.C.)  contain  many  refer- 
ences to  development,  and  many  of  them  are  already  referred  to  in  the  text.  He  taught  that  the 
embryo  receives  its  vascular  supply  through  the  umbilical  vessels,  and  that  the  placenta  sucked  the 
blood  from  the  vascular  uterus,  like  the  rootlets  of  a  tree  absorbing  moisture.  He  distinguished  the 
polycotyledonary  from  the  diffuse  placenta  ;  and  he  referred  the  former  to  animals  without  a  com- 
plete row  of  teeth  in  both  jaws.  In  the  incubated  egg  of  the  chick,  he  distinguished  the  blood 
vessels  of  the  umbilical  vesicle,  which  carried  food  from  the  cavity  of  the  latter,  and  also  the  allan- 
tois. He  also  observed  that  the  head  of  the  chick  lay  on  its  right  leg,  and  that  the  umbilical  sack 
was  ultimately  absorbed  into  the  body.  The  formation  of  double  monsters,  he  ascribed  to  the 
union  of  two  germs  or  two  embryos  Iving  near  each  other.  During  generation,  the  female  pro- 
duces the  malter,the  male  the  principle  which  gives  it  form  and  motion.  There  are  also  numerous 
references  to  reproduction  in  the  lower  animals.  Erasistratus  (304  B.C.)  described  the  embryo  as 
arising  Iiy  new  formations  with  the  ovum  or  Epigenesis,  while  his  contemporary,  Herophilus,  found 
that  the  pregnant  uterus  was  closed.  He  was  aware  of  the  glandular  nature  of  the  prostate,  and 
named  the  vesiculce  seminales  and  the  epididymis.  Galen  (131-203  A.D.)  was  acquainted  with  the 
existence  of  the  foramen  ovale,  and  the  course  of  the  blood  in  the  fretus  through  it,  and  through 
the  ductus  arteriosus.  He  was  also  aware  of  the  physiological  relation  between  the  breast  and  the 
blood  vessels  of  the  uterus,  and  he  described  how  the  uterus  contracted  on  pressure  being  applied 
to  it.  In  the  Talmud,  it  is  stated  that  an  animal  with  its  uterus  extirpated  may  live,  that  the  pubes 
separates  during  birth,  and  there  is  a  record  of  a  case  of  Caesarian  section,  the  child  being 
saved.  Sylvius  described  the  value  of  the  loramen  ovale;  Vesalius  (1540)  the  ovarian  follicles; 
Eustachius  (f  1570)  the  ductus  arteriosus  (Botalli)  and  the  branches  of  the  umbilical  vein  to  the 
liver.  Arantius  investigated  the  duct  which  bears  his  name,  and  he  asserted  that  the  umbilical  ar- 
teries do  not  anastomose  with  the  maternal  vessels  in  the  placenta.  In  Libavius  (1597)  it  is  stated 
that  the  child  may  cry  in  utero.  Riolan  (1618)  was  aware  of  the  existence  of  the  corpus  High- 
morianum  testis.  Pavius  (1657)  investigated  the  position  of  the  testes  in  the  lumbar  region  of  the 
foetus.  Harvey  (1633)  stated^  the  fundamental  axiom,  "0«Hf  vivunt  ex  ovo."  Fabricius  ab 
Aquapendente  (1600)  collected  the  materials  known  for  the  history  of  the  development  of  the 
chick.  Regner  de  Graaf  described  more  carefully  the  follicles  which  bear  his  name,  and  he  found 
a  mammalian  ovum  in  the  Fallopian  tube.  Swammerdam  (f  1685)  discovered  metamorphosis, 
and  he  dissected  a  butterfly  from  the  chrysalis  before  the  Grand  Duke  of  Tuscany.  He  described 
the  cleavage  of  the  frog's  egg.  Malpighi  (f  1694)  gave  a  good  description  of  the  development  o( 
the  chick  with  illustrations.  Hartsoecker  (1730)  asserted  that  the  spermatozoa  pass  into  the  ovum. 
The  first  half  of  the  iSth  century  was  occupied  with  a  discussion  as  to  whether  the  ovum  or  the 
sperm  was  the  more  important  for  the  new  formation  (the  Ovulists  and  Spermatists)  ;  and  also  as 
to  whether  the  fcetus  was  formed  or  developed  within  the  ovum  (Epigenesis),  or  if  it  merely  in- 
creased ill  growth.  The  question  of  spontaneous  generation  has  been  frequently  investigated  since 
the  time  of  Xeedham  in  1745. 

New  Epoch. — A  new  epoch  began  with  Caspar  Fried.  Woltf  (1759),  who  was  the  first  to 
teach  that  the  embryo  was  formed  from  layers,  and  that  the  tissues  were  composed  of  smaller  parts 
(corresponding  to  the  cells  of  the  present  period).  He  observed  exactly  the  fonnation  of  the  intes- 
tine. William  Hunter  (1775)  described  the  membranes  of  the  pregnant  uterus.  Soemmering 
(1799)  described  the  formation  of  the  external  human  configuration,  and  Oken  and  Kiesser  that  of 
the  intestines.  Oken  and  Goethe  taught  that  the  skull  was  composed  of  vertebra:.  Tiedemann 
described  the  formation  of  the  brain,  and  Meckel  that  of  monsters.  The  basis  for  the  study  of  the 
development  of  an  animal  from  the  layers  of  the  embryo,  was  laid  by  the  researches  of  Pander 
(1817),  Carl  Ernst  v.  Baer  (182S-1834),  Remak  and  many  other  observers;  and  Schwann  was  the 
first  to  trace  the  development  of  all  the  tissues  from  the  ovum.  [Schleiden  enunciated  the  cell 
theory  with  reference  to  the  minute  strucmre  ol  vegetable  tissues,  while  Schwann  applied  the 
theory  to  the  structure  of  animal  tissues,  .^niong  those  whose  names  are  most  prominent  in  con- 
nection with  the  evolution  of  this  theory  are  Martin  Barry,  von  Mohl,  Leydig,  Remak,  Goodsir, 
Virchow,  Beale,  Max  Schultze,  and  a  host  of  recent  observers.] 


INDEX. 


Abdominal  muscles  in  respira- 
tion, 200 
Abdominal  reflex,  666 
Abducens,  630 
Abiogenesis,  856 
Absolute  blindness,  722 
Absorption  by  fluids,  56 
by  solids,  56 
Absorption  of — 

Carbohydrates,  328 

Coloring  matter,  329 

Digested  food,  325 

Effusions,  344 

Fat  soaps,  329 

Forces  of,  330 

Grape  sugar,  328 

Influence  of  nerves  on,  331 

Inorganic  substances,  328 

Nutrient  enemata,  331 

Organs  of,  319 

Oxygen,  217 

Peptones,  328 

Small  particles,  330 

Solutions,  328 

Sugars,  328 

Unchanged  proteids,  329 

Absorption  spectra,  39 
Accelerans  nerve,  693 

in  frog,  695 
Accommodation  of  eye,  766 

defective,  772 
force  of,  772 
line  of,  770 
phosphtne,  780 
range  of,  772 
spot,  780 
time  for,  769 
Accord,  828 
Acetic  acid,  309 
Aceton,  292,  441,  452 
Acetona>mia,  292 
Acetylene,  42 
Achromatopsy,  795 
Achroodextrin,  244 
Acid  albumin,  409 
Acids,  free,  413 
Acoustic  nerve,  634 

tetanus,  585 
Acquired  movements,  727 
Acrylic  acid  series,  413 
Action  currents,  597 
Active  insufficiency,  537 
Addison's  disease,  486,  614 
Adelomorphous  cells,  267 
Adenoid  tissue,  335 
Adipocere,  398 


Adventitia,  112 

-Kgophony,  205 

Aerobes,  308 

.•Esthesiometer,  S47 

.-Esthesodic  substance,  670 

Afferent  nerves,  615 

After  birth,  902 

After  images,  797 

After  sensation,  749 

Ageusia,  843 

Agoraphobia,  637 

Agrammatism,  730 

Agraphia,  729 

Ague,  367 

Air,  changes  in  respiration,  212. 

collection  of,  209 

composition  of,  212 

diffusion  of,  216 

expired,  213 

impurities  in,  225 

quantity  exchanged,  213 
Air  cells,  184 
Alanin,  41 1 
Albuminoids,  411 
Albumins,  408 
Albuminuria,  445 
Albumoses,  vegetable,  410 
Alcohol,  3S5 
Alcohols,  415 
Alcoholic  drinks,  386 
Aleurone  grains,  410 
Alexia,  731 
Alkali  albumin,  409 
Alkaline  fermentation,  445 
Alkaloids,  3S5 
Alkophyr,  275 
Allantoin,  417,  439 
Allantois,  882 
Allochiria,  853 
Alloxan,  435 
Alm^n's  test,  450 
Alternate  hemiplegia,  68: 

paralysis,  681 
Alternation  of  generations,  857 
Amaurosis,  618 
Amblyopia,  618 
American  crow-bar  case,  704 
Amido  acids,  733 
Amido-caproic  acid,  281 
Amines,  417 
Aminia,  729 
Ammoniafmia,  469 
Amnesia,  730 
Amnion,  881 
Amniota,  881 
Amniotic  ffuid,  881 

905 


Amneboid  movement,  31 
Ampere's  rule,  578 
Amphiarthroses,  535 
Amphoric  breathing,  205 
Amygdalin,  344 
Amyloid  substance,  410 
Amylopsin,  280 
Amylum,  416 
Anabiosis,  856 
Anacrotism,  130 
Anaemia,  34,  65 

metabolism  in,  65 

pernicious,  35 
Anaerobes,  30S 
Ansesthesia  dolorosa,  853 
Anaesthetic  leprosy,  614 
Ancesthetics,  854 
Anabolic,  373 
Anakusis,  635 
Analgesia,  672 
Analgia,  854 
Anamnia,  88 1 
Anarthria,  729 
Anasarca,  345 
Anelectrotonus,  597 
Aneurism,  137 
Angiometer,  129 
Angioneuroses,  700 
Angiograph,  121 
Anidrosis,  488 

Animals,  characters  of,  xxxvii 
Animal  foods,  390 

magnetism,  708 
Anions,  579 

Anisotropous  substance,  495 
Ankle  clonus,  668 
Anode,  579 
Anosmia,  616 
Antagonistic  muscles,  538 
Anthracometcr,  209 
Anthracosis,  188,  226 
Anthropocholic  acid,  293 
Anti-albumin,  274 
Antiar,  344 
Antihydrotics,  486 
Antipeptone,  282 
Antiperislalsis,  259 
Anti-sialics,  241 
Aortic  valves,  72 
Aperistalsis,  262 
Apex  beat,  78,  86 
Aphakia,  757 
Aphasia,  729,  730 
Aphonia,  558 
Apncea,  687 
Appunn's  apparatus,  S33 


906 


INDEX. 


Apselaphesia.  853 

Aqueous  humor,  75S 

Arachnoid  mater,  743 

Archiblastic  cells,  878 

Area  opaca,  S65 

pellucida,  865 
vasculosa,  S79 

Argyll  Robertson  pupil,  777 

Arhythmia  cordis,  12S 

Aristotle's  experiment,  S49 

Aromatic  acids,  415 

oxyacids,  417 

Arrector  pili  muscle,  482 

Arteries,  11 1 

development  of,  894 
emptiness  of,  696 
rhythmical    contraction 

of,  698 
sounds  in, 164 
structure  of,  in 
tension  in,  145 
termination      in     veins, 
160 

Arteriogram,  121 

Arterial  tension,  125 

Arthrodial  joints,  535 

Articular  cartilage,  533 

Articulation    nerve    corpuscles, 

S45 
Artificial  cold-blooded  condition, 

371 
Artificial  digestion,  275 

gastric  juice,  273 
pancreatic  juice,  283 
Artificial  respiration,  224 

Marshall    Hall's    me- 
thod, 224 
Sylvester's        method, 
224 
Artificial  selection,  903 
Asparaginic  acid,  417 
Asphyxia,  222,  688 

artificial  respiration  in, 

224 
recovery  from,  224 
Aspirates,  55S 
Aspiration  of  heart,  152 
Assimilation,  373 
Associated  movement,  803 
.■\static  needles,  579 
Asteatosis,  4S9 
Asthma  nervosum,  643 

dyspepticum,  644 
Astigmatism,  774 

correction  of,  775 
test  for,  775 
Atavism,  903 
Ataxaphasia,  729 
Ataxia,  648,  721,  729,  731 
Ataxic  tabes,  672 
Atelectasis,  225 
Atmospheric  pressure,  229 

diminution  of,  229 
increase  of,  230 
Atresia  ani,  881 
Atrophy,  539 

of  the  face,  630 


Atropin,  511 

in  eye,  619,  777 
Attention,  time  for,  707 
Audible  tone,  lowest,  830 
Auditory  after  sensations,  837 

area,  723 

auras,  723 

centre,  723 

delusions,  635 

meatus,  S16 

nerve,  S14 

ossicles,  819 

paths,  724 

perception,  829 
Auerbach's  plexus,  262,  325 
Auricles  of  heart,  68,  75,  83 
Auscultation  of  heart,  93 

of  lungs,  195 
Automatic  excitement,  653 
Autonomy,  70S 
Auxocardia,  104 
Axis  of  vision,  787 

Bacillus.  66,  307 

amylobacter,  309 
anthracis,  66 
butyricus,  309 
subtilis,  310 
tubercle    and    others, 
226 
Bacterium,  66,  307,  313,  3S0 
aceti,  309 
cyanogeneum,  380 
fcetidum,  489 
lacticum,  308,  378 
synxanthum,  380 
termo,  313 
Ball  and  socket  joints,  535 
Bantingism,  399 
Barsesthesiometer,  850 
Bas.-il  ganglia,  733 
Base<lo\v's  disease,  180,  701 
Bases,  408 

Basilar  membrane,  S27 
Batteries,  galvanic,  579 
Bunsen's,  580 
Grennet's,  581 
Grove's.  5S0. 
Lechlanche's,  581 
Smee's,  581 
Beats,  S36 

isolated,  836 
successive,  836 
Bed  sore,  614 
Beef  tea,  383 
Beer,  387 
Bell's  law,  646 

deductions  from,  647 
Bell's  paralysis,  633 
Benzoic  acid,  415 
Bert's  experiment,  606 
Bidder's  ganglion,  94 
Bile  acids,  293 

composition  of,  293 
crystallized,  293 
diicts,  286 

ligature  of,  2S8 


Bile,  eflfect  of  drugs  on,  300 
excretion  of,  298 
fate  of,  302 
functions  of,  301 
pigments,  295 
pressure,  299 
reabsorption  of,  299 
secretion  of,  296 
spectrum  of,  295 
test  for,  294,  295 
Biliary  fistula,  298 
Bilicyanin,  295 
Bilifuscin,  295 
Biliprasin,  295 
Bilirubin,  295 
Biliverdin,  295 
Binocular  vision,  S03 
Biological  law,  903 
Biology,  xxxi 
Birth,  902 
Biuret  reaction,  275 
Blastoderm,  S64,  874 
Blastosphere,  874 
Blepharospasm,  634 
Blind  spot,  785 
Blood,  17 

abnormal,  63 

analysis,  45 

arterial,  62 

carbon  dioxide  in,  40 

clot,  47 

coagulation,  47 

color,  17 

coloring  matter,  35 

defibrinated,  47 

distribution  of,  167 

electrical  condition  of,  61 1 

extractives,  56 

fats  in,  55 

fibrin  in,  34,  47 

lake  colored,  23 

loss  of,  65 

microscopic    examination, 
18 

nitrogen  in,  61 

odor,  iS 

organisms  in,  66 

oxygen  in,  59 

ozone  in,  60 

plasma,  46 

plates,  33 

portal  vein,  62 

quantity,  63,  160 

reaction,  17 

salts  in,  56,  65 

serum,  46 

specific  gravity,  iS 

taste,  18 

temperature,  18 

transfusion  of,  63 

variations  in,  63 

venous,  62 

water  in,  54 
Blood  channels,  intercellular, 114 
Blood  corpuscles — stn  ma,  21 ,44 

abnormal  changes,  34 

action  of  reagents  on, 21, 32 


INDEX. 


907 


Bloo3      corpuscles  —  amoeboid 
movements,  32 

circulation  of,  67 

change  of  form,  22 

chemical  composition,  45 

color,  21 

conserN'ation  of,  ^^ 

crenation,  21 

decay,  28 

diapedesis,  32 

distribution  of,  157 

effect  of  drugs,  32 

effect  of  reagents,  21 

form,  iS,  24 

Gower's  method,  21 

human,  red,  iS 
white,  29 

intracellular  origin,  25 

Malassez's  method,  19 

nucleated,  34 

number,  19,  30 

of  newt,  30 

origin,  25 

pathological  changes,  28 

proteids  of,  44 

staining  of,  23 

size,  18,  24 

stroma,  21,  44 

transfusion  of,  63 

weight,  19 
Blood  current,  139 

in  capillaries,  140 

velocity  of,  155 
Blood  gase-,  59 

estimation  of  O,  CO,,  and 

N,  59 
extraction,  57 
gas  pumps  for,  57 
quantity,  59 
Blood  glands,  172 

islands,  25,  879 
plasma,  iS 
Blood  pressure,  141  , 

arterial,  145  1 

capillary,  151  1 

estimation  of,  141 
in  pulmonary  artery,  153 
in  veins,  152 
relation  to  pulse,  150 
variations  of,  145 
Blood  vessels,  1 1 1 

action     of    acids 

on,  115 
cohesion  of,  116 
elas'.icity  of,  1 16 
lymphatics,  114 
pathology  of,  116 
properties  of,  115 
structure  of,  1 1 1 
Blue  pus,  489 

sweat,  489 
Body,  vibrations  of.  137 

wall,  formation  of,  8S0 
Bone,  chemical  composition  of,  j 
891 
callus  of,  404 
development  of,  S92 


Bone,  effect  of  madder  on,  405 
fracture  of,  404 
growth  of,  S92 
histogenesis  of,  891 
red  marrow,  27 

Bones,  mechanism  of,  533 

Boihriocephalus,  857 

Bottger's  test,  246 

Bouton's  terminals,  S46 

Bowman's  tubes,  751 

Box  pulse  measurer,  117 

Bradyphasia,  730 

Brain,  675 

arteries  of,  711 
blood  vessels  of,  710 
general  scheme  of,  675 
impulses,  course  of,  679 
influence  of,  on  cord,  700 
in  invertebrata,  746 
membranes  of,  740 
motor    centres    of,    713, 

718,  719 
movements  of,  743 
pressure  on,  746 
protective   apparatus    of, 

742 
pulse  in,  137 
psychical    functions     of, 

703 
pyramidal  tracts  of,  678 
I  topography  of,  725 

I  weight  of,  706 

Brandy,  387 

Bread,  383 

Brenner's  formula,  635 
I  Broca's  convolution,  729 

Bromidrosis,  489 

Bronchial  breathing,  204 
fremitus,  205 

Bronchiole,  185 

Bronchophony,  205 

Bronchus  extra  pulmonary,  185 
1  intra-pulmonary,  1S5 

I  small,  185 

'  Bronzed  skin,  181 

Brownian  movement,  244 

Bruit,  164 

Jf  diahte,  1 64 

Brunner's  glands,  303,  324 

Buchanan's  experiments,  50 

Bulbar  paralysis,  686 

Butter,  378 

Butyric  acid,  309 

Caffein,  3S5 
Calabar  bean  on  eye,  619 
Calcic  phosphate,  458 
Calculi  biliary,  399 
salivary,  242 
urinary,  45S 
Callus,  404 
Calorimeter,  347 
Canal  of  cochlea,  825 

hyaloid.  757 

Nuck,  89S 

Petit,  757 

Schlemm,  753 


Canal,  semicircular,  826 
of  spinal  cord   654 
of  Stilling,  758 
Canalis  cochlearis,  825 

reuniens,  825 
Capillaries,  112 

action  of  silver  ni- 
trate on,  113 
blood      current     in, 

160 
circulation,  161 
contractility  of,  115 
development  of,  26 
form    and    arrange- 
ment of,  160 
pressure  in,  151 
stigmata  of,  113 
velocity  of  blood  in, 

»S7 
Capillary  electrometer,  5S9 
Capsule,  external.  735 
Glisson's,  2S5 
internal,  735 
of  Tenon,  758 
Carbolic  acid  urine,  440 
Carbohydrates,  415 

fermentation  of, 
30S 
Carbon  dioxide,  conditions   af- 
fecting, 213 
estimation  of,  209 
excretion  of,  217 
in  air,  212 
in  blood,  61 
in  expired  air,  212 
where  formed,  219 
Carbonic  haemoglobin,  40 
oxide,  40 
poisoning  by,  41 
Cardiac  cycle,  75 

dullness,  93 
ganglia,  94 
hypertrophy,  77 
impulse,  78 
murmurs,  91 
nerves,  93 
nutritive  fluids,  96 
plexus,  93 
poisons,  103 
revolution,  75 
sounds,  88 
Cardinal  points,  761 
Cardiogram,  78 
Cardiograph,  79 
Cardioinhibitory    centre,     14S, 
691 
nerves,  640 
Cardio  -  pneumatic     movement, 

104 
Caricin,  266 
Carnin,  417 
Cartilage.  533,  S80 
Carotid  gland,  114,  181 
Casein,  378,  410 
Catacrotic  pulse,  121 
Cataphoric  action,  583 
Cataract,  757 


908 


INDEX. 


Cathartics,  265 
Cathelectrotonus,  598 
Cathode,  579 
Caudal  heart  of  eel,  344 
Caudate  nucleus,  733 
Cavernous  formations,  114 
Cells,  division  of,  S56 
Cellulose,  416 
Cement,  251 

action  of  silver  nitrate 

on,  113,  333 
substance,  1 13 
Centre,  accelerans,  693 
ano-spinal,  669 
cardio-inhibitory,  69 1 
cilio-spinal,  668 
closure  ol  eyelids,  6S5 
dilator  of  pupil,  685 
ejaculation,  669 
erection.  669 
for  coughing,  685 
for  defiecation,  669 
for  mastication,  685 
heat  regulating,  702 
micturition,  669 
parturition,  669 
pupil,  6S5 
respiratory,  686 
for  saliva,  686 
sneezing,  685 
spasm,  6S5,  702 
speech,  729 
swallowing,  685 
sweat,  669,  703 
vasodilator,  669,  701 
vasomotor,  669,  695 
vesicospinal,  669 
vomiting,  6S5 
of  gravity,  540 
Centrifugal  nerves,  613 
Centiipetal  nerves,  615 
Centro-acinar  cells,  278 
Cereals,  3S3 
Cerebellum — 

Action  of  electricity  on,  742 
Connections  of,  677 
Function  of,  740 
Pathology  of,  742 
Removal  of,  740 
Structure  of,  739 
Cerebral  arteries,  711,  744 
epilepsy,  717,  728 
fissures,  dog,  715 
inspiratory  centre,  687, 
motor  centres,  713,718, 

719 
sensory  centres,  721 
vesicles,  S77 
Cerebrin,  413,  567 
Cerebrospinal  Huid,  743 
Cerebrum,  709 

bloodvessels  of,  710, 

743 
convolutions  of,  709 
epilepsy  of,  717 
excision   of   centres, 

721 


Cerebrum,  extirpation  of,  704 

Flourens'     doctrine, 

704 
functions  of,  704 
Golti's  theory  of,  725 
imperfect      develop- 
ment of,  704 
lobes  of,  711 
motor     centres     of, 

713,  718,  720 
motor  regions  of,  715, 

725 
movements  of.  743 
sensory  centres,  721 
sensory    regions    of, 

721.  731 
structure  of,  709 
sulci  and  gyri  of,  706 
tactile  areas  of,  724 
thermal    centres   of, 

724 
weight  of,  706 

Cerumen,  4S5 

Cervical  sympathetic,  section  of, 
651 

Chalaza:,  865 

Charcot's  crystals,  22S 
disease,  614 

Cheese,  380 

Chemical  affinity,  xxxv 

Chess-board  phenomenon,  809 

Chest,  dimensions  of,  201 

Cheyne-Stokes'      phenomenon, 
196 

Chiasma,  617 

Chitin,  413 

Chloasma,  486 

Chlorophane,  757 

Chlorosis,  34 

Chocolate,  385 

Chol.xmia,  301 

Cholalic  acid,  294,  415 

Cholester.Temia,  301 

Cholesterin,  45,  296,  302,  415 

Choletelin,  295 

Cholin,  567 

Choloidinic  acid,  294 

Choluria,  450 

Chondrin,  41 1 

Chondrogen,  412 

Chorda  dorsalis,  877 

Chorda  tympani,  631,  701 

Chorda."  tendineas,  76 

Chorion  l«ve,  884 

frondosum,  884 
primitive,  883 

Choroid,  753 

Choroidal  fissure,  901 

Christison's  formula,  427 

Chromatic  aberration,  774 

Chromatophores,  490 

Chromatopsia,  618 

Chromidrosis,  489 

Chromophanes,  757 

Chronograph,  515 

Chyle,  337,  339 

movement  of,  341 


Chyle  vessels,  341 
Chylous  urine,  457 
Chyme,  274 
Cicatricula,  864 
Cilia,  491 

conditions  for  movement, 

492 
effect  of  reagents  on,  492 
functions  of,  492 
Ciliary  motion,  491 

force  of,  492 
ganglion,  623 
muscle,  76S 

Ciliated  epithelium,  491 
Cilio  spinal  region,  668,  776 
Circle  of  Willis,  744 
Circulating  albumin,  3S9 
Circulation,  capillary,  161 
duration  of,  159 
first,  879 
portal,  67 
pulmonary,  67 
schemata  of,  140 
second,  879 
systemic,  67 
Circumpolarization,  247 
Claustrum,  735 
Cleavage  of  yelk,  S74 
lines  of,  874 
partial,  877 
Cleft  sternum,  77 
palate,  889 
Clerk  -  Maxwell's     experiment, 

781 
Climacteric,  867 
Clitoris,  899 
Closing,  continued   contraction, 

600 
Closing  shock,  584 
Clothing,  363 
Coagulable  fluids,  54 
Coagulated  protei<is,  410 
Coagulation  experiments,  52 
Coagulation  of  blood,  46-52 

theories  of,  52,  53 
Cocaine,  777. 

Coccygeal  gland,  114,  181,  490 
Cochlea,  825 
Cocoa,  385 
Coecilas  verbalis,  731 
Coelom,  880 
Coffee,  385 

Cold  blooded  animals,  350,  370 
Cold  on  the  body,  370,  371 

uses  of,  371 
Collagen,  277,  411 
Colloids,  327 
Coloboma,  901 
Color  associations,  837 
blindness,  794 

acquired,  795 
testing,  796 
sensation,  791 
Hering's  theory,  793 
Young- Helmholtz  theory, 
793 


INDEX. 


909 


Colorless  corpuscles,  29 
Color  top,  797 
Colors,  complementary,  791 
contrast,  79 1 
geometrical  table,  792 
methods  of  mixing,  791 
mixed,  791 
simple,  791 
Colostrum,  379 
Columella,  837 
Columns  of  the  cord,  614 
Coma,  diabetic,  292 
Comedo,  489 
Common  sensation,  853 
Comparative — 
Absorption,  346 
Circulation,  181 
Digestion,  317 
Hearing,  S37 
Heat,  372 

Kidney  and  urine,  476 
Metabolism,  417 
Motor  organs,  543 
Nerve  centres,  746 
Nerves  and  electro-physiology, 

611 
Peripheral  nerves,  652 
Reproiluction    and     develop- 
ment, 903 
Respiration,  230 
Sight,  312 
Skin,  490 

Voice  and  speech,  558 
Compensation,  589 
Complemental  air,  191 
Complementary  colors,  791 
Compound  eye,  312 
Condensed  milk,  380 
Condiments,  3S5 
Conduction  in  the  cord,  671 
Conductivity,  605 
Conglutin,  410 
Conjugate  deviation,  620,  727 
Conjugation,  857 
Connective-tissue  spaces,  332. 
Consonance,  835 
Consonants,  555 
Constant  current,  use  of,  518 
Constant  elements — 
Bunsen's,  580 
Daniell's,  5S1 
Grennet,  581 
Grove's,  5S0 
Leclanche's,  581 
Smee's,  581 
Constipation,  316 
Contraction,  cardiac,  105 

muscular(see  Myo 

gram). 
fibrillar,  512 
initial,  523 
of    blood     vessels, 

114. 
remainder,  520 
rhythmical,  510 
secondary,  592 
without  meials,  591 


Contracture,  520 
Contrast,  798 

colors,  791 
Convergent  lens,  action  of,  759 
Cornea,  750 
Coronary  vessels,  73 

effects   of  ligature   of, 
74 
Corpora  quadrigemina,  737 
Corpulence,  399 
Corpus  callosum,  739 

luteum,  869 

spongiosum,  869 

striatum,  733 
Cortical  blindness,  722 
Corti's  organ,  825 
Cotyledons,  886 
Coughing,  207 

centre  for,  685 
Cracked-pot  sound,  204 
Cramp,  855 
Cranial  flexures,  877 

nerves,  576 
Cranioscopy,  704 
Crepitation,  205 
Crescents  of  Gianuzzi,  234 
Crista  acustica,  826 
Crossed  reflexes,  663 
Crusta  petrosa,  250 

plilogistica,  47 
Crj'ing.  208 
Crystallin,  409,  757 
Crystalline  spheres,  812 
Crystallized  bile,  293 
Crystalloids,  327 
Cubic  space,  226 
Curara,  action  of,  507,  510 
Cutaneous  respiration,  219 

trophic  affections,  613 
Cuticular  membrane,  250 
Cyanogen,  42 
Cyanuric  acid,  417 
Cylindrical  lenses,  774 
Cyrtometer,  201 
Cysticercus,  857 
Cystin,  417 
Cytozoon,  22 

Daltonism,  795 
Damping  apparatus,  818 
Darby's  fluid  meat,  275 
Death  of  a  nerve,  576 
Debove's  membrane,  183 
Decidua  reflexa,  883 

serotina,  883 

vera,  882 
Decubitus  acutus,  735 
Defsecation,  261 

centre  for,  669 
Degeneration,  fatty,  400 
Deglutition,  254 

nerves  of,  255 
Deiter's  cells,  827 
Demarcation  current,  592 
Demodex  foUiculorum,  485 
Dentine,  249 
Dentition,  249 


Depressor  fibres,  697 

nerve,  146,  640 
Development,    chronology 


of, 


Dextrin,  416 
Dextrose,  415 
Diabetes  mellitus,  64,  451 
Diabetic  coma,  292 
Dialysis,  327 
Diapedesis,  32,  162 
Diaphragm,  197 
Diaphoretics,  486 
Diarrhoea,  316 

Diastatic  action,  245,  280,  412 
Diastole,  75,  78 
Dicrotic  pulse,  123 
wave,  124 
Diet,  adequate,  389 

effect  of  age  on,  393 

effect  of  work  on,  393 

flesh,  397 

flesh  and  fat,  397 

of  carbohydrates,  397 

quality  of,  391 

quantity,  392 
Difference  theory,  596 
Differential  rheotom,  594 

tones,  836 
Diffusion,  326 

circles,  766 
of  gases,  57 
Digestion  during  fever,  315 

in  plants,  317 
Digestion,  232 

artificial,  275,  315 
Digestive  apparatus,  248 
Dilatation   of  pupil,  centre   for, 

668 
Dilator  pupillae,  776 
Dioptric,  774 

observations,  759 
Diphthongia,  558 
Diphthongs,  557 
Diplopia,  619,  S04 
Direct  vision,  7S8 
Direction,  836 
Discharging  forces,  506 
Discus  proligerus,  863 
Disdiaclasts,  500 
Dissociation,  218 
Dissonance,  836 
Distance,  estimation  of,  809 

false  estimate  of,  810 
Diuretics,  460 

Double    conduction    in     nerve, 
605 
images,  neglect  of,  805 
Dreams,  707 
Drepanidium,  23 
Dromograph,  156 
Dropsy,  344 
Ductus  arteriosus,  886 

venosus,  886 
Dura  mater,  742 
Dusi  particles,  225 
Dyschromatopsy,  794 
Dyslysin,  294 


910 


INDEX. 


Dysperistalsis,  263 
Dyspnoea,  195,  222,  688 

Ear,  814 

conduction  in,  815 
development  of,  901 
external,  8t6 
fatigue  of,  837 
fineness  of,  830 
.    labyrinth  of,  825 
meatus  of,  816 
ossicles  of,  819 
speculum,  819 
tympanum  of,  816 
Earthy  phosphates,  442 
Eccentric  hypertrophy,  77 
Ecchymoses,  6gS 
Echo  speech,  70S 
Ectoderm,  S75 
Ectopia  cordis,  85 
Efferent  nerves,  O13 
Egg  albumin,  55 
Eggs,  381 

Ejaculation,  centre  for,  S70 
Elastic  after  effect,  1 16 
elevations,  126 
tension,  154,  190 
tubes,  no 
Elasticity  of  blood  vessels,  115 
lens,  768 
muscle,  526 
Elastin,  411 

Electrical  charge  of  body,  611 
fishes,  611 
nerves,  606 
organs,  612 
Electrical  currents  of  muscle, 588 
eye,  594 
glands,  591 
mucous    membranes, 

591 
nerve,  590 
skin,  591 
Electricity,    therapeutical    uses, 

606 
Electrodes,  non-polarizable,  582 

other  forms,  606 
Electrolysis,  579 
Electrometer,  5S9 
Electrotherapeutics,  606 
Electro-motive  force,  577 
Electro-physiology,  577 
Electrotonus,  594 

in  inhibitory  nerves, 

601 
in  motor  nerves,  598 
in  muscle,  601 
in    sensory    nerves, 
601 
Eleidin,  477 
Elementary   granules   of  blood, 

34 
Emetics,  259 
Emmetropic  eye,  770 
Emotions,  expression  of,  559 
Emulsification,  2S3 
Eniulson,  344 


Emydin,  410 
Enamel,  250 
Enamel  organ,  251 
End  arteries,  160 

bulbs,  846 

capsules,  846 

organ,  613 

plate,  498 
Endocardial  pressure,  85 
Endocardium,  71 
Endoderni,  875 
Endolymph,  825 
Endoneurium,  565 
Endosmometer,  326 
End  osmosis,  327 
Endosmotic  equivalent,  326 
Enemata,  331 
Energy,  conservation  of,  xxxvi 

potential,  xxxvi 
Entoptical  phenomena,  779 

pulse,  7S0 
Entotical  perceptions,  837 
Enuresis  nocturna,  475 
Enzym,  412 
Epiblast,  875 
Epicardium,  68 
Epidural  space,  947 
Epididymis,  858 
Epigenesis,  904 
Epiglottis,  255 
Epilepsy,  703,  717,  72S 
Epineurium,  565 
Epithelium  ciliated,  183,  225 

squamous,  232 
Eponychium,  480 
Equator,  5  88 
Erectile  tissue,  870 
Erection,  centre,  for,  870 

of  penis,  S69 
Erect  vision,  766 
Errhines,  207 
Erythrochlorophy,  795 
Erythrodextrin,  244 
Ether,  xxxii 
Eudiometer,  59 
Eukalyn,  417 
Euperr-talsis,  262 
Eupna?a,  6S8 
Eustachian  catheter,  824 

tube,  822 
Excitability,  action  of    poisons 

on,  671 
Excitable  points  of  a  nerve,  576 
Excito-motor  nerves,  615 
Excretin,  31 1 

Excretion  of  fcecal  matter,  260 
Exophthalmos,  799 
Expectorants,  227 
Expiration,  197 
Expiratory  muscles,  197 
Explosives,  557 
Extensor  tetanus,  663 
E.\ternal  genitals,  899 
Extra  current,  584 
Extrapolar  region,  598 
Extremities,     development     of. 


Exudation,  345 
Eye,  750 

accommodation  of,  766 

artificial,  765 

astigmatism,  775 

chromatic    aberration    of, 
774 

compound,  Sl2 

development  of,  901 

eff'ect  of  electrical  currents, 
7  So 

emmetropic,  773 

entoptical  phenomena,  779 

excised,  778 

fundus  of,  7S1 

hypermetropic,  771 

illumination  of,  781 

movements  of,  799 

muscles  of,  801 

myopic,  771 

presbyopic,  772 

protective  organs  of,  810 

structure  of,  750 
Eyeballs,  axis  of,  800 

movements  of,  801 
muscles  of,  801 
planes  of,  800 
positions  of,  800 
protrusion  of,  799 
retraction  of  799 
simultaneous      move- 
ments of,  803 
Eye  currents,  594 
Eyelids,  810 

Facial  nerve,  631 
Fsecal  matter,  312 
P'ainting,  78 
Fallopian  lubes,  866 
Falsetto  voice,  554 
Faradic  current,  5S4 
Faradization  in  paralysis,  607 
Far  pomt,  770 
Fascia,  lymphatics  of,  341 
Fatigue  of  muscle,  518 
stuffs,  519,  531 
Fats,  413 

decomposition  of,  282 
fermentation  of,  309 
metabolism  of,  397 
origin  of,  398 
Fat-splitting  ferment,  283 
Fatty  acids,  413 

degeneration,  400 
Fechner's  law,  749 
Fchling's  solution,  246,  452 
Ferments,  41  2 

fate  of,  306 
organized,  412 
unorganized,  412 
Fermentation,  3S6 

in  intestine,  307 
test,  247 
Fertilization  of  ovum,  872 
Fever,  367 

after  transfusion,  169 
Fibres  of  Tomes,  249 


INDEX. 


911 


Fibrillar  contraction,  $12 
Fibrin,  34,  46 
Fibrin  factors,  46 
Fibrin  ferment,  46,  52 
Fibrinogen,  50,410 
Fibrinoplastin,  50 
Fibroin,  411 
Field  of  vision,  765 

contest  of,  808 
Filaria  sanguinis,  457 
Filtration,  327 

First  respiration,  discharge   of, 
690 
effects  of,  on  thorax,  206 
Fish  extract,  3S3 
Fission,  856 
Fistula,  biliarj-,  29S 
gastric,  273 
intestinal,  304 
pancreatic,  279 
Thiry's,  304 
Vella's,  305 
Flame  spectra,  38 
Flavor,  S40 
Flcischl's    law   of    contraction, 

601 
Flesh,  38 1 
Floor  space,  226 
Flourens'  doctrine,  704 
Fluid  vein,  164 
Fluids,  flow  of,  108 

introduction  of,  248 
Fluorescence,  791 

of  eye,  766 
Fluorescin,  759 
Focal  line,  761 

point.  761 
Foetal  circulation,  885 
membranes,  886 
Follicles,  solitarj-,  324 
Fontana's  markings,  568 
Fontanelle,  pulse  m,  137 
Foods — 

isodynamic,  34S 
plastic,  389 
quantity,  392 
respiratory,  393 
Foramen  ovale,  886 

of  Magendie,  743 
Force  of  accommodation,  772 
Forced  movements,  73S 
Forces,  xxxiii 
Formatio  reticularis,  683 
Formative  cells,  877 
Fovea  cardica,  879 
centralis,  787 
Fractional      heat      coagulation, 

55 
Free  acid,  formation  of,  271 
Fremitus,  205 
Friction  sounds,  205 
Frog  current,  591 
Fromann's  lines,  563 
Fruits  384 

Fundamental  note,  817 
Fundus  glands,  266 
Fungi,  307 


Gaertner,  ducts  of,  889 
Galactorrhoea,  370 
Galactose,  415 
Gallop,  544 
Gall  stones,  315 
Galton's  whistle,  829 
Galvanic  battery,  577 

excitability,  609 
Galvano  cautery,  61 1 
Galvanometer,  578 

reflecting,  5S2 
Galvano-puncture,  611 

tetanus,  571 
Ganglionic  arteries,  744 
Gangrene,  614 
Gargling,  208 
Gas  pump  for  blood,  57 
Gaseous  exchanges,  213,  216 

eflects    on, 

2"3 

Gases,  307 

diflTusion  of,  216 
in  blood,  59 
in  stomach,  278 
indifferent,  225 
irrespirable,  225 
poisonous,  225 
respired,  191 
Gaskells  clamp,  97 
Gas  sphygmoscope,  122 
Gasserian  ganglion,  626 
Gastric  digestion,  274 

conditions  affecting,  275, 

3«4 
fistula,  315 

pathological    variations, 
3«4 
Gastric  giddiness,  636 
Gastric  juice,  269 

action  of  drugs  on,  273 
action  on  tissues,  277 
actions  of,  276 
artificial,  273 
Gaule's  experiment,  22 
Gelatin  f  albumin,  396 
Gemmation,  856 
Genital  cord,  89S 

eminence,  899 
Genu  valgum,  538 

varum,  53S 
Geometrical  color  table,  792 
Germ  epithelium,  S63 
Germinal  area,  S75 
Germs,  226 

Ciestation,  period  of,  8S7 
Giddiness,  625,  636 
Ginglymus,  534 
Giraldes,  oi^an  of,  899 
Girdle  sensation,  672 
Glance,  808 

Glands,  albuminous,  232 
Bowman's,  839 
Brunner's,  303 
buccal,  232 
carotid,  114,  181 
ceruminous.  4S2 
changes  in,  235,  253 


Glands,  coccygeal,  114,  iSl 

Ebner's,  232 

fundus,  266 

Harderian,  813 

lachrymal,  810 

Lieberkuhn's,  304 

lingual,  232 

lymph,  336 

mammary,  375 

Meibomian,  810 

mLxed,  232 

mucus,  232,  236 

Nuhn's,  232 

parotid,  233 

peptic,  266 

Fever's,  325 

pyloric,  267 

salivary,  233 

sebaceous,  4S2 

serous,  232,  235 

solitary,  324 

sublingual,  240 

sweat,  483 

uterine,  866 

Weber's,  233 
Glaucoma,  626 
Gliadin,  410 
Globin,  409 
Globulins,  410 
Glomerulus,  42 1 
Glosso-pharyngeal  nerve,  627 
Glossopiegia,  645 
Glossy  skin,  614 
Glottis,  547 
Glucose,  415 

tests  for,  246,  451 
Glucosides,  413 
Glutaminic  acid,  417 
Gluten,  3S4,  410 
Glycerin,  414,  415 

method,  273 
Glycerin-phosphoric  acid,  414 
Glycerinic  acid,  310 
Glycin,  310,  41 1 
Glycocholic  acid,  293 
Glycogen,  2S8,  416 
Glycolic  acids,  414 
Glycosuria,  290,  451 
Gmelin-Heintz,    reaction,    295, 

45 « 

Goblet  cells,  321 

Goitre,  180 

GoU's  column.  655 

Goltz's     croaking     experiment, 
663 
embrace  experiment,  664 

Gorham's  pupil  photometer,  778 

Gout,  65 

Graafian  follicle,  863 

Granules,  elementary,  34 

Granulosa,  244 

Grape  sugar,  415 

absorption  of,  328 
estimation  of,  247 
in  urine,  45 1 
tests  for,  246,  45 1 
volumetric  analysis,  452 


912 


INDEX. 


Gravitation,  xxxiii 

Great  auricular  nerve,  698 

Green  blindness,  795 

Green  vegetables,  384 

Growth,  388,  417 

of  bones,  613 

Guanidin,  519 

Guanin,  417 

Gubcrnaculum  testis,  898 

Gum,  416 

Gustatory  fibres,  632 
centre,  724 
region,  84 1 
sensations,  842 

Gymnastics,  538 

Gymnotus,  612 

Gyri,  675 

Hay's  reaction,  45 1 

Hx-macytometer,  21 

Ha^madynamometer,  141 

Haematin,  42,413 

Hjematoblasts,  33 

Hiiematohidrosis,  489 

H^matoidin,  44,  451,  869 

Hematoma  aurium,  614 

Hsematoporphyrin,  42 

Ha.nnaturia,  447 

Hxmautography,  122 

Hsemin  and  its  tests,  43 

Hi.T;mochromogen,  42 

Hjemocyanin,  25 

Haffmocytolysis,  22 

Hremocytometer,  21 

Hitmocytotrypsis,  22 

Hjemodromometer,  155 

Hsmodynamometer,  141 

Hsemoglobin,  35 

analysis,  35 
carbonic  oxide,  40 
compounds  of,  39 
crystals,  36 
decomposition  of, 

42 
estimation  of,  36 
nitric  oxide,  42 
pathological,  38 
preparation,  36 
proteids  of,  44 
reduced,  40 
spectrum,  39 

H;t?moglobinometer,  36 

Htcmoglobinuria,  170,  447 

Hi^mophilia,  48 

Hemorrhage,  death  by,  65 
effect  of,  696 

Ha;morrhagic  diathesis,  48 

Ha-motachometer,  156 

Haidinger's  brushes,  781 

Hair,  480 

follicle,  481 

Halisterisis,  539 

Hallucinations,  749 

Hammarsten  on  blood,  54 

Harderian  gland,  813 

Hare-lip,  8S9 

Harmony,  836 


Harrison's  groove,  195 
Hassall's  corpuscles,  177 
Hawking,  207 
Head-fold,  878 
Head -gut,  878 
Heart,  67 

accelerated  action,  84 
action  of  fluids  on,  96 
action  of  gases,  92,  103 
action  of  poisons  on,  103 
apex  beat,  99 
arrangement  of  fibres,  70 
aspiration  of,  152 
auricular  systole,  75 
automatic  centres,  95 
blood  vessels  of,  72 
changes  in  shape,  82 
chordce  tendinea?,  76 
cutting  experiments,   96, 

97 
development  ot,  879 
diastole,  75 
duration  of   movements, 

92 
endocardium,  141 
examination  of,  92 
frog's,  94 
ganglia  of,  93 
innervation  of,  93 
movements  of,  75 
muscular  fibres,  67 
myocardium,  68 
nerves,  93 
nutritive  fluids,  96 
palpitation  of,  78 
pause  of,  77 
pericardium,  71 
Purkinje's  fibres,  72 
regulation  of,  73 
sounds  of,  88,  91 
staircase  beats  of,  97 
systole,  75 
valves  of,  72 
weight.  73 
work  of,  (59 
Heat,  XXXV 

balance  of,  363 

calorimeter,  356 

conductivity,  357 

dyspnoea,  688 

employment  of,  369 

estimation  of,  356 

excretion  of,  362 

income   and   expenditure, 

363 
in  inflamed  parts,  372 
latent,  347 

regulating  centre,  702 
relation  to  work,  365 
sources  of,  347,  348 
specific,  356 
stiffening,  504 
storage  of,  367 
units,  XXV,  348 
variations    in   production, 
365 
Helicotrema,  825 


Heller's  test,  246,  446 
blood  test,  450 

Helmholtz's  modification,  585 

Hemeralopia,  618 

Hemialbumin,  274 

Hemialbumose,  274 

Hemianesthesia,  733 

Hemianopsia,  617 

Hemicrania,  701 

Hemiopia,  617,  732 

Hemipeptone,  282 

Hemiplegia,  726 

Hemisystule,  88 

Henle's  loop,  424 
sheath,  565 

Hen's  egg,  864 

Hensen's  experimen's,  835 

Hepatic  cells,  286 

chemical     composition 

of,  288 
zones,  286 

Hepatogenic  icterus,  299 

Herbst's  corpuscles,  846 

Hermann's  theory  of  tissue  cur- 
rents, 596 

Herpes,  614 

Heterologous  stimuli,  74S 

Hewson's  experiments,  49 

Hiccough,  208 

Hippuric  acid,  438,  465 

Hippus,  620 

Hi>torical — 
Absorption,  346 
Circulation,  182 
Digestion,  317 
Hearing,  837 
Heat,  372 

Kidney  and  urine,  475 
Nerves     and       electro- physi- 
ology, 611 
Nerve  centres,  746 
Peripheral  nerves,  652 
Reproduction    and    develop- 
ment, 903 
Respiration,  230 
Sight,  812 
Skin,  490 
Voice  and  speech,  559 

Hoarseness,  558 

Holoblastic  ova,  864 

Homoiothermal  animals,  350 

Homologous  stimuli,  748 

Horopter,  804 

Howship's  lacunce,  892 

Humor,  aqueous,  758 

Hunger  and  starvation,  394 

Hyaloid  canal,  757 

Hybernation,  371 

Hybrids,  S73 

Hydatids,  857 

Hydra-mia,  66 

Ilydramnion,  882 

Hydrobilirubin,  295 

Hydrocephalus,  745 

Hydrochinon,  440 

Hydrochloric  acid,  269 

Hydrocyanic  acid,  42 


INDEX. 


913 


Mydrogen  given  off,  418 

in  body,  407 
Ilydrolytic  ferments,  412 
Hydronephrosis,  475 
Hydrostatic  lest,  190 
Hydroxylbenzol,  440 
HypaUusis,  635 
Uypalgia,  854 
Hyperivsthesia,  671 
I  lyperakusis,  634,  635 
Hyperalgia,  854 
Hyperdicrotism,  127 
Hypergeusia,  843 
Hyperglobulie,  64 
Hyperidrosis,  4S8 
Hyperinosis,  65 
Hyperkinesia,  671 
Hypernietrojjia,  771,  774 
Hyperoptic,  771 
Hyperosmia,  616 
Hyperpselaphesia,  S53 
Hypertrophy  of  heart,  77 

muscle,  539 
Hypnotism,  708 
Hypoblast',  875 
Hypogeusia,  843 
Hypoglossal  nerve,  645 
Hypophysis  cerebri,  181,  900 
Hypopselaphesia,  853 
Hyposmia,  616 
Hypospadias,  899 
Hypoxanthin,  41 1 

Ichthidin,  410 

Icterus,  299 

Identical  points,  S03 

Ileo-colic  valve,  259 

Ileus,  259 

Illumination  of  eye,  781 

Illusion,  749 

Images,  formation  of,  761 

Imbibition  currents,  597 

Impregnation,  874 

Impulse,  cardiac,  78 

Impulses   in    brain,    course    of, 
671,678 

Inanition,  395 

Income,  389 

Indican,  440 

Indifferent  point,  590 

Indigo  blue,  440 

Indigogen,  440 

Indirect  vision,  7S4 

Indol,  310 

Induction,  584 

Inductorium,  586 

Inferior  maxillary  nerve,  627 

Inhibition,  nature  of,  665 

Inhibition  of  reflexes,  664 

Inhd^itory  action  of  brain,  725 
nerves,  614 
for  heart,  691 
for  intestine,  264 
for  respiration,  686 

Inosinic  acid,  417 

Inosit,  416 

Insectivorous  plants,  317 

5S 


Inspiration,  196 

muscles  of,  196  ' 
ordinary,  196 
Intelligence,  degree  of,  706 
Intercellular  blood  channels,  1 14 
Intercentral  nerves,  615 
Intercostal  muscles,  199 
Interference,  835 
Interglobular  spaces,  250 
Interlobular  vein,  285 
Internal  capsule,  734 

reproductive  organs,  S98 
respiration,  219 
Intestinal  fistula,  304 
gases,  307 
juice,  303 

actions  of,  305 
paresis,  264 
Intestine,  259 

artificial       circulation, 

265 
development  of,  895 
effect  of  drugs  on,  265 
fermentation  processes 

in,  307 
large,  311,  320 
movements  of,  259 
small,  319 
Intralobular  vein,  285 
Intraocular  pressure,  624,  758 
Intussusception,  259 
Inulin,  416 
Inunction,  489 
Invertin,  306 
Invert  sugar,  306 
Ions,  579 
Iris,  775 

Iris,  action  of  poisons  on,  777 
blood  vessels  of,  776 
functions  of,  775 
movements  of,  778 
muscles  of,  776 
nerves  of,  776 
Irradiation,  797 

of  pain,  672,  853 
Ischuria,  475 
Island  of  Reil,  711 
Isidynamic  foods,  348 
Isolated  beats,  836 
Isotropous,  500 

Jacksonian  epilepsy,  717,  728 

lacobson's  organ,  839 

Jaeger's  types,  771 

Jaundice,  299 

Jaw.jerk,  667 

Joints — 

Arthrodial,  535 
Hall  and  socket,  535 
Cinglymus,  534 
Mechanism  of,  533 
Kigid,  535 
Screw-hinge,  ^34 

Juice  canals,  332 

Karyokinesis,  856 

Kattibolic,  373,  615 
Katalepsy,  708 


Kations,  579 
Keratin,  411 
Keratitis,  633 
Key-note,  829 
Keys — 

Capillary  contact,  58S 

Friction,  588 

Plug,  588 
Kidney,  419 

blood  of,  424 

chemistry  of,  465 

conditions  affecting,  466 

reabsnrption  in,  463 

structure  of,  419 

volume  of,  467 
Kinaesodic  substance,  670 
Kinetic  energy,  347 
theory,  636 
Klang,  828,  836 
Knee  phenomenon,  667 

reflex,  667 
Koenig's  manometric  flames,  S33 
Koumiss,  380 
Krause's  end  bulbs,  845 
Kreatin,  417 
Kreatinin,  417,  436 

properties,  436 
quantity,  436 
test,  436 
Kresol,  417 

Kryplophanic  acid,  441 
Kymograph,  141 

Pick's,  143 
I.udwig's,  141 
Kyphosis,  53S 

Labials,  557 

Labor,  power  of,  902 

Labyrinth,  824 

Lachrymal  apparatus,  810 

Lacteals,  319 

Lactic  acid,  414,  441 

ferment,  277 

Lactoprotein,  378 

Lactose,  376 

Litvulose,  415 

Lagoplithalmus,  620 

Lambert's  method,  791 

Lamina  spiralis,  825 

Laminoa  dorsales,  877 

Language,  729 

Lanoline,  485 

Lanugo,  480 

Lapping,  248 

Lardacein,  410 

Large  intestine,  311,  319 
absorption  in,  311 

Laryngoscope,  551 

Larynx — 

Cartilages  of,  545 
During  respiration,  200 
Experiments  on,  552 
Illumination  of,  551 
Mucous  membrane  of,  550 
Muscles  of,  547 
View  of,  552 
Vocal  cords,  546 


914 


INDEX. 


Latent  heat,  347 

period,  664 
Lateral  plates,  S78 
Laughing,  208 

Law  of  conservation  of  energy, 
xxxvi 
contraction,  601 
isolated  conduction,  606 
peripheral  perception,  847 
specific  energy,  748 
Leaping,  542 
Lecithin,  45,  414,  567 
Legumin,  383,  410 
Ler.s,  chemistry  of,  757 

crystalline,  757 

development  of,  goi 
Lenticular  nucleus,  733 
Leptothrix  buccalis,  22S 
Leucic  acid,  414 
Leucin,  310,  414,  454 
Leucocytes,  29 
Leucoderma,  614 
Leukcemia,  35 
Levers,  536 
Lichenin,  416 
Lieberkiihn's  glands,  304 
Liebig's  extract,  383 
Life,  xxxix 

Liminal  intensity,  748 
Line  of  accommodation,  770 
Ling's  system,  538 
Lingual  nerve,  627 
Lipaemia,  65 
Liquor  sanguinis,  46 
Listing's  reduced  eye,  764 
Liver,  2S4 

chemical        composition, 
288 

cirrhosis  of,  2S8 

development  of,  897 

fat  in,  289 

functions  of,  292 

glycogen  in,  291 

influence  on  metabolism, 
298 

pathology  of,  28S 

pulse  in,  166 

regeneration  of,  2S8 

structure  of,  284 
Locality,  sense  of,  847 

illusions  of,  849 
Lochia,  903 
Locomotor  ataxia,  672 
Lordosis,  538 
Loss  of  weight,  395 
Loss  by  skin,  219 
Lowe's  ring,  781 
Lungs,  183 

chemical  composition  of, 
189 

development  of,  896 

elastic  tension  of,  154 

examination  of,  194 

excision  of,  190 

limits  of,  202 

physical  properties,  1 89 

structure  of,  1 88 


Lungs,  tonus,  189 

Lunule,  480 

Lutein,  869 

Luxus  consumption,  3S9 

Lymph,  332 

movement  of,  341 

gases  of,  220 
Lymph  corpuscles,  337 

origin  and  decay  of,  340 
Lymphatics,  332 

of  eye,  75S 
origin  of,  332 
Lymph  follicles,  335 

glands,  j^^ 

hearts,  343 

Macropia,  620 

Macula  lutea,  755 

Macula;  acusticie,  S26 

Madder,  feeding  with,  405 

Magnetization,  584 

Magneto-induction,  5S5 

Major  cord,  829 

MalapterUrus,  616 

Malt,  387 

Maltose,  244,  415 

Mammary  glands,  375 

changes  in,  375 
development  of,  376 
structure  of,  375 

Manometer,  106 

Manometric  flames,  S33 

Marey's  tambour,  80 

Margarin,  478 

Mariotte's  experiment,  785 

Mastication,  248 

muscles  of,  248 
nerves  of,  249 

Massage,  538 

Mate,  385 

Matter,  xxxii 

Maturation  of  ovum,  873 

Meat  soup,  383 

Meckel's  cartilage,  889 
ganglion,  626 

Meconium,  302 

Medulla  oblongata — 

Functions  of,  682 
Gray  matter  of,  6S2 
Reflex  centres  in,  685 
Structure  of,  681 

Medullary  groove,  875 
tube,  877 

Meiocardia,  104 

Meissner's  plexus,  262 

Melanivmia,  35 

Melanin,  413 

Melitose,  416 

Mellitxmia,  64 

Membrana  decidua  menstrualis, 
882 
flaccida,  817 
reticularis,  S27 
reuniens,  8S0 
secundaria,  S24 
tectoria,  S27 

Membranes  of  brain,  742 


Meniere's  disease,  637 

Menopause,  S67 

Menstruation,  867 

Merkel's  cells,  S46 

Merobiastic  ova,  S64 

Mesentery,  development  of,  S97 

Mesoblast,  875 

Mesonephros,  898 

Metabolic  equilibrium,  3SS 
phenomena,  373 

Metabolism,  xxxix,  373,  3S8 

Metakresol,  440 

Metalbumin,  409 

Metallic  tinkling,  205 

Metalloscopy,  854 

Metamorphosis,  857 

Metanephros,  89S 

Meteorism,  264 

Meth^moglobin,  39 

Methylamine,  417 

Meynert's     projection    systems, 
676 
theory,  706 

Micrococci,  66 

Micrococcus  ureoe,  445 

Microcytes,  34 

Micropyle,  863 

Micturition,  473 

centre  for,  669 

Migration  of  ovum,  S73 

Milk,  377 

action  of  drugs  on,  379 
coagulation  of,  378 
colostrum,  379 
composition  of,  379 
curdling  ferment,  276,  283, 

379 

digestion  of,  276 

fever,  377,  903 

globules  of,  377 

plasma,  378 

preparations  of,  380 

substitutes  for,  379 

sugar.  378.  415 

tests  for,  380 
Millon's  reagent,  275 
Mimetic  spasm,  634 
Mimicry,  559 
Minor  chord,  829 
Mixed  colors,  791 
Molecular  basis  of  chyle,  33S 
Molecules,  xxxii 
Monoplegia,  727 
Monospasm,  728 
Moore's  test,  246 
Moreau's  experiment,  306 
Morphology,  xxxii 
Morula,  874 
Motor  centres,  dog,  715 
excision  of,  721 
nerves,  613 
Motor  points  on  the  surface,  606 
Mouth,  232 

glands  of,  232 
Mouvement  de  Manege,  738 
Movements  of  the  eye,  799 
forced,  738 


INDEX. 


915 


Movements,  incoordinated,  648 

Mucedin,  411 

Mucigen,  321 

Mucin,  411 

Mucous  membrane  currents,  591 
tissue,  758 

Mucus,  effect  of  drugs  on,  227 
formation  of,  227 

Mulberry  mass,  S74 

Mulder's  test,  246 

Miiller's  ducts,  89S 

experiment,  106,  133 
fibres,  755 
valve,  209 

Multiplicator,  579 

Murexide  test,  435 

Murmurs,  cardiac,  91 
venous,  164 

Musca:  volitantes,  779 

Muscarin,  259 

Muscle,  493 

action   of    two   stimuli 

on,  520 
action  of  veratrin,  519 
active  changes  in,  511 
arrangement  of,  535 
atrophic  proliferation  of, 

539 
blood  vessels  of,  500 
cardiac,  498 
changes  during  contrac- 
tion, 511 
chemical    composition, 

500 
curve  of,  515 
degenerations  of,  539 
development  of,  499 
effect  of  acids  on,  506 
effect  of  cold  on,  507 
effect  of  distilled  water 

on,  505 
effect  of   exercise  on, 

502 
effect  of  fatigue  on,  51S 
effect  of  heat  on,  505 
elasticity  of,  526 
electricity  of,  588 
excitability  of,  506 
extractives  of,  503 
fatigue  of,  531 
formation  of  heat  in, 529 
glycogen  in,  503 
of  heart,  67 
involuntary,  493 
lymphatics  of,  497 
metabolism  of,  502 
myosin  of,  501 
nerves  of,  497 
nutrition  of,  538 
perimysium  of,  493 
physical  characters,  500 
plasma  of,  501 
polarized  light  on,  496 
red  and  pale,  49S,  523 
relation  to  tendons,  497 
rhythmical  contraction, 
510 


Muscle,  rigor  mortis  of,  504 
rods,  496 

sensibility,  529,  854 
serum  of,  501 
smooth,  499 
sound  of,  530 
spectrum  of,  498 
stimuli  of,  506 
structure  of  striped,  493 
tetanus,  521 
tonus,  529,  669 
uses  of,  535 
voluntary,  493 
work  of,  524 
Muscle  current,  591 

theories,  595 
Muscle  plate,  878 
Muscular  contraction  (see  Myo- 
gram), rate  of,  523 
Muscular  sense,  854 
work,  524 

laws  of,  525 
Mutes,  558 
Mydriasis,  619 
Mydriatics,  777 
Myelin  forms,  2S3,  564 
Myocardium,  68 
Myogram,  effect  of  weights  on, 
518 
effect  of  fatigue   on, 

518 
effect  of  constant  cur- 
rent on, 518 
method   of  studying, 

513 
stages  of,  515 
Myograph,  Helmholtz's,  514 

pendulum,  515 

Pfliiger's,  515 

simple,  515 

spring,  515 
Myohxmatin,  413 
Myopia,  771,  773 
Myoryctes  Weismanni,  500 
Myosin,  381,  409,  501 
Myosis,  620 
Myotics,  777 
Myxoedema,  179,  614 

Nails,  479 

Narcotics,  854 

Nasal  breathing,  207 
timbre,  557 

Nasmyth's  membrane,  250 

Native  albumins,  409 

Natural  selection,  903 

Near  point,  770 

Neef 's  hammer,  585 

Negative  accommodation,  766 
pressure,  327 
variation,  591,  593 

Nephrozymose,  441 

Nerve  cells,  bipolar,  566 

multipolar,  565,  659 
of  cerebrum,  709 
Purkinje's,  739 
with  a  spiral  fibre,  566 


Nerve  centres,  general  functions, 

653 
Nerve  current,  s8S 
Ner^'e  fibres,  561 

action  of  nitrate  of  silver 
on,  564 

chemical    properties    of, 
566 

classification  of,  613 

death  of,  576 

degeneration  of,  572 

development  of,  365 

division  of,  564 

effect  of  a  constant   cur- 
rent on, 571 

electrical  current  of,  591, 
594 

excitability  of,  568 

fatigue  of,  572 

incisures  of,  564 

mechanical  properties  of, 
568 

medullated,  562 

metabolism  of,  568 

nutrition  of,  572 

Ranvier's  nodes,  564 

reaction  of,  567 

regeneration  of,  575 

sheaths  of,  562 

stimuli  of,  568 

structure  of,  561 

suture  of,  575 

terminations  of,  844 

to  glands,  237 

traumatic      degeneration 
of.  574 

trophic  centres  of,  574 

unequal    excitability    of, 
572 
Nerve  impulse,  rate  of.  602 

method  of  measuring,  603 

modifying        conditions, 
603 

variations  of,  605 
Nerve  motion,  606 
Nerve-muscle  preparation,  593 
Nerves,  anabolic,  615 

cranial,  615 

electrical,  606 

imercentral,  615 

katabolic,  373,  615 

motor,  613 

secretory,  613 

sensory,  615 

special  sense,  615 

spinal,  645 

trophic,  613 

union  of,  575 

visceral,  61 5 
Nerve  stretching,  569 
Nervi  nervorum,  565 
Ner\'ous  system,  561 

development  of,  900 
Nervus  abducens,  630 
accessorius,  644 
acusticus,  634 
depressor,  132,  640 


916 


INDEX. 


Nervus  erigens,  669,  701,  870 
facialis,  631 
glossopharyngeiis,  637 
hypoglossus,  645 
oculomotorius,  618 
olfactorius.  615 
opticus,  616 
sympathicus,  649 
trigeminus,  621 
trochlearis,  621 
vagus,  63S 
Neubauer's  test,  346 
Neuralgia,  S54 
Neuraftube,  827 
Neurasthenia  gastrica,  315 
Neurin,  414 
Neuro-epitheliuni,  756 
Neuroglia,  657 
Neurokeratin,4ll,  564 
Neuro-niuscular  cells,  509 
New-born    child,  digestion    of, 
2S3 
•  pulse,  127 
size,  405 
temperature,  35S 
urine  of,  428 
weight,  405 
Nictitating  membrane,  813 
Nitrites,  42 
Nitrogen  in  air,  212 
in  blood,  62 
in  body,  407 
given  oft',  393 
Nceud  vital,  686 
Noises,  828 
Nose,  development  of,  901 

structure,  839 
Notochord,  877 
Nuclear  spindle,  873 
Nuclein,  45,  411 
Nucleus  of  Pander,  S65 
Nussbaum's  experiments,  462 
Nutrient  arteries,  744 
enemata,  331 
Nyctalopia,  61S 
Nystagmus,  620,  73S 

Oatmeal,  3S3 

( )culomotorius,  61S 

Odontoblasts,  249 

Gldema,  344 

cachectic,  345 
pulmonary,  207 

Oesophagus,  256 

Ohm's  law,  577 

Oidium  albicans,  229 

Oleic  acid,  414 

Oligsmia,  66 

Olfactory  centre,  724 
nerve,  941 
sensations,  819 

Omphalo-mesenteric  duct,  879 
vessels,  879 

Onamatopoesy,  559 

Oncograph,  467 

Oncometer,  467 

Ontogeny,  904 


Opening  shock,  5S4 
Ophthalmia       neuro-paralytica, 
624 
intermittens,  626 
sympathetic,  626 
Ophthalmic  nerve,  621 
Ophthalmometer,  765 
Ophthalmoscope,  7S3 
Optic  nerve,  616 

radiation,  616 
thalamus,  735 
tract,  616 
vesicle,  877 
Optical  cardinal  points,  764 
Optogram,  790 
Optometer,  772 
Organ  albumin,  388 
Organic  albumin,  389 

compounds,  408 
reflexes,  668 
Orthopncea,  196 
Orthoscope,  784 
Osmasome,  382 
Ossein,  41 1 
Osseous    system,    formation   of, 

888 
Osteoblasts,  89 1 
Osteoclasts,  892 
Osteomalacia,  539 
Otic  ganglion,  62S 
Ovarian  tubes,  863 
Ovary,  862,  898 
Overcrowding,  226 
Ovulation,  868 

theories  of,  868 
Ovum,  862 

development  of,  863 
discharge  of,  863 
fertilization  of,  872 
impregnation  of,  873 
maturation  of,  S73 
migration  of,  873 
structure  of,  S62 
Oxalic  acid,  414,  437 
series,  414 
Oxaluria,  437 
Oxaluric  acid,  437 
Oxy-acids,  417 
Oxygen,  absorption  of,  217 
in  blood,  59 
estimation  of,  209 
fonns  of,  61 
in  body,  407 
Oxyhemoglobin,  39 
Oxyakoia,  634 
Ozone  in  blood,  60 

Pacchionian  bodies,  743 
Pacini's  corpuscles,  844 
Pain,  853 

irradiation  of,  853 
Painful  impressions,  conduction 

of,  672 
Palmitic  acid,  414 
Palpitation,  78 
Pancreas,  27S 

changes  in,  279 


Pancreas,  development  of,  897 
fistula  of,  279 
juice  of,  279 
paralvtic       secretion, 

2Si 

Pancreatic  secretion,  2S3 
actions  of,  2S3 
artificial  juice,  2S2 
action  of  nerves   on, 

284 
action  of  poisons  on, 

2S4 
composition,  280 
extracts,  283 

Panophthalmia,  624 

Pansphygmograph,  120 

Papain,  282 

Papilla  foliata,  844 

Parablastic  cells,  878 

Paradoxical  contraction,  595 
reaction,  244 

Paraglobulin,  409 

Parakresol,  440 

Paralbumin,  409 

Paralgia,  854 

Paralytic     secretion    of    saliva, 

pancreatic  juice,  283 
Paramylum,  416 
Paraphasia,  731 
Paraxanthin,  417,  436 
Parelectronomy,  596 
Paridrosis,  4S9 
ParoSphoron,  899 
Parotid  gland,  233 
Parovarium,  898 
Parthenogenesis,  857 
Partial  pressure,  57 
reflexes,  661 
Particles,  xxxii 
Parturition,  centre  for,  669 
Passavant's  elevation,  254 
Passive  insufficiency,  537 
Patellar  reflex,  667 
Pathic  reflex,  666 
Pavy's  test,  246 
Pecten,  813,  901 
Pectoral  fremitus,  205 
PeduncuU  cerebri,  736 
Penis,  erection  of,  869 
Pepsin,  269 
Pepsinogen,  271 
Peptic  glands,  266 

changes  in,  270 
Peptone,  274 

forming  ferment,  270, 
280 

metabolism  of,  396 

tests  for,  275 
Peptonized  foods,  284 
Peptonuria,  447 
Percussion  of  heart,  93 

lungs.  195,  203 
Perforating   ulcer    of    the    foot, 

614 
Pericardium,  71 
Perilymph,  S26 


INDEX. 


917 


Perimeter,  Aiibert  and  Forster, 
78S 
McHardy's,  7SS 
Priestley  Smith's,  789 

Perimetric  chart,  789 

Perimetry,  78S 

Perimysium,  493 

Perineurium,  565 

Periodontal  membrane,  251 

Peristaltic  movement,  259 

action   of    blood    on, 

262 
action  of  nerves   on, 
264 

Peritoneum,     development     of, 
897 

Perivascular  spaces,  334 

Pettenkofer's  test,  294 

Peyer's  glands,  318 

Pfliiger's  law,  601 

law  of  reflexes,  662 

Phagocytes,  31 

Phakoscope,  769 

Phanakistoscope,  796 

Phases,  displacement  of,  S31 

Phenol,  311,  415,  440 

Phenolsulphuric  acid,  440 

Phlebogram,  165 

Phonation,  547 

Phonograph,  833 

Phonometry,  204 

Phosphoric  acid,  442 

Phosijhenes,  7S0 

Photophobia,  634 

Photopsia,  61 8 

Phrenograph,  194 

Phrenology,  704 

Phylogeny,  904 

Phytalbumose,  410 

Phytomycetes,  456 

Pia  mater,  742 

Picric  acid  test,  452 

Picrosaccharinieter,  453 

Pigment  cells,  492 

Pitch,  S28 

Placenta,  884 

Placental  bruit,  164 

Plantar  reflex,  666 

Plants,  characters  of,  xxxviii 

electrical      currents     in, 

597 

Plasma  cells,  742 

of  blood,  46,  54 
of  lymph,  338 
of  milk,  378 
of  muscle,  501 

Plasmine,  50 

Plethora,  64 

Plethysmography,  167 

Pleura,  187 

Pleuro-peritoneal  cavity,  878 

Pleximeter,  202 

Pneumatogram,  194 

Pneumatometer,  206 

Pneumograph,  194 

Pneumonia  after  section  of  vagi, 
641 


Pneumothorax,  190 
Poikilothermal  animals,  350 
Poiseuille's  space,  161 
Poisons,  heart,  103 

on    vasomotor    nerves, 

696 
spinal  cord,  664 
Polar  globules,  873 
Polarization,  galvanic,  579 
internal,  583 
Polarizing  after  currents,  595 
Politzer's  ear  bag,  824 
Polyitmia,  63 

apocoptica,  63 
aquosa,  64 
hyperalbuminosa,  64 
polycythixmica,  64 
serosa,  64 
transfusoria,  63 
Polyopia  monocularis,  775 
Pons  Varolii,  736 
Porret's  phenomenon,  500,  583 
Portal  canals,  2S5 

circulation,  67 

system,  development  of, 

89s 
vein  in  liver,  285 
vein,  ligature  of,  153 
Positive  accommodation,  768 

after  images,  796 
Potash  salts,  407 
Potassium  sulphocyanide,  441 
Potatoes,  384 
Presbyopia,  772 
Pressor  fibres,  673,  697 
Pressure,  arterial,  145 

atmospheric,  229 

intra-labyrinthine,  827 

of  blood,  141 

respiratory,  205 

sense  of,  850 
Presystolic  sound,  91 
Prickle  cells,  477 
Primitive  anus,  881 

chorion,  875,  883 

circulation,  S79 

groove,  875 

kidneys,  897 

mouth,  881 

streak,  875 
Primordial  cranium,  888 

ova,  803 
Principal  focus,  759 

point,  761 
Progressive   muscular    atrophy, 

539 
Pronephros,  898 
Pronucleus,  male,  874 

female,  873 
Propepsin,  271 
Propeptone,  274 
Protagon,  413,  567 
Proteids,  408 

coagulated,  410 
gastric     digestion     of, 

274 
fermentation  of,  310 


Proteids,  pancreatic  digestion  of, 
280 

reactions  of,  40S 

vegetable,  410 
Protista;,  xxxi 
Protodoeum,  875 
Protovertebrse,  878 
Pseudo-hypertrophic    paralysis , 

539 

Pseudo-motor  action,  632 

Pseudoscope,  80S 

Pseudo-stomata,  1 86 

Psychical  activities,  703 
blindness,  722 
deafness,  723 

Psycho-acoustic  centre,  732 
geusic  centre,  732 
motor  centre,  71S 
optic  centre,  731 
physical  law,  74S 
sensorial  centres,  721 
sensory  paths,  731 

Ptomaines,  275 

Ptosis,  619 

Ptyalin,  244 

Ptyalism,  241 

Puberty,  866 

Pulmonary  artery, pressure  in,  1 5  3 

Pulmonary  cedema,  207 

Pulp  of  tooth,  251 
spleen,  173 

Pulse,  117 

capillary,  140 
catacrotic,  121 
characters  of,  127 
conditions  afl'ecting,  127 
curve,  129 
dicrotic,  126 
entoptical,  137,  780 
historical,  116 
hyperdicrotic,  127 
in  animals,  1 28 
in  jugular  vein,  166 
influence  of  pressure  on, 

influence   of    respiration 
on,  131 

instruments    for   investi- 
gating, 1 17 

in  liver,  166 

monocrotic,  127 

of  various  arteries,  129 

paradoxical,  133 

pathological,  137 

recurrent,  130 

trigeminal,  128 

variatians  in,  128 

venous,  165 

wave,  132, 136 
Pulses,  383 
Pulsus  alternans,  128 

bigeminus,  12S 

caprizans,  127 

dicrotus,  126 

intercurrens,  12S 

myurus,  12S 
Pumping  mechanisms,  342 


918 


INDEX. 


Pupil,  776 

action  of  poisons  on,  777 
Argyll  Robertson,  777 
functions  of,  775 
movements  of,  776 
photometer,  77S 
size  of,  378 
Purgatives,  265 
Purkinje,  cells  of,  739 

fibres  of,  72,  49S 
figure,  779 
Sanson's  images,  76S 
Putrefactive  processes,  307 
Pyloric  glands,  267 

changes  in,  270 
Pyramidal  tracts,  67S 

degeneration  of,  727 
Pyrokatechin,  415,  440 

Quality  of  a  note,  S2S 
Quantity  of  blood,  63,  159 
food,  389 

Rales,  dry,  205 

moist,  205 
Rami  communicantes,  649 
Range  of  accommodation,  770 
Ranvier's  nodes,  564 
Raynaud's  disease.  614 
Reaction  impulse,  81 
Reaction  of  degeneration,  607, 

610 
Reaction  time,  605 
Recovery,  533 
Rectum,  265 
Recurrent  pulse,  130 

sensibility,  646 
Red  blindness,  794 
Reduced  eye  of  Listing,  764 
Reductions  in  intestine,  308 
Reflex  acts,  examples  of,  662 

inhibition  of,  664 

movements,  666 

movements,    theory    of, 
666 

nerves,  615 

spasms,  661 

tactile,  672 

time,  664 

tonus,  670 
Refracted  ray,  761 
Refractive  indices,  761 
Regeneration  of  tissues,  402 
nerve,  575 
Regio  olfactoria,  839 

respiratoria,  839 
Reissner's  membrane,  825 
Relative  proportions  of  diet,  389 
Remak's  ganglion,  94 
Renal  plexus,  461 
Rennet,  276,  37S 
Reproduction,  forms  of,  856 
Requisites    in    a    proper    diet, 

389 
Reserve  air,  191 
Residual  air,  191 


Resistance,  109 
Resonance  organs,  545 
Reson.ants,  557 
Resonators,  11,31 
Respiration,  1S3 

amphoric,  205 
artificial,  224 
bronchial,  204 
centre  for,  686 
chemistry  of,  209 
cog-wheel,  205 
cutaneous,  219 
forced,  195 
in    a   closed    space, 

221 
in  animals.  192 
internal,  219 
intestinal,  230 
mechanism  of,  190 
muscles  of,  196 
nasal,  207 
number  of,  192 
periodic,  196 
pressure  during,  205 
sounds  of,  204 
time  of,  192 
type,  195 
variations  of,  192 
vesicular,  204 
Respiratory  apparatus,  183 

Andral  and    Gavar- 

ret,  209 
centre,  686 
mechanism  of,  190 
v.  Pettenkofer,  211 
quotient,  212 
Regnault   and    Rei- 

set,  21 1 
Scharling,  210 
Rete  mirabile,  67 
Retina,  754 

activity  in  vision,  785 
blood  vessels  of,  753 
chemistry  of,  757 
capillaries,     movements 

in,  779 
epithelium  of,  756 
rods  and  cones  of,  756 
stimulation  of,  796 
structure  of,  757 
visual  purple  of,  756 
Retinal  image,  formation  of,  764 

size  of,  765 
Retinoscopy,  7S4 
Rigor  mortis,  504 
Rheocord,  578 
Rheometer,  155 
Rheophores,  606 
Rheoscopic  limb,  590 
Rheostat,  578 
Rheotom,  593 
Rhinoscopy,  552 
Rhodophane,  757 
Rhodopsin.  756 
Rickets,  539 

Ritter's   opening    tetanus,   600, 
602 


Ritter's  tetanus,  600 
Ritter-VaUi  law,  576 
Rods  and  cones,  756 
Rotatory  disk  for  colors,  791 
Running,  543 

Saccharomycetes,  386 

Saccharose,  415 

Saccule,  825 

Saftcanalchen,  332 

Saline  cathartics,  265 

Saliva,  action  of  nerves  on,  237 
action  of  poisons  on,  241 
action  on  starch,  244 
chorda,  238 
composition  of,  243 

Saliva  facial,  237 

functions  of,  244 
mixed,  243 
new-born  child,  244 
parotid,  240 
pathological,  314 
ptyalin,  245 
reflex  secretion  of,  2  38 
sublingual,  243 
submaxillary,  242 
sympathetic,  238 
theory  of  secretion,  239 

Salivary  corpuscles,  243 
glands,  233 
changes  in,  235 
development  of,  896 
nerves  of,  237 

Salts,  407 

Sanson-Purkinje's  images,  779 

Saponification,  283 

Sarcini  ventriculi,  315 

Sarcolactic  acid,  501 

Sarcolemma,  494 

Sarkin,4i7,  436 

Sarkosin,  417 

Saviotti's  canals,  279 

Scheiner's  experiment,  770 

Schift's  test,  436 

Schizomycetes,  66 

Schmidt's  researches,  50 

Schreger's  lines,  250 

Schwann's  sheath,  562 

Sclerotic,  753 

Scoliosis,  538 

Scotoma,  7S9 

Screw-hinge  joint,  534 

Scrotum,  formation  of,  S99 

Scurvy,  65 

Scyllit,  417 

Sebaceous  glands,  482 

secretion,  483 

Seborrhoea,  489 

Secondary  circulation,  879 
contraction,  592 
degeneration,  660 
tetanus,  592 

Secretion  currents,  596 

Secretory  nerves,  613 

Sectional  area,  157 

Segmentation  sphere,  874 

Self-stimulation  of  muscle,  59 1 


INDEX. 


919 


Semen,  composition  of,  860 
ejaculation  of,  872 
reception  of,  872 
Semicircular  canals,  826 
Sensation,  748 
Sense  organs,  748 

development  of,  901 
Sensory  areas,  724 

crossway,  679 
paths,  679 
Serin,  417 

Serum  of  blood,  46,  54 
Serum  albumin,  55,  409 
globulin,  54,  409 
Setschenovv's  centres,  665 
Sex,  difference  of,  900 
Shadows,  lens,  779 

colored,  79S 
Sharpey's  fibres,  892 
Short-sightedness,  771 
Shunt,  582 
Sialogogues.  241 
Sighing,  208 
Simple  colors,  791 
Simultaneous  contrast,  7S4 
Single  vision,  803 
Sitting,  540 
Sire,  405 

estimation  of,  808 
false  estimate  of,  808 
Skatol,  311,  441 
Skin,  absorption  by,  4S9 
chorium  of,  477 
epidermis,  477 
functions  of,  484 
galvanic  conduction  of,  4S9 
glands  of,  482 
historical,  490 
protective  covering,  483 
respiratory  organ,  484 
structure  of,  477 
varnishing  the,  371,  484 
Skin  currents,  591 
Sleep,  707 
Small  intestine,  319 

absorption  by,  327 
structure  of,  319 
Smegma,  485 
Smell,  sense  of,  839 
Sneezing,  207 
Snellen's  types,  772 
Sniffing,  840 
Snoring,  208 
Sodic  chloride,  407,  442 

salts,  408 
Solitary  follicles,  324 
Somatopleure,  878 
Sorbin,  417 
Sound,  815 

conduction  to  ear.  Si 5 
direction  of,  836 
distance  of,  837 
perception  of,  S37 
retlection  of,  815 
Sounds,  cardiac,  85 

cracked-pot,  204 
tymianilic,  203 


Sounds,  vesicular,  204 
Spasm  centre,  702 
Spasmus  nictitans,  634 
Specific  energy,  790 
Spectacles,'773,  813 
Spectra,  absorption,  38 
flame,  38 
optical,  781 
Spectroscope,  38 
Spectrum  mucro-Iacrimale,  779 
of  bile,  295 
of  blood,  39 
of  muscle,  496 
Speech,  555 

centre  for,  729 
pathological      variations, 

558 

Spermatin,  860 

Spermatozoa,  S60 

Spermatoblasts,  85S 

Spina  bifida,  743,  880 

Spinal  accessory  nerve,  644 

Spinal  cord,  654 

action  of  blood  and  poi- 
sons on,  671 
anterior  roots  of,  647 
blood  vessels  of,  658 
centres,  668 

conducting  paths  in,  671 
conducting  system  of,  659 
development  of,  901 
degeneration  of,  659 
excitability  of,  670 
Flechsig's  systems,  659 
ganglion,  645 
Gerlach's  theory,  657 
nerves,  645 
neuroglia  of,  657 
nutritive  centres  in,  660 
posterior  roots  of,  648 
reflexes,  661 
regeneration  of,  703 
secondary      degeneration 

of,  659 
segment  of,  680 
structure  of,  654 
time  of  development,  661 
transverse  section  of,  673 
unilateral  section  of,  674 
vasomotor  centres  in,  696 
Woroschiloff's      observa- 
tions, 656 

Sphenopalatine  ganglion,  626   ' 

Spherical  aberration,  774 

Sphincters,  535 

Sphincter  ani,  260 

pupilla^  754 
urethra",  472 

Sphymograph,  1 1 8 

r)udgeon's,  120 
Marey's,   118 

Sphygmometer,  129 

Sphygmogram,  122 

Sphygmomanometer,  144 

Sphygmoscope,  122 

Spiral  joints.  534 

Spirillum,  66 


Spiroclu'eta,  66 
Spirometer,  191 
Splanchnic  nerve,  65 1 
Splanchnopleure,  878 
.Spleen,  172 

action  of  drugs  on,  175 

chemical       composition, 
174 

contraction  of,  175 

extirpation  of,   1 74 

functions  of,  174 

influence   of   nerves   on, 
176 

oncograph,   175 

regeneration  of,  174 

structure,  172 

tumors  of,  177 
Spongin,  41 1 

.Spontaneous  generation,  S56 
Spores,  308 

Spring  kymograph,  143 
Spring  myograph,  515 
Springing,  542 
Sputum  abnormal,  229 

normal,  227 
Squint,  619 
Stammering,  559 
Standing,  539 
.Stannius's  experiment,  96 
Stapedius,  822 
Starch,  416 
Stasis,  162 

Statical  theory  of  Goltz,  637 
Stationary  vibrations,  816 
Steapsin,  283 
Stenopaic  spectacles,  774 
Stenosis,  88 

Stenson's  experiment,  505 
Stercobilin,  296,  312 
Stercorin,  313 
Stereoscope,  807 
Stereoscopic  vision,  805 
Sternutatories,  207 
Stethograph,  193 
Stigmata,  113 
.Stilling,  canal  of,  758 
Stimuli,  506 

adequate,  748 

heterologous,  74S 

homologous,  748 

muscular,  509 
Stoffwechsel,  xxxix 
Stomach,  266 

catarrh  of,  319 
changes  in  glands,  270 
diseases  of,  314 
gases  in,  278 
glands  of,  266 
movements  of,  256 
structure  of,  266 
Stomata,  113,  335 
Stomodceum,  875 
.Storage  albumin,  388 
Strabismus,  738 
Strangury,  475 
Strasburg's  test,  451 
Strobic  disks,  797 


920 


INDEX. 


Stroma  filniii  and  plasma  fibrin, 

54 
Struggle  for  existence,  903 
Strychnin,  action  of,  663 
Stuttering,  559 
Subarachnoid  space,  742 
fluid,  743 
Subdural  space,  742 
Subjective  sensations,  749 
Sublingual  gland,  240 
Submaxillary  ganglion,  628 
atropin  on,  239 
gland,  237 
saliva,  239 
Successive  beats,  836 

contrast,  799 
Succinic  acid,  414 
Succus  entericus,  303 

action  of  drugs  on,  306 
Suction,  24S 
Sudorifics,  486 
Sugars,  415 

estimation  of.  247 
tests  for,  246 
Sulphindigotate  of  soda,  461 
Summation  of  stimuli,  521,  622 
Summational  tones,  836 
Superfecundation,  873 
Superficial  reflexes,  666 
Superfcetation,  S73 
Superior  maxillary  nerve,  626 
Suprarenal  capsules,  i8o 
Surditas  verbalis,  732 
Sutures,  535 
Sweat,  4S4 

chemical       composition, 

48s 
conditions  influencing  se- 
cretion, 486 
excretion    of    substances 

by,  4S6 
glands,  483 
insensible,  485 
nerves,  487 
pathological  variations  of, 

488 
centre,  488 

spinal,  670 
Swimming,  544 
Sympathetic  ganglion,  649 
nerve,  649 
section,  651 
stimulation  of,  651 
Sympheses,  535 
Synchondroses,  535 
Syncope,  78 
Synergetic  muscles,  538 
Synovia,  534 
Syntonin,  274 
Systole,  cardiac,  75 

Tabes,  672 

Taches  cerebrales,  701 

Tactile,  areas,  724 

corpuscles,  846 

sensations,      conduction 
of,  846 


T.-enia,  857 
Tail.fdld,  878 
Talipes  calcaneus,  538 
equinus,  538 
varus,  538     ■ 
Tambour,  Marey's,  120 
Tapetum,  784 
Tapping  experiment,  691 
Taste  bulbs,  841 

organ  of,  841 
testing,  842 
Taurin,  417 
Taurocholic  acid,  293 
Tea,  385 
Tears,  8 10 
Tegmentum,  676 
Telestereoscope,  807 
Temperature  of  animals,  351 

accommodation  for, 

366 
artificial       increase 

of,  369 
estimation  of,  35 1 
how  influenced, 354 
lowering  of,  370 
postmortem,  369 
regulation  of,  361 
topography  of,  353 
variations  of,  358 
Temperature  sense,  852 

illusions  of,  853 
Tendon,  500 

nerves  of,  500,  846 
reflexes,  667 
Tensor,  choroideEe,  753 

tympani,  821 
Testicle,  descent  of,  887 
Testis,  857 
Tetanomotor,  569 
Tetanus,  521,  571,  663 

secondary,  592 
Thaumatrope,  796 
Theobromin,  385 
Thermal  cortical  centre,  160 
Thermo-electric  methods,  351 
needles,  353 
Thermometer,  351 

metastatic,  35 1 
maximal  and    mini- 
mal, 351 
outflow,  351 
Thermometry,  351 
Thirst,  390 
Thiry's  fistula,  304 
Thomson's  disease,  520 
Thoracometer,  201 
Thymus,  177 

development  of,  889 
Thyroid,  178 

development  of,  889 
Tibial  air,  191 

wave,  123 
Timbre,  557,  828 
Time    in    psychical     processes, 

707 
Time  sense,  830 
Tinnitus,  637 


Tissue  formers,  390 

regeneration  of,  402 

Tissue  metabolism,  400 

Tobin's  tubes,  227 

Tomes,  fibres  of,  249 

Tone  inductorium,  523 

Tones,  828 

Tongue,  glands  of,  232 

movements  of,  253 
nerves  of,  253 
taste  bulbs,  841 

Tonometer,  98 

Tonus,  670 

Tonsils,  233 

Tooth,  249 

action  of  drugs  on,  253 
chemistry  of,  251 
development  of,  251 
eruption  of,  252 
permanent,  252 
pulp  of,  251 
structure  of,  249 
temporary,  252 

Toricelli's  theorem,  108 

Torpedo,  612 

Torticollis,  644 

Touch  corpuscles,  844 

Touch,  sense  of,  844 

Trachea,  183 

Transfusion,  63,  168 

of  blood,  16S 

of  other  fluids,  171 

Transitional  epithelium,  471 

Transudations,  345 

Transplantation  of  tissues,  405 

Trapezius,  spasm  of,  644 

Traube-Hering  curves,  147 

Traumatic       degeneration       of 
nerves,  574 

Trichina,  857 

Trigeminus,  624 

ganglia  of,  623,  626,  628 
inferior  maxillary  branch, 

627 
neuralgia  of,  629 
ophthalmic  branch,  621 
paralysis  of,  629 
pathological,  629 
section  of,  628,  630 
superior  maxillary  branch, 

626 
trophic  functions  of,  624 

Triple  phosphate,  445 

Trismus,  629 

Trochlearis,  621 

Trommer's  test,  246 

Troiihic  centres,  575 
fibres,  624 
nerves,  613,  624 

Trophoneuroses,  614 

Trotting,  544 

Trypsin,  281 

Trypsinogen.  28 1 

Tryptone,  281 

Tube  casts,  456 

Tubes,  capillary,  115 
division  of,  115 


INDEX. 


921 


Tubes,  elastic,  115 

movements  of   fluids  in, 
116 

rigid,  134 
Tumultus  sermonis,  730 
Tunicin,  416 
Tiirck's  method,  666 
Twins,  S73 
Twitch,  515 
Tympanic  membrane,  S16 

artificial,  81 S 
Tyrosin,  310,  41 1,  454 

Ulcer  of  foot,  perforating,  614 
Unipolar  induction,  585 

stimulation,  572 
Umbilical  arteries,  882 
cord,  S85 
veins,  8S2,  886 
vesicle,  S79 
Upper  tones,  831 
Urachus,  882 
Ur,T:mia,  469 
Urates,  435 
Urea,  417,  430 

compounds  of,  432 
decomposition,  430 
eflfect  of  exercise  on,  431 
ferment,  443 
formation  of,  431,  463 
nitrate  of,  432 
occurrence  of,  431 
oxalate  of,  432 
pathological,  431 
phosphate  of,  432 
preparation  of,  432 
properties  of,  430 
qualitative   estimation  of, 

432 
quantitative  estimation  of, 

432 
quantity  of,  430 
relation   of,   to    muscular 
work,  431,  503 
Ureameter,  432 
Ureter,  ligature  of,  463 

structure   and   functions 
of,  470 
Uric  acid,  417 

diathesis,  470 
formation  of,  434,  464 
occurrence,  435 
properties  of,  434 
qualitative  estimation,  435 
quantitative  estimation,  436 
quantity,  434 
solubility,  435 
tests  for,  435 
Urinary  bladder,  471 
calculi,  458 
closure  of,  472 
deposits,  455 
development  of,  882 
organs,  419 
pressure  in,  475 
Urine,  426 

accumulation  of,  472 


Urine,  acid  fermentation,  443 
acidity,  430 
albumin  in,  445 
alkaline       fermentation, 

445 
alkaloids  in,  469 
amount  of  solids,  427 
bile  in,  450 
blood  in,  447 
calculi,  458 
changes   of   in   bladder, 

475 
color,  427 

coloring  matters  of,  428 
consistence,  429 
cyslin  in,  454 
deposits  in,  455 
dextrin  in,  453 
effect  of  blood  pressure 

on,  465 
egg  albumin  in,  447 
electrical     condition    of, 

611 
excretion  of  pigments  by, 

462 
fermentations  of,  443 
fluorescence,  429 
fungi  in,  455 
gases  in,  443 
globulin  in,  447 
incontinence  of,  475 
influence    of   nerves   on, 

465 
inorganic       constituents, 

441 
inosit  in,  454 
leucin  in,  454 
milk  sugar  in,  453 
movement  of,  470 
mucin  in,  447 
mucus  in,  447 
organisms  in,  455 
passage    of      substances 

into,  465 
peptone  in,  447 
phosphoric  acid  in,  442 
physical     characters    of, 

426 
pigments  of,  427 
preparation  of,  463 
propeptone  in,  447 
quantity,  426 
reaction,  429 
retention  of,  475 
secretion  of,  459 
silicic  acid  in,  443 
sodic  chloride  in,  442 
specific  gravity,  427 
spontaneous  changes  in, 

443 
sugar  in,  451 
sulphuric  acid  in,  443 
taste  of,  429 
test  for  albumin  in,  446 
tube  casts  in,  456 
tyrosin  in,  454 
volume  of,  467 


Urinometer,  427 

Urobilin,  439 

Urochrome,  439 

Uroerythrin,  439 

Uro-genital  sinus,  899 

Uroglaucin,  439 

Uromelanin,  439 

Urostealith,  458 

Uterine  milk,  885 

Uterus,  866 

development  of,  898 
involution  of,  903 
nerves  of,  902 

Utricle,  825 

Uvea,  753 

Vagus,  638 

cardiac  branches,  640 
depressor  nerve  of,  146, 

640 
effect  of  section,  641 
pathological,  643 
pneumonia    after    sec- 
tion, 641 
reflex  effects  of,  643 
stimulation  of,  1 50 
unequal  excitability  of, 

643 
Valleix's  points  douloureux,  854 
Valsalva's  experiment,  105,  132, 

822 
Valve,  ileo-colic,  259 

pyloric,  257 
Valves  of  heart,  71 
disease  of,  88 
injury  to,  78 
of  veins,  113 
sounds  of,  165 
Valvulie  conniventes,  319 
Varicose  fibres,  561 
Varix,  152 

Varnishing  the  skin,  484 
Vas  deferens,  859 
Vasa  vasorum,  1 14 
Vascular    system,    development 

of,  892 
Vaso-dilator  centre,  701 
nerves,  701 
Vaso-formative  cells,  26 
Vasomotor  centre,  695 
spinal,  700 
Vasomotor  nerves,  course  of,  696 
Vater's  corpuscles,  845 
Vegetable  albumin,  410 
casein,  410 
foods,  383 
proteids,  410 
Veins,  1 1 3 

cardinal,  894 
development  of,  894 
movement   of  blood    in, 

163 
murmurs  in,  164 
pressure  in,  152 
pulse  in,  152 
structure  of,  112 
tonus  of,  700 


922 


INDEX. 


Veins,  valves  in,  113 

valvular  sounds  in,  165 
varicose,  152 
velocity  of  blood  in,  157 
Velocity  of  blood  stream,  155 
Ventilation,  226 
Ventricles,  70,  75 

aspiration  of,  75 
capacity  of,  140,  159 
duration  of,  1 59 
impulse  of,  Si 
negative  pressure  in, 

77 
systole  of,  82 
Veratrin,  519 
Vernix  caseosa,  485 
Vertebra;,  mobility  of,  540 
Vertebral  column,  880 
Vertigo,  637 
Vibrations  of  body,  137 
Vibratives,  557 
Vibrio,  66 
Villus  intestinal,  320 

absorption  by,  32S 

chorionic,  875 

contractility  of,  322 

placental,  885 
Violet  blindness,  794 
Visceral  arches,  881 
clefts,  881 
Vision  binocular,  803 

single,  803 

stereoscopic,  805 
Visual  angle,  765 

apparatus,  750 

centre,  722 

purple,  756,  790 
Vital  capacity,  191 
Vitellin,  409,  866 
Vitelline  duct,  879 


Vitreous  humor,  757 
Vocal  cords,  546 

conditions   influencing 
the,  553 

varying  conditions  of, 

549 
Voice,  falsetto,  554 

in  animals,  559 
pathological  variations  of, 

558 
physics  of,  545 
pitch  of,  545 
production  of,  554 
range  of,  554 
Vomiting,  257 

centre  for,  25S 
Vowels,  S30 

analysis  of,  555 
artificial,  832 
formation  of,  555 
Koenig's  apparatus  for, 
833 

Waking,  707 

Walking,  541 

Wallerian  law  of  degeneration, 

574 
\\  arm-blooded  animals,  350 
Washed-blood  clot,  50 
Water,  373,  390,  407 

absorbed  by  skin,  4S9 

absorption  of,  328 

amount  of,  407 

exhaled     by     skin,    219, 
484 

exhaled  from  lungs,  212 

hardness  of,  374 

impurities,  374 

in  urine,  428 

vapor  of,  in  air,  212 


Wave  pulse,  122 

propagation  of,  136 
Wave  movements,  815 
Waves,  in  elastic  lubes,  134 
Weber's  paradox,  528 

law,  749 
Weight,  405 
Wharton's  jelly,  885 
Whispering,  555 
White  of  egg,  409 
Wine,  587 
Wolffian  bodies,  897 
ducts,  899 
Word  blindness,  730,  731 

deafness,  723 
Work,  524 

unit  of,  xxxiv 

Xanthin,  417,  436 
Xanthokyanopy,  795 
Xanthophane,  757 
Xanthoproteic,  reaction,  40S 
Xerosis,  624 

Yawning,  20S 
Yeast,  386 
Yelk,  865 

sack,  879 
Yellow  spot,  7S0 
Young- Hehnholtz  theory,  793 

Zimmermann,  particles  of,  34 
Zinn,  zonule  of,  757 
Zoetrope,  796 
Zollner's  lines,  810 
Zona  pellucida,  862 
Zoogloea,  308 
Zymogen,  281 
Zyraophytes,  277 


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